Science.gov

Sample records for cretaceous shark ptychodus

  1. A Gigantic Shark from the Lower Cretaceous Duck Creek Formation of Texas

    PubMed Central

    Frederickson, Joseph A.; Schaefer, Scott N.; Doucette-Frederickson, Janessa A.

    2015-01-01

    Three large lamniform shark vertebrae are described from the Lower Cretaceous of Texas. We interpret these fossils as belonging to a single individual with a calculated total body length of 6.3 m. This large individual compares favorably to another shark specimen from the roughly contemporaneous Kiowa Shale of Kansas. Neither specimen was recovered with associated teeth, making confident identification of the species impossible. However, both formations share a similar shark fauna, with Leptostyrax macrorhiza being the largest of the common lamniform sharks. Regardless of its actual identification, this new specimen provides further evidence that large-bodied lamniform sharks had evolved prior to the Late Cretaceous. PMID:26039066

  2. Lamniform Shark Teeth from the Late Cretaceous of Southernmost South America (Santa Cruz Province, Argentina)

    PubMed Central

    Schroeter, Elena R.; Egerton, Victoria M.; Ibiricu, Lucio M.; Lacovara, Kenneth J.

    2014-01-01

    Here we report multiple lamniform shark teeth recovered from fluvial sediments in the (Campanian-Maastrichtian) Cerro Fortaleza Formation, Santa Cruz Province, Argentina. This small tooth assemblage is compared to various lamniform sharks possessing similar dental morphologies, including Archaeolamna, Cretalamna, Dwardius, Dallasiella, and Cretodus. Although the teeth share numerous morphological features with the genus Archaeolamna, including a developed neck that maintains a relatively consistent width along the base of the crown, the small sample size and incomplete nature of these specimens precludes definitive taxonomic assignment. Regardless, the discovery of selachian teeth unique from those previously described for the region broadens the known diversity of Late Cretaceous South American sharks. Additionally, the discovery of the teeth in fluvial sandstone may indicate a euryhaline paleobiology in the lamniform taxon or taxa represented by this tooth assemblage. PMID:25141301

  3. Shark

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This false color composite image from the Pathfinder lander shows the rock 'Shark' at upper right (Shark is about 0.69 m wide, 0.40 m high, and 6.4 m from the lander). The rock looks like a conglomerate in Sojourner rover images, but only the large elements of its surface textures can be seen here. This demonstrates the usefulness of having a robot rover geologist able to examine rocks up close.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

  4. Denticle-embedded ampullary organs in a Cretaceous shark provide unique insight into the evolution of elasmobranch electroreceptors.

    PubMed

    Vullo, Romain; Guinot, Guillaume

    2015-10-01

    Here, we report a novel type of dermal denticle (or placoid scale), unknown among both living and fossil chondrichthyan fishes, in a Cretaceous lamniform shark. By their morphology and location, these dermal denticles, grouped into clusters in the cephalic region, appear to have been directly associated with the electrosensory ampullary system. These denticles have a relatively enlarged (∼350 μm in diameter), ornamented crown with a small (∼100 μm) asterisk- or cross-shaped central perforation connected to a multi-alveolate internal cavity. The formation of such a complex structure can be explained by the annular coalescence and fusion, around an ampullary vesicle, of several developmental units still at papillary stage (i.e. before mineralization), leading to a single denticle embedding an alveolar ampulla devoid of canal. This differs from larger typical ampullae of Lorenzini with a well-developed canal opening in a pore of the skin and may represent another adaptive response to low skin resistance. Since it has been recently demonstrated that ampullary organs arise from lateral line placodes in chondrichthyans, this highly specialized type of dermal denticle (most likely non-deciduous) may be derived from the modified placoid scales covering the superficial neuromasts (pit organs) of the mechanosensory lateral line system of many modern sharks.

  5. Denticle-embedded ampullary organs in a Cretaceous shark provide unique insight into the evolution of elasmobranch electroreceptors

    NASA Astrophysics Data System (ADS)

    Vullo, Romain; Guinot, Guillaume

    2015-10-01

    Here, we report a novel type of dermal denticle (or placoid scale), unknown among both living and fossil chondrichthyan fishes, in a Cretaceous lamniform shark. By their morphology and location, these dermal denticles, grouped into clusters in the cephalic region, appear to have been directly associated with the electrosensory ampullary system. These denticles have a relatively enlarged (˜350 μm in diameter), ornamented crown with a small (˜100 μm) asterisk- or cross-shaped central perforation connected to a multi-alveolate internal cavity. The formation of such a complex structure can be explained by the annular coalescence and fusion, around an ampullary vesicle, of several developmental units still at papillary stage (i.e. before mineralization), leading to a single denticle embedding an alveolar ampulla devoid of canal. This differs from larger typical ampullae of Lorenzini with a well-developed canal opening in a pore of the skin and may represent another adaptive response to low skin resistance. Since it has been recently demonstrated that ampullary organs arise from lateral line placodes in chondrichthyans, this highly specialized type of dermal denticle (most likely non-deciduous) may be derived from the modified placoid scales covering the superficial neuromasts (pit organs) of the mechanosensory lateral line system of many modern sharks.

  6. Sharks that pass in the night: using Geographical Information Systems to investigate competition in the Cretaceous Western Interior Seaway

    PubMed Central

    Myers, Corinne E.; Lieberman, Bruce S.

    2011-01-01

    One way the effects of both ecology and environment on species can be observed in the fossil record is as changes in geographical distribution and range size. The prevalence of competitive interactions and species replacements in the fossil record has long been investigated and many evolutionary perspectives, including those of Darwin, have emphasized the importance of competitive interactions that ultimately lead one species to replace another. However, evidence for such phenomena in the fossil record is not always manifest. Here we use new quantitative analytical techniques based on Geographical Information Systems and PaleoGIS tectonic reconstructions to consider this issue in greater detail. The abundant, well-preserved fossil marine vertebrates of the Late Cretaceous Western Interior Seaway of North America provide the component data for this study. Statistical analysis of distributional and range size changes in taxa confirms earlier ideas that the relative frequency of competitive replacement in the fossil record is limited to non-existent. It appears that typically, environmental gradients played the primary role in determining species distributions, with competitive interactions playing a more minor role. PMID:20843852

  7. Sharks senses and shark repellents.

    PubMed

    Hart, Nathan S; Collin, Shaun P

    2015-01-01

    Despite over 70 years of research on shark repellents, few practical and reliable solutions to prevent shark attacks on humans or reduce shark bycatch and depredation in commercial fisheries have been developed. In large part, this deficiency stems from a lack of fundamental knowledge of the sensory cues that drive predatory behavior in sharks. However, the widespread use of shark repellents is also hampered by the physical constraints and technical or logistical difficulties of deploying substances or devices in an open-water marine environment to prevent an unpredictable interaction with a complex animal. Here, we summarize the key attributes of the various sensory systems of sharks and highlight residual knowledge gaps that are relevant to the development of effective shark repellents. We also review the most recent advances in shark repellent technology within the broader historical context of research on shark repellents and shark sensory systems. We conclude with suggestions for future research that may enhance the efficacy of shark repellent devices, in particular, the continued need for basic research on shark sensory biology and the use of a multi-sensory approach when developing or deploying shark repellent technology.

  8. Shark scales

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Close examination of the skin of a fast-swimming shark appears to confirm Langley's aerodynamically efficient Riblet concept. This view magnified 30 times, reveals that projections on the shark skin -dermal denticles- line up to form grooves similar to those that have reduced drag in wind tunnels. L83-9167: Mother Nature's riblet, this shark's dermal denticle has been magnified 3,000 times. Photograph published in Winds of Change, 75th Anniversary NASA publication (page 123), by James Schultz.

  9. Shark Detectives

    ERIC Educational Resources Information Center

    Hitt, Dia

    2005-01-01

    Oceans are often considered mysterious, fascinating places filled with unique and scary animals. One of the most misunderstood and therefore scariest animals is the shark, yet the whale shark, the world's largest fish, is considered harmless to humans. This student-directed activity involves research, deductive reasoning, and students' own…

  10. Petrographic Evidence of Microbial Mats in the Upper Cretaceous Fish-Bearing, Organic-Rich Limestone, Agua Nueva Formation, Central Mexico

    NASA Astrophysics Data System (ADS)

    Blanco, A.; Maurrasse, F. J.; Hernández-Ávila, J.; Ángeles-Trigueros, S. A.; García-Cabrera, M. E.

    2013-05-01

    We document petrographic evidence of microbial mats in the Upper Cretaceous Agua Nueva Formation in the area of Xilitla (San Luis Potosí, Central Mexico), located in the southern part of the Tampico-Misantla basin. The sequence consists predominantly of alternating decimeter-thick beds of fossiliferous dark laminated limestone (C-org > 1.0wt%), and light gray, bioturbated limestone (C-org < 1.0wt%), with occasional brown shale and green bentonite layers. Well-preserved fossil-fish assemblages occur in the laminated dark limestone beds, which include shark teeth (cf. Ptychodus), scales of teleosteans (Ichthyodectiformes), as well as skeletal remains of holosteans (Nursallia. sp), and teleosteans (cf. Rhynchodercetis, Tselfatia, and unidentified Enchodontids). Thin section and SEM analyses of the laminated, dark limestones, reveal a micritic matrix consisting of dark and light sub-parallel wavy laminae, continuous and discontinuous folded laminae with shreds of organic matter, filaments, oncoids, and interlocking structures. The structures are identical to those previously described for the Cenomanian-Turonian Indidura Fm at Parras de la Fuente (Coahuila state) demonstrated to be of microbial origin (Duque-Botero and Maurrasse, 2005; 2008). These structures are also analogous to microbial mats in present environments, and Devonian deposits (Kremer, 2006). In addition, the laminae at Xilitla include filamentous bacterial structures, as thin and segmented red elements. In some thin sections, filaments appear to be embedded within the crinkly laminae and shreds showing the same pattern of folding, suggestive of biomorphic elements that represent the main producers of the organic matter associated with the laminae. Thus, exceptional bacterial activity characterizes sedimentation during the accumulation of the Agua Nueva Formation. Oxygen-deficient conditions related to the microbial mats were an important element in the mass mortality and preservation of the fish

  11. Shark Tagging Activities.

    ERIC Educational Resources Information Center

    Current: The Journal of Marine Education, 1998

    1998-01-01

    In this group activity, children learn about the purpose of tagging and how scientists tag a shark. Using a cut-out of a shark, students identify, measure, record data, read coordinates, and tag a shark. Includes introductory information about the purpose of tagging and the procedure, a data sheet showing original tagging data from Tampa Bay, and…

  12. Fish remains (Elasmobranchii, Actinopterygii) from the Late Cretaceous of the Benue Trough, Nigeria

    NASA Astrophysics Data System (ADS)

    Vullo, Romain; Courville, Philippe

    2014-09-01

    Selachian and ray-finned fish remains from various Late Cretaceous localities of Nigeria are described. Each locality has yielded only a very few specimens and the diversity is therefore very low. However, some taxa are recorded for the first time in Africa. The Ashaka locality in the Upper Benue Trough (northeastern Nigeria) has yielded a small but interesting late Cenomanian assemblage of microremains, including teeth of “Carcharias” amonensis, Rhombopterygia zaborskii sp. nov., Hamrabatis sp., “Stephanodus” sp., and a possible ionoscopiform. A large prearticular dentition coming from the early Turonian beds of this locality is assigned to the large pycnodontiform Acrotemnus, a poorly known genus here regarded as a senior synonym of Macropycnodon. In the Lower Benue Trough (southeastern Nigeria), several localities ranging in age from the late Cenomanian to the early Maastrichtian have yielded various widespread taxa such as Ptychodus, Scapanorhynchus, Squalicorax, Vidalamiinae indet., cf. Protosphyraena, and Eodiaphyodus. The seaway that occupied the Benue Trough during transgressive episodes (late Cenomanian-early Turonian and Maastrichtian) created opportunities for the dispersal of many marine fish taxa into new areas, such as the proto-South Atlantic.

  13. 85 million years of pelagic ecosystem evolution: Pacific Ocean deep-sea ichthyolith records reveal fish community dynamics and a long-term decline in sharks

    NASA Astrophysics Data System (ADS)

    Sibert, E. C.; Norris, R. D.; Cuevas, J. M.; Graves, L. G.

    2015-12-01

    The structure and productivity of open ocean consumers has undergone major changes over the past 85 million years. Here, we present the first long-term detailed records of pelagic fish and sharks utilizing the record of ichthyoliths (teeth and dermal scales) from the deep Pacific Ocean. While the North and South Pacific Oceans show similar patterns throughout the 85 million year history, the North Pacific ichthyolith accumulation is significantly higher than the South Pacific, suggesting that the basin has been a more productive region for tens of millions of years. Fish and sharks were not abundant in the Pacific gyres until ~75 million years ago (Ma) suggesting that neither group was quantitatively important in oligotrophic pelagic food webs prior to the latest Cretaceous. Relative to ray-finned fish, sharks were common in the ancient ocean. Most ichthyolith assemblages have >50% shark dermal scales (denticles), but denticle abundance has been declining in both absolute and relative abundance since the Cretaceous-Paleogene (K/Pg) mass extinction. The accumulation rate of ichthyoliths of both sharks and ray-finned fish was highest in the Early Eocene, during the peak of the Cenozoic 'greenhouse' climate where production of shark dermal denticles and fish teeth increased almost five times over Paleocene production rates. Ichthyolith fluxes fell with cooler climates in the later Eocene and Oligocene, but fish production is almost always higher than in the Cretaceous and Paleocene reflecting the expanded ecological roles and importance of pelagic fish in marine ecosystems. Shark denticle production fell to less than half that of the Cretaceous by 20 Ma when it dropped abruptly to near-zero levels. Currently denticles make up <2% of the ichthyolith assemblages when present at all. Ecologically, pelagic sharks appear to be falling as major pelagic consumers over the Late Cretaceous and Cenozoic, and particularly over the past 20 Ma, perhaps reflecting demographic

  14. Evidence of reworked Cretaceous fossils and their bearing on the existence of Tertiary dinosaurs

    SciTech Connect

    Eaton, J.G. ); Kirkland, J.I. ); Doi, K. )

    1989-06-01

    The Paleocene Shotgun fauna of Wyoming includes marine sharks as well as mammals. It has been suggested that the sharks were introduced from the Cannonball Sea. It is more likely that these sharks were reworked from a Cretaceous rock sequence that included both marine and terrestrial deposits as there is a mixture of marine and freshwater taxa. These taxa have not been recorded elsewhere after the Cretaceous and are not known from the Cannonball Formation. Early Eocene localities at Raven Ridge, Utah, similarly contain teeth of Cretaceous marine and freshwater fish, dinosaurs, and Eocene mammals. The Cretaceous teeth are well preserved, variably abraded, and serve to cast doubts on criteria recently used to claim that dinosaur teeth recovered from the Paleocene of Montana are not reworked. Another Eocene locality in the San Juan Basin has produced an Eocene mammalian fauna with diverse Cretaceous marine sharks. Neither the nature of preservation nor the degree of abrasion could be used to distinguish reworked from contemporaneous material. The mixed environments represented by the fish taxa and recognition of the extensive pre-Tertiary extinction of both marine and freshwater fish were employed to recognize reworked specimens.

  15. Cretaceous stem chondrichthyans survived the end-Permian mass extinction.

    PubMed

    Guinot, Guillaume; Adnet, Sylvain; Cavin, Lionel; Cappetta, Henri

    2013-01-01

    Cladodontomorph sharks are Palaeozoic stem chondrichthyans thought to go extinct at the end-Permian mass extinction. This extinction preceded the diversification of euselachians, including modern sharks. Here we describe an outer-platform cladodontomorph shark tooth assemblage from the Early Cretaceous of southern France, increasing the fossil record of this group by circa 120 million years. Identification of this material rests on new histological observations and morphological evidence. Our finding shows that this lineage survived mass extinctions most likely by habitat contraction, using deep-sea refuge environments during catastrophic events. The recorded gap in the cladodontomorph lineage represents the longest gap in the fossil record for an extinct marine vertebrate group. This discovery demonstrates that the deep-sea marine diversity, poorly known during most of the fish evolutionary history, contains essential data for a complete understanding of the long-term evolution of marine fish paleobiodiversity.

  16. Quantification of diagenesis in Cenozoic sharks: Elemental and mineralogical changes

    NASA Astrophysics Data System (ADS)

    Labs-Hochstein, Joann; MacFadden, Bruce J.

    2006-10-01

    Diagenesis of bone during fossilization is pervasive, however, the extent of this process varies with depositional environment. This study quantifies diagenesis of shark vertebral centra through analysis of a suite of physical and chemical characters including crystallinty index (CI), carbonate content, and elemental concentrations. Although shark skeletons are initially cartilaginous, the soft cartilage of the vertebral centra is replaced with carbonate hydroxyapatite during growth. Nine vertebral centra are analyzed from lamnoid (Lamnoidea) sharks ranging in age from the cretaceous to recent using Fourier transform infrared spectroscopy (FT-IR) and inductively coupled plasma mass spectrometry (ICPMS). The variables CI, carbonate content, rare earth element (REE) concentrations, Ca/P, Ba/Ca, Sr/Ba, (La/Yb) N, (La/Y) N, (La/Yb) N vs. (La/Sm) N, La/Yb, and Ce anomalies elucidate the diagenetic and depositional environments of the seven fossil vertebral centra. The two extant centra demonstrate the initial, unaltered end-member conditions for these variables. Two fossil vertebral centra ( Carcharodon megalodon and Isurus hastalis) demonstrate a strong terrestrial influence during diagenesis (distinctive flattening of shale-normalized REE patterns) that masked the seawater signal. Three centra ( Carcharodon auriculatus, Carcharodon angustidens, and Creotxyrhina mantelli) have indications of some terrestrial influx evident by some flattening of the REE patterns relative to seawater. The terrestrial influence in these five shark centra ( C. megalodon, I. hastalis, C. auriculatus, C. angustidens and C. mantelli) are interpreted to represent a primarily nearshore habitat for these species. In contrast, the two Otodus obliquus centra have REE patterns that represent the original seawater signal and have no indications of terrigenous input. These results indicate that fossil shark vertebral centra have the potential to understand diagenesis and reconstruct

  17. 50 CFR 600.1204 - Shark finning; possession at sea and landing of shark fins.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 10 2011-10-01 2011-10-01 false Shark finning; possession at sea and... PROVISIONS Shark Finning § 600.1204 Shark finning; possession at sea and landing of shark fins. (a)(1) No person aboard a U.S. fishing vessel shall engage in shark finning in waters seaward of the inner...

  18. 50 CFR 600.1204 - Shark finning; possession at sea and landing of shark fins.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 12 2013-10-01 2013-10-01 false Shark finning; possession at sea and... PROVISIONS Shark Finning § 600.1204 Shark finning; possession at sea and landing of shark fins. (a)(1) No person aboard a U.S. fishing vessel shall engage in shark finning in waters seaward of the inner...

  19. 50 CFR 600.1204 - Shark finning; possession at sea and landing of shark fins.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 50 Wildlife and Fisheries 12 2012-10-01 2012-10-01 false Shark finning; possession at sea and... PROVISIONS Shark Finning § 600.1204 Shark finning; possession at sea and landing of shark fins. (a)(1) No person aboard a U.S. fishing vessel shall engage in shark finning in waters seaward of the inner...

  20. 50 CFR 600.1204 - Shark finning; possession at sea and landing of shark fins.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Shark finning; possession at sea and... PROVISIONS Shark Finning § 600.1204 Shark finning; possession at sea and landing of shark fins. (a)(1) No person aboard a U.S. fishing vessel shall engage in shark finning in waters seaward of the inner...

  1. New Age of Fishes initiated by the Cretaceous-Paleogene mass extinction

    NASA Astrophysics Data System (ADS)

    Sibert, Elizabeth C.; Norris, Richard D.

    2015-07-01

    Ray-finned fishes (Actinopterygii) comprise nearly half of all modern vertebrate diversity, and are an ecologically and numerically dominant megafauna in most aquatic environments. Crown teleost fishes diversified relatively recently, during the Late Cretaceous and early Paleogene, although the exact timing and cause of their radiation and rise to ecological dominance is poorly constrained. Here we use microfossil teeth and shark dermal scales (ichthyoliths) preserved in deep-sea sediments to study the changes in the pelagic fish community in the latest Cretaceous and early Paleogene. We find that the Cretaceous-Paleogene (K/Pg) extinction event marked a profound change in the structure of ichthyolith communities around the globe: Whereas shark denticles outnumber ray-finned fish teeth in Cretaceous deep-sea sediments around the world, there is a dramatic increase in the proportion of ray-finned fish teeth to shark denticles in the Paleocene. There is also an increase in size and numerical abundance of ray-finned fish teeth at the boundary. These changes are sustained through at least the first 24 million years of the Cenozoic. This new fish community structure began at the K/Pg mass extinction, suggesting the extinction event played an important role in initiating the modern "age of fishes."

  2. New Age of Fishes initiated by the Cretaceous-Paleogene mass extinction.

    PubMed

    Sibert, Elizabeth C; Norris, Richard D

    2015-07-14

    Ray-finned fishes (Actinopterygii) comprise nearly half of all modern vertebrate diversity, and are an ecologically and numerically dominant megafauna in most aquatic environments. Crown teleost fishes diversified relatively recently, during the Late Cretaceous and early Paleogene, although the exact timing and cause of their radiation and rise to ecological dominance is poorly constrained. Here we use microfossil teeth and shark dermal scales (ichthyoliths) preserved in deep-sea sediments to study the changes in the pelagic fish community in the latest Cretaceous and early Paleogene. We find that the Cretaceous-Paleogene (K/Pg) extinction event marked a profound change in the structure of ichthyolith communities around the globe: Whereas shark denticles outnumber ray-finned fish teeth in Cretaceous deep-sea sediments around the world, there is a dramatic increase in the proportion of ray-finned fish teeth to shark denticles in the Paleocene. There is also an increase in size and numerical abundance of ray-finned fish teeth at the boundary. These changes are sustained through at least the first 24 million years of the Cenozoic. This new fish community structure began at the K/Pg mass extinction, suggesting the extinction event played an important role in initiating the modern "age of fishes."

  3. Control of luminescence from pygmy shark (Squaliolus aliae) photophores.

    PubMed

    Claes, Julien M; Ho, Hsuan-Ching; Mallefet, Jérôme

    2012-05-15

    The smalleye pygmy shark (Squaliolus aliae) is a dwarf pelagic shark from the Dalatiidae family that harbours thousands of tiny photophores. In this work, we studied the organisation and physiological control of these photogenic organs. Results show that they are mainly situated on the ventral side of the shark, forming a homogeneous ventral photogenic area that appears well suited for counterillumination, a well-known camouflage technique of pelagic organisms. Isolated ventral skin patches containing photophores did not respond to classical neurotransmitters and nitric oxide but produced light after melatonin (MT) application. Prolactin and α-melanocyte-stimulating hormone inhibited this hormonally induced luminescence as well as the spontaneous luminescence from the photogenic tissue. The action of MT seems to be mediated by binding to the MT(2) receptor subtype, as the MT(2) receptor agonist 4P-PDOT inhibited the luminescence induced by this hormone. Binding to this receptor probably decreases the intracellular cAMP concentration because forskolin inhibited spontaneous and MT-induced luminescence. In addition, a GABA inhibitory tonus seems to be present in the photogenic tissue as well, as GABA inhibited MT-induced luminescence and the application of bicuculline provoked luminescence from S. aliae photophores. Similarly to what has been found in Etmopteridae, the other luminous shark family, the main target of the luminescence control appears to be the melanophores covering the photocytes. Results suggest that bioluminescence first appeared in Dalatiidae when they adopted a pelagic style at the Cretaceous/Tertiary boundary, and was modified by Etmopteridae when they started to colonize deep-water niches and rely on this light for intraspecific behaviours.

  4. 50 CFR 600.1204 - Shark finning; possession at sea and landing of shark fins.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... (including any cargo vessel that received shark fins from a fishing vessel at sea) shall land shark fins... and who lands shark fins harvested in waters seaward of the inner boundary of the U.S. EEZ shall land... 50 Wildlife and Fisheries 12 2014-10-01 2014-10-01 false Shark finning; possession at sea...

  5. Shark Conservation: An Educational Approach Based on Children's Knowledge and Perceptions toward Sharks.

    PubMed

    Tsoi, Kwok Ho; Chan, Sau Ying; Lee, Yeung Chung; Ip, Brian Ho Yeung; Cheang, Chi Chiu

    Shark conservation has become a focus of current international conservation efforts. However, the misunderstanding of sharks and their negative public portrayal may hinder their conservation. More importantly, the consumption of shark fin, which is very common in Chinese cultures, poses a significant threat to sharks. Hong Kong has long been the world's largest shark fin trading center. Shark conservation would become more sustainable if public understanding of this predatory fish and an appreciation of its ecological significance could be promoted. It is possible that the demand for fins could be effectively managed through long-term educational efforts targeted at younger generations. To provide essential baseline data for planning of these educational efforts, this project investigated the perceptions of 11 to 12 year-old primary school students in Hong Kong about sharks, and their understanding of ecological concepts and shark-related knowledge. The findings indicate that these students lack sufficient knowledge and possess misconceptions about sharks and their ecological significance in the marine ecosystem. The students' conceptual understanding level is strongly correlated with their perceptions. Correlational analyses further demonstrated a positive association between formal education and perceptions toward shark conservation. The students who favoured shark fin consumption did so because of its tastiness, whereas concerns about shark population decline and the cruelty of shark hunting were the main reasons for not favoring shark fin consumption. This pilot study provides preliminary but important insights into primary school education regarding the conservation of sharks.

  6. Shark Conservation: An Educational Approach Based on Children’s Knowledge and Perceptions toward Sharks

    PubMed Central

    Chan, Sau Ying; Lee, Yeung Chung; Ip, Brian Ho Yeung; Cheang, Chi Chiu

    2016-01-01

    Shark conservation has become a focus of current international conservation efforts. However, the misunderstanding of sharks and their negative public portrayal may hinder their conservation. More importantly, the consumption of shark fin, which is very common in Chinese cultures, poses a significant threat to sharks. Hong Kong has long been the world’s largest shark fin trading center. Shark conservation would become more sustainable if public understanding of this predatory fish and an appreciation of its ecological significance could be promoted. It is possible that the demand for fins could be effectively managed through long-term educational efforts targeted at younger generations. To provide essential baseline data for planning of these educational efforts, this project investigated the perceptions of 11 to 12 year-old primary school students in Hong Kong about sharks, and their understanding of ecological concepts and shark-related knowledge. The findings indicate that these students lack sufficient knowledge and possess misconceptions about sharks and their ecological significance in the marine ecosystem. The students’ conceptual understanding level is strongly correlated with their perceptions. Correlational analyses further demonstrated a positive association between formal education and perceptions toward shark conservation. The students who favoured shark fin consumption did so because of its tastiness, whereas concerns about shark population decline and the cruelty of shark hunting were the main reasons for not favoring shark fin consumption. This pilot study provides preliminary but important insights into primary school education regarding the conservation of sharks. PMID:27684706

  7. Characteristics of the shark fisheries of Fiji

    PubMed Central

    Glaus, Kerstin B. J.; Adrian-Kalchhauser, Irene; Burkhardt-Holm, Patricia; White, William T.; Brunnschweiler, Juerg M.

    2015-01-01

    Limited information is available on artisanal and subsistence shark fisheries across the Pacific. The aim of this study was to investigate Fiji’s inshore fisheries which catch sharks. In January and February 2013, 253 semi-directive interviews were conducted in 117 villages and at local harbours on Viti Levu, Vanua Levu, Taveuni, Ovalau and a number of islands of the Mamanuca and Yasawa archipelagos. Of the 253 interviewees, 81.4% reported to presently catch sharks, and 17.4% declared that they did not presently catch any sharks. Of the 206 fishers that reported to catch sharks, 18.4% targeted sharks and 81.6% caught sharks as bycatch. When targeted, primary use of sharks was for consumption or for sale. Sharks caught as bycatch were frequently released (69.6%), consumed (64.9%) or shared amongst the community (26.8%). Fishers’ identification based on an identification poster and DNA barcoding revealed that at least 12 species of elasmobranchs, 11 shark and one ray species (Rhynchobatus australiae) were caught. This study, which is the first focused exploration of the shark catch in Fiji’s inshore fisheries, suggests that the country’s artisanal shark fisheries are small but have the potential to develop into larger and possibly more targeted fisheries. PMID:26626561

  8. Characteristics of the shark fisheries of Fiji.

    PubMed

    Glaus, Kerstin B J; Adrian-Kalchhauser, Irene; Burkhardt-Holm, Patricia; White, William T; Brunnschweiler, Juerg M

    2015-12-02

    Limited information is available on artisanal and subsistence shark fisheries across the Pacific. The aim of this study was to investigate Fiji's inshore fisheries which catch sharks. In January and February 2013, 253 semi-directive interviews were conducted in 117 villages and at local harbours on Viti Levu, Vanua Levu, Taveuni, Ovalau and a number of islands of the Mamanuca and Yasawa archipelagos. Of the 253 interviewees, 81.4% reported to presently catch sharks, and 17.4% declared that they did not presently catch any sharks. Of the 206 fishers that reported to catch sharks, 18.4% targeted sharks and 81.6% caught sharks as bycatch. When targeted, primary use of sharks was for consumption or for sale. Sharks caught as bycatch were frequently released (69.6%), consumed (64.9%) or shared amongst the community (26.8%). Fishers' identification based on an identification poster and DNA barcoding revealed that at least 12 species of elasmobranchs, 11 shark and one ray species (Rhynchobatus australiae) were caught. This study, which is the first focused exploration of the shark catch in Fiji's inshore fisheries, suggests that the country's artisanal shark fisheries are small but have the potential to develop into larger and possibly more targeted fisheries.

  9. Characteristics of the shark fisheries of Fiji

    NASA Astrophysics Data System (ADS)

    Glaus, Kerstin B. J.; Adrian-Kalchhauser, Irene; Burkhardt-Holm, Patricia; White, William T.; Brunnschweiler, Juerg M.

    2015-12-01

    Limited information is available on artisanal and subsistence shark fisheries across the Pacific. The aim of this study was to investigate Fiji’s inshore fisheries which catch sharks. In January and February 2013, 253 semi-directive interviews were conducted in 117 villages and at local harbours on Viti Levu, Vanua Levu, Taveuni, Ovalau and a number of islands of the Mamanuca and Yasawa archipelagos. Of the 253 interviewees, 81.4% reported to presently catch sharks, and 17.4% declared that they did not presently catch any sharks. Of the 206 fishers that reported to catch sharks, 18.4% targeted sharks and 81.6% caught sharks as bycatch. When targeted, primary use of sharks was for consumption or for sale. Sharks caught as bycatch were frequently released (69.6%), consumed (64.9%) or shared amongst the community (26.8%). Fishers’ identification based on an identification poster and DNA barcoding revealed that at least 12 species of elasmobranchs, 11 shark and one ray species (Rhynchobatus australiae) were caught. This study, which is the first focused exploration of the shark catch in Fiji’s inshore fisheries, suggests that the country’s artisanal shark fisheries are small but have the potential to develop into larger and possibly more targeted fisheries.

  10. Shark cartilage contains inhibitors of tumor angiogenesis.

    PubMed

    Lee, A; Langer, R

    1983-09-16

    Shark cartilage contains a substance that strongly inhibits the growth of new blood vessels toward solid tumors, thereby restricting tumor growth. The abundance of this factor in shark cartilage, in contrast to cartilage from mammalian sources, may make sharks an ideal source of the inhibitor and may help to explain the rarity of neoplasms in these animals.

