Evaluation of New Zealand's high-seas bottom trawl closures using predictive habitat models and quantitative risk assessment.

PubMed

Penney, Andrew J; Guinotte, John M

2013-01-01

United Nations General Assembly Resolution 61/105 on sustainable fisheries (UNGA 2007) establishes three difficult questions for participants in high-seas bottom fisheries to answer: 1) Where are vulnerable marine systems (VMEs) likely to occur?; 2) What is the likelihood of fisheries interaction with these VMEs?; and 3) What might qualify as adequate conservation and management measures to prevent significant adverse impacts? This paper develops an approach to answering these questions for bottom trawling activities in the Convention Area of the South Pacific Regional Fisheries Management Organisation (SPRFMO) within a quantitative risk assessment and cost : benefit analysis framework. The predicted distribution of deep-sea corals from habitat suitability models is used to answer the first question. Distribution of historical bottom trawl effort is used to answer the second, with estimates of seabed areas swept by bottom trawlers being used to develop discounting factors for reduced biodiversity in previously fished areas. These are used in a quantitative ecological risk assessment approach to guide spatial protection planning to address the third question. The coral VME likelihood (average, discounted, predicted coral habitat suitability) of existing spatial closures implemented by New Zealand within the SPRFMO area is evaluated. Historical catch is used as a measure of cost to industry in a cost : benefit analysis of alternative spatial closure scenarios. Results indicate that current closures within the New Zealand SPRFMO area bottom trawl footprint are suboptimal for protection of VMEs. Examples of alternative trawl closure scenarios are provided to illustrate how the approach could be used to optimise protection of VMEs under chosen management objectives, balancing protection of VMEs against economic loss to commercial fishers from closure of historically fished areas.

Lake Ontario benthic prey fish assessment, 2016

USGS Publications Warehouse

Weidel, Brian C.; Walsh, Maureen; Holden, Jeremy P.; Connerton, Michael J.

2017-01-01

Benthic prey fishes are a critical component of the Lake Ontario food web, serving as energy vectors from benthic invertebrates to native and introduced piscivores. Beginning in 1978, Lake Ontario benthic prey fishes were assessed using bottom trawls collected from the lake’s south shore (depth range: 8 – 150 m). Historically, the survey targeted the then dominant species, Slimy Sculpin, however in 2015, the Benthic Prey Fish Survey was cooperatively expanded to a whole-lake survey, to address resource management information needs related to Round Goby, Deepwater Sculpin, and nearshore native fishes. In 2016, 142 trawls were collected at 18 transects, and spanned depths from 6 – 225 m. Trawl catches indicated the benthic and demersal prey fish community was dominated by Round Goby, however the proportional importance of native Deepwater Sculpin is increasing. Species-specific assessments found lake-wide Round Goby density (~600 fish per hectare) was slightly lower in 2016 relative to 2015. Deepwater Sculpin density has generally increased since 2004. In 2016 their estimated density was greater than 100 fish per hectare. Slimy Sculpin density (15 fish/ha) was similar to the past 3 years. Catches of juvenile Slimy Sculpin continue to be low relative to historic catches and the timing of their decline coincides with the proliferation of Round Goby. Additionally, we found a strong negative relationship between trawl catches of Round Goby and near-shore native benthic and demersal fishes such as Trout-perch, Johnny Darter and Spottail Shiner. The introduction of Round Goby and the reappearance of native Deepwater Sculpin have shaped the Lake Ontario benthic prey fish community.

Influence of the hydrodynamic conditions on the accessibility of Aristeus antennatus and other demersal species to the deep water trawl fishery off the Balearic Islands (western Mediterranean)

NASA Astrophysics Data System (ADS)

Amores, Angel; Rueda, Lucía; Monserrat, Sebastià; Guijarro, Beatriz; Pasqual, Catalina; Massutí, Enric

2014-10-01

Monthly catches per unit of effort (CPUE) of adult red shrimp (Aristeus antennatus), reported in the deep water bottom trawl fishery developed on the Sóller fishing ground off northern Mallorca (Western Mediterranean), and the mean ocean surface vorticity in the surrounding areas are compared between 2000 and 2010. A good correlation is found between the rises in the surrounding surface vorticity and the drops in the CPUE of the adult red shrimp. This correlation could be explained by assuming that most of the surface vorticity episodes could reach the bottom, increasing the seabed velocities and producing sediment resuspension, which could affect the near bottom water turbidity. A. antennatus would respond to this increased turbidity disappearing from the fishing grounds, probably moving downwards to the deeper waters. This massive displacement of red shrimp specimens away from the fishing grounds would consequently decrease their accessibility to fishing exploitation. Similar although more intense responses have been observed during the downslope shelf dense water current episodes that occurred in a submarine canyon, northeast of the Iberian peninsula. The proposed mechanism suggesting how the surface vorticity observed can affect the bottom sediments is investigated using a year-long moored near-bottom current meter and a sediment trap moored near the fishing grounds. The relationship between vorticity and catches is also explored for fish species (Galeus melastomus, Micromesistius poutassou, Phycis blennoides) and other crustacean (Geryon longipes and Nephrops norvegicus), considered as by-catch of the deep water fishery in the area. Results appear to support the suggestion that the water turbidity generated by the vorticity episodes is significant enough to affect the dynamics of the demersal species.

Relationship between mid-water trawling effort and catch composition uncertainty in two large lakes (Huron and Michigan) dominated by alosines, osmerids, and coregonines

USGS Publications Warehouse

Warner, David M.; Claramunt, Randall M.; Schaeffer, Jeffrey S.; Yule, Daniel L.; Hrabik, Tom R.; Peintka, Bernie; Rudstam, Lars G.; Holuszko, Jeffrey D.; O'Brien, Timothy P.

2012-01-01

Because it is not possible to identify species with echosounders alone, trawling is widely used as a method for collecting species and size composition data for allocating acoustic fish density estimates to species or size groups. In the Laurentian Great Lakes, data from midwater trawls are commonly used for such allocations. However, there are no rules for how much midwater trawling effort is required to adequately describe species and size composition of the pelagic fish communities in these lakes, so the balance between acoustic sampling effort and trawling effort has been unguided. We used midwater trawl data collected between 1986 and 2008 in lakes Michigan and Huron and a variety of analytical techniques to develop guidance for appropriate levels of trawl effort. We used multivariate regression trees and re-sampling techniques to i. identify factors that influence species and size composition of the pelagic fish communities in these lakes, ii. identify stratification schemes for the two lakes, iii. determine if there was a relationship between uncertainty in catch composition and the number of tows made, and iv. predict the number of tows required to reach desired uncertainty targets. We found that depth occupied by fish below the surface was the most influential explanatory variable. Catch composition varied between lakes at depths <38.5 m below the surface, but not at depths ≥38.5 m below the surface. Year, latitude, and bottom depth influenced catch composition in the near-surface waters of Lake Michigan, while only year was important for Lake Huron surface waters. There was an inverse relationship between RSE [relative standard error = 100 × (SE/mean)] and the number of tows made for the proportions of the different size and species groups. We found for the fifth (Lake Huron) and sixth (Lake Michigan) largest lakes in the world, 15–35 tows were adequate to achieve target RSEs (15% and 30%) for ubiquitous species, but rarer species required much higher, and at times, impractical effort levels to reach these targets.

Modeling the impacts of bottom trawling and the subsequent recovery rates of sponges and corals in the Aleutian Islands, Alaska

NASA Astrophysics Data System (ADS)

Rooper, Christopher N.; Wilkins, Mark E.; Rose, Craig S.; Coon, Catherine

2011-11-01

The abundance of some marine fish species are correlated to the abundance of habitat-forming benthic organisms such as sponges and corals. A concern for fisheries management agencies is the recovery of these benthic invertebrates from removal or mortality from bottom trawling and other commercial fisheries activities. Using a logistic model, observations of available substrate and data from bottom trawl surveys of the Aleutian Islands, Alaska, we estimated recovery rates of sponges and corals following removal. The model predicted the observed sponge and coral catch in bottom trawl surveys relatively accurately ( R2=0.38 and 0.46). For sponges, the results show that intrinsic growth rates were slow ( r=0.107 yr -1). Results show that intrinsic growth rates of corals were also slow ( r=0.062 yr -1). The best models for corals and sponges were models that did not include the impacts of commercial fishing removals. Subsequent recovery times for both taxa were also predicted to be slow. Mortality of 67% of the initial sponge biomass would recover to 80% of the original biomass after 20 years, while mortality of 67% of the coral biomass would recover to 80% of the original biomass after 34 years. The modeled recovery times were consistent with previous studies in estimating that recovery times were of the order of decades, however improved data from directed studies would no doubt improve parameter estimates and reduce the uncertainty in the model results. Given their role as a major ecosystem component and potential habitat for marine fish, damage and removal of sponges and corals must be considered when estimating the impacts of commercial bottom trawling on the seafloor.

Great lakes prey fish populations: a cross-basin overview of status and trends based on bottom trawl surveys, 1978-2012

USGS Publications Warehouse

Gorman, Owen T.

2012-01-01

The assessment of prey fish stocks in the Great Lakes have been conducted annually with bottom trawls since the 1970s by the Great Lakes Science Center, sometimes assisted by partner agencies. These stock assessments provide data on the status and trends of prey fish that are consumed by important commercial and recreational fishes. Although all these annual surveys are conducted using bottom trawls, they differ among the lakes in the proportion of the lake covered, seasonal timing, bottom trawl gear used, and the manner in which the trawl is towed (across or along bottom contours). Because each assessment is unique in one or more important aspects, direct comparison of prey fish catches among lakes is not straightforward. However, all of the assessments produce indices of abundance or biomass that can be standardized to facilitate comparisons of status and trends across all the Great Lakes. In this report, population indices were standardized to the highest value for a time series within each lake for the following principal prey species: cisco (Coregonus artedi), bloater (C. hoyi), rainbow smelt (Osmerus mordax), and alewife (Alosa pseudoharengus). Indices were also provided for round goby (Neogobius melanostomus), an invasive fish that has proliferated throughout the basin over the past 18 years. These standardized indices represent the best available long-term indices of relative abundance for these fishes across all of the Great Lakes. In this report, standardized indices are presented in graphical form along with synopses to provide a short, informal cross-basin summary of the status and trends of principal prey fishes. In keeping with this intent, tables, references, and a detailed discussion were omitted.

Bottom trawl assessment of Lake Ontario prey fishes

USGS Publications Warehouse

Weidel, Brian C.; Connerton, Michael J.; Holden, Jeremy

2018-01-01

Managing Lake Ontario fisheries in an ecosystem-context requires prey fish community and population data. Since 1978, multiple annual bottom trawl surveys have quantified prey fish dynamics to inform management relative to published Fish Community Objectives. In 2017, two whole-lake surveys collected 341 bottom trawls (spring: 204, fall: 137), at depths from 8-225m, and captured 751,350 fish from 29 species. Alewife were 90% of the total fish catch while Deepwater Sculpin, Round Goby, and Rainbow Smelt comprised the majority of the remaining total catch (3.8, 3.1, and 1.1% respectively). The adult Alewife abundance index for US waters increased in 2017 relative to 2016, however the index for Canadian waters declined. Adult Alewife condition, assessed by the predicted weight of a 165 mm fish (6.5 inches), declined in 2017 from record high values observed in spring 2016. Spring 2017 Alewife condition was slightly less than the 10-year average, but the fall value was well below the 10-year average, likely due to increased Age-1 Alewife abundance. The Age-1 Alewife abundance index was the highest observed in 40 years, and 8-times higher than the previous year. The Age-1 index estimates Alewife reproductive success the preceding year. The warm summer and winter of 2016 likely contributed to the large year class. In contrast the relatively cool 2017 spring and cold winter may result in a lower than average 2017 year class. Abundance indices for Rainbow Smelt, Cisco, and Emerald Shiner either declined or remained at low levels in 2017. Pelagic prey fish diversity continues to be low since a single species, Alewife, dominates the catch. Deepwater Sculpin were the most abundant benthic prey fish in 2017 because Round Goby abundance declined sharply from 2016. Slimy Sculpin density continued to decline and the 2017 biomass index for US waters was the lowest ever observed. Prior to Round Goby proliferation, juvenile Slimy Sculpin comprised ~10% of the Slimy Sculpin catch, but since 2004, the percent of juveniles within the total catch is less than 0.5%, suggesting Round Goby are limiting Slimy Sculpin reproduction. Despite Slimy Sculpin declines, benthic prey fish community diversity has increased as Deepwater Sculpin and Round Goby comprise more of the community.

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.

77 FR 10463 - Fisheries of the Northeastern United States; Proposed 2012-2013 Northeast Skate Complex Fishery...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-22

... skate biomass. DATES: Public comments must be received no later than 5 p.m., eastern standard time, on... information on skates. The ABC is calculated by multiplying the median catch/biomass ratio by the most recent 3-year average skate biomass from the NMFS bottom trawl survey. A calibration workshop was conducted...

Relative abundance, age, growth, and fecundity of grubby Myoxocephalus aenaeus in Niantic River and Niantic Bay, Long Island Sound

USGS Publications Warehouse

Roseman, E.F.; Tomichek, C.A.; Maynard, T.; Burton, J.A.

2005-01-01

Grubby (Myoxocephalus aenaeus, Cottidae) is a common benthic fish of inshore waters and estuaries of eastern Long Island Sound; however, little information exists on their life history or population demographics. This study utilised a long-term data series (1976-2002) to assess grubby life history and population demographics and explores trends in the Niantic River and Niantic Bay populations. In addition, we examined the age, size, and fecundity of adult grubby in 2001-02 to determine the population characteristics in the region. Mean grubby catch per unit effort (CPUE) in Niantic Bay ranged from 0.4 per trawl in 1976 to 2.9 per trawl in 1984 while river CPUE ranged from 0.4 per trawl in 1977 to 7.6 per trawl in 1989. Catch of grubby in bottom trawls varied seasonally with highest CPUE occurring in winter. Highest entrainment of grubby larvae occurred in 2001 while the lowest entrainment observed was in 1991. Four age classes, 0+ through III+, were derived from otolith analysis (N = 51) although length frequency analysis suggested the possibility of older fish in the population. The total number of eggs in ovaries ranged from 286 to 16 451 for grubby (N = 64) between 52 mm and 155 mm TL. Results of this study indicated a decline in abundance of adult grubby over the 26-year period, possibly related to concurrent declines in eelgrass (Zostera marina) abundance and/or increased water temperature. ?? 2005 Elsevier B.V. All rights reserved.

Relative abundance, age, growth, and fecundity of grubby Myoxocephalus aenaeus in Niantic River and Niantic Bay, Long Island Sound

NASA Astrophysics Data System (ADS)

Roseman, Edward F.; Tomichek, Christine A.; Maynard, Tracy; Burton, Jennifer A.

2005-04-01

Grubby ( Myoxocephalus aenaeus, Cottidae) is a common benthic fish of inshore waters and estuaries of eastern Long Island Sound; however, little information exists on their life history or population demographics. This study utilised a long-term data series (1976-2002) to assess grubby life history and population demographics and explores trends in the Niantic River and Niantic Bay populations. In addition, we examined the age, size, and fecundity of adult grubby in 2001-02 to determine the population characteristics in the region. Mean grubby catch per unit effort (CPUE) in Niantic Bay ranged from 0.4 per trawl in 1976 to 2.9 per trawl in 1984 while river CPUE ranged from 0.4 per trawl in 1977 to 7.6 per trawl in 1989. Catch of grubby in bottom trawls varied seasonally with highest CPUE occurring in winter. Highest entrainment of grubby larvae occurred in 2001 while the lowest entrainment observed was in 1991. Four age classes, 0+ through III+, were derived from otolith analysis (N = 51) although length frequency analysis suggested the possibility of older fish in the population. The total number of eggs in ovaries ranged from 286 to 16 451 for grubby (N = 64) between 52 mm and 155 mm TL. Results of this study indicated a decline in abundance of adult grubby over the 26-year period, possibly related to concurrent declines in eelgrass ( Zostera marina) abundance and/or increased water temperature.

Benthic prey fish assessment, Lake Ontario 2013

USGS Publications Warehouse

Weidel, Brian C.; Walsh, Maureen; Connerton, Michael J.

2014-01-01

The 2013 benthic fish assessment was delayed and shortened as a result of the U.S. Government shutdown, however the assessment collected 51 of the 62 planned bottom trawls. Over the past 34 years, Slimy Sculpin abundance in Lake Ontario has fluctuated, but ultimately decreased by two orders of magnitude, with a substantial decline occurring in the past 10 years. The 2013 Slimy Sculpin mean bottom trawl catch density (0.001 ind.·m-2, s.d.= 0.0017, n = 52) and mean biomass density (0.015 g·m-2 , s.d.= 0.038, n = 52) were the lowest recorded in the 27 years of sampling using the original bottom trawl design. From 2011-2013, the Slimy Sculpin density and biomass density has decreased by approximately 50% each year. Spring bottom trawl catches illustrate Slimy Sculpin and Round Goby Neogobius melanostoma winter habitat overlaps for as much as 7 months out of a year, providing opportunities for competition and predation. Invasive species, salmonid piscivory, and declines in native benthic invertebrates are likely all important drivers of Slimy Sculpin population dynamics in Lake Ontario. Deepwater Sculpin Myoxocephalus thompsonii, considered rare or absent from Lake Ontario for 30 years, have generally increased over the past eight years. For the first time since they were caught in this assessment, Deepwater Sculpin density and biomass density estimates declined from the previous year. The 2013 abundance and density estimates for trawls covering the standard depths from 60m to 150m was 0.0001 fish per square meter and 0.0028 grams per square meter. In 2013, very few small (< 80 mm) Deepwater Sculpin were caught and most sculpin were at sites of 150 meters or greater, which is in contrast to previous years when juvenile fish were caught around 80-100 meters. The reduced effort and late seasonal timing of the 2013 assessment make it difficult to have high confidence in declines observed in 2013, however observed Alewife Alosa psuedoharengus abundance increases and reduced juvenile Deepwater Sculpin catches are consistent with the hypothesis that Alewife negatively influence Deepwater Sculpin recruitment. Nonnative Round Gobies were first detected in the USGS/NYSDEC Lake Ontario spring Alewife assessment in 2002. Since that assessment, observations indicate their population has expanded and they are now found along the entire south shore of Lake Ontario, with the highest densities in U.S. waters just east of the Niagara River confluence. In the 2013 spring-based assessment, both the abundance and weight indices increased slightly as compared to 2012. The number index value of 16.6 was 30% of the maximum number observed in 2008 when the number index was 95.2. Round Goby density estimates from the 2013 fall benthic prey fish survey were 33 times greater than fall Slimy Sculpin density, indicating Round Goby are now the dominant Lake Ontario benthic prey fish.

The environmental impacts of three different queen scallop (Aequipecten opercularis) fishing gears.

PubMed

Hinz, Hilmar; Murray, Lee G; Malcolm, Fraser R; Kaiser, Michel J

2012-02-01

The negative impact of demersal fishing gears on the marine environment may be mitigated by utilizing less damaging fishing gears. Within this context three queen scallop fishing gears were tested for their catch efficiencies and their environmental impact on benthos: a traditional 'Newhaven' dredge, a new dredge design with a rubber lip instead of the traditional teeth as its main new design feature and an otter trawl. Both, the new dredge and the otter trawl showed high catches and relatively low by-catches. Catches made with the traditional dredge were lower and contained larger amounts of non-target species. Both dredges primarily caught invertebrate species, while by-catches of the otter trawl were dominated by demersal fish. The impact of these gears on the benthic biota demonstrated that while no effects were detected for the otter trawl both dredges showed similar negative effects. Clear negative effects were evident for the brittlestar Ophiura ophiura while positive trends for the common starfish Asterias rubens and the hermit crab Pagurus bernhardus indicated scavenging effects. Due to its higher catch efficiency the new dredge caused less damage per unit catch compared to the traditional dredge, yet compared to the otter trawl it appears less environmentally friendly. However, the new dredge may be an alternative to the otter trawls for fisheries where the by-catch of demersal fish has been identified as a significant problem. Copyright © 2011 Elsevier Ltd. All rights reserved.

Retrospective analysis of Bering Sea bottom trawl surveys: regime shift and ecosystem reorganization

NASA Astrophysics Data System (ADS)

Conners, M. E.; Hollowed, A. B.; Brown, E.

2002-10-01

This paper compiles data from bottom trawl surveys using variations on a 400-mesh eastern trawl gear into a 38-year time series (1963-2000), using a robust index of median catch per unit effort (CPUE) as an indicator of regional abundance. Time series are presented for three index sites in the southeastern Bering Sea: the inner shelf in Bristol Bay, the middle shelf north of Unimak Island, and the outer shelf near the Pribilof Islands. All three sites show strong evidence of a shift in benthic biomass and community structure in the early to mid-1980s. During this period, all three sites showed substantial increases in the abundances of walleye pollock, Pacific cod, rock sole, flathead sole, cartilaginous fishes (skates) and non-crab benthic invertebrates. Species composition, especially of flatfish, differs at the three sites, but the trend for groundfish abundance to increase was consistent at all three sites. The similarity in trends both across the region and across both commercial and unexploited groups suggests to us that a complete reorganization of benthic and demersal food webs may have taken place. The timing of change in trawl catch weight is consistent with effects of the strong regime shift observed in climate indices in 1976-1977. There is little evidence of similar biological responses to subsequent, less pronounced changes in climate. Our data are also consistent with recently documented shifts in ecosystem dynamics resulting from changes in ice cover and thermal structure in the eastern Bering Sea. Our analysis indicates that there was a much higher biomass of groundfish at all three sites during 1980-2000 than in 1960-1980. This result provides evidence against the hypothesis that the overall productivity of the eastern Bering Sea has decreased. The precipitous decline of the endangered Steller sea lion in this region from 1975-1985 was concurrent with an overall increase in abundance of groundfish prey.

Species and size selectivity of two midwater trawls used in an acoustic survey of the Alaska Arctic

NASA Astrophysics Data System (ADS)

De Robertis, Alex; Taylor, Kevin; Williams, Kresimir; Wilson, Christopher D.

2017-01-01

Acoustic-trawl (AT) survey methods are widely used to estimate the abundance and distribution of pelagic organisms. This technique relies on estimates of size and species composition from trawl catches along with estimates of the acoustic properties of these animals to convert measurements of acoustic backscatter into animal abundance. However, trawls are selective samplers, and if the catch does not represent the size and species composition of the animals in the acoustic beam the resulting abundance estimates will be biased. We conducted an experiment to quantify trawl selectivity for species encountered during an AT survey of the Alaska Arctic. The pelagic assemblage in this environment was dominated by small young-of-the-year (age-0) fishes and jellyfish, which may be poorly retained in trawls. A large midwater trawl (Cantrawl) and a smaller midwater trawl (modified Marinovich) were used during the survey. The Marinovich was equipped with 8 small-mesh recapture nets which were used to estimate the probability that an individual that enters the trawl is retained. In addition, paired hauls were made with the Cantrawl and Marinovich to estimate the difference in selectivity between the two trawls. A statistical model was developed to combine the catches of the recapture nets and the paired hauls to estimate the length-dependent selectivity of the trawls for the most abundant species (e.g., age-0 fishes and jellyfish). The analysis indicated that there was substantial size and species selectivity: although the modified Marinovich generally had a higher catch per unit effort, many of the animals encountered in this environment were poorly retained by both trawls. The observed size and species selectivity of the trawls can be used to select appropriate nets for sampling pelagic fishes, and correct survey estimates for the biases introduced in the trawl capture process.

Assessing prey fish populations in Lake Michigan: Comparison of simultaneous acoustic-midwater trawling with bottom trawling

USGS Publications Warehouse

Fabrizio, Mary C.; Adams, Jean V.; Curtis, Gary L.

1997-01-01

The Lake Michigan fish community has been monitored since the 1960s with bottom trawls, and since the late 1980s with acoustics and midwater trawls. These sampling tools are limited to different habitats: bottom trawls sample fish near bottom in areas with smooth substrates, and acoustic methods sample fish throughout the water column above all substrate types. We compared estimates of fish densities and species richness from daytime bottom trawling with those estimated from night-time acoustic and midwater trawling at a range of depths in northeastern Lake Michigan in summer 1995. We examined estimates of total fish density as well as densities of alewife Alosa pseudoharengus (Wilson), bloater Coregonus hoyi (Gill), and rainbow smelt Osmerus mordax (Mitchell) because these three species are the dominant forage of large piscivores in Lake Michigan. In shallow water (18 m), we detected more species but fewer fish (in fish/ha and kg/ha) with bottom trawls than with acoustic-midwater trawling. Large aggregations of rainbow smelt were detected by acoustic-midwater trawling at 18 m and contributed to the differences in total fish density estimates between gears at this depth. Numerical and biomass densitites of bloaters from all depths were significantly higher when based on bottom trawl samples than on acoustic-midwater trawling, and this probably contributed to the observed significant difference between methods for total fish densities (kg/ha) at 55 m. Significantly fewer alewives per ha were estimated from bottom trawling than from acoustics-midwater trawling at 55 m, and in deeper waters, no alewives were taken by bottom trawling. The differences detected between gears resulted from alewife, bloater, and rainbow smelt vertical distributions, which varied with lake depth and time of day. Because Lake Michigan fishes are both demersal and pelagic, a single sampling method cannot be used to completely describe characteristics of the fish community.

The ‘W’ Prawn-Trawl with Emphasised Drag-Force Transfer to Its Centre Line to Reduce Overall System Drag

PubMed Central

Balash, Cheslav; Sterling, David; Binns, Jonathan; Thomas, Giles; Bose, Neil

2015-01-01

For prawn trawling systems, drag reduction is a high priority as the trawling process is energy intensive. Large benefits have occurred through the use of multiple-net rigs and thin twine in the netting. An additional positive effect of these successful twine-area reduction strategies is the reduced amount of otter board area required to spread the trawl systems, which leads to further drag reduction. The present work investigated the potential of redirecting the drag-strain within a prawn trawl away from the wings and the otter boards to the centre line of the trawl, where top and bottom tongues have been installed, with an aim to minimise the loading/size of the otter boards required to spread the trawl. In the system containing the new ‘W’ trawl, the drag redirected to the centre-line tongues is transferred forward through a connected sled and towing wires to the trawler. To establish the extent of drag redirection to the centre-line tongues and the relative drag benefits of the new trawl system, conventional and ‘W’ trawls of 3.65 m headline length were tested firstly over a range of spread ratios in the flume tank, and subsequently at optimum spread ratio in the field. The developed ‘W’ trawl effectively directed 64% of netting-drag off the wings and onto the centre tongues, which resulted in drag savings in the field of ∼20% for the associated ‘W’ trawl/otter-board/sled system compared to the traditional trawl/otter-board arrangement in a single trawl or twin rig configuration. Furthermore, based on previously published data, the new trawl when used in a twin rig system is expected to provide approximately 12% drag reduction compared to quad rig. The twin ‘W’ trawl system also has benefits over quad rig in that a reduced number of cod-end/By-catch Reduction Device units need to be installed and attended each tow. PMID:25751251

Trawling on seamounts: can we balance exploitation and conservation?

NASA Astrophysics Data System (ADS)

Clark, M. R.; O'Driscoll, R. L.; Rowden, A. A.

2006-12-01

Seamounts are prominent features of the worlds underwater topography. They are widely regarded as productive, but fragile, habitat. They are the focus of commercial fishing for a number of demersal and pelagic fish and invertebrate species. Most fishing operations have some impact, either on the target species, associated bycatch species, or the benthic communities and habitat. Longlines, gillnets, traps and pots can all have some effect on the seafloor, but bottom trawling is the most well-known for causing considerable impact on the benthic habitat. There are few published studies on seamounts specifically, and recent research in New Zealand will be described. This has focused on deepwater fisheries for species such as orange roughy, which can form large aggregations over seamount features. The research includes analysis of the distribution of commercial catch and effort data from deepwater seamount fisheries, and "compare and contrast" surveys of seamounts that indicate the effects of bottom trawling can be severe on benthic invertebrate fauna. Fishing has clear consequences for structural complexity of the benthic habitat, and can alter species composition, and abundance. The results of such research are discussed with respect to management of seamount habitat in New Zealand, and the search for a balance that can allow sustainable seamount fisheries, and biodiversity conservation.

Ecological Meltdown in the Firth of Clyde, Scotland: Two Centuries of Change in a Coastal Marine Ecosystem

PubMed Central

Thurstan, Ruth H.; Roberts, Callum M.

2010-01-01

Background The Firth of Clyde is a large inlet of the sea that extends over 100 km into Scotland's west coast. Methods We compiled detailed fisheries landings data for this area and combined them with historical accounts to build a picture of change due to fishing activity over the last 200 years. Findings In the early 19th century, prior to the onset of industrial fishing, the Firth of Clyde supported diverse and productive fisheries for species such as herring (Clupea harengus, Clupeidae), cod (Gadus morhua, Gadidae), haddock (Melanogrammus aeglefinus, Gadidae), turbot (Psetta maxima, Scophthalmidae) and flounder (Platichthys flesus, Pleuronectidae). The 19th century saw increased demand for fish, which encouraged more indiscriminate methods of fishing such as bottom trawling. During the 1880s, fish landings began to decline, and upon the recommendation of local fishers and scientists, the Firth of Clyde was closed to large trawling vessels in 1889. This closure remained in place until 1962 when bottom trawling for Norway lobster (Nephrops norvegicus, Nephropidae) was approved in areas more than three nautical miles from the coast. During the 1960s and 1970s, landings of bottomfish increased as trawling intensified. The trawl closure within three nautical miles of the coast was repealed in 1984 under pressure from the industry. Thereafter, bottomfish landings went into terminal decline, with all species collapsing to zero or near zero landings by the early 21st century. Herring fisheries collapsed in the 1970s as more efficient mid-water trawls and fish finders were introduced, while a fishery for mid-water saithe (Pollachius virens, Gadidae) underwent a boom and bust shortly after discovery in the late 1960s. The only commercial fisheries that remain today are for Nephrops and scallops (Pecten maximus, Pectinidae). Significance The Firth of Clyde is a marine ecosystem nearing the endpoint of overfishing, a time when no species remain that are capable of sustaining commercial catches. The evidence suggests that trawl closures helped maintain productive fisheries through the mid-20th century, and their reopening precipitated collapse of bottomfish stocks. We argue that continued intensive bottom trawling for Nephrops with fine mesh nets will prevent the recovery of other species. This once diverse and highly productive environment will only be restored if trawl closures or other protected areas are re-introduced. The Firth of Clyde represents at a small scale a process that is occurring ocean-wide today, and its experience serves as a warning to others. PMID:20686614

Satellite-based quantification of the bottom trawling induced sediment resuspension over an entire shelf

NASA Astrophysics Data System (ADS)

Oberle, F. J.; Cheriton, O. M.; Hanebuth, T. J. J.

2014-12-01

The effect of bottom trawling activities on continental shelves has been a topic of interest for both fishery resource studies and ecological impact studies for a while. However, the impact of demersal fishing gear was almost exclusively studied from a perspective of its effects on benthic fauna, but recently it has also attracted attention due to its profound impact on sediments. Here we present the first study to quantify the trawling-induced sediment resuspension effect by combining satellite-based spatial patterns of bottom trawling with quantitative measurements of induced sediment plumes. This study examined high-resolution GPS vessel monitoring data from one year (2011-2012) to quantify the sedimentary budget caused by bottom trawling activity for the entire NW Iberian shelf, an area that is widely affected by chronic (continuous and intensive) commercial bottom trawling and is exemplary for many other narrow shelves worldwide. By filtering the GPS data by vessel type, vessel speed, and geometry of the trawl path, we resolved geographically detailed bottom trawling activities with varying local trawling intensities depending both on legal restrictions and bedrock geomorphology. Initial results show that trawling-induced resuspended sediments mark a significant if not dominant factor for a source to sink sedimentary budget, as they are calculated to be approximately two times as large as fluvial sedimentary input to the shelf. Ultimately, these results not only allow for a trawling affected sediment budget but also significantly help with marine management decisions by allowing to predict the mobilization and transport of sediment caused by bottom trawling gear at the level of a specific fishing fleet or ecosystem.

Estimation of alewife biomass in Lake Michigan, 1967-1978

USGS Publications Warehouse

Hatch, Richard W.; Haack, Paul M.; Brown, Edward H.

1981-01-01

The buildup of salmonid populations in Lake Michigan through annual stockings of hatchery-reared fish may become limited by the quantity of forage fish, mainly alewives Alosa pseudoharengus, available for food. As a part of a continuing examination of salmonid predator-prey relations in Lake Michigan, we traced changes in alewife biomass estimated from bottom-trawl surveys conducted in late October and early November 1967–1978. Weight of adult alewives trawled per 0.5 hectare of bottom (10-minute drag) at 16 depths along eight transects between 1973 and 1977 formed a skewed distribution: 72 of 464 drags caught no alewives; 89 drags caught less than 1 kg; and 2 drags caught more than 100 kg (maximum 159 kg). Analysis of variance in normalized catch per tow indicated highly significant differences between the main effects of years and depths, and highly significant differences in the interactions of years and transects, years and depths, and transects and depths. Five geographic and depth strata, formed by combining parts of transects wherein mean catch rate did not differ significantly, were the basis for calculating annual estimates of adult alewife biomass (with 90% confidence intervals). Estimated biomass of alewives (±90% confidence limits) in Lake Michigan proper (Green Bay and Grand Traverse Bay excluded) rose gradually from 46,000 (±9,000) t in 1967 to 114,000 (±17,000) t in 1973, declined to 45,000 (±8,000) t in 1977, and rose to 77,000 (±19,000) t in 1978.

What a drag: Quantifying the global impact of chronic bottom trawling on continental shelf sediment

USGS Publications Warehouse

Oberle, Ferdinand K.J.; Storlazzi, Curt; Hanebuth, Till J.J.

2016-01-01

Continental shelves worldwide are subject to intense bottom trawling that causes sediment to be resuspended. The widely used traditional concepts of modern sedimentary transport systems on the shelf rely only on estimates for naturally driven sediment resuspension such as through storm waves, bottom currents, and gravity-driven flows but they overlook a critical anthropogenic factor. The strong influence of bottom trawling on a source-to-sink sediment budget is explored on the NW Iberian shelf. Use of Automated Information System vessel tracking data provides for a high-resolution vessel track reconstruction and the accurate calculation of the spatial distribution of bottom trawling intensity and associated resuspended sediment load. The mean bottom trawling-induced resuspended sediment mass for the NW Iberian shelf is 13.50 Mt yr− 1, which leads to a six-fold increase in off-shelf sediment transport when compared to natural resuspension mechanisms. The source-to-sink budget analysis provides evidence that bottom trawling causes a rapid erosion of the fine sediment on human time scales. Combining global soft sediment distribution data of the shelves with worldwide bottom trawling intensity estimates we show that the bottom trawling-induced resuspended sediment mass amounts to approximately the same mass of all sediment entering the shelves through rivers. Spatial delineations between natural and anthropogenic sediment resuspension areas are presented to aid in marine management questions.

Vertical migration and nighttime distribution of adult bloaters in Lake Michigan

USGS Publications Warehouse

TeWinkel, Leslie M.; Fleischer, Guy W.

1999-01-01

The vertical migration and nighttime vertical distribution of adult bloaters Coregonus hoyi were investigated during late summer in Lake Michigan using acoustics simultaneously with either midwater or bottom trawling. Bloaters remained on or near bottom during the day. At night, bloaters were distributed throughout 30-65 m of water, depending on bottom depth. Shallowest depths of migration were not related to water temperature or incident light. Maximum distances of migration increased with increasing bottom depth. Nighttime midwater densities ranged from 0.00 to 6.61 fish/1,000 mA? and decreased with increasing bottom depth. Comparisons of length distributions showed that migrating and nonmigrating bloaters did not differ in size. However, at most sites, daytime bottom catches collected a greater proportion of larger individuals compared with nighttime midwater or bottom catches. Mean target strengths by 5-m strata indicated that migrating bloaters did not stratify by size in the water column at night. Overall, patterns in frequency of empty stomachs and mean digestive state of prey indicated that a portion of the bloater population fed in the water column at night. Bloater diet composition indicated both midwater feeding and bottom feeding. In sum, although a portion of the bloater population fed in the water column at night, bloaters were not limited to feeding at this time. This research confirmed that bloaters are opportunistic feeders and did not fully support the previously proposed hypothesis that bloater vertical migration is driven by the vertically migrating macroinvertebrate the opossom shrimp Mysis relicta.

Growth, reproduction, mortality, distribution, and biomass of freshwater drum in Lake Erie

USGS Publications Warehouse

Bur, Michael T.

1984-01-01

Predominant age-groups in the Lake Erie freshwater drum Aplodinotus grunnienspopulation were 3, 4, and 5 as determined from gill net, trap net, bottom trawl, and midwater trawl samples. Age and growth calculations indicated that females grew faster than males. However, the length-weight relation did not differ between sexes and was described by the equation: log W = −5.4383 + 3.1987 log L. Some males became sexually mature at age 2 and all were mature by age 6. Females matured 1 year later than males. Three sizes of eggs were present in ovaries; the average total number was 127,000 per female for 20 females over a length range of 270 to 478 mm. Seasonal analysis of the ovary-body weight ratio indicated that spawning extended from June to August. A total annual mortality rate of 49% for drum aged 4 through 11 was derived from catch-curve analysis. Freshwater drum were widely distributed throughout Lake Erie in 1977–1979, the greatest concentration being in the western basin. They moved into warm, shallow water (less than 10 m deep) during summer, and returned to deeper water in late fall. Summer biomass estimates for the western basin, based on systematic surveys with bottom trawls, were 9,545 t in 1977 and 2,333 t in 1978.

Lake Michigan faces exotic species, dune sand mining, other challenges

NASA Astrophysics Data System (ADS)

Showstack, Randy

As Steve Pothoven scooped out his bottom trawl catch on the deck of a U.S. government research vessel in June, he expected the regular monitoring exercise to land alewives and a mound of zebra mussels. These two now-ubiquitous exotic aquatic species are among more than 130 that have entered the Great Lakes ecosystem over the past century. They have invaded by various means: hiding in ballast water, navigating through connecting channels such as the Welland Canal that was completed in 1829 as a route around Niagara Falls, or introduced on purpose.

Using marine reserves to manage impact of bottom trawl fisheries requires consideration of benthic food-web interactions.

PubMed

van Denderen, P Daniël; Rijnsdorp, Adriaan D; van Kooten, Tobias

2016-10-01

Marine protected areas (MPAs) are widely used to protect exploited fish species as well as to conserve marine habitats and their biodiversity. They have also become a popular management tool for bottom trawl fisheries, a common fishing technique on continental shelves worldwide. The effects of bottom trawling go far beyond the impact on target species, as trawls also affect other components of the benthic ecosystem and the seabed itself. This means that for bottom trawl fisheries, MPAs can potentially be used not only to conserve target species but also to reduce impact of these side effects of the fishery. However, predicting the protective effects of MPAs is complicated because the side effects of trawling potentially alter the food-web interactions between target and non-target species. These changes in predatory and competitive interactions among fish and benthic invertebrates may have important ramifications for MPAs as tools to manage or mitigate the effects of bottom trawling. Yet, in current theory regarding the functioning of MPAs in relation to bottom trawl fisheries, such predatory and competitive interactions between species are generally not taken into account. In this study, we discuss how food-web interactions that are potentially affected by bottom trawling may alter the effectiveness of MPAs to protect (1) biodiversity and marine habitats, (2) fish populations, (3) fisheries yield, and (4) trophic structure of the community. We make the case that in order to be applicable for bottom trawl fisheries, guidelines for the implementation of MPAs must consider their potential food-web effects, at the risk of failing management. © 2016 by the Ecological Society of America.

Inferring Fish Escape Behaviour in Trawls Based on Catch Comparison Data: Model Development and Evaluation Based on Data from Skagerrak, Denmark

PubMed Central

Karlsen, Junita Diana

2014-01-01

During the fishing process, fish react to a trawl with a series of behaviours that often are species and size specific. Thus, a thorough understanding of fish behaviour in relation to fishing gear and a scientific understanding of the ability of different gear designs to utilize or stimulate various behavioural patterns during the catching process are essential for developing more efficient, selective, and environmentally friendly trawls. Although many behavioural studies using optical and acoustic observation systems have been conducted, harsh observation conditions on the fishing grounds often hamper the ability to directly observe fish behaviour in relation to fishing gear. As an alternative to optical and acoustic methods, we developed and applied a new mathematical model to catch data to extract detailed and quantitative information about species- and size-dependent escape behaviour in towed fishing gear such as trawls. We used catch comparison data collected with a twin trawl setup; the only difference between the two trawls was that a 12 m long upper section was replaced with 800 mm diamond meshes in one of them. We investigated the length-based escape behaviour of cod (Gadus morhua), haddock (Melanogrammus aeglefinus), saithe (Pollachius virens), witch flounder (Glyptocephalus cynoglossus), and lemon sole (Microstomus kitt) and quantified the extent to which behavioural responses set limits for the large mesh panel’s selective efficiency. Around 85% of saithe, 80% of haddock, 44% of witch flounder, 55% of lemon sole, and 55% of cod (below 68 cm) contacted the large mesh panel and escaped. We also demonstrated the need to account for potential selectivity in the trawl body, as it can bias the assessment of length-based escape behaviour. Our indirect assessment of fish behaviour was in agreement with the direct observations made for the same species in a similar section of the trawl body reported in the literature. PMID:24586403

Influence of dreissenid mussels on catchability of benthic fishes in bottom trawls

USGS Publications Warehouse

Kocovsky, Patrick M.; Stapanian, Martin A.

2011-01-01

Inferring trends in true abundance of fish populations from catch per unit effort data requires either the knowledge of capture probability or the assumption that it is constant, both of which are unlikely contingencies. We developed and validated an index of catchability (a proxy measure for capture probability) from a long-term data set describing nearshore waters of western Lake Erie, and we used the index to test the hypothesis that catchability of four abundant benthic species captured in bottom trawls changed after the invasion of dreissenid mussels. We estimated daytime and nighttime catchability for 1972–1990 (predreissenid period) and 1991–2009 (dreissenid period); we then tested for differences between nighttime and daytime catchability in the predreissenid and dreissenid periods and the nighttime–daytime differential in catchability during the dreissenid period. We also tested relationships between Secchi depth and the catchability index via linear regression. Catchability indices for white perch Morone americana, yellow perch Perca flavescens, and trout-perch Percopsis omiscomaycus did not differ between daytime and nighttime during the predreissenid period. After establishment of dreissenids, all three of these species had lower daytime catchability than nighttime catchability and had positive nighttime–daytime differentials, indicating a shift toward higher nighttime catchability relative to daytime catchability. Changes in catchability indices for freshwater drum Aplodinotus grunniens were opposite the changes observed for the other three species, possibly because the freshwater drum is the only species that actively feeds on dreissenids. Catchability indices were negatively related to water clarity (Secchi depth) for three of the species. Our results are consistent with the hypothesis that catchability of the four most common benthic fish species captured in bottom trawls within nearshore waters of western Lake Erie changed after the dreissenid invasion because of increased water clarity and increased visibility, which led to greater daytime trawl avoidance.

Using multiple gears to assess acoustic detectability and biomass of fish species in lake superior

USGS Publications Warehouse

Yule, D.L.; Adams, J.V.; Stockwell, J.D.; Gorman, O.T.

2007-01-01

Recent predator demand and prey supply studies suggest that an annual daytime bottom trawl survey of Lake Superior underestimates prey fish biomass. A multiple-gear (acoustics, bottom trawl, and midwater trawl) nighttime survey has been recommended, but before abandoning a long-term daytime survey the effectiveness of night sampling of important prey species must be verified. We sampled three bottom depths (30, 60, and 120 m) at a Lake Superior site where the fish community included all commercially and ecologically important species. Day and night samples were collected within 48 h at all depths during eight different periods (one new and one full moon period during both early summer and late summer to early fall over 2 years). Biomass of demersal and benthic species was higher in night bottom trawl samples than in day bottom trawl samples. Night acoustic collections showed that pelagic fish typically occupied water cooler than 15°C and light levels less than 0.001 lx. Using biomass in night bottom trawls and acoustic biomass above the bottom trawl path, we calculated an index of acoustic detectability for each species. Ciscoes Coregonus artedi, kiyis C. kiyi, and rainbow smeltOsmerus mordax left the bottom at night, whereas bloaters C. hoyi stayed nearer the bottom. We compared the biomass of important prey species estimated with two survey types: day bottom trawls and night estimates of the entire water column (bottom trawl biomass plus acoustic biomass). The biomass of large ciscoes (>200 mm) was significantly greater when measured at night than when measured during daylight, but the differences for other sizes of important species did not vary significantly by survey type. Nighttime of late summer is a period when conditions for biomass estimation are largely invariant, and all important prey species can be sampled using a multiple-gear approach.

Hydroacoustic estimates of abundance and spatial distribution of pelagic prey fishes in western Lake Superior

USGS Publications Warehouse

Mason, Doran M.; Johnson, Timothy B.; Harvey, Chris J.; Kitchell, James F.; Schram, Stephen T.; Bronte, Charles R.; Hoff, Michael H.; Lozano, Stephen J.; Trebitz, Anett S.; Schreiner, Donald R.; Lamon, E. Conrad; Hrabik, Thomas R.

2005-01-01

Lake herring (Coregonus artedi) and rainbow smelt (Osmerus mordax) are a valuable prey resource for the recovering lake trout (Salvelinus namaycush) in Lake Superior. However, prey biomass may be insufficient to support the current predator demand. In August 1997, we assessed the abundance and spatial distribution of pelagic coregonines and rainbow smelt in western Lake Superior by combining a 120 kHz split beam acoustics system with midwater trawls. Coregonines comprised the majority of the midwater trawl catches and the length distributions for trawl caught fish coincided with estimated sizes of acoustic targets. Overall mean pelagic prey fish biomass was 15.56 kg ha−1 with the greatest fish biomass occurring in the Apostle Islands region (27.98 kg ha−1), followed by the Duluth Minnesota region (20.22 kg ha−1), and with the lowest biomass occurring in the open waters of western Lake Superior (9.46 kg ha−1). Biomass estimates from hydroacoustics were typically 2–134 times greater than estimates derived from spring bottom trawl surveys. Prey fish biomass for Lake Superior is about order of magnitude less than acoustic estimates for Lakes Michigan and Ontario. Discrepancies observed between bioenergetics-based estimates of predator consumption of coregonines and earlier coregonine biomass estimates may be accounted for by our hydroacoustic estimates.

Consistency of Bottom Fish Communities in the Beaufort Sea Within and Between Years

NASA Astrophysics Data System (ADS)

Norcross, B.; Holladay, B.

2016-02-01

Fish communities in the Arctic may be indicators of change due to climate and oil and gas exploration. An initial benchmark is generally established by sampling a set of sites in multiple years sequentially to estimate interannual variability. Standard practice is to conduct one trawl haul per station. Establishing the annual frequency of sampling and minimum number of hauls per station necessary to detect changes in demersal fish communities is essential to designing a monitoring program. Using small bottom trawls, we assessed interannual variability of bottom fish communities between 2013 and 2014 in the eastern US Beaufort Sea at eight depths 20-1000 m on each of four transects. In 2014, to determine if one haul per station was representative of a site, replicate hauls were made at stations along one transect at the US-Canada border. The similarity among replicate hauls within a single year was excellent, indicating that one haul per station was representative of fish communities. There were distinctly different bottom fish communities on the Beaufort Sea shelf (20-100 m) and slope (200-1000 m). Shelf communities had higher abundances of smaller fishes; whereas slope communities had fewer, but larger, individuals. There was no change in fish abundance between years, but there was interannual variability in the biomass of fish communities on the slope. However, as few fishes were captured at deep stations, the difference between catching and not catching a single large heavy fish affected relative biomass significantly, which may distort the conclusion of interannual variability. Furthermore, these replicate hauls occurred in the eastern Beaufort Sea, which appears to have fewer fish species and in lower abundance than the western Beaufort Sea. The similarity within replicates may not be as striking in a more diverse environment, however this study shows that in this region of the Arctic, it is likely sufficient to forego replicate sampling at a station in one year and season, and sequential years of sampling in that season, when characterizing bottom fish communities within a long-term study of community stability.

Long-term effects of bottom trawling on large sponges in the Gulf of Alaska

NASA Astrophysics Data System (ADS)

Malecha, Patrick; Heifetz, Jonathan

2017-11-01

Manipulative studies that characterize short-term effects of bottom trawls on seafloor habitats are numerous, but studies that examine long-term effects are rare. The long-term (13 years) effects of a single bottom trawl on large (>20 cm) erect sponges were investigated by revisiting the site of prior experimental trawling studies. In prior studies, large sponges were assessed immediately after trawling and 1 yr post-trawling. Thirteen years post-trawling, the average density of large sponges was 31.7% lower (range 1.5-53.0%) and the incidence of sponge damage (torn, necrotic, missing tissue, prone) was 58.8% higher within strip transects in trawled versus untrawled reference areas. For all sponge species combined, the mean density of large sponges was 3.19 individuals 100 m-2 in trawled areas and 4.67 individuals 100 m-2 in reference areas. The most abundant sponge species in both trawled and reference areas was Rhabdocalyptus dawsoni. Mean density of this species differed greatly between trawled (1.57 individuals 100 m-2) and reference areas (2.91 individuals 100 m-2). Thirteen years after trawling, the mean percentage of damaged sponges on strip transects was 15.3% in trawled areas and 6.3% in reference areas. The rate of damage in trawled areas was less than that observed both immediately after trawling and 1 year later. The persistence of damage (lower sponge densities and higher rates of injury in trawled areas) and the potential resultant changes to benthic communities where deepwater habitat-forming biota, such as large erect sponges, are present provide rationale for cautious management of the long term effects of bottom trawling.

78 FR 4391 - North Pacific Fishery Management Council; Public Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-22

...); Initial review of AFA Vessel Replacement GOA Sideboards. 4. GOA Trawl Issues: Discussion paper on Central Gulf of Alaska (CGOA) Trawl Economic Data Collection; Discussion paper on CGOA Trawl Catch Shares... paper on Bristol Bay red king crab. 3. Groundfish Issues: Discussion paper on crab bycatch limits in...

Management Implications of the Biodiversity and Socio-Economic Impacts of Shrimp Trawler By-Catch in Bahía de Kino, Sonora, México

PubMed Central

Meltzer, Lorayne; Blinick, Naomi S.; Fleishman, Abram B.

2012-01-01

The shrimp fishery is the most economically important fishery in Mexico. The trawler-based portion of this fishery results in high rates of by-catch. This study quantifies and describes the biodiversity of by-catch associated with trawling in the Bahía de Kino region of Sonora, Mexico. Data were collected from 55 trawls, on six boats, over 14 nights, during November of 2003, 2004, 2006–2009. By-catch rates within trawl samples averaged 85.9% measured by weight. A total of 183 by-catch species were identified during the course of this study, including 97 species of bony fish from 43 families, 19 species of elasmobranchs from 12 families, 66 species of invertebrates from eight phyla, and one species of marine turtle; seven of the documented by-catch species are listed on the IUCN Red List, CITES, or the Mexican NOM-059-ECOL-2010; 35 species documented in the by-catch are also targeted by local artisanal fishers. Some of the species frequently captured as juveniles in the by-catch are economically important to small-scale fishers in the region, and are particularly sensitive to overexploitation due to their life histories. This study highlights the need for further research quantifying the impacts of high levels of by-catch upon small-scale fishing economies in the region and presents strong ecological and economic rationale for by-catch management within the shrimp fishery of the Gulf of California. Site-specific by-catch management plans should be piloted in the Bahía de Kino region to address the growing momentum in national and international fisheries policy regimes toward the reduction of by-catch in shrimp fisheries. PMID:22719827

Management implications of the biodiversity and socio-economic impacts of shrimp trawler by-catch in Bahía de Kino, Sonora, México.

PubMed

Meltzer, Lorayne; Blinick, Naomi S; Fleishman, Abram B

2012-01-01

The shrimp fishery is the most economically important fishery in Mexico. The trawler-based portion of this fishery results in high rates of by-catch. This study quantifies and describes the biodiversity of by-catch associated with trawling in the Bahía de Kino region of Sonora, Mexico. Data were collected from 55 trawls, on six boats, over 14 nights, during November of 2003, 2004, 2006-2009. By-catch rates within trawl samples averaged 85.9% measured by weight. A total of 183 by-catch species were identified during the course of this study, including 97 species of bony fish from 43 families, 19 species of elasmobranchs from 12 families, 66 species of invertebrates from eight phyla, and one species of marine turtle; seven of the documented by-catch species are listed on the IUCN Red List, CITES, or the Mexican NOM-059-ECOL-2010; 35 species documented in the by-catch are also targeted by local artisanal fishers. Some of the species frequently captured as juveniles in the by-catch are economically important to small-scale fishers in the region, and are particularly sensitive to overexploitation due to their life histories. This study highlights the need for further research quantifying the impacts of high levels of by-catch upon small-scale fishing economies in the region and presents strong ecological and economic rationale for by-catch management within the shrimp fishery of the Gulf of California. Site-specific by-catch management plans should be piloted in the Bahía de Kino region to address the growing momentum in national and international fisheries policy regimes toward the reduction of by-catch in shrimp fisheries.

50 CFR 660.55 - Allocations.

Code of Federal Regulations, 2010 CFR

2010-10-01

... biennial fishing period's open access allocation. (B) [Reserved] (f) Catch accounting. Catch accounting... allocations in a given biennial cycle, catch of those species are counted against the limited entry/open... fisheries—(i) Catch accounting for the trawl allocation. Any groundfish caught by a vessel registered to a...

Defining trade-offs among conservation, profitability, and food security in the California current bottom-trawl fishery.

PubMed

Hilborn, Ray; Stewart, Ian J; Branch, Trevor A; Jensen, Olaf P

2012-04-01

Although it is recognized that marine wild-capture fisheries are an important source of food for much of the world, the cost of sustainable capture fisheries to species diversity is uncertain, and it is often questioned whether industrial fisheries can be managed sustainably. We evaluated the trade-off among sustainable food production, profitability, and conservation objectives in the groundfish bottom-trawl fishery off the U.S. West Coast, where depletion (i.e., reduction in abundance) of six rockfish species (Sebastes) is of particular concern. Trade-offs are inherent in this multispecies fishery because there is limited capacity to target species individually. From population models and catch of 34 stocks of bottom fish, we calculated the relation between harvest rate, long-term yield (i.e., total weight of fish caught), profit, and depletion of each species. In our models, annual ecosystem-wide yield from all 34 stocks was maximized with an overall 5.4% harvest rate, but profit was maximized at a 2.8% harvest rate. When we reduced harvest rates to the level (2.2% harvest rate) at which no stocks collapsed (<10% of unfished levels), biomass harvested was 76% of the maximum sustainable yield and profit 89% of maximum. A harvest rate under which no stocks fell below the biomass that produced maximum sustainable yield (1% harvest rate), resulted in 45% of potential yield and 67% of potential profit. Major reductions in catch in the late 1990s led to increase in the biomass of the most depleted stocks, but this rebuilding resulted in the loss of >30% of total sustainable yield, whereas yield lost from stock depletion was 3% of total sustainable yield. There are clear conservation benefits to lower harvest rates, but avoiding overfishing of all stocks in a multispecies fishery carries a substantial cost in terms of lost yield and profit. ©2011 Society for Conservation Biology.

An ecological model of the Northern and Central Adriatic Sea: Analysis of ecosystem structure and fishing impacts

NASA Astrophysics Data System (ADS)

Coll, Marta; Santojanni, Alberto; Palomera, Isabel; Tudela, Sergi; Arneri, Enrico

2007-08-01

A trophic mass-balance model was developed to characterise the food web structure and functioning of the Northern and Central Adriatic Sea and to quantify the ecosystem impacts of fishing during the 1990s. Forty functional groups were described, including target and non-target fish and invertebrate groups, and three detritus groups (natural detritus, discards and by-catch of cetaceans and marine turtles). Results highlighted that there was an important coupling between pelagic-benthic production of plankton, benthic invertebrates and detritus. Organisms located at low and medium trophic levels, (i.e. benthic invertebrates, zooplankton and anchovy), as well as dolphins, were identified as keystone groups of the ecosystem. Jellyfish were an important element in terms of consumption and production of trophic flows within the ecosystem. The analysis of trophic flows of zooplankton and detritus groups indirectly underlined the importance of the microbial food web in the Adriatic Sea. Fishing activities inflicted notable impacts on the ecosystem during the 1990s, with a high gross efficiency of the fishery, a high consumption of fishable production, high exploitation rates for various target and non target species, a low trophic level of the catch and medium values of primary production required to sustain the fishery. Moreover, the analysis of Odum's ecological indicators highlighted that the ecosystem was in a low-medium developmental stage. Bottom trawling ( Strascico), mid-water trawling ( Volante) and beam trawling ( Rapido) fleets had the highest impacts on both target and non target ecological groups. On the contrary, purse seining ( Lampara) showed medium to low impacts on the ecosystem; cetaceans, marine turtles and sea birds were not significantly involved in competition with fishing activity.

Identification and evaluation of shark bycatch in Georgia’s commercial shrimp trawl fishery with implications for management

USGS Publications Warehouse

Belcher, C.N.; Jennings, Cecil A.

2011-01-01

Many US states have recreational and commercial fisheries that occur in nursery areas occupied by subadult sharks and can potentially affect their survival. Georgia is one of few US states without a directed commercial shark fishery, but the state has a large, nearshore penaeid shrimp trawl fishery in which small sharks occur as bycatch. During our 1995-1998 investigation of bycatch in fishery-dependent sampling events, 34% of 127 trawls contained sharks. This bycatch totalled 217 individuals from six species, with Atlantic sharpnose shark, Rhizoprionodon terraenovae (Richardson), the most common and finetooth shark, Carcharhinus isodon (Müller & Henle) and spinner shark, Carcharhinus brevipinna (Müller & Henle), the least common. The highest catch rates for sharks occurred during June and July and coincided with the peak months of the pupping season for many species. Trawl tow speed and tow time did not significantly influence catch rates for shark species. Gear configurations [net type, turtle excluder device (TED), bycatch reduction device] affected catch rates for shark species. Results of this study indicate gear restrictions, a delayed season opening, or reduced bar spacing on TEDs may reduce shark bycatch in this fishery.

Identification and evaluation of shark bycatch in Georgia's commercial shrimp trawl fishery with implications for management

USGS Publications Warehouse

Belcher, C.N.; Jennings, C.A.

2011-01-01

Many US states have recreational and commercial fisheries that occur in nursery areas occupied by subadult sharks and can potentially affect their survival. Georgia is one of few US states without a directed commercial shark fishery, but the state has a large, nearshore penaeid shrimp trawl fishery in which small sharks occur as bycatch. During our 1995–1998 investigation of bycatch in fishery-dependent sampling events, 34% of 127 trawls contained sharks. This bycatch totalled 217 individuals from six species, with Atlantic sharpnose shark, Rhizoprionodon terraenovae (Richardson), the most common and finetooth shark, Carcharhinus isodon (Müller & Henle) and spinner shark, Carcharhinus brevipinna (Müller & Henle), the least common. The highest catch rates for sharks occurred during June and July and coincided with the peak months of the pupping season for many species. Trawl tow speed and tow time did not significantly influence catch rates for shark species. Gear configurations [net type, turtle excluder device (TED), bycatch reduction device] affected catch rates for shark species. Results of this study indicate gear restrictions, a delayed season opening, or reduced bar spacing on TEDs may reduce shark bycatch in this fishery.

75 FR 10757 - Proposed Information Collection; Comment Request; Alaska Region Amendment 80 Permits and Reports

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-09

... facilitates the formation of harvesting cooperatives in the head-and-gut trawl catcher/processor sector... catch, improved retention, improved utilization, and improved economic health of the head-and-gut trawl...

Trawling damage to Northeast Atlantic ancient coral reefs.

PubMed Central

Hall-Spencer, Jason; Allain, Valerie; Fosså, Jan Helge

2002-01-01

This contribution documents widespread trawling damage to cold-water coral reefs at 840-1300 m depth along the West Ireland continental shelf break and at 200 m off West Norway. These reefs are spectacular but poorly known. By-catches from commercial trawls for deep-water fish off West Ireland included large pieces (up to 1 m(2)) of coral that had been broken from reefs and a diverse array of coral-associated benthos. Five azooxanthellate scleractinarian corals were identified in these by-catches, viz. Desmophyllum cristagalli, Enallopsammia rostrata, Lophelia pertusa, Madrepora oculata and Solenosmilia variabilis. Dating of carbonate skeletons using (14)C accelerator mass spectrometry showed that the trawled coral matrix was at least 4550 years old. Surveys by remotely operated vehicles in Norway showed extensive fishing damage to L. pertusa reefs. The urgent need for deep-water coral conservation measures is discussed in a Northeast Atlantic context. PMID:11886643

50 CFR 665.605 - Gear restrictions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Gear restrictions. 665.605 Section 665.605... § 665.605 Gear restrictions. (a) Bottom trawls and bottom set gillnets. Fishing for PRIA bottomfish MUS with bottom trawls and bottom set gillnets is prohibited. (b) Possession of gear. Possession of a...

Community reorganization in the Gulf of Alaska following ocean climate regime shift

USGS Publications Warehouse

Anderson, P.J.; Piatt, John F.

1999-01-01

A shift in ocean climate during the late 1970s triggered a reorganization of community structure in the Gulf of Alaska ecosystem, as evidenced in changing catch composition on long-term (1953 to 1997) small-mesh trawl surveys. Forage species such as pandalid shrimp and capelin declined because of recruitment failure and predation, and populations have not yet recovered. Total trawl catch biomass declined >50% and remained low through the 1980s. In contrast, recruitment of high trophic-level groundfish improved during the 1980s, yielding a >250% increase in catch biomass during the 1990s. This trophic reorganization apparently had negative effects on piscivorous sea birds and marine mammals.

Bottom-trawling along submarine canyons impacts deep sedimentary regimes

PubMed Central

Paradis, Sarah; Puig, Pere; Masqué, Pere; Juan-Díaz, Xènia; Martín, Jacobo; Palanques, Albert

2017-01-01

Many studies highlight that fish trawling activities cause seafloor erosion, but the assessment of the remobilization of surface sediments and its relocation is still not well documented. These impacts were examined along the flanks and axes of three headless submarine canyons incised on the Barcelona continental margin, where trawling fleets have been operating for decades. Trawled grounds along canyon flanks presented eroded and highly reworked surface sediments resulting from the passage of heavy trawling gear. Sedimentation rates on the upper canyon axes tripled and quadrupled its natural (i.e. pre-industrialization) values after a substantial increase in total horsepower of the operating trawling fleets between 1960 s and 1970 s. These impacts affected the upper canyon reaches next to fishing grounds, where sediment resuspended by trawling can be transported towards the canyon axes. This study highlights that bottom trawling has the capacity to alter natural sedimentary environments by promoting sediment-starved canyon flanks, and by enhancing sedimentation rates along the contiguous axes, independently of canyons’ morphology. Considering the global mechanisation and offshore expansion of bottom trawling fisheries since the mid-20th century, these sedimentary alterations may occur in many trawled canyons worldwide, with further ecological impacts on the trophic status of these non-resilient benthic communities. PMID:28233856

Bottom-trawling along submarine canyons impacts deep sedimentary regimes

NASA Astrophysics Data System (ADS)

Paradis, Sarah; Puig, Pere; Masqué, Pere; Juan-Díaz, Xènia; Martín, Jacobo; Palanques, Albert

2017-02-01

Many studies highlight that fish trawling activities cause seafloor erosion, but the assessment of the remobilization of surface sediments and its relocation is still not well documented. These impacts were examined along the flanks and axes of three headless submarine canyons incised on the Barcelona continental margin, where trawling fleets have been operating for decades. Trawled grounds along canyon flanks presented eroded and highly reworked surface sediments resulting from the passage of heavy trawling gear. Sedimentation rates on the upper canyon axes tripled and quadrupled its natural (i.e. pre-industrialization) values after a substantial increase in total horsepower of the operating trawling fleets between 1960 s and 1970 s. These impacts affected the upper canyon reaches next to fishing grounds, where sediment resuspended by trawling can be transported towards the canyon axes. This study highlights that bottom trawling has the capacity to alter natural sedimentary environments by promoting sediment-starved canyon flanks, and by enhancing sedimentation rates along the contiguous axes, independently of canyons’ morphology. Considering the global mechanisation and offshore expansion of bottom trawling fisheries since the mid-20th century, these sedimentary alterations may occur in many trawled canyons worldwide, with further ecological impacts on the trophic status of these non-resilient benthic communities.

Bottom-trawling along submarine canyons impacts deep sedimentary regimes.

PubMed

Paradis, Sarah; Puig, Pere; Masqué, Pere; Juan-Díaz, Xènia; Martín, Jacobo; Palanques, Albert

2017-02-24

Many studies highlight that fish trawling activities cause seafloor erosion, but the assessment of the remobilization of surface sediments and its relocation is still not well documented. These impacts were examined along the flanks and axes of three headless submarine canyons incised on the Barcelona continental margin, where trawling fleets have been operating for decades. Trawled grounds along canyon flanks presented eroded and highly reworked surface sediments resulting from the passage of heavy trawling gear. Sedimentation rates on the upper canyon axes tripled and quadrupled its natural (i.e. pre-industrialization) values after a substantial increase in total horsepower of the operating trawling fleets between 1960 s and 1970 s. These impacts affected the upper canyon reaches next to fishing grounds, where sediment resuspended by trawling can be transported towards the canyon axes. This study highlights that bottom trawling has the capacity to alter natural sedimentary environments by promoting sediment-starved canyon flanks, and by enhancing sedimentation rates along the contiguous axes, independently of canyons' morphology. Considering the global mechanisation and offshore expansion of bottom trawling fisheries since the mid-20 th century, these sedimentary alterations may occur in many trawled canyons worldwide, with further ecological impacts on the trophic status of these non-resilient benthic communities.

A ‘Simple Anterior Fish Excluder’ (SAFE) for Mitigating Penaeid-Trawl Bycatch

PubMed Central

McHugh, Matthew J.; Broadhurst, Matt K.; Sterling, David J.; Millar, Russell B.

2015-01-01

Various plastic strips and sheets (termed ‘simple anterior fish excluders’−SAFEs) were positioned across the openings of penaeid trawls in attempts at reducing the unwanted bycatches of small teleosts. Initially, three SAFEs (a single wire without, and with small and large plastic panels) were compared against a control (no SAFE) on paired beam trawls. All SAFEs maintained targeted Metapenaeus macleayi catches, while the largest plastic SAFE significantly reduced total bycatch by 51% and the numbers of Pomatomus saltatrix, Mugil cephalus and Herklotsichthys castelnaui by up to 58%. A redesigned SAFE (‘continuous plastic’) was subsequently tested (against a control) on paired otter trawls, significantly reducing total bycatch by 28% and P. saltatrix and H. castelnaui by up to 42%. The continuous-plastic SAFE also significantly reduced M. macleayi catches by ~7%, but this was explained by ~5% less wing-end spread, and could be simply negated through otter-board refinement. Further work is required to refine the tested SAFEs, and to quantify species-specific escape mechanisms. Nevertheless, the SAFE concept might represent an effective approach for improving penaeid-trawl selectivity. PMID:25837892

Distribution of Bottom Trawling Effort in the Yellow Sea and East China Sea

PubMed Central

Zhang, Shengmao; Jin, Shaofei; Zhang, Heng; Fan, Wei; Tang, Fenghua; Yang, Shenglong

2016-01-01

Bottom trawling is one of the most efficient fishing activities, but serious and persistent ecological issues have been observed by fishers, scientists and fishery managers. Although China has applied the Beidou fishing vessel position monitoring system (VMS) to manage trawlers since 2006, little is known regarding the impacts of trawling on the sea bottom environments. In this study, continuous VMS data of the 1403 single-rig otter trawlers registered in the Xiangshan Port, 3.9% of the total trawlers in China, were used to map the trawling effort in 2013. We used the accumulated distance (AD), accumulated power distance (APD), and trawling intensity as indexes to express the trawling efforts in the Yellow Sea (YS) and East China Sea (ECS). Our results show that all three indexes had similar patterns in the YS and ECS, and indicated a higher fishing effort of fishing grounds that were near the port. On average, the seabed was trawled 0.73 times in 2013 over the entire fishing region, and 51.38% of the total fishing grounds were with no fishing activities. Because of VMS data from only a small proportion of Chinese trawlers was calculated fishing intensity, more VMS data is required to illustrate the overall trawling effort in China seas. Our results enable fishery managers to identify the distribution of bottom trawling activities in the YS and ECS, and hence to make effective fishery policy. PMID:27855215

Trawl disturbance on benthic communities: chronic effects and experimental predictions.

PubMed

Hinz, Hilmar; Prieto, Virginia; Kaiser, Michel J

2009-04-01

Bottom trawling has widespread impacts on benthic communities and habitats. While the direct impacts of trawl disturbances on benthic communities have been extensively studied, the consequences from long-term chronic disturbances are less well understood. The response of benthic macrofauna to chronic otter-trawl disturbance from a Nephrops norvegicus (Norway lobster) fishery was investigated along a gradient of fishing intensity over a muddy fishing ground in the northeastern Irish Sea. Chronic otter trawling had a significant, negative effect on benthic infauna abundance, biomass, and species richness. Benthic epifauna abundance and species richness also showed a significant, negative response, while no such effect was evident for epibenthic biomass. Furthermore, chronic trawl disturbance led to clear changes in community composition of benthic infauna and epifauna. The results presented indicate that otter-trawl impacts are cumulative and can lead to profound changes in benthic communities, which may have far-reaching implications for the integrity of marine food webs. Studies investigating the short-term effects of fishing manipulations previously concluded that otter trawling on muddy substrates had only modest effects on the benthic biota. Hence, the results presented by this study highlight that data from experimental studies can not be readily extrapolated to an ecosystem level and that subtle cumulative effects may only become apparent when fishing disturbances are examined over larger spatial and temporal scales. Furthermore, this study shows that data on chronic effects of bottom trawling on the benthos will be vital in informing the recently advocated move toward an ecosystem approach in fisheries management. As bottom-trawl fisheries are expanding into ever deeper muddy habitats, the results presented here are an important step toward understanding the global ecosystem effects of bottom trawling.

Fisheries research and monitoring activities of the Lake Erie Biological Station, 2015

USGS Publications Warehouse

Bodamer Scarbro, Betsy L.; Edwards, W.H.; Kocovsky, Patrick M.; Kraus, Richard T.; Rogers, M. R.; Schoonyan, A. L.; Stewart, T. R.

2016-01-01

In 2015, the U.S. Geological Survey’s (USGS) Lake Erie Biological Station (LEBS) successfully completed large vessel surveys in all three of Lake Erie’s basins. Lake Erie Biological Station’s primary vessel surveys included the Western Basin Forage Fish Assessment and East Harbor Fish Community Assessment as well as contributing to the cooperative multi-agency Central Basin Hydroacoustics Assessment, the Eastern Basin Coldwater Community Assessment, and Lower Trophic Level Assessment (see Forage and Coldwater Task Group reports). In 2015, LEBS also initiated a Lake Erie Central Basin Trawling survey in response to the need for forage fish data from Management Unit 3 (as defined by the Yellow Perch Task Group). Results from these surveys contribute to Lake Erie Committee Fish Community Goals and Objectives. Our 2015 vessel operations were initiated in early April and continued into late November. During this time, crews of the R/V Muskie and R/V Bowfin deployed 121 bottom trawls covering 83.2 ha of lake-bottom and catching 105,600 fish totaling 4,065 kg during four separate trawl surveys in the western and central basins of Lake Erie. We deployed and lifted 9.5 km of gillnet, which caught an additional 805 fish, 100 (337 kg) of which were the native coldwater predators Lake Trout, Burbot, and Lake Whitefish (these data are reported in the 2016 Coldwater Task Group report). We also conducted 317 km of hydroacoustic survey transects (reported in the 2016 Forage Task Group report), collected 114 lower trophic (i.e. zooplankton and benthos) samples, and obtained 216 water quality observations (e.g., temperature profiles, and water samples). The LEBS also assisted CLC member agencies with the maintenance and expansion of GLATOS throughout all three Lake Erie sub-basins. Within the following report sections, we describe results from three trawl surveys – the spring and autumn Western Basin Forage Fish Assessment and the East Harbor Forage Fish Assessment – and the Lower Trophic Level Assessment conducted in 2015, and examine trends in the fish community structure and trophic status of Lake Erie. Results of our central basin trawl survey are reported in the 2016 Yellow Perch Task Group report.

