Spatial and temporal use of a spawning site in the middle green river by wild and hatchery-reared razorback suckers

USGS Publications Warehouse

Modde, T.; Bowen, Z.H.; Kitcheyan, D.C.

2005-01-01

The population of endangered razorback suckers Xyrauchen texanus in the middle Green River (upper Colorado River basin) has declined during the last 40 years. The apparent cause for this decline is a lack of successful recruitment. This study used radiotelemetry to evaluate the ability of hatchery-reared razorback suckers to locate spawning areas where wild fish congregate during the ascending hydrographic limb of the snowmelt runoff. Hatchery-reared razorback suckers appeared to show similar reproductive behavior to wild fish. Both wild and hatchery-reared fish were found near the middle Green River spawning area between 1 and 25 May 2000. Hatchery fish occupied the same areas on the spawning site as wild fish, and remained on the spawning site during both nocturnal and diurnal hours. Males were more abundant on the spawning area than females, but the few females captured tended to stage away from the primary spawning area. The results from this study suggest hatchery-reared fish are capable of responding to natural cues that prompt spawning aggregations and are successful in locating existing spawning aggregations of wild fish. Given attention to stocking criteria, including genetic diversity and the size and time of stocking, the challenges of recovering razorback suckers will center on those factors that led to the population declines, particularly the survival of early life stages in off-channel habitats. ?? American Fisheries Society 2005.

Genetic differentiation of spring-spawning and fall-spawning male Atlantic sturgeon in the James River, Virginia

PubMed Central

Balazik, Matthew T.; Farrae, Daniel J.; Darden, Tanya L.; Garman, Greg C.

2017-01-01

Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus, Acipenseridae) populations are currently at severely depleted levels due to historic overfishing, habitat loss, and pollution. The importance of biologically correct stock structure for effective conservation and management efforts is well known. Recent improvements in our understanding of Atlantic sturgeon migrations, movement, and the occurrence of putative dual spawning groups leads to questions regarding the true stock structure of this endangered species. In the James River, VA specifically, captures of spawning Atlantic sturgeon and accompanying telemetry data suggest there are two discrete spawning groups of Atlantic sturgeon. The two putative spawning groups were genetically evaluated using a powerful microsatellite marker suite to determine if they are genetically distinct. Specifically, this study evaluates the genetic structure, characterizes the genetic diversity, estimates effective population size, and measures inbreeding of Atlantic sturgeon in the James River. The results indicate that fall and spring spawning James River Atlantic sturgeon groups are genetically distinct (overall FST = 0.048, F’ST = 0.181) with little admixture between the groups. The observed levels of genetic diversity and effective population sizes along with the lack of detected inbreeding all indicated that the James River has two genetically healthy populations of Atlantic sturgeon. The study also demonstrates that samples from adult Atlantic sturgeon, with proper sample selection criteria, can be informative when creating reference population databases. The presence of two genetically-distinct spawning groups of Atlantic sturgeon within the James River raises concerns about the current genetic assignment used by managers. Other nearby rivers may also have dual spawning groups that either are not accounted for or are pooled in reference databases. Our results represent the second documentation of genetically distinct dual spawning groups of Atlantic sturgeon in river systems along the U.S. Atlantic coast, suggesting that current reference population database should be updated to incorporate both new samples and our increased understanding of Atlantic sturgeon life history. PMID:28686610

Discrimination among spawning aggregations of lake herring from Lake Superior using whole-body morphometric characters

USGS Publications Warehouse

Hoff, Michael H.

2004-01-01

The lake herring (Coregonus artedi) was one of the most commercially and ecologically valuable Lake Superior fishes, but declined in the second half of the 20th century as the result of overharvest of putatively discrete stocks. No tools were previously available that described lake herring stock structure and accurately classified lake herring to their spawning stocks. The accuracy of discriminating among spawning aggregations was evaluated using whole-body morphometrics based on a truss network. Lake herring were collected from 11 spawning aggregations in Lake Superior and two inland Wisconsin lakes to evaluate morphometrics as a stock discrimination tool. Discriminant function analysis correctly classified 53% of all fish from all spawning aggregations, and fish from all but one aggregation were classified at greater rates than were possible by chance. Discriminant analysis also correctly classified 66% of fish to nearest neighbor groups, which were groups that accounted for the possibility of mixing among the aggregations. Stepwise discriminant analysis showed that posterior body length and depth measurements were among the best discriminators of spawning aggregations. These findings support other evidence that discrete stocks of lake herring exist in Lake Superior, and fishery managers should consider all but one of the spawning aggregations as discrete stocks. Abundance, annual harvest, total annual mortality rate, and exploitation data should be collected from each stock, and surplus production of each stock should be estimated. Prudent management of stock surplus production and exploitation rates will aid in restoration of stocks and will prevent a repeat of the stock collapses that occurred in the middle of the 20th century, when the species was nearly extirpated from the lake.

Discrimination among spawning concentrations of Lake Superior lake herring based on trace element profiles in sagittae

USGS Publications Warehouse

Bronte, Charles R.; Hesselberg, Robert J.; Shoesmith, John A.; Hoff, Michael H.

1996-01-01

Little is known about the stock structure of lake herring Coregonus artedi in Lake Superior, and recent increases in harvestable stock sizes has led to expanded exploitation in some areas. Research on marine teleosts has demonstrated that chemical differences in sagittal otoliths can be used for identification of fish stocks. We used plasma emission spectrophotometry to measure the concentrations of 10 trace elements in the sagittal otoliths from lake herring captured at eight spawning sites in Lake Superior and from Little Star Lake, an inland lake outside the Lake Superior basin. Discriminant function analysis indicated that elemental concentrations provided site-specific information but that considerable overlap existed among some locations, especially those in western Lake Superior. Correct classification rates varied from 12.0% to 86.1% and were generally higher for spawning locations from embayments in eastern Lake Superior and for the outgroup population from Little Star Lake. The results presented here demonstrate the potential usefulness of this technique for strictly freshwater species, especially those that live in highly oligotrophic waters such as Lake Superior.

Genetic evaluation of a Great Lakes lake trout hatchery program

USGS Publications Warehouse

Page, K.S.; Scribner, K.T.; Bast, D.; Holey, M.E.; Burnham-Curtis, M. K.

2005-01-01

Efforts over several decades to restore lake trout Salvelinus namaycush in U.S. waters of the upper Great Lakes have emphasized the stocking of juveniles from each of six hatchery broodstocks. Retention of genetic diversity across all offspring life history stages throughout the hatchery system has been an important component of the restoration hatchery and stocking program. Different stages of the lake trout hatchery program were examined to determine how effective hatchery practices have been in minimizing the loss of genetic diversity in broodstock adults and in progeny stocked. Microsatellite loci were used to estimate allele frequencies, measures of genetic diversity, and relatedness for wild source populations, hatchery broodstocks, and juveniles. We also estimated the effective number of breeders for each broodstock. Hatchery records were used to track destinations of fertilized eggs from all spawning dates to determine whether adult contributions to stocking programs were proportional to reproductive effort. Overall, management goals of maintaining genetic diversity were met across all stages of the hatchery program; however, we identified key areas where changes in mating regimes and in the distribution of fertilized gametes and juveniles could be improved. Estimates of effective breeding population size (Nb) were 9-41% of the total number of adults spawned. Low estimates of Nb were primarily attributed to spawning practices, including the pooling of gametes from multiple males and females and the reuse of males. Nonrandom selection and distribution of fertilized eggs before stocking accentuated declines in effective breeding population size and increased levels of relatedness of juveniles distributed to different rearing facilities and stocking locales. Adoption of guidelines that decrease adult reproductive variance and promote more equitable reproductive contributions of broodstock adults to juveniles would further enhance management goals of maintaining genetic diversity and minimize probabilities of consanguineous matings among stocked individuals when sexually mature. ?? Copyright by the American Fisheries Society 2005.

Models to compare management options for a protogynous fish.

PubMed

Heppell, Selina S; Heppell, Scott A; Coleman, Felicia C; Koenig, Christopher C

2006-02-01

Populations of gag (Mycteroperca microlepis), a hermaphroditic grouper, have experienced a dramatic shift in sex ratio over the past 25 years due to a decline in older age classes. The highly female-skewed sex ratio can be predicted as a consequence of increased fishing mortality that truncates the age distribution, and raises some concern about the overall fitness of the population. Management efforts may need to be directed toward maintenance of sex ratio as well as stock size, with evaluations of recruitment based on sex ratio or male stock size in addition to the traditional female-based stock-recruitment relationship. We used two stochastic, age-structured models to heuristically compare the effects of reducing fishing mortality on different life history stages and the relative impact of reductions in fertilization rates that may occur with highly skewed sex ratios. Our response variables included population size, sex ratio, lost egg fertility, and female spawning stock biomass. Population growth rates were highest for scenarios that reduced mortality for female gag (nearshore closure), while improved sex ratios were obtained most quickly with spawning reserves. The effect of reduced fertility through sex ratio bias was generally low but depended on the management scenario employed. Our results demonstrate the utility of evaluation of fishery management scenarios through model analysis and simulation, the synergistic interaction of life history and response to changes in mortality rates, and the importance of defining management goals.

Lake trout rehabilitation in Lake Huron

USGS Publications Warehouse

Eshenroder, Randy L.; Payne, N. Robert; Johnson, James E.; Bowen, Charles; Ebener, Mark P.

1995-01-01

Efforts to restore lake trout (Salvelinus namaycush) in Lake Huron after their collapse in the 1940s were underway in the early 1970s with completion of the first round of lampricide applications in tributary streams and the stocking of several genotypes. We assess results of rehabilitation and establish a historical basis for comparison by quantifying the catch of spawning lake trout from Michigan waters in 1929-1932. Sixty-eight percent of this catch occurred in northern waters (MH-1) and most of the rest (15%) was from remote reefs in the middle of the main basin. Sea lampreys (Petromyzon marinus) increased in the early 1980s in the main basin and depressed spawning populations of lake trout. This increase was especially severe in northern waters and appeared to be associated with untreated populations in the St. Marys River. Excessive commercial fishing stemming from unresolved treaty rights also contributed to loss of spawning fish in northern Michigan waters. Seneca-strain lake trout did not appear to be attacked by sea lampreys until they reached a size > 532 mm. At sizes > 632 mm, Seneca trout were 40-fold more abundant than the Marquette strain in matched-planting experiments. Natural reproduction past the fry stage has occurred in Thunder Bay and South Bay, but prospects for self-sustaining populations of lake trout in the main basin are poor because sea lampreys are too abundant, only one side of the basin is stocked, and stocking is deferred to allow commercial gillnetting in areas where most of the spawning occurred historically. Backcross lake trout, a lake trout x splake (s. Fontinalis x s. Namaycush) hybrid, did not reproduce in Georgian Bay, but this genotype is being replaced with pure-strain lake trout, whose early performance appears promising.

Genetic stock assessment of spawning arctic cisco (Coregonus autumnalis) populations by flow cytometric determination of DNA content.

PubMed

Lockwood, S F; Bickham, J W

1991-01-01

Intraspecific variation in cellular DNA content was measured in five Coregonus autumnalis spawning populations from the Mackenzie River drainage, Canada, using flow cytometry. The rivers assayed were the Peel, Arctic Red, Mountain, Carcajou, and Liard rivers. DNA content was determined from whole blood preparations of fish from all rivers except the Carcajou, for which kidney tissue was used. DNA content measurements of kidney and blood preparations of the same fish from the Mountain River revealed statistically indistinguishable results. Mosaicism was found in blood preparations from the Peel, Arctic Red, Mountain, and Liard rivers, but was not observed in kidney tissue preparations from the Mountain or Carcajou rivers. The Liard River sample had significantly elevated mean DNA content relative to the other four samples; all other samples were statistically indistinguishable. Significant differences in mean DNA content among spawning stocks of a single species reinforces the need for adequate sample sizes of both individuals and populations when reporting "C" values for a particular species.

Portfolio theory as a management tool to guide conservation and restoration of multi-stock fish populations

USGS Publications Warehouse

DuFour, Mark R.; May, Cassandra J.; Roseman, Edward F.; Ludsin, Stuart A.; Vandergoot, Christopher S.; Pritt, Jeremy J.; Fraker, Michael E.; Davis, Jeremiah J.; Tyson, Jeffery T.; Miner, Jeffery G.; Marschall, Elizabeth A.; Mayer, Christine M.

2015-01-01

Habitat degradation and harvest have upset the natural buffering mechanism (i.e., portfolio effects) of many large-scale multi-stock fisheries by reducing spawning stock diversity that is vital for generating population stability and resilience. The application of portfolio theory offers a means to guide management activities by quantifying the importance of multi-stock dynamics and suggesting conservation and restoration strategies to improve naturally occurring portfolio effects. Our application of portfolio theory to Lake Erie Sander vitreus (walleye), a large population that is supported by riverine and open-lake reef spawning stocks, has shown that portfolio effects generated by annual inter-stock larval fish production are currently suboptimal when compared to potential buffering capacity. Reduced production from riverine stocks has resulted in a single open-lake reef stock dominating larval production, and in turn, high inter-annual recruitment variability during recent years. Our analyses have shown (1) a weak average correlation between annual river and reef larval production (ρ̄ = 0.24), suggesting that a natural buffering capacity exists in the population, and (2) expanded annual production of larvae (potential recruits) from riverine stocks could stabilize the fishery by dampening inter-annual recruitment variation. Ultimately, our results demonstrate how portfolio theory can be used to quantify the importance of spawning stock diversity and guide management on ecologically relevant scales (i.e., spawning stocks) leading to greater stability and resilience of multi-stock populations and fisheries.

Repeat surveys of spawning cisco (Coregonus artedi) in western Lake Superior: timing, distribution and composition of spawning stocks

USGS Publications Warehouse

Yule, Daniel L.; Schreiner, Donald R.; Addison, Peter A.; Seider, Michael J.; Evrard, Lori M.; Geving, Steven A.; Quinlan, Henry R.

2012-01-01

Acoustic (AC) and midwater trawl (MT) surveys of spawning cisco (Coregonus artedi) in Lake Superior have been combined with commercial yield to estimate exploitation. To time surveys properly, it is important to understand when adults typically arrive at spawning grounds and how numbers change as the spawning season progresses. We conducted repeat autumn surveys during nighttime hours at coastal sites where commercial roe fisheries occur. Spawner densities increased significantly from October to mid-November, but differences measured at sites sampled from mid- to late-November were comparatively small. Spawners occupied the upper 20–30 m of the water column during mid-November before utilizing a wider range of depths by late-November. We compared repeat AC densities to temporal trends of catch-per-unit-effort (CPUE) in suspended commercial gillnets and found good agreement within sites. Because different gillnet mesh sizes were used in each roe fishery. CPUE and AC density were poorly correlated among sites. We recommend that future surveys be conducted between mid- and late-November, and that MT gear be used to measure cisco densities in the uppermost 10 m of the water column where AC estimates may be conservative. Given the short temporal window for assessing spawner density, we believe both AC-MT and gillnet surveys will be needed to ensure that harvest of different stocks is kept at a sustainable level.

First evidence of egg deposition by walleye (Sander vitreus) in the Detroit River

USGS Publications Warehouse

Manny, B.A.; Kennedy, G.W.; Allen, J.D.; French, J. R. P.

2007-01-01

The importance of fish spawning habitat in channels connecting the Great Lakes to fishery productivity in those lakes is poorly understood and has not been adequately documented. The Detroit River is a reputed spawning and nursery area for many fish, including walleye (Sander vitreus) that migrate between adjacent Lakes Erie and St. Clair. During April–May 2004, near the head of the Detroit River, we collected 136 fish eggs from the bottom of the river on egg mats. We incubated the eggs at the Great Lakes Science Center until they hatched. All eleven larvae that hatched from the eggs were identified as walleye. These eggs and larvae are the first credible scientific evidence that walleye spawn in the Detroit River. Their origin might be a stock of river-spawning walleye. Such a stock of walleye could potentially add resilience to production by walleye stocks that spawn and are harvested in adjacent waters.

Size and distribution of the 1975 striped bass spawning stock in the Potomac River. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zankel, K.L.; Kobler, B.; Haire, M.S.

1976-12-01

In the spring of 1975, an acoustic survey was made of a 40-mile section of the Potomac River. This survey was part of a program designed to estimate the distribution and abundance of spawning striped bass. The total number of striped bass in the 40-mile sector of the Potomac from Mockley Point to Morgantown was estimated to be between 2 and 4.5 million adult fish during spawning in late April. The highest population density was found between Douglas Point and Possum Point. The surveys were part of the Potomac River Fisheries Program and were conducted for the power plant sitingmore » program of the state of Maryland.« less

Updated analysis of flatfish recruitment response to climate variability and ocean conditions in the Eastern Bering Sea

NASA Astrophysics Data System (ADS)

Wilderbuer, Thomas; Stockhausen, William; Bond, Nicholas

2013-10-01

This study provides a retrospective analysis of the relationship between physical oceanography, biology and recruitment of three Eastern Bering Sea flatfish stocks: flathead sole (Hippoglossoides elassodon), northern rock sole (Lepidopsetta polyxystra), and arrowtooth flounder (Atheresthes stomias) during the period 1978-2005. Stock assessment model estimates of recruitment and spawning stock size indicate that temporal patterns in productivity are consistent with decadal scale (or shorter) patterns in climate variability, which may influence marine survival during the early life history phases. Density-dependence (through spawning stock size) was statistically significant in a Ricker stock-recruit model of flatfish recruitment that included environmental terms. Wind-driven advection of northern rock sole and flathead sole larvae to favorable nursery grounds was found to coincide with years of above-average recruitment. Ocean forcing of Bristol Bay surface waters during springtime was mostly on-shelf (eastward) during the 1980s and again in the early 2000s, but was off-shelf (westerly) during the 1990s, corresponding with periods of good and poor recruitment, respectively. Finally, the Arctic Oscillation was found to be an important indicator of arrowtooth flounder productivity. Model results were applied to IPCC (Intergovernmental Panel on Climate Change) future springtime wind scenarios to predict the future impact of climate on northern rock sole productivity and indicated that a moderate future increase in recruitment might be expected because the climate trends favor on-shelf transport but that density-dependence will dampen this effect such that northern rock sole abundance will not be substantially affected by climate change.

Accounting for escape mortality in fisheries: implications for stock productivity and optimal management.

PubMed

Baker, Matthew R; Schindler, Daniel E; Essington, Timothy E; Hilborn, Ray

2014-01-01

Few studies have considered the management implications of mortality to target fish stocks caused by non-retention in commercial harvest gear (escape mortality). We demonstrate the magnitude of this previously unquantified source of mortality and its implications for the population dynamics of exploited stocks, biological metrics, stock productivity, and optimal management. Non-retention in commercial gillnet fisheries for Pacific salmon (Oncorhynchus spp.) is common and often leads to delayed mortality in spawning populations. This represents losses, not only to fishery harvest, but also in future recruitment to exploited stocks. We estimated incidence of non-retention in Alaskan gillnet fisheries for sockeye salmon (O. nerka) and found disentanglement injuries to be extensive and highly variable between years. Injuries related to non-retention were noted in all spawning populations, and incidence of injury ranged from 6% to 44% of escaped salmon across nine river systems over five years. We also demonstrate that non-retention rates strongly correlate with fishing effort. We applied maximum likelihood and Bayesian approaches to stock-recruitment analyses, discounting estimates of spawning salmon to account for fishery-related mortality in escaped fish. Discounting spawning stock estimates as a function of annual fishing effort improved model fits to historical stock-recruitment data in most modeled systems. This suggests the productivity of exploited stocks has been systematically underestimated. It also suggests that indices of fishing effort may be used to predict escape mortality and correct for losses. Our results illustrate how explicitly accounting for collateral effects of fishery extraction may improve estimates of productivity and better inform management metrics derived from estimates of stock-recruitment analyses.

Side-scan sonar mapping of lake trout spawning habitat in northern Lake Michigan

USGS Publications Warehouse

Edsall, Thomas A.; Poe, Thomas P.; Nester, Robert T.; Brown, Charles L.

1989-01-01

Native stocks of lake trout Salvelinus namaycush were virtually or completely extirpated from the lower four Great Lakes by the early 1960s. The failure of early attempts to reestablish self-sustaining populations of lake trout was attributed partly to the practice of stocking hatcheryreared juveniles at locations and over substrates that had not been used in the past for spawning by native fish. Subsequent attempts to improve the selection of stocking locations were impeded by the lack of reliable information on the distribution of substrates on historical spawning grounds. Here we demonstrate the potential of side-scan sonar to substantially expand the data base needed to pinpoint the location of substrates where lake trout eggs, fry, or juveniles could be stocked to maximize survival and help ensure that survivors returning to spawn would encounter suitable substrates. We also describe the substrates and bathymetry of large areas on historical lake trout spawning grounds in the Fox Island Lake Trout Sanctuary in northern Lake Michigan. These areas could be used to support a contemporary self-sustaining lake trout population in the sanctuary and perhaps also in adjacent waters.

Relative abundance, site fidelity, and survival of adult lake trout in Lake Michigan from 1999 to 2001: Implications for future restoration strategies

USGS Publications Warehouse

Bronte, C.R.; Holey, M.E.; Madenjian, C.P.; Jonas, J.L.; Claramunt, R.M.; McKee, P.C.; Toneys, M.L.; Ebener, M.P.; Breidert, B.; Fleischer, G.W.; Hess, R.; Martell, A.W.; Olsen, E.J.

2007-01-01

We compared the relative abundance of lake trout Salvelinus namaycush spawners in gill nets during fall 1999–2001 in Lake Michigan at 19 stocked spawning sites with that at 25 unstocked sites to evaluate how effective site-specific stocking was in recolonizing historically important spawning reefs. The abundance of adult fish was higher at stocked onshore and offshore sites than at unstocked sites. This suggests that site-specific stocking is more effective at establishing spawning aggregations than relying on the ability of hatchery-reared lake trout to find spawning reefs, especially those offshore. Spawner densities were generally too low and too young at most sites to expect significant natural reproduction. However, densities were sufficiently high at some sites for reproduction to occur and therefore the lack of recruitment was attributable to other factors. Less than 3% of all spawners could have been wild fish, which indicates that little natural reproduction occurred in past years. Wounding by sea lamprey Petromyzon marinus was generally lower for Seneca Lake strain fish and highest for strains from Lake Superior. Fish captured at offshore sites in southern Lake Michigan had the lowest probability of wounding, while fish at onshore sites in northern Lake Michigan had the highest probability. The relative survival of the Seneca Lake strain was higher than that of the Lewis Lake or the Marquette strains for the older year-classes examined. Survival differences among strains were less evident for younger year-classes. Recaptures of coded-wire-tagged fish of five strains indicated that most fish returned to their stocking site or to a nearby site and that dispersal from stocking sites during spawning was about 100 km. Restoration strategies should rely on site-specific stocking of lake trout strains with good survival at selected historically important offshore spawning sites to increase egg deposition and the probability of natural reproduction in Lake Michigan.

Exploring life history characteristics of naturalized versus stocked chinook

USGS Publications Warehouse

Rogers, Mark W.; Kerns, Janice A; Bunnell, David B.; Claramunt, Randall M.; Collingsworth, Paris D.

2011-01-01

Naturalization of stocked populations can result in divergence of life-history traits from domestic stocks. Lake Michigan supports popular Chinook (Oncorhynchus tshawytscha) Salmon fisheries that have been sustained by stocking since the late 1960s. Natural recruitment of Chinook Salmon in Lake Michigan has increased in the last few decades and currently contributes over 50% of Chinook Salmon recruits. Samples collected as part of a lakewide mass-marking of Lake Michigan Chinook Salmon, starting with the 2006 year class, indicated hatchery fish average 30-mm longer and 130 grams heavier than naturalized fish at age-1. We hypothesized that selective forces differ for naturalized and hatchery populations resulting in divergent life-history characteristics with implications for Chinook Salmon population production and the Lake Michigan fishery. Specific life-history metrics of interest include: age- and size- at maturity, spawning run timing, fecundity, and sex ratio. Objectives: We evaluated life history characteristics between naturally recruited and stocked Chinook Salmon in Lake Michigan to help discern potential changes resulting from naturalization and implications for fisheries. A. Conduct an analysis of historical data to determine if life-history parameters changed through time as the Chinook Salmon population became increasingly naturalized. B. Conduct a two-year field study of naturalized and hatchery stocked Chinook Salmon spawning populations to quantify differences in life-history metrics of adults. C. Determine if reproductive potential differs between naturalized and hatchery stocked Chinook salmon by measuring egg thiamine levels.

Evidence of segregated spawning in a single marine fish stock: Sympatric divergence of ecotypes in icelandic cod?

USGS Publications Warehouse

Grabowski, T.B.; Thorsteinsson, Vilhjalmur; McAdam, B.J.; Marteinsdottir, G.

2011-01-01

There is increasing recognition of intraspecific diversity and population structure within marine fish species, yet there is little direct evidence of the isolating mechanisms that maintain it or documentation of its ecological extent. We analyzed depth and temperature histories collected by electronic data storage tags retrieved from 104 Atlantic cod at liberty ???1 year to evaluate a possible isolating mechanisms maintaining population structure within the Icelandic cod stock. This stock consists of two distinct behavioral types, resident coastal cod and migratory frontal cod, each occurring within two geographically distinct populations. Despite being captured together on the same spawning grounds, we show the behavioral types seem reproductively isolated by fine-scale differences in spawning habitat selection, primarily depth. Additionally, the different groups occupied distinct seasonal thermal and bathymetric niches that generally demonstrated low levels of overlap throughout the year. Our results indicate that isolating mechanisms, such as differential habitat selection during spawning, might contribute to maintaining diversity and fine-scale population structure in broadcast-spawning marine fishes.

Ecological factors affecting Rainbow Smelt recruitment in the main basin of Lake Huron, 1976-2010

USGS Publications Warehouse

O'Brien, Timothy P.; Taylor, William W.; Roseman, Edward F.; Madenjian, Charles P.; Riley, Stephen C.

2014-01-01

Rainbow Smelt Osmerus mordax are native to northeastern Atlantic and Pacific–Arctic drainages and have been widely introduced throughout North America. In the Great Lakes region, Rainbow Smelt are known predators and competitors of native fish and a primary prey species in pelagic food webs. Despite their widespread distribution, importance as a prey species, and potential to negatively interact with native fish species, there is limited information concerning stock–recruitment relationships for Rainbow Smelt. To better understand recruitment mechanisms, we evaluated potential ecological factors determining recruitment dynamics for Rainbow Smelt in Lake Huron using data from bottom trawl catches. We specifically evaluated influence of stock size, environmental factors (water temperature, lake levels, and precipitation), and salmonine predation on the production of age-0 recruits from 1976 to 2010. Rainbow Smelt recruitment was negatively related to stock size exceeding 10 kg/ha, indicating that compensatory, density-dependent mortality from cannibalism or intraspecific competition was an important factor related to the production of age-0 recruits. Recruitment was positively related to spring precipitation suggesting that the amount of stream-spawning habitat as determined by precipitation was important for the production of strong Rainbow Smelt recruitment. Additionally, density of age-0 Rainbow Smelt was positively related to Lake Trout Salvelinus namaycush abundance. However, spawning stock biomass of Rainbow Smelt, which declined substantially from 1989 to 2010, was negatively associated with Lake Trout catch per effort suggesting predation was an important factor related to the decline of age-2 and older Rainbow Smelt in Lake Huron. As such, we found that recruitment of Rainbow Smelt in Lake Huron was regulated by competition with or cannibalism by older conspecifics, spring precipitation influencing stream spawning habitats, and predation by Lake Trout on age-2 and older Rainbow Smelt.

Long-term change in a behavioural trait: truncated spawning distribution and demography in Northeast Arctic cod

PubMed Central

Opdal, Anders Frugård; Jørgensen, Christian

2015-01-01

Harvesting may be a potent driver of demographic change and contemporary evolution, which both may have great impacts on animal populations. Research has focused on changes in phenotypic traits that are easily quantifiable and for which time series exist, such as size, age, sex, or gonad size, whereas potential changes in behavioural traits have been under-studied. Here, we analyse potential drivers of long-term changes in a behavioural trait for the Northeast Arctic stock of Atlantic cod Gadus morhua, namely choice of spawning location. For 104 years (1866–1969), commercial catches were recorded annually and reported by county along the Norwegian coast. During this time period, spawning ground distribution has fluctuated with a trend towards more northerly spawning. Spawning location is analysed against a suite of explanatory factors including climate, fishing pressure, density dependence, and demography. We find that demography (age or age at maturation) had the highest explanatory power for variation in spawning location, while climate had a limited effect below statistical significance. As to potential mechanisms, some effects of climate may act through demography, and explanatory variables for demography may also have absorbed direct evolutionary change in migration distance for which proxies were unavailable. Despite these caveats, we argue that fishing mortality, either through demographic or evolutionary change, has served as an effective driver for changing spawning locations in cod, and that additional explanatory factors related to climate add no significant information. PMID:25336028

Comparisons of spawning areas and times for two runs of chinook salmon (Oncorhynchus tshawytscha) in the Kenai River, Alaska

USGS Publications Warehouse

Burger, C.V.; Wilmot, R.L.; Wangaard, D.B.

1985-01-01

From 1979 to 1982,188 chinook salmon (Oncorhynchus tshawytscha) were tagged with radio transmitters to locate spawning areas in the glacial Kenai River, southcentral Alaska. Results confirmed that an early run entered the river in May and June and spawned in tributaries, and a late run entered the river from late June through August and spawned in the main stem. Spawning peaked during August in tributaries influenced by lakes, but during July in other tributaries. Lakes may have increased fall and winter temperatures of downstream waters, enabling successful reproduction for later spawning fish within these tributaries. This hypothesis assumes that hatching and emergence can be completed in a shorter time in lake-influenced waters. The time of upstream migration and spawning (mid- to late August) of the late run is unique among chinook stocks in Cook Inlet. This behavior may have developed only because two large lakes (Kenai and Skilak) directly influence the main-stem Kenai River. If run timing is genetically controlled, and if the various components of the two runs are isolated stocks that have adapted to predictable stream temperatures, there are implications for stock transplantation programs and for any activities of man that alter stream temperatures.

Population diversity in Pacific herring of the Puget Sound, USA.

PubMed

Siple, Margaret C; Francis, Tessa B

2016-01-01

Demographic, functional, or habitat diversity can confer stability on populations via portfolio effects (PEs) that integrate across multiple ecological responses and buffer against environmental impacts. The prevalence of these PEs in aquatic organisms is as yet unknown, and can be difficult to quantify; however, understanding mechanisms that stabilize populations in the face of environmental change is a key concern in ecology. Here, we examine PEs in Pacific herring (Clupea pallasii) in Puget Sound (USA) using a 40-year time series of biomass data for 19 distinct spawning population units collected using two survey types. Multivariate auto-regressive state-space models show independent dynamics among spawning subpopulations, suggesting that variation in herring production is partially driven by local effects at spawning grounds or during the earliest life history stages. This independence at the subpopulation level confers a stabilizing effect on the overall Puget Sound spawning stock, with herring being as much as three times more stable in the face of environmental perturbation than a single population unit of the same size. Herring populations within Puget Sound are highly asynchronous but share a common negative growth rate and may be influenced by the Pacific Decadal Oscillation. The biocomplexity in the herring stock shown here demonstrates that preserving spatial and demographic diversity can increase the stability of this herring population and its availability as a resource for consumers.

Long-term change in a behavioural trait: truncated spawning distribution and demography in Northeast Arctic cod.

PubMed

Opdal, Anders Frugård; Jørgensen, Christian

2015-04-01

Harvesting may be a potent driver of demographic change and contemporary evolution, which both may have great impacts on animal populations. Research has focused on changes in phenotypic traits that are easily quantifiable and for which time series exist, such as size, age, sex, or gonad size, whereas potential changes in behavioural traits have been under-studied. Here, we analyse potential drivers of long-term changes in a behavioural trait for the Northeast Arctic stock of Atlantic cod Gadus morhua, namely choice of spawning location. For 104 years (1866-1969), commercial catches were recorded annually and reported by county along the Norwegian coast. During this time period, spawning ground distribution has fluctuated with a trend towards more northerly spawning. Spawning location is analysed against a suite of explanatory factors including climate, fishing pressure, density dependence, and demography. We find that demography (age or age at maturation) had the highest explanatory power for variation in spawning location, while climate had a limited effect below statistical significance. As to potential mechanisms, some effects of climate may act through demography, and explanatory variables for demography may also have absorbed direct evolutionary change in migration distance for which proxies were unavailable. Despite these caveats, we argue that fishing mortality, either through demographic or evolutionary change, has served as an effective driver for changing spawning locations in cod, and that additional explanatory factors related to climate add no significant information. © 2014 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

First-year growth, recruitment, and maturity of walleyes in western Lake Erie

USGS Publications Warehouse

Madenjian, Charles P.; Tyson, Jeffrey T.; Knight, Roger L.; Kershner, Mark W.; Hansen, Michael J.

1996-01-01

In some lakes, first-year growth of walleyes Stizostedion vitreum has been identified as an important factor governing recruitment of juveniles to the adult population. We developed a regression model for walleye recruitment in western Lake Erie by considering factors such as first-year growth, size of the spawning stock, the rate at which the lake warmed during the spring, and abundance of gizzard shad Dorosoma cepedianum. Gizzard shad abundance during the fall prior to spring walleye spawning explained over 40% of the variation in walleye recruitment. Gizzard shad are relatively high in lipids and are preferred prey for walleyes in Lake Erie. Therefore, the high degree of correlation between shad abundance and subsequent walleye recruitment supported the contention that mature females needed adequate lipid reserves during the winter to spawn the following spring. According to the regression analysis, spring warming rate and size of the parental stock also influenced walleye recruitment. Our regression model explained 92% of the variation in recruitment of age-2 fish into the Lake Erie walleye population from 1981 to 1993. The regression model is potentially valuable as a management tool because it could be used to forecast walleye recruitment to the fishery 2 years in advance. First-year growth was poorly correlated with recruitment, which may reflect the unusually low incidence of walleye cannibalism in western Lake Erie. In contrast, first-year growth was strongly linked to age at maturity.

76 FR 16698 - Fisheries of the Caribbean, Gulf of Mexico, and South Atlantic; Shrimp Fishery Off the Southern...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-25

... severely depleted by unusually cold weather conditions. DATES: The closure is effective March 22, 2011... shrimp spawning stock that has been severely depleted by cold weather. Consistent with those procedures... time and would potentially further harm the spawning stock that has been impacted due to cold weather...

Distribution and Food Habits of Juvenile Salmonids in the Duwamish Estuary, Washington, 1980

DTIC Science & Technology

1981-03-01

E.O. Salo, K. Garrison, and L. Matheson. 1979. Fish ecology studies in the Nisqually Reach area of southern Puget Sound , Washington. Univ. of Wash...Washington Department of Fisheries (WDF) indicate that Gteen River fall chinook are one of the largest naturally spawning stocks of this species in Puget Sound ...1977 Puget Sound summer-fall chinook methodology: Escapement estimates and goals, run size forecasts, and in-season run size updates. State of Wash

Use of existing hydrographic infrastructure to forecast the environmental spawning conditions for Eastern Baltic cod.

PubMed

von Dewitz, Burkhard; Tamm, Susanne; Höflich, Katharina; Voss, Rüdiger; Hinrichsen, Hans-Harald

2018-01-01

The semi-enclosed nature and estuarine characteristics, together with its strongly alternating bathymetry, make the Baltic Sea prone to much stronger interannual variations in the abiotic environment, than other spawning habitats of Atlantic cod (Gadus morhua). Processes determining salinity and oxygen conditions in the basins are influenced both by long term gradual climate change, e.g. global warming, but also by short-term meteorological variations and events. Specifically one main factor influencing cod spawning conditions, the advection of highly saline and well-oxygenated water masses from the North Sea, is observed in irregular frequencies and causes strong interannual variations in stock productivity. This study investigates the possibility to use the available hydrographic process knowledge to predict the annual spawning conditions for Eastern Baltic cod in its most important spawning ground, the Bornholm Basin, only by salinity measurements from a specific location in the western Baltic. Such a prediction could serve as an environmental early warning indicator to inform stock assessment and management. Here we used a hydrodynamic model to hindcast hydrographic property fields for the last 40+ years. High and significant correlations were found for months early in the year between the 33m salinity level in the Arkona Basin and the oxygen-dependent cod spawning environment in the Bornholm Basin. Direct prediction of the Eastern Baltic cod egg survival in the Bornholm Basin based on salinity values in the Arkona Basin at the 33 m depth level is shown to be possible for eggs spawned by mid-age and young females, which currently predominate the stock structure. We recommend to routinely perform short-term predictions of the Eastern Baltic cod spawning environment, in order to generate environmental information highly relevant for stock dynamics. Our statistical approach offers the opportunity to make best use of permanently existing infrastructure in the western Baltic to timely provide scientific knowledge on the spawning conditions of Eastern Baltic cod. Furthermore it could be a tool to assist ecosystem-based fisheries management with a cost-effective implementation by including the short term predictions as a simple indicator in the annual assessments.

Use of existing hydrographic infrastructure to forecast the environmental spawning conditions for Eastern Baltic cod

PubMed Central

Tamm, Susanne; Höflich, Katharina; Voss, Rüdiger; Hinrichsen, Hans-Harald

2018-01-01

The semi-enclosed nature and estuarine characteristics, together with its strongly alternating bathymetry, make the Baltic Sea prone to much stronger interannual variations in the abiotic environment, than other spawning habitats of Atlantic cod (Gadus morhua). Processes determining salinity and oxygen conditions in the basins are influenced both by long term gradual climate change, e.g. global warming, but also by short-term meteorological variations and events. Specifically one main factor influencing cod spawning conditions, the advection of highly saline and well-oxygenated water masses from the North Sea, is observed in irregular frequencies and causes strong interannual variations in stock productivity. This study investigates the possibility to use the available hydrographic process knowledge to predict the annual spawning conditions for Eastern Baltic cod in its most important spawning ground, the Bornholm Basin, only by salinity measurements from a specific location in the western Baltic. Such a prediction could serve as an environmental early warning indicator to inform stock assessment and management. Here we used a hydrodynamic model to hindcast hydrographic property fields for the last 40+ years. High and significant correlations were found for months early in the year between the 33m salinity level in the Arkona Basin and the oxygen-dependent cod spawning environment in the Bornholm Basin. Direct prediction of the Eastern Baltic cod egg survival in the Bornholm Basin based on salinity values in the Arkona Basin at the 33 m depth level is shown to be possible for eggs spawned by mid-age and young females, which currently predominate the stock structure. We recommend to routinely perform short-term predictions of the Eastern Baltic cod spawning environment, in order to generate environmental information highly relevant for stock dynamics. Our statistical approach offers the opportunity to make best use of permanently existing infrastructure in the western Baltic to timely provide scientific knowledge on the spawning conditions of Eastern Baltic cod. Furthermore it could be a tool to assist ecosystem-based fisheries management with a cost-effective implementation by including the short term predictions as a simple indicator in the annual assessments. PMID:29768443

Empirically based models of oceanographic and biological influences on Pacific Herring recruitment in Prince William Sound

NASA Astrophysics Data System (ADS)

Sewall, Fletcher; Norcross, Brenda; Mueter, Franz; Heintz, Ron

2018-01-01

Abundances of small pelagic fish can change dramatically over time and are difficult to forecast, partially due to variable numbers of fish that annually mature and recruit to the spawning population. Recruitment strength of age-3 Pacific Herring (Clupea pallasii) in Prince William Sound, Alaska, is estimated in an age-structured model framework as a function of spawning stock biomass via a Ricker stock-recruitment model, and forecasted using the 10-year median recruitment estimates. However, stock size has little influence on subsequent numbers of recruits. This study evaluated the usefulness of herring recruitment models that incorporate oceanographic and biological variables. Results indicated herring recruitment estimates were significantly improved by modifying the standard Ricker model to include an index of young-of-the-year (YOY) Walleye Pollock (Gadus chalcogrammus) abundance. The positive relationship between herring recruits-per-spawner and YOY pollock abundance has persisted through three decades, including the herring stock crash of the early 1990s. Including sea surface temperature, primary productivity, and additional predator or competitor abundances singly or in combination did not improve model performance. We suggest that synchrony of juvenile herring and pollock survival may be caused by increased abundance of their zooplankton prey, or high juvenile pollock abundance may promote prey switching and satiation of predators. Regardless of the mechanism, the relationship has practical application to herring recruitment forecasting, and serves as an example of incorporating ecosystem components into a stock assessment model.

Natural Reproductive Success and Demographic Effects of Hatchery-Origin Steelhead in Abernathy Creek, Washington : Annual Report 2008.

DOE Office of Scientific and Technical Information (OSTI.GOV)

U.S. Fish & Wildlife Service, Abernathy Fish Technology Center

2008-12-01

Many hatchery programs for steelhead pose genetic or ecological risks to natural populations because those programs release or outplant fish from non-native stocks. The goal of many steelhead programs has been to simply provide 'fishing opportunities' with little consideration given to conservation concerns. For example, the Washington Department of Fish and Wildlife (WDFW) has widely propagated and outplanted one stock of winter-run steelhead (Chambers Creek stock) and one stock of summer-run steelhead (Skamania stock) throughout western Washington. Biologists and managers now recognize potential negative effects can occur when non-native hatchery fish interact biologically with native populations. Not only do non-nativemore » stocks pose genetic and ecological risks to naturally spawning populations, but non-native fish stray as returning adults at a much higher rate than do native fish (Quinn 1993). Biologists and managers also recognize the need to (a) maintain the genetic resources associated with naturally spawning populations and (b) restore or recover natural populations wherever possible. As a consequence, the U.S. Fish & Wildlife Service (USFWS) and the NOAA Fisheries have been recommending a general policy that discourages the use of non-native hatchery stocks and encourages development of native broodstocks. There are two primary motivations for these recommendations: (1) reduce or minimize potential negative biological effects resulting from genetic or ecological interactions between hatchery-origin and native-origin fish and (2) use native broodstocks as genetic repositories to potentially assist with recovery of naturally spawning populations. A major motivation for the captive-rearing work described in this report resulted from NOAA's 1998 Biological Opinion on Artificial Propagation in the Columbia River Basin. In that biological opinion (BO), NOAA concluded that non-native hatchery stocks of steelhead jeopardize the continued existence of U.S. Endangered Species Act (ESA)-listed, naturally spawning populations in the Columbia River Basin. As a consequence of that BO, NOAA recommended - as a reasonable and prudent alternative (RPA) - that federal and state agencies phase out non-native broodstocks of steelhead and replace them with native broodstocks. However, NOAA provided no guidance on how to achieve that RPA. The development of native broodstocks of hatchery steelhead can potentially pose unacceptable biological risks to naturally spawning populations, particularly those that are already listed as threatened or endangered under the ESA. The traditional method of initiating new hatchery broodstocks of anadromous salmonid fishes is by trapping adults during their upstream, spawning migration. However, removing natural-origin adults from ESA listed populations may not be biologically acceptable because such activities may further depress those populations via 'broodstock mining'. In addition, trapping adult steelhead may be logistically unfeasible in many subbasins due to high water flows in the spring, when steelhead are moving upstream to spawn, that will often 'blow out' temporary weirs. Additional risks associated with trapping adults include genetic founder effects and difficulties meeting minimum, genetic effective number of breeders without 'mining' the wild population to potential extinction. As a result, alternative methods for developing native broodstocks are highly desired. One alternative for developing native broodstocks, particularly when the collection of adults is logistically unfeasible or biologically unacceptable, is captive rearing of natural-origin juveniles to sexual maturity. In this approach, pre-smolt juveniles are collected from the stream or watershed for which a native broodstock is desired, and those juveniles are raised to sexual maturity in a hatchery. Those hatchery-reared adults then become the broodstock source for gametes and initial progeny releases. Such a captive rearing program offers many genetic advantages over traditional adult-trapping programs for developing native broodstocks: (1) Large numbers of juveniles can be collected from the wild with only minimal impacts to naturally spawning populations because juvenile (age 0+parr)-to-adult survivals are typically very small (<1%) under natural conditions. (2) The genetic base of the broodstock (i.e. genetic effective population size) can be substantially larger for juveniles than adults because juveniles can theoretically represent the offspring of all adults that spawned successfully within a stream or watershed, as opposed to trapping only a small portion of returning adults for broodstock. (3) Collecting juveniles for broodstock can substantially reduce the risk of genetically 'swamping' naturally spawning populations with hatchery-origin fish (i.e. via a 'Ryman-Laikre effect') as occurs when hatchery-released fish represent the progeny of a relatively small number of trapped adults.« less

Marine reserves and reproductive biomass: a case study of a heavily targeted reef fish.

PubMed

Taylor, Brett M; McIlwain, Jennifer L; Kerr, Alexander M

2012-01-01

Recruitment overfishing (the reduction of a spawning stock past a point at which the stock can no longer replenish itself) is a common problem which can lead to a rapid and irreversible fishery collapse. Averting this disaster requires maintaining a sufficient spawning population to buffer stochastic fluctuations in recruitment of heavily harvested stocks. Optimal strategies for managing spawner biomass are well developed for temperate systems, yet remain uncertain for tropical fisheries, where the danger of collapse from recruitment overfishing looms largest. In this study, we explored empirically and through modeling, the role of marine reserves in maximizing spawner biomass of a heavily exploited reef fish, Lethrinus harak around Guam, Micronesia. On average, spawner biomass was 16 times higher inside the reserves compared with adjacent fished sites. Adult density and habitat-specific mean fish size were also significantly greater. We used these data in an age-structured population model to explore the effect of several management scenarios on L. harak demography. Under minimum-size limits, unlimited extraction and all rotational-closure scenarios, the model predicts that preferential mortality of larger and older fish prompt dramatic declines in spawner biomass and the proportion of male fish, as well as considerable declines in total abundance. For rotational closures this occurred because of the mismatch between the scales of recovery and extraction. Our results highlight how alternative management scenarios fall short in comparison to marine reserves in preserving reproductively viable fish populations on coral reefs.

Satellite monitoring temperature conditions spawning area of the Northeast Arctic cod in the Norwegian Sea and assessment its abundance

NASA Astrophysics Data System (ADS)

Vanyushin, George; Bulatova, Tatiana; Klochkov, Dmitriy; Troshkov, Anatoliy; Kruzhalov, Michail

2013-04-01

In this study, the attempt to consider the relationship between sea surface anomalies of temperature (SST anomalies °C) in spawning area of the Norwegian Arctic cod off the Lofoten islands in coastal zone of the Norwegian Sea and modern cod total stock biomass including forecasting assessment of future cod generation success. Continuous long-term database of the sea surface temperature (SST) was created on the NOAA satellites data. Mean monthly SST and SST anomalies are computed for the selected area on the basis of the weekly SST maps for the period of 1998-2012. These maps were plotted with the satellite SST data, as well as information of vessels, byoies and coastal stations. All data were classified by spawning seasons (March-April) and years. The results indicate that poor and low middle generations of cod (2001, 2006, 2007) occurred in years with negative or extremely high positive anomalies in the spawning area. The SST anomalies in years which were close to normal or some more normal significances provide conditions for appearance strong or very strong generations of cod (1998, 2000, 2002, 2004, 2005, 2006, 2008, 2009). Temperature conditions in concrete years influence on different indexes of cod directly. So, the mean temperature in spawning seasons in years 1999-2005 was ≈5,0°C and SST anomaly - +0,35°C, by the way average year significances indexes of cod were: total stock biomass - 1425,0 th.t., total spawning biomass - 460,0 th.t., recruitment (age 3+) - 535,0 mln. units and landings - 530,0 th.t. In spawning seasons 2006-2012 years the average data were following: mean SST ≈6,0°C, SST anomaly - +1,29°C, total stock biomass - 2185,0 th.t., total spawning biomass - 1211,0 th.t., recruitment (age 3+) - 821,0 mln. units and landings - 600,0 th.t. The SST and SST anomalies (the NOAA satellite data) characterize increase of decrease in input of warm Atlantic waters which form numerous eddies along the flows of the main warm currents thus creating favorable conditions for development of the cod larvae and fry and provide them with food stock, finally, direct influence on forming total stock biomass of cod and helping its population forecast. Key words: satellite monitoring of SST, Northeast Arctic cod, spawning area, maps of SST, prognosis.

Reproductive dynamics of Pacific sanddab, Citharichthys sordidus, off the central coast of California

NASA Astrophysics Data System (ADS)

Lefebvre, Lyndsey S.; Payne, Amber M.; Field, John C.

2016-01-01

Female Pacific sanddab were collected from the Monterey Bay, California to describe their reproductive strategy and annual reproductive cycle, as well as to estimate length at maturity, fecundity, spawning fraction (SF), and spawning interval (SI). Captive females were held to examine degradation of spawning markers and confirmed the biological spawning capabilities of the species. The reproductive season extended from May through January, as determined through macroscopic and histological examination of ovaries. Oocyte development was asynchronous, and an indeterminate fecundity pattern was displayed. Absolute and relative batch fecundity values were variable (means = 6663 eggs and 54 eggs g- 1 somatic weight, respectively) and significantly related to maternal length. During the period of highest reproductive activity, SF ranged from 0.42 to 0.98, suggesting some females were spawning on a daily basis. Monthly SF and SI were related to length, with smaller females having a truncated season and lower SF compared to larger females. Lengths at 50% (119 mm) and 95% (149 mm) maturity showed a downward shift relative to the 1940s, though the magnitude and cause of this shift remain unknown. This study highlights the importance of considering demographic shifts and size-related dynamics when modeling a stock's reproductive potential.

Spatial Dynamics of the Blue Crab Spawning Stock in the Gulf of Mexico: Local Processes Driving Regional Patterns.

NASA Astrophysics Data System (ADS)

Darnell, M. Z.

2016-02-01

Female blue crabs undertake a critical spawning migration seaward, migrating from low-salinity mating habitat to high-salinity waters of the lower estuaries and coastal ocean, where larval survival is highest. This migration occurs primarily through ebb tide transport, driven by an endogenous circatidal rhythm in vertical swimming that is modulated by behavioral responses to environmental cues. Blue crabs are typically considered an estuarine species and fisheries are managed on a state-by-state basis. Yet recent evidence from state and regional fishery independent survey programs suggests that the spawning migration can take females substantial distances offshore (>150 km), and that offshore waters are important spawning grounds for female blue crabs in the Gulf of Mexico. This is especially true in areas where freshwater inflow is high, resulting in low estuarine and coastal salinities. In low-salinity, high-inflow areas (e.g., Louisiana), spawning occurs further offshore while in high-salinity, low-inflow areas (e.g., South Texas), spawning takes place primarily within the estuary. Regional patterns in spawning locations both inshore and offshore are driven by interactions between behavioral mechanisms and local oceanographic conditions during the spawning migration. These environmentally driven differences in spawning locations have implications for larval survival and population connectivity, and emphasize the need for interjurisdictional assessment and management of the blue crab spawning stock.

Reestablishing a spawning population of lake trout in Lake Superior with fertilized eggs in artificial turf incubators

USGS Publications Warehouse

Bronte, Charles R.; Schram, Stephen T.; Selgeby, James H.; Swanson, Bruce L.

2002-01-01

Fertilized eggs from lake trout Salvelinus namaycush were placed in artificial turf incubators and deployed on Devils Island Shoal, Lake Superior, in an attempt to reestablish a spawning population on this once important spawning area. Efficacy was measured by the changes in catch rates, age composition, and origin of adult lake trout returning to the shoal in the fall in subsequent years. The abundance of lake trout spawners without fin clips, which implies that these fish hatched in the lake, increased throughout the sampling period, whereas the abundance of hatchery-reared fish (indicated by one or more fin clips) stocked for restoration purposes remained low. Year-class-specific stock-recruitment analysis suggested that the recruitment of unclipped spawners was related to the number of eggs planted in previous years rather than to spawning by the few adult lake trout visiting the reef. Increases in adult fish at Devils Island Shoal were independent of trends at adjacent sites, where unclipped spawner abundances remained low. Enhanced survival to hatch and apparent site imprinting of young lake trout make this technique a viable alternative to stocking fingerling and yearling lake trout to reestablish spawning populations on specific sites in the Great Lakes.

Stock discrimination of spottedtail goby ( Synechogobius ommaturus) in the Yellow Sea by analysis of otolith shape

NASA Astrophysics Data System (ADS)

Wang, Yingjun; Ye, Zhenjiang; Liu, Qun; Cao, Liang

2011-01-01

Otolith shape is species specific and is an ideal marker of fish population affiliation. In this study, otolith shape of spottedtail goby Synechogobius ommaturus is used to identify stocks in different spawning locations in the Yellow Sea. The main objectives of this study are to explore the potential existence of local stocks of spottedtail goby in the Yellow Sea by analysis of otolith shape, and to investigate ambient impacts on otolith shape. Spottedtail goby was sampled in five locations in the Yellow Sea in 2007 and 2008. Otoliths are described using variables correlated to size (otolith area, perimeter, length, width, and weight) and shape (rectangularity, circularity, and 20 Fourier harmonics). Only standardized otolith variables are used so that the effect of otolith size on the shape variables could be eliminated. There is no significant difference among variables of sex, year, and side (left and right). However, the otolith shapes of the spring stocks and the autumn stocks differ significantly. Otolith shape differences are greater among locations than between years. Correct classification rate of spottedtail goby with the otolith shape at different sampling locations range from 29.7%-77.4%.

Role of origin and release location in pre-spawning distribution and movements of anadromous alewife

USGS Publications Warehouse

Frank, Holly J.; Mather, M. E.; Smith, Joseph M.; Muth, Robert M.; Finn, John T.

2011-01-01

Capturing adult anadromous fish that are ready to spawn from a self sustaining population and transferring them into a depleted system is a common fisheries enhancement tool. The behaviour of these transplanted fish, however, has not been fully evaluated. The movements of stocked and native anadromous alewife, Alosa pseudoharengus (Wilson), were monitored in the Ipswich River, Massachusetts, USA, to provide a scientific basis for this management tool. Radiotelemetry was used to examine the effect of origin (native or stocked) and release location (upstream or downstream) on distribution and movement during the spawning migration. Native fish remained in the river longer than stocked fish regardless of release location. Release location and origin influenced where fish spent time and how they moved. The spatial mosaic of available habitats and the entire trajectory of freshwater movements should be considered to restore effectively spawners that traverse tens of kilometres within coastal rivers.

Historical changes in genotypic frequencies at the Pantophysin locus in Atlantic cod (Gadus morhua) in Icelandic waters: evidence of fisheries-induced selection?

PubMed Central

Jakobsdóttir, Klara B; Pardoe, Heidi; Magnússon, Árni; Björnsson, Höskuldur; Pampoulie, Christophe; Ruzzante, Daniel E; Marteinsdóttir, Guðrún

2011-01-01

The intense fishing mortality imposed on Atlantic cod in Icelandic waters during recent decades has resulted in marked changes in stock abundance, as well as in age and size composition. Using a molecular marker known to be under selection (Pan I) along with a suite of six neutral microsatellite loci, we analysed an archived data set and revealed evidence of distinct temporal changes in the frequencies of genotypes at the Pan I locus among spawning Icelandic cod, collected between 1948 and 2002, a period characterized by high fishing pressure. Concurrently, temporal stability in the composition of the microsatellite loci was established within the same data set. The frequency of the Pan IBB genotype decreased over a period of six decades, concomitant with considerable spatial and technical changes in fishing effort that resulted in the disappearance of older individuals from the fishable stock. Consequently, these changes have likely led to a change in the genotype frequencies at this locus in the spawning stock of Icelandic cod. The study highlights the value of molecular genetic approaches that combine functional and neutral markers examined in the same set of individuals for investigations of the selective effects of harvesting and reiterates the need for an evolutionary dimension to fisheries management. PMID:25568005

Stock-specific advection of larval walleye (Sander vitreus) in western Lake Erie: Implications for larval growth, mixing, and stock discrimination

USGS Publications Warehouse

Fraker, Michael E.; Anderson, Eric J.; May, Cassandra J.; Chen, Kuan-Yu; Davis, Jeremiah J.; DeVanna, Kristen M.; DuFour, Mark R.; Marschall, Elizabeth A.; Mayer, Christine M.; Miner, Jeffery G.; Pangle, Kevin L.; Pritt, Jeremy J.; Roseman, Edward F.; Tyson, Jeffrey T.; Zhao, Yingming; Ludsin, Stuart A

2015-01-01

Physical processes can generate spatiotemporal heterogeneity in habitat quality for fish and also influence the overlap of pre-recruit individuals (e.g., larvae) with high-quality habitat through hydrodynamic advection. In turn, individuals from different stocks that are produced in different spawning locations or at different times may experience dissimilar habitat conditions, which can underlie within- and among-stock variability in larval growth and survival. While such physically-mediated variation has been shown to be important in driving intra- and inter-annual patterns in recruitment in marine ecosystems, its role in governing larval advection, growth, survival, and recruitment has received less attention in large lake ecosystems such as the Laurentian Great Lakes. Herein, we used a hydrodynamic model linked to a larval walleye (Sander vitreus) individual-based model to explore how the timing and location of larval walleye emergence from several spawning sites in western Lake Erie (Maumee, Sandusky, and Detroit rivers; Ohio reef complex) can influence advection pathways and mixing among these local spawning populations (stocks), and how spatiotemporal variation in thermal habitat can influence stock-specific larval growth. While basin-wide advection patterns were fairly similar during 2011 and 2012, smaller scale advection patterns and the degree of stock mixing varied both within and between years. Additionally, differences in larval growth were evident among stocks and among cohorts within stocks which were attributed to spatiotemporal differences in water temperature. Using these findings, we discuss the value of linked physical–biological models for understanding the recruitment process and addressing fisheries management problems in the world's Great Lakes.

Traveling around Cape Horn: Otolith chemistry reveals a mixed stock of Patagonian hoki with separate Atlantic and Pacific spawning grounds

USGS Publications Warehouse

Schuchert, P.C.; Arkhipkin, A.I.; Koenig, A.E.

2010-01-01

Trace element fingerprints of edge and core regions in otoliths from 260 specimens of Patagonian hoki, Macruronus magellanicus L??nnberg, 1907, were analyzed by LA-ICPMS to reveal whether this species forms one or more population units (stocks) in the Southern Oceans. Fish were caught on their spawning grounds in Chile and feeding grounds in Chile and the Falkland Islands. Univariate and multivariate analyses of trace element concentrations in the otolith edges, which relate to the adult life of fish, could not distinguish between Atlantic (Falkland) and Pacific (Chile) hoki. Cluster analyses of element concentrations in the otolith edges produced three different clusters in all sample areas indicating high mixture of the stocks. Cluster analysis of trace element concentrations in the otolith cores, relating to juvenile and larval life stages, produced two separate clusters mainly distinguished by 137Ba concentrations. The results suggest that Patagonian hoki is a highly mixed fish stock with at least two spawning grounds around South America. ?? 2009 Elsevier B.V.

Recruitment of shrimp ( Pandalus borealis) in the Barents Sea related to spawning stock and environment

NASA Astrophysics Data System (ADS)

Aschan, Michaela; Ingvaldsen, Randi

2009-10-01

The shrimp spawn in autumn, and the females carry their eggs as out roe until spring when the larvae hatch. Within a period of 2 months the shrimp larvae settle to the bottom. It has been claimed that the year-class strength probably is determined during the larval phase. Today's assessment and forecast of the shrimp stock productivity and potential fishing yields are weak. This is partly due to poor knowledge on population dynamics from hatching until the shrimp are caught in the fishery at the age of 3 or 4 years. We, therefore, here identify the most important abiotic and biotic factors that affect recruitment in addition to spawning stock biomass. Since 1995, a net attached to the underbelly of the survey trawl used at the annual cruise in the Barents Sea has caught juvenile shrimp. The abundance of settled shrimp larvae varies in time and space. The recruitment to the fishery has been quite stable with the exception of the 1996 year-class, which was observed as 1-year-olds but has not been registered since. The temporal pattern of the three youngest year-classes is studied in relation to abiotic factors such as sea temperature, ice index and North Atlantic Oscillation, as well as biotic factors such as spawning stock biomass and presence of copepods, euphausiids and predating cod. Recruitment indices and factors identified by the Spearmann correlation to be significantly correlated with recruitment were used as input in a principal component analysis (PCA) and a generalized additive model (GAM) was applied. Abundance of 1-year-old shrimp is positively correlated to spawning stock biomass the previous year and to temperature of the previous winter, and negatively correlated with the number of 1-year-old cod. Two-year-old shrimp show significant correlation with temperature, whereas there is a strong negative correlation with euphausiids. Three-year-old shrimp are significantly correlated with the number of 2-year-old shrimp the previous year but negatively correlated to temperature at sampling time. This is probably due to less overlap with the main predator cod when cold. Ricker functions indicate an increased density-dependent mortality with age. When predicting the recruitment of shrimp to the fishery, the spawning stock biomass, the abundance of cod and euphausiids, as well as the temperature should be included.

Minimum size limits for yellow perch (Perca flavescens) in western Lake Erie

USGS Publications Warehouse

Hartman, Wilbur L.; Nepszy, Stephen J.; Scholl, Russell L.

1980-01-01

During the 1960's yellow perch (Perca flavescens) of Lake Erie supported a commercial fishery that produced an average annual catch of 23 million pounds, as well as a modest sport fishery. Since 1969, the resource has seriously deteriorated. Commercial landings amounted to only 6 million pounds in 1976, and included proportionally more immature perch than in the 1960's. Moreover, no strong year classes were produced between 1965 and 1975. An interagency technical committee was appointed in 1975 by the Lake Erie Committee of the Great Lakes Fishery Commission to develop an interim management strategy that would provide for greater protection of perch in western Lake Erie, where declines have been the most severe. The committee first determined the age structure, growth and mortality rates, maturation schedule, and length-fecundity relationship for the population, and then applied Ricker-type equilibrium yield models to determine the effects of various minimum length limits on yield, production, average stock weight, potential egg deposition, and the Abrosov spawning frequency indicator (average number of spawning opportunities per female). The committee recommended increasing the minimum length limit of 5.0 inches to at least 8.5 inches. Theoretically, this change would increase the average stock weight by 36% and potential egg deposition by 44%, without significantly decreasing yield. Abrosov's spawning frequency indicator would rise from the existing 0.6 to about 1.2.

Goosefish Lophius americanus fecundity and spawning frequency, with implications for population reproductive potential.

PubMed

McBride, R S; Johnson, A K; Lindsay, E K; Walsh, H J; Richards, R A

2017-05-01

To improve knowledge of goosefish Lophius americanus' reproductive biology, females were collected during 2009-2012 from the Mid-Atlantic Bight shelf region of the U.S. east coast. Batch fecundity increased with total length (L T ), from 229 100 to 2 243 300 mature oocytes per female (L T range: 55·5-112 cm; n = 54). This estimate of fecundity at L T is lower than one derived from a sample collected during 1982-1985. Examination of whole oocyte diameters in different months indicated that L. americanus is a serial spawner, releasing more than one egg veil per spawning season, as suspected or observed for other Lophius species. Seasonality of spawning was evident from whole oocytes and gonad histology, and from larval fish surveys spanning the U.S. north-east shelf, and confirmed a protracted (c. 6 months) spawning period. Peak spawning activity progressed northward from spring to autumn. The population-level implications of these results were explored by estimating population reproductive potential (P RP ), which considered the value of both current and future per capita reproduction using decade-specific age structure and fecundity at length. P RP is now more than 50% lower compared with the historical period (1982-1985), a result of the lower proportions of large females and reduced fecundity across all sizes. Mechanisms that could explain this loss of stock productivity are fishing-induced size-age truncation or regime shifts in egg production caused by changes in energy density of common forage species. © 2017 The Fisheries Society of the British Isles.

Immunological discrimination of Atlantic striped bass stocks

USGS Publications Warehouse

Schill, W.B.; Dorazio, R.M.

1990-01-01

Stocks of Atlantic striped bass Morone saxatilis that were assumed to be geographically isolated during spawning showed strong antigenic differences in blood serum albumin. A discriminant function was estimated from the immunologic responses of northern (Canadian and Hudson River) and southern (Chesapeake Bay and Roanoke River) stocks to two reference antisera. The function correctly classified 92% of the northern and 95% of the southern fish in the training set. Cross-validation revealed similar percentages of correct classification for fish that were of known origin but not used to estimate the discriminant function. Monte Carlo experiments were used to evaluate the ability of the discriminant function to predict the relative contribution of northern fish in samples of various size and stock composition. Averages of predicted proportions of northern fish in the samples agreed well with actual proportions. Coefficients of variation (100 × SD/mean) in the predicted proportions ranged from 1.5 to 36% for samples of 50–400 fish that contained at least 10% northern stock. In samples that contained only 2% northern stock, however, at least 1,600 fish were required to achieve similar levels of precision.

Predictions of realised fecundity and spawning time in Norwegian spring-spawning herring ( Clupea harengus)

NASA Astrophysics Data System (ADS)

Óskarsson, G. J.; Kjesbu, O. S.; Slotte, A.

2002-08-01

Maturing Norwegian spring-spawning (NSS) herring, Clupea harengus, were collected for reproductive analyses along the Norwegian coast prior to the spawning seasons of 1997-2000. Over this time period there was a marked change in weight (W) at length (TL) with 1998 showing extremely low values and 2000 high values in a historical perspective. Potential fecundity, amounting to about 20 000-100 000 developing (vitellogenic) oocytes per fish and positively related to fish size, increased significantly with fish condition. Relative somatic potential fecundity (RF P, number of oocytes per g ovary-free body weight) in NSS herring was found to vary by 35-55% between years. Unexpectedly, females in 2000 showed low RF P-values, possibly due to negative feedback from previous reproductive investments at low condition. A clear threshold value for Fulton's condition factor, K (K=100×W/TL 3), of 0.65-0.70 existed below which there was considerable atresia (resorption of vitellogenic oocytes). Thus, these components of the spawning stock, amounting to 1-46% in the period 1980-1999, obviously contributed relatively little to the total egg production. This was confirmed by low ovary weights and examples of delayed oocyte development in these individuals. An up-to-date atresia model is presented. The established oocyte growth curve, and to a lesser degree the assumed atretic oocytic turnover rate, was critical for the estimation of realised fecundity (number of eggs spawned). Modelled realised fecundity was significantly below observed potential fecundity. Females that had migrated the shortest distance from the over-wintering area, Vestfjorden, northern Norway, were in the poorest condition, had the least developed oocytes and the lowest potential and realised fecundities. In agreement with previously published studies on temporal and spatial changes in gonad weights, those females reaching the main spawning grounds in the south-western part of the coast (Møre) were the most successful ones in terms of egg production. Likewise, present results on oocyte diameter confirmed that repeat spawners spawn first and recruit spawners second. Our histological analyses on oocyte microstructure provided further evidence that oocyte size is a precise and accurate maturation criterion in herring. The methodological examinations also showed that the level of atresia as well as potential fecundity from oocyte and ovarian size can be estimated by the binocular microscope. This study shows that there is a large range in size- and condition-specific egg production in NSS herring, which should be taken into account in further recruitment studies.

Decline of lake herring (Coregonus artedii) in Lake Superior: an analysis of the Wisconsin herring fishery, 1936-78

USGS Publications Warehouse

Selgeby, James H.

1982-01-01

Annual harvests of lake herring (Coregonus artedii) in American waters of Lake Superior declined from an average of 2 million kg in 1936–62 to less than 25 000 kg in 1978. Analysis of commercial fishing records revealed that the sequential overexploitation of discrete unit stocks caused the collapse of the herring population in Wisconsin waters. In each of six major spawning areas, catch exceeded the productive capacity of the stock and the stock failed. Because stocks in the six areas were exploited sequentially, mostly in groups of two or three simultaneously, the demise of the stocks was not readily apparent until the last two failed in the early 1960s. After the collapse of the last major spawning stock, the fishery dwindled but may have continued to overexploit the remaining small stocks. The residual populations were apparently able only to replace themselves. Some form of density-independent mortality was apparently operating to prevent their recovery during the 1960s and 1970s.Key words: lake herring, overfishing, Lake Superior

Spatial and annual variation in fecundity and oocyte atresia of yellowtail flounder, Limanda ferruginea, in U.S. waters

NASA Astrophysics Data System (ADS)

McElroy, W. David; Wuenschel, Mark J.; Towle, Emilee K.; McBride, Richard S.

2016-01-01

Potential annual fecundity (PAF) was estimated over three years (2010-2012) for yellowtail flounder with individuals from the three stocks off the northeast U.S. coast. Down-regulation of PAF, the resorption of oocytes during development, was evident as the vitellogenic cohort advanced, so we directly measured atresia of vitellogenic oocytes using stereological techniques. PAF models including relative fish condition, stock area, year, and oocyte diameter of the leading cohort explained more variation than models with just size alone based on Akaike information criteria. In a given year, Gulf of Maine females had lower PAF at size than southern New England females. Interannual differences were evident: PAF of both stocks was higher in 2010 and lower in 2012, with 2011 showing less synchronization between these stocks. Differences in size at age and relative condition suggested that energy available for somatic and reproductive growth was lower in some years in the Gulf of Maine and Georges Bank, especially in 2011. Georges Bank PAF and condition were intermediate to the other stocks or more similar to the Gulf of Maine, varying annually. A latitudinal gradient in PAF is evident based on our results and relative to earlier studies that included Canadian stocks. The magnitude of down-regulation was variable across stocks and typically 3-25% of PAF. This can be accounted for in fecundity estimates, by the seasonal schedule of sampling and use of an oocyte diameter term in the fecundity model. Theoretical models of atresia patterns suggested variable rates over the later portion of clutch development. The timing of down-regulation varied among years, and its intensity was influenced by female relative condition. Fecundity was related to fish size, but was also affected by fish condition and oocyte diameter (a proxy for time until spawning), and spatial and temporal effects. A longer time series of PAF may identify environmental drivers that modulate annual stock reproductive potential.

Dispersal of Adult Black Marlin (Istiompax indica) from a Great Barrier Reef Spawning Aggregation

PubMed Central

Domeier, Michael L.; Speare, Peter

2012-01-01

The black marlin (Istiompax indica) is one of the largest bony fishes in the world with females capable of reaching a mass of over 700 kg. This highly migratory predator occurs in the tropical regions of the Pacific and Indian Oceans, and is the target of regional recreational and commercial fisheries. Through the sampling of ichthyoplankton and ovaries we provide evidence that the relatively high seasonal abundance of black marlin off the Great Barrier Reef is, in fact, a spawning aggregation. Furthermore, through the tracking of individual black marlin via satellite popup tags, we document the dispersal of adult black marlin away from the spawning aggregation, thereby identifying the catchment area for this spawning stock. Although tag shedding is an issue when studying billfish, we tentatively identify the catchment area for this stock of black marlin to extend throughout the Coral Sea, including the waters of Papua New Guinea, the Solomon Islands, Micronesia, New Caledonia, Kiribati, Vanuatu, Fiji, Tuvalu and Nauru. PMID:22363692

Dispersal of adult black marlin (Istiompax indica) from a Great Barrier Reef spawning aggregation.

PubMed

Domeier, Michael L; Speare, Peter

2012-01-01

The black marlin (Istiompax indica) is one of the largest bony fishes in the world with females capable of reaching a mass of over 700 kg. This highly migratory predator occurs in the tropical regions of the Pacific and Indian Oceans, and is the target of regional recreational and commercial fisheries. Through the sampling of ichthyoplankton and ovaries we provide evidence that the relatively high seasonal abundance of black marlin off the Great Barrier Reef is, in fact, a spawning aggregation. Furthermore, through the tracking of individual black marlin via satellite popup tags, we document the dispersal of adult black marlin away from the spawning aggregation, thereby identifying the catchment area for this spawning stock. Although tag shedding is an issue when studying billfish, we tentatively identify the catchment area for this stock of black marlin to extend throughout the Coral Sea, including the waters of Papua New Guinea, the Solomon Islands, Micronesia, New Caledonia, Kiribati, Vanuatu, Fiji, Tuvalu and Nauru.

The year-class phenomenon and the storage effect in marine fishes

NASA Astrophysics Data System (ADS)

Secor, David H.

2007-02-01

Factors contributing to population growth through strong year-class formation have driven a century of directed research in fisheries science. A central discovery of Hjort's paradigm was that multiple generations overlap and longevity is matched with frequency of strong recruitments. Here, I elaborate on this tenet by examining how intra-population modalities in spawning and early habitat use favour population resiliency. A modern theory that has application is the storage effect [Warner, R.R., Chesson, P.L., 1985. Coexistence mediated by recruitment fluctuations - a field guide to the storage effect. Am. Nat. 125, 769-787], whereby spawning stock biomass accumulates each year so that when early survival conditions are favourable, stored egg production can result in explosive population growth. I review two early life history behaviours that contribute to the storage effect: split cohorts (i.e., seasonal pulses of eggs and larvae) and contingent behaviour (i.e., dispersive and retentive patterns in early dispersal). Episodic and pulsed production of larvae is a common feature for marine fishes, well documented through otolith microstructure and hatch-date analyses. In temperate and boreal fishes, early and late spawned cohorts of larvae and juveniles may have differing fates dependent upon seasonal and inter-annual fluctuations in weather and climate. Often, a coastal fish may spawn for a protracted period, yet only a few days' egg production will result in successful recruitment. In these and other instances, it is clear that diversity in spawning behaviour can confer resilience against temporal variations in early survival conditions. Although many factors contribute to intra-population spawning modalities, size and age structure of adults play an important role. Contingent structure, an idea dating to Hjort (herring contingents) and Gilbert (salmon contingents), has been resurrected to describe the diversity of intra-population modalities observed through otolith microchemical and electronic tagging approaches. Retentive and dispersive behaviours confer resiliency against early survival conditions that vary spatially. Examples of contingent structure are increasingly numerous for diadromous fishes. Here, a nursery habitat associated with a contingent behaviour may make a small contribution in a given year, but over a decade contribute significantly to spawning stock biomass. For flatfish and other marine fishes, contingent structure is probable but not well documented. Proximate factors leading to contingent structure are poorly known, but for diadromous fishes, time of spawning and early life history energetic thresholds is hypothesized to lead to alternative life cycles. Here again time of spawning may lead to the storage effect by hedging against spatial variance in early vital rates. Managing for the storage effect will be promoted by conservation of adult age structure and early habitats upon which both strong and weak year-classes rely.

Demographic population model for American shad: will access to additional habitat upstream of dams increase population sizes?

USGS Publications Warehouse

Harris, Julianne E.; Hightower, Joseph E.

2012-01-01

American shad Alosa sapidissima are in decline in their native range, and modeling possible management scenarios could help guide their restoration. We developed a density-dependent, deterministic, stage-based matrix model to predict the population-level results of transporting American shad to suitable spawning habitat upstream of dams on the Roanoke River, North Carolina and Virginia. We used data on sonic-tagged adult American shad and oxytetracycline-marked American shad fry both above and below dams on the Roanoke River with information from other systems to estimate a starting population size and vital rates. We modeled the adult female population over 30 years under plausible scenarios of adult transport, effective fecundity (egg production), and survival of adults (i.e., to return to spawn the next year) and juveniles (from spawned egg to age 1). We also evaluated the potential effects of increased survival for adults and juveniles. The adult female population size in the Roanoke River was estimated to be 5,224. With no transport, the model predicted a slow population increase over the next 30 years. Predicted population increases were highest when survival was improved during the first year of life. Transport was predicted to benefit the population only if high rates of effective fecundity and juvenile survival could be achieved. Currently, transported adults and young are less likely to successfully out-migrate than individuals below the dams, and the estimated adult population size is much smaller than either of two assumed values of carrying capacity for the lower river; therefore, transport is not predicted to help restore the stock under present conditions. Research on survival rates, density-dependent processes, and the impacts of structures to increase out-migration success would improve evaluation of the potential benefits of access to additional spawning habitat for American shad.

Reintroduction of Lower Columbia River Chum Salmon into Duncan Creek, 2007 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hillson, Todd D.

2009-06-12

The National Marine Fisheries Service (NMFS) listed Lower Columbia River (LCR) chum salmon as threatened under the Endangered Species Act (ESA) in March, 1999 (64 FR 14508, March 25, 1999). The listing was in response to the reduction in abundance from historical levels of more than one-half million returning adults to fewer than 10,000 present-day spawners. Harvest, habitat degradation, changes in flow regimes, riverbed movement and heavy siltation have been largely responsible for this decline. The timing of seasonal changes in river flow and water temperatures is perhaps the most critical factor in structuring the freshwater life history of thismore » species. This is especially true of the population located directly below Bonneville Dam, where hydropower operations can block access to spawning sites, dewater redds, strand fry, cause scour or fill of redds and increase sedimentation of spawning gravels. Prior to 1997, only two chum salmon populations were recognized as genetically distinct in the Columbia River, although spawning had been documented in many Lower Columbia River tributaries. The first population was in the Grays River (RKm 34), a tributary of the Columbia River, and the second was a group of spawners utilizing the mainstem Columbia River just below Bonneville Dam (RKm 235) adjacent to Ives Island and in Hardy and Hamilton creeks. Using additional DNA samples, Small et al. (2006) grouped chum salmon spawning in the mainstem Columbia River and the Washington State tributaries into three groups: the Coastal, the Cascade and the Gorge. The Coastal group comprises those spawning in the Grays River, Skamokawa Creek and the broodstock used at the Sea Resources facility on the Chinook River. The Cascade group comprises those spawning in the Cowlitz (both summer and fall stocks), Kalama, Lewis, and East Fork Lewis rivers, with most supporting unique populations. The Gorge group comprises those spawning in the mainstem Columbia River from the I-205 Bridge up to Bonneville Dam and those spawning in Hamilton and Hardy creeks. Response to the federal ESA listing has been primarily through direct-recovery actions: reducing harvest, hatchery supplementation using local broodstock for populations at catastrophic risk, habitat restoration (including construction of spawning channels) and flow agreements to protect spawning and rearing areas. Both state and federal agencies have built controlled spawning areas. In 1998, the Washington Department of Fish and Wildlife (WDFW) began a chum salmon supplementation program using native stock on the Grays River. This program was expanded during 1999 - 2001 to include reintroduction into the Chinook River using eggs from the Grays River Supplementation Program. These eggs are incubated at the Grays River Hatchery, reared to release size at the Sea Resources Hatchery on the Chinook River, and the fry are released at the mouth of the Chinook River. Native steelhead, chum, and coho salmon are present in Duncan Creek, and are recognized as subpopulations of the Lower Gorge population, and are focal species in the Lower Columbia Fish Recovery Board (LCFRB) plan. Steelhead, chum and coho salmon that spawn in Duncan Creek are listed as Threatened under the ESA. Duncan Creek is classified by the LCFRB plan as a watershed for intensive monitoring (LCFRB 2004). This project was identified in the 2004 Federal Columbia River Power System (FCRPS) revised Biological Opinion (revised BiOp) to increase survival of chum salmon, 'BPA will continue to fund the program to re-introduce Columbia River chum salmon into Duncan Creek as long as NOAA Fisheries determines it to be an essential and effective contribution to reducing the risk of extinction for this ESU'. (USACE et al. 2004, page 85-86). The Governors Forum on Monitoring and Salmon Recovery and Watershed Health recommends one major population from each ESU have adult and juvenile monitoring. Duncan Creek chum salmon are identified in this plan to be intensively monitored. Planners recommended that a combination of natural and hatchery production would be the most likely way to produce the most rapid sustainable improvement in chum runs. Specifically, it was assumed that improving habitat conditions would promote efficient natural production, and that the most rapid way to rebuild the run would be to combine releases of an appropriate stock into the improved habitat. WDFW's recovery strategy for LCR chum salmon, as outlined in the WDFW Grays River and Washougal Hatchery Genetic Management Plans (HGMP), is as follows. First, determine if remnant populations of chum salmon exist in LCR tributaries. Second, if such populations exist, develop stock-specific recovery plans involving habitat restoration that include the creation of spawning refugias, supplementation where necessary, and a habitat and fish monitoring and evaluation plan.« less

Hypotheses of Spatial Stock Structure in Orange Roughy Hoplostethus atlanticus Inferred from Diet, Feeding, Condition, and Reproductive Activity

PubMed Central

Dunn, Matthew R.; Forman, Jeffrey S.

2011-01-01

We evaluate hypotheses for meso-scale spatial structure in an orange roughy (Hoplostethus atlanticus) stock using samples collected during research trawl surveys off the east coast of New Zealand. Distance-based linear models and generalised additive models were used to identify the most significant biological, environmental, and temporal predictors of variability in diet, proportion of stomachs containing prey, standardised weight of prey, fish somatic weight, fish total weight, and reproductive activity. The diet was similar to that observed elsewhere, and varied with ontogeny, depth, and surface water temperature. Smaller sized and female orange roughy in warmer bottom water were most likely to contain food. Fish condition and reproductive activity were highest at distances more than 20 km from the summit of the hills. Trawl survey catches indicated greater orange roughy densities in hill strata, suggesting hill habitat was favoured. However, analyses of feeding, condition, and reproductive activity indicated hill fish were not superior, despite fish densities on hills being reduced by fishing which, in principle, should have reduced intra-specific competition for food and other resources. Hypotheses for this result include: (1) fish in relatively poor condition visit hills to feed and regain condition and then leave, or (2) commercial fishing has disturbed feeding aggregations and/or caused habitat damage, making fished hills less productive. Mature orange roughy were observed on both flat and hill habitat during periods outside of spawning, and if this spatial structure was persistent then a proportion of the total spawning stock biomass would remain unavailable to fisheries targeting hills. Orange roughy stock assessments informed only by data from hills may well be misleading. PMID:22069464

Temporal and spatial comparisons of the reproductive biology of northern Gulf of Mexico (USA) red snapper (Lutjanus campechanus) collected a decade apart.

PubMed

Kulaw, Dannielle H; Cowan, James H; Jackson, Melissa W

2017-01-01

In studies done a decade apart, we provide evidence of a recent shift toward a slower progression to sexual maturity as well as reduced egg production, especially among young, small female red snapper, in the Gulf of Mexico (Gulf). Slower maturation rates (among fish ≤6 years old), lower GSI values and decreased spawning frequency were observed, and were especially pronounced in the northwestern Gulf. Furthermore, an Index of Reproductive Importance showed that young fish (ages 2-7) are contributing far less to the spawning stock in recent years, while older fish (>8 years) are contributing more, when compared to fish from the same age groups sampled in the previous decade. Coincident with these changes in reproductive output, fishing pressure has steadily declined gulf-wide, and spawning stock biomass and spawning potential ratio have increased. Thus, it is possible that the age structure of the red snapper stock is becoming less truncated, or that reproductive effort observed is due to the temporary influence of recent strong year classes produced in 2004 and 2006 as they begin to reach full reproductive potential. If the latter is true, careful documentation of the stock's reproductive dynamics during a time of population growth provides new understanding at the meta-population spatial and decadal temporal scales. In contrast, if the former is true, a truncated age structure due to overharvest can limit the productivity of the Gulf red snapper stock. In addition, we have learned that red snapper females in the northwestern Gulf collected on natural reefs and banks have much higher reproductive output than those on artificial reefs in the form of standing and toppled oil and gas platforms, thus making the need to know the relative abundance of females found on these disparate habitats an important next step toward better-understanding factors impacting the reproductive dynamics of this species.

Long-term retrospective analysis of mackerel spawning in the North Sea: a new time series and modeling approach to CPR data.

PubMed

Jansen, Teunis; Kristensen, Kasper; Payne, Mark; Edwards, Martin; Schrum, Corinna; Pitois, Sophie

2012-01-01

We present a unique view of mackerel (Scomber scombrus) in the North Sea based on a new time series of larvae caught by the Continuous Plankton Recorder (CPR) survey from 1948-2005, covering the period both before and after the collapse of the North Sea stock. Hydrographic backtrack modelling suggested that the effect of advection is very limited between spawning and larvae capture in the CPR survey. Using a statistical technique not previously applied to CPR data, we then generated a larval index that accounts for both catchability as well as spatial and temporal autocorrelation. The resulting time series documents the significant decrease of spawning from before 1970 to recent depleted levels. Spatial distributions of the larvae, and thus the spawning area, showed a shift from early to recent decades, suggesting that the central North Sea is no longer as important as the areas further west and south. These results provide a consistent and unique perspective on the dynamics of mackerel in this region and can potentially resolve many of the unresolved questions about this stock.

Long-Term Retrospective Analysis of Mackerel Spawning in the North Sea: A New Time Series and Modeling Approach to CPR Data

PubMed Central

Jansen, Teunis; Kristensen, Kasper; Payne, Mark; Edwards, Martin; Schrum, Corinna; Pitois, Sophie

2012-01-01

We present a unique view of mackerel (Scomber scombrus) in the North Sea based on a new time series of larvae caught by the Continuous Plankton Recorder (CPR) survey from 1948-2005, covering the period both before and after the collapse of the North Sea stock. Hydrographic backtrack modelling suggested that the effect of advection is very limited between spawning and larvae capture in the CPR survey. Using a statistical technique not previously applied to CPR data, we then generated a larval index that accounts for both catchability as well as spatial and temporal autocorrelation. The resulting time series documents the significant decrease of spawning from before 1970 to recent depleted levels. Spatial distributions of the larvae, and thus the spawning area, showed a shift from early to recent decades, suggesting that the central North Sea is no longer as important as the areas further west and south. These results provide a consistent and unique perspective on the dynamics of mackerel in this region and can potentially resolve many of the unresolved questions about this stock. PMID:22737221

Status and reproduction of Gulf coast strain walleye in a Tombigbee River tributary

USGS Publications Warehouse

Schramm, H.L.; Hart, J.; Hanson, L.A.

2004-01-01

Walleye (Sander vitreus [Mitchill]) are native to rivers and streams in the Mobile River basin in Mississippi and Alabama. These populations comprise a genetically unique strain (Gulf coast walleye, GCW) and represent the southernmost distribution of walleye in the United States. Luxapallila Creek was considered an important spawning site for GCW prior to and shortly after impoundment of the Tombigbee River in 1980. Extensive sampling in Luxapallila Creek in 2001 and 2002 collected only one larval walleye. Microsatellite DNA analysis suggested 14 of 16 adult walleye from Luxapallila Creek were hatchery-produced fish or their progeny. Controlled angling catch rates of adult walleye have declined since 1997. The scarcity of wild-spawned walleye and the similarity of wild-caught and hatchery broodstock walleye indicates that the GCW population in, or spawning in, Luxapallila Creek is sustained by stocking and recruitment from these stocked fish may be diminishing.

Genomic signatures predict migration and spawning failure in wild Canadian salmon.

PubMed

Miller, Kristina M; Li, Shaorong; Kaukinen, Karia H; Ginther, Norma; Hammill, Edd; Curtis, Janelle M R; Patterson, David A; Sierocinski, Thomas; Donnison, Louise; Pavlidis, Paul; Hinch, Scott G; Hruska, Kimberly A; Cooke, Steven J; English, Karl K; Farrell, Anthony P

2011-01-14

Long-term population viability of Fraser River sockeye salmon (Oncorhynchus nerka) is threatened by unusually high levels of mortality as they swim to their spawning areas before they spawn. Functional genomic studies on biopsied gill tissue from tagged wild adults that were tracked through ocean and river environments revealed physiological profiles predictive of successful migration and spawning. We identified a common genomic profile that was correlated with survival in each study. In ocean-tagged fish, a mortality-related genomic signature was associated with a 13.5-fold greater chance of dying en route. In river-tagged fish, the same genomic signature was associated with a 50% increase in mortality before reaching the spawning grounds in one of three stocks tested. At the spawning grounds, the same signature was associated with 3.7-fold greater odds of dying without spawning. Functional analysis raises the possibility that the mortality-related signature reflects a viral infection.

Historical evidence for discrete stocks of lake trout (Salvelinus namaycush) in Lake Michigan

USGS Publications Warehouse

Brown, Edward H.; Eck, G.W.; Foster, N.R.; Horrall, R.M.; Coberly, C.E.

1981-01-01

Although few biological data exist on the now extinct native lake trout, Salvelinus namaycush, of Lake Michigan, historical records and interviews with former commercial fishermen strongly suggest that this once widespread resource was composed of a number of discrete spawning populations or stocks. A natural division of the resource into distinct stocks is consistent with the size of Lake Michigan and its varied physiography. The native trout may have undergone subtle genetic changes over the millennia, although we cannot determine whether the physical and behavioral differences represented different genotypes or only temporary effects of the local environment. Because of physiographic similarities among the upper Great Lakes and probable interchanges of lake trout during the last glacial period, we recommend that progeny of extant wild stocks, particularly from Lake Superior, are genetically most suitable for recolonizing Lake Michigan. Moreover, the hatchery-held parents of such fish should be infused periodically with genes of the wild or feral donor populations. Despite the sound historical basis for these recommendations, we also recognize that sufficiently high stocking rates coupled with a reduction of heavy exploitation may be even more important than heritability in obtaining self-sustaining populations.

Genetic structure of lake whitefish (Coregonus clupeaformis) in Lake Michigan

USGS Publications Warehouse

VanDeHey, J.A.; Sloss, Brian L.; Peeters, Paul J.; Sutton, T.M.

2009-01-01

Genetic relationships among lake whitefish (Coregonus clupeaformis) spawning aggregates in Lake Michigan were assessed and used to predict a stock or management unit (MU) model for the resource. We hypothesized that distinct spawning aggregates represented potential MUs and that differences at molecular markers underlie population differentiation. Genetic stock identification using 11 microsatellite loci indicated the presence of six genetic MUs. Resolved MUs corresponded to geographically proximate spawning aggregates clustering into genetic groups. Within MUs, analyses suggested that all but one delineated MU was a stable grouping (i.e., no between-population differences), with the exception being the Hog Island - Traverse Bay grouping. Elk Rapids was the most genetically divergent population within Lake Michigan. However, low F st values suggested that moderate to high levels of gene flow occur or have occurred in the past between MUs. Significant tests of isolation by distance and low pairwise Fst values potentially led to conflicting results between traditional analyses and a Bayesian approach. This data set could provide baseline data from which a comprehensive mixed-stock analysis could be performed, allowing for more efficient and effective management of this economically and socially important resource.

Interannual and Spatial Variability in Maturity of Walleye Pollock Gadus chalcogrammus and Implications for Spawning Stock Biomass Estimates in the Gulf of Alaska

PubMed Central

Kruse, Gordon H.; Dorn, Martin W.

2016-01-01

Catch quotas for walleye pollock Gadus chalcogrammus, the dominant species in the groundfish fishery off Alaska, are set by applying harvest control rules to annual estimates of spawning stock biomass (SSB) from age-structured stock assessments. Adult walleye pollock abundance and maturity status have been monitored in early spring in Shelikof Strait in the Gulf of Alaska for almost three decades. The sampling strategy for maturity status is largely characterized as targeted, albeit opportunistic, sampling of trawl tows made during hydroacoustic surveys. Trawl sampling during pre-spawning biomass surveys, which do not adequately account for spatial patterns in the distribution of immature and mature fish, can bias estimated maturity ogives from which SSB is calculated. Utilizing these maturity data, we developed mixed-effects generalized additive models to examine spatial and temporal patterns in walleye pollock maturity and the influence of these patterns on estimates of SSB. Current stock assessment practice is to estimate SSB as the product of annual estimates of numbers at age, weight at age, and mean maturity at age for 1983-present. In practice, we found this strategy to be conservative for a time period from 2003–2013 as, on average, it underestimates SSB by a 4.7 to 11.9% difference when compared to our estimates of SSB that account for spatial structure or both temporal and spatial structure. Inclusion of spatially explicit information for walleye pollock maturity has implications for understanding stock reproductive biology and thus the setting of sustainable harvest rates used to manage this valuable fishery. PMID:27736982

Changing recruitment capacity in global fish stocks.

PubMed

Britten, Gregory L; Dowd, Michael; Worm, Boris

2016-01-05

Marine fish and invertebrates are shifting their regional and global distributions in response to climate change, but it is unclear whether their productivity is being affected as well. Here we tested for time-varying trends in biological productivity parameters across 262 fish stocks of 127 species in 39 large marine ecosystems and high-seas areas (hereafter LMEs). This global meta-analysis revealed widespread changes in the relationship between spawning stock size and the production of juvenile offspring (recruitment), suggesting fundamental biological change in fish stock productivity at early life stages. Across regions, we estimate that average recruitment capacity has declined at a rate approximately equal to 3% of the historical maximum per decade. However, we observed large variability among stocks and regions; for example, highly negative trends in the North Atlantic contrast with more neutral patterns in the North Pacific. The extent of biological change in each LME was significantly related to observed changes in phytoplankton chlorophyll concentration and the intensity of historical overfishing in that ecosystem. We conclude that both environmental changes and chronic overfishing have already affected the productive capacity of many stocks at the recruitment stage of the life cycle. These results provide a baseline for ecosystem-based fisheries management and may help adjust expectations for future food production from the oceans.