  11. Strontium mineralization of shark vertebrae.

    PubMed

    Raoult, Vincent; Peddemors, Victor M; Zahra, David; Howell, Nicholas; Howard, Daryl L; de Jonge, Martin D; Williamson, Jane E

    2016-07-18

    Determining the age of sharks using vertebral banding is a vital component of management, but the causes of banding are not fully understood. Traditional shark ageing is based on fish otolith ageing methods where growth bands are assumed to result from varied seasonal calcification rates. Here we investigate these assumptions by mapping elemental distribution within the growth bands of vertebrae from six species of sharks representing four different taxonomic orders using scanning x-ray fluorescence microscopy. Traditional visual growth bands, determined with light microscopy, were more closely correlated to strontium than calcium in all species tested. Elemental distributions suggest that vertebral strontium bands may be related to environmental variations in salinity. These results highlight the requirement for a better understanding of shark movements, and their influence on vertebral development, if confidence in age estimates is to be improved. Analysis of shark vertebrae using similar strontium-focused elemental techniques, once validated for a given species, may allow more successful estimations of age on individuals with few or no visible vertebral bands.

  12. Hydrodynamic aspects of shark scales

    NASA Technical Reports Server (NTRS)

    Raschi, W. G.; Musick, J. A.

    1986-01-01

    Ridge morphometrices on placoid scales from 12 galeoid shark species were examined in order to evaluate their potential value for frictional drag reduction. The geometry of the shark scales is similar to longitudinal grooved surfaces (riblets) that have been previously shown to give 8 percent skin-friction reduction for turbulent boundary layers. The present study of the shark scales was undertaken to determine if the physical dimensions of the ridges on the shark scales are of the right magnitude to be used by the sharks for drag reduction based on previous riblet work. The results indicate that the ridge heights and spacings are normally maintained between the predicted optimal values proposed for voluntary and burst swimming speeds throughout the individual's ontogeny. Moreover, the species which might be considered to be the faster posses smaller and more closely spaced ridges that based on the riblet work would suggest a greater frictional drag reduction value at the high swimming speeds, as compared to their more sluggish counterparts.

  13. Strontium mineralization of shark vertebrae

    PubMed Central

    Raoult, Vincent; Peddemors, Victor M.; Zahra, David; Howell, Nicholas; Howard, Daryl L.; de Jonge, Martin D.; Williamson, Jane E.

    2016-01-01

    Determining the age of sharks using vertebral banding is a vital component of management, but the causes of banding are not fully understood. Traditional shark ageing is based on fish otolith ageing methods where growth bands are assumed to result from varied seasonal calcification rates. Here we investigate these assumptions by mapping elemental distribution within the growth bands of vertebrae from six species of sharks representing four different taxonomic orders using scanning x-ray fluorescence microscopy. Traditional visual growth bands, determined with light microscopy, were more closely correlated to strontium than calcium in all species tested. Elemental distributions suggest that vertebral strontium bands may be related to environmental variations in salinity. These results highlight the requirement for a better understanding of shark movements, and their influence on vertebral development, if confidence in age estimates is to be improved. Analysis of shark vertebrae using similar strontium-focused elemental techniques, once validated for a given species, may allow more successful estimations of age on individuals with few or no visible vertebral bands. PMID:27424768

  14. [Dangerous sharks in tropical seas].

    PubMed

    Maslin, J; Menard, G; Drouin, C; Pollet, L

    2000-01-01

    Sightseeing travel in tropical zones is a growing industry. The risks incurred by travelers depend on the destination, duration of stay, individual behavior, and type of leisure activity. Water sports expose visitors to encounters with dangerous marine animals. Shark attacks are rare but always serious occurrences. Divers should handle any shark, regardless of size, with due precaution. Prevention of shark attack depends on avoiding encounters by not attracting the attention of the shark and knowing the proper attitude to adopt in case an encounter should occur. Active and passive protection can be used, but each method has advantages and disadvantages depending on the situation. Rescue operations are difficult due to the gravity of injuries and their occurrence in a marine environment. This along with the nature of the aggressor explain that many attacks are immediately fatal. Wounds are often deep with involvement of bone, blood vessels, and nerves. A possible source of complication in survivors is infection, which can involve uncommon microorganisms associated with bacteria in sharks mouth or marine environment.

  15. Fiji's largest marine reserve benefits reef sharks

    NASA Astrophysics Data System (ADS)

    Goetze, J. S.; Fullwood, L. A. F.

    2013-03-01

    To provide more information about whether sharks benefit from no-take marine reserves, we quantified the relative abundance and biomass of reef sharks inside and outside of Namena, Fiji's largest reserve (60.6 km2). Using stereo baited remote underwater video systems (stereo-BRUVs), we found that the abundance and biomass of sharks was approximately two and four times greater in shallow and deep locations, respectively, within the Namena reserve compared to adjacent fished areas. The greater abundance and biomass of reef sharks inside Namena is likely a result of greater prey availability rather than protection from fishing. This study demonstrates that marine reserves can benefit sharks.

  16. Oceanic sharks clean at coastal seamount.

    PubMed

    Oliver, Simon P; Hussey, Nigel E; Turner, John R; Beckett, Alison J

    2011-03-14

    Interactions between pelagic thresher sharks (Alopias pelagicus) and cleaner wrasse were investigated at a seamount in the Philippines. Cleaning associations between sharks and teleosts are poorly understood, but the observable interactions seen at this site may explain why these mainly oceanic sharks regularly venture into shallow coastal waters where they are vulnerable to disturbance from human activity. From 1,230 hours of observations recorded by remote video camera between July 2005 and December 2009, 97 cleaner-thresher shark events were analyzed, 19 of which were interrupted. Observations of pelagic thresher sharks interacting with cleaners at the seamount were recorded at all times of day but their frequency declined gradually from morning until evening. Cleaners showed preferences for foraging on specific areas of a thresher shark's body. For all events combined, cleaners were observed to conduct 2,757 inspections, of which 33.9% took place on the shark's pelvis, 23.3% on the pectoral fins, 22.3% on the caudal fin, 8.6% on the body, 8.3% on the head, 2.1% on the dorsal fin, and 1.5% on the gills respectively. Cleaners did not preferentially inspect thresher sharks by time of day or by shark sex, but there was a direct correlation between the amount of time a thresher shark spent at a cleaning station and the number of inspections it received. Thresher shark clients modified their behavior by "circular-stance-swimming," presumably to facilitate cleaner inspections. The cleaner-thresher shark association reflected some of the known behavioral trends in the cleaner-reef teleost system since cleaners appeared to forage selectively on shark clients. Evidence is mounting that in addition to acting as social refuges and foraging grounds for large visiting marine predators, seamounts may also support pelagic ecology by functioning as cleaning stations for oceanic sharks and rays.

  17. Enhanced visual fields in hammerhead sharks.

    PubMed

    McComb, D M; Tricas, T C; Kajiura, S M

    2009-12-01

    Several factors that influence the evolution of the unusual head morphology of hammerhead sharks (family Sphyrnidae) are proposed but few are empirically tested. In this study we tested the 'enhanced binocular field' hypothesis (that proposes enhanced frontal binocularity) by comparison of the visual fields of three hammerhead species: the bonnethead shark, Sphyrna tiburo, the scalloped hammerhead shark, Sphyrna lewini, and the winghead shark, Eusphyra blochii, with that of two carcharhinid species: the lemon shark, Negaprion brevirostris, and the blacknose shark, Carcharhinus acronotus. Additionally, eye rotation and head yaw were quantified to determine if species compensate for large blind areas anterior to the head. The winghead shark possessed the largest anterior binocular overlap (48 deg.) and was nearly four times larger than that of the lemon (10 deg.) and blacknose (11 deg.) sharks. The binocular overlap in the scalloped hammerhead sharks (34 deg.) was greater than the bonnethead sharks (13 deg.) and carcharhinid species; however, the bonnethead shark did not differ from the carcharhinids. These results indicate that binocular overlap has increased with lateral head expansion in hammerhead sharks. The hammerhead species did not demonstrate greater eye rotation in the anterior or posterior direction. However, both the scalloped hammerhead and bonnethead sharks exhibited greater head yaw during swimming (16.9 deg. and 15.6 deg., respectively) than the lemon (15.1 deg.) and blacknose (15.0 deg.) sharks, indicating a behavioral compensation for the anterior blind area. This study illustrates the larger binocular overlap in hammerhead species relative to their carcharhinid sister taxa and is consistent with the 'enhanced binocular field' hypothesis.

  18. Grey Nurse Shark ( Carcharias taurus) Diving Tourism: Tourist Compliance and Shark Behaviour at Fish Rock, Australia

    NASA Astrophysics Data System (ADS)

    Smith, Kirby; Scarr, Mark; Scarpaci, Carol

    2010-11-01

    Humans can dive with critically endangered grey nurse sharks ( Carcharias taurus) along the east coast of Australia. This study investigated both compliance of tourist divers to a code of conduct and legislation and the behaviour of grey nurse sharks in the presence of divers. A total of 25 data collection dives were conducted from December 2008 to January 2009. Grey nurse shark and diver behaviour were documented using 2-min scan samples and continuous observation. The proportion of time spent observing human-shark interactions was 9.4% of total field time and mean human-shark interaction time was 15.0 min. Results were used to gauge the effectiveness of current management practices for the grey nurse shark dive industry at Fish Rock in New South Wales, Australia. Grey nurse shark dive tourists were compliant to stipulations in the code of conduct and legislation (compliance ranged from 88 to 100%). The research detailed factors that may promote compliance in wildlife tourism operations such as the clarity of the stipulations, locality of the target species and diver perceptions of sharks. Results indicated that grey nurse sharks spent the majority of their time milling (85%) followed by active swimming (15%). Milling behaviour significantly decreased in the presence of more than six divers. Distance between sharks and divers, interaction time and number of sharks were not significantly correlated with grey nurse shark school behaviour. Jaw gaping, rapid withdrawal and stiff or jerky movement were the specific behaviours of grey nurse sharks that occurred most frequently and were associated with distance between divers and sharks and the presence of six or more divers. Revision of the number of divers allowed per interaction with a school of grey nurse sharks and further research on the potential impacts that shark-diving tourism may pose to grey nurse sharks is recommended.

  19. Grey nurse shark (Carcharias taurus) diving tourism: Tourist compliance and shark behaviour at Fish Rock, Australia.

    PubMed

    Smith, Kirby; Scarr, Mark; Scarpaci, Carol

    2010-11-01

    Humans can dive with critically endangered grey nurse sharks (Carcharias taurus) along the east coast of Australia. This study investigated both compliance of tourist divers to a code of conduct and legislation and the behaviour of grey nurse sharks in the presence of divers. A total of 25 data collection dives were conducted from December 2008 to January 2009. Grey nurse shark and diver behaviour were documented using 2-min scan samples and continuous observation. The proportion of time spent observing human-shark interactions was 9.4% of total field time and mean human-shark interaction time was 15.0 min. Results were used to gauge the effectiveness of current management practices for the grey nurse shark dive industry at Fish Rock in New South Wales, Australia. Grey nurse shark dive tourists were compliant to stipulations in the code of conduct and legislation (compliance ranged from 88 to 100%). The research detailed factors that may promote compliance in wildlife tourism operations such as the clarity of the stipulations, locality of the target species and diver perceptions of sharks. Results indicated that grey nurse sharks spent the majority of their time milling (85%) followed by active swimming (15%). Milling behaviour significantly decreased in the presence of more than six divers. Distance between sharks and divers, interaction time and number of sharks were not significantly correlated with grey nurse shark school behaviour. Jaw gaping, rapid withdrawal and stiff or jerky movement were the specific behaviours of grey nurse sharks that occurred most frequently and were associated with distance between divers and sharks and the presence of six or more divers. Revision of the number of divers allowed per interaction with a school of grey nurse sharks and further research on the potential impacts that shark-diving tourism may pose to grey nurse sharks is recommended.

  20. Cyanobacterial Neurotoxin BMAA and Mercury in Sharks.

    PubMed

    Hammerschlag, Neil; Davis, David A; Mondo, Kiyo; Seely, Matthew S; Murch, Susan J; Glover, William Broc; Divoll, Timothy; Evers, David C; Mash, Deborah C

    2016-08-16

    Sharks have greater risk for bioaccumulation of marine toxins and mercury (Hg), because they are long-lived predators. Shark fins and cartilage also contain β-N-methylamino-l-alanine (BMAA), a ubiquitous cyanobacterial toxin linked to neurodegenerative diseases. Today, a significant number of shark species have found their way onto the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Many species of large sharks are threatened with extinction due in part to the growing high demand for shark fin soup and, to a lesser extent, for shark meat and cartilage products. Recent studies suggest that the consumption of shark parts may be a route to human exposure of marine toxins. Here, we investigated BMAA and Hg concentrations in fins and muscles sampled in ten species of sharks from the South Atlantic and Pacific Oceans. BMAA was detected in all shark species with only seven of the 55 samples analyzed testing below the limit of detection of the assay. Hg concentrations measured in fins and muscle samples from the 10 species ranged from 0.05 to 13.23 ng/mg. These analytical test results suggest restricting human consumption of shark meat and fins due to the high frequency and co-occurrence of two synergistic environmental neurotoxic compounds.

  1. Cyanobacterial Neurotoxin BMAA and Mercury in Sharks

    PubMed Central

    Hammerschlag, Neil; Davis, David A.; Mondo, Kiyo; Seely, Matthew S.; Murch, Susan J.; Glover, William Broc; Divoll, Timothy; Evers, David C.; Mash, Deborah C.

    2016-01-01

    Sharks have greater risk for bioaccumulation of marine toxins and mercury (Hg), because they are long-lived predators. Shark fins and cartilage also contain β-N-methylamino-l-alanine (BMAA), a ubiquitous cyanobacterial toxin linked to neurodegenerative diseases. Today, a significant number of shark species have found their way onto the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Many species of large sharks are threatened with extinction due in part to the growing high demand for shark fin soup and, to a lesser extent, for shark meat and cartilage products. Recent studies suggest that the consumption of shark parts may be a route to human exposure of marine toxins. Here, we investigated BMAA and Hg concentrations in fins and muscles sampled in ten species of sharks from the South Atlantic and Pacific Oceans. BMAA was detected in all shark species with only seven of the 55 samples analyzed testing below the limit of detection of the assay. Hg concentrations measured in fins and muscle samples from the 10 species ranged from 0.05 to 13.23 ng/mg. These analytical test results suggest restricting human consumption of shark meat and fins due to the high frequency and co-occurrence of two synergistic environmental neurotoxic compounds. PMID:27537913

  2. Microspectrophotometric evidence for cone monochromacy in sharks.

    PubMed

    Hart, Nathan Scott; Theiss, Susan Michelle; Harahush, Blake Kristin; Collin, Shaun Patrick

    2011-03-01

    Sharks are apex predators, and their evolutionary success is in part due to an impressive array of sensory systems, including vision. The eyes of sharks are well developed and function over a wide range of light levels. However, whilst close relatives of the sharks-the rays and chimaeras-are known to have the potential for colour vision, an evolutionary trait thought to provide distinct survival advantages, evidence for colour vision in sharks remains equivocal. Using single-receptor microspectrophotometry, we measured the absorbance spectra of visual pigments located in the retinal photoreceptors of 17 species of shark. We show that, while the spectral tuning of the rod (wavelength of maximum absorbance, λ(max) 484-518 nm) and cone (λ(max) 532-561 nm) visual pigments varies between species, each shark has only a single long-wavelength-sensitive cone type. This suggests that sharks may be cone monochromats and, therefore, potentially colour blind. Whilst cone monochromacy on land is rare, it may be a common strategy in the marine environment: many aquatic mammals (whales, dolphins and seals) also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution. The spectral tuning of the rod and cone pigments of sharks is also discussed in relation to their visual ecology.

  3. Sharks and people: insight into the global practices of tourism operators and their attitudes to shark behaviour.

    PubMed

    Richards, Kirsty; O'Leary, Bethan C; Roberts, Callum M; Ormond, Rupert; Gore, Mauvis; Hawkins, Julie P

    2015-02-15

    Shark tourism is a popular but controversial activity. We obtained insights into this industry via a global e-mailed questionnaire completed by 45 diving/snorkelling operators who advertised shark experiences (shark operators) and 49 who did not (non-shark operators). 42% of shark operators used an attractant to lure sharks and 93% stated they had a formal code of conduct which 86% enforced "very strictly". While sharks were reported to normally ignore people, 9 operators had experienced troublesome behaviour from them. Whilst our research corroborates previous studies indicating minimal risk to humans from most shark encounters, a precautionary approach to provisioning is required to avoid potential ecological and societal effects of shark tourism. Codes of conduct should always stipulate acceptable diver behaviour and appropriate diver numbers and shark operators should have a moral responsibility to educate their customers about the need for shark conservation.

  4. Implantable Neural Interfaces for Sharks

    DTIC Science & Technology

    2007-05-01

    neural codes from peripheral nerve using electrode arrays; Use simple chemical stimuli & multiple locations Completed Amino acid – evoked...rosette · Odorant perfusion across the olfactory rosette (amino acids : histidine, glutamate, cysteine) Implantable Neural Interfaces for Sharks...methane sulphonate ) at 100 mg/L on spontaneous activity recorded in the olfactory lobe. Rate histograms in 5 sec bins as a function of time. The

  5. Microspectrophotometric evidence for cone monochromacy in sharks

    NASA Astrophysics Data System (ADS)

    Hart, Nathan Scott; Theiss, Susan Michelle; Harahush, Blake Kristin; Collin, Shaun Patrick

    2011-03-01

    Sharks are apex predators, and their evolutionary success is in part due to an impressive array of sensory systems, including vision. The eyes of sharks are well developed and function over a wide range of light levels. However, whilst close relatives of the sharks—the rays and chimaeras—are known to have the potential for colour vision, an evolutionary trait thought to provide distinct survival advantages, evidence for colour vision in sharks remains equivocal. Using single-receptor microspectrophotometry, we measured the absorbance spectra of visual pigments located in the retinal photoreceptors of 17 species of shark. We show that, while the spectral tuning of the rod (wavelength of maximum absorbance, λmax 484-518 nm) and cone (λmax 532-561 nm) visual pigments varies between species, each shark has only a single long-wavelength-sensitive cone type. This suggests that sharks may be cone monochromats and, therefore, potentially colour blind. Whilst cone monochromacy on land is rare, it may be a common strategy in the marine environment: many aquatic mammals (whales, dolphins and seals) also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution. The spectral tuning of the rod and cone pigments of sharks is also discussed in relation to their visual ecology.

  6. Muscle function and swimming in sharks.

    PubMed

    Shadwick, R E; Goldbogen, J A

    2012-04-01

    The locomotor system in sharks has been investigated for many decades, starting with the earliest kinematic studies by Sir James Gray in the 1930s. Early work on axial muscle anatomy also included sharks, and the first demonstration of the functional significance of red and white muscle fibre types was made on spinal preparations in sharks. Nevertheless, studies on teleosts dominate the literature on fish swimming. The purpose of this article is to review the current knowledge of muscle function and swimming in sharks, by considering their morphological features related to swimming, the anatomy and physiology of the axial musculature, kinematics and muscle dynamics, and special features of warm-bodied lamnids. In addition, new data are presented on muscle activation in fast-starts. Finally, recent developments in tracking technology that provide insights into shark swimming performance in their natural environment are highlighted.

  7. Cretaceous polar climates

    SciTech Connect

    Ziegler, A.M.; Horrell, M.A.; Lottes, A.L.; Gierlowski, T.C.

    1988-02-01

    The Cretaceous, like most Phanerozoic periods, was characterized by ice-free poles. Some still argue that the glaciers and sea ice were there, and that the tillites, etc, have been eroded or remain undiscovered. However, diverse floras, dense forests, and coal-forming cypress swamps, and dinosaurs, crocodilians, and lungfish are known from areas that were certainly at 75/degree/-80/degree/ north and south paleolatitude in the Cretaceous, implying that the coastal basins did not experience hard freezes. No deep marine connections to the North Pole existed in the Cretaceous, so oceanic polar heat transport can be discounted. However, the five north-south trending epeiric or rift-related seaways that connected or nearly connected the Tethys to the Arctic would have dampened the seasonal temperature cycle, bring maritime climates deep into the North American and Eurasian continents and, more importantly, would have served as an energy source and channel for winter storms, much as the Gulf Stream does today. Cyclones have a natural tendency to move poleward, because of the increase in the Coriolis Parameter, and they transport both sensible and latent heat. The coastal regions of the relatively warm polar ocean in the Cretaceous would have received continuous precipitation during the winter because cyclones would be entering from as many as five directions. Coastal rainfall would also have been abundant in the summer but for a different reason; the land-sea temperature profile would reverse, with the warm land surface drawing in moisture, while clear ice-free conditions over the ocean would allow for solar warming.

  8. Cretaceous polar climates

    SciTech Connect

    Ziegler, A.M.; Horrell, M.A.; Lottes, A.L.; Gierlowski, T.C.

    1988-01-01

    The Cretaceous, like most Phanerozooic periods, was characterized by ice-free poles. Some still argue that the glacier and sea ice were there, and that the tillites, etc, have been eroded or remain undiscovered. However, diverse floras, dense forests, coal-forming cypress swamps, and dinosaurs, crocodilians, and lungfish are known from areas that were certainly at 75/sup 0/-80/sup 0/ north and south paleolatitude in the Cretaceous, implying that the coastal basins did not experience hard freezes. No deep marine connections to the North Pole existed in the Cretaceous, so oceanic polar heat transport can be discounted. However, the five north-south trending epeiric or rift-related seaways that connected or nearly connected the Tethys to the Arctic would have dampened the seasonal temperature cycle, bringing maritime climates deep into the North American and Eurasian continents and, more importantly, would have served as an energy source and channel for winter storms, much as the Gulf Stream does today. Cyclones have a natural tendency to move poleward, because of the increase in the Coriolis Paramteter, and they transport both sensible and latent heat. The coastal regions of the relatively warm polar ocean in the Cretaceous would have received continuous precipitation during the winter because cyclones would be entering from as many as five directions. Coastal rainfall would also have been abundant in the summer but for a different reason; the land-sea temperature profile would reverse, with the warm land surface drawing in moisture, while clear ice-free conditions over the ocean would allow for solar warming.

  9. Shark tales: a molecular species-level phylogeny of sharks (Selachimorpha, Chondrichthyes).

    PubMed

    Vélez-Zuazo, Ximena; Agnarsson, Ingi

    2011-02-01

    Sharks are a diverse and ecologically important group, including some of the ocean's largest predatory animals. Sharks are also commercially important, with many species suffering overexploitation and facing extinction. However, despite a long evolutionary history, commercial, and conservation importance, phylogenetic relationships within the sharks are poorly understood. To date, most studies have either focused on smaller clades within sharks, or sampled taxa sparsely across the group. A more detailed species-level phylogeny will offer further insights into shark taxonomy, provide a tool for comparative analyses, as well as facilitating phylogenetic estimates of conservation priorities. We used four mitochondrial and one nuclear gene to investigate the phylogenetic relationships of 229 species (all eight Orders and 31 families) of sharks, more than quadrupling the number of taxon sampled in any prior study. The resulting Bayesian phylogenetic hypothesis agrees with prior studies on the major relationships of the sharks phylogeny; however, on those relationships that have proven more controversial, it differs in several aspects from the most recent molecular studies. The phylogeny supports the division of sharks into two major groups, the Galeomorphii and Squalimorphii, rejecting the hypnosqualean hypothesis that places batoids within sharks. Within the squalimorphs the orders Hexanchiformes, Squatiniformes, Squaliformes, and Pristiophoriformes are broadly monophyletic, with minor exceptions apparently due to missing data. Similarly, within Galeomorphs, the orders Heterodontiformes, Lamniformes, Carcharhiniformes, and Orectolobiformes are broadly monophyletic, with a couple of species 'misplaced'. In contrast, many of the currently recognized shark families are not monophyletic according to our results. Our phylogeny offers some of the first clarification of the relationships among families of the order Squaliformes, a group that has thus far received relatively

  10. The Effect of Background Music in Shark Documentaries on Viewers' Perceptions of Sharks.

    PubMed

    Nosal, Andrew P; Keenan, Elizabeth A; Hastings, Philip A; Gneezy, Ayelet

    2016-01-01

    Despite the ongoing need for shark conservation and management, prevailing negative sentiments marginalize these animals and legitimize permissive exploitation. These negative attitudes arise from an instinctive, yet exaggerated fear, which is validated and reinforced by disproportionate and sensationalistic news coverage of shark 'attacks' and by highlighting shark-on-human violence in popular movies and documentaries. In this study, we investigate another subtler, yet powerful factor that contributes to this fear: the ominous background music that often accompanies shark footage in documentaries. Using three experiments, we show that participants rated sharks more negatively and less positively after viewing a 60-second video clip of swimming sharks set to ominous background music, compared to participants who watched the same video clip set to uplifting background music, or silence. This finding was not an artifact of soundtrack alone because attitudes toward sharks did not differ among participants assigned to audio-only control treatments. This is the first study to demonstrate empirically that the connotative attributes of background music accompanying shark footage affect viewers' attitudes toward sharks. Given that nature documentaries are often regarded as objective and authoritative sources of information, it is critical that documentary filmmakers and viewers are aware of how the soundtrack can affect the interpretation of the educational content.

  11. Relative abundance and size of coastal sharks derived from commercial shark longline catch and effort data.

    PubMed

    Carlson, J K; Hale, L F; Morgan, A; Burgess, G

    2012-04-01

    In the north-west Atlantic Ocean, stock assessments conducted for some commercially harvested coastal sharks indicate declines from 64 to 80% with respect to virgin population levels. While the status of commercially important species is available, abundance trend information for other coastal shark species in the north-west Atlantic Ocean are unavailable. Using a generalized linear modelling (GLM) approach, a relative abundance index was derived from 1994 to 2009 using observer data collected in a commercial bottom longline fishery. Trends in abundance and average size were estimated for bull shark Carcharhinus leucas, spinner shark Carcharhinus brevipinna, tiger shark Galeocerdo cuvier and lemon shark Negaprion brevirostris. Increases in relative abundance for all shark species ranged from 14% for C. brevipinna, 12% for C. leucas, 6% for N. brevirostris and 3% for G. cuvier. There was no significant change in the size at capture over the time period considered for all species. While the status of shark populations should not be based exclusively on abundance trend information, but ultimately on stock assessment models, results from this study provide some cause for optimism on the status of these coastal shark species.

  12. Regional movements of the tiger shark, Galeocerdo cuvier, off Northeastern Brazil: inferences regarding shark attack hazard.

    PubMed

    Hazin, Fábio H V; Afonso, André S; De Castilho, Pedro C; Ferreira, Luciana C; Rocha, Bruno C L M

    2013-09-01

    An abnormally high shark attack rate verified off Recife could be related to migratory behavior of tiger sharks. This situation started after the construction of the Suape port to the south of Recife. A previous study suggested that attacking sharks could be following northward currents and that they were being attracted shoreward by approaching vessels. In this scenario, such northward movement pattern could imply a higher probability of sharks accessing the littoral area of Recife after leaving Suape. Pop-up satellite archival tags were deployed on five tiger sharks caught off Recife to assess their movement patterns off northeastern Brazil. All tags transmitted from northward latitudes after 7-74 days of freedom. The shorter, soak distance between deployment and pop-up locations ranged between 33-209 km and implied minimum average speeds of 0.02-0.98 km.h-1. Both pop-up locations and depth data suggest that tiger shark movements were conducted mostly over the continental shelf. The smaller sharks moved to deeper waters within 24 hours after releasing, but they assumed a shallower (< 50 m) vertical distribution for most of the monitoring period. While presenting the first data on tiger shark movements in the South Atlantic, this study also adds new information for the reasoning of the high shark attack rate verified in this region.

  13. The Effect of Background Music in Shark Documentaries on Viewers' Perceptions of Sharks

    PubMed Central

    Hastings, Philip A.; Gneezy, Ayelet

    2016-01-01

    Despite the ongoing need for shark conservation and management, prevailing negative sentiments marginalize these animals and legitimize permissive exploitation. These negative attitudes arise from an instinctive, yet exaggerated fear, which is validated and reinforced by disproportionate and sensationalistic news coverage of shark ‘attacks’ and by highlighting shark-on-human violence in popular movies and documentaries. In this study, we investigate another subtler, yet powerful factor that contributes to this fear: the ominous background music that often accompanies shark footage in documentaries. Using three experiments, we show that participants rated sharks more negatively and less positively after viewing a 60-second video clip of swimming sharks set to ominous background music, compared to participants who watched the same video clip set to uplifting background music, or silence. This finding was not an artifact of soundtrack alone because attitudes toward sharks did not differ among participants assigned to audio-only control treatments. This is the first study to demonstrate empirically that the connotative attributes of background music accompanying shark footage affect viewers’ attitudes toward sharks. Given that nature documentaries are often regarded as objective and authoritative sources of information, it is critical that documentary filmmakers and viewers are aware of how the soundtrack can affect the interpretation of the educational content. PMID:27487003

  14. Virgin birth in a hammerhead shark.

    PubMed

    Chapman, Demian D; Shivji, Mahmood S; Louis, Ed; Sommer, Julie; Fletcher, Hugh; Prodöhl, Paulo A

    2007-08-22

    Parthenogenesis has been documented in all major jawed vertebrate lineages except mammals and cartilaginous fishes (class Chondrichthyes: sharks, batoids and chimeras). Reports of captive female sharks giving birth despite being held in the extended absence of males have generally been ascribed to prior matings coupled with long-term sperm storage by the females. Here, we provide the first genetic evidence for chondrichthyan parthenogenesis, involving a hammerhead shark (Sphyrna tiburo). This finding also broadens the known occurrence of a specific type of asexual development (automictic parthenogenesis) among vertebrates, extending recently raised concerns about the potential negative effect of this type of facultative parthenogenesis on the genetic diversity of threatened vertebrate species.

  15. Brazilian continental cretaceous

    NASA Astrophysics Data System (ADS)

    Petri, Setembrino; Campanha, Vilma A.

    1981-04-01

    Cretaceous deposits in Brazil are very well developed, chiefly in continental facies and in thick sequences. Sedimentation occurred essentially in rift-valleys inland and along the coast. Three different sequences can be distinguished: (1) a lower clastic non-marine section, (2) a middle evaporitic section, (3) an upper marine section with non-marine regressive lithosomes. Continental deposits have been laid down chiefly between the latest Jurassic and Albian. The lower lithostratigraphic unit is represented by red shales with occasional evaporites and fresh-water limestones, dated by ostracods. A series of thick sandstone lithosomes accumulated in the inland rift-valleys. In the coastal basins these sequences are often incompletely preserved. Uplift in the beginning of the Aptian produced a widespread unconformity. In many of the inland rift-valleys sedimentation ceased at that time. A later transgression penetrated far into northeastern Brazil, but shortly after continental sedimentation continued, with the deposition of fluvial sandstones which once covered large areas of the country and which have been preserved in many places. The continental Cretaceous sediments have been laid down in fluvial and lacustrine environments, under warm climatic conditions which were dry from time to time. The fossil record is fairly rich, including besides plants and invertebrates, also reptiles and fishes. As faulting tectonism was rather strong, chiefly during the beginning of the Cretaceous, intercalations of igneous rocks are frequent in some places. Irregular uplift and erosion caused sediments belonging to the remainder of this period to be preserved only in tectonic basins scattered across the country.