Trawling-induced daily sediment resuspension in the flank of a Mediterranean submarine canyon

NASA Astrophysics Data System (ADS)

Martín, Jacobo; Puig, Pere; Palanques, Albert; Ribó, Marta

2014-06-01

Commercial bottom trawling is one of the anthropogenic activities causing the biggest impact on the seafloor due to its recurrence and global distribution. In particular, trawling has been proposed as a major driver of sediment dynamics at depths below the reach of storm waves, but the issue is at present poorly documented with direct observations. This paper analyses changes in water turbidity in a tributary valley of the La Fonera (=Palamós) submarine canyon, whose flanks are routinely exploited by a local trawling fleet down to depths of 800 m. A string of turbidimeters was deployed at 980 m water depth inside the tributary for two consecutive years, 2010-2011. The second year, an ADCP profiled the currents 80 m above the seafloor. The results illustrate that near-bottom water turbidity at the study site is heavily dominated, both in its magnitude and temporal patterns, by trawling-induced sediment resuspension at the fishing ground. Resuspended sediments are channelised along the tributary in the form of sediment gravity flows, being recorded only during working days and working hours of the trawling fleet. These sediment gravity flows generate turbid plumes that extend to at least 100 m above the bottom, reaching suspended sediment concentrations up to 236 mg l-1 close to the seafloor (5 m above bottom). A few hours after the end of daily trawling activities, water turbidity progressively decreases but resuspended particles remain in suspension for several hours, developing bottom and intermediate nepheloid layers that reach background levels ˜2 mg l-1 before trawling activities resume. The presence of these nepheloid layers was recorded in a CTD+turbidimeter transect conducted across the fishing ground a few hours after the end of a working day. These results highlight that deep bottom trawling can effectively replace natural processes as the main driving force of sediment resuspension on continental slope regions and generate increased near-bottom water turbidity that propagates from fishing grounds to wider and deeper areas via sediment gravity flows and nepheloid layer development.

When does fishing lead to more fish? Community consequences of bottom trawl fisheries in demersal food webs

PubMed Central

van Denderen, P. Daniel; van Kooten, Tobias; Rijnsdorp, Adriaan D.

2013-01-01

Bottom trawls are a globally used fishing gear that physically disturb the seabed and kill non-target organisms, including those that are food for the targeted fish species. There are indications that ensuing changes to the benthic invertebrate community may increase the availability of food and promote growth and even fisheries yield of target fish species. If and how this occurs is the subject of ongoing debate, with evidence both in favour and against. We model the effects of trawling on a simple ecosystem of benthivorous fish and two food populations (benthos), susceptible and resistant to trawling. We show that the ecosystem response to trawling depends on whether the abundance of benthos is top-down or bottom-up controlled. Fishing may result in higher fish abundance, higher (maximum sustainable) yield and increased persistence of fish when the benthos which is the best-quality fish food is also more resistant to trawling. These positive effects occur in bottom-up controlled systems and systems with limited impact of fish feeding on benthos, resembling bottom-up control. Fishing leads to lower yields and fish persistence in all configurations where susceptible benthos are more profitable prey. Our results highlight the importance of mechanistic ecosystem knowledge as a requirement for successful management. PMID:24004941

Sidescan-sonar mapping of benthic trawl marks on the shelf and slope off Eureka, California

USGS Publications Warehouse

Friedlander, A.M.; Boehlert, G.W.; Field, M.E.; Mason, J.E.; Gardner, J.V.; Dartnell, P.

1999-01-01

The abundance and orientation of trawl marks was quantified over an extensive portion (>2700 km2) of the Eureka, California, outer shelf and slope, an important commercial bottom trawling ground for such high-value species as rockfish, sole, and sablefish. Fishing logbook data indicate that the entire reporting area was trawled about one and a half times on an average annual basis and that some areas were trawled over three times annually. High-resolution sidescan-sonar images of the study area revealed deep gouges on the seafloor, caused by heavy steel trawl doors that act to weigh down and spread open the bottom trawls. These trawl marks are commonly oriented parallel to bathymetric contours and many could be traced for several kilometers. Trawl marks showed a quadratic relationship in relation to water depth, with the greatest number of trawl marks observed at ~400 m. There was a significant positive correlation between the number of trawl marks observed on the sidescan images and the number of annual trawl hours logged within reporting areas. This finding indicates that acoustic remote sensing is a promising independent approach to evaluate fishing effort on a scale consistent with commercial fishing activities. Bottom trawling gear is known to modify seafloor habitats by altering benthic habitat complexity and by removing or damaging infauna and sessile organisms. Identifying the extent of trawling in these areas may help determine the effects of this type of fishing gear on the benthos and develop indices of habitat disturbance caused by fishing activities.

Effects of bottom trawling on fish foraging and feeding.

PubMed

Johnson, Andrew Frederick; Gorelli, Giulia; Jenkins, Stuart Rees; Hiddink, Jan Geert; Hinz, Hilmar

2015-01-22

The effects of bottom trawling on benthic invertebrates include reductions of biomass, diversity and body size. These changes may negatively affect prey availability for demersal fishes, potentially leading to reduced food intake, body condition and yield of fishes in chronically trawled areas. Here, the effect of trawling on the prey availability and diet of two commercially important flatfish species, plaice (Pleuronectes platessa) and dab (Limanda limanda), was investigated over a trawling intensity gradient in the Irish Sea. Previous work in this area has shown that trawling negatively affects the condition of plaice but not of dab. This study showed that reductions in local prey availability did not result in reduced feeding of fish. As trawling frequency increased, both fish and prey biomass declined, such that the ratio of fish to prey remained unchanged. Consequently, even at frequently trawled sites with low prey biomass, both plaice and dab maintained constant levels of stomach fullness and gut energy contents. However, dietary shifts in plaice towards energy-poor prey items were evident when prey species were analysed individually. This, together with a potential decrease in foraging efficiency due to low prey densities, was seen as the most plausible cause for the reduced body condition observed. Understanding the relationship between trawling, benthic impacts, fish foraging and resultant body condition is an important step in designing successful mitigation measures for future management strategies in bottom trawl fisheries.

Effects of bottom trawling on fish foraging and feeding

PubMed Central

Johnson, Andrew Frederick; Gorelli, Giulia; Jenkins, Stuart Rees; Hiddink, Jan Geert; Hinz, Hilmar

2015-01-01

The effects of bottom trawling on benthic invertebrates include reductions of biomass, diversity and body size. These changes may negatively affect prey availability for demersal fishes, potentially leading to reduced food intake, body condition and yield of fishes in chronically trawled areas. Here, the effect of trawling on the prey availability and diet of two commercially important flatfish species, plaice (Pleuronectes platessa) and dab (Limanda limanda), was investigated over a trawling intensity gradient in the Irish Sea. Previous work in this area has shown that trawling negatively affects the condition of plaice but not of dab. This study showed that reductions in local prey availability did not result in reduced feeding of fish. As trawling frequency increased, both fish and prey biomass declined, such that the ratio of fish to prey remained unchanged. Consequently, even at frequently trawled sites with low prey biomass, both plaice and dab maintained constant levels of stomach fullness and gut energy contents. However, dietary shifts in plaice towards energy-poor prey items were evident when prey species were analysed individually. This, together with a potential decrease in foraging efficiency due to low prey densities, was seen as the most plausible cause for the reduced body condition observed. Understanding the relationship between trawling, benthic impacts, fish foraging and resultant body condition is an important step in designing successful mitigation measures for future management strategies in bottom trawl fisheries. PMID:25621336

Organic biomarkers in deep-sea regions affected by bottom trawling: pigments, fatty acids, amino acids and carbohydrates in surface sediments from the La Fonera (Palamós) Canyon, NW Mediterranean Sea

NASA Astrophysics Data System (ADS)

Sañé, E.; Martín, J.; Puig, P.; Palanques, A.

2012-12-01

Deep-sea ecosystems are in general adapted to a limited variability of physical conditions, resulting in high vulnerability and slow recovery rates from anthropogenic perturbations such as bottom trawling. Commercial trawling is the most recurrent and pervasive of human impacts on the deep-sea floor, but studies on its consequences on the biogeochemistry of deep-sea sediments are still scarce. Pigments, fatty acids, amino acids and carbohydrates were analyzed in sediments from the flanks of the La Fonera (Palamós) submarine canyon (NW Mediterranean Sea), where a commercial bottom trawling fishery has been active for more than 70 yr. More specifically, we investigated how trawling-induced sediment reworking affects the quality of sedimentary organic matter which reaches the seafloor and accumulates in the sediment column, which is fundamental for the development of benthic communities. Sediment samples were collected during two oceanographic cruises in spring and autumn 2011. The sampled sites included trawl fishing grounds as well as pristine (control) areas. We report that bottom trawling in the flanks of the La Fonera Canyon has caused an alteration of the quality of the organic matter accumulated in the upper 5 cm of the seafloor. The use of a wide pool of biochemical tracers characterized by different reactivity to degradation allowed us to discriminate the long-term effects of trawled-induced sediment reworking from the natural variability caused by the seasonal cycle of production and sinking of biogenic particles. Differences between untrawled and trawled areas were evidenced by labile amino acids, while differences between spring and autumn samples were detected only by the more labile indicators chlorophyll a and mono-unsaturated fatty acids. These results suggest that changes in the biochemical composition of the sedimentary organic matter caused by bottom trawling can be more relevant than those associated with natural seasonality and pose serious concerns about the ecological sustainability of deep-sea trawling activities.

Organic biomarkers in deep-sea regions affected by bottom trawling: pigments, fatty acids, amino acids and carbohydrates in surface sediments from the La Fonera (Palamós) Canyon, NW Mediterranean Sea

NASA Astrophysics Data System (ADS)

Sañé, E.; Martín, J.; Puig, P.; Palanques, A.

2013-12-01

Deep-sea ecosystems are in general adapted to a limited variability of physical conditions, resulting in high vulnerability and slow recovery rates from anthropogenic perturbations such as bottom trawling. Commercial trawling is the most recurrent and pervasive of human impacts on the deep-sea floor, but studies on its consequences on the biogeochemistry of deep-sea sediments are still scarce. Pigments, fatty acids, amino acids and carbohydrates were analysed in sediments from the flanks of the La Fonera (Palamós) submarine canyon (NW Mediterranean Sea), where a commercial bottom trawling fishery has been active for more than 70 yr. More specifically, we investigated how trawling-induced sediment reworking affects the quality of sedimentary organic matter which reaches the seafloor and accumulates in the sediment column, which is fundamental for the development of benthic communities. Sediment samples were collected during two oceanographic cruises in spring and autumn 2011. The sampled sites included trawl fishing grounds as well as pristine (control) areas. We report that bottom trawling in the flanks of the La Fonera Canyon has caused an alteration of the quality of the organic matter accumulated in the upper 5 cm of the seafloor. The use of a wide pool of biochemical tracers characterized by different reactivity to degradation allowed for us to discriminate the long-term effects of trawl-induced sediment reworking from the natural variability caused by the seasonal cycle of production and sinking of biogenic particles. Differences between untrawled and trawled areas were evidenced by labile amino acids, while differences between spring and autumn samples were detected only by the more labile indicators chlorophyll a and monounsaturated fatty acids. These results suggest that changes in the biochemical composition of the sedimentary organic matter caused by bottom trawling can be more relevant than those associated with natural seasonality and pose serious concerns about the ecological sustainability of deep-sea trawling activities.

Identifying ecological and fishing drivers of bycatch in a U.S. groundfish fishery.

PubMed

Jannot, Jason E; Holland, Daniel S

2013-10-01

Fisheries bycatch is driven by both ecological (e.g., area, season) and social (e.g., fisher behavior) factors that are often difficult to disentangle. We demonstrate a method for comparing fishery-dependent bycatch to fishery-independent catch to delineate the influence of ecological and social factors on bycatch and provide insights for bycatch management. We used data from commercial fishing vessels in the U.S. west coast trawl groundfish fishery (fishery-dependent data collected by fisheries observers) and scientific data from the U.S. west coast bottom trawl groundfish survey (fishery-independent data) to compare the relative effects of season, time of day, target group, depth, and latitude on the expected catch of 12 bycatch species of management interest. This comparison highlights two important relationships that help identify drivers of bycatch. First, when the effect of season, time of day, depth, or latitude on bycatch in both the commercial and scientific data is positive, ecological processes are likely strong drivers of bycatch, suggesting technical approaches (e.g., temporal or spatial closures, gear modifications) might effectively control bycatch. Alternatively, when the effects of season, time of day, depth, latitude, or target group appear only in the commercial data (but not in survey data), fisher behavior is likely the stronger driver of bycatch, suggesting a need to strengthen incentives for fishers to change behavior to avoid bycatch (e.g., regulatory quotas). Two other patterns emerge that suggest that fishery bycatch is not associated with temporal, target, or spatial variables, implying that either current incentives to avoid bycatch are working (i.e., when survey expected catch is positively correlated with variables, but fishery catch is not) or bycatch is a product of unstudied or stochastic processes (i.e., variables are not correlated with expected catch in either data set) and continued monitoring is recommended. Our analysis provides managers and fishers with a basic analytical framework to assess bycatch reduction alternatives and methods useful for researchers interested in comparing bycatch before and after a management shift.

Use of a fishery-independent trawl survey to evaluate distribution patterns of subadult sharks in Georgia

USGS Publications Warehouse

Belcher, C.N.; Jennings, Cecil A.

2009-01-01

We investigated the utility of a fishery-independent trawl survey for assessing a potential multispecies shark nursery in Georgia's nearshore and inshore waters. A total of 234 subadult sharks from six species were captured during 85 of 216 trawls. Catch rates and size distributions for subadult sharks and the ratio of neonates to juveniles were consistent among areas. The highest concentrations of subadult sharks occurred in creeks and sounds. Species composition varied among areas. The Atlantic sharpnose shark Rhizoprionodon terraenovae was the most abundant species in sound and nearshore stations, whereas the bonnethead Sphyrna tiburo was the most abundant species in creeks. The aggregate of other species occurred with higher frequency in the sounds and nearshore. Sampling characteristics of the trawl survey were compared with those from a fishery-independent longline survey of subadult sharks to assess the similarity of the two gears. A total of 193 subadult sharks from seven species were captured during 57 of 96 longline sets, whereas 52 subadults from four species were captured during 20 of 48 trawls. Selectivity and efficiency differed between the two gears. The trawl had lower catch rates, caught smaller sharks, and encountered a different suite of species than the longline. General seasonal trends in relative abundance also differed between the two gears; the longline showed an increasing trend in abundance, whereas the trawl showed a stable trend. Although trawls were not found to be efficient for sampling subadult sharks from most species, they can be a useful source of supplemental data.

77 FR 72242 - Fisheries of the Northeastern United States; Northeast Multispecies Fishery; White Hake Trimester...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-05

... Fishery; White Hake Trimester Total Allowable Catch Area Closure for the Common Pool Fishery AGENCY... Allowable Catch (TAC) Area to all common pool groundfish vessels fishing with trawl gear, sink gillnet gear... necessary to prevent the common pool fishery from exceeding its Trimester 2 TAC or its annual catch limit...

Abundance, distribution and diversity of gelatinous predators along the northern Mid-Atlantic Ridge: A comparison of different sampling methodologies

PubMed Central

Falkenhaug, Tone; Baxter, Emily J.

2017-01-01

The diversity and distribution of gelatinous zooplankton were investigated along the northern Mid-Atlantic Ridge (MAR) from June to August 2004.Here, we present results from macrozooplankton trawl sampling, as well as comparisons made between five different methodologies that were employed during the MAR-ECO survey. In total, 16 species of hydromedusae, 31 species of siphonophores and four species of scyphozoans were identified to species level from macrozooplankton trawl samples. Additional taxa were identified to higher taxonomic levels and a single ctenophore genus was observed. Samples were collected at 17 stations along the MAR between the Azores and Iceland. A divergence in the species assemblages was observed at the southern limit of the Subpolar Frontal Zone. The catch composition of gelatinous zooplankton is compared between different sampling methodologies including: a macrozooplankton trawl; a Multinet; a ringnet attached to bottom trawl; and optical platforms (Underwater Video Profiler (UVP) & Remotely Operated Vehicle (ROV)). Different sampling methodologies are shown to exhibit selectivity towards different groups of gelatinous zooplankton. Only ~21% of taxa caught during the survey were caught by both the macrozooplankton trawl and the Multinet when deployed at the same station. The estimates of gelatinous zooplankton abundance calculated using these two gear types also varied widely (1.4 ± 0.9 individuals 1000 m-3 estimated by the macrozooplankton trawl vs. 468.3 ± 315.4 individuals 1000 m-3 estimated by the Multinet (mean ± s.d.) when used at the same stations (n = 6). While it appears that traditional net sampling can generate useful data on pelagic cnidarians, comparisons with results from the optical platforms suggest that ctenophore diversity and abundance are consistently underestimated, particularly when net sampling is conducted in combination with formalin fixation. The results emphasise the importance of considering sampling methodology both when planning surveys, as well as when interpreting existing data. PMID:29095891

Abundance, distribution and diversity of gelatinous predators along the northern Mid-Atlantic Ridge: A comparison of different sampling methodologies.

PubMed

Hosia, Aino; Falkenhaug, Tone; Baxter, Emily J; Pagès, Francesc

2017-01-01

The diversity and distribution of gelatinous zooplankton were investigated along the northern Mid-Atlantic Ridge (MAR) from June to August 2004.Here, we present results from macrozooplankton trawl sampling, as well as comparisons made between five different methodologies that were employed during the MAR-ECO survey. In total, 16 species of hydromedusae, 31 species of siphonophores and four species of scyphozoans were identified to species level from macrozooplankton trawl samples. Additional taxa were identified to higher taxonomic levels and a single ctenophore genus was observed. Samples were collected at 17 stations along the MAR between the Azores and Iceland. A divergence in the species assemblages was observed at the southern limit of the Subpolar Frontal Zone. The catch composition of gelatinous zooplankton is compared between different sampling methodologies including: a macrozooplankton trawl; a Multinet; a ringnet attached to bottom trawl; and optical platforms (Underwater Video Profiler (UVP) & Remotely Operated Vehicle (ROV)). Different sampling methodologies are shown to exhibit selectivity towards different groups of gelatinous zooplankton. Only ~21% of taxa caught during the survey were caught by both the macrozooplankton trawl and the Multinet when deployed at the same station. The estimates of gelatinous zooplankton abundance calculated using these two gear types also varied widely (1.4 ± 0.9 individuals 1000 m-3 estimated by the macrozooplankton trawl vs. 468.3 ± 315.4 individuals 1000 m-3 estimated by the Multinet (mean ± s.d.) when used at the same stations (n = 6). While it appears that traditional net sampling can generate useful data on pelagic cnidarians, comparisons with results from the optical platforms suggest that ctenophore diversity and abundance are consistently underestimated, particularly when net sampling is conducted in combination with formalin fixation. The results emphasise the importance of considering sampling methodology both when planning surveys, as well as when interpreting existing data.

Fisheries research and monitoring activities of the Lake Erie Biological Station, 2016

USGS Publications Warehouse

Bodamer Scarbro, Betsy L.; Kraus, Richard T.; Kocovsky, Patrick; Vandergoot, Christopher

2017-01-01

We conducted a biomass-based assessment of the Lake Erie Western Basin fish community using data collected from 2013-2016 Western Basin (spring and autumn) bottom trawl surveys. Biomass of total catch per hectare has decreased 75 percent since 2013. Declines were observed across all functional groups, but most notable was the decline of Emerald Shiner, which decreased from 25.3 kg/ha in spring 2013 to <0.01 kg/ha by autumn 2013. The four primary predator species – Walleye, Yellow Perch, White Perch, and White Bass – all decreased from 2013 to 2015. In 2016, White Bass and Yellow Perch (all lifestages combined) continued to decline, while Walleye and White Perch (all ages combined) increased slightly from 5.6 kg/ha and 3.4 kg/ha to 9.0 kg/ha and 5.0 kg/ha, respectively (autumn catches). Despite decreasing trends in biomass, there was little change in biodiversity. Declines in forage biomass, i.e. Emerald Shiner and age-0 White Perch, resulted in an increased mean trophic level of catches. Forage fish to piscivore ratios reflected marked shifts in species composition toward greater forage in 2014 and 2016.

Trophic look at soft-bottom communities - Short-term effects of trawling cessation on benthos

NASA Astrophysics Data System (ADS)

Dannheim, Jennifer; Brey, Thomas; Schröder, Alexander; Mintenbeck, Katja; Knust, Rainer; Arntz, Wolf E.

2014-01-01

The trophic structure of the German Bight soft-bottom benthic community was evaluated for potential changes after cessation of bottom trawling. Species were collected with van-Veen grabs and beam trawls. Trophic position (i.e. nitrogen stable isotope ratios, δ15N) and energy flow (i.e. species metabolism approximated by body mass scaled abundance) of dominant species were compared in trawled areas and an area protected from fisheries for 14 months in order to detect trawling cessation effects by trophic characteristics. At the community level, energy flow was lower in the protected area, but we were unable to detect significant changes in trophic position. At the species level energy flow in the protected area was lower for predating/scavenging species but higher for interface feeders. Species trophic positions of small predators/scavengers were lower and of deposit feeders higher in the protected area. Major reasons for trophic changes after trawling cessation may be the absence of artificial and additional food sources from trawling likely to attract predators and scavengers, and the absence of physical sediment disturbance impacting settlement/survival of less mobile species and causing a gradual shift in food availability and quality. Our results provide evidence that species or community energy flow is a good indicator to detect trawling induced energy-flow alterations in the benthic system, and that in particular species trophic properties are suitable to capture subtle and short-term changes in the benthos following trawling cessation.

50 CFR 679.20 - General limitations.

Code of Federal Regulations, 2014 CFR

2014-10-01

...% (ii) Trawl CP 50% 30% 20% (2) Hook-and-line CP and hook-and-line CV ≥60 ft (18.3 m) LOA 60% 40% no C...-and-line CV ≥60 ft (18.3 m) LOA 0.2 (4) Hook-and-line CP 48.7 (5) Pot CV ≥60 ft (18.3 m) LOA 8.4 (6) Pot CP 1.5 (7) AFA trawl CP 2.3 (8) Amendment 80 sector 13.4 (9) Trawl CV 22.1 (B) Incidental catch...

Seasonal bathymetric distributions of 16 fishes in Lake Superior, 1958-75

USGS Publications Warehouse

Selgeby, James H.; Hoff, Michael H.

1996-01-01

The bathymetric distributions of fishes in Lake Superior, which is one of the largest and deepest lakes in the world, has not been studied on a lakewide scale. Knowledge about the bathymetric distributions will aid in designing fish sampling programs, estimating absolute abundances, and modeling energy flow in the lake. Seasonal bathymetric distributions were determined , by 10-m depth intervals, for 16 fishes collected with bottom trawls and bottom-set gill nets within the upper 150 m of Lake Superior during 1958-75. In spring trawl catches, maximum abundance occurred at these depths: 15 m for round whitefish (Prosopium cylindraceum); 25m for longnose sucker (Catostomus catostomus); 35 m for lake whitefish (Coregonus clupeaformis) and rainbow smelt (Osmerus mordax); 45 m for lake trout (Salvelinus namaycush); 65 m for pygmy whitefish (Prospoium coulteri) and bloater (Coregonus hoyi); 75 m for trout- perch (Percopsis omiscomaycus); 105 m for shortjaw cisco (Coregonus zenithicus); and 115 m for ninespine stickleback (Pungitius pungitius), burbot (Lota lota), slimy sculpin (Cottus cogantus), spoonhead sculpin (Cottus ricei), and deepwater sculpin (Myoxcephalus thompsoni). Bathymetric distributions in spring gill nets were similar to those in trawls, except that depths of maximum abundances in gill nets were shallower than those in trawls for lake trout, rainbow smelt, longnose sucker, and burbot. Lake herring (Coregonus artedi) and kiyi (Coregonus kiyi) were rarely caught in trawls, and their maximum abundances in spring gill net collections were at depths of 25 and 145 m, respectively. In summer, pygmy whitefish, shortjaw cisco, lake herring, kiyi, longnose sucker, burbot, ninespine stickleback, trout-perch, slimy sculpin, and spponhead sculpin were at shallower depths than in spring, whereas rainbow smelt were found in deeper water; there was no change for other species. In fall, shortjaw cisco was at shallower depths than in summer, whereas the remaining species were found deeper, except for lake whitefish and lake trout whose modal depths did not change. Distributions of lake trout and lake whitefish were analyzed by age group, and the young (ages 1-3) of both species were often found in shallower water than were older fish. The shallow-water species exhibited little seasonal changes in bathymetric distributions, whereas the species that inhabited the middepths of deeper water generally moved shallower as the seasons progressed. Most of the more pronounced seasaonl changes in bathymetric distribution were associated with spawning movements.

Night sampling improves indices used for management of yellow perch in Lake Erie

USGS Publications Warehouse

Kocovsky, P.M.; Stapanian, M.A.; Knight, C.T.

2010-01-01

Catch rate (catch per hour) was examined for age-0 and age-1 yellow perch, Perca flavescens (Mitchill), captured in bottom trawls from 1991 to 2005 in western Lake Erie: (1) to examine variation of catch rate among years, seasons, diel periods and their interactions; and (2) to determine whether sampling during particular diel periods improved the management value of CPH data used in models to project abundance of age-2 yellow perch. Catch rate varied with year, season and the diel period during which sampling was conducted as well as by the interaction between year and season. Indices of abundance of age-0 and age-1 yellow perch estimated from night samples typically produced better fitting models and lower estimates of age-2 abundance than those using morning or afternoon samples, whereas indices using afternoon samples typically produced less precise and higher estimates of abundance. The diel period during which sampling is conducted will not affect observed population trends but may affect estimates of abundance of age-0 and age-1 yellow perch, which in turn affect recommended allowable harvest. A field experiment throughout western Lake Erie is recommended to examine potential benefits of night sampling to management of yellow perch. Published 2010. The article is a US Government work and is in the public domain in the USA.

Global analysis of depletion and recovery of seabed biota after bottom trawling disturbance.

PubMed

Hiddink, Jan Geert; Jennings, Simon; Sciberras, Marija; Szostek, Claire L; Hughes, Kathryn M; Ellis, Nick; Rijnsdorp, Adriaan D; McConnaughey, Robert A; Mazor, Tessa; Hilborn, Ray; Collie, Jeremy S; Pitcher, C Roland; Amoroso, Ricardo O; Parma, Ana M; Suuronen, Petri; Kaiser, Michel J

2017-08-01

Bottom trawling is the most widespread human activity affecting seabed habitats. Here, we collate all available data for experimental and comparative studies of trawling impacts on whole communities of seabed macroinvertebrates on sedimentary habitats and develop widely applicable methods to estimate depletion and recovery rates of biota after trawling. Depletion of biota and trawl penetration into the seabed are highly correlated. Otter trawls caused the least depletion, removing 6% of biota per pass and penetrating the seabed on average down to 2.4 cm, whereas hydraulic dredges caused the most depletion, removing 41% of biota and penetrating the seabed on average 16.1 cm. Median recovery times posttrawling (from 50 to 95% of unimpacted biomass) ranged between 1.9 and 6.4 y. By accounting for the effects of penetration depth, environmental variation, and uncertainty, the models explained much of the variability of depletion and recovery estimates from single studies. Coupled with large-scale, high-resolution maps of trawling frequency and habitat, our estimates of depletion and recovery rates enable the assessment of trawling impacts on unprecedented spatial scales.

Global analysis of depletion and recovery of seabed biota after bottom trawling disturbance

PubMed Central

Hiddink, Jan Geert; Jennings, Simon; Sciberras, Marija; Szostek, Claire L.; Hughes, Kathryn M.; Ellis, Nick; Rijnsdorp, Adriaan D.; McConnaughey, Robert A.; Mazor, Tessa; Hilborn, Ray; Collie, Jeremy S.; Pitcher, C. Roland; Amoroso, Ricardo O.; Parma, Ana M.; Suuronen, Petri; Kaiser, Michel J.

2017-01-01

Bottom trawling is the most widespread human activity affecting seabed habitats. Here, we collate all available data for experimental and comparative studies of trawling impacts on whole communities of seabed macroinvertebrates on sedimentary habitats and develop widely applicable methods to estimate depletion and recovery rates of biota after trawling. Depletion of biota and trawl penetration into the seabed are highly correlated. Otter trawls caused the least depletion, removing 6% of biota per pass and penetrating the seabed on average down to 2.4 cm, whereas hydraulic dredges caused the most depletion, removing 41% of biota and penetrating the seabed on average 16.1 cm. Median recovery times posttrawling (from 50 to 95% of unimpacted biomass) ranged between 1.9 and 6.4 y. By accounting for the effects of penetration depth, environmental variation, and uncertainty, the models explained much of the variability of depletion and recovery estimates from single studies. Coupled with large-scale, high-resolution maps of trawling frequency and habitat, our estimates of depletion and recovery rates enable the assessment of trawling impacts on unprecedented spatial scales. PMID:28716926

Trophic Interactions and Distribution of Some Squaliforme Sharks, Including New Diet Descriptions for Deania calcea and Squalus acanthias

PubMed Central

Dunn, Matthew R.; Stevens, Darren W.; Forman, Jeffrey S.; Connell, Amelia

2013-01-01

Squaliforme sharks are a common but relatively vulnerable bycatch in many deep water fisheries. Eleven species of squaliforme shark are commonly caught at depths of 200–1200 m on Chatham Rise, New Zealand, and their diversity suggests they might occupy different niches. The diets of 133 Deania calcea and 295 Squalus acanthias were determined from examination of stomach contents. The diet of D. calcea was characterised by mesopelagic fishes, and S. acanthias by benthic to pelagic fishes, but was more adaptive and included likely scavenging. Multivariate analyses found the most important predictors of diet variability in S. acanthias were year, bottom temperature, longitude, and fish weight. The diet of the nine other commonly caught squaliforme sharks was reviewed, and the spatial and depth distribution of all species on Chatham Rise described from research bottom trawl survey catches. The eleven species had a variety of different diets, and depth and location preferences, consistent with niche separation to reduce interspecific competition. Four trophic groups were identified, characterised by: mesopelagic fishes and invertebrates (Centroselachus crepidater, D. calcea, and Etmopterus lucifer); mesopelagic and benthopelagic fishes and invertebrates (Centroscymnus owstoni, Etmopterus baxteri); demersal and benthic fishes (Centrophorus squamosus, Dalatias licha, Proscymnodon plunketi); and a generalist diet of fishes and invertebrates (S. acanthias). The trophic levels of the species in each of the four groups were estimated as 4.18–4.24, 4.20–4.23, 4.24–4.48, and 3.84 respectively. The diet of Oxynotus bruniensis and Squalus griffini are unknown. The different niches occupied by different species are likely to influence their vulnerability to bottom trawl fisheries. Some species may benefit from fisheries through an increased availability of scavenged prey. PMID:23536896

Trophic interactions and distribution of some Squaliforme sharks, including new diet descriptions for Deania calcea and Squalus acanthias.

PubMed

Dunn, Matthew R; Stevens, Darren W; Forman, Jeffrey S; Connell, Amelia

2013-01-01

Squaliforme sharks are a common but relatively vulnerable bycatch in many deep water fisheries. Eleven species of squaliforme shark are commonly caught at depths of 200-1200 m on Chatham Rise, New Zealand, and their diversity suggests they might occupy different niches. The diets of 133 Deania calcea and 295 Squalus acanthias were determined from examination of stomach contents. The diet of D. calcea was characterised by mesopelagic fishes, and S. acanthias by benthic to pelagic fishes, but was more adaptive and included likely scavenging. Multivariate analyses found the most important predictors of diet variability in S. acanthias were year, bottom temperature, longitude, and fish weight. The diet of the nine other commonly caught squaliforme sharks was reviewed, and the spatial and depth distribution of all species on Chatham Rise described from research bottom trawl survey catches. The eleven species had a variety of different diets, and depth and location preferences, consistent with niche separation to reduce interspecific competition. Four trophic groups were identified, characterised by: mesopelagic fishes and invertebrates (Centroselachus crepidater, D. calcea, and Etmopterus lucifer); mesopelagic and benthopelagic fishes and invertebrates (Centroscymnus owstoni, Etmopterus baxteri); demersal and benthic fishes (Centrophorus squamosus, Dalatias licha, Proscymnodon plunketi); and a generalist diet of fishes and invertebrates (S. acanthias). The trophic levels of the species in each of the four groups were estimated as 4.18-4.24, 4.20-4.23, 4.24-4.48, and 3.84 respectively. The diet of Oxynotus bruniensis and Squalus griffini are unknown. The different niches occupied by different species are likely to influence their vulnerability to bottom trawl fisheries. Some species may benefit from fisheries through an increased availability of scavenged prey.

Bottom trawling and oxygen minimum zone influences on continental slope benthic community structure off Vancouver Island (NE Pacific)

NASA Astrophysics Data System (ADS)

De Leo, Fabio C.; Gauthier, Maéva; Nephin, Jessica; Mihály, Steven; Juniper, S. Kim

2017-03-01

Understanding responses of benthic ecosystems to cumulative impacts of natural stressors, long-term ocean change and increasing resource exploitation is an emerging area of interest for marine ecologists and environmental managers. Few, if any, studies have quantitatively addressed cumulative effects in the deep sea. We report here on a study from the continental slope off Vancouver Island (Canada) in the northeast Pacific Ocean, where the Oxygen Minimum Zone impinges on seabed habitats that are subjected to widespread bottom trawling, primarily by the fishery for thornyhead (Sebastolobus ssp.). We examined how the benthic megafauna in this area was influenced by varying levels of dissolved oxygen and trawling activity, along a depth gradient that was also likely to shape community composition. Continuous video and sonar records from two ROV surveys (50 linear km total; depth range 300-1400 m) respectively provided data on faunal attributes (composition, abundance and diversity) and the frequency of trawl door marks on the seabed. Faunal and trawl data were compiled in a geo-referenced database along with corresponding dissolved oxygen data, and pooled into 500 m segments for statistical analysis. Trawl mark occurrence peaked between 500 and 1100 m, corresponding to areas of slope subjected to hypoxia (<1.4 ml l-1) and severe hypoxia (<0.5 ml l-1). A combined total of 266,251 megafauna organisms from 87 taxa were enumerated in the two transects. Significant megafaunal assemblages according to depth, trawling intensity and bottom water dissolved oxygen concentration were identified by PERMANOVA analyses, with characterizing taxa identified for all three factors. Depth, dissolved oxygen and trawl mark density accounted for 21% to 52% of the variability in benthic community structure according to multiple regression (DISTLM) models. Species richness was highest at intermediate depths and in areas subject to intermediate levels of trawling, and higher under hypoxia than under severe hypoxia. These statistically significant trends demonstrate that the structuring influences of bottom trawling on deep-sea benthic communities can be observed even where communities are being shaped by strong environmental gradients.

Avoidance of fisheries-induced evolution: management implications for catch selectivity and limit reference points.

PubMed

Hutchings, Jeffrey A

2009-08-01

I examined how the fitness (r) associated with early- and late-maturing genotypes varies with fishing mortality (F) and age-/size-specific probability of capture. Life-history data on Newfoundland's northern Atlantic cod (Gadus morhua) allowed for the estimation of r for individuals maturing at 4 and 7 year in the absence of fishing. Catch selectivity data associated with four types of fishing gear (trap, gillnet, handline, otter trawl) were then incorporated to examine how r varied with gear type and with F. The resulting fitness functions were then used to estimate the F above which selection would favour early (4 year) rather than delayed (7 year) maturity. This evolutionarily-sensitive threshold, F evol, identifies a limit reference point somewhat similar to those used to define overfishing (e.g., F msy, F 0.1). Over-exploitation of northern cod resulted in fishing mortalities considerably greater than those required to effect evolutionary change. Selection for early maturity is reduced by the dome-shaped selectivities characteristic of fixed gears such as handlines (the greater the leptokurtosis, the lower the probability of a selection response) and enhanced by the knife-edged selectivities of bottom trawls. Strategies to minimize genetic change are consistent with traditional management objectives (e.g., yield maximization, population increase). Compliance with harvest control rules guided by evolutionarily-sensitive limit reference points, which may be achieved by adherence to traditional reference points such as F msy and F 0.1, should be sufficient to minimize the probability of fisheries-induced evolution for commercially exploited species.

Seasonal dynamics of particulate organic matter in the Changjiang Estuary and adjacent coastal waters illustrated by amino acid enantiomers

NASA Astrophysics Data System (ADS)

Wu, Ying; Liu, Zongguang; Hu, Jun; Zhu, Zhuoyi; Liu, Sumei; Zhang, Jing

2016-02-01

Total suspended matter (TSM) was collected in the Changjiang Estuary and adjacent areas of the East China Sea in July, August, and November 2011, to study the composition and fate of particulate organic nitrogen (PON) during an August typhoon event and bottom trawling activities. Concentrations of particulate organic carbon (POC), particulate nitrogen (PN), and hydrolyzable particulate amino acids (PAA, D- and L-enantiomers) were higher during July and August than during November; however, D-arginine and alanine levels were significantly higher in November. Seasonal trends in the composition of PAAs indicate that in situ production is a key factor in their temporal distribution. No significant increase in TSM or decrease in labile organic matter was observed during the transit period following a typhoon event in August. In contrast, higher primary production was observed at this time as a result of the penetration of Changjiang Diluted Water caused by the typhoon event. Trawling effects were studied by comparing the calm season (July) with the bottom-trawling period (November) at similar sampling sites. The effect of trawling on the composition of bottom organic matter was studied by comparing D-amino acids concentrations and C/N ratios in the calm season (July) with the bottom-trawling period (November). A substantial contribution of microbial organic matter during the November cruise was indicated by a decrease in glutamic acid, an increase in TSM and D-alanine, and a lower carbon/nitrogen (C/N) ratio. In shallow coastal regions, anthropogenic activities (bottom trawling) may enhance the transfer of low-nutritional-value particulate organic matter into the benthic food chain.

Impact of bottom trawling on deep-sea sediment properties along the flanks of a submarine canyon.

PubMed

Martín, Jacobo; Puig, Pere; Masqué, Pere; Palanques, Albert; Sánchez-Gómez, Anabel

2014-01-01

The offshore displacement of commercial bottom trawling has raised concerns about the impact of this destructive fishing practice on the deep seafloor, which is in general characterized by lower resilience than shallow water regions. This study focuses on the flanks of La Fonera (or Palamós) submarine canyon in the Northwestern Mediterranean, where an intensive bottom trawl fishery has been active during several decades in the 400-800 m depth range. To explore the degree of alteration of surface sediments (0-50 cm depth) caused by this industrial activity, fishing grounds and control (untrawled) sites were sampled along the canyon flanks with an interface multicorer. Sediment cores were analyzed to obtain vertical profiles of sediment grain-size, dry bulk density, organic carbon content and concentration of the radionuclide 210Pb. At control sites, surface sediments presented sedimentological characteristics typical of slope depositional systems, including a topmost unit of unconsolidated and bioturbated material overlying sediments progressively compacted with depth, with consistently high 210Pb inventories and exponential decaying profiles of 210Pb concentrations. Sediment accumulation rates at these untrawled sites ranged from 0.3 to 1.0 cm y-1. Sediment properties at most trawled sites departed from control sites and the sampled cores were characterized by denser sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sediments caused by trawling gears. Other alterations of the physical sediment properties, including thorough mixing or grain-size sorting, as well as organic carbon impoverishment, were also visible at trawled sites. This work contributes to the growing realization of the capacity of bottom trawling to alter the physical properties of surface sediments and affect the seafloor integrity over large spatial scales of the deep-sea.

Impact of Bottom Trawling on Deep-Sea Sediment Properties along the Flanks of a Submarine Canyon

PubMed Central

Martín, Jacobo; Puig, Pere; Masqué, Pere; Palanques, Albert; Sánchez-Gómez, Anabel

2014-01-01

The offshore displacement of commercial bottom trawling has raised concerns about the impact of this destructive fishing practice on the deep seafloor, which is in general characterized by lower resilience than shallow water regions. This study focuses on the flanks of La Fonera (or Palamós) submarine canyon in the Northwestern Mediterranean, where an intensive bottom trawl fishery has been active during several decades in the 400–800 m depth range. To explore the degree of alteration of surface sediments (0–50 cm depth) caused by this industrial activity, fishing grounds and control (untrawled) sites were sampled along the canyon flanks with an interface multicorer. Sediment cores were analyzed to obtain vertical profiles of sediment grain-size, dry bulk density, organic carbon content and concentration of the radionuclide 210Pb. At control sites, surface sediments presented sedimentological characteristics typical of slope depositional systems, including a topmost unit of unconsolidated and bioturbated material overlying sediments progressively compacted with depth, with consistently high 210Pb inventories and exponential decaying profiles of 210Pb concentrations. Sediment accumulation rates at these untrawled sites ranged from 0.3 to 1.0 cm y−1. Sediment properties at most trawled sites departed from control sites and the sampled cores were characterized by denser sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sediments caused by trawling gears. Other alterations of the physical sediment properties, including thorough mixing or grain-size sorting, as well as organic carbon impoverishment, were also visible at trawled sites. This work contributes to the growing realization of the capacity of bottom trawling to alter the physical properties of surface sediments and affect the seafloor integrity over large spatial scales of the deep-sea. PMID:25111298

Goldeye, Hiodon alosoides, in Lake Oahe: abundance, age, growth, maturity, food, and the fishery, 1963-69

USGS Publications Warehouse

Miller, Grant L.; Nelson, William R.

1974-01-01

Reproductive success was relatively consistent, and adequate to maintain species abundance at a nearly constant level, during 1963-69. Both abundance and growth in length increased from the lower to the upper portion of the reservoir. In most characteristics -- growth in length, length-weight relation, age at maturity, and food -- goldeye in Lake Oahe were similar to those from other Missouri River impoundments. Experimental gill nets samples all lengths (range 80-460 mm; median, 320 mm) of goldeye, bottom trawls sampled mostly small fish, (median, 215 mm) and trap nets large ones (median, 345 mm). Commercial gill nets were highly size selective (median, 375 mm); fish of ages IV-VII made up 90% of the catch. Survival rates were 57 to 52% for ages II-X. Estimated survival rates for ages V-IX declined from 44 to 35% after the inception of the commercial fishery in 1966. The peak commercial catch was 151,432 kg (1.2 kg/hectare) in 1969. Unless recruitment declines, the population can support a fishery of that magnitude.

Vertical distribution of fish biomass in Lake Superior: Implications for day bottom trawl surveys

USGS Publications Warehouse

Stockwell, J.D.; Yule, D.L.; Hrabik, T.R.; Adams, J.V.; Gorman, O.T.; Holbrook, B.V.

2007-01-01

Evaluation of the biases in sampling methodology is essential for understanding the limitations of abundance and biomass estimates of fish populations. Estimates from surveys that rely solely on bottom trawls may be particularly vulnerable to bias if pelagic fish are numerous. We evaluated the variability in the vertical distribution of fish biomass during the U.S. Geological Survey's annual spring bottom trawl survey of Lake Superior using concurrent hydroacoustic observations to (1) test the assumption that fish are generally demersal during the day and (2) evaluate the potential for predictive models to improve bottom trawl–determined biomass estimates. Our results indicate that the assumption that fish exhibit demersal behavior during the annual spring bottom trawl survey in Lake Superior is unfounded. Bottom trawl biomass (BBT) estimates (mean ± SE) for species known to exhibit pelagic behavior (cisco Coregonus artedi, bloater C. hoyi, kiyi C. kiyi, and rainbow smelt Osmerus mordax; 3.01 ± 0.73 kg/ha) were not significantly greater than mean acoustic pelagic zone biomass (BAPZ) estimates (6.39 ± 2.03 kg/ha). Mean BAPZ estimates were 1.6- to 4.8-fold greater than mean BBT estimates over 4 years of sampling. The relationship between concurrent BAPZ and BBT estimates was marginally significant and highly variable. Predicted BAPZ estimates using cross-validation models were sensitive to adjustments for back-transforming from the logarithmic to the linear scale and poorly corresponded to observed BAPZ estimates. We conclude that statistical models to predict BAPZ from day BBT cannot be developed. We propose that night sampling with multiple gears will be necessary to generate better biomass estimates for management needs.

Seafloor habitat mapping of the New York Bight incorporating sidescan sonar data

USGS Publications Warehouse

Lathrop, R.G.; Cole, M.; Senyk, N.; Butman, B.

2006-01-01

The efficacy of using sidescan sonar imagery, image classification algorithms and geographic information system (GIS) techniques to characterize the seafloor bottom of the New York Bight were assessed. The resulting seafloor bottom type map was compared with fish trawl survey data to determine whether there were any discernable habitat associations. An unsupervised classification with 20 spectral classes was produced using the sidescan sonar imagery, bathymetry and secondarily derived spatial heterogeneity to characterize homogenous regions within the study area. The spectral classes, geologic interpretations of the study region, bathymetry and a bottom landform index were used to produce a seafloor bottom type map of 9 different bottom types. Examination of sediment sample data by bottom type indicated that each bottom type class had a distinct composition of sediments. Analysis of adult summer flounder, Paralichthys dentatus, and adult silver hake, Merluccius bilinearis, presence/absence data from trawl surveys did not show evidence of strong associations between the species distributions and seafloor bottom type. However, the absence of strong habitat associations may be more attributable to the coarse scale and geographic uncertainty of the trawl sampling data than conclusive evidence that no habitat associations exist for these two species. ?? 2006 Elsevier Ltd. All rights reserved.

Influence of bottom trawling on sediment resuspension in the `Grande-Vasière' area (Bay of Biscay, France)

NASA Astrophysics Data System (ADS)

Mengual, Baptiste; Cayocca, Florence; Le Hir, Pierre; Draye, Robin; Laffargue, Pascal; Vincent, Benoit; Garlan, Thierry

2016-09-01

Sea trials were performed on two zones with different fishing efforts on the continental shelf of the Bay of Biscay (`Grande-Vasière' area of muddy sand) in order to assess particulate matter resuspension and seabed disturbances (i.e., penetration, reworking, grain size changes) induced by different types of trawls. Optical and acoustic measurements made in the water column indicate a significant trawling-induced resuspension mainly due to the scraping action of doors. It manifests as a highly dynamic turbid plume confined near the seabed, where suspended sediment concentrations can reach 200 mg l-1. Concentration levels measured behind an "alternative" configuration (trawls with jumper doors instead of classical doors penetrating the sediment) are significantly lower (around 10-20 mg l-1), which indicates a potential limiting impact regarding the seabed. Grain size analyses of the surficial sediment led to highlight a potential reworking influence of bottom trawling. On the intensively trawled zone, this reworking manifests as an upward coarsening trend in the first 5 cm of the cores. A significant decrease in mud content (30 %) has been also witnessed on this zone between 1967 and 2014, which suggests an influence on the seabed evolution. The geometric analysis of bottom tracks (4-5-cm depth, 20-cm width) observed with a benthic video sledge was used to compute an experimental trawling-induced erosion rate of 0.13 kg m-2. This erosion rate was combined with fishing effort data, in order to estimate trawling-induced erosion fluxes which were then compared to natural erosion fluxes over the Grande-Vasière at monthly, seasonal and annual scales. Winter storms control the annual resuspended load and trawling contribution to annual resuspension is in the order of 1 %. However, results show that trawling resuspension can become dominant during the fishing high season (i.e., until several times the natural one in summer). In addition, the contribution of trawling-induced resuspension is shown to increase with water depth, because of the rapid decay of wave effects. Finally, the seasonal evolution of the respective contributions for erosion (mainly trawling and waves) could be mapped for the whole study area.

Continental shelf sediment dynamics in the Anthropocene: A global shift

NASA Astrophysics Data System (ADS)

Oberle, Ferdinand K. J.; Puig, Pere; Martin, Jacobo

2017-04-01

Recent technological advances in remote sensing and deep marine sampling have revealed the extent and magnitude of the anthropogenic impacts to the seafloor. In particular, bottom trawling, a fishing technique consisting of dragging a net and fishing gear over the seafloor to capture bottom-dwelling living resources has gained attention due to its destructive effects on the seabed. Trawling gear produces acute impacts on biota and the physical substratum of the seafloor by disrupting the sediment column structure, overturning boulders, resuspending sediments and imprinting deep scars on muddy bottoms. Also, the repetitive passage of trawling gear over the same areas creates long-lasting, cumulative impacts that modify the cohesiveness and texture of sediments. It can be asserted nowadays that due to its recurrence, mobility and wide geographical extent, industrial trawling has become a major force driving seafloor change and affecting not only its physical integrity on short spatial scales but also imprinting measurable modifications to the geomorphology of entire continental margins.

Response of soft-bottom macrobenthic assemblages to artisanal trawling fisheries in a subtropical estuary

NASA Astrophysics Data System (ADS)

Ortega, Ileana; Colling, Leonir André; Dumont, Luiz Felipe Cestari

2018-07-01

Bottom trawling is one of the most harmful and widespread activities affecting benthic habitats and fauna. In this study, we analyzed the impact of shrimp trawling fisheries on the densities, assemblage structure and vertical stratification of the benthic macrofauna in shallow mudflats of the Patos Lagoon Estuary (Brazil). Experimental trawls of different intensities were performed during three shrimp fishing seasons (2015-2017), comparing macrofauna among before and after trawling, and a control zone. The changes in macrofaunal assemblages were more consistently related to natural variability than to trawling impact, being mostly influenced by sediment structure and salinity variation. The trawling impact was mainly detected in the area with higher percentages of fine sediments, with different macrofaunal responses in each month and stratum. Some non-significant decreases on total densities after trawling were observed, mainly on the superficial stratum, and signs of burial activities. The response to trawling disturbance of each species was different and it highly depended on their natural variability. Only five species showed significant variation to the trawling treatment (Erodona mactroides, Heleobia australis, H. charruana, Heteromastus similis and Laeonereis acuta), with temporally different responses. Decreasing densities were more related to the high impact treatment. In some seasons, decreases on the abundance of Monokalliapseudes schubarti after high impact trawls were up to 60% of the seasonal mean densities. Trawling fisheries may reduce macrobenthic densities but not their vertical stratification. The impact of trawling on key species may compromise the ecosystem function, as benthic macrofauna provide food sources for many aquatic resources. This study highlights trawling impacts in an estuarine nursery area, which should be fully considered since they may be reflected in the trophic webs.

Can pelagic forage fish and spawning cisco (Coregonus artedi) biomass in the western arm of Lake Superior be assessed with a single summer survey?

USGS Publications Warehouse

Yule, D.L.; Stockwell, J.D.; Schreiner, D.R.; Evrard, L.M.; Balge, M.; Hrabik, T.R.

2009-01-01

Management efforts to rehabilitate lake trout Salvelinus namaycush in Lake Superior have been successful and the recent increase in their numbers has led to interest in measuring biomass of pelagic prey fish species important to these predators. Lake Superior cisco Coregonus artedi currently support roe fisheries and determining the sustainability of these fisheries is an important management issue. We conducted acoustic and midwater trawl surveys of the western arm of Lake Superior during three periods: summer (July-August), October, and November 2006 to determine if a single survey can be timed to estimate biomass of both prey fish and spawning cisco. We evaluated our methods by comparing observed trawl catches of small (<250 mm total length) and large fish to expected trawl catches based on acoustic densities in the trawl path. We found the relationship between observed and expected catches approached unity over a wide range of densities, suggesting that our acoustic method provided reasonable estimates of fish density, and that midwater trawling methods were free of species- and size-selectivity issues. Rainbow smelt Osmerus mordax was by number the most common species captured in the nearshore (<80 m bathymetric depth) stratum during all three surveys, while kiyi Coregonus kiyi was predominant offshore except during November. Total biomass estimates of rainbow smelt in the western arm were similar during all three surveys, while total biomass of kiyi was similar between summer and October, but was lower in November. Total biomass of large cisco increased substantially in November, while small bloater Coregonus hoyi biomass was lower. We compared our summer 2006 estimates of total fish biomass to the results of a summer survey in 1997 and obtained similar results. We conclude that the temporal window for obtaining biomass estimates of pelagic prey species in the western arm of Lake Superior is wide (July through October), but estimating spawning cisco abundance is best done with a November survey.

Modeling the Distribution of Geodia Sponges and Sponge Grounds in the Northwest Atlantic

PubMed Central

Knudby, Anders; Kenchington, Ellen; Murillo, Francisco Javier

2013-01-01

Deep-sea sponge grounds provide structurally complex habitat for fish and invertebrates and enhance local biodiversity. They are also vulnerable to bottom-contact fisheries and prime candidates for Vulnerable Marine Ecosystem designation and related conservation action. This study uses species distribution modeling, based on presence and absence observations of Geodia spp. and sponge grounds derived from research trawl catches, as well as spatially continuous data on the physical and biological ocean environment derived from satellite data and oceanographic models, to model the distribution of Geodia sponges and sponge grounds in the Northwest Atlantic. Most models produce excellent fits with validation data although fits are reduced when models are extrapolated to new areas, especially when oceanographic regimes differ between areas. Depth and minimum bottom salinity were important predictors in most models, and a Geodia spp. minimum bottom salinity tolerance threshold in the 34.3-34.8 psu range was hypothesized on the basis of model structure. The models indicated two currently unsampled regions within the study area, the deeper parts of Baffin Bay and the Newfoundland and Labrador slopes, where future sponge grounds are most likely to be found. PMID:24324768

50 CFR 660.116 - Trawl fishery-observer requirements.

Code of Federal Regulations, 2010 CFR

2010-10-01

...-sea processing vessels. The observer sampling station must include a table at least 0.6 m deep, 1.2 m... at sea must carry one NMFS-certified observer, from the time the vessel leaves port on a trip in which the catch is sorted at sea to the time that all catch from that trip has been offloaded. (2...

77 FR 48915 - Fisheries of the Northeastern United States; Northeast Multispecies Fishery; White Hake Trimester...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-15

... Fishery; White Hake Trimester Total Allowable Catch Area Closure for the Common Pool Fishery AGENCY... (TAC) Area to all common pool vessels fishing with trawl gear, sink gillnet gear, or longline/hook gear... common pool fishery from exceeding its Trimester 1 TAC or its annual catch limit for white hake. This...

Chronic and intensive bottom trawling impairs deep-sea biodiversity and ecosystem functioning

PubMed Central

Pusceddu, Antonio; Bianchelli, Silvia; Martín, Jacobo; Puig, Pere; Palanques, Albert; Masqué, Pere; Danovaro, Roberto

2014-01-01

Bottom trawling has many impacts on marine ecosystems, including seafood stock impoverishment, benthos mortality, and sediment resuspension. Historical records of this fishing practice date back to the mid-1300s. Trawling became a widespread practice in the late 19th century, and it is now progressively expanding to greater depths, with the concerns about its sustainability that emerged during the first half of the 20th century now increasing. We show here that compared with untrawled areas, chronically trawled sediments along the continental slope of the north-western Mediterranean Sea are characterized by significant decreases in organic matter content (up to 52%), slower organic carbon turnover (ca. 37%), and reduced meiofauna abundance (80%), biodiversity (50%), and nematode species richness (25%). We estimate that the organic carbon removed daily by trawling in the region under scrutiny represents as much as 60–100% of the input flux. We anticipate that such an impact is causing the degradation of deep-sea sedimentary habitats and an infaunal depauperation. With deep-sea trawling currently conducted along most continental margins, we conclude that trawling represents a major threat to the deep seafloor ecosystem at the global scale. PMID:24843122

Community stability within the St. Marys River fish community: Evidence from trawl surveys

USGS Publications Warehouse

Schaeffer, Jeffrey S.; Bowen, Anjanette K.; Fielder, David G.

2017-01-01

A trawl survey was conducted in the Saint Marys River during 2010–2011 and we compared our results to a prior trawl survey conducted during 1979–1983 to look for long-term changes in the fish community, especially in terms of changes induced by invasive species. We found no substantive temporal differences in fish density, fish biomass, or fish diversity; lower trawl biomass during 2010–2011 was likely a result of day versus night trawling. The Saint Marys River remains a center of high fish diversity, invasive species remain rare, and the system continues to exhibit overall long-term stability. Trawling captured a wide range of fish species, but was likely not an effective stock assessment tool for managed game fish because catch rates were low or variable for all game species except yellow perch. Trawling appeared to be an effective tool for sampling connecting channel diversity, especially when large numbers of individuals are needed for directed studies, but annual sampling would be needed to use data to assess recruitment.

Deep-water longline fishing has reduced impact on Vulnerable Marine Ecosystems

PubMed Central

Pham, Christopher K.; Diogo, Hugo; Menezes, Gui; Porteiro, Filipe; Braga-Henriques, Andreia; Vandeperre, Frederic; Morato, Telmo

2014-01-01

Bottom trawl fishing threatens deep-sea ecosystems, modifying the seafloor morphology and its physical properties, with dramatic consequences on benthic communities. Therefore, the future of deep-sea fishing relies on alternative techniques that maintain the health of deep-sea ecosystems and tolerate appropriate human uses of the marine environment. In this study, we demonstrate that deep-sea bottom longline fishing has little impact on vulnerable marine ecosystems, reducing bycatch of cold-water corals and limiting additional damage to benthic communities. We found that slow-growing vulnerable species are still common in areas subject to more than 20 years of longlining activity and estimate that one deep-sea bottom trawl will have a similar impact to 296–1,719 longlines, depending on the morphological complexity of the impacted species. Given the pronounced differences in the magnitude of disturbances coupled with its selectivity and low fuel consumption, we suggest that regulated deep-sea longlining can be an alternative to deep-sea bottom trawling. PMID:24776718

50 CFR Table 2a to Part 660... - 2012, and beyond, Specifications of OFL, ABC, ACL, ACT and Fishery Harvest guidelines (weights in...

Code of Federal Regulations, 2011 CFR

2011-10-01

... ACL of ACT any allocation for the Pacific Coast treaty Indian Tribes, projected research catch... fishery (16 mt) and research catch (5 mt), resulting in a fishery HG of 1,880 mt. c/ Lingcod south... swept area biomass (2003-2008) from the NMFS NWFSC trawl survey, between the northern and southern areas...

Modelling potential impacts of bottom trawl fisheries on soft sediment biogeochemistry in the North Sea†

PubMed Central

Duplisea, Daniel E; Jennings, Simon; Malcolm, Stephen J; Parker, Ruth; Sivyer, David B

2001-01-01

Bottom trawling causes physical disturbance to sediments particularly in shelf areas. The disturbance due to trawling is most significant in deeper areas with softer sediments where levels of natural disturbance due to wave and tidal action are low. In heavily fished areas, trawls may impact the same area of seabed more than four times per year. A single pass of a beam trawl, the heaviest gear routinely used in shelf sea fisheries, can kill 5–65% of the resident fauna and mix the top few cm of sediment. We expect that sediment community function, carbon mineralisation and biogeochemical fluxes will be strongly affected by trawling activity because the physical effects of trawling are equivalent to those of an extreme bioturbator, and yet, unlike bioturbating macrofauna, trawling does not directly contribute to community metabolism. We used an existing box-model of a generalised soft sediment system to examine the effects of trawling disturbance on carbon mineralisation and chemical concentrations. We contrasted the effects of a natural scenario, where bioturbation is a function of macrobenthos biomass, with an anthropogenic impact scenario where physical disturbance results from trawling rather than the action of bioturbating macrofauna. Simulation results suggest that the effects of low levels of trawling disturbance will be similar to those of natural bioturbators but that high levels of trawling disturbance prevent the modelled system from reaching equilibrium due to large carbon fluxes between oxic and anoxic carbon compartments. The presence of macrobenthos in the natural disturbance scenario allowed sediment chemical storage and fluxes to reach equilibrium. This is because the macrobenthos are important carbon consumers in the system whose presence reduces the magnitude of available carbon fluxes. In soft sediment systems, where the level physical disturbance due to waves and tides is low, model results suggest that intensive trawling disturbance could cause large fluctuations in benthic chemical fluxes and storage. PMID:16759420

Modelling potential impacts of bottom trawl fisheries on soft sediment biogeochemistry in the North Sea.

PubMed

Duplisea, D E; Jennings, S; Malcolm, S J; Parker, R; Sivyer, D B

2001-12-19

Bottom trawling causes physical disturbance to sediments particularly in shelf areas. The disturbance due to trawling is most significant in deeper areas with softer sediments where levels of natural disturbance due to wave and tidal action are low. In heavily fished areas, trawls may impact the same area of seabed more than four times per year. A single pass of a beam trawl, the heaviest gear routinely used in shelf sea fisheries, can kill 5-65% of the resident fauna and mix the top few cm of sediment. We expect that sediment community function, carbon mineralisation and biogeochemical fluxes will be strongly affected by trawling activity because the physical effects of trawling are equivalent to those of an extreme bioturbator, and yet, unlike bioturbating macrofauna, trawling does not directly contribute to community metabolism. We used an existing box-model of a generalised soft sediment system to examine the effects of trawling disturbance on carbon mineralisation and chemical concentrations. We contrasted the effects of a natural scenario, where bioturbation is a function of macrobenthos biomass, with an anthropogenic impact scenario where physical disturbance results from trawling rather than the action of bioturbating macrofauna. Simulation results suggest that the effects of low levels of trawling disturbance will be similar to those of natural bioturbators but that high levels of trawling disturbance prevent the modelled system from reaching equilibrium due to large carbon fluxes between oxic and anoxic carbon compartments. The presence of macrobenthos in the natural disturbance scenario allowed sediment chemical storage and fluxes to reach equilibrium. This is because the macrobenthos are important carbon consumers in the system whose presence reduces the magnitude of available carbon fluxes. In soft sediment systems, where the level physical disturbance due to waves and tides is low, model results suggest that intensive trawling disturbance could cause large fluctuations in benthic chemical fluxes and storage.

76 FR 14923 - Endangered and Threatened Species; Take of Anadromous Fish

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-18

... (i.e., surface and bottom water temperature, salinity, near bottom dissolved oxygen concentration...-water and bottom trawls) are adequately characterizing schools of hake. The IVC research would take...

How systematic age underestimation can impede understanding of fish population dynamics: Lessons learned from a Lake Superior cisco stock

USGS Publications Warehouse

Yule, D.L.; Stockwell, J.D.; Black, J.A.; Cullis, K.I.; Cholwek, G.A.; Myers, J.T.

2008-01-01

Systematic underestimation of fish age can impede understanding of recruitment variability and adaptive strategies (like longevity) and can bias estimates of survivorship. We suspected that previous estimates of annual survival (S; range = 0.20-0.44) for Lake Superior ciscoes Coregonus artedi developed from scale ages were biased low. To test this hypothesis, we estimated the total instantaneous mortality rate of adult ciscoes from the Thunder Bay, Ontario, stock by use of cohort-based catch curves developed from commercial gill-net catches and otolith-aged fish. Mean S based on otolith ages was greater for adult females (0.80) than for adult males (0.75), but these differences were not significant. Applying the results of a study of agreement between scale and otolith ages, we modeled a scale age for each otolith-aged fish to reconstruct catch curves. Using modeled scale ages, estimates of S (0.42 for females, 0.36 for males) were comparable with those reported in past studies. We conducted a November 2005 acoustic and midwater trawl survey to estimate the abundance of ciscoes when the fish were being harvested for roe. Estimated exploitation rates were 0.085 for females and 0.025 for males, and the instantaneous rates of fishing mortality were 0.089 for females and 0.025 for males. The instantaneous rates of natural mortality were 0.131 and 0.265 for females and males, respectively. Using otolith ages, we found that strong year-classes at large during November 2005 were caught in high numbers as age-1 fish in previous annual bottom trawl surveys, whereas weak or absent year-classes were not. For decades, large-scale fisheries on the Great Lakes were allowed to operate because ciscoes were assumed to be short lived and to have regular recruitment. We postulate that the collapse of these fisheries was linked in part to a misunderstanding of cisco biology driven by scale-ageing error. ?? Copyright by the American Fisheries Society 2008.

Impact of Natural (Storm) and Anthropogenic (Trawl) Resuspension the Sediment Transport on the Gulf of Lion's Shelf (NW Mediterranean)

NASA Astrophysics Data System (ADS)

Ferre, B.; Durrieu de Madron, X.; Estournel, C.; Ulses, C.; Le Corre, G.

2006-12-01

Modern sediment deposits on continental margins form a vast reservoir of particulate matter that is regularly affected by resuspension processes. On shelves with strong fishing activity, resuspension by bottom trawling processes can modify the scale of natural disturbance by waves and currents. Recent field data shows that the impact of bottom trawls on the resuspension of the fine sediments per unit surface is comparable with that of the largest storms. We assessed the impact of both natural and anthropogenic processes on the dispersal of river-borne particles and shelf sediments on the Gulf of Lion's Shelf. Realistic numerical simulations of resuspension and transport forced by currents and waves or by a fleet of bottom trawlers were developed. Simulations were conducted for a 16-month period to characterize the seasonal variability. The sediment dynamics takes into account bed armoring, ripple geometry and the cohesive and non-cohesive characteristics of the sediment. Essential but uncertain parameters (clay content, erosion fluxes and critical shear stress for cohesive sediment) were set with existing data. Resuspension by waves and currents is controlled by the shear stress, whereas resuspension by the bottom trawler fleet is controlled by its density and distribution. Natural resuspension by waves and currents mostly occurs during short winter episodes, and is concentrated on the inner-shelf. Trawling-induced resuspension, in contrast, occurs regularly throughout the year and is concentrated on the outer shelf. The total annual net resuspension by trawls (8×106 T y-1 is four orders of magnitude lower than the resuspension induced by waves and currents (4×1010 T y-1. However, because trawled regions are located on the outer shelf, closer to the continental slope, export of fine sediment resuspended by trawls (0.6×106 T y-1 is only one order of magnitude lower than export associated with natural resuspension (8×106 T y-1. A simulation combining both resuspension processes reveals a decrease of about 10% in resuspension and export rates, compared with the sum of each individual process.

Benthic microbial abundance and activities in an intensively trawled ecosystem (Thermaikos Gulf, Aegean Sea)

NASA Astrophysics Data System (ADS)

Polymenakou, Paraskevi N.; Pusceddu, Antonio; Tselepides, Anastasios; Polychronaki, Thalia; Giannakourou, Antonia; Fiordelmondo, Carla; Hatziyanni, Eleni; Danovaro, Roberto

2005-12-01

Abundance of benthic bacteria, heterotrophic nanoflagellates and ciliates, extracellular enzymatic activities, bacterial C production, C mineralisation and sediment community oxygen consumption rates were measured in the Thermaikos Gulf (Northeastern Mediterranean), before (September 2001), and during intense trawling activities (October 2001 and February 2002). The biochemical composition of sedimentary organic matter has revealed that bottom trawling had an effect on the trophic state of Thermaikos Gulf. Changes on the benthic microbial food web were also recorded, during the three sampling seasons. Even though trawling-induced sediment resuspension did not alter significantly the abundance of the microbial components, with the exception of the most impacted station, it determined changes regarding their relative importance. Thus, the ratios of bacterium to nanoflagellates and ciliate to nanoflagellates abundance increased in the trawled stations, causing a sudden increase in bacterial C production, in comparison to the non-trawled station. Four months later, the effects of trawling on the microbial food web were less evident, masked possibly by the drastic decrease in the water temperature. The results of the present work suggest that bottom trawling induces alteration of the sedimentological variables and can be considered as a factor affecting the function of the microbial food web in marine coastal ecosystems. These alterations cause faster mobilisation of organic C buried in the sediment and increase nutrient concentrations and availability in the system, thus inducing an effect that could lead to coastal eutrophication.

Fishing activities

USGS Publications Warehouse

Oberle, Ferdinand; Puig, Pere; Martin, Jacobo; Micallef, Aaron; Krastel, Sebastian; Savini, Alessandra

2018-01-01

Unlike the major anthropogenic changes that terrestrial and coastal habitats underwent during the last centuries such as deforestation, river engineering, agricultural practices or urbanism, those occurring underwater are veiled from our eyes and have continued nearly unnoticed. Only recent advances in remote sensing and deep marine sampling technologies have revealed the extent and magnitude of the anthropogenic impacts to the seafloor. In particular, bottom trawling, a fishing technique consisting of dragging a net and fishing gear over the seafloor to capture bottom-dwelling living resources has gained attention among the scientific community, policy makers and the general public due to its destructive effects on the seabed. Trawling gear produces acute impacts on biota and the physical substratum of the seafloor by disrupting the sediment column structure, overturning boulders, resuspending sediments and imprinting deep scars on muddy bottoms. Also, the repetitive passage of trawling gear over the same areas creates long-lasting, cumulative impacts that modify the cohesiveness and texture of sediments. It can be asserted nowadays that due to its recurrence, mobility and wide geographical extent, industrial trawling has become a major force driving seafloor change and affecting not only its physical integrity on short spatial scales but also imprinting measurable modifications to the geomorphology of entire continental margins.

Microplastic sampling with the AVANI trawl compared to two neuston trawls in the Bay of Bengal and South Pacific.

PubMed

Eriksen, Marcus; Liboiron, Max; Kiessling, Tim; Charron, Louis; Alling, Abigail; Lebreton, Laurent; Richards, Heather; Roth, Barent; Ory, Nicolas C; Hidalgo-Ruz, Valeria; Meerhoff, Erika; Box, Carolynn; Cummins, Anna; Thiel, Martin

2018-01-01

Many typical neuston trawls can only be used during relatively calm sea states and slow tow speeds. During two expeditions to the Bay of Bengal and the eastern South Pacific we investigated whether the new, high-speed AVANI trawl (All-purpose Velocity Accelerated Net Instrument) collects similar amounts and types of microplastics as two established scientific trawl designs, the manta trawl and the DiSalvo neuston net. Using a 335 μm net, the AVANI trawl can collect microplastics from the sea surface at speeds up to 8 knots as it "skis" across the surface, whereas the manta and DiSalvo neuston trawls must be towed slowly in a less turbulent sea state and often represent shorter tow lengths. Generally, the AVANI trawl collected a greater numerical abundance and weight of plastic particles in most size classes and debris types than the manta trawl and DiSalvo neuston net, likely because these trawls only skim the surface layer while the AVANI trawl, moving vertically in a random fashion, collects a "deeper" sample, capturing the few plastics that float slightly lower in the water column. However, the samples did not differ enough that results were significantly affected, suggesting that studies done with these different trawls are comparable. The advantage of the AVANI trawl over traditional research trawls is that it allows for collection on vessels underway at high speeds and during long transits, allowing for a nearly continuous sampling effort over long distances. As local surface currents make sea surface abundance widely heterogeneous, widely spaced short-tow trawls, such as the manta and DiSalvo trawls, can catch or miss hotspots or meso-scale variability of microplastic accumulations, whereas the AVANI trawl, if utilized for back-to-back tows of intermediate distances (5-10 km), can bridge variable wind conditions and debris concentrations potentially reducing variance and provide a greater resolution of spatial distribution. Copyright © 2017 Elsevier Ltd. All rights reserved.

An intercomparison of the taxonomic and size composition of tropical macrozooplankton and micronekton collected using three sampling gears

NASA Astrophysics Data System (ADS)

Kwong, Lian E.; Pakhomov, Evgeny A.; Suntsov, Andrey V.; Seki, Michael P.; Brodeur, Richard D.; Pakhomova, Larisa G.; Domokos, Réka

2018-05-01

A micronekton intercalibration experiment was conducted off the southwest coast of Oahu Island, Hawaii in October 2004. Day and night samples were collected in the epipelagic and mesopelagic zones using three micronekton sampling gears: the Cobb Trawl, the Isaacs-Kidd Midwater Trawl (IKMT), and the Hokkaido University Frame Trawl (HUFT). Taxonomic composition and contribution by main size groups to total catch varied among gear types. However, the three gears exhibited similar taxonomic composition for macrozooplankton and micronekton ranging from 20 to 100 mm length (MM20-100). The HUFT and IKMT captured more mesozooplankton and small MM20-100, while the Cobb trawl selected towards larger MM20-100 and nekton. Taxonomic composition was described and inter-compared among gears. The relative efficacy of the three gears was assessed, and size dependent intercalibration coefficients were developed for MM20-100.

Relating river discharge and water temperature to the recruitment of age‐0 White Sturgeon (Acipenser transmontanus Richardson, 1836) in the Columbia River using over‐dispersed catch data

USGS Publications Warehouse

Counihan, Timothy D.; Chapman, Colin G.

2018-01-01

The goals were to (i) determine if river discharge and water temperature during various early life history stages were predictors of age‐0 White Sturgeon, Acipenser transmontanus, recruitment, and (ii) provide an example of how over‐dispersed catch data, including data with many zero observations, can be used to better understand the effects of regulated rivers on the productivity of depressed sturgeon populations. An information theoretic approach was used to develop and select negative binomial and zero‐inflated negative binomial models that model the relation of age‐0 White Sturgeon survey data from three contiguous Columbia River reservoirs to river discharge and water temperature during spawning, egg incubation, larval, and post‐larval phases. Age‐0 White Sturgeon were collected with small mesh gill nets in The Dalles and John Day reservoirs from 1997 to 2014 and a bottom trawl in Bonneville Reservoir from 1989 to 2006. Results suggest that seasonal river discharge was positively correlated with age‐0 recruitment; notably that discharge, 16 June–31 July was positively correlated to age‐0 recruitment in all three reservoirs. The best approximating models for two of the three reservoirs also suggest that seasonal water temperature may be a determinant of age‐0 recruitment. Our research demonstrates how over‐dispersed catch data can be used to better understand the effects of environmental conditions on sturgeon populations caused by the construction and operation of dams.

Effects of dreissenids on monitoring and management of fisheries in western Lake Erie

USGS Publications Warehouse

Stapanian, Martin A.; Kocovsky, Patrick M.