Changing recruitment capacity in global fish stocks

PubMed Central

Britten, Gregory L.; Dowd, Michael; Worm, Boris

2016-01-01

Marine fish and invertebrates are shifting their regional and global distributions in response to climate change, but it is unclear whether their productivity is being affected as well. Here we tested for time-varying trends in biological productivity parameters across 262 fish stocks of 127 species in 39 large marine ecosystems and high-seas areas (hereafter LMEs). This global meta-analysis revealed widespread changes in the relationship between spawning stock size and the production of juvenile offspring (recruitment), suggesting fundamental biological change in fish stock productivity at early life stages. Across regions, we estimate that average recruitment capacity has declined at a rate approximately equal to 3% of the historical maximum per decade. However, we observed large variability among stocks and regions; for example, highly negative trends in the North Atlantic contrast with more neutral patterns in the North Pacific. The extent of biological change in each LME was significantly related to observed changes in phytoplankton chlorophyll concentration and the intensity of historical overfishing in that ecosystem. We conclude that both environmental changes and chronic overfishing have already affected the productive capacity of many stocks at the recruitment stage of the life cycle. These results provide a baseline for ecosystem-based fisheries management and may help adjust expectations for future food production from the oceans. PMID:26668368

Egg production of turbot, Scophthalmus maximus, in the Baltic Sea

NASA Astrophysics Data System (ADS)

Nissling, Anders; Florin, Ann-Britt; Thorsen, Anders; Bergström, Ulf

2013-11-01

In the brackish water Baltic Sea turbot spawn at ~ 6-9 psu along the coast and on offshore banks in ICES SD 24-29, with salinity influencing the reproductive success. The potential fecundity (the stock of vitellogenic oocytes in the pre-spawning ovary), egg size (diameter and dry weight of artificially fertilized 1-day-old eggs) and gonad dry weight were assessed for fish sampled in SD 25 and SD 28. Multiple regression analysis identified somatic weight, or total length in combination with Fulton's condition factor, as main predictors of fecundity and gonad dry weight with stage of maturity (oocyte packing density or leading cohort) as an additional predictor. For egg size, somatic weight was identified as main predictor while otolith weight (proxy for age) was an additional predictor. Univariate analysis using GLM revealed significantly higher fecundity and gonad dry weight for turbot from SD 28 (3378-3474 oocytes/g somatic weight) compared to those from SD 25 (2343 oocytes/g somatic weight), with no difference in egg size (1.05 ± 0.03 mm diameter and 46.8 ± 6.5 μg dry weight; mean ± sd). The difference in egg production matched egg survival probabilities in relation to salinity conditions suggesting selection for higher fecundity as a consequence of poorer reproductive success at lower salinities. This supports the hypothesis of higher size-specific fecundity towards the limit of the distribution of a species as an adaptation to harsher environmental conditions and lower offspring survival probabilities. Within SD 28 comparisons were made between two major fishing areas targeting spawning aggregations and a marine protected area without fishing. The outcome was inconclusive and is discussed with respect to potential fishery induced effects, effects of the salinity gradient, effects of specific year-classes, and effects of maturation status of sampled fish.

Reproductive patterns of blacktail comber ( Serranus atricauda, Serranidae) from south-west Portugal seamounts

NASA Astrophysics Data System (ADS)

Neves, Ana; Sequeira, Vera; Paiva, Rafaela Barros; Vieira, Ana Rita; Gordo, Leonel Serrano

2014-03-01

The knowledge of the reproductive strategy is essential for the comprehensive understanding of the population dynamics of any fish species. This study intends to define the spawning season, verify the type of fecundity regulation and estimate relative annual fecundity for Serranus atricauda inhabiting the south-west of Portugal seamounts (Gorringe, Ampère and Lion). Monthly samples, between September 2010 and December 2011, were obtained from commercial vessels. This species is synchronously hermaphroditic, and mature individuals were found all year round, with gonadosomatic index peak from February to September. No clear relation between hepatosomatic index and Fulton's condition factor and gonadal development was found, and therefore, it is probable that reproductive success depends more on environmental conditions and food availability during the spawning season than on body energy reserves. No gap exists between pre-vitellogenic and vitellogenic oocytes and the oocyte size-frequency distribution during the main spawning season show no dominant cohort progressing through time. The number of standing stock of advanced vitellogenic oocytes showed an increase trend along the spawning season decreasing only at its end and the relative intensity of α-atresia was always low throughout this period with an increase towards the end. All these criteria corroborate the indeterminate fecundity type assigned to S. atricauda in previous studies. Mean relative annual fecundity estimated was 5,655 ± 4,321 oocytes per gram of gutted weight.

Temporal variations in the fecundity of Arcto-Norwegian cod ( Gadus morhua) in response to natural changes in food and temperature

NASA Astrophysics Data System (ADS)

Kjesbu, O. S.; Witthames, P. R.; Solemdal, P.; Greer Walker, M.

1998-12-01

Sexually mature Arcto-Norwegian female cod, Gadus morhua, were sampled off northern Norway either during spawning migration (Vesterålen) or at spawning sites (Lofoten) from 1986 to 1996. This period comprised a dramatic, nearly cyclical change in the Barents Sea ecosystem. The stock of the main food item, viz. the Barents Sea capelin Mallotus villosus villosus, changed from a low (1986), to a high (1991) and again to a low (1994) level of abundance while the climate changed from a cold (≤1989) to a warm regime. The relative annual potential fecundity (i.e. number of vitellogenic oocytes per g prespawning fish) increased by approximately 40% from 1987 to 1991. However, information from a back-calculation technique calibrated in the laboratory using spawning fish indicated that this change might have been as high as 80 to 90%. Ovaries were analysed by the gravimetric, the automated particle counting and the stereometric method (modified to use with ovaries too large to section whole). All three methods gave similar fecundity estimates. The latter method was applied to quantify atresia of developing oocytes in the good-condition year of 1991. Atresia was rare, occurring in only 30% of the ovaries and where it was present in only 1 to 4% of the vitellogenic oocytes. Spawning females sampled from 1991 to 1996 gradually produced fewer eggs and demonstrated clear interannual variations in vitellogenic oocyte mean size and distribution thought to reflect a delicate reproductive tactic to minimise negative nutritional effects on egg size and egg quality. Estimates of annual potential fecundity for the duration of the study were significantly positively correlated with environmental temperature and the availability of capelin during vitellogenesis.

Mapping the spawning grounds of North Sea cod (Gadus morhua) by direct and indirect means.

PubMed

Fox, Clive J; Taylor, Martin; Dickey-Collas, Mark; Fossum, Petter; Kraus, Gerd; Rohlf, Norbert; Munk, Peter; van Damme, Cindy J G; Bolle, Loes J; Maxwell, David L; Wright, Peter J

2008-07-07

Despite recent evidence for sub-stock structuring, North Sea cod are assessed as a single unit. As a consequence, knowledge of sub-stock trends is poor. In particular, there are no recent evaluations of which spawning grounds are active. Here we report results from the first ichthyoplankton survey to cover the whole North Sea. Also, this survey, conducted in 2004, was the first to make extensive use of DNA-based molecular methods to unambiguously identify early developmental stage cod eggs. We compare the findings from the plankton survey with estimated egg production inferred from the distribution of mature cod in contemporaneous trawl surveys. Results from both approaches were in general agreement and showed hot spots of egg production around the southern and eastern edges of the Dogger Bank, in the German Bight, the Moray Firth and to the east of the Shetlands. These areas broadly coincide with known spawning locations from the period 1940 to 1970. We were, however, unable to directly detect significant numbers of cod eggs at the historic spawning ground off Flamborough (northeast coast of England). The results demonstrate that most of the major spawning grounds of cod in the North Sea are still active but that some localized populations may have been reduced to the point where it is now difficult to detect the presence of eggs in the plankton.

Mapping the spawning grounds of North Sea cod (Gadus morhua) by direct and indirect means

PubMed Central

Fox, Clive J; Taylor, Martin; Dickey-Collas, Mark; Fossum, Petter; Kraus, Gerd; Rohlf, Norbert; Munk, Peter; van Damme, Cindy J.G; Bolle, Loes J; Maxwell, David L; Wright, Peter J

2008-01-01

Despite recent evidence for sub-stock structuring, North Sea cod are assessed as a single unit. As a consequence, knowledge of sub-stock trends is poor. In particular, there are no recent evaluations of which spawning grounds are active. Here we report results from the first ichthyoplankton survey to cover the whole North Sea. Also, this survey, conducted in 2004, was the first to make extensive use of DNA-based molecular methods to unambiguously identify early developmental stage cod eggs. We compare the findings from the plankton survey with estimated egg production inferred from the distribution of mature cod in contemporaneous trawl surveys. Results from both approaches were in general agreement and showed hot spots of egg production around the southern and eastern edges of the Dogger Bank, in the German Bight, the Moray Firth and to the east of the Shetlands. These areas broadly coincide with known spawning locations from the period 1940 to 1970. We were, however, unable to directly detect significant numbers of cod eggs at the historic spawning ground off Flamborough (northeast coast of England). The results demonstrate that most of the major spawning grounds of cod in the North Sea are still active but that some localized populations may have been reduced to the point where it is now difficult to detect the presence of eggs in the plankton. PMID:18397869

Progress toward lake trout restoration in Lake Michigan

USGS Publications Warehouse

Holey, Mark E.; Rybicki, Ronald W.; Eck, Gary W.; Brown, Edward H.; Marsden, J. Ellen; Lavis, Dennis S.; Toneys, Michael L.; Trudeau, Tom N.; Horrall, Ross M.

1995-01-01

Progress toward lake trout restoration in Lake Michigan is described through 1993. Extinction of the native lake trout fishery by sea lamprey predation, augmented by exploitation and habitat destruction, resulted in an extensive stocking program of hatchery-reared lake trout that began in 1965. Sea lamprey abundance was effectively controlled using selective chemical toxicants. The initial stocking produced a measurable wild year class of lake trout by 1976 in Grand Traverse Bay, but failed to continue probably due to excessive exploitation. The overall lack of successful reproduction lakewide by the late 1970s led to the development and implementation in 1985 of a focused inter-agency lakewide restoration plan by a technical committee created through the Lake Committee structure of the Great Lakes Fishery Commission. Strategies implemented in 1985 by the plan included setting a 40% total mortality goal lakewide, creating two large refuges designed to encompass historically the most productive spawning habitat and protect trout stocked over their home range, evaluating several lake trout strains, and setting stocking priorities throughout the lake. Target levels for stocking in the 1985 Plan have never been reached, and are much less than the estimated lakewide recruitment of yearlings by the native lake trout stocks. Since 1985, over 90% of the available lake trout have been stocked over the best spawning habitat, and colonization of the historically productive offshore reefs has occurred. Concentrations of spawning lake trout large enough for successful reproduction, based on observations of successful hatchery and wild stocks, have developed at specific reefs. Continued lack of recruitment at these specific sites suggests that something other than stotk abundance has limited success. Poor survival of lake trout eggs, assumed to be related to contaminant burden, occurred in the late 1970s and early 1980s, but survival has since increased to equal survival in the hatchery. A recent increase in lamprey wounding rates in northern Lake Michigan appears to be related to the uncontrolled build-up of lampreys in the St. Marys River a tributary of Lake Huron. If left uncontrolled, further progress toward restoration in the Northern Refuge may be limited.

Multiscale Terrain Analysis of Multibeam Bathymetry Data for Lake Trout Spawning Habitat Mapping in the Drummond Island Refuge, northern Lake Huron

NASA Astrophysics Data System (ADS)

Wattrus, N. J.; Binder, T.

2012-12-01

Until the 1950s, lake trout supported a valuable commercial fishery in the Great Lakes. The introduction of sea lamprey into the Great Lakes and overfishing resulted in the loss of most populations. Despite consistent stocking efforts since the 1960s, restoration of these populations has been slow. The reasons are numerous, but may be related to differences in the spawning behavior between hatchery and wild trout. A four-year study initiated in 2010, utilizes acoustic telemetry to characterize and compare the spawning behaviors of hatchery and wild lake trout in the Drummond Island Refuge in northern Lake Huron. In this project, the movement of tagged fish are monitored by an array of over 125 lake floor hydrophones during the fall spawning period. Fish behavior is overlaid over detailed bathymetric and substrate data and compared with environmental variables (e.g. water temperature, wind speed and direction, and wave height and direction) to develop a conceptual behavioral model. Sites suspected of being spawning sites based upon telemetry data are verified through the use of divers and trapping eggs and fry. Prior to this study, the factors that influenced how the spawning fish utilize the lake floor shoals have been poorly understood. Among the factors thought to impact spawning success were: bathymetry and substrate composition. Diver and telemetry data suggest that the fish(both hatchery raised and wild) are particularly attracted to rocky substrates and that fragment size is important. High resolution multibeam bathymetric surveys conducted in 2010 and 2011 have been used to characterize the shape and composition of the lake floor in the study area. Classification of the substrate is a labor intensive process requiring divers, drop cameras and sediment sampling. To improve this, the traditional approach has been to use supervised and unsupervised classification techniques that are based upon measured acoustic backscatter from an echosounder or sidescan sonar. Bottom classification based upon backscatter measurements from the collected multibeam sonar data using Quester Tangent's Multiview software does not appear to readily resolve the various classes of rocky substrate, for example it appears to have difficulty differentiating between areas dominated by boulder sized rocks from areas covered predominantly by cobble sized fragments. The extremely shallow nature of the reef areas utilized by the spawning fish (z_av < 10 m) ensures that the bathymetric data has a very high spatial resolution (dx ~ 0.1m). Visual inspection of the bathymetry of the reefs clearly show variations in the texture and morphology of the lake floor that correlate with divers' observations of aggregations of fish in spawning condition. We describe the results of a study to investigate the application of terrain analysis for subdividing the reefs into regions based upon their texture and morphology. A variety of descriptors are evaluated as is the influence of scale on the analyses.

Synergies between climate and management for Atlantic cod fisheries at high latitudes

PubMed Central

Kjesbu, Olav Sigurd; Bogstad, Bjarte; Devine, Jennifer A.; Gjøsæter, Harald; Howell, Daniel; Ingvaldsen, Randi B.; Nash, Richard D. M.; Skjæraasen, Jon Egil

2014-01-01

The widespread depletion of commercially exploited marine living resources is often seen as a general failure of management and results in criticism of contemporary management procedures. When populations show dramatic and positive changes in population size, this invariably leads to questions about whether favorable climatic conditions or good management (or both) were responsible. The Barents Sea cod (Gadus morhua) stock has recently increased markedly and the spawning stock biomass is now at an unprecedented high. We identify the crucial social and environmental factors that made this unique growth possible. The relationship between vital rates of Barents Sea cod stock productivity (recruitment, growth, and mortality) and environment is investigated, followed by simulations of population size under different management scenarios. We show that the recent sustained reduction in fishing mortality, facilitated by the implementation of a “harvest control rule,” was essential to the increase in population size. Simulations show that a drastic reduction in fishing mortality has resulted in a doubling of the total population biomass compared with that expected under the former management regime. However, management alone was not solely responsible. We document that prevailing climate, operating through several mechanistic links, positively reinforced management actions. Heightened temperature resulted in an increase in the extent of the suitable feeding area for Barents Sea cod, likely offering a release from density-dependent effects (for example, food competition and cannibalism) through prolonged overlap with prey and improved adult stock productivity. Management and climate may thus interact to give a positive outlook for exploited high-latitude marine resources. PMID:24550465

Synergies between climate and management for Atlantic cod fisheries at high latitudes.

PubMed

Kjesbu, Olav Sigurd; Bogstad, Bjarte; Devine, Jennifer A; Gjøsæter, Harald; Howell, Daniel; Ingvaldsen, Randi B; Nash, Richard D M; Skjæraasen, Jon Egil

2014-03-04

The widespread depletion of commercially exploited marine living resources is often seen as a general failure of management and results in criticism of contemporary management procedures. When populations show dramatic and positive changes in population size, this invariably leads to questions about whether favorable climatic conditions or good management (or both) were responsible. The Barents Sea cod (Gadus morhua) stock has recently increased markedly and the spawning stock biomass is now at an unprecedented high. We identify the crucial social and environmental factors that made this unique growth possible. The relationship between vital rates of Barents Sea cod stock productivity (recruitment, growth, and mortality) and environment is investigated, followed by simulations of population size under different management scenarios. We show that the recent sustained reduction in fishing mortality, facilitated by the implementation of a "harvest control rule," was essential to the increase in population size. Simulations show that a drastic reduction in fishing mortality has resulted in a doubling of the total population biomass compared with that expected under the former management regime. However, management alone was not solely responsible. We document that prevailing climate, operating through several mechanistic links, positively reinforced management actions. Heightened temperature resulted in an increase in the extent of the suitable feeding area for Barents Sea cod, likely offering a release from density-dependent effects (for example, food competition and cannibalism) through prolonged overlap with prey and improved adult stock productivity. Management and climate may thus interact to give a positive outlook for exploited high-latitude marine resources.

Spawning stock and recruitment in North Sea cod shaped by food and climate

PubMed Central

Olsen, Esben Moland; Ottersen, Geir; Llope, Marcos; Chan, Kung-Sik; Beaugrand, Grégory; Stenseth, Nils Chr.

2011-01-01

In order to provide better fisheries management and conservation decisions, there is a need to discern the underlying relationship between the spawning stock and recruitment of marine fishes, a relationship which is influenced by the environmental conditions. Here, we demonstrate how the environmental conditions (temperature and the food availability for fish larvae) influence the stock–recruitment relationship and indeed what kind of stock–recruitment relationship we might see under different environmental conditions. Using unique zooplankton data from the Continuous Plankton Recorder, we find that food availability (i.e. zooplankton) in essence determines which model applies for the once large North Sea cod (Gadus morhua) stock. Further, we show that recruitment is strengthened during cold years and weakened during warm years. Our combined model explained 45 per cent of the total variance in cod recruitment, while the traditional Ricker and Beverton–Holt models only explained about 10 per cent. Specifically, our approach predicts that a full recovery of the North Sea cod stock might not be expected until the environment becomes more favourable. PMID:20810442

Temporal and spatial comparisons of the reproductive biology of northern Gulf of Mexico (USA) red snapper (Lutjanus campechanus) collected a decade apart

PubMed Central

Kulaw, Dannielle H.; Jackson, Melissa W.

2017-01-01

In studies done a decade apart, we provide evidence of a recent shift toward a slower progression to sexual maturity as well as reduced egg production, especially among young, small female red snapper, in the Gulf of Mexico (Gulf). Slower maturation rates (among fish ≤6 years old), lower GSI values and decreased spawning frequency were observed, and were especially pronounced in the northwestern Gulf. Furthermore, an Index of Reproductive Importance showed that young fish (ages 2–7) are contributing far less to the spawning stock in recent years, while older fish (>8 years) are contributing more, when compared to fish from the same age groups sampled in the previous decade. Coincident with these changes in reproductive output, fishing pressure has steadily declined gulf-wide, and spawning stock biomass and spawning potential ratio have increased. Thus, it is possible that the age structure of the red snapper stock is becoming less truncated, or that reproductive effort observed is due to the temporary influence of recent strong year classes produced in 2004 and 2006 as they begin to reach full reproductive potential. If the latter is true, careful documentation of the stock’s reproductive dynamics during a time of population growth provides new understanding at the meta-population spatial and decadal temporal scales. In contrast, if the former is true, a truncated age structure due to overharvest can limit the productivity of the Gulf red snapper stock. In addition, we have learned that red snapper females in the northwestern Gulf collected on natural reefs and banks have much higher reproductive output than those on artificial reefs in the form of standing and toppled oil and gas platforms, thus making the need to know the relative abundance of females found on these disparate habitats an important next step toward better-understanding factors impacting the reproductive dynamics of this species. PMID:28355239

Comparison of the Northeast Arctic cod year class strength (at the age of 3+) with the SST anomalies in main spawning ground (the Norwegian Shelf Waters) by results of analysis satellite monitoring data during last years.

NASA Astrophysics Data System (ADS)

Vanyushin, George

2015-04-01

Continuous long-term database (1998-2014) on the sea surface temperature (SST) comprising results of regional satellite monitoring (the Norwegian and the Barents seas) is used to resolve several applied problems. Authors have analyzed indirect influence the SST (the NOAA satellite data) on modern cod total stock biomass (abundance of the Northeast Arctic cod at age 3+). In this study, we went on the consideration of the relationship between the SST anomalies for March-April in the main spawning ground of the cod off the Lofoten islands in the Norwegian Shelf Waters and forecasting assessment of future cod generation success and its future abundance of 3 year old. Mean monthly SST and SST anomalies are computed for the selected area on the basis of the weekly SST maps which made by using the NOAA satellites data for the period 1998-2014. Comparison of the SST anomalies in the main spawning ground with abundance of the cod year class at age 3+ shows that survival of the cod generations was inhibited on the whole as negative (below -0,1C) well as positive SST anomalies (above +1,3C) during March and April. Finally, the results indicate that poor and low middle generations of cod at age 3+ (2002, 2004, 2010) occurred in years with negative or extremely high positive the SST anomalies in the spawning area. The SST anomalies in years which were close to normal significances provide conditions for appearance middle or strong generations of cod (2001-2003, 2005-2009, 2011-2013). So, the SST and SST anomalies (by the NOAA satellite data) characterize of increase in input of warm Atlantic waters which form numerous eddies along the main stream thus creating favorable conditions for spawning and development of the cod larvae and fry and provide them with food stock, finally direct influence on forming total stock biomass of cod and helping its population forecast. Key words: satellite monitoring of SST, the Northeast Arctic cod, spawning ground, forecast of the cod year class strength at age 3+.

Combining genetic and demographic information to prioritize conservation efforts for anadromous alewife and blueback herring

PubMed Central

Palkovacs, Eric P; Hasselman, Daniel J; Argo, Emily E; Gephard, Stephen R; Limburg, Karin E; Post, David M; Schultz, Thomas F; Willis, Theodore V

2014-01-01

A major challenge in conservation biology is the need to broadly prioritize conservation efforts when demographic data are limited. One method to address this challenge is to use population genetic data to define groups of populations linked by migration and then use demographic information from monitored populations to draw inferences about the status of unmonitored populations within those groups. We applied this method to anadromous alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis), species for which long-term demographic data are limited. Recent decades have seen dramatic declines in these species, which are an important ecological component of coastal ecosystems and once represented an important fishery resource. Results show that most populations comprise genetically distinguishable units, which are nested geographically within genetically distinct clusters or stocks. We identified three distinct stocks in alewife and four stocks in blueback herring. Analysis of available time series data for spawning adult abundance and body size indicate declines across the US ranges of both species, with the most severe declines having occurred for populations belonging to the Southern New England and the Mid-Atlantic Stocks. While all alewife and blueback herring populations deserve conservation attention, those belonging to these genetic stocks warrant the highest conservation prioritization. PMID:24567743

Implementation of genetic conservation practices in a muskellunge propagation and stocking program

USGS Publications Warehouse

Jennings, Martin J.; Sloss, Brian L.; Hatzenbeler, Gene R.; Kampa, Jeffrey M.; Simonson, Timothy D.; Avelallemant, Steven P.; Lindenberger, Gary A.; Underwood, Bruce D.

2010-01-01

Conservation of genetic resources is a challenging issue for agencies managing popular sport fishes. To address the ongoing potential for genetic risks, we developed a comprehensive set of recommendations to conserve genetic diversity of muskellunge (Esox masquinongy) in Wisconsin, and evaluated the extent to which the recommendations can be implemented. Although some details are specific to Wisconsin's muskellunge propagation program, many of the practical issues affecting implementation are applicable to other species and production systems. We developed guidelines to restrict future brood stock collection operations to lakes with natural reproduction and to develop a set of brood lakes to use on a rotational basis within regional stock boundaries, but implementation will require considering lakes with variable stocking histories. Maintaining an effective population size sufficient to minimize the risk of losing alleles requires limiting brood stock collection to large lakes. Recommendations to better approximate the temporal distribution of spawning in hatchery operations and randomize selection of brood fish are feasible. Guidelines to modify rearing and distribution procedures face some logistic constraints. An evaluation of genetic diversity of hatchery-produced fish during 2008 demonstrated variable success representing genetic variation of the source population. Continued evaluation of hatchery operations will optimize operational efficiency while moving toward genetic conservation goals.

Potential strategies for recovery of lake whitefish and lake herring stocks in eastern Lake Erie

USGS Publications Warehouse

Oldenburg, K.; Stapanian, M.A.; Ryan, P.A.; Holm, E.

2007-01-01

Lake Erie sustained large populations of ciscoes (Salmonidae: Coregoninae) 120 years ago. By the end of the 19th century, abundance of lake whitefish (Coregonus clupeaformis) had declined drastically. By 1925, the lake herring (a cisco) population (Coregonus artedii) had collapsed, although a limited lake herring fishery persisted in the eastern basin until the 1950s. In the latter part of the 20th century, the composition of the fish community changed as oligotrophication proceeded. Since 1984, a limited recovery of lake whitefish has occurred, however no recovery was evident for lake herring. Current ecological conditions in Lake Erie probably will not inhibit recovery of the coregonine species. Recovery of walleye (Sander vitreus) and efforts to rehabilitate the native lake trout (Salvelinus namaycush) in Lake Erie will probably assist recovery because these piscivores reduce populations of alewife (Alosa psuedoharengus) and rainbow smelt (Osmerus mordax), which inhibit reproductive success of coregonines. Although there are considerable spawning substrates available to coregonine species in eastern Lake Erie, eggs and fry would probably be displaced by storm surge from most shoals. Site selection for stocking or seeding of eggs should consider the reproductive life cycle of the stocked fish and suitable protection from storm events. Two potential sites in the eastern basin have been identified. Recommended management procedures, including commercial fisheries, are suggested to assist in recovery. Stocking in the eastern basin of Lake Erie is recommended for both species, as conditions are adequate and the native spawning population in the eastern basin is low. For lake herring, consideration should be given to match ecophenotypes as much as possible. Egg seeding is recommended. Egg seeding of lake whitefish should be considered initially, with fingerling or yearling stocking suggested if unsuccessful. Spawning stocks of whitefish in the western basin of Lake Erie could be utilized.

Evaluation of three gears for sampling spawning populations of rainbow trout in a large Alaskan river

USGS Publications Warehouse

Schwanke, C.J.; Hubert, W.A.

2004-01-01

Alternatives to electrofishing are needed for sampling sexually mature rainbow trout Oncorhynchus mykiss during the spawning season in large Alaskan rivers. We compared hook and line, beach seining, and actively fished gill nets as sampling tools. Beach seining and active gill netting yielded similar catch rates, length frequencies, and sex ratios of sexually mature fish. Hook-and-line sampling was less effective, with a lower catch rate and selectivity for immature fish and sexually mature females. We conclude that both beach seining and active gill netting can serve as alternatives to electrofishing for sampling sexually mature rainbow trout stocks during the spawning season in large rivers with stable spring flows and spawning areas with few snags.

2009 Spawning cisco investigations in the Canadian waters of Lake Superior

USGS Publications Warehouse

Yule, Daniel L.; Cholwek, Gary A.; Evrard, Lori M.; E. Berglund,; K.I. Cullis,

2010-01-01

We sampled with acoustics (AC) and midwater trawls (MT) to determine cisco abundance in Lake Superior’s Thunder and Black bays during 8-14 November, 2009. Total abundance of spawning-size (≥ 250 mm total length) ciscoes was estimated at 6.25 million in Thunder Bay and 1.12 million in Black Bay. Exploitation fractions of market-size (≥ age 6) females from Thunder and Black bays for 2009 were estimated at 7.1% and 11.3%, respectively; below the recommended maximum annual harvest of 15% recently adopted by Lake Superior fisheries managers. Given Thunder Bay spawner densities are on a downward trajectory, and recruitment since the 2003 year-class has been low, it is likely the exploitation fractions will increase in the future. After 2010, the Ontario Ministry of Natural Resources (OMNR) will carry on the AC program as a management activity. It is likely suspended experimental gill net (GN) samples will be used to ground truth future AC samples. In 2009, we characterized the length and age structure of Thunder Bay ciscoes using both MT samples and GN samples. Females represented 49% of the MT catch, but only 39% in GN samples. Catching a smaller proportion of females in GN samples resulted in a lower female population estimate and a higher estimated exploitation fraction (10.4%) compared to MT samples (7.1%). Experimental gill net effort was limited to 10-11.8 m water column depths where midwater trawl samples also caught roughly 40% females. Ciscoes ≥ age 17 (≥ 1992 year class) were common in Black Bay, but rare in Thunder Bay suggesting: 1) the stocks may be distinct; and 2) total mortality of ciscoes returning to spawn in Black Bay in recent years has been lower than ciscoes returning to Thunder Bay. Our mid-November 2009 effort to assess the Black Bay stock by sampling outside of the 3 bay in the lake proper was deemed successful, but this should be confirmed by sampling the Black Bay region during both mid- and late-November 2010.

Selenium impacts on razorback sucker, Colorado River, Colorado II. Eggs.

PubMed

Hamilton, Steven J; Holley, Kathy M; Buhl, Kevin J; Bullard, Fern A

2005-05-01

Effects on hatching and development of fertilized eggs in adult razorback sucker (Xyrauchen texanus) exposed to selenium in flooded bottomland sites near Grand Junction, Colorado, were determined. After 9 months exposure, fish were collected and induced to spawn and eggs collected for inorganic element analyses. A 9-day egg study was conducted with five spawns from Horsethief ponds, six spawns from Adobe Creek channel, and four spawns from North Pond using a reference water and site waters. Selenium concentrations in eggs were 6.5 microg/g from Horsethief, 46 microg/g from Adobe Creek, 38 microg/g from North Pond, and 6.0 microg/g from brood stock. Eggs from young adults had a smaller diameter and higher moisture content than brood stock. There were no differences among the four sources in viability, survival, hatch, hatchability, or mortality of deformed embryos or larvae. Adobe Creek larvae had more deformed embryos in eggs held in site water than held in reference water. There were significant negative correlations between selenium concentrations in adult muscle plugs and percent hatch, egg diameter, and deformities in embryos. Results from this study suggest that selenium contamination in parts of the upper basin of the Colorado River should be a major concern to recovery efforts for endangered fish.

Selenium impacts on razorback sucker, Colorado River, Colorado: II. Eggs

USGS Publications Warehouse

Hamilton, S.J.; Holley, K.M.; Buhl, K.J.; Bullard, F.A.

2005-01-01

Effects on hatching and development of fertilized eggs in adult razorback sucker (Xyrauchen texanus) exposed to selenium in flooded bottomland sites near Grand Junction, Colorado, were determined. After 9 months exposure, fish were collected and induced to spawn and eggs collected for inorganic element analyses. A 9-day egg study was conducted with five spawns from Horsethief ponds, six spawns from Adobe Creek channel, and four spawns from North Pond using a reference water and site waters. Selenium concentrations in eggs were 6.5 μg/g from Horsethief, 46 μg/g from Adobe Creek, 38 μg/g from North Pond, and 6.0 μg/g from brood stock. Eggs from young adults had a smaller diameter and higher moisture content than brood stock. There were no differences among the four sources in viability, survival, hatch, hatchability, or mortality of deformed embryos or larvae. Adobe Creek larvae had more deformed embryos in eggs held in site water than held in reference water. There were significant negative correlations between selenium concentrations in adult muscle plugs and percent hatch, egg diameter, and deformities in embryos. Results from this study suggest that selenium contamination in parts of the upper basin of the Colorado River should be a major concern to recovery efforts for endangered fish.

Morphological evidence for discrete stocks of yellow perch in Lake Erie

USGS Publications Warehouse

Kocovsky, Patrick M.; Knight, Carey T.

2012-01-01

Identification and management of unique stocks of exploited fish species are high-priority management goals in the Laurentian Great Lakes. We analyzed whole-body morphometrics of 1430 yellow perch Perca flavescens captured during 2007–2009 from seven known spawning areas in Lake Erie to determine if morphometrics vary among sites and management units to assist in identification of spawning stocks of this heavily exploited species. Truss-based morphometrics (n = 21 measurements) were analyzed using principal component analysis followed by ANOVA of the first three principal components to determine whether yellow perch from the several sampling sites varied morphometrically. Duncan's multiple range test was used to determine which sites differed from one another to test whether morphometrics varied at scales finer than management unit. Morphometrics varied significantly among sites and annually, but differences among sites were much greater. Sites within the same management unit typically differed significantly from one another, indicating morphometric variation at a scale finer than management unit. These results are largely congruent with recently-published studies on genetic variation of yellow perch from many of the same sampling sites. Thus, our results provide additional evidence that there are discrete stocks of yellow perch in Lake Erie and that management units likely comprise multiple stocks.

Age compositions of flatfish stocks as determined by a new otolithometric method, its application in the estimation of growth, spawning potential and fisheries management

NASA Astrophysics Data System (ADS)

Katayama, Satoshi; Yamamoto, Masayuki; Gorie, Shigeaki

2010-11-01

We developed an ageing methodology and examined age composition of three flatfish stocks inhabiting the Seto Inland Sea, Japan. Ages were difficult to determine for three-lined tongue sole ( Cynoglossus abbreviates) and ridged-eye flounder ( Pleuronichthys cornutus) because the first year annulus ring was often indistinct; therefore, we used directional change in otolith growth to distinguish it. Sectioning and etching methods were powerful tools for identifying annual checks for red tongue sole ( Cynoglossus joyneri). Using these ageing methods, we determined age-length relationships and growth curves. The age composition of the populations studied and of the landings showed that a large proportion of the latter consisted of individuals under the mean age of sexual maturity, thereby reducing the percent spawning potential ratio (%SPR) to ≈ 20% for all species. These findings suggest that fishing pressure on immature fish is leading to overfishing of these flatfish stocks.

Large scale, synchronous variability of marine fish populations driven by commercial exploitation.

PubMed

Frank, Kenneth T; Petrie, Brian; Leggett, William C; Boyce, Daniel G

2016-07-19

Synchronous variations in the abundance of geographically distinct marine fish populations are known to occur across spatial scales on the order of 1,000 km and greater. The prevailing assumption is that this large-scale coherent variability is a response to coupled atmosphere-ocean dynamics, commonly represented by climate indexes, such as the Atlantic Multidecadal Oscillation and North Atlantic Oscillation. On the other hand, it has been suggested that exploitation might contribute to this coherent variability. This possibility has been generally ignored or dismissed on the grounds that exploitation is unlikely to operate synchronously at such large spatial scales. Our analysis of adult fishing mortality and spawning stock biomass of 22 North Atlantic cod (Gadus morhua) stocks revealed that both the temporal and spatial scales in fishing mortality and spawning stock biomass were equivalent to those of the climate drivers. From these results, we conclude that greater consideration must be given to the potential of exploitation as a driving force behind broad, coherent variability of heavily exploited fish species.

Phenological and distributional shifts in ichthyoplankton associated with recent warming in the northeast Pacific Ocean.

PubMed

Auth, Toby D; Daly, Elizabeth A; Brodeur, Richard D; Fisher, Jennifer L

2018-01-01

Understanding changes in the migratory and reproductive phenology of fish stocks in relation to climate change is critical for accurate ecosystem-based fisheries management. Relocation and changes in timing of reproduction can have dramatic effects upon the success of fish populations and throughout the food web. During anomalously warm conditions (1-4°C above normal) in the northeast Pacific Ocean during 2015-2016, we documented shifts in timing and spawning location of several pelagic fish stocks based on larval fish samples. Total larval concentrations in the northern California Current (NCC) during winter (January-March) 2015 and 2016 were the highest observed since annual collections first occurred in 1998, primarily due to increased abundances of Engraulis mordax (northern anchovy) and Sardinops sagax (Pacific sardine) larvae, which are normally summer spawning species in this region. Sardinops sagax and Merluccius productus (Pacific hake) exhibited an unprecedented early and northward spawning expansion during 2015-16. In addition, spawning duration was greatly increased for E. mordax, as the presence of larvae was observed throughout the majority of 2015-16, indicating prolonged and nearly continuous spawning of adults throughout the warm period. Larvae from all three of these species have never before been collected in the NCC as early in the year. In addition, other southern species were collected in the NCC during this period. This suggests that the spawning phenology and distribution of several ecologically and commercially important fish species dramatically and rapidly changed in response to the warming conditions occurring in 2014-2016, and could be an indication of future conditions under projected climate change. Changes in spawning timing and poleward migration of fish populations due to warmer ocean conditions or global climate change will negatively impact areas that were historically dependent on these fish, and change the food web structure of the areas that the fish move into with unforeseen consequences. © 2017 John Wiley & Sons Ltd.

Lake trout (Salvelinus namaycush) populations in Lake Superior and their restoration in 1959-1993

USGS Publications Warehouse

Hansen, Michael J.; Peck, James W.; Schorfhaar, Richard G.; Selgeby, James H.; Schreiner, Donald R.; Schram, Stephen T.; Swanson, Bruce L.; MacCallum, Wayne R.; Burnham-Curtis, Mary K.; Curtis, Gary L.; Heinrich, John W.; Young, Robert J.

1995-01-01

Naturally-reproducing populations of lake trout (Salvelinus namaycush) have been reestablished in most of Lake Superior, but have not been restored to 1929-1943 average abundance. Progress toward lake trout restoration in Lake Superior is described, management actions are reviewed, and the effectiveness of those actions is evaluated; especially stocking lake trout as a tool for building spawning stocks, and subsequently, populations of wild recruits. Widespread destruction of lake trout stocks in the 1950s due to an intense fishery and sea lamprey (Petromyzon marinus) predation resulted in lower overall phenotypic diversity than was previously present. Stocking of yearling lake trout, begun in the 1950s, produced high densities of spawners that reproduced wherever inshore spawning habitat was widespread. Sea lampreys were greatly reduced, beginning in 1961, using selective chemical toxicants and barrier dams, but continue to exert substantial mortality. Fishery regulation was least effective in Wisconsin, where excessive gillnet effort caused high by-catch of lake trout until 1991, and in eastern Michigan, where lake trout restoration was deferred in favor of a tribal fishery for lake whitefish (Coregonus clupeaformis) in 1985. Restoration of stocks was quicker in offshore areas where remnant wild lake trout survived and fishing intensity was low, and was slower in inshore areas where stocked lake trout reproduced successfully and fishing intensity was high. Inshore stocks of wild lake trout are currently about 61 % of historic abundance in Michigan and 53% in Wisconsin. Direct comparison of modern and historic abundances of inshore lake trout stocks in Minnesota and Ontario is impossible due to lack of historic stock assessment data. Stocks in Minnesota are less abundant at present than in Michigan or Wisconsin, and stocks in Ontario are similar to those in Michigan. Further progress in stock recovery can only be achieved if sea lampreys are depressed and if fisheries are constrained further than at present.

Distribution, stock composition and timing, and tagging response of wild Chinook Salmon returning to a large, free-flowing river basin

USGS Publications Warehouse

Eiler, John H.; Masuda, Michele; Spencer, Ted R.; Driscoll, Richard J.; Schreck, Carl B.

2014-01-01

Chinook Salmon Oncorhynchus tshawytscha returns to the Yukon River basin have declined dramatically since the late 1990s, and detailed information on the spawning distribution, stock structure, and stock timing is needed to better manage the run and facilitate conservation efforts. A total of 2,860 fish were radio-tagged in the lower basin during 2002–2004 and tracked upriver. Fish traveled to spawning areas throughout the basin, ranging from several hundred to over 3,000 km from the tagging site. Similar distribution patterns were observed across years, suggesting that the major components of the run were identified. Daily and seasonal composition estimates were calculated for the component stocks. The run was dominated by two regional components comprising over 70% of the return. Substantially fewer fish returned to other areas, ranging from 2% to 9% of the return, but their collective contribution was appreciable. Most regional components consisted of several principal stocks and a number of small, spatially isolated populations. Regional and stock composition estimates were similar across years even though differences in run abundance were reported, suggesting that the differences in abundance were not related to regional or stock-specific variability. Run timing was relatively compressed compared with that in rivers in the southern portion of the species’ range. Most stocks passed through the lower river over a 6-week period, ranging in duration from 16 to 38 d. Run timing was similar for middle- and upper-basin stocks, limiting the use of timing information for management. The lower-basin stocks were primarily later-run fish. Although differences were observed, there was general agreement between our composition and timing estimates and those from other assessment projects within the basin, suggesting that the telemetry-based estimates provided a plausible approximation of the return. However, the short duration of the run, complex stock structure, and similar stock timing complicate management of Yukon River returns.

What is left? Macrophyte meadows and Atlantic herring (Clupea harengus) spawning sites in the Greifswalder Bodden, Baltic Sea

NASA Astrophysics Data System (ADS)

Kanstinger, Philipp; Beher, Jutta; Grenzdörffer, Görres; Hammer, Cornelius; Huebert, Klaus B.; Stepputis, Daniel; Peck, Myron A.

2018-02-01

Coastal zones are productive areas of marine ecosystems which are also hotspots of anthropogenic activities causing habitat degradation. In the southwest Baltic Sea, eutrophication is thought to have caused the massive reduction in submerged macrophytes observed in recent decades. Here, we surveyed the submarine vegetation and examined locations of spawning of herring (Clupea harengus) in the Greifswalder Bodden, one of the most important reproductive habitats of the Western Baltic Spring Spawner herring stock (WBSS). This stock deposits eggs onto submerged vegetation and changes in macrophyte coverage are expected to influence the availability of reproductive habitat. Aerial, underwater video tows and SCUBA surveys conducted in spring 2009 revealed that only ∼7% of the lagoon was vegetated. Herring eggs were observed on 12 of 32 SCUBA transects, at depths between 0.2 and 5 m and were attached to a variety of spermatophyte and algae species but not to stones or mussels. A classification tree model indicated that spawning sites were strongly associated with the vegetation cover within a 100- and 500-m radius, implying that herring schools preferentially spawn on dense and large underwater meadows. Only ∼5% of the lagoon now falls into this vegetation category. Despite 20 years of efforts to reduce eutrophication, no increase in macroalgae and spermatophyte vegetation towards the historical level of 90% coverage in the area is apparent.

The influence of environmental conditions on early life stages of flounder (Platichthys flesus) in the central Baltic Sea

NASA Astrophysics Data System (ADS)

Ustups, Didzis; Müller-Karulis, Bärbel; Bergstrom, Ulf; Makarchouk, Andrej; Sics, Ivo

2013-01-01

Flounder (Platichthys flesus) is a temperate marine fish that is well adapted to the brackish waters of the Baltic Sea. There are two sympatric flounder populations in the Baltic Sea, pelagic and demersal spawners, which differ in their spawning habitat and egg characteristics. In the present study, pelagic spawning flounder of the central Baltic Sea was studied. We examined whether variations in hydrological regime can explain fluctuations in flounder early life stages that have occurred over the past 30 years (1970-2005). Using generalized additive modeling to explain the abundance of flounder eggs and larvae in a Latvian ichthyoplankton dataset, we evaluate the hypothesis that the available reproductive volume, defined as the water column with dissolved oxygen larger than 1 ml/l and salinity between 10.6 and 12 PSU, affects the survival of flounder ichthyoplankton and determines recruitment success. Both reproductive volume and spawning stock biomass were significant factors determining flounder ichthyoplankton abundance. Different measures of water temperature did not contribute significantly to the variability of eggs or larvae. However, recruitment did not correlate to the supply of larvae. The findings presented in this study on the relationship between flounder reproduction, spawning stock biomass and reproductive volume, as well as the lack of correlation to recruitment, are valuable for the understanding of flounder ecology in the Baltic Sea, and for developing the management of the species.

Economic repercussions of fisheries-induced evolution

PubMed Central

Eikeset, Anne Maria; Richter, Andries; Dunlop, Erin S.; Dieckmann, Ulf; Stenseth, Nils Chr.

2013-01-01

Fish stocks experiencing high fishing mortality show a tendency to mature earlier and at a smaller size, which may have a genetic component and therefore long-lasting economic and biological effects. To date, the economic effects of such ecoevolutionary dynamics have not been empirically investigated. Using 70 y of data, we develop a bioeconomic model for Northeast Arctic cod to compare the economic yield in a model in which life-history traits can vary only through phenotypic plasticity with a model in which, in addition, genetic changes can occur. We find that evolutionary changes toward faster growth and earlier maturation occur consistently even if a stock is optimally managed. However, if a stock is managed optimally, the evolutionary changes actually increase economic yield because faster growth and earlier maturation raise the stock’s productivity. The optimal fishing mortality is almost identical for the evolutionary and nonevolutionary model and substantially lower than what it has been historically. Therefore, the costs of ignoring evolution under optimal management regimes are negligible. However, if fishing mortality is as high as it has been historically, evolutionary changes may result in economic losses, but only if the fishery is selecting for medium-sized individuals. Because evolution facilitates growth, the fish are younger and still immature when they are susceptible to getting caught, which outweighs the increase in productivity due to fish spawning at an earlier age. PMID:23836660

Spawning site fidelity of wild and hatchery lake trout (Salvelinus namaycush) in northern Lake Huron

USGS Publications Warehouse

Binder, Thomas; Riley, Stephen C.; Holbrook, Christopher; Hansen, Michael J.; Bergstedt, Roger A.; Bronte, Charles R.; He, Ji; Krueger, Charles C.

2016-01-01

Fidelity to high-quality spawning sites helps ensure that adults repeatedly spawn at sites that maximize reproductive success. Fidelity is also an important behavioural characteristic to consider when hatchery-reared individuals are stocked for species restoration, because artificial rearing environments may interfere with cues that guide appropriate spawning site selection. Acoustic telemetry was used in conjunction with Cormack–Jolly–Seber capture–recapture models to compare degree of spawning site fidelity of wild and hatchery-reared lake trout (Salvelinus namaycush) in northern Lake Huron. Annual survival was estimated to be between 77% and 81% and did not differ among wild and hatchery males and females. Site fidelity estimates were high in both wild and hatchery-reared lake trout (ranging from 0.78 to 0.94, depending on group and time filter), but were slightly lower in hatchery-reared fish than in wild fish. The ecological implication of the small difference in site fidelity between wild and hatchery-reared lake trout is unclear, but similarities in estimates suggest that many hatchery-reared fish use similar spawning sites to wild fish and that most return to those sites annually for spawning.

Alternative spawning strategy and temperature for larval emergence of longfin dace ( Agosia chrysogaster) in stream mesocosms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Troia, Matthew J.; Whitney, James E.; Gido, Keith B.

2014-06-01

To determine if the strategy of spawning in saucer-like depressions is obligate or facultative for longfin dace ( Agosia chrysogaster), we collected adults from four sites in the upper Gila River (southwestern New Mexico), stocked them in separate outdoor stream-mesocosms lined with cobble substrate, and made daily observations for the presence of saucer-nests and hatched larvae. Larvae were observed from three of the four mesocosms and emerged at temperatures ranging from 19.2 24.0 °C. Here, the absence of saucer-nests in all mesocosms throughout the study indicates that longfin dace can spawn over cobble substrate and have larvae hatch successfully, suggestingmore » that longfin dace can use an alternate spawning strategy when sand substrate is not available for construction of saucer-nests.« less

Life history and initial assessment of fishing impacts on the by-catch species Dules auriga (Teleostei: Serranidae) in southern Brazil.

PubMed

Rovani, A T; Cardoso, L G

2017-09-01

The life history of Dules auriga, a small hermaphrodite serranid species inhabiting deep waters and a frequent component of the discarded catch of bottom trawling in southern Brazil, was studied to assess the fishery effects on the stock through the estimation of the remaining spawning-potential ratio. Sampling was conducted throughout a year and included specimens to determine sex, maturity and age. Age was validated by the edge type and marginal-increment analysis. The oldest and the largest individuals were 9 years and 195 mm total length. Growth parameters fitted to the von Bertalanffy equation were L ∞ = 178·34 mm, k = 0·641 year -1 and t 0 = -0·341 years. Length and age at first maturity were 140·72 mm and 2 years, respectively. The reproductive season was throughout the austral spring and summer. The assessment of the effects of fishing showed that it may have resulted in a loss of 50% of the spawning potential. This loss may be higher when taking into account the uncertainty in the life-history parameters and could be considered of concern for the population. Fast growth, moderate longevity, long spawning season, small size and age at maturity make D. auriga relatively resilient to the removal of biomass by fishing. When considering the uncertainty, however, the losses of the spawning potential have been severely reducing the population resilience in the face of ecosystem changes. © 2017 The Fisheries Society of the British Isles.

Oyster larval transport in coastal Alabama: Dominance of physical transport over biological behavior in a shallow estuary

NASA Astrophysics Data System (ADS)

Kim, Choong-Ki; Park, Kyeong; Powers, Sean P.; Graham, William M.; Bayha, Keith M.

2010-10-01

Among the various factors affecting recruitment of marine invertebrates and fish, larval transport may produce spatial and temporal patterns of abundance that are important determinants of management strategies. Here we conducted a field and modeling study to investigate the larval transport of eastern oyster, Crassostrea virginica, in Mobile Bay and eastern Mississippi Sound, Alabama. A three-dimensional larval transport model accounting for physical transport, biological movement of larvae, and site- and larval-specific conditions was developed. A hydrodynamic model was used to simulate physical transport, and biological movement was parameterized as a function of swimming and sinking velocity of oyster larvae. Site- and larval-specific conditions, including spawning location, spawning stock size, spawning time, and larval period, were determined based on the previous studies. The model reasonably reproduced the observed gradient in oyster spat settlement and bivalve larval concentration, although the model results were less dynamic than the data, probably owing to the simplified biological conditions employed in the model. A persistent gradient decreasing from west to east in the model results at time scales of overall average, season, and each survey in 2006 suggests that the larval supply may be responsible for the corresponding gradient in oyster spat settlement observed over the past 40 years. Biological movement increased larval retention near the spawning area, thus providing a favorable condition for local recruitment of oysters. Inclusion of biological movement, however, caused little change in the overall patterns of larval transport and still resulted in a west-east gradient, presumably because of frequent destratification in the shallow Mobile Bay system.

Spawning by lake sturgeon (Acipenser fulvescens) in the Detroit River

USGS Publications Warehouse

Caswell, N.M.; Peterson, D.L.; Manny, B.A.; Kennedy, G.W.

2004-01-01

Overfishing and habitat destruction in the early 1900s devastated lake sturgeon (Acipenser fulvescens) populations in the Great Lakes. Although a comprehensive restoration strategy for this species was recently drafted by the Michigan Department of Natural Resources, a lack of current data on Great Lakes sturgeon stocks has hindered rehabilitation efforts. Historically, the Detroit River supported one of the largest lake sturgeon populations in the Great Lakes; however, little is known about the current population or its habitat use. The main objective of this study was to determine if lake sturgeon spawns in the Detroit River. As part of a larger study, baited setlines were used to capture lake sturgeon in the Detroit River in the spring and summer of 2000 and 2001. In each year of the study, ultrasonic transmitters were surgically implanted in 10 adult fish to track their movements, evaluate habitat use and identify possible spawning sites. Using telemetry and egg mats to verify spawning activity, one spawning site was located and verified in the Detroit River. Spawning was verified by recovering sturgeon eggs deposited on egg collection mats anchored at the site. Telemetry data suggested that several other possible spawning sites also may exist, however, spawning activity was not verified at these sites.

Sexual size dimorphism in three North Sea gadoids.

PubMed

Keyl, F; Kempf, A J; Sell, A F

2015-01-01

Existing biological data on whiting Merlangius merlangus, cod Gadus morhua and haddock Melanogrammus aeglefinus from a long-term international survey were analysed to address sexual size dimorphism (SSD) and its effect on their ecology and management. Results show that SSD, with larger females of the same age as males, is a result of higher growth rates in females. A direct consequence of SSD is the pronounced length-dependent female ratio that was found in all three gadoids in the North Sea. Female ratios of the three species changed from equality to female dominance at specific dominance transition lengths of c. 30, 35 and 60 cm for M. merlangus, G. morhua and M. aeglefinus, respectively. An analysis by area for M. merlangus also revealed length dependence of female ratios. SSD and length-dependent female ratios under most circumstances are inseparable. Higher overall energy demand as well as a higher energy uptake rate must result from the observed SSD and dimorphism in growth rates. Potential processes related to feeding, locomotion and physiology are proposed that could balance the increased energy investment of females. Potential consequences of SSD and length dependency of female ratios are the reduction of the reproductive potential of a stock due to size-selective fishing and biased assessment of the true size of the female spawning stock that could distort decisions in fisheries management. © 2014 The Fisheries Society of the British Isles.

Physiological indices of seawater readiness in postspawning steelhead kelts

USGS Publications Warehouse

Buelow, Jessica; Moffitt, Christine M.

2015-01-01

Management goals to improve the recovery of steelhead (Oncorhynchus mykiss) stocks at risk of extinction include increasing the proportion of postspawning fish that survive and spawn again. To be successful, postspawning steelhead (kelts) migrating downstream to the ocean must prepare physiologically and physically for a seawater transition. We sampled blood, gill filaments, and evaluated the external condition of migrating kelts from an ESA-listed population in the Snake/Columbia River system over two consecutive years to evaluate their physiological readiness for transition to seawater. We chose attributes often considered as measures of preparation for seawater in juveniles, including gill Na+,K+ ATPase activity, plasma electrolytes and hormones to consider factors related to external condition, size and sex. We found kelts in good external condition had plasma profiles similar to downstream-migrating smolts. In addition, we found more than 80% of kelts ranked in good external condition had smolt-like body silvering. We compared measures from migrating kelts with samples obtained from hatchery fish at the time of spawning to confirm that Na+, K+ ATPase activity in kelts was significantly elevated over spawning fish. We found significant differences in gill Na+, K+ ATPase activity in migrating kelts between the years of sampling, but little indication of influence of fish condition. We conclude that the postspawning steelhead sampled exhibited a suite of behaviours, condition and physiology characteristic of fish prepared for successful transition to a seawater environment.

Injuries from non-retention in gillnet fisheries suppress reproductive maturation in escaped fish.

PubMed

Baker, Matthew R; Swanson, Penny; Young, Graham

2013-01-01

Exploitation of fisheries resources has unintended consequences, not only in the bycatch and discard of non-target organisms, but also in damage to targeted fish that are injured by gear but not landed (non-retention). Delayed mortality due to non-retention represents lost reproductive potential in exploited stocks, while not contributing to harvest. Our study examined the physiological mechanisms by which delayed mortality occurs and the extent to which injuries related to disentanglement from commercial gear compromise reproductive success in spawning stocks of Pacific salmon (Oncorhynchus spp.). We found evidence for elevated stress in fish injured via non-retention in gillnet fisheries. Plasma cortisol levels correlated with the severity of disentanglement injury and were elevated in fish that developed infections related to disentanglement injuries. We also analyzed sex steroid concentrations in females (estradiol-17β and 17,20β-dihydroxy-4-pregnen-3-one) to determine whether non-retention impairs reproductive potential in escaped individuals. We demonstrate evidence for delayed or inhibited maturation in fish with disentanglement injuries. These findings have important implications for effective conservation and management of exploited fish stocks and suggest means to improve spawning success in such stocks if retention in commercial fisheries is improved and incidental mortality reduced.

Injuries from Non-Retention in Gillnet Fisheries Suppress Reproductive Maturation in Escaped Fish

PubMed Central

Baker, Matthew R.; Swanson, Penny; Young, Graham

2013-01-01

Exploitation of fisheries resources has unintended consequences, not only in the bycatch and discard of non-target organisms, but also in damage to targeted fish that are injured by gear but not landed (non-retention). Delayed mortality due to non-retention represents lost reproductive potential in exploited stocks, while not contributing to harvest. Our study examined the physiological mechanisms by which delayed mortality occurs and the extent to which injuries related to disentanglement from commercial gear compromise reproductive success in spawning stocks of Pacific salmon (Oncorhynchus spp.). We found evidence for elevated stress in fish injured via non-retention in gillnet fisheries. Plasma cortisol levels correlated with the severity of disentanglement injury and were elevated in fish that developed infections related to disentanglement injuries. We also analyzed sex steroid concentrations in females (estradiol-17β and 17,20β-dihydroxy-4-pregnen-3-one) to determine whether non-retention impairs reproductive potential in escaped individuals. We demonstrate evidence for delayed or inhibited maturation in fish with disentanglement injuries. These findings have important implications for effective conservation and management of exploited fish stocks and suggest means to improve spawning success in such stocks if retention in commercial fisheries is improved and incidental mortality reduced. PMID:23894510

Seasonal variation in the levels of organohalogen compounds in herring (Clupea harengus) from the Norwegian Sea.

PubMed

Frantzen, Sylvia; Måge, Amund; Iversen, Svein Arnholt; Julshamn, Kåre

2011-09-01

The Norwegian spring spawning (NSS) herring is an ecologically important fish stock in the Norwegian Sea, and with a catch volume exceeding one million tons a year it is also economically important and a valuable food source. In order to provide a baseline of the levels of contaminants in this fish stock, the levels of organohalogen compounds were determined in 800 individual herring sampled at 29 positions in the Norwegian Sea and off the coast of Norway. Due to seasonal migration, the herring were sampled where they were located during the different seasons. Concentrations of dioxins and dioxin-like PCBs, non-dioxin-like PCBs (PCB(7)) and PBDEs were determined in fillet samples of individual herring, and found to be relatively low, with means (min-max) of 0.77 (0.24-3.5) ng TEQ kg(-1) wet weight (ww), 5.0 (1.4-24) μg kg(-1) ww and 0.47 (0.091-3.1) μg kg(-1) ww, respectively. The concentrations varied throughout the year due to the feeding- and spawning cycle: Starved, pre-spawning herring caught off the Norwegian coast in January-February had the highest levels and those caught in the Norwegian Sea in April-June, after further starvation and spawning, had the lowest levels. These results show that the concentrations of organohalogen compounds in NSS herring are relatively low and closely tied to their physiological condition, and that in the future regular monitoring of NSS herring should be made in the spawning areas off the Norwegian coast in late winter. Copyright © 2011 Elsevier Ltd. All rights reserved.

Development of a stock-recruitment model and assessment of biological reference points for the Lake Erie walleye fishery

USGS Publications Warehouse

Zhao, Yingming; Kocovsky, Patrick M.; Madenjian, Charles P.

2013-01-01

We developed an updated stock–recruitment relationship for Lake Erie Walleye Sander vitreus using the Akaike information criterion model selection approach. Our best stock–recruitment relationship was a Ricker spawner–recruit function to which spring warming rate was added as an environmental variable, and this regression model explained 39% of the variability in Walleye recruitment over the 1978 through 2006 year-classes. Thus, most of the variability in Lake Erie Walleye recruitment appeared to be attributable to factors other than spawning stock size and spring warming rate. The abundance of age-0 Gizzard Shad Dorosoma cepedianum, which was an important term in previous models, may still be an important factor for Walleye recruitment, but poorer ability to monitor Gizzard Shad since the late 1990s could have led to that term failing to appear in our best model. Secondly, we used numerical simulation to demonstrate how to use the stock recruitment relationship to characterize the population dynamics (such as stable age structure, carrying capacity, and maximum sustainable yield) and some biological reference points (such as fishing rates at different important biomass or harvest levels) for an age-structured population in a deterministic way.

Genetic Analysis of Oncorhynchus Nerka : Life History and Genetic Analysis of Redfish Lake Oncorhynchus Nerka, 1993-1994 Completion Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brannon, E.L.; Thorgaard, G.H.; Cummings, S.A.

1994-10-01

The study has shown through life history examination and DNA analysis that three forms of O. nerka are present in Redfish Lake. The three forms are closely related, but may be sufficiently different to be considered three separate stocks. Fishhook Creek kokanee are temporally isolated from the beach spawners, and may represent the gene pool most similar to the historic sockeye population that once spawned there. Fishhook Creek offers the best spawning area available in the lake system, and should be considered for use in reestablishing an anadromous Fishhook Creek sockeye swain. The resident beach spawning strain of O. nerkamore » is likewise the most similar genetic form of the companion anadromous beach spawning O. nerka, and needs to be considered the most appropriate genetic source to help minimize reduced fitness of the sockeye from inbreeding.« less

Spatially-Resolved Influence of Temperature and Salinity on Stock and Recruitment Variability of Commercially Important Fishes in the North Sea

PubMed Central

Akimova, Anna; Núñez-Riboni, Ismael; Kempf, Alexander; Taylor, Marc H.

2016-01-01

Understanding of the processes affecting recruitment of commercially important fish species is one of the major challenges in fisheries science. Towards this aim, we investigated the relation between North Sea hydrography (temperature and salinity) and fish stock variables (recruitment, spawning stock biomass and pre-recruitment survival index) for 9 commercially important fishes using spatially-resolved cross-correlation analysis. We used high-resolution (0.2° × 0.2°) hydrographic data fields matching the maximal temporal extent of the fish population assessments (1948–2013). Our approach allowed for the identification of regions in the North Sea where environmental variables seem to be more influential on the fish stocks, as well as the regions of a lesser or nil influence. Our results confirmed previously demonstrated negative correlations between temperature and recruitment of cod and plaice and identified regions of the strongest correlations (German Bight for plaice and north-western North Sea for cod). We also revealed a positive correlation between herring spawning stock biomass and temperature in the Orkney-Shetland area, as well as a negative correlation between sole pre-recruitment survival index and temperature in the German Bight. A strong positive correlation between sprat stock variables and salinity in the central North Sea was also found. To our knowledge the results concerning correlations between North Sea hydrography and stocks’ dynamics of herring, sole and sprat are novel. The new information about spatial distribution of the correlation provides an additional help to identify mechanisms underlying these correlations. As an illustration of the utility of these results for fishery management, an example is provided that incorporates the identified environmental covariates in stock-recruitment models. PMID:27584155

Optimal reproduction in salmon spawning substrates linked to grain size and fish length

NASA Astrophysics Data System (ADS)

Riebe, Clifford S.; Sklar, Leonard S.; Overstreet, Brandon T.; Wooster, John K.

2014-02-01

Millions of dollars are spent annually on revitalizing salmon spawning in riverbeds where redd building by female salmon is inhibited by sediment that is too big for fish to move. Yet the conditions necessary for productive spawning remain unclear. There is no gauge for quantifying how grain size influences the reproductive potential of coarse-bedded rivers. Hence, managers lack a quantitative basis for optimizing spawning habitat restoration for reproductive value. To overcome this limitation, we studied spawning by Chinook, sockeye, and pink salmon (Oncorhynchus tshawytscha, O. nerka, and O. gorbuscha) in creeks and rivers of California and the Pacific Northwest. Our analysis shows that coarse substrates have been substantially undervalued as spawning habitat in previous work. We present a field-calibrated approach for estimating the number of redds and eggs a substrate can accommodate from measurements of grain size and fish length. Bigger fish can move larger sediment and thus use more riverbed area for spawning. They also tend to have higher fecundity, and so can deposit more eggs per redd. However, because redd area increases with fish length, the number of eggs a substrate can accommodate is maximized for moderate-sized fish. This previously unrecognized tradeoff raises the possibility that differences in grain size help regulate river-to-river differences in salmon size. Thus, population diversity and species resilience may be linked to lithologic, geomorphic, and climatic factors that determine grain size in rivers. Our approach provides a tool for managing grain-size distributions in support of optimal reproductive potential and species resilience.

Habitat selection and spawning success of walleye in a tributary to Owasco Lake, New York

USGS Publications Warehouse

Chalupnicki, Marc A.; Johnson, James H.; McKenna, James E.; Dittman, Dawn E.

2010-01-01

Walleyes Sander vitreus are stocked into Owasco Lake, New York, to provide a sport fishery, but the population must be sustained by annual hatchery supplementation despite the presence of appropriate habitat. Therefore, we evaluated walleye spawning success in Dutch Hollow Brook, a tributary of Owasco Lake, to determine whether early survival limited recruitment. Spawning success during spring 2006 and 2007 was evaluated by estimating egg densities from samples collected in the lower 725 m of the stream. Environmental variables were also recorded to characterize the selected spawning habitat. Drift nets were set downstream of the spawning section to assess egg survival and larval drift. We estimated that 162,596 larvae hatched in 2006. For 2007, we estimated that 360,026 eggs were deposited, with a hatch of 127,500 larvae and hatching success of 35.4%. Egg density was significantly correlated to percent cover, substrate type, and depth : velocity ratio. Two sections had significantly higher egg deposition than other areas. Adult spawning walleyes selected shallow, slow habitats with some cover and gravel substrate in the accessible reaches of Dutch Hollow Brook. Our results show that walleyes found suitable spawning habitat in Dutch Hollow Brook and that egg and larval development does not appear to limit natural reproduction.

Observations on the reproductive and larval biology of Blennius pavo (Pisces: Teleostei)

NASA Astrophysics Data System (ADS)

Westernhagen, H.

1983-09-01

Social behaviour and spawning of adult Blennius pavo kept in the laboratory are described. Eggs are deposited in batches on the walls of artificial spawning places (PVC pipes). One male guards and tends the eggs of different females in one spawning place. Larval hatching occurs in groups according to oviposition. Minimum incubation temperature is around 14 15°C. Larval survival in 1-1 rearing jars is not related to larval total length but to density of larval stock. An experimental population of laboratory reared juvenile and adolescent B. pavo displays a male to female ratio of 1:1.4. Factors possibly influencing the sex ratio of this littoral fish are discussed in view of the situation in its natural environment.

Net-mortality of Common Murres and Atlantic Puffins in Newfoundland, 1951-81

USGS Publications Warehouse

Piatt, John F.; Nettleship, David N.; Threlfall, William; Nettleship, David N.; Sanger, Gerald A.; Springer, Paul F.

1982-01-01

Band recoveries (N = 315) over 26 years (1951-77) and three surveys of seabird bycatch in inshore fishing nets (1972, 1980-81) indicate that there has been a substantial net-mortality of Atlantic Puffins (Fratercula arctica) and Common Murres (Uria aalge) in Newfoundland coastal waters for the past 2 decades. Offshore (e.g. Grand Banks) gill-netting is limited, but some data suggest that murre net-mortality also occurs offshore at murre wintering areas. The vast majority of inshore net-mortality incidents occur over a 2-week period during the annual inshore spawning migration of capelin (Mallotus villosus), the major prey item for alcids in eastern Canada. Most murres (83%) were drowned in bottom-set (30-185 m) cod (Gadus morhua) gill nets, whereas more puffins were drowned in surface-set salmon (Salmo salar) gill nets or cod traps (55%) than in cod gillnets (45%). Murre band recoveries, colony censuses, and fishing-effort data suggest that at the second largest Common Murre colony in Newfoundland (Witless Bay Seabird Sanctuary, 77,000 breeding pairs) net-mortality was relatively low in the 1950s and early 1960s, but increased during the 1960s as the murre population grew in size and gill-net fishing effort increased in the colony area. By 1971, net-mortality accounted for 70% of murre band recoveries and calculations show that almost 30,000 breeding adults, or about 20% of the local breeding population, were drowned in that year. More reliable estimates of alcid bycatch in the Witless Bay area have been made on the basis of actual bycatch surveys. In 1972 about 20,000 adult murres, or 13% of the breeding stock, were killed in gill-nets. Net-mortality of murres apparently diminished through the 1970s as capelin stocks declined and fewer birds foraged in heavily netted inshore areas. Bycatch surveys in the Witless Bay area in 1980-81 revealed that, relative to previous years, murre net-mortality was greatly reduced and resulted in the loss of only 3-4% of the breeding stock. Even these low mortality rates, however, are cause for concern as adult murre mortality from all sources (including hunting, oil, and natural mortality) should not exceed 6-12% per annum to maintain a stable breeding population. Little is known about the magnitude of net-mortality at other major Newfoundland murre colonies though it is known to be a problem in all colony areas. The bycatch of adult Atlantic Puffins in the Witless Bay area was low compared to murre bycatch and in 3 years of study never exceeded 1.6% of the breeding population. During the 1970s, fishing effort increased five-fold in colony areas and we predict that if capelin spawning stocks return to early 1970s size, then net-mortality of puffins and murres in Newfoundland coastal regions will increase dramatically. Indeed, preliminary examination of 1982 capelin spawning and seabird bycatch data suggests that capelin were much more abundant inshore and murre bycatch increased two- to three-fold over 1981.

Factors regulating early life history dispersal of Atlantic cod (Gadus morhua) from coastal Newfoundland.

PubMed

Stanley, Ryan R E; deYoung, Brad; Snelgrove, Paul V R; Gregory, Robert S

2013-01-01

To understand coastal dispersal dynamics of Atlantic cod (Gadus morhua), we examined spatiotemporal egg and larval abundance patterns in coastal Newfoundland. In recent decades, Smith Sound, Trinity Bay has supported the largest known overwintering spawning aggregation of Atlantic cod in the region. We estimated spawning and dispersal characteristics for the Smith Sound-Trinity Bay system by fitting ichthyoplankton abundance data to environmentally-driven, simplified box models. Results show protracted spawning, with sharply increased egg production in early July, and limited dispersal from the Sound. The model for the entire spawning season indicates egg export from Smith Sound is 13%•day(-1) with a net mortality of 27%•day(-1). Eggs and larvae are consistently found in western Trinity Bay with little advection from the system. These patterns mirror particle tracking models that suggest residence times of 10-20 days, and circulation models indicating local gyres in Trinity Bay that act in concert with upwelling dynamics to retain eggs and larvae. Our results are among the first quantitative dispersal estimates from Smith Sound, linking this spawning stock to the adjacent coastal waters. These results illustrate the biophysical interplay regulating dispersal and connectivity originating from inshore spawning of coastal northwest Atlantic.

The pre-spawning migratory behaviour of Atlantic salmon Salmo salar in a large lacustrine catchment.

PubMed

Kennedy, R J; Allen, M

2016-09-01

The movements of adult Atlantic salmon Salmo salar were determined as they migrated to spawning habitats in a large lacustrine catchment, Lough Neagh, in Northern Ireland. The minimum average ground speed of S. salar through the lake was 2·1 km day(-1) and the mean residence time was 11 days. Tagged S. salar tended to actively migrate through the lake which represented a transitory habitat for adult S. salar. Migration time from the release site, through the lake, to a spawning tributary decreased during the migratory period. During the 4 year study period between 20·5 and 41·6% of tagged S. salar which entered the lake each year, explored at least one other channel before ascending the final spawning tributary. Exploratory behaviour was more likely in S. salar which spawned in the tributaries furthest from the sea. Exploratory behaviour was also more likely to occur during periods of reduced discharge in the natal stream. The fishery management implications of complex pre-spawning behaviour in a mixed stock lacustrine system, are discussed. © 2016 The Fisheries Society of the British Isles.

Could a Mathematics Student Have Prevented the Collapse of the Atlanto-Scandian Herring?

ERIC Educational Resources Information Center

Sigurdsson, Thorir

2006-01-01

Herring in the ocean between Iceland and Norway was one of the largest fish stocks in the world until the fishery crashed in the late 1960s. The catch in 1971 was only 20 thousand metric tons in contrast with the record of 2 million tons in 1966 and the spawning stock declined from 10 million tons to 10 thousand tons in 20 years. After 25 years of…

Spawning areas of Engraulis anchoita in the Southeastern Brazilian Bight during late-spring and early summer

NASA Astrophysics Data System (ADS)

del Favero, Jana M.; Katsuragawa, Mario; Zani-Teixeira, Maria de Lourdes; Turner, Jefferson T.

2017-04-01

Analysis of fish egg density and distribution is indispensable for the understanding of the adult stock variability, and is a powerful tool for fisheries management. Thus, the objective of the present study was to characterize the spatial-temporal spawning patterns of Engraulis anchoita in the Southeastern Brazilian Bight, in terms of geographic location and abiotic factors. We analyzed data of eggs sampled during ten years, from 1974 to 1993, to create maps of the mean and the standard deviation (sd) of the estimated probability of egg presence, through indicative kriging. Preferred, tolerated and avoided temperature, salinity, local depth and distance for spawning of E. anchoita were defined by the estimation of bootstrapped confidence intervals of the quotient values (Q). Despite not having identified any recurrent spawning sites, a few occasional and unfavorable spawning sites were identified, showing that the spawning habit of E. anchoita not only varied spatially, but also temporally. The largest occasional spawning site and with the highest probability of egg presence (0.6-0.7) was located around 27°S, close to Florianópolis (Santa Catarina state). On the other hand, a well-marked unfavorable spawning site was located off São Sebastião Island (São Paulo state), with the probability of egg presence between 0-0.1. Abiotic and biotic factors that could be related to the changes in the spawning areas of E. anchoita were discussed, with shelf width, mesoscale hydrodynamic features and biological interactions apparently playing important roles in defining spawning sites.

Climate change and the green energy paradox: the consequences for twaite shad Alosa fallax from the River Severn, U.K.

PubMed

Aprahamian, M W; Aprahamian, C D; Knights, A M

2010-11-01

A stock-recruitment model with a temperature component was used to estimate the effect of an increase in temperature predicted by climate change projections on population persistence and distribution of twaite shad Alosa fallax. An increase of 1 and 2° C above the current mean summer (June to August) water temperature of 17·8° C was estimated to result in a three and six-fold increase in the population, respectively. Climate change is also predicted to result in an earlier commencement to their spawning migration into fresh water. The model was expanded to investigate the effect of any additional mortality that might arise from a tidal power barrage across the Severn Estuary. Turbine mortality was separated into two components: (1) juvenile (pre-maturation) on their out migration during their first year and on their first return to the river to spawn and (2) post-maturation mortality on adults on the repeat spawning component of the population. Under current conditions, decreasing pre-maturation and post-maturation survival by 8% is estimated to result in the stock becoming extinct. It is estimated that an increase in mean summer water temperature of 1° C would mean that survival pre and post-maturation would need to be reduced by c. 10% before the stock becomes extinct. Therefore, climate change is likely to be beneficial to populations of A. fallax within U.K. rivers, increasing survival and thus, population persistence. © 2010 The Authors. Journal of Fish Biology © 2010 The Fisheries Society of the British Isles.

Kootenai River Fisheries Investigations; Rainbow and Bull Trout Recruitment, 2002-2003 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walters, Jody P.

Rainbow trout Oncorhynchus mykiss provide the most important sport fishery in the Kootenai River, Idaho, but densities and catch rates are low. Low recruitment is one possible factor limiting the rainbow trout population. Bull trout Salvelinus confluentus also exist in the Kootenai River, but little is known about this population. Research reported here addresses the following objectives for the Kootenai River, Idaho: increase rainbow trout recruitment, identify rainbow and bull trout spawning tributaries and migration timing, establish baseline data on bull trout redd numbers in tributaries, and improve the rainbow trout population size structure. Six adult rainbow trout were movedmore » to spawning habitat upstream of a potential migration barrier on Caboose Creek, but numbers of redds and age-0 out-migrants did not appear to increase relative to a reference stream. Measurements taken on the Moyie River indicated the gradient is inadequate to deliver suitable flows to a proposed rainbow trout spawning channel. Summer water temperatures measured in the Deep Creek drainage sometimes exceeded 24 C, higher than those reported as suitable for rainbow trout. Radio-tagged rainbow trout were located in Boulder Creek during the spring spawning season, and bull trout were located in the Moyie River and O'Brien Creek, Montana in the fall. Bull trout spawning migration timing was related to increases in Kootenai River flows. Bull trout redd surveys documented 19 redds on Boulder Creek and North and South Callahan creeks. Fall 2002 electrofishing showed that the Kootenai River rainbow trout proportional stock density was 54, higher than prior years when more liberal fishing regulations were in effect. Boulder Creek produces the highest number of age-0 rainbow trout out-migrants upstream of Bonners Ferry, but the survival rate of these out-migrants upon reaching the Kootenai River is unknown. Determining juvenile survival rates and sources of mortality could aid management efforts to increase rainbow trout recruitment. North and South Callahan creeks support the largest spawning population of bull trout in the Kootenai River drainage, Idaho, so management of the watershed should consider bull trout as high priority.« less

How coarse is too coarse for salmon spawning substrates?

NASA Astrophysics Data System (ADS)

Wooster, J. K.; Riebe, C. S.; Ligon, F. K.; Overstreet, B. T.

2009-12-01

Populations of Pacific salmon species have declined sharply in many rivers of the western US. Reversing these declines is a top priority and expense of many river restoration projects. To help restore salmon populations, managers often inject gravel into rivers, to supplement spawning habitat that has been depleted by gravel mining and the effects of dams—which block sediment and thus impair habitat downstream by coarsening the bed where salmon historically spawned. However, there is little quantitative understanding nor a methodology for determining when a river bed has become too coarse for salmon spawning. Hence there is little scientific basis for selecting sites that would optimize the restoration benefits of gravel injection (e.g., sites where flow velocities are suitable but bed materials are too coarse for spawning). To develop a quantitative understanding of what makes river beds too coarse for salmon spawning, we studied redds and spawning use in a series of California and Washington rivers where salmon spawning ability appears to be affected by coarse bed material. Our working hypothesis is that for a given flow condition, there is a maximum “threshold” particle size that a salmon of a given size is able to excavate and/or move as she builds her redd. A second, related hypothesis is that spawning use should decrease and eventually become impossible with increasing percent coverage by immovable particles. To test these hypotheses, we quantified the sizes and spatial distributions of immovably coarse particles in a series of salmon redds in each river during the peak of spawning. We also quantified spawning use and how it relates to percent coverage by immovable particles. Results from our studies of fall-run chinook salmon (Oncorhynchus tshawytsha) in the Feather River suggest that immovable particle size varies as a function of flow velocity over the redd, implying that faster water helps fish move bigger particles. Our Feather River study also suggests that the immovable particle size varies as a function of particle shape. Results from our study of fall run chinook salmon in the Sacramento River suggest that spawning is not possible when the bed is more than 40% covered by immovable particles, consistent with our second hypotheses. We will explore these relationships further in fall 2009, when we collect data on threshold particle sizes and spawning use for both pink salmon (O. gorbuscha) in the Puyallup River, and chinook salmon in the Trinity River. Because pink salmon are significantly smaller than chinook salmon, we expect that their redd building success is constrained by a lower average threshold particle size. We expect that there will be a range of threshold sizes for each run, depending on intra-run variability in fish size and variations in flow velocity. Taken together we expect that our results will demonstrate the feasibility of a new methodology for determining when a bed has become too coarse, thus contributing to more effective management of rivers where monitoring of spawning suitability of natural gravels is a priority.

Measuring nighttime spawning behavior of chum salmon using a dual-frequency identification sonar (DIDSON)

USGS Publications Warehouse

Tiffan, K.F.; Rondorf, D.W.

2005-01-01

The striking body coloration and morphology that Pacific salmon display during spawning coupled with elaborate courtship behaviors suggest that visual cues are important during their reproductive period. To date, virtually all existing information on chum salmon (Oncorhynchus keta) spawning behavior has been derived from studies conducted during the daytime, and has contributed to the assumption that salmon do not spawn at night. We tested this assumption using a new technology - a dual-frequency identification sonar (DIDSON) - to describe and measure nighttime spawning behavior of wild chum salmon in the Columbia River. The DIDSON produces detailed, video-like images using sound, which enabled us to collect behavioral information at night in complete darkness. The display of DIDSON images enabled fish movements and behaviors to be spatially quantified. We collected continuous observational data on 14 pairs of chum salmon in a natural spawning channel during the daytime and nighttime. Spawners of both genders were observed chasing intruders during nighttime and daytime as nests were constructed. Regardless of diel period, females were engaged in digging to both construct nests and cover eggs, and courting males exhibited the pre-spawning behavior of tail crossing. We observed a total of 13 spawning events, of which nine occurred at night and four occurred during the day. The behaviors we observed at night suggest the assumption that chum salmon do not spawn at night is false. Once chum salmon begin nest construction, visual cues are apparently not required for courtship, nest defense, and spawning. We speculate that non-visual cues (e.g. tactile and auditory) enable chum salmon to carry out most spawning behaviors at night. Our findings have implications for how nighttime flows from hydroelectric dams on the Columbia River are managed for power production and protection of imperiled salmon stocks.

The spatial scale for cisco recruitment dynamics in Lake Superior during 1978-2007

USGS Publications Warehouse

Rook, Benjamin J.; Hansen, Michael J.; Gorman, Owen T.

2012-01-01

The cisco Coregonus artedi was once the most abundant fish species in the Great Lakes, but currently cisco populations are greatly reduced and management agencies are attempting to restore the species throughout the basin. To increase understanding of the spatial scale at which density‐independent and density‐dependent factors influence cisco recruitment dynamics in the Great Lakes, we used a Ricker stock–recruitment model to identify and quantify the appropriate spatial scale for modeling age‐1 cisco recruitment dynamics in Lake Superior. We found that the recruitment variation of ciscoes in Lake Superior was best described by a five‐parameter regional model with separate stock–recruitment relationships for the western, southern, eastern, and northern regions. The spatial scale for modeling was about 260 km (range = 230–290 km). We also found that the density‐independent recruitment rate and the rate of compensatory density dependence varied among regions at different rates. The density‐independent recruitment rate was constant among regions (3.6 age‐1 recruits/spawner), whereas the rate of compensatory density dependence varied 16‐fold among regions (range = −0.2 to −2.9/spawner). Finally, we found that peak recruitment and the spawning stock size that produced peak recruitment varied among regions. Both peak recruitment (0.5–7.1 age‐1 recruits/ha) and the spawning stock size that produced peak recruitment (0.3–5.3 spawners/ha) varied 16‐fold among regions. Our findings support the hypothesis that the factors driving cisco recruitment operate within four different regions of Lake Superior, suggest that large‐scale abiotic factors are more important than small‐scale biotic factors in influencing cisco recruitment, and suggest that fishery managers throughout Lake Superior and the entire Great Lakes basin should address cisco restoration and management efforts on a regional scale in each lake.

Effect of stock size, climate, predation, and trophic status on recruitment of alewives in Lake Ontario, 1978-2000

USGS Publications Warehouse

O'Gorman, Robert; Lantry, Brian F.; Schneider, Clifford P.

2004-01-01

The population of alewives Alosa pseudoharengus in Lake Ontario is of great concern to fishery managers because alewives are the principal prey of introduced salmonines and because alewives negatively influence many endemic fishes. We used spring bottom trawl catches of alewives to investigate the roles of stock size, climate, predation, and lake trophic status on recruitment of alewives to age 2 in Lake Ontario during 1978–2000. Climate was indexed from the temperature of water entering a south-shore municipal treatment plant, lake trophic status was indexed by the mean concentration of total phosphorus (TP) in surface water in spring, and predation was indexed by the product of the number of salmonines stocked and relative, first-year survival of Chinook salmonOncorhynchus tshawytscha. A Ricker-type parent–progeny model suggested that peak production of age-1 alewives could occur over a broad range of spawning stock sizes, and the fit of the model was improved most by the addition of terms for spring water temperature and winter duration. With the addition of the two climate terms, the Ricker model indicated that when water was relatively warm in spring and the winter was relatively short, peak potential production of young was nine times higher than when water temperature and winters were average, and 73 times higher than when water was cold in spring and winters were long. Relative survival from age 1 to recruitment at age 2 was best described by a multiple linear regression with terms for adult abundance, TP, and predation. Mean recruitment of age-2 fish in the 1978–1998 year-classes predicted by using the two models in sequence was only about 20% greater than the observed mean recruitment. Model estimates fit the measured data exceptionally well for all but the largest four year-classes, which suggests that the models will facilitate improvement in estimates of trophic transfer due to alewives.

Migratory salmonid redd habitat characteristics in the Salmon River, New York

USGS Publications Warehouse

Johnson, James H.; Nack, Christopher C.; McKenna, James E.

2010-01-01

Non-native migratory salmonids ascend tributaries to spawn in all the Great Lakes. In Lake Ontario, these species include Chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), steelhead (O. mykiss), and brown trout (Salmo trutta). Although successful natural reproduction has been documented for many of these species, little research has been conducted on their spawning habitat. We examined the spawning habitat of these four species in the Salmon River, New York. Differences in fish size among the species were significantly correlated with spawning site selection. In the Salmon River, the larger species spawned in deeper areas with larger size substrate and made the largest redds. Discriminant function analysis correctly classified redds by species 64–100% of the time. The size of substrate materials below Lighthouse Hill Dam is within the preferred ranges for spawning for these four species indicating that river armoring has not negatively impacted salmonid production. Intra-specific and inter-specific competition for spawning sites may influence redd site selection for smaller salmonids and could be an impediment for Atlantic salmon (S. salar) restoration.

Assessing the potential for rainbow trout reproduction in tributaries of the Mountain Fork River below Broken Bow Dam, southeastern Oklahoma

Treesearch

James M. Long; Trevor A. Starks; Tyler Farling; Robert Bastarache

2016-01-01

Stocked trout (Salmonidae) in reservoir tailwater systems in the Southern United States have been shown to use tributary streams for spawning and rearing. The lower Mountain Fork of the Little River below Broken Bow Dam is one of two year-round tailwater trout fisheries in Oklahoma, and the only one with evidence of reproduction by stocked rainbow trout (Oncorhynchus...

Fecundity of walleyes in western Lake Erie, 1966 and 1990-91

USGS Publications Warehouse

Muth, Kenneth M.; Ickes, Brian S.

1993-01-01

Ovaries were collected from walleyes (Stizostedion vitreum vitreum) in western Lake Erie just prior to spawning in 1990 and 1991 to determine current fecundity. Results were compared with fecundity determined in 1966 prior to stock rehabilitation when walleye abundance was lower and fish size at age was greater. Fecundity estimates determined from 121 fish aged 3-10 ranged from 53,000 to 426,000 eggs per female. Increases in egg production correlated with increases in length and weight, and weight accounting for most of the variability. In 1990-91 the mean egg production of the dominant age groups of spawners (ages 4 to 8) was approximately 25% lower than fishes of similar age in 1966. The mean egg diameter in 1990-91 (1.63 mm) was not related to the size or age of the fish and was not significantly smaller than the egg diameter in 1966 (1.72 mm).

75 FR 49466 - New England Fishery Management Council; Public Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-13

... Bank yellowtail flounder rebuilding strategies ABCs for stocks including Gulf of Maine winter flounder and pollock Whaleback area spawning closure Permit bank implementation Accountability measures... action to address the emergency. Special Accommodations This meeting is physically accessible to people...

Contemporary management issues confronting fisheries science

NASA Astrophysics Data System (ADS)

Frank, Kenneth T.; Brickman, David

2001-06-01

Stock collapses have occurred worldwide. The most frequently cited cause is over-fishing, suggesting that fisheries management has been ineffective in controlling exploitation rates. The progression of a fishery from an over-exploited to a collapsed state involves impairment of the reproductive capacity of the target species, i.e. recruitment over-fishing. In many cases, this occurs by reduction of the spawning stock biomass (SSB) through the systematic elimination of spawning components within a stock complex. While operational definitions of minimum levels of SSB have been developed, they have seldom been applied and never adopted in a Canadian groundfish management context. The answer to the question of how much is enough to perpetuate a stock under exploitation has been illusive. Serebryakov [J. Cons. Int. Explor. Mer, 47 (1990) 267] has advocated definition of critical levels of SSB based on survival rates (R/SSB). We review his method and discuss the utility of the approach. An alternative approach to the problem of estimating minimum SSB is through a fundamental revision of the traditional stock and recruitment relationship. Explicit theoretical SSB thresholds below which reproduction/recruitment is severely impaired based upon density-dependent mating success (or Allee effects) is considered a superior approach to the question of how much is enough because of its ecological grounding. However, the successful application of this approach will require re-definition of the space/time scales of the management unit. Finally, support is growing for the establishment of closed areas or "no-take zones" as an alternative approach to managing the problems of fishing a stock complex by enabling sub-populations to escape fishing. While the expected benefits of areas protected from fishing are numerous, clear demonstrations of benefits of such areas in marine temperate ecosystems are lacking. In fact, unintended negative consequences may result from such actions.

Spawning site fidelity and apparent annual survival of walleye (Sander vitreus) differ between a Lake Huron and Lake Erie tributary

USGS Publications Warehouse

Hayden, Todd A.; Binder, Thomas; Holbrook, Christopher; Vandergoot, Christopher; Fielder, David G.; Cooke, Steven J.; Dettmers, John M.; Krueger, Charles C.

2018-01-01

Fidelity to spawning habitats can maximise reproductive success of fish by synchronising movements to sites of previous recruitment. To determine the role of reproductive fidelity in structuring walleye Sander vitreus populations in the Laurentian Great Lakes, we used acoustic telemetry combined with Cormack–Jolly–Seber capture–recapture models to estimate spawning site fidelity and apparent annual survival for the Tittabawassee River in Lake Huron and Maumee River in Lake Erie. Walleye in spawning condition were tagged from the Tittabawassee River in Lake Huron and Maumee River in Lake Erie in 2011–2012. Site fidelity and apparent annual survival were estimated from return of individuals to the stream where tagged. Site fidelity estimates were higher in the Tittabawassee River (95%) than the Maumee River (70%) and were not related to sex or fish length at tagging. Apparent annual survival of walleye tagged in the Tittabawassee did not differ among spawning seasons but was higher for female than male walleye and decreased linearly as fish length increased. Apparent annual survival of walleye tagged in the Maumee River did not differ among spawning seasons but was higher for female walleye than male walleye and increased linearly as fish length increased. Greater fidelity of walleye tagged in the Tittabawassee River than walleye tagged in the Maumee River may be related to the close proximity to the Maumee River of other spawning aggregations and multiple spawning sites in Lake Erie. As spawning site fidelity increases, management actions to conserve population structure require an increasing focus on individual stocks.

Reproductive Biology of Albacore Tuna (Thunnus alalunga) in the Western Indian Ocean

PubMed Central

Dhurmeea, Zahirah; Zudaire, Iker; Chassot, Emmanuel; Cedras, Maria; Nikolic, Natacha; Bourjea, Jérôme; West, Wendy; Appadoo, Chandani

2016-01-01

The reproductive biology of albacore tuna, Thunnus alalunga, in the western Indian Ocean was examined through analysis of the sex ratio, spawning season, length-at-maturity (L50), spawning frequency and fecundity. From 2013 to 2015, a total of 923 female and 867 male albacore were sampled. A bias in sex ratio was found in favor of females with fork length (LF) < 100 cm. Using histological analyses and gonadosomatic index, spawning was found to occur between 10°S and 30°S, mainly to the east of Madagascar from October to January. Large females contributed more to reproduction through their longer spawning period compared to small individuals. The L50 (mean ± standard error) of female albacore was estimated at 85.3 ± 0.7 cm LF. Albacore spawn on average every 2.2 days within the spawning region and spawning months, from November to January. Batch fecundity ranged between 0.26 and 2.09 million oocytes and the relative batch fecundity (mean ± standard deviation) was estimated at 53.4 ± 23.2 oocytes g-1 of somatic-gutted weight. The study provides new information on the reproductive development and classification of albacore in the western Indian Ocean. The reproductive parameters will reduce uncertainty in current stock assessment models which will eventually assist the fishery to be sustainable for future generations. PMID:28002431

Life history characteristics of a recovering lake whitefish Coregonus clupeaformis stock in the Detroit River, North America

USGS Publications Warehouse

Roseman, Edward F.; Kennedy, Gregory W.; Manny, Bruce A.; Boase, James; McFee, James; Tallman, Ross F.; Howland, Kimberly L.; Rennie, Michael D.; Mills, Kenneth; Tallman, Ross F.; Howland, Kimberly L.; Rennie, Michael D.; Mills, Kenneth

2012-01-01

The Detroit River is part of a channel connecting Lakes Huron and Erie and was once a prolific spawning area for lake whitefish, Coregonus clupeaformis. Large numbers of lake whitefish migrated into the river to spawn where they were harvested by commercial fisheries and for fish culture operations. Prior to our study, the last lake whitefish was landed from the Detroit River in 1925. Loss of spawning habitat during shipping channel construction and over-fishing, likely reduced lake whitefish spawning runs. Because lake whitefish are recovering in Lake Erie, and spawning in the western basin, we suspected they may also be spawning in the Detroit River. We sampled in the Detroit River for lake whitefish adults and eggs in October–December 2005–07 and for larvae during March–May 2006–08. A total of 15 spawning-ready lake whitefish from 4 to 18 years old, were collected. Viable eggs were collected during mid-November 2006–07; highest egg densities were found mid-river. Sac-fry whitefish larvae were collected in the river and near the river mouth. No whitefish larvae were retained in the river. Because high numbers of larvae were collected from mid- and downstream river sites, reproduction of lake whitefish in the Detroit River could contribute substantially to the Lake Erie lake whitefish metapopulation.

Re-Introduction of Lower Columbia River Chum Salmon into Duncan Creek, 2001-2002 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hillson, Todd D.

2002-10-01

The National Marine Fisheries Service (NMFS) listed Lower Columbia River chum as threatened under the auspices of the Endangered Species Act (ESA) in March of 1999 (64 FR 14508, March 25, 1999). The listing was in response to reduction in abundance from historical levels of more than half a million returning adults to fewer than 10,000 spawners present day (Johnson et al. 1997). Harvest, loss of habitat, changes in flow regimes, riverbed movement and heavy siltation have been largely responsible for the decline in this species in the Columbia River. The timing of seasonal changes in river flow and watermore » temperatures is perhaps the most critical factor in structuring the freshwater life history of chum salmon (Johnson et al. 1997). This is especially true of the population located directly below Bonneville Dam where hydropower operations can block access to spawning sites, dewater redds, strand fry, cause scour or fill of redds and increase sedimentation of spawning gravels. The recovery strategy for Lower Columbia River chum as outlined in the Hatchery Genetic Management Plan (HGMP) for the Grays River project has four main tasks. First, determine if remnant populations of Lower Columbia River chum salmon exist in Lower Columbia River tributaries. Second, if such populations exist, develop stock-specific recovery plans that would involve habitat restoration including the creation of spawning refugias, supplementation if necessary and a habitat and fish monitoring and evaluation plan. If chum have been extirpated from previously utilized streams, develop re-introduction plans that utilize appropriate genetic donor stock(s) of Lower Columbia River chum salmon and integrate habitat improvement and fry-to-adult survival evaluations. Third, reduce the extinction risk to Grays River chum salmon population by randomly capturing adults in the basin for use in a supplementation program and reintroduction of Lower Columbia River chum salmon into the Chinook River basin. The Duncan Creek project has two goals: (1) re-introduction of chum into Duncan Creek by providing off channel high quality spawning and incubation areas and (2) to simultaneously evaluate natural re-colonization and a supplementation strategy where adults are collected and spawned artificially at a hatchery. The eggs from these artificial crossings are then either incubated at Duncan Creek or incubated and the fry reared at the hatchery to be released back into Duncan Creek. Tasks associated with the first goal include: (1) removing mud, sand and organics present in four of the creek branches and replace with gravels expected to provide maximum egg-to-fry survival rates to a depth of at least two feet; (2) armoring the sides of these channels to reduce importation of sediment by fish spawning on the margins; (3) planting native vegetation adjacent to these channels to stabilize the banks, trap silt and provide shade; (4) annual sampling of gravel in the spawning channels to detect changes in gravel composition and sedimentation levels.« less

Factors Regulating Early Life History Dispersal of Atlantic Cod (Gadus morhua) from Coastal Newfoundland

PubMed Central

Stanley, Ryan R. E.; deYoung, Brad; Snelgrove, Paul V. R.; Gregory, Robert S.