  16. Population trends in Pacific Oceanic sharks and the utility of regulations on shark finning.

    PubMed

    Clarke, Shelley C; Harley, Shelton J; Hoyle, Simon D; Rice, Joel S

    2013-02-01

    Accurate assessment of shark population status is essential for conservation but is often constrained by limited and unreliable data. To provide a basis for improved management of shark resources, we analyzed a long-term record of species-specific catches, sizes, and sexes of sharks collected by onboard observers in the western and central Pacific Ocean from 1995 to 2010. Using generalized linear models, we estimated population-status indicators on the basis of catch rate and biological indicators of fishing pressure on the basis of median size to identify trends for blue (Prionace glauca), mako (Isurus spp.), oceanic whitetip (Carcharhinus longimanus), and silky (Carcharhinus falciformis) sharks. Standardized catch rates of longline fleets declined significantly for blue sharks in the North Pacific (by 5% per year [CI 2% to 8%]), for mako sharks in the North Pacific (by 7% per year [CI 3% to 11%]), and for oceanic whitetip sharks in tropical waters (by 17% per year [CI 14% to 20%]). Median lengths of silky and oceanic whitetip sharks decreased significantly in their core habitat, and almost all sampled silky sharks were immature. Our results are consistent with results of analyses of similar data sets. Combined, these results and evidence of targeted fishing for sharks in some regional fisheries heighten concerns for sustainable utilization, particularly for oceanic whitetip and North Pacific blue sharks. Regional regulations that prohibit shark finning (removal of fins and discarding of the carcass) were enacted in 2007 and are in many cases the only form of control on shark catches. However, there is little evidence of a reduction of finning in longline fisheries. In addition, silky and oceanic whitetip sharks are more frequently retained than finned, which suggests that even full implementation of and adherence to a finning prohibition may not substantially reduce mortality rates for these species. We argue that finning prohibitions divert attention from

  17. Methylmercury in dried shark fins and shark fin soup from American restaurants.

    PubMed

    Nalluri, Deepthi; Baumann, Zofia; Abercrombie, Debra L; Chapman, Demian D; Hammerschmidt, Chad R; Fisher, Nicholas S

    2014-10-15

    Consumption of meat from large predatory sharks exposes human consumers to high levels of toxic monomethylmercury (MMHg). There also have been claims that shark fins, and hence the Asian delicacy shark fin soup, contain harmful levels of neurotoxic chemicals in combination with MMHg, although concentrations of MMHg in shark fins are unknown. We measured MMHg in dried, unprocessed fins (n=50) of 13 shark species that occur in the international trade of dried shark fins as well as 50 samples of shark fin soup prepared by restaurants from around the United States. Concentrations of MMHg in fins ranged from 9 to 1720 ng/g dry wt. MMHg in shark fin soup ranged from <0.01 to 34 ng/mL, with MMHg averaging 62 ± 7% of total Hg. The highest concentrations of MMHg and total Hg were observed in both fins and soup from large, high trophic level sharks such as hammerheads (Sphyrna spp.). Consumption of a 240 mL bowl of shark fin soup containing the average concentration of MMHg (4.6 ng/mL) would result in a dose of 1.1 μg MMHg, which is 16% of the U.S. EPA's reference dose (0.1 μg MMHg per 1 kg per day in adults) of 7.4 μg per day for a 74 kg person. If consumed, the soup containing the highest measured MMHg concentration would exceed the reference dose by 17%. While shark fin soup represents a potentially important source of MMHg to human consumers, other seafood products, particularly the flesh of apex marine predators, contain much higher MMHg concentrations and can result in substantially greater exposures of this contaminant for people.

  18. Cretaceous source rocks in Pakistan

    SciTech Connect

    Kari, I.B. )

    1993-02-01

    Pakistan is located at the converging boundaries of the Indian, Arabian, and Eurasian plates. Evolution of this tectonic setting has provided an array of environmental habitats for deposition of petroleum source rocks and development of structural forms. The potential Cretaceous source rocks in Central and South Indus Basin are spread over an area of about 300,000 km[sup 2]. With 2% cutoff on Total Organic Carbon, the average source rock thickness is 30-50 m, which is estimated to have generated more than 200 billion bbl of oil equivalent. To date, production of more than 30,000 bbl of oil and about 1200 million ft[sup 3] of gas per day can be directly attributed to Cretaceous source. This basin was an area of extensional tectonics during the Lower to Middle Cretaceous associated with slightly restricted circulation of the sea waters at the north-western margin of Indian Plate. Lower Cretaceous source rocks (Sembar Formation) were deposited while the basin was opening up and anoxia was prevailing. Similarly Middle to Upper Cretaceous clastics were deposited in setting favorable for preservation of organic matter. The time and depth of burial of the Cretaceous source material and optimum thermal regime have provided the requisite maturation level for generation of hydrocarbons in the basin. Central Indus basin is characterized by Cretaceous source rocks mature for gas generation. However, in South Indus Basin Cretaceous source rocks lie within the oil window in some parts and have gone past it in others.

  19. Systemic Scuticociliatosis (Philasterides dicentrarchi) in sharks.

    PubMed

    Stidworthy, M F; Garner, M M; Bradway, D S; Westfall, B D; Joseph, B; Repetto, S; Guglielmi, E; Schmidt-Posthaus, H; Thornton, S M

    2014-05-01

    Scuticociliatosis is an economically important, frequently fatal disease of marine fish in aquaculture, caused by histophagous ciliated protozoa in the subclass Scuticociliatida of the phylum Ciliophora. A rapidly lethal systemic scuticociliate infection is described that affected aquarium-captive zebra sharks (Stegostoma fasciatum), Port Jackson sharks (Heterodontus portusjacksoni), and a Japanese horn shark (Heterodontus japonicus). Animals died unexpectedly or after a brief period of lethargy or behavioral abnormality. Gross findings included necrohemorrhagic hepatitis and increased volumes of celomic fluid. Histologically, 1 or more of a triad of necrotizing hepatitis, necrotizing meningoencephalitis, and thrombosing branchitis were seen in all cases, with necrotizing vasculitis or intravascular fibrinocellular thrombi. Lesions contained variably abundant invading ciliated protozoa. Molecular identification by polymerase chain reaction from formalin-fixed tissues identified these as the scuticociliate Philasterides dicentrarchi (syn. Miamiensis avidus), a novel and potentially emergent pathogen in sharks.

  20. Preferred conservation policies of shark researchers.

    PubMed

    Shiffman, David S; Hammerschlag, Neil

    2016-08-01

    There is increasing concern about the conservation status of sharks. However, the presence of numerous different (and potentially mutually exclusive) policies complicates management implementation and public understanding of the process. We distributed an online survey to members of the largest professional shark and ray research societies to assess member knowledge of and attitudes toward different conservation policies. Questions covered society member opinions on conservation and management policies, personal histories of involvement in advocacy and management, and perceptions of the approach of conservation nongovernmental organizations (NGOs) to shark conservation. One hundred and two surveys were completed (overall response rate 21%). Respondents considered themselves knowledgeable about and actively involved in conservation and management policy; a majority believed scientists have a responsibility to advocate for conservation (75%), and majorities have sent formal public comments to policymakers (54%) and included policy suggestions in their papers (53%). They believe sustainable shark fisheries are possible, are currently happening today (in a few places), and should be the goal instead of banning fisheries. Respondents were generally less supportive of newer limit-based (i.e., policies that ban exploitation entirely without a species-specific focus) conservation policy tools, such as shark sanctuaries and bans on the sale of shark fins, than of target-based fisheries management tools (i.e., policies that allow for sustainable harvest of species whose populations can withstand it), such as fishing quotas. Respondents were generally supportive of environmental NGO efforts to conserve sharks but raised concerns about some NGOs that they perceived as using incorrect information and focusing on the wrong problems. Our results show there is an ongoing debate in shark conservation and management circles relative to environmental policy on target-based natural

  1. Bright spots of sustainable shark fishing.

    PubMed

    Simpfendorfer, Colin A; Dulvy, Nicholas K

    2017-02-06

    Sharks, rays and chimeras (class Chondrichthyes; herein 'sharks') today face possibly the largest crisis of their 420 million year history. Tens of millions of sharks are caught and traded internationally each year, many populations are overfished to the point where global catch peaked in 2003, and a quarter of species have an elevated risk of extinction [1-3]. To some, the solution is to simply stop taking them from our oceans, or prohibit carriage, sale or trade in shark fins [4]. Approaches such as bans and alternative livelihoods for fishers (e.g. ecotourism) may play some role in controlling fishing mortality but will not solve this crisis because sharks are mostly taken as incidental catch and play an important role in food security [5-7]. Here, we show that moving to sustainable fishing is a feasible solution. In fact, approximately 9% of the current global catch of sharks, from at least 33 species with a wide range of life histories, is biologically sustainable, although not necessarily sufficiently managed.

  2. 77 FR 57022 - Drawbridge Operation Regulation; Shark River, Avon, NJ

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-17

    ... SECURITY Coast Guard 33 CFR Part 117 Drawbridge Operation Regulation; Shark River, Avon, NJ AGENCY: Coast..., and the S35 bridge, mile 0.9, all of which are across the Shark River (South Channel), at Avon Township, NJ. This deviation is necessary to facilitate stringer replacement on the Shark River...

  3. 78 FR 3836 - Drawbridge Operation Regulation; Shark River, Avon, NJ

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-17

    ... SECURITY Coast Guard 33 CFR Part 117 Drawbridge Operation Regulation; Shark River, Avon, NJ AGENCY: Coast... which are across the Shark River (South Channel), at Avon Township, NJ. This deviation is necessary to facilitate machinery replacement on the Shark River railroad bridge. This temporary deviation will allow...

  4. Resilience of Pacific pelagic fish across the Cretaceous/Palaeogene mass extinction

    NASA Astrophysics Data System (ADS)

    Sibert, Elizabeth C.; Hull, Pincelli M.; Norris, Richard D.

    2014-09-01

    Open-ocean ecosystems experienced profound disruptions to biodiversity and ecological structure during the Cretaceous/Palaeogene mass extinction about 66 million years ago. It has been suggested that during this mass extinction, a collapse of phytoplankton production rippled up the food chain, causing the wholesale loss of consumers and top predators. Pelagic fish represent a key trophic link between primary producers and top predators, and changes in their abundance provide a means to examine trophic relationships during extinctions. Here we analyse accumulation rates of microscopic fish teeth and shark dermal scales (ichthyoliths) in sediments from the Pacific Ocean and Tethys Sea across the Cretaceous/Palaeogene extinction to reconstruct fish abundance. We find geographic differences in post-disaster ecosystems. In the Tethys Sea, fish abundance fell abruptly at the Cretaceous/Palaeogene boundary and remained depressed for at least 3 million years. In contrast, fish abundance in the Pacific Ocean remained at or above pre-boundary levels for at least four million years following the mass extinction, despite marked extinctions in primary producers and other zooplankton consumers in this region. We suggest that the mass extinction did not produce a uniformly dead ocean or microbially dominated system. Instead, primary production, at least regionally, supported ecosystems with mid-trophic-level abundances similar to or above those of the Late Cretaceous.

  5. Something worth remembering: visual discrimination in sharks.

    PubMed

    Fuss, Theodora; Schluessel, Vera

    2015-03-01

    This study investigated memory retention capabilities of juvenile gray bamboo sharks (Chiloscyllium griseum) using two-alternative forced-choice experiments. The sharks had previously been trained in a range of visual discrimination tasks, such as distinguishing between squares, triangles and lines, and their corresponding optical illusions (i.e., the Kanizsa figures or Müller-Lyer illusions), and in the present study, we tested them for memory retention. Despite the absence of reinforcement, sharks remembered the learned information for a period of up to 50 weeks, after which testing was terminated. In fish, as in other vertebrates, memory windows vary in duration depending on species and task; while it may seem beneficial to retain some information for a long time or even indefinitely, other information may be forgotten more easily to retain flexibility and save energy. The results of this study indicate that sharks are capable of long-term memory within the framework of selected cognitive skills. These could aid sharks in activities such as food retrieval, predator avoidance, mate choice or habitat selection and therefore be worth being remembered for extended periods of time. As in other cognitive tasks, intraspecific differences reflected the behavioral breadth of the species.

  6. Opportunity Studies Bait in Shark's Cage

    NASA Technical Reports Server (NTRS)

    2004-01-01

    In its 49th sol on Mars, NASA's Opportunity had nearly concluded its scientific examination of the extreme southwestern end of the outcrop in Meridiani Planum. In the 'Shark's Cage' area of the neighborhood called 'Shoemaker's Patio,' featured in this image from the front hazard avoidance camera, Opportunity deployed its arm to study the features called 'Shark's Tooth,' 'Shark Pellets,' and 'Lamination.' 'Shark's Tooth' is a piece of the unusual red rind that appears to fill cracks in the outcrop. This rind may be some kind of chemical alteration of the rocks. 'Shark Pellets' is an area of soil that was under investigation as part of the crater soil survey. 'Lamination' is a target with very thin layers that resemble uniform pages in a book, an indication of how the sediments were deposited. A final experiment in this area will be attempted on sol 51. Opportunity's front left wheel will 'scuff' the rock called 'Carousel.' 'Scuffing' involves scraping the rock with one wheel while holding all the others still. This experiment essentially turns the rover wheels into tools, to try and determine the hardness of the target rock.

  7. 75 FR 67251 - Atlantic Highly Migratory Species; Inseason Action To Close the Commercial Blacknose Shark and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-02

    ... Species; Inseason Action To Close the Commercial Blacknose Shark and Non-Blacknose Small Coastal Shark... blacknose shark and non- blacknose small coastal shark (SCS) fisheries. This action is necessary because landings for the 2010 blacknose shark fishing season are projected to have reached at least 80 percent...

  8. 50 CFR 635.24 - Commercial retention limits for sharks, swordfish, and BAYS tunas.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... storage of silky sharks, oceanic whitetip sharks, and scalloped, smooth, and great hammerhead sharks is... 50 Wildlife and Fisheries 12 2013-10-01 2013-10-01 false Commercial retention limits for sharks... Management Measures § 635.24 Commercial retention limits for sharks, swordfish, and BAYS tunas. The...

  9. 50 CFR 635.24 - Commercial retention limits for sharks, swordfish, and BAYS tunas.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... storage of silky sharks, oceanic whitetip sharks, and scalloped, smooth, and great hammerhead sharks is... 50 Wildlife and Fisheries 12 2014-10-01 2014-10-01 false Commercial retention limits for sharks... Management Measures § 635.24 Commercial retention limits for sharks, swordfish, and BAYS tunas. The...

  10. Cross matching of blood in carcharhiniform, lamniform, and orectolobiform sharks.

    PubMed

    Hadfield, Catherine A; Haines, Ashley N; Clayton, Leigh A; Whitaker, Brent R

    2010-09-01

    The transfusion of whole blood in elasmobranchs could provide cardiovascular support following hemorrhage. Since donor and recipient compatibility is not known, a technique was established to allow cross matching of red blood cells and serum in sharks. Cross matching was carried out among 19 individuals from seven species: the nurse shark (Ginglymostoma cirratum), sandbar shark (Carcharhinus plumbeus), sandtiger shark (Carcharias taurus), white-spotted bamboo shark (Chiloscyllium plagiosum), brown-banded bamboo shark (Chiloscyllium punctatum), zebra shark (Stegostoma fasciatum), and spotted wobbegong (Orectolobus maculatus). Negative cross-matches showed no agglutination or hemolysis, suggesting that donor and recipient would be compatible. Cross-matches between conspecifics were all negative (sandbar, sandtiger, nurse, and white-spotted bamboo sharks). All cross-matches between sandbar and sandtiger sharks were also negative. Positive crossmatches consisted of agglutination or hemolysis of red blood cells, suggesting that the donor and recipient would be incompatible. Strong positive reactions occurred, for example, with red blood cells from sandtiger and sandbar sharks and serum from nurse sharks. Cross matching should be carried out in elasmobranchs prior to any blood transfusion.

  11. Kinematics and critical swimming speed of juvenile scalloped hammerhead sharks

    PubMed

    Lowe

    1996-01-01

    Kinematics and critical swimming speed (Ucrit) of juvenile scalloped hammerhead sharks Sphyrna lewini were measured in a Brett-type flume (635 l). Kinematic parameters were also measured in sharks swimming in a large pond for comparison with those of sharks swimming in the flume. Sharks in the flume exhibited a mean Ucrit of 65±11 cm s-1 (± s.d.) or 1.17±0.21 body lengths per second (L s-1), which are similar to values for other species of sharks. In both the flume and pond, tailbeat frequency (TBF) and stride length (LS) increased linearly with increases in relative swimming speed (Urel=body lengths traveled per second). In the flume, tailbeat amplitude (TBA) decreased with increasing speed whereas TBA did not change with speed in the pond. Differences in TBF and LS between sharks swimming in the flume and the pond decreased with increases in Urel. Sharks swimming at slow speeds (e.g. 0.55 L s-1) in the pond had LS 19 % longer and TBF 21 % lower than sharks in the flume at the same Urel. This implies that sharks in the flume expended more energy while swimming at comparable velocities. Comparative measurements of swimming kinematics from sharks in the pond can be used to correct for effects of the flume on shark swimming kinematics and energetics.

  12. Biological responses of sharks to ocean acidification.

    PubMed

    Rosa, Rui; Rummer, Jodie L; Munday, Philip L

    2017-03-01

    Sharks play a key role in the structure of marine food webs, but are facing major threats due to overfishing and habitat degradation. Although sharks are also assumed to be at relatively high risk from climate change due to a low intrinsic rate of population growth and slow rates of evolution, ocean acidification (OA) has not, until recently, been considered a direct threat. New studies have been evaluating the potential effects of end-of-century elevated CO2 levels on sharks and their relatives' early development, physiology and behaviour. Here, we review those findings and use a meta-analysis approach to quantify the overall direction and magnitude of biological responses to OA in the species of sharks that have been investigated to date. While embryo survival and development time are mostly unaffected by elevated CO2, there are clear effects on body condition, growth, aerobic potential and behaviour (e.g. lateralization, hunting and prey detection). Furthermore, studies to date suggest that the effects of OA could be as substantial as those due to warming in some species. A major limitation is that all past studies have involved relatively sedentary, benthic sharks that are capable of buccal ventilation-no studies have investigated pelagic sharks that depend on ram ventilation. Future research should focus on species with different life strategies (e.g. pelagic, ram ventilators), climate zones (e.g. polar regions), habitats (e.g. open ocean), and distinct phases of ontogeny in order to fully predict how OA and climate change will impact higher-order predators and therefore marine ecosystem dynamics.

  13. Evolution of the trypanorhynch tapeworms: parasite phylogeny supports independent lineages of sharks and rays.

    PubMed

    Olson, Peter D; Caira, Janine N; Jensen, Kirsten; Overstreet, Robin M; Palm, Harry W; Beveridge, Ian

    2010-02-01

    rajiform batoids and carcharhiniform sharks. This fundamental split provides independent support for rejecting the notion that rays are derived sharks, and thus supports the most recent molecular phylogenies of the Neoselachii. Beyond the basal split between shark- and ray-inhabiting lineages, no pattern was found to suggest that the trypanorhynchs have closely tracked the evolutionary histories of these host lineages, but instead, it appears that host-switching has been common and that the subsequent evolution of the parasites has been ecologically driven primarily through overlap in the niches of their shark and ray hosts. Using a relaxed molecular clock model calibrated by means of host fossil data, the ray-inhabiting lineage is estimated to have diversified around the Jurassic-Cretaceous boundary, whereas the shark-inhabiting lineage is estimated to have diversified later, in the Middle Cretaceous. Although the large error associated with the estimated divergence dates prevents robust conclusions from being drawn, the dates are nevertheless found to be consistent in a relative sense with the origins of their major hosts groups. The erection and definition of the suborders Trypanobatoida and Trypanoselachoida, for the major clades of trypanorhynchs parasitizing primarily rays and sharks, respectively, is proposed for the two primary lineages recovered here.

  14. Fatal tiger shark, Galeocerdo cuvier attack in New Caledonia erroneously ascribed to great white shark, Carcharodon carcharias.

    PubMed

    Tirard, Philippe; Maillaud, Claude; Borsa, Philippe

    2015-07-01

    To understand the causes and patterns of shark attacks on humans, accurate identification of the shark species involved is necessary. Often, the only reliable evidence for this comes from the characteristics of the wounds exhibited by the victim. The present case report is intended as a reappraisal of the Luengoni, 2007 case (International Shark Attack File no. 4299) where a single shark bite provoked the death of a swimmer by haemorrhagic shock. Our examination of the wounds on the body of the victim, here documented by so-far unpublished photographic evidence, determined that the shark possessed large and homodontous jaws. This demonstrates that the attacker was a tiger shark, not a great white shark as previously published.

  15. Monogenoid infection of neonatal and older juvenile lemon sharks, Negaprion brevirostris (Carcharhinidae), in a shark nursery.

    PubMed

    Young, Joy M; Frasca, Salvatore; Gruber, Samuel H; Benz, George W

    2013-12-01

    Fifty lemon sharks, Negaprion brevirostris , were captured in a shallow, mangrove-fringed shark nursery at Bimini, Bahamas and examined for the presence of skin-dwelling ectoparasitic monogenoids (Monogenoidea). Sixteen sharks were infected by Dermophthirius nigrellii (Microbothriidae); the youngest host was estimated to be 3- to 4-wk-old. Infection prevalence, mean intensity, and median intensity (0.32, 2.63, and 2.0, respectively, for all sharks) were not significantly different between neonates (estimated ages 3- to 10-wk-old) and non-neonatal juveniles (estimated ages 1- to 4-yr-old), suggesting that soon after parturition lemon sharks acquire infection levels of D. nigrellii matching those of juvenile conspecifics. Monogenoids were only found on the trailing portion of the first and second dorsal fins and upper lobe of the caudal fin. The prevalence of D. nigrellii was highest on the first dorsal fin; however, the mean and median intensities of D. nigrellii were similar between fins in all but 1 case. These results raise important husbandry implications regarding the practice of preferentially seeking neonatal and other small lemon sharks for captivity.

  16. 77 FR 38775 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-29

    ... National Oceanic and Atmospheric Administration RIN 0648-XC042 Schedules for Atlantic Shark Identification... Shark Identification workshop originally scheduled for August 9, 2012, in Rosenberg, TX, has been... 77471. The July and September workshop dates remain unchanged. Atlantic Shark Identification...

  17. From Jaws to Laws--Now the Big, Bad Shark Needs Protection from Us.

    ERIC Educational Resources Information Center

    Conniff, Richard

    1993-01-01

    Discusses the National Marine Fisheries Service plan to protect sharks from the recent expansion in the shark fishing industry. Contains information about different shark species and their behavior. (MDH)

  18. 76 FR 57709 - Atlantic Highly Migratory Species; Atlantic Shark Management Measures

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-16

    ... Species; Atlantic Shark Management Measures AGENCY: National Marine Fisheries Service (NMFS), National... Atlantic shark landings; request for comments. SUMMARY: This notice announces the National Marine Fisheries... Atlantic shark fisheries. NMFS published an Advanced Notice of Proposed Rulemaking (ANPR) on September...

  19. Reef sharks: recent advances in ecological understanding to inform conservation.

    PubMed

    Osgood, G J; Baum, J K

    2015-12-01

    Sharks are increasingly being recognized as important members of coral-reef communities, but their overall conservation status remains uncertain. Nine of the 29 reef-shark species are designated as data deficient in the IUCN Red List, and three-fourths of reef sharks had unknown population trends at the time of their assessment. Fortunately, reef-shark research is on the rise. This new body of research demonstrates reef sharks' high site restriction, fidelity and residency on coral reefs, their broad trophic roles connecting reef communities and their high population genetic structure, all information that should be useful for their management and conservation. Importantly, recent studies on the abundance and population trends of the three classic carcharhinid reef sharks (grey reef shark Carcharhinus amblyrhynchos, blacktip reef shark Carcharhinus melanopterus and whitetip reef shark Triaenodon obesus) may contribute to reassessments identifying them as more vulnerable than currently realized. Because over half of the research effort has focused on only these three reef sharks and the nurse shark Ginglymostoma cirratum in only a few locales, there remain large taxonomic and geographic gaps in reef-shark knowledge. As such, a large portion of reef-shark biodiversity remains uncharacterized despite needs for targeted research identified in their red list assessments. A research agenda for the future should integrate abundance, life history, trophic ecology, genetics, habitat use and movement studies, and expand the breadth of such research to understudied species and localities, in order to better understand the conservation requirements of these species and to motivate effective conservation solutions.

  20. Shark Attack! Sinking Your Teeth into Anatomy.

    ERIC Educational Resources Information Center

    House, Herbert

    2002-01-01

    Presents a real life shark attack story and studies arm reattachment surgery to teach human anatomy. Discusses how knowledge of anatomy can be put to use in the real world and how the arm functions. Includes teaching notes and suggestions for classroom management. (YDS)

  1. Semiconductor gel in shark sense organs?

    PubMed

    Fields, R Douglas; Fields, Kyle D; Fields, Melanie C

    2007-10-22

    Sharks can sense bioelectric fields of prey and other animals in seawater using an extraordinary system of sense organs (ampullae of Lorenzini) [R.D. Fields, The shark's electric sense. Sci. Am. 297 (2007) 74-81]. A recent study reported that these sense organs also enable sharks to locate prey-rich thermal fronts using a novel mode of temperature reception without ion channels. The study reported that gel extracted from the organs operates as a thermoelectric semiconductor, generating electricity when it is heated or cooled [B.R. Brown, Neurophysiology: sensing temperature without ion channels, Nature 421 (2003) 495]. Here we report biophysical studies that call into question this mechanism of sensory transduction. Our experiments indicate that the material exhibits no unusual thermoelectric or electromechanical properties, and that the thermoelectric response is an artifact caused by temperature effects on the measurement electrodes. No response is seen when non-metallic electrodes (carbon or salt bridges) are used, and ordinary seawater produces the same effect as shark organ gel when silver wire electrodes are used. These data are consistent with the voltages arising from electrochemical electrode potentials rather generated intrinsically within the sample. This new evidence, together with the anatomy of the organs and behavioral studies in the literature, best support the conclusion that the biological function of these sense organs is to detect electric fields.

  2. 75 FR 22103 - Atlantic Coastal Fisheries Cooperative Management Act Provisions; Atlantic Coastal Shark Fishery

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-27

    ..., bull, lemon, nurse, scalloped hammerhead, great hammerhead, and smooth hammerhead sharks), pelagic... kilometers) from shore: Commission large coastal sharks (silky, tiger, blacktip, spinner, bull, lemon,...

  3. Seasonal and long-term changes in relative abundance of bull sharks from a tourist shark feeding site in Fiji.

    PubMed

    Brunnschweiler, Juerg M; Baensch, Harald

    2011-01-27

    Shark tourism has become increasingly popular, but remains controversial because of major concerns originating from the need of tour operators to use bait or chum to reliably attract sharks. We used direct underwater sampling to document changes in bull shark Carcharhinus leucas relative abundance at the Shark Reef Marine Reserve, a shark feeding site in Fiji, and the reproductive cycle of the species in Fijian waters. Between 2003 and 2009, the total number of C. leucas counted on each day ranged from 0 to 40. Whereas the number of C. leucas counted at the feeding site increased over the years, shark numbers decreased over the course of a calendar year with fewest animals counted in November. Externally visible reproductive status information indicates that the species' seasonal departure from the feeding site may be related to reproductive activity.

  4. Seasonal and Long-Term Changes in Relative Abundance of Bull Sharks from a Tourist Shark Feeding Site in Fiji

    PubMed Central

    Brunnschweiler, Juerg M.; Baensch, Harald

    2011-01-01

    Shark tourism has become increasingly popular, but remains controversial because of major concerns originating from the need of tour operators to use bait or chum to reliably attract sharks. We used direct underwater sampling to document changes in bull shark Carcharhinus leucas relative abundance at the Shark Reef Marine Reserve, a shark feeding site in Fiji, and the reproductive cycle of the species in Fijian waters. Between 2003 and 2009, the total number of C. leucas counted on each day ranged from 0 to 40. Whereas the number of C. leucas counted at the feeding site increased over the years, shark numbers decreased over the course of a calendar year with fewest animals counted in November. Externally visible reproductive status information indicates that the species' seasonal departure from the feeding site may be related to reproductive activity. PMID:21346792

  5. Thresher Sharks Use Tail-Slaps as a Hunting Strategy

    PubMed Central

    Oliver, Simon P.; Turner, John R.; Gann, Klemens; Silvosa, Medel; D'Urban Jackson, Tim

    2013-01-01

    The hunting strategies of pelagic thresher sharks (Alopias pelagicus) were investigated at Pescador Island in the Philippines. It has long been suspected that thresher sharks hunt with their scythe-like tails but the kinematics associated with the behaviour in the wild are poorly understood. From 61 observations recorded by handheld underwater video camera between June and October 2010, 25 thresher shark shunting events were analysed. Thresher sharks employed tail-slaps to debilitate sardines at all times of day. Hunting events comprised preparation, strike, wind-down recovery and prey item collection phases, which occurred sequentially. Preparation phases were significantly longer than the others, presumably to enable a shark to windup a tail-slap. Tail-slaps were initiated by an adduction of the pectoral fins, a manoeuvre that changed a thresher shark's pitch promoting its posterior region to lift rapidly, and stall its approach. Tail-slaps occurred with such force that they may have caused dissolved gas to diffuse out of the water column forming bubbles. Thresher sharks were able to consume more than one sardine at a time, suggesting that tail-slapping is an effective foraging strategy for hunting schooling prey. Pelagic thresher sharks appear to pursue sardines opportunistically by day and night, which may make them vulnerable to fisheries. Alopiids possess specialist pectoral and caudal fins that are likely to have evolved, at least in part, for tail-slapping. The evidence is now clear; thresher sharks really do hunt with their tails. PMID:23874415

  6. Survival of the Stillest: Predator Avoidance in Shark Embryos

    PubMed Central

    Kempster, Ryan M.; Hart, Nathan S.; Collin, Shaun P.

    2013-01-01

    Sharks use highly sensitive electroreceptors to detect the electric fields emitted by potential prey. However, it is not known whether prey animals are able to modulate their own bioelectrical signals to reduce predation risk. Here, we show that some shark (Chiloscyllium punctatum) embryos can detect predator-mimicking electric fields and respond by ceasing their respiratory gill movements. Despite being confined to the small space within the egg case, where they are vulnerable to predators, embryonic sharks are able to recognise dangerous stimuli and react with an innate avoidance response. Knowledge of such behaviours, may inform the development of effective shark repellents. PMID:23326342

  7. Thresher sharks use tail-slaps as a hunting strategy.

    PubMed

    Oliver, Simon P; Turner, John R; Gann, Klemens; Silvosa, Medel; D'Urban Jackson, Tim

    2013-01-01

    The hunting strategies of pelagic thresher sharks (Alopias pelagicus) were investigated at Pescador Island in the Philippines. It has long been suspected that thresher sharks hunt with their scythe-like tails but the kinematics associated with the behaviour in the wild are poorly understood. From 61 observations recorded by handheld underwater video camera between June and October 2010, 25 thresher shark shunting events were analysed. Thresher sharks employed tail-slaps to debilitate sardines at all times of day. Hunting events comprised preparation, strike, wind-down recovery and prey item collection phases, which occurred sequentially. Preparation phases were significantly longer than the others, presumably to enable a shark to windup a tail-slap. Tail-slaps were initiated by an adduction of the pectoral fins, a manoeuvre that changed a thresher shark's pitch promoting its posterior region to lift rapidly, and stall its approach. Tail-slaps occurred with such force that they may have caused dissolved gas to diffuse out of the water column forming bubbles. Thresher sharks were able to consume more than one sardine at a time, suggesting that tail-slapping is an effective foraging strategy for hunting schooling prey. Pelagic thresher sharks appear to pursue sardines opportunistically by day and night, which may make them vulnerable to fisheries. Alopiids possess specialist pectoral and caudal fins that are likely to have evolved, at least in part, for tail-slapping. The evidence is now clear; thresher sharks really do hunt with their tails.