2013-01-01

Water clarity increased in nearshore areas of western Lake Erie by the early-1990s mainly as a result of the filtering activities of dreissenid mussels (Dreissena spp.), which invaded in the mid-1980s. We hypothesized that increased water clarity would result in greater trawl avoidance and thus reduced ability to capture fish in bottom trawls during daytime compared to nighttime. We examined this hypothesis by summarizing three analyses on fish data collected in western Lake Erie. First, we used a two-tiered modeling approach on the ration (R) of catch per hour (CPH) of age-0 yellow perch (Perca flavencens Mitchell) at night to CPH during daytime in 1961-2005. The best a priori and a posteriori models indicated a shift to higher CPH at night (R > 1) between 1990 and 1991, which corresponded to 3 years after the dreissenid invasion and when water clarity noticeably increased at nearshore sites. Secondly, we examined effects of nighttime sampling on estimates of abundance of age-2 and older yellow perch, which form the basis for recommended allowable harvest (RAH). When data from night sampling were included in models that predict abundance of age-2 yellow perch from indices of abundance of age-0 and age-1 yellow perch, predicted abundance was lower and model precision, as measured by r-squared, was higher compared to models that excluded data collected at night. Furthermore, the use of only CPH data collected at night typically resulted in lower estimates of abundance and more precise models compared to models that included CPH data collected during both daytime and nighttime. Thirdly, we used presence/absence data from paired bottom trawl samples to calculate an index of capture probability (or catchability) to determine if our ability to capture the four most common benthic species in western Lake Erie was affected by dreissenid-caused increased water clarity. Three species of fish(white perch, Morone americana Gmelin; yellow perch; and trout-perch, Percopsis omiscomaycus Walbaum) had lower mean daytime catchability than nighttime catchability after dreissenids became established, which supported the hypothesis of greater trawl avoidance during daytime following establishment of dreissenids. Results from freshwater drum (Aplodinotus grunniens Rafinesque) were opposite those of the other three species, which may be a result of behavioral shifts due to freshwater drum feeding on dreissenids mussels. Collectively, these three studies suggest that dreissenids indirectly affected our ability to assess fish populations, which further affects estimates of fish densities and relationships between indices of abundance and true abundance.

Impact of natural (waves and currents) and anthropogenic (trawl) resuspension on the export of particulate matter to the open ocean: Application to the Gulf of Lion (NW Mediterranean)

NASA Astrophysics Data System (ADS)

Ferré, B.; Durrieu de Madron, X.; Estournel, C.; Ulses, C.; Le Corre, G.

2008-08-01

Modern sediment deposits on continental margins form a vast reservoir of particulate matter that is regularly affected by resuspension processes. Resuspension by bottom trawling on shelves with strong fishing activity can modify the scale of natural disturbance by waves and currents. Recent field data show that the impact of bottom trawls on fine sediment resuspension per unit surface is comparable with that of the largest storms. We assessed the impact of both natural and anthropogenic processes on the dispersal of riverborne particles and shelf sediments on the Gulf of Lion shelf. We performed realistic numerical simulations of resuspension and transport forced by currents and waves or by a fleet of bottom trawlers. Simulations were conducted for a 16-month period (January 1998-April 1999) to characterise the seasonal variability. The sediment dynamics takes into account bed armoring, ripple geometry and the cohesive and non-cohesive characteristics of the sediments. Essential but uncertain parameters (clay content, erosion fluxes and critical shear stress for cohesive sediment) were set with existing data. Resuspension by waves and currents was controlled by shear stress, whereas resuspension by trawls was controlled by density and distribution of the bottom trawler fleet. Natural resuspension by waves and currents mostly occurred during short seasonal episodes, and was concentrated on the inner shelf. Trawling-induced resuspension, in contrast, occurred regularly throughout the year and was concentrated on the outer shelf. The total annual erosion by trawls (5.6×10 6 t y -1, t for metric tonnes) was four orders of magnitude lower than the erosion induced by waves and currents (35.3×10 9 t y -1). However the net resuspension (erosion/deposition budget) for trawling (0.4×10 6 t y -1) was only one order of magnitude lower than that for waves and currents (9.2×10 6 t y -1). Off-shelf export concerned the finest fraction of the sediment (clays and fine silts) and took place primarily at the southwestern end of the Gulf. Off-shelf transport was favoured during the winter 1999 by a very intense episode of dense shelf water cascading. Export of sediment resuspended by trawls (0.4×10 6 t y -1) was one order of magnitude lower than export associated with natural resuspension (8.5×10 6 t y -1). Trawling-induced resuspension is thought to represent one-third of the total export of suspended sediment from the shelf. A simulation combining both resuspension processes reveals no significant changes in resuspension and export rates compared with the sum of each individual process, suggesting the absence of interference between both processes.

Measurement error associated with surveys of fish abundance in Lake Michigan

USGS Publications Warehouse

Krause, Ann E.; Hayes, Daniel B.; Bence, James R.; Madenjian, Charles P.; Stedman, Ralph M.

2002-01-01

In fisheries, imprecise measurements in catch data from surveys adds uncertainty to the results of fishery stock assessments. The USGS Great Lakes Science Center (GLSC) began to survey the fall fish community of Lake Michigan in 1962 with bottom trawls. The measurement error was evaluated at the level of individual tows for nine fish species collected in this survey by applying a measurement-error regression model to replicated trawl data. It was found that the estimates of measurement-error variance ranged from 0.37 (deepwater sculpin, Myoxocephalus thompsoni) to 1.23 (alewife, Alosa pseudoharengus) on a logarithmic scale corresponding to a coefficient of variation = 66% to 156%. The estimates appeared to increase with the range of temperature occupied by the fish species. This association may be a result of the variability in the fall thermal structure of the lake. The estimates may also be influenced by other factors, such as pelagic behavior and schooling. Measurement error might be reduced by surveying the fish community during other seasons and/or by using additional technologies, such as acoustics. Measurement-error estimates should be considered when interpreting results of assessments that use abundance information from USGS-GLSC surveys of Lake Michigan and could be used if the survey design was altered. This study is the first to report estimates of measurement-error variance associated with this survey.

Evaluating analytical approaches for estimating pelagic fish biomass using simulated fish communities

USGS Publications Warehouse

Yule, Daniel L.; Adams, Jean V.; Warner, David M.; Hrabik, Thomas R.; Kocovsky, Patrick M.; Weidel, Brian C.; Rudstam, Lars G.; Sullivan, Patrick J.

2013-01-01

Pelagic fish assessments often combine large amounts of acoustic-based fish density data and limited midwater trawl information to estimate species-specific biomass density. We compared the accuracy of five apportionment methods for estimating pelagic fish biomass density using simulated communities with known fish numbers that mimic Lakes Superior, Michigan, and Ontario, representing a range of fish community complexities. Across all apportionment methods, the error in the estimated biomass generally declined with increasing effort, but methods that accounted for community composition changes with water column depth performed best. Correlations between trawl catch and the true species composition were highest when more fish were caught, highlighting the benefits of targeted trawling in locations of high fish density. Pelagic fish surveys should incorporate geographic and water column depth stratification in the survey design, use apportionment methods that account for species-specific depth differences, target midwater trawling effort in areas of high fish density, and include at least 15 midwater trawls. With relatively basic biological information, simulations of fish communities and sampling programs can optimize effort allocation and reduce error in biomass estimates.

Deep-sea crustacean trawling fisheries in Portugal: quantification of effort and assessment of landings per unit effort using a Vessel Monitoring System (VMS)

NASA Astrophysics Data System (ADS)

Bueno-Pardo, Juan; Ramalho, Sofia P.; García-Alegre, Ana; Morgado, Mariana; Vieira, Rui P.; Cunha, Marina R.; Queiroga, Henrique

2017-01-01

Mapping and quantifying bottom trawling fishing pressure on the seafloor is pivotal to understand its effects on deep-sea benthic habitats. Using data from the Vessel Monitoring System of crustacean trawlers along the Portuguese margin, we have identified the most exploited areas and characterized the most targeted habitats and water depths. We estimated a total trawling effort of 69596, 66766, and 63427 h y-1 for the years 2012, 2013, and 2014 respectively which, considering the total landings estimated for this gear, yield values of 20.76, 21.06, and 19.11 kg of landed fish per trawled hour. The main trawling pressure is exerted in the South and Southwest Portuguese margins, on muddy and muddy-sand bottoms between 200 and 700 m water depths, while in the North and Central-West coasts a minor effort, at shallower waters and across a wider range of habitats, is also applied. The most landed species are crustaceans such as rose shrimp and Norway lobster, although this varies importantly between the different regions of Portugal, being fish and cephalopods the main captures in the Northern ports. We discuss the consequences of trawling for the impacted communities as well as the characteristics of the commercialization of these captures in Portugal.

Deep-sea crustacean trawling fisheries in Portugal: quantification of effort and assessment of landings per unit effort using a Vessel Monitoring System (VMS)

PubMed Central

Bueno-Pardo, Juan; Ramalho, Sofia P.; García-Alegre, Ana; Morgado, Mariana; Vieira, Rui P.; Cunha, Marina R.; Queiroga, Henrique

2017-01-01

Mapping and quantifying bottom trawling fishing pressure on the seafloor is pivotal to understand its effects on deep-sea benthic habitats. Using data from the Vessel Monitoring System of crustacean trawlers along the Portuguese margin, we have identified the most exploited areas and characterized the most targeted habitats and water depths. We estimated a total trawling effort of 69596, 66766, and 63427 h y−1 for the years 2012, 2013, and 2014 respectively which, considering the total landings estimated for this gear, yield values of 20.76, 21.06, and 19.11 kg of landed fish per trawled hour. The main trawling pressure is exerted in the South and Southwest Portuguese margins, on muddy and muddy-sand bottoms between 200 and 700 m water depths, while in the North and Central-West coasts a minor effort, at shallower waters and across a wider range of habitats, is also applied. The most landed species are crustaceans such as rose shrimp and Norway lobster, although this varies importantly between the different regions of Portugal, being fish and cephalopods the main captures in the Northern ports. We discuss the consequences of trawling for the impacted communities as well as the characteristics of the commercialization of these captures in Portugal. PMID:28098211

Shell-free biomass and population dynamics of dreissenids in offshore Lake Michigan, 2001-2003

USGS Publications Warehouse

French, J. R. P.; Adams, J.V.; Craig, J.; Stickel, R.G.; Nichols, S.J.; Fleischer, G.W.

2007-01-01

The USGS-Great Lakes Science Center has collected dreissenid mussels annually from Lake Michigan since zebra mussels (Dreissena polymorpha) became a significant portion of the bottom-trawl catch in 1999. For this study, we investigated dreissenid distribution, body mass, and recruitment at different depths in Lake Michigan during 2001-2003. The highest densities of dreissenid biomass were observed from depths of 27 to 46 m. The biomass of quagga mussels (Dreissena bugensis) increased exponentially during 2001-2003, while that of zebra mussels did not change significantly. Body mass (standardized for a given shell length) of both species was lowest from depths of 27 to 37m, highest from 55 to 64 m, and declined linearly at deeper depths during 2001-2003. Recruitment in 2003, as characterized by the proportion of mussels < 11 mm in the catch, varied with depth and lake region. For quagga mussels, recruitment declined linearly with depth, and was highest in northern Lake Michigan. For zebra mussels, recruitment generally declined non-linearly with depth, although the pattern was different for north, mid, and southern Lake Michigan. Our analyses suggest that quagga mussels could overtake zebra mussels and become the most abundant mollusk in terms of biomass in Lake Michigan.

50 CFR 660.302 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... change seasonally according to the different conservation needs of the different overfished species... any rollers, bobbins, or other material encircling or tied along the length of the footrope. (C) Small... mesh. (J) Trawl fishing line. A length of chain, rope, or wire rope in the bottom front end of a trawl...

Zooplankton Aggregations Near Sills

DTIC Science & Technology

2002-09-30

trawls is a larger concentration of Bracts (from siphonophores ) at these depths, suggesting that the scattering is due to pneumatophores (gas-filled...floats at the top of the siphonophore colony). This hypothesis will be more carefully examined. However, without net samples capable of catching

Trawling disturbance on the isotopic signature of a structure-building species, the sea urchin Gracilechinus acutus (Lamarck, 1816)

NASA Astrophysics Data System (ADS)

González-Irusta, José M.; Preciado, Izaskun; López-López, Lucia; Punzón, Antonio; Cartes, Joan E.; Serrano, Alberto

2014-08-01

Bottom trawling is one of the main sources of anthropogenic disturbance in benthic habitats with important direct and indirect effects on the ecosystem functional diversity. In this study, the effect of this impact on a structure-building species, the sea urchin Gracilechinus acutus, was studied in the Central Cantabrian Sea (southern Bay of Biscay) comparing its isotopic signature and additional population descriptors across different trawling pressures. Trawling disturbance had a significant effect on the studied descriptors. In trawling areas, this urchin showed significantly lower values of biomass and mean size and significantly higher values of fullness index. Moreover, the trawling disturbance effect was also significant in the isotopic signature of G. acutus. Urchins inhabiting untrawled areas showed significant lower values of δ15N than urchins dwelling areas under trawling pressure. The urchins' isotopic enrichment increased along the species ontogeny regardless of the trawling effort level. Stable isotope analyses are a suitable tool to detect trawling disturbance on the trophic pathways but do not suffice to explain these changes, especially if there is a lack of baseline information.

[Effects of macro-jellyfish abundance dynamics on fishery resource structure in the Yangtze River estuary and its adjacent waters].

PubMed

Shan, Xiu-Juan; Zhuang, Zhi-Meng; Jin, Xian-Shi; Dai, Fang-Qun

2011-12-01

Based on the bottom trawl survey data in May 2007 and May and June 2008, this paper analyzed the effects of the abundance dynamics of macro-jellyfish on the species composition, distribution, and abundance of fishery resource in the Yangtze River estuary and its adjacent waters. From May 2007 to June 2008, the average catch per haul and the top catch per haul of macro-jellyfish increased, up to 222.2 kg x h(-1) and 1800 kg x h(-1) in June 2008, respectively. The macro-jellyfish were mainly distributed in the areas around 50 m isobath, and not beyond 100 m isobath where was the joint front of the coastal waters of East China Sea, Yangtze River runoff, and Taiwan Warm Current. The main distribution area of macro-jellyfish in June migrated northward, as compared with that in May, and the highest catches of macro-jellyfish in May 2007 and May 2008 were found in the same sampling station (122.5 degrees E, 28.5 degrees N). In the sampling stations with higher abundance of macro-jellyfish, the fishery abundance was low, and the fishery species also changed greatly, mainly composed by small-sized species (Trachurus japonicus, Harpadon nehereus, and Acropoma japonicum) and pelagic species (Psenopsis anomala, Octopus variabilis) and Trichiurus japonicus, and P. anomala accounted for 23.7% of the total catch in June 2008. Larimichthys polyactis also occupied higher proportion of the total catch in sampling stations with higher macro-jellyfish abundance, but the demersal species Lophius litulon was not found, and a few crustaceans were collected. This study showed that macro-jellyfish had definite negative effects on the fishery community structure and abundance in the Yangtze River estuary fishery ecosystem, and further, changed the energy flow patterns of the ecosystem through cascading trophic interactions. Therefore, macro-jellyfish was strongly suggested to be an independent ecological group when the corresponding fishery management measures were considered.

A dataset from bottom trawl survey around Taiwan

PubMed Central

Shao, Kwang-Tsao; Lin, Jack; Wu, Chung-Han; Yeh, Hsin-Ming; Cheng, Tun-Yuan

2012-01-01

Abstract Bottom trawl fishery is one of the most important coastal fisheries in Taiwan both in production and economic values. However, its annual production started to decline due to overfishing since the 1980s. Its bycatch problem also damages the fishery resource seriously. Thus, the government banned the bottom fishery within 3 nautical miles along the shoreline in 1989. To evaluate the effectiveness of this policy, a four year survey was conducted from 2000–2003, in the waters around Taiwan and Penghu (Pescadore) Islands, one region each year respectively. All fish specimens collected from trawling were brought back to lab for identification, individual number count and body weight measurement. These raw data have been integrated and established in Taiwan Fish Database (http://fishdb.sinica.edu.tw). They have also been published through TaiBIF (http://taibif.tw), FishBase and GBIF (website see below). This dataset contains 631 fish species and 3,529 records, making it the most complete demersal fish fauna and their temporal and spatial distributional data on the soft marine habitat in Taiwan. PMID:22707908

Distributions of small nongame fishes in the lower Yellowstone River

USGS Publications Warehouse

Duncan, Michael B.; Bramblett, Robert G.; Zale, Alexander V.

2016-01-01

The Yellowstone River is the longest unimpounded river in the conterminous United States. It has a relatively natural flow regime, which helps maintain diverse habitats and fish assemblages uncommon in large rivers elsewhere. The lower Yellowstone River was thought to support a diverse nongame fish assemblage including several species of special concern. However, comprehensive data on the small nongame fish assemblage of the lower Yellowstone River is lacking. Therefore, we sampled the Yellowstone River downstream of its confluence with the Clark’s Fork using fyke nets and otter trawls to assess distributions and abundances of small nongame fishes. We captured 42 species (24 native and 18 nonnative) in the lower Yellowstone River with fyke nets. Native species constituted over 99% of the catch. Emerald shiners Notropis atherinoides, western silvery minnows Hybognathus argyritis, flathead chubs Platygobio gracilis, sand shiners Notropis stramineus, and longnose dace Rhinichthys cataractae composed nearly 94% of fyke net catch and were caught in every segment of the study area. We captured 24 species by otter trawling downstream of the Tongue River. Sturgeon chubs Macrhybopsis gelida, channel catfish Ictalurus punctatus, flathead chubs, stonecats Noturus flavus, and sicklefin chubs Macrhybopsis meeki composed 89% of the otter trawl catch. The upstream distributional limit of sturgeon chubs in the Yellowstone River was the Tongue River; few sicklefin chubs were captured above Intake Diversion Dam. This study not only provides biologists with baseline data for future monitoring efforts on the Yellowstone River but serves as a benchmark for management and conservation efforts in large rivers elsewhere as the Yellowstone River represents one of the best references for a naturally functioning Great Plains river.

Relationship between environment and the occurrence of the deep-water rose shrimp Aristeus antennatus (Risso, 1816) in the Blanes submarine canyon (NW Mediterranean)

NASA Astrophysics Data System (ADS)

Sardà, F.; Company, J. B.; Bahamón, N.; Rotllant, G.; Flexas, M. M.; Sánchez, J. D.; Zúñiga, D.; Coenjaerts, J.; Orellana, D.; Jordà, G.; Puigdefábregas, J.; Sánchez-Vidal, A.; Calafat, A.; Martín, D.; Espino, M.

2009-09-01

We performed a multidisciplinary study characterizing the relationships between hydrodynamic conditions (currents and water masses) and the presence and abundance of the deep-water rose shrimp Aristeus antennatus in a submarine canyon (Blanes canyon in the NW Mediterranean Sea). This species is heavily commercially exploited and is the main target species of a bottom trawl fishery. Seasonal fluctuations in landings are attributed to spatio-temporal movements by this species associated with submarine canyons in the study area. Despite the economic importance of this species and the decreases in catches in the area in recent years, few studies have provided significant insight into the environmental conditions driving shrimp distribution. We therefore measured daily A. antennatus catches over the course of an entire year and analyzed this time series in terms of daily average temperature, salinity, mean kinetic energy (MKE), and eddy kinetic energy (EKE) values using generalized additive models and decision trees. A. antennatus was captured between 600 and 900 m in the Blanes canyon, depths that include Levantine Intermediate Water (LIW) and the underlying Western Mediterranean Deep Water (WMDW). The greatest catches were associated with relatively salty waters (38.5-38.6), low MKE values (6 and 9 cm 2 s -2) and moderate EKE values (10 and 20 cm 2 s -2). Deep-water rose shrimp occurrence appears to be driven in a non-linear manner by environmental conditions including local temperature. A. antennatus appears to prefer relatively salty (LIW) waters and low currents (MKE) with moderate variability (EKE).

Hydrodynamic characteristics of the oval cambered double slotted otter board in bottom trawl fisheries

NASA Astrophysics Data System (ADS)

Liu, J.; Huang, H. L.; Li, L. Z.; Qu, T. C.; Wu, Y.; Chen, S.; Yang, J. L.; Rao, X.

2017-07-01

The otter board is one of the main components of single boat trawl fisheries. An oval cambered double slotted otter board was developed for improving the expansion performance of trawl net in bottom trawl fisheries. A flume model experiment was conducted to measure the lift coefficient (C L), drag coefficient (C D), and lift to drag ratio (K) in different angles of attack (α). The experimental results are as follows : (1) The C L and K value show a trend of increasing at the beginning and then decreasing with the increase of angle of attack, the C D value reflects an upward trend as the angle of attack increases; (2) The D3 otter board (front flow deflector angle at 29°) showed a better hydrodynamic performance. When α=30°, the max lift coefficient (C Lmax) was 1.464, in this case C D = 0.554 and K=2.643. When α=15°, the max lift to drag ratio (K max) was 4.165, C L =0.633, and C D = 0.152. This suggests that the best working scope for the angle of attack is between 15°~30°, in which case, C L>0.633 and K>2.643. The mean value of the lift coefficient was 1.071 and the mean of the lift to drag ratio was 3.482. Comparative analysis of the hydrodynamic performance of different types of otter boards showed that the D3 otter board both had good expansion performance and efficiency, which can provide a reference basis for further optimization of the bottom trawl otter board.

Elasmobranch bycatch in the Italian Adriatic pelagic trawl fishery

PubMed Central

Fortuna, Caterina Maria; Moro, Fabrizio; Sala, Antonello

2018-01-01

Elasmobranchs are among the most threatened long-lived marine species worldwide, and incidental capture is a major source of mortality. The northern central Adriatic Sea, though one of the most overfished basins of the Mediterranean Sea, supports a very valuable marine biodiversity, including elasmobranchs. This study assesses the impact of the northern central Adriatic pelagic trawl fishery on common smooth-hound (Mustelus mustelus), spiny dogfish (Squalus acanthias), common eagle ray (Myliobatis aquila), and pelagic stingray (Pteroplatytrygon violacea) by examining incidental catches recorded between 2006 and 2015. The distribution of bycatch events was evaluated using geo-referenced data. Generalized Linear Models were computed to standardize the catch of the four species and to predict the relative abundance of bycatch events. Data analysis shows that most bycatch events involving all four species occurred in the northern Adriatic Sea. The models predicted significant, distinct temporal patterns of standardized catches in line with previous investigations. Water depth, season, and fishing region were the best predictors to explain bycatch events. The present data suggest that the northern Adriatic may be an important nursery area for several elasmobranchs. They also highlight the urgent need for a better understanding of the interactions between elasmobranchs and fisheries to develop and apply suitable, ad hoc management measures. PMID:29377920

Elasmobranch bycatch in the Italian Adriatic pelagic trawl fishery.

PubMed

Bonanomi, Sara; Pulcinella, Jacopo; Fortuna, Caterina Maria; Moro, Fabrizio; Sala, Antonello

2018-01-01

Elasmobranchs are among the most threatened long-lived marine species worldwide, and incidental capture is a major source of mortality. The northern central Adriatic Sea, though one of the most overfished basins of the Mediterranean Sea, supports a very valuable marine biodiversity, including elasmobranchs. This study assesses the impact of the northern central Adriatic pelagic trawl fishery on common smooth-hound (Mustelus mustelus), spiny dogfish (Squalus acanthias), common eagle ray (Myliobatis aquila), and pelagic stingray (Pteroplatytrygon violacea) by examining incidental catches recorded between 2006 and 2015. The distribution of bycatch events was evaluated using geo-referenced data. Generalized Linear Models were computed to standardize the catch of the four species and to predict the relative abundance of bycatch events. Data analysis shows that most bycatch events involving all four species occurred in the northern Adriatic Sea. The models predicted significant, distinct temporal patterns of standardized catches in line with previous investigations. Water depth, season, and fishing region were the best predictors to explain bycatch events. The present data suggest that the northern Adriatic may be an important nursery area for several elasmobranchs. They also highlight the urgent need for a better understanding of the interactions between elasmobranchs and fisheries to develop and apply suitable, ad hoc management measures.

From Fishing to Fish Processing: Separation of Fish from Crustaceans in the Norway Lobster-Directed Multispecies Trawl Fishery Improves Seafood Quality

PubMed Central

Karlsen, Junita D.; Krag, Ludvig Ahm; Albertsen, Christoffer Moesgaard; Frandsen, Rikke Petri

2015-01-01

Fishing gears have negative impacts on seafood quality, especially on fish in the mixed trawl fishery targeting Norway lobster (Nephrops norvegicus). In this fishery, which is worth about €80 millions in Denmark alone, the quality of fish can be significantly improved by simple gear changes. A trawl codend divided into an upper and lower codend was designed to separate fish from Norway lobster during the fishing process by encourage fish to swim into the upper codend by using a frame at the entrance of the lower codend. Separate codends for fish and Norway lobster in the same gear provide the opportunity to selectively reduce small low-value fish, which will reduce catch weight and sorting time onboard the vessel. For this horizontally divided test codend and a standard codend, in which the catch was mixed, quality assessments were performed on the same batches of fish during three steps of the value chain: i) aboard the fishing vessel; ii) at the Fishermen’s Collection Central, and iii) in the production plant. Four species of fish and fillets from fish caught in the upper codend of the test codend were of significantly better quality for several of the assessed parameters compared with those caught in the standard codend: i) newly caught fish showed significantly less scale loss and discolourations and had significantly better texture; ii) landed fish had significantly better skin appearance and texture and significantly fewer discolourations; and iii) fillets showed significantly fewer blood spots and had significantly better texture. There were no differences in injuries for newly caught fish or gaping and bruises for fillets between the test and standard codends. The decrease in catch-related damages in the test codend is explained by little contact between fish and animals with hard or spiny surfaces due to successful separation of fish and Norway lobster into the upper and lower codends, respectively, and by lower catch weight in the upper codend of the test codend compared with the standard codend. The decrease in damages may also improve quality indirectly by inflicting less stress to the fish and subsequently give better texture, which offers advantages such as pre-rigor filleting and fresher products for the market. Significant improvements in fish quality can potentially increase the catch value in nationally important fisheries. PMID:26569413

Evidence for predatory control of the invasive round goby

USGS Publications Warehouse

Madenjian, C.P.; Stapanian, M.A.; Witzel, L.D.; Einhouse, D.W.; Pothoven, S.A.; Whitford, H.L.

2011-01-01

We coupled bioenergetics modeling with bottom trawl survey results to evaluate the capacity of piscivorous fish in eastern Lake Erie to exert predatory control of the invading population of round goby Neogobius melanostomus. In the offshore (>20 m deep) waters of eastern Lake Erie, burbot Lota lota is a native top predator, feeding on a suite of prey fishes. The round goby invaded eastern Lake Erie during the late 1990s, and round goby population size increased dramatically during 1999–2004. According to annual bottom trawl survey results, round goby abundance in offshore waters peaked in 2004, but then declined during 2004–2008. Coincidentally, round goby became an important component of burbot diet beginning in 2003. Using bottom trawling and gill netting, we estimated adult burbot abundance and age structure in eastern Lake Erie during 2007. Diet composition and energy density of eastern Lake Erie burbot were also determined during 2007. This information, along with estimates of burbot growth, burbot mortality, burbot water temperature regime, and energy densities of prey fish from the literature, were incorporated into a bioenergetics model application to estimate annual consumption of round goby by the adult burbot population. Results indicated that the adult burbot population in eastern Lake Erie annually consumed 1,361 metric tons of round goby. Based on the results of bottom trawling, we estimated the biomass of yearling and older round goby in offshore waters eastern Lake Erie during 2007–2008 to be 2,232 metric tons. Thus, the adult burbot population was feeding on round goby at an annual rate equal to 61% of the estimated round goby standing stock. We concluded that the burbot population had high potential to exert predatory control on round goby in offshore waters of eastern Lake Erie.

Pacific halibut bycatch in Pacific cod fisheries in the Bering Sea: an analysis to evaluate area-time management

NASA Astrophysics Data System (ADS)

Adlerstein, Sara A.; Trumble, Robert J.

1998-03-01

Mortality of discarded Pacific halibut bycatch from Pacific cod fisheries in the Bering Sea leads to significant losses in the halibut setline and in the Pacific cod fisheries. The commercial halibut fishery loses yield because of catch limit reductions to compensate the resource for lost spawning potential and because halibut killed as bycatch will not be available for subsequent harvest, and the cod fisheries may lose harvest if they reach a bycatch mortality limit before reaching allowed catch. In this study, significant differences in Pacific halibut bycatch rates and associated yield losses were found among months and areas of the Bering Sea in the longline and trawl fisheries for Pacific cod in 1990-1992. Bycatch rates were usually highest in late spring and early summer and in areas close to the Unimak Pass. With the exception of 1992, yield loss in the longline fishery was around 1 kg per kg of bycatch mortality, irrespective of where or when bycatch occurred. In the trawl fishery, loss of halibut yield varied from 1 to 4 kg per kg of bycatch mortality. Highest halibut net yield losses per tonne of groundfish harvest usually coincided with highest bycatch rates. When both fisheries operated in one area, trawl bycatch often imposed higher yield losses than longline bycatch, despite lower bycatch rates. Bycatch was affected by the strong 1987 halibut year class. Highest bycatch and yield loss rates occurred in the trawl fishery in 1990 and 1991 when the population was dominated by halibut age-3 and -4, and in the longline fishery in 1992 as fish reached age-5.

Patterns of Dolphin Bycatch in a North-Western Australian Trawl Fishery

PubMed Central

Allen, Simon J.; Tyne, Julian A.; Kobryn, Halina T.; Bejder, Lars; Pollock, Kenneth H.; Loneragan, Neil R.

2014-01-01

The bycatch of small cetaceans in commercial fisheries is a global wildlife management problem. We used data from skippers' logbooks and independent observers to assess common bottlenose dolphin (Tursiops truncatus) bycatch patterns between 2003 and 2009 in the Pilbara Trawl Fishery, Western Australia. Both datasets indicated that dolphins were caught in all fishery areas, across all depths and throughout the year. Over the entire datasets, observer reported bycatch rates (n = 52 dolphins in 4,124 trawls, or 12.6 dolphins/1,000 trawls) were ca. double those reported by skippers (n = 180 dolphins in 27,904 trawls, or 6.5 dolphins/1,000 trawls). Generalised Linear Models based on observer data, which better explained the variation in dolphin bycatch, indicated that the most significant predictors of dolphin catch were: (1) vessel - one trawl vessel caught significantly more dolphins than three others assessed; (2) time of day – the lowest dolphin bycatch rates were between 00:00 and 05:59; and (3) whether nets included bycatch reduction devices (BRDs) - the rate was reduced by ca. 45%, from 18.8 to 10.3 dolphins/1,000 trawls, after their introduction. These results indicated that differences among vessels (or skippers' trawling techniques) and dolphin behavior (a diurnal pattern) influenced the rates of dolphin capture; and that spatial or seasonal adjustments to trawling effort would be unlikely to significantly reduce dolphin bycatch. Recent skipper's logbook data show that dolphin bycatch rates have not declined since those reported in 2006, when BRDs were introduced across the fishery. Modified BRDs, with top-opening escape hatches from which dolphins might escape to the surface, may be a more effective means of further reducing dolphin bycatch. The vulnerability of this dolphin population to trawling-related mortality cannot be assessed in the absence of an ongoing observer program and without information on trawler-associated dolphin community size, broader dolphin population size and connectivity with adjacent populations. PMID:24695338

50 CFR 660.112 - Trawl fishery-prohibitions.

Code of Federal Regulations, 2011 CFR

2011-10-01

.../or file, retain or make available any and all reports of groundfish landings, containing all data... Bay/Canyon, Point Sur Deep, Big Sur Coast/Port San Luis, East San Lucia Bank, Point Conception, Hidden.... bleeding) before the observer has completed their data collection. (9) Mix catch from more than one haul...

50 CFR 660.711 - General catch restrictions.

Code of Federal Regulations, 2013 CFR

2013-10-01

... following are prohibited species: (1) Any species of salmon. (2) Great white shark. (3) Basking shark. (4..., or 3 individual sharks of the species in the management unit, whichever is greater. (3) Trawl and pot... or 2 individual sharks of the species in the management unit, whichever is greater. (c) Marlin...

50 CFR 660.711 - General catch restrictions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... following are prohibited species: (1) Any species of salmon. (2) Great white shark. (3) Basking shark. (4..., or 3 individual sharks of the species in the management unit, whichever is greater. (3) Trawl and pot... or 2 individual sharks of the species in the management unit, whichever is greater. (c) Marlin...

50 CFR 660.711 - General catch restrictions.

Code of Federal Regulations, 2011 CFR

2011-10-01

... following are prohibited species: (1) Any species of salmon. (2) Great white shark. (3) Basking shark. (4..., or 3 individual sharks of the species in the management unit, whichever is greater. (3) Trawl and pot... or 2 individual sharks of the species in the management unit, whichever is greater. (c) Marlin...

50 CFR 660.711 - General catch restrictions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... following are prohibited species: (1) Any species of salmon. (2) Great white shark. (3) Basking shark. (4..., or 3 individual sharks of the species in the management unit, whichever is greater. (3) Trawl and pot... or 2 individual sharks of the species in the management unit, whichever is greater. (c) Marlin...

50 CFR 660.711 - General catch restrictions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... following are prohibited species: (1) Any species of salmon. (2) Great white shark. (3) Basking shark. (4..., or 3 individual sharks of the species in the management unit, whichever is greater. (3) Trawl and pot... or 2 individual sharks of the species in the management unit, whichever is greater. (c) Marlin...

50 CFR 660.112 - Trawl fishery-prohibitions.

Code of Federal Regulations, 2012 CFR

2012-10-01

.../or file, retain or make available any and all reports of groundfish landings, containing all data... Bay/Canyon, Point Sur Deep, Big Sur Coast/Port San Luis, East San Lucia Bank, Point Conception, Hidden...) Discard any catch from the codend or net (i.e. bleeding) before the observer has completed their data...

White sturgeon mitigation and restoration in the Columbia and Snake rivers upstream from Bonneville Dam Report C, Annual Progress Report April 2003 - March 2004

USGS Publications Warehouse

Parsley, Michael J.; Gadomski, Dena M.; Kofoot, Pete

2005-01-01

River discharge and water temperatures that occurred during April through July 2003 provided conditions suitable for spawning by white sturgeon downstream from Bonneville, The Dalles, John Day, and McNary dams. Although optimal spawning temperatures in the four tailraces occurred for less than two weeks, they coincided with a period of relatively high river discharge. Bottom-trawl sampling in Bonneville and The Dalles Reservoirs revealed the presence of young-of-the-year (YOY) white sturgeon in Bonneville Reservoir, but none were captured in The Dalles Reservoir. A comparison of five years of indices of abundance of YOY sturgeon from sampling done by ODFW with gillnets and the USGS with bottom trawls was completed. Despite obvious differences in gear sampling characteristics (e.g. one gear is actively fished, one passively fished), it appears that either gear can be used to assess relative trends in YOY white sturgeon abundance. The analyses suffered due to poor catches of YOY fish, as YOY were only captured in The Dalles Reservoir during three of the five years of comparison sampling, and during only one of four years in John Day Reservoir. However, both gears detected the presence or absence of YOY white sturgeon within a reservoir equally. That is, if any YOY white sturgeon were captured in any year in a reservoir, both gears captured at least one fish, and if one gear failed to collect any YOY white sturgeon, both gears failed. Concerns have been raised that the Wang et al. (1985) egg development relationships for Sacramento River white sturgeon may not be applicable to Columbia Basin stocks. However, using laboratory experiments with white sturgeon eggs incubated at 10, 12, 15, and 18o C, we found no significant differences in development rates of eggs of Columbia, Kootenai, Snake, and Sacramento river fish.

Pattern of distribution and diversity of demersal assemblages in the central Mediterranean Sea

NASA Astrophysics Data System (ADS)

Colloca, F.; Cardinale, M.; Belluscio, A.; Ardizzone, G.

2003-03-01

A highly diversified mix of fish species, cephalopods and crustaceans, together with several macro-epibenthic organisms, compose trawl catches in the Mediterranean Sea. Management of Mediterranean trawling needs a multispecies approach that considers the community and not the single species as the basic unit of the analysis. While many studies have correlated several environmental factors to the spatial organizations of demersal organisms, few have focused on the role of macro-epibenthic communities in structuring demersal assemblages. In this paper, the following hypotheses were tested: (1) there are discrete demersal assemblages in the central Mediterranean Sea; (2) the distribution and diversity of demersal communities does not change on small temporal scales (1 year); (3) the demersal assemblages were segregated across both different epibenthic assemblages and depth gradients. Shallow stations were separated into coastal and middle-deep shelf assemblages while stations on the slope formed three main assemblages: slope edge, upper slope and middle slope assemblages. The demersal community did not show a substantial change at the small temporal scale. Sandy, sand-muddy and detritic epibenthic communities characterized coastal shelf assemblages, while epibenthic assemblage on muddy bottoms were dominant in the deeper areas of the shelf. A well-defined difference in macro-epibenthic faunal associations among stations on the slope (depth >200 m) was not found. Depth appeared to affect diversity of the main taxa of demersal organisms in different ways. Teleostean diversity did not show any trend with depth, the number of cephalopod species increased on the shelf and decreased on the slope while crustacean and elasmobranch species richness increased significantly from the shelf to the middle slope. The strong correlation shown in this study between epifaunal benthic communities and demersal fish assemblages requires the formulation of an ecosystem-based management for the Mediterranean Sea trawl fisheries. The existence of such biological diversity certainly contributes to the Mediterranean ecosystem health and its conservation should become one of the main objective of demersal resources management in the future.

50 CFR 660.112 - Trawl fishery-prohibitions.

Code of Federal Regulations, 2013 CFR

2013-10-01

..., retain or make available any and all reports of groundfish landings, containing all data, and in the... Bay/Canyon, Point Sur Deep, Big Sur Coast/Port San Luis, East San Lucia Bank, Point Conception, Hidden...) Discard any catch from the codend or net (i.e. bleeding) before the observer has completed their data...

50 CFR 660.112 - Trawl fishery-prohibitions.

Code of Federal Regulations, 2014 CFR

2014-10-01

..., retain or make available any and all reports of groundfish landings, containing all data, and in the... Bay/Canyon, Point Sur Deep, Big Sur Coast/Port San Luis, East San Lucia Bank, Point Conception, Hidden...) Discard any catch from the codend or net (i.e. bleeding) before the observer has completed their data...

77 FR 25097 - Fisheries of the Northeastern United States; 2012-2013 Northeast Skate Complex Fishery...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-27

... scientific information and reflect recent increases in skate biomass. DATES: This rule is effective May 1... average trawl survey biomass of clearnose skate declines by 40 percent or more. Additionally, this final... precautionary catch levels designed to promote biomass increases in all skates. Therefore, the commenter's...

The trophic fingerprint of marine fisheries.

PubMed

Branch, Trevor A; Watson, Reg; Fulton, Elizabeth A; Jennings, Simon; McGilliard, Carey R; Pablico, Grace T; Ricard, Daniel; Tracey, Sean R

2010-11-18

Biodiversity indicators provide a vital window on the state of the planet, guiding policy development and management. The most widely adopted marine indicator is mean trophic level (MTL) from catches, intended to detect shifts from high-trophic-level predators to low-trophic-level invertebrates and plankton-feeders. This indicator underpins reported trends in human impacts, declining when predators collapse ("fishing down marine food webs") and when low-trophic-level fisheries expand ("fishing through marine food webs"). The assumption is that catch MTL measures changes in ecosystem MTL and biodiversity. Here we combine model predictions with global assessments of MTL from catches, trawl surveys and fisheries stock assessments and find that catch MTL does not reliably predict changes in marine ecosystems. Instead, catch MTL trends often diverge from ecosystem MTL trends obtained from surveys and assessments. In contrast to previous findings of rapid declines in catch MTL, we observe recent increases in catch, survey and assessment MTL. However, catches from most trophic levels are rising, which can intensify fishery collapses even when MTL trends are stable or increasing. To detect fishing impacts on marine biodiversity, we recommend greater efforts to measure true abundance trends for marine species, especially those most vulnerable to fishing.

Integrating the provision of ecosystem services and trawl fisheries for the management of the marine environment.

PubMed

Muntadas, Alba; de Juan, Silvia; Demestre, Montserrat

2015-02-15

The species interaction and their biological traits (BT) determine the function of benthic communities and, hence, the delivery of ecosystem services. Therefore, disturbance of benthic communities by trawling may compromise ecosystem service delivery, including fisheries' catches. In this work, we explore 1) the impact of trawling activities on benthic functional components (after the BTA approach) and 2) how trawling impact may affect the ecosystem services delivered by benthic communities. To this aim, we assessed the provision of ecosystem services by adopting the concept of Ecosystem Service Providers (ESP), i.e. ecological units that perform ecosystem functions that will ultimately deliver ecosystem services. We studied thirteen sites subjected to different levels of fishing effort in the Mediterranean. From a range of environmental variables included in the study, we found ESPs to be mainly affected by fishing effort and grain size. Our results suggested that habitat type has significant effects on the distribution of ESPs and this natural variability influences ESP response to trawling at a specific site. In order to summarize the complex relationships between human uses, ecosystem components and the demand for ecosystem services in trawling grounds, we adapted a DPSIR (Drivers-Pressures-State Change-Impact-Response) framework to the study area, emphasizing the role of society as Drivers of change and actors demanding management Responses. This integrative framework aims to inform managers about the interactions between all the elements involved in the management of trawling grounds, highlighting the need for an integrated approach in order to ensure ecosystem service provision. Copyright © 2014 Elsevier B.V. All rights reserved.

Intervention analysis of power plant impact on fish populations

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

Madenjian, C.P.

1984-10-01

Intervention analysis was applied to 10 yr (years 1973-1982) of field fish abundance data at the D. C. Cook Nuclear Power Plant, southeastern Lake Michigan. Three log-transformed catch series, comprising monthly observations, were examined for each combination of two species (alewife, Alosa pseudoharenga, or yellow perch, Perca flavescens) and gear (trawl or gill net): catch at the plant discharged transect, catch at the reference transect, and the ratio of plant catch to reference catch. Time series separated by age groups were examined. Based on intervention analysis, no change in the abundance of fish populations could be attributed to plant operation.more » Additionally, a modification of the intervention analysis technique was applied to investigate trends in abundance at both the plant discharge and reference transects. Significant declines were detected for abundance of alewife adults at both of the transects. Results of the trend analysis support the contention that the alewives have undergone a lakewide decrease in abundance during the 1970s.« less

Stable isotopes reveal the effect of trawl fisheries on the diet of commercially exploited species.

PubMed

Hinz, Hilmar; Moranta, Joan; Balestrini, Stephen; Sciberras, Marija; Pantin, Julia R; Monnington, James; Zalewski, Alex; Kaiser, Michel J; Sköld, Mattias; Jonsson, Patrik; Bastardie, Francois; Hiddink, Jan Geert

2017-07-24

Bottom trawling can change food availability for benthivorous demersal species by (i) changing benthic prey composition through physical seabed impacts and (ii) by removing overall benthic consumer biomass increasing the net availability of benthic prey for remaining individuals. Thus trawling may both negatively and positively influence the quantity and quality of food available. Using δ 13 C and δ 15 N we investigated potential diet changes of three commercially exploited species across trawling gradients in the Kattegat (plaice, dab and Norway lobster (Nephrops)) and the Irish Sea (Nephrops). In the Kattegat, trawling affected primarily the biomass of benthic consumers, lowering competition. Nephrops showed significant positive relationships for δ 13 C and a domed relationship for δ 15 N with trawling. In the Irish Sea, intense trawling had a negative effect on benthic prey. δ 13 C and δ 15 N thus showed the inverse relationships to those observed in the Kattegat. Plaice from the Kattegat, showed a significant relationship with trawling intensity for δ 13 C, but not for δ 15 N. No relationship was found for dab. Changes of δ 13 C and δ 15 N correlated with changes in condition of species. The results show that the removal of demersal competitors and benthos by trawling can change the diets of commercial species, ultimately affecting their body condition.

Anguilliform larvae collected off North Carolina

USGS Publications Warehouse

Ross, Steve W.; Casazza, T.L.; Quattrini, A.M.; Sulak, K.J.

2007-01-01

The distinctive larval stage of eels (leptocephalus) facilitates dispersal through prolonged life in the open ocean. Leptocephali are abundant and diverse off North Carolina, yet data on distributions and biology are lacking. The water column (from surface to 1,293 m) was sampled in or near the Gulf Stream off Cape Hatteras, Cape Lookout, and Cape Fear, North Carolina during summer through fall of 1999-2005, and leptocephali were collected by neuston net, plankton net, Tucker trawl, and dip net. Additional samples were collected nearly monthly from a transect across southern Onslow Bay, North Carolina (from surface to 91 m) from April 2000 to December 2001 by bongo and neuston nets, Methot frame trawl, and Tucker trawl. Overall, 584 tows were completed, and 224 of these yielded larval eels. The 1,295 eel leptocephali collected (combining all methods and areas) represented at least 63 species (nine families). Thirteen species were not known previously from the area. Dominant families for all areas were Congridae (44% of individuals, 11 species), Ophichthidae (30% of individuals, 27 species), and Muraenidae (22% of individuals, ten species). Nine taxa accounted for 70% of the overall leptocephalus catches (in order of decreasing abundance): Paraconger caudilimbatus (Poey), Gymnothorax ocellatus Agassiz complex, Ariosoma balearicum (Delaroche), Ophichthus gomesii (Castelnau), Callechelys muraena Jordan and Evermann, Letharchus aliculatus McCosker, Rhynchoconger flavus (Goode and Bean), Ophichthus cruentifer (Goode and Bean), Rhynchoconger gracilior (Ginsburg). The top three species represented 52% of the total eel larvae collected. Most leptocephali were collected at night (79%) and at depths > 45 m. Eighty percent of the eels collected in discrete depth Tucker trawls at night ranged from mean depths of 59-353 m. A substantial number (38% of discrete depth sample total) of larval eels were also collected at the surface (neuston net) at night. Daytime leptocephalus distributions were less clear partly due to low catches and lower Tucker trawl sampling effort. While net avoidance may account for some of the low daytime catches, an alternative explanation is that many species of larval eels occur during the day at depths > 350 m. Larvae of 21 taxa of typically shallow water eels were collected at depths > 350 m, but additional discrete depth diel sampling is needed to resolve leptocephalus vertical distributions. The North Carolina adult eel fauna (estuary to at least 2,000 m) consists of 51 species, 41% of which were represented in these collections. Many species of leptocephali collected are not yet known to have juveniles or adults established in the South Atlantic Bight or north of Cape Hatteras. Despite Gulf Stream transport and a prolonged larval stage, many of these eel leptocephali may not contribute to their respective populations. ?? 2006 Springer-Verlag.

50 CFR 665.206 - Gear restrictions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Gear restrictions. 665.206 Section 665.206..., DEPARTMENT OF COMMERCE (CONTINUED) FISHERIES IN THE WESTERN PACIFIC Hawaii Fisheries § 665.206 Gear... MUS with bottom trawls and bottom set gillnets is prohibited. (b) Possession of gear. Possession of a...

Entering uncharted waters: Long-term dynamics of two data limited fish species, turbot and brill, in the North Sea

NASA Astrophysics Data System (ADS)

Kerby, Tina K.; Cheung, William W. L.; van Oosterhout, Cock; Engelhard, Georg H.

2013-11-01

In the North Sea, turbot (Scophthalmus maximus) and brill (Scophthalmus rhombus) represent highly valuable species in commercial fisheries. Still, available data for both species are limited, making stock assessment difficult. Long-term fisheries data have the potential to improve the understanding of stock dynamics such as long-term distribution changes or development in species' abundances. Historical British otter trawler lpue (landings-per-unit-effort) data from 1923 to 2009, and at the spatial scale of ICES rectangles, revealed that the distribution patterns of turbot and brill were different for most of the 20th century and only became similar in the recent decade. Further, between the 1920s and 1960s, turbot was commonly caught in the northern North Sea and in particular on Turbot Bank, at that time a turbot hotspot off the east coast of Scotland. Within a short time period turbot nearly disappeared from this region. Brill, in contrast, revealed a stable distribution in the southern and central North Sea with a slow expansion into the central North Sea. We used survey cpue (catch-per-unit-effort) from the International Bottom Trawl Survey (IBTS; 1970-2009) and the Beam Trawl Survey (BTS; 1985-2009), as well as British otter trawler lpue, as proxies for the abundance of adult turbot and brill. Commercial lpue suggested for brill and turbot a long-term decrease in abundance. IBTS cpue suggested an increase in abundance for turbot, but this was not confirmed by the BTS. For brill, both surveys did not show a clear trend.

75 FR 55689 - Fisheries of the Exclusive Economic Zone Off Alaska; Reallocation of Yellowfin Sole in the Bering...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-14

... Yellowfin Sole in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries... allowable catch (TAC) assigned to the Bering Sea and Aleutian Islands trawl limited access sector to the Amendment 80 cooperative in the Bering Sea and Aleutian Islands management area (BSAI). This action is...

76 FR 63204 - Fisheries of the Exclusive Economic Zone Off Alaska; Reallocation of Yellowfin Sole in the Bering...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-12

... Yellowfin Sole in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries... allowable catch (TAC) assigned to the Bering Sea and Aleutian Islands trawl limited access sector to the Amendment 80 cooperative in the Bering Sea and Aleutian Islands management area (BSAI). This action is...

76 FR 66856 - Fisheries of the Northeastern United States; Northeast Skate Complex Fishery; Secretarial...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-28

... catch target is increased from 30,810 mt to 37,826 mt; and 3. The total allowable landings (i.e., quota... overfished condition and vulnerability of the thorny skate population. Possession and landing of thorny... the trawl and gillnet fishing effort (that accounts for most of the skate landings) and the...

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...

Macrozooplankton community structure off East Antarctica (80 150°E) during the Austral summer of 1995/1996

NASA Astrophysics Data System (ADS)

Hosie, G. W.; Schultz, M. B.; Kitchener, J. A.; Cochran, T. G.; Richards, K.

2000-08-01

Zooplankton data from routine 0-200 m oblique trawls and targeted trawls were analysed using cluster analysis and non-metric multidimensional scaling to define the communities in Eastern Antarctica (80-150°E), their distribution patterns, indicator species, and species affinities. Three communities were defined based on routine trawls. The Main Oceanic Community comprising herbivorous copepods, chaetognaths, and the euphausiid Thysanoessa macrura dominated the area west of 120°E. The area east of 120°E was dominated by Salpa thompsoni. The third community located in the neritic zone was dominated by Euphausia crystallorophias. Antarctic krill Euphausia superba did not form a distinct community in its own right, unlike previous observations in Prydz Bay. Krill were distributed throughout most of the survey area but generally in higher abundances towards the shelf break. Overall, krill abundance was low compared with previous net surveys in Prydz Bay. Three main types of assemblages were identified based on target trawls. The first group was dominated by krill (mean 1149 individuals per 1000 m 3) which represented >99% of Group 1 catches in terms of numbers and biomass. Group 2 comprised the bulk of target trawls and comprised a wide diversity of species typical of the main oceanic community, with a mean abundance approximately half of that observed in the routine trawls. The third group comprised trawls in the neritic zone dominated by E. crystallorophias. No salp-dominated aggregation was found. While E. superba did not dominate a distinct community geographically as seen in previous Prydz Bay surveys, it did dominate discrete layers or aggregations, showing that both horizontal and vertical separation of communities exist.

Reply to comments by Riley and Dunlop on He et al. (2015)

USGS Publications Warehouse

Bence, James R.; Madenjian, Charles P.; He, Ji X.; Fielder, David G.; Pothoven, Steven A.; Dobiesz, Norine E.; Johnson, James E.; Ebener, Mark P.; Cottrill, R. Adam; Mohr, Lloyd C.; Koproski, Scott R.

2016-01-01

He et al. (2015) described piscivory patterns in the main basin of Lake Huron 1984-2010, during which there was also a pattern of stepwise declines in the abundance of dominant prey fish species. The approach of He et al. (2015) was to couple age-structured stock assessment and fish bioenergetics models to estimate prey fish consumption, and to compare these patterns with prey fish biomass from a bottom trawl survey. Riley and Dunlop (2015) were highly critical of the methods and conclusions reached by He et al. (2015). They claimed that we incorrectly interpreted the bottom trawl survey data, and did not account for uncertainty. We respond to these and other criticisms below, which we find do not undermine our findings.

Evaluating ecosystem-based management options: Effects of trawling in Torres Strait, Australia

NASA Astrophysics Data System (ADS)

Ellis, Nick; Pantus, Francis; Welna, Andrzej; Butler, Alan

2008-09-01

A suite of management options for a prawn trawl fishery in Torres Strait, Australia was assessed for impacts on the benthic fauna using a dynamic management strategy evaluation approach. The specification of the management options was gained through consultation with stakeholders. Data for the model was drawn from several sources: the fleet data from fishery logbooks and satellite vessel monitoring systems, benthic depletion rates from trawl-down experiments, benthic recovery rates from post-experiment recovery monitoring studies, and benthic distribution from large-scale benthic surveys. Although there were large uncertainties in the resulting indicators, robust measures relevant to management were obtained by taking ratios relative to the status quo. The management control with the biggest effect was total effort; reducing trawl effort always led to increases in benthic faunal density of up to 10%. Spatial closures had a smaller benefit of up to 2%. The effect of closing a set of buffer zones around reefs to trawling was indistinguishable from the status quo option. Closing a larger area, however, was largely beneficial especially for sea cucumbers. When the spatial distributions of fauna prior to fishing were accounted for, fauna with distributions positively correlated with effort improved relative to those negatively correlated. The reduction in prawn catch under effort reduction scenarios could be ameliorated by introducing temporal closures over the full-moon period.

Nearshore Fish Distributions in an Alaskan Estuary in Relation to Stratification, Temperature and Salinity

NASA Astrophysics Data System (ADS)

Abookire, A. A.; Piatt, J. F.; Robards, M. D.

2000-07-01

Fish were sampled with beach seines and small-meshed beam trawls in nearshore (<1 km) and shallow (<25 m) habitats on the southern coast of Kachemak Bay, Cook Inlet, Alaska, from June to August, 1996-1998. Fish distributions among habitats were analysed for species composition, catch-per-unit-effort (CPUE) and frequency of occurrence. Two oceanographically distinct areas of Kachemak Bay were sampled and compared: the Outer Bay and the Inner Bay. Outer Kachemak Bay is exposed and receives oceanic, upwelled water from the Gulf of Alaska, whereas the Inner Bay is more estuarine. Thermohaline properties of bottom water in the Outer and Inner Bay were essentially the same, whereas the Inner Bay water-column was stratified with warmer, less saline waters near the surface. Distribution and abundance of pelagic schooling fish corresponded with area differences in stratification, temperature and salinity. The Inner Bay supported more species and higher densities of schooling and demersal fish than the Outer Bay. Schooling fish communities sampled by beach seine differed between the Outer and Inner Bays. Juvenile and adult Pacific sand lance ( Ammodytes hexapterus), Pacific herring ( Clupea harengus pallasi), osmerids (Osmeridae) and sculpins (Cottidae) were all more abundant in the Inner Bay. Gadids (Gadidae) were the only schooling fish taxa more abundant in the Outer Bay. Thermohaline characteristics of bottom water were similar throughout Kachemak Bay. Correspondingly, bottom fish communities were similar in all areas. Relative abundances (CPUE) were not significantly different between areas for any of the five demersal fish groups: flatfishes (Pleuronectidae), ronquils (Bathymasteridae), sculpins (Cottidae), gadids (Gadidae) and pricklebacks (Stichaeidae).

Nearshore fish distributions in an Alaskan estuary in relation to stratification, temperature, and salinity

USGS Publications Warehouse

Abookire, Alisa A.; Piatt, John F.; Robards, Martin D.

2000-01-01

Fish were sampled with beach seines and small-meshed beam trawls in nearshore ( < 1 km) and shallow ( < 25 m) habitats on the southern coast of Kachemak Bay, Cook Inlet, Alaska, from June to August, 1996-1998. Fish distributions among habitats were analysed for species composition, catch-per-unit-effort (CPUE) and frequency of occurrence. Two oceanographically distinct areas of Kachemak Bay were sampled and compared: the Outer Bay and the Inner Bay. Outer Kachemak Bay is exposed and receives oceanic, upwelled water from the Gulf of Alaska, whereas the Inner Bay is more estuarine. Thermohaline properties of bottom water in the Outer and Inner Bay were essentially the same, whereas the Inner Bay water-column was stratified with warmer, less saline waters near the surface. Distribution and abundance of pelagic schooling fish corresponded with area differences in stratification, temperature and salinity. The Inner Bay supported more species and higher densities of schooling and demersal fish than the Outer Bay. Schooling fish communities sampled by beach seine differed between the Outer and Inner Bays. Juvenile and adult Pacific sand lance (Ammodytes hexapterus), Pacific herring (Clupea harengus pallasi), osmerids (Osmeridae) and sculpins (Cottidae) were all more abundant in the Inner Bay. Gadids (Gadidae) were the only schooling fish taxa more abundant in the Outer Bay. Thermohaline characteristics of bottom water were similar throughout Kachemak Bay. Correspondingly, bottom fish communities were similar in all areas. Relative abundances (CPUE) were not significantly different between areas for any of the five demersal fish groups: flatfishes (Pleuronectidae), ronquils (Bathymasteridae), sculpins (Cottidae), gadids (Gadidae) and pricklebacks (Stichaeidae).

An ecosystem-based assessment of hairtail ( Trichiurus lepturus) harvested by multi-gears and management implications in Korean waters

NASA Astrophysics Data System (ADS)

Kang, Hee Joong; Zhang, Chang Ik; Lee, Eun Ji; Seo, Young Il

2015-06-01

Hairtail ( Trichiurus lepturus) has been traditionally harvested by multi-gear types in the Yellow Sea and the East China Sea, except for the East Sea (Sea of Japan) in Korean waters. Six different fishery types such as offshore stownet fishery, offshore longline fishery, large pair-trawl fishery, large purse seine fishery, large otter trawl fishery and offshore angling fishery target to harvest the hairtail stock accounting for about 90% of the total annual catch. We attempted to develop an ecosystem-based fisheries assessment approach, which determines the optimal allocation of catch quotas and fishing efforts for major fisheries. We conducted standardization of fishing effort for six types of hairtail fisheries using a general linear model (GLM), and then estimated maximum sustainable yield (MSY) and maximum economic yield (MEY). Estimated MSY and MEY for the hairtail stock were estimated as 100,151 mt and 97,485 mt, respectively. In addition, we carried out an ecosystem-based risk analysis to obtain species risk index (SRI), which was applied to adjusting the optimal proportion of fishing effort for six hairtail fisheries as a penalty or an incentive. As a result, fishing effort ratios were adjusted by SRI for the six fisheries types. Also, the total allowable catch (TAC) was estimated as 97,485 mt and the maximum net profit at TAC by the hairtail fisheries was estimated as 778 billion won (USD 765 million).

78 FR 26526 - Magnuson-Stevens Act Provisions; Fisheries off West Coast States; Pacific Coast Groundfish...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-07

... base-case model using nine years of an acoustic survey biomass index as well as catches to estimate the scale of the current hake stock. The 2012 acoustic-trawl survey result was a relative biomass 1,380,000... series. The age-composition data from the aggregated fisheries (1975-2012) and the acoustic survey...

50 CFR 679.93 - Amendment 80 Program recordkeeping, permits, monitoring, and catch accounting.

Code of Federal Regulations, 2010 CFR

2010-10-01

... where the observer collects species composition samples. (5) Fish on deck. No fish are allowed to remain on deck unless an observer is present, except for fish inside the codend and fish accidentally... § 679.4(l)(2)(i) using trawl gear and fishing or receiving fish in the BSAI and in adjacent waters open...

Lake Ontario benthic prey fish assessment, 2015

USGS Publications Warehouse

Weidel, Brian C.; Walsh, Maureen; Holden, Jeremy P.; Connerton, Michael J.

2016-01-01

Benthic prey fishes are a critical component of the Lake Ontario food web, serving as energy vectors from benthic invertebrates to native and introduced piscivores. Since the late 1970’s, Lake Ontario benthic prey fish status was primarily assessed using bottom trawl observations confined to the lake’s south shore, in waters from 8 – 150 m (26 – 492 ft). In 2015, the Benthic Prey Fish Survey was cooperatively adjusted and expanded to address resource management information needs including lake-wide benthic prey fish population dynamics. Effort increased from 55 bottom trawl sites to 135 trawl sites collected in depths from 8 - 225m (26 – 738 ft). The spatial coverage of sampling was also expanded and occurred in all major lake basins. The resulting distribution of tow depths more closely matched the available lake depth distribution. The additional effort illustrated how previous surveys were underestimating lake-wide Deepwater Sculpin, Myoxocephalus thompsonii, abundance by not sampling in areas of highest density. We also found species richness was greater in the new sampling sites relative to the historic sites with 11 new fish species caught in the new sites including juvenile Round Whitefish, Prosopium cylindraceum, and Mottled sculpin, Cottus bairdii. Species-specific assessments found Slimy Sculpin, Cottus cognatus abundance increased slightly in 2015 relative to 2014, while Deepwater Sculpin and Round Goby, Neogobius melanostomus, dramatically increased in 2015, relative to 2014. The cooperative, lake-wide Benthic Prey Fish Survey expanded our understanding of benthic fish population dynamics and habitat use in Lake Ontario. This survey’s data and interpretations influence international resource management decision making, such as informing the Deepwater Sculpin conservation status and assessing the balance between sport fish consumption and prey fish populations. Additionally a significant Lake Ontario event occurred in May 2015 when a single juvenile Bloater Coregonus hoyi, was captured during the spring bottom trawl survey at 95m (312 ft) near Oswego, NY. This native, deep-water prey fish, last captured in Lake Ontario survey trawls in 1983, is part of an international, collaborative coregonid restoration effort in the Great Lakes.

The substantial first impact of bottom fishing on rare biodiversity hotspots: a dilemma for evidence-based conservation.

PubMed

Cook, Robert; Fariñas-Franco, Jose M; Gell, Fiona R; Holt, Rohan H F; Holt, Terry; Lindenbaum, Charles; Porter, Joanne S; Seed, Ray; Skates, Lucie R; Stringell, Thomas B; Sanderson, William G

2013-01-01

This study describes the impact of the first passage of two types of bottom-towed fishing gear on rare protected shellfish-reefs formed by the horse mussel Modiolus modiolus (L.). One of the study sites was trawled and the other was scallop-dredged. Divers collected HD video imagery of epifauna from quadrats at the two study sites and directed infaunal samples from one site. The total number of epifaunal organisms was significantly reduced following a single pass of a trawl (90%) or scallop dredge (59%), as was the diversity of the associated community and the total number of M. modiolus at the trawled site. At both sites declines in anthozoans, hydrozoans, bivalves, echinoderms and ascidians accounted for most of the change. A year later, no recovery was evident at the trawled site and significantly fewer infaunal taxa (polychaetes, malacostracans, bivalves and ophuroids) were recorded in the trawl track. The severity of the two types of impact reflected the undisturbed status of the habitats compared to previous studies. As a 'priority habitat' the nature of the impacts described on M. modiolus communities are important to the development of conservation management policy and indicators of condition in Marine Protected Areas (EU Habitats Directive) as well as indicators of 'Good Environmental Status' under the European Union Marine Strategy Framework Directive. Conservation managers are under pressure to support decisions with good quality evidence. Elsewhere, indirect studies have shown declines of M. modiolus biogenic communities in fishing grounds. However, given the protected status of the rare habitat, premeditated demonstration of direct impact is unethical or illegal in Marine Protected Areas. This study therefore provides a unique opportunity to investigate the impact from fishing gear whilst at the same time reflecting on the dilemma of evidence-based conservation management.

Distribution, abundance, and biology of the alewife in U.S. waters of Lake Superior

USGS Publications Warehouse

Bronte, Charles R.; Selgeby, James H.; Curtis, Gary L.

1991-01-01

Alewives (Alosa pseudoharengus) were first reported in Lake Superior in 1954 and gradually increased in abundance in the late 1950s. In the 1960s and early 1970s, the fish were widespread in the lake but scarce. We determined the more recent abundance and distribution of alewives by cross-contour trawling in the spring in 1978–1988. Alewives were scarce lake-wide; the mean catch rate was only 23 fish per 100 h of trawling and represented a density of 0.003 kg per hectare in the area swept by the trawls. Fish of six age groups were caught in trawls in spring and gill nets in fall in 1983–1987. Total annual mortality was 64%, a high natural rate in the absence of fishing. Alewives in Lake Superior were small at the end of their first growing season but later grew faster than those in the other Great Lakes. Fecundity, estimated to be 64,000 eggs (mean total length = 187 mm) was higher than in other freshwater stocks. Zooplankton was the major food of alewives < 100 mm long and Mysis was the main food of larger fish. Exposure to water temperatures below lethal minimums for overwintering fish and for developing eggs limits the success of this species in Lake Superior.

75 FR 62111 - Pacific Fishery Management Council; Public Hearings

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-07

...The Pacific Fishery Management Council (Council) will hold public hearings on development of community fishing association (CFAs) provisions for its groundfish trawl catch share plan, which was adopted through Amendments 20 and 21 to the groundfish FMP and is scheduled for implementation at the start of 2011. The Council will address this issue at its November 3-9, 2010 Council meeting, in Costa Mesa, CA.

77 FR 75966 - Control Date for Qualifying Landings History in the Central Gulf of Alaska Trawl Groundfish...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-26

.... 121121645-2645-01] RIN 0648-BC80 Control Date for Qualifying Landings History in the Central Gulf of Alaska... applicable to, but not limited to, qualifying landings and permit history for an allocation-based management... corresponds to the end of the fishing year for this fishery, so that the full catch history for 2012 may be...

78 FR 42023 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-15

..., Office of Sustainable Fisheries, National Marine Fisheries Service. [FR Doc. 2013-16764 Filed 7-9-13; 4... trawl limited access fishery. This action is necessary to fully use the 2013 total allowable catch (TAC...: Effective 1200 hrs, Alaska local time (A.l.t.), July 9, 2013, through 2400 hrs, A.l.t., December 31, 2013...

78 FR 13812 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catch Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-01

.... 1801 et seq. Dated: February 26, 2013. Kara Meckley, Acting Deputy Director, Office of Sustainable... hours. This action is necessary to fully use the A season allowance of the 2013 Pacific cod total...: Effective 1200 hours, Alaska local time (A.l.t.), March 1, 2013, through 1200 hours, A.l.t., March 3, 2013...

Fisheries research and monitoring activities of the Lake Erie Biological Station, 2013

USGS Publications Warehouse

Kraus, Richard T.; Rogers, Mark W.; Kocovsky, Patrick; Edwards, William; Bodamer Scarbro, Betsy L.; Keretz, Kevin R.; Berkman, Stephanie A.

2014-01-01

In 2013, the U.S. Geological Survey’s Lake Erie Biological Station successfully completed large vessel surveys in all three of Lake Erie’s basins. Lake Erie Biological Station’s primary vessel surveys included the Western Basin Forage Fish Assessment and East Harbor Forage Fish Assessment as well as contributing to the cooperative multi-agency Central Basin Hydroacoustics Assessment and the Eastern Basin Coldwater Community Assessment (see Forage Task Group and Coldwater Task Group reports, respectively). Further large vessel sampling included individual research data collection as well as assisting with University (e.g., University of Toledo) and agency (e.g., USFWS, USEPA) large vessel sampling needs. Our 2013 vessel operations began on April 4th and concluded on November 21 with a total of 77 large vessel sampling days (83 total days). During this time, crews of the R/V Muskie and R/V Bowfin deployed 174 trawls covering 147 km of lake-bottom, over 13 km of gillnet, collected hydroacoustic data that extended over 250 km of the central and eastern basins, and approximately 180 collective zooplankton, benthos, and water samples. 2013 was the first complete sampling year using the R/V Muskie. Technologies available on the new platform provided opportunities for LEBS to improve data sampling methods and results. An investment was made in mensuration gear for the trawls. This gear is attached to the trawl’s headrope, footrope, and wings; thus, allowing measurement of the area swept and conversion of catches to densities. Another improvement included real-time output of water parameter sonde profiles (e.g., temperature, dissolved oxygen). The ability to view profile data on a tablet allowed quick identification of thermoclines as well as the presence (or absence) of hypoxia. Minor modifications were made to survey designs relative to last year (see 2013 report), and thus, collection of long-term data from the R/V Muskie has commenced. One minor change was that we are now indexing yellow perch maturation data during our fall trawl surveys in response to a request from the Lake Erie Yellow Perch Task Group. Within the following sections, we describe results from our 2013 sampling efforts in Lake Erie.

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

Status of important prey fishes in the U.S. waters of Lake Ontario, 2013: Introduction and methods, alewife, rainbow smelt, sculpins, and round goby

USGS Publications Warehouse

Walsh, Maureen; Weidel, Brian C.; Connerton, Michael J.

2014-01-01

Lake Ontario has a mean depth of 86 m (282 ft) and a maximum depth of 244 m (801 ft) (Herdendorf 1982). The southern, New York portion of the lake has the deepest water (Figure 1). In New York waters, about 67% of the lake is <160 m (525 ft) deep and about 82% of the lake is <180 m (591 ft) deep. The U.S. Geological Survey (USGS) and New York State Department of Environmental Conservation (NYSDEC) have cooperatively assessed Lake Ontario prey fishes each year since 1978. Bottom trawl assessments were initially focused on Alewife Alosa pseudoharengus (April), Rainbow Smelt Osmerus mordax (June), and Slimy Sculpin Cottus cognatus (October). Seasonal survey timing corresponded to the peak catches in 1972 when collections were made every month May to October (Owens et al. 2003). Twelve transects were established at approximately 25-km intervals along the U.S. shoreline (Figure 2). Alewife assessment was conducted at all transects, Rainbow Smelt assessment at all transects except Fair Haven, and six transects representing eastern, southern, and western lake areas were sampled for Slimy Sculpin (Figure 2). Changes in the Lake Ontario ecosystem (species invasion, oligotrophication, native species rebound) require ongoing evaluation of current methods which sometimes necessitate redistribution of trawl effort, or changes in sampling designs and/or gear. For instance, the spring Alewife assessment is now used also to assess invasive Round Goby Neogobius melanostomus population dynamics. Likewise, the fall benthic fish assessment (formerly sculpin assessment) now also tracks dynamics of the rebounding native Deepwater Sculpin Myoxocephalus thompsonii population, the apparent declining population of Slimy Sculpin, and fall distribution of Round Goby.

How Many Fish Need to Be Measured to Effectively Evaluate Trawl Selectivity?

PubMed Central

Santos, Juan; Sala, Antonello

2016-01-01

The aim of this study was to provide practitioners working with trawl selectivity with general and easily understandable guidelines regarding the fish sampling effort necessary during sea trials. In particular, we focused on how many fish would need to be caught and length measured in a trawl haul in order to assess the selectivity parameters of the trawl at a designated uncertainty level. We also investigated the dependency of this uncertainty level on the experimental method used to collect data and on the potential effects of factors such as the size structure in the catch relative to the size selection of the gear. We based this study on simulated data created from two different fisheries: the Barents Sea cod (Gadus morhua) trawl fishery and the Mediterranean Sea multispecies trawl fishery represented by red mullet (Mullus barbatus). We used these two completely different fisheries to obtain results that can be used as general guidelines for other fisheries. We found that the uncertainty in the selection parameters decreased with increasing number of fish measured and that this relationship could be described by a power model. The sampling effort needed to achieve a specific uncertainty level for the selection parameters was always lower for the covered codend method compared to the paired-gear method. In many cases, the number of fish that would need to be measured to maintain a specific uncertainty level was around 10 times higher for the paired-gear method than for the covered codend method. The trends observed for the effect of sampling effort in the two fishery cases investigated were similar; therefore the guidelines presented herein should be applicable to other fisheries. PMID:27560696

77 FR 71786 - New England Fishery Management Council; Public Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-04

..., gear requirements for small-mesh bottom trawl vessels fishing on Georges Bank, and several other issues.... Special Accommodations This meeting is physically accessible to people with disabilities. Requests for...

Fish species and community distributions as proxies for seafloor habitat distributions: The Stellwagen Bank National Marine Sanctuary example (Northwest Atlantic, Gulf of Maine)

USGS Publications Warehouse

Auster, P.J.; Joy, K.; Valentine, P.C.

2001-01-01

Defining the habitats of fishes and associated fauna on outer continental shelves is problematic given the paucity of data on the actual types and distributions of seafloor habitats. However many regions have good data on the distributions of fishes from resource surveys or catch statistics because of the economic importance of the fisheries. Fish distribution data (species or communities) have been used as a proxy for the distribution of habitats to develop precautionary conservation strategies for habitat protection (e.g., marine protected areas, fishing gear restrictions). In this study we assessed the relationships between the distributions of fish communities and species derived from trawl survey data with the spatial distribution of sediment types determined by sampling and acoustic reflectance derived from multibeam sonar surveys in Stellwagen Bank National Marine Sanctuary. Fish communities were correlated with reflectance values but all communities did not occur in unique sediment types. This suggests that use of community distributions as proxies for habitats should include the caveat that a greater number of communities within an area could indicate a greater range of habitat types. Single species distributions showed relationships between abundance and reflectance values. Trawl catches with low abundances had wide variations in reflectance values while those with high abundances had narrower ranges indicating habitat affinities. Significant non-random frequency-dependent relationships were observed for 17 of 20 species although only 12 of 20 species had significant relationships based on rank correlation. These results suggest that species distributions based on trawl survey data can be used as proxies for the distribution of seafloor habitats. Species with known habitat associations can be used to infer habitat requirements of co-occurring species and can be used to identify a range of habitat types.