2013-01-01

To understand coastal dispersal dynamics of Atlantic cod (Gadus morhua), we examined spatiotemporal egg and larval abundance patterns in coastal Newfoundland. In recent decades, Smith Sound, Trinity Bay has supported the largest known overwintering spawning aggregation of Atlantic cod in the region. We estimated spawning and dispersal characteristics for the Smith Sound-Trinity Bay system by fitting ichthyoplankton abundance data to environmentally-driven, simplified box models. Results show protracted spawning, with sharply increased egg production in early July, and limited dispersal from the Sound. The model for the entire spawning season indicates egg export from Smith Sound is 13%•day−1 with a net mortality of 27%•day–1. Eggs and larvae are consistently found in western Trinity Bay with little advection from the system. These patterns mirror particle tracking models that suggest residence times of 10–20 days, and circulation models indicating local gyres in Trinity Bay that act in concert with upwelling dynamics to retain eggs and larvae. Our results are among the first quantitative dispersal estimates from Smith Sound, linking this spawning stock to the adjacent coastal waters. These results illustrate the biophysical interplay regulating dispersal and connectivity originating from inshore spawning of coastal northwest Atlantic. PMID:24058707

Importance of tributary streams for rainbow trout reproduction: insights from a small stream in Georgia and a bi-genomic approach

USGS Publications Warehouse

Lee, D.; Lack, Justin B.; Van Den Bussche, Ronald A.; Long, James M.

2012-01-01

Tributaries of tailwater fisheries in the southeastern USA have been used for spawning by stocked rainbow trout (Oncorhynchus mykiss), but their importance may have been underestimated using traditional fish survey methods such as electrofishing and redd counts. We used a bi-genomic approach, mitochondrial DNA sequences and nuclear microsatellite loci, to estimate the number of spawning adults in one small tributary (Cabin Creek) of the Chattahoochee River, Georgia, where rainbow trout are known to spawn and have successful recruitment. We extracted and analysed DNA from seven mature male rainbow trout and four juveniles that were captured in February 2006 in Cabin Creek and from 24 young-of-year (YOY) trout that were captured in April 2006. From these samples, we estimated that 24 individuals were spawning to produce the amount of genetic variation observed in the juveniles and YOY, although none of the mature males we sampled were indicated as sires. Analysis of the mitochondrial D-loop region identified four distinct haplotypes, suggesting that individuals representing four maternal lineages contributed to the offspring. Our analyses indicated that many more adults were spawning in this system than previously estimated with direct count methods and provided insight into rainbow trout spawning behavior.

Differential response of continental stock complexes of Atlantic salmon (Salmo salar) to the Atlantic Multidecadal Oscillation

NASA Astrophysics Data System (ADS)

Friedland, Kevin D.; Shank, Burton V.; Todd, Christopher D.; McGinnity, Philip; Nye, Janet A.

2014-05-01

Atlantic salmon, Salmo salar, in the North Atlantic are managed as a set of population complexes distributed in North America and Europe. In recent years, these complexes have experienced reduced marine survival and many populations within the complexes are at risk, especially those at the southern ends of the species amphi-Atlantic range. Atlantic salmon is an anadromous fish dividing its life history between residence in freshwater and the marine environment. The freshwater portion of the life history includes spawning and the rearing of juveniles where in-river production has tended to be relatively stable, whereas the first year at sea, termed the post-smolt year, is characterized by more variable rates of mortality. Although their habitats are widely separated geographically along the North Atlantic seaboards, strong recruitment coherence exists between North American and European stock complexes. This recruitment coherence is correlated with ocean temperature variation associated with the Atlantic Multidecadal Oscillation (AMO). The North Atlantic Oscillation (NAO) appears to be relatively unimportant as a driver of salmon abundance. The mechanism determining the link between AMO-related thermal variation and abundance appears to differ fundamentally for the two continental stock groupings. Whereas ocean climate variability during the first springtime months of juvenile salmon migration to sea appears to be important to the survival of North American stocks, summer climate variation appears to be central to adult recruitment variation for European stocks. This contrast in seasonal effects appears to be related to the varying roles of predation pressure and size-related mortality on the continental stock complexes. The anticipated warming due to global climate change will impose thermal conditions on salmon populations outside historical context and challenge the ability of many populations to persist.

Implementation of genetic conservation practices in a muskellunge propagation and stocking program

USGS Publications Warehouse

Jennings, Martin J.; Sloss, Brian L.; Hatzenbeler, Gene R.; Kampa, Jeffrey M.; Simonson, Timothy D.; Avelallemant, Steven P.; Lindenberger, Gary A.; Underwood, Bruce D.

2010-01-01

Conservation of genetic resources is a challenging issue for agencies managing popular sport fishes. To address the ongoing potential for genetic risks, we developed a comprehensive set of recommendations to conserve genetic diversity of muskellunge (Esox masquinongy) in Wisconsin, and evaluated the extent to which the recommendations can be implemented. Although some details are specific to Wisconsin's muskellunge propagation program, many of the practical issues affecting implementation are applicable to other species and production systems. We developed guidelines to restrict future broodstock collection operations to lakes with natural reproduction and to develop a set of brood lakes to use on a rotational basis within regional stock boundaries, but implementation will require considering lakes with variable stocking histories. Maintaining an effective population size sufficient to minimize the risk of losing alleles requires limiting broodstock collection to large lakes. Recommendations to better approximate the temporal distribution of spawning in hatchery operations and randomize selection of brood fish are feasible. Guidelines to modify rearing and distribution procedures face some logistic constraints. An evaluation of genetic diversity of hatchery-produced fish during 2008 demonstrated variable success representing genetic variation of the source population. Continued evaluation of hatchery operations will optimize operational efficiency while moving toward genetic conservation goals.

Spawning strategy in Atlantic bobtail squid Sepiola atlantica (Cephalopoda: Sepiolidae)

NASA Astrophysics Data System (ADS)

Rodrigues, Marcelo; Garcí, Manuel E.; Troncoso, Jesús S.; Guerra, Ángel

2011-03-01

This study aimed to determine the spawning strategy in the Atlantic bobtail squid Sepiola atlantica, in order to add new information to the knowledge of its reproductive strategy. A total of 12 females that spawned in aquaria were examined. Characteristics of the reproductive traits and egg clutches were similar to those of other known Sepiolidae. Clutch size varied from 31 up to 115 eggs. Females of this species had incorporated up to 1.58 times of their body weight into laid eggs. The size of laid eggs showed a positive correlation with maternal body size, supporting the idea that female size is a determinant of egg size. Our data suggest that S. atlantica is an intermittent terminal spawner , and that its spawning strategy comprises group-synchronous ovary maturation, multiple egg laying, and deposition of egg clutches in different locations. The obtained data provide insights for future comparative studies on reproductive allocation.

Reproductive Potential of Salmon Spawning Substrates Inferred from Grain Size and Fish Length

NASA Astrophysics Data System (ADS)

Riebe, C. S.; Sklar, L. S.; Overstreet, B. T.; Wooster, J. K.; Bellugi, D. G.

2014-12-01

The river restoration industry spends millions of dollars every year on improving salmon spawning in riverbeds where sediment is too big for fish to move and thus use during redd building. However, few studies have addressed the question of how big is too big in salmon spawning substrates. Hence managers have had little quantitative basis for gauging the amount of spawning habitat in coarse-bedded rivers. Moreover, the scientific framework has remained weak for restoration projects that seek to improve spawning conditions. To overcome these limitations, we developed a physically based, field-calibrated model for the fraction of the bed that is fine-grained enough to support spawning by fish of a given size. Model inputs are fish length and easy-to-measure indices of bed-surface grain size. Model outputs include the number of redds and eggs the substrate can accommodate when flow depth, temperature, and other environmental factors are not limiting. The mechanistic framework of the model captures the biophysical limits on sediment movement and the space limitations on redd building and egg deposition in riverbeds. We explored the parameter space of the model and found a previously unrecognized tradeoff in salmon size: bigger fish can move larger sediment and thus use more riverbed area for spawning; they also tend to have higher fecundity, and so can deposit more eggs per redd; however, because redd area increases with fish length, the number of eggs a substrate can accommodate is highest for moderate-sized fish. One implication of this tradeoff is that differences in grain size may help regulate river-to-river differences in salmon size. Thus, our model suggests that population diversity and, by extension, species resilience are linked to lithologic, geomorphic, and climatic factors that determine grain size in rivers. We cast the model into easy-to-use look-up tables, charts, and computer applications, including a JavaScript app that works on tablets and mobile phones. We explain how these tools can be used in a new, mechanistic approach to assessing spawning substrates and optimizing gravel augmentation projects in coarse-bedded rivers.

Quantifying six decades of fishery selection for size and age at maturity in sockeye salmon

PubMed Central

Kendall, Neala W; Hard, Jeffrey J; Quinn, Thomas P

2009-01-01

Life history traits of wild animals can be strongly influenced, both phenotypically and evolutionarily, by hunting and fishing. However, few studies have quantified fishery selection over long time periods. We used 57 years of catch and escapement data to document the magnitude of and trends in gillnet selection on age and size at maturity of a commercially and biologically important sockeye salmon stock. Overall, the fishery has caught larger fish than have escaped to spawn, but selection has varied over time, becoming weaker and less consistent recently. Selection patterns were strongly affected by fish age and sex, in addition to extrinsic factors including fish abundance, mesh size regulations, and fish length variability. These results revealed a more complex and changing pattern of selective harvest than the ‘larger is more vulnerable’ model, emphasizing the need for quantified, multi-year studies before conclusions can be drawn about potential evolutionary and ecological effects of fishery selection. Furthermore, the results indicate that biologically robust escapement goals and prevention of harvest of the largest individuals may help prevent negative effects of size-selective harvest. PMID:25567896

Flatfish recruitment response to decadal climatic variability and ocean conditions in the eastern Bering Sea

NASA Astrophysics Data System (ADS)

Wilderbuer, T. K.; Hollowed, A. B.; Ingraham, W. J.; Spencer, P. D.; Conners, M. E.; Bond, N. A.; Walters, G. E.

2002-10-01

This paper provides a retrospective analysis of the relationship of physical oceanography and biology and recruitment of three Eastern Bering Sea flatfish stocks: flathead sole ( Hippoglossoides elassodon), northern rock sole ( Lepidopsetta polyxystra), and arrowtooth flounder ( Atheresthes stomias) for the period 1978-1996. Temporal trends in flatfish production in the Eastern Bering Sea are consistent with the hypothesis that decadal scale climate variability influences marine survival during the early life history period. Density-dependence (spawning stock size) is statistically significant in a Ricker model of flatfish recruitment, which includes environmental terms. Wind-driven advection of flatfish larvae to favorable nursery grounds was also found to coincide with years of above-average recruitment through the use of an ocean surface current simulation model (OSCURS). Ocean forcing of Bristol Bay surface waters during springtime was mostly shoreward (eastward) during the 1980s and seaward (westerly) during the 1990s, corresponding with periods of good and poor recruitment. Distance from shore and water depth at the endpoint of 90-day drift periods (estimated time of settlement) were also found to correspond with flatfish productivity.

Incorporating covariates into fisheries stock assessment models with application to Pacific herring.

PubMed

Deriso, Richard B; Maunder, Mark N; Pearson, Walter H

2008-07-01

We present a framework for evaluating the cause of fishery declines by integrating covariates into a fisheries stock assessment model. This allows the evaluation of fisheries' effects vs. natural and other human impacts. The analyses presented are based on integrating ecological science and statistics and form the basis for environmental decision-making advice. Hypothesis tests are described to rank hypotheses and determine the size of a multiple covariate model. We extend recent developments in integrated analysis and use novel methods to produce effect size estimates that are relevant to policy makers and include estimates of uncertainty. Results can be directly applied to evaluate trade-offs among alternative management decisions. The methods and results are also broadly applicable outside fisheries stock assessment. We show that multiple factors influence populations and that analysis of factors in isolation can be misleading. We illustrate the framework by applying it to Pacific herring of Prince William Sound, Alaska (USA). The Pacific herring stock that spawns in Prince William Sound is a stock that has collapsed, but there are several competing or alternative hypotheses to account for the initial collapse and subsequent lack of recovery. Factors failing the initial screening tests for statistical significance included indicators of the 1989 Exxon Valdez oil spill, coho salmon predation, sea lion predation, Pacific Decadal Oscillation, Northern Oscillation Index, and effects of containment in the herring egg-on-kelp pound fishery. The overall results indicate that the most statistically significant factors related to the lack of recovery of the herring stock involve competition or predation by juvenile hatchery pink salmon on herring juveniles. Secondary factors identified in the analysis were poor nutrition in the winter, ocean (Gulf of Alaska) temperature in the winter, the viral hemorrhagic septicemia virus, and the pathogen Ichthyophonus hoferi. The implication of this result to fisheries management in Prince William Sound is that it may well be difficult to simultaneously increase the production of pink salmon and maintain a viable Pacific herring fishery. The impact can be extended to other commercially important fisheries, and a whole ecosystem approach may be needed to evaluate the costs and benefits of salmon hatcheries.

Ecology of Siberian Taimen Hucho taimen in the Lake Baikal Basin

USGS Publications Warehouse

Matveyev, Arcadi N.; Pronin, Nikolai M.; Samusenok, Vitali P.; Bronte, Charles R.

1998-01-01

Taimen Hucho taimen historically inhabited most tributaries and littoral areas of Lake Baikal, in south central Siberia, where they supported subsistence and commercial fisheries. Logging, pollution, and overfishing have caused dramatic population declines or local extinction of most stocks. Most of what is known about this species has been published in eastern journals and therefore is not readily available to western scientists. New data collected during the 1980s and 1990s have been combined with other reports to provide an overview of the biology and life history of this species. Taimen are long-lived fish and can reach ages of 29 years and sizes up to 60 kg. Populations can either be strictly riverine or anadromous. Adults from both life histories ascend rivers in spring to spawn and feed, and less extensive migrations occur in fall to prey on spawning omul (Coregonus autumnalis migratorius). Principal food items for age 1 and 2 taimen are macroinvertebrates, but young taimen quickly become piscivorous at age 2 when they consume mainly black Baikal grayling (Thymallus arcticus baicalensis), and sculpins (Taracottus kneri, Cottus kesslerij). Males reach sexual maturity at ages 7 to 8 and later for females at ages 8 to 9. Average egg production per female was about 22,000 eggs. Parasite burdens are heavy but composed of few species and mediated by prey items consumed. This fish is a highly-specialized predator and plays an indispensable role in the structure of fish communities in mountains and foothills. Taimen conservation in the Baikal region is impossible without adoption and implementation of a dedicated rehabilitation program that includes the protection of remaining populations and habitat, and possibly introduction of hatchery-reared fish in selected areas where habitat remains, but parental stocks are low.

A stockpile of ova in the grass frog Rana temporaria is established once for the life span. Do ovaries in amphibians and in mammals follow the same evolutionary strategy?

PubMed

Ogielska, Maria; Kotusz, Agnieszka; Augustyńska, Renata; Ihnatowicz, Jerzy; Paśko, Łukasz

2013-04-01

Most anuran amphibians produce high numbers of eggs during several consecutive breeding seasons. The question is still open whether oocytes are formed anew as a result of oogonial proliferation after each spawning or the definitive pool of oocytes is established during the juvenile period and is sufficient for the whole reproductive life span of a female. Our quantitative studies show that primary oogonia in adult female frogs can proliferate, but they fail to differentiate further and do not enter meiosis, and thereby there is no supplementation of new generations of oocytes after each spawning. Ovaries of one-year-old grass frogs contain (median) 53,447 diplotene oocytes, in two-years-old frogs this number decreased to 33,583 and eventually reached 25,679 in virgin mature females. More than 50% decrease in the total oocyte number was accompanied by massive degeneration (atresia) of oocytes. The final number of oocytes in a female forms a stock for 11-12 breeding seasons and exceeds the number of eggs produced during the potential reproductive life span of this species. The phylogenetic context of oocyte recruitment modes in the major clades of vertebrates is discussed in respect to their ability to replenish the stock (a renewable stock in ovaries named "open" vs. a non-renewable stock in ovaries named "closed"). Copyright © 2013 Wiley Periodicals, Inc.

Do walleye pollock exhibit flexibility in where or when they spawn based on variability in water temperature?

NASA Astrophysics Data System (ADS)

Bacheler, Nathan M.; Ciannelli, Lorenzo; Bailey, Kevin M.; Bartolino, Valerio

2012-06-01

Environmental variability is increasingly recognized as a primary determinant of year-class strength of marine fishes by directly or indirectly influencing egg and larval development, growth, and survival. Here we examined the role of annual water temperature variability in determining when and where walleye pollock (Theragra chalcogramma) spawn in the eastern Bering Sea. Walleye pollock spawning was examined using both long-term ichthyoplankton data (N=19 years), as well as with historical spatially explicit, foreign-reported, commercial catch data occurring during the primary walleye pollock spawning season (February-May) each year (N=22 years in total). We constructed variable-coefficient generalized additive models (GAMs) to relate the spatially explicit egg or adult catch-per-unit-effort (CPUE) to predictor variables including spawning stock biomass, season, position, and water temperature. The adjusted R2 value was 63.1% for the egg CPUE model and 35.5% for the adult CPUE model. Both egg and adult GAMs suggest that spawning progresses seasonally from Bogoslof Island in February and March to Outer Domain waters between the Pribilof and Unimak Islands by May. Most importantly, walleye pollock egg and adult CPUE was predicted to generally increase throughout the study area as mean annual water temperature increased. These results suggest low interannual variability in the spatial and temporal dynamics of walleye pollock spawning regardless of changes in environmental conditions, at least at the spatial scale examined in this study and within the time frame of decades.

Lake Characteristics Influencing Spawning Success of Muskellunge in Northern Wisconsin Lakes

Treesearch

Ashley J. Rust; James S. Diana; Terry L. Margenau; Clayton J. Edwards

2002-01-01

We determined the physical, chemical, biological, and land use characteristics that distinguish northern Wisconsin lakes with self-sustaining populations of muskellunge Esox masquinongy from lakes where stocking is required to maintain populations. Lakes that supported self-sustaining muskellunge populations were characterized by fewer shoreline...

Size of spawning population, residence time, and territory shifts of individuals in the spawning aggregation of a riverine catostomid

USGS Publications Warehouse

Grabowski, T.B.; Isely, J.J.

2008-01-01

Little is known about the behavior of individual fish in a spawning aggregation, specifically how long an individual remains in an aggregation. We monitored Moxostoma robustum (Cope) (Robust Redhorse) in a Savannah River spawning aggregation during spring 2004 and 2005 to provide an estimate of the total number of adults and the number of males comprising the aggregation and to determine male residence time and movements within a spawning aggregation. Robust Redhorse were captured using prepostioned grid electrofishers, identified to sex, weighed, measured, and implanted with a passive integrated transponder. Spawning aggregation size was estimated using a multiple census mark-and-recapture procedure. The spawning aggregation seemed to consist of approximately the same number of individuals (82-85) and males (50-56) during both years of this study. Individual males were present for a mean of 3.6 ?? 0.24 days (?? SE) during the 12-day spawning period. The mean distance between successive recaptures of individual males was 15.9 ?? 1.29 m (?? SE). We conclude that males establish spawning territories on a daily basis and are present within the spawning aggregation for at least 3-4 days. The relatively short duration of the aggregation may be the result of an extremely small population of adults. However, the behavior of individuals has the potential to influence population estimates made while fish are aggregated for spawning.

Population-regulating processes during the adult phase in flatfish

NASA Astrophysics Data System (ADS)

Rijnsdorp, A. D.

Flatfish support major fisheries and the study of regulatory processes are of paramount importance for evaluating the resilience of the resource to exploitation. This paper reviews the evidence for processes operating during the adult phase that may 1. generate interannual variability in recruitment; 2. contribute to population regulation through density-dependent growth, density-dependent ripening of adults and density-dependent egg production. With regard to (1), there is evidence that in the adult phase processes do occur that may generate recruitment variability through variation in size-specific fecundity, contraction of spawning season, reduction in egg quality, change in sex ratio and size composition of the adult population. However, time series of recruitment do not provide support for this hypothesis. With regard to (2), there is ample evidence that exploitation of flatfish coincides with an increase in growth, although the mechanisms involved are not always clear. The presence of density-dependent growth in the adult phase of unexploited populations appears to be the most likely explanation in some cases. From the early years of exploitation of flatfish stocks inhabiting cold waters, evidence exists that adult fish do not spawn each year. Fecundity schedules show annual variations, but the available information suggests that size-specific fecundity is stable over a broad range of population abundance and may only decrease at high population abundance. The analysis is complicated by the possibility of a trade-off between egg numbers and egg size. Nevertheless, a density-dependent decrease in growth will automatically result in a decrease in absolute fecundity because of the reduced body size. The potential contribution of these regulatory effects on population regulation is explored. Results indicate that density-dependent ripening and absolute fecundity, mediated through density-dependent growth, may control recruitment at high levels of population abundance. The effect of a density-dependent decrease in size-specific fecundity seems to play a minor role, although this role may become important at extremely high levels of population abundance.

Episootiology of viral hemorrhagic septicemia virus in Pacific herring from the spawn-on-kelp fishery in Prince William Sound, Alaska, USA

USGS Publications Warehouse

Hershberger, P.K.; Kocan, R.M.; Elder, N.E.; Meyers, T.R.; Winton, J.R.

1999-01-01

Both the prevalence and tissue titer of viral hemorrhagic septicemia virus (VHSV) increased in Pacific herring Clupea pallasi following their introduction into net pens (pounds) used in the closed pound spawn-on-kelp (SOK) fishery in Prince William Sound, Alaska. VHSV was also found in water samples from inside and outside the SOK pounds after herring had been confined for several days; however, water samples taken near wild free-ranging, spawning herring either failed to test positive or tested weakly positive for virus. Little or no virus was found in tissue samples from free-ranging, spawning herring captured from the vicinity of the pounds, nor did the prevalence of VHSV increase following spawning as it did in impounded herring. The data indicated that increased prevalences of VHSV were correlated with confinement of herring for the closed pound SOK fishery and that infection was spread within the pounds through waterborne exposure to virus particles originating from impounded fish. In addition, pounds containing predominantly young fish had higher prevalences of VHSV, suggesting that older fish may be partially immune, perhaps as a result of previous infection with the virus. Operation of SOK pounds during spawning seasons in which young herring predominate may amplify the disease and possibly exacerbate the population fluctuations observed in wild herring stocks.

Epizootiology of viral hemorrhagic septicemia virus in Pacific herring from the spawn-on-kelp fishery in Prince William Sound, Alaska, USA

USGS Publications Warehouse

Hershberger, P.K.; Kocan, R.M.; Elder, N.E.; Meyers, T.R.; Winton, J.R.

1999-01-01

Both the prevalence and tissue titer of viral hemorrhagic septicemia virus (VHSV) increased in Pacific herring Clupea pallasi following their introduction into net pens (pounds) used in the closed pound spawn-on-kelp (SOK) fishery in Prince William Sound, Alaska. VHSV was also found in water samples from inside and outside the SOK pounds after herring had been confined for several days; however, water samples taken near wild free-ranging, spawning herring either failed to test positive or tested weakly positive for virus. Little or no virus was found in tissue samples from free-ranging, spawning herring captured from the vicinity of the pounds, nor did the prevalence of VHSV increase following spawning as it did in impounded herring. The data indicated that increased prevalences of VHSV were correlated with confinement of herring for the closed pound SOK fishery and that infection was spread within the pounds through waterborne exposure to virus particles originating from impounded fish. In addition, pounds containing predominantly young fish had higher prevalences of VHSV, suggesting that older fish may be partially immune, perhaps as a result of previous infection with the virus. Operation of SOK pounds during spawning seasons in which young herring predominate may amplify the disease and possibly exacerbate the population fluctuations observed in wild herring stocks.

Habitat suitability of the Atlantic bluefin tuna by size class: An ecological niche approach

NASA Astrophysics Data System (ADS)

Druon, Jean-Noël; Fromentin, Jean-Marc; Hanke, Alex R.; Arrizabalaga, Haritz; Damalas, Dimitrios; Tičina, Vjekoslav; Quílez-Badia, Gemma; Ramirez, Karina; Arregui, Igor; Tserpes, George; Reglero, Patricia; Deflorio, Michele; Oray, Isik; Saadet Karakulak, F.; Megalofonou, Persefoni; Ceyhan, Tevfik; Grubišić, Leon; MacKenzie, Brian R.; Lamkin, John; Afonso, Pedro; Addis, Piero

2016-03-01

An ecological niche modelling (ENM) approach was used to predict the potential feeding and spawning habitats of small (5-25 kg, only feeding) and large (>25 kg) Atlantic bluefin tuna (ABFT), Thunnus thynnus, in the Mediterranean Sea, the North Atlantic and the Gulf of Mexico. The ENM was built bridging knowledge on ecological traits of ABFT (e.g. temperature tolerance, mobility, feeding and spawning strategy) with patterns of selected environmental variables (chlorophyll-a fronts and concentration, sea surface current and temperature, sea surface height anomaly) that were identified using an extensive set of precisely geo-located presence data. The results highlight a wider temperature tolerance for larger fish allowing them to feed in the northern - high chlorophyll levels - latitudes up to the Norwegian Sea in the eastern Atlantic and to the Gulf of Saint Lawrence in the western basin. Permanent suitable feeding habitat for small ABFT was predicted to be mostly located in temperate latitudes in the North Atlantic and in the Mediterranean Sea, as well as in subtropical waters off north-west Africa, while summer potential habitat in the Gulf of Mexico was found to be unsuitable for both small and large ABFTs. Potential spawning grounds were found to occur in the Gulf of Mexico from March-April in the south-east to April-May in the north, while favourable conditions evolve in the Mediterranean Sea from mid-May in the eastern to mid-July in the western basin. Other secondary potential spawning grounds not supported by observations were predicted in the Azores area and off Morocco to Senegal during July and August when extrapolating the model settings from the Gulf of Mexico into the North Atlantic. The presence of large ABFT off Florida and the Bahamas in spring was not explained by the model as is, however the environmental variables other than the sea surface height anomaly appeared to be favourable for spawning in part of this area. Defining key spatial and temporal habitats should further help in building spatially-explicit stock assessment models, thus improving the spatial management of bluefin tuna fisheries.

The sex lives of ctenophores: the influence of light, body size, and self-fertilization on the reproductive output of the sea walnut, Mnemiopsis leidyi.

PubMed

Sasson, Daniel A; Ryan, Joseph F

2016-01-01

Ctenophores (comb jellies) are emerging as important animals for investigating fundamental questions across numerous branches of biology (e.g., evodevo, neuroscience and biogeography). A few ctenophore species including, most notably, Mnemiopsis leidyi, are considered as invasive species, adding to the significance of studying ctenophore ecology. Despite the growing interest in ctenophore biology, relatively little is known about their reproduction. Like most ctenophores, M. leidyi is a simultaneous hermaphrodite capable of self-fertilization. In this study, we assess the influence of light on spawning, the effect of body size on spawning likelihood and reproductive output, and the cost of self-fertilization on egg viability in M. leidyi. Our results suggest that M. leidyi spawning is more strongly influenced by circadian rhythms than specific light cues and that body size significantly impacts spawning and reproductive output. Mnemiopsis leidyi adults that spawned alone produced a lower percentage of viable embryos versus those that spawned in pairs, suggesting that self-fertilization may be costly in this species. These results provide insight into the reproductive ecology of M. leidyi and provide a fundamental resource for researchers working with them in the laboratory.

Migration patterns of post-spawning Pacific herring in a subarctic sound

NASA Astrophysics Data System (ADS)

Bishop, Mary Anne; Eiler, John H.

2018-01-01

Understanding the distribution of Pacific herring (Clupea pallasii) can be challenging because spawning, feeding and overwintering may take place in different areas separated by 1000s of kilometers. Along the northern Gulf of Alaska, Pacific herring movements after spring spawning are largely unknown. During the fall and spring, herring have been seen moving from the Gulf of Alaska into Prince William Sound, a large embayment, suggesting that fish spawning in the Sound migrate out into the Gulf of Alaska. We acoustic-tagged 69 adult herring on spawning grounds in Prince William Sound during April 2013 to determine seasonal migratory patterns. We monitored departures from the spawning grounds as well as herring arrivals and movements between the major entrances connecting Prince William Sound and the Gulf of Alaska. Departures of herring from the spawning grounds coincided with cessation of major spawning events in the immediate area. After spawning, 43 of 69 tagged herring (62%) moved to the entrances of Prince William Sound over a span of 104 d, although most fish arrived within 10 d of their departure from the spawning grounds. A large proportion remained in these areas until mid-June, most likely foraging on the seasonal bloom of large, Neocalanus copepods. Pulses of tagged herring detected during September and October at Montague Strait suggest that some herring returned from the Gulf of Alaska. Intermittent detections at Montague Strait and the Port Bainbridge passages from September through early January (when the transmitters expired) indicate that herring schools are highly mobile and are overwintering in this area. The pattern of detections at the entrances to Prince William Sound suggest that some herring remain in the Gulf of Alaska until late winter. The results of this study confirm the connectivity between local herring stocks in Prince William Sound and the Gulf of Alaska.

Surficial substrates and bathymetry of five historical lake trout spawning reefs in near-shore waters of the Great Lakes

USGS Publications Warehouse

Edsall, Thomas A.; Brown, Charles L.; Kennedy, Gregory W.; French, John R. P.

1992-01-01

The reestablishment of self-sustaining stocks of lake trout (Salvelinus namaycush) in the lower four Great Lakes has been substantially impeded because planted fish do not produce enough progeny that survive and reproduce. The causes for this failure are unknown, but many historical spawning sites of lake trout have been degraded by human activities and can no longer produce viable swim-up fry. In this study, we used side-scan sonar and an underwater video camera to survey, map, and evaluate the sustainability of one reef in each of the five Great Lakes for lake trout spawning and fry production. At four of the reef sites, we found good-to-excellent substrate for spawning and fry production by the shallow-water strains of lake trout that are now being planted. These substrates were in water 6-22 m deep and were composed largely of rounded or angular rubble and cobble. Interstitial spaces in these substrates were 20 cm or deeper and would protect naturally spawned eggs and fry from predators, ice scour, and buffeting by waves and currents. Subsequent studies of egg survival by other researchers confirmed our evaluation that the best substrates at two of these sites still have the potential to produce viable swim-up fry.

Characterization of the spawning habitat of Atlantic bluefin tuna and related species in the Balearic Sea (western Mediterranean)

NASA Astrophysics Data System (ADS)

Alemany, F.; Quintanilla, L.; Velez-Belchí, P.; García, A.; Cortés, D.; Rodríguez, J. M.; Fernández de Puelles, M. L.; González-Pola, C.; López-Jurado, J. L.

2010-07-01

Within the framework of the TUNIBAL project that focused on Atlantic bluefin tuna ( Thunnus thynnus) larval ecology, ichthyoplankton surveys were conducted from 2001 to 2005 off the Balearic archipelago, which is recognized as one of the main spawning areas of the eastern Atlantic stock of this species. In each survey, a regular sampling grid of about 200 stations, 10 nautical miles apart were sampled. CTD casts and oblique Bongo 60 and surface Bongo 90 plankton tows were carried out. The occurrence frequencies of Atlantic bluefin tuna, albacore tuna ( Thunnus alalunga) and bullet tuna ( Auxis rochei) larvae in quantitative Bongo 60 samples were 0.14, 0.29 and 0.49 respectively. Mean larval abundances in these positive samples were relatively high: 31 larvae 10 m -2 for Atlantic bluefin tuna, 17 for albacore tuna and 31 for bullet tuna. All species had patchy distributions since more than 90% of the stations showed larval densities under 10 larvae 100 m -3 (70% showed even less than 2 larvae 100 m -3), whereas in some isolated spots, we recorded abundances as high as 867 (Atlantic bluefin) or 872 (bullet tuna) larvae 10 m -2. These results allowed us to relate larval distribution to mesoscale hydrographic features and to characterize the spawning habitat of these species. Single Quotient Parameter analyses were applied to spatial (depth), physical (temperature, salinity, dissolved oxygen and geostrophic current velocities) and biological (mesozooplankton biomass) variables to determine the environmental preferences of each species for spawning. Results showed that the complex hydrodynamic scenarios around the Balearic Islands, due to the interaction between the inflowing surface Atlantic water masses (AW) and Mediterranean surface waters (MW), play a key role in determining the abundance and distribution of tuna larvae in this area, especially in the case of Atlantic bluefin tuna. Spawning of this species seems to take place mainly in offshore mixed waters, as suggested by their preferences for waters with salinities between 36.9 and 37.7, located near frontal areas in the confluence of AW and MW. Atlantic bluefin tuna start to spawn once sea surface temperatures (SST) are over 20.5 °C, and preferentially in the range of 21.5-26.5 °C. Its larval distribution suggests that spawners reach the Balearic Sea in association with the inflowing AW. However, bullet tuna and albacore tuna larvae, species whose Mediterranean stocks stay in this sea year round, had a more widespread distribution and were found both in MW and AW. Bullet tuna starts to spawn in shallower waters near the shelf break once the SST reaches 19 °C, and shows significant preferences for waters over 23.5 °C. Similar to Atlantic bluefin tuna, albacore tuna spawn in offshore waters, but its spawning peak is later than its congeneric species, since it has a significant preference for even warmer waters, over 27 °C.

Morphological variation of siscowet lake trout in Lake Superior

USGS Publications Warehouse

Bronte, C.R.; Moore, S.A.

2007-01-01

Historically, Lake Superior has contained many morphologically distinct forms of the lake trout Salvelinus namaycush that have occupied specific depths and locations and spawned at specific times of the year. Today, as was probably the case historically, the siscowet morphotype is the most abundant. Recent interest in harvesting siscowets to extract oil containing omega-3 fatty acids will require additional knowledge of the biology and stock structure of these lightly exploited populations. The objective of this study was to determine whether shape differences exist among siscowet populations across Lake Superior and whether these shape differences can be used to infer stock structure. Morphometric analysis (truss protocol) was used to differentiate among siscowets sampled from 23 locations in Lake Superior. We analyzed 31 distance measurements among 14 anatomical landmarks taken from digital images of fish recorded in the field. Cluster analysis of size-corrected data separated fish into three geographic groups: The Isle Royale, eastern (Michigan), and western regions (Michigan). Finer scales of stock structure were also suggested. Discriminant function analysis demonstrated that head measurements contributed to most of the observed variation. Cross-validation classification rates indicated that 67–71% of individual fish were correctly classified to their region of capture. This is the first study to present shape differences associated with location within a lake trout morphotype in Lake Superior.

Atlantic salmon brood stock management and breeding handbook

USGS Publications Warehouse

Kincaid, Harold L.; Stanley, Jon G.

1989-01-01

Anadromus runs of Atlantic salmon have been restored to the Connecticut, Merrimack, Pawcatuck, Penobscot, and St. Croix rivers in New England by the stocking of more than 8 million smolts since 1948. Fish-breeding methods have been developed that minimize inbreeding and domestication and enhance natural selection. Methods are available to advance the maturation of brood stock, control the sex of production lots and store gametes. Current hatchery practices emphasize the use of sea-run brood stock trapped upon return to the rivers and a limited number of captive brood stock and rejuvenated kelts. Fish are allowed to mature naturally, after which they are spawned and incubated artificially. Generally, 1-year smolts are produced, and excess fish are stocked as fry in headwater streams. Smolts are stocked during periods of rising water in spring. Self-release pools are planned that enable smolts to choose the emigration time. Culturists keep good records that permit evaluation of the performance of strains and the effects of breeding practices. As Atlantic salmon populations expand, culturists must use sound breeding methods that enhance biotic potential while maintaining genetic diversity and protecting unique gene pools.

Utilizing individual fish biomass and relative abundance models to map environmental niche associations of adult and juvenile targeted fishes.

PubMed

Galaiduk, Ronen; Radford, Ben T; Harvey, Euan S

2018-06-21

Many fishes undergo ontogenetic habitat shifts to meet their energy and resource needs as they grow. Habitat resource partitioning and patterns of habitat connectivity between conspecific fishes at different life-history stages is a significant knowledge gap. Species distribution models were used to examine patterns in the relative abundance, individual biomass estimates and environmental niche associations of different life stages of three iconic West Australian fishes. Continuous predictive maps describing the spatial distribution of abundance and individual biomass of the study species were created as well predictive hotspot maps that identify possible areas for aggregation of individuals of similar life stages of multiple species (i.e. spawning grounds, fisheries refugia or nursery areas). The models and maps indicate that processes driving the abundance patterns could be different from the body size associated demographic processes throughout an individual's life cycle. Incorporating life-history in the spatially explicit management plans can ensure that critical habitat of the vulnerable stages (e.g. juvenile fish, spawning stock) is included within proposed protected areas and can enhance connectivity between various functional areas (e.g. nursery areas and adult populations) which, in turn, can improve the abundance of targeted species as well as other fish species relying on healthy ecosystem functioning.

Weirs: Counting and sampling adult salmonids in streams and rivers

USGS Publications Warehouse

Zimmerman, Christian E.; Zabkar, Laura M.; Johnson, David H.; Shrier, Brianna M.; O'Neal, Jennifer S.; Knutzen, John A.; Augerot, Xanthippe; O'Neal, Thomas A.; Pearsons, Todd N.

2007-01-01

Weirs—which function as porous barriers built across stream—have long been used to capture migrating fish in flowing waters. For example, the Netsilik peoples of northern Canada used V-shaped weirs constructed of river rocks gathered onsite to capture migrating Arctic char Salvelinus alpinus (Balikci 1970). Similarly, fences constructed of stakes and a latticework of willow branches or staves were used by Native Americans to capture migrating salmon in streams along the West Coast of North America (Stewart 1994). In modern times, weirs have also been used in terminal fisheries and to capture brood fish for use in fish culture. Weirs have been used to gather data on age structure, condition, sex ratio, spawning escapement, abundance, and migratory patterns of fish in streams. One of the critical elements of fisheries management and stock assessment of salmonids is a count of adult fish returning to spawn. Weirs are frequently used to capture or count fish to determine status and trends of populations or direct inseason management of fisheries; generally, weirs are the standard against which other techniques are measured. To evaluate fishery management actions, the number of fish escaping to spawn is often compared to river-specific target spawning requirements (O’Connell and Dempson 1995). A critical factor in these analyses is the determination of total run size (O’Connell 2003). O’Connell compared methods of run-size estimation against absolute counts from a rigid weir and concluded that, given the uncertainty of estimators, the absolute counts obtained at the weir wer significantly better than modeled estimates, which deviated as much as 50–60% from actual counts. The use of weirs is generally restricted to streams and small rivers because of construction expense, formation of navigation barriers, and the tendency of weirs to clog with debris, which can cause flooding and collapse of the structure (Hubert 1996). When feasible, however, weirs are generally regarded as the most accurate technique available to quantify escapement as the result is supposedly an absolute count (Cousens et al. 1982). Weirs also provide the opportunity to capture fish for observation and sampling of biological characteristics and tissues; they may also serve as recapture sites for basin-wide, mark–recapture population estimates. Temporary weirs are useful in monitoring wild populations of salmonids as well as for capturing broodstock for artificial propagation.

How Well Can We Predict Salmonid Spawning Habitat with LiDAR?

NASA Astrophysics Data System (ADS)

Pfeiffer, A.; Finnegan, N. J.; Hayes, S.

2013-12-01

Suitable salmonid spawning habitat is, to a great extent, determined by physical, landscape driven characteristics such as channel morphology and grain size. Identifying reaches with high-quality spawning habitat is essential to restoration efforts in areas where salmonid species are endangered or threatened. While both predictions of suitable habitat and observations of utilized habitat are common in the literature, they are rarely combined. Here we exploit a unique combination of high-resolution LiDAR data and seven years of 387 individually surveyed Coho and Steelhead redds in Scott Creek, a 77 km2 un-glaciated coastal California drainage in the Santa Cruz Mountains, to both make and test predictions of spawning habitat. Using a threshold channel assumption, we predict grain size throughout Scott Creek via a shear stress model that incorporates channel width, instead of height, using Manning's equation (Snyder et al., 2013). Slope and drainage area are computed from a LiDAR-derived DEM, and channel width is calculated via hydraulic modeling. Our results for median grain size predictions closely match median grain sizes (D50) measured in the field, with the majority of sites having predicted D50's within a factor of two of the observed values, especially for reaches with D50 > 0.02m. This success suggests that the threshold model used to predict grain size is appropriate for un-glaciated alluvial channel systems. However, it appears that grain size alone is not a strong predictor of salmon spawning. Reaches with a high (>0.1m) average predicted D50 do have lower redd densities, as expected based on spawning gravel sizes in the literature. However, reaches with lower (<0.1m) predicted D50 have a wide range of redd densities, suggesting that reach-average grain size alone cannot explain spawning site selection in the finer-grained reaches of Scott Creek. We turn to analysis of bedform morphology in order to explain the variation in redd density in the low-slope, finer-grained reaches of Lower Scott Creek. Because spawning is strongly correlated with riffle locations, we use a LiDAR-derived longitudinal profile to predict where riffle habitat is located within the watershed. To accomplish this, we use previous studies that constrain pool-riffle habitat to slopes <1.5%, then use wavelet analysis of the longitudinal profile within these pool-riffle reaches to investigate the spacing of drops in water surface slope, with the goal of identifying reaches with high riffle density. Our slope-based predictions of pool-riffle morphology closely match the extent of pool-riffle reaches observed in the field. Average redd density in pool-riffle reaches is more than double the average redd density in reaches of other channel morphologies. Initial wavelet analysis suggests that riffle spacing may be longer in the lower reaches of Scott Creek and shorter in the high-redd density upper reaches, a finding that agrees with the hypothesis that spawning habitat is limited by riffle density. Our results suggest that high resolution topographic data can be successfully used to identify reaches of utilized spawning habitat based on grain size predictions and wavelet analysis of bedform spacing.

Cle Elum Lake Sockeye Salmon Restoration Feasibility Study, 1986-1988 Progress Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flagg, Thomas A.

1988-10-01

In 1986, a multi-year project to evaluate the biological feasibility of reestablishing anadromous sockeye salmon (Oncorhynchus nerka) runs to Cle Elum Lake in the Yakima River Basin was established between the Bonneville Power Administration (BPA) and the National Marine Fisheries Service (NMFS). This program involves the capture, spawning, and rearing of disease-free donor stock in 1987 and 1988 and assessment of juvenile outmigration and survival from Cle Elum Lake in 1989 and 1990. Work in 1987--1988 involved collection of adult sockeye salmon from the Lake Wenatchee run and incubation and rearing of progeny as donor stock. In July 1987, 263more » adults were captured at the Dryden fishway on the Wenatchee River and transferred to net-pens in Lake Wenatchee. Adults were held approximately 90 days and spawned, and the eggs were transferred to a quarantine hatchery. Pre-spawning survival was 95.1%, and all spawners were certified as being free of Infectious Hematopoietic Necrosis (IHN) and other replicating viruses. Egg viability averaged about 40%; however, eyed egg to hatch survival was over 99%. Juveniles are being reared in quarantine, and survival to date is about 92%. The NMFS currently has over 131,000 fry (0.7 g average weight) in culture. Fry have been certified twice (at 0.12 g and 0.25 g average weight) as being free of IHN and other replicating viruses. Viral certification will continue throughout rearing. 13 refs., 4 figs., 3 tabs.« less

Characterizing and predicting the distribution of Baltic Sea flounder (Platichthys flesus) during the spawning season

NASA Astrophysics Data System (ADS)

Orio, Alessandro; Bergström, Ulf; Casini, Michele; Erlandsson, Mårten; Eschbaum, Redik; Hüssy, Karin; Lehmann, Andreas; Ložys, Linas; Ustups, Didzis; Florin, Ann-Britt

2017-08-01

Identification of essential fish habitats (EFH), such as spawning habitats, is important for nature conservation, sustainable fisheries management and marine spatial planning. Two sympatric flounder (Platichthys flesus) ecotypes are present in the Baltic Sea, pelagic and demersal spawning flounder, both displaying ecological and physiological adaptations to the low-salinity environment of this young inland sea. In this study we have addressed three main research questions: 1) What environmental conditions characterize the spatial distribution and abundance of adult flounder during the spawning season? 2) What are the main factors defining the habitats of the two flounder ecotypes during the spawning season? 3) Where are the potential spawning areas of flounder? We modelled catch per unit of effort (CPUE) of flounder from gillnet surveys conducted over the southern and central Baltic Sea in the spring of 2014 and 2015 using generalized additive models. A general model included all the stations fished during the survey while two other models, one for the demersal and one for the pelagic spawning flounder, included only the stations where each flounder ecotype should dominate. The general model captured distinct ecotype-specific signals as it identified dual salinity and water depth responses. The model for the demersal spawning flounder revealed a negative relation with the abundance of round goby (Neogobius melanostomus) and a positive relation with Secchi depth and cod abundance. Vegetation and substrate did not play an important role in the choice of habitat for the demersal ecotype. The model for the pelagic spawning flounder showed a negative relation with temperature and bottom current and a positive relation with salinity. Spatial predictions of potential spawning areas of flounder showed a decrease in habitat availability for the pelagic spawning flounder over the last 20 years in the central part of the Baltic Sea, which may explain part of the observed changes in populations' biomass. We conclude that spatiotemporal modelling of habitat availability can improve our understanding of fish stock dynamics and may provide necessary biological knowledge for the development of marine spatial plans.

Fishing-induced changes in adult length are mediated by skipped-spawning.

PubMed

Wang, Hui-Yu; Chen, Ying-Shiuan; Hsu, Chien-Chung; Shen, Sheng-Feng

2017-01-01

Elucidating fishing effects on fish population dynamics is a critical step toward sustainable fisheries management. Despite previous studies that have suggested age or size truncation in exploited fish populations, other aspects of fishing effects on population demography, e.g., via altering life histories and density, have received less attention. Here, we investigated the fishing effects altering adult demography via shifting reproductive trade-offs in the iconic, overexploited, Pacific bluefin tuna Thunnus orientalis. We found that, contrary to our expectation, mean lengths of catch increased over time in longline fisheries. On the other hand, mean catch lengths for purse seine fisheries did not show such increasing trends. We hypothesized that the size-dependent energetic cost of the spawning migration and elevated fishing mortality on the spawning grounds potentially drive size-dependent skipped spawning for adult tuna, mediating the observed changes in the catch lengths. Using eco-genetic individual-based modeling, we demonstrated that fishing-induced evolution of skipped spawning and size truncation interacted to shape the observed temporal changes in mean catch lengths for tuna. Skipped spawning of the small adults led to increased mean catch lengths for the longline fisheries, while truncation of small adults by the purse seines could offset such a pattern. Our results highlight the eco-evolutionary dynamics of fishing effects on population demography and caution against using demographic traits as a basis for fisheries management of the Pacific bluefin tuna as well as other migratory species. © 2016 by the Ecological Society of America.

Stream network geomorphology mediates predicted vulnerability of anadromous fish habitat to hydrologic change in southeast Alaska.

PubMed

Sloat, Matthew R; Reeves, Gordon H; Christiansen, Kelly R

2017-02-01

In rivers supporting Pacific salmon in southeast Alaska, USA, regional trends toward a warmer, wetter climate are predicted to increase mid- and late-21st-century mean annual flood size by 17% and 28%, respectively. Increased flood size could alter stream habitats used by Pacific salmon for reproduction, with negative consequences for the substantial economic, cultural, and ecosystem services these fish provide. We combined field measurements and model simulations to estimate the potential influence of future flood disturbance on geomorphic processes controlling the quality and extent of coho, chum, and pink salmon spawning habitat in over 800 southeast Alaska watersheds. Spawning habitat responses varied widely across watersheds and among salmon species. Little variation among watersheds in potential spawning habitat change was explained by predicted increases in mean annual flood size. Watershed response diversity was mediated primarily by topographic controls on stream channel confinement, reach-scale geomorphic associations with spawning habitat preferences, and complexity in the pace and mode of geomorphic channel responses to altered flood size. Potential spawning habitat loss was highest for coho salmon, which spawn over a wide range of geomorphic settings, including steeper, confined stream reaches that are more susceptible to streambed scour during high flows. We estimated that 9-10% and 13-16% of the spawning habitat for coho salmon could be lost by the 2040s and 2080s, respectively, with losses occurring primarily in confined, higher-gradient streams that provide only moderate-quality habitat. Estimated effects were lower for pink and chum salmon, which primarily spawn in unconfined floodplain streams. Our results illustrate the importance of accounting for valley and reach-scale geomorphic features in watershed assessments of climate vulnerability, especially in topographically complex regions. Failure to consider the geomorphic context of stream networks will hamper efforts to understand and mitigate the vulnerability of anadromous fish habitat to climate-induced hydrologic change. © 2016 John Wiley & Sons Ltd.

A phylogenetic analysis of egg size, clutch size, spawning mode, adult body size, and latitude in reef fishes

NASA Astrophysics Data System (ADS)

Kasimatis, Katja; Riginos, Cynthia

2016-06-01

Theoretical treatments of egg size in fishes suggest that constraints on reproductive output should create trade-offs between the size and number of eggs produced per spawn. For marine reef fishes, the observation of distinct reproductive care strategies (demersal guarding, egg scattering, and pelagic spawning) has additionally prompted speculation that these strategies reflect alternative fitness optima with selection on egg size differing by reproductive mode and perhaps latitude. Here, we aggregate data from 278 reef fish species and test whether clutch size, reproductive care, adult body size, and latitudinal bands (i.e., tropical, subtropical, and temperate) predict egg size, using a statistically unified framework that accounts for phylogenetic correlations among traits. We find no inverse relationship between species egg size and clutch size, but rather that egg size differs by reproductive mode (mean volume for demersal eggs = 1.22 mm3, scattered eggs = 0.18 mm3, pelagic eggs = 0.52 mm3) and that clutch size is strongly correlated with adult body size. Larger eggs were found in temperate species compared with tropical species in both demersal guarders and pelagic spawners, but this difference was not strong when accounting for phylogenetic correlations, suggesting that differences in species composition underlies regional differences in egg size. In summary, demersal guarders are generally small fishes with small clutch sizes that produce large eggs. Pelagic spawners and egg scatterers are variable in adult and clutch size. Although pelagic spawned eggs are variable in size, those of scatterers are consistently small.

A Stock Assessment of the Blue Swimming Crab Portunus pelagicus (Linnaeus, 1758) for Sustainable Management in Kung Krabaen Bay, Gulf of Thailand.

PubMed

Kunsook, Chutapa; Gajaseni, Nantana; Paphavasit, Nittharatana

2014-08-01

A stock assessment of blue swimming crabs, Portunus pelagicus was conducted with crab gill nets and collapsible crab traps at Kung Krabaen Bay, in the eastern Gulf of Thailand, from 2008 to 2009. Several key indicators show that P. pelagicus population is in crisis. Fishing mortality shows an increase to 4.14. The exploitation rate is 0.71, higher than the optimal value of 0.38. The size of the mature females has also decreased from 8.10±0.39 cm to 7.52±1.14 cm. The average fecundity is 0.572×10(6)±0.261×10(6) eggs per batch, and the sex ratio (male:female) is 1:0.92. Based on these results, a sustainable management program for P. pelagicus was proposed as follows: (i) closing the bay during the spawning season, (ii) restoration of the Enhalus acoroides seagrass beds, (iii) restocking crab larvae in the bay and (iv) educating and networking all stakeholders to develop a better understanding of the ecology of the crab to support sustainable fishery management in Kung Krabaen Bay.

Combined effects of fishing and oil spills on marine fish: Role of stock demographic structure for offspring overlap with oil.

PubMed

Stige, Leif Chr; Ottersen, Geir; Yaragina, Natalia A; Vikebø, Frode B; Stenseth, Nils Chr; Langangen, Øystein

2018-04-01

It has been proposed that the multiple pressures of fishing and petroleum activities impact fish stocks in synergy, as fishing-induced demographic changes in a stock may lead to increased sensitivity to detrimental effects of acute oil spills. High fishing pressure may erode the demographic structure of fish stocks, lead to less diverse spawning strategies, and more concentrated distributions of offspring in space and time. Hence an oil spill may potentially hit a larger fraction of a year-class of offspring. Such a link between demographic structure and egg distribution was recently demonstrated for the Northeast Arctic stock of Atlantic cod for years 1959-1993. We here estimate that this variation translates into a two-fold variation in the maximal proportion of cod eggs potentially exposed to a large oil spill. With this information it is possible to quantitatively account for demographic structure in prospective studies of population effects of possible oil spills. Copyright © 2018 Elsevier Ltd. All rights reserved.

Genetic variation in steelhead (Salmo gairdneri) from the north coast of Washington

USGS Publications Warehouse

Reisenbichler, R.R.; Phelps, S.R.

1989-01-01

Steelhead (Salmo gairdneri) collected from various sites in nine drainages in northwestern Washington were genetically characterized at 65 protein-coding loci by starch-gel electrophoresis. Genetic differentiation within and among drainages was not significant, and genetic variation among drainages was much less than that reported in British Columbia; these results may be the consequence of gene flow from hatchery stocks that have been released in Washington since the 1940's. Allele frequencies varied significantly among year-classes (hence, genetic characterization studies must include data from several year-classes), and also between hatchery fish (including a stock developed with local wild fish) and wild fish, indicating that few wild fish have been successfully and routinely included in hatchery brood stocks. Conservation of genetic diversity along the north coast of Washington should be facilitated by reducing the numbers of hatchery fish that spawn in streams and by including wild fish in hatchery brood stocks.

Increase in lake trout reproduction in Lake Huron following the collapse of alewife: Relief from thiamine deficiency or larval predation?

USGS Publications Warehouse

Fitzsimons, J.D.; Brown, S.; Brown, L.; Honeyfield, D.; He, J.; Johnson, J.E.

2010-01-01

In the Great Lakes there is still uncertainty as to the population level effects of a thiamine deficiency on salmonines caused by high consumption of alewives Alosa pseudoharengus. A resurgence of lake trout Salvelinus namaycush reproduction in Lake Huron following the crash of alewife stocks between 2002 and 2004 provided an opportunity to evaluate the relative effects of this crash on reproduction through relief from either alewife mediated thiamine deficiency or alewife predation on larval lake trout relative to possible changes in the size of the lake trout spawning stock. Changes in mean lake trout egg thiamine concentration post crash at one spawning reef in Parry Sound, where mean thiamine concentration increased by almost two-fold, were consistent with diet switching from alewives to rainbow smelt Osmerus mordax, the next most abundant prey fish in Lake Huron. Although thiamine levels for lake trout collected at a second reef in Parry Sound did not change post-crash, levels both pre- and post-crash were consistent with a rainbow smelt diet. A reef specific fry emergence index was found to be positively related to reef specific egg thiamine concentration but negatively related to reef specific occurrence of EMS, a thiamine deficiency related mortality syndrome. We found little evidence for overlap between the timing of spring shoreward migration of alewives and lake trout emergence, suggesting that relief from alewife predation effects had relatively little effect on the observed increase in lake trout recruitment. Numbers of spawners in the north, north-central, and southern zones of the lake increased from 2000 onwards. Overall the abundance post-2003 was higher than from pre-2004, suggesting that spawner abundance may also have contributed to increased lake trout reproduction. However, predicted numbers of spawners and measured abundance of wild recruits in assessment gear were poorly correlated suggesting that the increase in reproduction was not totally spawner dependent and hence relief from thiamine deficiency was also likely involved. We conclude from this that eliminating the effects of an alewife diet mediated thiamine deficiency can have positive effects on lake trout reproduction but more research is required to understand the effect of spawner number and the role of spawning habitat availability.

Decline in bloater fecundity in Southern Lake Michigan after decline of Diporeia

USGS Publications Warehouse

Bunnell, D.B.; David, S.R.; Madenjian, C.P.

2009-01-01

Population fecundity can vary through time, sometimes owing to changes in adult condition. Consideration of these fecundity changes can improve understanding of recruitment variation. Herein, we estimated fecundity of Lake Michigan bloater Coregonus hoyi during December 2005 and February 2006. Bloater recruitment has been highly variable from 1962 to present, and consistently poor since 1992. We compared our fecundity vs. weight regression to a previously published regression that used fish sampled in October 1969. We wanted to develop a new regression for two reasons. First, it should be more accurate because it uses fish collected closer to spawning, thus minimizing the potential for atresia (egg reabsorption) which could bias fecundity high. Second, we hypothesized that fecundity would be lower in 2006 because adult condition was 41% lower in 2006 compared to 1969, likely owing to the decline of Diporeia spp, a primary prey for bloater. Although the slope of the fecundity versus weight regression was similar between the years, fecundity was 24% lower in 2006 than in 1969 for bloater weighing between 70 and 240??g. Whether this was the result of the difference in sampling time prior to spawning or of differences in condition is unknown. We also found no relationship between maternal size and mature oocyte size. Incorporating our updated fecundity regression into a stock/recruit model failed to improve the model fit, indicating that the low bloater recruitment that has been observed since the early 1990s is not solely the result of reduced fecundity. ?? 2008 Elsevier Inc. All rights reserved.

Spatial patterns of copepod biodiversity in relation to a tidal front system in the main spawning and nursery area of the Argentine hake Merluccius hubbsi

NASA Astrophysics Data System (ADS)

Temperoni, B.; Viñas, M. D.; Martos, P.; Marrari, M.

2014-11-01

Copepods play an important role in marine ecosystems as a direct link of energy transfer between primary producers and higher trophic level consumers, such as fish. In the Argentine Sea, the Patagonian stock of Argentine hake Merluccius hubbsi spawns from late austral spring (December) to early autumn (April) in the northern Patagonian shelf region (43°-45°30‧S), in association with a highly productive tidal front system. Since hake larvae prey mainly upon copepods, the objective of this study was to assess the spatial variability in the abundance and diversity of these potential food items in different sectors of the front, as one of the possible factors affecting hake recruitment success. Two complementary mesh sizes (67 and 300 μm) were used to accurately target the entire copepod size spectrum. The copepod community was dominated by developmental stages < 1 mm in total length (eggs, nauplii, copepodites of cyclopoids and calanoids), and adults of the species Oithona helgolandica, Microsetella norvegica, Ctenocalanus vanus and Drepanopus forcipatus. Their spatial distribution was highly influenced by the across-shelf characteristics of the tidal front system, highlighting the impact of environmental features, mainly bottom temperature and salinity, in shaping the community. Abundances were higher in the transitional relative to the stratified sector of the system. Such sector would provide the appropriate conditions to sustain M. hubbsi larval growth resulting from high availability of adequate prey, the suitable thermal ranges, and the existence of retention mechanisms.

Species profiles: life histories and environmental requirements of coastal fishes and invertebrates (South Atlantic) - Atlantic sturgeon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Den Avyle, M.J.

1984-07-01

The Atlantic sturgeon, Acipenser oxyrhynchus oxyrhynchus, is an anadromous species that occupies rivers, estuaries, and nearshore waters along the entire Atlantic coast of the United States. The species once supported significant commercial fisheries throughout its range, but stocks have declined because of overfishing, deterioration of water quality, and damming of rivers. Atlantic sturgeon spawn in rivers and the young remain in freshwater for several years prior to emigration to the ocean. Little is known about spawning areas and associated environmental factors. Females typically do not mature until age X and the age at first spawning ranges from 5 to 13more » years for males and 7 to 19 years for females. Longevity may frequently exceed 25 years. Immature and adult sturgeons are bottom feeders and consume a variety of mollusks, crustaceans, worms, and other small bottom-dwelling invertebrates and fishes. Little is know about competitors, predators, or effects of environmental factors on recruitment. The long period required to reach maturity, possibly irregular spawning thereafter, and prolonged reliance on river systems make juvenile and adult Atlantic sturgeon highly susceptible to habitat alterations, pollution, and over exploitation. 49 references, 2 figures, 4 tables.« less

Aloe vera bathing improved physical and humoral protection in breeding stock after induced spawning in matrinxã (Brycon amazonicus).

PubMed

Zanuzzo, Fábio S; Zaiden, Sérgio F; Senhorini, José A; Marzocchi-Machado, Cleni M; Urbinati, Elisabeth C

2015-07-01

In this study, we show that induced spawning causes stress, an intense loss of epithelia and immunosuppression, decreasing physical and humoral protection in fish, effects that were prevented or improved in fish bathed with Aloe vera. A. vera has several medicinal properties, including wound healing and immunostimulatory effects, which we observed in this study. Fish bathed with A. vera had a higher number of epidermal goblet cells and, in general, an improved wound healing rate compared with the control after induced spawning. These effects might be related to (1) the stimulation of leukocyte activity, represented here by the increased leukocyte respiratory activity triggered by A. vera (leukocytes are recognized as playing an important role in wound repair); (2) the antimicrobial properties of A. vera, which decrease wound infection and accelerate the healing process; and (3) several mechanisms that explain the healing effect of A. vera (increased collagen synthesis, rate of epithelialization, and anti-inflammatory and moisturizing effects). Our results also suggest that caution is necessary during the induced spawning process, especially during stripping, and A. vera bathing is recommended after intensive aquaculture operations. Copyright © 2015 Elsevier Ltd. All rights reserved.

Spawning Cisco investigations in Canada waters of Lake Superior during 2007

USGS Publications Warehouse

Yule, Daniel L.; Evrard, Lori M.; Cholwek, Gary A.; Addison, Peter A.; Cullis, Ken I.

2008-01-01

Cisco Coregonus artedi form pre-spawning aggregations in Lake Superior during November with the bulk of spawning occurring during late November through early December (Dryer and Beil 1964). Eggs are broadcast into open water (Smith 1956) with fertilized eggs settling to the lakebed (Dryer and Beil 1964). Peak hatching occurs the following May (United States Geological Survey – Great Lakes Science Center, GLSC, unpublished data). Interannual variability in year class strength is high, but tends to be synchronous across different regions of Lake Superior (Bronte et al. 2003). November 2005 sampling of Thunder Bay showed 14 year-classes were present with the oldest fish being from the 1984 year-class (Yule et al. 2008). The ciscoes sampled were predominantly from five year classes that hatched during 1988, 1989, 1990, 1998, and 2003. These same strong year-classes were found in the western arm of Lake Superior during November 2006 (GLSC, unpublished data). Growth is rapid in the first few years of life with minimal growth after age-8 (Yule et al. 2008). Ciscoes exceeding 250 mm total length (TL) are typically sexually mature (Yule et al. 2006b, 2008). Thunder Bay ciscoes have high annual survival with rates for females and males averaging 0.80 and 0.75, respectively; females have higher rates of fishing-induced mortality compared to males but lower rates of natural mortality (Yule et al. 2008). Some Lake Superior stocks are currently commercially fished with the bulk of harvest occurring during November when fishers target females for their roe. The bulk of fish are harvested from Thunder Bay using suspended gillnets with mesh sizes ranging from 79-89 mm stretch measure. Ciscoes younger then age-5 make up a very small proportion (<0.1%) of the harvest (Yule, et al. 2008).

Population characteristics of a recovering US Virgin Islands red hind spawning aggregation following protection

PubMed Central

Nemeth, Richard S.

2006-01-01

Many species of groupers form spawning aggregations, dramatic events where 100s to 1000s of individuals gather annually at specific locations for reproduction. Spawning aggregations are often targeted by local fishermen, making them extremely vulnerable to over fishing. The Red Hind Bank Marine Conservation District located in St. Thomas, United States Virgin Islands, was closed seasonally in 1990 and closed permanently in 1999 to protect an important red hind Epinephelus guttatus spawning site. This study provides some of the first information on the population response of a spawning aggregation located within a marine protected area. Tag-and-release fishing and fish transects were used to evaluate population characteristics and habitat utilization patterns of a red hind spawning aggregation between 1999 and 2004. Compared with studies conducted before the permanent closure, the average size of red hind increased mostly during the seasonal closure period (10 cm over 12 yr), but the maximum total length of male red hind increased by nearly 7 cm following permanent closure. Average density and biomass of spawning red hind increased by over 60% following permanent closure whereas maximum spawning density more than doubled. Information from tag returns indicated that red hind departed the protected area following spawning and migrated 6 to 33 km to a ca. 500 km2 area. Protection of the spawning aggregation site may have also contributed to an overall increase in the size of red hind caught in the commercial fishery, thus increasing the value of the grouper fishery for local fishermen. PMID:16612415

77 FR 15991 - Fisheries of the Northeastern United States; Proposed 2012 Spiny Dogfish Fishery Specifications

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-19

... in spiny dogfish biomass. The proposed action is expected to result in positive economic impacts for... most recent catch data and biomass estimates from the 2011 spring trawl survey. Updated estimates indicate that the female spawning stock biomass (SSB) for 2011 is 169,415 mt, about 6 percent above the...

Annual variation of spawning Cutthroat Trout in a small Western USA stream: A case study with implications for the conservation of potamodromous trout life history diversity

USGS Publications Warehouse

Bennett, Stephen; Al-Chokhachy, Robert K.; Roper, Brett B.; Budy, Phaedra

2014-01-01

Little is known about the variability in the spatial and temporal distribution of spawning potamodromous trout despite decades of research directed at salmonid spawning ecology and the increased awareness that conserving life history diversity should be a focus of management. We monitored a population of fluvial–resident Bonneville Cutthroat Trout Oncorhynchus clarkii utah in a tributary to the Logan River, Utah, from 2006 to 2012 to gain insight into the distribution and timing of spawning and what factors may influence these spawning activities. We monitored Bonneville Cutthroat Trout using redd surveys with multiple observers and georeferenced redd locations. We documented an extended spawning period that lasted from late April to mid-July. The onset, median, and end of spawning was best predicted by the mean maximum water temperature during the first 13 weeks of the year (F = 130. 4, df = 5, R2 = 0.96, P < 0.0001) with spawning beginning and ending earlier in years that had warmer water temperatures prior to spawning. The distribution of redds was clumped each year and the relative density of redds was greater in a reach dominated by dams constructed by beavers Castor canadensis. Both dam failure and construction appeared to be responsible for creating new spawning habitat that was quickly occupied, demonstrating rapid temporal response to local habitat changes. Bonneville Cutthroat Trout appeared to establish and defend a redd for up to 2 d, and spawning most often occurred between similar-sized individuals. Spawning surveys for potamodromous trout are an underutilized tool that could be used to better understand the distribution and timing of spawning as well as determine the size and trends of the reproducing portion of populations of management concern. Without efforts to document the diversity of this important aspect of potamodromous trout life history, prioritization of conservation will be problematic.

Annual variation of spawning cutthroat trout in a small western USA stream: a case study with implications for the conservation of potamodromous trout life history diversity

USGS Publications Warehouse

Bennett, Stephen; Al-Chokhachy, Robert; Roper, Brett B.; Budy, Phaedra

2014-01-01

Little is known about the variability in the spatial and temporal distribution of spawning potamodromous trout despite decades of research directed at salmonid spawning ecology and the increased awareness that conserving life history diversity should be a focus of management. We monitored a population of fluvial–resident Bonneville Cutthroat Trout Oncorhynchus clarkii utah in a tributary to the Logan River, Utah, from 2006 to 2012 to gain insight into the distribution and timing of spawning and what factors may influence these spawning activities. We monitored Bonneville Cutthroat Trout using redd surveys with multiple observers and georeferenced redd locations. We documented an extended spawning period that lasted from late April to mid-July. The onset, median, and end of spawning was best predicted by the mean maximum water temperature during the first 13 weeks of the year (F = 130. 4, df = 5, R2 = 0.96, P < 0.0001) with spawning beginning and ending earlier in years that had warmer water temperatures prior to spawning. The distribution of redds was clumped each year and the relative density of redds was greater in a reach dominated by dams constructed by beavers Castor canadensis. Both dam failure and construction appeared to be responsible for creating new spawning habitat that was quickly occupied, demonstrating rapid temporal response to local habitat changes. Bonneville Cutthroat Trout appeared to establish and defend a redd for up to 2 d, and spawning most often occurred between similar-sized individuals. Spawning surveys for potamodromous trout are an underutilized tool that could be used to better understand the distribution and timing of spawning as well as determine the size and trends of the reproducing portion of populations of management concern. Without efforts to document the diversity of this important aspect of potamodromous trout life history, prioritization of conservation will be problematic.

INFLUENCE OF SPAWNING GROUP SIZE AND SPACE ON REPRODUCTION BY SHEEPSHEAD MINNOWS, CYPRINODON VARIEGATUS

EPA Science Inventory

Cripe, G.M., R.L. Hemmer and L.R. Goodman. In press. Influence of Spawning Group Size and Space on Reproduction Variability of Sheepshead Minnows, Cyprinodon variegatus (Abstract). To be presented at the SETAC Fourth World Congress, 14-18 November 2004, Portland, OR. 1 p. (ERL,GB...

Alternative reproductive tactics and inverse size-assortment in a high-density fish spawning aggregation.

PubMed

Karkarey, Rucha; Zambre, Amod; Isvaran, Kavita; Arthur, Rohan

2017-02-28

At high densities, terrestrial and marine species often employ alternate reproductive tactics (ARTs) to maximize reproductive benefits. We describe ARTs in a high-density and unfished spawning aggregation of the squaretail grouper (Plectropomus areolatus) in Lakshadweep, India. As previously reported for this species, territorial males engage in pair-courtship, which is associated with a pair-spawning tactic. Here, we document a previously unreported school-courtship tactic; where territorial males court multiple females in mid-water schools, which appears to culminate in a unique 'school-spawning' tactic. Courtship tactics were conditional on body size, local mate density and habitat, likely associated with changing trade-offs between potential mating opportunities and intra-sexual competition. Counter-intuitively, the aggregation showed a habitat-specific inverse size-assortment: large males courted small females on the reef slope while small males courted equal-sized or larger females on the shelf. These patterns remained stable across two years of observation at high, unfished densities. These unique density-dependent behaviours may disappear from this aggregation as overall densities decline due to increasing commercial fishing pressure, with potentially large consequences for demographics and fitness.

2008 Spawning Cisco Investigations in the Canadian Waters of Lake Superior

USGS Publications Warehouse

Yule, Daniel; Addison, Peter A.; Evrard, Lori M.; Cullis, Ken I.; Cholwek, Gary A.

2009-01-01

The Great Lakes Science Center of the United States Geological Survey (USGS) is working cooperatively with the Ontario Ministry of Natural Resources (OMNR) on a threeyear study to develop standard procedures for acoustic and midwater trawl (AC-MT) assessments of spawning cisco Coregonus artedi that the OMNR can carry forward as a management activity. In year two (2008), we conducted an AC-MT survey of the northern shore from Nipigon Bay to Thunder Bay. Spawning-cisco (> 250 mm total length) densities were lowest near Nipigon Bay (<10/ha), moderate in and around Black Bay (15- 30/ha), and highest in Thunder Bay (118/ha). Rainbow smelt Osmerus mordax densities were highest in Nipigon (2,179/ha) and Black (3,219/ha) bays, and lowest in Thunder Bay (961/ha). We combined our AC-MT survey results with commercial catch records to estimate exploitation fractions of female cisco in Thunder Bay during the 2008 fishery at 4% for ages 1-5, 8.7% for ages 6-12, and 4.4% for ages ≥ 13. Lake Superior fishery managers recently recommended that annual exploitation of adult female lake cisco be kept below 10-15%. Recruitment of cisco since 2003 has been low and there is a strong probability the Thunder Bay stock will decline into the future. Using a simple population dynamics approach we estimated that if the current total allowable catch (TAC) quota is held constant, exploitation fractions could exceed 10% by 2010 and 15% by 2011. Our 2008 collections suggested the survey of Black Bay was likely conducted before all spawners had returned there to spawn. Our data also suggested that cisco collected in Black Bay and east of this site in mid-November may be from the same stock. During November 2009 we will attempt to get better definition of the area occupied by cisco around Black Bay and also determine when surveys should be conducted at this location.

Kootenai River Fisheries Investigation[s]; Stock Status of Burbot, 2002-2003 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paragamian, Vaughn L.; Hoyle, Genevieve

2005-09-01

The Kootenai River Fisheries Investigation Project planned to monitor burbot Lota lota movement in the winter of 2002-2003 and test a hypothesis regarding the relationship of winter flow to upstream spawning migration success. The U.S. Army Corps of Engineers and the Bonneville Power Administration were unable to provide the consistent low winter flows needed to meet the experimental design criteria in that monitoring and evaluation plan (approximately 170 m{sup 3}/s from Libby Dam). Although conditions consistent with management for sustained minimum flows persisted throughout the winter, and stable low flows were maintained below Libby Dam from September 1 through Novembermore » 24, 2002 (158 m{sup 3}/s average) and from January 1, 2003 until May 1 (144 m{sup 3}/s average), flows in the intervening 37 d period from November 25 to December 31 were increased significantly by the U.S. Army Corps of Engineers. During that important December spawning migration period for burbot, flows were well above those proposed in the monitoring and evaluation plan and peaked at 741 m{sup 3}/s on December 21, 2002. Furthermore, despite the low flow conditions for much of the winter, our capture of 10 burbot was the lowest since this investigation began in 1993, evidence that the stock is extremely depressed and the numbers of burbot are declining. We captured a single burbot in 2002-2003 that provided circumstantial evidence reproduction occurred during the winter of 2000-2001. This burbot of 352 mm TL was among the smallest captured since sampling began in 1993. Seven burbot were monitored with sonic telemetry; two of those were tagged the previous winter. The capture of a female burbot at Ambush Rock during the spawning period supports results of previous findings that low flows during winter enhances burbot migration and spawning. Sampling for larval burbot was conducted, but no larval burbot were captured.« less

Results of Bayesian methods depend on details of implementation: An example of estimating salmon escapement goals

USGS Publications Warehouse

Adkison, Milo D.; Peterman, R.M.

1996-01-01

Bayesian methods have been proposed to estimate optimal escapement goals, using both knowledge about physical determinants of salmon productivity and stock-recruitment data. The Bayesian approach has several advantages over many traditional methods for estimating stock productivity: it allows integration of information from diverse sources and provides a framework for decision-making that takes into account uncertainty reflected in the data. However, results can be critically dependent on details of implementation of this approach. For instance, unintended and unwarranted confidence about stock-recruitment relationships can arise if the range of relationships examined is too narrow, if too few discrete alternatives are considered, or if data are contradictory. This unfounded confidence can result in a suboptimal choice of a spawning escapement goal.

Status of lake trout rehabilitation in the Northern Refuge of Lake Michigan

USGS Publications Warehouse

Madenjian, Charles P.; DeSorcie, Timothy J.

1999-01-01

The Northern Refuge in Lake Michigan was established in 1985 as part of a rehabilitation program to stock yearling lake trout Salvelinus namaycush in areas with the best potential for success. Stocking of hatchery-reared lake trout within the refuge began in 1986 at three reefs: Boulder Reef, Gull Island Reef, and Richards Reef. On each reef from 1991 to 1997 we conducted gill-net surveys during the fall spawning season to evaluate performance of adult lake trout, and we conducted beam trawl surveys for naturally reproduced age-0 lake trout in the spring. Criteria to evaluate performance included spawner density, growth, maturity, and mortality. We found no evidence of natural reproduction by lake trout from our surveys. Nevertheless, density of spawning lake trout on Boulder Reef (69 fish/305 m of gill net/night) and Gull Island Reef (34 fish/305 m of gill net/night) appeared to be sufficiently high to initiate a self-sustaining population. Growth and maturity rates of lake trout in the Northern Refuge were similar to those for lake trout stocked in the nearshore region of Lake Michigan. In the Northern Refuge, growth rate for the Marquette strain of lake trout was slightly higher than for the Lewis Lake strain. Annual mortality estimates from catch curve analyses ranged from 0.46 to 0.41, and therefore, these estimates approached a level that was considered to be sufficiently low to allow for a self-sustaining population. Thus, it appeared that the lack of evidence for natural reproduction by lake trout in the Northern Refuge should not be attributed to inability of the population to attain a sufficiently large stock of spawners.

Recruitment processes in Baltic sprat - A re-evaluation of GLOBEC Germany hypotheses

NASA Astrophysics Data System (ADS)

Voss, Rüdiger; Peck, Myron A.; Hinrichsen, Hans-Harald; Clemmesen, Catriona; Baumann, Hannes; Stepputtis, Daniel; Bernreuther, Matthias; Schmidt, Jörn O.; Temming, Axel; Köster, Fritz W.

2012-12-01

The GLOBEC Germany program (2002-2007) had the ambitious goal to resolve the processes impacting the recruitment dynamics of Baltic sprat (Sprattus sprattus L.) by examining various factors affecting early life history stages. At the start of the research program, a number of general recruitment hypotheses were formulated, i.e. focusing on (1) predation, (2) food availability, (3) physical parameters, (4) the impact of current systems, and finally (5) the importance of top-down vs bottom-up effects. The present study synthesizes the results of field sampling (2002 and 2003), laboratory experiments, and modeling studies to re-evaluate these hypotheses for the Baltic sprat stock. Recruitment success was quite different in the 2 years investigated. Despite a lower spawning stock biomass in 2003, the total number of recruits was almost 2-fold higher that year compared to 2002. The higher recruitment success in 2003 could be attributed to enhanced survival success during the post-larval/juvenile stage, a life phase that appears to be critical for recruitment dynamics. In the state of the Baltic ecosystem during the period of investigation, we consider bottom-up control (e.g. temperature, prey abundance) to be more important than top-down control (predation mortality). This ranking in importance does not vary seasonally. Prevailing water circulation patterns and the transport dynamics of larval cohorts have a strong influence on sprat recruitment success. Pronounced transport to coastal areas is detrimental for year-class strength particularly at high sprat stock sizes. A suggested mechanism is density-dependant regulation of survival via intra- and inter-specific competition for prey in coastal areas. A documented change in larval vertical migration behavior between the early 1990s and early 2000s increased the transport potential to the coast, strengthening the coupling between inter-annual differences in the magnitude and direction of wind-driven surface currents and year-to-year changes in reproductive success. However, due to the strong linkages and feed-back loops in the Baltic Sea food web, the most robust projections of the future strength of the Baltic sprat stock will need to take into account climate-driven changes in both abiotic (e.g., drift trajectories) and biotic (trophodynamic) factors. Although our understanding of processes affecting pre-recruit (larval) growth and survival has been advanced by the integrated research conducted within the GLOBEC Germany program, key mechanisms potentially affecting life stages outside of the spawning basins remain to be explored including the dynamics of coastal habitats of juveniles and the feeding and overwintering grounds of adults.

Migratory Patterns of Wild Chinook Salmon Oncorhynchus tshawytscha Returning to a Large, Free-Flowing River Basin

PubMed Central

Eiler, John H.; Evans, Allison N.; Schreck, Carl B.

2015-01-01

Upriver movements were determined for Chinook salmon Oncorhynchus tshawytscha returning to the Yukon River, a large, virtually pristine river basin. These returns have declined dramatically since the late 1990s, and information is needed to better manage the run and facilitate conservation efforts. A total of 2,860 fish were radio tagged during 2002–2004. Most (97.5%) of the fish tracked upriver to spawning areas displayed continual upriver movements and strong fidelity to the terminal tributaries entered. Movement rates were substantially slower for fish spawning in lower river tributaries (28–40 km d-1) compared to upper basin stocks (52–62 km d-1). Three distinct migratory patterns were observed, including a gradual decline, pronounced decline, and substantial increase in movement rate as the fish moved upriver. Stocks destined for the same region exhibited similar migratory patterns. Individual fish within a stock showed substantial variation, but tended to reflect the regional pattern. Differences between consistently faster and slower fish explained 74% of the within-stock variation, whereas relative shifts in sequential movement rates between “hares” (faster fish becoming slower) and “tortoises” (slow but steady fish) explained 22% of the variation. Pulses of fish moving upriver were not cohesive. Fish tagged over a 4-day period took 16 days to pass a site 872 km upriver. Movement rates were substantially faster and the percentage of atypical movements considerably less than reported in more southerly drainages, but may reflect the pristine conditions within the Yukon River, wild origins of the fish, and discrete run timing of the returns. Movement data can provide numerous insights into the status and management of salmon returns, particularly in large river drainages with widely scattered fisheries where management actions in the lower river potentially impact harvests and escapement farther upstream. However, the substantial variation exhibited among individual fish within a stock can complicate these efforts. PMID:25919286

Migratory Patterns of Chinook Salmon Oncorhynchus tshawytscha Returning to a Large, Free-flowing River Basin

USGS Publications Warehouse

Eiler, John H.; Evans, Allison N.; Schreck, Carl B.

2015-01-01

Upriver movements were determined for Chinook salmon Oncorhynchus tshawytscha returning to the Yukon River, a large, virtually pristine river basin. These returns have declined dramatically since the late 1990s, and information is needed to better manage the run and facilitate conservation efforts. A total of 2,860 fish were radio tagged during 2002–2004. Most (97.5%) of the fish tracked upriver to spawning areas displayed continual upriver movements and strong fidelity to the terminal tributaries entered. Movement rates were substantially slower for fish spawning in lower river tributaries (28–40 km d-1) compared to upper basin stocks (52–62 km d-1). Three distinct migratory patterns were observed, including a gradual decline, pronounced decline, and substantial increase in movement rate as the fish moved upriver. Stocks destined for the same region exhibited similar migratory patterns. Individual fish within a stock showed substantial variation, but tended to reflect the regional pattern. Differences between consistently faster and slower fish explained 74% of the within-stock variation, whereas relative shifts in sequential movement rates between “hares” (faster fish becoming slower) and “tortoises” (slow but steady fish) explained 22% of the variation. Pulses of fish moving upriver were not cohesive. Fish tagged over a 4-day period took 16 days to pass a site 872 km upriver. Movement rates were substantially faster and the percentage of atypical movements considerably less than reported in more southerly drainages, but may reflect the pristine conditions within the Yukon River, wild origins of the fish, and discrete run timing of the returns. Movement data can provide numerous insights into the status and management of salmon returns, particularly in large river drainages with widely scattered fisheries where management actions in the lower river potentially impact harvests and escapement farther upstream. However, the substantial variation exhibited among individual fish within a stock can complicate these efforts.

First direct confirmation of grass carp spawning in a Great Lakes tributary

USGS Publications Warehouse

Embke, Holly S.; Kocovsky, Patrick M.; Richter, Catherine A.; Pritt, Jeremy J.; Christine M. Mayer,; Qian, Song

2016-01-01

Grass carp (Ctenopharyngodon idella), an invasive species of Asian carp, has been stocked for many decades in the United States for vegetation control. Adult individuals have been found in all of the Great Lakes except Lake Superior, but no self-sustaining populations have yet been identified in Great Lakes tributaries. In 2012, a commercial fisherman caught four juvenile diploid grass carp in the Sandusky River, a major tributary to Lake Erie. Otolith microchemistry and the capture location of these fish permitted the conclusion that they were most likely produced in the Sandusky River. Due to this finding, we sampled ichthyoplankton using paired bongo net tows and larval light traps during June–August of 2014 and 2015 to determine if grass carp are spawning in the Sandusky River. From the samples collected in 2015, we identified and staged eight eggs that were morphologically consistent with grass carp. Five eggs were confirmed as grass carp using quantitative Polymerase Chain Reaction for a grass carp-specific marker, while the remaining three were retained for future analysis. Our finding confirms that grass carp are naturally spawning in this Great Lakes tributary. All eggs were collected during high-flow events, either on the day of peak flow or 1–2 days following peak flow, supporting an earlier suggestion that high flow conditions favor grass carp spawning. The next principal goal is to identify the spawning and hatch location(s) for the Sandusky River. Predicting locations and conditions where grass carp spawning is most probable may aid targeted management efforts.

Geographical distributions of lake trout strains stocked in Lake Ontario

USGS Publications Warehouse

Elrod, Joseph H.; O'Gorman, Robert; Schneider, Clifford P.; Schaner, Ted

1996-01-01

Geographical distributions of lake trout (Salvelinus namaycush) stocked at seven locations in U.S. waters and at four locations in Canadian waters of Lake Ontario were determined from fish caught with gill nets in September in 17 areas of U.S. waters and at 10 fixed locations in Canadian waters in 1986-95. For fish of a given strain stocked at a given location, geographical distributions were not different for immature males and immature females or for mature males and mature females. The proportion of total catch at the three locations nearest the stocking location was higher for mature fish than for immature fish in all 24 available comparisons (sexes combined) and was greater for fish stocked as yearlings than for those stocked as fingerlings in all eight comparisons. Mature fish were relatively widely dispersed from stocking locations indicating that their tendency to return to stocking locations for spawning was weak, and there was no appreciable difference in this tendency among strains. Mature lake trout were uniformly distributed among sampling locations, and the strain composition at stocking locations generally reflected the stocking history 5 to 6 years earlier. Few lake trout moved across Lake Ontario between the north and south shores or between the eastern outlet basin and the main lake basin. Limited dispersal from stocking sites supports the concept of stocking different genetic strains in various parts of the lake with the attributes of each strain selected to match environmental conditions in the portion of the lake where it is stocked.

Characteristics of the Norwegian Coastal Current during Years with High Recruitment of Norwegian Spring Spawning Herring (Clupea harengus L.)

PubMed Central

Skagseth, Øystein; Slotte, Aril; Stenevik, Erling Kåre; Nash, Richard D. M.

2015-01-01

Norwegian Spring Spawning herring (NSSH) Clupea harengus L. spawn on coastal banks along the west coast of Norway. The larvae are generally transported northward in the Norwegian Coastal Current (NCC) with many individuals utilizing nursery grounds in the Barents Sea. The recruitment to this stock is highly variable with a few years having exceptionally good recruitment. The principal causes of recruitment variability of this herring population have been elusive. Here we undertake an event analysis using data between 1948 and 2010 to gain insight into the physical conditions in the NCC that coincide with years of high recruitment. In contrast to a typical year when northerly upwelling winds are prominent during spring, the years with high recruitment coincide with predominantly southwesterly winds and weak upwelling in spring and summer, which lead to an enhanced northward coastal current during the larval drift period. Also in most peak recruitment years, low-salinity anomalies are observed to propagate northward during the spring and summer. It is suggested that consistent southwesterly (downwelling) winds and propagating low-salinity anomalies, both leading to an enhanced northward transport of larvae, are important factors for elevated recruitment. At the same time, these conditions stabilize the coastal waters, possibly leading to enhanced production and improved feeding potential along the drift route to Barents Sea. Further studies on the drivers of early life history mortality can now be undertaken with a better understanding of the physical conditions that prevail during years when elevated recruitment occurs in this herring stock. PMID:26636759

Comparative ecology of widely distributed pelagic fish species in the North Atlantic: Implications for modelling climate and fisheries impacts

NASA Astrophysics Data System (ADS)

Trenkel, V. M.; Huse, G.; MacKenzie, B. R.; Alvarez, P.; Arrizabalaga, H.; Castonguay, M.; Goñi, N.; Grégoire, F.; Hátún, H.; Jansen, T.; Jacobsen, J. A.; Lehodey, P.; Lutcavage, M.; Mariani, P.; Melvin, G. D.; Neilson, J. D.; Nøttestad, L.; Óskarsson, G. J.; Payne, M. R.; Richardson, D. E.; Senina, I.; Speirs, D. C.

2014-12-01

This paper reviews the current knowledge on the ecology of widely distributed pelagic fish stocks in the North Atlantic basin with emphasis on their role in the food web and the factors determining their relationship with the environment. We consider herring (Clupea harengus), mackerel (Scomber scombrus), capelin (Mallotus villosus), blue whiting (Micromesistius poutassou), and horse mackerel (Trachurus trachurus), which have distributions extending beyond the continental shelf and predominantly occur on both sides of the North Atlantic. We also include albacore (Thunnus alalunga), bluefin tuna (Thunnus thynnus), swordfish (Xiphias gladius), and blue marlin (Makaira nigricans), which, by contrast, show large-scale migrations at the basin scale. We focus on the links between life history processes and the environment, horizontal and vertical distribution, spatial structure and trophic role. Many of these species carry out extensive migrations from spawning grounds to nursery and feeding areas. Large oceanographic features such as the North Atlantic subpolar gyre play an important role in determining spatial distributions and driving variations in stock size. Given the large biomasses of especially the smaller species considered here, these stocks can exert significant top-down pressures on the food web and are important in supporting higher trophic levels. The review reveals commonalities and differences between the ecology of widely distributed pelagic fish in the NE and NW Atlantic basins, identifies knowledge gaps and modelling needs that the EURO-BASIN project attempts to address.

Comparative Influence of Ocean Conditions on Yellowfin and Atlantic Bluefin Tuna Catch from Longlines in the Gulf of Mexico

PubMed Central

Teo, Steven L. H.; Block, Barbara A.

2010-01-01

Directed fishing effort for Atlantic bluefin tuna in the Gulf of Mexico (GOM), their primary spawning grounds in the western Atlantic, has been prohibited since the 1980s due to a precipitous decline of the spawning stock biomass. However, pelagic longlines targeted at other species, primarily yellowfin tuna and swordfish, continue to catch Atlantic bluefin tuna in the GOM as bycatch. Spatial and temporal management measures minimizing bluefin tuna bycatch in the GOM will likely become important in rebuilding the western Atlantic bluefin stock. In order to help inform management policy and understand the relative distribution of target and bycatch species in the GOM, we compared the spatiotemporal variability and environmental influences on the catch per unit effort (CPUE) of yellowfin (target) and bluefin tuna (bycatch). Catch and effort data from pelagic longline fisheries observers (1993–2005) and scientific tagging cruises (1998–2002) were coupled with environmental and biological data. Negative binomial models were used to fit the data for both species and Akaike's Information Criterion (corrected for small sample size) was used to determine the best model. Our results indicate that bluefin CPUE had higher spatiotemporal variability as compared to yellowfin CPUE. Bluefin CPUE increased substantially during the breeding months (March-June) and peaked in April and May, while yellowfin CPUE remained relatively high throughout the year. In addition, bluefin CPUE was significantly higher in areas with negative sea surface height anomalies and cooler sea surface temperatures, which are characteristic of mesoscale cyclonic eddies. In contrast, yellowfin CPUE was less sensitive to environmental variability. These differences in seasonal variability and sensitivity to environmental influences suggest that bluefin tuna bycatch in the GOM can be reduced substantially by managing the spatial and temporal distribution of the pelagic longline effort without substantially impacting yellowfin tuna catches. PMID:20526356

Assessing the suitability of a partial water reuse system for rearing juvenile Chinook salmon Oncorhynchus tshawytscha for stocking in Washington State

USDA-ARS?s Scientific Manuscript database

Health and welfare of juvenile Chinook salmon Oncorhynchus tshawytsha reared in a pilot circular tank-based partial water reuse system in Washington State were evaluated in comparison to fish from the same spawn reared in a flow-through raceway, in order to assess the suitability of using water reus...

Effects of stream channel morphology on golden trout spawning habitat and recruitment.

Treesearch

R.A. Knapp; V.T. Vredenburg; K.R. Matthews

1998-01-01

Abstract. Populations of stream-dwelling salmonids (e.g., salmon and trout) are generally believed to be regulated by strong density-dependent mortality acting on the age-0 life stage, which produces a dome-shaped stock-recruitment curve. Although this paradigm is based largely on data from anadromous species, it has been widely applied to streamresident salmonids...

Grande Ronde Basin Chinook Salmon Captive Brood and Conventional Supplementation Programs, 2002 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carmichael, Richard W.

2003-07-01

Endangered Species Permit Number 1011 (formerly Permit No. 973) authorizes ODFW to take listed spring chinook salmon juveniles from Catherine Creek (CC), Lostine River (LR) and Grande Ronde River (GR) for research and enhancement purposes. Modification 2 of this permit authorizes ODFW to take adults for spawning and the production and release of smolts for the Captive and Conventional broodstock programs. This report satisfies the requirement that an annual report be submitted. Herein we report on activities conducted and provide cursory data analyses for the Grande Ronde spring chinook salmon Captive and Conventional broodstock projects from 1 January-31 December 2002.more » The Grande Ronde Basin Spring Chinook Salmon Captive Broodstock Project is designed to rapidly increase numbers of salmon in stocks that are in imminent danger of extirpation. Parr are captured in Catherine Creek, upper Grande Ronde River and Lostine River and reared to adulthood in captivity. Upon maturation, they are spawned (within stocks) and their progeny reared to smoltification before being released into the natal stream of their parents. This program is co-managed by ODFW, National Marine Fisheries Service, the Nez Perce Tribe and Confederated Tribes of the Umatilla Indian Reservation.« less

Basin-scale availability of salmonid spawning gravel as influenced by channel type and hydraulic roughness in mountain catchments.

Treesearch

John M. Buffington; David R. Montgomery; Harvey M. Greenberg

2004-01-01

A general framework is presented for examining the effects of channel type and associated hydraulic roughness on salmonid spawning-gravel availability in mountain catchments. Digital elevation models are coupled with grain-size predictions to provide basin-scale assessments of the potential extent and spatial pattern of spawning gravels. To demonstrate both the model...