  8. Social learning in juvenile lemon sharks, Negaprion brevirostris.

    PubMed

    Guttridge, Tristan L; van Dijk, Sander; Stamhuis, Eize J; Krause, Jens; Gruber, Samuel H; Brown, Culum

    2013-01-01

    Social learning is taxonomically widespread and can provide distinct behavioural advantages, such as in finding food or avoiding predators more efficiently. Although extensively studied in bony fishes, no such empirical evidence exists for cartilaginous fishes. Our aim in this study was to experimentally investigate the social learning capabilities of juvenile lemon sharks, Negaprion brevirostris. We designed a novel food task, where sharks were required to enter a start zone and subsequently make physical contact with a target in order to receive a food reward. Naive sharks were then able to interact with and observe (a) pre-trained sharks, that is, 'demonstrators', or (b) sharks with no previous experience, that is, 'sham demonstrators'. On completion, observer sharks were then isolated and tested individually in a similar task. During the exposure phase observers paired with 'demonstrator' sharks performed a greater number of task-related behaviours and made significantly more transitions from the start zone to the target, than observers paired with 'sham demonstrators'. When tested in isolation, observers previously paired with 'demonstrator' sharks completed a greater number of trials and made contact with the target significantly more often than observers previously paired with 'sham demonstrators'. Such experience also tended to result in faster overall task performance. These results indicate that juvenile lemon sharks, like numerous other animals, are capable of using socially derived information to learn about novel features in their environment. The results likely have important implications for behavioural processes, ecotourism and fisheries.

  9. Shark cartilage, cancer and the growing threat of pseudoscience.

    PubMed

    Ostrander, Gary K; Cheng, Keith C; Wolf, Jeffrey C; Wolfe, Marilyn J

    2004-12-01

    The promotion of crude shark cartilage extracts as a cure for cancer has contributed to at least two significant negative outcomes: a dramatic decline in shark populations and a diversion of patients from effective cancer treatments. An alleged lack of cancer in sharks constitutes a key justification for its use. Herein, both malignant and benign neoplasms of sharks and their relatives are described, including previously unreported cases from the Registry of Tumors in Lower Animals, and two sharks with two cancers each. Additional justifications for using shark cartilage are illogical extensions of the finding of antiangiogenic and anti-invasive substances in cartilage. Scientific evidence to date supports neither the efficacy of crude cartilage extracts nor the ability of effective components to reach and eradicate cancer cells. The fact that people think shark cartilage consumption can cure cancer illustrates the serious potential impacts of pseudoscience. Although components of shark cartilage may work as a cancer retardant, crude extracts are ineffective. Efficiencies of technology (e.g., fish harvesting), the power of mass media to reach the lay public, and the susceptibility of the public to pseudoscience amplifies the negative impacts of shark cartilage use. To facilitate the use of reason as the basis of public and private decision-making, the evidence-based mechanisms of evaluation used daily by the scientific community should be added to the training of media and governmental professionals. Increased use of logical, collaborative discussion will be necessary to ensure a sustainable future for man and the biosphere.

  10. Collapse and conservation of shark populations in the Northwest Atlantic.

    PubMed

    Baum, Julia K; Myers, Ransom A; Kehler, Daniel G; Worm, Boris; Harley, Shelton J; Doherty, Penny A

    2003-01-17

    Overexploitation threatens the future of many large vertebrates. In the ocean, tunas and sea turtles are current conservation concerns because of this intense pressure. The status of most shark species, in contrast, remains uncertain. Using the largest data set in the Northwest Atlantic, we show rapid large declines in large coastal and oceanic shark populations. Scalloped hammerhead, white, and thresher sharks are each estimated to have declined by over 75% in the past 15 years. Closed-area models highlight priority areas for shark conservation, and the need to consider effort reallocation and site selection if marine reserves are to benefit multiple threatened species.

  11. Predominance of genetic monogamy by females in a hammerhead shark, Sphyrna tiburo: implications for shark conservation.

    PubMed

    Chapman, Demian D; Prodöhl, Paulo A; Gelsleichter, James; Manire, Charles A; Shivji, Mahmood S

    2004-07-01

    There is growing interest in the mating systems of sharks and their relatives (Class Chondrichthyes) because these ancient fishes occupy a key position in vertebrate phylogeny and are increasingly in need of conservation due to widespread overexploitation. Based on precious few genetic and field observational studies, current speculation is that polyandrous mating strategies and multiple paternity may be common in sharks as they are in most other vertebrates. Here, we test this hypothesis by examining the genetic mating system of the bonnethead shark, Sphyrna tiburo, using microsatellite DNA profiling of 22 litters (22 mothers, 188 embryos genotyped at four polymorphic loci) obtained from multiple locations along the west coast of Florida. Contrary to expectations based on the ability of female S. tiburo to store sperm, the social nature of this species and the 100% multiple paternity observed in two other coastal shark species, over 81% of sampled bonnethead females produced litters sired by a single male (i.e. genetic monogamy). When multiple paternity occurred in S. tiburo, there was an indication of increased incidence in larger mothers with bigger litters. Our data suggest that sharks may exhibit complex genetic mating systems with a high degree of interspecific variability, and as a result some species may be more susceptible to loss of genetic variation in the face of escalating fishing pressure. Based on these findings, we suggest that knowledge of elasmobranch mating systems should be an important component of conservation and management programmes for these heavily exploited species.

  12. Unprovoked fatal shark attack in Lifou Island (Loyalty Islands, New Caledonia, South Pacific) by a great white shark, Carcharodon carcharias.

    PubMed

    Clua, Eric; Séret, Bernard

    2010-09-01

    The case of a fatal, unprovoked shark attack is reported and analyzed. The incident took place on the 30th of September 2007, in the lagoon of Luengoni Bay, Lifou Island (Loyalty Islands, New Caledonia). A young French woman who was snorkeling was severely bitten on the right thigh and died of hemorrhage. An analysis based in particular on the size and color of the shark, the characteristics of the wounds, and the behavior of the shark before and after the bite suggests that the aggressor was a great white shark, Carcharodon carcharias.

  13. Maneuvering in juvenile carcharhinid and sphyrnid sharks: the role of the hammerhead shark cephalofoil.

    PubMed

    Kajiura, Stephen M; Forni, Jesica B; Summers, Adam P

    2003-01-01

    The peculiar head morphology of hammerhead sharks has spawned a variety of untested functional hypotheses. One of the most intuitively appealing ideas is that the anterior foil acts, as in canard-winged aircraft, to increase maneuverability. We tested this hypothesis by determining whether juveniles of two hammerhead species (Sphyrna tiburo and S. lewini) turn more sharply, more often, and with greater velocity than a juvenile carcharhinid shark (Carcharhinus plumbeus). Although the hammerheads were more maneuverable, further investigation revealed that they do not roll their body during turns, suggesting that the cephalofoil does not act as a steering wing. We also show that hammerhead sharks demonstrate greater lateral flexure in a turn than carcharhinids, and that this flexibility may be due to cross sectional shape rather than number of vertebrae.

  14. Re-creating missing population baselines for Pacific reef sharks.

    PubMed

    Nadon, Marc O; Baum, Julia K; Williams, Ivor D; McPherson, Jana M; Zgliczynski, Brian J; Richards, Benjamin L; Schroeder, Robert E; Brainard, Russell E

    2012-06-01

    Sharks and other large predators are scarce on most coral reefs, but studies of their historical ecology provide qualitative evidence that predators were once numerous in these ecosystems. Quantifying density of sharks in the absence of humans (baseline) is, however, hindered by a paucity of pertinent time-series data. Recently researchers have used underwater visual surveys, primarily of limited spatial extent or nonstandard design, to infer negative associations between reef shark abundance and human populations. We analyzed data from 1607 towed-diver surveys (>1 ha transects surveyed by observers towed behind a boat) conducted at 46 reefs in the central-western Pacific Ocean, reefs that included some of the world's most pristine coral reefs. Estimates of shark density from towed-diver surveys were substantially lower (<10%) than published estimates from surveys along small transects (<0.02 ha), which is not consistent with inverted biomass pyramids (predator biomass greater than prey biomass) reported by other researchers for pristine reefs. We examined the relation between the density of reef sharks observed in towed-diver surveys and human population in models that accounted for the influence of oceanic primary productivity, sea surface temperature, reef area, and reef physical complexity. We used these models to estimate the density of sharks in the absence of humans. Densities of gray reef sharks (Carcharhinus amblyrhynchos), whitetip reef sharks (Triaenodon obesus), and the group "all reef sharks" increased substantially as human population decreased and as primary productivity and minimum sea surface temperature (or reef area, which was highly correlated with temperature) increased. Simulated baseline densities of reef sharks under the absence of humans were 1.1-2.4/ha for the main Hawaiian Islands, 1.2-2.4/ha for inhabited islands of American Samoa, and 0.9-2.1/ha for inhabited islands in the Mariana Archipelago, which suggests that density of reef sharks

  15. An investigation into ciguatoxin bioaccumulation in sharks.

    PubMed

    Meyer, Lauren; Capper, Angela; Carter, Steve; Simpfendorfer, Colin

    2016-09-01

    Ciguatoxins (CTXs) produced by benthic Gambierdiscus dinoflagellates, readily biotransform and bioaccumulate in food chains ultimately bioconcentrating in high-order, carnivorous marine species. Certain shark species, often feeding at, or near the top of the food-chain have the ability to bioaccumulate a suite of toxins, from both anthropogenic and algal sources. As such, these apex predators are likely sinks for CTXs. This assumption, in conjunction with anecdotal knowledge of poisoning incidents, several non-specific feeding trials whereby various terrestrial animals were fed suspect fish flesh, and a single incident in Madagascar in 1994, have resulted in the widespread acceptance that sharks may accumulate CTXs. This prompted a study to investigate original claims within the literature, as well as investigate CTX bioaccumulation in the muscle and liver of 22 individual sharks from nine species, across four locations along the east coast of Australia. Utilizing an updated ciguatoxin extraction method with HPLC-MS/MS, we were unable to detect P-CTX-1, P-CTX-2 or P-CTX-3, the three primary CTX congeners, in muscle or liver samples. We propose four theories to address this finding: (1) to date, methods have been optimized for teleost species and may not be appropriate for elasmobranchs, or the CTXs may be below the limit of detection; (2) CTX may be biotransformed into elasmobranch-specific congeners as a result of unique metabolic properties; (3) 22 individuals may be an inadequate sample size given the rare occurrence of high-order ciguatoxic organisms and potential for CTX depuration; and (4) the ephemeral nature and inconsistent toxin profiles of Gambierdiscus blooms may have undermined our classifications of certain areas as CTX hotspots. These results, in combination with the lack of clarity within the literature, suggest that ciguatoxin bioaccumulation in sharks remains elusive, and warrants further investigation to determine the dynamics of toxin production

  16. Vertebrate paleontological exploration of the Upper Cretaceous succession in the Dakhla and Kharga Oases, Western Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Sallam, Hesham M.; O'Connor, Patrick M.; Kora, Mahmoud; Sertich, Joseph J. W.; Seiffert, Erik R.; Faris, Mahmoud; Ouda, Khaled; El-Dawoudi, Iman; Saber, Sara; El-Sayed, Sanaa

    2016-05-01

    The Campanian and Maastrichtian stages are very poorly documented time intervals in Africa's record of terrestrial vertebrate evolution. Upper Cretaceous deposits exposed in southern Egypt, near the Dakhla and Kharga Oases in the Western Desert, preserve abundant vertebrate fossils in nearshore marine environments, but have not yet been the focus of intensive collection and description. Our recent paleontological work in these areas has resulted in the discovery of numerous new vertebrate fossil-bearing localities within the middle Campanian Qusier Formation and the upper Campanian-lower Maastrichtian Duwi Formation. Fossil remains recovered from the Campanian-aged Quseir Formation include sharks, rays, actinopterygian and sarcopterygian fishes, turtles, and rare terrestrial archosaurians, including some of the only dinosaurs known from this interval on continental Africa. The upper Campanian/lower Maastrichtian Duwi Formation preserves sharks, sawfish, actinopterygians, and marine reptiles (mosasaurs and plesiosaurs). Notably absent from these collections are representatives of Mammalia and Avialae, both of which remain effectively undocumented in the Upper Cretaceous rocks of Africa and Arabia. New age constraints on the examined rock units is provided by 23 nannofossil taxa, some of which are reported from the Duwi Formation for the first time. Fossil discoveries from rock units of this age are essential for characterizing the degree of endemism that may have developed as the continent became increasingly tectonically isolated from the rest of Gondwana, not to mention for fully evaluating origin and diversification hypotheses of major modern groups of vertebrates (e.g., crown birds, placental mammals).

  17. Skeletogenesis in the swell shark Cephaloscyllium ventriosum.

    PubMed

    Eames, B Frank; Allen, Nancy; Young, Jonathan; Kaplan, Angelo; Helms, Jill A; Schneider, Richard A

    2007-05-01

    Extant chondrichthyans possess a predominantly cartilaginous skeleton, even though primitive chondrichthyans produced bone. To gain insights into this peculiar skeletal evolution, and in particular to evaluate the extent to which chondrichthyan skeletogenesis retains features of an osteogenic programme, we performed a histological, histochemical and immunohistochemical analysis of the entire embryonic skeleton during development of the swell shark Cephaloscyllium ventriosum. Specifically, we compared staining properties among various mineralizing tissues, including neural arches of the vertebrae, dermal tissues supporting oral denticles and Meckel's cartilage of the lower jaw. Patterns of mineralization were predicted by spatially restricted alkaline phosphatase activity earlier in development. Regarding evidence for an osteogenic programme in extant sharks, a mineralized tissue in the perichondrium of C. ventriosum neural arches, and to a lesser extent a tissue supporting the oral denticle, displayed numerous properties of bone. Although we uncovered many differences between tissues in Meckel's cartilage and neural arches of C. ventriosum, both elements impart distinct tissue characteristics to the perichondral region. Considering the evolution of osteogenic processes, shark skeletogenesis may illuminate the transition from perichondrium to periosteum, which is a major bone-forming tissue during the process of endochondral ossification.

  18. Skeletogenesis in the swell shark Cephaloscyllium ventriosum

    PubMed Central

    Eames, B Frank; Allen, Nancy; Young, Jonathan; Kaplan, Angelo; Helms, Jill A; Schneider, Richard A

    2007-01-01

    Extant chondrichthyans possess a predominantly cartilaginous skeleton, even though primitive chondrichthyans produced bone. To gain insights into this peculiar skeletal evolution, and in particular to evaluate the extent to which chondrichthyan skeletogenesis retains features of an osteogenic programme, we performed a histological, histochemical and immunohistochemical analysis of the entire embryonic skeleton during development of the swell shark Cephaloscyllium ventriosum. Specifically, we compared staining properties among various mineralizing tissues, including neural arches of the vertebrae, dermal tissues supporting oral denticles and Meckel's cartilage of the lower jaw. Patterns of mineralization were predicted by spatially restricted alkaline phosphatase activity earlier in development. Regarding evidence for an osteogenic programme in extant sharks, a mineralized tissue in the perichondrium of C. ventriosum neural arches, and to a lesser extent a tissue supporting the oral denticle, displayed numerous properties of bone. Although we uncovered many differences between tissues in Meckel's cartilage and neural arches of C. ventriosum, both elements impart distinct tissue characteristics to the perichondral region. Considering the evolution of osteogenic processes, shark skeletogenesis may illuminate the transition from perichondrium to periosteum, which is a major bone-forming tissue during the process of endochondral ossification. PMID:17451531

  19. 76 FR 64074 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-17

    ... National Oceanic and Atmospheric Administration RIN 0648-XA670 Schedules for Atlantic Shark Identification... Shark Identification workshop scheduled for November 17, 2011, in Charleston, SC, has been changed. This.... Atlantic Shark Identification workshops are mandatory for Atlantic Shark Dealer permit holders or...

  20. 75 FR 44938 - Atlantic Coastal Fisheries Cooperative Management Act Provisions; Atlantic Coastal Shark Fishery

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-30

    ... 0648-XX28 Atlantic Coastal Fisheries Cooperative Management Act Provisions; Atlantic Coastal Shark... cancellation of the Federal moratorium on fishing for Atlantic coastal sharks in the State waters of New Jersey... Sharks (Coastal Shark Plan). DATES: Effective July 30, 2010. ADDRESSES: Emily Menashes, Acting...

  1. 77 FR 31562 - Atlantic Highly Migratory Species; Atlantic Shark Management Measures

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-29

    ... Species; Atlantic Shark Management Measures AGENCY: National Marine Fisheries Service (NMFS), National... considering the inclusion of Gulf of Mexico blacktip sharks in an amendment to the 2006 Consolidated Highly..., sandbar, and blacknose sharks. A new stock assessment is ongoing for Gulf of Mexico blacktip sharks,...

  2. 50 CFR 635.24 - Commercial retention limits for sharks and swordfish.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... whitetip sharks and scalloped, smooth, and great hammerhead sharks is prohibited on vessels issued a permit... 50 Wildlife and Fisheries 12 2012-10-01 2012-10-01 false Commercial retention limits for sharks... Management Measures § 635.24 Commercial retention limits for sharks and swordfish. Link to an...

  3. 33 CFR 117.751 - Shark River (South Channel).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Shark River (South Channel). 117.751 Section 117.751 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements New Jersey § 117.751 Shark River...

  4. 33 CFR 117.751 - Shark River (South Channel).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Shark River (South Channel). 117.751 Section 117.751 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements New Jersey § 117.751 Shark River...

  5. 33 CFR 117.751 - Shark River (South Channel).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Shark River (South Channel). 117.751 Section 117.751 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements New Jersey § 117.751 Shark River...

  6. 33 CFR 117.751 - Shark River (South Channel).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Shark River (South Channel). 117.751 Section 117.751 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements New Jersey § 117.751 Shark River...

  7. Ongoing collapse of coral-reef shark populations.

    PubMed

    Robbins, William D; Hisano, Mizue; Connolly, Sean R; Choat, J Howard

    2006-12-05

    Marine ecosystems are suffering severe depletion of apex predators worldwide; shark declines are principally due to conservative life-histories and fisheries overexploitation. On coral reefs, sharks are strongly interacting apex predators and play a key role in maintaining healthy reef ecosystems. Despite increasing fishing pressure, reef shark catches are rarely subject to specific limits, with management approaches typically depending upon no-take marine reserves to maintain populations. Here, we reveal that this approach is failing by documenting an ongoing collapse in two of the most abundant reef shark species on the Great Barrier Reef (Australia). We find an order of magnitude fewer sharks on fished reefs compared to no-entry management zones that encompass only 1% of reefs. No-take zones, which are more difficult to enforce than no-entry zones, offer almost no protection for shark populations. Population viability models of whitetip and gray reef sharks project ongoing steep declines in abundance of 7% and 17% per annum, respectively. These findings indicate that current management of no-take areas is inadequate for protecting reef sharks, even in one of the world's most-well-managed reef ecosystems. Further steps are urgently required for protecting this critical functional group from ecological extinction.

  8. 33 CFR 117.751 - Shark River (South Channel).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Shark River (South Channel). 117.751 Section 117.751 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements New Jersey § 117.751 Shark River...

  9. Sharks: a potential source of antiangiogenic factors and tumor treatments.

    PubMed

    Cho, Jung; Kim, Young

    2002-12-01

    Since angiogenesis is a key feature of tumor growth, inhibiting this process is one way to treat cancer. Cartilage is a natural source of material with strong antiangiogenic activity. This report reviews knowledge of the anticancer properties of shark cartilage and clinical information on drugs such as neovastat and squalamine. Because their entire endoskeleton is composed of cartilage, sharks are thought to be an ideal source of angiogenic and tumor growth inhibitors. Shark cartilage extract has shown antiangiogenic and antitumor activities in animals and humans. The oral administration of cartilage extract was efficacious in reducing angiogenesis. Purified antiangiogenic factors from shark cartilage, such as U-995 and neovastat (AE-941), also showed antiangiogenic and antitumor activity. AE-941 is under phase III clinical investigation. Squalamine, a low molecular weight aminosterol, showed strong antitumor activity when combined with chemotherapeutic materials. The angiogenic tissue inhibitor of metalloprotease 3 (TIMP-3) and tumor suppressor protein (snm23) genes from shark cartilage were cloned and characterized.

  10. Response of juvenile scalloped hammerhead sharks to electric stimuli.

    PubMed

    Kajiura, Stephen M; Fitzgerald, Timothy P

    2009-01-01

    Sharks can use their electrosensory system to detect electric fields in their environment. Measurements of their electrosensitivity are often derived by calculating the voltage gradient from a model of the charge distribution for an ideal dipole. This study measures the charge distribution around a dipole in seawater and confirms the close correspondence with the model. From this, it is possible to predict how the sharks will respond to dipolar electric fields comprised of differing parameters. We tested these predictions by exposing sharks to different sized dipoles and levels of applied current that simulated the bioelectric fields of their natural prey items. The sharks initiated responses from a significantly greater distance with larger dipole sizes and also from a significantly greater distance with increasing levels of electric current. This study is the first to provide empirical evidence supporting a popular theoretical model and test predictions about how sharks will respond to a variety of different electric stimuli.

  11. "Sharks in Your Hands"--A Case Study on Effects of Teaching Strategies to Change Knowledge and Attitudes towards Sharks

    ERIC Educational Resources Information Center

    Lee, Hung-Shan; Liu, Shiang-Yao; Yeh, Ting-Kuang

    2016-01-01

    This study was designed to exemplify how hands-on based teaching strategies enhanced students' knowledge and positive attitudes towards sharks. Hands-on activities for sharks' biological and morphological features were carried out. Eleven elementary school students from a remote area in Taiwan were recruited and assigned to the hands-on condition.…

  12. Biomimetic shark skin: design, fabrication and hydrodynamic function.

    PubMed

    Wen, Li; Weaver, James C; Lauder, George V

    2014-05-15

    Although the functional properties of shark skin have been of considerable interest to both biologists and engineers because of the complex hydrodynamic effects of surface roughness, no study to date has successfully fabricated a flexible biomimetic shark skin that allows detailed study of hydrodynamic function. We present the first study of the design, fabrication and hydrodynamic testing of a synthetic, flexible, shark skin membrane. A three-dimensional (3D) model of shark skin denticles was constructed using micro-CT imaging of the skin of the shortfin mako (Isurus oxyrinchus). Using 3D printing, thousands of rigid synthetic shark denticles were placed on flexible membranes in a controlled, linear-arrayed pattern. This flexible 3D printed shark skin model was then tested in water using a robotic flapping device that allowed us to either hold the models in a stationary position or move them dynamically at their self-propelled swimming speed. Compared with a smooth control model without denticles, the 3D printed shark skin showed increased swimming speed with reduced energy consumption under certain motion programs. For example, at a heave frequency of 1.5 Hz and an amplitude of ± 1 cm, swimming speed increased by 6.6% and the energy cost-of-transport was reduced by 5.9%. In addition, a leading-edge vortex with greater vorticity than the smooth control was generated by the 3D printed shark skin, which may explain the increased swimming speeds. The ability to fabricate synthetic biomimetic shark skin opens up a wide array of possible manipulations of surface roughness parameters, and the ability to examine the hydrodynamic consequences of diverse skin denticle shapes present in different shark species.

  13. A recent shark radiation: molecular phylogeny, biogeography and speciation of wobbegong sharks (family: Orectolobidae).

    PubMed

    Corrigan, Shannon; Beheregaray, Luciano B

    2009-07-01

    The elasmobranch fish are an ancient, evolutionarily successful, but under-researched vertebrate group, particularly in regard to their recent evolutionary history. Their lineage has survived four mass extinction events and most present day taxa are thought to be derived from Mesozoic forms. Here we present a molecular phylogenetic analysis of the family Orectolobidae that provides evidence for recent events of diversification in this shark group. Species interrelationships in Orectolobidae were reconstructed based on four mitochondrial and nuclear genes. In line with previous morphological work, our results do not support current taxonomic arrangements in Orectolobidae and indicate that a taxonomic revision of the family is warranted. We propose that the onset of diversification of orectolobid sharks is of Miocene age and occurred within the Indo-Australian region. Surprisingly, we also find evidence for a recent ( approximately last 2 million years) and rapid radiation of wobbegong sharks. Allopatric speciation followed by range expansion seems like the general most likely explanation to account for wobbegong relationships and distributions. We suggest that the evolution of this shark group was mostly influenced by two temporal scenarios of diversification. The oldest relates to major geological changes in the Indo-West Pacific associated with the Miocene collision of the Indo-Australian and Eurasian plates. The most recent scenario was influenced by changes in oceanography and the emergence of biogeographic barriers related to Pleistocene glacial cycles in Australian waters.

  14. How Close is too Close? The Effect of a Non-Lethal Electric Shark Deterrent on White Shark Behaviour.

    PubMed

    Kempster, Ryan M; Egeberg, Channing A; Hart, Nathan S; Ryan, Laura; Chapuis, Lucille; Kerr, Caroline C; Schmidt, Carl; Huveneers, Charlie; Gennari, Enrico; Yopak, Kara E; Meeuwig, Jessica J; Collin, Shaun P

    2016-01-01

    Sharks play a vital role in the health of marine ecosystems, but the potential threat that sharks pose to humans is a reminder of our vulnerability when entering the ocean. Personal shark deterrents are being marketed as the solution to mitigate the threat that sharks pose. However, the effectiveness claims of many personal deterrents are based on our knowledge of shark sensory biology rather than robust testing of the devices themselves, as most have not been subjected to independent scientific studies. Therefore, there is a clear need for thorough testing of commercially available shark deterrents to provide the public with recommendations of their effectiveness. Using a modified stereo-camera system, we quantified behavioural interactions between white sharks (Carcharodon carcharias) and a baited target in the presence of a commercially available, personal electric shark deterrent (Shark Shield Freedom7™). The stereo-camera system enabled an accurate assessment of the behavioural responses of C. carcharias when encountering a non-lethal electric field many times stronger than what they would naturally experience. Upon their first observed encounter, all C. carcharias were repelled at a mean (± std. error) proximity of 131 (± 10.3) cm, which corresponded to a mean voltage gradient of 9.7 (± 0.9) V/m. With each subsequent encounter, their proximity decreased by an average of 11.6 cm, which corresponded to an increase in tolerance to the electric field by an average of 2.6 (± 0.5) V/m per encounter. Despite the increase in tolerance, sharks continued to be deterred from interacting for the duration of each trial when in the presence of an active Shark Shield™. Furthermore, the findings provide no support to the theory that electric deterrents attract sharks. The results of this study provide quantitative evidence of the effectiveness of a non-lethal electric shark deterrent, its influence on the behaviour of C. carcharias, and an accurate method for testing

  15. How Close is too Close? The Effect of a Non-Lethal Electric Shark Deterrent on White Shark Behaviour

    PubMed Central

    Hart, Nathan S.; Ryan, Laura; Chapuis, Lucille; Kerr, Caroline C.; Schmidt, Carl; Huveneers, Charlie; Gennari, Enrico; Yopak, Kara E.; Meeuwig, Jessica J.; Collin, Shaun P.

    2016-01-01

    Sharks play a vital role in the health of marine ecosystems, but the potential threat that sharks pose to humans is a reminder of our vulnerability when entering the ocean. Personal shark deterrents are being marketed as the solution to mitigate the threat that sharks pose. However, the effectiveness claims of many personal deterrents are based on our knowledge of shark sensory biology rather than robust testing of the devices themselves, as most have not been subjected to independent scientific studies. Therefore, there is a clear need for thorough testing of commercially available shark deterrents to provide the public with recommendations of their effectiveness. Using a modified stereo-camera system, we quantified behavioural interactions between white sharks (Carcharodon carcharias) and a baited target in the presence of a commercially available, personal electric shark deterrent (Shark Shield Freedom7™). The stereo-camera system enabled an accurate assessment of the behavioural responses of C. carcharias when encountering a non-lethal electric field many times stronger than what they would naturally experience. Upon their first observed encounter, all C. carcharias were repelled at a mean (± std. error) proximity of 131 (± 10.3) cm, which corresponded to a mean voltage gradient of 9.7 (± 0.9) V/m. With each subsequent encounter, their proximity decreased by an average of 11.6 cm, which corresponded to an increase in tolerance to the electric field by an average of 2.6 (± 0.5) V/m per encounter. Despite the increase in tolerance, sharks continued to be deterred from interacting for the duration of each trial when in the presence of an active Shark Shield™. Furthermore, the findings provide no support to the theory that electric deterrents attract sharks. The results of this study provide quantitative evidence of the effectiveness of a non-lethal electric shark deterrent, its influence on the behaviour of C. carcharias, and an accurate method for testing

  16. No rainbow for grey bamboo sharks: evidence for the absence of colour vision in sharks from behavioural discrimination experiments.

    PubMed

    Schluessel, V; Rick, I P; Plischke, K

    2014-11-01

    Despite convincing data collected by microspectrophotometry and molecular biology, rendering sharks colourblind cone monochromats, the question of whether sharks can perceive colour had not been finally resolved in the absence of any behavioural experiments compensating for the confounding factor of brightness. The present study tested the ability of juvenile grey bamboo sharks to perceive colour in an experimental design based on a paradigm established by Karl von Frisch using colours in combination with grey distractor stimuli of equal brightness. Results showed that contrasts but no colours could be discriminated. Blue and yellow stimuli were not distinguished from a grey distractor stimulus of equal brightness but could be distinguished from distractor stimuli of varying brightness. In addition, different grey stimuli were distinguished significantly above chance level from one another. In conclusion, the behavioural results support the previously collected physiological data on bamboo sharks, which mutually show that the grey bamboo shark, like several marine mammals, is a cone monochromate and colourblind.

  17. Trophic ecology of sharks in the mid-east pacific ocean inferred from stable isotopes

    NASA Astrophysics Data System (ADS)

    Li, Yunkai; Gong, Yi; Chen, Xinjun; Dai, Xiaojie; Zhu, Jiangfeng

    2013-11-01

    As apex predators, sharks are of ecological and conservation importance in marine ecosystems. In this study, trophic positions of sharks were estimated using stable isotope ratios of carbon and nitrogen for five representative species caught by the Chinese longline fleet in the mid-east Pacific, i.e., the blue shark (Prionace glauca), the bigeye thresher shark (Alopias superciliosus), the silky shark (Carcharhinus falciformis), the scalloped hammerhead (Sphyrna lewini), and the oceanic whitetip shark (Carcharhinus longimanus). Of these species, oceanic whitetip shark has the lowest trophic level and mean δ15N value (3.9 and 14.93‰ ± 0.84‰), whereas bigeye thresher shark has the highest level/values (4.5 and 17.02‰ ± 1.21‰, respectively). The bigeye thresher shark has significantly higher δ15N value than other shark species, indicating its higher trophic position. The blue shark and oceanic whitetip shark has significantly higher δ13C values than bigeye thresher shark, silky shark and scalloped hammerhead, possibly due to different diets and/or living habitats. The stable isotope data and stomach content data are highly consistent, suggesting that stable isotope analysis supplements traditional feeding ecology study of sharks, and thus contributes to understanding their trophic linkage.