Fish species and community distributions as proxies for sea-floor habitat distributions: the Stellwagen Bank National Marine Sanctuary example (northwest Atlantic, Gulf Of Maine)

USGS Publications Warehouse

Auster, Peter J.; Joy, Kevin; Valentine, Page C.

2001-01-01

Defining the habitats of fishes and associated fauna on outer continental shelves is problematic given the paucity of data on the actual types and distributions of seafloor habitats. However many regions have good data on the distributions of fishes from resource surveys or catch statistics because of the economic importance of the fisheries. Fish distribution data (species or communities) have been used as a proxy for the distribution of habitats to develop precautionary conservation strategies for habitat protection (e.g., marine protected areas, fishing gear restrictions). In this study we assessed the relationships between the distributions of fish communities and species derived from trawl survey data with the spatial distribution of sediment types determined by sampling and acoustic reflectance derived from multibeam sonar surveys in Stellwagen Bank National Marine Sanctuary. Fish communities were correlated with reflectance values but all communities did not occur in unique sediment types. This suggests that use of community distributions as proxies for habitats should include the caveat that a greater number of communities within an area could indicate a greater range of habitat types. Single species distributions showed relationships between abundance and reflectance values. Trawl catches with low abundances had wide variations in reflectance values while those with high abundances had narrower ranges indicating habitat affinities. Significant non-random frequency-dependent relationships were observed for 17 of 20 species although only 12 of 20 species had significant relationships based on rank correlation. These results suggest that species distributions based on trawl survey data can be used as proxies for the distribution of seafloor habitats. Species with known habitat associations can be used to infer habitat requirements of co-occurring species and can be used to identify a range of habitat types.

Developing Spatial Management Options for the Protection of Vulnerable Marine Ecosystems in the South Pacific Ocean Region.

NASA Astrophysics Data System (ADS)

Rowden, A. A.; Lundquist, C. J.; Clark, M. R.; Anderson, O. F.; Guinotte, J. M.; Baird, S. J.; Roux, M. J.; Wadhwa, S.

2016-02-01

The South Pacific Regional Fisheries Management Organisation (SPRFMO) Convention includes specific provisions to protect vulnerable marine ecosystems (VMEs). The SPRFMO Commission has determined that the interim measures put in place to protect VMEs would be replaced by an improved system of fishable and closed areas. These closures would effectively represent a preliminary spatial management plan, whereby conservation and management measures are implemented that will result in sustainable fisheries and benthic protection. We used the conservation planning tool Zonation to develop spatial management options that balance the protection of VMEs with utilisation of high value areas for fishing. Input data included habitat suitability maps, and uncertainties associated with these model predictions, for eleven VME indicator taxa (4 Scleractinian coral species; 3 other cnidarian groups (Family Stylasteridae, Order Antipatharia, Order Pennatulacea; 2 classes of sponges (Demospongiae, Hexactinellidae), and 2 echninoderm groups (Crinoidea and Brisingida)) at bathyal depths across the entire SPRFMO area (divided into 1 km2 grid cells); New Zealand fishing catch data (for two different time periods and trawl types); naturalness (represented by proxy variable using the number of trawl tows); and a bioregionalisation scheme. Running various scenario models for spatial planning allowed for the cost to fishing to be determined, in terms of the amount of the trawl catch footprint lost if high priority areas for VME indicator taxa are protected. Generally, the cost to fishing was low given the relatively high proportion of suitable habitat for VME indicator taxa protected. The main outcome of the present study is a demonstration of the practical utility of using available data, including modelled data, and the Zonation conservation planning software tool to develop options for the spatial management of the SPRFMO area.

Community structure of the ichthyofauna associated with seagrass beds in Formoso River estuary - Pernambuco, Brazil.

PubMed

Pereira, Pedro H C; Ferreira, Beatrice P; Rezende, Sérgio M

2010-09-01

Seagrass beds are used by juvenile fishes in different ways, generally as nursery sites, shelter from predators, reducing competition and increasing availability of food resources, thus establishing a relationship of connectivity with other ecosystems. In the present study, the community structure of the ichthyofauna associated with seagrass beds on the Formoso River (Pernambuco - Brazil) was evaluated during the winter of 2008. Twenty-seven manual trawls (15 daytime and 12 nighttime) were performed, and a total of 358 fishes belonging to 18 families, 21 genus and 25 species were collected. The Catch Per Unit Effort (CPUE) by trawling average was 13.5 and 4.95 individuals per species per trawl. The most abundant families were Scaridae (n = 111), Tetraodontidae (n = 63), Lutjanidae (n = 56), Mullidae (n = 39) and Engraulidae (n = 19). Ecological indices for dial changes were always higher for the night period, confirming that such areas are used more frequently during this period. The need for measures to conserve these areas is emphasized, by its importance and vulnerability to human impacts.

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.

Epibenthic assemblages in the Celtic Sea and associated with the Jones Bank

NASA Astrophysics Data System (ADS)

Ellis, J. R.; Martinez, I.; Burt, G. J.; Scott, B. E.

2013-10-01

The epibenthic assemblages in the Celtic Sea are described from the catches from 2 m beam trawl surveys undertaken from 2000 to 2009. During this period 154 samples were collected. The most ubiquitous species in the study area were the natantid shrimps Processa spp. and Crangon allmanni, the hermit crabs Pagurus prideaux and Anapagurus laevis, sand star Astropecten irregularis and spotted dragonet Callionymus maculatus. Multivariate community analyses indicated that catches (numbers per tow) were distributed across six assemblages, two of which were predominant in the study area. Most catches were attributed to either a 'shelf edge assemblage', which was widespread in deeper waters (114-423 m water depth) or an 'outer shelf assemblage' that occurred across much of the Celtic Sea north of 49°N in waters 49-175 m deep. The dominant species along the edge of the continental shelf were the hormathid anemome Actinauge richardi, sea spider Pycnogonum littorale (which associated with A. richardi), Devonshire cup coral Caryophyllia smithii and the swimming crab Macropipus tuberculatus. The dominant species in the outer shelf assemblage included P. prideaux, C. allmanni, A. laevis and common starfish Asterias rubens. Stations closer to shore were relatively distinct and catches in this 'inner shelf assemblage' were composed primarily of an inshore fauna (e.g. Ophiura ophiura, C. allmanni and Liocarcinus holsatus). Stations in the southern part of the survey grid were also relatively distinct ('southern Celtic Sea assemblage'), and several large echinoderms (Porania pulvillus, Stichastrella rosea and Anseropoda placenta) dominated at these sites. Three of the deepest stations were also relatively distinct, as were a group of stations in the muddy habitat of the Celtic Deep and comparable grounds elsewhere in the region, where Nucula sulcata and Alpheus glaber were characteristic. Catches on the shallower parts of the Jones Bank (and on another bank in the region) were dominated by the anemone Paraphellia expansa, with off-bank sites comprising a greater number of species. In contrast to beam trawl sampling, baited camera observations on the Jones Bank showed a greater richness of species on the shallower part of the bank, and provided information on the nocturnal feeding behaviour of scavenging isopods.

Zero-inflated modeling of fish catch per unit area resulting from multiple gears: Application to channel catfish and shovelnose sturgeon in the Missouri River

USGS Publications Warehouse

Arab, A.; Wildhaber, M.L.; Wikle, C.K.; Gentry, C.N.

2008-01-01

Fisheries studies often employ multiple gears that result in large percentages of zero values. We considered a zero-inflated Poisson (ZIP) model with random effects to address these excessive zeros. By employing a Bayesian ZIP model that simultaneously incorporates data from multiple gears to analyze data from the Missouri River, we were able to compare gears and make more year, segment, and macrohabitat comparisons than did the original data analysis. For channel catfish Ictalurus punctatus, our results rank (highest to lowest) the mean catch per unit area (CPUA) for gears (beach seine, benthic trawl, electrofishing, and drifting trammel net); years (1998 and 1997); macrohabitats (tributary mouth, connected secondary channel, nonconnected secondary channel, and bend); and river segment zones (channelized, inter-reservoir, and least-altered). For shovelnose sturgeon Scaphirhynchus platorynchus, the mean CPUA was significantly higher for benthic trawls and drifting trammel nets; 1998 and 1997; tributary mouths, bends, and connected secondary channels; and some channelized or least-altered inter-reservoir segments. One important advantage of our approach is the ability to reliably infer patterns of relative abundance by means of multiple gears without using gear efficiencies. ?? Copyright by the American Fisheries Society 2008.

Biogeographical affinities of fish associated to the shrimp trawl fishery in the Gulf of Tehuantepec, Mexico.

PubMed

Martínez-Muñoz, Marco A; Lloris, Domènec; Gracia, Adolfo; Ramírez-Murillo, Ricardo; Sarmiento-Nafáte, Saul; Ramos-Cruz, Sebastián; Fernández, Felipe

2016-06-01

Fish by-catch of shrimp fishery from the Gulf of Tehuantepec is composed of several species that are mainly discarded. In this study, fish by-catch species composition, distribution and biogeographical affinities were analyzed. For this, a total of 15 cruises were carried out on the continental shelf, at depths from 15 to 64 m, during 2003, 2004, 2005 and 2013. Results showed that fish by-catch was represented by 58 families, 129 genera and 242 species. The families Haemulidae, Sciaenidae, Paralichthyidae, Gerreidae and Carangidae accounted for > 70 % of the catch. Haemulopsis axillaris, Syacium ovale, Selene peruviana, Diapterus peruvianus, Larimus acclivins and Stellifer erycimba were the most frequent species at < 40 m depth (inner shelf), and Prionotus stephanophrys, Scorpaena russula, Porichthys analis and Synodus scituliceps were dominant at 40-60 m depth (outer shelf). Analysis of biogeographical affinities showed that 36.1 % of species had a wide distribution, from San Diego Province to the Panamic Province, while 13.2 % had a restricted distribution in the Mexican and Panamic Provinces. The ichthyofaunal composition was markedly influenced by the local environment and seasonal conditions.

Great Lakes prey fish populations: a cross-basin overview of status and trends based on bottom trawl surveys, 1978-2013

USGS Publications Warehouse

Gorman, Owen T.; Weidel, Brian C.

2014-01-01

The assessment of Great Lakes prey fish stocks have been conducted annually with bottom trawls since the 1970s by the Great Lakes Science Center, sometimes assisted by partner agencies. These stock assessments provide data on the status and trends of prey fish that are consumed by important commercial and recreational fishes. Although all these annual surveys are conducted using bottom trawls, they differ among the lakes in the proportion of the lake covered, seasonal timing, trawl gear used, and the manner in which the trawl is towed (across or along bottom contours). Because each assessment is unique, population indices were standardized to the highest value for a time series within each lake for the following prey species: Cisco (Coregonus artedi), Bloater (C. hoyi), Rainbow Smelt (Osmerus mordax), Alewife (Alosa pseudoharengus), and Round Goby (Neogobius melanostomus). In this report, standardized indices are presented in graphical form along with synopses to provide a short, informal cross-basin summary of the status and trends of principal prey fishes. There was basin-wide agreement in the trends of age-1 and older biomass for all prey species, with the highest concordance occurring for coregonids and Rainbow Smelt, and weaker concordance for Alewife. For coregonids, the highest biomass occurred from the mid-1980s to the mid-1990s. Rainbow Smelt biomass declined slowly and erratically during the last quarter century. Alewife biomass was generally higher from the early 1980s through 1990s across the Great Lakes, but since the early 1990s, trends have been divergent across the lakes, though there has been a downward trend in all lakes since 2005. Recently, Lake Huron has shown resurgence in biomass of Bloater, achieving 75% of its maximum record in 2012 due to recruitment of a succession of strong and moderate year classes that appeared in 2005-2011. Also, strong recruitment of the 2010 year class of Alewife has led to a sharp increase in biomass of Alewife in Lake Michigan. In general, trends in year-class strengths were less concordant across the basin and only coregonids showed statistical agreement across the upper Great Lakes. The appearance of strong and moderate year-classes of Bloater in Lake Huron in 2005- 2011 countered the trend of continuing weak year-classes of coregonids in Lakes Michigan and Superior. Not shown in our analysis is the appearance of the 2013 year-class of Bloater in Huron, the largest to date. There was no agreement in cross-basin trends in year-class strengths for Rainbow Smelt and Alewife, although there was agreement between pairs of lakes. Although there was statistical agreement in trends of age-0 and older Round Goby biomass among lakes where this species has successfully invaded (Michigan, Huron, Erie and Ontario), temporal patterns of biomass in each lake were different. Round Goby may be approaching equilibrium in Lake Erie, peaking in Lake Huron, and expanding in Lake Michigan. The trend in Lake Ontario remains unclear. Declining abundance in Lake Erie has corresponded with evidence that Round Goby have become increasingly incorporated into piscivore diets, e.g., Lake Trout, Walleye, Smallmouth Bass, Yellow Perch, and Burbot in Lakes Michigan, Huron, Erie, and Ontario. Round Goby continue to be absent from spring bottom trawl assessments in Lake Superior, but their presence in the harbors and embayments of Duluth and Thunder Bay (U.S. Geological Survey and Ontario Ministry of Natural Resources, unpublished data), suggests that there is potential for future colonization.

Hudson Canyon benthic habitats characterization and mapping by integrated analysis of multidisciplinary data

NASA Astrophysics Data System (ADS)

Pierdomenico, Martina; Guida, Vincent G.; Rona, Peter A.; Macelloni, Leonardo; Scranton, Mary I.; Asper, Vernon; Diercks, Arne

2013-04-01

Hudson Canyon, about 180 km SE of New York City, is the largest eastern U.S. submarine canyon and is under consideration for HAPC (Habitat Area of Particular Concern) status, representing a fisheries and biodiversity hot spot. Interest in the area, within the perspective of ecosystem based management, marine spatial planning, habitat and species conservation, led to a joint project between NOAA Northeast Fisheries, U.S. Geological Survey (USGS), Mississippi Mineral Research Institute (MMRI), National Institute for Undersea Science and Technology (NIUST), Stony Brook and Rutgers Universities for the study of benthic habitats, that includes the assembly of existing data with newly collected ones: acoustic mapping, visual ground-truthing, hydrographic, sedimentological, and trawl data collections. Acoustic mapping, performed using AUV-mounted multibeam sonar, provided ultra-high resolution bathymetric and backscatter imagery (3m and 1m respectively) at all water depths for identification of geomorphological features and for the characterization of surficial sediments along the two thirds of the shelf portion of the canyon. Identification of benthic and demersal communities was accomplished by visual ground thruthing with underwater vehicle video and still cameras, and from trawl catch data. A CTD-rosette sampler provided water column salinity-temperature profiles and water samples for dissolved methane analysis in the vicinity of suspected bottom sources. Analysis of data revealed a complex of topographic structures and hydrological patterns that provide a wide range of physical habitats in a relatively small area. A mosaic of sandy and muddy substrates, gravel beds, rock outcrops, and semilithified clay outcrops host rich and varied faunal assemblages, including deepwater corals and sponge communities. Pockmark fields, occurring below 300 m depth, suggest that methane-based chemosynthetic carbonate deposition contributes to creation of specific hard bottom habitats. Previously described hummocky terrain associated with extensive, long-term burrowing activity by golden tilefish (Lopholatilus chamaeleonticeps) was clearly delineated along the canyon rims. Bedform fields and potential current deposits observed along the upper portion of canyon walls suggest the presence of intense bottom currents flowing parallel to canyon axis. A benthic habitat map of Hudson Canyon head was produced by integration of the different datasets. The distribution of habitats was primarily inferred from geophysical data characteristics. Furthermore habitat characteristics can be related to sedimentary and oceanographic processes acting on the seafloor. Comparison and refinement of bathymetric and backscatter imagery with ground truth data enabled validation of acoustic classification of the seafloor, allowing the definition of morpho-acoustic classes corresponding to as many habitats, and to extend the predictive results over larger areas.

The fish and fisheries of Jones Bank and the wider Celtic Sea

NASA Astrophysics Data System (ADS)

Martinez, I.; Ellis, J. R.; Scott, B.; Tidd, A.

2013-10-01

The Celtic Sea is a diverse fishing ground that supports important commercial fisheries for a range of demersal fish, large and small-bodied pelagic fish and a variety of cephalopods and other shellfish. A regional overview of the main commercial fish stocks of the Celtic Sea and of the fish that occur in the vicinity of Jones Bank are provided through analyses of landings data from English and Welsh vessels, and from scientific trawl surveys. Dedicated smaller scale sampling via trawl surveys combined with baited cameras on and around the Jones Bank were also analysed to investigate the importance of sandbank habitats with attention paid to the differences in the species occurring on the top of the bank in comparison to adjacent off-bank habitats. Official landing statistics for UK (English and Welsh) vessels indicated that the predominant commercial demersal species in ICES Divisions VIIg,h (in terms of quantities landed) were anglerfish, megrim, pollack and skates (Rajidae). There were, however, regional differences in the distribution of fish and fisheries, and the area surrounding Jones Bank (ICES Rectangles 28E1 and 28E2) supports fisheries for megrim, anglerfish, skates, hake, ling and turbot, with otter trawl, gillnet and beam trawl the main gears used. Recent survey data collected with GOV (Grande Ouverture Verticale) trawl from the Celtic Sea (ICES Divisions VIIe-h, 2007-2010) were used to highlight the broad scale distribution of the main fish assemblages in the Celtic Sea. Analyses of the fish and cephalopod catches from these surveys indicated that there were four broad assemblages in the area, including (i) a region around the Cornwall (which will also be partly influenced by the necessity to use rockhopper ground gear on these rough grounds), (ii) the shallower regions of the north-western Celtic Sea (including parts of the Bristol Channel), (iii) the deeper parts of the outer shelf and (iv) the central Celtic Sea. These data also provided information on the ichthyofauna of the Jones Bank. Further site-specific data for bank and off-bank habitats were collected during dedicated surveys on the Jones Bank in 2008 using commercial trawlers and baited camera deployments. Twenty-three species were recorded on the top of the bank, where horse mackerel, haddock and boarfish were the most abundant species; 18 species were found along the slope of the bank (with blue whiting, poor cod, hake and horse mackerel predominant) and 18 species observed off the bank (where catches were dominated by blue whiting, poor cod and hake). The differences between camera and trawls were important with cameras only picking up 28% of the species seen in the trawls. However both camera and trawl results suggest that some species are very habitat specific, with species such as haddock only observed on the top of the bank, whilst Nephrops norvegicus was abundant on the flat areas off the bank but was infrequent on the top of the bank. These results suggest that future surveys of offshore sandbank habitats should stratify sampling more specifically to deal with smaller scale features that may play an important role in providing a greater range of habitats than just their relative size would suggest.

The effects of trawling on the properties of surface sediments in the Lagoon of Venice, Italy.

NASA Astrophysics Data System (ADS)

Aspden, R.; Vardy, S.; Perkins, R.; Davidson, I.; Paterson, D. M.

2003-04-01

The effects of trawling for clams in two differently impacted areas of the Lagoon of Venice were investigated. The Lagoon has an area of 55,000 hectares and the trawling of clams (Tapes phippinarum) has important socio-economic and environmental implications for the area. Bottom trawling has been shown to have large disruptive effects on the structure of benthic communities but the relationship of this to the stability and structure of the surface sediments is still unclear. The sediment stability, grain size, bulk and colloidal carbohydrate content, total organic carbon, chlorophyll a content, and sediment dry bulk density were measured in order to determine the effects of dredging on the physical and biological properties of the lagoon surface sediments. The sediments were more stable at the less impacted site and biological measurements from the same site indicated a relatively low capacity for biogenic stabilisation of sediments. Measurements were taken before and after trawling had occurred. At the less impacted site all biological properties were significantly different before and after the disturbance event, the only physical property to be significantly different was water content. At the highly impacted site the disturbance event had only a small effect on the biological and physical properties of the sediments. Only chlorophyll a content was significantly different before and after the trawl. The results suggest that frequent trawling of the lagoon will reduce the stability of the surface sediments due to the effects on the bulk strength of the sediments and on the biological status of the surface sediments.

Call to protect deep-sea coral, sponge ecosystems

NASA Astrophysics Data System (ADS)

Showstack, Randy

2004-03-01

More than 1100 scientists are signatories to a 15 February consensus statement calling for the protection of deep sea coral and sponge ecosystems. The statement indicates that ``the greatest human threat'' to these ecosystems ``is commercial fishing, especially bottom trawling.''

Intercalibration of research survey vessels on Lake Erie

USGS Publications Warehouse

Tyson, J.T.; Johnson, T.B.; Knight, C.T.; Bur, M.T.

2006-01-01

Fish abundance indices obtained from annual research trawl surveys are an integral part of fisheries stock assessment and management in the Great Lakes. It is difficult, however, to administer trawl surveys using a single vessel-gear combination owing to the large size of these systems, the jurisdictional boundaries that bisect the Great Lakes, and changes in vessels as a result of fleet replacement. When trawl surveys are administered by multiple vessel-gear combinations, systematic error may be introduced in combining catch-per-unit-effort (CPUE) data across vessels. This bias is associated with relative differences in catchability among vessel-gear combinations. In Lake Erie, five different research vessels conduct seasonal trawl surveys in the western half of the lake. To eliminate this systematic bias, the Lake Erie agencies conducted a side-by-side trawling experiment in 2003 to develop correction factors for CPUE data associated with different vessel-gear combinations. Correcting for systematic bias in CPUE data should lead to more accurate and comparable estimates of species density and biomass. We estimated correction factors for the 10 most commonly collected species age-groups for each vessel during the experiment. Most of the correction factors (70%) ranged from 0.5 to 2.0, indicating that the systematic bias associated with different vessel-gear combinations was not large. Differences in CPUE were most evident for vessels using different sampling gears, although significant differences also existed for vessels using the same gears. These results suggest that standardizing gear is important for multiple-vessel surveys, but there will still be significant differences in catchability stemming from the vessel effects and agencies must correct for this. With standardized estimates of CPUE, the Lake Erie agencies will have the ability to directly compare and combine time series for species abundance. ?? Copyright by the American Fisheries Society 2006.

Distribution of the Euryhaline Squid Lolliguncula brevis in Chesapeake Bay: Effects of Selected Abiotic Factors

DTIC Science & Technology

2002-01-31

salinity , water temperature, dissolved oxy- gen and water clarity. Since temporal variation in the Chesapeake Bay ecosystem is high, the effects of year...temperature (p ɘ.001; ψ = 2.42) had significant impacts on squid catch probability, although the effects were con- founded by a water temperature × salinity ...commonly encountered in such waters during VIMS Trawl Surveys The synergistic and independent effects of salinity , water temperature and dissolved oxygen

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.

[Taxonomic and functional diversity of the bycatch fishes community of trawl fishing from Northern Gulf of California, Mexico].

PubMed

Herrera-Valdivia, Eloísa; López-Martínez, Juana; Castillo Vargasmachuca, Sergio; García-Juárez, Rosa

2016-06-01

The Northern Gulf of California (NGC) is a mega diverse area of high endemism with major economic interest because of the multi-specific fisheries developed, mainly shrimp. There is a lack of recent studies on bycatch fish assemblages, so during the fishing seasons from 2009-2010 and 2010-2011, on board 13 shrimp boats, 14 commercial fishing trips were performed from 5 m - 90 m in depth with a total of 119 catches. The 119 catches were analyzed to assess fish community structure using taxonomic diversity indices to detect changes in the community following the taxonomic distinctness average Δ+ and the diversity index Δ* (TAXDEST of the PRIMER v6 program). To confirm the structure of functional groups, we considered similarities of ecologic and morphologic traits among species. The results showed that the indices Δ+ and Δ* were within the expected average and confidence intervals at 95%, finding significant differences between the indices. The analyses showed a well-structured community because of the great variety of forms and functions of the species within the community. In the community of the functional groups, reproduction was the ecological attribute that contributed the most to their structure. The community structure was represented by intermediate trophic levels (3-3.9), preferably primary and secondary carnivores within the trophic categories of predators of benthic ichthyo-fauna that belong to demersal species of soft bottoms and mostly fusiform body. To conclude, the NGC showed high functional redundancy according to the estimated functional groups, thus the ecosystem was considered stable and with great diversity. This type of studies should be followed using fishing and environmental effort due to the great biological and ecologic importance in the area.

First description of a Lophelia pertusa reef complex in Atlantic Canada

NASA Astrophysics Data System (ADS)

Buhl-Mortensen, Pål; Gordon, Don C.; Buhl-Mortensen, Lene; Kulka, Dave W.

2017-08-01

For the first time, we describe a cold-water coral reef complex in Atlantic Canada, discovered at the shelf break, in the mouth of the Laurentian Channel. The study is based on underwater video and sidescan sonar. The reef complex covered an area of approximately 490×1300 m, at 280-400 m depth. It consisted of several small mounds (< 3 m high) where the scleractinian Lophelia pertusa occurred as live colonies, dead blocks and skeletal rubble. On the mounds, a total of 67 live colonies occurred within 14 patches at 300-320 m depth. Most of these (67%) were small (< 20 cm high). Dead coral (rubble and blocks), dominated (88% of all coral observations). Extensive signs of damage by bottom-fishing gear were observed: broken and tilted coral colonies, over-turned boulders and lost fishing gear. Fisheries observer data indicated that the reef complex was subjected to heavy otter trawling annually between 1980 and 2000. In June 2004, a 15 km2 conservation area excluding all bottom-fishing was established. Current bottom fisheries outside the closure include otter trawling for redfish and anchored longlines for halibut. Vessel monitoring system data indicate that the closure is generally respected by the fishing industry.

50 CFR Figure 26 to Part 679 - Modified Nonpelagic Trawl Gear

Code of Federal Regulations, 2014 CFR

2014-10-01

... § 679.24(f). The top image shows the location of the end elevating devices in the elevated section for gear with net bridles no greater than 185 feet in length. The bottom image shows the location of the...

Use of classification trees to apportion single echo detections to species: Application to the pelagic fish community of Lake Superior

USGS Publications Warehouse

Yule, Daniel L.; Adams, Jean V.; Hrabik, Thomas R.; Vinson, Mark R.; Woiak, Zebadiah; Ahrenstroff, Tyler D.

2013-01-01

Acoustic methods are used to estimate the density of pelagic fish in large lakes with results of midwater trawling used to assign species composition. Apportionment in lakes having mixed species can be challenging because only a small fraction of the water sampled acoustically is sampled with trawl gear. Here we describe a new method where single echo detections (SEDs) are assigned to species based on classification tree models developed from catch data that separate species based on fish size and the spatial habitats they occupy. During the summer of 2011, we conducted a spatially-balanced lake-wide acoustic and midwater trawl survey of Lake Superior. A total of 51 sites in four bathymetric depth strata (0–30 m, 30–100 m, 100–200 m, and >200 m) were sampled. We developed classification tree models for each stratum and found fish length was the most important variable for separating species. To apply these trees to the acoustic data, we needed to identify a target strength to length (TS-to-L) relationship appropriate for all abundant Lake Superior pelagic species. We tested performance of 7 general (i.e., multi-species) relationships derived from three published studies. The best-performing relationship was identified by comparing predicted and observed catch compositions using a second independent Lake Superior data set. Once identified, the relationship was used to predict lengths of SEDs from the lake-wide survey, and the classification tree models were used to assign each SED to a species. Exotic rainbow smelt (Osmerus mordax) were the most common species at bathymetric depths 100 m (384 million; 6.0 kt). Cisco (Coregonus artedi) were widely distributed over all strata with their population estimated at 182 million (44 kt). The apportionment method we describe should be transferable to other large lakes provided fish are not tightly aggregated, and an appropriate TS-to-L relationship for abundant pelagic fish species can be determined.

Trawling-induced alterations of deep-sea sediment accumulation rates during the Anthropocene

NASA Astrophysics Data System (ADS)

Puig, P.; Paradis, S.; Masque, P.; Martin, J.; Juan, X.; Palanques, A.

2015-12-01

Commercial bottom trawling causes direct physical disturbance of the marine sedimentary environments by scraping and ploughing the seabed, generating periodic resuspension of surface sediments. However, the quantification of the sediment that is removed by trawling and exported across the continental margin remains largely unaddressed, and the preservation of the signal of such impacts in the geological record have been mostly overlooked. The analysis of sediment cores collected along the Catalan margin (NW Mediterranean) has allowed evaluating the contribution of this anthropogenic activity to the present-day sediment dynamics. Sediment cores at intensively trawled sites are characterized by over-consolidated sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sedimentary deposits. In turn, combined 210Pb and 137Cs chronologies indicate a significant increase of sediment accumulation rates within submarine canyon environments since the 1970s, coincidently with a strong impulse in the industrialization of the trawling fleets of this region. Two sampling sites that exhibited high sediment accumulation rates (0.6-0.7 cm/y) were reoccupied 1-2 decades after the first studies and revealed a second and even larger increase of sediment accumulation rates (>2 cm/y) occurring at the beginning of the XXI century. This recent change has been attributed to a preferential displacement of the trawling fleet towards fishing grounds surrounding submarine canyons and, also, to technical improvements in trawling vessels, presumably related to financial subsidies provided to the fishing sector. The alteration of sediment accumulation rates described in this continental margin may occur in many regions of the World's oceans given the wide geographical distribution of this human activity, and therefore, it could represent a potential marker of the Anthropocene in deep-sea environments.

Overwintering Habitats of Migratory Juvenile American Shad in Chesapeake Bay

EPA Science Inventory

We describe overwintering habitats of age-0 American shad in the lower Chesapeake Bay estuary through analyses of multiple, complementary data sets, including bottom-trawls of the Virginia portion of Chesapeake Bay and its tributaries, stable isotope analysis of American shad a...

Change in diel catchability of young-of-year yellow perch associated with establishment of dreissenid mussels

USGS Publications Warehouse

Stapanian, Martin A.; Kocovsky, Patrick M.; Adams, Jean V.

2009-01-01

1. Non-native mussels have increased water clarity in many lakes and streams in North America and Europe. Diel variation in catchability of some fish species has been linked to visibility during survey trawls (used to measure escapement). 2. Water clarity increased in nearshore areas of western Lake Erie by the early 1990s, following passage of legislation in 1972 to improve water quality (e.g. reduce phosphorus loading) and the invasion of dreissenid mussels (Dreissena spp.) beginning in 1987. 3. We hypothesised that increased water clarity in Lake Erie resulted in decreased catchability of young-of-year (age-0) yellow perch (Perca flavescens Mitchill) during daylight compared to during night. We used a two-tiered modelling approach to test this hypothesis on the ratio (R) of catch per hour (CPH) during night to CPH during daylight in bottom trawl surveys conducted during 1961-2005. 4. First, we examined seven a priori models. The first model, the 'null' model, represented no change in R over time. Three more models tested whether the timing of the change in R was associated with passage of water quality legislation only, dreissenids only (two-period models) and both legislation and dreissenids (three-period models). Three additional models included a 3-year lag before the effects of legislation, dreissenids or both occurred. Secondly, all possible two- and three-period models with a minimum of 2 years per time period were explored a posteriori. The a posteriori procedure determined the temporal transitions to higher R that were best supported by the data, without regard to a priori hypotheses. 5. Night CPH was greater than daylight CPH in 3 of 11 years during 1961-72, in 10 of 15 years during 1973-87, and in 14 of 18 years during 1988-2005. During 1991-2005 night CPH exceeded daylight CPH in all years except one, and night CPH was more than twice daylight CPH in 10 years during this period. 6. The best a priori model had two periods, with a break between 1990 and 1991, corresponding to 3 years after the dreissenid invasion. Similarly, the best two- and three-period a posteriori models both had breaks between 1990 and 1991. The results supported our hypothesis that age-0 yellow perch exhibited a transition to lower catchability during daylight compared to night, and the timing of the transition coincided with the establishment of dreissenid mussels. 7. The most plausible mechanism for our results was increased visibility of the trawl during daylight, resulting in increased avoidance of the trawl. These results have potential applications wherever non-native mussels have increased water clarity.

50 CFR 648.84 - Gear-marking requirements and gear restrictions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... extension of a rope separator trawl must be 6-inch (15.2-cm) diamond mesh or 6.5-inch (16.5-cm) square mesh, or any combination thereof. Mesh in the bottom belly of the net must be 13-inch (33-cm) diamond mesh...

50 CFR 648.84 - Gear-marking requirements and gear restrictions.

Code of Federal Regulations, 2013 CFR

2013-10-01

... extension of a rope separator trawl must be 6-inch (15.2-cm) diamond mesh or 6.5-inch (16.5-cm) square mesh, or any combination thereof. Mesh in the bottom belly of the net must be 13-inch (33-cm) diamond mesh...

Indexing the relative abundance of age-0 white sturgeons in an impoundment of the lower Columbia River from highly skewed trawling data

USGS Publications Warehouse

Counihan, T.D.; Miller, Allen I.; Parsley, M.J.

1999-01-01

The development of recruitment monitoring programs for age-0 white sturgeons Acipenser transmontanus is complicated by the statistical properties of catch-per-unit-effort (CPUE) data. We found that age-0 CPUE distributions from bottom trawl surveys violated assumptions of statistical procedures based on normal probability theory. Further, no single data transformation uniformly satisfied these assumptions because CPUE distribution properties varied with the sample mean (??(CPUE)). Given these analytic problems, we propose that an additional index of age-0 white sturgeon relative abundance, the proportion of positive tows (Ep), be used to estimate sample sizes before conducting age-0 recruitment surveys and to evaluate statistical hypothesis tests comparing the relative abundance of age-0 white sturgeons among years. Monte Carlo simulations indicated that Ep was consistently more precise than ??(CPUE), and because Ep is binomially rather than normally distributed, surveys can be planned and analyzed without violating the assumptions of procedures based on normal probability theory. However, we show that Ep may underestimate changes in relative abundance at high levels and confound our ability to quantify responses to management actions if relative abundance is consistently high. If data suggest that most samples will contain age-0 white sturgeons, estimators of relative abundance other than Ep should be considered. Because Ep may also obscure correlations to climatic and hydrologic variables if high abundance levels are present in time series data, we recommend ??(CPUE) be used to describe relations to environmental variables. The use of both Ep and ??(CPUE) will facilitate the evaluation of hypothesis tests comparing relative abundance levels and correlations to variables affecting age-0 recruitment. Estimated sample sizes for surveys should therefore be based on detecting predetermined differences in Ep, but data necessary to calculate ??(CPUE) should also be collected.

Abundance and tidal behaviour of pelagic fish in the gateway to the Wadden Sea

NASA Astrophysics Data System (ADS)

Couperus, Bram; Gastauer, Sven; Fässler, Sascha M. M.; Tulp, Ingrid; van der Veer, Henk W.; Poos, Jan Jaap

2016-03-01

The shallow coast of The Netherlands is an important habitat for small pelagic fish. They form one of the major links between plankton and the higher trophic levels. Predatory fish, sea mammals and birds rely on small pelagic fish as a major food source. Currently, monitoring of fish in the Dutch coastal zone mainly focuses on demersal species, using bottom trawls and fykes. Four hydro-acoustic surveys were carried out in May and October 2010/2011 in the Marsdiep area, a relatively deep tidal inlet in the western Wadden Sea, to quantify abundances of pelagic fish. The aims of this study were to (1) describe temporal and vertical variations in fish distribution and school dimensions in relation to tide, and (2) estimate biomass of pelagic fish and their proportion to total fish biomass. The biomass of pelagic fish in the Marsdiep area ranged between 23 and 411 kg/ha. These were mainly sprat, but also young herring, anchovy and pilchard. The fish was scattered in small schools with volumes smaller than 5m3 and concentrated in the top 10 m below the surface. There was a clear effect of tidal cycle on school volume and fish abundance, with larger densities and larger schools at high tide compared to low tide. In May, sandeel contributed substantially to the pelagic assemblage, whereas in October sandeel was absent in the trawl catches, most likely because they stayed buried in the seabed from late summer to spring. The presence of pilchard and anchovy confirmed their re-establishment in the Southern North Sea and Wadden Sea. The abundance of pelagic fish exceeded the biomass of demersal fish in the western Wadden Sea by an order of magnitude. This finding is relevant for ecosystem studies. The fact that this study suggests that small pelagics outnumber demersal species to such a large extent calls for a rethinking of the allocation of monitoring effort in the Dutch coastal zone.

Comparing Trawl and Creel Fishing for Norway Lobster (Nephrops norvegicus): Biological and Economic Considerations

PubMed Central

Leocádio, Ana Maria; Castro, Margarida

2012-01-01

This study compares the fishing activity and landings of the trawl and creel fisheries for Norway lobster (Nephrops norvegicus (L.)) off the Portuguese coast, and evaluates the financial viability of two vessels typical of each fleet. Crustacean trawlers are part of an industrial fleet that, besides Nephrops, targets deep water shrimps. Creels are used by a multi-gear, multi-target artisanal fleet, fishing only in areas unavailable to trawlers and, when catching Nephrops, set specifically to target this species. Trawlers have in recent years contributed with 85% of the landings in weight, but only 74% in value (2005–2009 average). Despite smaller landings, the Nephrops creel fishery provides individuals of larger size and in better condition, thereby obtaining higher unit prices. Economic viability was also higher for the creel vessel, with trawling being only viable if major costs (such as labor and fuel) are covered by the revenue from other target species (e.g., the rose shrimp). At present, Nephrops populations on the South and SW coast are subject to intense fishing and to a recovery plan. The possibility of reallocation of some of the fishing effort directed at Nephrops from trawlers to creels is discussed in terms of the conservation of the resource and economic return. PMID:22848357

Linking hydrodynamic complexity to delta smelt (Hypomesus transpacificus) distribution in the San Francisco Estuary, USA

USGS Publications Warehouse

Bever, Aaron J.; MacWilliams, Michael L.; Herbold, Bruce; Brown, Larry R.; Feyrer, Frederick V.

2016-01-01

Long-term fish sampling data from the San Francisco Estuary were combined with detailed three dimensional hydrodynamic modeling to investigate the relationship between historical fish catch and hydrodynamic complexity. Delta Smelt catch data at 45 stations from the Fall Midwater Trawl (FMWT) survey in the vicinity of Suisun Bay were used to develop a quantitative catch-based station index. This index was used to rank stations based on historical Delta Smelt catch. The correlations between historical Delta Smelt catch and 35 quantitative metrics of environmental complexity were evaluated at each station. Eight metrics of environmental conditions were derived from FMWT data and 27 metrics were derived from model predictions at each FMWT station. To relate the station index to conceptual models of Delta Smelt habitat, the metrics were used to predict the station ranking based on the quantified environmental conditions. Salinity, current speed, and turbidity metrics were used to predict the relative ranking of each station for Delta Smelt catch. Including a measure of the current speed at each station improved predictions of the historical ranking for Delta Smelt catch relative to similar predictions made using only salinity and turbidity. Current speed was also found to be a better predictor of historical Delta Smelt catch than water depth. The quantitative approach developed using the FMWT data was validated using the Delta Smelt catch data from the San Francisco Bay Study. Complexity metrics in Suisun Bay were-evaluated during 2010 and 2011. This analysis indicated that a key to historical Delta Smelt catch is the overlap of low salinity, low maximum velocity, and low Secchi depth regions. This overlap occurred in Suisun Bay during 2011, and may have contributed to higher Delta Smelt abundance in 2011 than in 2010 when the favorable ranges of the metrics did not overlap in Suisun Bay.

Differences in habitat selection of male and female megrim ( Lepidorhombus whiffiagonis, Walbaum) to the west of Ireland. A result of differences in life-history strategies between the sexes?

NASA Astrophysics Data System (ADS)

Gerritsen, H. D.; McGrath, D.; Lordan, C.; Harlay, X.

2010-11-01

The sex ratio in the catches of megrim ( Lepidorhombus whiffiagonis, Walbaum) varied systematically with depth on three independent trawl survey series off the west coast of Ireland. Female megrim dominated the shallow catches, while males were more common in catches from deeper waters. The size difference between the sexes alone cannot explain this pattern because it remained evident when fish length was taken into account. Therefore size-specific habitat preferences or size-selective fishing mortality cannot fully explain the observed trend in the sex ratio of megrim. Female megrim grow to a larger size, at a faster rate than males and it is likely that their differences in habitat preferences are related to this. Shallower waters are warmer during the growing season and are likely to provide better conditions for fast growth. An understanding of the mechanisms behind these patterns is an important consideration in the management and conservation of this fish stock, which might be particularly vulnerable because the commercial landings are to a large extent dominated by female megrim.

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.

The Use of a Predictive Habitat Model and a Fuzzy Logic Approach for Marine Management and Planning

PubMed Central

Hattab, Tarek; Ben Rais Lasram, Frida; Albouy, Camille; Sammari, Chérif; Romdhane, Mohamed Salah; Cury, Philippe; Leprieur, Fabien; Le Loc’h, François

2013-01-01

Bottom trawl survey data are commonly used as a sampling technique to assess the spatial distribution of commercial species. However, this sampling technique does not always correctly detect a species even when it is present, and this can create significant limitations when fitting species distribution models. In this study, we aim to test the relevance of a mixed methodological approach that combines presence-only and presence-absence distribution models. We illustrate this approach using bottom trawl survey data to model the spatial distributions of 27 commercially targeted marine species. We use an environmentally- and geographically-weighted method to simulate pseudo-absence data. The species distributions are modelled using regression kriging, a technique that explicitly incorporates spatial dependence into predictions. Model outputs are then used to identify areas that met the conservation targets for the deployment of artificial anti-trawling reefs. To achieve this, we propose the use of a fuzzy logic framework that accounts for the uncertainty associated with different model predictions. For each species, the predictive accuracy of the model is classified as ‘high’. A better result is observed when a large number of occurrences are used to develop the model. The map resulting from the fuzzy overlay shows that three main areas have a high level of agreement with the conservation criteria. These results align with expert opinion, confirming the relevance of the proposed methodology in this study. PMID:24146867

Deepwater sculpin status and recovery in Lake Ontario

USGS Publications Warehouse

Weidel, Brian C.; Walsh, Maureen; Connerton, Michael J.; Lantry, Brian F.; Lantry, Jana R.; Holden, Jeremy P.; Yuille, Michael J.; Hoyle, James A.

2017-01-01

Deepwater sculpin are important in oligotrophic lakes as one of the few fishes that use deep profundal habitats and link invertebrates in those habitats to piscivores. In Lake Ontario the species was once abundant, however drastic declines in the mid-1900s led some to suggest the species had been extirpated and ultimately led Canadian and U.S. agencies to elevate the species' conservation status. Following two decades of surveys with no captures, deepwater sculpin were first caught in low numbers in 1996 and by the early 2000s there were indications of population recovery. We updated the status of Lake Ontario deepwater sculpin through 2016 to inform resource management and conservation. Our data set was comprised of 8431 bottom trawls sampled from 1996 to 2016, in U.S. and Canadian waters spanning depths from 5 to 225 m. Annual density estimates generally increased from 1996 through 2016, and an exponential model estimated the rate of population increase was ~ 59% per year. The mean total length and the proportion of fish greater than the estimated length at maturation (~ 116 mm) generally increased until a peak in 2013. In addition, the mean length of all deepwater sculpin captured in a trawl significantly increased with depth. Across all years examined, deepwater sculpin densities generally increased with depth, increasing sharply at depths > 150 m. Bottom trawl observations suggest the Lake Ontario deepwater sculpin population has recovered and current densities and biomass densities may now be similar to the other Great Lakes.

Dynamics of alewives in Lake Ontario following a mass mortality

USGS Publications Warehouse

O'Gorman, Robert; Schneider, Clifford P.

1986-01-01

The U.S. Fish and Wildlife Service and the New York Department of Environmental Conservation assessed the population of alewives Alosa pseudoharengus in U.S. waters of Lake Ontario during 1976–1982 with bottom trawls. Alewives were abundant in 1976 but a die-off greatly reduced their numbers during the winter of 1976–1977. The population quickly recovered, however, adult abundance increasing nearly sevenfold during 1978–1981. In spring 1981 the bottom population in southern Lake Ontario was estimated to be 5.25 × 109 fish weighing 128,500 t. Estimated average alewife biomass per hectare during 1978–1982 far exceeded the estimates for either Lake Michigan during 1967–1982 or western Lake Huron during 1973–1982. Recruitment of age-II fish to the population was affected by abundance of adults in two ways: (1) the number of yearlings produced was directly related to adult abundance at low population levels but inversely related at high population levels; and (2) survival of yearlings to age II was inversely related to adult abundance. Growth in 1977 was exceptional, leaving a wide, unmistakable band on scales of the previously slow-growing adults. This wide growth zone served as a marker to identify survivors of the 1976–1977 die-off and to show that each year after 1978 a successively larger proportion of survivors was failing to grow in length or to form an annulus (54% in 1979, 96% in 1980, and 100% in 1981). There was no marker on scales of alewives recruited after the die-off, but the apparent age composition of our catches strongly suggested that most of them also failed to grow in 1981.

Interactions between a Trawl Fishery and Spatial Closures for Biodiversity Conservation in the Great Barrier Reef World Heritage Area, Australia

PubMed Central

Grech, Alana; Coles, Rob

2011-01-01

Background The Queensland East Coast Otter Trawl Fishery (ECOTF) for penaeid shrimp fishes within Australia's Great Barrier Reef World Heritage Area (GBRWHA). The past decade has seen the implementation of conservation and fisheries management strategies to reduce the impact of the ECOTF on the seabed and improve biodiversity conservation. New information from electronic vessel location monitoring systems (VMS) provides an opportunity to review the interactions between the ECOTF and spatial closures for biodiversity conservation. Methodology and Results We used fishing metrics and spatial information on the distribution of closures and modelled VMS data in a geographical information system (GIS) to assess change in effort of the trawl fishery from 2001–2009 and to quantify the exposure of 70 reef, non-reef and deep water bioregions to trawl fishing. The number of trawlers and the number of days fished almost halved between 2001 and 2009 and new spatial closures introduced in 2004 reduced the area zoned available for trawl fishing by 33%. However, we found that there was only a relatively minor change in the spatial footprint of the fishery as a result of new spatial closures. Non-reef bioregions benefited the most from new spatial closures followed by deep and reef bioregions. Conclusions/Significance Although the catch of non target species remains an issue of concern for fisheries management, the small spatial footprint of the ECOTF relative to the size of the GBRWHA means that the impact on benthic habitats is likely to be negligible. The decline in effort as a result of fishing industry structural adjustment, increasing variable costs and business decisions of fishers is likely to continue a trend to fish only in the most productive areas. This will provide protection for most benthic habitats without any further legislative or management intervention. PMID:21695155

Benthic habitat characterisation of soft-bottom continental shelves: Integration of acoustic surveys, benthic samples and trawling disturbance intensity

NASA Astrophysics Data System (ADS)

de Juan, S.; Lo Iacono, C.; Demestre, M.

2013-01-01

Eleven sites were located on Mediterranean continental shelves to explore the link between the physical characteristics and epibenthic fauna from soft-sediment habitats. These sites, at 32-82 m in depth, were associated with fishing grounds and the trawling intensity was estimated at the site scale to assess the effects of trawling on benthic communities. Each site was surveyed with Multi-Beam (bathymetry and backscatter), side-scan sonar, benthic grabs and a surface dredge. The sites were clustered in three habitat types. Habitat 1, with moderate trawling disturbance, was characterised by homogeneous mud and associated epifauna that was also highly homogeneous across sites. Habitat 2, with sandy mud and scattered gravel and rocks, had a high abundance of sessile suspension feeders that probably attach to the coarser substratum and benefit from the low fishing disturbance in these sites. Habitat 3 included sites with heterogeneous sediments with maërl as the prevailing biocenosis and having the highest species richness, despite being subjected to variable trawling intensity. Statistical models were used to relate environmental parameters and the species abundance. More than 3 physical variables were necessary to explain the epifaunal patterns across sites, including the percentage of mud, sediment heterogeneity and fishing effort. These analyses are an essential step for extrapolating information from benthic samples to the larger scale of habitats, mapped through acoustic surveys. Despite this, a good integration is required between the mapping of physical habitat distribution and the ecological knowledge of communities.

Biases in determining the diet of jumbo squid Dosidicus gigas (D' Orbigny 1835) (Cephalopoda: Ommastrephidae) off southern-central Chile (34°S-40°S)

NASA Astrophysics Data System (ADS)

Ibáñez, Christian M.; Arancibia, Hugo; Cubillos, Luis A.

2008-12-01

The diet of jumbo squid ( Dosidicus gigas) off southern-central Chile is described to examine potential biases in the determination of their main prey. Specimens were collected from catches using different fishing gear (jigging, trawl and purse-seine), from July 2003 to January 2004, and from December 2005 to October 2006. The stomach contents were analyzed in terms of frequency of occurrence, number, and weight of prey items and the diet composition was analyzed using Detrended Correspondence Analysis. In the industrial purse-seine fleet for jack mackerel ( Trachurus murphyi), the dominant prey of D. gigas was T. murphyi. In the industrial mid-trawl fishery for Patagonian grenadier ( Macruronus magellanicus), the dominant species in the diet of D. gigas was M. magellanicus. Similarly, Chilean hake ( Merluccius gayi) was the main prey in the diet of D. gigas obtained in the industrial trawl fishery for Chilean hake; and, in both artisanal fisheries (purse-seine for small pelagics and jigging), small pelagic fish and D. gigas were the main prey in the stomach contents of D. gigas. Cannibalism in D. gigas varied between different fleets and probably is related to stress behavior during fishing. The Detrended Correspondence Analysis ordination showed that the main prey in the diet of D. gigas is associated with the target species of the respective fishery. Consequently, biases are associated with fishing gear, leading to an overestimate in the occurrence of the target species in the diet. We recommend analyzing samples from jigging taken at the same time and place where the trawl and purse-seine fleets are operating to avoid this problem, and the application of new tools like stable isotope, heavy metal, and fatty acid signature analyses.

A Drosera-bioinspired hydrogel for catching and killing cancer cells

PubMed Central

Li, Shihui; Chen, Niancao; Gaddes, Erin R.; Zhang, Xiaolong; Dong, Cheng; Wang, Yong

2015-01-01

A variety of bioinspired materials have been successfully synthesized to mimic the sophisticated structures or functions of biological systems. However, it is still challenging to develop materials with multiple functions that can be performed synergistically or sequentially. The purpose of this work was to demonstrate a novel bioinspired hydrogel that can interact with cancer cells, functionally similar to Drosera in catching and killing prey. This hydrogel had two layers with the top one functionalized with oligonucleotide aptamers and the bottom one functionalized with double-stranded DNA. The results show that the top hydrogel layer was able to catch target cells with high efficiency and specificity, and that the bottom hydrogel layer could sequester doxorubicin (Dox) for sustained drug release. Importantly, the released Dox could kill 90% of the cells after 1-h residence of the cells on the hydrogel. After the cell release, this bifunctional hydrogel could be regenerated for continuous cell catching and killing. Therefore, the data presented in this study has successfully demonstrated the potential of developing a material system with the functions of attracting, catching and killing diseased cells (e.g., circulating tumor cells) or even invading microorganisms (e.g., bacteria). PMID:26396063

Effects of experimental otter trawling on benthic assemblages on Western Bank, northwest Atlantic Ocean

NASA Astrophysics Data System (ADS)

Kenchington, Ellen L. R.; Gilkinson, Kent D.; MacIsaac, Kevin G.; Bourbonnais-Boyce, Cynthia; Kenchington, Trevor J.; Smith, Stephen J.; Gordon, Donald C., Jr.

2006-10-01

The effects of otter trawling on a hard-bottom ecosystem on Western Bank on Canada's Scotian Shelf were examined experimentally from 1997 to 1999 with an asymmetrical BACI design. The site was located within an area that had been closed to fishing since 1987 to protect juvenile haddock. An experimental line was trawled 12-14 times on three separate occasions over a 20 month period. The benthic macrofauna and megafauna were sampled before and after trawling on both impact and control lines with both a grab and a photographic system. The 100 grab samples collected contained 341 taxa, primarily polychaetes, amphipods and molluscs, the majority (60%) of which were epifaunal. Biomass was dominated by the horse-mussel Modiolus modiolus, a long-lived bivalve, while the tube-building amphipod Ericthonius fasciatus was the most abundant species. Through the study period the benthos on the control lines showed little qualitative or quantitative change in individual taxa or community metrics. However, the abundance of 24 individual taxa (polychaetes, amphipods, echinoderms and molluscs) changed significantly, with the majority of these increasing. This resulted in a significantly different relative abundance of taxa between years as detected through ANOSIM. A significant change in relative biomass amongst the taxa was also observed. Trawling had few detectable immediate effects on the abundance or biomass of individual taxa and none on community composition. A few taxa, primarily a mixture of polychaetes and amphipods, decreased significantly after trawling and data from fish stomachs collected during the experiment (Kenchington, E.L., Gordon Jr., D.C., Bourbonnais-Boyce, C., MacIsaac, K.G., Gilkinson, K.D., McKeown, D.L., Vass, W.P., 2005. Effects of experimental otter trawling on the feeding of demersal fish on Western Bank, Nova Scotia. Amer. Fish. Soc. Symp. 41, 391-409) showed that some of these were scavenged by demersal fish. Fifteen taxa showed significant decreases after trawling when the cumulative effects of trawling were considered. As in the analyses of individual years the species affected were primarily high turn-over species such as polychaetes and amphipods. Dominance curves prepared for both control and impact samples before trawling in 1997 and after trawling in 1999 showed a marked decrease in the biomass values of the highest ranking taxa, particularly of the first species, M. modiolus, only on the impact line at the conclusion of the experiment. The proportion of epifaunal biomass also declined significantly from 90% to 77% on the impact line by the conclusion of the experiment. These changes are in part due to trawl-induced damage and subsequent predation by demersal fish of the top ranking species. Analysis of the photographic images showed that the three top-ranking species in terms of biomass, M. modiolus, the tube-building polychaete Thelepus cincinnatus, and the brachiopod Terebratulina septentrionalis, were visibly damaged more than other species by the trawl gear. Two of these species, M. modiolus and T. cincinnatus, were preyed upon by scavenging demersal fish. The use of multiple sampling devices at the experimental site (grab, photographic system reported here and trawl and fish stomachs reported by Kenchington, E.L., Gordon Jr., D.C., Bourbonnais-Boyce, C., MacIsaac, K.G., Gilkinson, K.D., McKeown, D.L., Vass, W.P., 2005. Effects of experimental otter trawling on the feeding of demersal fish on Western Bank, Nova Scotia. Amer. Fish. Soc. Symp. 41, 391-409) enabled us to link trawl-induced changes to the benthos to predation by demersal fish.

A knowledge platform to inform on the effects of trawling on benthic communities

NASA Astrophysics Data System (ADS)

Muntadas, Alba; Lample, Michel; Demestre, Montserrat; Ballé-Béganton, Johanna; de Juan, Silvia; Maynou, Francesc; Bailly, Denis

2018-02-01

For a successful implementation of an Ecosystem Approach to Fisheries (EAF) management, it is necessary that all stakeholders involved in fisheries management are aware of the implications of fishing impacts on ecosystems and agree with the adopted measures to mitigate these impacts. In this context, there is a need for tools to share knowledge on the ecosystem effects of fisheries among these stakeholders. When managing bottom trawl fisheries under an EAF framework, one of the main concerns is the direct and indirect consequences of trawling impacts on benthic ecosystems. We developed a platform using the ExtendSim® software with a user-friendly interface that combines a simulation model based on existing knowledge, data collection and representation of predicted trawling impacts on the seabed. The platform aims to be a deliberation support tool for fisheries' stakeholders and, simultaneously, raise public awareness of the need for good benthic community knowledge to appropriately inform EAF management plans. The simulation procedure assumes that trawling affects benthic communities with an intensity that depends on the level of fishing effort exerted on benthic communities and on the habitat characteristics (i.e. sediment grain size). Data to build the simulation comes from epifaunal samples from 18 study sites located in Mediterranean continental shelves subjected to different levels of fishing effort. In this work, we present the simulation outputs of a 50% fishing effort increase (and decrease) in four of the study sites which cover different habitats and different levels of fishing effort. We discuss the platform strengths and weaknesses and potential future developments.

Impact of natural (storm) and anthropogenic (trawling) sediment resuspension on particulate organic matter in coastal environments

NASA Astrophysics Data System (ADS)

Pusceddu, A.; Grémare, A.; Escoubeyrou, K.; Amouroux, J. M.; Fiordelmondo, C.; Danovaro, R.

2005-12-01

In order to assess the impact of natural and anthropogenic sediment resuspension on quantity, biochemical composition and bioavailability of particulate organic matter (POM), two field investigations were carried out in two shallow coastal areas of the Mediterranean Sea. In the Gulf of Lions, we investigated the impact of a storm resuspension of sediment, whereas in the Thermaikos Gulf we investigated the impact of bottom trawling. Resuspension in the Gulf of Lions determined the increase of sedimentation rates, modified the composition of the organic fraction of settling particles and decreased the labile fraction of POM, as indicated by a drop in the enzymatically hydrolysable amino acid fraction. The increase in the refractory fraction, following short-term storm-induced resuspension, increased also the contribution of glycine and decreased the contribution of aspartic acid contents to the total amino acid pools. Trawling activities in Thermaikos Gulf determined a significant increase in suspended POM concentrations and important changes in its biochemical composition. After trawling, the protein to carbohydrate ratio decreased (as a result of a major input of sedimentary carbohydrates at the water-sediment interface) and the fraction of enzymatically hydrolysable biopolymeric C decreased by ≈30%, thus reducing the bioavailability of resuspended organic particles. Results of the present study indicate that changes in suspended POM, induced by storms and trawling activities, can have similar consequences on benthic systems and on food webs. In fact, the potential benefit of increased organic particle concentration for suspension feeders, is depressed by the shift of suspended food particles towards a more refractory composition.

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.

Changes in fish diversity and community structure in the central and southern Yellow Sea from 2003 to 2015

NASA Astrophysics Data System (ADS)

Chen, Yunlong; Shan, Xiujuan; Jin, Xianshi; Johannessen, Arne; Yang, Tao; Dai, Fangqun

2017-07-01

The central and southern Yellow Sea is an important overwintering ground for many fish species in the Bohai Sea and Yellow Sea. For better understanding the status of the fish community after years of heavy exploitation, variations in fish community structure and diversity were analyzed using data from bottom trawls during 2003-2015. Five fish assemblage indices all showed fluctuations without clear trends from 2003 to 2015, yet there were strong positive and significant correlations (P < 0.05) among them. The top-five dominant species accounted for a high weight percentage (49.7%-82.1%) in the annual fish catch. Multivariate analysis showed that two year groups could be pooled for the fish community: Group I consisted of the years 2006, 2007, 2008 and 2015, while Group II consisted of the years 2003, 2004, 2005, 2009, 2010 and 2014; the groups aggregated with 63.71% similarity, indicating a high level of similarity among all years. The multivariate dispersion values were 1.455 and 0.818 for Groups I and II, respectively, indicating greater variances in fish assemblage structure in Group I than that in Group II. Similarity of percentage analysis demonstrated that the average similarities for Group I and Group II were 71.58% and 67.51%, respectively. Size-spectra analysis revealed no consistent trend in the intercept and slope (P > 0.05); there were also no significant differences between the slope of the size-spectra and fishing effort. The catch per unit effort and mean individual weight analyses of the whole fish assemblage both showed a significantly decreasing trend over time. Overall, the results showed that the fish community structure in the central and southern Yellow Sea was relatively stable from 2003 to 2015 and the study could be used as a reference for supporting ecosystem-based fishery management.

Comparison between ROV video and Agassiz trawl methods for sampling deep water fauna of submarine canyons in the Northwestern Mediterranean Sea with observations on behavioural reactions of target species

NASA Astrophysics Data System (ADS)

Ayma, A.; Aguzzi, J.; Canals, M.; Lastras, G.; Bahamon, N.; Mecho, A.; Company, J. B.

2016-08-01

In this paper we present a comparison between Remotely Operated Vehicle (ROV) and Agassiz trawling methods for sampling deep-water fauna in three submarine canyons of the Northwestern Mediterranean Sea and describe the behavioural reactions of fishes and crustacean decapods to ROV approach. 10 ROV dives, where 3583 individuals were observed and identified to species level, and 8 Agassiz trawls were carried out in a depth range of 750-1500 m. As noticed in previous studies, abundances of fishes and decapod crustaceans were much higher in the ROV videos than in Agassiz trawl samples, as the latter are designed for the retrieval of benthic, less motile species in permanent contact with the bottom. In our observations fish abundance was one order of magnitude higher with ROV (4110.22 ind/km2) than with Agassiz trawl (350.88 ind/km2), whereas decapod crustaceans were six times more abundant in ROV videos (6362.40 ind/km2) than in Agassiz samples (1364.52 ind/km2). The behaviour of highly motile fishes was analysed in terms of stationary positioning over the seafloor and avoidance or attraction to ROV approach. The most frequently occurring fish species Coelorinchus mediterraneus, Nezumia aequalis, Bathypterois dubius, Lepidion lepidion, Trachyrincuss scabrus and Polyacanthonotus rissoanus did not react to the presence of the ROV in most cases (>50%). Only B. dubius (11%), Lepidion lepidion (14.8%), P. rissoanus (41%) and T. scabrus (14.3%) reacted to ROV approach. More than 60% of less motile species, such as crustacean decapods, did not respond to ROV presence either. Only 33.3% of Geryon longipes, 36.2% of Munida spp. and 29.79% of Pagurus spp. were observed avoiding or defensively reacting to the ROV. The comparison of results obtained with ROV and trawl sampling is of ecological relevance since ROV can report observations in areas where trawling is technically unfeasible. The lack of reaction by most fish and crustacean decapod specimens further confirms that ROV surveying is an efficient technique to assess abundance and species composition in deep-sea waters for these motile species and questions trawl-based estimations.

Species composition and distribution of the Antarctic plunderfishes (Pisces, Artedidraconidae) from the Ross Sea off Victoria Land

NASA Astrophysics Data System (ADS)

La Mesa, Mario; Cattaneo-Vietti, Riccardo; Vacchi, Marino

2006-04-01

Among the notothenioid fish, the Antarctic plunderfishes (family Artedidraconidae) are a poorly known component of the bottom fauna of the continental shelf despite their relative importance. The family is composed of 25 small- to medium-sized endemic species and four genera, Artedidraco, Dolloidraco, Histiodraco and Pogonophryne, which are the most benthic and sedentary of the notothenioid fish. In the framework of "Victoria Land Transect Project", several samples of plunderfishes were collected by means of an Agassiz trawl. Sampling activities were carried out between 100 and 500 m depth in five sites over nearly 4° latitude off Victoria Land. Overall, trawling yielded 80 specimens of plunderfish, including all species of Artedidraco reported from the Ross Sea, i.e. Artedidraco glareobarbatus, A. loennbergi, A. orianae, A. shackletoni and A. skottsbergi, and the monotypic genus Histiodraco. The use of multivariate statistical analyses on catch data indicated sampling site as the main factor affecting species composition. Histiodraco velifer and A. skottsbergi were caught almost exclusively in the southernmost sites, characterizing the artedidraconid fauna of Cape Russell. A. orianae was sampled only in the northernmost sites, such as Cape Adare and Hallett Peninsula. A. loennbergi appeared to be a ubiquitous species, whereas A. glareobarbatus was caught only at the Hallett Peninsula. Plunderfishes showed a particular distribution pattern in relation to depth as well. A. glareobarbatus was the shallowest species, being sampled within 100 m. A. orianae and A. shackletoni showed a similar distribution, being caught mostly at 100-200 m, whereas A. skottsbergi was mainly sampled at 200-300 m. H. velifer was caught in a wide depth range, but mostly in deeper waters (400 m). A. loennbergi was eurybathic, showing a wider depth distribution than other species. Univariate measures of diversity indicated Cape Adare as the poorer site in terms of species richness and diversity. Number of species, diversity and equitability were quite similar off Hallett Peninsula and Cape Russell, indicating the absence of a latitudinal trend. Generally, all univariate indices decreased from shallow (100 m) to deep waters (500 m).

Status and trends of the Lake Huron offshore demersal fish community, 1976-2012

USGS Publications Warehouse

Roseman, Edward F.; Riley, Stephen C.; Farha, Steve A.; Maitland, Bryan M.; Tucker, Taaja R.; Provo, Stacy A.; McLean, Matthew W.

2015-01-01

The USGS Great Lakes Science Center has conducted trawl surveys to assess annual changes in the offshore demersal fish community of Lake Huron since 1973. Sample sites include five ports in U.S. waters with less frequent sampling near Goderich, Ontario. The 2012 fall bottom trawl survey was carried out between 20 October – 5 November 2012 and included all U.S. ports as well as Goderich, ON. The 2012 main basin prey fish biomass estimate for Lake Huron was 97 kilotonnes, higher than the estimate in 2011 (63.2 Kt), approximately one third of the maximum estimate in the time series, and nearly 6 times higher than the minimum estimate in 2009. The biomass estimates for adult alewife in 2012 were higher than 2011, but remained much lower than observed before the crash in 2004, and populations were dominated by small fish. Estimated biomass of rainbow smelt also increased and was the highest observed since 2005. Estimated adult bloater biomass in Lake Huron has been increasing in recent years, and the 2012 biomass estimate was the third highest ever observed in the survey. Biomass estimates for trout-perch and ninespine stickleback were higher than in 2011 but still remained low compared to historic estimates. The estimated biomass of deepwater and slimy sculpins increased over 2011, and slimy sculpin in particular seem to be increasing in abundance. The 2012 biomass estimate for round goby was similar to that in 2011 and was the highest observed in the survey. Substantial numbers of wild juvenile lake trout were captured again in 2012, suggesting that natural reproduction by lake trout continues to occur. The 2012 Lake Huron bottom trawl survey results suggest that several species of offshore demersal fish are beginning to increase in abundance.

Long-term change in a meso-predator community in response to prolonged and heterogeneous human impact

PubMed Central

Ferretti, Francesco; Osio, Giacomo C.; Jenkins, Chris J.; Rosenberg, Andrew A.; Lotze, Heike K.

2013-01-01

Sharks and rays' abundance can decline considerably with fishing. Community changes, however, are more complex because of species interactions, and variable vulnerability and exposure to fishing. We evaluated long-term changes in the elasmobranch community of the Adriatic Sea, a heavily exploited Mediterranean basin where top-predators have been strongly depleted historically, and fishing developed unevenly between the western and eastern side. Combining and standardizing catch data from five trawl surveys from 1948–2005, we estimated abundance trends and explained community changes using life histories, fish-market and effort data, and historical information. We identified a highly depleted elasmobranch community. Since 1948, catch rates have declined by >94% and 11 species ceased to be detected. The exploitation history and spatial gradients in fishing pressure explained most patterns in abundance and diversity, including the absence of strong compensatory increases. Ecological corridors and large-scale protected areas emerged as potential management options for elasmobranch conservation. PMID:23308344

Living macromolluscs from a paleo-reef region on the northeastern Venezuelan continental shelf

NASA Astrophysics Data System (ADS)

Buitrago, Joaquín; Capelo, Juan; Gutiérrez, Javier; Rada, Martín; Hernández, Ricardo; Grune, Sylvia

2006-02-01

Drowned reefs, fossil reefs or paleo-reefs, are important ecologically as areas of high biodiversity, foraging, shelter environment, and as areas supporting the spawning aggregations of economically important reef fish species. This is particularly significant when the structures are situated in a wide soft-bottom continental shelf. The presence of limestone structures, fossil reefs and pinnacles dating from circa 8 to 9 ka, to the north of the Paria Peninsula in north-eastern Venezuela, has been known to local fishermen for decades. Using echograms obtained during acoustic fisheries evaluations and the scarce previously available information, an improved location map of hard-bottom structures was made. Benthic samples to study macromolluscs were taken at depths between 54 and 93 m using an unmodified 2-m beam trawl. Four trawl samples were located over fossil reef areas while another four were situated in soft-bottom valleys between limestone structures. Fossil reefs in the area showed a highly patchy distribution. A total of 91 species from 43 Bivalvia, Gastropoda and Scaphopoda families were found, Gastropoda being the dominant class with 49 species. Paleo-reef-covered areas showed higher species richness and only 21% of the species found were common to both substrates. Gastropods Tonna maculosa and Polystira albida were the most abundant species and occurred in both substrate types. Bivalve life habits, a mixture of organism-substrate relationships, shell fixation, mobility and feeding type, differed significantly according to bottom type. Six species are recorded for the first time for eastern Venezuelan waters. Bottom heterogeneity plays an important role in marine ecosystems, providing shelter to fish populations and may be significant as breeding and nursery areas. Its presence in a region with biogeographical interest, situated in the confluence of three major provinces and with oceanographic conditions varying seasonally from upwelling dominated to Orinoco River discharges, makes this the area of interest and it should be evaluated as a possible Marine Protected Area.

At-vessel mortality of skates (Rajidae) taken in coastal fisheries and evidence of longer-term survival.

PubMed

Ellis, J R; Burt, G J; Grilli, G; McCully Phillips, S R; Catchpole, T L; Maxwell, D L

2018-06-01

Data on the vigour and at-vessel mortality (AVM) of 6798 skates (comprising Raja clavata n = 6295; R. brachyura n = 208; R. undulata n = 185, R. montagui n = 98 and R. microocellata n = 12) captured by commercial fishing vessels in the inshore waters of the southern North Sea and English Channel were recorded. AVM in longline fisheries averaged 0·44% across five vessels (0-1·47%), although skates were usually unhooked manually and did not usually pass through a bait-stripper. AVM in otter trawls averaged 0·76% (0-2·35%), from four vessels fishing with tow durations of <1·5 h (southern North Sea) or 1-4 h (English Channel). No AVM was noted for skates taken as a by-catch in drift trammel nets (soak times <4 h). Anchored tangle nets resulted in an overall AVM of 2·0-2·7%, but increased from 1·47% (13-28 h soak time) to 6·16% (42-53 h soak time). There were significant differences in the vigour of skates between gears, with R. clavata caught by longline and tangle nets in better condition than those captured by otter trawl or drift trammel net. Similarly, R. undulata caught by tangle net were in better condition than those caught by otter trawl. The vigour of R. undulata was also found to be higher than other skate species for both trawl and tangle net. In total, 5283 skates were tagged with Petersen discs and released, with recapture rates for the various combinations of vessel and gear ranging up to 24·8% for R. clavata. Whilst confirming a degree of post-release survival, quantitative estimates of post-release mortality for skates remain unknown. © 2018 Crown Copyright. Journal of Fish Biology © 2018 The Fisheries Society of the British Isles.

Status and trends of prey fish populations in Lake Superior, 2008

USGS Publications Warehouse

Gorman, Owen T.; Evrard, Lori M.; Cholwek, Gary A.; Falck, Jill M.; Yule, Daniel

2009-01-01

The Great Lakes Science Center has conducted annual daytime bottom trawl surveys of the Lake Superior nearshore (15-80 m bathymetric depth zone) every spring since 1978 to provide a long-term index of relative abundance and biomass of the fish community. Between May 5 and June 14, 2008, 58 stations were sampled around the perimeter of the lake with 12-m wide bottom trawls. Trawls were deployed cross-contour at median start and end depths of 17 and 55 m, respectively. The lakewide mean relative biomass estimate for the entire fish community was 4.61 kg/ha which was similar to that measured in 2007, 4.81 kg/ha. Dominant species in the catch were lake whitefish, rainbow smelt, longnose sucker and cisco, which represented 49, 18, 11, and 7 % of the total community biomass, respectively. Compared to 2007 levels, lake whitefish and cisco biomass increased 35% and 55%, respectively, while bloater and rainbow smelt biomass declined 69% and 41%, respectively. Increased biomass of lake whitefish and decreased biomass in bloater represent trends observed since 2007; however, reversed trends in biomass were observed for cisco and rainbow smelt. Year-class strength for the 2007 cisco cohort (0.20 fish/ha) was below the long-term (1977-2007) average (73.31 fish/ha), as was year-class strength for the 2007 bloater cohort (0.33 fish/ha) compared to the long-term average (11.11 fish/ha). Smelt year class strength (226.26 fish/ha) continues a trend of increasing strength from a 31-year low of 56.75 fish/ha in 2001 and was above the long-term average of 193.81 fish/ha. The 2008 cisco age structure was dominated by age 5 and older fish, which accounted for 82% of the mean relative density. Wisconsin waters continue to be the most productive (mean total community biomass of 17.09 kg/ha), followed by western Ontario (5.40 kg/ha), eastern Ontario (3.08 kg/ha), Michigan (2.82 kg/ha), and Minnesota (0.89 kg/ha).Densities of small (400 mm) hatchery lake trout continued a pattern of decline observed since 1993-1996 to 0.04, 0.03 and 0.01 fish/ha in 2008, respectively. Densities of small and large wild (lean) lake trout continued a decreasing trend observed since 1996-1998. From 2007 to 2008, density of small lean lake trout declined from 0.29 to 0.15 fish/ha, the lowest value since 1978. Density of large lean lake trout has been relatively stable since 1986 but more recently density declined from 0.43 fish/ha in 2006 to 0.10 fish/ha in 2008. Density of intermediate size lean lake trout showed a small increase from 0.31 in 2007 to 0.41 fish/ha in 2008. Siscowet lake trout have shown a pattern of variable but increasing density since 1980. Since 2006, densities of small and intermediate size siscowet lake trout have increased from 0.10 to 0.12 and 0.08 to 0.15 fish/ha, respectively. Densities of large siscowet lake trout have fluctuated between 0.10 and 0.07 fish/ha since 2000. In 2008 the proportions of total lake trout density that were hatchery, lean and siscowet were 8, 60, and 32%, respectively.