Spawning Habitat Studies of Hanford Reach Fall Chinook Salmon (Oncorhynchus tshawytscha), Final Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geist, David R.; Arntzen, Evan V.; Chien, Yi-Ju

2009-03-02

The Pacific Northwest National Laboratory conducted this study for the Bonneville Power Administration (BPA) with funding provided through the Northwest Power and Conservation Council(a) and the BPA Fish and Wildlife Program. The study was conducted in the Hanford Reach of the Columbia River. The goal of study was to determine the physical habitat factors necessary to define the redd capacity of fall Chinook salmon that spawn in large mainstem rivers like the Hanford Reach and Snake River. The study was originally commissioned in FY 1994 and then recommissioned in FY 2000 through the Fish and Wildlife Program rolling review ofmore » the Columbia River Basin projects. The work described in this report covers the period from 1994 through 2004; however, the majority of the information comes from the last four years of the study (2000 through 2004). Results from the work conducted from 1994 to 2000 were covered in an earlier report. More than any other stock of Pacific salmon, fall Chinook salmon (Oncorhynchus tshawytscha) have suffered severe impacts from the hydroelectric development in the Columbia River Basin. Fall Chinook salmon rely heavily on mainstem habitats for all phases of their life cycle, and mainstem hydroelectric dams have inundated or blocked areas that were historically used for spawning and rearing. The natural flow pattern that existed in the historic period has been altered by the dams, which in turn have affected the physical and biological template upon which fall Chinook salmon depend upon for successful reproduction. Operation of the dams to produce power to meet short-term needs in electricity (termed power peaking) produces unnatural fluctuations in flow over a 24-hour cycle. These flow fluctuations alter the physical habitat and disrupt the cues that salmon use to select spawning sites, as well as strand fish in near-shore habitat that becomes dewatered. The quality of spawning gravels has been affected by dam construction, flood protection, and agricultural and industrial development. In some cases, the riverbed is armored such that it is more difficult for spawners to move, while in other cases the intrusion of fine sediment into spawning gravels has reduced water flow to sensitive eggs and young fry. Recovery of fall Chinook salmon populations may involve habitat restoration through such actions as dam removal and reservoir drawdown. In addition, habitat protection will be accomplished through set-asides of existing high-quality habitat. A key component to evaluating these actions is quantifying the salmon spawning habitat potential of a given river reach so that realistic recovery goals for salmon abundance can be developed. Quantifying salmon spawning habitat potential requires an understanding of the spawning behavior of Chinook salmon, as well as an understanding of the physical habitat where these fish spawn. Increasingly, fish biologists are recognizing that assessing the physical habitat of riverine systems where salmon spawn goes beyond measuring microhabitat like water depth, velocity, and substrate size. Geomorphic features of the river measured over a range of spatial scales set up the physical template upon which the microhabitat develops, and successful assessments of spawning habitat potential incorporate these geomorphic features. We had three primary objectives for this study. The first objective was to determine the relationship between physical habitats at different spatial scales and fall Chinook salmon spawning locations. The second objective was to estimate the fall Chinook salmon redd capacity for the Reach. The third objective was to suggest a protocol for determining preferable spawning reaches of fall Chinook salmon. To ensure that we collected physical data within habitat that was representative of the full range of potential spawning habitat, the study area was stratified based on geomorphic features of the river using a two-dimensional river channel index that classified the river cross section into one of four shapes based on channel symmetry, depth, and width. We found that this river channel classification system was a good predictor at the scale of a river reach ({approx}1 km) of where fall Chinook salmon would spawn. Using this two-dimensional river channel index, we selected study areas that were representative of the geomorphic classes. A total of nine study sites distributed throughout the middle 27 km of the Reach (study area) were investigated. Four of the study sites were located between river kilometer 575 and 580 in a section of the river where fall Chinook salmon have not spawned since aerial surveys were initiated in the 1940s; four sites were located in the spawning reach (river kilometer [rkm] 590 to 603); and one site was located upstream of the spawning reach (rkm 605).« less

Lake trout spawning habitat in the Great Lakes - a review of current knowledge

USGS Publications Warehouse

Marsden, J. Ellen; Casselman, John M.; Edsall, Thomas A.; Elliott, Robert F.; Fitzsimons, John D.; Horns, William H.; Manny, Bruce A.; McAughey, Scott C.; Sly, Peter G.; Swanson, Bruce L.

1995-01-01

We review existing information on lake trout spawning habitat, which might indicate whether habitat is now a limiting factor in lake trout reproductive success. Lake trout spawning habitat quality is defined by the presence or absence of olfactory cues for homing, reef location with respect to the shoreline, water depth, proximity to nursery areas, reef size, contour, substrate size and shape, depth of interstitial spaces, water temperature at spawning time, water quality in interstitial spaces, and the presence of egg and fry predators. Data on factors which attracted native spawners to spawning reefs are lacking, due to the absence of historic data on egg deposition. No direct evidence of egg deposition has been collected from sites deeper than 18 m. Interstitial space and, therefore, substrate size and shape, appear to be critical for both site selection by adults and protection of eggs and fry. Water quality is clearly important for egg incubation, but the critical parameters which define water quality have not yet been well determined in the field. Exposure to wave energy, dictated in part by reef location, may maintain high water quality but may also damage or dislodge eggs. The importance of olfactory cues, water temperature, and proximity to nursery habitat to spawning trout is unclear. Limited data suggest that egg and fry predators, particularly exotic species, may critically affect fry production and survival. Although availability of physical spawning habitat is probably not limiting lake trout reproduction, changes in water quality and species composition may negatively affect early life stages. This review of habitat factors that affect early life stages of lake trout suggests several priorities for research and management.

Modelling larval dispersal dynamics of common sole (Solea solea) along the western Iberian coast

NASA Astrophysics Data System (ADS)

Tanner, Susanne E.; Teles-Machado, Ana; Martinho, Filipe; Peliz, Álvaro; Cabral, Henrique N.

2017-08-01

Individual-based coupled physical-biological models have become the standard tool for studying ichthyoplankton dynamics and assessing fish recruitment. Here, common sole (Solea solea L.), a flatfish of high commercial importance in Europe was used to evaluate transport of eggs and larvae and investigate the connectivity between spawning and nursery areas along the western Iberian coast as spatio-temporal variability in dispersal and recruitment patterns can result in very strong or weak year-classes causing large fluctuations in stock size. A three-dimensional particle tracking model coupled to Regional Ocean Modelling System model was used to investigate variability of sole larvae dispersal along the western Iberian coast over a five-year period (2004-2009). A sensitivity analysis evaluating: (1) the importance of diel vertical migrations of larvae and (2) the size of designated recruitment areas was performed. Results suggested that connectivity patterns of sole larvae dispersal and their spatio-temporal variability are influenced by the configuration of the coast with its topographical structures and thus the suitable recruitment area available as well as the wind-driven mesoscale circulation along the Iberian coast.

An Investigation of Estuary Gate Effect on Freshwater Fish Biotope and a Study on Ecological Scheduling

NASA Astrophysics Data System (ADS)

Zhang, H. W.; Hu, P.; Ni, G.; Jia, Y. W.; Ge, J. J.

2017-12-01

The presence of an estuary gate changes the existing hydrologic regime and produces a far-reaching and accumulated impact on river biotopes and fish stocks. This work investigates the estuary gate effect in the Yong River valley on the species Elopichthys bambusa (E. bambusa). By combininge hydrodynamic results from the MIKE FLOOD model with observations of the E. bambusa habitat indicators. After the establishment of the gate, the hydrological conditions required for spawning, egg hatching and oviposition stimulation, were analysed, and the corresponding strategies for ecological water demand were proposed. This study finds that satisfactory fish egg hatching hydrodynamic conditions are created when the Fenghua River flow reaches 120 m3/s in the spawning season. With Fenghua River, Yao River gate, and Yong River gate discharges at 120 m3/s, 90 m3/s, and 210 m3/s respectively, an average flow speed increase above 0.2 m/s/day may be generated for E. bambusa spawning sites and migration passages. This hydraulic condition stimulates spawning in natural streams. At the most suitable spawning season temperature, an ecological scheduling scheme that maintains a pulse flow for 5-7 days provides E. bambusa with the hydrodynamic conditions required for the whole process of reproduction, thereby maintaining healthy stream ecology. The flow rate scheduling rules, as provided in this paper, may serve as references in watershed ecological scheduling after gate installation.

Validation of a side-scan sonar method for quantifying walleye spawning habitat availability in the littoral zone of northern Wisconsin Lakes

USGS Publications Warehouse

Richter, Jacob T.; Sloss, Brian L.; Isermann, Daniel A.

2016-01-01

Previous research has generally ignored the potential effects of spawning habitat availability and quality on recruitment of Walleye Sander vitreus, largely because information on spawning habitat is lacking for many lakes. Furthermore, traditional transect-based methods used to describe habitat are time and labor intensive. Our objectives were to determine if side-scan sonar could be used to accurately classify Walleye spawning habitat in the nearshore littoral zone and provide lakewide estimates of spawning habitat availability similar to estimates obtained from a transect–quadrat-based method. Based on assessments completed on 16 northern Wisconsin lakes, interpretation of side-scan sonar images resulted in correct identification of substrate size-class for 93% (177 of 191) of selected locations and all incorrect classifications were within ± 1 class of the correct substrate size-class. Gravel, cobble, and rubble substrates were incorrectly identified from side-scan images in only two instances (1% misclassification), suggesting that side-scan sonar can be used to accurately identify preferred Walleye spawning substrates. Additionally, we detected no significant differences in estimates of lakewide littoral zone substrate compositions estimated using side-scan sonar and a traditional transect–quadrat-based method. Our results indicate that side-scan sonar offers a practical, accurate, and efficient technique for assessing substrate composition and quantifying potential Walleye spawning habitat in the nearshore littoral zone of north temperate lakes.

Sex structure and potential female fecundity in a Epinephelus guttatus spawning aggregation: Applying ultrasonic imaging

USGS Publications Warehouse

Whiteman, E.A.; Jennings, C.A.; Nemeth, R.S.

2005-01-01

Ultrasonic imaging was used to determine the spawning population structure and develop a fecundity estimation model for a red hind Epinephelus guttatus spawning aggregation within the Red Hind Bank Marine Conservation District, St Thomas, U.S.V.I. The spawning population showed considerable within-month and between-month variation in population size- and sex-structure. In the spawning season studied, males appeared to arrive at the aggregation site first in December although females represented a large proportion of the catch early in the aggregation periods in January and February. Spawning occurred in January and February, and size frequency distributions suggested that an influx of small females occurred during the second spawning month. An overall sex ratio of 2.9:1 (female:male) was recorded for the whole reproductive season. The sex ratio, however, differed between months and days within months. More females per male were recorded in January than in February when the sex ratio was male biased. Fecundity estimates for this species predicted very high potential fecundities (2.4 ?? 105-2.4 ?? 106 oocytes). The ultrasound model also illustrated a rapid increase in potential female fecundity with total length. Ultrasonic imaging may prove a valuable tool in population assessment for many species and locations in which invasive fishing methods are clearly undesirable. ?? 2005 The Fisheries Society of the British Isles.

Spawning and nursery habitats of neotropical fish species in the tributaries of a regulated river

USGS Publications Warehouse

Makrakis, Maristela Cavicchioli; da Silva, Patrícia S.; Makrakis, Sergio; de Lima, Ariane F.; de Assumpção, Lucileine; de Paula, Salete; Miranda, Leandro E.; Dias, João Henrique Pinheiro

2012-01-01

This chapter provides information on ontogenetic patterns of neotropical fish species distribution in tributaries (Verde, Pardo, Anhanduí, and Aguapeí rivers) of the Porto Primavera Reservoir, in the heavily dammed Paraná River, Brazil, identifying key spawning and nursery habitats. Samplings were conducted monthly in the main channel of rivers and in marginal lagoons from October through March during three consecutive spawning seasons in 2007-2010. Most species spawn in December especially in Verde River. Main river channels are spawning habitats and marginal lagoons are nursery areas for most fish, mainly for migratory species. The tributaries have high diversity of larvae species: a total of 56 taxa representing 21 families, dominated by Characidae. Sedentary species without parental care are more abundant (45.7%), and many long-distance migratory fish species are present (17.4%). Migrators included Prochilodus lineatus, Rhaphiodon vulpinus, Hemisorubim platyrhynchos, Pimelodus maculatus, Pseudoplatystoma corruscans, Sorubim lima, two threatened migratory species: Salminus brasiliensis and Zungaro jahu, and one endangered migratory species: Brycon orbignyanus. Most of these migratory species are vital to commercial and recreational fishing, and their stocks have decreased drastically in the last decades, attributed to habitat alteration, especially impoundments. The fish ladder at Porto Primavera Dam appears to be playing an important role in re-establishing longitudinal connectivity among critical habitats, allowing ascent to migratory fish species, and thus access to upstream reaches and tributaries. Establishment of Permanent Conservation Units in tributaries can help preserve habitats identified as essential spawning and nursery areas, and can be key to the maintenance and conservation of the fish species in the Paraná River basin.

A two-stage information-theoretic approach to modeling landscape-level attributes and maximum recruitment of chinook salmon in the Columbia River basin

Treesearch

William L. Thompson; Danny C. Lee

2002-01-01

Many anadromous salmonid stocks in the Pacific Northwest are at their lowest recorded levels, which has raised questions regarding their long-term persistence under current conditions. There are a number of factors, such as freshwater spawning and rearing habitat, that could potentially influence their numbers. Therefore, we used the latest advances in information-...

Analysis of spawning behavior, habitat, and season of the federally threatened Etheostoma scotti, Cherokee darter (Osteichthyes: Percidae)

USGS Publications Warehouse

Storey, C.M.; Porter, B.A.; Freeman, Mary C.; Freeman, B.J.

2006-01-01

Etheostoma scotti (Cherokee darter) is a member of the subgenus Ulocentra and a federally threatened endemic to the Etowah River system, GA. Field observations of spawning behavior of the Cherokee darter were made at five stream sites to identify spawning season and habitat over two field seasons. Cherokee darters primarily spawn in pool habitats between mid-March and early June, at temperatures between 11 and 18 ?C. Egg deposition was typically on large gravel substrate, but ranged from gravel to bedrock in size and included woody debris. Spawning occurred in a variety of depths (0.09-0.59 m) and velocities (0-0.68 m/s).

Striped Bass, morone saxatilis, egg incubation in large volume jars

USGS Publications Warehouse

Harper, C.J.; Wrege, B.M.; Jeffery, Isely J.

2010-01-01

The standard McDonald jar was compared with a large volume jar for striped bass, Morone saxatilis, egg incubation. The McDonald jar measured 16 cm in diameter by 45 cm in height and had a volume of 6 L. The experimental jar measured 0.4 m in diameter by 1.3 m in height and had a volume of 200 L. The hypothesis is that there is no difference in percent survival of fry hatched in experimental jars compared with McDonald jars. Striped bass brood fish were collected from the Coosa River and spawned using the dry spawn method of fertilization. Four McDonald jars were stocked with approximately 150 g of eggs each. Post-hatch survival was estimated at 48, 96, and 144 h. Stocking rates resulted in an average egg loading rate (??1 SE) in McDonald jars of 21.9 ?? 0.03 eggs/mL and in experimental jars of 10.9 ?? 0.57 eggs/mL. The major finding of this study was that average fry survival was 37.3 ?? 4.49% for McDonald jars and 34.2 ?? 3.80% for experimental jars. Although survival in experimental jars was slightly less than in McDonald jars, the effect of container volume on survival to 48 h (F = 6.57; df = 1,5; P > 0.05), 96 h (F = 0.02; df = 1, 4; P > 0.89), and 144 h (F = 3.50; df = 1, 4; P > 0.13) was not statistically significant. Mean survival between replicates ranged from 14.7 to 60.1% in McDonald jars and from 10.1 to 54.4% in experimental jars. No effect of initial stocking rate on survival (t = 0.06; df = 10; P > 0.95) was detected. Experimental jars allowed for incubation of a greater number of eggs in less than half the floor space of McDonald jars. As hatchery production is often limited by space or water supply, experimental jars offer an alternative to extending spawning activities, thereby reducing labor and operations cost. As survival was similar to McDonald jars, the experimental jar is suitable for striped bass egg incubation. ?? Copyright by the World Aquaculture Society 2010.

[Effect of stock abundance and environmental factors on the recruitment success of small yellow croaker in the East China Sea].

PubMed

Liu, Zun-lei; Yuan, Xing-wei; Yang, Lin-lin; Yan, Li-ping; Zhang, Hui; Cheng, Jia-hua

2015-02-01

Multiple hypotheses are available to explain recruitment rate. Model selection methods can be used to identify the best model that supports a particular hypothesis. However, using a single model for estimating recruitment success is often inadequate for overexploited population because of high model uncertainty. In this study, stock-recruitment data of small yellow croaker in the East China Sea collected from fishery dependent and independent surveys between 1992 and 2012 were used to examine density-dependent effects on recruitment success. Model selection methods based on frequentist (AIC, maximum adjusted R2 and P-values) and Bayesian (Bayesian model averaging, BMA) methods were applied to identify the relationship between recruitment and environment conditions. Interannual variability of the East China Sea environment was indicated by sea surface temperature ( SST) , meridional wind stress (MWS), zonal wind stress (ZWS), sea surface pressure (SPP) and runoff of Changjiang River ( RCR). Mean absolute error, mean squared predictive error and continuous ranked probability score were calculated to evaluate the predictive performance of recruitment success. The results showed that models structures were not consistent based on three kinds of model selection methods, predictive variables of models were spawning abundance and MWS by AIC, spawning abundance by P-values, spawning abundance, MWS and RCR by maximum adjusted R2. The recruitment success decreased linearly with stock abundance (P < 0.01), suggesting overcompensation effect in the recruitment success might be due to cannibalism or food competition. Meridional wind intensity showed marginally significant and positive effects on the recruitment success (P = 0.06), while runoff of Changjiang River showed a marginally negative effect (P = 0.07). Based on mean absolute error and continuous ranked probability score, predictive error associated with models obtained from BMA was the smallest amongst different approaches, while that from models selected based on the P-value of the independent variables was the highest. However, mean squared predictive error from models selected based on the maximum adjusted R2 was highest. We found that BMA method could improve the prediction of recruitment success, derive more accurate prediction interval and quantitatively evaluate model uncertainty.

Spatial variation in the effects of size and age on reproductive dynamics of common coral trout Plectropomus leopardus.

PubMed

Carter, A B; Russ, G R; Tobin, A J; Williams, A J; Davies, C R; Mapstone, B D

2014-04-01

The effects of size and age on reproductive dynamics of common coral trout Plectropomus leopardus populations were compared between coral reefs open or closed (no-take marine reserves) to fishing and among four geographic regions of the Great Barrier Reef (GBR), Australia. The specific reproductive metrics investigated were the sex ratio, the proportion of vitellogenic females and the spawning fraction of local populations. Sex ratios became increasingly male biased with length and age, as expected for a protogyne, but were more male biased in southern regions of the GBR (Mackay and Storm Cay) than in northern regions (Lizard Island and Townsville) across all lengths and ages. The proportion of vitellogenic females also increased with length and age. Female P. leopardus were capable of daily spawning during the spawning season, but on average spawned every 4·3 days. Mature females spawned most frequently on Townsville reserve reefs (every 2·3 days) and Lizard Island fished reefs (every 3·2 days). Females on Mackay reefs open to fishing showed no evidence of spawning over 4 years of sampling, while females on reserve reefs spawned only once every 2-3 months. No effect of length on spawning frequency was detected. Spawning frequency increased with age on Lizard Island fished reefs, declined with age on Storm Cay fished reefs, and declined with age on reserve reefs in all regions. It is hypothesized that the variation in P. leopardus sex ratios and spawning frequency among GBR regions is primarily driven by water temperature, while no-take management zones influence spawning frequency depending on the region in which the reserve is located. Male bias and lack of spawning activity on southern GBR, where densities of adult P. leopardus are highest, suggest that recruits may be supplied from central or northern GBR. Significant regional variation in reproductive traits suggests that a regional approach to management of P. leopardus is appropriate and highlights the need for considering spatial variation in reproduction where reserves are used as fishery or conservation management tools. © 2014 The Fisheries Society of the British Isles.

Persistence of Salmonid Redds

NASA Astrophysics Data System (ADS)

Buffington, J. M.; Buxton, T.; Fremier, A. K.; Hassan, M. A.; Yager, E.

2013-12-01

The construction of redds by spawning salmonids modifies fluvial processes in ways that are beneficial to egg and embryo survival. Redd topography induces hyporheic flow that oxygenates embryos incubating within the streambed and creates form drag that reduces bed mobility and scour of salmonid eggs. Winnowing of fine material during redd construction also coarsens the streambed, increasing bed porosity and hyporheic flow and reducing bed mobility. In addition to the biological benefits, redds may influence channel morphology by altering channel hydraulics and bed load transport rates depending on the size and extent of redds relative to the size of the channel. A key question is how long do the physical and biological effects of redds last? Field observations indicate that in some basins redds are ephemeral, with redd topography rapidly erased by subsequent floods, while in other basins, redds can persist for years. We hypothesize that redd persistence is a function of basin hydrology, sediment supply, and characteristics of the spawning fish. Hydrology controls the frequency and magnitude of bed mobilizing flows following spawning, while bed load supply (volume and caliber) controls the degree of textural fining and consequent bed mobility after spawning, as well as the potential for burial of redd features. The effectiveness of flows in terms of their magnitude and duration depend on hydroclimate (i.e., snowmelt, rainfall, or transitional hydrographs), while bed load supply depends on basin geology, land use, and natural disturbance regimes (e.g., wildfire). Location within the stream network may also influence redd persistence. In particular, lakes effectively trap sediment and regulate downstream flow, which may promote long-lived redds in stream reaches below lakes. These geomorphic controls are modulated by biological factors: fish species (size of fish controls size of redds and magnitude of streambed coarsening); life history (timing of spawning and incubation relative to high flows); and population size (density of redds and extent of streambed alteration within a given reach). Species and life history also control the location of spawning within the basin, dictating the flow and sediment supply regimes. A theoretical framework is developed for predicting redd persistence as a function of the above physical and biological factors. We expect that long-lived redds will indicate either that the river is not competent to re-work the effects of spawning or that spawning occurs after peak flow events that are capable of modifying redd features. The longevity of redds and their associated effects on fluvial processes also provides a measure of the degree of potential ecological conditioning for future generations of fish. Future work will test the framework in field and laboratory settings.

Interannual variability in reproductive traits of the Patagonian toothfish Dissostichus eleginoides around the sub-Antarctic island of South Georgia.

PubMed

Brigden, K E; Marshall, C T; Scott, B E; Young, E F; Brickle, P

2017-07-01

Commercial fisheries data, collected as part of an observer programme and covering the period 1997-2014, were utilized in order to define key reproductive traits and spawning dynamics of the Patagonian toothfish Dissostichus eleginoides at South Georgia. Multi-year spawning site fidelity of D. eleginoides was revealed through the identification of previously unknown spawning hotspots. Timing of female spawning was shown to have shifted later, leading to a shorter spawning duration. A decrease in length and mass of female and male spawning fish and a reduced number of large spawning fish was found, evidence of a change in size structure of spawning D. eleginoides. During the study period fewer later maturity stage females (including spawning stage) were observed in conjunction with increased proportions of early stage female D. eleginoides. The findings are discussed in the context of reproductive success, with consideration of the possible effects such spawning characteristics and behaviours may have on egg and larval survival. This work presents the first long-term assessment of D. eleginoides spawning dynamics at South Georgia and provides valuable knowledge for both the ecology of the species and for future fisheries management of this commercially important species. © 2017 The Fisheries Society of the British Isles.

Salmon Supplementation Studies in Idaho Rivers; Field Activities Conducted on Clear and Pete King Creeks, 2001 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gass, Carrie; Olson, Jim M.

2004-11-01

In 2001 the Idaho Fisheries Resource Office continued as a cooperator on the Salmon Supplementation Studies in Idaho Rivers (ISS) project on Pete King and Clear creeks. Data relating to supplementation treatment releases, juvenile sampling, juvenile PIT tagging, brood stock spawning and rearing, spawning ground surveys, and snorkel surveys were used to evaluate project data points and augment past data. Due to low adult spring Chinook returns to Kooskia National Fish Hatchery (KNFH) in brood year 1999 there was no smolt supplementation treatment release into Clear Creek in 2001. A 17,014 spring Chinook parr supplementation treatment (containing 1000 PIT tags)more » was released into Pete King Creek on July 24, 2001. On Clear Creek, there were 412 naturally produced spring Chinook parr PIT tagged and released. Using juvenile collection methods, Idaho Fisheries Resource Office staff PIT tagged and released 320 naturally produced spring Chinook pre-smolts on Clear Creek, and 16 natural pre-smolts on Pete King Creek, for minimum survival estimates to Lower Granite Dam. There were no PIT tag detections of brood year 1999 smolts from Clear or Pete King creeks. A total of 2261 adult spring Chinook were collected at KNFH. Forty-three females were used for supplementation brood stock, and 45 supplementation (ventral fin-clip), and 45 natural (unmarked) adults were released upstream of KNFH to spawn naturally. Spatial and temporal distribution of 37 adults released above the KNFH weir was determined through the use of radio telemetry. On Clear Creek, a total of 166 redds (8.2 redds/km) were observed and data was collected from 195 carcasses. Seventeen completed redds (2.1 redds/km) were found, and data was collected data from six carcasses on Pete King Creek.« less

Kootenai River Fisheries Investigations; Rainbow and Bull Trout Recruitment, 2003-2004 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walters, Jody P.

2005-08-01

Rainbow trout Oncorhynchus mykiss provide the most important sport fishery in the Kootenai River, Idaho, but densities and catch rates are low. Low recruitment is one possible factor limiting the rainbow trout population. Bull trout Salvelinus confluentus also exist in the Kootenai River, but little is known about this population. Research reported here addresses the following objectives for the Kootenai River, Idaho: identify sources of rainbow and bull trout recruitment, monitor the rainbow trout population size structure to evaluate regulation changes initiated in 2002, and identify factors potentially limiting rainbow trout recruitment. A screw trap was used to estimate juvenilemore » redband and bull trout out-migration from the Callahan Creek drainage, and electrofishing was conducted to estimate summer densities of bull trout rearing in the Idaho portion of the drainage. An estimated 1,132 juvenile redband trout and 68 juvenile bull trout out-migrated from Callahan Creek to the Kootenai River from April 7 through July 15, 2003. Densities of bull trout {ge} age-1 in North and South Callahan creeks ranged from 1.6 to 7.7 fish/100m{sup 2} in August. Bull trout redd surveys were conducted in North and South Callahan creeks, Boulder Creek, and Myrtle Creek. Thirty-two bull trout redds were located in North Callahan Creek, while 10 redds were found in South Callahan Creek. No redds were found in the other two streams. Modeling of culverts in the Deep Creek drainage identified two as upstream migration barriers, preventing rainbow trout from reaching spawning and rearing habitat. Water temperature monitoring in Deep Creek identified two sites where maximum temperatures exceeded those suitable for rainbow trout. Boulder Creek produces the most rainbow trout recruits to the Kootenai River in Idaho upstream of Deep Creek, but may be below carrying capacity for rearing rainbow trout due to nutrient limitations. Monthly water samples indicate Boulder Creek is nutrient limited as soluble reactive and total dissolved phosphorus were typically at or below detection limits, and dissolved inorganic nitrogen concentrations were <30 {micro}/L. A fall 2003 electrofishing survey of the Kootenai River rainbow trout population showed that the proportional stock density (55) and quality stock density (6) increased for the second year in a row following implementation of more conservative harvest regulations. North and South Callahan creeks support the largest spawning population of bull trout in the Kootenai River drainage, Idaho, so management of the watershed should consider bull trout as high priority. Monitoring of the Kootenai River rainbow trout population size structure should continue for at least two to three years to help evaluate the conservative harvest regulations. Finally, options to improve or increase access to rainbow trout spawning and rearing habitat in the Deep Creek drainage should be investigated.« less

The distribution of life cycle stages of two deep-water pleuronectids, Dover sole ( Microstomus pacificus) and rex sole ( Glyptocephalus zachirus), at the northern extent of their range in the Gulf of Alaska

NASA Astrophysics Data System (ADS)

Abookire, Alisa A.; Bailey, Kevin M.

2007-02-01

Dover sole ( Microstomus pacificus) and rex sole ( Glyptocephalus zachirus) are both commercially valuable, long-lived pleuronectids that are distributed widely throughout the North Pacific. While their ecology and life cycle have been described for southern stocks, few investigations have focused on these species at higher latitudes. We synthesized historical research survey data among critical developmental stages to determine the distribution of life cycle stages for both species in the northern Gulf of Alaska (GOA). Bottom trawl survey data from 1953 to 2004 (25 519 trawls) were used to characterize adult distribution during the non-spawning and spawning seasons, ichthyoplankton data from 1972 to 2003 (10 776 tows) were used to determine the spatial and vertical distribution of eggs and larvae, and small-meshed shrimp trawl survey data from 1972 to 2004 (6536 trawls) were used to characterize areas utilized by immature stages. During the non-spawning season, adult Dover sole and rex sole were widely distributed from the inner shelf to outer slope. While both species concentrated on the continental slope to spawn, Dover sole spawning areas were more geographically specific than rex sole. Although spawned in deep water, eggs of both species were found in surface waters near spawning areas. Dover sole larvae did not appear to have an organized migration from offshore spawning grounds toward coastal nursery areas, and our data indicated facultative settling to their juvenile habitat in winter. Rex sole larvae progressively moved cross-shelf toward shore as they grew from April to September, and larvae presumably settled in coastal nursery areas in the autumn. In contrast with studies in the southern end of their range, we found no evidence in the GOA that Dover or rex sole have pelagic larval stages longer than nine months; however, more sampling for large larvae is needed in winter offshore of the continental shelf as well as sampling for newly settled larvae over the shelf to verify an abbreviated pelagic larval stage for both species at the northern end of their range.

Habitat quality of historic Snake River fall Chinook salmon spawning locations and implications for incubation survival: part 1, substrate quality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanrahan, Timothy P.; Geist, David R.; Arntzen, Evan V.

2005-07-01

We evaluated substrate quality at two historic fall Chinook salmon (Oncorhynchus tshawytscha) spawning sites in the Snake River, Idaho, USA. The primary objective of this evaluation was to measure sediment permeability within these areas to determine the potential quality of the habitat in the event that anadromous salmonids are reintroduced to the upper Snake River. Riverbed sediments within the two sites in the upper Snake River were sampled using freeze cores and hydraulic slug tests. Sediment grain size distributions at both sites were typical of gravel-bed rivers with the surface layer coarser than the underlying substrate, suggesting the riverbed surfacemore » was armored. Despite the armored nature of the bed, the size of the largest material present on the riverbed surface was well within the size limit of material capable of being excavated by spawning fall Chinook salmon. The percentage of fines was low, suggesting good quality substrate for incubating salmon embryos. Geometric mean particle sizes found in this study compared to a 55% to 80% survival to emergence based on literature values. Hydraulic slug tests showed moderate to high hydraulic conductivity and were comparable to values from current fall Chinook salmon spawning areas in the Hells Canyon Reach of the Snake River and the Hanford Reach of the Columbia River. Predicted estimates of mean egg survival at both sites (48% and 74%) equaled or exceeded estimates from fall Chinook salmon spawning areas in the Hells Canyon Reach and the Hanford Reach.« less

Using genetic and phenotypic comparisons to evaluate apparent segregation among Kokanee spawning groups

USGS Publications Warehouse

Whitlock, Steven L.; Campbell, Matthew R.; Quist, Michael C.; Dux, Andrew M.

2018-01-01

Genetic and phenotypic traits of spatially and temporally segregated kokanee Oncorhynchus nerka spawning groups in Lake Pend Oreille, Idaho, were compared to test for evidence of divergence on the basis of ecotype (stream spawners versus shoreline spawners) and spawn timing and to describe morphological, life history, and reproductive variation within and among groups. Early and late spawning runs were found to be reproductively isolated; however, there was no clear evidence of genetic differentiation between ecotypes. Spawning groups within the same ecotype differed in length, age distribution, mean length at age, fecundity, and egg size. Variation in reproductive attributes was due primarily to differences in length distributions. Larger‐bodied shore‐spawning kokanee were located in areas where egg survival is known to be enhanced by downwelling, suggesting that the distribution of shore‐spawning kokanee may be partly structured by competition for spawning habitats with groundwater influence. This study contributes to other research indicating that introduced kokanee populations are unlikely to undergo adaptive divergence if they have a history of population fluctuations and are supplemented regularly.

Genetics of Central Valley O. mykiss populations: drainage and watershed scale analyses

USGS Publications Warehouse

Nielsen, Jennifer L.; Pavey, Scott A.; Wiacek, Talia; Williams, Ian S.

2005-01-01

Genetic variation at 11 microsatellite loci described population genetic structure for Oncorhynchus mykiss in the Central Valley, California. Spatial and temporal variation was examined as well as relationships between hatchery and putative natural spawning anadromous stocks. Genetic diversity was analyzed at two distinct spatial scales: fine-scale within drainage for five populations on Clear Creek; between and among drainage diversity for 23 populations. Significant regional spatial structure was apparent, both within Clear Creek and among rainbow trout populations throughout the Central Valley. Significant differences in allelic frequencies were found among most river or drainage systems. Less than 1% of the molecular variance could be attributed to differences found between drainages. Hatchery populations were shown to carry similar genetic diversity to geographically proximate wild populations. Central Valley M = 0.626 (below the M < 0.68 threshold) supported recent population reductions within the Central Valley. However, average estimated effective population size was relatively high (Ne = 5066). Significant allelic differences were found in rainbow trout collected above and below impassable dams on the American, Yuba, Stanislaus and Tuolumne rivers. Rainbow trout sampled in Spring Creek were extremely bottlenecked with allelic variation at only two loci and an estimated effective population size of 62, suggesting some local freshwater O. mykiss stocks may be declining rapidly. These data support significant genetic population structure for steelhead and rainbow trout populations within the Central Valley across multiple scales. Careful consideration of this genetic diversity and its distribution across the landscape should be part of future conservation and restoration efforts. 

A two-stage information-theoretic approach to modeling landscape-level attributes and maximum recruitment of chinook salmon in the Columbia River basin [electronic resource

Treesearch

William L. Thompson; Danny C. Lee

2000-01-01

Many anadromous salmonid stocks in the Pacific Northwest are at their lowest recorded levels, which has raised questions regarding their long-term persistence under current conditions. There are a number of factors, such as freshwater spawning and rearing habitat, that could potentially influence their numbers. Therefore, we used the latest advances in information-...

Modeling hydraulic and sediment transport processes in white sturgeon spawning habitat on the Kootenai River, Idaho

USGS Publications Warehouse

McDonald, Richard R.; Nelson, Jonathan M.; Vaughn Paragamian,; Barton, Gary J.

2017-01-01

The Kootenai River white sturgeon currently spawn (2005) in an 18-kilometer reach of the Kootenai River, Idaho. Since completion of Libby Dam upstream from the spawning reach, there has been only one successful year of recruitment of juvenile fish. Where successful in other rivers, white sturgeon spawn over clean coarse material of gravel size or larger. The channel substrate in the current spawning reach is composed primarily of sand and some buried gravel; within a few kilometers upstream there is clean gravel. We used a 2-dimensional flow and sediment-transport model and the measured locations of sturgeon spawning from 1994-2002 to gain insight into the paradox between the current spawning location and the absence of suitable substrate. Spatial correlations between spawning locations and the model simulations of velocity and depth indicate the white sturgeon tend to select regions of highest velocity and depth within any river cross-section to spawn. These regions of high velocity and depth are independent of pre- or post-dam flow conditions. A simple sediment-transport simulation suggests that high discharge and relatively long duration flow associated with pre-dam flow events might be sufficient to scour the sandy substrate and expose existing lenses of gravel and cobble as lag deposits in the current spawning reach.

Coupling survey data with drift model results suggests that local spawning is important for Calanus finmarchicus production in the Barents Sea

NASA Astrophysics Data System (ADS)

Kvile, Kristina Øie; Fiksen, Øyvind; Prokopchuk, Irina; Opdal, Anders Frugård

2017-01-01

The copepod Calanus finmarchicus is an important part of the diet for several large fish stocks feeding in the Atlantic waters of the Barents Sea. Determining the origin of the new generation copepodites present on the Barents Sea shelf in spring can shed light on the importance of local versus imported production of C. finmarchicus biomass in this region. In this study, we couple large-scale spatiotemporal survey data (> 30 years in both Norwegian Sea and Barents Sea areas) with drift trajectories from a hydrodynamic model to back-calculate and map the spatial distribution of C. finmarchicus from copepod to egg, allowing us to identify potential adult spawning areas. Assuming the adult stage emerges from overwintering in the Norwegian Sea, our results suggest that copepodites sampled at the Barents Sea entrance are a mix of locally spawned individuals and long-distance-travellers advected northwards along the Norwegian shelf edge. However, copepodites sampled farther east in the Barents Sea (33°30‧E) are most likely spawned on the Barents Sea shelf, potentially from females that have overwintered locally. Our results support that C. finmarchicus dynamics in the Barents Sea are not, at least in the short-term, solely driven by advection from the Norwegian Sea, but that local production may be more important than commonly believed.

A new approach for the laboratory culture of the fathead minnow, Pimephales promelas.

PubMed

Gordon, Denise A; Smith, Mark E; Wratschko, Melissa; Agard, David; Holden, Lisa; Wilcox, Steve; Lazorchak, James M

2014-01-01

Fathead minnows are routinely cultured for use in aquatic toxicology studies. A new mass culture system described in the present study consisted of 6 stainless steel tanks, each containing 68 fish and 20 spawning substrates. Spawning results are compared with a previous system of 22 individual glass aquaria, which contained 16 fish and 4 spawning substrates per tank. During a 19-mo period, the new system produced an average of 4105 eggs/d, compared with an average of 2465 eggs/d with the previous system. Labor and maintenance were reduced with the new system. The stainless steel tanks eliminated aquaria glass breakage, and daily water use was reduced by 45%. Analysis of reference toxicant data from fish cultured using both systems indicated no change in the sensitivity of the test animals. Analyses of 2009 egg production data determined that a 6:1 to 7:1 female to male ratio had a significantly positive impact on egg production levels and that 6-mo-old breeding stock should be introduced to the spawning tanks in mid-spring for optimal egg production during the rest of the year. Implementing a stainless steel mass culture system significantly increased efficiency of egg production; reduced turnaround delay of mature animal availability for toxicity and molecular testing; and reduced labor time, costs, and inherent safety hazards, compared with glass aquaria systems. © 2013 SETAC.

TaqMan DNA technology confirms likely overestimation of cod (Gadus morhua L.) egg abundance in the Irish Sea: implications for the assessment of the cod stock and mapping of spawning areas using egg-based methods.

PubMed

Fox, C J; Taylor, M I; Pereyra, R; Villasana, M I; Rico, C

2005-03-01

Recent substantial declines in northeastern Atlantic cod stocks necessitate improved biological knowledge and the development of techniques to complement standard stock assessment methods (which largely depend on accurate commercial catch data). In 2003, an ichthyoplankton survey was undertaken in the Irish Sea and subsamples of 'cod-like' eggs were analysed using a TaqMan multiplex, PCR (polymerase chain reaction) assay (with specific probes for cod, haddock and whiting). The TaqMan method was readily applied to the large number of samples (n = 2770) generated during the survey and when combined with a manual DNA extraction protocol had a low failure rate of 6%. Of the early stage 'cod-like' eggs (1.2-1.75 mm diameter) positively identified: 34% were cod, 8% haddock and 58% whiting. As previous stock estimates based on egg surveys for Irish Sea cod assumed that the majority of 'cod-like' eggs were from cod, the TaqMan results confirm that there was probably substantial contamination by eggs of whiting and haddock that would have inflated estimates of the stock biomass.

An estimate of the historic population size of adult pallid sturgeon in the upper Missouri river basin, Montana and North Dakota

USGS Publications Warehouse

Braaten, P.J.; Fuller, D.B.; Lott, R.D.; Jordan, G.R.

2009-01-01

Juvenile pallid sturgeon Scaphirhynchus albus raised in hatcheries and stocked in the wild are used to augment critically imperiled populations of this federally endangered species in the United States. For pallid sturgeon in recovery priority management area 2 (RPMA 2) of the Missouri River and lower Yellowstone River where natural recruitment has not occurred for decades, restoration programs aim to stock an annual minimum of 9000 juvenile pallid sturgeon for 20 years to re-establish a minimum population of 1700 adults. However, establishment of this target was based on general guidelines for maintaining the genetic integrity of populations rather than pallid sturgeon-specific demographic information because data on the historical population size was lacking. In this study, information from a recent population estimate (158 wild adults in 2004, 95% confidence interval 129-193 adults) and an empirically derived adult mortality rate (5%) was used in a cohort population model to back-estimate the historic abundance of adult pallid sturgeon in RPMA 2. Three back-estimation age models were developed, and assumed that adults alive during 2004 were 30-, 40-, or 50-years old. Based on these age assumptions, population sizes [??95% confidence intervals; (CI)] were back-estimated to 1989, 1979, and 1969 to approximate size of the population when individuals would have been sexually mature (15 years old) and capable of spawning. Back-estimations yielded predictions of 344 adults in 1989 (95% CI 281-420), 577 adults in 1979 (95% CI 471-704), and 968 adults in 1969 (95% CI 790-1182) for the 30-, 40-, and 50-year age models, respectively. Although several assumptions are inherent in the back-estimation models, results suggest the juvenile stocking program for pallid sturgeon will likely re-establish an adult population that equals in the short-term and exceeds in the long-term the predicted population numbers that occurred during past decades in RPMA 2. However, re-establishment of a large population in RPMA 2 that exceeds populations present 40+ years ago should be considered conservatively, as this strategy will increase the number of reproductive adults and thereby increase the likelihood for natural recruitment in this recruitment-limited system. ?? 2009 Blackwell Verlag GmbH.

Evidence of offshore lake trout reproduction in Lake Huron

USGS Publications Warehouse

DeSorcie, Timothy J.; Bowen, Charles A.

2003-01-01

Six Fathom Bank-Yankee Reef, an offshore reef complex, was an historically important spawning area believed to represent some of the best habitat for the rehabilitation of lake trout Salvelinus namaycush in Lake Huron. Since 1986, lake trout have been stocked on these offshore reefs to reestablish self-sustaining populations. We sampled with beam trawls to determine the abundance of naturally reproduced age-0 lake trout on these offshore reefs during May-July in 1994-1998 and 2000-2002. In total, 123 naturally reproduced lake trout fry were caught at Six Fathom Bank, and 2 naturally reproduced lake trout fry were caught at nearby Yankee Reef. Our findings suggest that this region of Lake Huron contains suitable habitat for lake trout spawning and offers hope that lake trout rehabilitation can be achieved in the main basin of Lake Huron.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruggerone, G.T.; Rogers, D.E.

Adult sockeye salmon scales, which provide an index of annual salmon growth in fresh and marine waters during 1965--1997, were measured to examine the effects on growth and adult returns of large spawning escapements influenced by the Exxon Valdez oil spill. Scale growth in freshwater was significantly reduced by the large 1989 spawning escapements in the Kenai River system, Red Lake, and Akalura Lake, but not in Chignik Lake. These data suggest that sockeye growth in freshwater may be less stable following the large escapement. Furthermore, the observations of large escapement adversely affecting growth of adjacent brood years of salmonmore » has important implications for stock-recruitment modeling. In Prince William Sound, Coghill Lake sockeye salmon that migrated through oil-contaminated waters did not exhibit noticeably reduced marine growth, but a model was developed that might explain low adult returns in recent years.« less

Re-Introduction of Lower Columbia River Chum Salmon into Duncan Creek, 2002-2003 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hillson, Todd D.

2003-10-15

The National Marine Fisheries Service (NMFS) listed Lower Columbia River chum as threatened under the auspices of the Endangered Species Act (ESA) in March of 1999 (64 FR 14508, March 25, 1999). The listing was in response to reduction in abundance from historical levels of more than half a million returning adults to fewer than 10,000 present day spawners. Harvest, loss of habitat, changes in flow regimes, riverbed movement and heavy siltation have been largely responsible for the decline of Columbia River chum salmon. The timing of seasonal changes in river flow and water temperatures is perhaps the most criticalmore » factor in structuring the freshwater life history of this species. This is especially true of the population located directly below Bonneville Dam where hydropower operations can block access to spawning sites, dewater redds, strand fry, cause scour or fill of redds and increase sedimentation of spawning gravels. Currently, only two main populations are recognized as genetically distinct in the Columbia River, although spawning has been documented in most lower Columbia River tributaries. The first is located in the Grays River (RKm 34) (Grays population), a tributary of the Columbia, and the second is a group of spawners that utilize the Columbia River just below Bonneville Dam (RKm 235) adjacent to Ives Island and in Hardy and Hamilton creeks (Lower Gorge population). A possible third population of mainstem spawners, found in the fall of 1999, were located spawning above the I-205 bridge (approximately RKm 182), this aggregation is referred to as the Woods Landing/Rivershore population or the I-205 group. The recovery strategy for Lower Columbia River (LCR) chum as outlined in Hatchery Genetic Management Plans (HGMP) has three main tasks. First, determine if remnant populations of LCR chum salmon exist in LCR tributaries. Second, if such populations exist, develop stock-specific recovery plans involving habitat restoration including the creation of spawning refugias, supplementation if necessary and a habitat and fish monitoring and evaluation plan. If chum have been extirpated from previously utilized streams, develop re-introduction plans that utilize appropriate genetic donor stock(s) of LCR chum salmon and integrate habitat improvement and fry-to-adult survival evaluations. Third, reduce extinction risks to the Grays River chum salmon population by randomly capturing adults in the basin for use in a supplementation program and reintroduction into the Chinook River basin. The Duncan Creek project was developed using the same recovery strategy implemented for LCR chum. Biologists with the WDFW and Pacific States Marine Fisheries Commission (PSMFC) identified Duncan Creek as an ideal upriver location below Bonneville Dam for chum re-introduction. It has several attributes that make it a viable location for a re-introduction project: historically chum salmon were present, the creek is low gradient, has numerous springs/seeps, has a low potential for future development and is located close to a donor population of Lower Gorge chum. The Duncan Creek project has two goals: (1) re-introduction of chum into Duncan Creek by providing off channel high-quality spawning and incubation areas, and (2) to simultaneously evaluate natural recolonization and a supplementation strategy where adults are collected and spawned artificially at a hatchery. For supplementation, eggs are incubated and the fry reared at the Washougal Hatchery to be released back into Duncan Creek. The tasks associated with re-establishing a naturally self-sustaining population include: (1) removing mud, sand and organics present in four of the creek branches and replace with gravels expected to provide maximum egg-to-fry survival rates to a depth of at least two feet; (2) armoring the sides of these channels to reduce importation of sediment by fish spawning on the margins; (3) planting native vegetation adjacent to the channels to stabilize the banks, trap silt and provide shade; (4) annual sampling of gravel in the spawning channels to detect changes in gravel composition and sedimentation levels. Tasks associated with the second goal of the recovery strategy for Lower Columbia River chum are detailed in The Monitoring and Evaluation Plan for the Duncan Creek Chum Salmon Reintroduction Program. Four main questions are used to evaluate the success of this program: (1) what egg-to-fry survival rates are being achieved in the renovated channels, (2) what is the survival of the eggs and fry used in the artificial rearing program in Duncan Creek, (3) what is the survival and spawning ground distribution of adult chum salmon produced from the spawning channels and the artificial rearing program, and (4) what is the straying rate of non-program chum salmon into Duncan Creek. The monitoring portion of the Duncan M&E includes documenting and monitoring the physical attributes of the channels.« less

Use of oviduct-inserted acoustic transmitters and positional telemetry to estimate timing and location of spawning: a feasibility study in lake trout, Salvelinus namaycush

USGS Publications Warehouse

Binder, Thomas R.; Holbrook, Christopher M.; Miehls, Scott M.; Thompson, Henry T.; Krueger, Charles C.

2014-01-01

Our results satisfied the three assumptions of oviduct tagging and suggested that oviduct transmitters can be used with positional telemetry to estimate time and location of spawning in lake trout and other species. In situations where oviduct transmitters may be difficult to position once expelled into substrate, pairing oviduct transmitters with a normal-sized fish transmitter that remains in the fish is recommended, with spawning inferred when the two tags separate in space. Optimal transmitter delay will depend on expected degree of spawning site residency and swim speed.

Parapenaeus longirostris (Lucas, 1846) an early warning indicator species of global warming in the central Mediterranean Sea

NASA Astrophysics Data System (ADS)

Colloca, Francesco; Mastrantonio, Gianluca; Lasinio, Giovanna Jona; Ligas, Alessandro; Sartor, Paolo

2014-10-01

The effect of temperature increase on the stock of the deep-sea pink shrimp (Parapenaeus longirostris) was analysed along the western coasts of Italy (North Tyrrhenian-Ligurian Sea: Geographical Sub-Area 9). This crustacean is currently one of the most important commercial species of the trawl fisheries in the Mediterranean Sea. Landings of the species in the North Tyrrhenian-Ligurian Sea have grown consistently during the last years following a rapid increase in the stock size. Since the deep-sea pink shrimp stock is exploited on the same fishing ground of other heavily overexploited stocks in a full mixed and poorly selective fishery, its condition seems to be largely independent of the current fishing exploitation pattern suggesting a positive role of climate change on the dynamic of the stock. To test this hypothesis we investigated the effect of sea surface temperature (SST) on density and distribution of P. longirostris by means of general additive models (GAMs). Two different models were developed for the whole stock and for the recruits (CL < 20 mm) using time series of MEDITS (International bottom trawl survey in the Mediterranean) survey density indices (n km- 2) covering the period 1995-2010. Predictors included were geographical coordinates, quarterly averaged minimum SST, sampling depth and year. Spawners density was included as predictor into the GAM for recruits. The best GAM for the whole stock explained 67.1% of the total deviance, showing a clear increase in density in concomitance with the expansion of the stock northward. We found a significant positive effect of the min SST of all seasons, as expected considering that P. longirostris spawn all year round, with the highest influence played by summer min SST, either in the same or previous year. The best model for recruits explained 64.9% of the total deviance. Recruitment increased linearly with the density of spawners showing a positive temporal trend and an expansion northward. The observed trend in recruitment appeared significantly linked to minimum SST in summer and during the autumn of the previous year, with a positive effect on shrimp density over 23.5 °C and 14 °C respectively. The climate-related changes in recruitment appeared to be the key process driving the dynamics of the stock, involving either higher production or survival in the planktonic stages, or owing to changes in the quality/quantity of nursery habitats.

Evidence for spawning aggregations of the endangered Atlantic goliath grouper Epinephelus itajara in southern Brazil.

PubMed

Bueno, L S; Bertoncini, A A; Koenig, C C; Coleman, F C; Freitas, M O; Leite, J R; De Souza, T F; Hostim-Silva, M

2016-07-01

In this study, seasonal numerical abundance of the critically endangered Atlantic goliath grouper Epinephelus itajara was estimated by conducting scuba dive surveys and calculating sightings-per-unit-effort (SPUE) at three sites in southern Brazil. Seasonal differences in size and reproductive condition of captured or confiscated specimens were compared. The SPUE differed significantly with season, increasing in late spring and peaking during the austral summer months. A significant effect was observed in the number of fish relative to the lunar cycle. All females sampled during the summer were spawning capable, while all those sampled during other seasons were either regressing or regenerating. What these data strongly infer is that the E. itajara spawning aggregation sites have been located in the southern state of Paraná and the northern state of Santa Catarina and summer is the most likely spawning season. Size frequency distributions, abundance and reproductive state were estimated and correlated with environmental variables. © 2016 The Fisheries Society of the British Isles.

Spawning characteristics of redband trout in a headwater stream in Montana

USGS Publications Warehouse

Muhlfeld, Clint C.

2002-01-01

I investigated the spawning characteristics of redband trout Oncorhynchus mykiss gairdneri (a rainbow trout subspecies) during the spring of 1998 in Basin Creek, a third-order headwater stream located in the Kootenai River drainage in northwestern Montana. I examined the timing of spawning as related to discharge and water temperature and analyzed microhabitat selection of 30 completed redds in a low-gradient (0.5–1.5%) reach. Redband trout spawned as flow declined after peak runoff and as mean daily water temperature exceeded 6.0C and maximum daily temperature exceeded 7.0C. Redband trout began spawning on 6 June (mean daily discharge = 2.1 m3/s), 10 d after the peak discharge (8.7 m3/s) occurred. The last redd was completed on 24 June, when discharge was 1.5 m3/s. The mean total redd length was 53 cm (SD = 14; range = 31–91 cm), and the mean total area was 51 cm2 (SD = 8; range= 46– 76 cm2). Eighty percent of the redds were located in pool tailouts, 13% in runs, and 7% in riffles. Spawning redband trout selected redd sites based on substrate size and water depth but not water velocity. Fish selected substrate sizes of 2–6 mm, water depths of 20–30 cm, and water velocities of 40–70 cm/s. My results suggest that redband trout in a low-gradient, third-order mountain stream found suitable spawning habitat in pool tail-outs that contained abundant gravels.

Bayesian stock assessment of Pacific herring in Prince William Sound, Alaska.

PubMed

Muradian, Melissa L; Branch, Trevor A; Moffitt, Steven D; Hulson, Peter-John F

2017-01-01

The Pacific herring (Clupea pallasii) population in Prince William Sound, Alaska crashed in 1993 and has yet to recover, affecting food web dynamics in the Sound and impacting Alaskan communities. To help researchers design and implement the most effective monitoring, management, and recovery programs, a Bayesian assessment of Prince William Sound herring was developed by reformulating the current model used by the Alaska Department of Fish and Game. The Bayesian model estimated pre-fishery spawning biomass of herring age-3 and older in 2013 to be a median of 19,410 mt (95% credibility interval 12,150-31,740 mt), with a 54% probability that biomass in 2013 was below the management limit used to regulate fisheries in Prince William Sound. The main advantages of the Bayesian model are that it can more objectively weight different datasets and provide estimates of uncertainty for model parameters and outputs, unlike the weighted sum-of-squares used in the original model. In addition, the revised model could be used to manage herring stocks with a decision rule that considers both stock status and the uncertainty in stock status.

Food web dynamics affect Northeast Arctic cod recruitment.

PubMed

Hjermann, Dag Ø; Bogstad, Bjarte; Eikeset, Anne Maria; Ottersen, Geir; Gjøsaeter, Harald; Stenseth, Nils Chr

2007-03-07

Proper management of ecosystems requires an understanding of both the species interactions as well as the effect of climate variation. However, a common problem is that the available time-series are of different lengths. Here, we present a general approach for studying the dynamic structure of such interactions. Specifically, we analyse the recruitment of the world's largest cod stock, the Northeast Arctic cod. Studies based on data starting in the 1970-1980s indicate that this stock is affected by temperature through a variety of pathways. However, the value of such studies is somewhat limited by the fact that they are based on a quite specific ecological and climatic situation. Recently, this stock has consisted of fairly young fish and the spawning stock has consisted of relatively few age groups. In this study, we develop a model for the effect of capelin (the cod's main prey) and herring on cod recruitment since 1973. Based on this model, we analyse data on cod, herring and temperature going back to 1921 and find that food-web effects explain a significant part of the cod recruitment variation back to around 1950.

Bayesian stock assessment of Pacific herring in Prince William Sound, Alaska

PubMed Central

Moffitt, Steven D.; Hulson, Peter-John F.

2017-01-01

The Pacific herring (Clupea pallasii) population in Prince William Sound, Alaska crashed in 1993 and has yet to recover, affecting food web dynamics in the Sound and impacting Alaskan communities. To help researchers design and implement the most effective monitoring, management, and recovery programs, a Bayesian assessment of Prince William Sound herring was developed by reformulating the current model used by the Alaska Department of Fish and Game. The Bayesian model estimated pre-fishery spawning biomass of herring age-3 and older in 2013 to be a median of 19,410 mt (95% credibility interval 12,150–31,740 mt), with a 54% probability that biomass in 2013 was below the management limit used to regulate fisheries in Prince William Sound. The main advantages of the Bayesian model are that it can more objectively weight different datasets and provide estimates of uncertainty for model parameters and outputs, unlike the weighted sum-of-squares used in the original model. In addition, the revised model could be used to manage herring stocks with a decision rule that considers both stock status and the uncertainty in stock status. PMID:28222151

Spawning behavior in Atlantic cod: analysis by use of data storage tags

USGS Publications Warehouse

Grabowski, Timothy B.; Thorsteinsson, Vilhjalmur; Marteinsdóttir, Gudrún

2014-01-01

 Electronic data storage tags (DSTs) were implanted into Atlantic cod captured in Icelandic waters from 2002 to 2007 and the depth profiles recovered from these tags (females: n = 31, males: n = 27) were used to identify patterns consistent with published descriptions of cod courtship and spawning behavior. The individual periods of time that males spent exhibiting behavior consistent with being present in a spawning aggregation—i.e. periods consisting of a clear tidal signature in the DST depth profile associated with an individual remaining on or near the substrate—were longer than those of females. Over the course of a spawning season, male cod spent approximately twice the amount of time in spawning aggregations than females, but female cod visited more aggregations per unit time. On average, males participated in approximately 57% more putative spawning events, i.e. vertical ascents potentially corresponding to gamete release, than did females. However, males <85 cm total length participated in the same number of putative spawning events as females of comparable size. In both sexes, larger individuals and/or individuals that spent a longer period of time within an aggregation participated in a larger number of putative spawning events. Although further validation and refinement is necessary, particularly in the identification of spawning events, the ability offered by DSTs to quantify cod spawning behavior may aid in the development of management and conservation plans.

Problems of stock definition in estimating relative contributions of Atlantic striped bass to the coastal fishery

USGS Publications Warehouse

Waldman, John R.; Fabrizio, Mary C.

1994-01-01

Stock contribution studies of mixed-stock fisheries rely on the application of classification algorithms to samples of unknown origin. Although the performance of these algorithms can be assessed, there are no guidelines regarding decisions about including minor stocks, pooling stocks into regional groups, or sampling discrete substocks to adequately characterize a stock. We examined these questions for striped bass Morone saxatilis of the U.S. Atlantic coast by applying linear discriminant functions to meristic and morphometric data from fish collected from spawning areas. Some of our samples were from the Hudson and Roanoke rivers and four tributaries of the Chesapeake Bay. We also collected fish of mixed-stock origin from the Atlantic Ocean near Montauk, New York. Inclusion of the minor stock from the Roanoke River in the classification algorithm decreased the correct-classification rate, whereas grouping of the Roanoke River and Chesapeake Bay stock into a regional (''southern'') group increased the overall resolution. The increased resolution was offset by our inability to obtain separate contribution estimates of the groups that were pooled. Although multivariate analysis of variance indicated significant differences among Chesapeake Bay substocks, increasing the number of substocks in the discriminant analysis decreased the overall correct-classification rate. Although the inclusion of one, two, three, or four substocks in the classification algorithm did not greatly affect the overall correct-classification rates, the specific combination of substocks significantly affected the relative contribution estimates derived from the mixed-stock sample. Future studies of this kind must balance the costs and benefits of including minor stocks and would profit from examination of the variation in discriminant characters among all Chesapeake Bay substocks.

Genetic assessment of strain-specific sources of lake trout recruitment in the Great Lakes

USGS Publications Warehouse

Page, Kevin S.; Scribner, Kim T.; Bennett, Kristine R.; Garzel, Laura M.; Burnham-Curtis, Mary K.

2003-01-01

Populations of wild lake trout Salvelinus namaycush have been extirpated from nearly all their historical habitats across the Great Lakes. Efforts to restore self-sustaining lake trout populations in U.S. waters have emphasized the stocking of coded-wire-tagged juveniles from six hatchery strains (Seneca Lake, Lewis Lake, Green Lake, Apostle Islands, Isle Royale, and Marquette) into vacant habitats. Strain-specific stocking success has historically been based on estimates of the survival and catch rates of coded-wire-tagged adults returning to spawning sites. However, traditional marking methods and estimates of relative strain abundance provide no means of assessing strain fitness (i.e., the realized contributions to natural recruitment) except by assuming that young-of-the-year production is proportional to adult spawner abundance. We used microsatellite genetic data collected from six hatchery strains with likelihood-based individual assignment tests (IA) and mixed-stock analysis (MSA) to identify the strain composition of young of the year recruited each year. We show that strain classifications based on IA and MSA were concordant and that the accuracy of both methods varied based on strain composition. Analyses of young-of-the-year lake trout samples from Little Traverse Bay (Lake Michigan) and Six Fathom Bank (Lake Huron) revealed that strain contributions differed significantly from estimates of the strain composition of adults returning to spawning reefs. The Seneca Lake strain contributed the majority of juveniles produced on Six Fathom Bank and more young of the year than expected within Little Traverse Bay. Microsatellite markers provided a method for accurately classifying the lake trout hatchery strains used for restoration efforts in the Great Lakes and for assessment of strain-specific reproductive success.

Limitations to lake trout (Salvelinus namaycush) rehabilitation in the Great Lakes imposed by biotic interactions occurring at early life stages

USGS Publications Warehouse

Jones, Michael L.; Eck, Gary W.; Evans, David O.; Fabrizio, Mary C.; Hoff, Michael H.; Hudson, Patrick L.; Janssen, John; Jude, David; O'Gorman, Robert; Savino, Jacqueline F.

1995-01-01

We examine evidence that biotic factors, particularly predation, may be limiting early survival of wild lake trout (Salvelinus namaycush) juveniles in many areas of the Great Lakes. The Great Lakes contain numerous potential predators of lake trout eggs and fry, some of which are recent invaders, and most of which were probably absent when lake trout most recently re-invaded the Great Lakes after the last ice age. Simple quantitative models of predation suggest that plausible assumptions about prey densities, predator feeding rates, and duration of exposure of predator to prey can lead to very high estimates of predation mortality, in some instances approaching 100%. Indirect evidence from inter-Great Lake comparisons and inland lake examples also suggest that biotic factors may impede successful lake trout colonization. Our synthesis of the evidence leads to recommendations for research to better define field feeding rates of lake trout egg and fry predators and comparative studies of densities of potential egg and fry predators on lake trout spawning reefs. Management options should be designed to provide useful information as well as achieve short-term goals. From a management standpoint we recommend that: newly constructed lake trout reefs should be placed well away from concentrations of potential predators; offshore spawning reefs should be stocked; salmonine stocking, nutrient abatement, and commercial harvest of alewives should all be considered as options to enhance survival of young lake trout; hatchery lake trout should not be stocked at sites where wild lake trout are showing signs of recovery; and exotic species expansions or introductions must be curtailed to maintain or improve on our recent successes in lake trout rehabilitation.

Stocking activities for the Arctic charr in Lake Geneva: Genetic effects in space and time.

PubMed

Savary, Romain; Dufresnes, Christophe; Champigneulle, Alexis; Caudron, Arnaud; Dubey, Sylvain; Perrin, Nicolas; Fumagalli, Luca

2017-07-01

Artificial stocking practices are widely used by resource managers worldwide, in order to sustain fish populations exploited by both recreational and commercial activities, but their benefits are controversial. Former practices involved exotic strains, although current programs rather consider artificial breeding of local fishes (supportive breeding). Understanding the complex genetic effects of these management strategies is an important challenge with economic and conservation implications, especially in the context of population declines. In this study, we focus on the declining Arctic charr ( Salvelinus alpinus ) population from Lake Geneva (Switzerland and France), which has initially been restocked with allochtonous fishes in the early eighties, followed by supportive breeding. In this context, we conducted a genetic survey to document the evolution of the genetic diversity and structure throughout the last 50 years, before and after the initiation of hatchery supplementation, using contemporary and historical samples. We show that the introduction of exotic fishes was associated with a genetic bottleneck in the 1980-1990s, a break of Hardy-Weinberg Equilibrium (HWE), a reduction in genetic diversity, an increase in genetic structure among spawning sites, and a change in their genetic composition. Together with better environmental conditions, three decades of subsequent supportive breeding using local fishes allowed to re-establish HWE and the initial levels of genetic variation. However, current spawning sites have not fully recovered their original genetic composition and were extensively homogenized across the lake. Our study demonstrates the drastic genetic consequences of different restocking tactics in a comprehensive spatiotemporal framework and suggests that genetic alteration by nonlocal stocking may be partly reversible through supportive breeding. We recommend that conservation-based programs consider local diversity and implement adequate protocols to limit the genetic homogenization of this Arctic charr population.

Otolith chemistry discriminates natal signatures of yellowfin tuna (Thunnus albacares) in the Atlantic Ocean

NASA Astrophysics Data System (ADS)

Kitchens, L. L.; Rooker, J. R.

2016-02-01

In this study, the otolith chemistry of young-of-the-year (YOY) yellowfin tuna (Thunnus albacares) was examined to determine whether chemical signatures are distinct across different putative spawning areas in the Atlantic Ocean. Yellowfin tuna is a highly migratory species that is currently managed as a single panmictic stock in the Atlantic Ocean; however, uncertainty remains regarding the population structure of yellowfin in this region, particularly concerning the degree of mixing between spawning populations. Analysis of naturally occurring chemical tracers in otoliths provides a valuable means to reconstruct a fish's environmental history and is thus a promising approach for delineating stock structure of Atlantic yellowfin tuna. YOY yellowfin tuna otoliths were collected from 5 locations in the Atlantic Ocean (Gulf of Mexico, SE Caribbean, Brazil, Cape Verde, and Gulf of Guinea) from 2013-2015 and trace element (Li, Mg, Mn, Co, Cu, Sr, Zn, and Ba) and stable isotope (δ13C and δ18O) analyses were conducted to investigate regional variation in otolith chemical composition. Results show significant differences among nursery areas in both trace element (MANOVA, p<0.001) and δ13C and δ18O signatures (ANOVA, p=0.017 and p=0.001, respectively). Particularly high spatial separation was observed based on eastern Atlantic (Gulf of Guinea + Cape Verde) and western Atlantic (Gulf of Mexico + Brazil + Martinique) nursery areas, indicating the approach has promise for distinguishing migrants displaying trans-ocean movement. These chemical signatures will be used to assign adult yellowfin tuna to their nursery of origin, ultimately providing an improved understanding of the stock structure and movement of yellowfin tuna in the Atlantic Ocean.

Management adaptation of invertebrate fisheries to an extreme marine heat wave event at a global warming hot spot.

PubMed

Caputi, Nick; Kangas, Mervi; Denham, Ainslie; Feng, Ming; Pearce, Alan; Hetzel, Yasha; Chandrapavan, Arani

2016-06-01

An extreme marine heat wave which affected 2000 km of the midwest coast of Australia occurred in the 2010/11 austral summer, with sea-surface temperature (SST) anomalies of 2-5°C above normal climatology. The heat wave was influenced by a strong Leeuwin Current during an extreme La Niña event at a global warming hot spot in the Indian Ocean. This event had a significant effect on the marine ecosystem with changes to seagrass/algae and coral habitats, as well as fish kills and southern extension of the range of some tropical species. The effect has been exacerbated by above-average SST in the following two summers, 2011/12 and 2012/13. This study examined the major impact the event had on invertebrate fisheries and the management adaption applied. A 99% mortality of Roei abalone ( Haliotis roei ) and major reductions in recruitment of scallops ( Amusium balloti ), king ( Penaeus latisulcatus ) and tiger ( P. esculentus ) prawns, and blue swimmer crabs were detected with management adapting with effort reductions or spatial/temporal closures to protect the spawning stock and restocking being evaluated. This study illustrates that fisheries management under extreme temperature events requires an early identification of temperature hot spots, early detection of abundance changes (preferably using pre-recruit surveys), and flexible harvest strategies which allow a quick response to minimize the effect of heavy fishing on poor recruitment to enable protection of the spawning stock. This has required researchers, managers, and industry to adapt to fish stocks affected by an extreme environmental event that may become more frequent due to climate change.

Implications of facultative catadromy in Anguilla anguilla. Does individual migratory behaviour influence eel spawner quality?

NASA Astrophysics Data System (ADS)

Marohn, Lasse; Jakob, Eva; Hanel, Reinhold

2013-03-01

European eel (Anguilla anguilla) recruitment is declining dramatically since the 1980s. Causes for this decline are explained by a combination of environmental changes basically affecting oceanic larval stages and a variety of anthropogenic impacts during the continental phase. Today, evidence is growing that poor silver eel quality has a major impact on reproductive success, implying that habitat quality plays a key role in stock decline. Since eels are frequently moving through a variety of different habitats during their life cycle, a better understanding of the implications of individual diadromous behaviour and habitat choice on spawner quality are crucial for management considerations for a stock recovery. The present study tested whether individual migratory behaviour and habitat choice of European eels affect spawner quality. Therefore, the migratory behaviour of 287 European eels from marine, brackish and freshwater stations in the North Sea, the Baltic Sea and from Northern German inland waters was examined by otolith strontium/calcium analysis. All individuals were classified either as freshwater residents, coastal residents, downstream shifters, upstream shifters or interhabitat shifters. As indicators for eel quality, muscle fat content, infection with the introduced swimbladder nematode Anguillicoloides crassus and body length at onset of spawning migration were assessed. Results indicate that individuals that exclusively inhabited freshwaters had significantly lower muscle fat contents and were more seriously infected with A. crassus than eels that never entered freshwaters. Since high fat contents are considered as prerequisites for a successful transoceanic spawning migration and high A. crassus loads have a negative impact on condition, this study outlines the importance of brackish waters as eel habitats in temperate latitudes. Furthermore, it questions the net benefit of stocking programs for the European eel population, since they include the translocation of eels from coastal waters into freshwaters.

Impact of El Niño events on pelagic fisheries in Peruvian waters

NASA Astrophysics Data System (ADS)

Ñiquen, Miguel; Bouchon, Marilú

2004-03-01

Using data from stock assesment surveys on pelagic resources during El Niño events of 1972/73, 1982/83, 1997/98, we analyze biological changes on pelagic ecosystems and pelagic fisheries during different stages of development of El Niño phenomenon: emergence, full, final and post-Niño. Results indicate changes in spatial distribution of resources, their concentration and size structure. In anchovy (Engraulis ringens) a decrease in biomass was observed, which was estimated at 1.2 million tons in September 1998, the lowest throughout the 1990s. This resource showed an asymmetric distribution towards the south of Peru. Other pelagic resources increased their biomass during or after Niño events, primarily sardine (Sardinops sagax), jack mackerel (Trachurus murphyi), pacific mackerel (Scomber japonicus), and longnose anchovy (Anchoa nasus). At the end of the El Niño phenomenon we found less productivity but more diversity in the pelagic ecosystem. During the 1997/98 El Niño, the diversity index (Manual de Ecologia, 1a Edition, Editorial Trillas, Mexico, 267pp) increased from 0.87 to 1.23-1.70. In both the emergence stage and fully developed stages of El Niño we found large numbers of sardine and longnose anchovy present simultaneously. Size structure of sardine, jack mackerel, and pacific mackerel showed an increase in juveniles. Anchovy during El Niño showed a single modal group composed of adults, but the post-Niño phase indicated an increase in juveniles with an average length of 6-7 cm. In El Niño conditions spawning among anchovy was low, but among sardine and pacific mackerel it was high. We observed, for the first time during full spawning, juvenile sardines with a total length of 18-20 cm. The anchovy spawning season during the post-Niño phase was considerably lengthened, from April to December 1998. Drastic change occurred in fisheries when monospecific fisheries, based on anchovy before El Niño, became multispecific fisheries based on sardine, jack mackerel, pacific mackerel, longnose anchovy and other species typical of tropical and warm oceans. Landings of anchovy decreased substantially, but those of longnose anchovy, jack mackerel, pacific mackerel, and sardine increased.

Myxobolus arcticus and Parvicapsula minibicornis infections in sockeye salmon Oncorhynchus nerka following downstream migration in British Columbia.

PubMed

Mahony, A M; Johnson, S C; Neville, C M; Thiess, M E; Jones, S R M

2017-10-18

Factors influencing the health of sockeye salmon Oncorhynchus nerka in British Columbia, Canada, are important for fisheries management and conservation. Juvenile salmon originating from the Fraser River were screened for 3 enzootic parasites (Myxobolus arcticus, Parvicapsula minibicornis, Ceratonova shasta) and the bacterium Renibacterium salmoninarum. Fish were collected from the Strait of Georgia in 2010, 2011 and 2012 and genotyped to stock of origin. Trends in infection status were estimated by year, spawning zone and catch area. The annual prevalences of P. minibicornis (n = 1448) were 23.3, 6.5 and 8.1%, and for M. arcticus (n = 1343), annual prevalences were 40.4, 66.3 and 27.4%, respectively. Logistic regression showed that P. minibicornis was most strongly associated with salmon from the lower Fraser River spawning zone and increased with distance caught from the mouth of the Fraser River. In contrast, infection with M. arcticus was most strongly associated with salmon from the middle Fraser River spawning zone, and there was no trend related to distance from the Fraser River. Neither R. salmoninarum nor C. shasta were detected. These observations are discussed in the context of salmon life history and pathogen biology.

Sole larval supply to coastal nurseries: Interannual variability and connectivity at interregional and interpopulation scales

NASA Astrophysics Data System (ADS)

Savina, M.; Lunghi, M.; Archambault, B.; Baulier, L.; Huret, M.; Le Pape, O.

2016-05-01

Simulating fish larval drift helps assess the sensitivity of recruitment variability to early life history. An individual-based model (IBM) coupled to a hydrodynamic model was used to simulate common sole larval supply from spawning areas to coastal and estuarine nursery grounds at the meta-population scale (4 assessed stocks), from the southern North Sea to the Bay of Biscay (Western Europe) on a 26-yr time series, from 1982 to 2007. The IBM allowed each particle released to be transported by currents, to grow depending on temperature, to migrate vertically depending on development stage, to die along pelagic stages or to settle on a nursery, representing the life history from spawning to metamorphosis. The model outputs were analysed to explore interannual patterns in the amounts of settled sole larvae at the population scale; they suggested: (i) a low connectivity between populations at the larval stage, (ii) a moderate influence of interannual variation in the spawning biomass, (iii) dramatic consequences of life history on the abundance of settling larvae and (iv) the effects of climate variability on the interannual variability of the larvae settlement success.

Species profiles: Life histories and environmental requirements of coastal fishes and invertebrates (Mid-Atlantic)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grimes, B.H.; Huish, M.T.; Kerby, J.H.

1989-08-01

Species profiles are literature summaries of the taxonomy, morphology, range, life history, and environmental requirements of coastal species. They are designed to assist in environmental impact assessments. The summer flounder supports an important commercial and recreational fishery in the Mid-Atlantic and are important constituent of estuarine and continental shelf systems throughout the region. Summer flounder spawning begins in September and winter flounder spawning begins in June. Summer flounder eggs are pelagic whereas winter flounder eggs are demersal. Summer flounder larvae are more abundant in inlets, and juveniles are found in estuarine seagrass beds in salinities {>=}12 ppt. Winter flounder juvenilesmore » are abundant in shallow bays and estuaries, moving seaward in spring and summer. Growth of winter flounder and summer flounder is seasonal. There are probably three spawning populations of both species which produce a complex stock pattern. Summer flounder are tolerant of a wide range of chemical and physica faactors, but prefer {gt}10 ppt salinities. Winter flounder optimal temperature is 18.5 {degree}C. Diseases of winter flounder are more prevalent in polluted waters. Summer flounder are tolerant of sediments laden with contaminants. 64 refs., 5 figs., 2 tabs.« less

Ecological relationship between freshwater sculpins (Genus cottus) and beach-spawning sockeye salmon (Oncorhynchus nerka) in Iliamna Lake, Alaska

USGS Publications Warehouse

Foote, C.J.; Brown, G.S.

1998-01-01

The interaction between two sculpin species, Cottus cognatus and Cottus aleuticus, and island beach spawning sockeye salmon (Oncorhynchus nerka) was examined in Iliamna Lake, Alaska. We conclude that sculpins actively move to specific spawning beaches and that the initiation of their movements precedes the start of spawning. Sculpin predation on sockeye eggs is positively dependent on sculpin size and on the state of the eggs (fresh versus water hardened), with the largest sculpins able to consume nearly 50 fresh eggs at a single feeding and 130 over a 7-day period. The number of sculpins in sockeye nests is greatest at the beginning of the spawning run, lowest in the middle, and high again at the end, with peak numbers of over 100 sculpins per nest (1 m2). We discuss the results in terms of energy flow of marine-derived nutrients into an oligotrophic system and in terms of the coevolution of sockeye spawning behavior and the predatory behavior of sculpins.

Influence of breeding habitat on bear predation and age at maturity and sexual dimorphism of sockeye salmon populations

USGS Publications Warehouse

Quinn, Thomas P.; Wetzel, Lisa A.; Bishop, Susan; Overberg, Kristi; Rogers, Donald E.

2001-01-01

Age structure and morphology differ among Pacific salmon (Oncorhynchus spp.) populations. Sexual selection and reproductive capacity (fecundity and egg size) generally favor large (old), deep-bodied fish. We hypothesized that natural selection from physical access to spawning grounds and size-biased predation by bears, Ursus spp., opposes such large, deep-bodied salmon. Accordingly, size and shape of salmon should vary predictably among spawning habitats. We tested this hypothesis by measuring the age composition and body depth of sockeye salmon, Oncorhynchus nerka, and the intensity of predation in a range of breeding habitats in southwestern Alaska. Stream width was positively correlated with age at maturity and negatively correlated with predation level. However, salmon spawning on lake beaches were not consistently old, indicating that different factors affect age in riverine- and beach-spawning populations. Body depths of male and female salmon were positively correlated with water depth across all sites, as predicted. However, the mouths of some streams were so shallow that they might select against large or deep-bodied salmon, even in the absence of bear predation. Taken together, the results indicated that habitat has direct and indirect effects (via predation) on life history and morphology of mature salmon.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ford, Michael J.; Williamson, Kevin S.

We investigated differences in the statistical power to assign parentage between an artificially propagated and wild salmon population. The propagated fish were derived from the wild population, and are used to supplement its abundance. Levels of genetic variation were similar between the propagated and wild groups at 11 microsatellite loci, and exclusion probabilities were >0.999999 for both groups. The ability to unambiguously identify a pair of parents for each sampled progeny was much lower than expected, however. Simulations demonstrated that the proportion of cases the most likely pair of parents were the true parents was lower for propagated parents thanmore » for wild parents. There was a clear relationship between parentage assignment ability and the degree of linkage disequilibrium, the estimated effective number of breeders that produced the parents, and the size of the largest family within the potential parents. If a stringent threshold for parentage assignment was used, estimates of relative fitness were biased downward for the propagated fish. The bias appeared to be largely eliminated by either fractionally assigning progeny among parents in proportion to their likelihood of parentage, or by assigning progeny to the most likely set of parents without using a statistical threshold. We used a DNA-based parentage analysis to measure the relative reproductive success of hatchery- and natural-origin spring Chinook salmon in the natural environment. Both male and female hatchery-origin fish produced far fewer juvenile progeny per parent when spawning naturally than did natural origin fish. Differences in age structure, spawning location, weight and run timing were responsible for some of the difference in fitness. Male size and age had a large influence on fitness, with larger and older males producing more offspring than smaller or younger individuals. Female size had a significant effect on fitness, but the effect was much smaller than the effect of size on male fitness. For both sexes, run time had a smaller but still significant effect on fitness, with earlier returning fish favored. Spawning location within the river had a significant effect on fitness for both males and females, and for females explained most of the reduced fitness observed for hatchery fish in this population. While differences have been reported in the relative reproductive success of hatchery and naturally produced salmonids Oncorhynchus spp., factors explaining the differences are often confounded. We examined the spawning site habitat and redd structure variables of hatchery and naturally produced spring Chinook salmon O. tshawytscha of known size that spawned in two tributaries of the Wenatchee River. We controlled for variability in spawning habitat by limiting our analysis to redds found within four selected reaches. No difference in the instantaneous spawner density or location of the redd in the stream channel was detected between reaches. Within each reach, no difference in the fork length or weight of hatchery and naturally produced fish was detected. While most variables differed between reaches, we found no difference in redd characteristics within a reach between hatchery and naturally produced females. Correlation analysis of fish size and redd characteristics found several weak but significant relationships suggesting larger fish contract larger redds in deeper water. Spawner density was inversely related to several redd structure variables suggesting redd size may decrease as spawner density increases. Results should be considered preliminary until samples size and statistical power goals are reached in future years. Trends in relative reproductive success of hatchery and naturally produced spring Chinook salmon Oncorhynchus tshawytscha in the Wenatchee Basins suggest females that spawn in the upper reaches of the tributaries produced a great number of offspring compared to females that spawn in the lower reaches of the tributaries. To better understand this trend, redd microhabitat data was collected from spring Chinook salmon that spawned in the Chiwawa River and Nason Creek, the primary spawning tributaries in the Wenatchee Basin. The objective of the study was to examine the influence of habitat and spawner density on spawning site and redd structure characteristics. We analyzed 27 variables of redd microhabitat data collected from the upper and lower most reaches of each study stream. In both streams, we found redds in the upper most reaches to be significantly larger (length and width) and deeper (bowl depth). Spawner density was significantly greater in the lower Chiwawa River compared to the upper reach. No difference in spawner density was detected between reaches in Nason Creek (P = 0.54). Data should be considered preliminary until sample size goals are achieved.« less

Internal tidal mixing as a control on continental margin ecosystems

NASA Astrophysics Data System (ADS)

Sharples, Jonathan; Moore, C. Mark; Hickman, Anna E.; Holligan, Patrick M.; Tweddle, Jacqueline F.; Palmer, Matthew R.; Simpson, John H.

2009-12-01

We show that a breaking internal tide at a shelf edge is a fundamental control on the structural and functional properties of ecosystems. Contrasts in vertical mixing of nitrate between the shelf and the open ocean correspond with horizontal and vertical changes in phytoplankton communities, with largest cells found in surface waters at the shelf edge. Intense fishing activity is commonly seen at continental shelf edges, targeting spawning fish stocks. We suggest that the internal tide, a globally ubiquitous physical process at steep shelf edge bathymetry, supports shelf edge fisheries by providing large-celled phytoplankton for first-feeding fish larvae. The repeatability of the internal tide removes fish from the need to time spawning with a spring bloom. Also, with large phytoplankton cells dominating particulate organic carbon export, the internal tides could be an important influence on spatial and temporal variability in patterns of global carbon sequestration in deep water and sediments.

Benzocaine as a fish anesthetic: efficacy and safety for spawning-phase salmon

USGS Publications Warehouse

Gilderhus, P.A.

1990-01-01

The anesthetic benzocaine was tested for efficacy and safety for spawning-phase chinook salmon (Oncorhynchus tshawytscha) and Atlantic salmon (Salmo salar) at federal fish hatcheries. Tests were conducted in the existing hatchery water supplies (soft water; temperatures, 10–13 °C. Crystalline benzocaine was dissolved in ethanol (1 g/30 mL), and aliquots of that stock solution were added to the water in test tanks. Benzocaine concentrations of 25–30 mg/L anesthetized most fish in less than 3.5 min, and most fish recovered in less than 10 min after 15 min of exposure. Safety margins were narrow; both species tolerated 30 mg/L for about 20 min, but 25 min of exposure caused deaths. For 15 min exposures, concentrations of 35 mg/L for chinook salmon and 40 mg/L for Atlantic salmon were lethal.

Overview of biology and aquaculture of Amur sturgeon (Acipenser schrenckii) in China

USGS Publications Warehouse

Zhuang, P.; Kynard, B.; Zhang, L.; Zhang, T.; Zhang, Z.; Li, D.

2002-01-01

Amur sturgeon, Acipenser schrenckii is a large riverine species (max. 3 m length and 190 kg weight) native to the Amur River. In the middle Amur River, males first spawn at 7-8 years of age and females at 9-10 years. Due to overfishing and habitat alteration, the abundance of wild stocks has rapidly declined in recent years. Using wild adults, artificial spawning began in the 1950s in China, and since the early 1990s Amur sturgeon has become the most popular sturgeon for aquaculture. The species is adaptive to many conditions of artificial culture, including traditional Chinese fish culture ponds, lakes, reservoirs, and cages. It will grow well on many types of food, and 1-year-old fish reared on commercial diets weigh 900-1200 g. Based on the examination of females reared for broodstock, first full sexual maturity is expected at 5-6 years of age.

Chapter 3. Effects of climate change and commercial fishing on Atlantic cod Gadus morhua.

PubMed

Mieszkowska, Nova; Genner, Martin J; Hawkins, Stephen J; Sims, David W

2009-01-01

During the course of the last century, populations of Atlantic cod Gadus morhua L. have undergone dramatic declines in abundance across their biogeographic range, leading to debate about the relative roles of climatic warming and overfishing in driving these changes. In this chapter, we describe the geographic distributions of this important predator of North Atlantic ecosystems and document extensive evidence for limitations of spatial movement and local adaptation from population genetic markers and electronic tagging. Taken together, this evidence demonstrates that knowledge of spatial population ecology is critical for evaluating the effects of climate change and commercial harvesting. To explore the possible effects of climate change on cod, we first describe thermal influences on individual physiology, growth, activity and maturation. We then evaluate evidence that temperature has influenced population-level processes including direct effects on recruitment through enhanced growth and activity, and indirect effects through changes to larval food resources. Although thermal regimes clearly define the biogeographic range of the species, and strongly influence many aspects of cod biology, the evidence that population declines across the North Atlantic are strongly linked to fishing activity is now overwhelming. Although there is considerable concern about low spawning stock biomasses, high levels of fishing activity continues in many areas. Even with reduced fishing effort, the potential for recovery from low abundance may be compromised by unfavourable climate and Allee effects. Current stock assessment and management approaches are reviewed, alongside newly advocated methods for monitoring stock status and recovery. However, it remains uncertain whether the rebuilding of cod to historic population sizes and demographic structures will be possible in a warmer North Atlantic.

Grande Ronde Basin Chinook Salmon Captive Brood and Conventional Supplementation Programs, 2003 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoffnagle, Timothy L.; Hair, Don; Carmichael, Richard W.

2004-07-01

BPA Fish and Wildlife Program Project Number 1998-01-001 provides funding for the Grande Ronde Basin Spring Chinook Salmon Captive Broodstock Program. This report satisfies the requirement that an annual report be submitted for FY 2003. The Grande Ronde Basin Spring Chinook Salmon Captive Broodstock Project is designed to rapidly increase numbers of salmon in stocks that are in imminent danger of extirpation. Parr are captured in Catherine Creek, upper Grande Ronde River and Lostine River and reared to adulthood in captivity. Upon maturation, these fish are spawned (within stocks) and their progeny reared to smoltification before being released into themore » natal stream of their parents. This program is co-managed by ODFW, National Marine Fisheries Service, Nez Perce Tribe and Confederated Tribes of the Umatilla Indian Reservation. This report covers activities conducted and provides data analyses for the Grande Ronde Spring Chinook Salmon Captive broodstock Program from 1 January--31 December 2003. Since the fiscal year ends in the middle of the spawning period, an annual report based on calendar year is more logical. This document is the FY 2003 annual report. Detailed information on historic and present population status, project background, goals and objectives, significance to regional programs and relationships to other programs, methods and previous results are available in the 1995-2002 Project Status Report (Hoffnagle et al 2003).« less

An accurate method for measuring triploidy of larval fish spawns

USGS Publications Warehouse

Jenkins, Jill A.; Draugelis-Dale, Rassa O.; Glennon, Robert; Kelly, Anita; Brown, Bonnie L.; Morrison, John

2017-01-01

A standard flow cytometric protocol was developed for estimating triploid induction in batches of larval fish. Polyploid induction treatments are not guaranteed to be 100% efficient, thus the ability to quantify the proportion of triploid larvae generated by a particular treatment helps managers to stock high-percentage spawns and researchers to select treatments for efficient triploid induction. At 3 d posthatch, individual Grass Carp Ctenopharyngodon idella were mechanically dissociated into single-cell suspensions; nuclear DNA was stained with propidium iodide then analyzed by flow cytometry. Following ploidy identification of individuals, aliquots of diploid and triploid cell suspensions were mixed to generate 15 levels (0–100%) of known triploidy (n = 10). Using either 20 or 50 larvae per level, the observed triploid percentages were lower than the known, actual values. Using nonlinear regression analyses, quadratic equations solved for triploid proportions in mixed samples and corresponding estimation reference plots allowed for predicting triploidy. Thus, an accurate prediction of the proportion of triploids in a spawn can be made by following a standard larval processing and analysis protocol with either 20 or 50 larvae from a single spawn, coupled with applying the quadratic equations or reference plots to observed flow cytometry results. Due to the universality of triploid DNA content being 1.5 times the diploid level and because triploid fish consist of fewer cells than diploids, this method should be applicable to other produced triploid fish species, and it may be adapted for use with bivalves or other species where batch analysis is appropriate.

Lake trout in northern Lake Huron spawn on submerged drumlins

USGS Publications Warehouse

Riley, Stephen C.; Binder, Thomas; Wattrus, Nigel J.; Faust, Matthew D.; Janssen, John; Menzies, John; Marsden, J. Ellen; Ebener, Mark P.; Bronte, Charles R.; He, Ji X.; Tucker, Taaja R.; Hansen, Michael J.; Thompson, Henry T.; Muir, Andrew M.; Krueger, Charles C.

2014-01-01

Recent observations of spawning lake trout Salvelinus namaycush near Drummond Island in northern Lake Huron indicate that lake trout use drumlins, landforms created in subglacial environments by the action of ice sheets, as a primary spawning habitat. From these observations, we generated a hypothesis that may in part explain locations chosen by lake trout for spawning. Most salmonines spawn in streams where they rely on streamflows to sort and clean sediments to create good spawning habitat. Flows sufficient to sort larger sediment sizes are generally lacking in lakes, but some glacial bedforms contain large pockets of sorted sediments that can provide the interstitial spaces necessary for lake trout egg incubation, particularly if these bedforms are situated such that lake currents can penetrate these sediments. We hypothesize that sediment inclusions from glacial scavenging and sediment sorting that occurred during the creation of bedforms such as drumlins, end moraines, and eskers create suitable conditions for lake trout egg incubation, particularly where these bedforms interact with lake currents to remove fine sediments. Further, these bedforms may provide high-quality lake trout spawning habitat at many locations in the Great Lakes and may be especially important along the southern edge of the range of the species. A better understanding of the role of glacially-derived bedforms in the creation of lake trout spawning habitat may help develop powerful predictors of lake trout spawning locations, provide insight into the evolution of unique spawning behaviors by lake trout, and aid in lake trout restoration in the Great Lakes.

Temporal patterns of migration and spawning of river herring in coastal Massachusetts

USGS Publications Warehouse

Rosset, Julianne; Roy, Allison; Gahagan, Benjamin I.; Whiteley, Andrew R.; Armstrong, Michael P.; Sheppard, John J.; Jordaan, Adrian

2017-01-01

Migrations of springtime Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis, collectively referred to as river herring, are monitored in many rivers along the Atlantic coast to estimate population sizes. While these estimates give an indication of annual differences in the number of returning adults, links to the subsequent timing and duration of spawning and freshwater juvenile productivity remain equivocal. In this study, we captured juvenile river herring at night in 20 coastal Massachusetts lakes using a purse seine and extracted otoliths to derive daily fish ages and back-calculate spawn dates. Estimates of spawning dates were compared with fishway counts of migrating adults to assess differences in migration timing and the timing and duration of spawning. We observed a distinct delay between the beginning of the adult migration run and the start of spawning, ranging from 7 to 28 d across the 20 lakes. Spawning continued 13–48 d after adults stopped migrating into freshwater, further demonstrating a pronounced delay in spawning following migration. Across the study sites the duration of spawning (43–76 d) was longer but not related to the duration of migration (29–66 d). The extended spawning period is consistent with recent studies suggesting that Alewives are indeterminate spawners. The long duration in freshwater provides the opportunity for top-down (i.e., predation on zooplankton) and bottom-up (i.e., food for avian, fish, and other predators) effects, with implications for freshwater food webs and nutrient cycling. General patterns of spawn timing and duration can be incorporated into population models and used to estimate temporal changes in productivity associated with variable timing and density of spawning river herring in lakes.

Working with, not against, coral-reef fisheries

NASA Astrophysics Data System (ADS)

Birkeland, Charles

2017-03-01

The fisheries policies of some Pacific island nations are more appropriate to the biology of their resources than are some of the fisheries policies of more industrialized countries. Exclusive local ownership of natural resources in Palau encourages adjustive management on biologically relevant scales of time and space and promotes responsibility by reducing the tragedy of the commons. The presence of large individuals in fish populations and adequate size of spawning aggregations are more efficient and meaningful cues for timely management than are surveys of abundance or biomass. Taking fish from populations more than halfway to their carrying capacity is working favorably with the fishery because removing fish potentially increases resource stability by negative feedback between stock size and population production. Taking the same amount of fish from a population below half its carrying capacity is working against the fishery, making the population unstable, because reducing the reproductive stock potentially accelerates reduction of the population production by positive feedback. Reef fish are consumed locally, while Palauan laws ban the export of reef resources. This is consistent with the high gross primary production with little excess net production from undisturbed coral-reef ecosystems. The relatively rapid growth rates, short life spans, reliable recruitment and wide-ranging movements of open-ocean fishes such as scombrids make them much more productive than coral-reef fishes. The greater fisheries yield per square kilometer in the open ocean multiplied by well over a thousand times the area of the exclusive economic zone than that of Palau's coral reefs should encourage Palauans to keep reef fishes for subsistence and to feed tourists open-ocean fishes. Fisheries having only artisanal means should be encouraged to increase the yield and sustainability by moving away from coral reefs to bulk harvesting of nearshore pelagics.

Roles of density-dependent growth and life history evolution in accounting for fisheries-induced trait changes.

PubMed

Eikeset, Anne Maria; Dunlop, Erin S; Heino, Mikko; Storvik, Geir; Stenseth, Nils C; Dieckmann, Ulf

2016-12-27

The relative roles of density dependence and life history evolution in contributing to rapid fisheries-induced trait changes remain debated. In the 1930s, northeast Arctic cod (Gadus morhua), currently the world's largest cod stock, experienced a shift from a traditional spawning-ground fishery to an industrial trawl fishery with elevated exploitation in the stock's feeding grounds. Since then, age and length at maturation have declined dramatically, a trend paralleled in other exploited stocks worldwide. These trends can be explained by demographic truncation of the population's age structure, phenotypic plasticity in maturation arising through density-dependent growth, fisheries-induced evolution favoring faster-growing or earlier-maturing fish, or a combination of these processes. Here, we use a multitrait eco-evolutionary model to assess the capacity of these processes to reproduce 74 y of historical data on age and length at maturation in northeast Arctic cod, while mimicking the stock's historical harvesting regime. Our results show that model predictions critically depend on the assumed density dependence of growth: when this is weak, life history evolution might be necessary to prevent stock collapse, whereas when a stronger density dependence estimated from recent data is used, the role of evolution in explaining fisheries-induced trait changes is diminished. Our integrative analysis of density-dependent growth, multitrait evolution, and stock-specific time series data underscores the importance of jointly considering evolutionary and ecological processes, enabling a more comprehensive perspective on empirically observed stock dynamics than previous studies could provide.