  18. Mercury and zinc differentially inhibit shark and human CFTR orthologues: involvement of shark cysteine 102.

    PubMed

    Weber, Gerhard J; Mehr, Ali Poyan; Sirota, Jeffrey C; Aller, Stephen G; Decker, Sarah E; Dawson, David C; Forrest, John N

    2006-03-01

    The apical membrane is an important site of mercury toxicity in shark rectal gland tubular cells. We compared the effects of mercury and other thiol-reacting agents on shark CFTR (sCFTR) and human CFTR (hCFTR) chloride channels using two-electrode voltage clamping of cRNA microinjected Xenopus laevis oocytes. Chloride conductance was stimulated by perfusing with 10 microM forskolin (FOR) and 1 mM IBMX, and then thio-reactive species were added. In oocytes expressing sCFTR, FOR + IBMX mean stimulated Cl(-) conductance was inhibited 69% by 1 microM mercuric chloride and 78% by 5 microM mercuric chloride (IC(50) of 0.8 microM). Despite comparable stimulation of conductance, hCFTR was insensitive to 1 microM HgCl(2) and maximum inhibition was 15% at the highest concentration used (5 microM). Subsequent exposure to glutathione (GSH) did not reverse the inhibition of sCFTR by mercury, but dithiothreitol (DTT) completely reversed this inhibition. Zinc (50-200 microM) also reversibly inhibited sCFTR (40-75%) but did not significantly inhibit hCFTR. Similar inhibition of sCFTR but not hCFTR was observed with an organic mercurial, p-chloromercuriphenylsulfonic acid (pCMBS). The first membrane spanning domain (MSD1) of sCFTR contains two unique cysteines, C102 and C303. A chimeric construct replacing MSD1 of hCFTR with the corresponding sequence of sCFTR was highly sensitive to mercury. Site-specific mutations introducing the first but not the second shark unique cysteine in hCFTR MSD1 resulted in full sensitivity to mercury. These experiments demonstrate a profound difference in the sensitivity of shark vs. human CFTR to inhibition by three thiol-reactive substances, an effect that involves C102 in the shark orthologue.

  19. Long-term changes in species composition and relative abundances of sharks at a provisioning site.

    PubMed

    Brunnschweiler, Juerg M; Abrantes, Kátya G; Barnett, Adam

    2014-01-01

    Diving with sharks, often in combination with food baiting/provisioning, has become an important product of today's recreational dive industry. Whereas the effects baiting/provisioning has on the behaviour and abundance of individual shark species are starting to become known, there is an almost complete lack of equivalent data from multi-species shark diving sites. In this study, changes in species composition and relative abundances were determined at the Shark Reef Marine Reserve, a multi-species shark feeding site in Fiji. Using direct observation sampling methods, eight species of sharks (bull shark Carcharhinus leucas, grey reef shark Carcharhinus amblyrhynchos, whitetip reef shark Triaenodon obesus, blacktip reef shark Carcharhinus melanopterus, tawny nurse shark Nebrius ferrugineus, silvertip shark Carcharhinus albimarginatus, sicklefin lemon shark Negaprion acutidens, and tiger shark Galeocerdo cuvier) displayed inter-annual site fidelity between 2003 and 2012. Encounter rates and/or relative abundances of some species changed over time, overall resulting in more individuals (mostly C. leucas) of fewer species being encountered on average on shark feeding dives at the end of the study period. Differences in shark community composition between the years 2004-2006 and 2007-2012 were evident, mostly because N. ferrugineus, C. albimarginatus and N. acutidens were much more abundant in 2004-2006 and very rare in the period of 2007-2012. Two explanations are offered for the observed changes in relative abundances over time, namely inter-specific interactions and operator-specific feeding protocols. Both, possibly in combination, are suggested to be important determinants of species composition and encounter rates, and relative abundances at this shark provisioning site in Fiji. This study, which includes the most species from a spatially confined shark provisioning site to date, suggests that long-term provisioning may result in competitive exclusion among shark

  20. Science or slaughter: need for lethal sampling of sharks.

    PubMed

    Heupel, M R; Simpfendorfer, C A

    2010-10-01

    General consensus among scientists, commercial interests, and the public regarding the status of shark populations is leading to an increasing need for the scientific community to provide information to help guide effective management and conservation actions. Experience from other marine vertebrate taxa suggests that public, political, and media pressures will play an increasingly important part in setting research, management, and conservation priorities. We examined the potential implications of nonscientific influences on shark research. In particular, we considered whether lethal research sampling of sharks is justified. Although lethal sampling comes at a cost to a population, especially for threatened species, the conservation benefits from well-designed studies provide essential data that cannot be collected currently in any other way. Methods that enable nonlethal collection of life-history data on sharks are being developed (e.g., use of blood samples to detect maturity), but in the near future they will not provide widespread or significant benefits. Development of these techniques needs to continue, as does the way in which scientists coordinate their use of material collected during lethal sampling. For almost half of the known shark species there are insufficient data to determine their population status; thus, there is an ongoing need for further collection of scientific data to ensure all shark populations have a future. Shark populations will benefit most when decisions about the use of lethal sampling are made on the basis of scientific evidence that is free from individual, political, public, and media pressures.

  1. Box-Jenkins analysis for shark landings in Costa Rica.

    PubMed

    Bonilla, Roger; Chavarría, Juan B

    2004-12-01

    Sharks are highly vulnerable to intense and prolonged fishery extraction. This article analyzes the data on shark landings from the artisan fishing fleet on Costa Rica's Pacific coast between 1988 and 1997. The data come from an invoicing system administered by the Costa Rican Fisheries Institute (Instituto Costarricense de la Pesca y Acuacultura, INCOPESCA). Pacific coast shark fishing during the period under study represented approximately 20% of the total national fisheries volume. According to data from the invoicing system, the Northern Pacific region was the most productive, reporting 58% of the shark catch nationwide. Within this region, shark fishing in Papagayo Gulf represented 91% and 53% of the landings by fishery region and nationwide, respectively. The mid-sized and advanced (length of boat > 10 meters) artisan fishing fleets reported 96% of the shark catches in the zone. The study of shark fisheries in the Papagayo Gulf zone is crucial for an understanding of fishery dynamics for this resource at the national level. A monthly chronological series was constructed with the landings in the Papagayo Gulf zone, and a Univariate Box-Jenkins (UBJ) Model was estimated for first-order moving averages MA(1) with a seasonal component of the Yt = lamda(t-1) + gammaS12 + a(t) type.

  2. Shark as viewed by Sojourner Rover

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This close-up image of Shark, in the Bookshelf at the back of the Rock Garden, was taken by Sojourner Rover on Sol 75. Also in the image are Half Dome (right) and Desert Princess (lower right). At the bottom left, a thin 'crusty' soil layer has been disturbed by the rover wheels.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

  3. Global diversity hotspots and conservation priorities for sharks.

    PubMed

    Lucifora, Luis O; García, Verónica B; Worm, Boris

    2011-05-05

    Sharks are one of the most threatened groups of marine animals, as high exploitation rates coupled with low resilience to fishing pressure have resulted in population declines worldwide. Designing conservation strategies for this group depends on basic knowledge of the geographic distribution and diversity of known species. So far, this information has been fragmented and incomplete. Here, we have synthesized the first global shark diversity pattern from a new database of published sources, including all 507 species described at present, and have identified hotspots of shark species richness, functional diversity and endemicity from these data. We have evaluated the congruence of these diversity measures and demonstrate their potential use in setting priority areas for shark conservation. Our results show that shark diversity across all species peaks on the continental shelves and at mid-latitudes (30-40 degrees N and S). Global hotspots of species richness, functional diversity and endemicity were found off Japan, Taiwan, the East and West coasts of Australia, Southeast Africa, Southeast Brazil and Southeast USA. Moreover, some areas with low to moderate species richness such as Southern Australia, Angola, North Chile and Western Continental Europe stood out as places of high functional diversity. Finally, species affected by shark finning showed different patterns of diversity, with peaks closer to the Equator and a more oceanic distribution overall. Our results show that the global pattern of shark diversity is uniquely different from land, and other well-studied marine taxa, and may provide guidance for spatial approaches to shark conservation. However, similar to terrestrial ecosystems, protected areas based on hotspots of diversity and endemism alone would provide insufficient means for safeguarding the diverse functional roles that sharks play in marine ecosystems.

  4. Movement patterns of silvertip sharks ( Carcharhinus albimarginatus) on coral reefs

    NASA Astrophysics Data System (ADS)

    Espinoza, Mario; Heupel, Michelle. R.; Tobin, Andrew J.; Simpfendorfer, Colin A.

    2015-09-01

    Understanding how sharks use coral reefs is essential for assessing risk of exposure to fisheries, habitat loss, and climate change. Despite a wide Indo-Pacific distribution, little is known about the spatial ecology of silvertip sharks ( Carcharhinus albimarginatus), compromising the ability to effectively manage their populations. We examined the residency and movements of silvertip sharks in the central Great Barrier Reef (GBR). An array of 56 VR2W acoustic receivers was used to monitor shark movements on 17 semi-isolated reefs. Twenty-seven individuals tagged with acoustic transmitters were monitored from 70 to 731 d. Residency index to the study site ranged from 0.05 to 0.97, with a mean residency (±SD) of 0.57 ± 0.26, but most individuals were detected at or near their tagging reef. Clear seasonal patterns were apparent, with fewer individuals detected between September and February. A large proportion of the tagged population (>71 %) moved regularly between reefs. Silvertip sharks were detected less during daytime and exhibited a strong diel pattern in depth use, which may be a strategy for optimizing energetic budgets and foraging opportunities. This study provides the first detailed examination of the spatial ecology and behavior of silvertip sharks on coral reefs. Silvertip sharks remained resident at coral reef habitats over long periods, but our results also suggest this species may have more complex movement patterns and use larger areas of the GBR than common reef shark species. Our findings highlight the need to further understand the movement ecology of silvertip sharks at different spatial and temporal scales, which is critical for developing effective management approaches.

  5. Global Diversity Hotspots and Conservation Priorities for Sharks

    PubMed Central

    Lucifora, Luis O.; García, Verónica B.; Worm, Boris

    2011-01-01

    Sharks are one of the most threatened groups of marine animals, as high exploitation rates coupled with low resilience to fishing pressure have resulted in population declines worldwide. Designing conservation strategies for this group depends on basic knowledge of the geographic distribution and diversity of known species. So far, this information has been fragmented and incomplete. Here, we have synthesized the first global shark diversity pattern from a new database of published sources, including all 507 species described at present, and have identified hotspots of shark species richness, functional diversity and endemicity from these data. We have evaluated the congruence of these diversity measures and demonstrate their potential use in setting priority areas for shark conservation. Our results show that shark diversity across all species peaks on the continental shelves and at mid-latitudes (30–40 degrees N and S). Global hotspots of species richness, functional diversity and endemicity were found off Japan, Taiwan, the East and West coasts of Australia, Southeast Africa, Southeast Brazil and Southeast USA. Moreover, some areas with low to moderate species richness such as Southern Australia, Angola, North Chile and Western Continental Europe stood out as places of high functional diversity. Finally, species affected by shark finning showed different patterns of diversity, with peaks closer to the Equator and a more oceanic distribution overall. Our results show that the global pattern of shark diversity is uniquely different from land, and other well-studied marine taxa, and may provide guidance for spatial approaches to shark conservation. However, similar to terrestrial ecosystems, protected areas based on hotspots of diversity and endemism alone would provide insufficient means for safeguarding the diverse functional roles that sharks play in marine ecosystems. PMID:21573162

  6. Shark predation on cephalopods in the Mexican and Ecuadorian Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Galván-Magaña, Felipe; Polo-Silva, Carlos; Berenice Hernández-Aguilar, Sandra; Sandoval-Londoño, Alejandro; Ruth Ochoa-Díaz, Maria; Aguilar-Castro, Nallely; Castañeda-Suárez, David; Cabrera Chavez-Costa, Alejandra; Baigorrí-Santacruz, Álvaro; Eden Torres-Rojas, Yassir; Andrés Abitia-Cárdenas, Leonardo

    2013-10-01

    Pelagic predators such as sharks have been shown to be effective cephalopod samplers, because they have high consumption rates and swimming speeds. The stomach contents of these predators allow us to determine the distribution and abundance of cephalopods, considering the scarcity of biological information and the difficulty of catching squids and octopi using traditional methods. The silky shark (Carcharhinus falciformis), blue shark (Prionace glauca), scalloped hammerhead (Sphyrna lewini), smooth hammerhead (Sphyrna zygaena), pelagic thresher shark (Alopias pelagicus), and bigeye thresher shark (Alopias superciliosus) were caught off both coasts of Baja California Sur, Mexico, and in the Ecuadorian Pacific Ocean. Cephalopod sizes (mantle lengths, ML) were calculated based on the beak measurements to determine the size of cephalopods consumed by the sharks. We identified 21 cephalopod species based on beak items found in the shark stomachs. The most abundant cephalopods consumed by sharks in both areas were Dosidicus gigas, Ancistrocheirus lesueurii, Onychoteuthis banksii, Sthenoteuthis ovalaniensis, Argonauta spp., Abraliopsis affinis, and Mastigoteuthis dentata. The cephalopod's habitat provides information about the depth at which these sharks capture their prey. The blue shark feeds on cephalopods in epipelagic, mesopelagic, and bathypelagic waters; the silky shark feeds on cephalopods in epipelagic waters; and the scalloped hammerhead shark preys on cephalopods in neritic (bottom) and oceanic waters (epipelagic and mesopelagic). The pelagic thresher shark consumed epipelagic and neritic species; whereas the bigeye thresher shark feeds mainly on epipelagic and mesopelagic squids in Ecuadorian waters. The smooth hammerhead preys on epipelagic and mesopelagic squids off Mexico and Ecuador.

  7. Dramatic increase in sea otter mortality from white sharks in California

    USGS Publications Warehouse

    Tinker, M. Tim; Hatfield, Brian B.; Harris, Michael D.; Ames, Jack A.

    2016-01-01

    Although southern sea otters (Enhydra lutris nereis) are not considered prey for white sharks (Carcharodon carcharias), sharks do nonetheless bite sea otters. We analyzed spatial and temporal trends in shark bites on sea otters in California, assessing the frequency of shark bite wounds in 1,870 carcasses collected since 1985. The proportion of stranded sea otters having shark bites has increased sharply since 2003, and white shark bites now account for >50% of recovered carcasses. The trend was most pronounced in the southern part of the range, from Estero Bay to Point Conception, where shark bite frequency has increased eightfold. Seasonal trends were also evident: most shark-bitten carcasses are recovered in late summer and fall; however, the period of elevated shark bite frequency has lengthened. The causes of these trends are unclear, but possible contributing factors include increased white shark abundance and/or changes in white shark behavior and distribution. In particular, the spatiotemporal patterns of shark-bitten sea otters match increases in pinniped populations, and the increased availability of marine mammal prey for white sharks may have led to more sharks spending more time in nearshore waters utilized by both sea otters and pinnipeds.

  8. Philopatry and migration of Pacific white sharks

    PubMed Central

    Jorgensen, Salvador J.; Reeb, Carol A.; Chapple, Taylor K.; Anderson, Scot; Perle, Christopher; Van Sommeran, Sean R.; Fritz-Cope, Callaghan; Brown, Adam C.; Klimley, A. Peter; Block, Barbara A.

    2010-01-01

    Advances in electronic tagging and genetic research are making it possible to discern population structure for pelagic marine predators once thought to be panmictic. However, reconciling migration patterns and gene flow to define the resolution of discrete population management units remains a major challenge, and a vital conservation priority for threatened species such as oceanic sharks. Many such species have been flagged for international protection, yet effective population assessments and management actions are hindered by lack of knowledge about the geographical extent and size of distinct populations. Combining satellite tagging, passive acoustic monitoring and genetics, we reveal how eastern Pacific white sharks (Carcharodon carcharias) adhere to a highly predictable migratory cycle. Individuals persistently return to the same network of coastal hotspots following distant oceanic migrations and comprise a population genetically distinct from previously identified phylogenetic clades. We hypothesize that this strong homing behaviour has maintained the separation of a northeastern Pacific population following a historical introduction from Australia/New Zealand migrants during the Late Pleistocene. Concordance between contemporary movement and genetic divergence based on mitochondrial DNA demonstrates a demographically independent management unit not previously recognized. This population's fidelity to discrete and predictable locations offers clear population assessment, monitoring and management options. PMID:19889703

  9. The anatomy of a shark attack: a case report and review of the literature.

    PubMed

    Caldicott, D G; Mahajani, R; Kuhn, M

    2001-07-01

    Shark attacks are rare but are associated with a high morbidity and significant mortality. We report the case of a patient's survival from a shark attack and their subsequent emergency medical and surgical management. Using data from the International Shark Attack File, we review the worldwide distribution and incidence of shark attack. A review of the world literature examines the features which make shark attacks unique pathological processes. We offer suggestions for strategies of management of shark attack, and techniques for avoiding adverse outcomes in human encounters with these endangered creatures.

  10. Cartilage (Bovine and Shark) (PDQ®)—Health Professional Version

    Cancer.gov

    Expert-reviewed information summary about the use of bovine and shark cartilage as a treatment for people with cancer. Note: The information in this summary is no longer being updated and is provided for reference purposes only.

  11. Cartilage (Bovine and Shark) (PDQ®)—Patient Version

    Cancer.gov

    Expert-reviewed information summary about the use of bovine and shark cartilage as a treatment for people with cancer. Note: The information in this summary is no longer being updated and is provided for reference purposes only.

  12. Adaptation and Communication in the Stromatolites of Shark Bay Australia

    NASA Astrophysics Data System (ADS)

    Dharmawan, J.; Oliver, M.; Burke, K.; Rice, S.; Burns, B. P.

    2010-04-01

    The goal of this ongoing study is to characterise adaptive and signaling mechanisms in Shark Bay stromatolite microorganisms, and this will provide a better understanding of essential processes affecting ecosystem function in modern stromatolite systems.

  13. Shark immunity bites back: affinity maturation and memory response in the nurse shark, Ginglymostoma cirratum.

    PubMed

    Dooley, Helen; Flajnik, Martin F

    2005-03-01

    The cartilaginous fish are the oldest phylogenetic group in which all of the molecular components of the adaptive immune system have been found. Although early studies clearly showed that sharks could produce an IgM-based response following immunization, evidence for memory, affinity maturation and roles for the other isotypes (notably IgNAR) in this group remained inconclusive. The data presented here illustrate that the nurse shark (Ginglymostoma cirratum) is able to produce not only an IgM response, but we also show for the first time a highly antigen-specific IgNAR response. Additionally, under appropriate conditions, a memory response for both isotypes can be elicited. Analysis of the response shows differential expression of pentameric and monomeric IgM. Pentameric IgM provides the 'first line of defense' through high-avidity, low-affinity interaction with antigen. In contrast, monomeric IgM and IgNAR seem responsible for the specific, antigen-driven response. We propose the presence of distinct lineages of B cells in sharks. As there is no conventional isotype switching, each lineage seems pre-determined to express a single isotype (IgM versus IgNAR). However, our data suggest that there may also be specific lineages for the different forms (pentameric versus monomeric) of the IgM isotype.

  14. Predicting occurrence of juvenile shark habitat to improve conservation planning.

    PubMed

    Oh, Beverly Z L; Sequeira, Ana M M; Meekan, Mark G; Ruppert, Jonathan L W; Meeuwig, Jessica J

    2016-11-30

    Fishing and habitat degradation have increased the extinction risk of sharks, and conservation strategies recognize that survival of juveniles is critical for the effective management of shark populations. Despite the rapid expansion of marine protected areas (MPAs) globally, the paucity of shark-monitoring data on large scales (100s-1000s km) means that the effectiveness of MPAs in halting shark declines remains unclear. Using data collected by baited remote underwater video systems (BRUVS) in northwestern Australia, we developed generalized linear models to elucidate the ecological drivers of habitat suitability for juvenile sharks. We assessed occurrence patterns at the order and species levels. We included all juvenile sharks sampled and the 3 most abundant species sampled separately (grey reef [Carcharhinus amblyrhynchos], sandbar [Carcharhinus plumbeus], and whitetip reef sharks [Triaenodon obesus]). We predicted the occurrence of juvenile sharks across 490,515 km(2) of coastal waters and quantified the representation of highly suitable habitats within MPAs. Our species-level models had higher accuracy (ĸ ≥ 0.69) and deviance explained (≥48%) than our order-level model (ĸ = 0.36 and deviance explained of 10%). Maps of predicted occurrence revealed different species-specific patterns of highly suitable habitat. These differences likely reflect different physiological or resource requirements between individual species and validate concerns over the utility of conservation targets based on aggregate species groups as opposed to a species-focused approach. Highly suitable habitats were poorly represented in MPAs with the most restrictions on extractive activities. This spatial mismatch possibly indicates a lack of explicit conservation targets and information on species distribution during the planning process. Non-extractive BRUVS provided a useful platform for building the suitability models across large scales to assist conservation planning across

  15. Movements of blue sharks (Prionace glauca) across their life history.

    PubMed

    Vandeperre, Frederic; Aires-da-Silva, Alexandre; Fontes, Jorge; Santos, Marco; Serrão Santos, Ricardo; Afonso, Pedro

    2014-01-01

    Spatial structuring and segregation by sex and size is considered to be an intrinsic attribute of shark populations. These spatial patterns remain poorly understood, particularly for oceanic species such as blue shark (Prionace glauca), despite its importance for the management and conservation of this highly migratory species. This study presents the results of a long-term electronic tagging experiment to investigate the migratory patterns of blue shark, to elucidate how these patterns change across its life history and to assess the existence of a nursery area in the central North Atlantic. Blue sharks belonging to different life stages (n = 34) were tracked for periods up to 952 days during which they moved extensively (up to an estimated 28.139 km), occupying large parts of the oceanic basin. Notwithstanding a large individual variability, there were pronounced differences in movements and space use across the species' life history. The study provides strong evidence for the existence of a discrete central North Atlantic nursery, where juveniles can reside for up to at least 2 years. In contrast with previously described nurseries of coastal and semi-pelagic sharks, this oceanic nursery is comparatively vast and open suggesting that shelter from predators is not its main function. Subsequently, male and female blue sharks spatially segregate. Females engage in seasonal latitudinal migrations until approaching maturity, when they undergo an ontogenic habitat shift towards tropical latitudes. In contrast, juvenile males generally expanded their range southward and apparently displayed a higher degree of behavioural polymorphism. These results provide important insights into the spatial ecology of pelagic sharks, with implications for the sustainable management of this heavily exploited shark, especially in the central North Atlantic where the presence of a nursery and the seasonal overlap and alternation of different life stages coincides with a high fishing

  16. Trends in the exploitation of South Atlantic shark populations.

    PubMed

    Barreto, Rodrigo; Ferretti, Francesco; Flemming, Joanna M; Amorim, Alberto; Andrade, Humber; Worm, Boris; Lessa, Rosangela

    2016-08-01

    Approximately 25% of globally reported shark catches occur in Atlantic pelagic longline fisheries. Strong declines in shark populations have been detected in the North Atlantic, whereas in the South Atlantic the situation is less clear, although fishing effort has been increasing in this region since the late 1970s. We synthesized information on shark catch rates (based on 871,177 sharks caught on 86,492 longline sets) for the major species caught by multiple fleets in the South Atlantic between 1979 and 2011. We complied records from fishing logbooks of fishing companies, fishers, and onboard observers that were supplied to Brazilian institutions. By using exploratory data analysis and literature sources, we identified 3 phases of exploitation in these data (Supporting Information). From 1979 to 1997 (phase A), 5 fleets (40 vessels) fished mainly for tunas. From 1998 to 2008 (phase B), 20 fleets (100 vessels) fished for tunas, swordfishes, and sharks. From 2008 to 2011 (phase C), 3 fleets (30 vessels) fished for multiple species, but restrictive measures were implemented. We used generalized linear models to standardize catch rates and identify trends in each of these phases. Shark catch rates increased from 1979 to 1997, when fishing effort was low, decreased from 1998 to 2008, when fishing effort increased substantially, and remained stable or increased from 2008 to 2011, when fishing effort was again low. Our results indicate that most shark populations affected by longlines in the South Atlantic are currently depleted, but these populations may recover if fishing effort is reduced accordingly. In this context, it is problematic that comprehensive data collection, monitoring, and management of these fisheries ceased after 2012. Concurrently with the fact that Brazil is newly identified by FAO among the largest (and in fastest expansion) shark sub-products consumer market worldwide.

  17. Movements of Blue Sharks (Prionace glauca) across Their Life History

    PubMed Central

    Vandeperre, Frederic; Aires-da-Silva, Alexandre; Fontes, Jorge; Santos, Marco; Serrão Santos, Ricardo; Afonso, Pedro

    2014-01-01

    Spatial structuring and segregation by sex and size is considered to be an intrinsic attribute of shark populations. These spatial patterns remain poorly understood, particularly for oceanic species such as blue shark (Prionace glauca), despite its importance for the management and conservation of this highly migratory species. This study presents the results of a long-term electronic tagging experiment to investigate the migratory patterns of blue shark, to elucidate how these patterns change across its life history and to assess the existence of a nursery area in the central North Atlantic. Blue sharks belonging to different life stages (n = 34) were tracked for periods up to 952 days during which they moved extensively (up to an estimated 28.139 km), occupying large parts of the oceanic basin. Notwithstanding a large individual variability, there were pronounced differences in movements and space use across the species' life history. The study provides strong evidence for the existence of a discrete central North Atlantic nursery, where juveniles can reside for up to at least 2 years. In contrast with previously described nurseries of coastal and semi-pelagic sharks, this oceanic nursery is comparatively vast and open suggesting that shelter from predators is not its main function. Subsequently, male and female blue sharks spatially segregate. Females engage in seasonal latitudinal migrations until approaching maturity, when they undergo an ontogenic habitat shift towards tropical latitudes. In contrast, juvenile males generally expanded their range southward and apparently displayed a higher degree of behavioural polymorphism. These results provide important insights into the spatial ecology of pelagic sharks, with implications for the sustainable management of this heavily exploited shark, especially in the central North Atlantic where the presence of a nursery and the seasonal overlap and alternation of different life stages coincides with a high fishing

  18. Assessment of hydro/oleophobicity for shark skin replica with riblets.

    PubMed

    Kim, Tae Wan

    2014-10-01

    The shark skin has a unique skin structure which enables the shark to swim faster and more efficiently due to an intriguing three-dimensional rib pattern. Shark skin has also known as having functional performances such as self cleaning and anti-fouling as well as excellent drag reduction due to a hierarchical structure built up by micro grooves and nano-long chain mucus drag reduction interface around the shark body. In this study, the wetting properties for the biomimetic surfaces that replicate shark skin are assessed. First of all, the shark skin replicas are obtained using the micro molding technique directly from a shark skin template. The quantitative replication precision of the shark skin replicas is evaluated comparing with the geometry of shark skin template using 3D and 2D surface profiles are measured. Then contact angles in the conditions of solid-air-water, solid-air-oil and solid-water-oil interfaces are evaluated for shark skin replicas. The effect of Teflon coating on the wetting properties of shark skin replicas is also observed. The results show the shark skin replica by the micro molding technique gives better effect on the wetting performance, and the micro riblets on shark skin improve the wettability feature.

  19. Olfaction Contributes to Pelagic Navigation in a Coastal Shark.

    PubMed

    Nosal, Andrew P; Chao, Yi; Farrara, John D; Chai, Fei; Hastings, Philip A

    2016-01-01

    How animals navigate the constantly moving and visually uniform pelagic realm, often along straight paths between distant sites, is an enduring mystery. The mechanisms enabling pelagic navigation in cartilaginous fishes are particularly understudied. We used shoreward navigation by leopard sharks (Triakis semifasciata) as a model system to test whether olfaction contributes to pelagic navigation. Leopard sharks were captured alongshore, transported 9 km offshore, released, and acoustically tracked for approximately 4 h each until the transmitter released. Eleven sharks were rendered anosmic (nares occluded with cotton wool soaked in petroleum jelly); fifteen were sham controls. Mean swimming depth was 28.7 m. On average, tracks of control sharks ended 62.6% closer to shore, following relatively straight paths that were significantly directed over spatial scales exceeding 1600 m. In contrast, tracks of anosmic sharks ended 37.2% closer to shore, following significantly more tortuous paths that approximated correlated random walks. These results held after swimming paths were adjusted for current drift. This is the first study to demonstrate experimentally that olfaction contributes to pelagic navigation in sharks, likely mediated by chemical gradients as has been hypothesized for birds. Given the similarities between the fluid three-dimensional chemical atmosphere and ocean, further research comparing swimming and flying animals may lead to a unifying paradigm explaining their extraordinary navigational abilities.

  20. Vertebral bomb radiocarbon suggests extreme longevity in white sharks.

    PubMed

    Hamady, Li Ling; Natanson, Lisa J; Skomal, Gregory B; Thorrold, Simon R

    2014-01-01

    Conservation and management efforts for white sharks (Carcharodon carcharias) remain hampered by a lack of basic demographic information including age and growth rates. Sharks are typically aged by counting growth bands sequentially deposited in their vertebrae, but the assumption of annual deposition of these band pairs requires testing. We compared radiocarbon (Δ(14)C) values in vertebrae from four female and four male white sharks from the northwestern Atlantic Ocean (NWA) with reference chronologies documenting the marine uptake of (14)C produced by atmospheric testing of thermonuclear devices to generate the first radiocarbon age estimates for adult white sharks. Age estimates were up to 40 years old for the largest female (fork length [FL]: 526 cm) and 73 years old for the largest male (FL: 493 cm). Our results dramatically extend the maximum age and longevity of white sharks compared to earlier studies, hint at possible sexual dimorphism in growth rates, and raise concerns that white shark populations are considerably more sensitive to human-induced mortality than previously thought.

  1. Acoustic telemetry reveals cryptic residency of whale sharks.

    PubMed

    Cagua, E Fernando; Cochran, Jesse E M; Rohner, Christoph A; Prebble, Clare E M; Sinclair-Taylor, Tane H; Pierce, Simon J; Berumen, Michael L

    2015-04-01

    Although whale sharks (Rhincodon typus) have been documented to move thousands of kilometres, they are most frequently observed at a few predictable seasonal aggregation sites. The absence of sharks at the surface during visual surveys has led to the assumption that sharks disperse to places unknown during the long 'off-seasons' at most of these locations. Here we compare 2 years of R. typus visual sighting records from Mafia Island in Tanzania to concurrent acoustic telemetry of tagged individuals. Sightings revealed a clear seasonal pattern with a peak between October and February and no sharks observed at other times. By contrast, acoustic telemetry demonstrated year-round residency of R. typus. The sharks use a different habitat in the off-season, swimming deeper and further away from shore, presumably in response to prey distributions. This behavioural change reduces the sharks' visibility, giving the false impression that they have left the area. We demonstrate, for the first time to our knowledge, year-round residency of unprovisioned, individual R. typus at an aggregation site, and highlight the importance of using multiple techniques to study the movement ecology of marine megafauna.