Brief notes on habitat geology and clay pipe habitat on Stellwagen Bank

USGS Publications Warehouse

Valentine, Page C.; Dorsey, Eleanor M.; Pederson, Judith

1998-01-01

In our studies of sea floor habitats, my colleagues and I use both biological and geological approaches. We call our studies “habitat geology,” a term coined by a biologist friend of mine. We view it as the study of sea floor materials and biological and geological processes that influence where species live. Some of the factors that we consider are the following:composition of the sea bed, which ranges from mud to sand, gravel, bedrock, and shell beds;shape and steepness of the bottom;roughness of the bottom, which is enhanced by the presence of cobbles, boulders, sand waves and ripples, burrows into the bottom, and species that extend above the bottom;bottom currents generated by storm waves and tides, which can move sediment and expose or cover habitats; andthe way in which the sea bed is utilized by species.In addition, we take into account the impact of sea bed disturbance by bottom fishing trawls and dredges. Habitats characterized by attached and burrowing species that protrude above the sea bed appear to be most vulnerable to disturbance.

Foraging behavior of lactating South American sea lions (Otaria flavescens) and spatial-temporal resource overlap with the Uruguayan fisheries

NASA Astrophysics Data System (ADS)

Riet-Sapriza, Federico G.; Costa, Daniel P.; Franco-Trecu, Valentina; Marín, Yamandú; Chocca, Julio; González, Bernardo; Beathyate, Gastón; Louise Chilvers, B.; Hückstadt, Luis A.

2013-04-01

Resource competition between fisheries and marine mammal continue to raise concern worldwide. Understanding this complex conflict requires data on spatial and dietary overlap of marine mammal and fisheries. In Uruguay the South American sea lions population has been dramatically declining over the past decade. The reasons for this population decline are unknown but may include the following: (1) direct harvesting; (2) reduced prey availability and distribution as a consequence of environmental change; or (3) biological interaction with fisheries. This study aims to determine resource overlap and competition between South American sea lions (SASL, Otaria flavescens, n=10) and the artisanal fisheries (AF), and the coastal bottom trawl fisheries (CBTF). We integrated data on sea lions diet (scat analysis), spatial and annual consumption estimates; and foraging behavior-satellite-tracking data from lactating SASL with data on fishing effort areas and fisheries landings. We found that lactating SASL are benthic divers and forage in shallow water within the continental shelf. SASL's foraging areas overlapped with CBTF and AF fisheries operational areas. Dietary analysis indicated a high degree of overlap between the diet of SASL and the AF and CBTF fisheries catch. The results of our work show differing degrees of spatial resource overlap with AF and CBTF, highlighting that there are differences in potential impact from each fishery; and that different management/conservation approaches may need to be taken to solve the fisheries-SASL conflict.

77 FR 29905 - Sea Turtle Conservation; Shrimp and Summer Flounder Trawling Requirements

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-21

... a bottom-opening, straight-bar grid with 2-inch bar spacing installed at an angle of 55 degrees. As...: Using \\1/4\\ inch (0.63 cm) thick and 1\\1/2\\ inch (3.8 cm) deep flat bar, and rectangular and oval pipe... currently-approved TED grids; increasing maximum mesh size on escape flaps from 1\\5/8\\ to 2 inches (4.1 to 5...

Fisheries research and monitoring activities of the Lake Erie Biological Station, 2014

USGS Publications Warehouse

Bodamer Scarbro, Betsy L.; Edwards, William; Gawne, Carrie; Kocovsky, Patrick M.; Kraus, Richard T.; Rogers, Mark W.; Stewart, Taylor

2015-01-01

In 2014, the USGS LEBS successfully completed large vessel surveys in all three of Lake Erie’s basins. Lake Erie Biological Station’s primary vessel surveys included the Western Basin Forage Fish Assessment and East Harbor Forage Fish Assessment as well as contributing to the cooperative multi-agency Central Basin Hydroacoustics Assessment, the Eastern Basin Coldwater Community Assessment, and LTLA (see FTG, CWTG, and FTG reports, respectively). Results from the surveys contribute to Lake Erie Committee Task Group data needs and analyses of trends in Lake Erie’s fish communities. The cruise survey schedule in 2014 was greatly increased by LEBS’s participation in the Lake Erie CSMI, which consisted of up-to two weeks of additional sampling per month from April to October. CSMI is a bi-national effort that occurs at Lake Erie every five years with the purpose of addressing data and knowledge gaps necessary to management agencies and the Lake Erie LaMP. LEBS deepwater science capabilities also provided a platform for data collection by Lake Erie investigators from multiple agencies and universities including: the USGS GLSC, ODW, KSU, OSU, UM, PU, UT, and the USNRL. Samples from this survey are being processed and a separate report of the findings will be made available in a separate document. Our 2014 vessel operations were initiated in mid-April, as soon after ice-out as possible, and continued into early December. During this time, crews of the R/V Muskie and R/V Bowfin deployed 196 bottom trawls covering 48.5 km of lake-bottom, nearly 6 km of gillnet, collected data from 60 hydroacoustics transects, 285 lower trophic (i.e., zooplankton and benthos) samples, and 330 water quality measures (e.g., temperature profiles, water samples). Thus, 2014 was an intensive year of field activity. Our June and September bottom trawl surveys in the Western Basin were numerically dominated by Emerald Shiner, White Perch, and Yellow Perch; however, Freshwater Drum were dominant by biomass. Age-2+ Yellow Perch and White Perch diets from our western basin trawl had highest occurrences of benthic invertebrates in spring and fall. Hexagenia spp. accounted for >25% of Yellow Perch and White Perch diet composition (dry weight) in spring. We conducted an analysis using data from the past 6 years of our East Harbor survey to determine to what degree our new research vessel and trawl is affecting our ability to detect trends across the 50+ year time series. We also evaluated trends in water temperatue, dissolved oxygen, secchi depth and total Phosphorus from our LTLA sites near Vermilion, Ohio. Within the following report sections, we describe specific results from our primary surveys conducted in 2014.

From discard ban to exemption: How can gear technology help reduce catches of undersized Nephrops and hake in the Bay of Biscay trawling fleet?

PubMed

Vogel, Camille; Kopp, Dorothée; Méhault, Sonia

2017-01-15

On January 1st, 2016, the French mixed Nephrops and hake fishery of the Grande Vasière, an area located in the Bay of Biscay, fell under the discard ban implemented as part of the new European Common Fisheries Policy. The fleet records historically high levels of discard despite numerous gear selectivity studies. Together with high discards survival, new technological solutions to minimize catches of undersized individuals could justify local exemptions from the discard ban. Our study focuses on the effects of two selective devices, a square mesh cylinder (SMC) and a grid, on the escapement of undersized individuals and discard reduction. Relative catch probability of the modified gear compared with the traditional gear was modelled using the catch comparison method. Potential losses from the commercial fraction of the catch were taken into account to assess their influence on the economic viability of fishing with the modified gears. The two devices had similar effects on undersized Nephrops escapement and on discard reduction, with median values of 26.5% and 23.6% for the SMC and of 30.4% and 21.4% for the grid, respectively. Only the grid was efficient for undersized hake, recording median values of escapement and discard reduction equal to 25.0% and 20.6%, respectively. Some loss from the commercial fraction of the catch was to be expected with both devices, which could be compensated for in the long term by the contribution of undersized individuals to the stock biomass. Our results support the use of selective gears technology as part of an integrated framework including control and management measures to mitigate the effect of the discard ban both for fishers and for the ecosystem. Further work is needed to quantify the effect of additional escapement from the gear on stock dynamics. Copyright © 2016 Elsevier Ltd. All rights reserved.

Reproduction and community structure of fish from winter catch sites from industrial shrimp bycatch from the northeast and southeast Mexican Pacific.

PubMed

Tirado-Ibarra, Jorge de Jesus; Loya-Rodriguez, Mariany; Morales-Arevalo, Jose Carlos; Muñoz-Garcia, Isabel Rosario; Martinez-Perez, Francisco; Ramirez-Perez, Jorge Saul; Jimenez-Gutierrez, Laura Rebeca

2018-01-01

The shrimp fishery is one of the most important fisheries in the world, although the low selectivity from trawling nets has led to the capture of a large number of non-target species. Shrimp-bycatch species include a large number of fish and invertebrate species, of which fish species are the most abundant. The present study aims to determine the community structure as well as the average sizes at first maturity of the fish species from shrimp-bycatch caught from industrial fisheries in the Mexican Pacific from Sinaloa to Guerrero, from January to March 2015. The shrimp-bycatch fish diversity value was found to be 2.22. A total of 37 species of finfish were found, of which five were considered rare. The fish species with the highest Importance Value Index (IVI) levels were Pseudupeneus grandisquamis , Paralichthys woolmani , Lutjanus peru and Diapterus peruvianus . The average size at first maturity was calculated for all species. Of the analysed organisms, 90% were in the juvenile stage, including species with riverine and artisanal fisheries. The present study demonstrates the risk within marine populations to different non-target species due to the poor selectivity of shrimp trawls.

Status and trends in the Lake Superior fish community, 2014

USGS Publications Warehouse

Vinson, Mark; Evrard, Lori M.; Gorman, Owen T.; Yule, Daniel

2015-01-01

In 2014, the Lake Superior fish community was sampled with daytime bottom trawls at 73 nearshore and 30 offshore stations. Spring and summer water temperatures were the coldest measured for the period of records for the surveys. In the nearshore zone, a total of 15,372 individuals from 28 species or morphotypes were collected. Nearshore lakewide mean biomass was 6.9 kg/ha, which was higher than that observed in the past few years, but below the long-term average of 9.2 kg/ha. In the offshore zone, a total 12,462 individuals from 11 species were collected lakewide. Offshore lakewide mean biomass was 6.6 kg/ha. The mean of the three previous years was 8.6 kg/ha. We collected larval Coregonus in surface trawls at 94 locations and estimated a lakewide average density of 577 fish/ha with a total lakewide population estimate of 14.2 billion (standard error + 30 million).

Sustainable use of flatfish resources: Addressing the credibility crisis in mixed fisheries management

NASA Astrophysics Data System (ADS)

Rijnsdorp, A. D.; Daan, N.; Dekker, W.; Poos, J. J.; Van Densen, W. L. T.

2007-02-01

Many flatfish species are caught in mixed demersal trawl fisheries and managed by Total Allowable Catch (TAC). Despite decades of fisheries management, several major stocks are severely depleted. Using the Common Fisheries Policy (CFP) as an example, the failure of mixed-fisheries management is analysed by focussing on: the management system; the role of science; the role of managers and politicians; the response of fisheries to management. Failure of the CFP management could be ascribed to: incorrect management advice owing to bias in stock assessments; the tendency of politicians to set the TAC well above the recommended level; and non-compliance of the fisheries with the management regulations. We conclude that TAC management, although apparently successful in some single-species fisheries, inevitably leads to unsustainable exploitation of stocks caught in mixed demersal fisheries as it promotes discarding of over-quota catch and misreporting of catches, thereby corrupting the basis of the scientific advice and increasing the risk of stock collapse. This failure in mixed demersal fisheries has resulted in the loss of credibility of both scientists and managers, and has undermined the support of fishermen for management regulations. An approach is developed to convert the TAC system into a system that controls the total allowable effort (TAE). The approach takes account of the differences in catch efficiency between fleets as well as seasonal changes in the distribution of the target species and can also be applied in the recovery plans for rebuilding specific components of the demersal fish community, such as plaice, cod and hake.

Process-driven and biological characterisation and mapping of seabed habitats sensitive to trawling.

PubMed

Foveau, Aurélie; Vaz, Sandrine; Desroy, Nicolas; Kostylev, Vladimir E

2017-01-01

The increase of anthropogenic pressures on the marine environment together with the necessity of a sustainable management of marine living resources have underlined the need to map and model coastal environments, particularly for the purposes of spatial planning and for the implementation of integrated ecosystem-based management approach. The present study compares outputs of a process-driven benthic habitat sensitivity (PDS) model to the structure, composition and distribution of benthic invertebrates in the Eastern English Channel and southern part of the North Sea. Trawl disturbance indicators (TDI) computed from species biological traits and benthic community composition were produced from samples collected with a bottom trawl. The TDI was found to be highly correlated to the PDS further validating the latter's purpose to identify natural process-driven pattern of sensitivity. PDS was found to reflect an environmental potential that may no longer be fully observable in the field and difference with in situ biological observations could be partially explained by the spatial distribution of fishery pressure on the seafloor. The management implication of these findings are discussed and we suggest that, used in conjunction with TDI approaches, PDS may help monitor management effort by evaluating the difference between the current state and the presumed optimal environmental status of marine benthic habitats.

An electric beam trawl for the capture of larval lampreys

USGS Publications Warehouse

McLain, Alberton; Dahl, Frederick H.

1968-01-01

The chemicals used to control the sea lamprey, Petromyzon marinus, in the Great Lakes have drastically reduced populations of larval lampreys in tributary streams. These larvicides are too costly and difficult to apply, however, in inland lakes, estuaries, and bays. Populations of sea lampreys in these areas constitute a threat to the refinement of the control. The gear available to locate, ample, and evaluate larval populations in deep water are inefficient. Electric shockers, satisfactory for collecting ammocoetes in streams, are limited to shallow water. The use of mechanical devices such as the Petersen dredge, anchor dredge, and the orange-peel dredge is time consuming, inefficient, and relatively ineffective in providing reliable quantitative evaluation of population size and composition over large areas of bottom. A device was required to sample adequately many areas in a short period of time, regardless of the depth of water. Mobility also was essential to permit operation of the unit in the various Great Lakes and in inland waters. An electrified beam trawl has been developed that most nearly meets these requirements. It has been used successfully to collect larvae of the sea lamprey, American brook lamprey (Lampetra lamottei), northern brook lamprey (Ichthyomyzon fossor), and silver lamprey (I. unicuspis). Effectiveness of the trawl did not appear to differ with species.

Process-driven and biological characterisation and mapping of seabed habitats sensitive to trawling

PubMed Central

Desroy, Nicolas; Kostylev, Vladimir E.

2017-01-01

The increase of anthropogenic pressures on the marine environment together with the necessity of a sustainable management of marine living resources have underlined the need to map and model coastal environments, particularly for the purposes of spatial planning and for the implementation of integrated ecosystem-based management approach. The present study compares outputs of a process-driven benthic habitat sensitivity (PDS) model to the structure, composition and distribution of benthic invertebrates in the Eastern English Channel and southern part of the North Sea. Trawl disturbance indicators (TDI) computed from species biological traits and benthic community composition were produced from samples collected with a bottom trawl. The TDI was found to be highly correlated to the PDS further validating the latter’s purpose to identify natural process-driven pattern of sensitivity. PDS was found to reflect an environmental potential that may no longer be fully observable in the field and difference with in situ biological observations could be partially explained by the spatial distribution of fishery pressure on the seafloor. The management implication of these findings are discussed and we suggest that, used in conjunction with TDI approaches, PDS may help monitor management effort by evaluating the difference between the current state and the presumed optimal environmental status of marine benthic habitats. PMID:28981504

77 FR 59852 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-01

...NMFS publishes regulations to implement Amendment 97 to the Fishery Management Plan for Groundfish of the Bering Sea and Aleutian Islands Management Area (FMP). Amendment 97 allows the owner of a trawl catcher/processor vessel authorized to participate in the Amendment 80 catch share program to replace that vessel with a vessel that meets certain requirements. This action establishes the regulatory process for replacement of vessels in the Amendment 80 fleet and the requirements for Amendment 80 replacement vessels, such as a limit on the overall length of a replacement vessel, a prohibition on the use of an AFA vessel as a replacement vessel, measures to prevent a replaced vessel from participating in Federal groundfish fisheries off Alaska that are not Amendment 80 fisheries, and measures that extend specific catch limits (known as Amendment 80 sideboards) to a replacement vessel. This action is necessary to promote safety-at-sea by allowing Amendment 80 vessel owners to replace their vessels for any reason at any time and by requiring replacement vessels to meet certain U.S. Coast Guard vessel safety standards, and to improve the retention and utilization of groundfish catch by these vessels by facilitating an increase in the processing capabilities of the fleet. This action is intended to promote the goals and objectives of the Magnuson-Stevens Fishery Conservation and Management Act, the FMP, and other applicable laws.

Summer distributions of forage fish in the eastern Bering Sea

NASA Astrophysics Data System (ADS)

Parker-Stetter, Sandra L.; Horne, John K.; Farley, Edward V.; Barbee, David H.; Andrews, Alexander G.; Eisner, Lisa B.; Nomura, Jennifer M.

2013-10-01

Juvenile and small adult fish, typically called forage fish, are an important but poorly studied part of the eastern Bering Sea (EBS) ecosystem. Acoustic and trawl data from a non-target survey were used to evaluate distributions of capelin (Mallotus villosus), age-0 Pacific cod (Gadus macrocephalus), and age-0 walleye pollock (Theragra chalcogramma, herein pollock) in 2006-2010. Within the surface zone (15 m to ~35 m, evaluated 2006-2010), capelin occurred throughout the EBS but primarily in the middle shelf. Capelin were also present in the midwater zone (~35 m to 0.5 m off-bottom) in both 2009 and 2010 (evaluated 2009-2010), and resulted in water column zone (15 m to 0.5 m off-bottom) distributions that differed from surface zone characterizations. Age-0 Pacific cod occurred primarily in the surface zone of the middle and outer shelf regions in all years. As midwater and surface zone age-0 Pacific cod were often coincident, water column zone distributions in 2009-2010 were similar to surface zone distributions. Age-0 pollock were found in the EBS surface zone in all years, primarily in the middle and outer shelf regions. High densities of age-0 pollock occurred in the midwater zone in 2006-2007 and 2009-2010. Water column zone distributions of age-0 pollock were similar to surface zone distributions in 2006-2007, but differed in 2009-2010 due to low numbers of age-0 pollock in the surface zone and presence of high densities in the midwater zone of the outer shelf region. While general patterns in capelin distribution in the surface zone were similar between the present and the previous studies, the acoustic-trawl characterization suggested that capelin densities were high in the middle shelf region. As expected, surface zone distributions of age-0 Pacific cod and age-0 pollock were similar to previous characterizations. Observed high densities of midwater age-0 pollock have not been described by previous studies. Annual abundance indices based on bottom or surface trawl data alone will not be sufficient in all years. Data and conclusions from non-target surveys may be constrained compared to dedicated survey efforts, but can provide baseline distributions, potential abundance indices, and insight for planning future research.

Megabenthic assemblages in the continental shelf edge and upper slope of the Menorca Channel, Western Mediterranean Sea

NASA Astrophysics Data System (ADS)

Grinyó, Jordi; Gori, Andrea; Greenacre, Michael; Requena, Susana; Canepa, Antonio; Lo Iacono, Claudio; Ambroso, Stefano; Purroy, Ariadna; Gili, Josep-Maria

2018-03-01

Highly diverse megabenthic assemblages dominated by passive and active suspension feeders have been recently reported in shelf edge environments of the Mediterranean Sea. Due to their frequent association with species of commercial interest, these assemblages have been heavily impacted by fishing. The vulnerability and low resilience of these assemblages, composed mainly by long-living and slow-growing species, have motivated the implementation of management measures such as the restriction of bottom trawling, and the establishment of large protected areas embracing these environments. The Menorca Channel is one of such areas recently included in the European Union Natura 2000 network. Quantitative analysis of video transects recorded at 95-360 m depth by manned submersible and remotely operated vehicles were used to characterize megabenthic assemblages and to assess their geographical and bathymetric distribution. Six different assemblages were identified, mainly segregated by substrate type and depth. Hard substrates hosted coral gardens and sponge grounds, whereas soft sediments were mainly characterized by large extensions of the crinoid Leptometra phalangium and the brachiopod Gryphus vitreus. The good preservation of most of the observed assemblages is probably related to a low bottom trawling pressure, which mainly concentrates deeper on the adjacent continental slope. Because of their biological and ecological value, management and conservation measures need to be established to preserve these benthic assemblages.

Practicality of marine protected areas - Can there be solutions for the River Indus delta?

NASA Astrophysics Data System (ADS)

Kidwai, Samina; Fanning, Paul; Ahmed, Waqar; Tabrez, Mohsin; Zhang, Jing; Khan, Muhammad Wasim

2016-12-01

The River Indus delta is the most prominent feature on the Pakistan coast. Owing to its prominence, mangrove ecosystem, historical, ecological and economic significance it is also a proposed Marine Protected Area (MPA). Currently there are no designated MPAs in Pakistan. This paper presents findings of the Fishery Resource Appraisal Project of Pakistan (FRAPP) a fishery stock assessment carried out for the pelagic and demersal fishery resource of Pakistan from 2009 to 2015 and the Creek Survey Program (CSP) which was part of FRAPP. And discusses how the delta suffers from physical stress. The observations from FRAPP indicates deterioration in the mangrove ecosystem, that are evident in the form of loss of biodiversity and biological productivity. The 600 observations from 10 major creeks showed that trawl catches were a mix of generally small size fish and shrimp. Catches averaged less than 1 kg per tow in all the creeks sampled. Catch weights were somewhat higher in Isaro, WadiKhuddi, Paitiani, Dabbo, Richaal Creeks all of which were near mangrove areas and open sea. The most frequently occurring species of shrimps caught in the trawls belonged to 7 major taxa. The Khobar Creek and Upper Wari Creek are notable for the high rates of occurrence of every group except the Caridea. They are also the only two creeks where the freshwater family Paleomonidae is common. The size composition of the important penaeid family of shrimps in all study areas combined suggests that the smallest shrimps (0.5-1.5 cm carapace length CL) enter the creeks in February/March and adults (5-6 cm CL) move out again 6-12 months later. Four species of Penaeus (monodon, japonicus, semisulcatus, merguiensis), two species of Metapenaeus (monoceros, affinis), Parapeneoposis stylifera and Solenosera sp. were caught, all in low abundance, less than 0.5 Kg tow-1. The shrimp catches in the area off the Sindh coast, the catches averaged 4.30 ± 13.40 kg h-1 on the inner shelf (20-50 m) and 1.7 ± 6.6 kg h-1 on the outer shelf (51-200 m). Further east, on the Kori bank, the shrimp catch averaged 4.40 ± 6.6 kg h-1 (inner shelf) and 1.7 ± 6.6 kg h-1 (outer shelf). Penaeus spp. were more abundant in the inshore and Metapenaeus spp. on the outer shelf. The creeks that have a direct connection to the sea and support a natural mangrove stand are significantly more productive than the smaller creeks. Scientific and management questions have arisen that are addressed in order to help revive the delta and hope that this results in a spillover effect that will spread on to the shelf areas. Fisher communities depend heavily on the delta and coastal waters and its natural resources for their livelihood. Their participation and ownership on the resource is over generations, and therefore their involvement is key to proposing any management and conservation initiatives. The study proposes how the delta and its ecosystem in parts should be protected and why and how it is a prime candidate for being declared nationally as protected. This paper proposes a way forward.

SMART: A Spatially Explicit Bio-Economic Model for Assessing and Managing Demersal Fisheries, with an Application to Italian Trawlers in the Strait of Sicily

PubMed Central

Russo, Tommaso; Parisi, Antonio; Garofalo, Germana; Gristina, Michele; Cataudella, Stefano; Fiorentino, Fabio

2014-01-01

Management of catches, effort and exploitation pattern are considered the most effective measures to control fishing mortality and ultimately ensure productivity and sustainability of fisheries. Despite the growing concerns about the spatial dimension of fisheries, the distribution of resources and fishing effort in space is seldom considered in assessment and management processes. Here we propose SMART (Spatial MAnagement of demersal Resources for Trawl fisheries), a tool for assessing bio-economic feedback in different management scenarios. SMART combines information from different tasks gathered within the European Data Collection Framework on fisheries and is composed of: 1) spatial models of fishing effort, environmental characteristics and distribution of demersal resources; 2) an Artificial Neural Network which captures the relationships among these aspects in a spatially explicit way and uses them to predict resources abundances; 3) a deterministic module which analyzes the size structure of catches and the associated revenues, according to different spatially-based management scenarios. SMART is applied to demersal fishery in the Strait of Sicily, one of the most productive fisheries of the Mediterranean Sea. Three of the main target species are used as proxies for the whole range exploited by trawlers. After training, SMART is used to evaluate different management scenarios, including spatial closures, using a simulation approach that mimics the recent exploitation patterns. Results evidence good model performance, with a noteworthy coherence and reliability of outputs for the different components. Among others, the main finding is that a partial improvement in resource conditions can be achieved by means of nursery closures, even if the overall fishing effort in the area remains stable. Accordingly, a series of strategically designed areas of trawling closures could significantly improve the resource conditions of demersal fisheries in the Strait of Sicily, also supporting sustainable economic returns for fishermen if not applied simultaneously for different species. PMID:24465971

Temporal and geographic variation in fish communities of lower Cook Inlet, Alaska

USGS Publications Warehouse

Robards, Martin D.; Piatt, John F.; Kettle, Arthur B.; Abookire, Alisa A.

1999-01-01

Nearshore and shelf fish communities were studied in three areas of lower Cook Inlet, Alaska: the Barren Islands (oceanic and well-mixed waters), Kachemak Bay (mixed oceanic waters with significant freshwater runoff), and Chisik Island (estuarine waters). Fish were sampled with beach seines (n=413 sets) and midwater trawls (n=39 sets). We found that lower Cook Inlet supported a diverse nearshore fish community of at least 52 species. Fifty of these species were caught in Kachemak Bay, 24 at Chisik Island, and 12 at the Barren Islands. Pacific sand lance dominated Barren Islands and Kachemak Bay nearshore habitats, comprising 99% and 71% of total individuals, respectively. The nearshore Chisik Island fish community was not dominated by any one species; instead it exhibited higher diversity. These spatial differences appeared linked to local oceanographic regimes and sediment influx. Analysis of historical data revealed that the nearshore Kachemak Bay fish community changed significantly between 1976 and 1996, showing increased diversity and abundance in several taxa, notably gadids, salmonids, pleuronectids, and sculpins. Decadal differences appeared to be related to large-scale climate changes in the North Pacific. Catches of most taxa peaked in May-August, and were low during other months of the year. Several species were present for only part of the summer. Species composition of seine catches differed significantly between consecutive high and low tides, but not between consecutive sets or years. Midwater trawls took 26 species, 14 of which were present in Kachemak Bay, 19 near Chisik Island, and 7 at the Barren Islands. Community structures in shelf and nearshore waters were similar: diversity was high and abundance low at Chisik Island, whereas a few abundant species dominated at both Kachemak Bay and the Barren Islands. In addition, the low fish abundance near Chisik Island appeared to be related to declining seabird numbers at this colony.

Diet of juvenile lake trout in southern Lake Ontario in relation to abundance and size of prey fishes, 1979-1987

USGS Publications Warehouse

Elrod, Joseph H.; O'Gorman, Robert

1991-01-01

We examined the diet of juvenile lake trout Salvelinus namaycush (<450 mm, total length) in Lake Ontario during four sampling periods (April–May, June, July–August, and October 1979–1987) in relation to changes in prey fish abundance in the depth zone where we caught the lake trout. Over all years combined, slimy sculpins Cottus cognatus contributed the most (39–52%) by wet weight to the diet, followed by alewives Alosa pseudoharengus(3–38%), rainbow smelt Osmerus mordax (17–43%), and johnny darters Etheostoma nigrum(2–10%). Over 90% of alewives eaten during April–May and June were age 1, and 98% of those eaten during October were age 0 (few alewives were eaten in July–August). Mean lengths of rainbow smelt and slimy sculpins in stomachs increased with size of lake trout. Juvenile lake trout generally fed opportunistically—seasonal and annual changes in diet usually reflected seasonal and annual changes in abundance of prey fishes near bottom where we captured the lake trout. Furthermore, diet within a given season varied with depth of capture of lake trout, and changes with depth in proportions of prey species in lake trout stomachs mirrored changes in proportions of the prey species in trawl catches at the same depth. Alewives (ages 0 and 1) were the only prey fish eaten in substantial quantities by both juvenile lake trout and other salmonines, and thus are a potential focus of competition between these predators.

Temporal Variation in Black Sea Bass (Centropristis striata) Abundance in the Maryland Coastal Bays

NASA Astrophysics Data System (ADS)

Peters, R.; Chigbu, P.

2016-02-01

Black sea bass (Centropristis striata) is a warm temperate species associated with structured habitats along the Atlantic Coast of the United States. Currently, the northern stock is considered data poor, and the lack of information about the abundance and ecology of these fish in estuaries is a major concern. The Maryland Coastal Bays (MCBs) serves as a habitat for 0+ and 1+ black sea bass. The Maryland Department of Natural Resources conducts annual surveys of juvenile finfish including black sea bass in the MCBs from April to October. Highest mean Catch-Per-Unit efforts (CPUE) were in sites 7 (Isle of Wight Bay), 9 (Sinepuxent Bay), and 20 (Chincoteague Bay), which are also sites closet to the Ocean City and Chincoteague Inlets. Length frequency distribution from data collected from 1989-2013 in these trawls show that there are two year classes in the MCBs. Juveniles (1+) began to enter the bays in April, and (YoY) 0+ fish were caught in the trawls beginning in June. Juvenile abundance peaked in July, while 0+ abundance peaked in September. The abundance of both 0+ and 1+ fish varied over the years with abundances peaking in the same years. YoY black sea bass abundance was positively correlated (r2=0.22, p≤0.05) with average salinity each year and negatively correlated (r2=0.15, p≤0.05) with average NAO winter index. The negative NAO winter years could cause the increase in salinity, which could favor high recruitment. This could be caused by the warmer winters increasing rainfall and reducing salinity during that time. However, abundance of YoY was low in the MCBs, which could be from the trawl gear used to sample the structure oriented fish, and therefore could be a source of bias in this study. Nevertheless, other studies have also used trawls to assess distribution and trends of YoY black sea bass. Studies using traps to assess the relative abundance of the fish in the MCBs are ongoing, and could provide more insight into climatic factors affecting recruitment.

Reproduction and community structure of fish from winter catch sites from industrial shrimp bycatch from the northeast and southeast Mexican Pacific

PubMed Central

Muñoz-Garcia, Isabel Rosario; Martinez-Perez, Francisco; Ramirez-Perez, Jorge Saul

2018-01-01

The shrimp fishery is one of the most important fisheries in the world, although the low selectivity from trawling nets has led to the capture of a large number of non-target species. Shrimp-bycatch species include a large number of fish and invertebrate species, of which fish species are the most abundant. The present study aims to determine the community structure as well as the average sizes at first maturity of the fish species from shrimp-bycatch caught from industrial fisheries in the Mexican Pacific from Sinaloa to Guerrero, from January to March 2015. The shrimp-bycatch fish diversity value was found to be 2.22. A total of 37 species of finfish were found, of which five were considered rare. The fish species with the highest Importance Value Index (IVI) levels were Pseudupeneus grandisquamis, Paralichthys woolmani, Lutjanus peru and Diapterus peruvianus. The average size at first maturity was calculated for all species. Of the analysed organisms, 90% were in the juvenile stage, including species with riverine and artisanal fisheries. The present study demonstrates the risk within marine populations to different non-target species due to the poor selectivity of shrimp trawls. PMID:29507841

78 FR 72 - Fisheries Off West Coast States; Pacific Coast Groundfish Fishery Management Plan; Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-02

...This action proposes revisions to several portions of the Pacific Coast Groundfish Fishery Trawl Rationalization Program regulations and requests comments on NMFS' preliminary conclusion that the Pacific Fishery Management Council's (Council's) selection of the no action alternative regarding the reconsideration of initial allocation of Pacific whiting (whiting) is consistent with the Magnuson-Stevens Fishery Conservation and Management Act (MSA), the Pacific Coast Groundfish Fishery Management Plan (FMP), and other applicable law.. This action is necessary to comply with a court order requiring NMFS to reconsider the initial allocation of whiting to the shorebased individual fishing quota (IFQ) fishery and the at-sea mothership fishery. These proposed regulatory changes would affect the transfer of quota share (QS) and individual bycatch quota (IBQ) between QS accounts in the shorebased IFQ fishery, and severability of catch history assignments in the mothership fishery, both of which would be allowed on specified dates with the exception of widow rockfish. Widow rockfish is no longer an overfished species and transfer of QS for this species will be reinstated pending reconsideration of the allocation of widow rockfish QS in a future action. The divestiture period for widow rockfish QS in the IFQ fishery is also proposed to be delayed indefinitely.

Status and trends in the Lake Superior fish community, 2015

USGS Publications Warehouse

Vinson, Mark; Evrard, Lori M.; Gorman, Owen T.; Yule, Daniel L.

2016-01-01

In 2015, the Lake Superior fish community was sampled with daytime bottom trawls at 76 nearshore and 33 offshore stations. Spring and summer water temperatures in 2015 were colder than average, but warmer than that observed in 2014. In the nearshore zone, a total of 11,882 individuals from 22 species or morphotypes were collected. Nearshore lakewide mean biomass was 1.8 kg/ha, which was near the lowest biomass on record for this survey since it began in 1978. In the offshore zone, a total 12,433 individuals from 8 species or morphotypes were collected lakewide. Offshore lakewide mean biomass was 5.9 kg/ha. The mean of the four previous years was 7.1 kg/ha. The abundance of age-1 Cisco was 14.3 fish/ha which was similar to that measured in 2009. We collected larval Coregonus in surface trawls at 94 locations and estimated a nearshore lakewide average density of 1,459 fish/ha which was nearly twice that measured in 2014.

Benthic marine debris, with an emphasis on fishery-related items, surrounding Kodiak Island, Alaska, 1994-1996

USGS Publications Warehouse

Hess, N.A.; Ribic, C.A.; Vining, I.

1999-01-01

Composition and abundance of benthic marine debris were investigated during three bottom trawl surveys in inlet and offshore locations surrounding Kodiak Island, Alaska, 1994-1996. Debris items were primarily plastic and metal regardless of trawl location. Plastic bait jars, fishing line, and crab pots were the most common fishery-related debris items and were encountered in large amounts in inlets (20-25 items km-2), but were less abundant outside of inlets (4.5-11 items km-2). Overall density of debris was also significantly greater in inlets than outside of inlets. Plastic debris densities in inlets ranged 22-31.5 items km-2, 7.8-18.8 items km-2 outside of inlets. Trawls in inlets contained almost as much metal debris as plastic debris. Density of metal debris ranged from 21.2 to 23.7 items km-2 in inlets, a maximum of 2.7 items km-2 outside of inlets. Inlets around the town of Kodiak had the highest densities of fishery-related and total benthic debris. Differences in benthic debris density between inlets and outside of inlets and differences by area may be due to differences in fishing activity and water circulation patterns. At the current reduced levels of fishing activity, however, yearly monitoring of benthic debris appears unnecessary. Copyright (C) 1999.

1993 annual status report: a summary of fish data in six reaches of the upper Mississippi River system

USGS Publications Warehouse

Gutreuter, Steve; Burkhardt, Randy W.; Stopyro, Mark; Bartels, Andrew; Kramer, Eric; Bowler, Melvin C.; Cronin, Frederick A.; Soergel, Dirk W.; Petersen, Michael D.; Herzog, David P.; Raibley, Paul T.; Irons, Kevin S.; O'Hara, Timothy M.

1997-01-01

The Long Term Resource Monitoring Program (LTRMP) completed 1,994 collections of fishes from stratified random and permanently fixed sampling locations in six study reaches of the Upper Mississippi River System during 1993. Collection methods included day and night electrofishing, hoop netting, fyke netting (two net sizes), gill netting, seining, and trawling in select aquatic area classes. The six LTRMP study reaches are Pools 4 (excluding Lake Pepin), 8, 13, and 26 of the Upper Mississippi River, an unimpounded reach of the Mississippi River near Cape Girardeau, Missouri, and the La Grange Pool of the Illinois River. A total of 62-78 fish species were detected in each study reach. For each of the six LTRMP study reaches, this report contains summaries of: (1) sampling efforts in each combination of gear type and aquatic area class, (2) total catches of each species from each gear type, (3) mean catch-per-unit of gear effort statistics and standard errors for common species from each combination of aquatic area class and selected gear type, and (4) length distributions of common species from selected gear types.

1994 annual status report: a summary of fish data in six reaches of the upper Mississippi River system

USGS Publications Warehouse

Gutreuter, Steve; Burkhardt, Randy W.; Stopyro, Mark; Bartels, Andrew; Kramer, Eric; Bowler, Melvin C.; Cronin, Frederick A.; Soergel, Dirk W.; Petersen, Michael D.; Herzog, David P.; Raibley, Paul T.; Irons, Kevin S.; O'Hara, Timothy M.

1997-01-01

The Long Term Resource Monitoring Program (LTRMP) completed 2,653 collections of fishes from stratified random and permanently fixed sampling locations in six study reaches of the Upper Mississippi River System during 1994. Collection methods included day and night electrofishing, hoop netting, fyke netting (two net sizes), gill netting, seining, and trawling in select aquatic area classes. The six LTRMP study areas are Pools 4 (excluding Lake Pepin), 8, 13, and 26 of the Upper Mississippi River, and unimpounded reach of the Mississippi River near Cape Girardeau, Missouri, and the La Grange Pool of the Illinois River. A total of 61-79 fish species were detected in each study area. For each of the six LTRMP study areas, this report contains summaries of (1) sampling efforts in each combination of gear type and aquatic area class, (2) total catches of each species from each gear type, (3) mean catch-per-unit of gear effort statistics and standard errors for common species from each combination of aquatic area class and selected gear type, and (4) length distributions of common species from selected gear types.

Relationship between Prevailing Oceanographic conditions on the fishing operations in the Northern Indian Ocean

NASA Astrophysics Data System (ADS)

Moazzam Khan, Muhammad

2014-05-01

Marked seasonality in fishing operation and catch composition was observed in the Northern Indian Ocean. These variations are more pronounced and noticeable in case of trawling for fish and shrimp as well as in the surface gillnetting for tuna and large pelagics. Although oceanographic conditions of the Northern Indian Ocean has been studied comprehensively, some facets of these are not well understood especially their relation with the fish distribution and abundance. Important oceanographic factors especially migration of oxygen minimum layer towards coastal areas after the cessation of South-West Monsoon seems to the most important factor responsible for the seasonal variation in the fishing intensity and species composition. Distribution and abundance of some of the commercially important marine animals especially billfishes was observed to be associated with the physical features of the area especially their abundance was noticed along continental margin and on the ridges in the Arabian Sea. The paper describes seasonal variation in abundance and catch composition of various fishing operations in the Indian Ocean and relates its to prevailing oceanographic conditions. Fishermen traditional knowledge about the seasonality of these conditions is also documented in the paper.

Expansion of Dreissena into offshore waters of Lake Michigan and potential impacts on fish populations

USGS Publications Warehouse

Bunnell, D.B.; Madenjian, C.P.; Holuszko, J.D.; Adams, J.V.; French, J. R. P.

2009-01-01

Lake Michigan was invaded by zebra mussels (Dreissena polymorpha) in the late 1980s and then followed by quagga mussels (D. bugensis) around 1997. Through 2000, both species (herein Dreissena) were largely restricted to depths less than 50??m. Herein, we provide results of an annual lake-wide bottom trawl survey in Lake Michigan that reveal the relative biomass and depth distribution of Dreissena between 1999 and 2007 (although biomass estimates from a bottom trawl are biased low). Lake-wide mean biomass density (g/m2) and mean depth of collection revealed no trend between 1999 and 2003 (mean = 0.7??g/m2 and 37??m, respectively). Between 2004 and 2007, however, mean lake-wide biomass density increased from 0.8??g/m2 to 7.0??g/m2, because of increased density at depths between 30 and 110??m, and mean depth of collection increased from 42 to 77??m. This pattern was confirmed by a generalized additive model. Coincident with the Dreissena expansion that occurred beginning in 2004, fish biomass density (generally planktivores) declined 71% between 2003 and 2007. Current understanding of fish population dynamics, however, indicates that Dreissena expansion is not the primary explanation for the decline of fish, and we provide a species-specific account for more likely underlying factors. Nonetheless, future sampling and research may reveal a better understanding of the potential negative interactions between Dreissena and fish in Lake Michigan and elsewhere.

Deep-water fisheries at the Atlantic Frontier

NASA Astrophysics Data System (ADS)

Gordon, J. D. M.

2001-05-01

The deep sea is often thought of as a cold, dark and uniform environment with a low-fish biomass, much of which is highly adapted for life in a food-poor environment. While this might be true of the pelagic fish living in the water column, it is certainly not true of the demersal fish which live on or close to the bottom on the continental slopes around the British Isles (the Atlantic Frontier). These fish are currently being commercially exploited. There is growing evidence to support the view that success of the demersal fish assemblages depends on the pelagic or benthopelagic food sources that impinge both vertically and horizontally onto the slope. There are several quite separate and distinct deep-water fisheries on the Atlantic Frontier. It is a physical barrier, the Wyville-Thomson Ridge, which results in the most significant division of the fisheries. The Ridge, which has a minimum depth of about 500 m, separates the warmer deep Atlantic waters from the much colder Norwegian Sea water and as a result, the deep-water fisheries to the west of the Hebrides and around the offshore banks are quite different from those of the Faroe-Shetland Channel (West of Shetland). The fisheries to the West of the Hebrides can be further divided by the fishing method used into bottom trawl, semipelagic trawl and longline. The bottom-trawl fisheries extend from the shelf-slope break down to about 1700 m and the target species varies with depth. The smallest vessels in the fleet fish on the upper slope, where an important target species is the anglerfish or monkfish ( Lophius spp.). On the mid-slope the main target species are blue ling ( Molva dypterygia) and roundnose grenadier ( Coryphaenoides rupestris), with bycatches of black scabbardfish ( Aphanopus carbo) and deep-water sharks. On the lower slope orange roughy ( Hoplostethus atlanticus) is an important target species. The major semipelagic trawl fishery is a seasonal fishery on spawning aggregations of blue whiting ( Micromesistius poutassou). The other semipelagic fishery is on spawning aggregations of the greater silver smelt or argentine ( Argentina silus). Spanish and UK vessels that target mainly hake ( Merluccius merluccius) and a Norwegian fleet that targets ling ( Molva molva), blue ling and tusk ( Brosme brosme) dominate the upper slope longline fishery. West of Shetland, the fishery on the upper slope has some similarities with that of the Hebridean slope, with anglerfish and blue ling being important target species. A quite different fishery occurs in the transition zone between the Atlantic and Norwegian Sea waters. Here the main target species is Greenland halibut ( Reinhardtius hippoglossoides). Below the transition zone biomass decreases rapidly and there is no fishery. It is generally agreed that many deep-water species have slow growth, a high age at first maturity and a low fecundity, which makes them vulnerable to over-exploitation. Other features of these fishes such as high mortality of discards and escapees will add to the problems. Despite this the only management procedures in place are general limitation of effort measures within the area of jurisdiction of the European Union.

15. VIEW DIRECTLY INTO CENTER FISH HOLD, STARBOARD SIDE. THE ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

15. VIEW DIRECTLY INTO CENTER FISH HOLD, STARBOARD SIDE. THE HORIZONTAL SCANTLINGS ON EACH BULKHEAD ARE 57" ABOVE THE BOTTOM OF THE HOLD. EXPERIENCE SHOWED THAT THE WEIGHT OF ICE PILED TO GREATER DEPTHS WOULD DAMAGE FISH ON THE BOTTOM OF THE HOLD. CONSEQUENTLY, MOST HOLDS ON FISHING BOATS HAVE A SHELF AT THIS HEIGHT TO PREVENT DAMAGING THE CATCH. - Auxiliary Fishing Schooner "Evelina M. Goulart", Essex Shipbuilding Museum, 66 Main Street, Essex, Essex County, MA

Puget Sound Dredged Disposal Analysis (PSDDA). Unconfined, Open-Water Disposal Sites for Dredged Material. Phase 1 (Central Puget Sound). National Environmental Policy Act (NEPA)/State Environmental Policy Act (SEPA)

DTIC Science & Technology

1988-06-01

confined to a relatively small area. In 400 feet of water the descending cloud is approximately 250 feet in diameter (B. Trawle, personal communica- tion...when it hits the bottom, occuring 30 seconds after disposal is initiated. The collapsing cloud then spreads out in all directions. Ten minutes later...Compliance inspection6. Environ- mental monitorig an permin dp&nce insp ecti, arso part -disposal site management, are described in the MPR and the Management

Temporal and spatial distribution of young Brachyplatystoma spp. (Siluriformes: Pimelodidae) along the rapids stretch of the Madeira River (Brazil) before the construction of two hydroelectric dams.

PubMed

Cella-Ribeiro, A; Assakawa, L F; Torrente-Vilara, G; Zuanon, J; Leite, R G; Doria, C; Duponchelle, F

2015-04-01

Monthly (April 2009 to May 2010) bottom-trawl sampling for Brachyplatystoma species along the rapids stretch of the Madeira River in Brazil revealed that Brachyplatystoma rousseauxii larvae and juveniles were present in low abundances in all areas and during all hydrological periods. The presence of larvae and juveniles throughout the hydrological cycle suggests asynchronous spawning in the headwaters of the Madeira River. © 2015 The Fisheries Society of the British Isles.

Monitoring biodiversity using ecosystem assessment surveys and regional ocean models within the California Current

NASA Astrophysics Data System (ADS)

Schroeder, I. D.; Santora, J. A.; Field, J. C.; Hazen, E. L.; Bograd, S. J.

2016-02-01

The National Marine Fisheries Service has conducted an annual midwater trawl survey for juvenile rockfish and other pelagic micronekton every May and June from 1983 to the present. Although both the spatial and temporal coverage have varied over time, a "core" region has been sampled continuously for the region that extends from Monterey Bay to just north of San Francisco Bay, California. Stations are located from nearshore waters to the offshore environment, but generally within 60 km from land. The mid-water trawl targets a diverse micronekton community spanning a range of juvenile stages of fishes, adult forage fishes and various invertebrates. Here we use the historical catch data to investigate biodiversity across space and time, specifically through developing indices of richness, diversity and evenness. The interannual variability of these indices is coherent over three unique ecological regions located along the shelf, Monterey Bay submarine canyon, and offshore habitats. Spatiotemporal changes in diversity reflect different taxa such as juvenile groundfish, rockfish and forage fish, and influx of oceanic species to nearshore habitat during anomalous years. Finally, data from CTD casts and from a data-assimilative ROMS model links changes in biodiversity with changing environmental conditions. The results of this project will be used to help inform researchers in the creation of a Marine Biodiversity Observation Network (MBON) in the Monterey Bay National Marine Sanctuary.

Exploration of the "larval pool": development and ground-truthing of a larval transport model off leeward Hawai'i.

PubMed

Wren, Johanna L K; Kobayashi, Donald R

2016-01-01

Most adult reef fish show site fidelity thus dispersal is limited to the mobile larval stage of the fish, and effective management of such species requires an understanding of the patterns of larval dispersal. In this study, we assess larval reef fish distributions in the waters west of the Big Island of Hawai'i using both in situ and model data. Catches from Cobb midwater trawls off west Hawai'i show that reef fish larvae are most numerous in offshore waters deeper than 3,000 m and consist largely of pre-settlement Pomacanthids, Acanthurids and Chaetodontids. Utilizing a Lagrangian larval dispersal model, we were able to replicate the observed shore fish distributions from the trawl data and we identified the 100 m depth strata as the most likely depth of occupancy. Additionally, our model showed that for larval shore fish with a pelagic larval duration longer than 40 days there was no significant change in settlement success in our model. By creating a general additive model (GAM) incorporating lunar phase and angle we were able to explain 67.5% of the variance between modeled and in situ Acanthurid abundances. We took steps towards creating a predictive larval distribution model that will greatly aid in understanding the spatiotemporal nature of the larval pool in west Hawai'i, and the dispersal of larvae throughout the Hawaiian archipelago.

Recent changes in burbot growth in Lake Erie

USGS Publications Warehouse

Stapanian, M.A.; Edwards, W.H.; Witzel, L.D.

2011-01-01

Recruitment of burbot Lota lota in eastern Lake Erie, estimated by catches of age-4 burbot, was high during 1997–2001 and then abruptly declined to low levels during 2002–2007. The invasive round goby Neogobius melanostomus, a benthic species, was first collected in trawl assessments in eastern Lake Erie in 1999, and was first found in stomachs of burbot in 2001. By 2003, round goby became an important prey in the diet of burbot. We hypothesized that the combined effects of low recruitment and consumption of round goby would result in increased size-at-age in burbot. We reasoned that: (i) decreased competition for resources among juveniles should result in larger adults, and (ii) consumption of a benthic prey by a bottom-dwelling predator such as burbot should require less foraging in the water column, and thus less energetic expenditure. We divided our data into two temporal periods: one in which burbot belonged to strong year classes and ate few, if any round goby (i.e., year classes 1989–1997 collected during 1997–2001) and one in which burbot belonged to weak year classes and probably ate round gobies by age 4 (year classes 1998–2003 collected during 2002–2007). Mass and total lengths at ages 4–7 were generally higher during the second period. However, the rates of growth between ages 4 and 7 were not different for the two periods. The results indicate that greater growth at ages 0–4 resulted in larger size at ages 4–7 in the latter period. More information on juvenile diet and growth in burbot is needed for effective conservation of burbot stocks.

Temporal trends of young-of-year fishes in Lake Erie and comparison of diel sampling periods

USGS Publications Warehouse

Stapanian, M.A.; Bur, M.T.; Adams, J.V.

2007-01-01

We explored temporal trends of young-of-year (YOY) fishes caught in bottom trawl hauls at an established offshore monitoring site in Lake Erie in fall during 1961–2001. Sampling was conducted during morning, afternoon, and night in each year. Catches per hour (CPH) of alewife (Alosa pseudoharengus) YOY were relatively low and exhibited no temporal trend. This result was consistent with the species’ intolerance to Lake Erie’s adverse winter water temperatures. Gizzard shad (Dorosoma cepedianum) YOY decreased sharply after 1991, which was consistent with recent oligotrophication of the lake. Following the establishment in 1979 and rapid increase of white perch (Morone americana) YOY, white bass (Morone chrysops) and freshwater drum (Aplodinotus grunniens) YOY decreased. Trout-perch (Percopsis omiscomaycus) YOY decreased during 1986–1991, but recovered to previous levels during 1991–2001. The recovery coincided with the resurgence of mayflies (Ephemoptera) in the lake. CPH of spottail shiner (Notropis hudsonius) and emerald shiner (N. atherinoides) YOY exhibited no temporal trend between 1961 and the late 1970s to early 1980s. CPH of yellow perch (Perca flavescens) YOY decreased during 1961–1988, and walleye (Sander vitreum) YOY increased overall during the time series. These observations were consistent with published studies of adults in the region. CPH of 4 of the 10 species of YOY considered were greatest during night. CPH for walleye YOY was higher in the morning than in the afternoon, but there was no significant difference between night and morning abundances. The results suggest that (1) CPH of YOY fishes may be a useful monitoring tool for Lake Erie, and (2) offshore monitoring programs that do not include night sampling periods may underestimate recruitment for several common species.

Status and trends in the Lake Superior fish community, 2016

USGS Publications Warehouse

Vinson, Mark; Evrard, Lori M.; Gorman, Owen T.; Yule, Daniel

2017-01-01

In 2016, the Lake Superior fish community was sampled with daytime bottom trawls at 76 nearshore and 35 offshore stations. Spring and summer water temperatures in 2016 were warmer than average and considerably warmer than observed in 2014 and 2015. In the nearshore zone, a total of 17,449 individuals from 20 species or morphotypes were collected. Nearshore lakewide mean biomass was 2.2 kg/ha, which was near the lowest biomass on record for this survey since it began in 1978. In the offshore zone, a total 8,487 individuals from 16 species or morphotypes were collected lakewide. Offshore lakewide mean biomass was 4.5 kg/ha, which was the lowest biomass recorded since the offshore survey began in 2011. The density of age-1 Cisco was 5.0 fish/ha, which was 35% of that measured in 2015. Larval Coregonus were collected in surface trawls at 144 locations lakewide from May to July. The average nearshore lakewide larval Coregonus density estimate was 1,630 fish/ha, which was similar to that estimated in 2015.

The seascape of demersal fish nursery areas in the North Mediterranean Sea, a first step towards the implementation of spatial planning for trawl fisheries.

PubMed

Colloca, Francesco; Garofalo, Germana; Bitetto, Isabella; Facchini, Maria Teresa; Grati, Fabio; Martiradonna, Angela; Mastrantonio, Gianluca; Nikolioudakis, Nikolaos; Ordinas, Francesc; Scarcella, Giuseppe; Tserpes, George; Tugores, M Pilar; Valavanis, Vasilis; Carlucci, Roberto; Fiorentino, Fabio; Follesa, Maria C; Iglesias, Magdalena; Knittweis, Leyla; Lefkaditou, Eugenia; Lembo, Giuseppe; Manfredi, Chiara; Massutí, Enric; Pace, Marie Louise; Papadopoulou, Nadia; Sartor, Paolo; Smith, Christopher J; Spedicato, Maria Teresa

2015-01-01

The identification of nursery grounds and other essential fish habitats of exploited stocks is a key requirement for the development of spatial conservation planning aimed at reducing the adverse impact of fishing on the exploited populations and ecosystems. The reduction in juvenile mortality is particularly relevant in the Mediterranean and is considered as one of the main prerequisites for the future sustainability of trawl fisheries. The distribution of nursery areas of 11 important commercial species of demersal fish and shellfish was analysed in the European Union Mediterranean waters using time series of bottom trawl survey data with the aim of identifying the most persistent recruitment areas. A high interspecific spatial overlap between nursery areas was mainly found along the shelf break of many different sectors of the Northern Mediterranean indicating a high potential for the implementation of conservation measures. Overlap of the nursery grounds with existing spatial fisheries management measures and trawl fisheries restricted areas was also investigated. Spatial analyses revealed considerable variation depending on species and associated habitat/depth preferences with increased protection seen in coastal nurseries and minimal protection seen for deeper nurseries (e.g. Parapenaeus longirostris 6%). This is partly attributed to existing environmental policy instruments (e.g. Habitats Directive and Mediterranean Regulation EC 1967/2006) aiming at minimising impacts on coastal priority habitats such as seagrass, coralligenous and maerl beds. The new knowledge on the distribution and persistence of demersal nurseries provided in this study can support the application of spatial conservation measures, such as the designation of no-take Marine Protected Areas in EU Mediterranean waters and their inclusion in a conservation network. The establishment of no-take zones will be consistent with the objectives of the Common Fisheries Policy applying the ecosystem approach to fisheries management and with the requirements of the Marine Strategy Framework Directive to maintain or achieve seafloor integrity and good environmental status.

The Seascape of Demersal Fish Nursery Areas in the North Mediterranean Sea, a First Step Towards the Implementation of Spatial Planning for Trawl Fisheries

PubMed Central

Colloca, Francesco; Garofalo, Germana; Bitetto, Isabella; Facchini, Maria Teresa; Grati, Fabio; Martiradonna, Angela; Mastrantonio, Gianluca; Nikolioudakis, Nikolaos; Ordinas, Francesc; Scarcella, Giuseppe; Tserpes, George; Tugores, M. Pilar; Valavanis, Vasilis; Carlucci, Roberto; Fiorentino, Fabio; Follesa, Maria C.; Iglesias, Magdalena; Knittweis, Leyla; Lefkaditou, Eugenia; Lembo, Giuseppe; Manfredi, Chiara; Massutí, Enric; Pace, Marie Louise; Papadopoulou, Nadia; Sartor, Paolo; Smith, Christopher J.; Spedicato, Maria Teresa

2015-01-01

The identification of nursery grounds and other essential fish habitats of exploited stocks is a key requirement for the development of spatial conservation planning aimed at reducing the adverse impact of fishing on the exploited populations and ecosystems. The reduction in juvenile mortality is particularly relevant in the Mediterranean and is considered as one of the main prerequisites for the future sustainability of trawl fisheries. The distribution of nursery areas of 11 important commercial species of demersal fish and shellfish was analysed in the European Union Mediterranean waters using time series of bottom trawl survey data with the aim of identifying the most persistent recruitment areas. A high interspecific spatial overlap between nursery areas was mainly found along the shelf break of many different sectors of the Northern Mediterranean indicating a high potential for the implementation of conservation measures. Overlap of the nursery grounds with existing spatial fisheries management measures and trawl fisheries restricted areas was also investigated. Spatial analyses revealed considerable variation depending on species and associated habitat/depth preferences with increased protection seen in coastal nurseries and minimal protection seen for deeper nurseries (e.g. Parapenaeus longirostris 6%). This is partly attributed to existing environmental policy instruments (e.g. Habitats Directive and Mediterranean Regulation EC 1967/2006) aiming at minimising impacts on coastal priority habitats such as seagrass, coralligenous and maerl beds. The new knowledge on the distribution and persistence of demersal nurseries provided in this study can support the application of spatial conservation measures, such as the designation of no-take Marine Protected Areas in EU Mediterranean waters and their inclusion in a conservation network. The establishment of no-take zones will be consistent with the objectives of the Common Fisheries Policy applying the ecosystem approach to fisheries management and with the requirements of the Marine Strategy Framework Directive to maintain or achieve seafloor integrity and good environmental status. PMID:25785737

Macrofauna community inside and outside of the Darwin Mounds SAC, NE Atlantic

NASA Astrophysics Data System (ADS)

Serpetti, N.; Gontikaki, E.; Narayanaswamy, B. E.; Witte, U.

2012-11-01

Over the past two decades, growing concerns have been raised regarding the effects of towed fishing gears, such as trawls and dredges, on deep-sea biodiversity and ecosystem functioning. Trawling disturbs the benthic communities both physically and biologically, and can eliminate the most vulnerable organisms and modify habitat structure; chronically disturbed communities are often dominated by opportunistic species. The European Union is under obligation to designate a network of offshore Special Areas of Conservation (SACs) and Marine Protected Areas (MPAs) by the end of 2012 based on the perceived expectation that these networks will help protect marine biodiversity and that within these areas, faunal abundance and diversity will be higher than the surrounding fished areas. The Darwin Mounds, only discovered in 1998, are located in the Rockall Trough, NE Atlantic at a depth of ~ 1000 m. Deep-water trawling regularly took place in the region of the Darwin Mounds; however in 2004 the mounds were designated as the first offshore SAC in UK and the area is now closed to bottom trawling. As part of the HERMIONE programme the influence of human impact on the Oceans was one of the key themes and in June 2011, an investigation of the macrofaunal community structure at comparable sites both inside and outside of the Darwin Mound SAC was undertaken. Macrofaunal communities were found to differ significantly, with the difference mostly driven by changes in the abundance of polychaetes, crustaceans and nematodes whilst no significant differences were seen for the other phyla. Whereas overall macrofaunal abundance was higher outside the SAC compared to within, this pattern varies considerably between phyla. Diversity indices showed no significant differences between protected and unprotected sites. This could indicate that a few years of preservation are not enough time to determine a recovery by the macrofaunal community of cold-water ecosystems and that a continued monitoring over a longer term is necessary to fully understand the impact of fishery closures.

Effectiveness of three best management practices for highway-runoff quality along the Southeast Expressway, Boston, Massachusetts

USGS Publications Warehouse

Smith, Kirk P.

2002-01-01

Best management practices (BMPs) near highways are designed to reduce the amount of suspended sediment and associated constituents, including debris and litter, discharged from the roadway surface. The effectiveness of a deep-sumped hooded catch basin, three 2-chambered 1,500-gallon oil-grit separators, and mechanized street sweeping in reducing sediment and associated constituents was examined along the Southeast Expressway (Interstate Route 93) in Boston, Massachusetts. Repeated observations of the volume and distribution of bottom material in the oil-grit separators, including data on particle-size distributions, were compared to data from bottom material deposited during the initial 3 years of operation. The performance of catch-basin hoods and the oil-grit separators in reducing floating debris was assessed by examining the quantity of material retained by each structural BMP compared to the quantity of material retained by and discharged from the oil-grit separators, which received flow from the catch basins. The ability of each structural BMP to reduce suspended-sediment loads was assessed by examining (a) the difference in the concentrations of suspended sediment in samples collected simultaneously from the inlet and outlet of each BMP, and (b) the difference between inlet loads and outlet loads during a 14-month monitoring period for the catch basin and one separator, and a 10-month monitoring period for the second separator. The third separator was not monitored continuously; instead, samples were collected from it during three visits separated in time by several months. Suspended-sediment loads for the entire study area were estimated on the basis of the long-term average annual precipitation and the estimated inlet and outlet loads of two of the separators. The effects of mechanized street sweeping were assessed by evaluating the differences between suspended-sediment loads before and after street sweeping, relative to storm precipitation totals, and by comparing the particle-size distributions of sediment samples collected from the sweepers to bottom-material samples collected from the structural BMPs. A mass-balance calculation was used to quantify the accuracy of the estimated sediment-removal efficiency for each structural BMP. The ability of each structural BMP to reduce concentrations of inorganic and organic constituents was assessed by determining the differences in concentrations between the inlets and outlets of the BMPs for four storms. The inlet flows of the separators were sampled during five storms for analysis of fecal-indicator bacteria. The particle-size distribution of bottom material found in the first and second chambers of the separators was similar for all three separators. Consistent collection of floatable debris at the outlet of one separator during 12 storms suggests that floatable debris were not indefinitely retained.Concentrations of suspended sediment in discrete samples of runoff collected from the inlets of the two separators ranged from 8.5 to 7,110 mg/L. Concentrations of suspended sediment in discrete samples of runoff collected from the outlets of the separators ranged from 5 to 2,170 mg/L. The 14-month sediment-removal efficiency was 35 percent for one separator, and 28 percent for the second separator. In the combined-treatment system in this study, where catch basins provided primary suspended-sediment treatment, the separators reduced the mass of the suspended sediment from the pavement by about an additional 18 percent. The concentrations of suspended sediment in discrete samples of runoff collected from the inlet of the catch basin ranged from 32 to 13,600 mg/L. Concentrations of suspended sediment in discrete samples of runoff collected from the outlet of the catch basin ranged from 25.7 to 7,030 mg/L. The sediment-removal efficiency for individual storms during the 14-month monitoring period for the deep-sumped hooded catch basin was 39 percent.The concentrations of 29 in

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.

Ninespine Stickleback Abundance in Lake Michigan Increases After Dreissenid Mussel Invasion

USGS Publications Warehouse

Madenjian, Charles P.; Bunnell, David B.; Gorman, Owen T.

2010-01-01

Based on data from our annual lakewide bottom trawl survey of Lake Michigan, we determined that density of ninespine sticklebacks Pungitius pungitius increased from an average of 0.234 kg/ha during 1973–1995 to an average of 1.318 kg/ha during 1996–2007. This greater-than-fivefold increase in density coincided with the dreissenid mussel invasion of Lake Michigan. Intervention analysis revealed that ninespine stickleback density in Lake Michigan significantly increased between the two time periods. In contrast, based on data from our annual bottom trawl survey of U.S. waters of Lake Superior, ninespine stickleback density decreased from an average of 0.133 kg/ha during 1978–1999 to an average of only 0.026 kg/ha during 2000–2007. This greater-than-fivefold density decrease, which was found to be significant via intervention analysis, coincided with population recovery for both lean and fat morphotypes of lake trout Salvelinus namaycush in Lake Superior. In contrast to Lake Michigan, dreissenid mussels have not invaded Lake Superior on a lakewide basis. Thus, a comparison of these two lakes indicated that the increase in ninespine stickleback abundance in Lake Michigan was most likely attributable to the dreissenid mussel invasion. In addition, based on our correlation analysis, alewives Alosa pseudoharengus did not have an adverse effect on ninespine stickleback abundance in Lake Michigan. Perhaps the recent increase in biomass of green algae Cladophora spp. associated with the dreissenid mussel invasion improved spawning habitat quality for ninespine sticklebacks and led to their stepwise abundance increase in Lake Michigan beginning in 1996

Making robust policy decisions using global biodiversity indicators.

PubMed

Nicholson, Emily; Collen, Ben; Barausse, Alberto; Blanchard, Julia L; Costelloe, Brendan T; Sullivan, Kathryn M E; Underwood, Fiona M; Burn, Robert W; Fritz, Steffen; Jones, Julia P G; McRae, Louise; Possingham, Hugh P; Milner-Gulland, E J

2012-01-01

In order to influence global policy effectively, conservation scientists need to be able to provide robust predictions of the impact of alternative policies on biodiversity and measure progress towards goals using reliable indicators. We present a framework for using biodiversity indicators predictively to inform policy choices at a global level. The approach is illustrated with two case studies in which we project forwards the impacts of feasible policies on trends in biodiversity and in relevant indicators. The policies are based on targets agreed at the Convention on Biological Diversity (CBD) meeting in Nagoya in October 2010. The first case study compares protected area policies for African mammals, assessed using the Red List Index; the second example uses the Living Planet Index to assess the impact of a complete halt, versus a reduction, in bottom trawling. In the protected areas example, we find that the indicator can aid in decision-making because it is able to differentiate between the impacts of the different policies. In the bottom trawling example, the indicator exhibits some counter-intuitive behaviour, due to over-representation of some taxonomic and functional groups in the indicator, and contrasting impacts of the policies on different groups caused by trophic interactions. Our results support the need for further research on how to use predictive models and indicators to credibly track trends and inform policy. To be useful and relevant, scientists must make testable predictions about the impact of global policy on biodiversity to ensure that targets such as those set at Nagoya catalyse effective and measurable change.

Making Robust Policy Decisions Using Global Biodiversity Indicators

PubMed Central

Nicholson, Emily; Collen, Ben; Barausse, Alberto; Blanchard, Julia L.; Costelloe, Brendan T.; Sullivan, Kathryn M. E.; Underwood, Fiona M.; Burn, Robert W.; Fritz, Steffen; Jones, Julia P. G.; McRae, Louise; Possingham, Hugh P.; Milner-Gulland, E. J.

2012-01-01

In order to influence global policy effectively, conservation scientists need to be able to provide robust predictions of the impact of alternative policies on biodiversity and measure progress towards goals using reliable indicators. We present a framework for using biodiversity indicators predictively to inform policy choices at a global level. The approach is illustrated with two case studies in which we project forwards the impacts of feasible policies on trends in biodiversity and in relevant indicators. The policies are based on targets agreed at the Convention on Biological Diversity (CBD) meeting in Nagoya in October 2010. The first case study compares protected area policies for African mammals, assessed using the Red List Index; the second example uses the Living Planet Index to assess the impact of a complete halt, versus a reduction, in bottom trawling. In the protected areas example, we find that the indicator can aid in decision-making because it is able to differentiate between the impacts of the different policies. In the bottom trawling example, the indicator exhibits some counter-intuitive behaviour, due to over-representation of some taxonomic and functional groups in the indicator, and contrasting impacts of the policies on different groups caused by trophic interactions. Our results support the need for further research on how to use predictive models and indicators to credibly track trends and inform policy. To be useful and relevant, scientists must make testable predictions about the impact of global policy on biodiversity to ensure that targets such as those set at Nagoya catalyse effective and measurable change. PMID:22815938

Status of the deepwater cisco population of Lake Michigan

USGS Publications Warehouse

Smith, Stanford H.

1964-01-01

The species and size composition and the abundance of the cisco (Leucichthys spp.) population of Lake Michigan have undergone drastic changes since the sea lamprey became established in the 1940's. The changes were measured by the catches of gill nets of identical specifications fished at the same seasons, depths, and locations in 1930-32, 1954-55, and 1960-61. The two largest ciscoes (johannae and nigripinnis), exploited heavily in a highly selective fishery from the midnineteenth century to the early 1900's, were only sparsely represented in the catch in the 1930's and were absent from catches of the comparison surveys in 1954-55 and 1960-61. The species of intermediate size (alpenae, artedi, kiyi, reighardi, and zenithicus) constituted about two-thirds of the cisco stocks of the deepwater zone in the 1930's but declined to 23.9 and 6.4 percent in the 1950's and 1960's, respectively. Major causes of change were the increased fishing pressure and sea lamprey predation that accompanied the disappearance of the lake trout. The small, slow-growing cisco (hoyi) - the primary food of lake trout - which was not fished intensively, and was too small to suffer greatly from sea lamprey predation, increased from 31.0 percent of the catch in the 1930's to 76.1 percent in the 1950's and 93.6 percent in the 1960's. Consequences of the extreme imbalance of the cisco population have been a reduction in mean size of all species, extension of the range of the very abundant hoyi (formerly most abundant in moderately shallow areas) to almost all depths and sections of the lake, and possibly introgressive hybridization among the various species. The primary change in the fishery has been a shift from gill nets to more extensive use of trawls which can take the now abundant smaller fish.

How Are Fishing Patterns and Fishing Communities Responding to Climate Change? A Test Case from the Northwest Atlantic

NASA Astrophysics Data System (ADS)

Young, T.; Fuller, E.; Coleman, K.; Provost, M.; Pinsky, M. L.; St Martin, K.

2016-02-01

We know climate is changing and fish are moving in response to those changes. But we understand less about how harvesters are responding to these changes in fish distribution and the ramifications of those changes for fishing communities. Ecological and evolutionary theory suggests that organisms must move, adapt, or die in response to environmental changes, and a related frame may be relevant for human harvesters in the face of climate change. Furthermore, research suggests that there may be a portfolio effect: a wider diversity of catch may buffer harvesters from some effects of climate change. To get at these questions, we explored changes in fishing patterns among commercial fishing communities in the northeast US from 1997-2014 using NOAA-collected logbook data. We found that communities using more mobile gear (large trawl vessels) demonstrated a greater range of latitudinal shift than communities using any other gear. Latitudinal shift was also inversely related to species diversity of catch and port latitude in those communities: southern communities that caught few species shifted dramatically northward, and northern communities that caught many species did not demonstrate marked latitudinal shifts. Those communities that demonstrated larger latitudinal shifts also demonstrated smaller changes in catch composition than their more stationary counterparts. We also found that vessels are indeed leaving many, but not all, fisheries in this region. These results suggest that harvesters are moving, adapting, and leaving fisheries, and that there does appear to be a portfolio effect, with catch diversity mediating some of these responses. While these changes in fishing patterns cannot all be directly attributed to climate change per se, marine fishes in this region are shifting north rapidly, as is expected under climate change. This study provides a valuable test case for exploring the potential ramifications of climate change on coastal socio-ecological systems.

Ecological metrics of biomass removed by three methods of purse-seine fishing for tunas in the eastern tropical Pacific Ocean.

PubMed

Gerrodette, Tim; Olson, Robert; Reilly, Stephen; Watters, George; Perrin, William

2012-04-01

An ecosystem approach to fisheries management is a widely recognized goal, but describing and measuring the effects of a fishery on an ecosystem is difficult. Ecological information on the entire catch (all animals removed, whether retained or discarded) of both species targeted by the fishery and nontarget species (i.e., bycatch) is required. We used data from the well-documented purse-seine fishery for tunas (Thunnus albacares, T. obesus, and Katsuwonus pelamis) in the eastern tropical Pacific Ocean to examine the fishery's ecological effects. Purse-seine fishing in the eastern tropical Pacific is conducted in 3 ways that differ in the amount and composition of target species and bycatch. The choice of method depends on whether the tunas are swimming alone (unassociated sets), associated with dolphins (dolphin sets), or associated with floating objects (floating-object sets). Among the fishing methods, we compared catch on the basis of weight, number of individuals, trophic level, replacement time, and diversity. Floating-object sets removed 2-3 times as much biomass as the other 2 methods, depending on how removal was measured. Results of previous studies suggest the ecological effects of floating-object sets are thousands of times greater than the effects of other methods, but these results were derived from only numbers of discarded animals. Management of the fishery has been driven to a substantial extent by a focus on reducing bycatch, although discards are currently 4.8% of total catch by weight, compared with global averages of 7.5% for tuna longline fishing and 30.0% for midwater trawling. An ecosystem approach to fisheries management requires that ecological effects of fishing on all animals removed by a fishery, not just bycatch or discarded catch, be measured with a variety of metrics. ©2012 Society for Conservation Biology.

Great Lakes prey fish populations: A cross-basin overview of status and trends in 2008

USGS Publications Warehouse

Gorman, Owen T.; Bunnell, David B.

2009-01-01

Assessments of prey fishes in the Great Lakes have been conducted annually since the 1970s by the Great Lakes Science Center, sometimes assisted by partner agencies. Prey fish assessments differ among lakes in the proportion of a lake covered, seasonal timing, bottom trawl gear used, sampling design, and the manner in which the trawl is towed (across or along bottom contours). Because each assessment is unique in one or more important aspects, a direct comparison of prey fish catches among lakes is problematic. All of the assessments, however, produce indices of abundance or biomass that can be standardized to facilitate comparisons of trends among lakes and to illustrate present status of the populations. We present indices of abundance for important prey fishes in the Great Lakes standardized to the highest value for a time series within each lake: cisco (Coregonus artedi), bloater (C. hoyi), rainbow smelt (Osmerus mordax), and alewife (Alosa pseudoharengus). We also provide indices for round goby (Neogobius melanostomus), an invasive fish presently spreading throughout the basin. Our intent is to provide a short, informal report emphasizing data presentation rather than synthesis; for this reason we intentionally avoid use of tables and cited references.For each lake, standardized relative indices for annual biomass and density estimates of important prey fishes were calculated as the fraction relative to the largest value observed in the times series. To determine whether basin-wide trends were apparent for each species, we first ranked standardized index values within each lake. When comparing ranked index values from three or more lakes, we calculated the Kendall coefficient of concordance (W), which can range from 0 (complete discordance or disagreement among trends) to 1 (complete concordance or agreement among trends). The P-value for W provides the probability of agreement across the lakes. When comparing ranked index values from two lakes, we calculated the Kendall correlation coefficient (τ), which ranges from -1 (inverse association, perfect disagreement) to 1 (direct association, perfect agreement). Here, the P-value for τ provides the probability of either inverse or direct association between the lakes. First, we present trends in relative biomass of age-1 and older prey fishes to show changes in populations within each lake. Then, we present standardized indices of numerical abundance of a single age class to show changes in relative year-class strength within each lake. Indices of year-class strength reliably reflect the magnitude of the cohort size at subsequent ages. However, because of differences in survey timing across lakes, the age class that is used for each species to index year-class strength varies across lakes and, just as surveys differ among lakes, methods for determining fish age-class differ also. For Lake Superior cisco, bloater, smelt, and Lake Michigan alewife, year- class strengths are based on aged fish and age-length keys, and for all other combinations of lakes and species, age-classes are assigned based on fish length cut-offs. Our intent with this report is to provide a cross-lakes view of population trends but not to propose reasons for those trends.