Fishing and temperature effects on the size structure of exploited fish stocks.

PubMed

Tu, Chen-Yi; Chen, Kuan-Ting; Hsieh, Chih-Hao

2018-05-08

Size structure of fish stock plays an important role in maintaining sustainability of the population. Size distribution of an exploited stock is predicted to shift toward small individuals caused by size-selective fishing and/or warming; however, their relative contribution remains relatively unexplored. In addition, existing analyses on size structure have focused on univariate size-based indicators (SBIs), such as mean length, evenness of size classes, or the upper 95-percentile of the length frequency distribution; these approaches may not capture full information of size structure. To bridge the gap, we used the variation partitioning approach to examine how the size structure (composition of size classes) responded to fishing, warming and the interaction. We analyzed 28 exploited stocks in the West US, Alaska and North Sea. Our result shows fishing has the most prominent effect on the size structure of the exploited stocks. In addition, the fish stocks experienced higher variability in fishing is more responsive to the temperature effect in their size structure, suggesting that fishing may elevate the sensitivity of exploited stocks in responding to environmental effects. The variation partitioning approach provides complementary information to univariate SBIs in analyzing size structure.

A quantitative life history of endangered humpback chub that spawn in the Little Colorado River: variation in movement, growth, and survival

USGS Publications Warehouse

Yackulic, Charles B.; Yard, Michael D.; Korman, Josh; Van Haverbeke, David R.

2014-01-01

While the ecology and evolution of partial migratory systems (defined broadly to include skip spawning) have been well studied, we are only beginning to understand how partial migratory populations are responding to ongoing environmental change. Environmental change can lead to differences in the fitness of residents and migrants, which could eventually lead to changes in the frequency of the strategies in the overall population. Here, we address questions concerning the life history of the endangered Gila cypha (humpback chub) in the regulated Colorado River and the unregulated tributary and primary spawning area, the Little Colorado River. We develop eight multistate models for the population based on three movement hypotheses, in which states are defined in terms of fish size classes and river locations. We fit these models to mark–recapture data collected in 2009–2012. We compare survival and growth estimates between the Colorado River and Little Colorado River and calculate abundances for all size classes. The best model supports the hypotheses that larger adults spawn more frequently than smaller adults, that there are residents in the spawning grounds, and that juveniles move out of the Little Colorado River in large numbers during the monsoon season (July–September). Monthly survival rates for G. cypha in the Colorado River are higher than in the Little Colorado River in all size classes; however, growth is slower. While the hypothetical life histories of life-long residents in the Little Colorado River and partial migrants spending most of its time in the Colorado River are very different, they lead to roughly similar fitness expectations when we used expected number of spawns as a proxy. However, more research is needed because our study period covers a period of years when conditions in the Colorado River for G. cypha are likely to have been better than has been typical over the last few decades.

Reproductive ecology of lampreys

USGS Publications Warehouse

Johnson, Nicholas S.; Buchinger, Tyler J.; Li, Weiming

2014-01-01

Lampreys typically spawn in riffle habitats during the spring. Spawning activity and diel (i.e., during daylight and at night) behavioral patterns are initiated when spring water temperatures increase to levels that coincide with optimal embryologic development. Nests are constructed in gravel substrate using the oral disc to move stones and the tail to fan sediment out of the nest. Spawning habitat used by individual species is generally a function of adult size, where small-bodied species construct nests in shallower water with slower flow and smaller gravel than large-bodied species. The mating system of lampreys is primarily polygynandrous (i.e., where multiple males mate with multiple females). Lamprey species with adult total length less than 30 cm generally spawn communally, where a nest may contain 20 or more individuals of both sexes. Lamprey species with adult sizes greater than 35 cm generally spawn in groups of two to four. Operational sex ratios of lampreys are highly variable across species, populations, and time, but are generally male biased. The act of spawning typically starts with the male attaching with his oral disc to the back of the female’s head; the male and female then entwine and simultaneously release gametes. However, alternative mating behaviors (e.g., release of gametes without paired courtship and sneaker males) have been observed. Future research should determine how multiple modalities of communication among lampreys (including mating pheromones) are integrated to inform species recognition and mate choice. Such research could inform both sea lamprey control strategies and provide insight into possible evolution of reproductive isolation mechanisms between paired lamprey species in sympatry.

Re-Introduction of Lower Columbia River Chum Salmon into Duncan Creek, 2003-2004 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hillson, Todd D.

2004-09-01

Currently, two methods of reintroduction are being simultaneously evaluated at Duncan Creek. Recolonization is occurring by introducing adult chum salmon from the Lower Gorge (LG) population into Duncan Creek and allowing them to naturally reproduce. The supplementation strategy required adults to be collected and artificially spawned, incubated, reared, and released at the mouth of Duncan Creek. All eggs from the artificial crossings at Washougal Hatchery were incubated and the fry reared to release size at the hatchery. The Duncan Creek chum salmon project was very successful in 2003-04, providing knowledge and experience that will improve program execution in future years.more » The gear used to collect adult brood stock was changed from tangle nets to beach seines. This increased efficiency and the speed at which adults could be processed in the field, and most likely reduced stress on the adults handled. Certain weaknesses exposed in past seasons still exist and new ones were exposed (e.g. inadequate incubation and rearing space at Washougal Hatchery for any large salvage operation and having to move the rearing troughs outside the raceway in 2004). Egg-to-fry survival rates of 64% and 58% showed that the channels are functioning at the upper end of what can be expected from them. Possibly the most important event this season was the ability to strontium mark and release all naturally-produced fry from the spawning channels. Channel and floodplain modifications reduced the likelihood that floods will damage the channels and negatively impact survival rates.« less

Identification of American shad spawning sites and habitat use in the Pee Dee River, North Carolina and South Carolina

USGS Publications Warehouse

Harris, Julianne E.; Hightower, Joseph E.

2011-01-01

We examined spawning site selection and habitat use by American shad Alosa sapidissima in the Pee Dee River, North Carolina and South Carolina, to inform future management in this flow-regulated river. American shad eggs were collected in plankton tows, and the origin (spawning site) of each egg was estimated; relocations of radio-tagged adults on spawning grounds illustrated habitat use and movement in relation to changes in water discharge rates. Most spawning was estimated to occur in the Piedmont physiographic region within a 25-river-kilometer (rkm) section just below the lowermost dam in the system; however, some spawning also occurred downstream in the Coastal Plain. The Piedmont region has a higher gradient and is predicted to have slightly higher current velocities and shallower depths, on average, than the Coastal Plain. The Piedmont region is dominated by large substrates (e.g., boulders and gravel), whereas the Coastal Plain is dominated by sand. Sampling at night (the primary spawning period) resulted in the collection of young eggs (≤1.5 h old) that more precisely identified the spawning sites. In the Piedmont region, most radio-tagged American shad remained in discrete areas (average linear range = 3.6 rkm) during the spawning season and generally occupied water velocities between 0.20 and 0.69 m/s, depths between 1.0 and 2.9 m, and substrates dominated by boulder or bedrock and gravel. Tagged adults made only small-scale movements with changes in water discharge rates. Our results demonstrate that the upstream extent of migration and an area of concentrated spawning occur just below the lowermost dam. If upstream areas have similar habitat, facilitating upstream access for American shad could increase the spawning habitat available and increase the population's size.

Spawning bed sedimentation studies in northern California streams

Treesearch

James W. Burns

1970-01-01

Changes in the size composition of spawning bed materials in six coastal streams were monitored for 3 years to determine the effects of logging on the habitat of silver salmon (Oncorhynchus kisutch) and trout (Salmo gairdnerii gairdnerii and S. clarkii clarkii). Four test streams were sampled before, during and after logging. Two streams in unlogged watersheds and...

Timing and locations of reef fish spawning off the southeastern United States

PubMed Central

Heyman, William D.; Karnauskas, Mandy; Kobara, Shinichi; Smart, Tracey I.; Ballenger, Joseph C.; Reichert, Marcel J. M.; Wyanski, David M.; Tishler, Michelle S.; Lindeman, Kenyon C.; Lowerre-Barbieri, Susan K.; Switzer, Theodore S.; Solomon, Justin J.; McCain, Kyle; Marhefka, Mark; Sedberry, George R.

2017-01-01

Managed reef fish in the Atlantic Ocean of the southeastern United States (SEUS) support a multi-billion dollar industry. There is a broad interest in locating and protecting spawning fish from harvest, to enhance productivity and reduce the potential for overfishing. We assessed spatiotemporal cues for spawning for six species from four reef fish families, using data on individual spawning condition collected by over three decades of regional fishery-independent reef fish surveys, combined with a series of predictors derived from bathymetric features. We quantified the size of spawning areas used by reef fish across many years and identified several multispecies spawning locations. We quantitatively identified cues for peak spawning and generated predictive maps for Gray Triggerfish (Balistes capriscus), White Grunt (Haemulon plumierii), Red Snapper (Lutjanus campechanus), Vermilion Snapper (Rhomboplites aurorubens), Black Sea Bass (Centropristis striata), and Scamp (Mycteroperca phenax). For example, Red Snapper peak spawning was predicted in 24.7–29.0°C water prior to the new moon at locations with high curvature in the 24–30 m depth range off northeast Florida during June and July. External validation using scientific and fishery-dependent data collections strongly supported the predictive utility of our models. We identified locations where reconfiguration or expansion of existing marine protected areas would protect spawning reef fish. We recommend increased sampling off southern Florida (south of 27° N), during winter months, and in high-relief, high current habitats to improve our understanding of timing and location of reef fish spawning off the southeastern United States. PMID:28264006

Incubation success and habitat selection of shore-spawning kokanee Onchorhynchus nerka: effects of water level regulation and habitat characteristics.

USGS Publications Warehouse

Whitlock, Steven L.; Quist, Michael C.; Dux, Andrew M.

2014-01-01

Changes to water-level regimes have been known to restructure fish assemblages and interfere with the population dynamics of both littoral and pelagic species. The effect of altered water-level regimes on shore-spawning kokanee Oncorhynchus nerka incubation success was evaluated using a comprehensive in situ study in Lake Pend Oreille, ID, USA. Survival was not related to substrate size composition or depth, indicating that shore-spawning kokanee do not currently receive a substrate-mediated survival benefit from higher winter water levels. Substrate composition also did not differ among isobaths in the nearshore area. On average, the odds of an egg surviving to the preemergent stage were more than three times greater for sites in downwelling areas than those lacking downwelling. This study revealed that shoreline spawning habitat is not as limited as previously thought. Downwelling areas appear to contribute substantially to shore-spawning kokanee recruitment. This research illustrates the value of rigorous in situ studies both for testing potential mechanisms underlying population trends and providing insight into spawning habitat selection.

Seasonal and annual variation in Chilean hake Merluccius gayi spawning locations and egg size off central Chile

NASA Astrophysics Data System (ADS)

Landaeta, Mauricio F.; Castro, Leonardo R.

2012-01-01

Variability in Chilean hake reproductive tactics off central Chile was assessed by analyzing ichthyoplankton samples from nine oceanographic cruises (1996-2005) and through experimental trials with early life stages (eggs, yolk-sac larvae) during the main (austral spring) and secondary (late summer-early autumn) spawning seasons. Abundant eggs in the plankton (1300-2000 eggs per 10 m 2) and historical adult reproductive data showed the highest reproductive activity in austral spring, with large egg aggregations near shelf break (50-100 m depth). Large, recently spawned eggs (1.15-1.20 mm diameter) were advected nearshore by coastward subsurface flows in the spring upwelling season. Experimental trials indicated that recently hatched larvae (3.4-3.5 mm) consumed their yolk-sac (0.17-0.41 mm 3) in 3-4 days at 10-12 °C; plankton sampling indicated that larval hake remained at mid-depth (50-100 m) without showing daily vertical migrations until completing their caudal fin formation (∼15 mm). During the secondary reproductive peak, hake spawned nearshore, when smaller eggs (0.95-1.13 mm) and recently hatched larvae (2.2-2.6 mm notochord length) occurred in surface waters (0-10 m depth). Their relatively large yolk-sac volumes (0.57 ± 0.11 mm 3) provided endogenous nourishment for at least 5 days at 10 °C, according to experiments. In the field, preflexion larvae occurred mainly in the mixed layer (0-25 m) and started ontogenetic daily vertical migrations at 7 mm. A strong decline occurred after 2002 in the adult Chilean hake biomass (estimated by hydroacoustic surveys) and body size, coinciding with variations in spawning locations (more coastward in early spring 2004 and 2005) and decline in egg size. Thus, recent variations in Chilean hake reproductive tactics may reflect an indirect effect of declines in the parental population size.

Fish and fisher behaviour influence the vulnerability of groupers (Epinephelidae) to fishing at a multispecies spawning aggregation site

NASA Astrophysics Data System (ADS)

Robinson, J.; Graham, N. A. J.; Cinner, J. E.; Almany, G. R.; Waldie, P.

2015-06-01

Targeted fishing of spawning aggregations is a major contributor to extinction risk in numerous species of grouper (Epinephelidae). Marine reserves are often used to protect spawning aggregation sites, including multispecies sites shared by several species of grouper. However, marine reserves may be biologically, socioeconomically or culturally unviable in some fisheries, and alternative management actions must be explored. Implementing effective management actions that control rather than prohibit fishing requires an improved understanding of how species vary in their vulnerability to fishing gears and respond to changes in fishing effort. To estimate sources of variability in vulnerability to fishing (i.e. catchability), catch-per-unit-effort (CPUE) and other fisheries data were collected in parallel with underwater visual census-derived estimates of aggregation size at a multispecies spawning site of Epinephelus fuscoguttatus and E. polyphekadion. Despite having similar abundances, E. polyphekadion was eightfold more vulnerable to capture by hook-and-line gear, clearly outcompeting its congener for bait. Contrasting with the common assumption of a proportional relationship, the CPUE of both species was unrelated to the size of their respective aggregations. Moreover, the CPUE of each species was unrelated to hook size and depth fished. However, E. polyphekadion CPUE declined as the density of fishing effort increased at the site, with gear saturation identified as the likely mechanism for this effect. E. fuscoguttatus CPUE was negatively related to the size of aggregations formed by its congener, stemming from the superior competitiveness and therefore higher selectivity of the gear for E. polyphekadion. Our findings demonstrate that CPUE is an unreliable indicator of spawning aggregation status. The other sources of variation in CPUE that we identify have implications for gear-based management, which must be based on understanding of gear selectivity for aggregating species, and fishing effort controls, which must consider the potential for effort-dependent patterns in catchability.

Characteristics of Fishes with the Potential to Cause Acoustic Clutter off Oregon and Washington during the Summer of 2012

DTIC Science & Technology

2014-05-10

14. Barboza, T., "West Coast sardine crash could radiate throughout ecosystem," Los Angeles Times, January 5, 2014. 15. Enticknap, B., Letter to the...AND SURVEYS Much of the Pacific sardine and Pacific hake stocks undertake annual north-south migrations . They migrate in late spring from off...California to the Pacific Northwest to feed during the summer. In the fall they migrate back to California to spawn during the winter and spring. The

Reproductive strategies and seasonal changes in the somatic indices of seven small-bodied fishes in Atlantic Canada in relation to study design for environmental effects monitoring.

PubMed

Barrett, Timothy J; Brasfield, Sandra M; Carroll, Leslie C; Doyle, Meghan A; van den Heuvel, Michael R; Munkittrick, Kelly R

2015-05-01

Small-bodied fishes are more commonly being used in environmental effects monitoring (EEM) studies. There is a lack of understanding of the biological characteristics of many small-bodied species, which hinders study designs for monitoring studies. For example, 72% of fish population surveys in Canada's EEM program for pulp and paper mills that used small-bodied fishes were conducted outside of the reproductive period of the species. This resulted in an inadequate assessment of the EEM program's primary effect endpoint (reproduction) for these studies. The present study examined seasonal changes in liver size, gonad size, and condition in seven freshwater and estuarine small-bodied fishes in Atlantic Canada. These data were used to examine differences in reproductive strategies and patterns of energy storage among species. Female gonadal recrudescence in all seven species began primarily in the 2-month period in the spring before spawning. Male gonadal development was concurrent with females in five species; however, gonadal recrudescence began in the fall in male three-spined stickleback (Gasterosteus aculeatus) and slimy sculpin (Cottus cognatus). The spawning period for each species was estimated from the decline in relative ovary size after its seasonal maximum value in spring. The duration of the spawning period reflected the reproductive strategy (single vs multiple spawning) of the species. Optimal sampling periods to assess reproductive impacts in each species were determined based on seasonal changes in ovary size and were identified to be during the prespawning period when gonads are developing and variability in relative gonad size is at a minimum.

Reproductive traits of shovelnose sturgeon Scaphirhynchus platorynchus (Rafinesque, 1820) in the lower Platte River, Nebraska

USGS Publications Warehouse

Hamel, M. J.; Rugg, M.L.; Pegg, M.A.; Patino, Reynaldo; Hammen, J.J.

2015-01-01

We assessed reproductive status, fecundity, egg size, and spawning dynamics of shovelnose sturgeon Scaphirhynchus platorynchus in the lower Platte River. Shovelnose sturgeon were captured throughout each year during 2011 and 2012 using a multi-gear approach designed to collect a variety of fish of varying sizes and ages. Fish were collected monthly for a laboratory assessment of reproductive condition. Female shovelnose sturgeon reached fork length at 50% maturity (FL50) at 547 mm and at a minimum length of 449 mm. The average female spawning cycle was 3–5 years. Mean egg count for adult females was 16 098 ± 1103 (SE), and mean egg size was 2.401 ± 0.051 (SE) mm. Total fecundity was positively correlated with length (r2 = 0.728; P < 0.001), mass (r2 = 0.896; P < 0.001), and age (r2 = 0.396; P = 0.029). However, fish size and age did not correlate to egg size (P > 0.05). Male shovelnose sturgeon reached FL50 at 579 mm and at a minimum length of 453 mm. The average male spawning cycle was 1–2 years. Reproductively viable male and female sturgeon occurred during the spring (March–May) and autumn (September–October) in both years, indicating spring and potential autumn spawning events. Shovelnose sturgeon in the lower Platte River are maturing at a shorter length and younger age compared to populations elsewhere. Although it is unknown if the change is plastic or evolutionary, unfavorable environmental conditions or over-harvest may lead to hastened declines compared to other systems.

The influence of oceanographic scenarios on the population dynamics of demersal resources in the western Mediterranean: Hypothesis for hake and red shrimp off Balearic Islands

NASA Astrophysics Data System (ADS)

Massutí, Enric; Monserrat, Sebastià; Oliver, Pere; Moranta, Joan; López-Jurado, José Luis; Marcos, Marta; Hidalgo, Manuel; Guijarro, Beatriz; Carbonell, Aina; Pereda, Pilar

2008-06-01

The aim of the present paper is to study the relationships between some climatic indices and parental stock, recruitment and accessibility to trawl fishery of hake ( Merluccius merluccius) and red shrimp ( Aristeus antennatus) off Balearic Islands (western Mediterranean). Available annual catch per unit effort, recruitment and spawning stock biomass have been used as biological data. As environmental data, the meso-scale IDEA index and the large-scale North Atlantic Oscillation (NAO) and Mediterranean Oscillation (MO) indices have been used. To analyze possible links between these indices with the population dynamics of demersal resources, two non-linear approaches have been applied: (i) stock-recruitment relationships from Ricker and Beverton-Holt models, by sequentially incorporating environment factors; (ii) generalized additive modelling, both classical general and threshold non-additive models were considered. The latter simulate an abrupt change in explicative variables across different phases (time periods or climatic index values). The results have shown that two oceanographic scenarios around the Balearic Islands, associated with macro and meso-scale climate regimes, can influence the population dynamics of hake and red shrimp. This is especially true for recruitment, which seems to be enhanced during low NAO and IDEA indices periods. During these periods, colder-than-normal winters generate high amounts of cold Western Mediterranean Intermediate Waters (WIW) in the Gulf of Lions, which flow southwards and reach the Balearic Islands channels in spring, increasing the productivity in the area. This oceanographic scenario could also be favourable to the distribution of hake on the fishing grounds where the trawl fleet targets this species, increasing its accessibility to the fishery. Both spawning stock and abundance of red shrimp seems to be also enhanced by high MO index periods, which could reflect the increased presence of the saline and warm Levantine Intermediate Waters (LIW) in the study area, extending over the fishing grounds of this species. The proposed interactions can be useful to assess and manage these important demersal resources.

Common sole in the northern and central Adriatic Sea: Spatial management scenarios to rebuild the stock

NASA Astrophysics Data System (ADS)

Scarcella, Giuseppe; Grati, Fabio; Raicevich, Saša; Russo, Tommaso; Gramolini, Roberto; Scott, Robert D.; Polidori, Piero; Domenichetti, Filippo; Bolognini, Luca; Giovanardi, Otello; Celić, Igor; Sabatini, Laura; Vrgoč, Nedo; Isajlović, Igor; Marčeta, Bojan; Fabi, Gianna

2014-05-01

The northern and central Adriatic Sea represents an important spawning and aggregation area for common sole (Solea solea) and provides for around 20% of the Mediterranean landings. In this area, this resource is mainly exploited with rapido trawl and set nets. The stock is not yet depleted and faces a situation of growth overfishing. The comparison between the spatial distribution by age of S. solea and the geographic patterns of the rapido trawl fishing effort evidenced an overlapping of this fishing activity with the area where juveniles concentrate (age groups 0-2). The majority of spawners inhabits specific offshore areas, here defined as ‘sole sanctuaries', where high concentrations of debris and benthic communities make difficult trawling with rapido. The aim of this study was to evaluate existing spatial management regimes and potential new spatial and temporal closures in the northern and central Adriatic Sea using a simple modelling tool. Two spatial simulations were carried out in order to verify the effectiveness of complementary methods for the management of fisheries: the ban of rapido trawling from October to December within 6 nautical miles and 9 nautical miles of the Italian coast. The focus of the simulation is that the effort of the rapido trawl is moved far from the coast during key sole recruitment periods, when the juveniles are moving from the inshore nursery area toward the offshore feeding grounds. The management scenarios showed that a change in selectivity would lead to a clear increase in the spawning stock biomass and an increase in landings of S. solea in the medium-term. The rapido trawl activity could be managed by using a different logic, bearing in mind that catches and incomes would increase with small changes in the spatial pattern of the fishing effort. The present study highlights the importance of taking into account spatial dimensions of fishing fleets and the possible interactions that can occur between fleets and target species, facilitating the development of control measures to achieve a healthy balance between stock exploitation and socio-economic factors.

A baseline study of metals in herring (Clupea harengus) from the Norwegian Sea, with focus on mercury, cadmium, arsenic and lead.

PubMed

Frantzen, Sylvia; Maage, Amund; Duinker, Arne; Julshamn, Kaare; Iversen, Svein A

2015-05-01

The Norwegian spring spawning (NSS) herring is an ecologically and economically important fish population in the Norwegian Sea. It was the first of several Norwegian fish stocks subject to a baseline study designed to give a comprehensive account of the levels of contaminants in a fish species from most of its area of distribution and during different seasons. During 2006 and 2007, 800 individual herring were sampled in their feeding areas in the Norwegian Sea in spring and autumn and at their spawning grounds off the coast of Norway during late winter. Metals including Hg, Cd, As and Pb were determined in muscle samples of individual herring, and mean concentrations±sd (mg kg(-1) ww) were: Hg: 0.04±0.03, Cd: 0.010±0.006, As: 2.2±0.6 and Pb: <0.01-0.10. Apart from one sample, no individual herring exceeded the EU's maximum level for any of these elements, as has been seen also in previous monitoring. Hg and Cd concentration increased with increasing fish age and As concentration varied seasonally, possibly due to uptake during feeding (summer), elimination during starvation (winter) and up-concentration during spawning (spring). Copyright © 2015 Elsevier Ltd. All rights reserved.

Reproductive life history of the introduced peacock grouper Cephalopholis argus in Hawaii.

PubMed

Schemmel, E M; Donovan, M K; Wiggins, C; Anzivino, M; Friedlander, A M

2016-08-01

This research investigated the reproductive biology (sex ratio, hermaphroditic pattern, size and age at maturity) of Cephalopholis argus, known locally in Hawaii by its Tahitian name roi. The results suggest that C. argus exhibits monandric protogyny (female gonad differentiation with female to male sex change) with females reaching sexual maturity at 1.2 years (95% c.i.: 0.6, 1.6) and 20.0 cm total length (LT ; 95% c.i.: 19.6, 21.2). The female to male sex ratio was 3.9:1. The average age and LT at sex change was 11.5 years (95% c.i.: 11.1, 12.9) and 39.9 cm (95% c.i.: 39.5, 41.2), respectively. Current information on spawning seasonality of this species is incomplete, but based on the occurrence of spawning capable and actively spawning females, spawning probably takes place from May to October. Evidence of lunar spawning periodicity was found, with an increased proportion of spawning capable and actively spawning females, and an increased female gonado-somatic index during first quarter and full-moon phases. This information fills a valuable information gap in Hawaii and across the species' native range. © 2016 The Fisheries Society of the British Isles.

Five-year evaluation of habitat remediation in Thunder Bay, Lake Huron: Comparison of constructed reef characteristics that attract spawning lake trout

USGS Publications Warehouse

Marsden, J. Ellen; Binder, Thomas R.; Johnson, James; He, Ji; Dingledine, Natalie; Adams, Janice; Johnson, Nicholas S.; Buchinger, Tyler J.; Krueger, Charles C.

2016-01-01

Degradation of aquatic habitats has motivated construction and research on the use of artificial reefs to enhance production of fish populations. However, reefs are often poorly planned, reef design characteristics are not evaluated, and reef assessments are short-term. We constructed 29 reefs in Thunder Bay, Lake Huron, in 2010 and 2011 to mitigate for degradation of a putative lake trout spawning reef. Reefs were designed to evaluate lake trout preferences for height, orientation, and size, and were compared with two degraded natural reefs and a high-quality natural reef (East Reef). Eggs and fry were sampled on each reef for five years post-construction, and movements of 40 tagged lake trout were tracked during three spawning seasons using acoustic telemetry. Numbers of adults and spawning on the constructed reefs were initially low, but increased significantly over the five years, while remaining consistent on East Reef. Adult density, egg deposition, and fry catch were not related to reef height or orientation of the constructed reefs, but were related to reef size and adjacency to East Reef. Adult lake trout visited and spawned on all except the smallest constructed reefs. Of the metrics used to evaluate the reefs, acoustic telemetry produced the most valuable and consistent data, including fine-scale examination of lake trout movements relative to individual reefs. Telemetry data, supplemented with diver observations, identified several previously unknown natural spawning sites, including the high-use portions of East Reef. Reef construction has increased the capacity for fry production in Thunder Bay without apparently decreasing the use of the natural reef. Results of this project emphasize the importance of multi-year reef assessment, use of multiple assessment methods, and comparison of reef characteristics when developing artificial reef projects. Specific guidelines for construction of reefs focused on enhancing lake trout spawning are suggested.

Lipid reserve dynamics and magnification of persistent organic pollutants in spawning sockeye salmon (Oncorhynchus nerka) from the Fraser River, British Columbia.

PubMed

Kelly, Barry C; Gray, Samantha L; Ikonomou, Michael G; Macdonald, J Steve; Bandiera, Stelvio M; Hrycay, Eugene G

2007-05-01

Pacific sockeye salmon (Oncorhynchus nerka) can travel several hundred kilometers to reach native spawning grounds and fulfill semelparous reproduction. The dramatic changes in lipid reserves during upstream migration can greatly affect internal toxicokinetics of persistent organic pollutants (POPs) such as PCBs, PCDDs, and PCDFs. We measured lipid content changes and contaminant concentrations in tissues (liver, muscle, roe/gonads) and biomarker responses (ethoxyresorufin O-deethylase or EROD activity and CYP1A levels) in two Pacific sockeye salmon stocks sampled at several locations along their spawning migration in the Fraser River, British Columbia. Muscle lipid contents declined significantly with increasing upstream migration distance and corresponded to elevated lipid normalized concentrations of PCBs and PCDD/Fs in spawning sockeye. Post-migration magnification factors (MFs) in spawning sockeye ranged between 3 and 12 and were comparable to model-predicted MFs. sigmaPCBs(150-500 ng x g(-1) lipid), sigmaPCDD/Fs (1-1000 pg x g(-1) lipid) and 2,3,7,8-TCDD toxic equivalent or TEQ levels (0.1-15 pg x g(-1) lipid) in spawning sockeye were relatively low and did not affect hepatic EROD activity/CYP1A induction. Despite a 3-fold magnification, TEQ levels in eggs of spawning Fraser River sockeye did not exceed 0.3 pg x g(-1) wet wt, a threshold level associated with 30% egg mortality in salmonids. PCBs in Fraser River sockeye are comparable to previous levels in Pacific sockeye. In contrast to Pacific sockeye from more remote coastal locations, PCDDs and PCDFs in Fraser River sockeye were generally minor components (<25%) of TEQ levels, compared to dioxin like PCB contributions (>75%). The data suggest that (i) the Fraser River is not a major contamination source of PCBs or PCDD/Fs and (ii) marine contaminant distribution, food-chain dynamics, and ocean-migration pathway are likely important factors controlling levels and patterns of POPs in returning Pacific sockeye. We estimate an annual chemical flux entering the Fraser River of up to 150 g for sigmaPCBs and 40 mg for sigmaPCDD/ Fs via returning sockeye. The results indicate that historical concentrations of PCBs and PCDD/Fs remain a potential threat to organism and ecosystem health on the west coast of Canada.

Windowpane flounder (Scophthalmus aquosus) and winter flounder (Pseudopleuronectes americanus) responses to cold temperature extremes in a Northwest Atlantic estuary

NASA Astrophysics Data System (ADS)

Wilber, Dara H.; Clarke, Douglas G.; Alcoba, Catherine M.; Gallo, Jenine

2016-01-01

The effect of climate variability on flatfish includes not only the effects of warming on sensitive life history stages, but also impacts from more frequent or unseasonal extreme cold temperatures. Cold weather events can affect the overwintering capabilities of flatfish near their low temperature range limits. We examined the responses of two flatfish species, the thin-bodied windowpane (Scophthalmus aquosus) and cold-tolerant winter flounder (Pseudopleuronectes americanus), to variable winter temperatures in a Northwest Atlantic estuary using abundance and size data collected during a monitoring study, the Aquatic Biological Survey, conducted from 2002 to 2010. Winter and spring abundances of small (50 to 120 mm total length) juvenile windowpane were positively correlated with adult densities (spawning stock) and fall temperatures (thermal conditions experienced during post-settlement development for the fall-spawned cohort) of the previous year. Windowpane abundances in the estuary were significantly reduced and the smallest size class was nearly absent after several consecutive years with cold (minimum temperatures < 1 °C) winters. Interannual variation in winter flounder abundances was unrelated to the severity of winter temperatures. A Paulik diagram illustrates strong positive correlations between annual abundances of sequential winter flounder life history stages (egg, larval, Age-1 juvenile, and adult male) within the estuary, reflecting residency within the estuary through their first year of life. Temperature variables representing conditions during winter flounder larval and post-settlement development were not significant factors in multiple regression models exploring factors that affect juvenile abundances. Likewise, densities of predators known to consume winter flounder eggs and/or post-settlement juveniles were not significantly related to interannual variation in winter flounder juvenile abundances. Colder estuarine temperatures through the first year of life were associated with smaller Age-1 winter flounder body size. For example, Age-1 winter flounder developing under conditions that differed by 1.9 °C in mean daily water temperature, averaged 98.7 mm total length (TL) and 123.1 mm TL, for the relatively cold vs. moderate years, respectively. More frequent cold temperature extremes associated with climate variability may negatively impact the overwintering capabilities of some flatfish near their cold temperature range limits, whereas cold-tolerant species may experience reduced growth, which imparts the ecological challenges associated with smaller body size.

Demographic analysis of Lost River sucker and shortnose sucker populations in Upper Klamath Lake, Oregon

USGS Publications Warehouse

Janney, E.C.; Shively, R.S.; Hayes, B.S.; Barry, P.M.; Perkins, D.

2008-01-01

We used 13 years (1995-2007) of capture-mark-recapture data to assess population dynamics of endangered Lost River suckers Deltistes luxatus and shortnose suckers Chasmistes brevirostris in Upper Klamath Lake, Oregon. The Cormack-Jolly-Seber method was used to estimate survival, and information theoretic modeling was used to assess variation due to time, gender, species, and spawning subpopulations. Length data were used to detect multiple year-class failures and events of high recruitment into adult spawning populations. Average annual survival probability was 0.88 for Lost River suckers and 0.76 for shortnose suckers. Mean life span estimates based on these survival rates indicated that Lost River suckers survived long enough on average to attempt reproduction eight times, whereas shortnose suckers only survived to spawn three to four times. Shortnose sucker survival was not only poor in years of fish kills (1995-1997) but also was low in years without fish kills (i.e., 2002 and 2004). This suggests that high mortality occurs in some years but is not necessarily associated with fish kills. Annual survival probabilities were not only different between the two species but also differed between two spawning subpopulations of Lost River suckers. Length composition data indicated that recruitment into spawning populations only occurred intermittently. Populations of both species transitioned from primarily old individuals with little size diversity and consistently poor recruitment in the late 1980s and early 1990s to mostly small, recruit-sized fish by the late 1990s. A better understanding of the factors influencing adult survival and recruitment into spawning populations is needed. Monitoring these vital parameters will provide a quantitative means to evaluate population status and assess the effectiveness of conservation and recovery efforts.

Seasonal variations in seminal plasma and sperm characteristics of wild-caught and cultivated Atlantic cod, Gadus morhua.

PubMed

Butts, I A E; Litvak, M K; Trippel, E A

2010-04-15

The objective was to investigate changes, throughout the spawning season, in body size attributes and quantitative semen characteristics of wild-caught and cultivated Atlantic cod, Gadus morhua L. Sperm velocity increased significantly throughout the spawning season of cod from both origins. Curvilinear velocity (VCL; 30 sec post-activation) increased from 78.9+/-6.5 to 128.2+/-6.5 microm/sec (mean+/-SEM) between the beginning and end of the spawning season, respectively, for wild-caught cod, whereas for cultivated fish, it increased from 26.6+/-2.4 to 48.9+/-3.1 microm/sec between January and March. Spermatocrit did not undergo a significant seasonal change in wild-caught cod but did thicken for cultivated cod (24.6+/-4.2% in January to 40.5+/-4.4% in April; P<0.01). Sperm head area, perimeter, length, and width declined significantly at the end of the spawning season of cod from both origins (all P values<0.01). Seminal plasma osmolality and Na(+) ion concentration followed a dome-shaped function through the spawning season for both wild-caught and cultivated cod (P<0.05). For cultivated cod, seminal plasma pH was significantly lower at the start of the spawning season (P<0.001), whereas Ca(2+) increased then decreased (P<0.05). Body size attributes, spermatocrit, and seminal plasma constituents had significant relationships with sperm activity variables. These relationships varied as a function of time post-activation, month, and fish origin. Our findings may be used to (i) assess spermiation stage without killing males; (ii) optimize semen collection for hatchery production; (iii) characterize the potential impact of farming on sperm quality; and (iv) improve success of sperm cryopreservation and short-term storage. Copyright 2010 Elsevier Inc. All rights reserved.

Length-Based Assessment of Coral Reef Fish Populations in the Main and Northwestern Hawaiian Islands

PubMed Central

Nadon, Marc O.; Ault, Jerald S.; Williams, Ivor D.; Smith, Steven G.; DiNardo, Gerard T.

2015-01-01

The coral reef fish community of Hawaii is composed of hundreds of species, supports a multimillion dollar fishing and tourism industry, and is of great cultural importance to the local population. However, a major stock assessment of Hawaiian coral reef fish populations has not yet been conducted. Here we used the robust indicator variable “average length in the exploited phase of the population (L¯)”, estimated from size composition data from commercial fisheries trip reports and fishery-independent diver surveys, to evaluate exploitation rates for 19 Hawaiian reef fishes. By and large, the average lengths obtained from diver surveys agreed well with those from commercial data. We used the estimated exploitation rates coupled with life history parameters synthesized from the literature to parameterize a numerical population model and generate stock sustainability metrics such as spawning potential ratios (SPR). We found good agreement between predicted average lengths in an unfished population (from our population model) and those observed from diver surveys in the largely unexploited Northwestern Hawaiian Islands. Of 19 exploited reef fish species assessed in the main Hawaiian Islands, 9 had SPRs close to or below the 30% overfishing threshold. In general, longer-lived species such as surgeonfishes, the redlip parrotfish (Scarus rubroviolaceus), and the gray snapper (Aprion virescens) had the lowest SPRs, while short-lived species such as goatfishes and jacks, as well as two invasive species (Lutjanus kasmira and Cephalopholis argus), had SPRs above the 30% threshold. PMID:26267473

The Principles of Buoyancy in Marine Fish Eggs and Their Vertical Distributions across the World Oceans.

PubMed

Sundby, Svein; Kristiansen, Trond

2015-01-01

Buoyancy acting on plankton, i.e. the difference in specific gravity between plankton and the ambient water, is a function of salinity and temperature. From specific gravity measurements of marine fish eggs salinity appears to be the only determinant of the buoyancy indicating that the thermal expansions of the fish egg and the ambient seawater are equal. We analyze the mechanisms behind thermal expansion in fish eggs in order to determine to what extent it can be justified to neglect the effects of temperature on buoyancy. Our results confirm the earlier assumptions that salinity is the basic determinant on buoyancy in marine fish eggs that, in turn, influence the vertical distributions and, consequently, the dispersal of fish eggs from the spawning areas. Fish populations have adapted accordingly by producing egg specific gravities that tune the egg buoyancy to create specific vertical distributions for each local population. A wide variety of buoyancy adaptations are found among fish populations. The ambient physical conditions at the spawning sites form a basic constraint for adaptation. In coastal regions where salinity increases with depth, and where the major fraction of the fish stocks spawns, pelagic and mesopelagic egg distributions dominate. However, in the larger part of worlds' oceans salinity decreases with depth resulting in different egg distributions. Here, the principles of vertical distributions of fish eggs in the world oceans are presented in an overarching framework presenting the basic differences between regions, mainly coastal, where salinity increases with depth and the major part of the world oceans where salinity decreases with depth. We show that under these latter conditions, steady-state vertical distribution of mesopelagic fish eggs cannot exist as it does in most coastal regions. In fact, a critical spawning depth must exist where spawning below this depth threshold results in eggs sinking out of the water column and become lost for recruitment to the population. An example of adaptation to such conditions is Cape hake spawning above the critical layer in the Northern Benguela upwelling ecosystem. The eggs rise slowly in the onshore subsurface current below the Ekman layer, hence being advected inshore where the hatched larvae concentrate with optimal feeding conditions.

Acoustic telemetry reveals large-scale migration patterns of walleye in Lake Huron

USGS Publications Warehouse

Hayden, Todd A.; Holbrook, Christopher; Fielder, David G.; Vandergoot, Christopher S.; Bergstedt, Roger A.; Dettmers, John M.; Krueger, Charles C.; Cooke, Steven J.

2014-01-01

Fish migration in large freshwater lacustrine systems such as the Laurentian Great Lakes is not well understood. The walleye (Sander vitreus) is an economically and ecologically important native fish species throughout the Great Lakes. In Lake Huron walleye has recently undergone a population expansion as a result of recovery of the primary stock, stemming from changing food web dynamics. During 2011 and 2012, we used acoustic telemetry to document the timing and spatial scale of walleye migration in Lake Huron and Saginaw Bay. Spawning walleye (n = 199) collected from a tributary of Saginaw Bay were implanted with acoustic tags and their migrations were documented using acoustic receivers (n = 140) deployed throughout U.S. nearshore waters of Lake Huron. Three migration pathways were described using multistate mark-recapture models. Models were evaluated using the Akaike Information Criterion. Fish sex did not influence migratory behavior but did affect migration rate and walleye were detected on all acoustic receiver lines. Most (95%) tagged fish migrated downstream from the riverine tagging and release location to Saginaw Bay, and 37% of these fish emigrated from Saginaw Bay into Lake Huron. Remarkably, 8% of walleye that emigrated from Saginaw Bay were detected at the acoustic receiver line located farthest from the release location more than 350 km away. Most (64%) walleye returned to the Saginaw River in 2012, presumably for spawning. Our findings reveal that fish from this stock use virtually the entirety of U.S. nearshore waters of Lake Huron.

Acoustic telemetry reveals large-scale migration patterns of walleye in Lake Huron.

PubMed

Hayden, Todd A; Holbrook, Christopher M; Fielder, David G; Vandergoot, Christopher S; Bergstedt, Roger A; Dettmers, John M; Krueger, Charles C; Cooke, Steven J

2014-01-01

Fish migration in large freshwater lacustrine systems such as the Laurentian Great Lakes is not well understood. The walleye (Sander vitreus) is an economically and ecologically important native fish species throughout the Great Lakes. In Lake Huron walleye has recently undergone a population expansion as a result of recovery of the primary stock, stemming from changing food web dynamics. During 2011 and 2012, we used acoustic telemetry to document the timing and spatial scale of walleye migration in Lake Huron and Saginaw Bay. Spawning walleye (n = 199) collected from a tributary of Saginaw Bay were implanted with acoustic tags and their migrations were documented using acoustic receivers (n = 140) deployed throughout U.S. nearshore waters of Lake Huron. Three migration pathways were described using multistate mark-recapture models. Models were evaluated using the Akaike Information Criterion. Fish sex did not influence migratory behavior but did affect migration rate and walleye were detected on all acoustic receiver lines. Most (95%) tagged fish migrated downstream from the riverine tagging and release location to Saginaw Bay, and 37% of these fish emigrated from Saginaw Bay into Lake Huron. Remarkably, 8% of walleye that emigrated from Saginaw Bay were detected at the acoustic receiver line located farthest from the release location more than 350 km away. Most (64%) walleye returned to the Saginaw River in 2012, presumably for spawning. Our findings reveal that fish from this stock use virtually the entirety of U.S. nearshore waters of Lake Huron.

Acoustic Telemetry Reveals Large-Scale Migration Patterns of Walleye in Lake Huron

PubMed Central

Hayden, Todd A.; Holbrook, Christopher M.; Fielder, David G.; Vandergoot, Christopher S.; Bergstedt, Roger A.; Dettmers, John M.; Krueger, Charles C.; Cooke, Steven J.

2014-01-01

Fish migration in large freshwater lacustrine systems such as the Laurentian Great Lakes is not well understood. The walleye (Sander vitreus) is an economically and ecologically important native fish species throughout the Great Lakes. In Lake Huron walleye has recently undergone a population expansion as a result of recovery of the primary stock, stemming from changing food web dynamics. During 2011 and 2012, we used acoustic telemetry to document the timing and spatial scale of walleye migration in Lake Huron and Saginaw Bay. Spawning walleye (n = 199) collected from a tributary of Saginaw Bay were implanted with acoustic tags and their migrations were documented using acoustic receivers (n = 140) deployed throughout U.S. nearshore waters of Lake Huron. Three migration pathways were described using multistate mark-recapture models. Models were evaluated using the Akaike Information Criterion. Fish sex did not influence migratory behavior but did affect migration rate and walleye were detected on all acoustic receiver lines. Most (95%) tagged fish migrated downstream from the riverine tagging and release location to Saginaw Bay, and 37% of these fish emigrated from Saginaw Bay into Lake Huron. Remarkably, 8% of walleye that emigrated from Saginaw Bay were detected at the acoustic receiver line located farthest from the release location more than 350 km away. Most (64%) walleye returned to the Saginaw River in 2012, presumably for spawning. Our findings reveal that fish from this stock use virtually the entirety of U.S. nearshore waters of Lake Huron. PMID:25506913

Etheostoma brevirostrum (Holiday Darter)

USGS Publications Warehouse

Burkhead, Noel M.

2015-01-01

The life history of the Holiday Darter is incompletely known. Only reproductive behavior (Johnston and Shute 1997; Anderson 2009), habitat use, and spawning seasons (Anderson 2009) have been studied. However, based on similarity of life history attributes among snubnose darters (Carney and Burr 1989; Johnston and Haag 1996; Khudamrongsawat et al. 2005), the Holiday darter probably lives 3+ years and matures in the first year. It is likely a benthic omnivore, feeding primarily on chironomid (midge) larvae and other common orders of aquatic insects and occasional microcrustaceans. Spawning occurs from late March to early June, with most activity occurring in April. Based on four females from the Amicalola Creek system, fecundity ranged from 50 to 150 mature eggs, egg sizes ranged from 1.2mm to 1.6mm diameter. The Holiday Darter is an “egg attacher” (sensu Page and Swofford 1984). A spawning female is courted by multiple males, but a dominant (alpha) male aggressively rebuts encroaching males and defends a “roving territory” of the receptive female. The alpha male is the principal spawning partner although satellite males often rush a spawning pair. The receptive female slowly swims along the stream bottom, frequently stopping, apparently to assess substrate attributes, and selects each spawning site where only one or two eggs are spawned. The process is repeated and often covers several meters of stream bottom until the courted female finishes spawning and is abandoned by the alpha male. Water temperatures during spawning in Amicalola Creek and the upper Etowah River ranged 10 to 17° C (Anderson 2009).

Shelf spawning habitat of Emmelichthys nitidus in south-eastern Australia - Implications and suitability for egg-based biomass estimation

NASA Astrophysics Data System (ADS)

Neira, Francisco J.; Lyle, Jeremy M.; Keane, John P.

2009-03-01

The spawning habitat of Emmelichthys nitidus (Emmelichthyidae) in south-eastern Australia is described from vertical ichthyoplankton samples collected along the shelf region off eastern through to south-western Tasmania during peak spawning in October 2005-06. Surveys covered eastern waters in 2005 (38.8-43.5°S), and both eastern and southern waters in 2006 (40.5°S around to 43.5°S off the south-west). Eggs ( n = 10,393) and larvae ( n = 378) occurred along eastern Tasmania in both years but were rare along southern waters south and westwards of 43.5°S in 2006. Peak egg abundances (1950-2640 per m -2) were obtained off north-eastern Tasmania (40.5-41.5°S) between the shelf break and 2.5 nm inshore from the break. Eggs were up to 5-days old, while nearly 95% of larvae were at the early preflexion stage, i.e. close to newly emerged. Average abundances of aged eggs pooled across each survey declined steadily from day-1 to day-5 eggs both in 2005 (97-18) and 2006 (175-34). Moreover, day-1 egg abundances were significantly greater 2.5 nm at either side of the break, including at the break, than in waters ≥5 nm both inshore and offshore from the break. These results, complemented with egg and larval data obtained in shelf waters off New South Wales (NSW; 35.0-37.7°S) in October 2002-03, indicate that the main spawning area of E. nitidus in south-eastern Australia lies between 35.5°S off southern NSW and 43.5°S off south-eastern Tasmania, and that spawning activity declines abruptly south and westwards of 43.5°S around to the south-west coast. In addition, quotient analyses of day-1 egg abundances point to a preferred spawning habitat contained predominantly within a 5 nm corridor along the shelf break, where waters are 125-325 m deep and median temperatures 13.5-14.0 °C. Spawning off eastern Tasmania is timed with the productivity outburst typical of the region during the austral spring, and the temperature increase from the mixing between the southwards advancing, warm East Australian Current and cooler subantarctic water over the shelf. Overall, ichthyoplankton data, coupled with reproductive information from adults trawled off Tasmania, indicate that E. nitidus constitutes a suitable species for the application of the daily egg production method (DEPM) to estimate spawning biomass. This finding, together with evidence in support of a discrete eastern spawning stock extending from southern NSW to southern Tasmania, strengthens the need for DEPM-based biomass estimates of E. nitidus prior to further fishery expansion.

Simulation of the effects of time and size at stocking on PCB accumulation in lake trout

USGS Publications Warehouse

Madenjian, Charles P.; Carpenter, Stephen R.

1993-01-01

Manipulations of size at stocking and timing of stocking have already been used to improve survival of stocked salmonines in the Great Lakes. It should be possible to stock salmonines into the Great Lakes in a way that reduces the rate of polychlorinated biphenyl (PCB) accumulation in these fishes. An individual-based model (IBM) was used to investigate the effects of size at stocking and timing of stocking on PCB accumulation by lake trout Salvelinus namaycush in Lake Michigan. The individual-based feature of the model allowed lake trout individuals to encounter prey fish individuals and then consume sufficiently small prey fish. The IBM accurately accounted for the variation in PCB concentrations observed within the Lake Michigan lake trout population. Results of the IBM simulations revealed that increasing the average size at stocking from 110 to 160 mm total length led to an increase in the average PCB concentration in the stocked cohort at age 5, after the fish had spent 4 years in the lake, from 2.33 to 2.65 mg/kg; the percentage of lake trout in the cohort at the end of the simulated time period with PCB concentration of 2 mg/kg or more increased from 62% to 79%. Thus, PCB contamination was reduced when the simulated size at stocking was smallest. An overall stocking strategy for lake trout into Lake Michigan should weigh this advantage regarding PCB contamination against the poor survival of lake trout that may occur if the trout are stocked at too small a size.

Compensatory mechanisms in Great Lakes sea lamprey populations: implications for alternative control strategies

USGS Publications Warehouse

Jones, Michael L.; Bergstedt, R.A.; Twohey, Michael B.; Fodale, Michael F.; Cuddy, Douglas W.; Slade, Jeffrey W.

2003-01-01

Compensatory mechanisms are demographic processes that tend to increase population growth rates at lower population density. These processes will tend to reduce the effectiveness of actions that use controls on reproductive success to suppress sea lamprey (Petromyzon marinus), an economically important pest in the Great Lakes. Historical evidence for compensatory mechanisms in sea lamprey populations was reviewed, and revealed: (1) strong evidence for shifts in sex ratios as sea lamprey abundance was reduced in the early years of the control program; (2) weak and equivocal evidence for increased growth rates of sea lamprey cohorts re-colonizing streams following a lampricide treatment; and (3) suggestions of other compensatory processes, such as earlier ages at metamorphosis, but with little empirical evidence. Larval size distribution data for cohorts in the first and second years following a lampricide treatment (26 pairs of cohorts in 20 streams) was analyzed and did not indicate a consistent pattern of more rapid growth of the first colonizing cohort (only 11 of 33 cases). To test for compensation between spawning and age-1 in sea lamprey populations, data were analyzed for 49 stream-years for which spawning female abundance was known and age-1 abundance was estimated in the following year. A fit of these data to a Ricker stock-recruitment function showed evidence for compensation, measured as reduced survival to age 1 at higher abundance of spawning females. More obvious, however, was a large amount of density-independent variation in survival, which tends to mask evidence for compensatory survival. The results were applied to a simple model that simulates sea lamprey populations and their control in a hypothetical lake. Control strategies that targeted reproductive success performed far less well than comparable strategies that targeted larval populations, because density-independent recruitment variation leads to occasional strong year classes even when spawner abundance is reduced to low levels through alternative control. It is concluded that further study of recruitment variation in lamprey populations is critical to rationalizing alternative controls that target reproductive success, and that recruitment variation needs to be incorporated into models used to evaluate sea lamprey control options.

Determining stocking, forest type and stand-size class from forest inventory data

Treesearch

Mark H. Hansen; Jerold T. Hahn

1992-01-01

This paper describes the procedures used by North Central Forest Experiment Station's Forest Inventory and Analysis Work Unit (NCFIA) in determining stocking, forest type, and stand-size class. The stocking procedure assigns a portion of the stocking to individual trees measured on NCFIA 10-point field plots. Stand size and forest type are determined as functions...

Response of ecosystem metabolism to low densities of spawning Chinook salmon

USGS Publications Warehouse

Benjamin, Joseph R.; Bellmore, J. Ryan; Watson, Grace A.

2016-01-01

Marine derived nutrients delivered by large runs of returning salmon are thought to subsidize the in situ food resources that support juvenile salmon. In the Pacific Northwest, USA, salmon have declined to <10% of their historical abundance, with subsequent declines of marine derived nutrients once provided by large salmon runs. We explored whether low densities (<0.001 spawners/m2) of naturally spawning Chinook Salmon (Oncorhynchus tshawytscha) can affect ecosystem metabolism. We measured gross primary production (GPP) and ecosystem respiration (ER) continuously before, during, and after salmon spawning. We compared downstream reaches with low densities of spawning salmon to upstream reaches with fewer or no spawners in 3 mid-sized (4th-order) rivers in northern Washington. In addition, we measured chemical, physical, and biological factors that may be important in controlling rates of GPP and ER. We observed that low densities of spawning salmon can increase GPP by 46% during spawning, but values quickly return to those observed before spawning. No difference in ER was observed between up- and downstream reaches. Based on our results, salmon density, temperature, and the proximity to salmon redds were the most important factors controlling rates of GPP, whereas temperature was most important for ER. These results suggest that even at low spawning densities, salmon can stimulate basal resources that may propagate up the food web. Understanding how recipient ecosystems respond to low levels of marine derived nutrients may inform nutrient augmentation studies aimed at enhancing fish populations.

Aquatic biology in Nederlo Creek, southwestern Wisconsin

USGS Publications Warehouse

Kammerer, Phil A.; Lidwin, R.A.; Mason, J.W.; Narf, R.P.

1982-01-01

The aquatic community is diverse and reasonably stable with little indication of environmental disturbance. Aquatic macrophyte population (dominated by Ranunculus aquatilis L., Veronica catenata Penn., and Nasturtium offlcinale) varies little from spring to fall. Periphytic and planktonic algae are predominantly diatoms, with the genus Achnanthes dominating both communities. Most genera of planktonic algae originate in the periphyton, but some true planktonic algae were identified. The benthic invertebrate population is dominated by Trichoptera and is a major food source for trout and forage fish. Biotic index values calculated from benthic invertebrate data indicate that water quality is very good to excellent. The trout population is low and represents only a small part of the total fish population both in biomass and numbers. Brown trout are usually stocked annually in the spring to enhance sport fishing, but by fall most trout are wild. The major environmental factors limiting trout population seem to be insufficient cover, insufficient pool depth and volume, and small spawning areas. The wild trout population is highly dependent on spawning success the previous fall.

Salmon as drivers of physical and biological disturbance in river channels

NASA Astrophysics Data System (ADS)

Albers, S. J.; Petticrew, E. L.

2012-04-01

Large migrations across landscapes and ecosystem boundaries combined with disturbances of riverine spawning habitats through nest construction indicate the huge potential that Pacific salmon (Onchorhynchus sp.) have to disturb and alter regional energy flow. Nutrients derived from ocean-reared dead and decaying salmon are released into surrounding aquatic ecosystems fertilizing the water column, recently disturbed by increased suspended sediments due to nest construction. These opposing forces of disturbance and fertilization on spawning habitat have been demonstrated to impact local geomorphic and ecological cycles within salmon streams. An often cited, yet not fully tested, hypothesis is that this pulse of nutrients provided by decaying salmon can shift freshwater habitats to higher production levels. This hypothesis, however, remains contested and uncertain. Fine sediments are increasingly being recognized as important delivery and storage vectors for marine-derived nutrients (MDNs) in spawning streams. The temporal and spatial significance of these sediment vectors on gravelbed storage of MDN have not been quantified thereby restricting our ability to estimate the impact of gravelbed storage of MDNs on the riverine habitats. The objectives of this study were to i) quantify the magnitude of sediment deposition and retention in an active spawning area and ii) determine the contribution of MDN associated with the fine sediment storage. The Horsefly River spawning channel (HFC), an artificial salmon stock enhancement stream, was used to examine the biogeomorphic impacts of salmon spawning. We organized the HFC in an upstream-downstream paired treatment approach where the upstream enclosure was kept free of salmon and the downstream enclosure was loaded with actively spawning salmon. We used the difference in suspended sediment concentration between the salmon enclosure and the control enclosure to determine the contribution of salmon nest construction to suspended sediment concentration. To monitor sediment infiltration into the gravelbed we used modified infiltration bag samplers. Lastly, to examine the contribution of salmon nutrients to the infiltrated sediment we sampled for the presence of a marine isotope signature (15N) in the sediment. Increased sediment in the water column of the salmon enclosure during the active spawn period indicated salmon-mediated sediment resuspension. A gravelbed response to this water column disturbance was detected via increased sediment infiltration during salmon spawning. This stored sediment was enriched in organic matter and 15N indicating a marine salmon signal. Significant relationships between sediment infiltration and salmon enrichment provided further evidence that salmon organic matter, using resuspended sediment as a vector, was infiltrating into the gravelbed. During the post-spawn period organic sediment was elevated in the water column and gravelbed infiltration was reduced reflecting respectively, the release of decay products from salmon carcasses and MDN release from temporary gravelbed storage. This study demonstrated that localized patterns of sediment deposition are regulated by salmon activity, which control gravelbed MDN storage and release. Salmon-mediated, sediment vector influences on riverine habitat have been quantified here on a small experimental scale, but we expect that the effect is replicated and magnified, as it occurs regionally throughout the spawning grounds, with significant ecosystem implications.

Effect of stress during handling, seawater acclimation, confinement, and induced spawning on plasma ion levels and somatolactin-expressing cells in mature female Liza ramada.

PubMed

Khalil, Noha A; Hashem, Amal M; Ibrahim, Amal A E; Mousa, Mostafa A

2012-08-01

The present experiments were designed to determine the effect of different stress factors; handling, seawater acclimation, confinement, and induced spawning on plasma cortisol, hydro mineral balance as well as changes in size, number and integrated intensity of somatolactin (SL)-expressing cells in Liza ramada mature females confined to fresh water ponds. The plasma levels of cortisol, PO(4)(3-), Na(+), and K(+) were higher, while Ca(2+) and Mg(2+) were lower than controls during transportation without anesthesia. By using clove oil (5 mg L(-1)) as an anesthetic during transportation, the plasma cortisol, PO(4) (3-), Na(+), and K(+) were similar to controls, while Ca(2+) and Mg(2+) were higher. During seawater acclimation, the plasma cortisol and minerals were significantly higher except Na(+) which was lower than controls. In addition, during induction of spawning, the plasma levels of cortisol, PO(4)(3-), Na(+), K(+), and Mg(2+) were significantly higher than controls. The SL-producing cells are located in the pars intermedia (PI) bordering the neurohypophysis. The stress affected the number, size, and immunostaining of SL-expressing cells. During seawater acclimation, the size and the integrated intensity of SL immunoreactivity were lower, but the number of these cells was higher than controls. Furthermore, the number, size, and the integrated intensity of SL immunoreactivity were significantly lower than controls during handling and after spawning, which was opposite to confinement. The response of SL-expressing cells in PI in parallel with changes in cortisol and hydro mineral balance induced by stress support the possible role of SL in the adaptive response of fish to stress. © 2012 WILEY PERIODICALS, INC.

Evidence of sexually dimorphic introgression in Pinaleno Mountain Apache trout

USGS Publications Warehouse

Porath, M.T.; Nielsen, J.L.

2003-01-01

The high-elevation headwater streams of the Pinaleno Mountains support small populations of threatened Apache trout Oncorhynchus apache that were stocked following the chemical removal of nonnative salmonids in the 1960s. A fisheries survey to assess population composition, growth, and size structure confirmed angler reports of infrequent occurrences of Oncorhynchus spp. exhibiting the external morphological characteristics of both Apache trout and rainbow trout O. mykiss. Nonlethal tissue samples were collected from 50 individuals in the headwaters of each stream. Mitochondrial DNA (mtDNA) sequencing and amplification of nuclear microsatellite loci were used to determine the levels of genetic introgression by rainbow trout in Apache trout populations at these locations. Sexually dimorphic introgression from the spawning of male rainbow trout with female Apache trout was detected using mtDNA and microsatellites. Estimates of the degree of hybridization based on three microsatellite loci were 10-88%. The use of nonlethal DNA genetic analyses can supplement information obtained from standard survey methods and be useful in assessing the relative importance of small and sensitive populations with a history of nonnative introductions.

Status and trends of adult Lost River (Deltistes luxatus) and shortnose (Chasmistes brevirostris) sucker populations in Upper Klamath Lake, Oregon, 2017

USGS Publications Warehouse

Hewitt, David A.; Janney, Eric C.; Hayes, Brian S.; Harris, Alta C.

2018-04-24

Executive SummaryData from a long-term capture-recapture program were used to assess the status and dynamics of populations of two long-lived, federally endangered catostomids in Upper Klamath Lake, Oregon. Lost River suckers (LRS; Deltistes luxatus) and shortnose suckers (SNS; Chasmistes brevirostris) have been captured and tagged with passive integrated transponder (PIT) tags during their spawning migrations in each year since 1995. In addition, beginning in 2005, individuals that had been previously PIT-tagged were re-encountered on remote underwater antennas deployed throughout sucker spawning areas. Captures and remote encounters during the spawning season in spring 2016 were incorporated into capture-recapture analyses of population dynamics.Cormack-Jolly-Seber (CJS) open population capture-recapture models were used to estimate annual survival probabilities, and a reverse-time analog of the CJS model was used to estimate recruitment of new individuals into the spawning populations. In addition, data on the size composition of captured fish were examined to provide corroborating evidence of recruitment. Model estimates of survival and recruitment were used to derive estimates of changes in population size over time and to determine the status of the populations through 2015. Separate analyses were done for each species and also for each subpopulation of LRS. Shortnose suckers and one subpopulation of LRS migrate into tributary rivers to spawn, whereas the other LRS subpopulation spawns at groundwater upwelling areas along the eastern shoreline of the lake.Capture-recapture analyses indicated that with a few exceptions, the survival of males and females in both Lost River sucker subpopulations was high (greater than 0.88) from 1999 to 2015. Survival was notably lower for males from the river in 2000, 2006, and 2012, and for the shoreline areas in 2002. From 2001 to 2015, the abundance of males in the lakeshore spawning subpopulation decreased by at least 64 percent and the abundance of females decreased by at least 56 percent. Capture-recapture models suggested that the abundance of both sexes in the river spawning subpopulation of LRS had increased substantially since 2006; increases were mostly due to large estimated recruitment events in 2006 and 2008. We know that the estimates in 2006 are substantially biased in favor of recruitment because of a sampling issue. We are skeptical of the magnitude of recruitment indicated by the 2008 estimates as well because (1) few small individuals that would indicate the presence of new recruits were captured in that year, and (2) recapture probabilities in recruitment models based on just physical recaptures of fish were lower than desired for robust inferences from capture-recapture models. If we assume instead that little or no recruitment occurred for this subpopulation, the abundance of both sexes in the river spawning subpopulation likely has decreased at rates similar to the rates for the lakeshore spawning subpopulation from 2002 to 2015.Shortnose suckers experienced lower and more variable annual survival than either LRS subpopulation. Annual survival of both sexes was relatively low in 2003, 2004, 2010, and 2012. In addition, female survival was low in 1999 and 2000 while male survival was low in 2002. Survival estimate precision in early years of the study; however, are poor. Capture-recapture models and size composition data indicate that recruitment of new individuals into the SNS spawning population was trivial from 2001 to 2005. Models indicate that more than 10 percent of the population was new recruits in a number of more recent years. As a result, capture-recapture modeling suggests that the abundance of adult spawning SNS was relatively stable from 2006 to 2010. We are skeptical of the estimated recruitment in 2006 because of the known sampling issue. We also are skeptical of the estimated recruitment in other recent years because few small individuals that would indicate the presence of new recruits were captured in any of those years, and recapture probabilities in recruitment models were low. The best-case scenario for SNS, based on capture-recapture recruitment modeling, indicates that the abundance of males in the spawning population decreased by 78 percent and the abundance of females decreased by 77 percent from 2001 to 2015. Decreases in abundance for both sexes are likely greater than these estimates indicate.Despite relatively high survival in most years, we conclude that both species have experienced substantial decreases in the abundance of spawning adults because losses from mortality have not been balanced by recruitment of new individuals. Although capture-recapture data indicate substantial recruitment of new individuals into the spawning populations for SNS and river spawning LRS in some years, size data do not corroborate these estimates. As a result, the status of the endangered sucker populations in Upper Klamath Lake remains distressed, especially for SNS. Our monitoring program provides a robust platform for estimating vital population parameters, evaluating the status of the populations, and assessing the effectiveness of conservation and recovery efforts.

Reproductive ecology, spawning behavior, and juvenile distribution of Mountain Whitefish in the Madison River, Montana

USGS Publications Warehouse

Boyer, Jan K.; Guy, Christopher S.; Webb, Molly A. H.; Horton, Travis B.; McMahon, Thomas E.

2017-01-01

Mountain Whitefish Prosopium williamsoni were historically common throughout much of the U.S. Intermountain West. However, within the last decade Mountain Whitefish have exhibited population-level declines in some rivers. In the Madison River, Montana, anecdotal evidence indicates Mountain Whitefish abundance has declined and the population is skewed toward larger individuals, which is typically symptomatic of recruitment problems. Describing reproductive development, spawning behavior, and juvenile distribution will form a foundation for investigating mechanisms influencing recruitment. We collected otoliths and gonadal samples from fish of all size-classes to characterize fecundity, age at maturity, and spawning periodicity. We implanted radio tags in mature Mountain Whitefish and relocated tagged fish in autumn 2012–2014. Timing of spawning was determined from spawning status of captured females and from density of eggs collected on egg mats. In spring 2014, we seined backwater and channel sites to describe age-0 whitefish distribution. Mountain Whitefish were highly fecund (18,454 eggs/kg body weight) annual spawners, and age at 50% maturity was 2.0 years for males and 2.6 years for females. In 2013 and 2014, spawning occurred between the third week of October and first week of November. During spawning, spawning adults and collected embryos were concentrated in the downstream 26 km of the study site, a reach characterized by a complex, braided channel. This reach had the highest CPUE of age-0 Mountain Whitefish, and the percentage of spawning adults in the 25 km upstream from a sampling site was positively associated with juvenile CPUE. Within this reach, age-0 Mountain Whitefish were associated with silt-laden backwater and eddy habitats. Future investigations on mechanisms influencing recruitment should be focused on the embryological phase and age-0 fish.

The conservation and management of tunas and their relatives: setting life history research priorities.

PubMed

Juan-Jordá, Maria José; Mosqueira, Iago; Freire, Juan; Dulvy, Nicholas K

2013-01-01

Scombrids (tunas, bonitos, Spanish mackerels and mackerels) support important fisheries in tropical, subtropical and temperate waters around the world, being one of the most economically- and socially-important marine species globally. Their sustainable exploitation, management and conservation depend on accurate life history information for the development of quantitative fisheries stock assessments, and in the fishery data-poor situations for the identification of vulnerable species. Here, we assemble life history traits (maximum size, growth, longevity, maturity, fecundity, spawning duration and spawning interval) for the 51 species of scombrids globally. We identify major biological gaps in knowledge and prioritize life history research needs in scombrids based on their biological gaps in knowledge, the importance of their fisheries and their current conservation status according to the International Union for Conservation of Nature Red List. We find that the growth and reproductive biology of tunas and mackerel species have been more extensively studied than for Spanish mackerels and bonitos, although there are notable exceptions in all groups. We also reveal that reproductive biology of species, particular fecundity, is the least studied biological aspect in scombrids. We identify two priority groups, including 32 species of scombrids, and several populations of principal market tunas, for which life history research should be prioritized following the species-specific life history gaps identified in this study in the coming decades. By highlighting the important gaps in biological knowledge and providing a priority setting for life history research in scombrid species this study provides guidance for management and conservation and serves as a guide for biologists and resource managers interested in the biology, ecology, and management of scombrid species.

The Conservation and Management of Tunas and Their Relatives: Setting Life History Research Priorities

PubMed Central

Juan-Jordá, Maria José; Mosqueira, Iago; Freire, Juan; Dulvy, Nicholas K.

2013-01-01

Scombrids (tunas, bonitos, Spanish mackerels and mackerels) support important fisheries in tropical, subtropical and temperate waters around the world, being one of the most economically- and socially-important marine species globally. Their sustainable exploitation, management and conservation depend on accurate life history information for the development of quantitative fisheries stock assessments, and in the fishery data-poor situations for the identification of vulnerable species. Here, we assemble life history traits (maximum size, growth, longevity, maturity, fecundity, spawning duration and spawning interval) for the 51 species of scombrids globally. We identify major biological gaps in knowledge and prioritize life history research needs in scombrids based on their biological gaps in knowledge, the importance of their fisheries and their current conservation status according to the International Union for Conservation of Nature Red List. We find that the growth and reproductive biology of tunas and mackerel species have been more extensively studied than for Spanish mackerels and bonitos, although there are notable exceptions in all groups. We also reveal that reproductive biology of species, particular fecundity, is the least studied biological aspect in scombrids. We identify two priority groups, including 32 species of scombrids, and several populations of principal market tunas, for which life history research should be prioritized following the species-specific life history gaps identified in this study in the coming decades. By highlighting the important gaps in biological knowledge and providing a priority setting for life history research in scombrid species this study provides guidance for management and conservation and serves as a guide for biologists and resource managers interested in the biology, ecology, and management of scombrid species. PMID:23950930

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, Steven W.

Bull trout (Salvelinus confluentus) are native to many tributaries of the Snake River in southeast Washington. The Washington Department of Wildlife (WDW) and the American Fisheries Society (AFS) have identified bull trout as a species of special concern which means that they may become threatened or endangered by relatively, minor disturbances to their habitat. Steelhead trout/rainbow trout (Oncorhynchus mykiss) and spring chinook salmon (O.tshawytscha) are also native to several tributaries of the Snake river in southeast Washington. These species of migratory fishes are depressed, partially due to the construction of several dams on the lower Snake river. In response tomore » decreased run size, large hatchery program were initiated to produce juvenile steelhead and salmon to supplement repressed tributary stocks, a practice known as supplementation. There is a concern that supplementing streams with artificially high numbers of steelhead and salmon may have an impact on resident bull trout in these streams. Historically, these three species of fish existed together in large numbers, however, the amount of high-quality habitat necessary for reproduction and rearing has been severely reduced in recent years, as compared to historic amounts. The findings of the first year of a two year study aimed at identifying species interactions in southeast Washington streams are presented in this report. Data was collected to assess population dynamics; habitat utilization and preference, feeding habits, fish movement and migration, age, condition, growth, and the spawning requirements of bull trout in each of four streams. A comparison of the indices was then made between the study streams to determine if bull trout differ in the presence of the putative competitor species. Bull trout populations were highest in the Tucannon River (supplemented stream), followed by Mill Creek (unsupplemented stream). Young of the year bull trout utilized riffle and cascade habitat the most in all four streams. Juvenile bull trout utilized scour pool and run habitat the most in all four streams. YOY bull trout preferred plunge pool and scour pool habitat, as did juvenile bull trout in all four streams. These data show that while in the presence of the putative competitors, bull trout prefer the same habitat as in the absence of the putative competitors. Juvenile bull trout preferred mayflies and stoneflies in Mill Creek, while in the presence of the competitor species they preferred caddisflies, stoneflies, and Oligochaeta. It is felt that this difference is due to the differences in food items available and not species interactions, bull trout consume what is present. Adult bull trout were difficult to capture, and therefore it was difficult to determine the migratory habits in the Tucannon River. It is recommended that future studies use radio telemetry to determine the migratory habitat of these fish. The age, condition, and growth rates of bull trout differed only minimally between streams, indicating that if competitive interactions are occurring between these species it is not reflected by: (1) the length at age of bull trout; (2) the length-weight relationship of bull trout; or (3) the rate of growth of bull trout. The spawning habits of bull trout and spring chinook salmon are similar in the Tucannon River, however it was found that they spawn in different river locations. The salmon spawn below river kilometer 83, while 82% of bull trout spawn above that point. The peak of spawning for salmon occurred 10 days before the peak of bull trout spawning, indicating that very little competition for spawning locations occurs between these species in the Tucannon River. Future species interactions study recommendations include the use of electrofishing to enumerate bull trout populations, snorkeling to identify micro-habitat utilization, seasonal diet analysis, and radio transmitters to identify seasonal migration patterns of bull trout.« less

Age estimations of wild pallid sturgeon (Scaphirhynchus albus, Forbes & Richardson 1905) based on pectoral fin spines, otoliths and bomb radiocarbon: inferences on recruitment in the dam-fragmented Missouri River

USGS Publications Warehouse

Braaten, P. J.; Campana, S. E.; Fuller, D. B.; Lott, R. D.; Bruch, R. M.; Jordan, G. R.

2015-01-01

An extant stock of wild pallid sturgeon Scaphirhynchus albus persists in the fragmented upper Missouri River basin of Montana and North Dakota. Although successful spawning and hatch of embryos has been verified, long-term catch records suggest that recruitment has not occurred for several decades as the extant stock lacks juvenile size classes and is comprised exclusively of large, presumably old individuals. Ages of 11 deceased (death years 1997–2007) wild S. albus (136–166 cm fork length) were estimated based on pectoral fin spines, sagittal otoliths and bomb radiocarbon (14C) assays of otoliths to test the hypothesis that members of this stock are old and to provide inferences on recruitment years that produced the extant stock. Age estimations based on counts of presumed annuli were about 2 years greater for otoliths (mean = 51 years, range = 43–57 years) than spines (mean = 49 years, range = 37–59 years). Based on 14C assays, confirmed birth years for all individuals occurred prior to 1957, thus establishing known longevity of at least 50 years. Estimated age based on presumed otolith annuli for one S. albus was validated to at least age 49. Although 14C assays confirmed pre-1957 birth years for all S. albus, only 56% of estimated ages from spines and 91% of estimated ages from otoliths depicted pre-1957 birth years. Both ageing structures were subject to under-ageing error (up to 15 years). Lack of or severe curtailment of S. albus recruitment in the upper Missouri River basin since the mid-1950s closely parallels the 1953–1957 timeframe when a mainstem reservoir was constructed and started to fill. This reservoir may function as a system-wide stressor to diminish recruitment success of S. albus in the upper Missouri River basin.

Are life histories of Norwegian fjord herring populations of Pacific ancestry similar to those of Atlantic or Pacific herring?

NASA Astrophysics Data System (ADS)

Mikkelsen, Nina; Pedersen, Torstein; dos Santos Schmidt, Thassya Christina; Falk-Petersen, Inger-Britt; Slotte, Aril

2018-04-01

Herring from two unexploited fjord populations, Lake Rossfjord (LRH, n = 100) and Balsfjord (BFH, n = 420) in northern Norway, were sampled in 2014 and 2015. Life history characteristics were analysed and compared to the oceanic Norwegian spring-spawning herring (NSSH), and other Atlantic and Pacific herring stocks. Genetic studies have shown that LRH and BFH are ancestors evolved from Pacific herring that hybridized with Atlantic herring. This study shows that both LRH and BFH mature at a relatively early age, at 2-3 years and ca. 4 years respectively, compared to ca. 5 years for NSSH. The spawning stocks of LRH and BFH consist of small fish and contain relatively few age classes. Both fjord populations have slow growth after sexual maturity; LRH has a very low asymptotic length (L∞ = 19.8 cm), while that of BFH is higher (L∞ of 28.5 cm); both these values being lower than that of NSSH (L∞ of ca. 37 cm). The somatic relative fecundity of LRH is 176.6 oocytes g- 1, while the somatic relative fecundity of recruit and repeat BFH spawners is 152.4 and 183.1 oocytes g- 1, respectively. These estimates are lower than those for NSSH and other Atlantic herring fjord populations, but comparable with other Pacific herring. Due to the smaller body sizes of the spawners in the LRH and BFH populations, absolute fecundity is much lower than in NSSH. The gonadosomatic indices of prespawning fish are similar in LRH and BFH, being slightly higher compared to the NSSH, but lower than values reported for Pacific herring. The natural mortality rates of LRH and BFH (M = 0.64 year- 1 and M = 0.76 year- 1, respectively) are much higher than in NSSH (M = 0.15 year- 1) and most other Atlantic herring populations, except the Lusterfjord herring. However, these high mortality rates are similar to those of several Pacific herring populations. It is concluded that LRH and BFH show low somatic growth and high natural mortality rate. These life history characteristics differ from those of NSSH, but are similar to some Pacific herring populations adapted to a coastal high-mortality risk environment.

Status and trends of adult Lost River (Deltistes luxatus) and shortnose (Chasmistes brevirostris) sucker populations in Upper Klamath Lake, Oregon, 2015

USGS Publications Warehouse

Hewitt, David A.; Janney, Eric C.; Hayes, Brian S.; Harris, Alta C.

2017-07-21

Executive SummaryData from a long-term capture-recapture program were used to assess the status and dynamics of populations of two long-lived, federally endangered catostomids in Upper Klamath Lake, Oregon. Lost River suckers (LRS; Deltistes luxatus) and shortnose suckers (SNS; Chasmistes brevirostris) have been captured and tagged with passive integrated transponder (PIT) tags during their spawning migrations in each year since 1995. In addition, beginning in 2005, individuals that had been previously PIT-tagged were re-encountered on remote underwater antennas deployed throughout sucker spawning areas. Captures and remote encounters during the spawning season in spring 2015 were incorporated into capture-recapture analyses of population dynamics. Cormack-Jolly-Seber (CJS) open population capture-recapture models were used to estimate annual survival probabilities, and a reverse-time analog of the CJS model was used to estimate recruitment of new individuals into the spawning populations. In addition, data on the size composition of captured fish were examined to provide corroborating evidence of recruitment. Separate analyses were done for each species and also for each subpopulation of LRS. Shortnose suckers and one subpopulation of LRS migrate into tributary rivers to spawn, whereas the other LRS subpopulation spawns at groundwater upwelling areas along the eastern shoreline of the lake. Characteristics of the spawning migrations in 2015, such as the effects of temperature on the timing of the migrations, were similar to past years.Capture-recapture analyses for the LRS subpopulation that spawns at the shoreline areas included encounter histories for 13,617 individuals, and analyses for the subpopulation that spawns in the rivers included 39,321 encounter histories. With a few exceptions, the survival of males and females in both subpopulations was high (greater than or equal to 0.86) between 1999 and 2013. Survival was notably lower for males from the rivers in 2000, 2006, and 2012. Survival probabilities were lower for males from the shoreline areas in 2002. Between 2001 and 2014, the abundance of males in the lakeshore spawning subpopulation decreased by at least 59 percent and the abundance of females decreased by at least 53 percent. By combining information from capture-recapture models and size composition data, we concluded that the abundance of both sexes in the river spawning subpopulation of LRS likely has decreased at rates similar to the rates for the lakeshore spawning subpopulation between 2002 and 2014. Capture-recapture analyses for SNS included encounter histories for 20,981 individuals. Most annual survival estimates between 2005 and 2009 were high (greater than 0.88), but both sexes of SNS experienced lower and more variable survival in 2001–04 and 2010–13. The best-case scenario for SNS, based on capture-recapture recruitment modeling, indicates that the abundance of males in the spawning population decreased by 77 percent and the abundance of females decreased by 74 percent between 2001 and 2014. Decreases in abundance for both sexes likely are greater than these estimates indicate. Despite relatively high survival in most years, we conclude that both species have experienced substantial decreases in the abundance of spawning adults because losses from mortality have not been balanced by recruitment of new individuals. The status of the endangered sucker populations in Upper Klamath Lake remains worrisome, especially for SNS.

Steelhead Supplementation in Idaho Rivers, 2000 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Byrne, Alan

In 2000, we continued our assessment of the Sawtooth Hatchery steelhead stock to reestablish natural populations in Beaver and Frenchman creeks in the upper Salmon River. We stocked both streams with 15 pair of hatchery adults and estimated the potential smolt production from the 1999 outplant. I estimated that about nine smolts per female could be produced in both streams from the 1999 outplant. The smolt-to-adult return would need to exceed 20% to return two adults at this level of production. In the Red River drainage, we stocked Dworshak hatchery stock fingerlings and smolts, from 1993 to 1999, to assessmore » which life-stage produces more progeny when the adults return to spawn. In 2000, we operated the Red River weir to trap adults that returned from these stockings, but none were caught from either group. We continued to monitor wild steelhead populations in the Lochsa and Selway river drainages. We estimated that 26 wild adult steelhead returned to Fish Creek. This is the lowest adult escapement we have documented (when the weir was intact all spring) since we began monitoring Fish Creek in 1992. I estimated that nearly 25,000 juvenile steelhead migrated out of Fish Creek this year. Juvenile steelhead densities in Lochsa and Selway tributaries were similar to those observed in 1999. In 2000, we obtained funding for a DNA analysis to assess Idaho's steelhead stock structure. We collected fin samples from wild steelhead in 70 streams of the Clearwater, Snake, and Salmon River drainages and from our five hatchery stocks. The DNA analysis was subcontracted to Dr. Jennifer Nielsen, Alaska Biological Science Center, Anchorage, and will be completed in 2001.« less

[Effective size of subpopulation of the early run sockeye salmon Oncorhynchus nerka from Azabach's Lake (Kamchatka): effect of density on variance of reproductive success].

PubMed

Efremov, V V; Parenskiĭ, V A

2004-04-01

Using Parensky's approach for estimating the number of breeding pairs, we determined effective subpopulation size Ne in early-run sockeye salmon Oncorhynchus nerka from Azabach'e Lake (Kamchatka) in 1977 through 1981. On average (over years and populations), biased sex ratio decreased Ne by 7% as compared to the number of fish on the spawning sites (Ni). High density reduced the Ne/Ni ratio by 62-66% because some fish were excluded from spawning. Dominance polygyny as compared to monogamy and random union of gametes could reduce Ne by about 17%.

Comparison of the response of Atlantic cod ( Gadus morhua) in the high-latitude regions of the North Atlantic during the warm periods of the 1920s-1960s and the 1990s-2000s

NASA Astrophysics Data System (ADS)

Drinkwater, Ken

2009-10-01

Concern about future anthropogenic warming has lead to demands for information on what might happen to fish and fisheries under various climate-change scenarios. One suggestion has been to use past events as a proxy for what will happen in the future. In this paper a comparison between the responses of Atlantic cod ( Gadus morhua) to two major warm periods in the North Atlantic during the 20th century is carried out to determine how reliable the past might be as a predictor of the future. The first warm period began during the 1920s, remained relatively warm through the 1960s, and was limited primarily to the northern regions (>60°N). The second warm period, which again covered the northern regions but also extended farther south (30°N), began in the 1990s and has continued into the present century. During the earlier warm period, the most northern of the cod stocks (West Greenland, Icelandic, and Northeast Arctic cod in the Barents Sea) increased in abundance, individual growth was high, recruitment was strong, and their distribution spread northward. Available plankton data suggest that these cod responses were driven by bottom-up processes. Fishing pressure increased during this period of high cod abundance and the northern cod stocks began to decline, as early as the 1950s in the Barents Sea but during the 1960s elsewhere. Individual growth declined as temperatures cooled and the cod distributions retracted southward. During the warming in the 1990s, the spawning stock biomass of cod in the Barents Sea again increased, recruitment rose, and the stock spread northward, but the individual growth did not improve significantly. Cod off West Greenland also have shown signs of improving recruitment and increasing biomass, albeit they are still very low in comparison to the earlier warming period. The abundance of Icelandic cod, on the other hand, has remained low through the recent warm period and spawning stock biomass and total biomass are at levels near the lowest on record. The different responses of cod to the two warm events, in particular the reduced cod production during the recent warm period, are attributed to the effects of intense fishing pressure and possibly related ecosystem changes. The implications of the results of the comparisons on the development of cod scenarios under future climate change are addressed.

Salmon and steelhead in the White Salmon River after the removal of Condit Dam–Planning efforts and recolonization results

USGS Publications Warehouse

Allen, Brady; Engle, Rod O; Zendt, Joseph S; Shrier, Frank C; Wilson, Jeremy T; Connolly, Patrick J.

2016-01-01

Condit Dam, at river kilometer 5.3 on the White Salmon River, Washington, was breached in 2011 and completely removed in 2012. This action opened habitat to migratory fish for the first time in 100 years. The White Salmon Working Group was formed to create plans for fish salvage in preparation for fish recolonization and to prescribe the actions necessary to restore anadromous salmonid populations in the White Salmon River after Condit Dam removal. Studies conducted by work group members and others served to inform management decisions. Management options for individual species were considered, including natural recolonization, introduction of a neighboring stock, hatchery supplementation, and monitoring natural recolonization for some time period to assess the need for hatchery supplementation. Monitoring to date indicates that multiple species and stocks of anadromous salmonids are finding and spawning in the now accessible and recovering habitat.

Conflict in the Currents: The Cross-boundary Consequences of Larval Dispersal

NASA Astrophysics Data System (ADS)

Rising, J. A.; Ramesh, N.; Dookie, D.

2016-02-01

As commercial fish populations decline in many regions, the increasing demand for ocean resources can create conflicts along international boundaries. Because fish stock ranges do not respect political boundaries, neighboring countries can impact each other through the management of the stocks within their exclusive economic zones. By combining spawning and larvae information from the FishBase database with current velocities from ocean reanalyses using a particle tracking scheme, we construct a measure of the cross-boundary diffusion of fish larvae for 40 major exploited species. These flows represent important connections both for fish populations and for fisheries and the people who depend on them, but these connections rely on fisheries management in the 'source' countries. We then use socioeconomic data on the national importance of these fish to identify hotspots for potential conflict. Finally, we consider how ranges will shift under climate change, and the social impacts of these shifts.

Acoustic estimates of abundance and distribution of spawning lake trout on Sheboygan Reef in Lake Michigan

USGS Publications Warehouse

Warner, D.M.; Claramunt, R.M.; Janssen, J.; Jude, D.J.; Wattrus, N.

2009-01-01

Efforts to restore self-sustaining lake trout (Salvelinus namaycush) populations in the Laurentian Great Lakes have had widespread success in Lake Superior; but in other Great Lakes, populations of lake trout are maintained by stocking. Recruitment bottlenecks may be present at a number of stages of the reproduction process. To study eggs and fry, it is necessary to identify spawning locations, which is difficult in deep water. Acoustic sampling can be used to rapidly locate aggregations of fish (like spawning lake trout), describe their distribution, and estimate their abundance. To assess these capabilities for application to lake trout, we conducted an acoustic survey covering 22 km2 at Sheboygan Reef, a deep reef (<40 m summit) in southern Lake Michigan during fall 2005. Data collected with remotely operated vehicles (ROV) confirmed that fish were large lake trout, that lake trout were 1–2 m above bottom, and that spawning took place over specific habitat. Lake trout density exhibited a high degree of spatial structure (autocorrelation) up to a range of ~190 m, and highest lake trout and egg densities occurred over rough substrates (rubble and cobble) at the shallowest depths sampled (36–42 m). Mean lake trout density in the area surveyed (~2190 ha) was 5.8 fish/ha and the area surveyed contained an estimated 9500–16,000 large lake trout. Spatial aggregation in lake trout densities, similarity of depths and substrates at which high lake trout and egg densities occurred, and relatively low uncertainty in the lake trout density estimate indicate that acoustic sampling can be a useful complement to other sampling tools used in lake trout restoration research.

Recruitment constraints in Singapore's fluted giant clam (Tridacna squamosa) population—A dispersal model approach

PubMed Central

Neo, Mei Lin; Erftemeijer, Paul L. A.; van Beek, Jan K. L.; van Maren, Dirk S.; Teo, Serena L-M.; Todd, Peter A.

2013-01-01

Recruitment constraints on Singapore's dwindling fluted giant clam, Tridacna squamosa, population were studied by modelling fertilisation, larval transport, and settlement using real-time hydrodynamic forcing combined with knowledge of spawning characteristics, larval development, behaviour, and settlement cues. Larval transport was simulated using a finite-volume advection-diffusion model coupled to a three-dimensional hydrodynamic model. Three recruitment constraint hypotheses were tested: 1) there is limited connectivity between Singapore's reefs and other reefs in the region, 2) there is limited exchange within Singapore's Southern Islands, and 3) there exist low-density constraints to fertilisation efficacy (component Allee effects). Results showed that connectivity among giant clam populations was primarily determined by residual hydrodynamic flows and spawning time, with greatest chances of successful settlement occurring when spawning and subsequent larval dispersal coincided with the period of lowest residual flow. Simulations suggested poor larval transport from reefs located along the Peninsular Malaysia to Singapore, probably due to strong surface currents between the Andaman Sea and South China Sea combined with a major land barrier disrupting larval movement among reefs. The model, however, predicted offshore coral reefs to the southeast of Singapore (Bintan and Batam) may represent a significant source of larvae. Larval exchange within Singapore's Southern Islands varied substantially depending on the locations of source and sink reefs as well as spawning time; but all simulations resulted in low settler densities (2.1–68.6 settled individuals per 10,000 m2). Poor fertilisation rates predicted by the model indicate that the low density and scattered distribution of the remaining T. squamosa in Singapore are likely to significantly inhibit any natural recovery of local stocks. PMID:23555597

How stock of origin affects performance of individuals across a meta-ecosystem: an example from sockeye salmon.

PubMed

Griffiths, Jennifer R; Schindler, Daniel E; Seeb, Lisa W

2013-01-01

Connectivity among diverse habitats can buffer populations from adverse environmental conditions, influence the functioning of meta-ecosystems, and ultimately affect the reliability of ecosystem services. This stabilizing effect on populations is proposed to derive from complementarity in growth and survival conditions experienced by individuals in the different habitats that comprise meta-ecosystems. Here we use the fine scale differentiation of salmon populations between diverse lake habitats to assess how rearing habitat and stock of origin affect the body condition of juvenile sockeye salmon. We use genetic markers (single nucleotide polymorphisms) to assign individuals of unknown origin to stock group and in turn characterize ecologically relevant attributes across habitats and stocks. Our analyses show that the body condition of juvenile salmon is related to the productivity of alternative habitats across the watershed, irrespective of their stock of origin. Emigrants and residents with genetic origins in the high productivity lake were also differentiated by their body condition, poor and high respectively. These emigrants represented a substantial proportion of juvenile sockeye salmon rearing in the lower productivity lake habitat. Despite emigrants originating from the more productive lake, they did not differ in body condition from the individuals spawned in the lower productivity, recipient habitat. Genetic tools allowed us to assess the performance of different stocks groups across the diverse habitats comprising their meta-ecosystem. The ability to characterize the ecological consequences of meta-ecosystem connectivity can help develop strategies to protect and restore ecosystems and the services they provide to humans.

How Stock of Origin Affects Performance of Individuals across a Meta-Ecosystem: An Example from Sockeye Salmon

PubMed Central

Griffiths, Jennifer R.; Schindler, Daniel E.; Seeb, Lisa W.

2013-01-01

Connectivity among diverse habitats can buffer populations from adverse environmental conditions, influence the functioning of meta-ecosystems, and ultimately affect the reliability of ecosystem services. This stabilizing effect on populations is proposed to derive from complementarity in growth and survival conditions experienced by individuals in the different habitats that comprise meta-ecosystems. Here we use the fine scale differentiation of salmon populations between diverse lake habitats to assess how rearing habitat and stock of origin affect the body condition of juvenile sockeye salmon. We use genetic markers (single nucleotide polymorphisms) to assign individuals of unknown origin to stock group and in turn characterize ecologically relevant attributes across habitats and stocks. Our analyses show that the body condition of juvenile salmon is related to the productivity of alternative habitats across the watershed, irrespective of their stock of origin. Emigrants and residents with genetic origins in the high productivity lake were also differentiated by their body condition, poor and high respectively. These emigrants represented a substantial proportion of juvenile sockeye salmon rearing in the lower productivity lake habitat. Despite emigrants originating from the more productive lake, they did not differ in body condition from the individuals spawned in the lower productivity, recipient habitat. Genetic tools allowed us to assess the performance of different stocks groups across the diverse habitats comprising their meta-ecosystem. The ability to characterize the ecological consequences of meta-ecosystem connectivity can help develop strategies to protect and restore ecosystems and the services they provide to humans. PMID:23505539

Diverse juvenile life-history behaviours contribute to the spawning stock of an anadromous fish population

USGS Publications Warehouse

Walsworth, Timothy E.; Schindler, Daniel E.; Griffiths, Jennifer R.; Zimmerman, Christian E.

2015-01-01

Habitat quality often varies substantially across space and time, producing a shifting mosaic of growth and mortality trade-offs across watersheds. Traditional studies of juvenile habitat use have emphasised the evolution of single optimal strategies that maximise recruitment to adulthood and eventual fitness. However, linking the distribution of individual behaviours that contribute to recruitment at the population level has been elusive, particularly for highly fecund aquatic organisms. We examined juvenile habitat use within a population of sockeye salmon (Oncorhynchus nerka) that spawn in a watershed consisting of two interconnected lakes and a marine lagoon. Otolith microchemical analysis revealed that the productive headwater lake accounted for about half of juvenile growth for those individuals surviving to spawn in a single river in the upper watershed. However, 47% of adults had achieved more than half of their juvenile growth in the downstream less productive lake, and 3% of individuals migrated to the estuarine environment during their first summer and returned to freshwater to overwinter before migrating back to sea. These results describe a diversity of viable habitat-use strategies by juvenile sockeye salmon that may buffer the population against poor conditions in any single rearing environment, reduce density-dependent mortality and have implications for the designation of critical habitat for conservation purposes. A network of accessible alternative habitats providing trade-offs in growth and survival may be important for long-term viability of populations.

Does small-bodied salmon spawning activity enhance streambed mobility?

NASA Astrophysics Data System (ADS)

Hassan, Marwan A.; Tonina, Daniele; Buxton, Todd H.