  2. Patterns and ecosystem consequences of shark declines in the ocean.

    PubMed

    Ferretti, Francesco; Worm, Boris; Britten, Gregory L; Heithaus, Michael R; Lotze, Heike K

    2010-08-01

    Whereas many land predators disappeared before their ecological roles were studied, the decline of marine apex predators is still unfolding. Large sharks in particular have experienced rapid declines over the last decades. In this study, we review the documented changes in exploited elasmobranch communities in coastal, demersal, and pelagic habitats, and synthesize the effects of sharks on their prey and wider communities. We show that the high natural diversity and abundance of sharks is vulnerable to even light fishing pressure. The decline of large predatory sharks reduces natural mortality in a range of prey, contributing to changes in abundance, distribution, and behaviour of small elasmobranchs, marine mammals, and sea turtles that have few other predators. Through direct predation and behavioural modifications, top-down effects of sharks have led to cascading changes in some coastal ecosystems. In demersal and pelagic communities, there is increasing evidence of mesopredator release, but cascading effects are more hypothetical. Here, fishing pressure on mesopredators may mask or even reverse some ecosystem effects. In conclusion, large sharks can exert strong top-down forces with the potential to shape marine communities over large spatial and temporal scales. Yet more empirical evidence is needed to test the generality of these effects throughout the ocean.

  3. Shark recreational fisheries: Status, challenges, and research needs.

    PubMed

    Gallagher, Austin J; Hammerschlag, Neil; Danylchuk, Andy J; Cooke, Steven J

    2016-12-19

    For centuries, the primary manner in which humans have interacted with sharks has been fishing. A combination of their slow-growing nature and high use-values have resulted in population declines for many species around the world, and to date the vast majority of fisheries-related work on sharks has focused on the commercial sector. Shark recreational fishing remains an overlooked area of research despite the fact that these practices are popular globally and could present challenges to their populations. Here we provide a topical overview of shark recreational fisheries, highlighting their history and current status. While recreational fishing can provide conservation benefits under certain circumstances, we focus our discourse on the relatively understudied, potentially detrimental impacts these activities may have on shark physiology, behavior, and fitness. We took this angle given the realized but potentially underestimated significance of recreational fishing for shark conservation management plans and stock assessments, in hopes of creating a dialogue around sustainability. We also present a series of broad and focused research questions and underpin areas of future research need to assist with the development of this emergent area of research.

  4. Immunoglobulins in the eggs of the nurse shark, Ginglymostoma cirratum.

    PubMed

    Haines, Ashley N; Flajnik, Martin F; Rumfelt, Lynn L; Wourms, John P

    2005-01-01

    Elasmobranchs, which include the sharks, skates, and rays, emerged over 450 million years ago and are the oldest vertebrates to possess an adaptive immune system. They have evolved diverse reproductive modes, with a variety of physiological adaptations that enhance reproductive success. The nurse shark, Ginglymostoma cirratum, is an aplacental, viviparous elasmobranch in which the egg and its associated vitelline vasculature are the primary route for maternal-embryonic interactions. During gestation, nurse shark embryos hatch from their eggcases and develop free in the uterus, which is flushed regularly with seawater. Similar to higher vertebrates, embryonic and neonatal nurse sharks possess an immune system that is not fully competent. In birds and bony fishes, maternal immunoglobulins (Ig) stored in the egg during oogenesis confer protective immunity to embryos during gestation. However, early research suggested that such transfer of passive immunity does not occur in sharks. To better understand how elasmobranch embryos are protected from waterborne pathogens during this potentially vulnerable time, we have re-examined the existence of Igs in elasmobranch eggs. Using monoclonal antibodies, we establish the presence of two classes of Igs in nurse shark eggs: 7S IgM and IgNAR. The potential transfer of immunoglobulins from elasmobranch eggs is discussed.

  5. Acoustic telemetry reveals cryptic residency of whale sharks

    PubMed Central

    Cagua, E. Fernando; Cochran, Jesse E. M.; Rohner, Christoph A.; Prebble, Clare E. M.; Sinclair-Taylor, Tane H.; Pierce, Simon J.; Berumen, Michael L.

    2015-01-01

    Although whale sharks (Rhincodon typus) have been documented to move thousands of kilometres, they are most frequently observed at a few predictable seasonal aggregation sites. The absence of sharks at the surface during visual surveys has led to the assumption that sharks disperse to places unknown during the long ‘off-seasons’ at most of these locations. Here we compare 2 years of R. typus visual sighting records from Mafia Island in Tanzania to concurrent acoustic telemetry of tagged individuals. Sightings revealed a clear seasonal pattern with a peak between October and February and no sharks observed at other times. By contrast, acoustic telemetry demonstrated year-round residency of R. typus. The sharks use a different habitat in the off-season, swimming deeper and further away from shore, presumably in response to prey distributions. This behavioural change reduces the sharks' visibility, giving the false impression that they have left the area. We demonstrate, for the first time to our knowledge, year-round residency of unprovisioned, individual R. typus at an aggregation site, and highlight the importance of using multiple techniques to study the movement ecology of marine megafauna. PMID:25832816

  6. Electroreception in juvenile scalloped hammerhead and sandbar sharks.

    PubMed

    Kajiura, Stephen M; Holland, Kim N

    2002-12-01

    The unique head morphology of sphyrnid sharks might have evolved to enhance electrosensory capabilities. The 'enhanced electroreception' hypothesis was tested by comparing the behavioral responses of similarly sized carcharhinid and sphyrnid sharks to prey-simulating electric stimuli. Juvenile scalloped hammerhead sharks Sphyrna lewini and sandbar sharks Carcharhinus plumbeus oriented to dipole electric fields from the same maximum distance (approximately 30 cm) and thus demonstrated comparable behavioral-response thresholds (<1 nV cm(-1)). Despite the similarity of response threshold, the orientation pathways and behaviors differed for the two species. Scalloped hammerheads typically demonstrated a pivot orientation in which the edge of the cephalofoil closest to the dipole remained stationary while the shark bent its trunk to orient to the center of the dipole. By contrast, sandbars swam in a broader arc towards the center of the dipole. The different orientation patterns are attributed to the hydrodynamic properties of the cephalofoil, which enables the hammerheads to execute sharp turns at high speed. The greater trunk width of the sandbar sharks prevented them from demonstrating the same degree of flexibility. Therefore, although the sphyrnid head morphology does not appear to confer a greater sensitivity to prey-simulating dipole electric fields, it does provide (1). a greater lateral search area, which may increase the probability of prey encounter, and (2). enhanced maneuverability, which may aid in prey capture.

  7. Olfaction Contributes to Pelagic Navigation in a Coastal Shark

    PubMed Central

    Nosal, Andrew P.; Chao, Yi; Farrara, John D.; Chai, Fei; Hastings, Philip A.

    2016-01-01

    How animals navigate the constantly moving and visually uniform pelagic realm, often along straight paths between distant sites, is an enduring mystery. The mechanisms enabling pelagic navigation in cartilaginous fishes are particularly understudied. We used shoreward navigation by leopard sharks (Triakis semifasciata) as a model system to test whether olfaction contributes to pelagic navigation. Leopard sharks were captured alongshore, transported 9 km offshore, released, and acoustically tracked for approximately 4 h each until the transmitter released. Eleven sharks were rendered anosmic (nares occluded with cotton wool soaked in petroleum jelly); fifteen were sham controls. Mean swimming depth was 28.7 m. On average, tracks of control sharks ended 62.6% closer to shore, following relatively straight paths that were significantly directed over spatial scales exceeding 1600 m. In contrast, tracks of anosmic sharks ended 37.2% closer to shore, following significantly more tortuous paths that approximated correlated random walks. These results held after swimming paths were adjusted for current drift. This is the first study to demonstrate experimentally that olfaction contributes to pelagic navigation in sharks, likely mediated by chemical gradients as has been hypothesized for birds. Given the similarities between the fluid three-dimensional chemical atmosphere and ocean, further research comparing swimming and flying animals may lead to a unifying paradigm explaining their extraordinary navigational abilities. PMID:26735492

  8. Cyanobacteria/Foraminifera Association from Anoxic/Dysoxic Beds of the Agua Nueva Formation (Upper Cretaceous - Cenomanian/Turonian) at Xilitla, San Luis Potosi, Central Mexico

    NASA Astrophysics Data System (ADS)

    Blanco-Piñón, A.; Maurrasse, F. J.; Rojas-León, A.; Duque-Botero, F.

    2008-05-01

    The Agua Nueva Formation in the vicinity of Xilitla, State of San Luis Potosí, Central Mexico, consists of interbedded brown shale (Grayish orange 10YR 7/4 to Moderate yellowish brown 10YR 5/4) and dark-gray fossiliferous limestone (Bluish gray 5B 6/1 to Dark bluish gray 5B 4/1), varying between 10 and 20 cm in thickness. The sequence also includes 2 to 4 cm- thick intermittent bentonite layers (Moderate greenish yellow 10Y 7/4, to dark greenish yellow 10Y 6/6 and Light olive 10Y 5/4). At the field scale, shaly intervals show no apparent internal structures, whereas most limestone beds show primary lamination at the millimeter scale (1-2 mm), and intermittent layers of black chert of about 5 cm thick. Pyrite is present as disseminated crystals and as 2 cm-thick layers. Bioturbation or macrobenthic organisms other than inoceramids do not occur in the Agua Nueva Formation at Xilitla. Unusual macrofossils are present only in limestone strata, and consist of well- preserved diverse genera of fishes such as sharks, Ptychodus sp. and teleosteans, Rhynchodercetis sp., Tselfatia sp., Goulmimichthys sp., and scales of Ichtyodectiformes, as well as ammonites and inoceramids (Blanco et al., 2006). The presence of Inoceramus (Mytyloides) labiatus (Maldonado-Koederll, 1956) indicates an Early Turonian age for the sequence. Total carbonate content (CaCO3 = TIC) varies between 62 and 94% in the Limestone beds, which yield Total Organic Carbon (TOC) from 0.4% to 2.5%; the shale intervals contain TIC values consistently lower than 33% and TOC lower than 0.8% Microscopically the limestone beds vary from mudstone to packstone composed essentially of coccoid cyanobacteria similar to coeval deposits in northeastern Mexico, Coahuila State, at Parras de La Fuente (Duque- Botero 2006). Similarly, the microspheroids are spherical to sub-spherical, and occur as isolated elements or aggregates forming series of chains of parallel-packed light lamina 1-2 mm thick. Filamentous cyanobacteria

  9. A new genus of fossil Mymaridae (Hymenoptera) from Cretaceous amber and key to Cretaceous mymarid genera.

    PubMed

    Poinar, George; Huber, John T

    2011-01-01

    Myanmymar aresconoidesgen n., sp. n. is described from one female in Burmese amber, dated as about 100 my. It is similar to Arescon on wing features but is unique among Mymaridae in having distinctly segmented palpi. It is the fifth mymarid genus definitely referable to the Cretaceous period. A key to Cretaceous mymarid genera is presented and the features of Myanmymar are compared with the other Cretaceous and extant mymarid genera.

  10. Essential and non-essential element concentrations in two sleeper shark species collected in arctic waters.

    PubMed

    McMeans, Bailey C; Borgå, Katrine; Bechtol, William R; Higginbotham, David; Fisk, Aaron T

    2007-07-01

    A number of elements/metals have increased in arctic biota and are of concern due to their potential toxicity. Most studies on elements in the Arctic have focused on marine mammals and seabirds, but concentrations in the Greenland shark (Somniosus microcephalus) and Pacific sleeper shark (Somniosus pacificus), the only two shark species known to regularly inhabit arctic waters, have never been reported. To address this data gap, concentrations and patterns of 25 elements were analyzed in liver of Greenland sharks collected about Cumberland Sound (n=24) and Pacific sleeper sharks collected about Prince William Sound (n=14). Several non-essential elements differed between species/locations, which could suggest geographical exposure differences or ecological (e.g., diet) differences between the species. Certain essential elements also differed between the two sleeper sharks, which may indicate different physiological requirements between these closely related shark species, although information on such relationships are lacking for sharks and fish.

  11. Learning and memory in the Port Jackson shark, Heterodontus portusjacksoni.

    PubMed

    Guttridge, Tristan L; Brown, Culum

    2014-03-01

    Basic understanding of the fundamental principles and mechanisms involved in learning is lacking for elasmobranch fishes. Our aim in this study was to experimentally investigate the learning and memory capacity of juvenile Port Jackson sharks, Heterodontus portusjacksoni. Sharks (N = 30) were conditioned over a 19-day period to associate an underwater LED light or stream of air-bubbles [conditioned stimulus (CS)] with a food reward [unconditioned stimulus (US)], using three procedures (delay, trace and control). During experiments, the CS signalled at a random time between 180 and 300 s for 30 s (six times per day). For the delay the US overlapped in time with the CS, for the trace the US delivered 10 s after the CS and for our control the US was delivered at random time between 180 and 300 s after the CS. H. portusjacksoni sharks trained in all procedures improved consistently in their time to obtain food, indicative of Pavlovian learning. Importantly, the number of sharks in the feeding area 5 s prior to CS onset did not change over time for any procedures. However, significantly more sharks were present 5 s after CS onset for delay for both air-bubble and light CS. Sharks trained in the delay and trace procedures using air-bubbles as the CS also displayed significantly more anticipatory behaviours, such as turning towards the CS and biting. Sharks trained with the light CS did not exhibit such behaviours; however, trace procedural sharks did show a significant improvement in moving towards the CS at its onset. At 20 and 40 days after the end of the conditioning experiments, some sharks were presented the CS without reward. Two sharks trained in the delay procedure using air-bubbles as the CS exhibited biting behaviours: one at 20 and the other at 40 days. This study demonstrates that H. portusjacksoni have the capacity to learn a classical conditioning procedure relatively quickly (30 trials during 5 days) and associate two time-separated events and

  12. Early Cretaceous angiosperms and beetle evolution

    PubMed Central

    Wang, Bo; Zhang, Haichun; Jarzembowski, Edmund A.

    2013-01-01

    The Coleoptera (beetles) constitute almost one–fourth of all known life-forms on earth. They are also among the most important pollinators of flowering plants, especially basal angiosperms. Beetle fossils are abundant, almost spanning the entire Early Cretaceous, and thus provide important clues to explore the co-evolutionary processes between beetles and angiosperms. We review the fossil record of some Early Cretaceous polyphagan beetles including Tenebrionoidea, Scarabaeoidea, Curculionoidea, and Chrysomeloidea. Both the fossil record and molecular analyses reveal that these four groups had already diversified during or before the Early Cretaceous, clearly before the initial rise of angiosperms to widespread floristic dominance. These four beetle groups are important pollinators of basal angiosperms today, suggesting that their ecological association with angiosperms probably formed as early as in the Early Cretaceous. With the description of additional well-preserved fossils and improvements in phylogenetic analyses, our knowledge of Mesozoic beetle–angiosperm mutualisms will greatly increase during the near future. PMID:24062759

  13. Early Cretaceous angiosperms and beetle evolution.

    PubMed

    Wang, Bo; Zhang, Haichun; Jarzembowski, Edmund A

    2013-09-12

    The Coleoptera (beetles) constitute almost one-fourth of all known life-forms on earth. They are also among the most important pollinators of flowering plants, especially basal angiosperms. Beetle fossils are abundant, almost spanning the entire Early Cretaceous, and thus provide important clues to explore the co-evolutionary processes between beetles and angiosperms. We review the fossil record of some Early Cretaceous polyphagan beetles including Tenebrionoidea, Scarabaeoidea, Curculionoidea, and Chrysomeloidea. Both the fossil record and molecular analyses reveal that these four groups had already diversified during or before the Early Cretaceous, clearly before the initial rise of angiosperms to widespread floristic dominance. These four beetle groups are important pollinators of basal angiosperms today, suggesting that their ecological association with angiosperms probably formed as early as in the Early Cretaceous. With the description of additional well-preserved fossils and improvements in phylogenetic analyses, our knowledge of Mesozoic beetle-angiosperm mutualisms will greatly increase during the near future.

  14. Biostratigraphy of Echinoid spines, Cretaceous of Texas

    SciTech Connect

    Kirkland, P.L.

    1984-04-01

    Echinoid (sea urchin) spines from Cretaceous strata have widely varying morphology. They are common, and most are small enough to be recovered from well cuttings. Many forms have restricted ranges; consequently, echinoid spine have substantial biostratigraphic utility. There have been established 115 form taxa of echinoid spines and 14 form taxa of ophiuroid-asteroid spines for the Cretaceous of Texas. The specimens used for establishing the form taxa were processed from 533 outcrop samples (78 localities) from 30 Cretaceous formations, each with a well-defined age based on faunal zones of ammonites and Foraminifera. A dichotomous key in 9 parts and a catalog of scanning electron micrographs (87 plates) have been set up to assist identification of the form taxa. Range charts for the echinoid and ophiuroid-asteroid form taxa have utility through the Cretaceous of much of the Gulf Coastal area. The most precise zonation has been possible for the Albian.

  15. Upper Cretaceous Brachycythere (Ostr., Crust.) from Iran

    NASA Astrophysics Data System (ADS)

    Emami, V.

    Five new species of Brachycythere (Crustacea, Ostracoda) are described and figured from the Gurpi Formation (Campanian, Upper Cretaceous). The new species are B. reymenti. B. ilamensis, B. iranensis, B. labioforma, B. posterotruncata and « Brachycythereå sp.nov.?

  16. 77 FR 37647 - Atlantic Highly Migratory Species; Silky Shark Management Measures

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-22

    ... ecological risk assessment for Atlantic sharks. In this proposed rule, NMFS considers changes to the Atlantic.... Silky sharks were included in the 2010 ecological risk assessment conducted for the ICCAT Standing... susceptibility of silky sharks to pelagic longline fisheries as noted in the ecological risk assessment,...

  17. 78 FR 54456 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-04

    ... National Oceanic and Atmospheric Administration RIN 0648-XC810 Schedules for Atlantic Shark Identification... of public workshops. SUMMARY: Free Atlantic Shark Identification Workshops and Protected Species Safe.... Certain fishermen and shark dealers are required to attend a workshop to meet regulatory requirements...

  18. 76 FR 72383 - Atlantic Highly Migratory Species; Atlantic Shark Management Measures

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-23

    ... Administration 50 CFR Part 635 RIN 0648-BA17 Atlantic Highly Migratory Species; Atlantic Shark Management...) and fishery management plan (FMP) amendment that would consider catch shares for the Atlantic shark... design elements for potential catch shares programs in the Atlantic shark fisheries. Additionally,...

  19. 77 FR 32950 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-04

    ... National Oceanic and Atmospheric Administration RIN 0648-XC042 Schedules for Atlantic Shark Identification... of public workshops. SUMMARY: Free Atlantic Shark Identification Workshops and Protected Species Safe.... Certain fishermen and shark dealers are required to attend a workshop to meet regulatory requirements...

  20. 77 FR 12574 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-01

    ... National Oceanic and Atmospheric Administration RIN 0648-XB037 Schedules for Atlantic Shark Identification... of public workshops. SUMMARY: Free Atlantic Shark Identification Workshops and Protected Species Safe... fishermen and shark dealers are required to attend a workshop to meet regulatory requirements and...

  1. 75 FR 29991 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-28

    ... National Oceanic and Atmospheric Administration RIN 0648-XW44 Schedules for Atlantic Shark Identification... of public workshops. SUMMARY: Free Atlantic Shark Identification Workshops and Protected Species Safe.... Certain fishermen and shark dealers are required to attend a workshop to meet regulatory requirements...

  2. 75 FR 10217 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-05

    ...-XU40 Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling, Release... Atlantic Shark Identification Workshops and Protected Species Safe Handling, Release, and Identification Workshops to be held in April, May, and June of 2010. Certain fishermen and shark dealers are required...

  3. 77 FR 55464 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-10

    ... National Oceanic and Atmospheric Administration RIN 0648-XC174 Schedules for Atlantic Shark Identification... of public workshops. SUMMARY: Free Atlantic Shark Identification Workshops and Protected Species Safe.... Certain fishermen and shark dealers are required to attend a workshop to meet regulatory requirements...

  4. Mercury accumulation in sharks from the coastal waters of southwest Florida.

    PubMed

    Rumbold, Darren; Wasno, Robert; Hammerschlag, Neil; Volety, Aswani

    2014-10-01

    As large long-lived predators, sharks are particularly vulnerable to exposure to methylmercury biomagnified through the marine food web. Accordingly, nonlethal means were used to collect tissues for determining mercury (Hg) concentrations and stable isotopes of carbon (δ(13)C) and nitrogen (δ(15)N) from a total of 69 sharks, comprising 7 species, caught off Southwest Florida from May 2010 through June 2013. Species included blacknose (Carcharhinus acronotus), blacktip (C. limbatus), bull (C. leucas), great hammerhead (Sphyrna mokarran), lemon (Negaprion brevirostris), sharpnose (Rhizoprionodon terraenovae), and tiger sharks (Galeocerdo cuvier). The sharks contained Hg concentrations in their muscle tissues ranging from 0.19 mg/kg (wet-weight basis) in a tiger shark to 4.52 mg/kg in a blacktip shark. Individual differences in total length and δ(13)C explained much of the intraspecific variation in Hg concentrations in blacknose, blacktip, and sharpnose sharks, but similar patterns were not evident for Hg and δ(15)N. Interspecific differences in Hg concentration were evident with greater concentrations in slower-growing, mature blacktip sharks and lower concentrations in faster-growing, young tiger sharks than other species. These results are consistent with previous studies reporting age-dependent growth rate can be an important determinant of intraspecific and interspecific patterns in Hg accumulation. The Hg concentrations observed in these sharks, in particular the blacktip shark, also suggested that Hg may pose a threat to shark health and fitness.

  5. 76 FR 34209 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-13

    ... National Oceanic and Atmospheric Administration RIN 0648-XA450 Schedules for Atlantic Shark Identification... of public workshops. SUMMARY: Free Atlantic Shark Identification Workshops and Protected Species Safe.... Certain fishermen and shark dealers are required to attend a workshop to meet regulatory requirements...

  6. 75 FR 53665 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-01

    ... RIN 0648-XY59 Schedules for Atlantic Shark Identification Workshops and Protected Species Safe... Atlantic Shark Identification Workshops and Protected Species Safe Handling, Release, and Identification Workshops will be held in October, November, and December of 2010. Certain fishermen and shark dealers...

  7. Ocean-wide tracking of pelagic sharks reveals extent of overlap with longline fishing hotspots.

    PubMed

    Queiroz, Nuno; Humphries, Nicolas E; Mucientes, Gonzalo; Hammerschlag, Neil; Lima, Fernando P; Scales, Kylie L; Miller, Peter I; Sousa, Lara L; Seabra, Rui; Sims, David W

    2016-02-09

    Overfishing is arguably the greatest ecological threat facing the oceans, yet catches of many highly migratory fishes including oceanic sharks remain largely unregulated with poor monitoring and data reporting. Oceanic shark conservation is hampered by basic knowledge gaps about where sharks aggregate across population ranges and precisely where they overlap with fishers. Using satellite tracking data from six shark species across the North Atlantic, we show that pelagic sharks occupy predictable habitat hotspots of high space use. Movement modeling showed sharks preferred habitats characterized by strong sea surface-temperature gradients (fronts) over other available habitats. However, simultaneous Global Positioning System (GPS) tracking of the entire Spanish and Portuguese longline-vessel fishing fleets show an 80% overlap of fished areas with hotspots, potentially increasing shark susceptibility to fishing exploitation. Regions of high overlap between oceanic tagged sharks and longliners included the North Atlantic Current/Labrador Current convergence zone and the Mid-Atlantic Ridge southwest of the Azores. In these main regions, and subareas within them, shark/vessel co-occurrence was spatially and temporally persistent between years, highlighting how broadly the fishing exploitation efficiently "tracks" oceanic sharks within their space-use hotspots year-round. Given this intense focus of longliners on shark hotspots, our study argues the need for international catch limits for pelagic sharks and identifies a future role of combining fine-scale fish and vessel telemetry to inform the ocean-scale management of fisheries.

  8. 75 FR 57235 - Atlantic Highly Migratory Species; Atlantic Shark Management Measures

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-20

    ... Species; Atlantic Shark Management Measures AGENCY: National Marine Fisheries Service (NMFS), National....S. Atlantic shark fishery to address several specific issues currently affecting management of the shark fishery and to identify specific goals for management of fishery in the future. NMFS is...

  9. 77 FR 32036 - Atlantic Highly Migratory Species; Commercial Porbeagle Shark Fishery Closure

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-31

    ... Species; Commercial Porbeagle Shark Fishery Closure AGENCY: National Marine Fisheries Service (NMFS.... SUMMARY: NMFS is closing the commercial fishery for porbeagle sharks. This action is necessary because... commercial porbeagle shark fishery is closed effective 11:30 p.m. local time May 30, 2012, until, and...

  10. 76 FR 11679 - Drawbridge Operation Regulation; Shark River (South Channel), Belmar, NJ

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-03

    ... SECURITY Coast Guard 33 CFR Part 117 Drawbridge Operation Regulation; Shark River (South Channel), Belmar... operation of the S71 Bridge across Shark River (South Channel), mile 0.8, at Belmar, NJ. The deviation is... INFORMATION: The S71 Bridge, a bascule lift drawbridge, across Shark River (South Channel), at mile 0.8,...

  11. 50 CFR 635.24 - Commercial retention limits for sharks and swordfish.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Commercial retention limits for sharks and... Management Measures § 635.24 Commercial retention limits for sharks and swordfish. The retention limits in this section are subject to the quotas and closure provisions in §§ 635.27 and 635.28. (a) Sharks....

  12. 76 FR 59661 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-27

    ... National Oceanic and Atmospheric Administration RIN 0648-XA670 Schedules for Atlantic Shark Identification... of public workshops. SUMMARY: Free Atlantic Shark Identification Workshops and Protected Species Safe.... Certain fishermen and shark dealers are required to attend a workshop to meet regulatory requirements...

  13. 75 FR 53871 - Atlantic Highly Migratory Species; Inseason Action To Close the Commercial Porbeagle Shark Fishery

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-02

    ... Species; Inseason Action To Close the Commercial Porbeagle Shark Fishery AGENCY: National Marine Fisheries... closure. SUMMARY: NMFS is closing the commercial fishery for porbeagle sharks. This action is necessary...: The commercial porbeagle shark fishery is closed effective 11:30 p.m. local time September 4,...

  14. 76 FR 11762 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-03

    ... National Oceanic and Atmospheric Administration RIN 0648-XA213 Schedules for Atlantic Shark Identification... of public workshops. SUMMARY: Free Atlantic Shark Identification Workshops and Protected Species Safe... fishermen and shark dealers are required to attend a workshop to meet regulatory requirements and...

  15. 75 FR 50715 - Atlantic Highly Migratory Species; Atlantic Shark Management Measures; Amendment 3

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-17

    ... Migratory Species; Atlantic Shark Management Measures; Amendment 3 AGENCY: National Marine Fisheries Service.... This change ensures that the process is preserved for adjusting annual shark quotas based on over- and..., among other things, pelagic shark quotas and annual quota adjustments. The instructions,...

  16. 75 FR 74693 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-01

    ... National Oceanic and Atmospheric Administration RIN 0648-XAO61 Schedules for Atlantic Shark Identification... of public workshops. SUMMARY: Free Atlantic Shark Identification Workshops and Protected Species Safe.... Certain fishermen and shark dealers are required to attend a workshop to meet regulatory requirements...

  17. 78 FR 15709 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-12

    ... National Oceanic and Atmospheric Administration RIN 0648-XC512 Schedules for Atlantic Shark Identification... of public workshops. SUMMARY: Free Atlantic Shark Identification Workshops and Protected Species Safe... fishermen and shark dealers are required to attend a workshop to meet regulatory requirements and...

  18. 77 FR 35357 - Atlantic Highly Migratory Species; Commercial Atlantic Region Non-Sandbar Large Coastal Shark...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-13

    ...; Commercial Atlantic Region Non-Sandbar Large Coastal Shark Fishery Opening Date AGENCY: National Marine...-sandbar large coastal shark fishery. This action is necessary to inform fishermen and dealers about the fishery opening date. DATES: The commercial Atlantic region non-sandbar large coastal shark fishery...

  19. 77 FR 70372 - Drawbridge Operation Regulation; Shark River (South Channel), Avon Township, NJ

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-26

    ... SECURITY Coast Guard 33 CFR Part 117 RIN 1625-AA09 Drawbridge Operation Regulation; Shark River (South..., across Shark River (South Channel) at Avon Township, NJ. The existing regulation contains a drawbridge... Transportation (NJDOT) to replace the existing bascule bridge, which carries S35 over Shark River (South...

  20. 75 FR 54598 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-08

    ... National Oceanic and Atmospheric Administration RIN 0648-XW44 Schedules for Atlantic Shark Identification... cancelling the Atlantic Shark Identification workshop that was scheduled for September 2, 2010, in Wilmington... South College Road, Wilmington, NC 28403. DATES: The Atlantic Shark Identification Workshop...

  1. 76 FR 77214 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-12

    ... National Oceanic and Atmospheric Administration RIN 0648-XA843 Schedules for Atlantic Shark Identification... of public workshops. SUMMARY: Free Atlantic Shark Identification Workshops and Protected Species Safe.... Certain fishermen and shark dealers are required to attend a workshop to meet regulatory requirements...

  2. 77 FR 73451 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-10

    ... National Oceanic and Atmospheric Administration RIN 0648-XC361 Schedules for Atlantic Shark Identification... of public workshops. SUMMARY: Free Atlantic Shark Identification Workshops and Protected Species Safe.... Certain fishermen and shark dealers are required to attend a workshop to meet regulatory requirements...

  3. 78 FR 34349 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-07

    ... National Oceanic and Atmospheric Administration RIN 0648-XC681 Schedules for Atlantic Shark Identification... of public workshops. SUMMARY: Free Atlantic Shark Identification Workshops and Protected Species Safe.... Certain fishermen and shark dealers are required to attend a workshop to meet regulatory requirements...

  4. 78 FR 58878 - Safety Zone; San Diego Shark Fest Swim; San Diego Bay, San Diego, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-25

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; San Diego Shark Fest Swim; San Diego Bay... Diego Shark Fest Swim. This safety zone is necessary to provide for the safety of the participants, crew... this rule because the logistical details of the San Diego Shark Fest Swim were not finalized...

  5. Ocean-wide tracking of pelagic sharks reveals extent of overlap with longline fishing hotspots

    PubMed Central

    Queiroz, Nuno; Humphries, Nicolas E.; Hammerschlag, Neil; Miller, Peter I.; Sousa, Lara L.; Seabra, Rui; Sims, David W.

    2016-01-01

    Overfishing is arguably the greatest ecological threat facing the oceans, yet catches of many highly migratory fishes including oceanic sharks remain largely unregulated with poor monitoring and data reporting. Oceanic shark conservation is hampered by basic knowledge gaps about where sharks aggregate across population ranges and precisely where they overlap with fishers. Using satellite tracking data from six shark species across the North Atlantic, we show that pelagic sharks occupy predictable habitat hotspots of high space use. Movement modeling showed sharks preferred habitats characterized by strong sea surface-temperature gradients (fronts) over other available habitats. However, simultaneous Global Positioning System (GPS) tracking of the entire Spanish and Portuguese longline-vessel fishing fleets show an 80% overlap of fished areas with hotspots, potentially increasing shark susceptibility to fishing exploitation. Regions of high overlap between oceanic tagged sharks and longliners included the North Atlantic Current/Labrador Current convergence zone and the Mid-Atlantic Ridge southwest of the Azores. In these main regions, and subareas within them, shark/vessel co-occurrence was spatially and temporally persistent between years, highlighting how broadly the fishing exploitation efficiently “tracks” oceanic sharks within their space-use hotspots year-round. Given this intense focus of longliners on shark hotspots, our study argues the need for international catch limits for pelagic sharks and identifies a future role of combining fine-scale fish and vessel telemetry to inform the ocean-scale management of fisheries. PMID:26811467

  6. 50 CFR 635.24 - Commercial retention limits for sharks and swordfish.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ..., smooth, and great hammerhead sharks is prohibited on vessels issued a permit under this part that have... 50 Wildlife and Fisheries 10 2011-10-01 2011-10-01 false Commercial retention limits for sharks... Management Measures § 635.24 Commercial retention limits for sharks and swordfish. The retention limits...