Interpreting large-scale experiments on effects of trawling on benthic fauna: an empirical test of the potential effects of spatial confounding in experiments without replicated control and trawled areas.

PubMed

Lindegarth; Valentinsson; Hansson; Ulmestrand

2000-03-15

Disturbances due to trawling and dredging is a serious threat to assemblages of benthic marine animals. We tested hypotheses about effects of trawling on benthic assemblages in a manipulative field experiment, using gear and intensities relevant to future management of trawling in a Swedish fjord. Three trawled and three control sites were sampled at several times before and after trawling was initiated. This paper describes how conclusions about effects of trawling might differ between experiments involving replicate sites and experiments using only one trawled and one control site, as in several recent studies. Analyses of selected taxa showed that abundances of many species changed differently among control sites. Differences in temporal change between pairs of single trawled and control sites were also frequent. Neither the quantitative nor the qualitative nature of differences between treatments could, however, be coherently interpreted among the different combinations of trawled and control sites. This is consistent with results obtained from analyses using all sites, which showed no consistent effects of trawling on any of these taxa. These results provide empirical evidence that spatial confounding may cause serious problems to formal interpretation of experiments, which use only one control and one trawled area. Such potential problems can best be solved by ensuring that the study incorporates more than one control site.

Evidence of Trawl-Induced Resuspension at the Whittard Canyon, NE Atlantic?

NASA Astrophysics Data System (ADS)

Wilson, A. M.; Kiriakoulakis, K.; Raine, R.; Gerritsen, H. D.; Blackbird, S.; Allcock, A. L.; White, M. G.

2016-02-01

Four research surveys (2011-2014) to the Whittard Canyon have taken place as part of an Irish Bio-discovery and Ecosystem functioning project. Hydrographic observations including turbidity measurements and samples for biogeochemical analysis were collected in order to improve our understanding of sediment transport, biogeochemical cycling and trophic food webs within canyons. Benthic and intermediate nepheloid layers were detected during all four surveys, in eastern and western branches of the canyon. These layers act as a pathway from productive shelf environments to the deep abyss. Unusual peaks in turbidity were detected in two branches of the canyon in June 2013. These turbidity peaks, termed Enhanced Nepheloid Layers (ENLs), had elevated suspended particulate matter concentrations exceeding 1 mg L-1. Typically, concentrations of material in nepheloid layers range between 0.28-0.6 mg L-1, while the largest ENLs measured between 2-8 mg L-1. The ENLs measured 100-260 m in vertical height and were detected in water depths of between 640-2880 m. Vessel Monitoring System data showed that high spatial and temporal activity of potential bottom trawling vessels coincided with the occurrence of the ENLs. Molar C/N ratios of the suspended organic material from the ENLs showed a high degree of degradation. While trawling has previously been suspected to affect the Whittard Canyon, this is the first study to provide evidence of such activity. Regular occurrences of these events are likely to have implications for increased sediment fluxes, burial of organic carbon and alteration of benthic and canyon ecosystems.

15 CFR 922.164 - Additional activity regulations by Sanctuary area.

Code of Federal Regulations, 2011 CFR

2011-01-01

..., breaking, cutting, spearing or similarly injuring any coral or other marine invertebrate, or any plant... injuring any coral, marine invertebrate, fish, bottom formation, algae, seagrass or other living or dead...) Except for catch and release fishing by trolling in the Conch Reef, Alligator Reef, Sombrero Reef, and...

50 CFR 229.2 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... is designed for or is capable of, catching species including but not limited to lobster, crab (red... any gillnet gear, including an anchored float gillnet, sink gillnet or stab net, that is set anywhere in the water column and which is anchored, secured, or weighted to the bottom of the sea. Also called...

50 CFR 229.2 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... is designed for or is capable of, catching species including but not limited to lobster, crab (red... any gillnet gear, including an anchored float gillnet, sink gillnet or stab net, that is set anywhere in the water column and which is anchored, secured, or weighted to the bottom of the sea. Also called...

50 CFR 635.71 - Prohibitions.

Code of Federal Regulations, 2011 CFR

2011-10-01

... HMS. (36) Fish with bottom or pelagic longline and shark gillnet gear for HMS without adhering to the... Atlantic shark identification workshop certificate as specified at § 635.8. (53) Fish for, catch, possess....8. (12) Fish for Atlantic sharks with unauthorized gear or possess Atlantic sharks on board a vessel...

50 CFR 660.111 - Trawl fishery-definitions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Trawl fishery-definitions. 660.111 Section... Entry Trawl Fisheries § 660.111 Trawl fishery—definitions. These definitions are specific to the limited entry trawl fisheries covered in this subpart. General groundfish definitions are found at § 660.11...

50 CFR 679.20 - General limitations.

Code of Federal Regulations, 2012 CFR

2012-10-01

... season (1) Trawl 60% 20% 20% (i) Trawl CV 70% 10% 20% (ii) Trawl CP 50% 30% 20% (2) Hook-and-line CP and...-line CP 48.7 (5) Pot CV ≥60 ft (18.3 m) LOA 8.4 (6) Pot CP 1.5 (7) AFA trawl CP 2.3 (8) Amendment 80...) Trawl CV 74 % 11 % 15 % (ii) Trawl CP 75 % 25 % 0 % (2) Hook-and-line CP, hook-and-line CV ≥60 ft (18.3...

50 CFR 679.20 - General limitations.

Code of Federal Regulations, 2013 CFR

2013-10-01

... season (1) Trawl 60% 20% 20% (i) Trawl CV 70% 10% 20% (ii) Trawl CP 50% 30% 20% (2) Hook-and-line CP and...-line CP 48.7 (5) Pot CV ≥60 ft (18.3 m) LOA 8.4 (6) Pot CP 1.5 (7) AFA trawl CP 2.3 (8) Amendment 80...) Trawl CV 74 % 11 % 15 % (ii) Trawl CP 75 % 25 % 0 % (2) Hook-and-line CP, hook-and-line CV ≥60 ft (18.3...

Photographic evaluation of the impacts of bottom fishing on benthic epifauna

USGS Publications Warehouse

Collie, J.S.; Escanero, G.A.; Valentine, P.C.

2000-01-01

The gravel sediment habitat on the northern edge of Georges Bank (East coast of North America) is an important nursery area for juvenile fish, and the site of a productive scallop fishery. During two cruises to this area in 1994 we made photographic transects at sites of varying depths that experience varying degrees of disturbance from otter trawling and scallop dredging. Differences between sites were quantified by analyzing videos and still photographs of the sea bottom. Videos were analyzed for sediment types and organism abundance. In the still photos, the percentages of the bottom covered by bushy, plant-like organisms and colonial worm tubes (Filograna implexa) were determined, as was the presence/absence of encrusting bryozoa. Non-colonial organisms were also identified as specifically as possible and sediment type was quantified. Significant differences between disturbed and undisturbed areas were found for the variables measured in the still photos; colonial epifaunal species were conspicuously less abundant at disturbed sites. Results from the videos and still photos were generally consistent although less detail was visible in the videos. Emergent colonial epifauna provide a complex habitat for shrimp, polychaetes, brittle stars and small fish at undisturbed sites. Bottom fishing removes this epifauna, thereby reducing the complexity and species diversity of the benthic community. (C) 2000 International Council for the Exploration of the Sea.

Life history of the deep-sea cephalopod family Histioteuthidae in the western Mediterranean

NASA Astrophysics Data System (ADS)

Quetglas, Antoni; de Mesa, Aina; Ordines, Francesc; Grau, Amàlia

2010-08-01

The life cycle of the two species of the deep-sea family Histioteuthidae inhabiting the Mediterranean Sea ( Histioteuthis reversa and Histioteuthis bonnellii) was studied from monthly samples taken throughout the year during daytime hours by bottom trawl gears. A small sample of individuals found floating dead on the sea surface was also analyzed. Both species were caught exclusively on the upper slope at depths greater than 300 m. Their frequency of occurrence increased with depth and showed two different peaks, at 500-600 m and 600-700 m depth in H. bonnellii and H. reversa, respectively, which might indicate spatial segregation. Maturity stages were assigned using macroscopic determination and confirmed with histological analyses. Although mature males were caught all year round, no mature females were found, which suggests that their sexual maturation in the western Mediterranean takes place deeper than the maximum depth sampled (800 m). In fact, the increase in mean squid size with increasing depth in H. reversa indicates an ontogenetic migration to deeper waters. The individuals of both species found floating dead on the sea surface were spent females which had a relatively large cluster of small atresic eggs and a small number of remaining mature eggs scattered in the ovary and mantle cavity. The sizes of these females were clearly larger than the largest individuals caught with bottom trawls. A total of 12 and 7 different types of prey, belonging to three major taxonomic groups (crustaceans, osteichthyes and cephalopods), were identified in the stomach contents of H. reversa and H. bonnellii, respectively. In both species fishes were by far the main prey followed by crustaceans, whereas cephalopods were found only occasionally. The preys identified, mainly myctophids and natantian crustaceans, indicate that both histioteuthids base their diet on pelagic nictemeral migrators.

Predicted deep-sea coral habitat suitability for the U.S. West coast.

PubMed

Guinotte, John M; Davies, Andrew J

2014-01-01

Regional scale habitat suitability models provide finer scale resolution and more focused predictions of where organisms may occur. Previous modelling approaches have focused primarily on local and/or global scales, while regional scale models have been relatively few. In this study, regional scale predictive habitat models are presented for deep-sea corals for the U.S. West Coast (California, Oregon and Washington). Model results are intended to aid in future research or mapping efforts and to assess potential coral habitat suitability both within and outside existing bottom trawl closures (i.e. Essential Fish Habitat (EFH)) and identify suitable habitat within U.S. National Marine Sanctuaries (NMS). Deep-sea coral habitat suitability was modelled at 500 m×500 m spatial resolution using a range of physical, chemical and environmental variables known or thought to influence the distribution of deep-sea corals. Using a spatial partitioning cross-validation approach, maximum entropy models identified slope, temperature, salinity and depth as important predictors for most deep-sea coral taxa. Large areas of highly suitable deep-sea coral habitat were predicted both within and outside of existing bottom trawl closures and NMS boundaries. Predicted habitat suitability over regional scales are not currently able to identify coral areas with pin point accuracy and probably overpredict actual coral distribution due to model limitations and unincorporated variables (i.e. data on distribution of hard substrate) that are known to limit their distribution. Predicted habitat results should be used in conjunction with multibeam bathymetry, geological mapping and other tools to guide future research efforts to areas with the highest probability of harboring deep-sea corals. Field validation of predicted habitat is needed to quantify model accuracy, particularly in areas that have not been sampled.

Predicted Deep-Sea Coral Habitat Suitability for the U.S. West Coast

PubMed Central

Guinotte, John M.; Davies, Andrew J.

2014-01-01

Regional scale habitat suitability models provide finer scale resolution and more focused predictions of where organisms may occur. Previous modelling approaches have focused primarily on local and/or global scales, while regional scale models have been relatively few. In this study, regional scale predictive habitat models are presented for deep-sea corals for the U.S. West Coast (California, Oregon and Washington). Model results are intended to aid in future research or mapping efforts and to assess potential coral habitat suitability both within and outside existing bottom trawl closures (i.e. Essential Fish Habitat (EFH)) and identify suitable habitat within U.S. National Marine Sanctuaries (NMS). Deep-sea coral habitat suitability was modelled at 500 m×500 m spatial resolution using a range of physical, chemical and environmental variables known or thought to influence the distribution of deep-sea corals. Using a spatial partitioning cross-validation approach, maximum entropy models identified slope, temperature, salinity and depth as important predictors for most deep-sea coral taxa. Large areas of highly suitable deep-sea coral habitat were predicted both within and outside of existing bottom trawl closures and NMS boundaries. Predicted habitat suitability over regional scales are not currently able to identify coral areas with pin point accuracy and probably overpredict actual coral distribution due to model limitations and unincorporated variables (i.e. data on distribution of hard substrate) that are known to limit their distribution. Predicted habitat results should be used in conjunction with multibeam bathymetry, geological mapping and other tools to guide future research efforts to areas with the highest probability of harboring deep-sea corals. Field validation of predicted habitat is needed to quantify model accuracy, particularly in areas that have not been sampled. PMID:24759613

Impacts of Bottom Fishing on Sediment Biogeochemical and Biological Parameters in Cohesive and Non-cohesive Sediments

NASA Astrophysics Data System (ADS)

Sciberras, M.; Hiddink, J. G.; Powell, C.; Parker, R.; Krӧger, S.; Bolam, S. G.; Robertson, C.

2016-02-01

Sediment resuspension and bed reworking by tides, waves and biological activity are frequent in the energetic coastal environments. Sediment mixing by tides and waves are generally more important in regulating sediment processes in advection-dominated system such as sandy sediments, whereas sediment reworking by bioturbation is more important in diffusion-dominated systems such as muddy sediments. Bottom fishing constitutes an additional significant impact on benthic communities and sediment biogeochemical processes in coastal areas through physical changes in sediment resuspension and mixing and changes to bioturbating fauna. This study examined the biological (macro-infaunal) and biogeochemical responses to fishing at a muddy and sandy site in the Irish Sea that were predominantly impacted by otter trawls and scallop dredges, respectively. The sandy habitat (>90% sand) was typical of a hydrodynamic environment characterized by a diverse array of small infaunal species, low organic carbon levels and fast remineralisation of organic matter in the sediment. The muddier habitat (>65% fines) was dominated by fewer but larger bioturbating species compared to sand, and illustrated highly diffusional solute transport, higher organic carbon content and a shallower oxygen penetration depth. Generally there appeared to be no clear statistically significant changes in the biogeochemistry of the sandy or muddy habitat that could be attributed to different intensities of fishing. However, pore-water nutrient profiles of ammonium, phosphate and silicate provided clear evidence of organic matter burial and/or mixing as a result of trawling at the muddy site. The biogeochemistry at the sandy site appeared to remain dominated by the natural physical environment, so impact of fishing disturbance was less evident. These results suggest that fishing does not have comparable effects on the biology and biogeochemical processes in all benthic habitats.

A quantitative analysis of fishing impacts on shelf-sea benthos.

PubMed

Collie, Jeremy S; Hall, Stephen J; Kaiser, Michel J; Poiner, Ian R

2000-09-01

1. The effects of towed bottom-fishing gear on benthic communities is the subject of heated debate, but the generality of trawl effects with respect to gear and habitat types is poorly understood. To address this deficiency we undertook a meta-analysis of 39 published fishing impact studies. 2. Our analysis shows that inter-tidal dredging and scallop dredging have the greatest initial effects on benthic biota, while trawling has less effect. Fauna in stable gravel, mud and biogenic habitats are more adversely affected than those in less consolidated coarse sediments. 3. Recovery rate appears most rapid in these less physically stable habitats, which are generally inhabited by more opportunistic species. However, defined areas that are fished in excess of three times per year (as occurs in parts of the North Sea and Georges Bank) are likely to be maintained in a permanently altered state. 4. We conclude that intuition about how fishing ought to affect benthic communities is generally supported, but that there are substantial gaps in the available data, which urgently need to be filled. In particular, data on impacts and recovery of epifaunal structure-forming benthic communities are badly needed.

Empirical evaluation of predator-driven diel vertical migration in Lake Superior

USGS Publications Warehouse

Stockwell, J.D.; Hrabik, T.R.; Jensen, O.P.; Yule, D.L.; Balge, M.

2010-01-01

Recent studies on Lake Superior suggest that diel vertical migration (DVM) of prey (generalized Coregonus spp.) may be influenced by the density of predatory siscowet (Salvelinus namaycush). We empirically evaluated this hypothesis using data from acoustic, midwater trawl, and bottom trawl sampling at eight Lake Superior sites during three seasons in 2005 and a subset of sites in 2006. We expected the larger-bodied cisco (Coregonus artedi) to exhibit a shallower DVM compared with the smaller-bodied kiyi (Coregonus kiyi). Although DVM of kiyi and cisco were consistent with expectations of DVM as a size-dependent, predator-mediated process, we found no relationship between siscowet density and the magnitude of DVM of either coregonid. Cisco appear to have a size refuge from siscowet predation. Kiyi and siscowet co-occur in demersal habitat > 150 m during the day, where visual predation is unlikely, suggesting predator avoidance is not a factor in the daytime distribution of kiyi. Seasonal patterns of kiyi DVM were consistent with reported DVM of their primary prey Mysis relicta. Our results suggest that consideration of nonvisual foraging, rather than lightbased foraging theory (i.e., the antipredation window), is necessary to understand the processes driving DVM in deepwater systems.

50 CFR 660.70 - Groundfish conservation areas.

Code of Federal Regulations, 2011 CFR

2011-10-01

... points for the RCAs. (1) Trawl (Limited Entry and Open Access Nongroundfish Trawl Gears) Rockfish....71 through 660.74. (2) Non-Trawl (Limited Entry Fixed Gear and Open Access Non-trawl Gears) Rockfish...

77 FR 26103 - Magnuson-Stevens Fishery Conservation and Management Act Provisions; Fisheries of the...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-02

...NMFS approves Framework Adjustment 47 (Framework 47) to the Northeast (NE) Multispecies Fishery Management Plan (FMP) and implements the approved measures. The New England Fishery Management Council (Council) developed and adopted Framework 47 based on the biennial review process established in the NE Multispecies FMP to develop annual catch limits (ACLs) and revise management measures necessary to rebuild overfished groundfish stocks and achieve the goals and objectives of the FMP. This action also implements management measures and revises existing regulations that are not included in Framework 47, including common pool management measures for fishing year (FY) 2012, modification of the Ruhle trawl definition, and clarification of the regulations for charter/party and recreational groundfish vessels fishing in groundfish closed areas. This action is intended to prevent overfishing, rebuild overfished stocks, achieve optimum yield, and ensure that management measures are based on the best available scientific information at the time Framework 47 was submitted.

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 the coastal southeastern Bering Sea for juvenile flatfishes from the relationships between diet, body condition and prey availability

NASA Astrophysics Data System (ADS)

Yeung, Cynthia; Yang, Mei-Sun

2017-01-01

The distribution and body condition of juvenile northern rock sole (NRS), Lepidopsetta polyxystra, and yellowfin sole (YFS), Limanda aspera, were studied in relation to prey availability across the coastal shelf at the Alaska Peninsula boundary of the eastern Bering Sea (EBS) to assess spatial variability in habitat quality. Juveniles of ≤ 20 cm and adults of ≥ 30 cm total length were collected from bottom trawl catch samples at stations located 10 to 120 km from the Alaska Peninsula coast, and in bottom depths of 28 to 85 m. Stomach contents and stable isotopes of carbon and nitrogen from muscle tissue were analyzed to describe diet composition. The quantity and quality of prey did not significantly affect the distribution of juvenile NRS and YFS. Spatial mismatch between the diet composition and the infauna prey assemblage suggested that prey availability was not limiting across the area, allowing fish to select for prey, presumably to maximize net energy gain. The body condition of juvenile NRS was higher in the eastern section of the area (Bristol Bay) - where they shared spatial and dietary niches with juvenile YFS, than in the west section (Unimak Island) where juvenile YFS were largely absent. A difference in body condition suggests that habitat quality may be higher in Bristol Bay. For NRS, stomach contents and stable isotopes in muscle tissue indicated an ontogenetic diet shift from amphipods to polychaetes from juvenile to adult stages. In contrast, for YFS, amphipods seemed to remain the primary prey and polychaetes the least important prey from juvenile to adult stage. Given that the high prey availability found in this south coastal area of EBS extends to areas across the EBS shelf, favorable habitat for juvenile flatfishes should be extensive. However, much of this potential juvenile habitat is underutilized by NRS, which were mainly limited to Bristol Bay and the Alaska Peninsula, whereas YFS did extend north over 500 km from Bristol Bay along the inner shelf domain (≤ 50 m deep). Abiotic factors, particularly ocean currents and water temperature, may be more significant than prey availability in the spatial distribution of juveniles. Thus, changes in the hydrographic and thermal regime of the EBS are likely to impact juvenile flatfish distribution and habitat productivity.

Population biology and feeding habits of the nephropid lobster Metanephrops thomsoni (Bate, 1888) in the East China Sea.

PubMed

Choi, Jung Hwa; Kim, Jung Nyun; Kim, Mi Hyang; Chang, Dae Soo; Yoo, Joon Taek; Kim, Jin Koo

2008-07-01

Population biology and feeding habits of the nephropidlobsterMetanephrops thomsoni (Bate) was studied from a field survey sampled with bottom trawls in the East China Sea. The female/male ratio was 1.06:1. Three size-class groups were discriminated for both sexes, which may correspond to one to three year-old cohorts. The average stage fecundity was 471 in each brood. Larger than two-year-size-class females are multi broods during the breeding season. Gut analysis showed that this lobster is a common camivore and mainly consume crustaceans and fishes, regardless of sex and carapace length size.

Survey of Lake Ontario bottom sediment off Rochester, New York, to define the extent of jettisoned World War II material and its potential for sediment contamination

USGS Publications Warehouse

Kennedy, Gregory; Kappel, William M.

2000-01-01

Military-type mat??riel was recovered from the bottom of Lake Ontario near Rochester, N.Y., during bottom-trawl, fish-stock surveys at depths of 75 to 180 feet each year from 1978 through 1996. The recovered mat??riel included many shell-detonator nose cones (2 inches in diameter by about 3.5 inches long); several electronic components; one corroded box of detonators; a corrugated container of mercury-filled capsules; and corroded batteries. Most of the recovered mat??riel has been identified as defective components of shell detonators (proximity-fuze assemblies) that were jettisoned in the lake to protect them from discovery during World War II. Side-scan SONAR, metal-detector, and ROV (remotely-operated-vehicle) surveys found no evidence of any large piles of mat??riel containing potentially hazardous, toxic, or polluting materials within the 17-square-mile study site. Many scattered magnetic anomalies were detected in this area, but chemical analysis of bottom sediment and of zebra- and quagga-mussel (Dreissena spp.) tissue indicate that the concentrations of mercury and other heavy metals are within the previously documented ranges for Lake Ontario sediment. The failure of ROV videos and of SCUBA-diver surveys and probes of the lake bottom to locate any debris indicates that most, if not all, of the debris is scattered and buried under a layer of fine-grained sediment and, possibly, mussels.

Resource partitioning within major bottom fish species in a highly productive upwelling ecosystem

NASA Astrophysics Data System (ADS)

Abdellaoui, Souad; El Halouani, Hassan; Tai, Imane; Masski, Hicham

2017-09-01

The Saharan Bank (21-26°N) is a wide subtropical continental shelf and a highly productive upwelling ecosystem. The bottom communities are dominated by octopus and sparid fish, which are the main targets of bottom-trawl fishing fleets. To investigate resource partitioning within the bottom fish community, adult fish from 14 of the most abundant species were investigated for stomach content analysis. Samples were collected during two periods: October 2003 and May 2007. The diet of the analysed species showed more variation between periods than between size classes, suggesting that temporal or spatial variability in prey availability appears to play a significant role in their diet. Multivariate analysis and subsequent clustering led to a grouping of the species within five trophic guilds. Two species were fish feeders, and the others mainly fed on benthic invertebrates, where epibenthic crustaceans, lamellibranchs and fish were the most important groups in defining trophic guilds. We found that the studied species had a high rate of overlapping spatial distributions and overlapping trophic niches. In this highly productive upwelling ecosystem, where food resources may not be a limiting factor, inter-specific competition did not appear to be an important factor in structuring bottom fish communities. For the species that showed differences in the proportions of prey categories in comparison with other ecosystems, the rise of the proportion of epibenthic crustaceans in their diet was a common feature; a possible consequence of the benthic productivity of this highly productive upwelling ecosystem.

30 CFR 250.1743 - How do I certify that a site is clear of obstructions?

Code of Federal Regulations, 2010 CFR

2010-07-01

... (6) A post-trawling job plot or map showing the trawled area. (b) For a platform or other facility... recovered; and (7) A post-trawling job plot or map showing the trawled area. [67 FR 35406, May 17, 2002; 67...

Inter-cohort growth patterns of pharaoh cuttlefish Sepia pharaonis (Sepioidea: Sepiidae) in Eastern Arabian Sea.

PubMed

Sasikumarl, Geetha; Mohamed, K S; Bhat, U S

2013-03-01

Sepia pharaonis is an important commercial species endemic to the tropical Indo-Pacific region. Despite its commercial significance, only few information on natural populations is available. This study was aimed to describe the aspects of size-composition, length-weight relationship, catch rates, seasonal recruitment and inter-cohort growth patterns of S. pharaonis population (Clade C), distributed along the Eastern Arabian Sea (South-West coast of India). For this, the Dorsal Mantle Length (DML) and weight of cuttlefishes was obtained from commercial trawl catches, from April 2002 to October 2006. Data was analyzed by normal length-weight methods such as von Bertalanffy. A total of 12454 cuttlefishes, ranging in length from four to 41cm were analyzed. Size-composition patterns discriminated two pulses in recruitment to the fishery, discernible by a decrease in the monthly mean size of the population. The DMLs of the two seasonal cohorts were subjected to modal-progression analysis using the Bhattacharya's method for the estimation of growth. The estimated parameters Linfinity and K in von Bertalanffy Growth Function (VBGF) were used to model growth curves in length for the cohorts. The first cohort, (post-monsoon cohort) which supports the major fishery, was composed of medium-sized, fast growing individuals, whereas the second cohort (pre-monsoon cohort), comprised of slow growing and large-sized individuals. There were differential growth characteristics between the sexes and the life span was estimated at less than 2.3 years for males and 2.1 years for females. Negative allometric growth in weight (W) with length (L) was observed for males (W=0.33069.L2.5389) and females (W=0.32542.L26057). The females were heavier compared to males at any given mantle length, and the males were found to attain larger ultimate lengths. The major fishing season for cuttlefish was from May to November, when higher monthly catch rates of 1.67-13.02kg/h were observed in comparison with 0.03-0.85kg/h in December-April. Seasonal catch rates indicated a migratory life cycle ofS. pharaonis between offshore and inshore coastal zones.

Distribution and trajectories of floating and benthic marine macrolitter in the south-eastern North Sea.

PubMed

Gutow, Lars; Ricker, Marcel; Holstein, Jan M; Dannheim, Jennifer; Stanev, Emil V; Wolff, Jörg-Olaf

2018-06-01

In coastal waters the identification of sources, trajectories and deposition sites of marine litter is often hampered by the complex oceanography of shallow shelf seas. We conducted a multi-annual survey on litter at the sea surface and on the seafloor in the south-eastern North Sea. Bottom trawling was identified as a major source of marine litter. Oceanographic modelling revealed that the distribution of floating litter in the North Sea is largely determined by the site of origin of floating objects whereas the trajectories are strongly influenced by wind drag. Methods adopted from species distribution modelling indicated that resuspension of benthic litter and near-bottom transport processes strongly influence the distribution of litter on the seafloor. Major sink regions for floating marine litter were identified at the west coast of Denmark and in the Skagerrak. Our results may support the development of strategies to reduce the pollution of the North Sea. Copyright © 2018 Elsevier Ltd. All rights reserved.

Fatty acid profiles of benthic environment associated with artificial reefs in subtropical Hong Kong.

PubMed

Cheung, Siu Gin; Wai, Ho Yin; Shin, Paul K S

2010-02-01

Artificial reefs can enhance habitat heterogeneity, especially in seabed degraded by bottom-dredging and trawling. However, the trophodynamics of such reef systems are not well understood. This study provided baseline data on trophic relationships in the benthic environment associated with artificial reefs in late spring and mid summer of subtropical Hong Kong, using fatty acid profiles as an indicator. Data from sediments collected at the reef base, materials from sediment traps deployed on top and bottom of the reefs, total particulate matter from the water column and oyster tissues from reef surface were subjected to principal component analysis. Results showed variations of fatty acid profiles in the total particulate matter, upper sediment trap and oyster tissue samples collected in the two samplings, indicating seasonal, trophodynamic changes within the reef system. The wastes produced by fish aggregating at the reefs can also contribute a source of biodeposits to the nearby benthic environment. Copyright 2009 Elsevier Ltd. All rights reserved.

50 CFR 660.114 - Trawl fishery-economic data collection program.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Trawl fishery-economic data collection... West Coast Groundfish-Limited Entry Trawl Fisheries § 660.114 Trawl fishery—economic data collection program. (a) General. The economic data collection (EDC) program collects mandatory economic data from...

50 CFR 660.114 - Trawl fishery-economic data collection program.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Trawl fishery-economic data collection... West Coast Groundfish-Limited Entry Trawl Fisheries § 660.114 Trawl fishery—economic data collection program. (a) General. The economic data collection (EDC) program collects mandatory economic data from...

50 CFR 660.114 - Trawl fishery-economic data collection program.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Trawl fishery-economic data collection... West Coast Groundfish-Limited Entry Trawl Fisheries § 660.114 Trawl fishery—economic data collection program. (a) General. The economic data collection (EDC) program collects mandatory economic data from...

50 CFR 660.114 - Trawl fishery-economic data collection program.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Trawl fishery-economic data collection... West Coast Groundfish-Limited Entry Trawl Fisheries § 660.114 Trawl fishery—economic data collection program. (a) General. The economic data collection (EDC) program collects mandatory economic data from...

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

Snake River fall Chinook salmon life history investigations: Annual report 2011 (April 2011 - March 2012)

USGS Publications Warehouse

Tiffan, Kenneth F.; Connor, William P.; Bellgraph, Brian J.; Kock, Tobias J.; Mullins, Frank; Steinhorst, R. Kirk; Christiansen, Helena E.; McCormick, Stephen D.; Ortega, Lori A.; Carter, Kathleen M.; Arntzen, Evan V.; Klett, Katherine J.C.; Deng, Z. Daniel; Abel, Tylor K.; Linley, Timothy J.; Cullinan, Valerie I.; St John, Scott J.; Erhardt, John M.; Bickford, Brad; Schmidt, Amanda; Rhodes, Tobyn N.

2013-01-01

Chapter Four – We conducted monthly beam trawling in Lower Granite and Little Goose reservoirs to describe the seasonal abundance of benthic epifauna that are potentially important as prey to juvenile fall Chinook salmon. The predominant taxa collected were Siberian prawns, the opossum shrimp Neomysis mercedis, and the amphipod Corophium sp. Prawns were relatively abundant at shallow sites in both reservoirs in June, but were more abundant at deep sites in lower and middle reservoir reaches in autumn. Prawn densities were commonly <0.2/m2. Prawn length-frequency data indicated that there were at least two size classes. Juvenile prawns present in shallow water more often than adult prawns, which were generally only found in deep water by autumn. Ovigerous prawns had an average of 171 eggs, which represented about 11.5% of their body weight. Limited diet analyses suggested that prawns consumed Corophium, Neomysis, and aquatic insects. Neomysis dominated all catches both in terms of abundance and biomass, and they were more abundant in Lower Granite compared to Little Goose reservoir. Neomysis were more abundant at shallow sites than at deep sites. Corophium were present in our collections but were never abundant, probably because our trawl was not effective at capturing them. The caloric content of prawns (4,782 Kcal), Neomysis (4,962 Kcal), and Corophium (4,926 Kcal) indicates that these prey would be energetically profitable for juvenile salmon. Subyearling fall Chinook salmon prey heavily on Neomysis and Corophium at times, but the importance of prawns as prey is uncertain.

77 FR 66577 - Fisheries Off West Coast States; Pacific Coast Groundfish Fishery; Trawl Rationalization Program...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-06

... Pacific Fishery Management Council's Web site at http://www.pcouncil.org/ . Background In January 2011... groundfish fishery's trawl fleet. The trawl rationalization program consists of an IFQ program for the shorebased trawl fleet (including whiting and non-whiting fisheries); and cooperative (coop) programs for the...

VMSbase: an R-package for VMS and logbook data management and analysis in fisheries ecology.

PubMed

Russo, Tommaso; D'Andrea, Lorenzo; Parisi, Antonio; Cataudella, Stefano

2014-01-01

VMSbase is an R package devised to manage, process and visualize information about fishing vessels activity (provided by the vessel monitoring system--VMS) and catches/landings (as reported in the logbooks). VMSbase is primarily conceived to be user-friendly; to this end, a suite of state-of-the-art analyses is accessible via a graphical interface. In addition, the package uses a database platform allowing large datasets to be stored, managed and processed vey efficiently. Methodologies include data cleaning, that is removal of redundant or evidently erroneous records, and data enhancing, that is interpolation and merging with external data sources. In particular, VMSbase is able to estimate sea bottom depth for single VMS pings using an on-line connection to the National Oceanic and Atmospheric Administration (NOAA) database. It also allows VMS pings to be assigned to whatever geographic partitioning has been selected by users. Standard analyses comprise: 1) métier identification (using a modified CLARA clustering approach on Logbook data or Artificial Neural Networks on VMS data); 2) linkage between VMS and Logbook records, with the former organized into fishing trips; 3) discrimination between steaming and fishing points; 4) computation of spatial effort with respect to user-selected grids; 5) calculation of standard fishing effort indicators within Data Collection Framework; 6) a variety of mapping tools, including an interface for Google viewer; 7) estimation of trawled area. Here we report a sample workflow for the accessory sample datasets (available with the package) in order to explore the potentialities of VMSbase. In addition, the results of some performance tests on two large datasets (1×10(5) and 1×10(6) VMS signals, respectively) are reported to inform about the time required for the analyses. The results, although merely illustrative, indicate that VMSbase can represent a step forward in extracting and enhancing information from VMS/logbook data for fisheries studies.

Age and growth of alewives in the changing pelagia of Lake Ontario, 1978-1992

USGS Publications Warehouse

O'Gorman, Robert; Johannsson, Ora E.; Schneider, Clifford P.

1997-01-01

We documented the age and growth of alewives Alosa pseudoharenqus in Lake Ontario during 1978-1992 and determined if growth was affected by intraspecific competition for epilimnetic zooplankton, lake temperature, or demand of salmonine piscivores for prey. Ages of juvenile alewives were determined from scales during 1978-1983, and ages of juvenile and adult alewives were determined from otoliths during 1984-1992. Indices of abundance for alewives were calculated from spring bottom trawl catches in 1978-1992; zooplankton density and epilimnetic temperature were monitored at two stations during 1981-1991; and salmonine demand each year during 1978-1992 was calculated with a simulation model. Although we encountered 11-year-old alewives, few fish lived longer than 7 years, and most fish in the population were younger than 6 years. Mean sizes at ages 1, 2, and 3 in spring averaged 93 mm (5.1 g), 133 mm (17 g), and 149 mm (22 g), but from age 3 to age 8, mean size increased by only 5-7 mm and 2-3 g per year. Female alewives lived longer than male alewives and were always longer than male alewives at age 4 and older. Epilimnetic temperatures were suitable for rapid growth of juvenile alewives each year. Lake temperature had the potential to affect growth of adults but adult growth was not correlated with temperature suitability indices perhaps because temperature regimes differed among lake regions and alewives were mobile. Growth of alewives was not correlated with salmonine demand for prey. Competition for zooplankton among the two youngest alewife cohorts affected growth of age-1 alewives. Zooplankton density declined sharply in 1986, and should it decline again, growth of age-1 alewives will slow, unless numbers of age-0 alewives fall. Whether growth of age-1 fish declines or numbers of age-0 fish fall, the result of another decline in zooplankton density will be a reduction in the production of alewives needed to support piscivores.

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.

Surficial geology of the sea floor in Central Rhode Island Sound Southeast of Point Judith, Rhode Island

USGS Publications Warehouse

McMullen, K.Y.; Poppe, L.J.; Ackerman, S.D.; Blackwood, D.S.; Schaer, J.D.; Nadeau, M.A.; Wood, D.A.

2011-01-01

The U.S. Geological Survey (USGS) and the National Oceanic and Atmospheric Administration (NOAA) are working together to study sea-floor environments off the northeast coast of the United States. During 2008, NOAA survey H11996 collected multibeam echosounder data in a 65-square kilometer area in central Rhode Island Sound, southeast of Point Judith, Rhode Island. During 2010, the USGS collected bottom photographs and sediment samples from 25 stations in this study area. The bathymetry, photography, and sediment data are used to interpret sea-floor features including scour depressions, sand waves, trawl marks, and dredge spoils. Scour depressions cover the bathymetric highs in much of the study area. Sand waves are located mostly in the southwest, and trawl marks tend to be in the northern regions. Dredge spoils are located at a disposal site in a bathymetric low in the western end of the study area. Most stations have a sea-floor surface of sand or silty sand, but eight of the stations have boulders to pea-sized gravel or gravelly sediment on the surface. Photographs show sandy areas typically have scattered burrows, shells, amphipod communities, and worm tubes. Boulders and cobbles are commonly overgrown with hydrozoans and anemones.

Long-term changes of the Lake Michigan fish community following the reduction of exotic alewife (Alosa pseudoharengus)

USGS Publications Warehouse

Bunnell, D.B.; Madenjian, C.P.; Claramunt, R.M.

2006-01-01

We used our long-term annual bottom trawl survey (1973–2004) in Lake Michigan to reveal the response of the native fish community to the biological control of a dominant exotic fish, alewife (Alosa pseudoharengus), as well as to changes in total phosphorus and salmonine biomass. Through nonmetric multidimensional scaling, we documented a 1970s community largely dominated by alewife, and then a shift to a community dominated by several native species during the 1980s through 1990s, when alewife remained at relatively low levels. We argue that the recovery of burbot (Lota lota), deepwater sculpin (Myoxocephalus thompsonii), and yellow perch (Perca flavescens) was partially or fully aided by the alewife reduction. We argue that changes in phosphorus or salmonines were not directly related to abundance increases of native species. An additional community shift occurred during 1999–2004, which coincided with a reduction in species richness and total fish biomass in our trawl. The mechanisms underlying this latest shift may be related to reductions in nutrients, but further research is required. The restoration of the native fish community has been incomplete, however, as emerald shiner (Notropis atherinioides), cisco (Coregonus artedii), and lake trout (Salvelinus namaycush) have yet to demonstrate recovery.

76 FR 22057 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-20

... Catcher Vessels Using Trawl Gear in the Bering Sea and Aleutian Islands Management Area AGENCY: National... catcher vessels using trawl gear in the Bering Sea and Aleutian Islands Management Area (BSAI). This... Pacific cod allocated to catcher vessels using trawl gear in the BSAI. DATES: Effective 1200 hrs, Alaska...

76 FR 20891 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-14

... Catcher Vessels Using Trawl Gear in the Bering Sea and Aleutian Islands Management Area AGENCY: National... catcher vessels using trawl gear in the Bering Sea and Aleutian Islands Management Area (BSAI). This... Pacific cod allocated to catcher vessels using trawl gear in the BSAI. DATES: Effective 1200 hrs, Alaska...

Megafauna of vulnerable marine ecosystems in French mediterranean submarine canyons: Spatial distribution and anthropogenic impacts

NASA Astrophysics Data System (ADS)

Fabri, M.-C.; Pedel, L.; Beuck, L.; Galgani, F.; Hebbeln, D.; Freiwald, A.

2014-06-01

Vulnerable Marine Ecosystems (VME) in the deep Mediterranean Sea have been identified by the General Fisheries Commission for the Mediterranean as consisting of communities of Scleractinia (Lophelia pertusa and Madrepora oculata), Pennatulacea (Funiculina quadrangularis) and Alcyonacea (Isidella elongata). This paper deals with video data recorded in the heads of French Mediterranean canyons. Quantitative observations were extracted from 101 video films recorded during the MEDSEACAN cruise in 2009 (Aamp/Comex). Qualitative information was extracted from four other cruises (two Marum/Comex cruises in 2009 and 2011 and two Ifremer cruises in 1995 and 2010) to support the previous observations in the Cassidaigne and Lacaze-Duthiers canyons. All the species, fishing impacts and litter recognized in the video films recorded from 180 to 700 m depth were mapped using GIS. The abundances and distributions of benthic fishing resources (marketable fishes, Aristeidae, Octopodidae), Vulnerable Marine Species, trawling scars and litter of 17 canyons were calculated and compared, as was the open slope between the Stoechades and Toulon canyons. Funiculina quadrangularis was rarely observed, being confined for the most part to the Marti canyon and, I. elongata was abundant in three canyons (Bourcart, Marti, Petit-Rhône). These two cnidarians were encountered in relatively low abundances, and it may be that they have been swept away by repeated trawling. The Lacaze-Duthiers and Cassidaigne canyons comprised the highest densities and largest colony sizes of scleractinian cold-water corals, whose distribution was mapped in detail. These colonies were often seen to be entangled in fishing lines. The alcyonacean Callogorgia verticillata was observed to be highly abundant in the Bourcart canyon and less abundant in several other canyons. This alcyonacean was also severely affected by bottom fishing gears and is proposed as a Vulnerable Marine Species. Our studies on anthropogenic impacts show that seafloor disturbance by benthic fishing is mainly attributable to trawling in the Gulf of Lion and to long lines where rocky substrates are present. The bauxite residue (red mud) expelled in the Cassidaigne canyon was seen to prevent fauna from settling at the bottom of the canyon and it covered much of the flanks. Litter was present in all of the canyons and especially in considerable quantities in the Ligurian Sea, where the heads of the canyons are closer to the coast. Three Marine Protected Areas and one fishing area with restricted access have recently been established and should permit the preservation of these deep ecosystems.

Reproductive biology of Raja clavata (Elasmobranchii: Rajidae) from Southern Black Sea coast around Turkey

NASA Astrophysics Data System (ADS)

Saglam, Hacer; Ak, Orhan

2012-06-01

Specimens of Raja clavata were monthly collected at the coast of Havaalanı (Trabzon/Turkey) from January 2009 to December 2009 at depths between 20 and 40 m. A total of 230 individuals of thornback ray (131 females and 99 males) were collected by bottom trawls during research cruises. Using logistic regression, it was determined that TL at 50% maturity of males was 718 mm TL and of females 746 mm TL. The ovarian fecundity ranged from 27 to 60 yellow follicles in both ovaries. Females carrying egg cases were found in July and October. Variations in the gonadosomatic and hepatosomatic indices indicated a continuous reproductive cycle during the year.

Rainbow smelt (Osmerus mordax) as predators on young bloaters (Coregonus hoyi) in Lake Michigan

USGS Publications Warehouse

Stedman, Ralph M.; Argyle, Ray L.

1985-01-01

Examination of the stomach contents of rainbow smelt caught in bottom trawls in Lake Michigan during mid October, 1982, revealed that of 267 rainbow smelt (Osmerus mordax) with food in their stomachs, 56% (150) had eaten young-of-the-year fish. Nearly 15% of the prey fish consumed were bloaters (Coregonus hoyi), 21 % were alewives(Alosa pseudoharengus), and the rest could not be positively identified but were probably bloaters and alewives. Although smelt predation did not appear to have affected bloater abundance, continued increases in smelt abundance and declines in alewife populations could lead to increased predator pressure on bloater stocks, which are in the process of rebuilding.

White sturgeon mitigation and restoration in the Columbia and Snake rivers upstream from Bonneville Dam, Annual Progress Report April 2004 - March 2005. Report C

USGS Publications Warehouse

Parsley, M.J.; Kofoot, P.

2006-01-01

River discharge and water temperatures that occurred during April through July 2004 provided conditions suitable for spawning by white sturgeon downstream from Bonneville, The Dalles, John Day, and McNary dams. Optimal spawning temperatures in the four tailraces occurred for 3-4 weeks and coincided with the peak of the river hydrograph. However, the peak of the hydrograph was relatively low compared to past years, which is reflected in the relatively low monthly and annual indices of suitable spawning habitat. Bottom-trawl sampling in the Bonneville Reservoir revealed the presence of young-of-theyear (YOY) white sturgeon.

30 CFR 250.1741 - If I drag a trawl across a site, what requirements must I meet?

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 2 2011-07-01 2011-07-01 false If I drag a trawl across a site, what... OUTER CONTINENTAL SHELF Decommissioning Activities Site Clearance for Wells, Platforms, and Other Facilities § 250.1741 If I drag a trawl across a site, what requirements must I meet? If you drag a trawl...

77 FR 19564 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-02

... Catcher Vessels Using Trawl Gear in the Central Regulatory Area of the Gulf of Alaska AGENCY: National... (CVs) using trawl gear in the Central Regulatory Area of the Gulf of Alaska (GOA). This action is... apportioned to CVs using trawl gear in the Central Regulatory Area of the GOA. DATES: Effective 1200 hrs...

76 FR 17569 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-30

... Vessels Using Trawl Gear in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine... using trawl gear in the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary... for catcher vessels using trawl gear in the BSAI. DATES: Effective 1200 hrs, Alaska local time (A.l.t...

78 FR 11790 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-20

... Catcher Vessels Using Trawl Gear in the Western Regulatory Area of the Gulf of Alaska AGENCY: National... (CVs) using trawl gear in the Western Regulatory Area of the Gulf of Alaska (GOA). This action is... apportioned to CVs using trawl gear in the Western Regulatory Area of the GOA. DATES: Effective 1200 hours...

75 FR 16359 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-01

... Vessels Using Trawl Gear in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine... using trawl gear in the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary... for catcher vessels using trawl gear in the BSAI. DATES: Effective 1200 hrs, Alaska local time (A.l.t...

77 FR 13013 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-05

... Catcher Vessels Using Trawl Gear in the Bering Sea and Aleutian Islands Management Area AGENCY: National... using trawl gear in the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary... vessels using trawl gear in the BSAI. After the effective date of this closure the maximum retainable...

77 FR 11412 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-27

... Vessels Using Trawl Gear in the Western Regulatory Area of the Gulf of Alaska AGENCY: National Marine... (CVs) using trawl gear in the Western Regulatory Area of the Gulf of Alaska (GOA). This action is... apportioned to CVs using trawl gear in the Western Regulatory Area of the GOA. DATES: Effective 1200 hrs...

76 FR 18663 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-05

... Catcher Vessels Using Trawl Gear in the Bering Sea and Aleutian Islands Management Area AGENCY: National... using trawl gear in the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary... for catcher vessels using trawl gear in the BSAI. DATES: Effective 1200 hrs, Alaska local time (A.l.t...

78 FR 18528 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-27

... Catcher Vessels Using Trawl Gear in the Central Regulatory Area of the Gulf of Alaska AGENCY: National... (CVs) using trawl gear in the Central Regulatory Area of the Gulf of Alaska (GOA). This action is... apportioned to CVs using trawl gear in the Central Regulatory Area of the GOA. DATES: Effective 1200 hrs...

75 FR 12463 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-16

... Vessels Using Trawl Gear in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine... using trawl gear in the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary... for catcher vessels using trawl gear in the BSAI. DATES: Effective 1200 hrs, Alaska local time (A.l.t...

77 FR 23159 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-18

... Catcher Vessels Using Trawl Gear in the Bering Sea and Aleutian Islands Management Area AGENCY: National... using trawl gear in the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary... fishing for Pacific cod by catcher vessels using trawl gear in the BSAI. After the effective date of this...

78 FR 15643 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-12

... Catcher Vessels Using Trawl Gear in the Bering Sea and Aleutian Islands Management Area AGENCY: National... using trawl gear in the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary... catcher vessels using trawl gear in the BSAI. After the effective date of this closure the maximum...

Habitat, Fauna, and Conservation of Florida's Deep-Water Coral Reefs

NASA Astrophysics Data System (ADS)

Reed, J. K.; Pomponi, S. A.; Messing, C. G.; Brooke, S.

2008-05-01

Various types of deep-water coral habitats are common off the southeastern United States from the Blake Plateau through the Straits of Florida to the eastern Gulf of Mexico. Expeditions in the past decade with the Johnson-Sea- Link manned submersibles, ROVs, and AUVs have discovered, mapped and compiled data on the status, distribution, habitat, and biodiversity for many of these relatively unknown deep-sea coral ecosystems. We have discovered over three hundred, high relief (15-152-m tall) coral mounds (depth 700-800 m) along the length of eastern Florida (700 km). The north Florida sites are rocky lithoherms, whereas the southern sites are primarily classic coral bioherms, capped with dense 1-2 m tall thickets of Lophelia pertusa and Enallopsammia profunda. Off southeastern Florida, the Miami Terrace escarpment (depth 300-600 m) extends nearly 150 km as a steep, rocky slope of Miocene-age phosphoritic limestone, which provides habitat for a rich biodiversity of fish and benthic invertebrates. Off the Florida Keys, the Pourtalès Terrace (depth 200- 460 m) has extensive high-relief bioherms and numerous deep-water sinkholes to depths of 250-610 m and diameters up to 800 m. The dominant, deep-water, colonial scleractinian corals in this region include Oculina varicosa, L. pertusa, E. profunda, Madrepora oculata, and Solenosmilia variabilis. Other coral species include hydrozoans (Stylasteridae), bamboo octocorals (Isididae), numerous other gorgonians, and black corals (Antipatharia). These structure-forming taxa provide habitat and living space for a relatively unknown but biologically rich and diverse community of crustaceans, mollusks, echinoderms, polychaete and sipunculan worms, and associated fishes. We have identified 142 taxa of benthic macro-invertebrates, including 66 Porifera and 57 Cnidaria. Nearly 100 species of fish have been identified to date in association with these deep-water coral habitats. Paull et al. (2000) estimated that over 40,000 individual deep-water lithoherms may occur on the Blake Plateau and Straits of Florida, perhaps exceeding the areal extent of all the shallow-water reefs of the southeastern U.S. Our research program has provided data on the status of knowledge concerning these deep-reef habitats to the South Atlantic Fishery Management Council (SAFMC). Currently pending is a proposal by the SAFMC for a deep- water coral Habitat Area of Particular Concern (HAPC) that would extend from North Carolina to south Florida (78,888 km2) to protect these diverse and irreplaceable resources from destructive fishing activities such as bottom trawling. Deep-water reefs worldwide have been severely impacted by bottom trawling, including the deep-water Oculina coral reefs off central eastern Florida, which are structurally similar to the Lophelia reefs. Over a 30-year period, up to 99% of unprotected portions of the Oculina reefs were destroyed by rock shrimp trawling, whereas reefs designated as the Oculina HAPC in 1984 were protected from trawling and long-lines and are still relatively healthy. Numerous fisheries may target the deep-water Lophelia reef habitat including royal red shrimp, golden crab, and various fin fish.

30 CFR 250.1741 - If I drag a trawl across a site, what requirements must I meet?

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false If I drag a trawl across a site, what... Decommissioning Activities Site Clearance for Wells, Platforms, and Other Facilities § 250.1741 If I drag a trawl across a site, what requirements must I meet? If you drag a trawl across the site in accordance with...

30 CFR 250.1741 - If I drag a trawl across a site, what requirements must I meet?

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 2 2012-07-01 2012-07-01 false If I drag a trawl across a site, what... SHELF Decommissioning Activities Site Clearance for Wells, Platforms, and Other Facilities § 250.1741 If I drag a trawl across a site, what requirements must I meet? If you drag a trawl across the site in...

30 CFR 250.1741 - If I drag a trawl across a site, what requirements must I meet?

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 2 2014-07-01 2014-07-01 false If I drag a trawl across a site, what... SHELF Decommissioning Activities Site Clearance for Wells, Platforms, and Other Facilities § 250.1741 If I drag a trawl across a site, what requirements must I meet? If you drag a trawl across the site in...

30 CFR 250.1741 - If I drag a trawl across a site, what requirements must I meet?

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 2 2013-07-01 2013-07-01 false If I drag a trawl across a site, what... SHELF Decommissioning Activities Site Clearance for Wells, Platforms, and Other Facilities § 250.1741 If I drag a trawl across a site, what requirements must I meet? If you drag a trawl across the site in...

“Once upon a Time in the Mediterranean” Long Term Trends of Mediterranean Fisheries Resources Based on Fishers’ Traditional Ecological Knowledge

PubMed Central

Damalas, Dimitrios; Maravelias, Christos D.; Osio, Giacomo C.; Maynou, Francesc; Sbrana, Mario; Sartor, Paolo

2015-01-01

We investigate long-term changes in the Mediterranean marine resources driving the trawl fisheries by analysing fishers’ perceptions (Traditional Ecological Knowledge, TEK) throughout the Mediterranean Sea during the last 80 years. To this end, we conducted an extended set of interviews with experienced fishers that enabled us to classify species (or taxa) as ‘decreasing’ or ‘increasing’ both in terms of abundance, as well as average size in the catch. The aspect that most clearly emerged in all the investigated areas over time was the notable increase of fishing capacity indicators, such as engine power and fishing depth range. Atlantic mackerel, poor cod, scorpionfishes, striped seabream, and John Dory demonstrated a decreasing trend in the fishers’ perceived abundance, while Mediterranean parrotfish, common pandora, cuttlefish, blue and red shrimp, and mullets gave indications of an increasing temporal trend. Although, as a rule, trawler captains did not report any cataclysmic changes (e.g. extinctions), when they were invited to estimate total catches, a clear decreasing pattern emerged; this being a notable finding taking into account the steep escalation of fishing efficiency during the past century. The overall deteriorating status of stocks in most Mediterranean regions calls for responsible management and design of rebuilding plans. This should include historical information accounting for past exploitation patterns that could help defining a baseline of fish abundance prior to heavy industrial fisheries exploitation. PMID:25781459

An AIS-based approach to calculate atmospheric emissions from the UK fishing fleet

NASA Astrophysics Data System (ADS)

Coello, Jonathan; Williams, Ian; Hudson, Dominic A.; Kemp, Simon

2015-08-01

The fishing industry is heavily reliant on the use of fossil fuel and emits large quantities of greenhouse gases and other atmospheric pollutants. Methods used to calculate fishing vessel emissions inventories have traditionally utilised estimates of fuel efficiency per unit of catch. These methods have weaknesses because they do not easily allow temporal and geographical allocation of emissions. A large proportion of fishing and other small commercial vessels are also omitted from global shipping emissions inventories such as the International Maritime Organisation's Greenhouse Gas Studies. This paper demonstrates an activity-based methodology for the production of temporally- and spatially-resolved emissions inventories using data produced by Automatic Identification Systems (AIS). The methodology addresses the issue of how to use AIS data for fleets where not all vessels use AIS technology and how to assign engine load when vessels are towing trawling or dredging gear. The results of this are compared to a fuel-based methodology using publicly available European Commission fisheries data on fuel efficiency and annual catch. The results show relatively good agreement between the two methodologies, with an estimate of 295.7 kilotons of fuel used and 914.4 kilotons of carbon dioxide emitted between May 2012 and May 2013 using the activity-based methodology. Different methods of calculating speed using AIS data are also compared. The results indicate that using the speed data contained directly in the AIS data is preferable to calculating speed from the distance and time interval between consecutive AIS data points.

Humpback Dolphins (Genus Sousa) in India: An Overview of Status and Conservation Issues.

PubMed

Sutaria, Dipani; Panicker, Divya; Jog, Ketki; Sule, Mihir; Muralidharan, Rahul; Bopardikar, Isha

2015-01-01

This chapter aims to collate recent work done by different research teams along the Indian coast and presents research plans for the conservation and management of the genus Sousa in Indian waters. Humpback dolphins are the most common nearshore cetaceans found along the Indian coast. The taxonomy is confused, but two or more species of humpback dolphins may be present in India. Dedicated research on humpback dolphins and other cetaceans has been initiated only in the past few years and vast gaps in the ecology and conservation of the genus from the region remain. Dedicated and opportunistic research indicates that humpback dolphin presence is continuous along the west coast of India, owing to the contiguous favourable habitat of shallow nearshore waters, while along the east coast humpback dolphins are apparently found in pockets. Humpback dolphins are also the most numerous in incidental catch records from the coast, owing to the large overlap in space use with nearshore fisheries like small gillnets, trawls, shore seines and purse seines. Along many coastal sites, humpback dolphins are known to cause damage and depredation of fish catch of certain fishing gears, making them unpopular. At the same time, many fishers along the west coast have developed local dolphin-watching programmes as an alternate source of livelihood, providing positive impetus for conservation. However, research on the long-term effects of dolphin watching and its management is required. Some recommendations for more effective management of this species are made. © 2015 Elsevier Ltd All rights reserved.

Sensitivity of macrobenthic secondary production to trawling in the English sector of the Greater North Sea: A biological trait approach

NASA Astrophysics Data System (ADS)

Bolam, S. G.; Coggan, R. C.; Eggleton, J.; Diesing, M.; Stephens, D.

2014-01-01

Demersal trawling constitutes the most significant human impact on both the structure and functioning of coastal seabed fauna. While a number of studies have assessed the impacts of trawling on faunal community structure and the degree to which different taxa are vulnerable to trawling, few have focused on how these impacts affect important ecological functions of the seabed. In this study, we use biological trait analysis (BTA) to assess the relative sensitivity of benthic macrofauna to trawling, in both the short- and long-term, and use this information to describe the spatial variation in sensitivity of secondary production for the Greater North Sea (GNS). Within the GNS, estimates of total production varied by almost three orders of magnitude, from 1.66 kJ m- 2 y- 1 to 968.9 kJ m- 2 y- 1. Large-scale patterns were observed in the proportion of secondary production derived from trawling-sensitive taxa. In the southern North Sea, total production is predominantly governed by taxa with low sensitivity to trawling, whereas production is relatively trawling-sensitive in the northern North Sea and western English Channel. In general, the more sensitive and productive regions are associated with poorly-sorted, gravelly or muddy sediments, while the less sensitive and less productive regions are associated with well-sorted, sandy substrates. These relationships between production sensitivity and environmental features are primarily due to variations in long-term recovery; total production of most assemblages is highly sensitive to the direct impacts of trawling. We discuss the implications of these findings for management 1decisions to improve the environmental sustainability of trawling.

Configuring the Mesh Size, Side Taper and Wing Depth of Penaeid Trawls to Reduce Environmental Impacts

PubMed Central

Broadhurst, Matt K.; Sterling, David J.; Millar, Russell B.

2014-01-01

The effects of reducing mesh size while concomitantly varying the side taper and wing depth of a generic penaeid-trawl body were investigated to improve engineering performance and minimize bycatch. Five trawl bodies (with the same codends) were tested across various environmental (e.g. depth and current) and biological (e.g. species and sizes) conditions. The first trawl body comprised 41-mm mesh and represented conventional designs (termed the ‘41 long deep-wing'), while the remaining trawl bodies were made from 32-mm mesh and differed only in their side tapers, and therefore length (i.e. 1N3B or ‘long’ and ∼28o to the tow direction vs 1N5B or ‘short’ and ∼35o) and wing depths (‘deep’–97 T vs ‘shallow’–60 T). There were incremental drag reductions (and therefore fuel savings – by up to 18 and 12% per h and ha trawled) associated with reducing twine area via either modification, and subsequently minimizing otter-board area in attempts to standardize spread. Side taper and wing depth had interactive and varied effects on species selectivity, but compared to the conventional 41 long deep-wing trawl, the 32 short shallow-wing trawl (i.e. the least twine area) reduced the total bycatch by 57% (attributed to more fish swimming forward and escaping). In most cases, all small-meshed trawls also caught more smaller school prawns Metapenaeus macleayi but to decrease this effect it should be possible to increase mesh size slightly, while still maintaining the above engineering benefits and species selectivity. The results support precisely optimizing mesh size as a precursor to any other anterior penaeid-trawl modifications designed to improve environmental performance. PMID:24911786

Utility of a Work Process Classification System for characterizing non-fatal injuries in the Alaskan commercial fishing industry

PubMed Central

Syron, Laura N.; Lucas, Devin L.; Bovbjerg, Viktor E.; Bethel, Jeffrey W.; Kincl, Laurel D.

2016-01-01

Background The US commercial fishing industry is hazardous, as measured by mortality data. However, research on non-fatal injuries is limited. Non-fatal injuries constitute the majority of occupational injuries and can result in workers’ lowered productivity and wages, lost quality of life, and disability. In the United States, a Work Process Classification System (WPCS) has previously been applied in Alaskan freezer-trawl and freezer-longline fleets to identify causes of injuries and specific hazards, but not to other fishing fleets. Objectives This descriptive epidemiologic study aimed to explore the application and modification of the WPCS in multiple Alaskan fleets, characterize non-fatal occupational injuries in these fleets, and identify work processes that could be targeted for further investigation and future injury prevention efforts. Design Traumatic, non-fatal injuries on-board Alaskan commercial fishing vessels were identified through United States Coast Guard investigative reports. Characteristics of injuries, as well as worker characteristics, were analysed. Injuries were coded using the WPCS. Results We successfully utilized the WPCS to code non-fatal injury cases (n = 136). The most frequent main work processes associated with non-fatal injuries included: on-board trawlers, handling frozen fish and processing the catch; on-board vessels using pot/trap gear, handling the gear and shooting/setting the gear; on-board longliners, traffic on board and hauling the gear; and on-board processor vessels, processing the catch, other work with the catch, and handling frozen fish. Conclusions The study confirmed that a WPCS can be applied to multiple Alaskan fleets to identify hazardous tasks. Hazards were unique for each vessel gear type. Future injury prevention efforts should target work processes associated with the most frequent and most severe injuries. Future studies should establish time estimates for work processes in order to determine risk estimates. Efforts to improve non-fatal injury reporting, especially on smaller commercial fishing vessels, should be undertaken. PMID:26782030

Understanding the sources and effects of abandoned, lost, and discarded fishing gear on marine turtles in northern Australia.

PubMed

Wilcox, Chris; Heathcote, Grace; Goldberg, Jennifer; Gunn, Riki; Peel, David; Hardesty, Britta Denise

2015-02-01

Globally, 6.4 million tons of fishing gear are lost in the oceans annually. This gear (i.e., ghost nets), whether accidently lost, abandoned, or deliberately discarded, threatens marine wildlife as it drifts with prevailing currents and continues to entangle marine organisms indiscriminately. Northern Australia has some of the highest densities of ghost nets in the world, with up to 3 tons washing ashore per kilometer of shoreline annually. This region supports globally significant populations of internationally threatened marine fauna, including 6 of the 7 extant marine turtles. We examined the threat ghost nets pose to marine turtles and assessed whether nets associated with particular fisheries are linked with turtle entanglement by analyzing the capture rates of turtles and potential source fisheries from nearly 9000 nets found on Australia's northern coast. Nets with relatively larger mesh and smaller twine sizes (e.g., pelagic drift nets) had the highest probability of entanglement for marine turtles. Net size was important; larger nets appeared to attract turtles, which further increased their catch rates. Our results point to issues with trawl and drift-net fisheries, the former due to the large number of nets and fragments found and the latter due to the very high catch rates resulting from the net design. Catch rates for fine-mesh gill nets can reach as high as 4 turtles/100 m of net length. We estimated that the total number of turtles caught by the 8690 ghost nets we sampled was between 4866 and 14,600, assuming nets drift for 1 year. Ghost nets continue to accumulate on Australia's northern shore due to both legal and illegal fishing; over 13,000 nets have been removed since 2005. This is an important and ongoing transboundary threat to biodiversity in the region that requires attention from the countries surrounding the Arafura and Timor Seas. © 2014 Society for Conservation Biology.

Utility of a Work Process Classification System for characterizing non-fatal injuries in the Alaskan commercial fishing industry.

PubMed

Syron, Laura N; Lucas, Devin L; Bovbjerg, Viktor E; Bethel, Jeffrey W; Kincl, Laurel D

2016-01-01

Background The US commercial fishing industry is hazardous, as measured by mortality data. However, research on non-fatal injuries is limited. Non-fatal injuries constitute the majority of occupational injuries and can result in workers' lowered productivity and wages, lost quality of life, and disability. In the United States, a Work Process Classification System (WPCS) has previously been applied in Alaskan freezer-trawl and freezer-longline fleets to identify causes of injuries and specific hazards, but not to other fishing fleets. Objectives This descriptive epidemiologic study aimed to explore the application and modification of the WPCS in multiple Alaskan fleets, characterize non-fatal occupational injuries in these fleets, and identify work processes that could be targeted for further investigation and future injury prevention efforts. Design Traumatic, non-fatal injuries on-board Alaskan commercial fishing vessels were identified through United States Coast Guard investigative reports. Characteristics of injuries, as well as worker characteristics, were analysed. Injuries were coded using the WPCS. Results We successfully utilized the WPCS to code non-fatal injury cases (n = 136). The most frequent main work processes associated with non-fatal injuries included: on-board trawlers, handling frozen fish and processing the catch; on-board vessels using pot/trap gear, handling the gear and shooting/setting the gear; on-board longliners, traffic on board and hauling the gear; and on-board processor vessels, processing the catch, other work with the catch, and handling frozen fish. Conclusions The study confirmed that a WPCS can be applied to multiple Alaskan fleets to identify hazardous tasks. Hazards were unique for each vessel gear type. Future injury prevention efforts should target work processes associated with the most frequent and most severe injuries. Future studies should establish time estimates for work processes in order to determine risk estimates. Efforts to improve non-fatal injury reporting, especially on smaller commercial fishing vessels, should be undertaken.

Utility of a Work Process Classification System for characterizing non-fatal injuries in the Alaskan commercial fishing industry.

PubMed

Syron, Laura N; Lucas, Devin L; Bovbjerg, Viktor E; Bethel, Jeffrey W; Kincl, Laurel D

2016-01-01

The US commercial fishing industry is hazardous, as measured by mortality data. However, research on non-fatal injuries is limited. Non-fatal injuries constitute the majority of occupational injuries and can result in workers' lowered productivity and wages, lost quality of life, and disability. In the United States, a Work Process Classification System (WPCS) has previously been applied in Alaskan freezer-trawl and freezer-longline fleets to identify causes of injuries and specific hazards, but not to other fishing fleets. This descriptive epidemiologic study aimed to explore the application and modification of the WPCS in multiple Alaskan fleets, characterize non-fatal occupational injuries in these fleets, and identify work processes that could be targeted for further investigation and future injury prevention efforts. Traumatic, non-fatal injuries on-board Alaskan commercial fishing vessels were identified through United States Coast Guard investigative reports. Characteristics of injuries, as well as worker characteristics, were analysed. Injuries were coded using the WPCS. We successfully utilized the WPCS to code non-fatal injury cases (n = 136). The most frequent main work processes associated with non-fatal injuries included: on-board trawlers, handling frozen fish and processing the catch; on-board vessels using pot/trap gear, handling the gear and shooting/setting the gear; on-board longliners, traffic on board and hauling the gear; and on-board processor vessels, processing the catch, other work with the catch, and handling frozen fish. The study confirmed that a WPCS can be applied to multiple Alaskan fleets to identify hazardous tasks. Hazards were unique for each vessel gear type. Future injury prevention efforts should target work processes associated with the most frequent and most severe injuries. Future studies should establish time estimates for work processes in order to determine risk estimates. Efforts to improve non-fatal injury reporting, especially on smaller commercial fishing vessels, should be undertaken.

Human Activities on the Deep Seafloor in the North East Atlantic: An Assessment of Spatial Extent

PubMed Central

Benn, Angela R.; Weaver, Philip P.; Billet, David S. M.; van den Hove, Sybille; Murdock, Andrew P.; Doneghan, Gemma B.; Le Bas, Tim

2010-01-01

Background Environmental impacts of human activities on the deep seafloor are of increasing concern. While activities within waters shallower than 200 m have been the focus of previous assessments of anthropogenic impacts, no study has quantified the extent of individual activities or determined the relative severity of each type of impact in the deep sea. Methodology The OSPAR maritime area of the North East Atlantic was chosen for the study because it is considered to be one of the most heavily impacted by human activities. In addition, it was assumed data would be accessible and comprehensive. Using the available data we map and estimate the spatial extent of five major human activities in the North East Atlantic that impact the deep seafloor: submarine communication cables, marine scientific research, oil and gas industry, bottom trawling and the historical dumping of radioactive waste, munitions and chemical weapons. It was not possible to map military activities. The extent of each activity has been quantified for a single year, 2005. Principal Findings Human activities on the deep seafloor of the OSPAR area of the North Atlantic are significant but their footprints vary. Some activities have an immediate impact after which seafloor communities could re-establish, while others can continue to make an impact for many years and the impact could extend far beyond the physical disturbance. The spatial extent of waste disposal, telecommunication cables, the hydrocarbon industry and marine research activities is relatively small. The extent of bottom trawling is very significant and, even on the lowest possible estimates, is an order of magnitude greater than the total extent of all the other activities. Conclusions/Significance To meet future ecosystem-based management and governance objectives for the deep sea significant improvements are required in data collection and availability as well as a greater awareness of the relative impact of each human activity. PMID:20856885

Human activities on the deep seafloor in the North East Atlantic: an assessment of spatial extent.

PubMed

Benn, Angela R; Weaver, Philip P; Billet, David S M; van den Hove, Sybille; Murdock, Andrew P; Doneghan, Gemma B; Le Bas, Tim

2010-09-13

Environmental impacts of human activities on the deep seafloor are of increasing concern. While activities within waters shallower than 200 m have been the focus of previous assessments of anthropogenic impacts, no study has quantified the extent of individual activities or determined the relative severity of each type of impact in the deep sea. The OSPAR maritime area of the North East Atlantic was chosen for the study because it is considered to be one of the most heavily impacted by human activities. In addition, it was assumed data would be accessible and comprehensive. Using the available data we map and estimate the spatial extent of five major human activities in the North East Atlantic that impact the deep seafloor: submarine communication cables, marine scientific research, oil and gas industry, bottom trawling and the historical dumping of radioactive waste, munitions and chemical weapons. It was not possible to map military activities. The extent of each activity has been quantified for a single year, 2005. Human activities on the deep seafloor of the OSPAR area of the North Atlantic are significant but their footprints vary. Some activities have an immediate impact after which seafloor communities could re-establish, while others can continue to make an impact for many years and the impact could extend far beyond the physical disturbance. The spatial extent of waste disposal, telecommunication cables, the hydrocarbon industry and marine research activities is relatively small. The extent of bottom trawling is very significant and, even on the lowest possible estimates, is an order of magnitude greater than the total extent of all the other activities. To meet future ecosystem-based management and governance objectives for the deep sea significant improvements are required in data collection and availability as well as a greater awareness of the relative impact of each human activity.

Manta A New BroadBand OBS

NASA Astrophysics Data System (ADS)

Hello, Y.; Yegikyan, M.; Charvis, P.; Philippe, O.

2017-12-01

Manta is a new BroadBand OBS developed at Geoazur and commercialized by Osean. The design is inspired by 3-years autonomy MUG-OBS a Multiparameter Ocean Bottom System which carry a lot of sort of sensor types. As Mug-OBS, Manta-OBS rated 6000m is designed to resist a trawling. All the components are non corrosive such polyethylene, titanium and buoyancy is ensured by syntactic foam. Equipped in standard version with a Trillium compact OBS Manta has an autonomy of 18 months, but can accept on its 4 input channels any kind of signal as low as from an hydrophone or larger from other type of a seismometer or accelerometer. Tri-axial geophones unit (2 Hz or 4.5 Hz ) can replace the seismometer and will expend the lifespan for the instrument. The seismometer is encapsulated in a central well established by four panels of the main structure to protect it from sea current convection and is decoupled from main chassis. An health bulletin is recoverable by acoustic any time to facilitate the installation and during a visit when instrument is deployed. Main parameters for acquisition can be changed by acoustics command from surface at any time. Once at the bottom, release for the main sensor installation is programmed on a timer but controlled by the tilt of the OBS. If the tilt is too important based on programmed limits, sensor will not released automatically, but this can be forced by acoustic command after returning the tilt informations to the boat operator. Manta is equipped with flash light and AIS system for easy location at recovery, and can also send it's position by Iridium satellite in case of an unexpected ascent such caused by a possible trawling if deployed in shallow water. Clock drift calculation is automatically made against GPS time signal once the OBS return at the surface. The recovery of the OBS is initiated by an acoustic command. These new features made Manta a very versatile instrument for monitoring earthquakes.

Food habits of Juvenile American Shad and dynamics of zooplankton in the lower Columbia River

USGS Publications Warehouse

Haskell, C.A.; Tiffan, K.F.; Rondorf, D.W.