2015-09-01

Female salmonids bury and lay their eggs in streambeds by digging a pit, which is then covered with sediment from a second pit that is dug immediately upstream. The spawning process alters streambed topography, winnows fine sediment, and mixes sediment in the active layer. The resulting egg nests (redds) contain coarser and looser sediments than those of unspawned streambed areas, and display a dune-like shape with an amplitude and length that vary with fish size, substrate conditions, and flow conditions. Redds increase local bed surface roughness (<10-1 channel width, W), but may reduce the size of macro bedforms by eroding reach-scale topography (100-101W). Research has suggested that spawning may increase flow resistance due to redd form drag, resulting in lower grain shear stress and less particle mobility. Spawning, also prevents streambed armoring by mixing surface and subsurface material, potentially increasing particle mobility. Here we use two-dimensional hydraulic modeling with detailed prespawning and postspawning bathymetries and field observations to test the effect of spawning by small-bodied salmonids on sediment transport. Our results show that topographical roughness from small salmon redds has negligible effects on shear stress at the reach-unit scale, and limited effects at the local scale. Conversely, results indicate sediment mixing reduces armoring and enhances sediment mobility, which increases potential bed load transport by subsequent floods. River restoration in fish-bearing streams should take into consideration the effects of redd excavation on channel stability. This is particularly important for streams that historically supported salmonids and are the focus of habitat restoration actions.

Lake trout spawning habitat in the Six Fathom Bank-Yankee Reef lake trout sanctuary, Lake Huron

USGS Publications Warehouse

Edsall, Thomas A.; Brown, Charles L.; Kennedy, Gregory W.; Poe, Thomas P.

1992-01-01

Attempts to reestablish self-sustaining stocks of lake trout (Salvelinus namaycush) in the lower four Great Lakes, where the species was extinguished in the 1950s and 1960s, have been largely unsuccessful. To avoid many of the problems believed to be contributing to this failure, the fishery management community recently established several sanctuaries in the offshore waters of the Great Lakes where the development and protection of self-sustaining stocks of lake trout would be a primary management objective. One of these, the Six Fathom Bank-Yankee Reef sanctuary, was created in the south-central portion of Lake Huron. This sanctuary covers 168,000 ha and includes the shallower portions of the Six Fathom and Ipperwash scarps, which are major bathymetric features in the southern half of the lake. Historical accounts describe Six Fathom Bank as the most important lake trout spawning ground in the lake. Here we present the results of lake bed surveys conducted in the sanctuary with side-scan sonar, underwater videocamera systems, and a small research submarine. Our observations of the lake bed are consistent with what is known of the bedrock stratigraphy, glacial history, and karst geomorphology of the Lake Huron basin. Most of the loose rock we found seemed to be derived from local carbonate bedrock formations, although non-carbonate rock probably from Precambrian sources to the north was also present in some areas. Much of the bedrock and loose rock displayed karst solution features described for the Bruce Peninsula on the Ontario shoreline. Our surveys revealed substantial areas of lake bed at water depths of 20–36 m that resembled suitable spawning and fry production habitat for the shallow-water strains of lake trout that are the focus of the rehabilitation effort. Low mid-lake nutrient levels documented recently by others and the extremely high abundance of Mysis relicta (an important item in the diet of young lake trout) that we documented on Yankee Reef also contributed to our evaluation of the sanctuary as a site with high potential to support a self-sustaining population of lake trout.

Substrate conditions and abundance of lake trout eggs in a traditional spawning area in southeastern Lake Michigan

USGS Publications Warehouse

Dorr, John A.; O'Connor, Daniel V.; Foster, Neal R.; Jude, David J.

1981-01-01

Spawning by planted lake trout (Salvelinus namaycush) was documented by sampling with a diver-assisted pump in a traditional spawning area in southeastern Lake Michigan near Saugatuck, Michigan in mid-November in 1978 and 1979. Bottom depths at the 11 locations sampled ranged from 3 to 12 m and substrate size from boulders to sand. Periphyton (Cladophora and associated biota) was several millimeters thick at most stations but sparse at the shallowest. The most eggs recovered from a single sample occurred at the shallowest depth (3 m). In both years, some of the small numbers of eggs collected (9 in 1978, 14 in 1979) were alive and fertilized. Laboratory incubation of viable eggs resulted in successful hatching of larvae. When compared with egg densities measured at spawning sites used by self-sustaining populations of lake trout in other lakes, densities in the study are (0-13/m2) appeared to be critically low. Insufficient numbers of eggs, combined with harsh incubation conditions (turbulence, ice scour, sedimentation), were implicated as prime causes for lake trout reproductive failure in the study area, although other factors, such as inappropriate spawning behavior (selection of suboptimal spawning location, depth, or substrate) also may have reduced survival of eggs and larvae.

Habitat selection and quality for multiple cohorts of young-of-the-year bluefish ( Pomatomus saltatrix): Comparisons between estuarine and ocean beaches in southern New Jersey

NASA Astrophysics Data System (ADS)

Taylor, David L.; Nichols, Ryan S.; Able, Kenneth W.

2007-07-01

In this study, seasonal and annual variability in the use of estuarine and ocean beaches by young-of-the-year bluefish, Pomatomus saltatrix, was evaluated by indices of abundance in coastal areas of southern New Jersey (1998-2000). Biological and physical factors measured at specific sites were correlated with bluefish abundance to determine the mechanisms underlying habitat selection. In addition, integrative and discrete indicators of bluefish growth were used to examine spatio-temporal dynamics in habitat quality and its effect on habitat selection by multiple cohorts of bluefish. Intra-annual recruitment to coastal areas of southern New Jersey was episodic, and resulted from the ingress of spring-spawned bluefish (hatch-date ˜April) to estuarine beaches in late May to early June, followed by the recruitment of summer-spawned fish (hatch-date ˜early July) to ocean beaches from July to October. Bluefish utilized estuarine and ocean beaches in a facultative manner that was responsive to dynamics in prey composition and temperature conditions. The recruitment and residency of bluefish in the estuary (1998-1999) and ocean beaches (1998), for example, was coincidental with the presence of the Atlantic silverside Menidia menidia and bay anchovy Anchoa mitchilli, the principal prey species for bluefish occupying these respective habitat-types. Bluefish abundance in the estuary (2000) and ocean beaches (1999-2000) was also correlated with water temperature, with the greatest catches of juveniles coinciding with their optimal growth temperature (24 °C). Bluefish growth, estimated as the slope of age-length relationships and daily specific growth rates, equaled 1.27-2.63 mm fork length (FL) d -1 and 3.8-8.7% body length increase d -1, respectively. The growth of sagittal otoliths was also used as a proxy for changes in bluefish size during and shortly before their time of capture. Accordingly, otolith growth rates of summer-spawned bluefish were greater at ocean beaches relative to the estuary and were explained by the more suitable temperature conditions found at ocean beaches during the mid- to late summer. Notwithstanding the fast growth of oceanic summer-spawned bluefish, individuals spawned in the spring were still larger in absolute body size at the end of the summer growing season (˜240 and 50-200 mm FL for spring- and summer-spawned bluefish, respectively). The size discrepancy between spring- and summer-spawned bluefish at the onset of autumn migrations and during overwintering periods may account for the differential recruitment success of the respective cohorts.

Strong Predictability Of Spatially Distributed Physical Habitat Preferences For O. Mykiss Spawning Across Three Spatial Scales

NASA Astrophysics Data System (ADS)

Kammel, L.; Pasternack, G. B.; Wyrick, J. R.; Massa, D.; Bratovich, P.; Johnson, T.

2012-12-01

Currently accepted perception assumes Oncorhynchus mykiss prefer different ranges of similar physical habitat elements for spawning than Chinook salmon (Oncorhynchus tshawytscha), taking into account their difference in size. While there is increasing research interest regarding O. mykiss habitat use and migratory behavior, research conducted to date distinguishing the physical habitat conditions utilized for O. mykiss spawning has not provided quantified understanding of their spawning habitat preferences. The purpose of this study was to use electivity indices and other measures to assess the physical habitat characteristics preferred for O. mykiss spawning in terms of both 1-m scale microhabitat attributes, and landforms at different spatial scales from 0.1-100 times channel width. The testbed for this study was the 37.5-km regulated gravel-cobble Lower Yuba River (LYR). Using spatially distributed 2D hydrodynamic model results, substrate mapping, and a census of O. mykiss redds from two years of observation, micro- and meso-scale representations of physical habitat were tested for their ability to predict spawning habitat preference and avoidance. Overall there was strong stratification of O. mykiss redd occurrence for all representation types of physical habitat. A strong preference of hydraulic conditions was shown for mean water column velocities of 1.18-2.25 ft/s, and water depths of 1.25-2.76 ft. There was a marked preference for the two most upstream alluvial reaches of the LYR (out of 8 total reaches), accounting for 92% of all redds observed. The preferred morphological units (MUs) for O. mykiss spawning were more variable than for Chinook salmon and changed with increasing discharge, demonstrating that O. mykiss shift spawning to different MUs in order to utilize their preferred hydraulic conditions. The substrate range preferred for O. mykiss spawning was within 32-90 mm. Overall, O. mykiss spawning behavior was highly predictable and required a holistic blend of hydraulic and geomorphic representations to explain.

Sexual maturation in kokanee Oncorhynchus nerka

USGS Publications Warehouse

Patterson, S.D.; Scarnecchia, D.L.; Congleton, J.L.

2008-01-01

We used observational and experimental approaches to obtain information on factors affecting the timing of maturation of kokanee Oncorhynchus nerka, a semelparous, landlocked salmon. Gonadal staging criteria were developed and applied to three kokanee populations in Idaho lakes and reservoirs. Testes were classified into three stages: immature (stage one, S1), maturing (S2), and mature (S3). Ovaries were classified into eight stages: immature (S1-S3), transitional (stage S4), maturing (S5-S7), and mature (S8). Males entered the maturing stage (S2) in February through April of the spawning year. Females entered maturing stage (S5) as early as July of the year before the spawning year, and as late as March of the spawning year. Three hatchery experiments demonstrated that attainment of a larger body size 10 to 16 months before spawning increased the likelihood of initiation of maturation in both sexes. No gonads in a state of regression were observed. A gonadosomatic index above 0.1 by early July was a good indicator of a maturing male, and a gonadosomatic index above 1.0 by early July was a good indicator of a maturing female. Instantaneous growth rates were not good predictors of maturation, but attaining a size threshold of 18 to 19 cm in the fall was a good predictor of maturation the following year. This improved knowledge of kokanee maturation will permit more effectively management of the species for age, growth and size at maturity as well as for contributions to fisheries. ?? 2008 by the Northwest Scientific Association. All rights reserved.

Spatial and seasonal dynamics of brook trout populations inhabiting a central Appalachian watershed

USGS Publications Warehouse

Petty, J.T.; Lamothe, P.J.; Mazik, P.M.

2005-01-01

We quantified the watershed-scale spatial population dynamics of brook trout Salvelinus fontinalis in the Second Fork, a third-order tributary of Shavers Fork in eastern West Virginia. We used visual surveys, electrofishing, and mark-recapture techniques to quantify brook trout spawning intensity, population density, size structure, and demographic rates (apparent survival and immigration) throughout the watershed. Our analyses produced the following results. Spawning by brook trout was concentrated in streams with small basin areas (i.e., segments draining less than 3 km2), relatively high alkalinity (>10 mg CaCO3/L), and high amounts of instream cover. The spatial distribution of juvenile and small-adult brook trout within the watershed was relatively stable and was significantly correlated with spawning intensity. However, no such relationship was observed for large adults, which exhibited highly variable distribution patterns related to seasonally important habitat features, including instream cover, stream depth and width, and riparian canopy cover. Brook trout survival and immigration rates varied seasonally, spatially, and among size-classes. Differential survival and immigration tended to concentrate juveniles and small adults in small, alkaline streams, whereas dispersal tended to redistribute large adults at the watershed scale. Our results suggest that spatial and temporal variations in spawning, survival, and movement interact to determine the distribution, abundance, and size structure of brook trout populations at a watershed scale. These results underscore the importance of small tributaries for the persistence of brook trout in this watershed and the need to consider watershed-scale processes when designing management plans for Appalachian brook trout populations. ?? Copyright by the American Fisheries Society 2005.

Unravelling the Gordian knot! Key processes impacting overwintering larval survival and growth: A North Sea herring case study

NASA Astrophysics Data System (ADS)

Hufnagl, Marc; Peck, Myron A.; Nash, Richard D. M.; Dickey-Collas, Mark

2015-11-01

Unraveling the key processes affecting marine fish recruitment will ultimately require a combination of field, laboratory and modelling studies. We combined analyzes of long-term (30-year) field data on larval fish abundance, distribution and length, and biophysical model simulations of different levels of complexity to identify processes impacting the survival and growth of autumn- and winter-spawned Atlantic herring (Clupea harengus) larvae. Field survey data revealed interannual changes in intensity of utilization of the five major spawning grounds (Orkney/Shetland, Buchan, Banks north, Banks south, and Downs) as well as spatio-temporal variability in the length and abundance of overwintered larvae. The mean length of larvae captured in post-winter surveys was negatively correlated to the proportion of larvae from the southern-most (Downs) winter-spawning component. Furthermore, the mean length of larvae originating from all spawning components has decreased since 1990 suggesting ecosystem-wide changes impacting larval growth potential, most likely due to changes in prey fields. A simple biophysical model assuming temperature-dependent growth and constant mortality underestimated larval growth rates suggesting that larval mortality rates steeply declined with increasing size and/or age during winter as no match with field data could be obtained. In contrast better agreement was found between observed and modelled post-winter abundance for larvae originating from four spawning components when a more complex, physiological-based foraging and growth model was employed using a suite of potential prey field and size-based mortality scenarios. Nonetheless, agreement between field and model-derived estimates was poor for larvae originating from the winter-spawned Downs component. In North Sea herring, the dominant processes impacting larval growth and survival appear to have shifted in time and space highlighting how environmental forcing, ecosystem state and other factors can form a Gordian knot of marine fish recruitment processes. We highlight gaps in process knowledge and recommend specific field, laboratory and modelling studies which, in our opinion, are most likely to unravel the dominant processes and advance predictive capacity of the environmental regulation of recruitment in autumn and winter-spawned fishes in temperate areas such as herring in the North Sea.

Impact of entrainment and impingement on fish populations in the Hudson River Estuary. Volume II. Impingement impact analyses, evaluations of alternative screening devices, and critiques of utility testimony relating to density-dependent growth, the age-composition of the striped bass spawning stock, and the LMS real-time life cycle model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnthouse, L. W.; Van Winkle, W.; Golumbek, J.

1982-04-01

This volume includes a series of four exhibits relating to impacts of impingement on fish populations, together with a collection of critical evaluations of testimony prepared for the utilities by their consultants. The first exhibit is a quantitative evaluation of four sources of bias (collection efficiency, reimpingement, impingement on inoperative screens, and impingement survival) affecting estimates of the number of fish killed at Hudson River power plants. The two following exhibits contain, respectively, a detailed assessment of the impact of impingement on the Hudson River white perch population and estimates of conditional impingement mortality rates for seven Hudson River fishmore » populations. The fourth exhibit is an evaluation of the engineering feasibility and potential biological effectiveness of several types of modified intake structures proposed as alternatives to cooling towers for reducing impingement impacts. The remainder of Volume II consists of critical evaluations of the utilities' empirical evidence for the existence of density-dependent growth in young-of-the-year striped bass and white perch, of their estimate of the age-composition of the striped bass spawning stock in the Hudson River, and of their use of the Lawler, Matusky, and Skelly (LMS) Real-Time Life Cycle Model to estimate the impact of entrainment and impingement on the Hudson River striped bass population.« less

Investigations into the Early Life History of Naturally Produced Spring Chinook Salmon in the Grande Ronde Riiver Basin : Fish Research Project Oregon : Annual Progress Report 1 September 1995 to 1 August 1996.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jonasson, Brian C.; Carmichael, Richard W.; Keefe, MaryLouise

1997-09-01

Historically, the Grande Ronde River produced an abundance of salmonids including stocks of spring, summer and fall chinook salmon, sockeye salmon, coho salmon, and summer steelhead. During the past century, numerous factors have caused the reduction of salmon stocks such that only sustainable stocks of spring chinook salmon and summer steelhead remain. The sizes of spring chinook salmon populations in the Grande Ronde River basin also have been declining steadily and are substantially depressed from estimates of historic levels. In addition to a decline in population abundance, a reduction of spring chinook salmon spawning distribution is evident in the Grandemore » Ronde River basin. Numerous factors are thought to contribute to the decline of spring chinook salmon in the Snake River and its tributaries. These factors include passage problems and increased mortality of juvenile and adult migrants at mainstem Columbia and Snake river dams, overharvest, and habitat degradation associated with timber, agricultural, and land development practices. This study was designed to describe aspects of the life history strategies exhibited by spring chinook salmon in the Grande Ronde River basin. During the past year the focus was on rearing and migration patterns of juveniles in the upper Grande Ronde River and Catherine Creek. The study design included three objectives: (1) document the annual in-basin migration patterns for spring chinook salmon juveniles in the upper Grande Ronde River and Catherine Creek, including the abundance of migrants, migration timing and duration; (2) estimate and compare smolt survival indices to mainstem Columbia and Snake river dams for fall and spring migrating spring chinook salmon; and (3) determine summer and winter habitat utilization and preference of juvenile spring chinook salmon in the upper Grande Ronde River and Catherine Creek.« less

Atlantic Bluefin Tuna: A Novel Multistock Spatial Model for Assessing Population Biomass

PubMed Central

Taylor, Nathan G.; McAllister, Murdoch K.; Lawson, Gareth L.; Carruthers, Tom; Block, Barbara A.

2011-01-01

Atlantic bluefin tuna (Thunnus thynnus) is considered to be overfished, but the status of its populations has been debated, partly because of uncertainties regarding the effects of mixing on fishing grounds. A better understanding of spatial structure and mixing may help fisheries managers to successfully rebuild populations to sustainable levels while maximizing catches. We formulate a new seasonally and spatially explicit fisheries model that is fitted to conventional and electronic tag data, historic catch-at-age reconstructions, and otolith microchemistry stock-composition data to improve the capacity to assess past, current, and future population sizes of Atlantic bluefin tuna. We apply the model to estimate spatial and temporal mixing of the eastern (Mediterranean) and western (Gulf of Mexico) populations, and to reconstruct abundances from 1950 to 2008. We show that western and eastern populations have been reduced to 17% and 33%, respectively, of 1950 spawning stock biomass levels. Overfishing to below the biomass that produces maximum sustainable yield occurred in the 1960s and the late 1990s for western and eastern populations, respectively. The model predicts that mixing depends on season, ontogeny, and location, and is highest in the western Atlantic. Assuming that future catches are zero, western and eastern populations are predicted to recover to levels at maximum sustainable yield by 2025 and 2015, respectively. However, the western population will not recover with catches of 1750 and 12,900 tonnes (the “rebuilding quotas”) in the western and eastern Atlantic, respectively, with or without closures in the Gulf of Mexico. If future catches are double the rebuilding quotas, then rebuilding of both populations will be compromised. If fishing were to continue in the eastern Atlantic at the unregulated levels of 2007, both stocks would continue to decline. Since populations mix on North Atlantic foraging grounds, successful rebuilding policies will benefit from trans-Atlantic cooperation. PMID:22174745

Sex-ratio, seasonality and long-term variation in maturation and spawning of the brown shrimp Crangon crangon (L.) in the German Bight (North Sea)

NASA Astrophysics Data System (ADS)

Siegel, V.; Damm, U.; Neudecker, T.

2008-12-01

Aspects of the reproductive and maturation biology of the brown shrimp Crangon crangon (L.) were studied in various subareas of the German Bight (North Sea). The size-specific sex ratio of C. crangon was examined based on length frequency distribution data. The sex ratio for the smallest size groups at which sex was determined was typically around 0.5, indicating an even ratio between males and females. The proportion of females decreased in the 30-45 mm size range. In length classes larger than 50 mm, the proportion of females constantly increases to 100% at around 60 mm total length. We concluded that sex reversal from male to female may not occur in C. crangon. Size at sexual maturity was determined from the proportion of ovigerous females. Size at maturity ( L 50) was estimated as 55.4 and 62.0 mm total length for spring and winter data, respectively. The seasonal spawning cycle was studied over the period 1958-2005. Between mid February and late June and for size classes larger than 65 mm ovigerous shrimps exceeded 80% and reached up to 100% of the females in the population. This period can be seen as the core spawning season. From early August to early December the proportion of ovigerous shrimps in the female population is very low. Interannual differences in the seasonal process are obvious with a dramatic decline in C. crangon reproductive success in the late 1980s. Various options are discussed for the reasons of the decline and recovery of the reproductive performance.

Potential effects of maternal contribution on egg and larva population dynamics of striped bass: Integrated individual-based model and directed field sampling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cowan, J.H., Jr.; Rose, K.A.

1991-01-01

We have used a bioenergetically-driven, individual-based model (IBM) of striped bass as a framework for synthesizing available information on population biology and quantifying, in a relative sense, factors that potentially affect year class success. The IBM has been configured to simulate environmental conditions experienced by several striped bass populations; i.e., in the Potomac River, MD; in Hudson River, NY; in the Santee-Cooper River System, SC, and; in the San Joaquin-Sacramento River System CA. These sites represent extremes in the geographic distribution and thus, environmental variability of striped bass spawning. At each location, data describing the physio-chemical and biological characteristics ofmore » the spawning population and nursery area are being collected and synthesized by means of a prioritized, directed field sampling program that is organized by the individual-based recruitment model. Here, we employ the striped bass IBM configured for the Potomac River, MD from spawning into the larval period to evaluate the potential for maternal contribution to affect larva survival and growth. Model simulations in which the size distribution and spawning day of females are altered indicate that larva survival is enhanced (3.3-fold increase) when a high fraction of females in the spawning population are large. Larva stage duration also is less ({bar X} = 18.4 d and 22.2 d) when large and small females, respectively, are mothers in simulations. Although inconclusive, these preliminary results for Potomac River striped bass suggest that the effects of female size, timing of spawning nad maternal contribution on recruitment dynamics potentially are important and illustrate our approach to the study of recruitment in striped bass. We hope to use the model, field collections and management alternatives that vary from site to site, in an iterative manner for some time to come. 54 refs., 4 figs., 1 tab.« less

Reproductive Biology of the Blue Swimming Crab Portunus pelagicus (Brachyura: Portunidae) in East Lampung Waters, Indonesia: Fecundity and Reproductive Potential

PubMed Central

Zairion; Wardiatno, Yusli; Boer, Mennofatria; Fahrudin, Achmad

2015-01-01

The blue swimming crab Portunus pelagicus is an important catch species for many coastal villages along the Java Sea coastline, but little is known regarding its reproductive biology or stock status. We examined the batch fecundity of female crabs that were collected monthly at landing sites from June 2011 to May 2012, calculated the relationships with body size, egg mass and month of the year, and determined the size at which females became potentially reproductive in the population inhabiting East Lampung waters (western Java Sea). Fecundity values ranged from 229,468 to 2,236,355 (mean = 926,638±30,975 [±SE]). The fecundity was positively and linearly correlated with carapace width (CW), but the relationships with body weight and egg mass were best described by logarithmic regression. A peaked, temporally cyclical pattern in fecundity was observed, with a peak period that was significantly different (F = 226.36; df = 22, p<0.05) from March to May 2012. Reproductive females were within the 111.0–155.9 mm CW size range; significantly higher reproductive potentials (F = 14.59; df = 30, p<0.05) were found in females within the 126.0–130.9 mm CW size group. The current minimum legal size (MLS = 100 mm CW) is not an appropriate limit reference point, and a precautionary approach is needed for a sustainable harvesting strategy. Resetting the MLS to 115 mm CW would potentially provide adequate protection for spawning females and increase total egg production, thereby maintaining population productivity and enhancing resilience in the face of current fishing pressures. PMID:26019748

Lake-specific variation in growth, migration timing and survival of juvenile sockeye salmon Oncorhynchus nerka: separating environmental from genetic influences.

PubMed

Reed, T E; Martinek, G; Quinn, T P

2010-08-01

Time series on juvenile life-history traits obtained from sockeye salmon Oncorhynchus nerka were analysed to assess lake-specific environmental influences on juvenile migration timing, size and survival of fish from a common gene pool. Every year for the past two decades, O. nerka have been spawned at a hatchery facility, and the progeny released into two lakes that differ in average summer temperatures, limnological attributes and growth opportunities. Juveniles reared in the warmer, more productive Crosswind Lake were larger and heavier as smolts compared to those from the cooler, less productive Summit Lake and had higher in-lake and subsequent marine survival. Crosswind Lake smolts migrated from the lake to sea slightly earlier in the season but the migration timing distributions overlapped considerably across years. Fry stocking density had a negative effect on smolt length for both lakes, and a negative effect on in-lake survival in Summit Lake. Taken together, the results revealed a strong effect of lake-rearing environment on the expression of life-history variation in O. nerka. The stocking of these lakes each year with juveniles from a single mixed-source population provided a large-scale reverse common-garden experiment, where the same gene pool was exposed to different environments, rather than the different gene pools in the same environment approach typical of evolutionary ecology studies. Other researchers are encouraged to seek and exploit similar serendipitous situations, which might allow environmental and genetic influences on ecologically important traits to be distinguished in natural or semi-natural settings.

The Principles of Buoyancy in Marine Fish Eggs and Their Vertical Distributions across the World Oceans

PubMed Central

Sundby, Svein; Kristiansen, Trond

2015-01-01

Buoyancy acting on plankton, i.e. the difference in specific gravity between plankton and the ambient water, is a function of salinity and temperature. From specific gravity measurements of marine fish eggs salinity appears to be the only determinant of the buoyancy indicating that the thermal expansions of the fish egg and the ambient seawater are equal. We analyze the mechanisms behind thermal expansion in fish eggs in order to determine to what extent it can be justified to neglect the effects of temperature on buoyancy. Our results confirm the earlier assumptions that salinity is the basic determinant on buoyancy in marine fish eggs that, in turn, influence the vertical distributions and, consequently, the dispersal of fish eggs from the spawning areas. Fish populations have adapted accordingly by producing egg specific gravities that tune the egg buoyancy to create specific vertical distributions for each local population. A wide variety of buoyancy adaptations are found among fish populations. The ambient physical conditions at the spawning sites form a basic constraint for adaptation. In coastal regions where salinity increases with depth, and where the major fraction of the fish stocks spawns, pelagic and mesopelagic egg distributions dominate. However, in the larger part of worlds’ oceans salinity decreases with depth resulting in different egg distributions. Here, the principles of vertical distributions of fish eggs in the world oceans are presented in an overarching framework presenting the basic differences between regions, mainly coastal, where salinity increases with depth and the major part of the world oceans where salinity decreases with depth. We show that under these latter conditions, steady-state vertical distribution of mesopelagic fish eggs cannot exist as it does in most coastal regions. In fact, a critical spawning depth must exist where spawning below this depth threshold results in eggs sinking out of the water column and become lost for recruitment to the population. An example of adaptation to such conditions is Cape hake spawning above the critical layer in the Northern Benguela upwelling ecosystem. The eggs rise slowly in the onshore subsurface current below the Ekman layer, hence being advected inshore where the hatched larvae concentrate with optimal feeding conditions. PMID:26465149

Research on Captive Broodstock Programs for Pacific Salmon; Assessment of Captive Broodstock Technologies, Annual Report 2002-2003.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berejikian, Barry

The success of captive broodstock programs depends on high in-culture survival, appropriate development of the reproductive system, and the behavior and survival of cultured salmon after release, either as adults or juveniles. Continuing captive broodstock research designed to improve technology is being conducted to cover all major life history stages of Pacific salmon. Current velocity in rearing vessels had little if any effect on reproductive behavior of captively reared steelhead. However, males and females reared in high velocity vessels participated a greater number of spawning events than siblings reared in low velocity tanks. Observations of nesting females and associated malesmore » in a natural stream (Hamma Hamma River) were consistent with those observed in a controlled spawning channel. DNA pedigree analyses did not reveal significant differences in the numbers of fry produced by steelhead reared in high and low velocity vessels. To determine the critical period(s) for imprinting for sockeye salmon, juvenile salmon are being exposed to known odorants at key developmental stages. Subsequently they will be tested for development of long-term memories of these odorants. In 2002-2003, the efficacy of EOG analysis for assessing imprinting was demonstrated and will be applied in these and other behavioral and molecular tools in the current work plan. Results of these experiments will be important to determine the critical periods for imprinting for the offspring of captively-reared fish destined for release into natal rivers or lakes. By early August, the oocytes of all of Rapid River Hatchery chinook salmon females returning from the ocean had advanced to the tertiary yolk globule stage; whereas, only some of the captively reared Lemhi River females sampled had advanced to this stage, and the degree of advancement was not dependent on rearing temperature. The mean spawning time of captive Lemhi River females was 3-4 weeks after that of the Rapid River fish. Captive Lemhi River females produced smaller and fewer eggs than the Rapid River females; however, relative fecundity was higher than that of the Rapid River fish. Female coho salmon that ceased or slowed oocyte development in the spring had lower body growth from the previous August onward compared with females that continued oocyte growth. This indicates that growth during the late summer and fall, one year prior to spawning, can determine the decision to mature the following spring. Therefore it is important to maintain the growth of broodstock during the summer/fall period to ensure the continuation of ovary development in the subsequent spring. A combined whole cell vaccine of Renogen with killed R. salmoninarum strain MT239 may be effective in reducing the occurrence of BKD during the period immediately after seawater transfer, but not in yearling seawater-adapted chinook salmon. Control of BKD is likely to require an integrated disease management plan, utilizing three components, namely broodstock segregation, antibiotics, and vaccination. Vaccine results incorporated with antibiotic treatment will be used to work toward an integrated disease management plan to help to reduce the cycle of BKD transmission in the captive stocks to increase survival safely. Patterns of estimated survival in one chinook salmon stock (Grovers Creek) were generally consistent with inbreeding depression: progeny of fish that were full siblings (approximate increment in F of 0.25) survived to return at much lower rates than did progeny of fish that were half siblings (F {approx} 0.125) or unrelated individuals (F {approx} 0). Growth at sea of Grovers Creek Hatchery stock study fish was lower than that of UWH stock fish. Among the inbreeding groups alone, no clear differences in growth were detectable. However, preliminary results suggest the general pattern of growth was opposite that expected if inbreeding depression reduced growth: the highest growth was in progeny of related parents.« less

Research on Captive Broodstock Programs for Pacific Salmon, 2002-2003 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berejikian, Barry A.

The success of captive broodstock programs depends on high in-culture survival, appropriate development of the reproductive system, and the behavior and survival of cultured salmon after release, either as adults or juveniles. Continuing captive broodstock research designed to improve technology is being conducted to cover all major life history stages of Pacific salmon. Current velocity in rearing vessels had little if any effect on reproductive behavior of captively reared steelhead. However, males and females reared in high velocity vessels participated a greater number of spawning events than siblings reared in low velocity tanks. Observations of nesting females and associated malesmore » in a natural stream (Hamma Hamma River) were consistent with those observed in a controlled spawning channel. DNA pedigree analyses did not reveal significant differences in the numbers of fry produced by steelhead reared in high and low velocity vessels. To determine the critical period(s) for imprinting for sockeye salmon, juvenile salmon are being exposed to known odorants at key developmental stages. Subsequently they will be tested for development of long-term memories of these odorants. In 2002-2003, the efficacy of EOG analysis for assessing imprinting was demonstrated and will be applied in these and other behavioral and molecular tools in the current work plan. Results of these experiments will be important to determine the critical periods for imprinting for the offspring of captively-reared fish destined for release into natal rivers or lakes. By early August, the oocytes of all of Rapid River Hatchery chinook salmon females returning from the ocean had advanced to the tertiary yolk globule stage; whereas, only some of the captively reared Lemhi River females sampled had advanced to this stage, and the degree of advancement was not dependent on rearing temperature. The mean spawning time of captive Lemhi River females was 3-4 weeks after that of the Rapid River fish. Captive Lemhi River females produced smaller and fewer eggs than the Rapid River females; however, relative fecundity was higher than that of the Rapid River fish. Female coho salmon that ceased or slowed oocyte development in the spring had lower body growth from the previous August onward compared with females that continued oocyte growth. This indicates that growth during the late summer and fall, one year prior to spawning, can determine the decision to mature the following spring. Therefore it is important to maintain the growth of broodstock during the summer/fall period to ensure the continuation of ovary development in the subsequent spring. A combined whole cell vaccine of Renogen with killed R. salmoninarum strain MT239 may be effective in reducing the occurrence of BKD during the period immediately after seawater transfer, but not in yearling seawater-adapted chinook salmon. Control of BKD is likely to require an integrated disease management plan, utilizing three components, namely broodstock segregation, antibiotics, and vaccination. Vaccine results incorporated with antibiotic treatment will be used to work toward an integrated disease management plan to help to reduce the cycle of BKD transmission in the captive stocks to increase survival safely. Patterns of estimated survival in one chinook salmon stock (Grovers Creek)were generally consistent with inbreeding depression: progeny of fish that were full siblings (approximate increment in F of 0.25) survived to return at much lower rates than did progeny of fish that were half siblings (F {approx} 0.125) or unrelated individuals (F {approx} 0). Growth at sea of Grovers Creek Hatchery stock study fish was lower than that of UWH stock fish. Among the inbreeding groups alone, no clear differences in growth were detectable. However, preliminary results suggest the general pattern of growth was opposite that expected if inbreeding depression reduced growth: the highest growth was in progeny of related parents.« less

Steelhead Supplementation in Idaho Rivers : 2001 Project Progress Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Byrne, Alan

In 2001, Idaho Department of Fish and Game (IDFG) continued an assessment of the Sawtooth Hatchery steelhead Oncorhynchus mykiss stock to reestablish natural populations in Beaver and Frenchman creeks in the upper Salmon River. Crews stocked both streams with 20 pair of hatchery adults, and I estimated the potential smolt production from the 2000 adult outplants. n the Red River drainage, IDFG stocked Dworshak hatchery stock fingerlings and smolts from 1993 to 1999 to assess which life stage produces more progeny when the adults return to spawn. In 2001, IDFG operated the Red River weir to trap adults that returnedmore » from these stockings, but none were caught from either group. Wild steelhead populations in the Lochsa and Selway river drainages were assessed and the chinook salmon Oncorhynchus tshawytscha escapement was enumerated in Fish Creek. I estimated that 75 wild adult steelhead and 122 adult chinook salmon returned to Fish Creek in 2001. I estimated that slightly more than 30,000 juvenile steelhead migrated out of Fish Creek. This is the largest number of steelhead to migrate out of Fish Creek in a single year since I began estimating the yearly migration in 1994. Juvenile steelhead densities in Lochsa and Selway tributaries were somewhat higher in 2001 than those observed in 2000. Crews from IDFG collected over 4,800 fin samples from wild steelhead in 74 streams of the Clearwater, Snake, and Salmon river drainages and from five hatchery stocks during the summer of 2000 for a DNA analysis to assess Idaho's steelhead stock structure. The DNA analysis was subcontracted to Dr. Jennifer Nielsen, Alaska Biological Science Center, Anchorage. Her lab developed protocols to use for the analysis in 2001 and is continuing to analyze the samples. Dr. Nielsen plans to have the complete set of wild and hatchery stocks analyzed in 2002.« less

Movement of reservoir-stocked riverine fish between tailwaters and rivers

USGS Publications Warehouse

Spoelstra, J.A.; Stein, R.A.; Royle, J. Andrew; Marschall, E.A.

2008-01-01

The movement of fish from onstream impoundments into connected streams and rivers has traditionally been overlooked in fish stocking decisions but is critical to the ultimate impact of stocking riverine species into reservoirs. Hybrid saugeyes (female walleye Sander vitreus x male sauger S. canadensis) stocked into Deer Creek Reservoir, Ohio, readily move from the reservoir to the tailwater below. Downstream movement of these saugeyes from the tailwater may have consequences for native prey species and parental stocks downstream. We used fixed-station radiotelemetry to quantify the temporal movement patterns of 203 reservoir-stocked saugeyes from the tailwater of the reservoir, the stream flowing from the tailwater, and the river into which the stream flowed. From October 1998 through July 2000, most (75%) saugeyes never left the tailwater, and those that left returned 75% of the time. Overall, saugeyes spent 90% of their time in the tailwater, 7-8% of their time downstream in small streams, and 2-3% of their time farther downstream in the Scioto River (45 km downstream). No radio-tagged saugeyes moved to the Ohio River (155 km downstream). The probability of downstream movement generally increased with increasing flow and when dissolved oxygen dropped to lethal levels in summer. The probability of movement was highest in winter and spring, when it was probably related to spawning, and low in summer (except when dissolved oxygen was low) and fall. The patterns of movement seemed to reflect the relative suitability of tailwater over stream habitat. The predominant use of and return to tailwater habitat after downstream movement limited overall stream and river residence time. Although the daily movement probability for an individual was low, when we apply these rates to all of the stocked saugeyes in the Ohio River drainage, we cannot safely conclude that only small numbers move from reservoir tailwaters to downstream river systems. We recommend that managers refrain from stocking systems for which there are concerns about native species in connected drainages.

Status and trends of adult Lost River (Deltistes luxatus) and shortnose (Chasmistes brevirostris) sucker populations in Upper Klamath Lake, Oregon, 2014

USGS Publications Warehouse

Hewitt, David A.; Janney, Eric C.; Hayes, Brian S.; Harris, Alta C.

2015-10-02

Despite relatively high survival in most years, we conclude that both species have experienced substantial decreases in the abundance of spawning adults because losses from mortality have not been balanced by recruitment of new individuals. Although capture-recapture data indicate substantial recruitment of new individuals into the spawning populations for SNS and river spawning LRS in some years, size data do not corroborate these estimates. As a result, the status of the endangered sucker populations in Upper Klamath Lake remains worrisome, especially for shortnose suckers. Our monitoring program provides a robust platform for estimating vital population parameters, evaluating the status of the populations, and assessing the effectiveness of conservation and recovery efforts.

Atlantic Bluefin Tuna (Thunnus thynnus) Biometrics and Condition.

PubMed

Rodriguez-Marin, Enrique; Ortiz, Mauricio; Ortiz de Urbina, José María; Quelle, Pablo; Walter, John; Abid, Noureddine; Addis, Piero; Alot, Enrique; Andrushchenko, Irene; Deguara, Simeon; Di Natale, Antonio; Gatt, Mark; Golet, Walter; Karakulak, Saadet; Kimoto, Ai; Macias, David; Saber, Samar; Santos, Miguel Neves; Zarrad, Rafik

2015-01-01

The compiled data for this study represents the first Atlantic and Mediterranean-wide effort to pool all available biometric data for Atlantic bluefin tuna (Thunnus thynnus) with the collaboration of many countries and scientific groups. Biometric relationships were based on an extensive sampling (over 140,000 fish sampled), covering most of the fishing areas for this species in the North Atlantic Ocean and Mediterranean Sea. Sensitivity analyses were carried out to evaluate the representativeness of sampling and explore the most adequate procedure to fit the weight-length relationship (WLR). The selected model for the WLRs by stock included standardized data series (common measurement types) weighted by the inverse variability. There was little difference between annual stock-specific round weight-straight fork length relationships, with an overall difference of 6% in weight. The predicted weight by month was estimated as an additional component in the exponent of the weight-length function. The analyses of monthly variations of fish condition by stock, maturity state and geographic area reflect annual cycles of spawning and feeding behavior. We update and improve upon the biometric relationships for bluefin currently used by the International Commission for the Conservation of Atlantic Tunas, by incorporating substantially larger datasets than ever previously compiled, providing complete documentation of sources and employing robust statistical fitting. WLRs and other conversion factors estimated in this study differ from the ones used in previous bluefin stock assessments.

Kootenai River Fisheries Investigations; Stock Status of Burbot, 1999-2000 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paragamian, Vaughn L.; Kozfkay, Joseph R.; Whitman, Vint

2001-10-01

In Idaho, the burbot Lota lota are native only to the Kootenai River and are genetically distinct from burbot in the Montana reach of the river. Burbot once provided a substantial fishery with tens of thousands of burbot harvested annually. Burbot now number fewer than 1000 in the Kootenai River and Kootenay Lake and may be nearing demographic extinction. Studies completed in the winter of 1997-1998 indicated flow management at Libby Dam likely affected burbot spawning migration during winter. The objective of our study was to monitor the movement of burbot during a period of normal winter operation and amore » low flow period to test the null hypothesis (H{sub o}) that winter operation of Libby Dam does not affect burbot migration distance or travel rate. In addition, we monitored the stock status of burbot. We captured 36 burbot in Idaho and British Columbia with baited hoop nets. Twenty-three burbot were caught in Idaho, including 12 at Ambush Rock. The remaining 13 burbot were caught in British Columbia, including eight in the Kootenai River and five in the Goat River. One burbot escaped and was not measured, and one recaptured burbot was not measured. Burbot ranged from 332 mm to 705 mm total length (TL) (mean = 541 mm, SE = 14.02) and weighed from 350 g to 2,850 g (mean = 1,059 g, SE = 90.51). Relative weight (W{sub r}) ranged from 40.5 to 127.6 and averaged 88.6 (SE = 2.44). Population estimates for 1996, 1997, and 1998 were made for the Kootenai River from Bonners Ferry to Kootenay Lake; they were 738, 540, and 43 fish respectively. These estimates were not considered valid because we had so few recaptures, and confidence intervals could not be provided. Four burbot were implanted with sonic transmitters and their movement was monitored. We requested a low flow test (170 m{sup 3}/s) period of five weeks from the US Army Corps of Engineers (USACE) to study burbot migration distance or travel rate. The USACE could not provide an adequate low flow test period. Mitochondrial DNA (MtDNA) analysis indicated Duncan Lake, British Columbia burbot are genetically similar to Kootenai River fish and are a potential donor stock. The capture of eight post-spawn burbot and the subsequent examination of milt and gonadal tissue indicated they were in at least four different stages of reproductive readiness. These findings further support the hypothesis that high fluctuating flows from Libby Dam, which have continuously disrupted burbot migrations, may also be responsible for the failure of some burbot to spawn.« less

Prey resources before spawning influence gonadal investment of female, but not male, white crappie

USGS Publications Warehouse

Bunnell, D.B.; Thomas, S.E.; Stein, R.A.

2007-01-01

In this study, an outdoor pool experiment was used to evaluate the effect of prey resources during 4 months before spawning on the gonadal investments of male and female white crappie Pomoxis annularis, a popular freshwater sportfish that exhibits erratic recruitment. Fish were assigned one of three feeding treatments: starved, fed once every 5 days (intermediate) or fed daily (high). All measurements of male testes (i.e. wet mass, energy density and spermatocrit) were similar across treatments. Conversely, high-fed females produced larger ovaries than those of intermediate-fed and starved fish, and invested more energy in their ovaries than starved fish. Compared to pre-experiment fish, starved and intermediate-fed females appeared to increase their ovary size by relying on liver energy stores (‘capital’ spawning). Conversely, high-fed females increased liver and gonad mass, implying an ‘income’-spawning strategy (where gonads are built from recently acquired energy). Fecundity did not differ among treatments, but high-fed fish built larger eggs than those starved. Females rarely ‘skipped’ spawning opportunities when prey resources were low, as only 8% of starved females and 8% of intermediate-fed females lacked vitellogenic eggs. These results suggest that limited prey resources during the months before spawning can limit ovary production, which, in turn, can limit reproductive success of white crappies.

Microphytoplankton variations during coral spawning at Los Roques, Southern Caribbean

PubMed Central

Zubillaga, Ainhoa L.; Bastidas, Carolina

2016-01-01

Phytoplankton drives primary productivity in marine pelagic systems. This is also true for the oligotrophic waters in coral reefs, where natural and anthropogenic sources of nutrients can alter pelagic trophic webs. In this study, microphytoplankton assemblages were characterized for the first time in relation to expected coral spawning dates in the Caribbean. A hierarchical experimental design was used to examine these assemblages in Los Roques archipelago, Venezuela, at various temporal and spatial scales for spawning events in both 2007 and 2008. At four reefs, superficial water samples were taken daily for 9 days after the full moon of August, including days before, during and after the expected days of coral spawning. Microphytoplankton assemblages comprised 100 microalgae taxa at up to 50 cells per mL (mean ± 8 SD) and showed temporal and spatial variations related to the coral spawning only in 2007. However, chlorophyll a concentrations increased during and after the spawning events in both years, and this was better matched with analyses of higher taxonomical groups (diatoms, cyanophytes and dinoflagellates), that also varied in relation to spawning times in 2007 and 2008, but asynchronously among reefs. Heterotrophic and mixotrophic dinoflagellates increased in abundance, correlating with a decrease of the diatom Cerataulina pelagica and an increase of the diatom Rhizosolenia imbricata. These variations occurred during and after the coral spawning event for some reefs in 2007. For the first time, a fresh-water cyanobacteria species of Anabaena was ephemerally found (only 3 days) in the archipelago, at reefs closest to human settlements. Variability among reefs in relation to spawning times indicated that reef-specific processes such as water residence time, re-mineralization rates, and benthic-pelagic coupling can be relevant to the observed patterns. These results suggest an important role of microheterotrophic grazers in re-mineralization of organic matter in coral reef waters and highlight the importance of assessing compositional changes of larger size fractions of the phytoplankton when evaluating primary productivity and nutrient fluxes. PMID:27019774

Froude Number is the Single Most Important Hydraulic Parameter for Salmonid Spawning Habitat.

NASA Astrophysics Data System (ADS)

Gillies, E.; Moir, H. J.

2015-12-01

Many gravel-bed rivers exhibit historic straightening or embanking, reducing river complexity and the available habitat for key species such as salmon. A defensible method for predicting salmonid spawning habitat is an important tool for anyone engaged in assessing a river restoration. Most empirical methods to predict spawning habitat use lookup tables of depth, velocity and substrate. However, natural site selection is different: salmon must pick a location where they can successfully build a redd, and where eggs have a sufficient survival rate. Also, using dimensional variables, such as depth and velocity, is problematic: spawning occurs in rivers of differing size, depth and velocity range. Non-dimensional variables have proven useful in other branches of fluid dynamics, and instream habitat is no different. Empirical river data has a high correlation between observed salmon redds and Froude number, without insight into why. Here we present a physics based model of spawning and bedform evolution, which shows that Froude number is indeed a rational choice for characterizing the bedform, substrate, and flow necessary for spawning. It is familiar for Froude to characterize surface waves, but Froude also characterizes longitudinal bedform in a mobile bed river. We postulate that these bedforms and their hydraulics perform two roles in salmonid spawning: allowing transport of clasts during redd building, and oxygenating eggs. We present an example of this Froude number and substrate based habitat characterization on a Scottish river for which we have detailed topography at several stages during river restoration and subsequent evolution of natural processes. We show changes to the channel Froude regime as a result of natural process and validate habitat predictions against redds observed during 2014 and 2015 spawning seasons, also relating this data to the Froude regime in other, nearby, rivers. We discuss the use of the Froude spectrum in providing an indicator of salmonid spawning and the success of river restoration.

Using an experimental manipulation to determine the effectiveness of a stock enhancement program

USGS Publications Warehouse

Stewart, David R.; Long, James M.

2015-01-01

We used an experimental manipulation to determine the impact of stocking 178 mm channel catfish Ictalurus punctatus in six impoundments. The study design consisted of equal numbers (two) of control, ceased-stock, and stocked treatments that were sampled one year before and two years after stocking. Relative abundance, growth, size structure, and average weight significantly changed over time based on samples collected with hoop nets. Catch rates decreased at both ceased-stock lakes and increased for one stocked lake, while growth rates changed for at least one ceased-stock and stocked lake. The average weight of channel catfish in the ceased-stock treatment increased by 6% and 25%, whereas weight decreased by 28% and 78% in both stocked lakes. The variability in observed responses between lakes in both ceased-stock and stocked treatments indicates that a one-size-fits-all stocking agenda is impractical, suggesting lake specific and density-dependent mechanisms affect channel catfish population dynamics.

Evaluation of three harvest control rules for Bigeye Tuna ( Thunnus obesus) fisheries in the Indian Ocean

NASA Astrophysics Data System (ADS)

Tong, Yuhe; Chen, Xinjun; Kolody, Dale

2014-10-01

The stock of Bigeye tuna ( Thunnus obesus) in the Indian Ocean supports an important international fishery and is considered to be fully exploited. The responsible management agency, the Indian Ocean Tuna Commission (IOTC), does not have an explicit management decision-making framework in place to prevent over-fishing. In this study, we evaluated three harvest control rules, i) constant fishing mortality (CF), from 0.2 to 0.6, ii) constant catch (CC), from 60000 to 140000 t, and iii) constant escapement (CE), from 0.3 to 0.7. The population dynamics simulated by the operating model was based on the most recent stock assessment using Stock Synthesis version III (SS3). Three simulation scenarios (low, medium and high productivity) were designed to cover possible uncertainty in the stock assessment and biological parameters. Performances of three harvest control rules were compared on the basis of three management objectives (over 3, 10 and 25 years): i) the probability of maintaining spawning stock biomass above a level that can sustain maximum sustainable yield (MSY) on average, ii) the probability of achieving average catches between 0.8 MSY and 1.0 MSY, and iii) inter-annual variability in catches. The constant escapement strategy ( CE=0.5), constant fishing mortality strategy ( F=0.4) and constant catch ( CC=80000) were the most rational among the respective management scenarios. It is concluded that the short-term annual catch is suggested at 80000 t, and the potential total allowable catch for a stable yield could be set at 120000 t once the stock had recovered successfully. All the strategies considered in this study to achieve a `tolerable' balance between resource conservation and utilization have been based around the management objectives of the IOTC.

Why are reproductively parasitic fish males so small?—influence of tactic-specific selection

NASA Astrophysics Data System (ADS)

Ota, Kazutaka; Kohda, Masanori; Sato, Tetsu

2010-12-01

Despite the wide prevalence of alternative reproductive tactics, little attention has been paid to why reproductively parasitic males are so small. In this study, we tackled this issue in a shell-brooding fish Lamprologus callipterus. Sneaky `dwarf males' of this fish remain much smaller than bourgeois conspecifics throughout their life and employ a unique parasitic tactic, i.e. entering into a gastropod shell where a female is spawning, passing through the space between the female and shell wall and staying behind her to ejaculate throughout the spawning event. Here, we tested the prediction that they remain small to get past her through the shell spaces by interpopulation comparison. We showed, across populations, a negative allometry for sexual size dimorphism, an exponential increase of female size with an increase in shell size and a negative correlation between the magnitude of sexual size dimorphism and shell size. These results suggest that the inner spaces strongly regulate dwarf male size. We conclude that the small bodies of dwarf males arise from adaptation to their unique reproductive behaviour.

California salmon and steelhead: Beyond the crossroads

USGS Publications Warehouse

Mills, Terry J.; McEwan, Dennis R.; Jennings, Mark R.; Stouder, Deanna J.; Bisson, Peter A.; Naiman, Robert J.

1997-01-01

Virtually all California salmon (Oncorhynchus spp.) and steelhead (O. mykiss) stocks have declined to record or near-record low levels during 1980-95. Escapement of naturally spawning Klamath and Sacramento basin fall-run chinook salmon (O. tshawytscha) stocks has fallen consistently below the goals of 35,000 adults (Klamath) and 120,000 adults (Sacramento) established by the Pacific Fishery Management Council. These two stocks constitute the primary management units for ocean harvest regulations in California and southern Oregon. This decline triggered a mandatory review of ocean harvest and inland production conditions in each basin. The Sacramento winter-run chinook salmon, once numbering >100,000 adult spawners, was listed as threatened in 1990 and endangered in 1994 under the Endangered Species Act. The listing occurred as a result of a precipitous decline in abundance (to <200 adult spawners) and significant threats to this stock’s continued existence.Spring-run chinook salmon, historically an abundant component of California’s inland fish fauna with >500,000 adult spawners, has been extirpated from the San Joaquin River basin. However, remnant populations of this naturally spawning stock remain within the Klamath, Smith, and Sacramento river basins. Unfortunately, annual counts of 3,000-25,000 spawners in the Sacramento River basin during the past 25 years are largely of hatchery origin. Recent steelhead data from the same region indicate that many stocks are close to extinction, and nearly all steel-head in the Sacramento River are also of hatchery origin. Both spring-run chinook salmon and summer steelhead are considered to be species of special concern by the California Department of Fish and Game because of their limited distributions and sensitivities to degraded habitat conditions. The southern race of winter steelhead south of Point Conception is nearly extinct and remnant populations have been recently recorded in only 9 streams.Coastal cutthroat trout (O. clarki), which are restricted to lowland drainages from the Eel River northward, are greatly depleted. Coho salmon (O. kisutch),which once probably numbered close to 1,000,000 fish per year in coastal California streams, have dwindled to —5,000 natural spawners per year. Chum salmon (O. keta), never a significant part of the state’s native fish fauna, are currently restricted to <10 spawners in three different streams in the Sacramento River basin and occasionally in the South Fork of the Trinity River. The historically small runs of pink salmon (O. gorbuscha) in the Sacramento and Russian rivers are probably now extirpated. Anadromous sockeye salmon (O. nerka) are only recorded as strays.In response to serious declines in salmon and steelhead stocks, numerous legislative and congressional actions have been undertaken and California has embarked on an ambitious planto restore riparian habitats, improve fish passage, and increase natural production. Additionally, many currently unlisted California salmon and steelhead stocks are potential candidates for protection under the Endangered Species Act. These include coho, chum, spring-run chinook, and San Joaquin fall-run chinook salmon, as well as summer steelhead and the southern race of winter steelhead.

A rehabilitation plan for walleye populations and habitats in Lake Superior

USGS Publications Warehouse

Hoff, Michael H.

2003-01-01

The walleye (Stizostedion vitreum vitreum) has been historically important in regional fisheries and fish communities in large bays, estuaries, and rivers of Lake Superior. Significant negative impacts on the species caused by overharvesting, habitat degradation, and pollution during the late 1800s and early 1900s have led to the preparation of a strategic rehabilitation plan. The lakewide goal is to maintain, enhance, and rehabilitate habitat for walleye and to establish self-sustaining populations in areas where walleyes historically lived. Population objectives that support the goal are to increase the abundance of juvenile and adult walleyes in selected areas. Habitat objectives that support the goal include increasing spawning and nursery habitat in four areas: enhancing fish passage, reducing sedimentation, increasing water quality, and reducing contaminants in walleyes. Progress toward achieving the habitat objectives should be measured by documenting increases in spawning and nursery habitats, resolving fish-passage issues, reducing sediments in rivers, and reducing contaminant levels in walleyes. Stocking various life stages of walleye should be considered to rehabilitate certain degraded populations. Total annual mortality of walleye populations should be less than 45% to allow populations to either increase or be maintained at target levels of abundance. Routine assessments should focus on gathering the data necessary to evaluate abundance and mortality and on taking inventories of spawning and nursery habitats. Research should be conducted to understand the specific habitat requirements for Lake Superior walleye populations and the habitat-abundance relationships for populations and for the lake as a whole.

Demographics and run timing of adult Lost River (Deltistes luxatus) and short nose (Chasmistes brevirostris) suckers in Upper Klamath Lake, Oregon, 2012

USGS Publications Warehouse

Hewitt, David A.; Janney, Eric C.; Hayes, Brian S.; Harris, Alta C.

2014-01-01

Data from a long-term capture-recapture program were used to assess the status and dynamics of populations of two long-lived, federally endangered catostomids in Upper Klamath Lake, Oregon. Lost River suckers (Deltistes luxatus) and shortnose suckers (Chasmistes brevirostris) have been captured and tagged with passive integrated transponder (PIT) tags during their spawning migrations in each year since 1995. In addition, beginning in 2005, individuals that had been previously PIT-tagged were re-encountered on remote underwater antennas deployed throughout sucker spawning areas. Captures and remote encounters during spring 2012 were used to describe the spawning migrations in that year and also were incorporated into capture-recapture analyses of population dynamics. Cormack-Jolly-Seber (CJS) open population capture-recapture models were used to estimate annual survival probabilities, and a reverse-time analog of the CJS model was used to estimate recruitment of new individuals into the spawning populations. In addition, data on the size composition of captured fish were examined to provide corroborating evidence of recruitment. Model estimates of survival and recruitment were used to derive estimates of changes in population size over time and to determine the status of the populations in 2011. Separate analyses were conducted for each species and also for each subpopulation of Lost River suckers (LRS). Shortnose suckers (SNS) and one subpopulation of LRS migrate into tributary rivers to spawn, whereas the other LRS subpopulation spawns at groundwater upwelling areas along the eastern shoreline of the lake. In 2012, we captured, tagged, and released 749 LRS at four lakeshore spawning areas and recaptured an additional 969 individuals that had been tagged in previous years. Across all four areas, the remote antennas detected 6,578 individual LRS during the spawning season. Spawning activity peaked in April and most individuals were encountered at Cinder Flats and Sucker Springs. In the Williamson River, we captured, tagged, and released 3,376 LRS and 299 SNS, and recaptured 551 LRS and 125 SNS that had been tagged in previous years. Remote PIT tag antennas in the traps at the weir on the Williamson River and remote antenna systems that spanned the river at four different locations on the Williamson and Sprague Rivers detected a total of 19,321 LRS and 6,124 SNS. Most LRS passed upstream between late April and mid-May when water temperatures were increasing and greater than 10 °C. In contrast, most upstream passage for SNS occurred in early and mid-May when water temperatures were increasing and near or greater than 12 °C. Finally, an additional 1,188 LRS and 1,665 SNS were captured in trammel net sampling at pre-spawn staging areas in the northeastern part of the lake. Of these, 291 of the LRS and 653 of the SNS had been PIT-tagged in previous years. For LRS captured at the staging areas that had encounter histories that were informative about their spawning location, over 90 percent of the fish were members of the subpopulation that spawns in the rivers. Capture-recapture analyses for the LRS subpopulation that spawns at the shoreline areas included encounter histories for more than 12,150 individuals, and analyses for the subpopulation that spawns in the rivers included more than 29,500 encounter histories. With a few exceptions, the survival of males and females in both subpopulations was high (greater than 0.9) between 1999 and 2010. Notably lower survival occurred for both sexes from the rivers in 2000, for both sexes from the shoreline areas in 2002, and for males from the rivers in 2006. Between 2001 and 2011, the abundance of males in the lakeshore spawning subpopulation decreased by 53–65 percent and the abundance of females decreased by 36–48 percent. Capture-recapture models suggested that the abundance of both sexes in the river spawning subpopulation of LRS had increased substantially since 2006; increases were due to large estimated recruitment events in 2006 and 2008. We know that the estimates in 2006 are substantially biased in favor of recruitment because of a sampling issue. We are skeptical of the magnitude of recruitment indicated by the 2008 estimates as well because (1) few small individuals that would indicate the presence of new recruits were captured in that year, and (2) recapture probabilities in recruitment models based on just physical recaptures were lower than desired for robust inferences from capture-recapture models. If we assume that little or no recruitment occurred in 2006 or 2008, the abundance of both sexes in the river spawning subpopulation likely has decreased at rates similar to the rates for the lakeshore spawning subpopulation between 2002 and 2011. Capture-recapture analyses for SNS included encounter histories for more than 17,700 individuals. Most annual survival estimates between 2001 and 2010 were high (greater than 0.8), but SNS experienced more years of low survival than either LRS subpopulation. Annual survival of both sexes was particularly low in 2001, 2004, and 2010. In addition, male survival was somewhat low in 2002. Capture-recapture models and size composition data indicate that recruitment of new individuals into the SNS spawning population was trivial between 2001 and 2005. Models indicate substantial recruitment of new individuals into the SNS spawning population in 2006, 2008, and 2009. As a result, capture-recapture modeling suggests that the abundance of adult spawning SNS was relatively stable between 2006 and 2010. We are skeptical of the estimated recruitment in 2006, 2008, and 2009 because few small individuals that would indicate the presence of new recruits were captured in any of those years, and recapture probabilities in recruitment models were low. The best-case scenario for SNS, based on capture-recapture recruitment modeling, indicates that the abundance of males in the spawning population decreased by 71 percent and the abundance of females decreased by 69 percent between 2001 and 2011. The worst-case scenario, which assumes no recruitment and seems more likely, suggests an 86 percent decrease for males and an 81 percent decrease for females. Despite relatively high survival in most years, we conclude that both species have experienced substantial declines in the abundance of spawning fish because losses from mortality have not been balanced by recruitment of new individuals. Although capture-recapture data indicate substantial recruitment of new individuals into the adult spawning populations for SNS and river spawning LRS in some years, size data do not corroborate these estimates. In fact, fork length data indicate that all populations are largely comprised of fish that were present in the late 1990s and early 2000s. As a result, the status of the endangered sucker populations in Upper Klamath Lake remains worrisome, and the situation is especially dire for shortnose suckers. Future investigations should explore the connections between sucker recruitment and survival and various environmental factors, such as water quality and disease. Our monitoring program provides a robust platform for estimating vital population parameters, evaluating the status of the populations, and assessing the effectiveness of conservation and recovery efforts.

Roles of density-dependent growth and life history evolution in accounting for fisheries-induced trait changes

PubMed Central

Eikeset, Anne Maria; Dunlop, Erin S.; Heino, Mikko; Storvik, Geir; Stenseth, Nils C.; Dieckmann, Ulf

2016-01-01

The relative roles of density dependence and life history evolution in contributing to rapid fisheries-induced trait changes remain debated. In the 1930s, northeast Arctic cod (Gadus morhua), currently the world’s largest cod stock, experienced a shift from a traditional spawning-ground fishery to an industrial trawl fishery with elevated exploitation in the stock’s feeding grounds. Since then, age and length at maturation have declined dramatically, a trend paralleled in other exploited stocks worldwide. These trends can be explained by demographic truncation of the population’s age structure, phenotypic plasticity in maturation arising through density-dependent growth, fisheries-induced evolution favoring faster-growing or earlier-maturing fish, or a combination of these processes. Here, we use a multitrait eco-evolutionary model to assess the capacity of these processes to reproduce 74 y of historical data on age and length at maturation in northeast Arctic cod, while mimicking the stock’s historical harvesting regime. Our results show that model predictions critically depend on the assumed density dependence of growth: when this is weak, life history evolution might be necessary to prevent stock collapse, whereas when a stronger density dependence estimated from recent data is used, the role of evolution in explaining fisheries-induced trait changes is diminished. Our integrative analysis of density-dependent growth, multitrait evolution, and stock-specific time series data underscores the importance of jointly considering evolutionary and ecological processes, enabling a more comprehensive perspective on empirically observed stock dynamics than previous studies could provide. PMID:27940913

Escapement and Productivity of Spring Chinook Salmon and Summer Steelhead in the John Day River Basin, 2005-2006 Annual Technical Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schultz, Terra Lang; Wilson, Wayne H.; Ruzycki, James R.

The objectives are: (1) Estimate number and distribution of spring Chinook salmon Oncorhynchus tshawytscha redds and spawners in the John Day River subbasin; and (2) Estimate smolt-to-adult survival rates (SAR) and out-migrant abundance for spring Chinook and summer steelhead O. mykiss and life history characteristics of summer steelhead. The John Day River subbasin supports one of the last remaining intact wild populations of spring Chinook salmon and summer steelhead in the Columbia River Basin. These populations, however, remain depressed relative to historic levels. Between the completion of the life history and natural escapement study in 1984 and the start ofmore » this project in 1998, spring Chinook spawning surveys did not provide adequate information to assess age structure, progeny-to-parent production values, smolt-to-adult survival (SAR), or natural spawning escapement. Further, only very limited information is available for steelhead life history, escapement, and productivity measures in the John Day subbasin. Numerous habitat protection and rehabilitation projects to improve salmonid freshwater production and survival have also been implemented in the basin and are in need of effectiveness monitoring. While our monitoring efforts outlined here will not specifically measure the effectiveness of any particular project, they will provide much needed background information for developing context for project-specific effectiveness monitoring efforts. To meet the data needs as index stocks, to assess the long-term effectiveness of habitat projects, and to differentiate freshwater and ocean survival, sufficient annual estimates of spawner escapement, age structure, SAR, egg-to-smolt survival, smolt-per-redd ratio, and freshwater habitat use are essential. We have begun to meet this need through spawning ground surveys initiated for spring Chinook salmon in 1998 and smolt PIT-tagging efforts initiated in 1999. Additional sampling and analyses to meet these goals include an estimate of smolt abundance and SAR rates, and an updated measure of the freshwater distribution of critical life stages. Because Columbia Basin managers have identified the John Day subbasin spring Chinook population as an index population for assessing the effects of alternative future management actions on salmon stocks in the Columbia Basin (Schaller et al. 1999) we continue our ongoing studies. This project is high priority based on the high level of emphasis the NWPPC Fish and Wildlife Program, Subbasin Summaries, NMFS, and the Oregon Plan for Salmon and Watersheds have placed on monitoring and evaluation to provide the real-time data to guide restoration and adaptive management in the region. By implementing the proposed program we have been able to address many of the goals for population status monitoring, such as defining areas currently used by spring Chinook for holding and spawning habitats and determining range expansion or contraction of summer rearing and spawning populations. The BiOp describes these goals as defining population growth rates (adult monitoring), detecting changes in those growth rates or relative abundance in a reasonable time (adult/juvenile monitoring), estimating juvenile abundance and survival rates (juvenile/smolt monitoring), and identifying stage-specific survival (adult-to-smolt, smolt-to-adult).« less

Research, monitoring, and evaluation of emerging issues and measures to recover the Snake River fall Chinook salmon ESU, 1/1/2014 - 12/31/2014

USGS Publications Warehouse

Connor, William P.; Mullins, Frank L.; Tiffan, Kenneth F.; Perry, Russell W.; Erhardt, John M.; St John, Scott J.; Bickford, Brad; Rhodes, Tobyn N.

2015-01-01

The portion of the Snake River fall Chinook Salmon Oncorhynchus tshawytscha ESU that spawns upstream of Lower Granite Dam transitioned from low to high abundance during 1992–2014 in association with U.S. Endangered Species Act recovery efforts and other Federally mandated actions. This annual report focuses on (1) numeric and habitat use responses by natural- and hatchery-origin spawners, (2) phenotypic and numeric responses by natural-origin juveniles, and (3) predator responses in the Snake River upper and lower reaches as abundance of adult and juvenile fall Chinook Salmon increased. Spawners have located and used most of the available spawning habitat and that habitat is gradually approaching redd capacity. Timing of spawning and fry emergence has been relatively stable; whereas the timing of parr dispersal from riverine rearing habitat into Lower Granite Reservoir has become earlier as apparent abundance of juveniles has increased. Growth rate (g/d) and dispersal size of parr also declined as apparent abundance of juveniles increased. Passage timing of smolts from the two Snake River reaches has become earlier and downstream movement rate faster as estimated abundance of fall Chinook Salmon smolts in Lower Granite Reservoir has increased. In 2014, consumption of subyearlings by Smallmouth Bass was highest in the upper reach which had the highest abundance of Bass. With a few exceptions, predation tended to decrease seasonally from April through early July. A release of hatchery fish in mid-May significantly increased subyearling consumption by the following day. We estimated that over 600,000 subyearling fall Chinook Salmon were lost to Smallmouth Bass predation along the free-flowing Snake River in 2014. More information on predation is presented in Appendix A.3 (page 51). These findings coupled with stock-recruitment analyses presented in this report provide evidence for density-dependence in the Snake River reaches and in Lower Granite Reservoir that was influenced by the expansion of the recovery program. The long-term goal is to use the information covered here in a comprehensive modeling effort to conduct action effectiveness and uncertainty research and to inform fish population, hydrosystem, harvest, hatchery, and predation and invasive species management RM&E.

Research, monitoring, and evaluation of emerging issues and measures to recover the Snake River fall Chinook salmon ESU, 1/1/2012 – 12/31/2013: Annual report, 1991-029-00

USGS Publications Warehouse

Connor, William P.; Mullins, Frank; Tiffan, Kenneth F.; Perry, Russell W.; Erhardt, John M.; St. John, Scott J.; Bickford, Brad; Rhodes, Tobyn N.

2014-01-01

The portion of the Snake River fall Chinook Salmon Oncorhynchus tshawytscha ESU that spawns upstream of Lower Granite Dam transitioned from low to high abundance during 1992–2014 in association with U.S. Endangered Species Act recovery efforts and other Federally mandated actions. This annual report focuses on (1) numeric and habitat use responses by natural- and hatchery-origin spawners, (2) phenotypic and numeric responses by natural-origin juveniles, and (3) predator responses in the Snake River upper and lower reaches as abundance of adult and juvenile fall Chinook Salmon increased. Spawners have located and used most of the available spawning habitat and that habitat is gradually approaching redd capacity. Timing of spawning and fry emergence has been relatively stable; whereas the timing of parr dispersal from riverine rearing habitat into Lower Granite Reservoir has become earlier as apparent abundance of juveniles has increased. Growth rate (g/d) and dispersal size of parr also declined as apparent abundance of juveniles increased. Passage timing of smolts from the two Snake River reaches has become earlier and downstream movement rate faster as estimated abundance of fall Chinook Salmon smolts in Lower Granite Reservoir has increased. In 2014, consumption of subyearlings by Smallmouth Bass was highest in the upper reach which had the highest abundance of Bass. With a few exceptions, predation tended to decrease seasonally from April through early July. A release of hatchery fish in mid-May significantly increased subyearling consumption by the following day. We estimated that over 600,000 subyearling fall Chinook Salmon were lost to Smallmouth Bass predation along the free-flowing Snake River in 2014. More information on predation is presented in Appendix A.3 (page 51). These findings coupled with stock-recruitment analyses presented in this report provide evidence for density-dependence in the Snake River reaches and in Lower Granite Reservoir that was influenced by the expansion of the recovery program. The long-term goal is to use the information covered here in a comprehensive modeling effort to conduct action effectiveness and uncertainty research and to inform fish population, hydrosystem, harvest, hatchery, and predation and invasive species management RM&E.

Habitat dynamics, marine reserve status, and the decline and recovery of coral reef fish communities.

PubMed

Williamson, David H; Ceccarelli, Daniela M; Evans, Richard D; Jones, Geoffrey P; Russ, Garry R

2014-02-01

Severe climatic disturbance events often have major impacts on coral reef communities, generating cycles of decline and recovery, and in some extreme cases, community-level phase shifts from coral-to algal-dominated states. Benthic habitat changes directly affect reef fish communities, with low coral cover usually associated with low fish diversity and abundance. No-take marine reserves (NTRs) are widely advocated for conserving biodiversity and enhancing the sustainability of exploited fish populations. Numerous studies have documented positive ecological and socio-economic benefits of NTRs; however, the ability of NTRs to ameliorate the effects of acute disturbances on coral reefs has seldom been investigated. Here, we test these factors by tracking the dynamics of benthic and fish communities, including the important fishery species, coral trout (Plectropomus spp.), over 8 years in both NTRs and fished areas in the Keppel Island group, Great Barrier Reef, Australia. Two major disturbances impacted the reefs during the monitoring period, a coral bleaching event in 2006 and a freshwater flood plume in 2011. Both disturbances generated significant declines in coral cover and habitat complexity, with subsequent declines in fish abundance and diversity, and pronounced shifts in fish assemblage structure. Coral trout density also declined in response to the loss of live coral, however, the approximately 2:1 density ratio between NTRs and fished zones was maintained over time. The only post-disturbance refuges for coral trout spawning stocks were within the NTRs that escaped the worst effects of the disturbances. Although NTRs had little discernible effect on the temporal dynamics of benthic or fish communities, it was evident that the post-disturbance refuges for coral trout spawning stocks within some NTRs may be critically important to regional-scale population persistence and recovery.

A review of the factors influencing spawning, early life stage survival and recruitment variability in the common cuttlefish (Sepia officinalis).

PubMed

Bloor, Isobel S M; Attrill, Martin J; Jackson, Emma L

2013-01-01

Global landings of cephalopods (cuttlefish, squid and octopus) have increased dramatically over the past 50 years and now constitute almost 5% of the total world's fisheries production. At a time when landings of many traditional fin-fish stocks are continuing to experience a global decline as a result of over-exploitation, it is expected that fishing pressure on cephalopod stocks will continue to rise as the fishing industry switch their focus onto these non-quota species. However, long-term trends indicate that landings may have begun to plateau or even decrease. In European waters, cuttlefish are among the most important commercial cephalopod resource and are currently the highest yielding cephalopod group harvested in the north-east Atlantic, with the English Channel supporting the main fishery for this species. Recruitment variability in this short-lived species drives large fluctuations in landings. In order to provide sustainable management for Sepia officinalis populations, it is essential that we first have a thorough understanding of the ecology and life history of this species, in particular, the factors affecting spawning, early life stage (ELS) survival and recruitment variability. This review explores how and why such variability exists, starting with the impact of maternal effects (e.g. navigation, migration and egg laying), moving onto the direct impact of environmental variation on embryonic and ELSs and culminating on the impacts that these variations (maternal and environmental) have at a population level on annual recruitment success. Understanding these factors is critical to the effective management of expanding fisheries for this species. Copyright © 2013 Elsevier Ltd. All rights reserved.

Habitat dynamics, marine reserve status, and the decline and recovery of coral reef fish communities

PubMed Central

Williamson, David H; Ceccarelli, Daniela M; Evans, Richard D; Jones, Geoffrey P; Russ, Garry R

2014-01-01

Severe climatic disturbance events often have major impacts on coral reef communities, generating cycles of decline and recovery, and in some extreme cases, community-level phase shifts from coral-to algal-dominated states. Benthic habitat changes directly affect reef fish communities, with low coral cover usually associated with low fish diversity and abundance. No-take marine reserves (NTRs) are widely advocated for conserving biodiversity and enhancing the sustainability of exploited fish populations. Numerous studies have documented positive ecological and socio-economic benefits of NTRs; however, the ability of NTRs to ameliorate the effects of acute disturbances on coral reefs has seldom been investigated. Here, we test these factors by tracking the dynamics of benthic and fish communities, including the important fishery species, coral trout (Plectropomus spp.), over 8 years in both NTRs and fished areas in the Keppel Island group, Great Barrier Reef, Australia. Two major disturbances impacted the reefs during the monitoring period, a coral bleaching event in 2006 and a freshwater flood plume in 2011. Both disturbances generated significant declines in coral cover and habitat complexity, with subsequent declines in fish abundance and diversity, and pronounced shifts in fish assemblage structure. Coral trout density also declined in response to the loss of live coral, however, the approximately 2:1 density ratio between NTRs and fished zones was maintained over time. The only post-disturbance refuges for coral trout spawning stocks were within the NTRs that escaped the worst effects of the disturbances. Although NTRs had little discernible effect on the temporal dynamics of benthic or fish communities, it was evident that the post-disturbance refuges for coral trout spawning stocks within some NTRs may be critically important to regional-scale population persistence and recovery. PMID:24634720

Population biology of alewives, Alosa pseudoharengus, in Lake Michigan, 1949-70

USGS Publications Warehouse

Brown, Edward H.

1972-01-01

Alewives were unknown in Lake Michigan before 1949, but became extremely abundant in the 1960s and soon exceeded the carrying capacity of the lake. In 1967 they were decimated by a lakewide mass mortality, and have since been less abundant as 'adults' (a?Y 120 mm long), although numerous young were produced in 1969-70 and the adult population appeared to be gradually increasing. Alewives were studied intensively during 1962-70 on the basis of collections made primarily with bottom trawls. Principal considerations in the population study include effects of seasonal changes in distribution on length composition of young and adults, sex and maturity in relation to size and age at recruitment into adult stocks, and changes in age, growth, condition, and population structure that accompanied the drastic changes in abundance. A substantial increase in the age of adults in the bottom stocks and on the spawning grounds was among the important population changes after the 1967 die-off. Growth of older adults also increased appreciably immediately after the die-off, and a sharp increase in average weight (16-26%) over a standard range of lengths was maintained in 1968-70. Selective depletion of zooplankton by alewives was evidence that overabundance decreased the food supply, depressed growth, and caused the poor condition that made alewives vulnerable to excessive mortality in 1967. Although poor condition in fall undoubtedly increased winter and spring mortality in the mid-1960s, alewives apparently were stressed by below-average temperature in the winter of 1969-70, and experiences a light die-off through May 1970 despite their good condition and relatively low population density the preceding fall. The population upsurge that preceded the 1967 die-off was reflected by a fivefold increase of adults in the fall index catch (in trawls) from 1962 to 1965 and 1966. The index catch then dropped 70% in fall 1967. Mortality among the 1960-64 year-classes, as represented by annual losses from age III to age IV in the index catch during 1964-68, ranged from 40% in 1965 to 89% in 1967, and averaged 68%. Assessment of mortality from the index catches was difficult because the age of alewives at full recruitment into bottom stocks increased from III in the mid-1960s to IV or older in 1968-70, when alewives remained longer at midlevels, possibly because of a delay in sexual maturity. Annual mortality after the fifth year of life, on the basis of average percentage age composition of the trawl catches in 1964-70, was tentatively estimated at 79-80%. The number of alewives recruited to the adult population from the 1962-67 year-classes over several ages in the fall index catch was inversely related to the abundance of their parents in the fall immediately preceding the year in which each year-class was spawned. Annual commercial production in the 1960s (peak in 1967, 42 million lb) may not have exceeded 7.7-18.6% of the bottom stocks, on the basis of the estimated weights of alewives available to trawls in the spring of 1964 and 1969. Yield per recruitment to the commercial fishery was low because of slow growth and high natural mortality.

Chinook salmon use of spawning patches: relative roles of habitat quality, size, and connectivity.

PubMed

Isaak, Daniel J; Thurow, Russell F; Rieman, Bruce E; Dunham, Jason B

2007-03-01

Declines in many native fish populations have led to reassessments of management goals and shifted priorities from consumptive uses to species preservation. As management has shifted, relevant environmental characteristics have evolved from traditional metrics that described local habitat quality to characterizations of habitat size and connectivity. Despite the implications this shift has for how habitats may be prioritized for conservation, it has been rare to assess the relative importance of these habitat components. We used an information-theoretic approach to select the best models from sets of logistic regressions that linked habitat quality, size, and connectivity to the occurrence of chinook salmon (Oncorhynchus tshawytscha) nests. Spawning distributions were censused annually from 1995 to 2004, and data were complemented with field measurements that described habitat quality in 43 suitable spawning patches across a stream network that drained 1150 km2 in central Idaho. Results indicated that the most plausible models were dominated by measures of habitat size and connectivity, whereas habitat quality was of minor importance. Connectivity was the strongest predictor of nest occurrence, but connectivity interacted with habitat size, which became relatively more important when populations were reduced. Comparison of observed nest distributions to null model predictions confirmed that the habitat size association was driven by a biological mechanism when populations were small, but this association may have been an area-related sampling artifact at higher abundances. The implications for habitat management are that the size and connectivity of existing habitat networks should be maintained whenever possible. In situations where habitat restoration is occurring, expansion of existing areas or creation of new habitats in key areas that increase connectivity may be beneficial. Information about habitat size and connectivity also could be used to strategically prioritize areas for improvement of local habitat quality, with areas not meeting minimum thresholds being deemed inappropriate for pursuit of restoration activities.

Chinook salmon use of spawning patches: Relative roles of habitat quality, size, and connectivity

USGS Publications Warehouse

Isaak, D.J.; Thurow, R.F.; Rieman, B.E.; Dunham, J.B.

2007-01-01

Declines in many native fish populations have led to reassessments of management goals and shifted priorities from consumptive uses to species preservation. As management has shifted, relevant environmental characteristics have evolved from traditional metrics that described local habitat quality to characterizations of habitat size and connectivity. Despite the implications this shift has for how habitats may be prioritized for conservation, it has been rare to assess the relative importance of these habitat components. We used an information-theoretic approach to select the best models from sets of logistic regressions that linked habitat quality, size, and connectivity to the occurrence of chinook salmon (Oncorhynchus tshawytscha) nests. Spawning distributions were censused annually from 1995 to 2004, and data were complemented with field measurements that described habitat quality in 43 suitable spawning patches across a stream network that drained 1150 km 2 in central Idaho. Results indicated that the most plausible models were dominated by measures of habitat size and connectivity, whereas habitat quality was of minor importance. Connectivity was the strongest predictor of nest occurrence, but connectivity interacted with habitat size, which became relatively more important when populations were reduced. Comparison of observed nest distributions to null model predictions confirmed that the habitat size association was driven by a biological mechanism when populations were small, but this association may have been an area-related sampling artifact at higher abundances. The implications for habitat management are that the size and connectivity of existing habitat networks should be maintained whenever possible. In situations where habitat restoration is occurring, expansion of existing areas or creation of new habitats in key areas that increase connectivity may be beneficial. Information about habitat size and connectivity also could be used to strategically prioritize areas for improvement of local habitat quality, with areas not meeting minimum thresholds being deemed inappropriate for pursuit of restoration activities. ?? 2007 by the Ecological Society of America.

Spatial scale, means and gradients of hydrographic variables define pelagic seascapes of bluefin and bullet tuna spawning distribution.

PubMed

Alvarez-Berastegui, Diego; Ciannelli, Lorenzo; Aparicio-Gonzalez, Alberto; Reglero, Patricia; Hidalgo, Manuel; López-Jurado, Jose Luis; Tintoré, Joaquín; Alemany, Francisco

2014-01-01

Seascape ecology is an emerging discipline focused on understanding how features of the marine habitat influence the spatial distribution of marine species. However, there is still a gap in the development of concepts and techniques for its application in the marine pelagic realm, where there are no clear boundaries delimitating habitats. Here we demonstrate that pelagic seascape metrics defined as a combination of hydrographic variables and their spatial gradients calculated at an appropriate spatial scale, improve our ability to model pelagic fish distribution. We apply the analysis to study the spawning locations of two tuna species: Atlantic bluefin and bullet tuna. These two species represent a gradient in life history strategies. Bluefin tuna has a large body size and is a long-distant migrant, while bullet tuna has a small body size and lives year-round in coastal waters within the Mediterranean Sea. The results show that the models performance incorporating the proposed seascape metrics increases significantly when compared with models that do not consider these metrics. This improvement is more important for Atlantic bluefin, whose spawning ecology is dependent on the local oceanographic scenario, than it is for bullet tuna, which is less influenced by the hydrographic conditions. Our study advances our understanding of how species perceive their habitat and confirms that the spatial scale at which the seascape metrics provide information is related to the spawning ecology and life history strategy of each species.

The biology and fisheries of European hake, Merluccius merluccius, in the north-east Atlantic.

PubMed

Murua, Hilario

2010-01-01

The aim of this chapter is to review the biology and fishery, including the management, of European hake in the north-east Atlantic. The European hake is widely distributed throughout the north-east Atlantic, from Norway in the north to the Guinea Gulf in the south, and throughout the Mediterranean and Black Sea, being more abundant from the British Isles to the south of Spain. In this area, ICES (International Council for the Exploration of the Sea) recognises the existence of two stocks: the northern stock and the southern stock. Both stocks have been extensively and intensively harvested and since the beginning of the 90s have been considered to be outside safe biological limits. The northern stock, however, is currently considered to lie within safe biological limits. In any case, recovery plans were implemented for the northern stock in 2004 and for the southern stock in 2006. Despite its commercial importance, knowledge of the biology and ecology of the European hake in the North Atlantic is still quite scarce. For example, recent investigations suggest that European hake grows much faster, by a factor of two, than was considered previously. This faster growth also affects the maturity-at-age pattern of hake and the agreed maturity-at-age ogive used in the assessments. European hake is a top predator in the demersal community in the north-east Atlantic area; mainly preying on blue whiting, horse mackerel and other cupleids. In relation to the reproductive biology, European hake is considered to be a batch spawner species with indeterminate fecundity and spawning activity all year round. All these characteristics could, in turn, be interpreted as European hake adopting a more opportunistic life strategy, which is unusual for a gadoid and demersal species, and raises several questions about hake biology and ecology that require further investigation. Copyright © 2010 Elsevier Ltd. All rights reserved.

Reproduction and mating behavior of the atlantic flyingfish, Cheilopogon melanurus (Exocoetidae), off North Carolina

USGS Publications Warehouse

Casazza, Tara L.; Ross, Steve W.; Necaise, Ann Marie; Sulak, Kenneth J.

2005-01-01

The reproductive biology of Cheilopogon melanurus (Valenciennes, 1847) was examined off North Carolina during the summers of 1991–1992 and 1999–2003. Specimens were collected using a small mesh neuston net and dip nets. A spawning event, the first observation of mating behavior for this species, was recorded off Cape Fear, North Carolina, on 19 August 2003. It was considered to be a spawning event due to: 1) unusual coloration of both sexes, 2) unusual swimming behavior of both sexes, and 3) ready release of gametes by both sexes upon capture. The spawning event occurred in the presence of small clumps of floating Sargassum, but the fish did not appear to use the algae. Over all collections, female gonadosomatic indices were highest in June and July, but mature females were collected each month (June, July, and August). The overall female to male sex ratio did not vary significantly from 1:1. Number of ova increased with increasing fish size, but the relationship was not strong. Our data indicate a spawning season of at least June through August off North Carolina due to high female gonadosomatic indices, large egg diameters, presence of egg filaments, presence of spent females in July and August, and presence of small juveniles (≤ 25 mm) in July and August. This is the first report of single pair spawning for this family; other species reportedly spawn in large aggregations.

Population specific sperm production in European flounder Platichthys flesus: adaptation to salinity at spawning.

PubMed

Nissling, A; Larsson, R

2018-06-07

Marine teleosts inhabiting the brackish Baltic Sea have adapted to the less saline water with activation of spermatozoa at low salinity hypo-osmotic conditions but with shorter longevity and lower swimming speed that affect the fertilization capacity. Aiming to elucidate if the fertilization capacity may be maintained by increasing the number of spermatozoa produced, testis size for the euryhaline flounder Platichthys flesus with external fertilization was assessed along a salinity gradient; with spawning at a salinity of c. 7, 10-18 and 30-35. Fulton's condition factor K = 0.881 ± 0.085 (mean ± S.D.), 0.833 ± 0.096 and 0.851 ± 0.086, for fish spawning at salinities of c. 7, 10-18 and 30-35, respectively, with no difference between areas, i.e. analysed fish were in similar nutritional condition. A general linear model, with testes dry mass as the dependent variable and somatic mass as covariate resulted in a significant difference between areas-populations with larger testes for P. flesus spawning at a salinity of c. 7 but no difference between fish spawning at a salinity of 10-18 and 30-35. The result suggests that adaptation by increasing the number of spermatozoa produced may be a key mechanism for marine teleosts spawning in areas with low salinities to sustain the fertilization capacity as shown here for the euryhaline P. flesus. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Fall and winter survival of brook trout and brown trout in a north-central Pennsylvania watershed

USGS Publications Warehouse

Sweka, John A.; Davis, Lori A.; Wagner, Tyler

2017-01-01

Stream-dwelling salmonids that spawn in the fall generally experience their lowest survival during the fall and winter due to behavioral changes associated with spawning and energetic deficiencies during this time of year. We used data from Brook Trout Salvelinus fontinalis and Brown Trout Salmo trutta implanted with radio transmitters in tributaries of the Hunts Run watershed of north-central Pennsylvania to estimate survival from the fall into the winter seasons (September 2012–February 2013). We examined the effects that individual-level covariates (trout species, size, and movement rates) and stream-level covariates (individual stream and cumulative drainage area of a stream) have on survival. Brook Trout experienced significantly lower survival than Brown Trout, especially in the early fall during their peak spawning period. Besides a significant species effect, none of the other covariates examined influenced survival for either species. A difference in life history between these species, with Brook Trout having a shorter life expectancy than Brown Trout, is likely the primary reason for the lower survival of Brook Trout. However, Brook Trout also spawn earlier in the fall than Brown Trout and low flows during Brook Trout spawning may have resulted in a greater risk of predation for Brook Trout compared with Brown Trout, thereby also contributing to the observed differences in survival between these species. Our estimates of survival can aid parameterization of future population models for Brook Trout and Brown Trout through the spawning season and into winter.

Depressed resilience of bluefin tuna in the western atlantic and age truncation.

PubMed

Secor, D H; Rooker, J R; Gahagan, B I; Siskey, M R; Wingate, R W

2015-04-01

Following intense overfishing in the 1970s, the western stock of Atlantic bluefin tuna (Thunnus thynnus) experienced a long period of depressed abundance, which has been attributed to failure of the population to periodically produce large numbers of juveniles, the western stock mixing with the more highly exploited eastern stock (fisheries in the Northeast Atlantic Ocean and Mediterranean Sea), and regime shift in the population's ecosystem resulting in lower replacement rates. To evaluate the presence of relatively strong years of juvenile production, we analyzed age structure from a recent sample of otoliths (ear stones) collected from the western stock (2011-2013, North Carolina, U.S.A., winter fishery). Mixing levels for the recent sample were analyzed using otolith stable isotopes to test whether age structure might be biased through immigration of eastern stock bluefin tuna. Age structure from historical samples collected from United States and Canadian fisheries (1975-1981) was compared with more recent samples (1996-2007) to examine whether demographic changes had occurred to the western stock that might have disrupted juvenile production. Relatively high juvenile production occurred in 2003, 2005, and 2006. Otolith stable isotope analysis showed that these recruitments were mostly of western stock origin. However, these high recruitments were >2-fold less than historical recruitment. We found substantial age truncation in the sampled fisheries. Half the historical sample was >20 years old (mean age = 20.1 [SD 3.7]; skewness = -0.3), whereas <5% of the recent sample was >20 years old (mean age = 13.4 [SD 3.8]; skewness = 1.3). Loss of age structure is consistent with changes in fishing selectivity and trends in the stock assessment used for management. We propose that fishing, as a forcing variable, brought about a threshold shift in the western stock toward lower biomass and production, a shift that emulates the regime shift hypothesis. An abbreviated reproductive life span compromised resilience by reducing the period over which adults spawn and thereby curtailing the stock's ability to sample year-to-year variability in conditions that favor offspring survival (i.e., storage effect). Because recruitment dynamics by the western stock exhibit threshold dynamics, returning it to a higher production state will entail greater reductions in exploitation rates. © 2014 Society for Conservation Biology.

Effects of dam removal on Tule Fall Chinook salmon spawning habitat in the White Salmon River, Washington

USGS Publications Warehouse

Hatten, James R.; Batt, Thomas R.; Skalicky, Joseph J.; Engle, Rod; Barton, Gary J.; Fosness, Ryan L.; Warren, Joe

2016-01-01

Condit Dam is one of the largest hydroelectric dams ever removed in the USA. Breached in a single explosive event in October 2011, hundreds-of-thousands of cubic metres of sediment washed down the White Salmon River onto spawning grounds of a threatened species, Columbia River tule fall Chinook salmon Oncorhynchus tshawytscha. We investigated over a 3-year period (2010–2012) how dam breaching affected channel morphology, river hydraulics, sediment composition and tule fall Chinook salmon (hereafter ‘tule salmon’) spawning habitat in the lower 1.7 km of the White Salmon River (project area). As expected, dam breaching dramatically affected channel morphology and spawning habitat due to a large load of sediment released from Northwestern Lake. Forty-two per cent of the project area that was previously covered in water was converted into islands or new shoreline, while a large pool near the mouth filled with sediments and a delta formed at the mouth. A two-dimensional hydrodynamic model revealed that pool area decreased 68.7% in the project area, while glides and riffles increased 659% and 530%, respectively. A spatially explicit habitat model found the mean probability of spawning habitat increased 46.2% after dam breaching due to an increase in glides and riffles. Shifting channels and bank instability continue to negatively affect some spawning habitat as sediments continue to wash downstream from former Northwestern Lake, but 300 m of new spawning habitat (river kilometre 0.6 to 0.9) that formed immediately post-breach has persisted into 2015. Less than 10% of tule salmon have spawned upstream of the former dam site to date, but the run sizes appear healthy and stable. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Population ecology of turbot and brill: What can we learn from two rare flatfish species?

NASA Astrophysics Data System (ADS)

van der Hammen, Tessa; Poos, Jan Jaap; van Overzee, Harriët M. J.; Heessen, Henk J. L.; Magnusson, Arni; Rijnsdorp, Adriaan D.

2013-11-01

Turbot and brill are widely distributed in the Northeast Atlantic but occur at low abundance. They are ecologically very similar and closely related. The low abundance and the similarities make them particularly interesting to study the population dynamics because it raises the questions how the populations can sustain themselves at low abundances and how turbot and brill avoid strong interspecific competition. Knowledge of both species is hampered by lack of analysed data. The main objective of this study is therefore to increase the knowledge of turbot and brill and in particular to compare the two species in order to address the above questions. Based on biological samples collected in the North Sea, we calculated seasonal von Bertalanffy growth parameters, maturity ogives, monthly gonado-somatic indices (GSI) and condition factors (Fulton's K) and indices of inter- and intraspecific mean crowding and compared the results for turbot and brill. The main differences between the two species were found in their spawning period, with brill having a more protracted spawning period. Brill also showed an earlier peak in their GSI values, suggesting an earlier start of their spawning period. The mean crowding showed that interspecific competition was lower than intraspecific competition. The exploitation pattern was also studied. Turbot and brill are exploited as a bycatch species in the mixed demersal fishery. We found that productivity is highest in areas where the maximum temperature is close to the optimal temperature for growth (16-18 °C) and landings decrease where salinity falls below ~ 5 psu (turbot) and ~ 15 psu (brill). Recent fishing mortality rates of North Sea turbot are around 0.5-0.7, but there is no indication that recruitment is impaired at low levels of spawning stock biomass. We conclude that although both species have similar ecological characteristics, differences may reduce inter-specific competition.

Spawning aggregation behavior and reproductive ecology of the giant bumphead parrotfish, Bolbometopon muricatum, in a remote marine reserve

PubMed Central

Zgliczynski, Brian J.; Teer, Bradford Z.; Laughlin, Joseph L.