  7. Laser photogrammetry improves size and demographic estimates for whale sharks.

    PubMed

    Rohner, Christoph A; Richardson, Anthony J; Prebble, Clare E M; Marshall, Andrea D; Bennett, Michael B; Weeks, Scarla J; Cliff, Geremy; Wintner, Sabine P; Pierce, Simon J

    2015-01-01

    Whale sharks Rhincodon typus are globally threatened, but a lack of biological and demographic information hampers an accurate assessment of their vulnerability to further decline or capacity to recover. We used laser photogrammetry at two aggregation sites to obtain more accurate size estimates of free-swimming whale sharks compared to visual estimates, allowing improved estimates of biological parameters. Individual whale sharks ranged from 432-917 cm total length (TL) (mean ± SD = 673 ± 118.8 cm, N = 122) in southern Mozambique and from 420-990 cm TL (mean ± SD = 641 ± 133 cm, N = 46) in Tanzania. By combining measurements of stranded individuals with photogrammetry measurements of free-swimming sharks, we calculated length at 50% maturity for males in Mozambique at 916 cm TL. Repeat measurements of individual whale sharks measured over periods from 347-1,068 days yielded implausible growth rates, suggesting that the growth increment over this period was not large enough to be detected using laser photogrammetry, and that the method is best applied to estimating growth rates over longer (decadal) time periods. The sex ratio of both populations was biased towards males (74% in Mozambique, 89% in Tanzania), the majority of which were immature (98% in Mozambique, 94% in Tanzania). The population structure for these two aggregations was similar to most other documented whale shark aggregations around the world. Information on small (<400 cm) whale sharks, mature individuals, and females in this region is lacking, but necessary to inform conservation initiatives for this globally threatened species.

  8. Is Centrophorus squamosus a highly migratory deep-water shark?

    NASA Astrophysics Data System (ADS)

    Rodríguez-Cabello, Cristina; Sánchez, Francisco

    2014-10-01

    Deep-water sharks are considered highly vulnerable species due to their life characteristics and very low recovery capacity against overfishing. However, there is still limited information on the ecology or population connectivity of these species. The aim of this study was to investigate if the species Centrophorus squamosus could make long displacements and thus confirm the existence of connectivity between different deep-water areas. In addition, the study was the first attempt to use tagging techniques on deep-water sharks, since it has never been undertaken before. Five C. squamosus were tagged with satellite tags (PAT) in the El Cachucho Marine Protected Area (Le Danois Bank) located in waters of the North of Spain, Cantabrian Sea (NE Atlantic). Data from four of these tags were recovered. One of the sharks travelled approximately 287 nm toward the north east (French continental shelf) hypothetically following the continental slope at a mean depth of 901±109 m for 45 days. Two other sharks spent almost 4 months traveling, in which time they moved 143 and 168 nm, respectively, to the west (Galician coast). Finally, another leafscale gulper shark travelled to the NW (Porcupine Bank) during a period of 3 months at a mean depth of 940±132 m. Depth and temperature preferences for all the sharks are discussed. Minimum and maximum depths recorded were 496 and 1848 m, respectively. The temperature range was between 6.2 and 11.4 °C, but the mean temperature was approximately 9.9±0.7 °C. The sharks made large vertical displacements throughout the water column with a mean daily depth range of 345±27 m. These preliminary results support the suggestion of a whole population in the NE Atlantic and confirm the capacity of this species to travel long distances.

  9. Laser photogrammetry improves size and demographic estimates for whale sharks

    PubMed Central

    Richardson, Anthony J.; Prebble, Clare E.M.; Marshall, Andrea D.; Bennett, Michael B.; Weeks, Scarla J.; Cliff, Geremy; Wintner, Sabine P.; Pierce, Simon J.

    2015-01-01

    Whale sharks Rhincodon typus are globally threatened, but a lack of biological and demographic information hampers an accurate assessment of their vulnerability to further decline or capacity to recover. We used laser photogrammetry at two aggregation sites to obtain more accurate size estimates of free-swimming whale sharks compared to visual estimates, allowing improved estimates of biological parameters. Individual whale sharks ranged from 432–917 cm total length (TL) (mean ± SD = 673 ± 118.8 cm, N = 122) in southern Mozambique and from 420–990 cm TL (mean ± SD = 641 ± 133 cm, N = 46) in Tanzania. By combining measurements of stranded individuals with photogrammetry measurements of free-swimming sharks, we calculated length at 50% maturity for males in Mozambique at 916 cm TL. Repeat measurements of individual whale sharks measured over periods from 347–1,068 days yielded implausible growth rates, suggesting that the growth increment over this period was not large enough to be detected using laser photogrammetry, and that the method is best applied to estimating growth rates over longer (decadal) time periods. The sex ratio of both populations was biased towards males (74% in Mozambique, 89% in Tanzania), the majority of which were immature (98% in Mozambique, 94% in Tanzania). The population structure for these two aggregations was similar to most other documented whale shark aggregations around the world. Information on small (<400 cm) whale sharks, mature individuals, and females in this region is lacking, but necessary to inform conservation initiatives for this globally threatened species. PMID:25870776

  10. Indicators of fishing mortality on reef-shark populations in the world's first shark sanctuary: the need for surveillance and enforcement

    NASA Astrophysics Data System (ADS)

    Vianna, Gabriel M. S.; Meekan, Mark G.; Ruppert, Jonathan L. W.; Bornovski, Tova H.; Meeuwig, Jessica J.

    2016-09-01

    Shark sanctuaries are promoted as a management tool to achieve conservation goals following global declines of shark populations. We assessed the status of reef-shark populations and indicators of fishing pressure across the world's first shark sanctuary in Palau. Using underwater surveys and stereophotogrammetry, we documented large differences in abundance and size structure of shark populations across the sanctuary, with a strong negative relationship between shark densities and derelict fishing gear on reefs. Densities of 10.9 ± 4.7 (mean ± SE) sharks ha-1 occurred on reefs adjacent to the most populated islands of Palau, contrasting with lower densities of 1.6 ± 0.8 sharks ha-1 on remote uninhabited reefs, where surveillance and enforcement was limited. Our observations suggest that fishing still remains a major factor structuring shark populations in Palau, demonstrating that there is an urgent need for better enforcement and surveillance that targets both illegal and licensed commercial fisheries to provide effective protection for sharks within the sanctuary.

  11. 78 FR 40687 - Magnuson-Stevens Act Provisions; Implementation of the Shark Conservation Act of 2010; Extension...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-08

    ... Provisions; Implementation of the Shark Conservation Act of 2010; Extension of Comment Period AGENCY..., 2013, to implement provisions of the Shark Conservation Act of 2010 (SCA) that prohibit any person from removing any of the fins of a shark at sea, possessing shark fins on board a fishing vessel unless they...

  12. 78 FR 36149 - Magnuson-Stevens Act Provisions; Implementation of the Shark Conservation Act of 2010; Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-17

    ... Provisions; Implementation of the Shark Conservation Act of 2010; Correction AGENCY: National Marine..., to implement provisions of the Shark Conservation Act of 2010 (SCA) that prohibit any person from removing any of the fins of a shark at sea, possessing shark fins on board a fishing vessel unless they...

  13. Residency and spatial use by reef sharks of an isolated seamount and its implications for conservation.

    PubMed

    Barnett, Adam; Abrantes, Kátya G; Seymour, Jamie; Fitzpatrick, Richard

    2012-01-01

    Although marine protected areas (MPAs) are a common conservation strategy, these areas are often designed with little prior knowledge of the spatial behaviour of the species they are designed to protect. Currently, the Coral Sea area and its seamounts (north-east Australia) are under review to determine if MPAs are warranted. The protection of sharks at these seamounts should be an integral component of conservation plans. Therefore, knowledge on the spatial ecology of sharks at the Coral Sea seamounts is essential for the appropriate implementation of management and conservation plans. Acoustic telemetry was used to determine residency, site fidelity and spatial use of three shark species at Osprey Reef: whitetip reef sharks Triaenodon obesus, grey reef sharks Carcharhinus amblyrhynchos and silvertip sharks Carcharhinus albimarginatus. Most individuals showed year round residency at Osprey Reef, although five of the 49 individuals tagged moved to the neighbouring Shark Reef (~14 km away) and one grey reef shark completed a round trip of ~250 km to the Great Barrier Reef. Additionally, individuals of white tip and grey reef sharks showed strong site fidelity to the areas they were tagged, and there was low spatial overlap between groups of sharks tagged at different locations. Spatial use at Osprey Reef by adult sharks is generally restricted to the north-west corner. The high residency and limited spatial use of Osprey Reef suggests that reef sharks would be highly vulnerable to targeted fishing pressure and that MPAs incorporating no-take of sharks would be effective in protecting reef shark populations at Osprey and Shark Reef.

  14. Residency and Spatial Use by Reef Sharks of an Isolated Seamount and Its Implications for Conservation

    PubMed Central

    Barnett, Adam; Abrantes, Kátya G.; Seymour, Jamie; Fitzpatrick, Richard

    2012-01-01

    Although marine protected areas (MPAs) are a common conservation strategy, these areas are often designed with little prior knowledge of the spatial behaviour of the species they are designed to protect. Currently, the Coral Sea area and its seamounts (north-east Australia) are under review to determine if MPAs are warranted. The protection of sharks at these seamounts should be an integral component of conservation plans. Therefore, knowledge on the spatial ecology of sharks at the Coral Sea seamounts is essential for the appropriate implementation of management and conservation plans. Acoustic telemetry was used to determine residency, site fidelity and spatial use of three shark species at Osprey Reef: whitetip reef sharks Triaenodon obesus, grey reef sharks Carcharhinus amblyrhynchos and silvertip sharks Carcharhinus albimarginatus. Most individuals showed year round residency at Osprey Reef, although five of the 49 individuals tagged moved to the neighbouring Shark Reef (∼14 km away) and one grey reef shark completed a round trip of ∼250 km to the Great Barrier Reef. Additionally, individuals of white tip and grey reef sharks showed strong site fidelity to the areas they were tagged, and there was low spatial overlap between groups of sharks tagged at different locations. Spatial use at Osprey Reef by adult sharks is generally restricted to the north-west corner. The high residency and limited spatial use of Osprey Reef suggests that reef sharks would be highly vulnerable to targeted fishing pressure and that MPAs incorporating no-take of sharks would be effective in protecting reef shark populations at Osprey and Shark Reef. PMID:22615782

  15. Vulnerability of the Oceanic Whitetip Shark to Pelagic Longline Fisheries

    PubMed Central

    Tolotti, Mariana Travassos; Bach, Pascal; Hazin, Fábio; Travassos, Paulo; Dagorn, Laurent

    2015-01-01

    A combination of fisheries dependent and independent data was used to assess the vulnerability of the oceanic whitetip shark to pelagic longline fisheries. The Brazilian tuna longline fleet, operating in the equatorial and southwestern Atlantic, is used as a case study. Fisheries dependent data include information from logbooks (from 1999 to 2011) and on-board observers (2004 to 2010), totaling 65,277 pelagic longline sets. Fisheries independent data were obtained from 8 oceanic whitetip sharks tagged with pop-up satellite archival tags in the area where longline fleet operated. Deployment periods varied from 60 to 178 days between 2010 and 2012. Tagging and pop-up sites were relatively close to each other, although individuals tended to travel long distances before returning to the tagging area. Some degree of site fidelity was observed. High utilization hotspots of tagged sharks fell inside the area under strongest fishing pressure. Despite the small sample size, a positive correlation between tag recorded information and catch data was detected. All sharks exhibited a strong preference for the warm and shallow waters of the mixed layer, spending on average more than 70% of the time above the thermocline and 95% above 120 m. Results indicate that the removal of shallow hooks on longline gear might be an efficient mitigation measure to reduce the bycatch of this pelagic shark species. The work also highlights the potential of tagging experiments to provide essential information for the development of spatio-temporal management measures. PMID:26492091

  16. Biased Immunoglobulin Light Chain Gene Usage in the Shark.

    PubMed

    Iacoangeli, Anna; Lui, Anita; Naik, Ushma; Ohta, Yuko; Flajnik, Martin; Hsu, Ellen

    2015-10-15

    This study of a large family of κ L chain clusters in nurse shark completes the characterization of its classical Ig gene content (two H chain isotypes, μ and ω, and four L chain isotypes, κ, λ, σ, and σ-2). The shark κ clusters are minigenes consisting of a simple VL-JL-CL array, where V to J recombination occurs over an ~500-bp interval, and functional clusters are widely separated by at least 100 kb. Six out of ~39 κ clusters are prerearranged in the germline (germline joined). Unlike the complex gene organization and multistep assembly process of Ig in mammals, each shark Ig rearrangement, somatic or in the germline, appears to be an independent event localized to the minigene. This study examined the expression of functional, nonproductive, and sterile transcripts of the κ clusters compared with the other three L chain isotypes. κ cluster usage was investigated in young sharks, and a skewed pattern of split gene expression was observed, one similar in functional and nonproductive rearrangements. These results show that the individual activation of the spatially distant κ clusters is nonrandom. Although both split and germline-joined κ genes are expressed, the latter are prominent in young animals and wane with age. We speculate that, in the shark, the differential activation of the multiple isotypes can be advantageously used in receptor editing.

  17. Vulnerability of the Oceanic Whitetip Shark to Pelagic Longline Fisheries.

    PubMed

    Tolotti, Mariana Travassos; Bach, Pascal; Hazin, Fábio; Travassos, Paulo; Dagorn, Laurent

    2015-01-01

    A combination of fisheries dependent and independent data was used to assess the vulnerability of the oceanic whitetip shark to pelagic longline fisheries. The Brazilian tuna longline fleet, operating in the equatorial and southwestern Atlantic, is used as a case study. Fisheries dependent data include information from logbooks (from 1999 to 2011) and on-board observers (2004 to 2010), totaling 65,277 pelagic longline sets. Fisheries independent data were obtained from 8 oceanic whitetip sharks tagged with pop-up satellite archival tags in the area where longline fleet operated. Deployment periods varied from 60 to 178 days between 2010 and 2012. Tagging and pop-up sites were relatively close to each other, although individuals tended to travel long distances before returning to the tagging area. Some degree of site fidelity was observed. High utilization hotspots of tagged sharks fell inside the area under strongest fishing pressure. Despite the small sample size, a positive correlation between tag recorded information and catch data was detected. All sharks exhibited a strong preference for the warm and shallow waters of the mixed layer, spending on average more than 70% of the time above the thermocline and 95% above 120 m. Results indicate that the removal of shallow hooks on longline gear might be an efficient mitigation measure to reduce the bycatch of this pelagic shark species. The work also highlights the potential of tagging experiments to provide essential information for the development of spatio-temporal management measures.

  18. Body condition predicts energy stores in apex predatory sharks

    PubMed Central

    Gallagher, Austin J.; Wagner, Dominique N.; Irschick, Duncan J.; Hammerschlag, Neil

    2014-01-01

    Animal condition typically reflects the accumulation of energy stores (e.g. fatty acids), which can influence an individual's decision to undertake challenging life-history events, such as migration and reproduction. Accordingly, researchers often use measures of animal body size and/or weight as an index of condition. However, values of condition, such as fatty acid levels, may not always reflect the physiological state of animals accurately. While the relationships between condition indices and energy stores have been explored in some species (e.g. birds), they have yet to be examined in top predatory fishes, which often undertake extensive and energetically expensive migrations. We used an apex predatory shark (Galeocerdo cuvier, the tiger shark) as a model species to evaluate the relationship between triglycerides (energy metabolite) and a metric of overall body condition. We captured, blood sampled, measured and released 28 sharks (size range 125–303 cm pre-caudal length). In the laboratory, we assayed each plasma sample for triglyceride values. We detected a positive and significant relationship between condition and triglyceride values (P < 0.02). This result may have conservation implications if the largest and highest-condition sharks are exploited in fisheries, because these individuals are likely to have the highest potential for successful reproduction. Our results suggest that researchers may use either plasma triglyceride values or an appropriate measure of body condition for assessing health in large sharks. PMID:27293643

  19. Biased immunoglobulin light chain gene usage in the shark1

    PubMed Central

    Iacoangeli, Anna; Lui, Anita; Naik, Ushma; Ohta, Yuko; Flajnik, Martin; Hsu, Ellen

    2015-01-01

    This study of a large family of kappa light (L) chain clusters in nurse shark completes the characterization of its classical immunoglobulin (Ig) gene content (two heavy chain classes, mu and omega, and four L chain isotopes, kappa, lambda, sigma, and sigma-2). The shark kappa clusters are minigenes consisting of a simple VL-JL-CL array, where V to J recombination occurs over a ~500 bp interval, and functional clusters are widely separated by at least 100 kb. Six out of ca. 39 kappa clusters are pre-rearranged in the germline (GL-joined). Unlike the complex gene organization and multistep assembly process of Ig in mammals, each shark Ig rearrangement, somatic or in the germline, appears to be an independent event localized to the minigene. This study examined the expression of functional, non-productive, and sterile transcripts of the kappa clusters compared to the other three L chain isotypes. Kappa cluster usage was investigated in young sharks, and a skewed pattern of split gene expression was observed, one similar in functional and non-productive rearrangements. These results show that the individual activation of the spatially distant kappa clusters is non-random. Although both split and GL-joined kappa genes are expressed, the latter are prominent in young animals and wane with age. We speculate that, in the shark, the differential activation of the multiple isotypes can be advantageously used in receptor editing. PMID:26342033

  20. The effect of habitat on modern shark diversification.

    PubMed

    Sorenson, L; Santini, F; Alfaro, M E

    2014-08-01

    Sharks occupy marine habitats ranging from shallow, inshore environments to pelagic, and deepwaters, and thus provide a model system for testing how gross habitat differences have shaped vertebrate macroevolution. Palaeontological studies have shown that onshore lineages diversify more quickly than offshore taxa. Among onshore habitats, coral reef-association has been shown to increase speciation rates in several groups of fishes and invertebrates. In this study, we investigated whether speciation rates are habitat dependent by generating the first comprehensive molecular timescale for shark divergence. Using phylogenetic comparative methods, we rejected the hypothesis that shelf (i.e. onshore) lineages have higher speciation rates compared to those occupying deepwater and oceanic (i.e. offshore) habitats. Our results, however, support the hypothesis of increased speciation rates in coral reef-associated lineages within the Carcharhinidae. Our new timetree suggests that the two major shark lineages leading to the extant shark diversity began diversifying mostly after the end-Permian mass extinction: the squalimorphs into deepwater and the galeomorphs into shelf habitats. We suggest that the breakdown of the onshore-offshore speciation rate pattern in sharks is mediated by success in deepwater environments through ecological partitioning, and in some cases, the evolution of morphological novelty.

  1. Turbulent Flows Over Three-Dimensional Shark Skin

    NASA Astrophysics Data System (ADS)

    Boomsma, Aaron; Wen, Li; Lauder, George; Sotiropoulos, Fotis

    2012-11-01

    Shark skin is covered with thousands of small tooth-like structures called denticles. It has long been hypothesized that denticles act as riblets do in a turbulent boundary layer and help reduce friction drag and enhance shark swimming efficiency. We employ the Curvilinear Immersed Boundary (CURVIB) method (Ge and Sotiropoulos, J. Comp. Physics, 2008) to carry out high-resolution large eddy simulations of turbulent flow past a series of anatomically realistic shark denticles mounted on a flat plate. The denticle shapes used in our simulations were obtained by scanning Mako Short Fin shark skin with micro-CT. The computed results are analyzed to elucidate the three-dimensional structure of the flow past the denticles and identify possible drag reduction mechanics. Drag measurements obtained in a laboratory flume for various denticle spacings and arrangements are also reported and analyzed in tandem with the LES results to explore similarities between shark skin and engineered riblets. Computational Resources were provided by the University of Minnesota Supercomputing Institute.

  2. Cretaceous shelf-sea chalk deposits

    SciTech Connect

    Hattin, D.E.

    1988-01-01

    The word ''chalk'' is linked etymologically to the Cretaceous, but chalky facies neither dominate that system nor are confined to it. As used commonly, the term ''chalk'' refers to a variety of marine limestone that is white to light gray very fine grained, soft and friable, porous, and composed predominantly of calcitic skeletal remains, especially those derived from coccolithophores. No simple definition suffices to embrace all Cretaceous chalks, which include sandy, marly, shelly, phospatic, glauconitic, dolomitic, pyritic and organic-rich lithotypes. Most of the world's exposed Cretaceous chalk deposits were formed at shelf depths rather than in the deep sea. Cretaceous shelf-sea chalks are developed most extensively in northern Europe, the U.S. Gulf Coastal Plain and Western Interior, and the Middle East, with lesser occurrences alo in Australia. Most Cretaceous shelf-sea chalks formed in the temperature zones, and in relatively deep water. Cretaceous chalks deposited on well-oxygenated sea floors are bioturbated and massive where deficient in terrigenous detritus, or bioturbated and rhythmically interbedded with argillaceous units where influx of terrigenous detritus varied systematically with climate changes. Accumulation of sufficient pelagic mud to form vast deposits of Cretaceous shelf-sea chalk required (1) sustained high productivity of calareous plankton, (2) extensive development of stable shelf and continental platform environments, (3) highstands of seal level, (4) deficiency of aragonitic skeletal material in chalk-forming sediments, and (5) low rates of terrigenous detrital influx. These conditions were met at different times in different places, even within the same general region.

  3. Are Caribbean reef sharks, Carcharhinus perezi, able to perceive human body orientation?

    PubMed

    Ritter, Erich K; Amin, Raid

    2014-05-01

    The present study examines the potential capability of Caribbean reef sharks to perceive human body orientation, as well as discussing the sharks' swimming patterns in a person's vicinity. A standardized video method was used to record the scenario of single SCUBA divers kneeling in the sand and the approach patterns of sharks, combined with a control group of two divers kneeling back-to-back. When approaching a single test-subject, significantly more sharks preferred to swim outside the person's field of vision. The results suggest that these sharks are able to identify human body orientation, but the mechanisms used and factors affecting nearest distance of approach remain unclear.

  4. The race against the "septic shark"

    PubMed Central

    2015-01-01

    Great white sharks are responsible for about 10 cases of death annually worldwide, as compared with millions of deaths caused by sepsis. However, the basic principles of avoiding shark attacks and fighting sepsis seem to be similar: avoidance, attention, and speed, if necessary. The present review discusses the current status of the systemic inflammatory response syndrome (SIRS) criteria, which are actually content for discussion because of their low specificity. Current data suggest that one in eight patients with severe sepsis does not fulfill the SIRS criteria and is consequently missed, and therefore the calls for new definitions of sepsis are getting louder. Furthermore, the need for early treatment of sepsis and fast admission to an intensive care unit (ICU) with experienced stuff is reviewed as well as the early and appropriate initiation of therapy, namely antibiotic and volume therapy. A key feature is the analysis of the studies from the so-called "Sepsis Trilogy" (ProCESS, ARISE, and ProMiSe studies), with a focus on the status of early goal-directed therapy (EGDT). The authors of the "Sepsis Trilogy" concluded that there is no benefit regarding survival in septic patients by using EGDT as compared with standard therapy. However, the low mortality of the control groups within the "Sepsis Trilogy" studies as compared with the Rivers et al. study from 2001 leads to the conclusion that there has been an improvement in the therapy of septic patients, most probably due to the early initiation of therapy as a kind of "standard" in sepsis therapy. Finally, the phenomenon of a "large trial disease" is discussed, exemplary in a trial which investigated the maintenance of the "right" mean arterial pressure in sepsis patients. Even if the result of a large randomized trial might be that there is no difference between two study groups, the real exercise is to identify the patient collectives who might benefit or experience harm due to an intervention. In summary, as

  5. Shark is the man!”: ethnoknowledge of Brazil’s South Bahia fishermen regarding shark behaviors

    PubMed Central

    2014-01-01

    Background Fishermen’s knowledge is a source of indispensable information in decision-making processes related to efforts to stimulate the management and conservation of fishing resources, especially in developing countries. This study analyzed the knowledge of fishermen from three municipal areas of Bahia in northeast Brazil regarding the behavior repertoire of sharks and the possible influence that these perceptions may have on the inclination to preserve these animals. This is a pioneering study on the ethnobiological aspects of elasmobranchs in Brazil. Methods Open, semi-structured interviews with shark fishing specialists were conducted between September 2011 and October 2012. The interviews addressed the fishermen’s profile, fishing techniques and knowledge about sharks, focusing on the behaviours exhibited by sharks. The data were analysed with quantitative approach and conducted with the use of descriptive statistical techniques. Results Sixty-five fishermen were interviewed. They descend from the rafting subculture of Brazil’s northeast, which has historically been disregarded by public policies addressing the management and conservation of fishing resources. The fishing fleet involved in shark fishing includes rafts, fishing boats and lobster boats equipped with fishing lines, gillnets, longlines and “esperas”. The informers classified sharks’ behaviour repertoire into 19 ethological categories, related especially to feeding, reproduction, and social and migratory behaviours. Because they identify sharks as predators, the detailed recognition of the behaviours exhibited is crucial both for an efficient catch and to avoid accidents. Therefore, this knowledge is doubly adaptive as it contributes to safer, more lucrative fishing. A feeling of respect for sharks predominates, since informers recognize the ecological role of these animals in marine ecosystems, attributing them the status of leader (or “the man”) in the sea. Conclusions This

  6. High post-capture survival for sharks, rays and chimaeras discarded in the main shark fishery of Australia?

    PubMed

    Braccini, Matias; Van Rijn, Jay; Frick, Lorenz

    2012-01-01

    Most sharks, rays and chimaeras (chondrichthyans) taken in commercial fisheries are discarded (i.e. returned to the ocean either dead or alive). Quantifying the post-capture survival (PCS) of discarded species is therefore essential for the improved management and conservation of this group. For all chondrichthyans taken in the main shark fishery of Australia, we quantified the immediate PCS of individuals reaching the deck of commercial shark gillnet fishing vessels and applied a risk-based method to semi-quantitatively determine delayed and total PCS. Estimates of immediate, delayed and total PCS were consistent, being very high for the most commonly discarded species (Port Jackson shark, Australian swellshark, and spikey dogfish) and low for the most important commercial species (gummy and school sharks). Increasing gillnet soak time or water temperature significantly decreased PCS. Chondrichthyans with bottom-dwelling habits had the highest PCS whereas those with pelagic habits had the lowest PCS. The risk-based approach can be easily implemented as a standard practice of on-board observing programs, providing a convenient first-step assessment of the PCS of all species taken in commercial fisheries.

  7. High Post-Capture Survival for Sharks, Rays and Chimaeras Discarded in the Main Shark Fishery of Australia?

    PubMed Central

    Braccini, Matias; Van Rijn, Jay; Frick, Lorenz

    2012-01-01

    Most sharks, rays and chimaeras (chondrichthyans) taken in commercial fisheries are discarded (i.e. returned to the ocean either dead or alive). Quantifying the post-capture survival (PCS) of discarded species is therefore essential for the improved management and conservation of this group. For all chondrichthyans taken in the main shark fishery of Australia, we quantified the immediate PCS of individuals reaching the deck of commercial shark gillnet fishing vessels and applied a risk-based method to semi-quantitatively determine delayed and total PCS. Estimates of immediate, delayed and total PCS were consistent, being very high for the most commonly discarded species (Port Jackson shark, Australian swellshark, and spikey dogfish) and low for the most important commercial species (gummy and school sharks). Increasing gillnet soak time or water temperature significantly decreased PCS. Chondrichthyans with bottom-dwelling habits had the highest PCS whereas those with pelagic habits had the lowest PCS. The risk-based approach can be easily implemented as a standard practice of on-board observing programs, providing a convenient first-step assessment of the PCS of all species taken in commercial fisheries. PMID:22384270

  8. 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.

  9. Digestive enzyme activities are higher in the shortfin mako shark, Isurus oxyrinchus, than in ectothermic sharks as a result of visceral endothermy.

    PubMed

    Newton, Kyle C; Wraith, James; Dickson, Kathryn A

    2015-08-01

    Lamnid sharks are regionally endothermic fishes that maintain visceral temperatures elevated above the ambient water temperature. Visceral endothermy is thought to increase rates of digestion and food processing and allow thermal niche expansion. We tested the hypothesis that, at in vivo temperatures, the endothermic shortfin mako shark, Isurus oxyrinchus, has higher specific activities of three digestive enzymes-gastric pepsin and pancreatic trypsin and lipase-than the thresher shark, Alopias vulpinus, and the blue shark, Prionace glauca, neither of which can maintain elevated visceral temperatures. Homogenized stomach or pancreas tissue obtained from sharks collected by pelagic longline was incubated at both 15 and 25 °C, at saturating substrate concentrations, to quantify tissue enzymatic activity. The mako had significantly higher enzyme activities at 25 °C than did the thresher and blue sharks at 15 °C. This difference was not a simple temperature effect, because at 25 °C the mako had higher trypsin activity than the blue shark and higher activities for all enzymes than the thresher shark. We also hypothesized that the thermal coefficient, or Q 10 value, would be higher for the mako shark than for the thresher and blue sharks because of its more stable visceral temperature. However, the mako and thresher sharks had similar Q 10 values for all enzymes, perhaps because of their closer phylogenetic relationship. The higher in vivo digestive enzyme activities in the mako shark should result in higher rates of food processing and may represent a selective advantage of regional visceral endothermy.

  10. A new metric for measuring condition in large predatory sharks.

    PubMed

    Irschick, D J; Hammerschlag, N

    2014-09-01

    A simple metric (span condition analysis; SCA) is presented for quantifying the condition of sharks based on four measurements of body girth relative to body length. Data on 104 live sharks from four species that vary in body form, behaviour and habitat use (Carcharhinus leucas, Carcharhinus limbatus, Ginglymostoma cirratum and Galeocerdo cuvier) are given. Condition shows similar levels of variability among individuals within each species. Carcharhinus leucas showed a positive relationship between condition and body size, whereas the other three species showed no relationship. There was little evidence for strong differences in condition between males and females, although more male sharks are needed for some species (e.g. G. cuvier) to verify this finding. SCA is potentially viable for other large marine or terrestrial animals that are captured live and then released.

  11. Maternal transfer of organohalogenated compounds in sharks and stingrays.

    PubMed

    Weijs, Liesbeth; Briels, Nathalie; Adams, Douglas H; Lepoint, Gilles; Das, Krishna; Blust, Ronny; Covaci, Adrian

    2015-03-15

    Elasmobranchs can bioaccumulate considerable amounts of persistent organic pollutants (POPs) and utilize several reproductive strategies thereby influencing maternal transfer of contaminants. This study provides preliminary data on the POP transfer from pregnant females to offspring of three species (Atlantic stingrays, bonnethead, blacktip sharks) with different reproduction modes (aplacental, placental viviparity). Polychlorinated biphenyl (PCB) levels were generally higher than any other POPs. Stingrays and blacktip shark embryos contained the lowest POP concentrations while bonnetheads and the blacktip adult female had the highest concentrations. Results suggest that POPs are more readily transferred from the mother to the embryo compared to what is transferred to ova in stingrays. Statistically significant differences in levels of selected POPs were found between embryos from the left and right uterus within the same litter as well as between female and male embryos within the same litter for bonnetheads, but not for the blacktip sharks.