2006-01-01

As many as 2.4 million adult American shad annually pass John Day Dam, Columbia River to spawn upriver, yet food web interactions of juvenile shad rearing in John Day Reservoir are unexplored. We collected zooplankton and conducted mid-water trawls in McNary (June-July) and John Day reservoirs (August-November) from 1994 through 1996 during the outmigration of subyearling American shad and Chinook salmon. Juvenile American shad were abundant and represented over 98% of the trawl catch in late summer. The five major taxa collected in zooplankton tows were Bosmina longirostris, Daphnia, cyclopoid cope-pods, rotifers, and calanoid copepods. We evaluated total crustacean zooplankton abundance and Daphnia biomass in relation to water temperature, flow, depth, diel period, and cross-sectional location using multiple regression. Differences in zooplankton abundance were largely due to differences in water temperature and flow. Spatial variation in total zooplankton abundance was observed in McNary Reservoir, but not in John Day Reservoir. Juvenile American shad generally fed on numerically abundant prey, despite being less preferred than larger bodied zooplankton. A decrease in cladoceran abundance and size in August coupled with large percentages of Daphnia in juvenile American shad stomachs indicated heavy planktivory. Smaller juvenile American shad primarily fed on Daphnia in August, but switched to more evasive copepods as the mean size of fish increased and Daphnia abundance declined. Because Daphnia are particularly important prey items for subyearling Chinook salmon in mainstem reservoirs in mid to late summer, alterations in the cladoceran food base is of concern for the management of outmigrating salmonids and other Columbia River fishes. ?? 2006 by the Northwest Scientific Association. All rights reserved.

The Impact of Subsidies on the Ecological Sustainability and Future Profits from North Sea Fisheries

PubMed Central

Heymans, Johanna Jacomina; Mackinson, Steven; Sumaila, Ussif Rashid; Dyck, Andrew; Little, Alyson

2011-01-01

Background This study examines the impact of subsidies on the profitability and ecological stability of the North Sea fisheries over the past 20 years. It shows the negative impact that subsidies can have on both the biomass of important fish species and the possible profit from fisheries. The study includes subsidies in an ecosystem model of the North Sea and examines the possible effects of eliminating fishery subsidies. Methodology/Principal Findings Hindcast analysis between 1991 and 2003 indicates that subsidies reduced the profitability of the fishery even though gross revenue might have been high for specific fisheries sectors. Simulations seeking to maximise the total revenue between 2004 and 2010 suggest that this can be achieved by increasing the effort of Nephrops trawlers, beam trawlers, and the pelagic trawl-and-seine fleet, while reducing the effort of demersal trawlers. Simulations show that ecological stability can be realised by reducing the effort of the beam trawlers, Nephrops trawlers, pelagic- and demersal trawl-and-seine fleets. This analysis also shows that when subsidies are included, effort will always be higher for all fleets, because it effectively reduces the cost of fishing. Conclusions/Significance The study found that while removing subsidies might reduce the total catch and revenue, it increases the overall profitability of the fishery and the total biomass of commercially important species. For example, cod, haddock, herring and plaice biomass increased over the simulation when optimising for profit, and when optimising for ecological stability, the biomass for cod, plaice and sole also increased. When subsidies are eliminated, the study shows that rather than forcing those involved in the fishery into the red, fisheries become more profitable, despite a decrease in total revenue due to a loss of subsidies from the government. PMID:21637848

78 FR 55061 - North Pacific Fishery Management Council; Public Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-09

... paper on GOA Trawl Bycatch Management; Final action on GOA Trawl Data Collection; Initial review of GOA... following issues: 1. BS/AI Crab 2. Groundfish Specifications 3. Observer Program 4. GOA Trawl Issues In...

Catch and post-release mortalities of deep-water sharks caught by bottom longlines in the Cantabrian Sea (NE Atlantic)

NASA Astrophysics Data System (ADS)

Rodríguez-Cabello, Cristina; Sánchez, Francisco

2017-12-01

The majority of deep-water fish have very low capacity to survive discarding as fishery bycatch due to their biological characteristics and adaptation to depth. This study explores the catch and post-release mortalities of several deep-water shark species caught by bottom longline in the El Cachucho (Le Danois Bank) MPA in northern Spanish waters (NE Atlantic). Survivorship was qualitatively evaluated according to health condition and responses of individuals after capture and subsequent release. A total of 15 species were caught, of which the most abundant were leafscale gulper shark Centrophorus squamosus (39%), birdbeak dogfish Deania calcea (39%) and Portuguese dogfish Centroscymnus coelolepis (10%). Catch or at-vessel mortality (AVM) for these species was lower than expected, 1.2%, 8.8% and 4.5%, respectively but 18.9%, 37.4% and 38.6% including both those specimens dead on retrieval and those scored in poor condition). The species with the highest vitality rate was C. squamosus (37.3% in good condition; 43.8% in moderate condition), followed by D. calcea (22.8% in good condition; 39.8% in moderate condition) and C. coelolepis (6.8% and 54.5%). Post-release mortality (PRM) was examined using electronic tags (PSATs, n = 14). Of the nine C. squamosus tagged successfully, three died within 5-10 weeks after release, whereas the other six survived for periods of at least 45-120 days, when tags were programmed to release). In the case of C. coelolepis, two of the four tagged specimens died almost immediately after release, whereas the other two tags indicated that the fish survived immediate release, but data were too limited to gauge survival due to tag failure.

Impacts of trawling on benthic macro-fauna and -flora of the Spencer Gulf prawn fishing grounds

NASA Astrophysics Data System (ADS)

Svane, Ib; Hammett, Zoe; Lauer, Peter

2009-05-01

The overall effects of trawling on benthic habitats and their assemblages are dependent on the distribution and intensity of trawl effort. The benthic habitats of the Spencer Gulf prawn trawling grounds are subjected to known variable levels of trawling disturbance recorded from fisher's logbooks. These habitats have not been quantitatively investigated. The aim of the study was firstly to characterise the macro-faunal and -floral assemblages and secondly, to comparatively assess trawl impact by testing the null hypothesis of no differences between five sites exposed to different intensity of trawl effort. The distribution and abundance of benthic macro-fauna and -flora were studied at two sampling resolutions by using beam trawl sampling (˜10,000 m 2) and underwater stereophotography (˜4.5 m 2) at five sites with different levels of trawl disturbance (effort). The results showed that the Spencer Gulf prawn trawling grounds are characterised by sandy sediments with a low content of silt and clay, with the exception of one site with very fine gravel. Biomass, abundance and cover of macro-fauna and -flora were generally low throughout, but with large differences among sites. Biomass, abundance and cover were found to be negatively correlated to both trawl hours from 1994-1998 and during the period of study. ANOSIM and SIMPER analyses using biomass, abundance and percentage cover as variables showed significant differences between sites with eight species or taxonomic groups contributing more than 10% to the observed similarity within sites. The two northern sites were dominated by sponges and the bearded mussel, Trichomya hirsutus, and the southern hammer oyster, Malleus meridianus. Other species that contributed to the similarity within sites were the ascidian, Polycarpa viridis, mobile epifauna (the blue swimmer crab, Portunus pelagicus, and the western king prawn, Penaeus (Melicertus) latisulcatus) and demersal fish species (Degens leatherjacket, Thamnaconus degeni, and the Melbourne silver belly, Parequula melbournensis). Simpson's Index of Diversity (1 - λ) and species richness in the beam trawl samples were fairly even across all sites, but a significant effect of site was found in the stereophotographic transect samples. It was concluded that prawn trawling has a strong influence on the structure of the benthic habitats of the Spencer Gulf prawn fishing grounds highlighted by the magnitude of change and the strength of the gradient of effects. Confounding factors linked to the biophysical attributes of the sites are believed to be minor.

Euros vs. Yuan: Comparing European and Chinese Fishing Access in West Africa

PubMed Central

Belhabib, Dyhia; Sumaila, U. Rashid; Lam, Vicky W. Y.; Zeller, Dirk; Le Billon, Philippe; Abou Kane, Elimane; Pauly, Daniel

2015-01-01

We compare the performance of European Union (EU) and Chinese fisheries access agreements with West African countries in terms of illegal and unreported fishing, economic equity, and patterns of exploitation. Bottom-up re-estimations of catch reveal that the EU (1.6 million t•year-1) and China (2.3 million t•year-1) report only 29% and 8%, respectively, of their estimated total catches (including estimated discards whenever possible) from West African countries between 2000 and 2010. EU catches are declining, while Chinese catches are increasing and are yet to reach the historic maximum level of EU catches (3 million t•year-1 on average in the 1970s-1980s). The monetary value of EU fishing agreements, correlated in theory with reported catches, is straightforward to access, in contrast to Chinese agreements. However, once quantified, the value of Chinese agreements is readily traceable within the African economy through the different projects they directly cover, in contrast to the funds disbursed [to host governments] by the EU. Overall, China provides resources equivalent to about 4% of the ex-vessel value [value at landing] of the catch taken by Chinese distant-water fleets from West African waters, while the EU pays 8%. We address the difficulties of separating fees directly related to fishing from other economic or political motivations for Chinese fees, which could introduce a bias to the present findings as this operation is not performed for EU access fees officially related to fishing. Our study reveals that the EU and China perform similarly in terms of illegal fishing, patterns of exploitation and sustainability of resource use, while under-reporting by the EU increases and that by China decreases. The EU agreements provide, in theory, room for improving scientific research, monitoring and surveillance, suggesting a better performance than for Chinese agreements, but the end-use of the EU funds are more difficult, and sometime impossible to ascertain. PMID:25793775

Large-scale spatio-temporal monitoring highlights hotspots of demersal fish diversity in the Mediterranean Sea

NASA Astrophysics Data System (ADS)

Granger, Victoria; Fromentin, Jean-Marc; Bez, Nicolas; Relini, Giulio; Meynard, Christine N.; Gaertner, Jean-Claude; Maiorano, Porzia; Garcia Ruiz, Cristina; Follesa, Cristina; Gristina, Michele; Peristeraki, Panagiota; Brind'Amour, Anik; Carbonara, Pierluigi; Charilaou, Charis; Esteban, Antonio; Jadaud, Angélique; Joksimovic, Aleksandar; Kallianiotis, Argyris; Kolitari, Jerina; Manfredi, Chiara; Massuti, Enric; Mifsud, Roberta; Quetglas, Antoni; Refes, Wahid; Sbrana, Mario; Vrgoc, Nedo; Spedicato, Maria Teresa; Mérigot, Bastien

2015-01-01

Increasing human pressures and global environmental change may severely affect the diversity of species assemblages and associated ecosystem services. Despite the recent interest in phylogenetic and functional diversity, our knowledge on large spatio-temporal patterns of demersal fish diversity sampled by trawling remains still incomplete, notably in the Mediterranean Sea, one of the most threatened marine regions of the world. We investigated large spatio-temporal diversity patterns by analysing a dataset of 19,886 hauls from 10 to 800 m depth performed annually during the last two decades by standardised scientific bottom trawl field surveys across the Mediterranean Sea, within the MEDITS program. A multi-component (eight diversity indices) and multi-scale (local assemblages, biogeographic regions to basins) approach indicates that only the two most traditional components (species richness and evenness) were sufficient to reflect patterns in taxonomic, phylogenetic or functional richness and divergence. We also put into question the use of widely computed indices that allow comparing directly taxonomic, phylogenetic and functional diversity within a unique mathematical framework. In addition, demersal fish assemblages sampled by trawl do not follow a continuous decreasing longitudinal/latitudinal diversity gradients (spatial effects explained up to 70.6% of deviance in regression tree and generalised linear models), for any of the indices and spatial scales analysed. Indeed, at both local and regional scales species richness was relatively high in the Iberian region, Malta, the Eastern Ionian and Aegean seas, meanwhile the Adriatic Sea and Cyprus showed a relatively low level. In contrast, evenness as well as taxonomic, phylogenetic and functional divergences did not show regional hotspots. All studied diversity components remained stable over the last two decades. Overall, our results highlight the need to use complementary diversity indices through different spatial scales when developing conservation strategies and defining delimitations for protected areas.

Preface and brief synthesis for the FOODBANCS volume

NASA Astrophysics Data System (ADS)

Smith, Craig R.; DeMaster, David J.

2008-11-01

In this volume we present results from the FOODBANCS Project, which examined the fate and benthic community impact of summer bloom material on the West Antarctic Peninsula shelf floor. The project involved a 5-cruise, 15-month time-series program in which sediment-trap moorings, core sampling, radiochemical profiling, sediment respirometry, bottom photography, and bottom trawling were used to evaluate: (1) seafloor deposition and lability of POC, (2) patterns of labile POC consumption and sediment mixing by benthos, and (3) seasonal and inter-annual variations in biotic abundance, biomass, reproductive condition, recruitment, and sediment community respiration. We find that the seafloor flux and accumulation of particulate organic carbon on the West Antarctic Peninsula shelf exhibit intense seasonal and interannual variability. Nonetheless, many key benthic processes, including organic-matter degradation, bioturbation, deposit feeding, and faunal abundance, reproduction and recruitment, show relatively muted response to this intense seasonal and inter-annual variability in export flux. We thus hypothesize that benthic ecosystems on the Antarctic shelf act as "low-pass" filters, and may be extremely useful in resolving the impacts of climatic change over periods of years to decades in Antarctic Peninsula region.

Drone Use in Monioring Open Ocean Surface Debris, Including Paired Manta and Tucker Trawls for Relateing Sea State to Vertical Debris Distribution

NASA Astrophysics Data System (ADS)

Lattin, G.

2016-02-01

Monitoring debris at sea presents challenges not found in beach or riverine habitats, and is typically done with trawl nets of various apertures and mesh sizes, which limits the size of debris captured and the area surveyed. To partially overcome these limitations in monitoring floating debris, a Quadcopter drone with video transmitting and recording capabilities was deployed at the beginning and the end of manta trawl transects within the North Pacific Subtropical Gyre's eastern convergence zone. Subsurface tucker trawls at 10 meters were conducted at the same time as the manta trawls, in order to assess the effect of sea state on debris dispersal. Trawls were conducted on an 11 station grid used repeatedly since 1999. For drone observations, the operator and observer were stationed on the mother ship while two researchers collected observed debris using a rigid inflatable boat (RIB). The drone was flown to a distance of approximately 100 meters from the vessel in a zigzag or circular search pattern. Here we examine issues arising from drone deployment during the survey: 1) relation of area surveyed by drone to volume of water passing through trawl; 2) retrieval of drone-spotted and associated RIB spotted debris. 3) integrating post- flight image analysis into retrieved debris quantification; and 4) factors limiting drone effectiveness at sea. During the survey, debris too large for the manta trawl was spotted by the drone, and significant debris not observed using the drone was recovered by the RIB. The combination of drone sightings, RIB retrieval, and post flight image analysis leads to improved monitoring of debris at sea. We also examine the issue of the distribution of floating debris during sea states varying from 0-5 by comparing quantities from surface manta trawls to the tucker trawls at a nominal depth of 10 meters.

The contribution of Niels Daan to fisheries science: Changing the perspective from single-species to the ecosystem

NASA Astrophysics Data System (ADS)

Rijnsdorp, Adriaan D.; Dekker, Willem; Heessen, Henk J. L.

We describe the career of Professor Niels Daan at the governmental Netherlands Institute for Fisheries Research (RIVO) and analyse his role in the development of fisheries science, in the Netherlands as well as in the International Council for the Exploration of the Sea (ICES). Major contributions are (i) his research on the interactions between cod and its prey; (ii) the standardization, data base development and quality control of the ICES International Bottom Trawl Survey; (iii) his role as editor-in-chief of the ICES Journal of Marine Science; (iv) his role in stimulating new approaches and critically questioning the science behind the advice; (v) his often silent support to a wide group of young fisheries scientists.

Spatio-temporal variations in the diversity and abundance of commercially important Decapoda and Stomatopoda in subtropical Hong Kong waters

NASA Astrophysics Data System (ADS)

Lui, Karen K. Y.; Ng, Jasmine S. S.; Leung, Kenneth M. Y.

2007-05-01

In subtropical Hong Kong, western waters (WW) are strongly influenced by the freshwater input from the Pearl River estuary, especially during summer monsoon, whereas eastern waters (EW) are predominantly influenced by oceanic currents throughout the year. Such hydrographical differences may lead to spatio-temporal differences in biodiversity of benthic communities. This study investigated the diversity and abundance of commercially important decapods and stomatopods in EW (i.e. Tolo Harbour and Channel) and WW (i.e. Tuen Mun and Lantau Island) of Hong Kong using monthly trawl surveys (August 2003-May 2005). In total, 22 decapod and nine stomatopod species were recorded. The penaeid Metapenaeopsis sp. and stomatopod Oratosquillina interrupta were the most abundant and dominant crustaceans in EW and WW, respectively. Both univariate and multivariate analyses showed that WW supported significantly higher abundance, biomass and diversity of crustaceans than EW, although there were significant between-site and within-site variations in community structure. Higher abundance and biomass of crustaceans were recorded in summer than winter. Such spatio-temporal variations could be explained by differences in the hydrography, environmental conditions and anthropogenic impacts between the two areas. Temporal patterns in the abundance-biomass comparison curves and negative W-statistics suggest that the communities have been highly disturbed in both areas, probably due to anthropogenic activities such as bottom trawling and marine pollution.

Meiofaunal community structure in Thermaikos Gulf: Response to intense trawling pressure

NASA Astrophysics Data System (ADS)

Lampadariou, N.; Hatziyanni, E.; Tselepides, A.

2005-12-01

Among the most important impacts of trawling is the disturbance of the benthic environment as well as the mortality of the larger benthic organisms, which is caused by the passage of the fishing gear. Meiofauna, which are among the smallest benthic organisms, may be more resistant to disturbance by trawling since they are likely to be re-suspended rather than killed by trawls. Their short generation times allow populations to withstand elevated mortality. In this study, we determined the effect of trawling disturbance, season and sediment type on the structure of meiofaunal communities in a commercial fishing ground in Thermaikos Gulf, north Aegean Sea, Greece. The trawling season is limited to 8 months between October and May. A grid of five nearshore stations was chosen along a north-south productivity gradient and an additional offshore station was included as a reference point. Sediment chemistry and meiofaunal community structure were studied before the trawling season started, as well as 1 and 4 months after the initiation of the fishing period. Results showed that there were no short term (30 days) trawling impacts on meiofauna in terms of abundance and community structure but that there were recognizable effects on the community structure of nematodes and the abundance of polychaetes. In contrast, most meiofaunal taxa displayed significant seasonal variability, 4 months after the initiation of the fishing period; however, other closely related factors such as temperature, sediment particle size and primary productivity are more likely to be responsible for the observed patterns.

75 FR 4684 - Fisheries off West Coast States; Pacific Coast Groundfish Fishery; Data Collection for the Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-29

... Coast groundfish fishery. The trawl rationalization program is intended to increase net economic benefits, create individual economic stability, provide full utilization of the trawl sector allocation... one time reporting will have a significant economic impact on small entities, as the estimated...

By-Catch Impacts in Fisheries: Utilizing the IUCN Red List Categories for Enhanced Product Level Assessment in Seafood LCAs

NASA Astrophysics Data System (ADS)

Hornborg, Sara; Svensson, Mikael; Nilsson, Per; Ziegler, Friederike

2013-11-01

Overexploitation of fish stocks causes concern not only to fisheries managers and conservation biologists, but also engages seafood consumers; more integrated product perspectives would be useful. This could be provided by life cycle assessment (LCA); however, further complements of present LCA methodology are needed to assess seafood production, one being by-catch impacts. We studied the scientific rationale behind using the IUCN Red List of Threatened Species™ for assessment of impacts relating to fish species’ vulnerability. For this purpose, the current Red List status of marine fish in Sweden was compared to the advice given in fisheries as well as key life history traits known to indicate sensitivity to high fishing pressure. Further, we quantified the amount of threatened fish (vulnerable, endangered, or critically endangered) that was discarded in demersal trawl fisheries on the Swedish west coast. The results showed that not only did the national Red List of marine fish have a high consistency with advice given in fisheries and indices of vulnerability, the different fishing practices studied were also found to have vastly different amounts of threatened fish discarded per kilo landing. The suggested approach is therefore promising as a carrier of aggregated information on the extent to which seafood production interferes with conservation priorities, in particular for species lacking adequate stock assessment. To enable extensive product comparisons, it is important to increase coverage of fish species by the global IUCN Red List, and to reconsider the appropriate assessment unit (species or stocks) in order to avoid false alarms.

By-catch impacts in fisheries: utilizing the IUCN red list categories for enhanced product level assessment in seafood LCAs.

PubMed

Hornborg, Sara; Svensson, Mikael; Nilsson, Per; Ziegler, Friederike

2013-11-01

Overexploitation of fish stocks causes concern not only to fisheries managers and conservation biologists, but also engages seafood consumers; more integrated product perspectives would be useful. This could be provided by life cycle assessment (LCA); however, further complements of present LCA methodology are needed to assess seafood production, one being by-catch impacts. We studied the scientific rationale behind using the IUCN Red List of Threatened Species™ for assessment of impacts relating to fish species' vulnerability. For this purpose, the current Red List status of marine fish in Sweden was compared to the advice given in fisheries as well as key life history traits known to indicate sensitivity to high fishing pressure. Further, we quantified the amount of threatened fish (vulnerable, endangered, or critically endangered) that was discarded in demersal trawl fisheries on the Swedish west coast. The results showed that not only did the national Red List of marine fish have a high consistency with advice given in fisheries and indices of vulnerability, the different fishing practices studied were also found to have vastly different amounts of threatened fish discarded per kilo landing. The suggested approach is therefore promising as a carrier of aggregated information on the extent to which seafood production interferes with conservation priorities, in particular for species lacking adequate stock assessment. To enable extensive product comparisons, it is important to increase coverage of fish species by the global IUCN Red List, and to reconsider the appropriate assessment unit (species or stocks) in order to avoid false alarms.

A statistical model for monitoring shell disease in inshore lobster fisheries: A case study in Long Island Sound

PubMed Central

Chen, Yong

2017-01-01

The expansion of shell disease is an emerging threat to the inshore lobster fisheries in the northeastern United States. The development of models to improve the efficiency and precision of existing monitoring programs is advocated as an important step in mitigating its harmful effects. The objective of this study is to construct a statistical model that could enhance the existing monitoring effort through (1) identification of potential disease-associated abiotic and biotic factors, and (2) estimation of spatial variation in disease prevalence in the lobster fishery. A delta-generalized additive modeling (GAM) approach was applied using bottom trawl survey data collected from 2001–2013 in Long Island Sound, a tidal estuary between New York and Connecticut states. Spatial distribution of shell disease prevalence was found to be strongly influenced by the interactive effects of latitude and longitude, possibly indicative of a geographic origin of shell disease. Bottom temperature, bottom salinity, and depth were also important factors affecting the spatial variability in shell disease prevalence. The delta-GAM projected high disease prevalence in non-surveyed locations. Additionally, a potential spatial discrepancy was found between modeled disease hotspots and survey-based gravity centers of disease prevalence. This study provides a modeling framework to enhance research, monitoring and management of emerging and continuing marine disease threats. PMID:28196150

Temperature induced changes in size dependent distributions of two boreal and three Lusitanian flatfish species: A comparative study

NASA Astrophysics Data System (ADS)

van Hal, Ralf; van Kooten, Tobias; Rijnsdorp, Adriaan D.

2016-01-01

Changes in spatial distribution in several fish species have been related to recent increase in global temperature. In the North Sea, both a poleward shift and a shift to deeper water have been observed. Here, we study the underlying mechanism of these shifts in a comparative study of the changes in distribution of two boreal flatfish species (plaice Pleuronectes platessa and dab Limanda limanda) and three Lusitanian flatfish species (sole Solea solea, solenette Buglossidium luteum, and scaldfish Arnoglossus laterna) as recorded in annual bottom trawl surveys carried out in the North Sea in late summer since 1985. The distribution is analysed in relation to the bottom temperature at the time of the survey as well as to the seasonal maximum bottom temperature earlier in the year. It is shown that the boreal species plaice and dab moved to deeper water and maintained the seasonal maximum temperature that they experienced in earlier periods, while the Lusitanian species sole, solenette, and scaldfish experienced an increase in the seasonal maximum temperature that they experienced while maintaining their depth distribution. This overall response varied between length classes, reflecting a preference for higher temperature of the smaller length classes. The results lend support to the hypothesis that the fish displayed a direct response to the maximum temperature that occurred during the growth season before the time of sampling.

Recovery of Seamount Precious Coral Beds From Heavy Trawling Disturbance with Links to Carbonate Chemistry Changes

NASA Astrophysics Data System (ADS)

Roark, E. B.; Baco-Taylor, A.; Morgan, N. B.; Shamberger, K.; Miller, K.; Brooks, J.

2016-12-01

Increasing anthropogenic impacts in the deep sea make studies of resilience and recovery time critical, with deep-sea hard-substrate habitats and large-scale disturbances having received little attention. Seamount hard-substrate habitats in particular are thought to have low resilience due to the slow growth rates and recruitment limitations of key structure-forming taxa. Seamounts of the far Northwestern Hawaiian Islands and Emperor Chain have had some of the heaviest trawl impacts in the world, from both fish and precious coral fisheries, and include sites that are still trawled and recovering ones that have been protected since establishment of the EEZ in 1977. To test the hypothesis of low resilience we compare these impacted seamounts to untrawled sites. We used the AUV Sentry in 2014 and 2015 to image nine features (three per "treatment") and analyze for substrate and visible megafauna. Sites in the "still trawled" treatment were characterized by extensive areas of bare substrate with abundant trawl scars. Sites in the "recovering" and "never trawled" locations had abundant megafauna in hard substrate areas. Initial comparisons of transects at 700m depth for three sites indicate that Yuryaku in the "still trawled" treatment had lower diversity and abundance of megafauna compared to the "recovering" and "never trawled" locations with a dominance of sea urchins. The "recovering" and "never trawled" sites were dominated by cnidarians, fishes, and echinoderms, but differed in dominant species, diversity, abundances and occurrence of dead coral skeletons. These preliminary results suggest that the recovering sites have not returned to a pre-impact community type in the 38 years since they were trawled. The megafauna distribution, in particular that of deep-sea corals, was compared to environmental water column variables at the study sites across the Northwestern Hawaiian Islands. Deep-sea corals with calcium carbonate skeletons were found living below the aragonite saturation horizon (ASH; Ωarg=1), which ranges from 500-600 m depth and deepens moving northwest along the island chain. How deep-sea corals build and maintain their skeletons in undersaturated waters is poorly understood, but it is possible that saturation horizons may play a role in their recovery rates.

SUMMER FISH COMMUNITY OF THE COASTAL NORTHERN GULF OF MEXICO: CHARACTGERIZATION OF A LARGE-SCALE TRAWL SURVEY

EPA Science Inventory

This paper summarizes the trawled fish assemblage collected during 1992 - 1994 at 119 locations in the northern Gulf of Mexico. The 367 collection sites were located adjacent to five states and represented seven estuarine categories. Fish were collected using an otter trawl durin...

Biodiversity of suprabenthic peracarid assemblages from the Blanes Canyon region (NW Mediterranean Sea) in relation to natural disturbance and trawling pressure

NASA Astrophysics Data System (ADS)

Almeida, Mariana; Frutos, Inmaculada; Company, Joan B.; Martin, Daniel; Romano, Chiara; Cunha, Marina R.

2017-03-01

Blanes Canyon and its adjacent margin are important fishery areas (mainly by bottom trawling) located in a highly energetic oceanographic setting in the NW Mediterranean Sea. Here we assess the spatial and temporal variability in abundance, diversity and community structure of the suprabenthic peracarid assemblages in this region and examine this variability in relation to the natural and anthropogenic (trawling fisheries) disturbance regimes. The sampling was conducted between March 2003 and May 2004 in three main fishing grounds, the canyon head (average depth: 490 m), the canyon wall (average depth: 550 m) and the eastern adjacent slope (average depth: 820 m), as well as in two non-exploited areas in the western (at 900 m depth) and eastern (at 1500 m depth) slope near the canyon mouth. A total of 138 species were identified, with amphipods being the most speciose and abundant group, followed by mysids in terms of abundance. Our results show high spatial and temporal variability in suprabenthic assemblages. Densities were higher in the canyon head and western slope, which appear to be the preferential routes for water masses and particle fluxes in months of flood events, and other energetic processes. In the canyon head, where periodic erosion processes are more active, low diversity, high dominance and higher turnover (β-diversity) were observed, apparently coupled with significant temporal fluctuations in the densities of the highly motile component of suprabenthos (mysids, predatory and scavenging amphipods). In the sedimentary more stable eastern slope, high diversity values were observed, accompanied by a higher relative contribution of the less motile groups (i.e. amphipods, most isopods, cumaceans). These groups have a closer interaction with the sediment where they exploit different food sources and are more susceptible to physical disturbance. Temporal variability in their diversity may be related to changes in food quality rather than quantity. In the canyon wall, temporal fluctuations in diversity indices were only revealed in relation to the overall higher and more continued fishing pressure observed in the canyon wall fishing ground (Cara Norte/Sot site). Here, species richness and abundance declined with increasing fishing pressure but the lowest trophic and taxonomic diversities were observed under intermediate levels of disturbance. These findings underline (i) the differences between relatively low and highly motile taxa in terms of response to disturbance events; (ii) the differences between assemblages subjected to different levels of natural disturbance and trawling pressure, which modify the common bathymetric patterns of abundance and diversity often described from continental margins.

Dynamics of Bacillus thuringiensis var. israelensis and Lysinibacillus sphaericus Spores in Urban Catch Basins after Simultaneous Application against Mosquito Larvae

PubMed Central

Guidi, Valeria; Lehner, Angelika; Lüthy, Peter; Tonolla, Mauro

2013-01-01

Bacillus thuringiensis var. israelensis (Bti) and Lysinibacillus sphaericus (Lsph) are extensively used in mosquito control programs. These biocides are the active ingredients of a commercial larvicide. Quantitative data on the fate of both Bti and Lsph applied together for the control of mosquitoes in urban drainage structures such as catch basins are lacking. We evaluated the dynamics and persistence of Bti and Lsph spores released through their concomitant application in urban catch basins in southern Switzerland. Detection and quantification of spores over time in water and sludge samples from catch basins were carried out using quantitative real-time PCR targeting both cry4A and cry4B toxin genes for Bti and the binA gene for Lsph. After treatment, Bti and Lsph spores attained concentrations of 3.76 (±0.08) and 4.13 (±0.09) log ml−1 in water, then decreased progressively over time, reaching baseline values. For both Bti and Lsph, spore levels in the order of 105 g−1 were observed in the bottom sludge two days after the treatment and remained constant for the whole test period (275 days). Indigenous Lsph strains were isolated from previously untreated catch basins. A selection of those was genotyped using pulsed field gel electrophoresis of SmaI-digested chromosomal DNA, revealing that a subset of isolates were members of the clonal population of strain 2362. No safety issues related to the use of this biopesticide in the environment have been observed during this study, because no significant increase in the number of spores was seen during the long observation period. The isolation of native Lysinibacillus sphaericus strains belonging to the same clonal population as strain 2362 from catch basins never treated with Lsph-based products indicates that the use of a combination of Bti and Lsph for the control of mosquitoes does not introduce non-indigenous microorganisms in this area. PMID:23390547

Historical Arctic Logbooks Provide Insights into Past Diets and Climatic Responses of Cod

PubMed Central

Townhill, Bryony L.; Maxwell, David; Engelhard, Georg H.; Simpson, Stephen D.; Pinnegar, John K.

2015-01-01

Gadus morhua (Atlantic cod) stocks in the Barents Sea are currently at levels not seen since the 1950s. Causes for the population increase last century, and understanding of whether such large numbers will be maintained in the future, are unclear. To explore this, we digitised and interrogated historical cod catch and diet datasets from the Barents Sea. Seventeen years of catch data and 12 years of prey data spanning 1930–1959 cover unexplored spatial and temporal ranges, and importantly capture the end of a previous warm period, when temperatures were similar to those currently being experienced. This study aimed to evaluate cod catch per unit effort and prey frequency in relation to spatial, temporal and environmental variables. There was substantial spatio-temporal heterogeneity in catches through the time series. The highest catches were generally in the 1930s and 1940s, although at some localities more cod were recorded late in the 1950s. Generalized Additive Models showed that environmental, spatial and temporal variables are all valuable descriptors of cod catches, with the highest occurring from 15–45°E longitude and 73–77°N latitude, at bottom temperatures between 2 and 4°C and at depths between 150 and 250 m. Cod diets were highly variable during the study period, with frequent changes in the relative frequencies of different prey species, particularly Mallotus villosus (capelin). Environmental variables were particularly good at describing the importance of capelin and Clupea harengus (herring) in the diet. These new analyses support existing knowledge about how the ecology of the region is controlled by climatic variability. When viewed in combination with more recent data, these historical relationships will be valuable in forecasting the future of Barents Sea fisheries, and in understanding how environments and ecosystems may respond. PMID:26331271

76 FR 57679 - Fisheries of the Exclusive Economic Zone Off Alaska; Shallow-Water Species by Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-16

.... 101126522-0640-02] RIN 0648-XA704 Fisheries of the Exclusive Economic Zone Off Alaska; Shallow- Water... closure. SUMMARY: NMFS is opening directed fishing for shallow-water species by vessels using trawl gear... apportionment of the 2011 Pacific halibut bycatch allowance specified for the trawl shallow-water species...

75 FR 56017 - Fisheries of the Exclusive Economic Zone Off Alaska; Shallow-Water Species by Vessels Using Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-15

.... 0910131362-0087-02] RIN 0648-XZ06 Fisheries of the Exclusive Economic Zone Off Alaska; Shallow- Water Species... closure. SUMMARY: NMFS is opening directed fishing for shallow-water species by vessels using trawl gear... of the 2010 Pacific halibut bycatch allowance specified for the trawl shallow-water species fishery...

Ideal free distribution or dynamic game? An agent-based simulation study of trawling strategies with varying information

NASA Astrophysics Data System (ADS)

Beecham, J. A.; Engelhard, G. H.

2007-10-01

An ecological economic model of trawling is presented to demonstrate the effect of trawling location choice strategy on net input (rate of economic gain of fish caught per time spent less costs). Fishing location choice is considered to be a dynamic process whereby trawlers chose from among a repertoire of plastic strategies that they modify if their gains fall below a fixed proportion of the mean gains of the fleet as a whole. The distribution of fishing across different areas of a fishery follows an approximate ideal free distribution (IFD) with varying noise due to uncertainty. The least-productive areas are not utilised because initial net input never reaches the mean yield of better areas subject to competitive exploitation. In cases, where there is a weak temporal autocorrelation between fish stocks in a specific location, a plastic strategy of local translocation between trawls mixed with longer-range translocation increases realised input. The trawler can change its translocation strategy in the light of information about recent trawling success compared to its long-term average but, in contrast to predictions of the Marginal Value Theorem (MVT) model, does not know for certain what it will find by moving, so may need to sample new patches. The combination of the two types of translocation mirrored beam-trawling strategies used by the Dutch fleet and the resultant distribution of trawling effort is confirmed by analysis of historical effort distribution of British otter trawling fleets in the North Sea. Fisheries exploitation represents an area where dynamic agent-based adaptive models may be a better representation of the economic dynamics of a fleet than classically inspired optimisation models.

Recovery of Seamount Precious Coral Beds From Heavy Trawling Disturbance

NASA Astrophysics Data System (ADS)

Morgan, N.; Baco-Taylor, A.; Roark, B.

2016-02-01

Resilience and the related concept of recovery provide insights into ecosystem function, connectivity, and succession. Most marine resilience studies have focused on shallow-water ecosystems. However, increasing anthropogenic impacts in the deep sea make studies of resilience and recovery in the deep sea time-critical, with deep-sea hard-substrate habitats and large-scale disturbances having received the least attention. Ironically one of the key anthropogenic impacts to the seafloor, trawling, provides an ideal experimental design to understand processes of recovery from large-scale disturbance in the deep sea. Seamount hard-substrate habitats in particular are thought to have low resilience due to the slow growth rates and recruitment limitations of key structure-forming taxa. The goal of our project is to test the hypothesis of low resilience by examining a series of locations in the far Northwestern Hawaiian Islands and the Emperor Seamount Chain. These sites have had some of the heaviest trawl impacts in the world, from both fish and precious coral fisheries, and include sites that are still trawled as well as ones that have been protected since the establishment of the US Exclusive Economic Zone in 1977. We compare these to untrawled sites as part of a three "treatment" design. During two cruises in 2014 and 2015 we used the AUV Sentry to image nine features (three per treatment). CTD data were also collected. Images were analyzed for all visible megafauna as well as substrate parameters (rugosity, slope, composition, relief). Yuryaku, in the "still trawled" treatment was characterized by extensive areas of bare substrate with abundant trawl scars. This feature also had lower diversity and lower abundance of megafauna compared to the recovering and never trawled locations. Preliminary data suggest recovering and never trawled features have overlapping species, but not in comparable abundances.

50 CFR Figure 6 to Part 223 - TED Extension in Summer Flounder Trawl

Code of Federal Regulations, 2013 CFR

2013-10-01

... 50 Wildlife and Fisheries 10 2013-10-01 2013-10-01 false TED Extension in Summer Flounder Trawl 6 Figure 6 to Part 223 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND.... 223, Fig. 6 Figure 6 to Part 223—TED Extension in Summer Flounder Trawl ER15OC99.001 [64 FR 55864, Oct...

50 CFR Figure 6 to Part 223 - TED Extension in Summer Flounder Trawl

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 9 2011-10-01 2011-10-01 false TED Extension in Summer Flounder Trawl 6 Figure 6 to Part 223 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND.... 223, Fig. 6 Figure 6 to Part 223—TED Extension in Summer Flounder Trawl ER15OC99.001 [64 FR 55864, Oct...

50 CFR Figure 6 to Part 223 - TED Extension in Summer Flounder Trawl

Code of Federal Regulations, 2012 CFR

2012-10-01

... 50 Wildlife and Fisheries 10 2012-10-01 2012-10-01 false TED Extension in Summer Flounder Trawl 6 Figure 6 to Part 223 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND.... 223, Fig. 6 Figure 6 to Part 223—TED Extension in Summer Flounder Trawl ER15OC99.001 [64 FR 55864, Oct...

50 CFR Figure 6 to Part 223 - TED Extension in Summer Flounder Trawl

Code of Federal Regulations, 2014 CFR

2014-10-01

... 50 Wildlife and Fisheries 10 2014-10-01 2014-10-01 false TED Extension in Summer Flounder Trawl 6 Figure 6 to Part 223 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND.... 223, Fig. 6 Figure 6 to Part 223—TED Extension in Summer Flounder Trawl ER15OC99.001 [64 FR 55864, Oct...

78 FR 33040 - Fisheries of the Exclusive Economic Zone Off Alaska; Fisheries of the Gulf of Alaska; Amendment...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-03

..., the Council initially reviewed alternative bycatch control measures, subsequently revised and refined... the gear. Nonpelagic trawl gear uses a pair of long lines called ``sweeps'' to herd fish into the net... fishing, which account only for crabs that come up in the trawl net. As noted in Section 2.9 of the Trawl...

Environmental drivers of megafaunal assemblage composition and biomass distribution over mainland and insular slopes of the Balearic Basin (Western Mediterranean)

NASA Astrophysics Data System (ADS)

Fanelli, E.; Cartes, J. E.; Papiol, V.; López-Pérez, C.

2013-08-01

The influence of mesoscale physical and trophic variables on deep-sea megafauna, a scale of variation often neglected in deep-sea studies, is crucial for understanding their role in the ecosystem. Drivers of megafaunal assemblage composition and biomass distribution have been investigated in two contrasting areas of the Balearic basin in the NW Mediterranean: on the mainland slope (Catalonian coasts) and on the insular slope (North of Mallorca, Balearic Islands). An experimental bottom trawl survey was carried out during summer 2010, at stations in both sub-areas located between 450 and 2200 m water depth. Environmental data were collected simultaneously: near-bottom physical parameters, and the elemental and isotopic composition of sediments. Initially, data were analysed along the whole depth gradient, and then assemblages from the two areas were compared. Analysis of the trawls showed the existence of one group associated with the upper slope (US=450-690 m), another with the middle slope (MS=1000-1300 m) and a third with the lower slope (LS=1400-2200 m). Also, significant differences in the assemblage composition were found between mainland and insular slopes at MS. Dominance by different species was evident when the two areas were compared by SIMPER analysis. The greatest fish biomass was recorded in both areas at 1000-1300 m, a zone linked to minimum temperature and maximum O2 concentration on the bottom. Near the mainland, fish assemblages were best explained (43% of total variance, DISTLM analysis) by prey availability (gelatinous zooplankton biomass). On the insular slope, trophic webs seemed less complex and were based on vertical input of surface primary production. Decapods, which reached their highest biomass values on the upper slope, were correlated with salinity and temperature in both the areas. However, while hydrographic conditions (temperature and salinity) seemed to be the most important variables over the insular slope, resource availability (gelatinous zooplankton and Calocaris macandreae) predominated and explained 59% of decapod assemblage variation over the mainland slope. Both fish and decapods were linked to net primary production recorded over the mainland 3 months before sampling, while the delay between the input of food from the surface and fish abundance was only 1 month on the insular slope. Our results suggest that trophic relationships over insular slopes probably involve a shorter food chain than over mainland slopes and one that is likely more efficient in terms of energy transfer.

Monitoring of ichthyic fauna in artificial reefs along the Adriatic coast of the Abruzzi Region of Italy.

PubMed

Giansante, Carla; Fatigati, Marianna; Ciarrocchi, Floriana; Milillo, Giuseppe S; Onori, Luciano; Ferri, Nicola

2010-01-01

With the support of European Community funds, three submerged artificial reefs composed of concrete cubes, bell-shaped modules and natural rocks were deployed along the Adriatic coast of the Abruzzi Region to increase the fish population and to prevent illegal trawling. The Provincial governments of Teramo and Pescara requested the Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise 'G. Caporale' to monitor nectobenthic populations. Three sampling operations were conducted each year for each artificial reef. The authors present the results of a study conducted between 2005 and 2007, comparing the catches from the artificial reefs with those from the control sites using several diversity indexes. Artificial reef areas revealed greater species diversity and richness than the control sites. This study demonstrates the value of artificial reefs in response to the problem of low income, non-commercial fisheries as well as to the issue of over-exploitation of halieutic resources. In addition, the authors suggest that artificial reefs may be capable of activating habitat diversification processes that will increase biodiversity.

Declining survival of lake trout stocked during 1963-1986 in U.S. waters of Lake Superior

USGS Publications Warehouse

Hansen, Michael J.; Ebener, Mark P.; Schorfhaar, Richard G.; Schram, Stephen T.; Schreiner, Donald R.; Selgeby, James H.

1994-01-01

The average catch per effort (CPE) values for the 1963–1982 year-classes of stocked lake trout Salvelinus namaycush caught at age 7 in gill nets and for the 1976–1986 year-classes caught at ages 2–4 in trawls declined significantly in U.S. waters of Lake Superior. The declines in CPE were not explained by reduced stocking, but rather by significant declines in survival indices of the year-classes of stocked lake trout. Increases in mortality occurred in year-classes before the fish reached ages 2–4, before they were recruited into the sport and commercial fisheries, and before they reached sizes vulnerable to sea lamprey predation. We conclude that declining abundance of stocked lake trout resulted from increased mortality, which may have been caused by competition, predation, or by a combination of these and other factors. Restoration of lake trout in Lake Superior may now depend on prudent management of naturally reproducing stocks rather than on stocking of hatchery-reared fish.

Fish and fishery historical data since the 19th century in the Adriatic Sea, Mediterranean

NASA Astrophysics Data System (ADS)

Fortibuoni, Tomaso; Libralato, Simone; Arneri, Enrico; Giovanardi, Otello; Solidoro, Cosimo; Raicevich, Saša

2017-09-01

Historic data on biodiversity provide the context for present observations and allow studying long-term changes in marine populations. Here we present multiple datasets on fish and fisheries of the Adriatic Sea covering the last two centuries encompassing from qualitative observations to standardised scientific monitoring. The datasets consist of three groups: (1) early naturalists' descriptions of fish fauna, including information (e.g., presence, perceived abundance, size) on 255 fish species for the period 1818-1936 (2) historical landings from major Northern Adriatic fish markets (Venice, Trieste, Rijeka) for the period 1902-1968, Italian official landings for the Northern and Central Adriatic (1953-2012) and landings from the Lagoon of Venice (1945-2001) (3) trawl-survey data from seven surveys spanning the period 1948-1991 and including Catch per Unit of Effort data (kgh-1 and/or nh-1) for 956 hauls performed at 301 stations. The integration of these datasets has already demonstrated to be useful to analyse historical marine community changes over time, and its availability through open-source data portal will facilitate analyses in the framework of marine historical ecology.

Fish and fishery historical data since the 19th century in the Adriatic Sea, Mediterranean.

PubMed

Fortibuoni, Tomaso; Libralato, Simone; Arneri, Enrico; Giovanardi, Otello; Solidoro, Cosimo; Raicevich, Saša

2017-09-12

Historic data on biodiversity provide the context for present observations and allow studying long-term changes in marine populations. Here we present multiple datasets on fish and fisheries of the Adriatic Sea covering the last two centuries encompassing from qualitative observations to standardised scientific monitoring. The datasets consist of three groups: (1) early naturalists' descriptions of fish fauna, including information (e.g., presence, perceived abundance, size) on 255 fish species for the period 1818-1936; (2) historical landings from major Northern Adriatic fish markets (Venice, Trieste, Rijeka) for the period 1902-1968, Italian official landings for the Northern and Central Adriatic (1953-2012) and landings from the Lagoon of Venice (1945-2001); (3) trawl-survey data from seven surveys spanning the period 1948-1991 and including Catch per Unit of Effort data (kgh -1 and/or nh -1 ) for 956 hauls performed at 301 stations. The integration of these datasets has already demonstrated to be useful to analyse historical marine community changes over time, and its availability through open-source data portal will facilitate analyses in the framework of marine historical ecology.

Reassessment of the predatory effects of rainbow smelt on ciscoes in Lake Superior

USGS Publications Warehouse

Myers, Jared T.; Jones, Michael L.; Stockwell, Jason D.; Yule, Daniel L.

2009-01-01

Evidence from small lakes suggests that predation on larval ciscoes Coregonus artedi by nonnative rainbow smelt Osmerus mordax can lead to cisco suppression or extirpation. However, evidence from larger lakes has led to equivocal conclusions. In this study, we examine the potential predation effects of rainbow smelt in two adjacent but contrasting embayments in Lake Superior (Thunder and Black bays, Ontario). During May 2006, we sampled the ichthyoplankton, pelagic fish communities, and diet composition of rainbow smelt in both bays. Using acoustics and midwater trawling, we estimated rainbow smelt densities to be 476 ± 34/ha (mean ± SE) in Thunder Bay and 3,435 ± 460/ha in Black Bay. We used a bioenergetics model to estimate the proportion of cisco larvae consumed by rainbow smelt. Our results suggest that predation by rainbow smelt accounts for 15–52% and 37–100% of the mortality of larval ciscoes in Thunder and Black bays, respectively, depending on the predator feeding rate and the scale of predator–prey overlap. We also examined the sensitivity of past conclusions (based on 1974 field collections) to assumptions of temporal overlap between rainbow smelt and larval ciscoes and estimates of rainbow smelt abundance derived from bottom trawl samples. After adjusting these parameters to reflect current understanding, we found that the previous predation estimates may have been conservative. We conclude that rainbow smelt may have been a more important contributor to the demise and slow recovery of ciscoes in Lake Superior than previously thought.

Impacts of crowding, trawl duration and air exposure on the physiology of stingarees (family: Urolophidae)

PubMed Central

Heard, Matthew; Van Rijn, Jason A.; Reina, Richard D.; Huveneers, Charlie

2014-01-01

Research on physiological stress and post-capture mortality of threatened species caught as bycatch is critical for the management of fisheries. The present study used laboratory simulations to examine the physiological stress response of sparsely spotted stingarees (Urolophus paucimaculatus) subjected to one of four different trawl treatments, including two different trawl durations as well as ancillary stressors of either air exposure or crowding. Physiological indicators (plasma lactate, urea, potassium and glucose) and changes in white blood cell counts were measured from blood samples taken throughout a 48 h recovery period. Mortality was low throughout this study (15% overall) and occurred only after >48 h following air exposure, crowding and 3 h trawl simulations. Plasma lactate, glucose and urea concentrations were identified as potential indicators of physiological stress, while plasma potassium and white blood cell counts were too variable to identify changes that would be expected to have biological consequences for stingarees. The characterization of the temporal profiles of physiological indicators facilitates a more accurate assessment of secondary stressors by identifying the best timing to sample stingaree blood when investigating post-capture stress physiology. High levels of lactate, increasing glucose and depressed urea were all recorded in response to air exposure following trawling, indicating that this is the primary source of stress in stingarees caught in trawling operations. These findings highlight the importance of improving bycatch sorting procedures to reduce the time out of the water for trawl-caught stingarees. PMID:27293661

On gonadic maturation and reproductive strategy in deep-sea benthic octopus Graneledone macrotyla

NASA Astrophysics Data System (ADS)

Guerra, Ángel; Sieiro, María Pilar; Roura, Álvaro; Portela, Julio M.; del Río, José Luís

2013-09-01

The new information reported in this paper is based on five maturing and mature females of the large-tuberculate octopus Graneledone macrotyla. These specimens were caught in bottom trawl surveys ATLANTIS 2009 (February 24 to April 1, 2009) and ATLANTIS 2010 (March 9 to April 5, 2010) carried out off the Argentinean Economic Exclusive Zone. Capture depth ranged from 475 to 921 m and sea bottom temperature between 2.8 and 3.1 °C. Development of the complex ovary, oviducts, and oviducal glands during gonadic maturation is described. The absence of spermathecae in the oviducal glands and the presence of fertilized eggs inside the ovary suggested that fertilization took place within the ovary. Histological techniques showed the presence of four types of oocytes. Maturing oocyte size-frequency distribution was polymodal. Fluorescence reaction showed that atresia occurred in both early and later oocyte maturation stages. Atresia affected 48-55 % of the initial number of oocytes. The maximum observed potential fecundity was estimated at 250-300 eggs. G. macrotyla showed a group-synchronous ovulation pattern, regulative atresia, and a batching spawning pattern with a few egg batches spawned intermittently over an extended period of spawning.

Population dynamics of the red shrimp Aristeus antennatus in the Balearic Islands (western Mediterranean): Short spatio-temporal differences and influence of environmental factors

NASA Astrophysics Data System (ADS)

Guijarro, Beatriz; Massutí, Enric; Moranta, Joan; Díaz, Paz

2008-06-01

The red shrimp Aristeus antennatus is one of the target species of the bottom trawl fishery of the Balearic Islands. The objective of the present paper is to study the short spatial and temporal differences of this important economic resource between two different locations off Mallorca (Cabrera: CA; Sóller: SO), where a fleet mobility pattern has been detected, and to study the influence of environmental conditions on this species. Six simultaneous bottom-trawl and oceanographic surveys were carried out at these two locations in order to collect data from the demersal species, hydrography (temperature and salinity), trophic resources and sediment characteristics. The commercial fleet from both locations was monitored by monthly on-board sampling, log-books and daily landings obtained from sales slips. Additional data was obtained from other fishing surveys. Short spatial and temporal differences have been detected between both locations. The population at CA was more demographically homogeneous, while that at SO showed important variations, like high abundance of juveniles recruiting to fishing grounds in autumn-winter and high abundance of large females during summer. Several differences have also been found in the biology of the species between locations, such as males were more abundant in SO than in CA. Also, the reproductive period started sooner in SO than in CA, and the condition of pre-spawning females was better in SO. The percentage of total lipids in the hepatopancreas was minimal during the spawning period, showing their importance as a reserve of energy for the ovary ripening. Water masses could play an important role in these differences, the characteristics of water masses being more stable in CA than in SO. Red shrimp adult females seemed to be more correlated with the warmer and more saline Levantine Intermediate Waters, while juveniles (males and females) and adult males were more correlated with the colder Western Mediterranean Deep Waters, detected only in SO during autumn-winter. Two different hypothesis of mobility patterns for the species are discussed in relation to these observed differences.

White sturgeon mitigation and restoration in the Columbia and Snake rivers upstream from Bonneville Dam, Annual progress report April 2002 - March 2003. Report C

USGS Publications Warehouse

Gadomski, D.M.; Parsley, M.J.; Kofoot, P.

2004-01-01

During 1 April 2002 through 31 March 2003, the U.S. Geological Survey (USGS) continued work on several tasks, including quantifying habitat suitable for white sturgeon Acipenser transmontanus spawning, a long-term survey of young-of-the-year (YOY) white sturgeon recruitment in the lower Columbia River, and a laboratory study investigating predation on larval and juvenile white sturgeon. River discharge and water temperatures that occurred during April through July 2002 provided relatively good conditions for spawning by white sturgeon downstream from Bonneville, The Dalles, John Day, and McNary dams. Optimal spawning temperatures in the four tailraces occurred for approximately three weeks and during a period of relatively high river discharge. Our monthly estimates of the index of spawning habitat showed that the availability of habitat for spawning peaked in June at levels higher than the average of past years. However, indices for the month of May were less than average in all four tailraces. YOY white sturgeon were collected during bottom trawling in Bonneville and The Dalles reservoirs, but none were captured in the John Day Reservoir. In an ongoing comparison of indices of abundance derived from bottom trawls and gill nets, the Oregon Department of Fish and Wildlife also caught YOY white sturgeon in gill nets set in The Dalles Reservoir, but none in the John Day Reservoir. The third year of a three-year laboratory predation study was completed. Adult channel catfish ingested white sturgeon up to a mean total length of about 120 mm, and juvenile walleye ate white sturgeon up to a mean length of 53 mm. When white sturgeon and coho salmon were both available as prey, northern pikeminnow continued to ingest white sturgeon, but in most cases preferred salmon. Conversely, prickly sculpins preferred white sturgeon over goldfish as prey. The presence of cover and also lower light levels reduced predation by sculpins on white sturgeon larvae, but cover did not reduce predation on white sturgeon juveniles. Similar to the past two years, turbidity affected predation of white sturgeon larvae by prickly sculpins, with less sturgeon ingested at higher turbidities.

78 FR 4346 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher/Processors Using...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-22

.../Processors Using Trawl Gear in the Western Regulatory Area of the Gulf of Alaska AGENCY: National Marine... (C/Ps) using trawl gear in the Western Regulatory Area of the Gulf of Alaska (GOA). This action is... apportioned to C/Ps using trawl gear in the Western Regulatory Area of the GOA. DATES: Effective 1200 hours...

78 FR 23683 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher/Processors Using...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-22

... Catcher/Processors Using Trawl Gear in the Central Regulatory Area of the Gulf of Alaska AGENCY: National... (C/Ps) using trawl gear in the Central Regulatory Area of the Gulf of Alaska (GOA). This action is... apportioned to C/Ps using trawl gear in the Central Regulatory Area of the GOA. DATES: Effective 1200 hours...

77 FR 9589 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher/Processors Using...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-17

.../Processors Using Trawl Gear in the Western Regulatory Area of the Gulf of Alaska AGENCY: National Marine... (C/Ps) using trawl gear in the Western Regulatory Area of the Gulf of Alaska (GOA). This action is... apportioned to C/Ps using trawl gear in the Western Regulatory Area of the GOA. DATES: Effective 1200 hrs...

50 CFR 648.91 - Monkfish regulated mesh areas and restrictions on gear and methods of fishing.

Code of Federal Regulations, 2010 CFR

2010-10-01

... while on a monkfish DAS. Except as provided in paragraph (c)(1)(ii) of this section, the minimum mesh size for any trawl net, including beam trawl nets, used by a vessel fishing under a monkfish DAS is 10... area being fished. (ii) Trawl nets while on a monkfish and NE multispecies DAS. Vessels issued a...

Fine-scale spatial patterns in the demersal fish and invertebrate community in a northwest Atlantic ecosystem

NASA Astrophysics Data System (ADS)

Malek, Anna J.; Collie, Jeremy S.; Gartland, James

2014-06-01

The abundance, biomass, diversity, and species composition of the demersal fish and invertebrate community in Rhode Island Sound and Block Island Sound, an area identified for offshore renewable energy development, were evaluated for spatial and seasonal structure. We conducted 58 otter trawls and 51 beam trawls in the spring, summer and fall of 2009-2012, and incorporated additional data from 88 otter trawls conducted by the Northeast Area Monitoring and Assessment Program. We used regionally-grouped abundance, biomass, diversity, and size spectra to assess spatial patterns in the aggregate fish community, and hierarchical cluster analysis to evaluate trends in species assemblages. Our analyses revealed coherent gradients in fish community biomass, diversity and species composition extending from inshore to offshore waters, as well as patterns related to the differing bathymetry of Rhode Island and Block Island Sounds. The fish communities around Block Island and Cox's Ledge are particularly diverse, suggesting that the proximity of hard bottom habitat may be important in structuring fish communities in this area. Species assemblages in Rhode Island and Block Island Sounds are characterized by a combination of piscivores (silver hake, summer flounder, spiny dogfish), benthivores (American lobster, black sea bass, Leucoraja spp. skates, scup) and planktivores (sea scallop), and exhibit geographic patterns that are persistent from year to year, yet variable by season. Such distributions reflect the cross-shelf migration of fish and invertebrate species in the spring and fall, highlighting the importance of considering seasonal fish behavior when planning construction schedules for offshore development projects. The fine spatial scale (10 s of kms) of this research makes it especially valuable for local marine spatial planning efforts by identifying local-scale patterns in fish community structure that will enable future assessment of the ecological impacts of offshore development. As such, this knowledge of the spatial and temporal structure of the demersal fish community in Rhode Island and Block Island Sounds will help to guide the placement of offshore structures so as to preserve the ecological and economic value of the area.

Rhode Island's got the Blues. But the state's Blues plan isn't the only one drawing fire over its reserves, executive perks and compensation.

PubMed

Benko, Laura B

2004-05-17

It's been a strained few months at Blue Cross and Blue Shield of Rhode Island. Outrage over corporate excess led to a flurry of reforms at the insurer, headed by Chairman Frank Montanaro, left, including banning loans to employees and dropping lavish perks. Other Blues have been catching flak for their burgeoning bottom lines, but executives say they need ample reserves since that's their only capital.

50 CFR Figure 7 to Part 679 - Location of Trawl Gear Test Areas in the GOA and the BSAI

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Location of Trawl Gear Test Areas in the GOA and the BSAI 7 Figure 7 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT... EXCLUSIVE ECONOMIC ZONE OFF ALASKA Pt. 679, Fig. 7 Figure 7 to Part 679—Location of Trawl Gear Test Areas in...

Prenatal stress from trawl capture affects mothers and neonates: a case study using the southern fiddler ray (Trygonorrhina dumerilii)

NASA Astrophysics Data System (ADS)

Guida, L.; Awruch, C.; Walker, T. I.; Reina, R. D.

2017-04-01

Assessing fishing effects on chondrichthyan populations has predominantly focused on quantifying mortality rates. Consequently, sub-lethal effects of capture stress on the reproductive capacity of chondrichthyans are largely unknown. We investigated the reproductive consequences of capture on pregnant southern fiddler rays (Trygonorrhina dumerilii) collected from Swan Bay, Australia, in response to laboratory-simulated trawl capture (8 h) followed immediately by air exposure (30 min). Immediately prior to, and for up to 28 days post trawling, all females were measured for body mass (BM), sex steroid concentrations (17-β estradiol, progesterone, testosterone) and granulocyte to lymphocyte (G:L) ratio. At parturition, neonates were measured for total length (TL), BM and G:L ratio. Trawling reduced maternal BM and elevated the G:L ratio for up to 28 days. Trawling did not significantly affect any sex steroid concentrations relative to controls. Neonates from trawled mothers were significantly lower in BM and TL than control animals, and had an elevated G:L ratio. Our results show that capture of pregnant T. dumerilii can influence their reproductive potential and affect the fitness of neonates. We suggest other viviparous species are likely to be similarly affected. Sub-lethal effects of capture, particularly on reproduction, require further study to improve fisheries management and conservation of chondrichthyans.

Rhythmic behaviour of marine benthopelagic species and the synchronous dynamics of benthic communities

NASA Astrophysics Data System (ADS)

Aguzzi, Jacopo; Sbragaglia, Valerio; Tecchio, Samuele; Navarro, Joan; Company, Joan B.

2015-01-01

Light-intensity cycles drive the relentless motion of species in the oceans, and water column migrants may cyclically make contact with the seabed, hence influencing the temporal dynamism of benthic ecosystems. The influence of light on this process remains largely unknown to date. In this study, we focus on the occurrence of day-night changes in benthic communities on the western Mediterranean continental shelf (100 m depth) and slope (400 m depth) as a potential result of a behaviourally sustained benthopelagic coupling. We analysed fluctuations in species abundance based on trawling at hourly intervals over a 4-day period as a proxy of activity rhythms at the seabed. We also measured light in situ to assess how the depth-related decrease of its intensity influences species rhythms and the occurrence of the putative benthopelagic synchronisation. Temporal similarities in the catch patterns for different species were screened by dendrogram analysis. On the continental shelf, species performing diel migrations (i.e., over a 24 h period) that were either vertical (i.e., benthopelagic) or horizontal across depths (i.e., nektobenthic) clustered together separately from the more sedentary endobenthic and epibenthic species. At the same depth, waveform analysis showed a significant diurnal increase in the catch of water column species and benthic species at night. Such coupling was absent on the continental slope, where light intensity was several orders of magnitude lower than that on the shelf. Our data indicate that diel activity rhythms, which are well known for vertical pelagic migrators, are also evident in the benthos. We discuss the role of light as a major evolutionary driver shaping the composition and biodiversity of benthic communities via visual predation.

Some observations on the biology of two rarely seen deep-sea chimaerids, Chimaera carophila and Hydrolagus homonycteris.

PubMed

Finucci, B; Stevens, D W; Jones, E G; Dunn, M R

2017-05-01

Chimaera carophila (n = 45) and Hydrolagus homonycteris (n = 11), two deep-sea chimaerids rarely caught in the waters off New Zealand, were collected from research trawl catches and commercial fishery catches around New Zealand at depths between 400 and 1300 m, between 2014 and 2016. Additional preserved specimens of both species (n = 58) from museum collections were analysed for size, sex and maturity. External assessment of male claspers and a combination of internal assessments of female gonad mass and oviducal gland width, were used to determine maturity. For both species, length at first maturity was 0·70-0·82 of their maximum observed chimaera length (L C ), with females maturing at a larger size. Length at maturity for C. carophila (L C range: 28·7-103·9 cm) was estimated at 72·5 cm L C for males (n = 163) and 82·5 L C for females (n = 58). In H. homonycteris, length at maturity (length range: 78·6-99·8 cm L C ) was estimated at 79·1 cm L C for males (n = 51) and 80·1 cm L C for females (n = 17). Ovarian fecundity was up to 31 for C. carophila and sperm storage was confirmed in the oviducal gland of this species. Both species preyed on benthic invertebrates. Some C. carophila and H. homonycteris inhabit depths beyond most current fisheries, but both species appear to be relatively rare and have reproductive parameters characteristic of low productivity, which may make these species vulnerable to population decline if mortality was to increase in the future. © 2017 The Fisheries Society of the British Isles.

Biogeographic patterns in the cartilaginous fauna (Pisces: Elasmobranchii and Holocephali) in the southeast Pacific Ocean

PubMed Central

Vargas-Caro, Carolina; Bennett, Michael B.

2014-01-01

The abundance and species richness of the cartilaginous fish community of the continental shelf and slope off central Chile is described, based on fishery-independent trawl tows made in 2006 and 2007. A total of 194,705 specimens comprising 20 species (9 sharks, 10 skates, 1 chimaera) were caught at depths of 100–500 m along a 1,000 km transect between 29.5°S and 39°S. Sample site locations were grouped to represent eight geographical zones within this latitudinal range. Species richness fluctuated from 1 to 6 species per zone. There was no significant latitudinal trend for sharks, but skates showed an increased species richness with latitude. Standardised catch per unit effort (CPUE) increased with increasing depth for sharks, but not for skates, but the observed trend for increasing CPUE with latitude was not significant for either sharks or skates. A change in community composition occurred along the depth gradient with the skates, Psammobatis rudis, Zearaja chilensis and Dipturus trachyderma dominating communities between 100 and 300 m, but small-sized, deep-water dogfishes, such as Centroscyllium spp. dominated the catch between 300 and 500 m. Cluster and ordination analysis identified one widespread assemblage, grouping 58% of sites, and three shallow-water assemblages. Assemblages with low diversity (coldspots) coincided with highly productive fishing grounds for demersal crustaceans and bony fishes. The community distribution suggested that the differences between assemblages may be due to compensatory changes in mesopredator species abundance, as a consequence of continuous and unselective species removal. Distribution patterns and the quantitative assessment of sharks, skates and chimaeras presented here complement extant biogeographic knowledge and further the understanding of deep-water ecosystem dynamics in relation to fishing activity in the south-east Pacific Ocean. PMID:24918036

Biogeographic patterns in the cartilaginous fauna (Pisces: Elasmobranchii and Holocephali) in the southeast Pacific Ocean.

PubMed

Bustamante, Carlos; Vargas-Caro, Carolina; Bennett, Michael B

2014-01-01

The abundance and species richness of the cartilaginous fish community of the continental shelf and slope off central Chile is described, based on fishery-independent trawl tows made in 2006 and 2007. A total of 194,705 specimens comprising 20 species (9 sharks, 10 skates, 1 chimaera) were caught at depths of 100-500 m along a 1,000 km transect between 29.5°S and 39°S. Sample site locations were grouped to represent eight geographical zones within this latitudinal range. Species richness fluctuated from 1 to 6 species per zone. There was no significant latitudinal trend for sharks, but skates showed an increased species richness with latitude. Standardised catch per unit effort (CPUE) increased with increasing depth for sharks, but not for skates, but the observed trend for increasing CPUE with latitude was not significant for either sharks or skates. A change in community composition occurred along the depth gradient with the skates, Psammobatis rudis, Zearaja chilensis and Dipturus trachyderma dominating communities between 100 and 300 m, but small-sized, deep-water dogfishes, such as Centroscyllium spp. dominated the catch between 300 and 500 m. Cluster and ordination analysis identified one widespread assemblage, grouping 58% of sites, and three shallow-water assemblages. Assemblages with low diversity (coldspots) coincided with highly productive fishing grounds for demersal crustaceans and bony fishes. The community distribution suggested that the differences between assemblages may be due to compensatory changes in mesopredator species abundance, as a consequence of continuous and unselective species removal. Distribution patterns and the quantitative assessment of sharks, skates and chimaeras presented here complement extant biogeographic knowledge and further the understanding of deep-water ecosystem dynamics in relation to fishing activity in the south-east Pacific Ocean.

Acoustic discrimination of Southern Ocean zooplankton

NASA Astrophysics Data System (ADS)

Brierley, Andrew S.; Ward, Peter; Watkins, Jonathan L.; Goss, Catherine

Acoustic surveys in the vicinity of the sub-Antarctic island of South Georgia during a period of exceptionally calm weather revealed the existence of a number of horizontally extensive yet vertically discrete scattering layers in the upper 250 m of the water column. These layers were fished with a Longhurst-Hardy plankton recorder (LHPR) and a multiple-opening 8 m 2 rectangular mid-water trawl (RMT8). Analysis of catches suggested that each scattering layer was composed predominantly of a single species (biovolume>95%) of either the euphausiids Euphausia frigida or Thysanöessa macrura, the hyperiid amphipod Themisto gaudichaudii, or the eucalaniid copepod Rhincalanus gigas. Instrumentation on the nets allowed their trajectories to be reconstructed precisely, and thus catch data to be related directly to the corresponding acoustic signals. Discriminant function analysis of differences between mean volume backscattering strength at 38, 120 and 200 kHz separated echoes originating from each of the dominant scattering layers, and other signals identified as originating from Antarctic krill ( Euphausia superba), with an overall correct classification rate of 77%. Using echo intensity data alone, gathered using hardware commonly employed for fishery acoustics, it is therefore possible to discriminate in situ between several zooplanktonic taxa, taxa which in some instances exhibit similar gross morphological characteristics and have overlapping length- frequency distributions. Acoustic signals from the mysid Antarctomysis maxima could also be discriminated once information on target distribution was considered, highlighting the value of incorporating multiple descriptors of echo characteristics into signal identification procedures. The ability to discriminate acoustically between zooplankton taxa could be applied to provide improved acoustic estimates of species abundance, and to enhance field studies of zooplankton ecology, distribution and species interactions.

Inventory of marine and estuarine fishes in southeast and central Alaska National Parks

USGS Publications Warehouse

Arimitsu, Mayumi L.; Litzow, Michael A.; Piatt, John F.; Robards, Martin D.; Abookire, Alisa A.; Drew, Gary S.

2003-01-01

As part of a national inventory program funded by the National Park Service, we conducted an inventory of marine and estuarine fishes in Glacier Bay National Park and Preserve, Wrangell-St. Elias National Park and Preserve, Sitka National Historical Park, and Klondike Gold Rush National Historical Park in 2001 and 2002. In addition, marine fish data from a previous project that focused on forage fishes and marine predators during 1999 and 2000 in Glacier Bay proper were compiled for this study. Sampling was conducted with modified herring and Isaacs-Kidd midwater trawls, a plumb staff beam trawl, and beach seines. Species lists of relative abundance were generated for nearshore fishes in all parks, and for demersal and pelagic fishes in Glacier Bay National Park and Preserve and Wrangell-St. Elias National Park and Preserve. With a total sampling effort of 531 sets, we captured 100 species in Glacier Bay National Park and Preserve, 31 species in Wrangell-St. Elias National Park and Preserve, 23 species in Sitka National Historical Park, and 11 species in Klondike Gold Rush National Historical Park. We estimated that between 59 and 85 percent of the total marine fish species present were sampled by us in the various habitat-park units. We also combined these data with historical records and prepared an annotated species list of 160 marine and estuarine fishes known to occur in Glacier Bay National Park and Preserve. Shannon-Wiener diversity index and catch per unit effort were used to assess the effects of depth and latitude (distance from tidewater glaciers) on marine fish community ecology in Glacier Bay proper. Our findings suggest that demersal fishes are more abundant and diverse with increased distance from tidewater glaciers, and that pelagic fishes sampled deeper than 50 m are more abundant in areas closer to tidewater glaciers.

50 CFR Table 51 to Part 679 - Modified Gear Trawl Zone

Code of Federal Regulations, 2014 CFR

2014-10-01

... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Modified Gear Trawl Zone 51 Table 51 to..., Table 51 Table 51 to Part 679—Modified Gear Trawl Zone Longitude Latitude 171 45.00 W 61 00.00 N 169 00.00 W 61 00.00 N 169 00.00 W 60 35.48 N 171 45.00 W 60 06.15 N Note: The area is delineated by...

50 CFR Table 51 to Part 679 - Modified Gear Trawl Zone

Code of Federal Regulations, 2013 CFR

2013-10-01

... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Modified Gear Trawl Zone 51 Table 51 to..., Table 51 Table 51 to Part 679—Modified Gear Trawl Zone Longitude Latitude 171 45.00 W 61 00.00 N 169 00.00 W 61 00.00 N 169 00.00 W 60 35.48 N 171 45.00 W 60 06.15 N Note: The area is delineated by...

50 CFR Table 51 to Part 679 - Modified Gear Trawl Zone

Code of Federal Regulations, 2012 CFR

2012-10-01

... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Modified Gear Trawl Zone 51 Table 51 to..., Table 51 Table 51 to Part 679—Modified Gear Trawl Zone Longitude Latitude 171 45.00 W 61 00.00 N 169 00.00 W 61 00.00 N 169 00.00 W 60 35.48 N 171 45.00 W 60 06.15 N Note: The area is delineated by...

50 CFR Table 51 to Part 679 - Modified Gear Trawl Zone

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Modified Gear Trawl Zone 51 Table 51 to..., Table 51 Table 51 to Part 679—Modified Gear Trawl Zone Longitude Latitude 171 45.00 W 61 00.00 N 169 00.00 W 61 00.00 N 169 00.00 W 60 35.48 N 171 45.00 W 60 06.15 N Note: The area is delineated by...

Evaluation of pheromone-baited traps for winter moth and Bruce spanworm (Lepidoptera: Geometridae).

PubMed

Elkinton, Joseph S; Lance, David; Boettner, George; Khrimian, Ashot; Leva, Natalie

2011-04-01

We tested different pheromone-baited traps for surveying winter moth, Operophtera brumata (L.) (Lepidoptera: Geometridae), populations in eastern North America. We compared male catch at Pherocon 1C sticky traps with various large capacity traps and showed that Universal Moth traps with white bottoms caught more winter moths than any other trap type. We ran the experiment on Cape Cod, MA, where we caught only winter moth, and in western Massachusetts, where we caught only Bruce spanworm, Operophtera bruceata (Hulst) (Lepidoptera: Geometridae), a congener of winter moth native to North America that uses the same pheromone compound [(Z,Z,Z)-1,3,6,9-nonadecatetraene] and is difficult to distinguish from adult male winter moths. With Bruce spanworm, the Pherocon 1C sticky traps caught by far the most moths. We tested an isomer of the pheromone [(E,Z,Z)-1,3,6,9-nonadecatetraene] that previous work had suggested would inhibit captures of Bruce spanworm but not winter moths. We found that the different doses and placements of the isomer suppressed captures of both species to a similar degree. We are thus doubtful that we can use the isomer to trap winter moths without also catching Bruce spanworm. Pheromone-baited survey traps will catch both species.