2014-01-01

The giant bumphead parrotfish (Bolbometopon muricatum) has experienced precipitous population declines throughout its range due to its importance as a highly-prized fishery target and cultural resource. Because of its diet, Bolbometopon may serve as a keystone species on Indo-Pacific coral reefs, yet comprehensive descriptions of its reproductive ecology do not exist. We used a variety of underwater visual census (UVC) methods to study an intact population of Bolbometopon at Wake Atoll, a remote and protected coral atoll in the west Pacific. Key observations include spawning activities in the morning around the full and last quarter moon, with possible spawning extending to the new moon. We observed peaks in aggregation size just prior to and following the full and last quarter moon, respectively, and observed a distinct break in spawning at the site that persisted for four days; individuals returned to the aggregation site one day prior to the last quarter moon and resumed spawning the following day. The mating system was lek-based, characterized by early male arrival at the spawning site followed by vigorous defense (including head-butting between large males) of small territories. These territories were apparently used to attract females that arrived later in large schools, causing substantial changes in the sex ratio on the aggregation site at any given time during the morning spawning period. Aggression between males and courtship of females led to pair spawning within the upper water column. Mating interference was not witnessed but we noted instances suggesting that sperm competition might occur. Densities of Bolbometopon on the aggregation site averaged 10.07(±3.24 SE) fish per hectare (ha) with maximum densities of 51.5 fish per ha. By comparing our observations to the results of biennial surveys conducted by the National Oceanic and Atmospheric Administration (NOAA) Coral Reef Ecosystem Division (CRED), we confirmed spatial consistency of the aggregation across years as well as a temporal break in spawning activity and aggregation that occurred during the lunar phase. We estimated the area encompassed by the spawning aggregation to be 0.72 ha, suggesting that spawning site closures and temporal closures centered around the full to the new moon might form one component of a management and conservation plan for this species. Our study of the mating system and spawning aggregation behavior of Bolbometopon from the protected, relatively pristine population at Wake Atoll provides crucial baselines of population density, sex ratio composition, and productivity of a spawning aggregation site from an oceanic atoll. Such information is key for conservation efforts and provides a basic platform for the design of marine protected areas for this threatened iconic coral reef fish, as well as for species with similar ecological and life history characteristics. PMID:25469322

A spatial ecosystem and populations dynamics model (SEAPODYM) Modeling of tuna and tuna-like populations

NASA Astrophysics Data System (ADS)

Lehodey, Patrick; Senina, Inna; Murtugudde, Raghu

2008-09-01

An enhanced version of the spatial ecosystem and population dynamics model SEAPODYM is presented to describe spatial dynamics of tuna and tuna-like species in the Pacific Ocean at monthly resolution over 1° grid-boxes. The simulations are driven by a bio-physical environment predicted from a coupled ocean physical-biogeochemical model. This new version of SEAPODYM includes expanded definitions of habitat indices, movements, and natural mortality based on empirical evidences. A thermal habitat of tuna species is derived from an individual heat budget model. The feeding habitat is computed according to the accessibility of tuna predator cohorts to different vertically migrating and non-migrating micronekton (mid-trophic) functional groups. The spawning habitat is based on temperature and the coincidence of spawning fish with presence or absence of predators and food for larvae. The successful larval recruitment is linked to spawning stock biomass. Larvae drift with currents, while immature and adult tuna can move of their own volition, in addition to being advected by currents. A food requirement index is computed to adjust locally the natural mortality of cohorts based on food demand and accessibility to available forage components. Together these mechanisms induce bottom-up and top-down effects, and intra- (i.e. between cohorts) and inter-species interactions. The model is now fully operational for running multi-species, multi-fisheries simulations, and the structure of the model allows a validation from multiple data sources. An application with two tuna species showing different biological characteristics, skipjack ( Katsuwonus pelamis) and bigeye ( Thunnus obesus), is presented to illustrate the capacity of the model to capture many important features of spatial dynamics of these two different tuna species in the Pacific Ocean. The actual validation is presented in a companion paper describing the approach to have a rigorous mathematical parameter optimization [Senina, I., Sibert, J., Lehodey, P., 2008. Parameter estimation for basin-scale ecosystem-linked population models of large pelagic predators: application to skipjack tuna. Progress in Oceanography]. Once this evaluation and parameterization is complete, it may be possible to use the model for management of tuna stocks in the context of climate and ecosystem variability, and to investigate potential changes due to anthropogenic activities including global warming and fisheries pressures and management scenarios.

Experimental evaluation of size-dependent predation by adult post-spawned rainbow smelt (Osmerus mordax) on larval lake whitefish (Coregonus clupeaformis)

USGS Publications Warehouse

Zydlewski, Joseph D.; Gorsky, Dimitry

2013-01-01

Introduced landlocked Rainbow Smelt Osmerus mordax are hypothesized to be a major factor in the decline of Lake Whitefish Coregonus clupeaformis populations in many lakes. We sought to identify the size of Lake Whitefish preyed upon by adult Rainbow Smelt and how the efficiency of Rainbow Smelt predation changes Lake Whitefish ontogeny. In a laboratory setting, we exposed larval Lake Whitefish of increasing sizes to groups of seven Rainbow Smelt (>100 mm) for a 1-h period and observed predation behaviors and efficiencies. In each trial, the group of Rainbow Smelt consumed at least one larval Lake Whitefish, which were up to 45 mm in length (up to 89% of Rainbow Smelt gape width). Predation efficiency, the total number of Lake Whitefish consumed by Rainbow Smelt during trials, was 100% after Lake Whitefish hatching and followed a decreasing sigmoidal response to increasing lengths of Lake Whitefish. The apparent predatory window of Rainbow Smelt on Lake Whitefish is from Lake Whitefish size at hatch (∼12 mm) to approximately 34 mm. Rainbow Smelt generally required multiple attacks to capture a single Lake Whitefish. The capture efficiencies of Rainbow Smelt decreased from 30% as Lake Whitefish length increased and were highly variable within each Lake Whitefish size-group. The overall impact that Rainbow Smelt predation will have on Lake Whitefish populations is dependent on the growth rate of Lake Whitefish, environmental conditions that cause the Lake Whitefish hatching period to coincide with Rainbow Smelt spawning events, and the degree of overlap in habitat use between spawning Rainbow Smelt, nonspawning subadult Rainbow Smelt, and hatching Lake Whitefish.

Recruitment and connectivity influence the role of seagrass as a penaeid nursery habitat in a wave dominated estuary.

PubMed

Taylor, Matthew D; Fry, Brian; Becker, Alistair; Moltschaniwskyj, Natalie

2017-04-15

Estuaries provide a diverse mosaic of habitats which support both juveniles and adults of exploited species. In particular, estuaries play an important role in the early life history of many penaeid prawn species. This study used a combination of stable isotope ecology and quantitative sampling to examine recruitment and the nursery function of seagrass habitats for Eastern King Prawn (Penaeus [Melicertus] plebejus), and the processes that contributed to this nursery role. Stable isotopes were used to assign prawns joining the adult stock to putative nursery habitat areas within the estuary. Emigrating prawns originated from only 11 of the 20 sites surveyed. Of these, 8 sites were designated as Effective Juvenile Habitat (EJH), and 5 sites designated as Nursery Habitat (NH). The contribution of individuals from different nursery areas to the adult stock was related to both the abundance of prawns within an area and the distance to the mouth of the estuary, and with the exception of 1 site all EJH and NH were located in the northern section of the estuary. Quantitative sampling in this area indicated that prawns were present at an average density of 165±11 per 100m 2 , and density formed non-linear relationships with the distance to the mouth of the estuary, seagrass cover and temperature. Prawn size also formed non-linear relationships with prawn density and seagrass cover. Spatial patterns in abundance were consistent with wind-driven recruitment patterns, which in turn affected the nursery role of particular areas within the system. These findings have implications for targeted fishery restoration efforts for both Eastern King Prawn and other ocean spawned species in wave dominated estuaries where circulation is primarily wind-driven. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

Comparing histology and gonadosomatic index for determining spawning condition of small-bodied riverine fishes

USGS Publications Warehouse

Brewer, S.K.; Rabeni, C.F.; Papoulias, D.M.

2008-01-01

We compared gonadosomatic index (GSI) and histological analysis of ovaries for identifying reproductive periods of fishes to determine the validity of using GSI in future studies. Four small-bodied riverine species were examined in our comparison of the two methods. Mean GSI was significantly different between all histological stages for suckermouth minnow and red shiner. Mean GSI was significantly different between most stages for slenderhead darter; whereas stages 3 and 6 were not significantly different, the time period when these stages are present would allow fisheries biologists to distinguish between the two stages. Mean GSI was not significantly different for many histological stages in stonecat. Difficulties in distinguishing between histological stages and GSI associated with stonecat illustrate potential problems obtaining appropriate sample sizes from species that move to alternative habitats to spawn. We suggest that GSI would be a useful tool in identifying mature ovaries in many small-bodied, multiple-spawning fishes. This information could be combined with data from histology during mature periods to pinpoint specific spawning events. ?? 2007 Blackwell Munksgaard.

Influence of habitat characteristics on shore-spawning kokanee

USGS Publications Warehouse

Whitlock, Steven L.; Quist, Michael C.; Dux, Andrew M.

2014-01-01

Sockeye Salmon Oncorhynchus nerka and kokanee (lacustrine Sockeye Salmon) commonly spawn in both lentic and lotic environments; however, the habitat requirements of shore spawners are virtually unknown relative to those of stream spawners. A laboratory experiment and an in situ incubation study were conducted to better understand the influence of habitat characteristics on the shoreline incubation success of kokanee. The laboratory experiment assessed kokanee intragravel survival, fry emergence, and fry condition in response to eight substrate treatments. The in situ study, conducted at three major shoreline spawning sites in Lake Pend Oreille, Idaho, evaluated the effect of depth, substrate composition, dissolved oxygen, shoreline slope, and groundwater on intragravel survival. Substrate size composition was generally a poor predictor of survival in both the laboratory experiment and in situ study; although, fry condition and counts of emerged fry in the laboratory were lowest for the substrate treatment that had the highest proportion of fine sediment. Results of the in situ study suggest that groundwater flow plays an important role in enhancing intragravel survival in habitats generally considered unsuitable for spawning.

Goliath catfish spawning in the far western Amazon confirmed by the distribution of mature adults, drifting larvae and migrating juveniles.

PubMed

Barthem, Ronaldo B; Goulding, Michael; Leite, Rosseval G; Cañas, Carlos; Forsberg, Bruce; Venticinque, Eduardo; Petry, Paulo; Ribeiro, Mauro L de B; Chuctaya, Junior; Mercado, Armando

2017-02-06

We mapped the inferred long-distance migrations of four species of Amazonian goliath catfishes (Brachyplatystoma rousseauxii, B. platynemum, B. juruense and B. vaillantii) based on the presence of individuals with mature gonads and conducted statistical analysis of the expected long-distance downstream migrations of their larvae and juveniles. By linking the distribution of larval, juvenile and mature adult size classes across the Amazon, the results showed: (i) that the main spawning regions of these goliath catfish species are in the western Amazon; (ii) at least three species-B. rousseauxii, B. platynemum, and B. juruense-spawn partially or mainly as far upstream as the Andes; (iii) the main spawning area of B. rousseauxii is in or near the Andes; and (iv) the life history migration distances of B. rousseauxii are the longest strictly freshwater fish migrations in the world. These results provide an empirical baseline for tagging experiments, life histories extrapolated from otolith microchemistry interpretations and other methods to establish goliath catfish migratory routes, their seasonal timing and possible return (homing) to western headwater tributaries where they were born.

Fewer but not smaller schools in declining fish and krill populations.

PubMed

Brierley, Andrew S; Cox, Martin J

2015-01-05

Many pelagic species (species that live in the water column), including herring and krill, aggregate to form schools, shoals, or swarms (hereafter simply "schools," although the words are not synonyms). Schools provide benefits to individual members, including locomotory economy and protection from predators that prey on individuals, but paradoxically make schooling species energetically viable and commercially attractive targets for predators of groups and for fishers. Large schools are easier to find and yield greater prey/catch than small schools, and there is a requirement from fields as diverse as theoretical ecology and fisheries management to understand whether and how aggregation sizes change with changing population size. We collated data from vertical echosounder surveys of taxonomically diverse pelagic stocks from geographically diverse ecosystems. The data contain common significant positive linear stock-biomass to school-number relationships. They show that the numbers of schools in the stocks change with changing stock biomass and suggest that the distributions of school sizes do not change with stock biomass. New data that we collected using a multibeam sonar, which can image entire schools, contained the same stock-biomass to school-number relationship and confirm that the distribution of school sizes is not related to changing stock size: put simply, as stocks decline, individuals are distributed among fewer schools, not smaller schools. Since school characteristics affect catchability (the ease or difficulty with which fishers can capture target species) and availability of prey to predators, our findings have commercial and ecological implications, particularly within the aspirational framework of ecosystem-based management of marine systems. Copyright © 2015 Elsevier Ltd. All rights reserved.

[Spontaneous spawning, ontogeny and growth in captivity of Cynoscion squamipinnis (Perciformes: Sciaenidae)].

PubMed

Boza-Abarca, Jorge; Ramírez-Alvarado, Marvin; Barquero-Chanto, Juan; Calvo-Vargas, Emilia; Berrocal-Artavia, Karen

2016-09-01

The croakers or drums are commercial species, which have been overfished in the Nicoya Gulf, Costa Rica. This study aimed to describe, for the first time, the reproduction and the ontogeny of weakfish, Cynoscion squamipinnis in captivity, in order to perform restocking and mariculture proyects. Wild fish (n= 6, 1-2 Kg) were captured and maintained in the Estación de Biología Marina Juan Bertoglia Richards (Puntarenas, Costa Rica) for a two years period (October 2006- December 2008). During this period, maturation stage was monitored periodically by cannula samples in the females (n= 3) and gentle massage in males (n= 3). All fish were stocked in an 18 t tank, with aeration, 33-35 ups of salinity, and a constant temperature (29 ± 1 °C). The spawning period occurred from January to March 2009, producing 162 000 eggs in three spontaneous spawns. The fertilization percentage was 50-60%, and survival after hatching was 60-85%. The egg diameter was 0.852 mm (Standard deviation (SD)= 0.039), and oil drop of 0.269 mm (SD= 0.016). In the embryonary development, the first mitotic division (MD) was observed one hour after spawning (has), the second MD was 1:30 has, the third MD was 2:00 has, the fourth MD was 2:30 has, and fifth MD at 3:00 has. Morule was observed 3:30 has, the blastule 4:30 has, the gastrule 8:30 has, C shape at 10:00 has, and C shape at 12:00 has. After 19 has hatching larvae occurred. The total length (TL) of the larvae was 2.234 mm (SD= 0.122), and the nothochordial length (NL) was 2.179 mm (SD= 0.119). Preflexion stage was observed 49 has, flexion stage was 11 days after spawn (das) (3.767 mm LT (SD= 0.209)), and postflexion stage was 14 das (4.015 mm LT (SD= 0.302)). After 45 das, the juvenile weights 3.68 g (SD= 1.09). Hatch time of the weakfish larvae was minor than of others croaker species. The stages times of embrionary development were a little different from others croaker species, and probably respond to genetic characteristics of each species and the eggs incubation temperature. The spontaneously spawning without broodstock hormonal applications, and the juveniles production in captivity showed that weakfish is a potential species for restocking programs and mariculture projects.

76 FR 11857 - Magnuson-Stevens Fishery Conservation and Management Act Provisions; Fisheries of the...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-03

...NMFS proposes regulations to implement measures in Framework Adjustment (FW) 45 to the NE Multispecies Fishery Management Plan (FMP). FW 45 was developed by the New England Fishery Management Council (Council) to prevent overfishing, rebuild overfished stocks, achieve optimum yield (OY), and minimize the economic impact of management measures on affected vessels, pursuant to the Magnuson- Stevens Fishery Conservation and Management Act (Magnuson-Stevens Act). This action would revise the biological reference points and stock status for pollock, update annual catch limits (ACLs) for several stocks for fishing years (FYs) 2011-2012, adjust the rebuilding program for Georges Bank (GB) yellowtail flounder, increase scallop vessel access to the Great South Channel Exemption Area, approve five new sectors, modify the existing dockside and at-sea monitoring requirements, revise several sector administrative provisions, establish a Gulf of Maine (GOM) Cod Spawning Protection Area, and refine measures affecting the catch of limited access NE multispecies Handgear A vessels. This action would disapprove the Council's proposed catch limits for GB yellowtail flounder for FY 2011, and instead propose new catch limits for this stock through emergency action authority based on new flexibility provided by the International Fisheries Agreement Clarification Act. This action is necessary to ensure that the fishery is managed on the basis of the best available science, to comply with the acceptable biological catch (ABC) control rules adopted in Amendment 16 to the FMP, and to enhance the viability of the fishery following the transition to sector management in 2010.

Environmental variability and chum salmon production at the northwestern Pacific Ocean

NASA Astrophysics Data System (ADS)

Kim, Suam; Kang, Sukyung; Kim, Ju Kyoung; Bang, Minkyoung

2017-12-01

Chum salmon, Oncorhynchus keta, are distributed widely in the North Pacific Ocean, and about 76% of chum salmon were caught from Russian, Japanese, and Korean waters of the northwestern Pacific Ocean during the last 20 years. Although it has been speculated that the recent increase in salmon production was aided by not only the enhancement program that targeted chum salmon but also by favorable ocean conditions since the early 1990s, the ecological processes for determining the yield of salmon have not been clearly delineated. To investigate the relationship between yield and the controlling factors for ocean survival of chum salmon, a time-series of climate indices, seawater temperature, and prey availability in the northwestern Pacific including Korean waters were analyzed using some statistical tools. The results of cross-correlation function (CCF) analysis and cumulative sum (CuSum) of anomalies indicated that there were significant environmental changes in the North Pacific during the last century, and each regional stock of chum salmon responded to the Pacific Decadal Oscillation (PDO) differently: for Russian stock, the correlations between PDO index and catch were significantly negative with a time-lag of 0 and 1 years; for Japanese stock, significantly positive with a timelag of 0-2 years; and for Korean stock, positive but no significant correlation. The results of statistical analyses with Korean chum salmon also revealed that a coastal seawater temperature over 14°C and the return rate of spawning adults to the natal river produced a significant negative correlation.

Incorporation of habitat information in the development of indices of larval bluefin tuna (Thunnus thynnus) in the Western Mediterranean Sea (2001-2005 and 2012-2013)

NASA Astrophysics Data System (ADS)

Ingram, G. Walter; Alvarez-Berastegui, Diego; Reglero, Patricia; Balbín, Rosa; García, Alberto; Alemany, Francisco

2017-06-01

Fishery independent indices of bluefin tuna larvae in the Western Mediterranean Sea are presented utilizing ichthyoplankton survey data collected from 2001 through 2005 and 2012 through 2013. Indices were developed using larval catch rates collected using two different types of bongo sampling, by first standardizing catch rates by gear/fishing-style and then employing a delta-lognormal modeling approach. The delta-lognormal models were developed three ways: 1) a basic larval index including the following covariates: time of day, a systematic geographic area variable, month and year; 2) a standard environmental larval index including the following covariates: mean water temperature over the mixed layer depth, mean salinity over the mixed layer depth, geostrophic velocity, time of day, a systematic geographic area variable, month and year; and 3) a habitat-adjusted larval index including the following covariates: a potential habitat variable, time of day, a systematic geographic area variable, month and year. Results indicated that all three model-types had similar precision in index values. However, the habitat-adjusted larval index demonstrated a high correlation with estimates of spawning stock biomass from the previous stock assessment model, and, therefore, is recommended as a tuning index in future stock assessment models.

Genetic diversity of sockeye salmon (`oncorhynchus nerka`) of Cook Inlet, Alaska, and its application to restoration of injured populations of the Kenai River. Exxon Valdez Oil Spill Restoration Project 93012 and 94255-2. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seeb, L.W.; Habicht, C.; Templin, W.D.

1995-11-01

Genetic data from sockeye salmon (Oncorhynchus nerka) were collected from all significant spawning populations contributing to mixed-stock harvests in Cook Inlet. A total of 68 allozyme loci were resolved from 37 populations. Mitochondrial DNA data from the NADH subunits 5 and 6 were collected from 19 of the populations. Mixed-stock analyses using maximum likelihood methods with 27 loci were evaluated to estimate the proportion of Kenai River populations in Central District drift fisheries. Simulations indicate that Kenai River populations can be identified in mixtures at a level of precision and accuracy useful for restoration and fishery management. Mixed-stock samples frommore » Cook Inlet drift net fisheries were analyzed both inseason (48 hr) and post-season. Samples from fish wheels from the Kenai, Kasilof, Yentna, and Susitna River systems were also analyzed. Inclusion of mtDNA data in the analysis is being investigated to determine if it improves precision and accuracy. Results from this study are currently being used in the management and restoration of Kenai River sockeye salmon injured in the 1989 Exxon Valdex oil spill.« less

Comparing the transcriptomes of embryos from domesticated and wild Atlantic salmon (Salmo salar L.) stocks and examining factors that influence heritability of gene expression.

PubMed

Bicskei, Beatrix; Taggart, John B; Glover, Kevin A; Bron, James E

2016-03-17

Due to selective breeding, domesticated and wild Atlantic salmon are genetically diverged, which raises concerns about farmed escapees having the potential to alter the genetic composition of wild populations and thereby disrupting local adaptation. Documenting transcriptional differences between wild and domesticated stocks under controlled conditions is one way to explore the consequences of domestication and selection. We compared the transcriptomes of wild and domesticated Atlantic salmon embryos, by using a custom 44k oligonucleotide microarray to identify perturbed gene pathways between the two stocks, and to document the inheritance patterns of differentially-expressed genes by examining gene expression in their reciprocal hybrids. Data from 24 array interrogations were analysed: four reciprocal cross types (W♀ × W♂, D♀ × W♂; W♀ × D♂, D♀ × D♂) × six biological replicates. A common set of 31,491 features on the microarrays passed quality control, of which about 62 % were assigned a KEGG Orthology number. A total of 6037 distinct genes were identified for gene-set enrichment/pathway analysis. The most highly enriched functional groups that were perturbed between the two stocks were cellular signalling and immune system, ribosome and RNA transport, and focal adhesion and gap junction pathways, relating to cell communication and cell adhesion molecules. Most transcripts that were differentially expressed between the stocks were governed by additive gene interaction (33 to 42 %). Maternal dominance and over-dominance were also prevalent modes of inheritance, with no convincing evidence for a stock effect. Our data indicate that even at this relatively early developmental stage, transcriptional differences exist between the two stocks and affect pathways that are relevant to wild versus domesticated environments. Many of the identified differentially perturbed pathways are involved in organogenesis, which is expected to be an active process at the eyed egg stage. The dominant effects are more largely due to the maternal line than to the origin of the stock. This finding is particularly relevant in the context of potential introgression between farmed and wild fish, since female escapees tend to have a higher spawning success rate compared to males.

Spatio-temporal segregation of calling behavior at a multispecies fish spawning site in Little Cayman

NASA Astrophysics Data System (ADS)

Cameron, K. C.; Sirovic, A.; Jaffe, J. S.; Semmens, B.; Pattengill-Semmens, C.; Gibb, J.

2016-02-01

Fish spawning aggregation (FSA) sites are extremely vulnerable to over-exploitation. Accurate understanding of the spatial and temporal use of such sites is necessary for effective species management. The size of FSAs can be on the order of kilometers and peak spawning often occurs at night, posing challenges to visual observation. Passive acoustics are an alternative method for dealing with these challenges. An array of passive acoustic recorders and GoPro cameras were deployed during Nassau grouper (Epinephelus striatus) spawning from February 7th to 12th, 2015 at a multispecies spawning aggregation site in Little Cayman, Cayman Islands. In addition to Nassau grouper, at least 10 other species are known to spawn at this location including tiger grouper (Mycteroperca tigris), red hind (Epinephelus guttatus), black grouper (Mycteroperca bonaci), and yellowfin grouper (Mycteroperca venenosa). During 5 days of continuous recordings, over 21,000 fish calls were detected. These calls were classified into 15 common types. Species identification and behavioral context of unknown common call types were determined by coupling video recordings collected during this time with call localizations. There are distinct temporal patterns in call production of different species. For example, red hind and yellowfin grouper call predominately at night with yellowfin call rates increasing after midnight, and black grouper call primarily during dusk and dawn. In addition, localization methods were used to reveal how the FSA area was divided among species. These findings facilitate a better understanding of the behavior of these important reef fish species allowing policymakers to more effectively manage and protect them.

Ichthyoplankton transport from the African coast to the Canary Islands

NASA Astrophysics Data System (ADS)

Brochier, Timothée; Mason, Evan; Moyano, Marta; Berraho, Amina; Colas, Francois; Sangrà, Pablo; Hernández-León, Santiago; Ettahiri, Omar; Lett, Christophe

2011-08-01

The Canary Upwelling System (CUS), a major eastern boundary upwelling system, sustains large cross-border fisheries of small pelagic fish, which poses the question of stock connectivity. Studies suggest that ichthyoplankton transport from the northwest African coast to the Canary Islands (CI) is facilitated by coastal-upwelling associated filaments. Here we analyze connections between larval supply to the CI and sardine and anchovy populations that spawn over the continental shelf. For both species, ichthyoplankton observations (1) at the shelf and (2) near the island of Gran Canaria (GC) are used. Predictions of ichthyoplankton transport to GC are obtained from the Ichthyop Lagrangian transport model, which is forced by a high-resolution hydrodynamic model (ROMS) that reproduces the regional circulation. Results show that upwelling filaments play an important role in the transport of larvae to GC. However, (1) filaments are not the only mechanism, and (2) filament presence does not necessarily imply larval transport. Anchovy and sardine larval presence at GC appears to be independent of the respective adult spawning seasonality. Combining of observed and modeled data does not succeed in reproducing the observed larval patterns at GC. Various hypotheses are proposed to explain this discrepancy in larval transport to GC.

Comparing the Reproductive Success of Yakima River Hatchery-and Wild-Origin Spring Chinook; Yakima/Klickitat Fisheries Project Monitoring and Evaluation, 2000-2001 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroder, S.L.; Knudsen, C.M.; Rau, J.A.

In the Yakima Spring Chinook supplementation program, wild fish are brought into the Cle Elum Hatchery, artificially crossed, reared, transferred to acclimation sites, and released into the upper Yakima River as smolts. When these fish mature and return to the Yakima River most of them will be allowed to spawn naturally; a few, however, will be brought back to the hatchery and used for research purposes. In order for this supplementation approach to be successful, hatchery-origin fish must be able to spawn and produce offspring under natural conditions. Recent investigations on salmonid fishes have indicated that exposure to hatchery environmentsmore » during juvenile life may cause significant behavioral, physiological, and morphological changes in adult fish. These changes appear to reduce the reproductive competence of hatchery fish. In general, males are more affected than females; species with prolonged freshwater rearing periods are more strongly impacted than those with shorter rearing periods; and stocks that have been exposed to artificial culture for multiple generations are more impaired than those with a relatively short exposure history to hatchery conditions.« less

Annual variation in habitat-specific recruitment success: Implications from an individual-based model of Lake Michigan alewife (Alosa pseudoharengus)

USGS Publications Warehouse

Hook, T.O.; Rutherford, E.S.; Croley, T.E.; Mason, D.M.; Madenjian, C.P.

2008-01-01

The identification of important spawning and nursery habitats for fish stocks can aid fisheries management, but is complicated by various factors, including annual variation in recruitment success. The alewife (Alosa pseudoharengus) is an ecologically important species in Lake Michigan that utilizes a variety of habitats for spawning and early life growth. While productive, warm tributary mouths (connected to Lake Michigan) may contribute disproportionately more recruits (relative to their habitat volume) to the adult alewife population than cooler, less productive nearshore habitats, the extent of interannual variation in the relative contributions of recruits from these two habitat types remains unknown. We used an individual-based bioenergetics simulation model and input data on daily temperatures to estimate alewife recruitment to the adult population by these different habitat types. Simulations suggest that nearshore lake habitats typically produce the vast majority of young alewife recruits. However, tributary habitats may contribute the majority of alewife recruits during years of low recruitment. We suggest that high interannual variation in the relative importance of habitats for recruitment is a common phenomenon, which should be considered when developing habitat management plans for fish populations. ?? 2008 NRC.

Chinook salmon use of spawning patches: Relative roles of habitat quality, size, and connectivity

Treesearch

Daniel J. Isaak; Russell F. Thurow; Bruce E. Rieman; Jason B. Dunham

2007-01-01

Declines in many native fish populations have led to reassessments of management goals and shifted priorities from consumptive uses to species preservation. As management has shifted, relevant environmental characteristics have evolved from traditional metrics that described local habitat quality to characterizations of habitat size and connectivity. Despite the...

Biotic and abiotic factors related to lake herring recruitment in the Wisconsin waters of Lake Superior, 1984-1998

USGS Publications Warehouse

Hoff, Michael H.

2004-01-01

Lake Superior lake herring (Coregonus artedi) recruitment to 13-14 months of age in the Wisconsin waters of Lake Superior varied by a factor of 5,233 during 1984-1998. Management agencies have sought models that accurately predict recruitment, but no satisfactory model had previously been developed. Lake herring recruitment was modeled to determine which factors most explained recruitment variability. The Ricker stock-recruitment model derived from only the paired stock and recruit data explained 35% of the variability in the recruitment data. The functional relationship that explained the greatest amount of recruitment variation (93%) included lake herring stock size, lake trout (Salvelinus namaycush) population size, slimy sculpin (Cottus cognatus) biomass, the interaction of mean daily wind speed in April (month of hatch) and lake herring stock size, and mean air temperature in April (when lake herring are 12-months old). Model results were interpreted to mean that lake herring recruitment was affected negatively by: slimy sculpin predation on lake herring ova; predation on age-0 lake herring by lake trout; and adult cannibalism on lake herring larvae, which was reduced by increased wind speed. April temperature was the variable that explained the least amount of variability in recruitment, but lake herring recruitment was positively affected by a warm April, which shortened winter and apparently reduced first-winter mortality. Stock size caused compensatory, density-dependent mortality on lake herring recruits. Management efforts appear best targeted at stock size protection, and empirical data implies that stock size in the Wisconsin waters of the lake should be maintained at 2.1-15.0 adults/ha in spring, bottom-trawl surveys.

Size of age-0 crappies (Pomoxis spp.) relative to reservoir habitats and water levels

USGS Publications Warehouse

Kaczka, Levi J.; Miranda, Leandro E.

2014-01-01

Variable year-class strength is common in crappie Pomoxis spp. populations in many reservoirs, yet the mechanisms behind this variability are poorly understood. Size-dependent mortality of age-0 fishes has long been recognized in the population ecology literature; however, investigations about the effects of environmental factors on age-0 crappie size are lacking. The objective of this study was to determine if differences existed in total length of age-0 crappies between embayment and floodplain habitats in reservoirs, while accounting for potential confounding effects of water level and crappie species. To this end, we examined size of age-0 crappies in four flood-control reservoirs in northwest Mississippi over 4years. Age-0 crappies inhabiting uplake floodplain habitats grew to a larger size than fish in downlake embayments, but this trend depended on species, length of time a reservoir was dewatered in the months preceding spawning, and reservoir water level in the months following spawning. The results from our study indicate that water-level management may focus not only on allowing access to quality nursery habitat, but that alternating water levels on a multiyear schedule could increase the quality of degraded littoral habitats.

Evaluation of removal of the size effect using data scaling and elliptic Fourier descriptors in otolith shape analysis, exemplified by the discrimination of two yellow croaker stocks along the Chinese coast

NASA Astrophysics Data System (ADS)

Zhao, Bo; Liu, Jinhu; Song, Junjie; Cao, Liang; Dou, Shuozeng

2017-11-01

Removal of the length effect in otolith shape analysis for stock identification using length scaling is an important issue; however, few studies have attempted to investigate the effectiveness or weakness of this methodology in application. The aim of this study was to evaluate whether commonly used size scaling methods and normalized elliptic Fourier descriptors (NEFDs) could effectively remove the size effect of fish in stock discrimination. To achieve this goal, length groups from two known geographical stocks of yellow croaker, Larimichthys polyactis, along the Chinese coast (five groups from the Changjiang River estuary of the East China Sea and three groups from the Bohai Sea) were subjected to otolith shape analysis. The results indicated that the variation of otolith shape caused by intra-stock fish length might exceed that due to inter-stock geographical separation, even when otolith shape variables are standardized with length scaling methods. This variation could easily result in misleading stock discrimination through otolith shape analysis. Therefore, conclusions about fish stock structure should be carefully drawn from otolith shape analysis because the observed discrimination may primarily be due to length effects, rather than differences among stocks. The application of multiple methods, such as otoliths shape analysis combined with elemental fingering, tagging or genetic analysis, is recommended for sock identification.

Yakima/Klickitat Fisheries Project Genetic Studies; Yakima/Klickitat Fisheries Project Monitoring and Evaluation Report 1 of 7, 2003-2004 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Busack, Craig A.; Frye, Alice; Kassler, Todd

2004-05-01

Genetic work for 2003, as in previous years, was quite diverse. In chapter 1 we report on the use of DNA microsatellite markers to sex spring chinook collected at Roza. We have learned through comparison of sex determinations at Roza and then at CESRF that sexing green fish on the basis of morphology is somewhat inaccurate, and accurate sexing of fish at Roza is needed to estimate sex ratios of fish on the spawning grounds. Using DNA microsatellite markers, sexing accuracy was high, but not perfect. In chapter 2 we report on new genetic risk concepts currently being developed andmore » their implications for the YKFP spring chinook program. The impact on domestication of gene flow between the natural and hatchery spawning components is now much better understood. It is now possible to compare the risk of different hatchery programs much more quantitatively in the past. Thus, we can now make good predictions of how much less domesticating the Yakima spring chinook supplementation effort is than other programs. In chapter 3 we present the initial results of morphological comparisons of adult (1) hatchery-origin Upper Yakima spring chinook, (2) natural-origin U. Yakima spring chinook, and (3) Naches spring chinook. Canonical variate analysis allowed both sexes of the three groups to be classified correctly with over accuracy. The differences are subtle, but hatchery-origin fish appear to be someone thinner than natural-origin fish. This is consistent with observations of hatchery vs wild morphology in coho. In chapter 4 we describe the ongoing work to refine the Domestication Research/Monitoring Plan. Work for last year included analysis of the impact of HC line precocious males spawning in the wild, development of a misting incubation system for off-site incubation of Naches eggs, and refinement of some aspects of experimental design. The misting incubation system has broad applicability outside the project. The most recent version of the domestication monitoring plan is included as an appendix. In chapter 5 we present a final report on computer simulations of factorial mating designs. Using three different schemes for combining breeding values of fish, we found that full factorial mating offers a substantial increase in effective size over single-pair mating. Although full factorial mating may be too difficult logistically, but a significant proportion of the full factorial mating advantage can be obtained by using 2 x 2 partial factorials. We have developed a method that allows us to determine the relative effective size advantage of mixed partial factorial designs. In chapter 6 we report on an analysis of stock origin of smolts collected at Chandler. The 702 Chinook salmon smolts collected at the Chandler trap in 2003 were screened at 12 microsatellite DNA loci. A new Yakima basin baseline, consisting of spring chinook from the upper Yakima, Naches, and American River populations and fall chinook from the Marion Drain and lower Yakima populations, was created for these same 12 loci. DNA template problems with the tissue collections from the Naches, and American River populations prompted the omission of four loci prior to analysis. The results indicated: 80% Naches spring, 13% American River spring, 7% upper Yakima spring, and less than 1% for the two fall populations combined. The estimated stock proportions in the 2003 Chandler collection differed substantially from those for the 2002 collection. The temporal pattern of sampling in both Chandler smolt collections was not proportional to the observed outmigration in each year, suggesting that both of these estimates should be regarded with caution. Strengthening of the baseline data set will be a high priority for future work with Chandler smolts.« less

[Reproduction of the fish Brotula clarkae (Pisces: Ophidiidae) in the Colombian Pacific].

PubMed

Acevedo, Jenny; Angulo, Wilberto; Ramírez, Manuel; Zapata, Luis A

2007-01-01

We studied the reproductive ecology of the fish Brotula clarkae based on 754 individuals obtained from the industrial and artisanal fisheries in the Colombian Pacific (March 1994 to December 1996). Histological sections (paraplast embedding and Harris's hematoxylin-eosin stain) were made from 151 females (26-100 cm total length). Additionally, mean diameter and particular features are described for oocyte phases and ovarian development stages. The mean size at initial sexual maturity of females was determined with two methods (graphic and statistic) in 61.3 cm and 62.3 cm respectively. The general sex ratio was 1:1. There are several spawn pulses between May and October. The mean fecundity by spawn pulse was 1,005,657 eggs. We recommend a fishing ban during the reproduction period and a minimal catch size above 62.3 cm.

Lack of Healthy Food in Small-Size to Mid-Size Retailers Participating in the Supplemental Nutrition Assistance Program, Minneapolis-St. Paul, Minnesota, 2014.

PubMed

Laska, Melissa N; Caspi, Caitlin E; Pelletier, Jennifer E; Friebur, Robin; Harnack, Lisa J

2015-08-27

The US Department of Agriculture has stocking criteria for healthy foods among Supplemental Nutrition Assistant Program (SNAP)-authorized retailers. Increased access to healthy food could improve diet quality among SNAP participants, which has implications for chronic disease prevention. The objective of this study was to quantify healthy foods stocked in small-size to mid-size retailers who are authorized under SNAP but not under the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). We used formative, cross-sectional data from a large policy evaluation to conduct secondary analyses. Store audits were conducted in 2014 in 91 randomly selected, licensed food stores in Minneapolis and St. Paul, Minnesota. Supermarkets and retailers participating in WIC, which are required to stock healthy foods, were excluded as were other stores not reasonably expected to stock staple foods, such as specialty stores or produce stands. Availability of milk, fruits, vegetables, and whole-grain-rich foods was assessed. The 91 stores studied were corner stores, food-gas marts, dollar stores, and pharmacies. More than half carried 1 or more varieties of fat-free or low-fat milk, fresh or canned fruit, and whole-grain-rich cereal. However, only one-third stocked 1 or more varieties of fresh vegetables and only one-quarter stocked whole-grain-rich products, such as whole-grain-rich bread (26%) or tortillas (21%) or brown rice (25%). Few stores stocked at least 2 varieties of each product. Many stores did not stock a variety of healthy foods. The US Department of Agriculture should change policies to improve minimum stocking requirements for SNAP-authorized retailers.

Lack of Healthy Food in Small-Size to Mid-Size Retailers Participating in the Supplemental Nutrition Assistance Program, Minneapolis–St. Paul, Minnesota, 2014

PubMed Central

Caspi, Caitlin E.; Pelletier, Jennifer E.; Friebur, Robin; Harnack, Lisa J.

2015-01-01

Introduction The US Department of Agriculture has stocking criteria for healthy foods among Supplemental Nutrition Assistant Program (SNAP)-authorized retailers. Increased access to healthy food could improve diet quality among SNAP participants, which has implications for chronic disease prevention. The objective of this study was to quantify healthy foods stocked in small-size to mid-size retailers who are authorized under SNAP but not under the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). Methods We used formative, cross-sectional data from a large policy evaluation to conduct secondary analyses. Store audits were conducted in 2014 in 91 randomly selected, licensed food stores in Minneapolis and St. Paul, Minnesota. Supermarkets and retailers participating in WIC, which are required to stock healthy foods, were excluded as were other stores not reasonably expected to stock staple foods, such as specialty stores or produce stands. Availability of milk, fruits, vegetables, and whole-grain–rich foods was assessed. Results The 91 stores studied were corner stores, food–gas marts, dollar stores, and pharmacies. More than half carried 1 or more varieties of fat-free or low-fat milk, fresh or canned fruit, and whole-grain–rich cereal. However, only one-third stocked 1 or more varieties of fresh vegetables and only one-quarter stocked whole-grain–rich products, such as whole-grain-rich bread (26%) or tortillas (21%) or brown rice (25%). Few stores stocked at least 2 varieties of each product. Conclusions Many stores did not stock a variety of healthy foods. The US Department of Agriculture should change policies to improve minimum stocking requirements for SNAP-authorized retailers. PMID:26312380

Impacts of Cropping Systems on Aggregates Associated Organic Carbon and Nitrogen in a Semiarid Highland Agroecosystem

PubMed Central

Chu, Jiashu; Zhang, Tianzhe; Chang, Weidong; Zhang, Dan; Zulfiqar, Saman; Fu, Aigen; Hao, Yaqi

2016-01-01

The effect of cropping system on the distribution of organic carbon (OC) and nitrogen (N) in soil aggregates has not been well addressed, which is important for understanding the sequestration of OC and N in agricultural soils. We analyzed the distribution of OC and N associated with soil aggregates in three unfertilized cropping systems in a 27-year field experiment: continuously cropped alfalfa, continuously cropped wheat and a legume-grain rotation. The objectives were to understand the effect of cropping system on the distribution of OC and N in aggregates and to examine the relationships between the changes in OC and N stocks in total soils and in aggregates. The cropping systems increased the stocks of OC and N in total soils (0–40 cm) at mean rates of 15.6 g OC m-2 yr-1 and 1.2 g N m-2 yr-1 relative to a fallow control. The continuous cropping of alfalfa produced the largest increases at the 0–20 cm depth. The OC and N stocks in total soils were significantly correlated with the changes in the >0.053 mm aggregates. 27-year of cropping increased OC stocks in the >0.053 mm size class of aggregates and N stocks in the >0.25 mm size class but decreased OC stocks in the <0.053 mm size class and N stocks in the <0.25 mm size class. The increases in OC and N stocks in these aggregates accounted for 99.5 and 98.7% of the total increases, respectively, in the continuous alfalfa system. The increases in the OC and N stocks associated with the >0.25 mm aggregate size class accounted for more than 97% of the total increases in the continuous wheat and the legume-grain rotation systems. These results suggested that long-term cropping has the potential to sequester OC and N in soils and that the increases in soil OC and N stocks were mainly due to increases associated with aggregates >0.053 mm. PMID:27764209

Dynamics and fishery of the Peruvian hake: Between nature and man

NASA Astrophysics Data System (ADS)

Guevara-Carrasco, Renato; Lleonart, Jordi

Mean length in the catch of Peruvian hake ( Merluccius gayi peruanus) declined drastically by 8 cm in a few months in 1992. The 1991-93 El Niño event marked the beginning of changes in bottom environmental conditions, that along with other changes in the ecosystem, were the cause of the disappearance of large sized old hake from the traditional fishing grounds and the invasion of these areas by high concentrations of small sized young hake, traditionally distributed in the southern areas. A misinterpretation of this change gave an optimistic perception of the state of the stock, leading to a large increase of the fishing fleet and therefore to an increase of the fishing pressure on this resource. Catch increased quickly to very high levels in 1996, the fishery indicators of relative abundance remained stable, while global abundance of hake was diminishing. The resource responded to these natural variations of environment and to the intense fishing pressure with changes in some aspects of its biology and ecology. The most remarkable was the decrease of the length and age at first maturity that led to spawning by 1 year old (19 cm) individuals in a species whose observed longevity was 14 years. In 2002 a total and indefinite fishery closure was established by the Peruvian government and a technical commission for the hake recovery was created, which carried out continuous monitoring of the stock. After a closure of 20 months the indicators showed signs of recovery and the fishery was reopened in 2004. However, after an encouraging beginning during 2004 and the first quarter of 2005, neither abundance nor age structure had improved by the end of 2005, and in fact were deteriorating by the start of 2006. The survival of the age 2 and 3 groups was very low and few 4+ years old individuals were observed. Several factors working at different time scales have been proposed to explain the status of hake. The impact of the fishery, variations in the abiotic environment, predation by the jumbo squid ( Dosidicus gigas) and cannibalism were considered as potential causal factors of this decline.

Goliath catfish spawning in the far western Amazon confirmed by the distribution of mature adults, drifting larvae and migrating juveniles

PubMed Central

Barthem, Ronaldo B.; Goulding, Michael; Leite, Rosseval G.; Cañas, Carlos; Forsberg, Bruce; Venticinque, Eduardo; Petry, Paulo; Ribeiro, Mauro L. de B.; Chuctaya, Junior; Mercado, Armando

2017-01-01

We mapped the inferred long-distance migrations of four species of Amazonian goliath catfishes (Brachyplatystoma rousseauxii, B. platynemum, B. juruense and B. vaillantii) based on the presence of individuals with mature gonads and conducted statistical analysis of the expected long-distance downstream migrations of their larvae and juveniles. By linking the distribution of larval, juvenile and mature adult size classes across the Amazon, the results showed: (i) that the main spawning regions of these goliath catfish species are in the western Amazon; (ii) at least three species—B. rousseauxii, B. platynemum, and B. juruense—spawn partially or mainly as far upstream as the Andes; (iii) the main spawning area of B. rousseauxii is in or near the Andes; and (iv) the life history migration distances of B. rousseauxii are the longest strictly freshwater fish migrations in the world. These results provide an empirical baseline for tagging experiments, life histories extrapolated from otolith microchemistry interpretations and other methods to establish goliath catfish migratory routes, their seasonal timing and possible return (homing) to western headwater tributaries where they were born. PMID:28165499

A Mixed-Method Approach for Quantifying Illegal Fishing and Its Impact on an Endangered Fish Species.

PubMed

Free, Christopher M; Jensen, Olaf P; Mendsaikhan, Bud

2015-01-01

Illegal harvest is recognized as a widespread problem in natural resource management. The use of multiple methods for quantifying illegal harvest has been widely recommended yet infrequently applied. We used a mixed-method approach to evaluate the extent, character, and motivations of illegal gillnet fishing in Lake Hovsgol National Park, Mongolia and its impact on the lake's fish populations, especially that of the endangered endemic Hovsgol grayling (Thymallus nigrescens). Surveys for derelict fishing gear indicate that gillnet fishing is widespread and increasing and that fishers generally use 3-4 cm mesh gillnet. Interviews with resident herders and park rangers suggest that many residents fish for subsistence during the spring grayling spawning migration and that some residents fish commercially year-round. Interviewed herders and rangers generally agree that fish population sizes are decreasing but are divided on the causes and solutions. Biological monitoring indicates that the gillnet mesh sizes used by fishers efficiently target Hovsgol grayling. Of the five species sampled in the monitoring program, only burbot (Lota lota) showed a significant decrease in population abundance from 2009-2013. However, grayling, burbot, and roach (Rutilus rutilus) all showed significant declines in average body size, suggesting a negative fishing impact. Data-poor stock assessment methods suggest that the fishing effort equivalent to each resident family fishing 50-m of gillnet 11-15 nights per year would be sufficient to overexploit the grayling population. Results from the derelict fishing gear survey and interviews suggest that this level of effort is not implausible. Overall, we demonstrate the ability for a mixed-method approach to effectively describe an illegal fishery and suggest that these methods be used to assess illegal fishing and its impacts in other protected areas.

A Mixed-Method Approach for Quantifying Illegal Fishing and Its Impact on an Endangered Fish Species

PubMed Central

Free, Christopher M.; Jensen, Olaf P.; Mendsaikhan, Bud

2015-01-01

Illegal harvest is recognized as a widespread problem in natural resource management. The use of multiple methods for quantifying illegal harvest has been widely recommended yet infrequently applied. We used a mixed-method approach to evaluate the extent, character, and motivations of illegal gillnet fishing in Lake Hovsgol National Park, Mongolia and its impact on the lake’s fish populations, especially that of the endangered endemic Hovsgol grayling (Thymallus nigrescens). Surveys for derelict fishing gear indicate that gillnet fishing is widespread and increasing and that fishers generally use 3–4 cm mesh gillnet. Interviews with resident herders and park rangers suggest that many residents fish for subsistence during the spring grayling spawning migration and that some residents fish commercially year-round. Interviewed herders and rangers generally agree that fish population sizes are decreasing but are divided on the causes and solutions. Biological monitoring indicates that the gillnet mesh sizes used by fishers efficiently target Hovsgol grayling. Of the five species sampled in the monitoring program, only burbot (Lota lota) showed a significant decrease in population abundance from 2009–2013. However, grayling, burbot, and roach (Rutilus rutilus) all showed significant declines in average body size, suggesting a negative fishing impact. Data-poor stock assessment methods suggest that the fishing effort equivalent to each resident family fishing 50-m of gillnet 11–15 nights per year would be sufficient to overexploit the grayling population. Results from the derelict fishing gear survey and interviews suggest that this level of effort is not implausible. Overall, we demonstrate the ability for a mixed-method approach to effectively describe an illegal fishery and suggest that these methods be used to assess illegal fishing and its impacts in other protected areas. PMID:26625154

Identifying and Quantifying Sources of Fall Chinook Salmon Spawning Gravel to the Snake River in Hells Canyon

NASA Astrophysics Data System (ADS)

Welcker, C. W.; Burke, M.

2015-12-01

The Snake River in Hells Canyon supports a growing population of spawning Fall Chinook Salmon (Oncorhynchus tshawytscha) immediately downstream of the Hells Canyon Complex (HCC) of hydroelectric dams for the last 60 years. The long-term survival of this salmon run depends on the input of spawning gravel (25-150 mm) from local tributaries balancing the losses of spawning gravel through attrition and export out of the reach between the HCC and the Salmon River confluence. We are working to quantify the gravel input of these local tributaries at different time-scales and put this into the context of historical supply and transport. Long-term total sediment production rates of these tributaries estimated through various methods have varied by over 2 orders of magnitude, but we have recently completed 10Be work to constrain these estimates. We are measuring the change in storage of Fall Chinook spawning-size gravel through repeat multibeam echosounder surveys of the riverbed. The limited amount of repeat data collected to date has shown complex patterns of change in the riverbed. One possible driver of this complexity is the episodic and spatially variable nature of sediment inputs from these tributaries. We are attempting to quantify the frequency of the debris flows or floods capable of transporting spawning gravel through digitizing historic imagery of the last 60 years to determine the recurrence interval. We are measuring the magnitude of these events by surveying tributary fans pre and post-event to measure the sediment volume and particle size produced by specific events. These floods and debris flows are driven by extreme rainfall or snowmelt events, so we have also reconstructed historical meteorological conditions to identify the triggering conditions for transport, and identify the areas where snowmelt or rainfall is the more likely trigger. We are currently testing whether the unique bedrock geology of Hells Canyon can be used as a tracer to identify the source areas and downstream transport of sediment in the canyon. While the HCC has trapped gravel transported from the Snake River immediately upstream, this input has been quite low due to particle attrition across long transport distances and low transport capacity of the reach just upstream of the HCC.

Stocking, Forest Type, and Stand Size Class - The Southern Forest Inventory and Analysis Unit's Calculation of Three Important Stand Descriptors

Treesearch

Dennis M. May

1990-01-01

The procedures by which the Southern Forest Inventory and Analysis unit calculates stocking from tree data collected on inventory sample plots are described in this report. Stocking is then used to ascertain two other important stand descriptors: forest type and stand size class. Inventory data for three plots from the recently completed 1989 Tennessee survey are used...

Evaluating the potential for stock size to limit recruitment in largemouth bass

USGS Publications Warehouse

Allen, Michael S.; Rogers, Mark W.; Catalano, Mathew J.; Gwinn, Daniel G.; Walsh, Stephen J.

2011-01-01

Compensatory changes in juvenile survival allow fish stocks to maintain relatively constant recruitment across a wide range of stock sizes (and levels of fishing), but few studies have experimentally explored recruitment compensation in fish populations. We evaluated the potential for recruitment compensation in largemouth bass Micropterus salmoides by stocking six 0.4-ha hatchery ponds with adult densities ranging from 6 to 40 fish over 2 years. Ponds were drained in October each year, and the age-0 fish densities were used as a measure of recruitment. We found no relationship between stock abundance and recruitment; ponds with low adult densities produced nearly as many recruits as the higher-density ponds in some cases. Both prey abundance and the growth of age-0 largemouth bass declined with age-0 fish density. Recruit abundance was highly variable both within and among the adult density groups, and thus we were unable to identify a clear stock–recruit relationship for largemouth bass. Our results indicate that reducing the number of effective spawners via angling practices would not reduce recruitment over a relatively large range in stock size.

Effect of horseshoe crab spawning density on nest disturbance and exhumation of eggs: A simulation study

USGS Publications Warehouse

Smith, D.R.

2007-01-01

Because the Delaware Bay horseshoe crab (Limulus polyphemus) population is managed to provide for dependent species, such as migratory shorebirds, there is a need to understand the process of egg exhumation and to predict eggs available to foraging shorebirds. A simple spatial model was used to simulate horseshoe crab spawning that would occur on a typical Delaware Bay beach during spring tide cycles to quantify density-dependent nest disturbance. At least 20% of nests and eggs were disturbed for levels of spawning greater than one third of the average density in Delaware Bay during 2004. Nest disturbance increased approximately linearly as spawning density increased from one half to twice the 2004 level. As spawning density increased further, the percentage of eggs that were disturbed reached an asymptote of 70% for densities up to 10 times the density in 2004. Nest disturbance was heaviest in the mid beach zone. Nest disturbance precedes entrainment and begins the process of exhumation of eggs to surface sediments. Model predictions were combined with observations from egg surveys to estimate a snap-shot exhumation rate of 5-9% of disturbed eggs. Because an unknown quantity of eggs were exhumed and removed from the beach prior to the survey, cumulative exhumation rate was likely to have been higher than the snap-shot estimate. Because egg exhumation is density-dependent, in addition to managing for a high population size, identification and conservation of beaches where spawning horseshoe crabs concentrate in high densities (i.e., hot spots) are important steps toward providing a reliable food supply for migratory shorebirds. ?? 2007 Estuarine Research Federation.

Hungry Horse Dam Fisheries Mitigation; Kokanee Stocking and Monitoring in Flathead Lake, 1995 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fredenberg, Wade; Carty, Daniel; Cavigli, Jon

1996-06-01

The operation of Hungry Horse Dam on the South Fork-of the Flathead River reduced the reproductive success of kokanee (Oncorhynchus nerka) spawning in the Flathead River. Montana Fish, Wildlife and Parks (MFWP) and the Confederated Salish and Kootenai Tribes (CSKT) authored a mitigation plan to offset those losses. The mitigation goal, stated in the Fisheries Mitigation Plan for Losses Attributed to the Construction and Operation of Hungry Horse Dam, is to: {open_quotes}Replace lost annual production of 100,000 kokanee adults, initially through hatchery production and pen rearing in Flathead Lake, partially replacing lost forage for lake trout (Salvelinus namaycush) in Flatheadmore » Lake.{close_quotes}« less

Spring-summer movements of bonytail in a Colorado River reservoir, Lake Mohave, Arizona and Nevada

USGS Publications Warehouse

Marsh, Paul C.; Mueller, Gordon

1999-01-01

Bonytail can move substantial distances in a short time (10s of km in a few days). Fish in both years apparently favored the same areas, where they may remain for weeks. Unmarked bonytail were observed or captured by setting nets in places favored by tagged fish, a significant result since future use of the technique may enhance our ability to monitor reintroductions, locate and document spawning, examine habitat use, and acquire desperately needed brood stock for this critically imperiled species. External tagging techniques developed for juvenile razorback sucker may provide a method of minimizing telemetry induced stress while allowing us to focus sampling on congregation sites.

Assessing conditions influencing the longitudinal distribution of exotic brown trout (Salmo trutta) in a mountain stream: a spatially-explicit modeling approach

USGS Publications Warehouse

Meredith, Christy S.; Budy, Phaedra; Hooten, Mevin B.; Oliveira Prates, Marcos

2017-01-01

Trout species often segregate along elevational gradients, yet the mechanisms driving this pattern are not fully understood. On the Logan River, Utah, USA, exotic brown trout (Salmo trutta) dominate at low elevations but are near-absent from high elevations with native Bonneville cutthroat trout (Onchorhynchus clarkii utah). We used a spatially-explicit Bayesian modeling approach to evaluate how abiotic conditions (describing mechanisms related to temperature and physical habitat) as well as propagule pressure explained the distribution of brown trout in this system. Many covariates strongly explained redd abundance based on model performance and coefficient strength, including average annual temperature, average summer temperature, gravel availability, distance from a concentrated stocking area, and anchor ice-impeded distance from a concentrated stocking area. In contrast, covariates that exhibited low performance in models and/or a weak relationship to redd abundance included reach-average water depth, stocking intensity to the reach, average winter temperature, and number of days with anchor ice. Even if climate change creates more suitable summer temperature conditions for brown trout at high elevations, our findings suggest their success may be limited by other conditions. The potential role of anchor ice in limiting movement upstream is compelling considering evidence suggesting anchor ice prevalence on the Logan River has decreased significantly over the last several decades, likely in response to climatic changes. Further experimental and field research is needed to explore the role of anchor ice, spawning gravel availability, and locations of historical stocking in structuring brown trout distributions on the Logan River and elsewhere.

Differences in Ichthyophonus prevalence and infection severity between upper Yukon River and Tanana River chinook salmon, Oncorhynchus tshawytscha (Walbaum), stocks

USGS Publications Warehouse

Kocan, R.; Hershberger, P.

2006-01-01

Two genetically distinct populations of chinook salmon, Oncorhynchus tshawytscha (Walbaum), were simultaneously sampled at the confluence of the Yukon and Tanana rivers in 2003. Upper Yukon-Canadian fish had significantly higher infection prevalence as well as more severe infections (higher parasite density in heart tissue) than the lower Yukon-Tanana River fish. Both populations had migrated the same distance from the mouth of the Yukon River at the time of sampling but had significantly different distances remaining to swim before reaching their respective spawning grounds. Multiple working hypotheses are proposed to explain the differences between the two stocks: (1) the two genetically distinct populations have different inherent resistance to infection, (2) genetically influenced differences in feeding behaviour resulted in temporal and/or spatial differences in exposure, (3) physiological differences resulting from different degrees of sexual maturity influenced the course of disease, and (4) the most severely infected Tanana River fish either died en route or fatigued and were unable to complete their migration to the Tanana River, thus leaving a population of apparently healthier fish. ?? 2006 Blackwell Publishing Ltd.

Severe tissue damage in Atlantic cod larvae under increasing ocean acidification

NASA Astrophysics Data System (ADS)

Frommel, Andrea Y.; Maneja, Rommel; Lowe, David; Malzahn, Arne M.; Geffen, Audrey J.; Folkvord, Arild; Piatkowski, Uwe; Reusch, Thorsten B. H.; Clemmesen, Catriona

2012-01-01

Ocean acidification, caused by increasing atmospheric concentrations of CO2 (refs , , ), is one of the most critical anthropogenicthreats to marine life. Changes in seawater carbonate chemistry have the potential to disturb calcification, acid-base regulation, blood circulation and respiration, as well as the nervous system of marine organisms, leading to long-term effects such as reduced growth rates and reproduction. In teleost fishes, early life-history stages are particularly vulnerable as they lack specialized internal pH regulatory mechanisms. So far, impacts of relevant CO2 concentrations on larval fish have been found in behaviour and otolith size, mainly in tropical, non-commercial species. Here we show detrimental effects of ocean acidification on the development of a mass-spawning fish species of high commercial importance. We reared Atlantic cod larvae at three levels of CO2, (1) present day, (2) end of next century and (3) an extreme, coastal upwelling scenario, in a long-term ( months) mesocosm experiment. Exposure to CO2 resulted in severe to lethal tissue damage in many internal organs, with the degree of damage increasing with CO2 concentration. As larval survival is the bottleneck to recruitment, ocean acidification has the potential to act as an additional source of natural mortality, affecting populations of already exploited fish stocks.

Reproduction and early-life accommodations of landlocked alewives to a southern range extension

USGS Publications Warehouse

Nigro, A.A.; Ney, John J.

1982-01-01

Reproduction and first-year growth and food habits of landlocked alewives Alosa pseudoharengus in Claytor Lake, Virginia were examined and compared to descriptions for populations in the species' established New England-Great Lakes range. Alewives in mesothermal (2–27 C) Claytor Lake are shorter-lived (3 years) but grow faster, mature earlier (age 1), and have higher relative and absolute fecundities than have been reported for populations in colder northern waters. The 1979 spawning period extended from early May to early August, beginning at least 1 month earlier and lasting 4–9 weeks longer than in northern lakes. Changes in ovary condition during the spawning period suggest that alewives may be fractional spawners. Evidence of spawning was found in littoral areas throughout the lower 15 km of the reservoir. Growth in length of age-0 Claytor Lake alewives was linear through September and terminated in late autumn. Total first-year growth was reduced in 1979 (maximum of 130 mm total length, TL) from previous years (average of 160 mm TL), although it was substantially greater than recorded in the Great Lakes and the northeastern United States. The longer growing season, rather than accelerated in-season growth, appears to account for larger size achieved in Claytor Lake. High annual growth limits predation by Claytor Lake game fish on early spawned age-0 alewives by late summer. As elsewhere, larval and juvenile alewives (6–70 mm TL) fed primarily on copepods and cladocerans. Age-0 alewives longer than 35 mm TL demonstrated positive size-selection for cyclopoid copepods comparable to that shown by adults. Our findings suggest that self-sustaining alewife populations can be established in many inland waters but raise concerns regarding their forage value and community impacts.

The influence of photoperiod and temperature on the Neosho Madtom (norturus placidus) reproductive cycle

USGS Publications Warehouse

Albers, J.L.; Wildhaber, M.L.; Noltie, Douglas B.

2001-01-01

The key to successful fish culture is to understand the environmental cues that trigger spawning. In temperate fishes, photoperiod and temperature are important in many species including the family Ictaluridae. The object of this study was to examine whether natural photo-thermal conditions in the laboratory could stimulate the reproductive cycle of Neosho madtoms (Noturus placidus). For three years a small population of Neosho madtoms were maintained under natural conditions and continually sampled using ultrasound to examine interior gonad state and exterior body measurements. The purpose was to examine the secondary sexual characteristics that normally occur during the spawning period. Every year the fish cycled in and out of spawning condition, including production and reabsorbtion of eggs. The best external measurement found to distinguish between sexes was the ratio of head length to total length. Internal measurements found the average number of eggs per female increased as the fish length increased and over time but the average sizes of the eggs were constant. After years in the simulated environment 13 different fish were involved in ten spawns. The use of ultrasound to examine gonad in madtoms is promising, especially the lack of injury associated with the procedure. Overall laboratory conditions that simulated the natural photo-thermal environment, especially daily temperature fluctuations, were successful at stimulating the reproductive cycle of Neosho madtoms including egg cycling and spawning. These results show promise towards culture of madtoms especially for those species that are rare and endangered.

Oncorhynchus nerka population monitoring in the Sawtooth Valley Lakes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teuscher, D.M.; Taki, D.; Ariwite, K.

1996-05-01

Critical habitat for endangered Snake River sockeye salmon includes five rearing lakes located in the Sawtooth Valley of central Idaho. Most of the lakes contain either introduced or endemic kokanee populations. Snake River sockeye occur naturally in Redfish Lake, and are being stocked in Redfish and Pettit Lakes. Because kokanee compete with sockeye for limited food resources, understanding population characteristics of both species such as spawn timing, egg-to-fry survival, distribution and abundance are important components of sockeye recovery. This chapter describes some of those characteristics. In 1995, hydroacoustic estimates of O. nerka densities in the Sawtooth Valley Lakes ranged frommore » 57 to 465 fish/ha. Densities were greatest in Pettit followed by Redfish (167), Alturas (95), and Stanley Lakes. O. nerka numbers increased from 1994 values in Pettit and Alturas Lakes, but declined in Redfish and Stanley. Despite a decline in total lake abundance, O. nerka biomass estimates in Redfish Lake increased. Approximately 144,000 kokanee fry recruited to Redfish Lake from Fishhook Creek. O. nerka fry recruitment to Stanley and Alturas lake was 5,000 and 30,000 fry, respectively. Egg-to-fry survival was 14% in Fishhook and 7% in Stanley Lake Creek. In Fishhook Creek, kokanee spawning escapement was estimated using stream surveys and a weir. Escapement estimates were 4,860 from weir counts, and 7,000 from stream surveys. As part of the kokanee reduction program, 385 of the spawning female kokanee were culled. Escapement for Stanley Lake Creek was only 60 fish, a ten fold decrease from 1994. In Alturas Lake, kokanee spawners dropped by 50% to 1,600.« less

Snake River Sockeye Salmon Habitat and Limnological Research : 2008 Annual Progress Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kohler, Andre E.; Griswold, Robert G.; Taki, Doug

2009-07-31

In March 1990, the Shoshone-Bannock Tribes petitioned the National Marine Fisheries Service (NMFS) to list Snake River sockeye salmon (Oncorhynchus nerka) as endangered. Snake River sockeye salmon were officially listed as endangered in November 1991 under the Endangered Species Act (56 FR 58619). In 1991, the Snake River Sockeye Salmon Habitat and Limnological Research Project was implemented. This project is part of an interagency effort to prevent the extinction of the Redfish Lake stock of Snake River sockeye salmon. The Shoshone-Bannock Tribal goal for this project is two tiered: the immediate goal is to increase the population of Snake Rivermore » sockeye salmon while preserving the unique genetic characteristics of the evolutionarily significant unit (ESU). The Tribes long term goal is to maintain a viable population that warrants delisting and provides Tribal harvest opportunities. The Bonneville Power Administration (BPA) provides funding for this interagency Recovery effort. Collaborators in the recovery effort include the National Oceanic and Atmospheric Administration (NOAA), the Idaho Department of Fish and Game (IDFG), the University of Idaho (UI), and the Shoshone-Bannock Tribes (SBT). This report summarizes activities conducted by Shoshone-Bannock Tribal Fisheries Department personnel during the 2008 calendar year. Project tasks include: (1) monitor limnological parameters of the Sawtooth Valley lakes to assess lake productivity; (2) conduct lake fertilization in Pettit and Alturas lakes; (3) reduce the number of mature kokanee salmon spawning in Alturas Lake Creek; (4) monitor, enumerate, and evaluate sockeye salmon smolt migration from Pettit and Alturas lakes; (5) monitor spawning kokanee salmon escapement and estimate fry recruitment in Fishhook and Alturas Lake creeks; (6) conduct sockeye and kokanee salmon population surveys; (7) evaluate potential competition and predation between stocked juvenile sockeye salmon and a variety of fish species in Redfish, Pettit, and Alturas lakes; and (8) assist IDFG with captive broodstock production activities.« less

Matching watershed and otolith chemistry to establish natal origin of an endangered desert lake sucker

USGS Publications Warehouse

Strohm, Deanna D.; Budy, Phaedra; Crowl, Todd A.

2017-01-01

Stream habitat restoration and supplemental stocking of hatchery-reared fish have increasingly become key components of recovery plans for imperiled freshwater fish; however, determining when to discontinue stocking efforts, prioritizing restoration areas, and evaluating restoration success present a conservation challenge. In this study, we demonstrate that otolith microchemistry is an effective tool for establishing natal origin of the June Sucker Chasmistes liorus, an imperiled potamodromous fish. This approach allows us to determine whether a fish is of wild or hatchery origin in order to assess whether habitat restoration enhances recruitment and to further identify areas of critical habitat. Our specific objectives were to (1) quantify and characterize chemical variation among three main spawning tributaries; (2) understand the relationship between otolith microchemistry and tributary chemistry; and (3) develop and validate a classification model to identify stream origin using otolith microchemistry data. We quantified molar ratios of Sr:Ca, Ba:Ca, and Mg:Ca for water and otolith chemistry from three main tributaries to Utah Lake, Utah, during the summer of 2013. Water chemistry (loge transformed Sr:Ca, Ba:Ca, and Mg:Ca ratios) differed significantly across all three spawning tributaries. We determined that Ba:Ca and Sr:Ca ratios were the most important variables driving our classification models, and we observed a strong linear relationship between water and otolith values for Sr:Ca and Ba:Ca but not for Mg:Ca. Classification models derived from otolith element : Ca signatures accurately sorted individuals to their experimental tributary of origin (classification tree: 89% accuracy; random forest model: 91% accuracy) and determined wild versus hatchery origin with 100% accuracy. Overall, this study aids in evaluating the effectiveness of restoration, tracking progress toward recovery, and prioritizing future restoration plans for fishes of conservation concern. Our results have further application, such as identifying subpopulations that provide the greatest reproductive contribution to a metapopulation or finding the reproductive area and origin of invasive fishes.

Feeding Ecology of Northeast Atlantic Mackerel, Norwegian Spring-Spawning Herring and Blue Whiting in the Norwegian Sea.

PubMed

Bachiller, Eneko; Skaret, Georg; Nøttestad, Leif; Slotte, Aril

2016-01-01

The Norwegian spring-spawning (NSS) herring (Clupea harengus), blue whiting (Micromesistius poutassou) and Northeast Atlantic (NEA) mackerel (Scomber scombrus) are extremely abundant pelagic planktivores that feed in the Norwegian Sea (NS) during spring and summer. This study investigated the feeding ecology and diet composition of these commercially important fish stocks on the basis of biological data, including an extensive set of stomach samples in combination with hydrographical data, zooplankton samples and acoustic abundance data from 12 stock monitoring surveys carried out in 2005-2010. Mackerel were absent during the spring, but had generally high feeding overlap with herring in the summer, with a diet mainly based on calanoid copepods, especially Calanus finmarchicus, as well as a similar diet width. Stomach fullness in herring diminished from spring to summer and feeding incidence was lower than that of mackerel in summer. However, stomach fullness did not differ between the two species, indicating that herring maintain an equally efficient pattern of feeding as mackerel in summer, but on a diet that is less dominated by copepods and is more reliant on larger prey. Blue whiting tended to have a low dietary overlap with mackerel and herring, with larger prey such as euphausiids and amphipods dominating, and stomach fullness and feeding incidence increasing with length. For all the species, feeding incidence increased with decreasing temperature, and for mackerel so did stomach fullness, indicating that feeding activity is highest in areas associated with colder water masses. Significant annual effects on diet composition and feeding-related variables suggested that the three species are able to adapt to different food and environmental conditions. These annual effects are likely to have an important impact on the predation pressure on different plankton groups and the carrying capacity of individual systems, and emphasise the importance of regular monitoring of pelagic fish diets.

Multiple SNP Markers Reveal Fine-Scale Population and Deep Phylogeographic Structure in European Anchovy (Engraulis encrasicolus L.)

PubMed Central

Zarraonaindia, Iratxe; Iriondo, Mikel; Albaina, Aitor; Pardo, Miguel Angel; Manzano, Carmen; Grant, W. Stewart; Irigoien, Xabier; Estonba, Andone

2012-01-01

Geographic surveys of allozymes, microsatellites, nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) have detected several genetic subdivisions among European anchovy populations. However, these studies have been limited in their power to detect some aspects of population structure by the use of a single or a few molecular markers, or by limited geographic sampling. We use a multi-marker approach, 47 nDNA and 15 mtDNA single nucleotide polymorphisms (SNPs), to analyze 626 European anchovies from the whole range of the species to resolve shallow and deep levels of population structure. Nuclear SNPs define 10 genetic entities within two larger genetically distinctive groups associated with oceanic variables and different life-history traits. MtDNA SNPs define two deep phylogroups that reflect ancient dispersals and colonizations. These markers define two ecological groups. One major group of Iberian-Atlantic populations is associated with upwelling areas on narrow continental shelves and includes populations spawning and overwintering in coastal areas. A second major group includes northern populations in the North East (NE) Atlantic (including the Bay of Biscay) and the Mediterranean and is associated with wide continental shelves with local larval retention currents. This group tends to spawn and overwinter in oceanic areas. These two groups encompass ten populations that differ from previously defined management stocks in the Alboran Sea, Iberian-Atlantic and Bay of Biscay regions. In addition, a new North Sea-English Channel stock is defined. SNPs indicate that some populations in the Bay of Biscay are genetically closer to North Western (NW) Mediterranean populations than to other populations in the NE Atlantic, likely due to colonizations of the Bay of Biscay and NW Mediterranean by migrants from a common ancestral population. Northern NE Atlantic populations were subsequently established by migrants from the Bay of Biscay. Populations along the Iberian-Atlantic coast appear to have been founded by secondary waves of migrants from a southern refuge. PMID:22860082

Changes in movements of Chinook Salmon between lakes Huron and Michigan after Alewife population collapse

USGS Publications Warehouse

Clark, Richard D.; Bence, James R.; Claramunt, Randall M.; Clevenger, John A.; Kornis, Matthew S.; Bronte, Charles R.; Madenjian, Charles P.; Roseman, Edward

2017-01-01

Alewives Alosa pseudoharengus are the preferred food of Chinook Salmon Oncorhynchus tshawytscha in the Laurentian Great Lakes. Alewife populations collapsed in Lake Huron in 2003 but remained comparatively abundant in Lake Michigan. We analyzed capture locations of coded-wire-tagged Chinook Salmon before, during, and after Alewife collapse (1993–2014). We contrasted the pattern of tag recoveries for Chinook Salmon released at the Swan River in northern Lake Huron and Medusa Creek in northern Lake Michigan. We examined patterns during April–July, when Chinook Salmon were primarily occupied by feeding, and August–October, when the salmon were primarily occupied by spawning. We found evidence that Swan River fish shifted their feeding location from Lake Huron to Lake Michigan after the collapse. Over years, proportions of Swan River Chinook Salmon captured in Lake Michigan increased in correspondence with the Alewife decline in Lake Huron. Mean proportions of Swan River fish captured in Lake Michigan were 0.13 (SD = 0.14) before collapse (1993–1997) and 0.82 (SD = 0.22) after collapse (2008–2014) and were significantly different. In contrast, proportions of Medusa Creek fish captured in Lake Michigan did not change; means were 0.98 (SD = 0.05) before collapse and 0.99 (SD = 0.01) after collapse. The mean distance to the center of the coastal distribution of Swan River fish during April–July shifted 357 km (SD = 169) from central Lake Huron before collapse to central Lake Michigan after collapse. The coastal distributions during August–October were centered on the respective sites of origin, suggesting that Chinook Salmon returned to release sites to spawn regardless of their feeding locations. Regarding the impact on Alewife populations, this shift in interlake movement would be equivalent to increasing the Chinook Salmon stocking rate within Lake Michigan by 30%. The primary management implication is that interlake coordination of Chinook Salmon stocking policies would be expected to benefit the recreational fishery.

Monitoring of adult Lost River and shortnose suckers in Clear Lake Reservoir, California, 2008–2010

USGS Publications Warehouse

Hewitt, David A.; Hayes, Brian S.

2013-01-01

Problems with inferring status and population dynamics from size composition data can be overcome by a robust capture-recapture program that follows the histories of PIT-tagged individuals. Inferences from such a program are currently hindered by poor detection rates during spawning seasons with low flows in Willow Creek, which indicate that a key assumption of capture-recapture models is violated. We suggest that the most straightforward solution to this issue would be to collect detection data during the spawning season using remote PIT tag antennas in the strait between the west and east lobes of the lake.

A stand density management diagram for sawtimber-sized mixed upland central hardwoods

Treesearch

J.A., Jr. Kershaw; B.C. Fischer

1991-01-01

Data from 190 CFI plots located in southern and west-central Indiana are used to develop a stand density diagram for sawtimber-sized mixed upland hardwoods in the Central States. The stand density diagram utilizes the concepts of self-thinning to establish a maximum size-density curve, and the stocking standards of Gingrich (1967) to formulate imtermediate stocking...

Population size and relative abundance of adult Alabama shad reaching jim woodruff lock and dam, Apalachicola River, Florida

USGS Publications Warehouse

Ely, Patrick C.; Young, S.P.; Isely, J.J.

2008-01-01

We estimated the population size of migrating Alabama shad Alosa alabamae below Jim Woodruff Lock and Dam in the Apalachicola River (located in the central panhandle of northwestern Florida) using mark-recapture and relative abundance techniques. After adjustment for tag loss, emigration, and mortality, the population size was estimated as 25,935 (95% confidence interval, 17,715-39,535) in 2005, 2,767 (838-5,031) in 2006, and 8,511 (5,211-14,674) in 2007. The cumulative catch rate from boat electrofishing averaged 20.47 Alabama shad per hour in 2005, 6.10 per hour in 2006, and 13.17 per hour in 2007. The relationship between population size (N) and electrofishing catch per unit effort (CPUE) was modeled by the equation N = -9008.2 + (electrofishing CPUE X 1616.4). Additionally, in 2007 the hook-and-line catch rate averaged 1.94 Alabama shad per rod hour. A predictive model relating the population size and hook-and-line CPUE of spawning American shad A. sapidissima was applied to Alabama shad hook-and-line CPUE and produced satisfactory results. Recent spawning populations of Alabama shad in the Apalachicola River are low relative to American shad populations in other southeastern U.S. rivers. ?? Copyright by the American Fisheries Society 2008.

Biophysical Controls over Carbon and Nitrogen Stocks in Desert Playa Wetlands

NASA Astrophysics Data System (ADS)

McKenna, O. P.; Sala, O. E.

2014-12-01

Playas are ephemeral desert wetlands situated at the bottom of closed catchments. Desert playas in the Southwestern US have not been intensively studied despite their potential importance for the functioning of desert ecosystems. We want to know which geomorphic and ecological variables control of the stock size of soil organic carbon, and soil total nitrogen in playas. We hypothesize that the magnitude of carbon and nitrogen stocks depends on: (a) catchment size, (b) catchment slope, (d) catchment vegetation cover, (e) bare-ground patch size, and (f) catchment soil texture. We chose thirty playas from across the Jornada Basin (Las Cruces, NM) ranging from 0.5-60ha in area and with varying catchment characteristics. We used the available 5m digital elevation map (DEM) to calculate the catchment size and catchment slope for these thirty playas. We measured percent cover, and patch size using the point-intercept method with three 10m transects in each catchment. We used the Bouyoucos-hydrometer soil particle analysis to determine catchment soil texture. Stocks of organic carbon and nitrogen were measured from soil samples at four depths (0-10 cm, 10-30 cm, 30-60 cm, 60-100 cm) using C/N combustion analysis. In terms of nitrogen and organic carbon storage, we found soil nitrogen values in the top 10cm ranging from 41.963-214.365 gN/m2, and soil organic carbon values in the top 10cm ranging from 594.339-2375.326 gC/m2. The results of a multiple regression analysis show a positive relationship between catchment slope and both organic carbon and nitrogen stock size (nitrogen: y= 56.801 +47.053, R2=0.621; organic carbon: y= 683.200 + 499.290x, R2= 0.536). These data support our hypothesis that catchment slope is one of factors controlling carbon and nitrogen stock in desert playas. We also applied our model to the 69 other playas of the Jornada Basin and estimated stock sizes (0-10cm) between 415.07-447.97 Mg for total soil nitrogen and 4627.99-5043.51 Mg for soil organic carbon.

Demographics and run timing of adult Lost River (Deltistes luxatus) and shortnose (Chasmistes brevirostris) suckers in Upper Klamath Lake, Oregon, 2011

USGS Publications Warehouse

Hewitt, David A.; Janney, Eric C.; Hayes, Brian S.; Harris, Alta C.

2012-01-01

Despite relatively high survival in most years, both species have experienced substantial declines in the abundance of spawning fish because losses from mortality have not been balanced by recruitment of new individuals. Although capture-recapture data indicate substantial recruitment of new individuals into the adult spawning populations for SNS and river spawning LRS in some years, size data do not corroborate these estimates. In fact, fork length data indicate that all populations are largely comprised of fish that were present in the late 1990s and early 2000s. As a result, the status of the endangered sucker populations in Upper Klamath Lake remains worrisome, and the situation is most dire for shortnose suckers. Future investigations should explore the connections between sucker recruitment and survival and various environmental factors, such as water quality and disease. Our monitoring program provides a robust platform for estimating vital population parameters, evaluating the status of the populations, and assessing the effectiveness of conservation and recovery efforts.

Ameliorative effect of chitosan-conjugated 17α-methyltestosterone on testicular development in Clarias batrachus.

PubMed

Saha, Ratnadeep; Bhat, Irfan Ahmed; Charan, Ravi; Purayil, Suresh Babu Padinhate; Krishna, Gopal; Kumar, Annam Pavan; Sharma, Rupam

2018-06-01

Chitosan nanoparticles conjugated with 17α-methyltestosterone (CS + MT) were used for studying their effect on the testicular development of Clarias batrachus during different reproductive phases. The size of chitosan nanoparticles was 127.2 nm and the nano-conjugated 17α methyltestosterone (17α-MT) was 196.1 nm (20 mg/100 ml of chitosan). Single injections of CS + MT at different doses such as 0.01, 0.1 and 0.5 μg/g body weight were administered to adults during the pre-spawning, spawning and post-spawning phase. Nano-conjugated steroid was effective at the lower dose; showing an increase in the Gonadosomatic Index (GSI) and 11-ketotestosterone level compared to the control group. Histological observations confirmed the dose-dependent advancement in spermatogenesis. These findings indicate the possibility of using CS + MT for enhancing gonadal maturity of C. batrachus. Copyright © 2018 Elsevier B.V. All rights reserved.

Predicting the thermal effects of dam removal on the Klamath River

USGS Publications Warehouse

Bartholow, J.M.; Campbell, S.G.; Flug, M.

2004-01-01

The Klamath River once supported large runs of anadromous salmonids. Water temperature associated with multiple mainstem hydropower facilities might be one of many factors responsible for depressing Klamath salmon stocks. We combined a water quantity model and a water quality model to predict how removing the series of dams below Upper Klamath Lake might affect water temperatures, and ultimately fish survival, in the spawning and rearing portions of the mainstem Klamath. We calibrated the water quantity and quality models and applied them for the hydrometeorological conditions during a 40-year postdam period. Then, we hypothetically removed the dams and their impoundments from the models and reestimated the river’s water temperatures. The principal thermal effect of dam and reservoir removal would be to restore the timing (phase) of the river’s seasonal thermal signature by shifting it approximately 18 days earlier in the year, resulting in river temperatures that more rapidly track ambient air temperatures. Such a shift would likely cool thermal habitat conditions for adult fall chinook (Oncorhynchus tshawytscha) during upstream migration and benefit mainstem spawning. By contrast, spring and early summer temperatures could be warmer without dams, potentially harming chinook rearing and outmigration in the mainstem. Dam removal might affect the river’s thermal regime during certain conditions for over 200 km of the mainstem.

Connectivity between migrating and landlocked populations of a diadromous fish species investigated using otolith microchemistry.

PubMed

Tulp, Ingrid; Keller, Marieke; Navez, Jacques; Winter, Hendrik V; de Graaf, Martin; Baeyens, Willy

2013-01-01

Smelt Osmerus eperlanus has two different life history strategies in The Netherlands. The migrating population inhabits the Wadden Sea and spawns in freshwater areas. After the closure of the Afsluitdijk in 1932, part of the smelt population became landlocked. The fresh water smelt population has been in severe decline since 1990, and has strongly negatively impacted the numbers of piscivorous water birds relying on smelt as their main prey. The lakes that were formed after the dike closure, IJsselmeer and Markermeer have been assigned as Natura 2000 sites, based on their importance for (among others) piscivorous water birds. Because of the declining fresh water smelt population, the question arose whether this population is still supported by the diadromous population. Opportunities for exchange between fresh water and the sea are however limited to discharge sluices. The relationship between the diadromous and landlocked smelt population was analysed by means of otolith microchemistry. Our interpretation of otolith strontium ((88)Sr) patterns from smelt specimens collected in the fresh water area of Lake IJsselmeer and Markermeer, compared to those collected in the nearby marine environment, is that there is currently no evidence for a substantial contribution from the diadromous population to the spawning stock of the landlocked population.

Influence of sperm and phytoplankton on spawning in the echinoid Lytechinus variegatus.

PubMed

Reuter, Kim E; Levitan, Don R

2010-12-01

The cues triggering large-scale broadcast-spawning events in marine invertebrates are not fully understood. Using the sea urchin Lytechinus variegatus, we tested the effectiveness of a variety of potential spawning cues in eliciting a spawning response. In the laboratory, during two consecutive spawning seasons, about 400 isolated sea urchins were exposed to phytoplankton, sperm, or eggs, singly or in combination. The likelihood of spawning, time to spawning, and spawning behavior were recorded for both sexes. Sperm was most successful at inducing spawning. No response to eggs was noted. Phytoplankton alone did not trigger spawning, but when a phytoplankton cue was followed by the addition of sperm, spawning behavior was induced, the time between addition of sperm and spawning was reduced, and the variance among individuals in the time of spawning initiation was reduced. Males spawned sooner in response to cues than females and rarely spawned spontaneously in phytoplankton or control treatments. A semilunar pattern in the sensitivity to spawning cues was noted. During time periods when sea urchins were less ripe, the ratio of spawning males to spawning females increased. Our results indicate that seasonal and lunar cycles, together with the presence of phytoplankton, increase the sensitivity of these sea urchins to spawning cues and the precision of their responses to conspecific sperm.

Influence of behavior and mating success on brood-specific contribution to fish recruitment in ponds.

PubMed

Parkos, Joseph J; Wahl, David H; Philipp, David P

2011-10-01

One source of uncertainty in predicting the response of populations to exploitation is individual differences within a population in both vulnerability to capture and contribution to population renewal. For species with parental care, individuals engaged in nesting behavior are often targeted for exploitation, but predicting outcomes of this nonrandom vulnerability will depend in part on an understanding of how parental traits are related to potential for brood contribution to the population. Variation in brood-specific contribution to recruitment of largemouth bass (Micropterus salmoides), a fish species with extended parental care, was quantified to determine if differences in mating success, parental care behaviors, and timing of reproduction influenced offspring recruitment. Dependence of these relationships on brood predation was tested in communities that differed in the presence of bluegill, Lepomis macrochirus, an important nest predator. Daily snorkel surveys were conducted in experimental ponds during spring to monitor male spawning and parental care behaviors in populations of largemouth bass. Tissue samples collected from larvae in nests were used to develop brood-specific DNA fingerprints for determining nest origins of fall recruits. Largemouth bass spawning period in bluegill ponds was longer and more variable in duration, with lower, more variable mating success, than in ponds without bluegill. In all populations, only one or two broods provided the majority of recruits, and these were broods produced during the earliest days of spawning by the oldest, largest males. In bluegill ponds, brood contribution from earliest nests also increased with brood size. Earliest nesters were the oldest males, and recruits from these nests were often above average in body size. Offspring needed to be guarded to at least swim-up larval stage to contribute any recruits. Termination of parental protection before offspring were free swimming mainly occurred with broods guarded by smaller males in ponds with brood predators. These age- and size-specific differences in timing of spawning and duration of parental care are consistent with influences of residual reproductive value and energetic constraints on reproductive behavior. Furthermore, these patterns of individual contribution to recruitment imply that fisheries that selectively target either nesting individuals or larger, older males could potentially decrease recruitment at the population scale.

Tactic changes in dusky frillgoby Bathygobius fuscus sneaker males: effects of body size and nest availability.

PubMed

Takegaki, T; Kaneko, T; Matsumoto, Y

2013-02-01

Field and laboratory studies were conducted to examine the effects of nest availability and body size on changes in male mating tactics from sneaking to nest-holding in the dusky frillgoby Bathygobius fuscus. In the field, the body size of nest-holding males decreased from early to mid-breeding season, suggesting the possibility of a change in the tactics of sneaker males to nest-holding. Many sneaker males did not use vacant spawning nests even when size-matched nests were available, but they continued to reproduce as sneakers. Similarly, in aquarium experiments with available vacant nests, some sneaker males became nest-holders irrespective of their body size, but some did not. These results showed that nest availability is not a limiting factor for changes in tactics by sneaker males in this species. Because tactic-unchanged sneaker males were co-housed with larger nest-holding males in the tanks, the body size of nearby nest-holding males may have affected the decision to change tactics for sneaker males. Moreover, smaller individuals among tactic-changed males tended to spend more time until spawning, probably because they had relatively larger costs and smaller benefits of reproduction as nest-holding males compared to larger males. © 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles.

An assessment of sauger population characteristics on two Tennessee River reservoirs

USGS Publications Warehouse

Graham, Christy L.; Bettoli, Phillip William; Churchill, Timothy N.

2015-01-01

In 1992, a 356-mm minimum length limit (MLL) was enacted on Kentucky Lake and a 381-mm MLL was enacted on Watts Bar Lake, two mainstem reservoirs on the Tennessee River, in an attempt to reduce exploitation and improve the size structure of the sauger (Sander canadensis) populations. The objectives of this study were to compare sauger population characteristics immediately following (1993–1994) and 15 years after (2008–2009) the regulations took effect, examine spatial and temporal patterns in growth, examine recruitment patterns in each reservoir using a recruitment variability index (RVI), and assess the current likelihood of overfishing. Saugers were collected with experimental gill nets in each reservoir and aged using otoliths. A Beverton-Holt yield-per-recruit model was used to simulate angler yields and estimate the likelihood of growth overfishing. Recruitment overfishing was assessed by examining spawning potential ratios under various MLL and exploitation rate scenarios. The sauger population in Kentucky Lake experienced modest improvements in size and age structure over the 15 years following enactment of more restrictive harvest regulations, whereas the population in Watts Bar Lake changed very little, if at all, in terms of size and age structure. Mean lengths of age-3 sauger were significantly greater in Watts Bar Lake than in Kentucky Lake in both time periods. The RVI values indicated that between 1993 and 2009 the sauger in Kentucky Lake displayed more stable recruitment than the Watts Bar Lake population. Neither population exhibited signs of growth overfishing in 2008–09 under the current length limits; however, the Watts Bar Lake population would be susceptible to recruitment overfishing at high (>40%) exploitation rates if natural mortality was as low as 20%. These analyses have demonstrated that the Watts Bar Lake and Kentucky Lake populations, in terms of size and age structure, have remained relatively stable over 15+ years and the MLLs appear to be conserving the stocks.

Reproductive biology of the black coral Antipathella wollastoni (Cnidaria: Antipatharia) in the Azores (NE Atlantic)

NASA Astrophysics Data System (ADS)

Rakka, Maria; Orejas, Covadonga; Sampaio, Iris; Monteiro, João; Parra, Hugo; Carreiro-Silva, Marina

2017-11-01

Antipathella wollastoni is an antipatharian species common to Macaronesia, occurring in depths between 20 and 1425 m. Despite its importance as a habitat-forming species, there is no information about its basic biology. The aim of the current study is to describe its reproductive strategy, gametogenic cycle and reproductive timing. Sampling was performed monthly on six tagged colonies during one year and specimens were histologically processed. A. wollastoni was found to be a gonochoric broadcast spawner. Gametogenesis took place within the primary transversal mesenteries, and followed an annual cycle. The reproductive season coincided with an increase in seawater temperature but spawning, inferred from the disappearance of gametes, likely happened after the sea surface temperature peak of the year (September 2009). Polyp fecundity ranged from 1 to 309 oocytes/polyp. A decrease in polyp fecundity was detected in samples at the higher pre-spawning maturity stage, indicating possible repetitive spawning or oocyte absorption. Intra-colonial comparisons revealed a longer duration of the reproductive cycle in the medial colony section, and a gradient of increased oocyte size towards the apical section, possibly due to intra-colonial differences in energy allocation between reproduction and other biological processes, or as a strategy against predation on gametes/larvae. Colony height was positively correlated with polyp fecundity indicating that the reproductive output increases with colony size.

Effects of Hydroelectric Dam Operations on the Restoration Potential of Snake River Fall Chinook Salmon (Oncorhynchus tshawytscha) Spawning Habitat Final Report, October 2005 - September 2007.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanrahan, Timothy P.; Richmond, Marshall C.; Arntzen, Evan V.