Infaunal community responses to a gradient of trawling disturbance and a long-term Fishery Exclusion Zone in the Southern Tyrrhenian Sea

NASA Astrophysics Data System (ADS)

Mangano, M. Cristina; Kaiser, Michel J.; Porporato, Erika M. D.; Lambert, Gwladys I.; Rinelli, Paola; Spanò, Nunziacarla

2014-03-01

Historically the majority of Mediterranean trawl fisheries occur on the continental shelf with a smaller proportion focused on the shelf slope and deep sea areas. Understanding how trawl fisheries affect the wider ecosystem is an important component of the ecosystem-based approach to fisheries management. In this context the current study examined the impact of the otter trawl fishery on the infaunal communities found on the continental shelf and upper slope off the coast of Sicily and Calabria, Italy. A total of thirty six sites were sampled across a gradient of fishing intensity and from within a large bay from which trawling has been excluded for 22 years. Fishing intensities were ascertained post-hoc from vessel monitoring system data. Seabed characteristics of the sites studied were uniform across the continental shelf and slope areas that were studied, such that the only factor that varied was fishing intensity. The density index (DI) and total number of species (S) were significantly higher in the fishery closure area compared with other continental shelf sites. In particular, bioturbating decapod fauna occurred only within the fishery closure area. Fished sites were dominated primarily by burrowing deposit feeding worms, small bivalves and scavenging biota. In contrast, the response to fishing on the upper slope was less clear. This observation was treated with caution as the power to detect fishing effects was lower for the upper slope sites as a result of possible illegal fishing that had compromised two of the four replicate sites within the closed area. While the present study was able to quantify the effect of the demersal trawl fleet on the benthic infauna of the continental shelf, the effects of trawling on the upper shelf slope remain unclear and warrant further study.

Prenatal stress from trawl capture affects mothers and neonates: a case study using the southern fiddler ray (Trygonorrhina dumerilii)

PubMed Central

Guida, L.; Awruch, C.; Walker, T. I.; Reina, R. D.

2017-01-01

Assessing fishing effects on chondrichthyan populations has predominantly focused on quantifying mortality rates. Consequently, sub-lethal effects of capture stress on the reproductive capacity of chondrichthyans are largely unknown. We investigated the reproductive consequences of capture on pregnant southern fiddler rays (Trygonorrhina dumerilii) collected from Swan Bay, Australia, in response to laboratory-simulated trawl capture (8 h) followed immediately by air exposure (30 min). Immediately prior to, and for up to 28 days post trawling, all females were measured for body mass (BM), sex steroid concentrations (17-β estradiol, progesterone, testosterone) and granulocyte to lymphocyte (G:L) ratio. At parturition, neonates were measured for total length (TL), BM and G:L ratio. Trawling reduced maternal BM and elevated the G:L ratio for up to 28 days. Trawling did not significantly affect any sex steroid concentrations relative to controls. Neonates from trawled mothers were significantly lower in BM and TL than control animals, and had an elevated G:L ratio. Our results show that capture of pregnant T. dumerilii can influence their reproductive potential and affect the fitness of neonates. We suggest other viviparous species are likely to be similarly affected. Sub-lethal effects of capture, particularly on reproduction, require further study to improve fisheries management and conservation of chondrichthyans. PMID:28401959

50 CFR Table 3 (north) to Part 660... - Non-Trawl Rockfish Conservation Areas and Trip Limits for Open Access Gears North of 40°10′ N. Lat.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Non-Trawl Rockfish Conservation Areas and Trip Limits for Open Access Gears North of 40°10â² N. Lat. 3 Table 3 (North) to Part 660, Subpart F...) to Part 660, Subpart F—Non-Trawl Rockfish Conservation Areas and Trip Limits for Open Access Gears...

50 CFR Table 3 (south) to Part 660... - Non-Trawl Rockfish Conservation Areas and Trip Limits for Open Access Gears South of 40°10′ N. Lat.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Non-Trawl Rockfish Conservation Areas and Trip Limits for Open Access Gears South of 40°10â² N. Lat. 3 Table 3 (South) to Part 660, Subpart F...) to Part 660, Subpart F—Non-Trawl Rockfish Conservation Areas and Trip Limits for Open Access Gears...

50 CFR 679.20 - General limitations.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Type A season B season C season (1) Trawl 60% 20% 20% (i) Trawl CV 70% 10% 20% (ii) Trawl CP 50% 30% 20% (2) Hook-and-line CP and hook-and-line CV ≥60 ft (18.3 m) LOA 60% 40% no C season (3) Jig 40% 20% 40....3 m) LOA 0.2 (4) Hook-and-line CP 48.7 (5) Pot CV ≥60 ft (18.3 m) LOA 8.4 (6) Pot CP 1.5 (7) AFA...

Interannual Variability of Fisheries Economic Returns and Energy Ratios Is Mostly Explained by Gear Type

PubMed Central

Trenkel, Verena M.; Daurès, Fabienne; Rochet, Marie-Joëlle; Lorance, Pascal

2013-01-01

According to portfolio theory applied to fisheries management, economic returns are stabilised by harvesting in a portfolio stocks of species whose returns are negatively correlated and for which the portfolio economic return variance is smaller than the sum of stock specific return variances. Also, variability is expected to decrease with portfolio width. Using a range of indicators, these predictions were tested for the French fishing fleets in the Bay of Biscay (Northeast Atlantic) during the period 2001–2009. For this, vessels were grouped into eight fishing fleets based on the gears used and exploited species were grouped into five functional groups. The portfolio width of fleets ranged from 1–3 functional groups, or 4–19 species. Economic fleet returns (sale revenues minus fishing costs) varied strongly between years; the interannual variability was independent of portfolio width (species or functional groups). Energy ratio expressed by the ratio between fuel energy used for fishing and energy contained in landings varied from 0.3 for purse seines to 9.7 for trawlers using bottom trawls alone or in combination with pelagic trawls independent of portfolio width. Interannual variability in total sale revenues was larger than the sum of species specific sales revenue variability, except for fleets using hooks and pelagic trawlers; it increased with the number of species exploited. In conclusion, the interannual variability of economic returns or energy ratios of French fisheries in the Bay of Biscay did not decrease with the number of species or functional groups exploited, though it varied between fleets. PMID:23922951

Status and trends of the Lake Huron offshore demersal fish community, 1976-2015

USGS Publications Warehouse

Roseman, Edward; Chriscinske, Margret Ann; Castle, Dana Kristina; Prichard, Carson G.

2016-01-01

The USGS Great Lakes Science Center has conducted trawl surveys to assess annual changes in the offshore demersal fish community of Lake Huron since 1973. Sample sites include five ports in U.S. waters with less frequent sampling near Goderich, Ontario. The 2015 fall bottom trawl survey was carried out between 14 and 28 October and included all U.S. ports, as well as Goderich, ON. The 2015 main basin prey fish biomass estimate for Lake Huron was 19.4 kilotonnes, a decline of about 50 percent from 2014. This estimate is the second lowest in the time series, and is approximately 5 percent of the maximum estimate in the time series observed in 1987. No adult alewife were collected in 2015 and YOY alewife was the second lowest in the time series, up slightly from the record low in 2014. The estimated biomass of yearling and older rainbow smelt also decreased and was the lowest observed in the time series. Estimated adult bloater biomass in Lake Huron declined to about half of the 2014 estimate. YOY alewife, rainbow smelt, and bloater abundance and biomass decreased over 2014. Biomass estimates for deepwater sculpins declined while trout-perch and ninespine stickleback increased over 2014 values, but all remained low compared to historic estimates. The 2014 biomass estimate for round goby increased from 2014 but remains at only 7 percent of the maximum observed in 2003. Wild juvenile lake trout were captured again in 2015, suggesting that natural reproduction by lake trout continues to occur.

Short-term impacts and value of a periodic no take zone (NTZ) in a community-managed small-scale lobster fishery, Madagascar

PubMed Central

2017-01-01

The small-scale lobster fisheries of Madagascar’s impoverished southeast coast account for the majority of national catch and export, making a significant contribution to the regional economy. Data suggests catches have declined, likely due to over-exploitation. In response, the community of Sainte Luce has established a locally managed marine area (LMMA) to manage their lobster fishery, including a 13 km2 periodic no take zone (NTZ). Participatory monitoring data were used to assess compliance, identify changes in catch per unit effort (CPUE) associated with the NTZ and consider the short-term value of the NTZ. Compliance is low for measures dictated by national legislation (minimum landing size (MLS), national closed season, prohibition on landing berried females), but may be higher for those designed by the community (NTZ). Upon NTZ opening in July 2015, an estimated 435% increase in catch was observed compared with the mean for the preceding five months, a product of increased effort and significantly higher CPUE. Zero Altered Negative Binomial modelling showed CPUE was significantly higher during the NTZ opening in 2015 and in 2016 when the opening period had been moved. Whilst it is unlikely that tangible ecological benefits have accrued from NTZ operation, there have been important socio-economic effects. Specifically, there was a 33% increase in the price fishers received, a significant effect at the bottom of the value chain. Temporary increases in catch and income acted as a catalyst, engaging neighbouring communities in fishery management, resulting in two additional NTZs. Attention is drawn to the fact that current national legislation may be sub-optimal and should be reviewed. Successful management of the regional fishery will require the state and industry to support communities in adopting community-based management. The NTZ measure considered here may be an effective tool to achieve this. PMID:28542323

Short-term impacts and value of a periodic no take zone (NTZ) in a community-managed small-scale lobster fishery, Madagascar.

PubMed

Long, Stephen

2017-01-01

The small-scale lobster fisheries of Madagascar's impoverished southeast coast account for the majority of national catch and export, making a significant contribution to the regional economy. Data suggests catches have declined, likely due to over-exploitation. In response, the community of Sainte Luce has established a locally managed marine area (LMMA) to manage their lobster fishery, including a 13 km2 periodic no take zone (NTZ). Participatory monitoring data were used to assess compliance, identify changes in catch per unit effort (CPUE) associated with the NTZ and consider the short-term value of the NTZ. Compliance is low for measures dictated by national legislation (minimum landing size (MLS), national closed season, prohibition on landing berried females), but may be higher for those designed by the community (NTZ). Upon NTZ opening in July 2015, an estimated 435% increase in catch was observed compared with the mean for the preceding five months, a product of increased effort and significantly higher CPUE. Zero Altered Negative Binomial modelling showed CPUE was significantly higher during the NTZ opening in 2015 and in 2016 when the opening period had been moved. Whilst it is unlikely that tangible ecological benefits have accrued from NTZ operation, there have been important socio-economic effects. Specifically, there was a 33% increase in the price fishers received, a significant effect at the bottom of the value chain. Temporary increases in catch and income acted as a catalyst, engaging neighbouring communities in fishery management, resulting in two additional NTZs. Attention is drawn to the fact that current national legislation may be sub-optimal and should be reviewed. Successful management of the regional fishery will require the state and industry to support communities in adopting community-based management. The NTZ measure considered here may be an effective tool to achieve this.

50 CFR 660.381 - Limited entry trawl fishery management measures.

Code of Federal Regulations, 2010 CFR

2010-10-01

... conditions: vessels fishing with mid-water trawl gear on Pacific whiting trips during the primary whiting... Cave, Anacapa Island, Carrington Point, Judith Rock, Skunk Point, Footprint, Gull Island, South Point...

Radiocarbon-based ages and growth rates of bamboo corals from the Gulf of Alaska

NASA Astrophysics Data System (ADS)

Roark, E. Brendan; Guilderson, Thomas P.; Flood-Page, Sarah; Dunbar, Robert B.; Ingram, B. Lynn; Fallon, Stewart J.; McCulloch, Malcolm

2005-02-01

Deep-sea coral communities have long been recognized by fisherman as areas that support large populations of commercial fish. As a consequence, many deep-sea coral communities are threatened by bottom trawling. Successful management and conservation of this widespread deep-sea habitat requires knowledge of the age and growth rates of deep-sea corals. These organisms also contain important archives of intermediate and deep-water variability, and are thus of interest in the context of decadal to century-scale climate dynamics. Here, we present Δ14C data that suggest that bamboo corals from the Gulf of Alaska are long-lived (75-126 years) and that they acquire skeletal carbon from two distinct sources. Independent verification of our growth rate estimates and coral ages is obtained by counting seasonal Sr/Ca cycles and probable lunar cycle growth bands.

White sturgeon mitigation and restoration in the Columbia and Snake rivers upstream from Bonneville Dam, Annual Progress Report April 2005 - March 2006. Report C.

USGS Publications Warehouse

Parsley, M.J.; Kofoot, P.

2007-01-01

River discharge and water temperatures that occurred during April through July 2005 provided conditions suitable for spawning by white sturgeon downstream from Bonneville, The Dalles, John Day, and McNary dams. Optimal spawning temperatures in the four tailraces occurred for 3-4 weeks and coincided with the peak of the river hydrograph. However, the peak of the hydrograph occurred in mid May and discharges dropped quickly and water temperature rose during June, which is reflected in the monthly and annual indices of suitable spawning habitat. Indices of available spawning habitat for the month of June 2005 were less than one-half of the average of the period from 1985-2004. Bottom-trawl sampling in the Bonneville Reservoir revealed the presence of young-of-the-year (YOY) white sturgeon but the proportion of positive tows was quite low at 0.06.

Length-weight relationship of eleven species of marine catfishes from the northern Arabian Sea coast of Pakistan

NASA Astrophysics Data System (ADS)

Farooq, Noureen; Qamar, Nazia; Rashid, Shahnaz; Panhwar, Sher Khan

2017-09-01

This study records length-weight relationships (LWRs) for eleven commercially important marine catfish species of the family Ariidae (sea catfishes) and Plotosidae (eel catfishes) from the northern Arabian Sea coast of Pakistan. The specimens were sampled from December 2014 to November 2015, using bottom trawls with various mesh sizes by commercial vessels. The species were Nemapteryx caelatus, Sciades sona, Arius gagora, Batrachocephalus mino, Netuma thalassina, N. bilineata, Osteogeneiosus militaris, Plicofollis dussumieri, P. tenuispinis, Plotosus limbatus, and P. lineatus. Of the eleven species, two species A. gagora and N. bilineata were recorded for the first time and LWRs for four species A. gagora, N. bilineata, S. sona, and B. mino still have no data in the FishBase database. In addition, new maximum length for each of the three species N. bilineata, O. militaris and B. mino was also found.

Radiocarbon-Based Ages and Growth Rates of Bamboo Corals from the Gulf of Alaska

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

Roark, E B; Guilderson, T P; Flood-Page, S

2004-12-12

Deep-sea coral communities have long been recognized by fisherman as areas that support large populations of commercial fish. As a consequence, many deep-sea coral communities are threatened by bottom trawling. Successful management and conservation of this widespread deep-sea habitat requires knowledge of the age and growth rates of deep-sea corals. These organisms also contain important archives of intermediate and deep-water variability, and are thus of interest in the context of decadal to century-scale climate dynamics. Here, we present {Delta}{sup 14}C data that suggest that bamboo corals from the Gulf of Alaska are long-lived (75-126 years) and that they acquire skeletalmore » carbon from two distinct sources. Independent verification of our growth rate estimates and coral ages is obtained by counting seasonal Sr/Ca cycles and probable lunar cycle growth bands.« less

Isolation and Antifouling Activity of Azulene Derivatives from the Antarctic Gorgonian Acanthogorgia laxa.

PubMed

Patiño Cano, Laura P; Quintana Manfredi, Rodrigo; Pérez, Miriam; García, Mónica; Blustein, Guillermo; Cordeiro, Ralf; Pérez, Carlos D; Schejter, Laura; Palermo, Jorge A

2018-01-01

Three azulenoid sesquiterpenes (1 - 3) were isolated from the Antarctic gorgonian Acanthogorgia laxa collected by bottom trawls at -343 m. Besides linderazulene (1), and the known ketolactone 2, a new brominated C 16 linderazulene derivative (3) was also identified. This compound has an extra carbon atom at C(7) of the linderazulene framework. The antifouling activity of compounds 1 and 2 was assayed in the laboratory with Artemia salina larvae, and also in field tests, by incorporation in soluble-matrix experimental antifouling paints. The results obtained after a 45 days field trial of the paints, showed that compounds 1 and 2 displayed good antifouling potencies against a wide array of organisms. Compound 3, a benzylic bromide, was unstable and for this reason was not submitted to bioassays. Two known cembranolides: pukalide and epoxypukalide, were also identified as minor components of the extract. © 2018 Wiley-VHCA AG, Zurich, Switzerland.

Female reproductive traits of a commercially exploited skate: Atlantoraja platana (Günther, 1880) (Chondrichthyes, Rajidae). Ovarian morphology, gametogenesis and microscopic verification of maturity criteria.

PubMed

Moya, A C; Wehitt, A; Díaz Andrade, M C; Di Giacomo, E E; Galíndez, E J

2017-10-01

Atlantoraja platana is an endemic species of the Southwest Atlantic Ocean, and is one of the most captured by the local bottom trawl industrial fisheries. In this work, the microscopic architecture of mature female's gonads and the dynamics of follicle development are studied as a contribution to raise awareness of reproductive biology of the species. Folliculogenesis depicts the same histologic pattern as in other Elasmobranchs. Follicles in different degrees of maturation coexist in mature animals. The oogonia were only found in immature individuals. Likewise, atretic follicles were recorded in ovaries of all sexual maturity stages. The microscopic size recorded from the beginning of yolk input is smallest than the detected with the necked eye. This study provides valuable information about female's gametogenesis that could be taken into account in the development of fisheries management. Copyright © 2017 Elsevier Ltd. All rights reserved.

Bottom-up effects of a no-take zone on endangered penguin demographics.

PubMed

Sherley, Richard B; Winker, Henning; Altwegg, Res; van der Lingen, Carl D; Votier, Stephen C; Crawford, Robert J M

2015-07-01

Marine no-take zones can have positive impacts for target species and are increasingly important management tools. However, whether they indirectly benefit higher order predators remains unclear. The endangered African penguin (Spheniscus demersus) depends on commercially exploited forage fish. We examined how chick survival responded to an experimental 3-year fishery closure around Robben Island, South Africa, controlling for variation in prey biomass and fishery catches. Chick survival increased by 18% when the closure was initiated, which alone led to a predicted 27% higher population compared with continued fishing. However, the modelled population continued to decline, probably because of high adult mortality linked to poor prey availability over larger spatial scales. Our results illustrate that small no-take zones can have bottom-up benefits for highly mobile marine predators, but are only one component of holistic, ecosystem-based management regimes. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Relative importance of population size, fishing pressure and temperature on the spatial distribution of nine Northwest Atlantic groundfish stocks.

PubMed

Adams, Charles F; Alade, Larry A; Legault, Christopher M; O'Brien, Loretta; Palmer, Michael C; Sosebee, Katherine A; Traver, Michele L

2018-01-01

The spatial distribution of nine Northwest Atlantic groundfish stocks was documented using spatial indicators based on Northeast Fisheries Science Center spring and fall bottom trawl survey data, 1963-2016. We then evaluated the relative importance of population size, fishing pressure and bottom temperature on spatial distribution with an information theoretic approach. Northward movement in the spring was generally consistent with prior analyses, whereas changes in depth distribution and area occupancy were not. Only two stocks exhibited the same changes in spatiotemporal distribution in the fall as compared with the spring. Fishing pressure was the most important predictor of the center of gravity (i.e., bivariate mean location of the population) for the majority of stocks in the spring, whereas in the fall this was restricted to the east-west component. Fishing pressure was also the most important predictor of the dispersion around the center of gravity in both spring and fall. In contrast, biomass was the most important predictor of area occupancy for the majority of stocks in both seasons. The relative importance of bottom temperature was ranked highest in the fewest number of cases. This study shows that fishing pressure, in addition to the previously established role of climate, influences the spatial distribution of groundfish in the Northwest Atlantic. More broadly, this study is one of a small but growing body of literature to demonstrate that fishing pressure has an effect on the spatial distribution of marine resources. Future work must consider both fishing pressure and climate when examining mechanisms underlying fish distribution shifts.

Relative importance of population size, fishing pressure and temperature on the spatial distribution of nine Northwest Atlantic groundfish stocks

PubMed Central

Alade, Larry A.; Legault, Christopher M.; O’Brien, Loretta; Palmer, Michael C.; Sosebee, Katherine A.; Traver, Michele L.

2018-01-01

The spatial distribution of nine Northwest Atlantic groundfish stocks was documented using spatial indicators based on Northeast Fisheries Science Center spring and fall bottom trawl survey data, 1963–2016. We then evaluated the relative importance of population size, fishing pressure and bottom temperature on spatial distribution with an information theoretic approach. Northward movement in the spring was generally consistent with prior analyses, whereas changes in depth distribution and area occupancy were not. Only two stocks exhibited the same changes in spatiotemporal distribution in the fall as compared with the spring. Fishing pressure was the most important predictor of the center of gravity (i.e., bivariate mean location of the population) for the majority of stocks in the spring, whereas in the fall this was restricted to the east-west component. Fishing pressure was also the most important predictor of the dispersion around the center of gravity in both spring and fall. In contrast, biomass was the most important predictor of area occupancy for the majority of stocks in both seasons. The relative importance of bottom temperature was ranked highest in the fewest number of cases. This study shows that fishing pressure, in addition to the previously established role of climate, influences the spatial distribution of groundfish in the Northwest Atlantic. More broadly, this study is one of a small but growing body of literature to demonstrate that fishing pressure has an effect on the spatial distribution of marine resources. Future work must consider both fishing pressure and climate when examining mechanisms underlying fish distribution shifts. PMID:29698454

Fish and fishery historical data since the 19th century in the Adriatic Sea, Mediterranean

PubMed Central

Fortibuoni, Tomaso; Libralato, Simone; Arneri, Enrico; Giovanardi, Otello; Solidoro, Cosimo; Raicevich, Saša

2017-01-01

Historic data on biodiversity provide the context for present observations and allow studying long-term changes in marine populations. Here we present multiple datasets on fish and fisheries of the Adriatic Sea covering the last two centuries encompassing from qualitative observations to standardised scientific monitoring. The datasets consist of three groups: (1) early naturalists’ descriptions of fish fauna, including information (e.g., presence, perceived abundance, size) on 255 fish species for the period 1818–1936; (2) historical landings from major Northern Adriatic fish markets (Venice, Trieste, Rijeka) for the period 1902–1968, Italian official landings for the Northern and Central Adriatic (1953–2012) and landings from the Lagoon of Venice (1945–2001); (3) trawl-survey data from seven surveys spanning the period 1948–1991 and including Catch per Unit of Effort data (kgh−1 and/or nh−1) for 956 hauls performed at 301 stations. The integration of these datasets has already demonstrated to be useful to analyse historical marine community changes over time, and its availability through open-source data portal will facilitate analyses in the framework of marine historical ecology. PMID:28895949

Behavioural responses to human-induced change: Why fishing should not be ignored.

PubMed

Diaz Pauli, Beatriz; Sih, Andrew

2017-03-01

Change in behaviour is usually the first response to human-induced environmental change and key for determining whether a species adapts to environmental change or becomes maladapted. Thus, understanding the behavioural response to human-induced changes is crucial in the interplay between ecology, evolution, conservation and management. Yet the behavioural response to fishing activities has been largely ignored. We review studies contrasting how fish behaviour affects catch by passive (e.g., long lines, angling) versus active gears (e.g., trawls, seines). We show that fishing not only targets certain behaviours, but it leads to a multitrait response including behavioural, physiological and life-history traits with population, community and ecosystem consequences. Fisheries-driven change (plastic or evolutionary) of fish behaviour and its correlated traits could impact fish populations well beyond their survival per se , affecting predation risk, foraging behaviour, dispersal, parental care, etc., and hence numerous ecological issues including population dynamics and trophic cascades . In particular, we discuss implications of behavioural responses to fishing for fisheries management and population resilience. More research on these topics, however, is needed to draw general conclusions, and we suggest fruitful directions for future studies.

Experimental evidence for modifying the current physical model for ice accretion on aircraft surfaces

NASA Technical Reports Server (NTRS)

Olsen, W.; Walker, E.

1986-01-01

Closeup movies, still photographs, and other experimental data suggest that the current physical model for ice accretion needs significant modification. At aircraft airspeeds there was no flow of liquid over the surface of the ice after a short initial flow, even at barely subfreezing temperatures. Instead, there were very large stationary drops on the ice surface that lose water from their bottoms by freezing and replenish their liquid by catching the microscopic cloud droplets. This observation disagrees with the existing physical model, which assumes there is a thin liquid film continuously flowing over the ice surface. With no such flow, the freezing-fraction concept of the model fails when a mass balance is performed on the surface water. Rime ice does, as the model predicts, form when the air temperature is low enough to cause the cloud droplets to freeze almost immediately on impact. However, the characteristic shapes of horn-glaze ice or rime ice are primarily caused by the ice shape affecting the airflow locally and consequently the droplet catch and the resulting ice shape. Ice roughness greatly increases the heat transfer coefficient, stops the movement of drops along the surface, and may also affect the airflow initially and thereby the droplet catch. At high subreezing temperatures the initial flow and shedding of surface drops have a large effect on the ice shape. At the incipient freezing limit, no ice forms.

77 FR 29586 - Sea Turtle Conservation; Shrimp Trawling Requirements; Correction

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-18

... DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Part 223 RIN 0648-BC10 Sea Turtle Conservation; Shrimp Trawling Requirements; Correction AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce. ACTION...

Status and trends of the Lake Huron deepwater demersal fish ommunity, 2008

USGS Publications Warehouse

Roseman, Edward F.; O'Brien, Timothy P.; Riley, Stephen C.; Farha, Steve A.; French, John R.

2009-01-01

The U.S.Geological Survey Great Lakes Science Center has conducted trawl surveys to assess annual changes in the deepwater demersal fish community of Lake Huron since 1973. Since 1992, surveys have been carried out using a 21 m wing trawl towed on-contour at depths ranging from 9 to 110 m on fixed transects. Sample sites include five ports in U.S. waters with less frequent sampling near Goderich, Ontario. The 2008 fall bottom trawl survey was carried out between October 24 and November 20, 2008 and sampled only the three northern U.S. ports at DeTour, Hammond Bay, and Alpena due to mechanical problems with the research vessel and prolonged periods of bad weather. Therefore, all data presented for 2008 are based on samples collected from these ports. Compared to previous years, alewife populations in Lake Huron remain at low levels after collapsing in 2004. Age-0 alewife density and biomass appears to have increased slightly but overall levels remain near the nadir observed in 2004. Density and biomass of adult and juvenile rainbow smelt showed a decrease from 2007 despite record-high abundance of juveniles observed in 2005, suggesting recruitment was low. Numbers of adult and juvenile bloater were low despite recent high year-classes. Abundances for most other prey species were similar to the low levels observed in 2005 - 2007. We captured one wild juvenile lake trout in 2008 representing the fifth consecutive year that wild lake trout were captured in the survey. Based on pairwise graphical comparisons and nonparametric correlation analyses, dynamics of prey abundance at the three northern ports followed lakewide trends since 1992. Density of benthic macroinvertebrates was at an all-time low in 2008 since sampling began in 2001. The decline in abundance was due to decreases in all taxonomic groups and a large reduction in recruitment of quagga mussels. Density of Diporeia at northern ports in 2008 was the lowest observed. Diporeia were found only at 73-m sites of three ports sampled in northern Lake Huron. While no lakewide estimate of prey biomass was calculated due to the limited spatial scope of the 2008 survey, existing data suggest prey biomass remains depressed. Prey available to salmonids during 2009 will likely be small alewives, small rainbow smelt and small bloaters. Predators in Lake Huron will continue to face potential prey shortages.

Partitioning the contributions of mega-, macro- and meiofauna to benthic metabolism on the upper continental slope of New Zealand: Potential links with environmental factors and trawling intensity

NASA Astrophysics Data System (ADS)

Leduc, Daniel; Pilditch, Conrad A.; Nodder, Scott D.

2016-02-01

Understanding and predicting change in deep-sea benthic ecosystem function remains a major challenge. Here, we conducted analyses combining data on the abundance and biomass of benthic fauna and sediment community oxygen consumption (SCOC) on New Zealand's continental margin to estimate and compare the contributions of meio-, macro-, and megafauna to total benthic metabolism and identify potential links with environmental factors and trawling intensity. We focussed on two regions in close proximity-the high surface primary productivity Chatham Rise and low surface productivity Challenger Plateau. Mean megafauna biomass was twenty times greater on Chatham Rise than Challenger Plateau, likely reflecting differences in food supply between the two regions; this contrast in megafaunal biomass was mainly due to differences in mean body weight rather than abundance. Meio- and macrofauna made similar contributions to SCOC and together accounted for 12% of benthic metabolism on average. In contrast, the estimated contribution of megafauna never exceeded 1.5%. Significant positive correlations between faunal respiration and food availability indicate a link between food supply and benthic community function. Our analyses also show that fauna made a greater contribution to SCOC in conditions of high food availability, and that microorganisms (i.e., the proportion of SCOC not accounted for by the fauna) tended to be more dominant at sites with low food availability. These findings provide support for the concept that large organisms are more strongly affected by a reduction in food resources than small organisms, which in turn underlies one of the most widely described patterns in the deep-sea benthos, i.e., the reduction in organism body size with depth. Because metabolism in deep-sea sediments is typically dominated by microorganisms and small fauna, the absence of a relationship between bottom trawling intensity and the respiration of benthic fauna in the present study may be explained by benthic communities shifting towards smaller body size following physical disturbance. Future studies of deep-sea benthic ecosystem function will need to quantify the indirect influence of fauna on microbial metabolism through activities such as feeding and bioturbation in order to better understand the total contribution of benthic fauna to benthic processes.

50 CFR 660.111 - Trawl fishery-definitions.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Trawl fishery-definitions. 660.111 Section 660.111 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE (CONTINUED) FISHERIES OFF WEST COAST STATES West Coast...

77 FR 37647 - Sea Turtle Conservation; Shrimp Trawling Requirements; Public Hearing Notification

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-22

... DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Part 223 RIN 0648-BC10 Sea Turtle Conservation; Shrimp Trawling Requirements; Public Hearing Notification AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce...

77 FR 38266 - Sea Turtle Conservation; Shrimp Trawling Requirements; Public Hearing

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-27

... DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Part 223 RIN 0648-BC10 Sea Turtle Conservation; Shrimp Trawling Requirements; Public Hearing AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce. ACTION: Proposed...

76 FR 52354 - Notice of Permit Application Received Under the Antarctic Conservation Act of 1978

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-22

... release of a designated pollutant in Antarctica, and for the release of waste in Antarctica. NSF has... volcanic, ice scoured and highly variable in makeup, trawls can be lost if the trawl is snagged on boulders...

78 FR 7371 - Fisheries Off West Coast States; Pacific Coast Groundfish Fishery; Trawl Rationalization Program...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-01

... trawl fishery and associated corollary fisheries of Dungeness crab and pink shrimp off the California... fishing year how much money would be due to NMFS for cost recovery at the end of the year. Under this...

Hydrology and water resources in Caspian Sea

NASA Astrophysics Data System (ADS)

Haddadi Moghaddam, Kourosh

2016-10-01

Precipitation is the main driver of the water balance variability of the water over space and time, and changes in precipitation have very important implications for hydrology and water resources. Variations in precipitation over daily, seasonal, annual, and decadal time scales influence hydrological variability over time in a catchment. Flood frequency is affected by changes in the year-to-year variability in precipitation and by changes in short-term rainfall properties. Desiccation of the Caspian Sea is one of the world's most serious ecosystem catastrophes. The Persian Sturgeon (Acipenser persicus) caught under 10 m depth using bottom trawl net by research vessel during winter 2012, summer and winter 2013 and spring 2014 in east, central and west of southern parts of Caspian Sea, then, their diets were investigated. During 136 trawling in the aimed seasons, Persian sturgeon with 1 to 2 years old and 179.67 × 0.2 g (body weight) and 29.97 ± 0.4 cm (Total length) captured. Examination of stomach contents in the sturgeon specimens revealed that the food spectrum was composed of bony fishes (Neogobius sp., Atherina sp. and Clupeonella delicatula), invertebrates belonging to the family Ampharetidae polychaeta worms including (Hypanai sp. and Nereis diversicolor), various crustaceans (Gammarus sp. and Paramysis sp.). Investigation on stomach contents of sturgeon Acipenser persicus caught under 10 m depth in 2012 to 2013 surveys showed that there is significant difference in the consumed food. The most food diversity have been observed in winter 2013, also Polychaeta is the primary consumed food and crustacean is the secondary one (P > 0.05), no new types of food (such as bony fishes or benthics) have been observed on food chain of Acipenser persicus and shows no significant difference (P > 0.05).

Green sturgeon distribution in the Pacific Ocean estimated from modeled oceanographic features and migration behavior.

PubMed

Huff, David D; Lindley, Steven T; Wells, Brian K; Chai, Fei

2012-01-01

The green sturgeon (Acipenser medirostris), which is found in the eastern Pacific Ocean from Baja California to the Bering Sea, tends to be highly migratory, moving long distances among estuaries, spawning rivers, and distant coastal regions. Factors that determine the oceanic distribution of green sturgeon are unclear, but broad-scale physical conditions interacting with migration behavior may play an important role. We estimated the distribution of green sturgeon by modeling species-environment relationships using oceanographic and migration behavior covariates with maximum entropy modeling (MaxEnt) of species geographic distributions. The primary concentration of green sturgeon was estimated from approximately 41-51.5° N latitude in the coastal waters of Washington, Oregon, and Vancouver Island and in the vicinity of San Francisco and Monterey Bays from 36-37° N latitude. Unsuitably cold water temperatures in the far north and energetic efficiencies associated with prevailing water currents may provide the best explanation for the range-wide marine distribution of green sturgeon. Independent trawl records, fisheries observer records, and tagging studies corroborated our findings. However, our model also delineated patchily distributed habitat south of Monterey Bay, though there are few records of green sturgeon from this region. Green sturgeon are likely influenced by countervailing pressures governing their dispersal. They are behaviorally directed to revisit natal freshwater spawning rivers and persistent overwintering grounds in coastal marine habitats, yet they are likely physiologically bounded by abiotic and biotic environmental features. Impacts of human activities on green sturgeon or their habitat in coastal waters, such as bottom-disturbing trawl fisheries, may be minimized through marine spatial planning that makes use of high-quality species distribution information.

The importance of benchmarking habitat structure and composition for understanding the extent of fishing impacts in soft sediment ecosystems

NASA Astrophysics Data System (ADS)

Handley, Sean J.; Willis, Trevor J.; Cole, Russell G.; Bradley, Anna; Cairney, Daniel J.; Brown, Stephen N.; Carter, Megan E.

2014-02-01

Trawling and dredge fisheries remove vulnerable fauna, homogenise sediments and assemblages, and break down biogenic habitats, but the full extent of these effects can be difficult to quantify in the absence of adequate control sites. Our study utilised rare control sites containing biogenic habitat, the Separation Point exclusion zone, formally protected for 28 years, as the basis for assessing the degree of change experienced by adjacent areas subject to benthic fishing. Sidescan sonar surveys verified that intensive trawling and dredging occurred in areas adjacent to, but not inside, the exclusion area. We compared sediment composition, biogenic cover, macrofaunal assemblages, biomass, and productivity of the benthos, inside and outside the exclusion zone. Disturbed sites were dominated by fine mud, with little or no shell-gravel, reduced number of species, and loss of large bodied animals, with concomitant reductions in biomass and productivity. At protected sites, large, rarer molluscs were more abundant and contributed the most to size-based estimates of productivity and biomass. Functional changes in fished assemblages were consistent with previously reported relative increases in scavengers, predators and deposit feeders at the expense of filter feeders and a grazer. We propose that the colonisation of biogenic species in protected sites was contingent on the presence of shell-gravel atop these soft sediments. The process of sediment homogenisation by bottom fishing and elimination of shell-gravels from surficial sediments appeared to have occurred over decades - a ‘shifting baseline’. Therefore, benchmarking historical sediment structure at control site like the Separation Point exclusion zone is necessary to determine the full extent of physical habitat change wrought by contact gears on sheltered soft sediment habitats to better underpin appropriate conservation, restoration or fisheries management goals.

78 FR 75268 - Fisheries Off West Coast States; Pacific Coast Groundfish Fishery; Trawl Rationalization Program...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-11

... toward environmental conservation and economic sustainability before cost recovery. NMFS should... fleet's flexibility and economic efficiency will enhance the trawl rationalization program's durability... before economic benefits have been adequately realized and while fishermen are struggling to pay...

50 CFR 660.120 - Trawl fishery-crossover provisions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Trawl fishery-crossover provisions. 660.120 Section 660.120 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE (CONTINUED) FISHERIES OFF WEST COAST STATES West Coast...

50 CFR 660.120 - Trawl fishery-crossover provisions.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Trawl fishery-crossover provisions. 660.120 Section 660.120 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE (CONTINUED) FISHERIES OFF WEST COAST STATES West Coast...

50 CFR 679.21 - Prohibited species bycatch management.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Region Web site (http://alaskafisheries.noaa.gov/). (c) Salmon taken in the BS pollock fisheries... GOA groundfish species or species group. (B) Deep-water species fishery. Fishing with trawl gear... combine management of available trawl halibut PSC limits in the second season deep-water and shallow-water...

77 FR 48106 - Sea Turtle Conservation; Shrimp and Summer Flounder Trawling Requirements; Correction

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-13

... DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Part 223 [Docket No. 120427423-2423-02] RIN 0648-AW93 Sea Turtle Conservation; Shrimp and Summer Flounder Trawling Requirements; Correction AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration...

78 FR 9024 - Sea Turtle Conservation; Shrimp Trawling Requirements

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-07

...-BC10 Sea Turtle Conservation; Shrimp Trawling Requirements AGENCY: National Marine Fisheries Service... Environmental Impact Statement (DEIS) to Reduce Incidental Bycatch and Mortality of Sea Turtles in the... DEIS and proposed rule in response to elevated sea turtle strandings in the Northern Gulf of Mexico...

Environmental Drivers of the Canadian Arctic Megabenthic Communities

PubMed Central

Roy, Virginie; Iken, Katrin; Archambault, Philippe

2014-01-01

Environmental gradients and their influence on benthic community structure vary over different spatial scales; yet, few studies in the Arctic have attempted to study the influence of environmental gradients of differing spatial scales on megabenthic communities across continental-scales. The current project studied for the first time how megabenthic community structure is related to several environmental factors over 2000 km of the Canadian Arctic, from the Beaufort Sea to northern Baffin Bay. Faunal trawl samples were collected between 2007 and 2011 at 78 stations from 30 to 1000 m depth and patterns in biomass, density, richness, diversity, and taxonomic composition were examined in relation to indirect/spatial gradients (e.g., depth), direct gradients (e.g., bottom oceanographic variables), and resource gradients (e.g., food supply proxies). Six benthic community types were defined based on their biomass-based taxonomic composition. Their distribution was significantly, but moderately, associated with large-scale (100–1000 km) environmental gradients defined by depth, physical water properties (e.g., bottom salinity), and meso-scale (10–100 km) environmental gradients defined by substrate type (hard vs. soft) and sediment organic carbon content. We did not observe a strong decline of bulk biomass, density and richness with depth or a strong increase of those community characteristics with food supply proxies, contrary to our hypothesis. We discuss how local- to meso-scale environmental conditions, such as bottom current regimes and polynyas, sustain biomass-rich communities at specific locations in oligotrophic and in deep regions of the Canadian Arctic. This study demonstrates the value of considering the scales of variability of environmental gradients when interpreting their relevance in structuring of communities. PMID:25019385

Changes of benthic fauna in the Kattegat - An indication of climate change at mid-latitudes?

NASA Astrophysics Data System (ADS)

Göransson, Peter

2017-07-01

Several predictions point to changes in the marine benthic macrofauna associated with climate change, but so far only a few and minor changes have been reported. This study relates observed changes in the species composition to climate change by looking on the past decades in the Kattegat between Denmark and Sweden. A reduction of the total number species and a reduction of species with a northern range parallel to an increase of species with a southern range have been observed. The most likely explanation of the changes is the increase in temperature of the bottom water. Increased temperature could change the species distributions but also decrease primary production which impacts recruitment and growth. Hypoxia and bottom trawling could also act synergistic in this process. A sparse occurrence of previously encountered Arctic-Boreal species and critical foundation species, which gives the area its special character, suggests a change in biodiversity and might therefore be designated as early warning signals of a warmer climate. The northern fauna below the halocline with limited capacity of dispersal and low reproduction potential, can be considered as sensitive with low adaptive capacity to climate change. Therefore, not only tropical and high-latitude species, but also benthos on deep bottoms at mid-latitudes, could be vulnerable to warming. As many species live at the edge of their range in the Kattegat, and also are dependent of distant recruitment, large scale changes will probably be detected here at an early stage. It is important to protect relatively undisturbed reference areas in the Kattegat for future studies, but also for preserving a large number of ecosystem services, biotopes, habitats, and fish species.

Cascadia Initiative Ocean Bottom Seismograph Performance

NASA Astrophysics Data System (ADS)

Evers, B.; Aderhold, K.

2017-12-01

The Ocean Bottom Seismograph Instrument Pool (OBSIP) provided instrumentation and operations support for the Cascadia Initiative community experiment. This experiment investigated geophysical processes across the Cascadia subduction zone through a combination of onshore and offshore seismic data. The recovery of Year 4 instruments in September 2015 marked the conclusion of a multi-year experiment that utilized 60 ocean-bottom seismographs (OBSs) specifically designed for the subduction zone boundary, including shallow/deep water deployments and active fisheries. The new instruments featured trawl-resistant enclosures designed by Lamont-Doherty Earth Observatory (LDEO) and Scripps Institution of Oceanography (SIO) for shallow deployment [water depth ≤ 500 m], as well as new deep-water instruments designed by Woods Hole Oceanographic Institute (WHOI). Existing OBSIP instruments were also deployed along the Blanco Transform Fault and on the Gorda Plate through complementary experiments. Station instrumentation included weak and strong motion seismometers, differential pressure gauges (DPG) and absolute pressure gauges (APG). All data collected from the Cascadia, Blanco, and Gorda deployments is available through the Incorporated Research Institutions for Seismology (IRIS) Data Management Center (DMC). The Cascadia Initiative is the largest amphibious seismic experiment undertaken to date, encompassing a diverse technical implementation and demonstrating an effective structure for community experiments. Thus, the results from Cascadia serve as both a technical and operational resource for the development of future community experiments, such as might be contemplated as part of the SZ4D Initiative. To guide future efforts, we investigate and summarize the quality of the Cascadia OBS data using basic metrics such as instrument recovery and more advanced metrics such as noise characteristics through power spectral density analysis. We also use this broad and diverse deployment to explore other environmental and configuration factors that can impact sensor and network performance and inform the design of future deployments.

Bio-Physical Coupling of Seabirds and Prey with a Dynamic River Plume

NASA Astrophysics Data System (ADS)

Phillips, E. M.; Horne, J. K.; Zamon, J. E.; Adams, J.

2016-02-01

Freshwater plumes and plume density fronts are important regions of bio-physical coupling. On the west coast of North America, discharge from the Columbia River into the northern California Current creates a large, dynamic plume and multiple plume fronts. These nutrient-rich, productive waters fuel primary and secondary production, supporting a wide variety of small pelagic prey fish, large populations of Pacific salmon, seabirds, and marine mammals. To determine the influence of the Columbia River plume on marine predators, we analyzed at-sea seabird counts, in situ environmental data, surface trawl densities of prey fish, and acoustic backscatter measurements collected from research vessels in May and June 2010-2012. Concurrent distribution patterns of satellite-tagged sooty shearwaters (Puffinus griseus) and common murres (Uria aalge) were compared with seabird counts from ship surveys. To evaluate plume use by satellite-tagged birds, daily surface salinity values from SELFE hindcast models were extracted at each tag location. Both seabird species occurred in plume waters disproportionate to the total surveyed area, concentrating in the river plume when river flow and plume volume decreased. Murres were consistently within 20 km of the geographic mean center of the river plume. In contrast, shearwaters consistently occurred 100 km to the north of the plume center, where high densities of prey fish occur. Although acoustically detected prey also occurred in greater densities within the plume when volume decreased, surface catches of prey in the plume did not vary with changing plume conditions. Geographic indices of colocation (GIC) were low between murres and prey species caught in surface trawls, whereas GICs were >0.5 between shearwaters and prey species including squid (Loligo opalescens), juvenile Chinook salmon (Oncorhynchus tshawytscha), and coho (O. kisutch) salmon. We conclude that the river plume and associated fronts are identifiable, predictable, and persistent physical features that foraging seabirds track to maximize prey encounter rates. Given projected changes in flow regimes related to climate change, our results suggest that seabird use of the river plume may have significant impacts on anadromous salmonid species, which use the plume to migrate to the ocean.

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.

[Distribution and abundance of fish community in the littoral area of "Los Petenes" Biosphere Reserve, Campeche, Mexico].

PubMed

Muñoz-Rojas, Sandra; Ayala-Pérez, Luis Amado; Sosa-López, Atahualpa; Villalobos-Zapata, Guillermo Jorge

2013-03-01

"Los Petenes" Biosphere Reserve (RBLP) is a critical habitat for many aquatic and terrestrial species. It has the biggest and better conserved seagrass beds, and it represents an important habitat for food, protection and breeding of aquatic organisms, and a temporal refuge for migratory species. The objective of this study was to describe the ichthyofauna diversity in the littoral coastal area of the RBLP, to identify the ecological dominant species, and to analyze the abundance of the fish community and its temporal and spatial changes, and their relationship with some environmental variables. Monthly fish samples were obtained with the aid of trawl nets, from 24 samplings sites distributed along the reserve, between May 2009 and April 2010. The trawl net was operated 288 times and 21 795 individuals with 279.5kg of weight were collected. A total of 46 fish species grouped in 34 genera and 23 families were identified. In a spatial scale, the abundance showed the next ranges: 0.018-0.094ind./m2; 0.249-1.072 g/m2 and 9.75-19.32g/ind.; the diversity indexes obtained were: H'n=1.46-2.15, J'=0.45-0.71 and D'=2.08-3.92. In a temporal scale, the abundance and diversity ranged between: 0.026-0.066ind./m2; 0.342-0.764g/m2 and 6.49-22.98g/ind.; H'n=1.76-2.08; J'=0.52-0.64 and D'=3.07-4.18. Eleven dominant species were identified with a representation of the 94.39% in number of individuals, and 89.66% in weight of the total catch. From the total, eight species had economic or commercial importance, especially Lagodon rhomboides and Haemulon plumierii. The cluster analyses identified four fish associations; these results are discussed in order to identify relationships between habitat-species. Finally, the canonical correspondence analysis evidenced an association between H. plumierii with salinity and dissolved solids. The RBLP has high habitat diversity and its fish community has developed strategies to use all the spatial and temporal conditions and to satisfy the needs of their life cycles.

Cooperation between scientists, NGOs and industry in support of sustainable fisheries: the South African hake Merluccius spp. trawl fishery experience.

PubMed

Field, J G; Attwood, C G; Jarre, A; Sink, K; Atkinson, L J; Petersen, S

2013-10-01

This paper examines the increasingly close interaction between natural and social scientists, non-governmental organizations (NGO) and industry, in pursuit of responsible ecosystem-based management of fisheries. South Africa has committed to implementing an ecosystem approach to fisheries management. Management advice stems from multi-stakeholder representation on government-led scientific and management working groups. In the hake Merluccius capensis and Merluccius paradoxus fishery, the primary management measure is an annual total allowable catch (TAC), the level of which is calculated using a management procedure (MP) that is revised approximately every 4 years. Revision of the MP is a consultative process involving most stakeholders, and is based on simulation modelling of projected probable scenarios of resource and fishery dynamics under various management options. NGOs, such as the Worldwide Fund for Nature in South Africa (WWF-SA), have played an important role in influencing consumers, the fishing industry and government to develop responsible fishing practices that minimize damage to marine ecosystems. Cooperation between industry, government and scientists has helped to improve sustainability and facilitated the meeting of market-based incentives for more responsible fisheries. Research includes ecosystem modelling, spatial analysis and ecosystem risk assessment with increasing research focus on social and economic aspects of the fishery. A four-year cooperative experiment to quantify the effect of trawling on benthic community structure is being planned. The food requirements of top predators still need to be included in the TAC-setting formulae and more social and economic research is needed. This paper also demonstrates how NGO initiatives such as Marine Stewardship Council certification and the Southern African Sustainable Seafood Initiative, a traffic light system of classifying seafood for consumers, have contributed to responsible fishing practices, increased ecosystem research and public awareness. This fishery appears to have a good future, provided that the monitoring, control and surveillance systems continue to function, TACs remain within ecologically sustainable limits and the effective collaboration between government, industry, scientists and NGOs continues to drive positive change. © 2013 The Authors. Journal of Fish Biology © 2013 The Fisheries Society of the British Isles.

Effects of wave energy converters on the surrounding soft-bottom macrofauna (west coast of Sweden).

PubMed

Langhamer, O

2010-06-01

Offshore wave energy conversion is expected to develop, thus contributing to an increase in submerged constructions on the seabed. An essential concern related to the deployment of wave energy converters (WECs) is their possible impact on the surrounding soft-bottom habitats. In this study, the macrofaunal assemblages in the seabed around the wave energy converters in the Lysekil research site on the Swedish west coast and a neighbouring reference site were examined yearly during a period of 5 years (2004-2008). Macrobenthic communities living in the WECs' surrounding seabed were mainly composed by organisms typical for the area and depth off the Swedish west coast. At both sites the number of individuals, number of species and biodiversity were low, and were mostly small, juvenile organisms. The species assemblages during the first years of sampling were significantly different between the Lysekil research site and the nearby reference site with higher species abundance in the research site. The high contribution to dissimilarities was mostly due to polychaetes. Sparse macrofaunal densities can be explained by strong hydrodynamic forces and/or earlier trawling. WECs may alter the surrounding seabed with an accumulation of organic matter inside the research area. This indicates that the deployment of WECs in the Lysekil research site tends to have rather minor direct ecological impacts on the surrounding benthic community relative to the natural high variances.

Gear and seasonal bias associated with abundance and size structure estimates for lentic freshwater fishes

USGS Publications Warehouse

Fischer, Jesse R.; Quist, Michael C.

2014-01-01

All freshwater fish sampling methods are biased toward particular species, sizes, and sexes and are further influenced by season, habitat, and fish behavior changes over time. However, little is known about gear-specific biases for many common fish species because few multiple-gear comparison studies exist that have incorporated seasonal dynamics. We sampled six lakes and impoundments representing a diversity of trophic and physical conditions in Iowa, USA, using multiple gear types (i.e., standard modified fyke net, mini-modified fyke net, sinking experimental gill net, bag seine, benthic trawl, boat-mounted electrofisher used diurnally and nocturnally) to determine the influence of sampling methodology and season on fisheries assessments. Specifically, we describe the influence of season on catch per unit effort, proportional size distribution, and the number of samples required to obtain 125 stock-length individuals for 12 species of recreational and ecological importance. Mean catch per unit effort generally peaked in the spring and fall as a result of increased sampling effectiveness in shallow areas and seasonal changes in habitat use (e.g., movement offshore during summer). Mean proportional size distribution decreased from spring to fall for white bass Morone chrysops, largemouth bass Micropterus salmoides, bluegill Lepomis macrochirus, and black crappie Pomoxis nigromaculatus, suggesting selectivity for large and presumably sexually mature individuals in the spring and summer. Overall, the mean number of samples required to sample 125 stock-length individuals was minimized in the fall with sinking experimental gill nets, a boat-mounted electrofisher used at night, and standard modified nets for 11 of the 12 species evaluated. Our results provide fisheries scientists with relative comparisons between several recommended standard sampling methods and illustrate the effects of seasonal variation on estimates of population indices that will be critical to the future development of standardized sampling methods for freshwater fish in lentic ecosystems.

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.

30 CFR 250.1740 - How must I verify that the site of a permanently plugged well, removed platform, or other removed...

Code of Federal Regulations, 2010 CFR

2010-07-01

...: (1) Drag a trawl over the site; (2) Scan across the location using sonar equipment; (3) Inspect the...) Drag a trawl over the site; (2) Scan across the site using sonar equipment; or (3) Use another method...

30 CFR 250.1740 - How must I verify that the site of a permanently plugged well, removed platform, or other removed...

Code of Federal Regulations, 2011 CFR

2011-07-01

..., you must either: (1) Drag a trawl over the site; (2) Scan across the location using sonar equipment..., you must either: (1) Drag a trawl over the site; (2) Scan across the site using sonar equipment; or (3...

30 CFR 250.1740 - How must I verify that the site of a permanently plugged well, removed platform, or other removed...

Code of Federal Regulations, 2013 CFR

2013-07-01

..., you must either: (1) Drag a trawl over the site; (2) Scan across the location using sonar equipment..., you must either: (1) Drag a trawl over the site; (2) Scan across the site using sonar equipment; or (3...

30 CFR 250.1740 - How must I verify that the site of a permanently plugged well, removed platform, or other removed...

Code of Federal Regulations, 2014 CFR

2014-07-01

..., you must either: (1) Drag a trawl over the site; (2) Scan across the location using sonar equipment..., you must either: (1) Drag a trawl over the site; (2) Scan across the site using sonar equipment; or (3...

30 CFR 250.1740 - How must I verify that the site of a permanently plugged well, removed platform, or other removed...

Code of Federal Regulations, 2012 CFR

2012-07-01

..., you must either: (1) Drag a trawl over the site; (2) Scan across the location using sonar equipment..., you must either: (1) Drag a trawl over the site; (2) Scan across the site using sonar equipment; or (3...

77 FR 27411 - Sea Turtle Conservation; Shrimp Trawling Requirements

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-10

.... 120328230-1019-01] RIN 0648-BC10 Sea Turtle Conservation; Shrimp Trawling Requirements AGENCY: National... proposed rule is to reduce incidental bycatch and mortality of sea turtles in the southeastern U.S. shrimp fisheries, and to aid in the protection and recovery of listed sea turtle populations. DATES: Written...

50 CFR Figure 12 to Part 679 - Bristol Bay Trawl Closure Area

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Bristol Bay Trawl Closure Area 12 Figure 12 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE (CONTINUED) FISHERIES OF THE EXCLUSIVE ECONOMIC ZONE OFF...

50 CFR Figure 1 to Part 660... - Diagram of Selective Flatfish Trawl

Code of Federal Regulations, 2014 CFR

2014-10-01

... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Diagram of Selective Flatfish Trawl 1 Figure 1 to Part 660, Subpart D Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE (CONTINUED) FISHERIES OFF WEST COAST STATES...

50 CFR 648.90 - NE multispecies assessment, framework procedures and specifications, and flexible area action...

Code of Federal Regulations, 2010 CFR

2010-10-01

...; survey results; stock status; current estimates of fishing mortality and overfishing levels; social and...; sea sampling and trawl survey data or, if sea sampling data are unavailable, length frequency information from trawl surveys; impact of other fisheries on herring mortality; and any other relevant...

50 CFR 679.80 - Allocation and transfer of rockfish QS.

Code of Federal Regulations, 2014 CFR

2014-10-01

... from which that LLP license was derived during the calendar years 2000 and 2001, unless clear and...) Determine the Total Entry Level Trawl Fishery Transition Rockfish QS pool for each rockfish primary species... Rockfish QS pools. (v) Multiply the Percentage of the Total Entry Level Trawl Fishery Transition Rockfish...

50 CFR 679.80 - Allocation and transfer of rockfish QS.

Code of Federal Regulations, 2013 CFR

2013-10-01

... from which that LLP license was derived during the calendar years 2000 and 2001, unless clear and...) Determine the Total Entry Level Trawl Fishery Transition Rockfish QS pool for each rockfish primary species... Rockfish QS pools. (v) Multiply the Percentage of the Total Entry Level Trawl Fishery Transition Rockfish...

50 CFR 679.80 - Allocation and transfer of rockfish QS.

Code of Federal Regulations, 2012 CFR

2012-10-01

... from which that LLP license was derived during the calendar years 2000 and 2001, unless clear and...) Determine the Total Entry Level Trawl Fishery Transition Rockfish QS pool for each rockfish primary species... Rockfish QS pools. (v) Multiply the Percentage of the Total Entry Level Trawl Fishery Transition Rockfish...

50 CFR 622.25 - Exemptions for Gulf groundfish trawling.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 50 Wildlife and Fisheries 12 2014-10-01 2014-10-01 false Exemptions for Gulf groundfish trawling. 622.25 Section 622.25 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... which is ground up for animal feed or industrial products. (a) Other provisions of this part...

Job Satisfaction in the Shrimp Trawl Fisheries of Chennai, India

ERIC Educational Resources Information Center

Bavinck, Maarten

2012-01-01

Shrimp trawling represents an important fishing metier in South India, generating high levels of employment and economic value. It is also a contested metier, ostensibly contributing to environmental degradation and social inequality. This paper investigates the job satisfaction of crew members (captains and workers) on board the shrimp trawlers…

Neural bases of enhanced attentional control: Lessons from action video game players.

PubMed

Föcker, Julia; Cole, Daniel; Beer, Anton L; Bavelier, Daphne

2018-06-19

The ability to resist distraction and focus on-task-relevant information while being responsive to changes in the environment is fundamental to goal-directed behavior. Such attentional control abilities are regulated by a constant interplay between previously characterized bottom-up and top-down attentional networks. Here we ask about the neural changes within these two attentional networks that may mediate enhanced attentional control. To address this question, we contrasted action video game players (AVGPs) and nonvideo game players (NVGPs) in a Posner-cueing paradigm, building on studies documenting enhanced attentional control in AVGPs. Behavioral results indicated a trend for more efficient target processing in AVGPs, and better suppression in rare catch trials for which responses had to be withheld. During the cue period, AVGPs recruited the top-down network less than NVGPs, despite showing comparable validity effects, in line with a greater efficiency of that network in AVGPs. During target processing, as previously shown, recruitment of top-down areas correlated with greater processing difficulties, but only in NVGPs. AVGPs showed no such effect, but rather greater activation across the two networks. In particular, the right temporoparietal junction, middle frontal gyrus, and superior parietal cortex predicted better task performance in catch trials. A functional connectivity analysis revealed enhanced correlated activity in AVGPs compared to NVGPs between parietal and visual areas. These results point to dynamic functional reconfigurations of top-down and bottom-up attentional networks in AVGPs as attentional demands vary. Aspects of this functional reconfiguration that may act as key signatures of high attentional control are discussed. © 2018 The Authors. Brain and Behavior published by Wiley Periodicals, Inc.

78 FR 68764 - Fisheries Off West Coast States; Pacific Coast Groundfish Fishery Management Plan; Commercial...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-15

... (coop) programs for the at-sea mothership and catcher/processor trawl fleets (whiting only). Since that... permit holder (vessel owner) to change their vessel ownership, 9. Clarify that the processor obligation..., Mothership Coop (MS) Program--Whiting At-sea Trawl Fishery, and Catcher-Processor (C/P) Coop Program--Whiting...

75 FR 73979 - Fisheries of the Northeastern United States; Discard Provision for Herring Midwater Trawl Vessels...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-30

.... The publication of this action is part of a Court-approved joint motion to stay pending litigation...), National Oceanic and Atmospheric Administration (NOAA), Commerce. ACTION: Final rule. SUMMARY: Through this action, NMFS removes a regulatory exemption for midwater trawl herring vessels, which was originally...

76 FR 50449 - Fisheries off West Coast States; Pacific Coast Groundfish Fishery Management Plan; Trawl...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-15

... decision making did not clearly state that Amendment 21 allocations supersede the previous limited entry... 21 supersedes the limited entry/open access allocations for groundfish species allocated through... the limited entry trawl fishery. DATES: Comments on Amendment 21-1 must be received no later than 5 p...

78 FR 13161 - Fisheries of the Exclusive Economic Zone Off Alaska; Gulf of Alaska; Final 2013 and 2014 Harvest...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-26

... halibut PSC trawl limits between the trawl gear deep-water and the shallow-water species fishery... for pollock, sablefish, deep-water flatfish, rex sole, Pacific ocean perch, northern rockfish... less than the ABCs for Pacific cod, shallow-water flatfish, arrowtooth flounder, flathead sole, ``other...

76 FR 65973 - Fisheries of the Exclusive Economic Zone Off Alaska; Reallocation of Crab Prohibited Species...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-25

... Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce. ACTION... Sector and Non-Trawl Fisheries Prohibited species and area \\1\\ Red king C. bairdi (animals) BSAI trawl limited access fisheries Halibut mortality crab C. opilio (mt) BSAI (animals) (animals) Zone 1 COBLZ Zone...

Conservation and management of seahorses and other Syngnathidae.

PubMed

Vincent, A C J; Foster, S J; Koldewey, H J

2011-06-01

This article analyses the pressures on seahorses and explores conservation responses. It focuses on seahorses (Hippocampus spp.) but also considers pipefishes and seadragons, especially where they can fill gaps in seahorse knowledge. The charisma of many syngnathids can make them good flagship species for threats and solutions in marine conservation. The article combines a synthesis of published literature with new data on the trade in seahorses for traditional medicine, aquarium display and curiosities. Most traded seahorses come from trawl by-catch, although seahorses are also targeted. The total extraction is large, tens of millions of animals annually, and unsustainable. A first review of the effect of habitat change on syngnathids raises many questions, while suggesting that some species may cope better than others. The combination of pressures means that many species of syngnathid are now included in the IUCN Red List of Threatened Species or national equivalents. In addition, seahorse exports from 175 countries are limited to sustainable levels under the Convention on International Trade in Endangered Species (CITES) of Wild Fauna and Flora. Possible conservation measures include marine protected areas, fisheries management, select aquaculture ventures, trade regulation, improved governance (particularly) and consumer engagement. © 2011 The Authors. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles.

Seabird, fish, marine mammal, and oceanography coordinated investigations (SMMOCI) in Sitka Sound, Alaska, July 2000

USGS Publications Warehouse

Piatt, John F.; Dragoo, Donald E.

2005-01-01

Surveys for seabirds and marine mammals were conducted in and near Sitka Sound, Alaska (Fig. 1) from the M/V Tiĝlax̂ during 12-16 July 2000 (Table 1, Fig. 1). The objective was to characterize the marine environment in the vicinity of St. Lazaria Island, one of ten seabird colonies monitored annually by the Alaska Maritime National Wildlife Refuge (See Dragoo et al. 2003). In addition to censusing seabirds and mammals encountered on line transects, local oceanography was characterized by measuring water temperature and salinity continuously at the sea surface, and by taking profiles of the water column on a series of CTD transects. The relative abundance of zooplankton and fish biomass was measured using a dual -frequency echosounder. Significant acoustic targets were sampled with a m id-water trawl net. Long-lines were se t twice to catch and characterize diets of large demersal fish species.Rosenthal et al. (1981 and 1982) studied the bottomfish component of the nearshore habitats in southeastern Alaska including the Sitka Sound area during the summers of 1980 and 1981, allowing comparisons of our findings to those from the earlier works. There are no previous surveys for seabirds or marine mammals in this area with which we can compare our surveys.

Application of the Oxidation-Reduction Potential (ORP) for Pre-grading Tuna Freshness On-board

NASA Astrophysics Data System (ADS)

Cheevaporanapivat, Mongkol; Sakai, Hisaharu; Mine, Yuuji; Watanabe, Manabu; Suzuki, Toru

Application of ORP as a rapid indicator for grading tuna's freshness on the ship was studied. The long line trawling process was used for catching the sample tuna in the South Pacific Ocean. All captured sample tuna were weighed, gender identified and investigated for their mortality, then measured ORP and K value. Three species of tuna were caught: blue marlin (Makaira mazara), yellow fin tuna (Thunnus albacares), and swordfish (Xiphia gladius). Most of the fish captured were male and they had been dead after picking onboard. The measured ORP values of blue marlin varied in the range of 0.295-0.362 Volt, with pH between 5.35-5.84. Both ORP and pH of swordfish was similar to that of blue marlin. But for yellow fin tuna, the ORP value was about the same as blue marlin while its pH was significantly higher. ORP value in all species tended to increase with pH of the fish meat decrease. It is interesting that ORP value of tuna increased in correlation with K value. These results suggested that ORP and pH change, which are measured in the short time, are the effective indicators for grading tuna's freshness on-board.

Juvenile groundfish habitat in Kachemak Bay, Alaska, during late summer

USGS Publications Warehouse

Abookire, Alisa A.; Piatt, John F.; Norcross, Brenda L.

2001-01-01

We investigated the habitat of juvenile groundfishes in relation to depth, water temperature, and salinity in Kachemak Bay, Alaska. Stations ranging in depth from 10 to 70 m and with sand or mud-sand substrates were sampled with a small-meshed beam trawl in August-September of 1994 to 1999. A total of 8,201 fishes were captured, comprising at least 52 species. Most fishes (91%) had a total length 5% of the total catch) were flathead sole Hippoglossoides elassodon, slim sculpin Radulinus asprellus, Pacific halibut Hippoglossus stenolepis, and arrowtooth flounder Atheresthes stomias. Depth accounted for most of the spatial variability in juvenile groundfish abundance, and neither temperature nor salinity was correlated with fish abundance. Juvenile groundfishes concentrated in either shallow (less than or equal to 20 m) or deep (50-70 m) water, with co-occurrence of some species between 30-40 m. Shallow fishes were the rock soles, Pacific halibut, and great sculpin Myoxocephalus polyacanthocephalus. Deep species were flathead sole, slim sculpin, spinycheek starsnout Bathyagonus infraspinatus, rex sole Glyptocephalus zachirus, tadpole sculpin Psychrolutes paradoxus, and whitebarred prickleback Poroclinus rothrocki. This 6-year study provides baseline data on relative abundance and distribution of juvenile groundfishes in Kachemak Bay and may provide a useful tool for predicting the presence of species in similar habitats in other areas of Alaska.

Abundances of Demersal Sharks and Chimaera from 1994-2009 Scientific Surveys in the Central Mediterranean Sea

PubMed Central

Ragonese, Sergio; Vitale, Sergio; Dimech, Mark; Mazzola, Salvatore

2013-01-01

Bibliographic and data gathered in scientific bottom trawl surveys carried out off the Southern Coasts of Sicily (Mediterranean Sea), from 1994 to 2009 and between a depth of 10 and 800 m, were analysed in order to prepare a checklist of demersal sharks and chimaera, which are species sensitive to fisheries exploitation. Out of the 27 previously reported demersal shark and chimaera taxa in the Mediterranean, only 23 were found in literature and 20 sampled during the surveys in the investigated area. Among the species sampled in the surveys, only 2 ubiquitous ( Squalus blainville and Scyliorhinus canicula ) and 3 deep-water ( Chimaera monstrosa , Centrophorus granulosus and Galeus melastomus ) species showed a wide geographical distribution with a consistent abundance. Excluding the rare (such as Oxynotus centrina ) or uncommon shark (e.g. Squalus acanthias ), the estimated frequencies of occurrence and abundance indexes show a possible risk of local extinction for the almost exclusively (e.g. angelshark, Squatina spp.) or preferential (e.g. Scyliorhinus stellaris ) neritic species. PMID:24086386

Abundances of demersal sharks and chimaera from 1994-2009 scientific surveys in the central Mediterranean Sea.

PubMed

Ragonese, Sergio; Vitale, Sergio; Dimech, Mark; Mazzola, Salvatore

2013-01-01

Bibliographic and data gathered in scientific bottom trawl surveys carried out off the Southern Coasts of Sicily (Mediterranean Sea), from 1994 to 2009 and between a depth of 10 and 800 m, were analysed in order to prepare a checklist of demersal sharks and chimaera, which are species sensitive to fisheries exploitation. Out of the 27 previously reported demersal shark and chimaera taxa in the Mediterranean, only 23 were found in literature and 20 sampled during the surveys in the investigated area. Among the species sampled in the surveys, only 2 ubiquitous (Squalusblainville and Scyliorhinuscanicula) and 3 deep-water (Chimaeramonstrosa , Centrophorusgranulosus and Galeusmelastomus) species showed a wide geographical distribution with a consistent abundance. Excluding the rare (such as Oxynotuscentrina) or uncommon shark (e.g. Squalusacanthias), the estimated frequencies of occurrence and abundance indexes show a possible risk of local extinction for the almost exclusively (e.g. angelshark, Squatina spp.) or preferential (e.g. Scyliorhinusstellaris) neritic species.

Marine debris and human impacts on sea turtles in southern Brazil.

PubMed

Bugoni, L; Krause, L; Petry, M V

2001-12-01

Dead stranded sea turtles were recovered and examined to determine the impact of anthropogenic debris and fishery activities on sea turtles on the coast of Rio Grande do Sul State, Brazil. Esophagus/stomach contents of 38 juvenile green Chelonia mydas, 10 adults and sub-adults loggerhead Caretta caretta, and two leatherback Dermochelys coriacea turtles (adult or sub-adult) included plastic bags as the main debris ingested, predominated by white and colorless pieces. The ingestion of anthropogenic debris accounted for the death of 13.2% of the green turtles examined. Signs of damage over the body and carapace indicated that fishing activities caused the death of 13.6% (3/22) of loggerheads and 1.5% (1/56) of green turtles. Therefore, it appears that direct and indirect effects of fishing activities may pose a threat to these species in Brazilian waters. Other sources of plastic debris should be investigated as well as the direct impact of fisheries, especially bottom trawl and gill nets, in order to establish effective conservation action.

Distribution and abundance of anthropogenic marine debris along the shelf and slope of the US West Coast.

PubMed

Keller, Aimee A; Fruh, Erica L; Johnson, Melanie M; Simon, Victor; McGourty, Catherine

2010-05-01

As marine debris levels continue to grow worldwide, defining sources, composition, and distribution of debris, as well as potential effects, becomes increasingly important. We investigated composition and abundance of man-made, benthic marine debris at 1347 randomly selected stations along the US West Coast during Groundfish Bottom Trawl Surveys in 2007 and 2008. Anthropogenic debris was observed in 469 tows at depths of 55-1280 m. Plastic and metallic debris occurred in the greatest number of hauls followed by fabric and glass. Mean density was 67.1 items km(-2) throughout the study area but was significantly higher south of 36 degrees 00'N latitude. Mean density significantly increased with depth, ranging from 30 items km(-2) in shallow (55-183 m) water to 128 items km(-2) in the deepest depth stratum (550-1280 m). Debris densities observed along the US West Coast were comparable to those seen elsewhere and provide a valuable backdrop for future comparisons. (c) 2010 Elsevier Ltd. All rights reserved.

Comparison of live and dead molluscan assemblages suggests recent human-driven decline in benthic diversity in Phetchaburi (NW Gulf of Thailand)

NASA Astrophysics Data System (ADS)

Negri, Mauro Pietro; Sanfilippo, Rossana; Basso, Daniela; Rosso, Antonietta

2015-12-01

Dead and live molluscan assemblages from the coastal area of Phetchaburi (NW Gulf of Thailand) were compared by means of multivariate analysis. Seven thanatofacies were recognized, thriving in the area after the 1960s. Five of them, scattered along the tidal flat, represent oligotypic intertidal biotopes linked to a variety of environmental factors; the remaining two mirror high-diversity infralittoral associations. Conversely, only two poor, ill-defined biofacies thrive at present between the intertidal and the shallow infralittoral zones, somewhat resembling two of the thanatofacies. Diversity indexes reveal a dramatic biodiversity decline occurred from the 1960s onwards, far beyond the effects of time-averaging and accumulation. The responsibility for this reduction is largely attributable to the high impact of human activities, such as the intensive sea bottom trawling, the wastewaters from aquaculture (shrimp and fish ponds) and dense coastal villages, and, at a minor extent, the digging of edible molluscs from the tidal flat.

50 CFR 648.203 - Gear restrictions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Gear restrictions. 648.203 Section 648.203... Herring Fishery § 648.203 Gear restrictions. (a) Midwater trawl gear may only be used by a vessel issued a... Lightship Area as described in § 648.81(c)(1), provided it complies with the midwater trawl gear exemption...

76 FR 39789 - Fisheries of the Exclusive Economic Zone Off Alaska; Northern Rockfish and Pelagic Shelf Rockfish...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-07

.... 101126522-0640-02] RIN 0648-XA546 Fisheries of the Exclusive Economic Zone Off Alaska; Northern Rockfish and Pelagic Shelf Rockfish for Trawl Catcher Vessels Participating in the Entry Level Rockfish Fishery in the...) for trawl catcher vessels participating in the entry level rockfish fishery in the Central Regulatory...

75 FR 38936 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch for Catcher Vessels...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-07

.... 0910131362-0087-02] RIN 0648-XX35 Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch for Catcher Vessels Participating in the Rockfish Entry Level Trawl Fishery in the Central Regulatory... directed fishing for Pacific ocean perch by trawl catcher vessels participating in the rockfish entry level...

76 FR 39790 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch for Catcher Vessels...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-07

.... 101126522-0640-02] RIN 0648-XA543 Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch for Catcher Vessels Participating in the Rockfish Entry Level Trawl Fishery in the Central Regulatory... directed fishing for Pacific ocean perch by trawl catcher vessels participating in the rockfish entry level...

Job Satisfaction in the Shrimp Trawl Fisheries of Vietnam

ERIC Educational Resources Information Center

Sinh, Le Xuan

2012-01-01

This paper investigates the job satisfaction of small-scale shrimp trawl fishers in the vicinity of Camau National Park in southern Vietnam. The research sample consisted of 77 fishers who belong to a growing population of shrimp fishers in the region. The results suggest that 60% would change their fishing metier, 78% would leave fishing for…