2007-11-13

This report describes research conducted by the Pacific Northwest National Laboratory for the Bonneville Power Administration (BPA) as part of the Fish and Wildlife Program directed by the Northwest Power and Conservation Council. The study evaluated the restoration potential of Snake River fall Chinook salmon spawning habitat within the impounded lower Snake River. The objective of the research was to determine if hydroelectric dam operations could be modified, within existing system constraints (e.g., minimum to normal pool levels; without partial removal of a dam structure), to increase the amount of available fall Chinook salmon spawning habitat in the lower Snakemore » River. Empirical and modeled physical habitat data were used to compare potential fall Chinook salmon spawning habitat in the Snake River, under current and modified dam operations, with the analogous physical characteristics of an existing fall Chinook salmon spawning area in the Columbia River. The two Snake River study areas included the Ice Harbor Dam tailrace downstream to the Highway 12 bridge and the Lower Granite Dam tailrace downstream approximately 12 river kilometers. These areas represent tailwater habitat (i.e., riverine segments extending from a dam downstream to the backwater influence from the next dam downstream). We used a reference site, indicative of current fall Chinook salmon spawning areas in tailwater habitat, against which to compare the physical characteristics of each study site. The reference site for tailwater habitats was the section extending downstream from the Wanapum Dam tailrace on the Columbia River. Fall Chinook salmon spawning habitat use data, including water depth, velocity, substrate size and channelbed slope, from the Wanapum reference area were used to define spawning habitat suitability based on these variables. Fall Chinook salmon spawning habitat suitability of the Snake River study areas was estimated by applying the Wanapum reference reach habitat suitability criteria to measured and modeled habitat data from the Snake River study areas. Channel morphology data from the Wanapum reference reach and the Snake River study areas were evaluated to identify geomorphically suitable fall Chinook salmon spawning habitat. The results of this study indicate that a majority of the Ice Harbor and Lower Granite study areas contain suitable fall Chinook salmon spawning habitat under existing hydrosystem operations. However, a large majority of the currently available fall Chinook salmon spawning habitat in the Ice Harbor and Lower Granite study areas is of low quality. The potential for increasing, through modifications to hydrosystem operations (i.e., minimum pool elevation of the next downstream dam), the quantity or quality of fall Chinook salmon spawning habitat appears to be limited. Estimates of the amount of potential fall Chinook salmon spawning habitat in the Ice Harbor study area decreased as the McNary Dam forebay elevation was lowered from normal to minimum pool elevation. Estimates of the amount of potential fall Chinook salmon spawning habitat in the Lower Granite study area increased as the Little Goose Dam forebay elevation was lowered from normal to minimum pool elevation; however, 97% of the available habitat was categorized within the range of lowest quality. In both the Ice Harbor and Lower Granite study areas, water velocity appears to be more of a limiting factor than water depth for fall Chinook salmon spawning habitat, with both study areas dominated by low-magnitude water velocity. The geomorphic suitability of both study areas appears to be compromised for fall Chinook salmon spawning habitat, with the Ice Harbor study area lacking significant bedforms along the longitudinal thalweg profile and the Lower Granite study area lacking cross-sectional topographic diversity. To increase the quantity of available fall Chinook salmon spawning habitat in the Ice Harbor and Lower Granite study area, modifications to hydroelectric dam operations beyond those evaluated in this study likely would be necessary. Modifications may include operational and structural changes, such as lowering downstream dam forebay elevations to less than minimum pool. There is a large amount of uncertainty as to whether or not such modifications could increase the quantity of available fall Chinook salmon spawning habitat in the Ice Harbor and Lower Granite study area. The results from this study provide some certainty that the quantity and quality of fall Chinook salmon spawning habitat within the lower Snake River are not likely to be increased within the existing hydroelectric dam operations.« less

Stocking of Offsite Waters for Hungry Horse Dam Mitigation Creston National Fish Hatchery, FY 2006 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hooley, Sharon

2009-03-20

A total of 350,000, M012 strain, westslope cutthroat trout (WCT) eggs were received from Montana Fish Wildlife & Parks (MFWP), Washoe Park State Fish Hatchery in June of 2005 to accomplish this fishery management objective. These eggs were incubated, hatched and reared entirely inside the hatchery nursery building using a protected well water supply. Fish grew according to schedule and survival was excellent. The hatchery achieved a 0.78 feed fed to pounds gained conversion ratio for this group of WCT. Not all of the progenies from this fish lot were used for Hungry Horse Dam Fishery Mitigation Implementation. Some weremore » used for other regional fishery management projects. Westslope cutthroat trout were reared using approved fish culture techniques as recommended in the USFWS Fish Hatchery Management Handbook and also utilizing a regimen adapted for hatchery specific site conditions. The fish health for these WCT was very good. Survival from first feeding fry stage to stocking was 79%. The hatchery had an annual fish health inspection performed by the USFWS Bozeman Fish Health Center in mid March of 2006. This inspection found all fish lots at Creston to be disease free. The Montana State Fish Health Board has placed the hatchery under a limited quarantine since May of 2005 due to an epizootic of Furunculosis. This classification has allowed the Creston NFH to stock disease free fish in locations approved by regional fish managers. The hatchery has been working with the State Fish Pathologist to remove the limited quarantine classification from the facility. Although fish health for all station fish lots remains disease free, MFWP has asserted it will not remove the limited quarantine until the new influent water treatment system, including the ultraviolet disinfection unit, is running full time, year round. The USFWS is working to secure the additional funding necessary to operate the treatment building year round. Distribution of the WCT took place from March through June. The stocking locations on the Flathead Reservation and State managed waters were identified by Confederated Salish and Kootenai Tribe (CSKT) and MFWP fishery biologists. Post release survival and angler success is monitored routinely by CSKT and MFWP fishery technicians. Stocking numbers and locations vary annually based on the results of biological monitoring, creel evaluations and adaptive management decisions. A total of 99,126 WCT were stocked during nine distribution trips in management approved waters (see Table 1). The average size of WCT at stocking was 3.91-inches. A total of 101,600, Arlee strain, rainbow trout (RBT) eggs were received from the Ennis National Fish Hatchery, Ennis, Montana, in December of 2005 and 35,000 Kamloops strain eggs were received from Murray Springs SFH, Eureka, Montana, in March of 2006 to accomplish this fishery management objective. The RBT were reared using approved fish culture techniques as recommended in the USFWS Fish Hatchery Management Handbook. There was no fish health related problems associated with this lot of fish. Survival from swim up fry stage to stocking was 93% for the Arlee's and 79% for the Kamloops. The hatchery achieved a 0.68 feed fed to pounds gained conversion ratio for the Arlee and 0.97 for the Kamloops RBT. The excellent feed conversion ratio can be attributed to refined feeding techniques and the use of an extruded high performance fry feed made with premium fish meal and marine fish oil. The Arlee strain of rainbow trout is requested for this fishery mitigation objective because the chosen stocking locations are terminal basin reservoirs or lakes, habitat conditions prevent natural spawning runs and returns to the creel are more favorable then for native westslope cutthroat trout. MFWP also requested a fall plant of Kamloops strain RBT and they will be evaluated for performance and future fall stockings in Echo Lake. Post release survival and angler success is monitored routinely by the Confederated Salish and Kootenai Tribe (CSKT) and Montana Fish Wildlife & Parks (MFWP) fishery technicians. Stocking numbers and locations vary annually based on the results of biological monitoring, creel evaluations and habitat conditions. The RBT were stocked in six distribution trips from June through September. The number of fish stocked and the receiving waters are identified below (see Table 2).« less

A new method for reporting and interpreting textural composition of spawning gravel.

Treesearch

Fredrick B. Lotspeich; Fred H. Everest

1981-01-01

A new method has been developed for collecting, sorting, and interpreting gravel quality. Samples are collected with a tri-tube freeze-core device and dry-sorted by using sieves based on the Wentworth scale. An index to the quality of gravel is obtained by dividing geometric mean particle size by the sorting coefficient (a measure of the distribution of grain sizes) of...

Ecological, morphological, genetic and life history characteristics of two sockeye salmon populations, Tustumena Lake, Alaska

USGS Publications Warehouse

Woody, Carol Ann

1998-01-01

Populations can differ in both phenotypic and molecular genetic traits. Phenotypic differences likely result from differential selection pressures in the environment, whereas differences in neutral molecular markers result from genetic drift associated with some degree of reproductive isolation. Two sockeye salmon, Oncorhynchus nerka, populations were compared using both phenotypic and genotypic characters, and causal factors were examined. Salmon spawning in a short (<3 km), shallow (<21 cm), clear, homogenous spring-fed study site spawned later, were younger, smaller, and produced fewer and smaller eggs than salmon spawning in a longer (∼80 km), deeper, stained, diverse, precipitation-dominated stream. Run timing differences were associated with differences in stream thermal regimes. Age and size at maturity differences are likely due to differences in age-specific mortality rates. Fish in the shallow spring-fed system suffered higher adult predation rates and exhibited greater egg to fry survival compared to fish in the precipitation-fed system. Salmon in both streams exhibited non-random nest site selection for deeper habitats and smaller substrates (≥2 to <64 mm mean diameter) relative to available habitat; fish from the precipitation system avoided low velocity habitats containing fine (<2 mm) substrates. Genetic comparisons of six microsatellite loci indicated that run time was a more effective reproductive isolating mechanism than geographical distance. Differences between and within the tributary spawning populations are discussed in terms of selection, genetic drift, and the homogenizing effects of gene flow. This study indicates important adaptive differences may exist between proximate spawning groups of salmon which should be considered when characterizing populations for conservation or management purposes.

Titre distribution patterns of infectious haematopoietic necrosis virus in ovarian fluids of hatchery and feral salmon populations

USGS Publications Warehouse

Mulcahy, D.; Pascho, R.J.; Jenes, C.K.

1983-01-01

Infectious haematopoietic mecrosis virus (IHNV) is enzootic in virtually all populations of sockeye salmon, Oncorhynchus nerka (Walbaum), and in populations of chinook salmon, O. tshawytscha (Walbaum), of the Sacramento River drainage in California. This disease is an obstacle in hatcheries using brood stocks from these populations. However, naturally spawning sockeye salmon are highly successful and are the most important commercially fished salmon species in the United States. Most of the commercial landings of sockeye salmon are of feral fish originating in Alaska. The success of natural populations of salmon in which IHNV is enzootic, and the recurrent outbreaks of the disease in hatchery fish, led us to compare IHNW prevalence rates in hatchery and feral salmon populations.

Impacts of extensive driftnet fishery and late 1990s climate regime shift on dominant epipelagic nekton in the Transition Region and Subtropical Frontal Zone: Implications for fishery management

NASA Astrophysics Data System (ADS)

Ichii, T.; Nishikawa, H.; Igarashi, H.; Okamura, H.; Mahapatra, K.; Sakai, M.; Wakabayashi, T.; Inagake, D.; Okada, Y.

2017-01-01

We investigated the impacts of extensive anthropogenic (high seas driftnet squid fishery) and natural (late 1990s major climate regime shift) events on dominant epipelagic fish, squid, and shark in the central North Pacific Transition Region based on a driftnet survey covering the years 1979-2006. Fishing was conducted by Japan, Korea and Taiwan to target neon flying squid in the period 1979-1992, resulting in a decline in stocks of the target species and non-target species (Pacific pomfret and juvenile blue shark), which were by-catch of this fishery. The catch was found to be at the maximum sustainable yield (MSY) level for neon flying squid, the underfished level for juvenile blue shark, but the overfished level for Pacific pomfret. The MSY of Pacific pomfret indicated that this species is more susceptible to exploitation than previously considered. In response to the late 1990s regime shift, neon flying squid and Pacific saury showed low stock levels in 1999-2002 and 1998-2002, respectively, as a result of reduced productivity in their nursery grounds (the Subtropical Frontal Zone and Kuroshio Extension Bifurcation Region, respectively). On the other hand, Pacific pomfret showed no decreasing trend in stock during the low- and intermediate-productivity regimes because of the high productivity of their main spawning/nursery ground (Transition Zone Chlorophyll Front), which was independent of the regime shifts. Thus, squid and saury appear to be more susceptible to the regime shift than pomfret. We discuss the implications for stock management of the species-specific responses to the fishery and the regime shift.

Lake trout status in the main basin of Lake Huron, 1973-2010

USGS Publications Warehouse

He, Ji X.; Ebener, Mark P.; Riley, Stephen C.; Cottrill, Adam; Kowalski, Adam; Koproski, Scott; Mohr, Lloyd; Johnson, James E.

2012-01-01

We developed indices of lake trout Salvelinus namaycush status in the main basin of Lake Huron (1973-2010) to understand increases in the relative abundance of wild year-classes during 1995-2010. Sea lamprey Petromyzon marinus wounds per 100 lake trout declined from 23.63 in 2000 to 5.86-10.64 in 2002-2010. The average age-7 lake trout catch per effort per recruitment (CPE/R; fish•305mof gill net-1•million stocked yearlings-1) increased from 0.56 for the 1973-1990 year-classes to 0.92 for the 1991-2001 year-classes. Total CPE (fish/305 m of gill net) declined from 16.4 fish in 1996 to 4.1 fish in 2010, but the percentage of age-5 and younger lake trout steadily decreased from more than 70% before 1996 to less than 10% by 2009. The modal age in gill-net catches increased from age 5 before 1996 to age 7 by 2005. The average adult CPE increased from 2.8 fish/305 m of gill net during 1978-1995 to 5.34 fish/305 m of gill net during 1996-2010. The 1995-2010 year-classes of wild fish weremore abundant than previous year-classes and were associated with the relatively high adult abundance during 1996-2010. Until the 2002 year-class, there was no decline in age-7 CPE/R; until 2008, there was no decline in adult CPE. Low survival of the 2002 and 2003 year-classes of stocked fish was related to the event of alewife Alosa pseudoharengus population collapse in 2003-2004. Lake trout in the main basin of Lake Huron are undergoing a transition from a hatchery stock to a wild stock, accompanied by an increased uncertainty in delayed recruitment. Future management should pay more attention to the protection of wild recruitment and the abundance of the spawning stock.

Levels-of-growing-stock cooperative study in Douglas-fir: report no. 15—The Hoskins Study, 1963-1998.

Treesearch

David D. Marshall; Robert O. Curtis

2001-01-01

The cooperative levels-of-growing-stock (LOGS) study in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) was begun to study the relations between growing stock, growth, cumulative wood production, and tree size in repeatedly thinned stands. This report summarizes results from the Hoskins installation through age 55. Growing stock has been allowed...

Effect of size of unfed fry at release on survival and growth of juvenile steelhead in streams and a hatchery (Study sites: Dworshak Hatchery, Silver Creek, and Twenty-Mile Creek; Stock: Dworshak hatchery; Year classes: 1996 and 1999): Chapter 7

USGS Publications Warehouse

Rubin, Stephen P.; Reisenbichler, Reginald R.; Wetzel, Lisa A.; Stenberg, Karl D.

2012-01-01

We tested whether differences in size of unfed fry at release affected survival and growth of juvenile steelhead Oncorhynchus mykiss in hatchery ponds and streams. Differences in fry size were produced by selecting and spawning females that differed in the mean size of their eggs. Experiments were initiated in 1996 and 1999 with hatchery steelhead returning to the Clearwater River, Idaho. Fry size groups were small (mean fork length=26.7 mm, mean weight=0.149 g) and large (28.1 mm, 0.197 g) in 1996 and small (27.5 mm, 0.159 g), medium (28.2 mm, 0.190 g), and large (28.9 mm, 0.201 g) in 1999. Survival in the hatchery to near the end of the standard one year rearing period and in streams to late summer, three months after release, was higher for the large than for the small group in 1996 but was similar among groups in 1999. Survival in streams to age - 1 appeared to show the same pattern (large>small in 1996; no difference in 1999), but differences among fry size groups in emigration as well as mortality may have been involved. The inconsistency between years may have resulted because some 1996 female parents of the small group had exceptionally small eggs and were a year younger than the other 1996 females and all 1999 females. Growth in the hatchery was similar among groups in both years whereas growth in streams was faster for the large than for the small group in both years and intermediate for the medium group in 1999. Growth in streams appeared to be limited by food availability. Initially large fry probably out - competed smaller fry for limited food; however, we found no evidence that dispersal from release sites or emigration from streams was caused by competitive displacement of small by larger fish. 

Biological consequences of the coaster brook trout restoration stocking program in Lake Superior tributaries with Pictured Rocks National Lakeshore

USGS Publications Warehouse

Leonard, Jill B.K.; Stott, Wendylee; Loope, Delora M.; Kusnierz, Paul C.; Sreenivasan, Ashwin

2013-01-01

The coaster Brook Trout Salvelinus fontinalis is a Lake Superior ecotype representing intraspecific variation that has been impacted by habitat loss and overfishing. Hatchery strains of Brook Trout derived from populations in Lake Superior were stocked into streams within Pictured Rocks National Lakeshore, Michigan, as part of an effort to rehabilitate adfluvial coaster Brook Trout. Wild and hatchery Brook Trout from three streams (Mosquito River, Hurricane River, and Sevenmile Creek) were examined for movement behavior, size, physiology, and reproductive success. Behavior and size of the stocked fish were similar to those of wild fish, and less than 15% of the stocked, tagged Brook Trout emigrated from the river into which they were stocked. There was little evidence of successful reproduction by stocked Brook Trout. Similar to the results of other studies, our findings suggest that the stocking of nonlocal Brook Trout strains where a local population already exists results in limited natural reproduction and should be avoided, particularly if the mechanisms governing the ecotype of interest are poorly understood.

Long-term consequences of variation in timing and manner of fry introduction on juvenile Atlantic salmon (Salmo salar) growth, survival, and life-history expression

USGS Publications Warehouse

Letcher, B.H.; Dubreuil, T.; O'Donnell, M. J.; Obedzinski, M.; Griswold, K.; Nislow, K.H.

2004-01-01

We tested the influence of introduction time and the manner of introduction on growth, survival, and life-history expression of Atlantic salmon (Salmo salar). Introduction treatments included three fry stocking times and stream rearing of embryos. Despite poor growth conditions during the early stocking period, early-stocked fish were larger throughout the entire study period, likely the result of prior residence advantage. This interpretation was reinforced by the laboratory study, where early-stocked fish outgrew late-stocked fish when reared together, but not when they were reared separately. In contrast to growth, abundance of stocked fish was greatest for fish stocked during the middle period, and this stocking group produced the greatest number of smolts. Despite smaller size, survival of stream-incubated fish was generally greater than survival of stocked fish. Introduction timing had a pronounced effect on smolt age but a weak effect on extent of parr maturation. Overall, these observations indicate that small differences (???2 weeks) in introduction time can have long-term effects on size, survival, and life-history expression. Results suggest stabilizing selection on introduction times, mediated by the interaction between prior residence (advantage to fish introduced earlier) and habitat suitability (advantage to fish introduced later). ?? 2004 NRC Canada.

50 CFR 600.315 - National Standard 2-Scientific Information.

Code of Federal Regulations, 2010 CFR

2010-10-01

... sources to improve understanding and management of the resource, marine ecosystem, and the fishery... any stock or stock complex is approaching the minimum stock size threshold. (ii) Any management..., social, and ecological information pertinent to the success of management or the achievement of...

50 CFR 600.315 - National Standard 2-Scientific Information.

Code of Federal Regulations, 2011 CFR

2011-10-01

... sources to improve understanding and management of the resource, marine ecosystem, and the fishery... any stock or stock complex is approaching the minimum stock size threshold. (ii) Any management..., social, and ecological information pertinent to the success of management or the achievement of...

Salmon Spawning Effects on Streambed Stability

NASA Astrophysics Data System (ADS)

Buxton, T. H.; Buffington, J. M.; Yager, E.; Fremier, A. K.; Hassan, M. A.

2014-12-01

Female salmon build nests ("redds") in streambeds to protect their eggs from predation and damage by bed scour. During spawning, streambed material is mixed, fine sediment is winnowed downstream, and sediment is moved into a tailspill mound resembling the shape of a dune. Redd surfaces are coarser and better sorted than unspawned beds, which is thought to increase redd stability because larger grains are heavier and harder to move and sorting leads to higher friction angles for grain mobility. However, spawning also loosens sediment and creates topography that accelerates flow, both of which may increase particle mobility. We address factors controlling the relative stability of redds and unspawned beds using simulated salmon redds and water worked ("unspawned") beds composed of mixed-grain surfaces in a laboratory flume. Results show that simulated spawning lowered packing resistance to particle mobility on redds by an average of 32-39% compared to unspawned beds. Reductions in packing were sufficient to counter the higher inherent stability of relatively coarse, well sorted grains on redds, overall reducing critical shear stress by 8-20% relative to unspawned beds. In addition, boundary shear stress was 13-41% higher on redds due to flow convergence over the tailspill structure. Finally, redd instability relative to unspawned beds was observed in visual measurements of grain mobility, where bed-averaged shear stress was 22% lower at incipient motion and 29% lower at the discharge that mobilized all grain sizes on redds. Results of these complementary observations, along with sediment mass transport rates being nearly five times higher on a redd than an unspawned bed, indicate that redds are unstable compared to unspawned beds. Given these findings, further research is needed to investigate linkages between spawning disturbance and streambed mobility that may affect salmon reproduction in streams, and to assess whether a certain level of bed disturbance from spawning is required to restore ecosystem functions in streams with threatened populations of salmon.

Seasonal movements and habitat use of Potamodromous Rainbow Trout across a complex Alaska riverscape

USGS Publications Warehouse

Fraley, Kevin M.; Falke, Jeffrey A.; Yanusz, Richard; Ivey, Sam S.

2016-01-01

Potamodromous Rainbow Trout Oncorhynchus mykiss are an important ecological and recreational resource in freshwater ecosystems of Alaska, and increased human development, hydroelectric projects, and reduced escapement of Chinook Salmon Oncorhynchus tshawytscha may threaten their populations. We used aerial and on-the-ground telemetry tracking, a digital landscape model, and resource selection functions to characterize seasonal movements and habitat use of 232 adult (>400 mm FL) Rainbow Trout across the complex, large (31,221 km2) Susitna River basin of south-central Alaska during 2003–2004 and 2013–2014. We found that fish overwintered in main-stem habitats near tributary mouths from November to April. After ice-out in May, fish ascended tributaries up to 51 km to spawn and afterward moved downstream to lower tributary reaches, assumedly to intercept egg and flesh subsidies provided by spawning salmonids in July and August. Fish transitioned back to main-stem overwintering habitats at the onset of autumn when salmonid spawning waned. Fidelity to tributaries where fish were initially tagged varied across seasons but was high (>0.75) in three out of four drainages. Model-averaged resource selection functions suggested that Rainbow Trout habitat use varied seasonally; fish selected low-gradient, sinuous, main-stem stream reaches in the winter, reaches with suitably sized substrate during spawning, larger reaches during the feeding season prior to the arrival of spawning salmonids, and reaches with high Chinook Salmon spawning habitat potential following the arrival of adult fish. We found little difference in movement patterns between males and females among a subset of fish for which sex was determined using genetic analysis. As most Rainbow Trout undertake extensive movements within and among tributaries and make use of a variety of seasonal habitats to complete their life histories, it will be critical to take a basinwide approach to their management (i.e., habitat protection and angling bag limits) in light of anticipated land-use changes.

Deepwater Spawning of Fall Chinook Salmon (Oncorhynchus tshawtscha) Near Ives and Pierce Island of the Columbia River, 2002-2003 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mueller, Robert

2003-09-01

Pacific Northwest National Laboratory conducted video-based boat surveys to identify fall chinook salmon (Oncorhynchus tshawytscha) spawning areas located in deep water (>1 m) downstream of Bonneville Dam in the fall of 2002. This report documents the number and extent of chinook salmon spawning near Ives and Pierce Islands of the Columbia River, and is the fourth in a series of reports prepared since 1999. The main objective of this study was to find deepwater spawning locations of fall chinook salmon in the main Columbia River channel, collect additional data on physical habitat parameters at spawning sites, and provide estimates ofmore » adult spawners in the surveyed area. The secondary objective was to document the occurrence of any chum salmon (O. keta) redds located in the deeper sections near below Hamilton Creek. There was a significant increase in the number of fall chinook salmon redds found in the locations surveyed during the 2002 surveys when compared to previous surveys by Pacific Northwest National Laboratory. A total of 192 redds were found in two general locations adjacent to Pierce Island (river km 228.5) encompassing an area of approximately 9.31 ha. Peak spawning activity, based on redd counts and live fish seen near redds, was on or near November 15, 2002. An estimated 1,768 fall chinook salmon redds at water depths exceeding {approx}1.m ({approx} 125 kcfs) were documented in 2002. This estimate is the expanded number based on the number of redds found within the pre-defined survey area. Fall chinook salmon redds were found at water depths from 0.9 to 8.5 m and were constructed in gravel to large cobble ranging in size from 4.83 to 13.4 cm in diameter. No chum salmon redds were found in areas surveyed during 2002, although several carcasses were found at the mouth of Woodward Creek and in the deeper sections below Hamilton Creek.« less

Stocking density effects on production characteristics and body composition of market size cobia, Rachycentron canadum, reared in recirculating aquaculture systems

USDA-ARS?s Scientific Manuscript database

Production density in excess of a critical threshold can result in a negative relationship between stocking density and fish production. This study was conducted to evaluate production characteristics of juvenile cobia Rachycentron canadum, reared to market size in production-scale recirculating aq...

Tick size and stock returns

NASA Astrophysics Data System (ADS)

Onnela, Jukka-Pekka; Töyli, Juuso; Kaski, Kimmo

2009-02-01

Tick size is an important aspect of the micro-structural level organization of financial markets. It is the smallest institutionally allowed price increment, has a direct bearing on the bid-ask spread, influences the strategy of trading order placement in electronic markets, affects the price formation mechanism, and appears to be related to the long-term memory of volatility clustering. In this paper we investigate the impact of tick size on stock returns. We start with a simple simulation to demonstrate how continuous returns become distorted after confining the price to a discrete grid governed by the tick size. We then move on to a novel experimental set-up that combines decimalization pilot programs and cross-listed stocks in New York and Toronto. This allows us to observe a set of stocks traded simultaneously under two different ticks while holding all security-specific characteristics fixed. We then study the normality of the return distributions and carry out fits to the chosen distribution models. Our empirical findings are somewhat mixed and in some cases appear to challenge the simulation results.

Predation by fallfish (Semotilus corporalis) on Pacific salmon eggs in the Salmon River, New York

USGS Publications Warehouse

Johnson, J. H.; Nack, C.C.; Chalupnicki, M.A.

2009-01-01

Fallfish (Semotilus corporalis) are the largest native cyprinid in the northeastern United States and are the most abundant native species in the Salmon River, New York. The Salmon River is a high-quality spawning and nursery river for Pacific salmon (Oncorhynchus spp.) migrating from Lake Ontario. Because of the large number of Pacific salmon spawning in the river in the fall extensive redd superimposition occurs resulting in salmonid eggs being available on the substrate. We examined the fall diet of 647 fallfish in 2007 and 2008 to determine the extent of predation on Pacific salmon eggs. The contribution of eggs in the diet significantly increased once fallfish attained a size of 100 mm total length. The largest size category of fallfish examined (≥150 mm) had the highest proportion (86.1%) of salmon eggs in their diet. The contribution of Zooplankton and chironomids in the diet of fallfish decreased with fish size. Except for the two largest groups of fallfish examined (i.e., 100–149 mm and ≥150 mm) diet overlap among size groups was low. The high contribution in the diet during the fall and high caloric value of Pacific salmon eggs could increase growth and survival of this species in the Salmon River.

Oyster mushroom cultivation with rice and wheat straw.

PubMed

Zhang, Ruihong; Li, Xiujin; Fadel, J G

2002-05-01

Cultivation of the oyster mushroom, Pleurotus sajor-caju, on rice and wheat straw without nutrient supplementation was investigated. The effects of straw size reduction method and particle size, spawn inoculation level, and type of substrate (rice straw versus wheat straw) on mushroom yield, biological efficiency, bioconversion efficiency, and substrate degradation were determined. Two size reduction methods, grinding and chopping, were compared. The ground straw yielded higher mushroom growth rate and yield than the chopped straw. The growth cycles of mushrooms with the ground substrate were five days shorter than with the chopped straw for a similar particle size. However, it was found that when the straw was ground into particles that were too small, the mushroom yield decreased. With the three spawn levels tested (12%, 16% and 18%), the 12% level resulted in significantly lower mushroom yield than the other two levels. Comparing rice straw with wheat straw, rice straw yielded about 10% more mushrooms than wheat straw under the same cultivation conditions. The dry matter loss of the substrate after mushroom growth varied from 30.1% to 44.3%. The straw fiber remaining after fungal utilization was not as degradable as the original straw fiber, indicating that the fungal fermentation did not improve the feed value of the straw.

Phenologically distinct phytoplankton regions on the Faroe Shelf - identified by satellite data, in-situ observations and model

NASA Astrophysics Data System (ADS)

Eliasen, Sólvá Káradóttir; Hátún, Hjálmar; Larsen, Karin Margretha H.; Hansen, Bogi; Rasmussen, Till Andreas S.

2017-05-01

Marked inter-annual fluctuations in the primary production on the Faroe shelf propagate to higher trophic levels and influence commercial fish stocks. This has previously been demonstrated based on weekly chlorophyll samples from a coastal station, dating back to 1997. However, the spatial extent, for which the coastal samples are representative, has not been well defined, and potential bio-geographical segregations of the shelf have not been considered. By integrating 18 years of chlorophyll satellite data, supplemented by in-situ, model, and meteorological reanalysis data, we identify three regions with unique characteristics with regards to surface chlorophyll and vertical structure - the Central Shelf, the Outer Shelf and the Eastern Banks. The observed difference in timing of the spring bloom in these regions helps explain different spawning patterns of important fish stocks, and the spatial division of the Faroe Shelf should be considered when studying biology and hydrography in these waters. A positive correlation between annual means on the outer Faroe Shelf and parts of the outer northwest Scottish Shelf indicates similarities between these neighbouring regions. We suggest that this similarity arises from the commonality in nutrient composition of the water masses shared by these neighbouring regions.

Volatility measurement with directional change in Chinese stock market: Statistical property and investment strategy

NASA Astrophysics Data System (ADS)

Ma, Junjun; Xiong, Xiong; He, Feng; Zhang, Wei

2017-04-01

The stock price fluctuation is studied in this paper with intrinsic time perspective. The event, directional change (DC) or overshoot, are considered as time scale of price time series. With this directional change law, its corresponding statistical properties and parameter estimation is tested in Chinese stock market. Furthermore, a directional change trading strategy is proposed for invest in the market portfolio in Chinese stock market, and both in-sample and out-of-sample performance are compared among the different method of model parameter estimation. We conclude that DC method can capture important fluctuations in Chinese stock market and gain profit due to the statistical property that average upturn overshoot size is bigger than average downturn directional change size. The optimal parameter of DC method is not fixed and we obtained 1.8% annual excess return with this DC-based trading strategy.

Pattern-set generation algorithm for the one-dimensional multiple stock sizes cutting stock problem

NASA Astrophysics Data System (ADS)

Cui, Yaodong; Cui, Yi-Ping; Zhao, Zhigang

2015-09-01

A pattern-set generation algorithm (PSG) for the one-dimensional multiple stock sizes cutting stock problem (1DMSSCSP) is presented. The solution process contains two stages. In the first stage, the PSG solves the residual problems repeatedly to generate the patterns in the pattern set, where each residual problem is solved by the column-generation approach, and each pattern is generated by solving a single large object placement problem. In the second stage, the integer linear programming model of the 1DMSSCSP is solved using a commercial solver, where only the patterns in the pattern set are considered. The computational results of benchmark instances indicate that the PSG outperforms existing heuristic algorithms and rivals the exact algorithm in solution quality.

Spatial and temporal variability of macroinvertebrates in spawning and non-spawning habitats during a salmon run in Southeast Alaska.

PubMed

Campbell, Emily Y; Merritt, Richard W; Cummins, Kenneth W; Benbow, M Eric

2012-01-01

Spawning salmon create patches of disturbance through redd digging which can reduce macroinvertebrate abundance and biomass in spawning habitat. We asked whether displaced invertebrates use non-spawning habitats as refugia in streams. Our study explored how the spatial and temporal distribution of macroinvertebrates changed during a pink salmon (Oncorhynchus gorbuscha) spawning run and compared macroinvertebrates in spawning (riffle) and non-spawning (refugia) habitats in an Alaskan stream. Potential refugia included: pools, stream margins and the hyporheic zone, and we also sampled invertebrate drift. We predicted that macroinvertebrates would decline in riffles and increase in drift and refugia habitats during salmon spawning. We observed a reduction in the density, biomass and taxonomic richness of macroinvertebrates in riffles during spawning. There was no change in pool and margin invertebrate communities, except insect biomass declined in pools during the spawning period. Macroinvertebrate density was greater in the hyporheic zone and macroinvertebrate density and richness increased in the drift during spawning. We observed significant invertebrate declines within spawning habitat; however in non-spawning habitat, there were less pronounced changes in invertebrate density and richness. The results observed may be due to spawning-related disturbances, insect phenology, or other variables. We propose that certain in-stream habitats could be important for the persistence of macroinvertebrates during salmon spawning in a Southeast Alaskan stream.

Spatial and Temporal Variability of Macroinvertebrates in Spawning and Non-Spawning Habitats during a Salmon Run in Southeast Alaska

PubMed Central

Campbell, Emily Y.; Merritt, Richard W.; Cummins, Kenneth W.; Benbow, M. Eric

2012-01-01

Spawning salmon create patches of disturbance through redd digging which can reduce macroinvertebrate abundance and biomass in spawning habitat. We asked whether displaced invertebrates use non-spawning habitats as refugia in streams. Our study explored how the spatial and temporal distribution of macroinvertebrates changed during a pink salmon (Oncorhynchus gorbuscha) spawning run and compared macroinvertebrates in spawning (riffle) and non-spawning (refugia) habitats in an Alaskan stream. Potential refugia included: pools, stream margins and the hyporheic zone, and we also sampled invertebrate drift. We predicted that macroinvertebrates would decline in riffles and increase in drift and refugia habitats during salmon spawning. We observed a reduction in the density, biomass and taxonomic richness of macroinvertebrates in riffles during spawning. There was no change in pool and margin invertebrate communities, except insect biomass declined in pools during the spawning period. Macroinvertebrate density was greater in the hyporheic zone and macroinvertebrate density and richness increased in the drift during spawning. We observed significant invertebrate declines within spawning habitat; however in non-spawning habitat, there were less pronounced changes in invertebrate density and richness. The results observed may be due to spawning-related disturbances, insect phenology, or other variables. We propose that certain in-stream habitats could be important for the persistence of macroinvertebrates during salmon spawning in a Southeast Alaskan stream. PMID:22745724

Broodstock History Strongly Influences Natural Spawning Success in Hatchery Steelhead (Oncorhynchus mykiss).

PubMed

Ford, Michael J; Murdoch, Andrew R; Hughes, Michael S; Seamons, Todd R; LaHood, Eric S

2016-01-01

We used genetic parentage analysis of 6200 potential parents and 5497 juvenile offspring to evaluate the relative reproductive success of hatchery and natural steelhead (Onchorhynchus mykiss) when spawning in the wild between 2008 and 2011 in the Wenatchee River, Washington. Hatchery fish originating from two prior generation hatchery parents had <20% of the reproductive success of natural origin spawners. In contrast, hatchery females originating from a cross between two natural origin parents of the prior generation had equivalent or better reproductive success than natural origin females. Males originating from such a cross had reproductive success of 26-93% that of natural males. The reproductive success of hatchery females and males from crosses consisting of one natural origin fish and one hatchery origin fish was 24-54% that of natural fish. The strong influence of hatchery broodstock origin on reproductive success confirms similar results from a previous study of a different population of the same species and suggests a genetic basis for the low reproductive success of hatchery steelhead, although environmental factors cannot be entirely ruled out. In addition to broodstock origin, fish size, return time, age, and spawning location were significant predictors of reproductive success. Our results indicate that incorporating natural fish into hatchery broodstock is clearly beneficial for improving subsequent natural spawning success, even in a population that has a decades-long history of hatchery releases, as is the case in the Wenatchee River.

Photoperiod, temperature, and food availability as drivers of the annual reproductive cycle of the sea urchin Echinometra sp. from the Gulf of Aqaba (Red Sea)

NASA Astrophysics Data System (ADS)

Bronstein, Omri; Loya, Yossi

2015-03-01

In spite of the efforts invested in the search for the environmental factors that regulate discrete breeding periods in marine invertebrates, they remain poorly understood. Here, we present the first account of the annual reproductive cycle of the pantropical sea urchin Echinometra sp. from the Gulf of Aqaba/Eilat (Red Sea) and explore some of the main environmental variables that drive echinoid reproduction. Monthly measurements of gonado-somatic indexes and histological observations of 20 specimens revealed a single seasonal reproductive cycle, with gametogenesis in males and females being highly synchronized. Gametogenesis commenced in June and peak spawning occurred between September and October. Gonado-somatic indexes were significantly correlated with seawater temperatures but not with photoperiod. The latter cycle lagged behind the gonado-somatic cycle by two months, suggesting that the onset of gametogenesis corresponds to shortening day length, while spawning may be driven by warming seawater temperatures. Gonads remained quiescent throughout the winter and spring (January through May) when temperatures were at their lowest. Chlorophyll- a concentrations increased significantly in the months following spawning (October through January). These high concentrations are indicative of high phytoplankton abundance and may reflect the increase in food availability for the developing larvae. Of the external test dimensions, length presented the highest correlation to body weight, indicating length as the best predictor for body size in Echinometra. Neither sexual dimorphism nor size differences between males and females were detected, and the sex ratios were approximately 1:1 in three distant Echinometra populations. Environmentally regulated reproduction, as occurs in sea urchins, might face severe outcomes due to anthropogenic disturbances to the marine environment. Consequently, there is a need to deepen our understanding of the mechanisms that drive and regulate this process in broadcast-spawning species.

Behavioral tactics of male sockeye salmon (Oncorhynchus nerka) under varying operating sex ratios

USGS Publications Warehouse

Quinn, Thomas P.; Adkison, Milo D.; Ward, Michael B.

1996-01-01

Previous studies have demonstrated several reproductive-behavior patterns in male salmon, including competitive and sneaking tactics, the formation of hierarchies, and non-hierarchical aggregations around ripe females. Through behavioral observations at varying spatial and temporal scales, we examined the hypothesis that operational sex ratio (OSR) determines male sockeye salmon (Oncorhynchus nerka) distribution and breeding tactics. Patterns of male distribution and behavior varied over both coarse and fine scales, associated with apparent shifts in reproductive opportunities, the physical characteristics of the breeding sites, and the deterioration of the fish as they approached death. Females spawned completely within a few days of arriving on the spawning grounds, whereas males courted the available ripe females from the date of their arrival on the spawning ground until their death. This difference in reproductive lifespans tended to elevate late-season OSRs but was partially counterbalanced by male departures and the arrival of other ripe females. The proportion of males able to dominate access to ripe females decreased and the number of large courting groups increased over the course of the season, apparently related to both increasing OSR and the deteriorating physical condition of males. However, great variation in OSR was observed within the spawning sites on a given day. OSRs were generally higher in shallow than in deep water, perhaps because larger females or more desirable breeding sites were concentrated in shallow water. The aggregations of males courting females were not stable (i.e. many arrivals and departures took place) and male aggression varied with group size. Aggression was most frequent at low OSRs and in groups of intermediate size (2–4 males per female), and much less frequent in larger groups, consistent with the needs of maximizing reproductive opportunities while minimizing unproductive energy expenditure. These results indicate that, while OSR strongly influences male distribution and behavior, other factors such as physical condition, limited movement and habitat choice may also affect male reproductive opportunities.

Production of stocker-size hybrid tilapia in an outdoor biofloc production system

USDA-ARS?s Scientific Manuscript database

Production efficiency per unit volume of water can be improved when stocking rate is adjusted to allow rapid growth of the culture organism to the desired target weight. Fingerlings often are grown to stocker size (ca. 100-150 g/fish) at high stocking rates and then the population is thinned to allo...

Recruitment variability of alewives in Lake Michigan

USGS Publications Warehouse

Madenjian, C.P.; Hook, T.O.; Rutherford, E.S.; Mason, D.M.; Croley, T.E.; Szalai, E.B.; Bence, J.R.

2005-01-01

We used a long-term series of observations on alewife Alosa pseudoharengus abundance that was based on fall bottom-trawl catches to assess the importance of various abiotic and biotic factors on alewife recruitment in Lake Michigan during 1962–2002. We first fit a basic Ricker spawner–recruit model to the lakewide biomass estimates of age-3 recruits and the corresponding spawning stock size; we then fit models for all possible combinations of the following four external variables added to the basic model: an index of salmonine predation on an alewife year-class, an index for the spring–summer water temperatures experienced by alewives during their first year in the lake, an index of the severity of the first winter experienced by alewives in the lake, and an index of lake productivity during an alewife year-class's second year in the lake. Based on an information criterion, the best model for alewife recruitment included indices of salmonine predation and spring–summer water temperatures as external variables. Our analysis corroborated the contention that a decline in alewife abundance during the 1970s and early 1980s in Lake Michigan was driven by salmonine predation. Furthermore, our findings indicated that the extraordinarily warm water temperatures during the spring and summer of 1998 probably led to a moderately high recruitment of age-3 alewives in 2001, despite abundant salmonines.

Dietary fatty acid enrichment increases egg size and quality of yellow seahorse Hippocampus kuda.

PubMed

Saavedra, M; Masdeu, M; Hale, P; Sibbons, C M; Holt, W V

2014-02-01

Seahorses populations in the wild have been declining and to restore them a better knowledge of seahorse reproduction is required. This study examines the effect of dietary quality on seahorse fecundity and egg quality. Two different diets were tested with Hippocampus kuda females: frozen mysis (control) and frozen mysis enriched with a liposome spray containing essential fatty acids. Diets were given to females (two groups of five) over a seven week period. After this period, males (fed the control diet) and females were paired and the eggs dropped by the females were collected. Fatty acid profile were analysed and eggs were counted and measured. Results showed that females fed on enriched mysis had larger eggs and that these had a higher content of total polyunsaturated fatty acids. The size of the egg was especially affected in the first spawn, where egg size for females fed the enriched diet was significantly higher than the egg size from control females. This effect was reduced in the following spawning where no significant differences were found. Egg size is an important quality descriptor as seahorse juveniles originating from smaller eggs and/or eggs of poor quality will have less chances of overcoming adverse conditions in the wild and consequently have lower survival and growth rates. This study shows that enriching frozen mysis with polyunsaturated fatty acids increases egg size and egg quality of H. kuda. Copyright © 2013 Elsevier B.V. All rights reserved.

Telemetry narrows the search for sea lamprey spawning locations in the St. Clair-Detroit River System

USGS Publications Warehouse

Holbrook, Christopher; Jubar, Aaron K.; Barber, Jessica M.; Tallon, Kevin; Hondorp, Darryl W.

2016-01-01

Adult sea lamprey (Petromyzon marinus) abundance in Lake Erie has remained above targets set by fishery managers since 2005, possibly due to increased recruitment in the St. Clair-Detroit River System (SCDRS). Sea lamprey recruitment in the SCDRS poses an enormous challenge to sea lamprey control and assessment in Lake Erie because the SCDRS contains no dams to facilitate capture and discharge is at least an order of magnitude larger in the SCDRS than most other sea lamprey-producing tributaries in the Great Lakes. As a first step toward understanding population size, spatial distribution, and spawning habitat of adult sea lampreys in the SCDRS, we used acoustic telemetry to determine where sea lampreys ceased migration (due to spawning, death, or both) among major regions of the SCDRS. All tagged sea lampreys released in the lower Detroit River (N = 27) moved upstream through the Detroit River and entered Lake St. Clair. After entering Lake St. Clair, sea lampreys entered the St. Clair River (N = 22), Thames River (N = 1), or were not detected again (N = 4). Many sea lampreys (10 of 27) were last observed moving downstream (“fallback”) but we were unable to determine if those movements occurred before or after spawning, or while sea lampreys were dead or alive. Regardless of whether estimates of locations where sea lampreys ceased migration were based on the most upstream region occupied or final region occupied, most sea lampreys ceased migration in the St. Clair River or Lake St. Clair. Results suggest that spawning and rearing in the St. Clair River could be an important determinant of sea lamprey recruitment in the SCDRS and may direct future assessment and control activities in that system.

Spatial ecological processes and local factors predict the distribution and abundance of spawning by steelhead (Oncorhynchus mykiss) across a complex riverscape

USGS Publications Warehouse

Falke, Jeffrey A.; Dunham, Jason B.; Jordan, Christopher E.; McNyset, Kris M.; Reeves, Gordon H.

2013-01-01

Processes that influence habitat selection in landscapes involve the interaction of habitat composition and configuration and are particularly important for species with complex life cycles. We assessed the relative influence of landscape spatial processes and local habitat characteristics on patterns in the distribution and abundance of spawning steelhead (Oncorhynchus mykiss), a threatened salmonid fish, across ~15,000 stream km in the John Day River basin, Oregon, USA. We used hurdle regression and a multi-model information theoretic approach to identify the relative importance of covariates representing key aspects of the steelhead life cycle (e.g., site access, spawning habitat quality, juvenile survival) at two spatial scales: within 2-km long survey reaches (local sites) and ecological neighborhoods (5 km) surrounding the local sites. Based on Akaike’s Information Criterion, models that included covariates describing ecological neighborhoods provided the best description of the distribution and abundance of steelhead spawning given the data. Among these covariates, our representation of offspring survival (growing-season-degree-days, °C) had the strongest effect size (7x) relative to other predictors. Predictive performances of model-averaged composite and neighborhood-only models were better than a site-only model based on both occurrence (percentage of sites correctly classified = 0.80±0.03 SD, 0.78±0.02 vs. 0.62±0.05, respectively) and counts (root mean square error = 3.37, 3.93 vs. 5.57, respectively). The importance of both temperature and stream flow for steelhead spawning suggest this species may be highly sensitive to impacts of land and water uses, and to projected climate impacts in the region and that landscape context, complementation, and connectivity will drive how this species responds to future environments.

Infilling of Cobble Substrate used by White Sturgeon on the Nechako River, at Vanderhoof BC

NASA Astrophysics Data System (ADS)

Zimmermann, A. E.; Argast, T.; Sary, Z.

2013-12-01

Nechako white sturgeon are experiencing a recruitment failure, which has been attributed to the failure of eggs and larvae to survive as a result of changes in the substrate at the locations where they are known to spawn. As part of the overall recovery effort initiative, cobble substrate was placed at two locations to provide clean spawning substrate. Subsequently, the condition of the substrate has been investigated using an underwater camera and freeze core sampling. These observations have shown that coarse sand and fine gravels (fine bedoad) have in-filled the coarse substrate where it was placed along the inside corner of the bends, while placed substrate located on the outside of the bends has remained free of this size fraction. This observation has lead to the quandary: Is placed cobble substrate on the outside corner of the bends not being filled in with fine bedload because fine bedload is not moving past these sites, or are post-regulation flood flows sufficient to ensure fines remain suspended and are not deposited in the interstitial spaces? To assess this question a number of field based techniques will be used in August of 2013 during high flows to examine the movement of fine bedload. The techniques employed will include an underwater camera, P61 suspended sediment sampler, a HellySmith and KAROLYI bedload sampler and an ADCP with RTK for bottom tracking. The intent is to examine the movement of fine bedload across the channel at a number of potential spawning sites. The poster will summarize the observations to date about the movement of fine bedload at the spawning sites, and discuss the implications for spawning substrate improvement efforts.

Intra-lake variation in maturity, fecundity, and spawning of slimy sculpins (Cottus cognatus) in southern Lake Ontario

USGS Publications Warehouse

Owens, Randall W.; Noguchi, George E.

1998-01-01

Knowledge of the spawning cycle and factors affecting fecundity of slimy sculpins (Cottus cognatus) are important in understanding the population dynamics of this species in large lake systems, like Lake Ontario. Fecundity and the spawning cycle of slimy sculpins were described from samples of slimy sculpins and their egg masses collected with bottom trawls during four annual surveys, April to October, 1988 to 1994. Incidence of gravid females and collections of their egg masses indicated that spawning by slimy sculpins likely occurred from late April to mid October in Lake Ontario. Protracted spawning by slimy sculpins in Lake Ontario is probably a function of the annual water temperature cycle at various depths. Mean length of gravid females was inversely related to density of slimy sculpins. Fecundity ranged from 55 to 1,157 eggs among fish 55 to 127 mm long, and for similar-sized fish, fecundity was inversely related to density of slimy sculpins. Fecundity was about 50% higher at Olcott, where population indices of slimy sculpins were low, compared with Nine Mile Point where indices were much higher. Somatic weight or total length were both good predictors of fecundity. Lipid content of slimy sculpins was lower in an area of high sculpin abundance than in an area of low sculpin abundance, suggesting that fecundity was a function of density-dependent food availability. In large aquatic ecosystems, samples from more than one area may be necessary to describe fecundity of a sedentary species like slimy sculpin, especially if fish densities vary considerably among geographic areas. Large geographic variations in fecundity may be an indicator of spatial imbalance of a species with its prey. Low fecundity may be a compensatory response to slimy sculpins to low food supplies, thereby limiting population growth.

Maternal and environmental influences on egg size and juvenile life-history traits in Pacific salmon

PubMed Central

Braun, Douglas C; Patterson, David A; Reynolds, John D

2013-01-01

Life-history traits such as fecundity and offspring size are shaped by investment trade-offs faced by mothers and mediated by environmental conditions. We use a 21-year time series for three populations of wild sockeye salmon (Oncorhynchus nerka) to test predictions for such trade-offs and responses to conditions faced by females during migration, and offspring during incubation. In years when their 1100 km upstream migration was challenged by high water discharges, females that reached spawning streams had invested less in gonads by producing smaller but not fewer eggs. These smaller eggs produced lighter juveniles, and this effect was further amplified in years when the incubation water was warm. This latter result suggests that there should be selection for larger eggs to compensate in populations that consistently experience warm incubation temperatures. A comparison among 16 populations, with matching migration and rearing environments but different incubation environments (i.e., separate spawning streams), confirmed this prediction; smaller females produced larger eggs for their size in warmer creeks. Taken together, these results reveal how maternal phenotype and environmental conditions can shape patterns of reproductive investment and consequently juvenile fitness-related traits within and among populations. PMID:23789081

A trait database for marine copepods

NASA Astrophysics Data System (ADS)

Brun, Philipp; Payne, Mark R.; Kiørboe, Thomas

2017-02-01

The trait-based approach is gaining increasing popularity in marine plankton ecology but the field urgently needs more and easier accessible trait data to advance. We compiled trait information on marine pelagic copepods, a major group of zooplankton, from the published literature and from experts and organized the data into a structured database. We collected 9306 records for 14 functional traits. Particular attention was given to body size, feeding mode, egg size, spawning strategy, respiration rate, and myelination (presence of nerve sheathing). Most records were reported at the species level, but some phylogenetically conserved traits, such as myelination, were reported at higher taxonomic levels, allowing the entire diversity of around 10 800 recognized marine copepod species to be covered with a few records. Aside from myelination, data coverage was highest for spawning strategy and body size, while information was more limited for quantitative traits related to reproduction and physiology. The database may be used to investigate relationships between traits, to produce trait biogeographies, or to inform and validate trait-based marine ecosystem models. The data can be downloaded from PANGAEA, doi:10.1594/PANGAEA.862968.

Migration and spawning of female surubim (Pseudoplatystoma corruscans, Pimelodidae) in the São Francisco river, Brazil

USGS Publications Warehouse

Godinho, Alexandre L.; Kynard, Boyd; Godinho, Hugo P.

2007-01-01

Surubim, Pseudoplatystoma corruscans, is the most valuable commercial and recreational fish in the São Francisco River, but little is known about adult migration and spawning. Movements of 24 females (9.5–29.0 kg), which were radio-tagged just downstream of Três Marias Dam (TMD) at river kilometer 2,109 and at Pirapora Rapids (PR) 129 km downstream of TMD, suggest the following conceptual model of adult female migration and spawning. The tagged surubims used only 274 km of the main stem downstream of TMD and two tributaries, the Velhas and Abaeté rivers. Migration style was dualistic with non-migratory (resident) and migratory fish. Pre-spawning females swam at ground speeds of up to 31 km day-1 in late September–December to pre-spawning staging sites located 0–11 km from the spawning ground. In the spawning season (November–March), pre-spawning females migrated back and forth from nearby pre-spawning staging sites to PR for short visits to spawn, mostly during floods. Multiple visits to the spawning site suggest surubim is a multiple spawner. Most post-spawning surubims left the spawning ground to forage elsewhere, but some stayed at the spawning site until the next spawning season. Post-spawning migrants swam up or downstream at ground speeds up to 29 km day-1 during January–March. Construction of proposed dams in the main stem and tributaries downstream of TMD will greatly reduce surubim abundance by blocking migrations and changing the river into reservoirs that eliminate riverine spawning and non-spawning habitats, and possibly, cause extirpation of populations.

Evaluation of methods for identifying spawning sites and habitat selection for alosines

USGS Publications Warehouse

Harris, Julianne E.; Hightower, Joseph E.

2010-01-01

Characterization of riverine spawning habitat is important for the management and restoration of anadromous alosines. We examined the relative effectiveness of oblique plankton tows and spawning pads for collecting the eggs of American shad Alosa sapidissima, hickory shad A. mediocris, and “river herring” (a collective term for alewife A. pseudoharengus and blueback herring A. aestivalis) in the Roanoke River, North Carolina. Relatively nonadhesive American shad eggs were only collected by plankton tows, whereas semiadhesive hickory shad and river herring eggs were collected by both methods. Compared with spawning pads, oblique plankton tows had higher probabilities of collecting eggs and led to the identification of longer spawning periods. In assumed spawning areas, twice-weekly plankton sampling for 15 min throughout the spawning season had a 95% or greater probability of collecting at least one egg for all alosines; however, the probabilities were lower in areas with more limited spawning. Comparisons of plankton tows, spawning pads, and two other methods of identifying spawning habitat (direct observation of spawning and examination of female histology) suggested differences in effectiveness and efficiency. Riverwide information on spawning sites and timing for all alosines is most efficiently obtained by plankton sampling. Spawning pads and direct observations of spawning are the best ways to determine microhabitat selectivity for appropriate species, especially when spawning sites have previously been identified. Histological examination can help determine primary spawning sites but is most useful when information on reproductive biology and spawning periodicity is also desired. The target species, riverine habitat conditions, and research goals should be considered when selecting methods with which to evaluate alosine spawning habitat.

Can mesophotic reefs replenish shallow reefs? Reduced coral reproductive performance casts a doubt.

PubMed

Shlesinger, Tom; Grinblat, Mila; Rapuano, Hanna; Amit, Tal; Loya, Yossi

2018-02-01

Mesophotic coral ecosystems (i.e., deep coral reefs at 30-120 m depth) appear to be thriving while many shallow reefs in the world are declining. Amid efforts to understand and manage their decline, it was suggested that mesophotic reefs might serve as natural refuges and a possible source of propagules for the shallow reefs. However, our knowledge of how reproductive performance of corals alters with depth is sparse. Here, we present a comprehensive study of the reproductive phenology, fecundity, and abundance of seven reef-building conspecific corals in shallow and mesophotic habitats. Significant differences were found in the synchrony and timing of gametogenesis and spawning between shallow and mesophotic coral populations. Thus, mesophotic populations exhibited delayed or protracted spawning events, which led to spawning of the mesophotic colonies in large proportions at times where the shallow ones had long been depleted of reproductive material. All species investigated demonstrated a substantial reduction in fecundity and/or oocyte sizes at mesophotic depths (40-60 m). Two species (Seriatopora hystrix and Galaxea fascicularis) displayed a reduction in both fecundity and oocyte size at mesophotic depths. Turbinaria reniformis had only reduced fecundity and Acropora squarrosa and Acropora valida only reduced oocyte size. In Montipora verrucosa, reduced fecundity was found during one annual reproductive season while, in the following year, only reduced oocyte size was found. In contrast, reduced oocyte size in mesophotic populations of Acropora squarrosa was consistent along three studied years. One species, Acropora pharaonis, was found to be infertile at mesophotic depths along two studied years. This indicates that reproductive performance decreases with depth; and that although some species are capable of reproducing at mesophotic depths, their contribution to the replenishment of shallow reefs may be inconsequential. Reduced reproductive performance with depth, combined with the possible narrower tolerance to environmental factors, further suggests that mesophotic corals may in fact be more vulnerable than previously conceived. Furthermore, we posit that the observed temporal segregation in reproduction could lead to assortative mating, and this, in turn, may facilitate adaptive divergence across depth. © 2017 by the Ecological Society of America.

Habitat use in irrigation channels by the golden venus chub (Hemigrammocypris rasborella) at different growth stages.

PubMed

Onikura, Norio; Nakajima, Jun; Kouno, Hiromi; Sugimoto, Yoshiko; Kaneto, Jun

2009-06-01

Ecological information on the golden venus chub (Hemigrammocypris rasborella Fowler, 1910) was collected during field surveys and used to analyze habitat use by this species at each growth stage. Surveys were conducted every month for approximately 2 years In an irrigation ditch near the Ushizu River, Kyushu Island, Japan. Based on the characteristic nuptial coloration of males, it was estimated that H. rasborella spawns between spring and summer. Size measurements of 2697 individuals indicated two size classes. The population of age class 1 decreased rapidly after the spawning period. On the basis of growth patterns, the life cycle of H. rasborella was classified into three stages: the growth stage (GS) of age class 0 fish from August to November, the no-growth stage (NGS) of age class 0 fish from December to March, and the growing and spawning stage (GSS) of age class 0 and 1 fish from April to August. Habitat use by GS, NGS, and GSS fish was analyzed with a stepwise multiple linear regression. The average number of fish was negatively correlated with the presence of a concrete revetment in the GS; positively and negatively correlated with minimum water depth and submerged plants, respectively, in the NGS; and positively correlated with maximum water temperature in the GSS. These results suggest that maintenance of the water level in the fallow season and not using concrete revetments are essential for the conservation of this species under the present conditions in Japanese rice fields.

Numerical Model of Channel and Aquatic Habitat Response to Sediment Pulses in Mountain Rivers of Central Idaho

NASA Astrophysics Data System (ADS)

Lewicki, M.; Buffington, J. M.; Thurow, R. F.; Isaak, D. J.

2006-12-01

Mountain rivers in central Idaho receive pulsed sediment inputs from a variety of mass wasting processes (side-slope landslides, rockfalls, and tributary debris flows). Tributary debris flows and hyperconcentrated flows are particularly common due to winter "rain-on-snow" events and summer thunderstorms, the effects of which are amplified by frequent wildfire and resultant changes in vegetation, soil characteristics, and basin hydrology. Tributary confluences in the study area are commonly characterized by debris fans built by these repeated sediment pulses, providing long-term controls on channel slope, hydraulics and sediment transport capacity in the mainstem channel network. These long-term impacts are magnified during debris-flow events, which deliver additional sediment and wood debris to the fan and may block the mainstem river. These changes in physical conditions also influence local and downstream habitat for aquatic species, and can impact local human infrastructure (roads, bridges). Here, we conduct numerical simulations using a modified version of Cui's [2005] network routing model to examine bedload transport and debris-fan evolution in medium- sized watersheds (65-570 km2) of south-central Idaho. We test and calibrate the model using data from a series of postfire debris-flow events that occurred from 2003-4. We investigate model sensitivity to different controlling factors (location of the pulse within the stream network, volume of the pulse, and size distribution of the input material). We predict that on decadal time scales, sediment pulses cause a local coarsening of the channel bed in the vicinity of the sediment input, and a wave of downstream fining over several kilometers of the river (as long as the pulse material is not coarser than the stream bed itself). The grain-size distribution of the pulse influences its rate of erosion, the rate and magnitude of downstream fining, and the time required for system recovery. The effects of textural fining on spawning habitat depend on the size of sediment in the wave relative to that of the downstream channel; fining can improve spawning habitat availability in channels that are otherwise too coarse, or degrade habitat availability in finer-grained channels. Despite the perceived negative effects of sediment pulses, they can be important sources of gravel and wood debris, creating downstream spawning sites and productive wood-forced habitats. Field observations illustrate that opportunistic salmonids will spawn along the margins of recently deposited debris fans, emphasizing the biological value of such disturbances and the plasticity of salmonids to natural disturbances.

Examining Neosho madtom reproductive biology using ultrasound and artificial photothermal cycles

USGS Publications Warehouse

Bryan, J.L.; Wildhaber, M.L.; Noltie, Douglas B.

2005-01-01

We examined whether extended laboratory simulation of natural photothermal conditions could stimulate reproduction in the Neosho madtom Noturus placidus, a federally threatened species. For 3 years, a captive population of Neosho madtoms was maintained under simulated natural conditions and monitored routinely with ultrasound for reproductive condition. Female Neosho madtoms cycled in and out of spawning condition, producing and absorbing oocytes annually. Internal measurements made by means of ultrasound indicated the summer mean oocyte size remained consistent over the years, although estimated fecundity increased with increasing fish length. In the summer of 2001, after 3 years in the simulated natural environment, 13 out of 41 fish participated in 10 spawnings. Simulation of the natural photothermal environment, coupled with within-day temperature fluctuations during the spring rise, seemed important for the spawning of captive Neosho madtoms. The use of ultrasound to assess the reproductive status in Neosho madtoms was effective and resulted in negligible stress or injury to the fish. These procedures may facilitate future culture of this species and other madtoms Noturus spp., especially when species are rare, threatened, or endangered. ?? Copyright by the American Fisheries Society 2005.

Demographics and run timing of adult Lost River (Deltistes luxatus) and short nose (Chasmistes brevirostris) suckers in Upper Klamath Lake, Oregon, 2009

USGS Publications Warehouse

Hewitt, David A.; Hayes, Brian S.; Janney, Eric C.; Harris, Alta C.; Koller, Justin P.; Johnson, Mark A.

2011-01-01

Data from a long-term capture-recapture program were used to assess the status and dynamics of populations of two long-lived, federally endangered catostomids in Upper Klamath Lake, Oregon. Lost River suckers (Deltistes luxatus) and shortnose suckers (Chasmistes brevirostris) have been captured and tagged with passive integrated transponder (PIT) tags during their spawning migrations in each year since 1995. In addition, beginning in 2005, individuals that had been previously PIT-tagged were reencountered on remote underwater antennas deployed throughout the spawning areas. Captures and remote encounters during spring 2009 were used to describe the spawning migrations in that year and also were incorporated into capture-recapture analyses of population dynamics over the last decade. Cormack-Jolly-Seber (CJS) open population capture-recapture models were used to estimate annual survival probabilities, and a reverse-time analog of the CJS model was used to estimate recruitment of new individuals into the spawning populations. In addition, data on the size composition of captured fish was examined for any additional evidence of recruitment. Survival and recruitment estimates were combined to estimate changes in population size over time and to determine the status of the populations through 2007. Separate analyses were conducted for each species and also for each subpopulation of Lost River suckers (LRS). One subpopulation of LRS migrates into tributaries to spawn, similar to shortnose suckers (SNS), whereas the other subpopulation spawns at upwelling areas along the eastern shoreline of the lake. In 2009, we captured and tagged 781 LRS at four shoreline areas and recaptured an additional 638 individuals that had been tagged in previous years. Across all four areas, the remote antennas detected 6,056 individual LRS during the spawning season. Spawning activity peaked in April and most individuals were encountered at Sucker Springs and Cinder Flats. In the Williamson River, we captured and tagged 3,008 LRS and 287 SNS, and recaptured 271 LRS and 81 SNS that had been tagged in previous years. Remote antennas that spanned the river downstream of the tributary spawning areas detected a total of 12,509 LRS and 5,023 SNS. Most LRS passed upstream in mid-April when water temperatures were rising and near or greater than 10°C. In contrast, peaks in upstream passage of SNS occurred in late April and early May when water temperatures were rising and near or greater than 12°C. Finally, an additional 1,569 LRS and 1,794 SNS were captured in trammel net sampling at prespawn staging areas in the northeastern portion of the lake. Of these, 209 of the LRS and 452 of the SNS had been PIT-tagged in previous years. For LRS, encounter histories showed that nearly all of the fish captured at the staging areas were members of the subpopulation that spawns in the tributaries.Capture-recapture analyses for the LRS subpopulation that spawns at the shoreline areas included encounter histories for more than 9,000 individuals, and analyses for the subpopulation that spawns in the tributaries included more than 14,000 encounter histories. With a few exceptions, the survival of males and females in both subpopulations was high (>0.9) between 1999 and 2007. Notably lower survival occurred for both sexes from the tributaries in 2000, for males from the shoreline areas in 2002, and for males from the tributaries in 2006. Recruitment of new individuals into either spawning population was trivial in all years between 2002 and 2007. Over that period, the abundance of males in the lakeshore spawning subpopulation declined by 44–53 percent and the abundance of females declined by 25–38 percent. Similarly, the abundance of males in the tributary spawning subpopulation declined by as much as 39 percent and the abundance of females declined by as much as 33 percent. Capture-recapture analyses for SNS included encounter histories for more than 12,000 individuals. The majority of annual survival estimates between 2001 and 2007 were high (>0.8), but SNS experienced more years of low survival than either LRS subpopulation. The survival of both sexes was particularly low in both 2001 and 2004, and male survival also was somewhat low in 2002 and 2006. Similar to LRS, recruitment of new individuals into the spawning population was trivial in all years between 2001 and 2007. Over that period, the abundance of male SNS declined by 58–80 percent and the abundance of females declined by 52–73 percent. Despite relatively high survival in most years, both species have experienced substantial declines in the abundance of spawning fish because losses from mortality have not been balanced by recruitment of new individuals. Indeed, all populations appear to be largely comprised of fish that were present in the late 1990s and early 2000s. As a result, the status of the endangered sucker populations in Upper Klamath Lake remains worrisome, and the situation is most dire for shortnose suckers. Survival analyses show that the two species do not necessarily experience poor survival in the same years and that poor survival on an annual scale is not predictable from fish die-offs observed in the summer and fall. Future analyses will explore the connections between annual sucker survival and environmental factors of interest, such as water quality and disease. Our monitoring program provides a robust platform for estimating vital population parameters, evaluating the status of the populations, and assessing the effectiveness of conservation and recovery efforts.

Summer spawning of Porites lutea from north-western Australia

NASA Astrophysics Data System (ADS)

Stoddart, C. W.; Stoddart, J. A.; Blakeway, D. R.

2012-09-01

Most coral species off Australia's west coast spawn in the austral autumn (March-April), with a few species also spawning in the southern spring or early summer (November-December). This is the reverse timing to spawning recorded off Australia's east coast. Porites lutea, a gonochoric broadcast spawner that is common on Australia's west coast, is shown here to spawn in the months of November or December, as it does on Australia's east coast. Spawning occurred between 2 and 5 nights after full moon, with the majority of spawning activity on night 3. Gametes developed over three to four months with rapid development in the last two weeks before spawning. Zooxanthellae were typically observed in mature oocytes, only a week before spawning so their presence may provide a useful indicator of imminent spawning.

Modeling and Scaling of the Distribution of Trade Avalanches in a STOCK Market

NASA Astrophysics Data System (ADS)

Kim, Hyun-Joo

We study the trading activity in the Korea Stock Exchange by considering trade avalanches. A series of successive trading with small trade time interval is regarded as a trade avalanche of which the size s is defined as the number of trade in a series of successive trades. We measure the distribution of trade avalanches sizes P(s) and find that it follows the power-law behavior P(s) ~ s-α with the exponent α ≈ 2 for two stocks with the largest number of trades. A simple stochastic model which describes the power-law behavior of the distribution of trade avalanche size is introduced. In the model it is assumed that the some trades induce the accompanying trades, which results in the trade avalanches and we find that the distribution of the trade avalanche size also follows power-law behavior with the exponent α ≈ 2.

Research, monitoring, and evaluation of emerging issues and measures to recover the Snake River Fall Chinook Salmon ESU, 1/1/2016 - 12/31/2016

USGS Publications Warehouse

Connor, William P.; Mullins, Frank L.; Tiffan, Kenneth F.; Plumb, John M.; Perry, Russell W.; Erhardt, John M.; Hemingway, Rulon J.; Bickford, Brad; Rhodes, Tobyn N.

2017-01-01

The portion of the Snake River fall Chinook Salmon Oncorhynchus tshawytscha ESU that spawns upstream of Lower Granite Dam transitioned from low to high abundance during 1992–2016 in association with U.S. Endangered Species Act recovery efforts and other federally mandated actions. This annual report focuses on (1) numeric and habitat use responses by natural- and hatchery-origin spawners, (2) phenotypic and numeric responses by natural-origin juveniles, and (3) predator responses in the Snake River upper and lower reaches as abundance of adult and juvenile fall Chinook Salmon increased. Spawners have located and used most of the available spawning habitat and that habitat is gradually approaching redd capacity. Timing of spawning and fry emergence has been relatively stable; whereas the timing of parr dispersal from riverine rearing habitat into Lower Granite Reservoir has become earlier as apparent abundance of juveniles has increased. Growth rate (g/d) and dispersal size of parr also declined as apparent abundance of juveniles increased. Passage timing of smolts from the two Snake River reaches has become earlier and downstream movement rate faster as estimated abundance of fall Chinook Salmon smolts in Lower Granite Reservoir has increased. In 2016, we described estimated the consumption rate and loss of subyearlings by Smallmouth Bass before, during, and after four hatchery releases. Before releases, Smallmouth Bass consumption rates of subyearling was low (0–0.36 fish/bass/d), but the day after the releases consumption rates reached as high as 1.6 fish/bass/d. Bass consumption in the upper portion of Hells Canyon was high for about 1–2 d before returning to pre-release levels, but in the lower river consumption rates were reduced but took longer to return to pre-release levels. We estimated that most of the subyearlings consumed by bass were of hatchery origin. Smallmouth Bass predation on subyearlings is intense following a hatchery release, but the predation pressure is relatively short-lived as subyearlings quickly disperse downstream. This information will allow us to better estimate subyearling loss to predation from our past efforts at time intervals less than 2 weeks. These findings coupled with stock-recruitment analyses presented in this report provide evidence for density-dependence in the Snake River reaches and in Lower Granite Reservoir that was influenced by the expansion of the recovery program. The long-term goal is to use the information covered here in a comprehensive modeling effort to conduct action effectiveness and uncertainty research and to inform Fish Population, Hydrosystem, Harvest, Hatchery, and Predation and Invasive Species Management RM&E.

Ichthyophonus-induced cardiac damage: a mechanism for reduced swimming stamina in salmonids.

PubMed

Kocan, R; Lapatra, S; Gregg, J; Winton, J; Hershberger, P

2006-09-01

Swimming stamina, measured as time-to-fatigue, was reduced by approximately two-thirds in rainbow trout experimentally infected with Ichthyophonus. Intensity of Ichthyophonus infection was most severe in cardiac muscle but multiple organs were infected to a lesser extent. The mean heart weight of infected fish was 40% greater than that of uninfected fish, the result of parasite biomass, infiltration of immune cells and fibrotic (granuloma) tissue surrounding the parasite. Diminished swimming stamina is hypothesized to be due to cardiac failure resulting from the combination of parasite-damaged heart muscle and low myocardial oxygen supply during sustained aerobic exercise. Loss of stamina in Ichthyophonus-infected salmonids could explain the poor performance previously reported for wild Chinook and sockeye salmon stocks during their spawning migration.

Habitat Suitability Index Models and Instream Flow Suitability Curves: American shad

USGS Publications Warehouse

Stier, David J.; Crance, Johnie H.

1985-01-01

INTRODUCTION The American shad, an anadromous species, is the largest member of the herring family (Clupeidae) and is native to North America (Talbot and Sykes 1958; Hildebrand 1963; Walburg and Nichols 1967). Historically, the commercial fishery for American shad on the Atlantic coast was widespread and intense; in 1896 the estimated catch was 22.7 million kg (50 million lb). By 1960, however, the estimated catch had dropped to slightly more than 3.6 million kg (8 million lb), according to Walburg and Nichols (1967). Pollution, overfishing, and dams constructed across streams that prevent shad from reaching their spawning grounds have caused partial or total depletion of stocks (Hildebrand 1963). Several programs aimed at restoring American shad to their former range have been initiated by Federal and State agencies.

Ichthyophonus-induced cardiac damage: a mechanism for reduced swimming stamina in salmonids

USGS Publications Warehouse

Kocan, R.; LaPatra, S.; Gregg, J.; Winton, J.; Hershberger, P.

2006-01-01

Swimming stamina, measured as time-to-fatigue, was reduced by approximately two-thirds in rainbow trout experimentally infected with Ichthyophonus. Intensity of Ichthyophonus infection was most severe in cardiac muscle but multiple organs were infected to a lesser extent. The mean heart weight of infected fish was 40% greater than that of uninfected fish, the result of parasite biomass, infiltration of immune cells and fibrotic (granuloma) tissue surrounding the parasite. Diminished swimming stamina is hypothesized to be due to cardiac failure resulting from the combination of parasite-damaged heart muscle and low myocardial oxygen supply during sustained aerobic exercise. Loss of stamina in Ichthyophonus-infected salmonids could explain the poor performance previously reported for wild Chinook and sockeye salmon stocks during their spawning migration. ?? 2006 Blackwell Publishing Ltd.

Seasonal movements among river reaches, migration strategies, and population structure of the divided Connecticut River shortnose sturgeon population: the effects of Holyoke Dam

USGS Publications Warehouse

Kynard, Boyd; Kieffer, Micah; Vinogradov, Phil; Kynard, B.; Bronzi, P.; Rosenthal, H.

2012-01-01

Even after 155 years, each population segment seasonally migrates toward the other attempting to maintain the natural connection. Migration timing and style of pre-spawning and post-spawning males and females is discussed, as is homing. The impact of Holyoke Dam on population size and growth is characterized and turbine mortality of adult sturgeon passing through a Kaplan turbine at the dam is estimated. The chapter also identifies a behavioral dysfunction that results when migrations are blocked by a dam and are not completed at the correct stage of life. Many unknown effects of damming on other long-lived riverine fishes are likely captured in this 16-year study.

Stock size affects early growth of a loblolly pine

Treesearch

David B. South; Al Lyons; Russ Pohl

2015-01-01

For decades, forest researchers in the South have known that early gains in survival and growth of loblolly pine (Pinus taeda L.) can be achieved by planting large-diameter seedlings (South 1993; Wakeley 1949). For P. radiata, increasing size of planting stock also increases early growth of both seedlings (Mason and others 1996) and cuttings (South and others 2005)....

Evaluating subsoiling and herbaceous weed control on shortleaf pine planted in retired farm land

Treesearch

John D. Kushla

2010-01-01

In March 2005, shortleaf pine was planted on retired fields of the Mississippi Agriculture and Forestry Experiment Station in Holly Springs. The objectives were to evaluate subsoiling and herbaceous weed control on first year seedling stocking, survival, and size. First year seedling measurements were made on stocking, survival, and size. Only results for first year...

Characterization of channel substrate, and changes in suspended-sediment transport and channel geometry in white sturgeon spawning habitat in the Kootenai River near Bonners Ferry, Idaho, following the closure of Libby Dam

USGS Publications Warehouse

Barton, Gary J.

2004-01-01

Many local, State, and Federal agencies have concerns over the declining population of white sturgeon (Acipenser transmontanus) in the Kootenai River and the possible effects of the closure and subsequent operation of Libby Dam in 1972. In 1994, the Kootenai River white sturgeon was listed as an Endangered Species. A year-long field study was conducted in cooperation with the Kootenai Tribe of Idaho along a 21.7-kilometer reach of the Kootenai River including the white sturgeon spawning reach near Bonners Ferry, Idaho, approximately 111 to 129 kilometers below Libby Dam. During the field study, data were collected in order to map the channel substrate in the white sturgeon spawning reach. These data include seismic subbottom profiles at 18 cross sections of the river and sediment cores taken at or near the seismic cross sections. The effect that Libby Dam has on the Kootenai River white sturgeon spawning substrate was analyzed in terms of changes in suspended-sediment transport, aggradation and degradation of channel bed, and changes in the particle size of bed material with depth below the riverbed. The annual suspended-sediment load leaving the Kootenai River white sturgeon spawning reach decreased dramatically after the closure of Libby Dam in 1972: mean annual pre-Libby Dam load during 1966–71 was 1,743,900 metric tons, and the dam-era load during 1973–83 was 287,500 metric tons. The amount of sand-size particles in three suspended-sediment samples collected at Copeland, Idaho, 159 kilometers below Libby Dam, during spring and early summer high flows after the closure of Libby Dam is less than in four samples collected during the pre-Libby Dam era. The supply of sand to the spawning reach is currently less due to the reduction of high flows and a loss of 70 percent of the basin after the closure of Libby Dam. The river's reduced capacity to transport sand out of the spawning reach is compensated to an unknown extent by a reduced load of sand entering the spawning reach. Since the closure of Libby Dam, the most notable change in channel geometry at the Copeland streamflow gaging station was the initiation of cyclical aggradation and degradation of the riverbed in the center of the channel. The aggradation and degradation of the riverbed are reflected in a twofold increase, from 1.3 to 2.5 meters, in the fluctuation of the minimum riverbed elevation, which suggests that during the Libby Dam era, parts of the riverbed in the spawning reach may have aggraded or degraded by as much as 2.5 meters. Before the closure of Libby Dam, there was a greater propensity for aggradation and degradation of sand over the discontinuous gravel and cobble layers in the buried gravelcobble reach at Bonners Ferry. The gravel and cobble in this reach, 111.3 to 115.9 kilometers below Libby Dam, are buried by sand. Unregulated spring snowmelt-runoff flows flushed part of the sand layer and exposed some of the buried gravel-cobble layer because streamflow velocities were higher at that time. Unregulated autumn-winter base flows gradually deposited silt and sand and reestablished a sand layer, burying the gravel-cobble layer. This cyclical process of aggradation and degradation of the riverbed sediment is reflected in the alternating gravel-cobble layers and sand layers found in sediment core K18-TH taken as part of this project. White sturgeon spawning substrate in the Kootenai River meander reach is currently composed of alluvial sand that forms sand dunes and of minor amounts of lacustrine clay and silt that generally are found in the river's thalweg. The present substrate composition in the meander reach is considered similar to that which existed prior to closure of Libby Dam, with one possible exception. Prior to closure of Libby Dam, minor amounts of gravel and cobble may have been exposed on the riverbed in the spawning reach just below the mouth of Myrtle Creek 230 kilometers below Libby Dam. The substrate composition near Shorty Island, 234 kilometers below Libby Dam, a notable white sturgeon spawning reach, is predominantly sand and is similar to that which existed prior to closure of Libby Dam.

Evaluation of Salmon Spawning Below Bonneville Dam, Annual Report October 2005 - September 2006.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arntzen, Evan V.; Mueller, Robert P.; Murray, Christopher J.

2007-09-21

Since FY 2000, scientists at Pacific Northwest National Laboratory (PNNL) have conducted research to assess the extent of spawning by chum salmon (Oncorhynchus keta) and fall Chinook salmon (O. tshawytscha) in the lower mainstem Columbia River. Their work supports a larger project funded by the Bonneville Power Administration (BPA) aimed at characterizing the physical habitat used by mainstem fall Chinook and chum salmon populations. Multiple collaborators in addition to PNNL are involved in the BPA project--counterparts include the Washington Department of Fish and Wildlife (WDFW), U.S. Fish and Wildlife Service (USFWS), Pacific States Marine Fisheries Commission (PSMFC), U.S. Geological Surveymore » (USGS), and Oregon Department of Fish and Wildlife (ODFW). Data resulting from the individual tasks each agency conducts are providing a sound scientific basis for developing strategies to operate the Federal Columbia River Power System (FCRPS) in ways that will effectively protect and enhance the chum and tule fall Chinook salmon populations--both listed as threatened under the Endangered Species Act (ESA). Fall Chinook salmon, thought to originate from Bonneville Hatchery, were first noted to be spawning downstream of Bonneville Dam by WDFW biologists in 1993. Known spawning areas include gravel beds on the Washington side of the river near Hamilton Creek and near Ives Island. Limited surveys of spawning ground were conducted in the area around Ives and Pierce islands from 1994 through 1997. Based on those surveys, it is believed that fall Chinook salmon are spawning successfully in this area. The size of this population from 1994 to 1996 was estimated at 1800 to 5200 fish. Chum salmon also have been documented spawning downstream of Bonneville Dam. Chum salmon were listed as threatened under the ESA in March 1999. At present there is a need to determine the number of fall Chinook and chum salmon spawning downstream of Bonneville Dam, the characteristics of their spawning areas, and the flows necessary to ensure their long-term survival. Ongoing discussions regarding the minimum and maximum flows will result in optimal spawning habitat usage and survival of embryos of both species. Collection of additional data as part of this project will ensure that established flow guidelines are appropriate and provide adequate protection for the species of concern. This is consistent with the high priority placed by the Northwest Power and Conservation Council Independent Scientific Advisory Board and the salmon managers on determining the importance of mainstem habitats to the production of salmon in the Columbia River Basin. Thus, there is a need to better understand the physical habitat variables used by mainstem fall Chinook and chum salmon populations and the effects of hydropower project operations on spawning and incubation. Pacific Northwest National Laboratory was asked to participate in the cooperative study during FY 2000. Since then, we have focused on (1) investigating the interactions between groundwater and surface water near fall Chinook and chum salmon spawning areas; (2) providing in-season hyporheic temperature data and assisting state agencies with emergence timing estimates; (3) locating and mapping deep-water fall Chinook salmon spawning areas; and (4) providing support to the WDFW for analysis of stranding data. Work conducted during FY 2006 addressed these same efforts. This report documents the studies and tasks performed by PNNL during FY 2006. Chapter 1 provides a description of the searches conducted for deepwater redds--adjacent to Pierce and Ives islands for fall Chinook salmon and near the Interstate 205 bridge for chum salmon. The chapter also provides data on redd location, information about habitat associations, and estimates of total spawning populations. Chapter 2 documents the collection of data on riverbed and river temperatures and water surface elevations, from the onset of spawning to the end of emergence, and the provision of those data in-season to fisheries management agencies to assist with emergence timing estimates and evaluations of redd dewatering. Technical assistance provided to the WDFW and PSMFC in evaluation of stranding data is summarized in Chapter 3.« less

Evaluation of Salmon Spawning Below Bonneville Dam, 2005-2006 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arntzen, Evan; Mueller, Robert; Murray, Christopher

2007-03-01

Since FY 2000, scientists at Pacific Northwest National Laboratory (PNNL) have conducted research to assess the extent of spawning by chum salmon (Oncorhynchus keta) and fall Chinook salmon (O. tshawytscha) in the lower mainstem Columbia River. Their work supports a larger project funded by the Bonneville Power Administration (BPA) aimed at characterizing the physical habitat used by mainstem fall Chinook and chum salmon populations. Multiple collaborators in addition to PNNL are involved in the BPA project--counterparts include the Washington Department of Fish and Wildlife (WDFW), U.S. Fish and Wildlife Service (USFWS), Pacific States Marine Fisheries Commission (PSMFC), U.S. Geological Surveymore » (USGS), and Oregon Department of Fish and Wildlife (ODFW). Data resulting from the individual tasks each agency conducts are providing a sound scientific basis for developing strategies to operate the Federal Columbia River Power System (FCRPS) in ways that will effectively protect and enhance the chum and tule fall Chinook salmon populations--both listed as threatened under the Endangered Species Act (ESA). Fall Chinook salmon, thought to originate from Bonneville Hatchery, were first noted to be spawning downstream of Bonneville Dam by WDFW biologists in 1993. Known spawning areas include gravel beds on the Washington side of the river near Hamilton Creek and near Ives Island. Limited surveys of spawning ground were conducted in the area around Ives and Pierce islands from 1994 through 1997. Based on those surveys, it is believed that fall Chinook salmon are spawning successfully in this area. The size of this population from 1994 to 1996 was estimated at 1800 to 5200 fish. Chum salmon also have been documented spawning downstream of Bonneville Dam. Chum salmon were listed as threatened under the ESA in March 1999. At present there is a need to determine the number of fall Chinook and chum salmon spawning downstream of Bonneville Dam, the characteristics of their spawning areas, and the flows necessary to ensure their long-term survival. Ongoing discussions regarding the minimum and maximum flows will result in optimal spawning habitat usage and survival of embryos of both species. Collection of additional data as part of this project will ensure that established flow guidelines are appropriate and provide adequate protection for the species of concern. This is consistent with the high priority placed by the Northwest Power and Conservation Council Independent Scientific Advisory Board and the salmon managers on determining the importance of mainstem habitats to the production of salmon in the Columbia River Basin. Thus, there is a need to better understand the physical habitat variables used by mainstem fall Chinook and chum salmon populations and the effects of hydropower project operations on spawning and incubation. Pacific Northwest National Laboratory was asked to participate in the cooperative study during FY 2000. Since then, we have focused on (1) investigating the interactions between groundwater and surface water near fall Chinook and chum salmon spawning areas; (2) providing in-season hyporheic temperature data and assisting state agencies with emergence timing estimates; (3) locating and mapping deep-water fall Chinook salmon spawning areas; and (4) providing support to the WDFW for analysis of stranding data. Work conducted during FY 2006 addressed these same efforts. This report documents the studies and tasks performed by PNNL during FY 2006. Chapter 1 provides a description of the searches conducted for deepwater redds--adjacent to Pierce and Ives islands for fall Chinook salmon and near the Interstate 205 bridge for chum salmon. The chapter also provides data on redd location, information about habitat associations, and estimates of total spawning populations. Chapter 2 documents the collection of data on riverbed and river temperatures and water surface elevations, from the onset of spawning to the end of emergence, and the provision of those data in-season to fisheries management agencies to assist with emergence timing estimates and evaluations of redd dewatering. Technical assistance provided to the WDFW and PSMFC in evaluation of stranding data is summarized in Chapter 3.« less

Power-law tails in the distribution of order imbalance

NASA Astrophysics Data System (ADS)

Zhang, Ting; Gu, Gao-Feng; Xu, Hai-Chuan; Xiong, Xiong; Chen, Wei; Zhou, Wei-Xing

2017-10-01

We investigate the probability distribution of order imbalance calculated from the order flow data of 43 Chinese stocks traded on the Shenzhen Stock Exchange. Two definitions of order imbalance are considered based on the order number and the order size. We find that the order imbalance distributions of individual stocks have power-law tails. However, the tail index fluctuates remarkably from stock to stock. We also investigate the distributions of aggregated order imbalance of all stocks at different timescales Δt. We find no clear trend in the tail index with respect Δt. All the analyses suggest that the distributions of order imbalance are asymmetric.

Variability of spawning time (lunar day) in Acropora versus merulinid corals: a 7-yr record of in situ coral spawning in Taiwan

NASA Astrophysics Data System (ADS)

Lin, Che-Hung; Nozawa, Yoko

2017-12-01

Despite the global accumulation of coral spawning records over the past three decades, information on inter-annual variation in spawning time is still insufficient, resulting in difficulty in predicting coral spawning time. Here, we present new information on in situ spawning times of scleractinian corals at Lyudao, Taiwan, covering their inter-annual variations over a 7-yr period (2010-2016). Spawning of 42 species from 16 genera in eight families was recorded. The majority were hermaphroditic spawners (38 of 42 species), and their spawning occurred 2-4 h after sunset on 1-11 d after the full moon (AFM), mostly in April and May. There were two distinct patterns in the two dominant taxa, the genus Acropora (14 species) and the family Merulinidae (18 species in eight genera). The annual spawning of Acropora corals mostly occurred on a single night in May with high inter-annual variation of spawning (lunar) days between 1 and 11 d AFM. In contrast, the annual spawning of merulinid corals commonly occurred over 2-3 consecutive nights in two consecutive months, April and May, with the specific range of spawning days around the last quarter moon (between 5 and 8 d AFM). The distinct spawning patterns of these taxa were also documented at Okinawa and Kochi, Japan, where similar long-term monitoring of in situ coral spawning has been conducted. This variability in spawning days implies different regulatory mechanisms of synchronous spawning where Acropora corals might be more sensitive to exogenous environmental factors (hourglass mechanism), compared to merulinid corals, which may rely more on endogenous biological rhythms (oscillator mechanism).

Effects of lake surface elevation on shoreline-spawning Lost River Suckers

USGS Publications Warehouse

Burdick, Summer M.; Hewitt, David A.; Rasmussen, J.E.; Hayes, Brian; Janney, Eric; Harris, Alta C.

2015-01-01

We analyzed remote detection data from PIT-tagged Lost River Suckers Deltistes luxatus at four shoreline spawning areas in Upper Klamath Lake, Oregon, to determine whether spawning of this endangered species was affected by low water levels. Our investigation was motivated by the observation that the surface elevation of the lake during the 2010 spawning season was the lowest in 38 years. Irrigation withdrawals in 2009 that were not replenished by subsequent winter-spring inflows caused a reduction in available shoreline spawning habitat in 2010. We compared metrics of skipped spawning, movement among spawning areas, and spawning duration across 8 years (2006-2013) that had contrasting spring water levels. Some aspects of sucker spawning were similar in all years, including few individuals straying from the shoreline areas to spawning locations in lake tributaries and consistent effects of increasing water temperatures on the accumulation of fish at the spawning areas. During the extreme low water year of 2010, 14% fewer female and 8% fewer male suckers joined the shoreline spawning aggregation than in the other years. Both males and females visited fewer spawning areas within Upper Klamath Lake in 2010 than in other years, and the median duration at spawning areas in 2010 was at least 36% shorter for females and 20% shorter for males relative to other years. Given the imperiled status of the species and the declining abundance of the population in Upper Klamath Lake, any reduction in spawning success and egg production could negatively impact recovery efforts. Our results indicate that lake surface elevations above 1,262.3-1,262.5 m would be unlikely to limit the number of spawning fish and overall egg production.

Broad-scale climate influences on spring-spawning herring (Clupea harengus, L.) recruitment in the Western Baltic Sea.

PubMed

Gröger, Joachim P; Hinrichsen, Hans-Harald; Polte, Patrick

2014-01-01

Climate forcing in complex ecosystems can have profound implications for ecosystem sustainability and may thus challenge a precautionary ecosystem management. Climatic influences documented to affect various ecological functions on a global scale, may themselves be observed on quantitative or qualitative scales including regime shifts in complex marine ecosystems. This study investigates the potential climatic impact on the reproduction success of spring-spawning herring (Clupea harengus) in the Western Baltic Sea (WBSS herring). To test for climate effects on reproduction success, the regionally determined and scientifically well-documented spawning grounds of WBSS herring represent an ideal model system. Climate effects on herring reproduction were investigated using two global indices of atmospheric variability and sea surface temperature, represented by the North Atlantic Oscillation (NAO) and the Atlantic Multi-decadal Oscillation (AMO), respectively, and the Baltic Sea Index (BSI) which is a regional-scale atmospheric index for the Baltic Sea. Moreover, we combined a traditional approach with modern time series analysis based on a recruitment model connecting parental population components with reproduction success. Generalized transfer functions (ARIMAX models) allowed evaluating the dynamic nature of exogenous climate processes interacting with the endogenous recruitment process. Using different model selection criteria our results reveal that in contrast to NAO and AMO, the BSI shows a significant positive but delayed signal on the annual dynamics of herring recruitment. The westward influence of the Siberian high is considered strongly suppressing the influence of the NAO in this area leading to a higher explanatory power of the BSI reflecting the atmospheric pressure regime on a North-South transect between Oslo, Norway and Szczecin, Poland. We suggest incorporating climate-induced effects into stock and risk assessments and management strategies as part of the EU ecosystem approach to support sustainable herring fisheries in the Western Baltic Sea.

Broad-Scale Climate Influences on Spring-Spawning Herring (Clupea harengus, L.) Recruitment in the Western Baltic Sea

PubMed Central

Gröger, Joachim P.; Hinrichsen, Hans-Harald; Polte, Patrick

2014-01-01

Climate forcing in complex ecosystems can have profound implications for ecosystem sustainability and may thus challenge a precautionary ecosystem management. Climatic influences documented to affect various ecological functions on a global scale, may themselves be observed on quantitative or qualitative scales including regime shifts in complex marine ecosystems. This study investigates the potential climatic impact on the reproduction success of spring-spawning herring (Clupea harengus) in the Western Baltic Sea (WBSS herring). To test for climate effects on reproduction success, the regionally determined and scientifically well-documented spawning grounds of WBSS herring represent an ideal model system. Climate effects on herring reproduction were investigated using two global indices of atmospheric variability and sea surface temperature, represented by the North Atlantic Oscillation (NAO) and the Atlantic Multi-decadal Oscillation (AMO), respectively, and the Baltic Sea Index (BSI) which is a regional-scale atmospheric index for the Baltic Sea. Moreover, we combined a traditional approach with modern time series analysis based on a recruitment model connecting parental population components with reproduction success. Generalized transfer functions (ARIMAX models) allowed evaluating the dynamic nature of exogenous climate processes interacting with the endogenous recruitment process. Using different model selection criteria our results reveal that in contrast to NAO and AMO, the BSI shows a significant positive but delayed signal on the annual dynamics of herring recruitment. The westward influence of the Siberian high is considered strongly suppressing the influence of the NAO in this area leading to a higher explanatory power of the BSI reflecting the atmospheric pressure regime on a North-South transect between Oslo, Norway and Szczecin, Poland. We suggest incorporating climate-induced effects into stock and risk assessments and management strategies as part of the EU ecosystem approach to support sustainable herring fisheries in the Western Baltic Sea. PMID:24586279

Comparative bioenergetics modeling of two Lake Trout morphotypes

USGS Publications Warehouse

Kepler, Megan V.; Wagner, Tyler; Sweka, John A.

2014-01-01

Efforts to restore Lake Trout Salvelinus namaycush in the Laurentian Great Lakes have been hampered for decades by several factors, including overfishing and invasive species (e.g., parasitism by Sea Lampreys Petromyzon marinus and reproductive deficiencies associated with consumption of Alewives Alosa pseudoharengus). Restoration efforts are complicated by the presence of multiple body forms (i.e., morphotypes) of Lake Trout that differ in habitat utilization, prey consumption, lipid storage, and spawning preferences. Bioenergetics models constitute one tool that is used to help inform management and restoration decisions; however, bioenergetic differences among morphotypes have not been evaluated. The goal of this research was to investigate bioenergetic differences between two actively stocked morphotypes: lean and humper Lake Trout. We measured consumption and respiration rates across a wide range of temperatures (4–22°C) and size-classes (5–100 g) to develop bioenergetics models for juvenile Lake Trout. Bayesian estimation was used so that uncertainty could be propagated through final growth predictions. Differences between morphotypes were minimal, but when present, the differences were temperature and weight dependent. Basal respiration did not differ between morphotypes at any temperature or size-class. When growth and consumption differed between morphotypes, the differences were not consistent across the size ranges tested. Management scenarios utilizing the temperatures presently found in the Great Lakes (e.g., predicted growth at an average temperature of 11.7°C and 14.4°C during a 30-d period) demonstrated no difference in growth between the two morphotypes. Due to a lack of consistent differences between lean and humper Lake Trout, we developed a model that combined data from both morphotypes. The combined model yielded results similar to those of the morphotype-specific models, suggesting that accounting for morphotype differences may not be necessary in bioenergetics modeling of lean and humper Lake Trout.

Linking fishery management and conservation in a tropical estuarine lagoon: biological and physical effects of an artisanal fishing gear

NASA Astrophysics Data System (ADS)

Rueda, M.; Defeo, O.

2003-04-01

Information coming from fishery monitoring, surveys and experimental fishing with participation of fishers was employed to determine the impact of an artisanal gear, 'boliche', on the biodiversity of the Ciénaga Grande de Santa Marta (CGSM), an estuarine lagoon on the Caribbean coast of Colombia. Fishery monitoring (catch data) included landings before (1968 and 1978) and after (1994-1996) the introduction of the boliche in the CGSM (1985), whereas surveys were conducted seasonally during 1993-1994. Fishing experiments involved evaluating different mesh sizes and the short-term effect of physical disturbance by the boliche. Monitoring suggested potential trophic effects of this fishing gear: the catch of large, long-lived, carnivorous species declined after the introduction of the boliche in the CGSM, whereas catch rates of smaller, shorter-lived, and lower trophic level species increased. Surveys revealed that the boliche retained 41 species. The by-catch made up 62% of the total catch and the remaining 38% involved the three target species Eugerres plumieri, Mugil incilis and Cathorops spixii. Selectivity experiments showed that 2.5 in. stretched mesh size gill nets caught more species than the 3.0-in. mesh. The smaller mesh also increased the risk of a critical reduction in the spawning stock of target species (notably E. plumieri); a situation that could affect the fish community if mesh sizes lower than 2.5 in. were intensively used. Suspended particulate matter significantly increased after fishing activity, with higher resuspension on mud-shells and mud substrata, whereas dissolved oxygen showed no appreciable changes after fishing operations. Notwithstanding, the activity of the boliche would generate sediment resuspension between 382 and 470 t day -1, which could lead to potential cascade impacts on water quality. We propose a framework of redundancy in management measures in order to simultaneously reach management and conservation goals.