  12. Switch from sexual to parthenogenetic reproduction in a zebra shark

    PubMed Central

    Dudgeon, Christine L.; Coulton, Laura; Bone, Ren; Ovenden, Jennifer R.; Thomas, Severine

    2017-01-01

    Parthenogenesis is a natural form of asexual reproduction in which embryos develop in the absence of fertilisation. Most commonly found in plants and invertebrate organisms, an increasing number of vertebrate species have recently been reported employing this reproductive strategy. Here we use DNA genotyping to report the first demonstration of an intra-individual switch from sexual to parthenogenetic reproduction in a shark species, the zebra shark Stegostoma fasciatum. A co-housed, sexually produced daughter zebra shark also commenced parthenogenetic reproduction at the onset of maturity without any prior mating. The demonstration of parthenogenesis in these two conspecific individuals with different sexual histories provides further support that elasmobranch fishes may flexibly adapt their reproductive strategy to environmental circumstances. PMID:28091617

  13. Shark Bay, Australia as seen from STS-67 Endeavour

    NASA Technical Reports Server (NTRS)

    1995-01-01

    An oblique view of the Shark Bay complex from the east. Hamelin Pool at the center of the photo and Shark Bay proper are separated from Freycinet Estuary and Denham Sound by the Peron Peninsula. These, in turn, are separated from the Indian Ocean by Edel Land Peninsula and Dirk Hartog Island. This arid western coast of western Australia is very sparsely populated, but a few roads can be seen. A complex set of lime-sediment shoals and tidal passes forms the Disappointment Reach shallows. Some red, land-derived mud does make its way into the inter tidal zone along the coast north of the reach. The clouds of light-colored water in Shark Bay and Denham Sound may either be lime sediment, perhaps percipitated from sea water (whitings), or a plankton bloom.

  14. Studies toward the synthesis of the shark repellent pavoninin-5.

    PubMed

    Williams, John R; Chai, Deping; Gong, Hua; Zhao, Wei; Wright, Dominic

    2002-12-01

    Sharks are the most dangerous predators of people in the sea, resulting in people being mauled and killed each year. A shark repellent could help to diminish this danger. The aglycone of the shark repellent pavoninin-5, (25R)-cholest-5-en-3beta,15alpha,26-triol (5a), was synthesized from diosgenin (9). Removing mercury from the Clemmensen reduction of 9 gave a higher yield of (25R)-cholest-5-en-3beta,16beta,26-triol, 10a, and was also more environmentally friendly. Attempted methods for the transposition of the C-16beta hydroxyl to the 15alpha position are described. A successful method for this transposition via the 15alpha-hydroxy-16-ketone, 8a, using the Barton deoxygenation reaction on the 16-alcohol 14b, is reported.

  15. Inefficacy of cooking methods on mercury reduction from shark.

    PubMed

    Chicourel, E L; Sakuma, A M; Zenebon, O; Tenuta-Filho, A

    2001-09-01

    Shark and other carnivorous fishes present high potential risk of excessive contamination by mercury. The distribution of mercury throughout the body of blue shark--Prionace glauca--was analysed, and the effects on mercury levels by frying and baking in a laboratory oven, and in a microwave oven, were measured. There was no significant statistical difference in mercury levels in the samples taken from regions near the head, or from central and tail parts, indicating homogeneous distribution of the metal in muscles throughout the body. Frying and baking did not affect original mercury levels present in blue shark. This study indicates that specific studies are needed to define the efficacy or inefficacy of the cooking methods on mercury reduction from fish, in order to clearly resolve divergent opinions in the literature.

  16. Switch from sexual to parthenogenetic reproduction in a zebra shark.

    PubMed

    Dudgeon, Christine L; Coulton, Laura; Bone, Ren; Ovenden, Jennifer R; Thomas, Severine

    2017-01-16

    Parthenogenesis is a natural form of asexual reproduction in which embryos develop in the absence of fertilisation. Most commonly found in plants and invertebrate organisms, an increasing number of vertebrate species have recently been reported employing this reproductive strategy. Here we use DNA genotyping to report the first demonstration of an intra-individual switch from sexual to parthenogenetic reproduction in a shark species, the zebra shark Stegostoma fasciatum. A co-housed, sexually produced daughter zebra shark also commenced parthenogenetic reproduction at the onset of maturity without any prior mating. The demonstration of parthenogenesis in these two conspecific individuals with different sexual histories provides further support that elasmobranch fishes may flexibly adapt their reproductive strategy to environmental circumstances.

  17. White Sharks Exploit the Sun during Predatory Approaches.

    PubMed

    Huveneers, Charlie; Holman, Dirk; Robbins, Rachel; Fox, Andrew; Endler, John A; Taylor, Alex H

    2015-04-01

    There is no conclusive evidence of any nonhuman animal using the sun as part of its predation strategy. Here, we show that the world's largest predatory fish-the white shark (Carcharodon carcharias)-exploits the sun when approaching baits by positioning the sun directly behind them. On sunny days, sharks reversed their direction of approach along an east-west axis from morning to afternoon but had uniformly distributed approach directions during overcast conditions. These results show that white sharks have sufficient behavioral flexibility to exploit fluctuating environmental features when predating. This sun-tracking predation strategy has a number of potential functional roles, including improvement of prey detection, avoidance of retinal overstimulation, and predator concealment.

  18. Direct evidence of hybodont shark predation on Late Jurassic ammonites

    NASA Astrophysics Data System (ADS)

    Vullo, Romain

    2011-06-01

    Sharks are known to have been ammonoid predators, as indicated by analysis of bite marks or coprolite contents. However, body fossil associations attesting to this predator-prey relationship have never been described so far. Here, I report a unique finding from the Late Jurassic of western France: a complete specimen of the Kimmeridgian ammonite Orthaspidoceras bearing one tooth of the hybodont shark Planohybodus. Some possible tooth puncture marks are also observed. This is the first direct evidence of such a trophic link between these two major Mesozoic groups, allowing an accurate identification of both organisms. Although Planohybodus displays a tearing-type dentition generally assumed to have been especially adapted for large unshelled prey, our discovery clearly shows that this shark was also able to attack robust ammonites such as aspidoceratids. The direct evidence presented here provides new insights into the Mesozoic marine ecosystem food webs.

  19. The influence of culture on the international management of shark finning.

    PubMed

    Dell'Apa, Andrea; Smith, M Chad; Kaneshiro-Pineiro, Mahealani Y

    2014-08-01

    Shark finning is prohibited in many countries, but high prices for fins from the Asian market help maintain the international black-market and poaching. Traditional shark fin bans fail to recognize that the main driver of fin exploitation is linked to cultural beliefs about sharks in traditional Chinese culture. Therefore, shark finning should be addressed considering the social science approach as part of the fishery management scheme. This paper investigates the cultural significance of sharks in traditional Chinese and Hawaiian cultures, as valuable examples of how specific differences in cultural beliefs can drive individuals' attitudes toward the property of shark finning. We suggest the use of a social science approach that can be useful in the design of successful education campaigns to help change individuals' attitudes toward shark fin consumption. Finally, alternative management strategies for commercial fishers are provided to maintain self-sustainability of local coastal communities.

  20. Polybrominated diphenyl ethers in thirteen shark species from offshore and coastal waters of Korea.

    PubMed

    Lee, Hyun-Kyung; Kim, Sang-Jo; Jeong, Yunsun; Lee, Sunggyu; Jeong, Woochang; Lee, Won-Chan; Choy, Eun-Jung; Kang, Chang-Keun; Moon, Hyo-Bang

    2015-06-15

    Limited reports are available on polybrominated diphenyl ethers (PBDEs) in sharks. In this study, PBDEs were measured in dorsal muscles (n=105) from 13 shark species collected from offshore and coastal waters of Korea. The PBDE concentrations varied greatly not only among species but also within species of sharks. The major PBDE congeners detected in our samples were BDEs 47, 28, 99, 153, 100, and 154. Concentrations of PBDEs in sharks in this study were lower than those reported for previous studies. The high PBDE concentrations were found for aggressive shark species. Inter-species differences in the concentrations and accumulation profiles of PBDEs are explained by differences in feeding habits and sampling locations. Several contributing factors such as growth velocity, trophic level, and local contamination may affect the bioaccumulation of PBDEs in sharks. The present study provides baselines for the occurrence and accumulation status of PBDEs in various shark species.

  1. The use of positive reinforcement in training zebra sharks (Stegostoma fasciatum).

    PubMed

    Marranzino, Ashley

    2013-01-01

    Positive reinforcement training (PRT) was used on 4 adult zebra sharks, Stegostoma fasciatum, housed at the Downtown Aquarium, Denver, to determine the ability of zebra sharks to become desensitized to various stimuli associated with veterinary procedures. One male and 3 female sharks were trained for 12 weeks. As a result of PRT, all 4 zebra sharks were desensitized to staying within a closed holding tank off of the main exhibit, the presence of multiple trainers in the closed holding tank, and tactile stimulation. One of the 4 zebra sharks was also successfully desensitized to the presence of a stretcher being brought into the holding tank. All of these procedures are common in veterinary examinations, and it is hoped that desensitization to these stimuli will reduce the stress associated with examinations. The training accomplished has allowed for easier maintenance of the zebra sharks by the aquarium staff and an improvement in the care of the sharks.

  2. The Influence of Culture on the International Management of Shark Finning

    NASA Astrophysics Data System (ADS)

    Dell'Apa, Andrea; Chad Smith, M.; Kaneshiro-Pineiro, Mahealani Y.

    2014-08-01

    Shark finning is prohibited in many countries, but high prices for fins from the Asian market help maintain the international black-market and poaching. Traditional shark fin bans fail to recognize that the main driver of fin exploitation is linked to cultural beliefs about sharks in traditional Chinese culture. Therefore, shark finning should be addressed considering the social science approach as part of the fishery management scheme. This paper investigates the cultural significance of sharks in traditional Chinese and Hawaiian cultures, as valuable examples of how specific differences in cultural beliefs can drive individuals' attitudes toward the property of shark finning. We suggest the use of a social science approach that can be useful in the design of successful education campaigns to help change individuals' attitudes toward shark fin consumption. Finally, alternative management strategies for commercial fishers are provided to maintain self-sustainability of local coastal communities.

  3. Diving behaviour of whale sharks in relation to a predictable food pulse.

    PubMed

    Graham, Rachel T; Roberts, Callum M; Smart, James C R

    2006-02-22

    We present diving data for four whale sharks in relation to a predictable food pulse (reef fish spawn) and an analysis of the longest continuous fine-resolution diving record for a planktivorous shark. Fine-resolution pressure data from a recovered pop-up archival satellite tag deployed for 206 days on a whale shark were analysed using the fast Fourier Transform method for frequency domain analysis of time-series. The results demonstrated that a free-ranging whale shark displays ultradian, diel and circa-lunar rhythmicity of diving behaviour. Whale sharks dive to over 979.5 m and can tolerate a temperature range of 26.4 degrees C. The whale sharks made primarily diurnal deep dives and remained in relatively shallow waters at night. Whale shark diving patterns are influenced by a seasonally predictable food source, with shallower dives made during fish spawning periods.

  4. The mammalian Cretaceous cochlear revolution.

    PubMed

    Manley, Geoffrey A

    2016-12-19

    The hearing organs of amniote vertebrates show large differences in their size and structure between the species' groups. In spite of this, their performance in terms of hearing sensitivity and the frequency selectivity of auditory-nerve units shows unexpectedly small differences. The only substantial difference is that therian, defined as live-bearing, mammalian groups are able to hear ultrasonic frequencies (above 15-20 kHz), whereas in contrast monotreme (egg laying) mammals and all non-mammalian amniotes cannot. This review compares the structure and physiology of the cochleae of the main groups and asks the question as to why the many structural differences seen in therian mammals arose, yet did not result in greater differences in physiology. The likely answers to this question are found in the history of the mammals during the Cretaceous period that ended 65 million years ago. During that period, the therian cochlea lost its lagenar macula, leading to a fall in endolymph calcium levels. This likely resulted in a small revolution and an auditory crisis that was compensated for by a subsequent series of structural and physiological adaptations. The end result was a system of equivalent performance to that independently evolved in other amniotes but with the additional - and of course "unforeseen" - advantage that ultrasonic-frequency responses became an available option. That option was not always availed of, but in most groups of therian mammals it did evolve and is used for communication and orientation based on improved sound localization, with micro-bats and toothed whales relying on it for prey capture.

  5. Experimental evaluation of shark detection rates by aerial observers.

    PubMed

    Robbins, William D; Peddemors, Victor M; Kennelly, Steven J; Ives, Matthew C

    2014-01-01

    Aerial surveys are a recognised technique to identify the presence and abundance of marine animals. However, the capability of aerial observers to reliably sight coastal sharks has not been previously assessed, nor have differences in sighting rates between aircraft types been examined. In this study we investigated the ability of observers in fixed-wing and helicopter aircraft to sight 2.5 m artificial shark analogues placed at known depths and positions. Initial tests revealed that the shark analogues could only be detected at shallow depths, averaging only 2.5 m and 2.7 m below the water surface for observers in fixed-wing and helicopter aircraft, respectively. We then deployed analogues at shallower depths along a 5 km-long grid, and assessed their sightability to aircraft observers through a series of transects flown within 500 m. Analogues were seen infrequently from all distances, with overall sighting rates of only 12.5% and 17.1% for fixed-wing and helicopter observers, respectively. Although helicopter observers had consistently higher success rates of sighting analogues within 250 m of their flight path, neither aircraft observers sighted more than 9% of analogues deployed over 300 m from their flight paths. Modelling of sighting rates against environmental and experimental variables indicated that observations were affected by distance, aircraft type, sun glare and sea conditions, while the range of water turbidities observed had no effect. We conclude that aerial observers have limited ability to detect the presence of submerged animals such as sharks, particularly when the sharks are deeper than ∼ 2.6 m, or over 300 m distant from the aircraft's flight path, especially during sunny or windy days. The low rates of detections found in this study cast serious doubts on the use of aerial beach patrols as an effective early-warning system to prevent shark attacks.

  6. Dynamics of Whale Shark Occurrence at Their Fringe Oceanic Habitat

    PubMed Central

    Afonso, Pedro; McGinty, Niall; Machete, Miguel

    2014-01-01

    Studies have shown that the whale shark (Rhincodon typus), a vulnerable large filter feeder, seasonally aggregates at highly productive coastal sites and that individuals can perform large, trans-boundary migrations to reach these locations. Yet, the whereabouts of the whale shark when absent from these sites and the potential oceanographic and biological drivers involved in shaping their present and future habitat use, including that located at the fringes of their suitable oceanic habitat, are largely unknown. We analysed a 16-year (1998–2013) observer dataset from the pole-and-line tuna fishery across the Azores (mid-North Atlantic) and used GAM models to investigate the spatial and temporal patterns of whale shark occurrence in relation to oceanographic features. Across this period, the whale shark became a regular summer visitor to the archipelago after a sharp increase in sighting frequency seen in 2008. We found that SST helps predicting their occurrence in the region associated to the position of the seasonal 22°C isotherm, showing that the Azores are at a thermal boundary for this species and providing an explanation for the post 2007 increase. Within the region, whale shark detections were also higher in areas of increased bathymetric slope and closer to the seamounts, coinciding with higher chl-a biomass, a behaviour most probably associated to increased feeding opportunities. They also showed a tendency to be clustered around the southernmost island of Santa Maria. This study shows that the region integrates the oceanic habitat of adult whale shark and suggests that an increase in its relative importance for the Atlantic population might be expected in face of climate change. PMID:25028929

  7. DNA capture reveals transoceanic gene flow in endangered river sharks.

    PubMed

    Li, Chenhong; Corrigan, Shannon; Yang, Lei; Straube, Nicolas; Harris, Mark; Hofreiter, Michael; White, William T; Naylor, Gavin J P

    2015-10-27

    For over a hundred years, the "river sharks" of the genus Glyphis were only known from the type specimens of species that had been collected in the 19th century. They were widely considered extinct until populations of Glyphis-like sharks were rediscovered in remote regions of Borneo and Northern Australia at the end of the 20th century. However, the genetic affinities between the newly discovered Glyphis-like populations and the poorly preserved, original museum-type specimens have never been established. Here, we present the first (to our knowledge) fully resolved, complete phylogeny of Glyphis that includes both archival-type specimens and modern material. We used a sensitive DNA hybridization capture method to obtain complete mitochondrial genomes from all of our samples and show that three of the five described river shark species are probably conspecific and widely distributed in Southeast Asia. Furthermore we show that there has been recent gene flow between locations that are separated by large oceanic expanses. Our data strongly suggest marine dispersal in these species, overturning the widely held notion that river sharks are restricted to freshwater. It seems that species in the genus Glyphis are euryhaline with an ecology similar to the bull shark, in which adult individuals live in the ocean while the young grow up in river habitats with reduced predation pressure. Finally, we discovered a previously unidentified species within the genus Glyphis that is deeply divergent from all other lineages, underscoring the current lack of knowledge about the biodiversity and ecology of these mysterious sharks.

  8. Laminar separation control effects of shortfin mako shark skin

    NASA Astrophysics Data System (ADS)

    Bradshaw, Michael Thomas

    Shark skin is investigated as a means of laminar flow separation control due to its preferential flow direction as well as the potential for scales to erect and obstruct low-momentum backflow resulting from an adverse pressure gradient acting on the boundary layer. In this study, the effect of the scales on flow reversal is observed in laminar flow conditions. This is achieved by comparing the flow over a pectoral fin from a shortfin mako shark to that over the same fin that is painted to neutralize the effect of the scales on the flow. The effect of the scales on flow reversal is also observed by comparing the flow over a smooth PVC cylinder to that over the same cylinder with samples of mako shark skin affixed to the entire circumference of the cylinder. These samples were taken from the flank region of the shark because the scales at this location have been shown to have the greatest angle of erection compared to the scales on the rest of the shark's body. Scales at this location have an average crown length of 220 microm with a maximum bristling angle of proximately 50 degrees. Because these scales have the highest bristling angle, they have the best potential for separation control. All data was taken using time-resolved Digital Particle Image Velocimetry. The flow over the pectoral fin was analyzed at multiple angles of attack. It was found that the shark skin had the effect of decreasing the size of the separated region over both the pectoral fin and the cylinder as well as decreasing the magnitudes of the reversing flow found in these regions. For all Reynolds numbers tested, drag reduction over 28% was found when applying the sharkskin to the cylinder.

  9. Dynamics of whale shark occurrence at their fringe oceanic habitat.

    PubMed

    Afonso, Pedro; McGinty, Niall; Machete, Miguel

    2014-01-01

    Studies have shown that the whale shark (Rhincodon typus), a vulnerable large filter feeder, seasonally aggregates at highly productive coastal sites and that individuals can perform large, trans-boundary migrations to reach these locations. Yet, the whereabouts of the whale shark when absent from these sites and the potential oceanographic and biological drivers involved in shaping their present and future habitat use, including that located at the fringes of their suitable oceanic habitat, are largely unknown. We analysed a 16-year (1998-2013) observer dataset from the pole-and-line tuna fishery across the Azores (mid-North Atlantic) and used GAM models to investigate the spatial and temporal patterns of whale shark occurrence in relation to oceanographic features. Across this period, the whale shark became a regular summer visitor to the archipelago after a sharp increase in sighting frequency seen in 2008. We found that SST helps predicting their occurrence in the region associated to the position of the seasonal 22°C isotherm, showing that the Azores are at a thermal boundary for this species and providing an explanation for the post 2007 increase. Within the region, whale shark detections were also higher in areas of increased bathymetric slope and closer to the seamounts, coinciding with higher chl-a biomass, a behaviour most probably associated to increased feeding opportunities. They also showed a tendency to be clustered around the southernmost island of Santa Maria. This study shows that the region integrates the oceanic habitat of adult whale shark and suggests that an increase in its relative importance for the Atlantic population might be expected in face of climate change.

  10. Dental patterning in the earliest sharks: Implications for tooth evolution.

    PubMed

    Maisey, John G; Turner, Susan; Naylor, Gavin J P; Miller, Randall F

    2014-05-01

    Doliodus problematicus is the oldest known fossil shark-like fish with an almost intact dentition (Emsian, Lower Devonian, c. 397Ma). We provide a detailed description of the teeth and dentition in D. problematicus, based on tomographic analysis of NBMG 10127 (New Brunswick Museum, Canada). Comparisons with modern shark dentitions suggest that Doliodus was a ram-feeding predator with a dentition adapted to seizing and disabling prey. Doliodus provides several clues about the early evolution of the "shark-like" dentition in chondrichthyans and also raises new questions about the evolution of oral teeth in jawed vertebrates. As in modern sharks, teeth in Doliodus were replaced in a linguo-labial sequence within tooth families at fixed positions along the jaws (12-14 tooth families per jaw quadrant in NBMG 10127). Doliodus teeth were replaced much more slowly than in modern sharks. Nevertheless, its tooth formation was apparently as highly organized as in modern elasmobranchs, in which future tooth positions are indicated by synchronized expression of shh at fixed loci within the dental epithelium. Comparable dental arrays are absent in osteichthyans, placoderms, and many "acanthodians"; a "shark-like" dentition, therefore, may be a synapomorphy of chondrichthyans and gnathostomes such as Ptomacanthus. The upper anterior teeth in Doliodus were not attached to the palatoquadrates, but were instead supported by the ethmoid region of the prechordal basicranium, as in some other Paleozoic taxa (e.g., Triodus, Ptomacanthus). This suggests that the chondrichthyan dental lamina was originally associated with prechordal basicranial cartilage as well as jaw cartilage, and that the modern elasmobranch condition (in which the oral dentition is confined to the jaws) is phylogenetically advanced. Thus, oral tooth development in modern elasmobranchs does not provide a complete developmental model for chondrichthyans or gnathostomes.

  11. Experimental Evaluation of Shark Detection Rates by Aerial Observers

    PubMed Central

    Robbins, William D.; Peddemors, Victor M.; Kennelly, Steven J.; Ives, Matthew C.

    2014-01-01

    Aerial surveys are a recognised technique to identify the presence and abundance of marine animals. However, the capability of aerial observers to reliably sight coastal sharks has not been previously assessed, nor have differences in sighting rates between aircraft types been examined. In this study we investigated the ability of observers in fixed-wing and helicopter aircraft to sight 2.5 m artificial shark analogues placed at known depths and positions. Initial tests revealed that the shark analogues could only be detected at shallow depths, averaging only 2.5 m and 2.7 m below the water surface for observers in fixed-wing and helicopter aircraft, respectively. We then deployed analogues at shallower depths along a 5 km-long grid, and assessed their sightability to aircraft observers through a series of transects flown within 500 m. Analogues were seen infrequently from all distances, with overall sighting rates of only 12.5% and 17.1% for fixed-wing and helicopter observers, respectively. Although helicopter observers had consistently higher success rates of sighting analogues within 250 m of their flight path, neither aircraft observers sighted more than 9% of analogues deployed over 300 m from their flight paths. Modelling of sighting rates against environmental and experimental variables indicated that observations were affected by distance, aircraft type, sun glare and sea conditions, while the range of water turbidities observed had no effect. We conclude that aerial observers have limited ability to detect the presence of submerged animals such as sharks, particularly when the sharks are deeper than ∼2.6 m, or over 300 m distant from the aircraft's flight path, especially during sunny or windy days. The low rates of detections found in this study cast serious doubts on the use of aerial beach patrols as an effective early-warning system to prevent shark attacks. PMID:24498258

  12. Airflow Actuation of Shortfin Mako Shark Denticles

    NASA Astrophysics Data System (ADS)

    Devey, Sean; Hubner, Paul; Lang, Amy

    2016-11-01

    The shortfin mako shark is covered in microscopic scales called denticles, which may act as a mechanism for passive flow control. Recent research has investigated the theory that reversing flow could passively bristle these denticles, which could delay flow separation. Water tunnel studies have supported this theory, yet a wind tunnel study at a greater dynamic pressure found no significant differences between an airfoil covered with mako skin and a smooth airfoil. A likely cause is that surface tension between denticles, which must be wet to retain flexibility, prevented bristling. This would not be an issue in water. To determine what reverse airflow characteristics cause denticle bristling in air, a benchtop study was conducted in which a jet of air was impinged upon a sample of wet mako skin in the reverse flow direction. A microscope and camera captured video of the denticles under the air jet, and image analysis techniques were used to detect bristling. Analysis shows sporadic bristling around 16 m/s (q = 150 Pa) but full bristling does not occur until above 35 m/s (q = 740 Pa). The free stream velocities required to achieve such reversal speeds are much higher. For this reason, mechanical analogues will be used rather than real skin in future studies of this mechanism. Funding from Boeing and NSF REU site Grant EEC 1358991 is greatly appreciated.

  13. Dental homologies in lamniform sharks (Chondrichthyes: Elasmobranchii).

    PubMed

    Shimada, Kenshu

    2002-01-01

    The dentitions of lamniform sharks are said to exhibit a unique heterodonty called the "lamnoid tooth pattern." The presence of an inflated hollow "dental bulla" on each jaw cartilage allows the recognition of homologous teeth across most modern macrophagous lamniforms based on topographic correspondence through the "similarity test." In most macrophagous lamniforms, three tooth rows are supported by the upper dental bulla: two rows of large anterior teeth followed by a row of small intermediate teeth. The lower tooth row occluding between the two rows of upper anterior teeth is the first lower anterior tooth row. Like the first and second lower anterior tooth rows, the third lower tooth row is supported by the dental bulla and may be called the first lower intermediate tooth row. The lower intermediate tooth row occludes between the first and second upper lateral tooth rows situated distal to the upper dental bulla, and the rest of the upper and lower tooth rows, all called lateral tooth rows, occlude alternately. Tooth symmetry cannot be used to identify their dental homology. The presence of dental bullae can be regarded as a synapomorphy of Lamniformes and this character is more definable than the "lamnoid tooth pattern." The formation of the tooth pattern appears to be related to the evolution of dental bullae. This study constitutes the first demonstration of supraspecific tooth-to-tooth dental homologies in nonmammalian vertebrates.

  14. SHARK-NIR system design analysis overview

    NASA Astrophysics Data System (ADS)

    Viotto, Valentina; Farinato, Jacopo; Greggio, Davide; Vassallo, Daniele; Carolo, Elena; Baruffolo, Andrea; Bergomi, Maria; Carlotti, Alexis; De Pascale, Marco; D'Orazi, Valentina; Fantinel, Daniela; Magrin, Demetrio; Marafatto, Luca; Mohr, Lars; Ragazzoni, Roberto; Salasnich, Bernardo; Verinaud, Christophe

    2016-08-01

    In this paper, we present an overview of the System Design Analysis carried on for SHARK-NIR, the coronagraphic camera designed to take advantage of the outstanding performance that can be obtained with the FLAO facility at the LBT, in the near infrared regime. Born as a fast-track project, the system now foresees both coronagraphic direct imaging and spectroscopic observing mode, together with a first order wavefront correction tool. The analysis we here report includes several trade-offs for the selection of the baseline design, in terms of optical and mechanical engineering, and the choice of the coronagraphic techniques to be implemented, to satisfy both the main scientific drivers and the technical requirements set at the level of the telescope. Further care has been taken on the possible exploitation of the synergy with other LBT instrumentation, like LBTI. A set of system specifications is then flown down from the upper level requirements to finally ensure the fulfillment of the science drivers. The preliminary performance budgets are presented, both in terms of the main optical planes stability and of the image quality, including the contributions of the main error sources in different observing modes.

  15. Quantification of Massive Seasonal Aggregations of Blacktip Sharks (Carcharhinus limbatus) in Southeast Florida

    PubMed Central

    Kajiura, Stephen M.; Tellman, Shari L.

    2016-01-01

    Southeast Florida witnesses an enormous seasonal influx of upper trophic level marine predators each year as massive aggregations of migrating blacktip sharks (Carcharhinus limbatus) overwinter in nearshore waters. The narrow shelf and close proximity of the Gulf Stream current to the Palm Beach County shoreline drive tens of thousands of sharks to the shallow, coastal environment. This natural bottleneck provides a unique opportunity to estimate relative abundance. Over a four year period from 2011–2014, an aerial survey was flown approximately biweekly along the length of Palm Beach County. A high definition video camera and digital still camera mounted out of the airplane window provided a continuous record of the belt transect which extended 200 m seaward from the shoreline between Boca Raton Inlet and Jupiter Inlet. The number of sharks within the survey transect was directly counted from the video. Shark abundance peaked in the winter (January-March) with a maximum in 2011 of 12,128 individuals counted within the 75.6 km-2 belt transect. This resulted in a maximum density of 803.2 sharks km-2. By the late spring (April-May), shark abundance had sharply declined to 1.1% of its peak, where it remained until spiking again in January of the following year. Shark abundance was inversely correlated with water temperature and large numbers of sharks were found only when water temperatures were less than 25°C. Shark abundance was also correlated with day of the year but not with barometric pressure. Although shark abundance was not correlated with photoperiod, the departure of the sharks from southeast Florida occurred around the vernal equinox. The shark migration along the United States eastern seaboard corresponds spatially and temporally with the spawning aggregations of various baitfish species. These baseline abundance data can be compared to future studies to determine if shark population size is changing and if sharks are restricting their southward

  16. Feeding of the megamouth shark (Pisces: Lamniformes: Megachasmidae) predicted by its hyoid arch: a biomechanical approach.

    PubMed

    Tomita, Taketeru; Sato, Keiichi; Suda, Kenta; Kawauchi, Junro; Nakaya, Kazuhiro

    2011-05-01

    Studies of the megamouth shark, one of three planktivorous sharks, can provide information about their evolutionary history. Megamouth shark feeding has never been observed in life animals, but two alternative hypotheses on biomechanics suggest either feeding, i.e., ram feeding or suction feeding. In this study, the second moment of area of the ceratohyal cartilages, which is an indicator of the flexural stiffness of the cartilages, is calculated for 21 species of ram- and suction-feeding sharks using computed tomography. The results indicate that suction-feeding sharks have ceratohyal cartilages with a larger second moment of area than ram-feeding sharks. The result also indicates that the ram-suction index, which is an indicator of relative contribution of ram and suction behavior, is also correlated with the second moment of area of the ceratohyal. Considering that large bending stresses are expected to be applied to the ceratohyal cartilage during suction, the larger second moment of area of the ceratohyal of suction-feeding sharks can be interpreted as an adaptation for suction feeding. Based on the small second moment of area of the ceratohyal cartilage of the megamouth shark, the feeding mode of the megamouth shark is considered to be ram feeding, similar to the planktivorous basking shark. From these results, an evolutionary scenario of feeding mechanics of three species of planktivorous sharks can be suggested. In this scenario, the planktivorous whale shark evolved ram feeding from a benthic suction-feeding ancestor. Ram feeding in the planktivorous megamouth shark and the basking shark evolved from ram feeding swimming-type ancestors and that both developed their unique filtering system to capture small-sized prey.

  17. Quantification of Massive Seasonal Aggregations of Blacktip Sharks (Carcharhinus limbatus) in Southeast Florida.

    PubMed

    Kajiura, Stephen M; Tellman, Shari L

    2016-01-01

    Southeast Florida witnesses an enormous seasonal influx of upper trophic level marine predators each year as massive aggregations of migrating blacktip sharks (Carcharhinus limbatus) overwinter in nearshore waters. The narrow shelf and close proximity of the Gulf Stream current to the Palm Beach County shoreline drive tens of thousands of sharks to the shallow, coastal environment. This natural bottleneck provides a unique opportunity to estimate relative abundance. Over a four year period from 2011-2014, an aerial survey was flown approximately biweekly along the length of Palm Beach County. A high definition video camera and digital still camera mounted out of the airplane window provided a continuous record of the belt transect which extended 200 m seaward from the shoreline between Boca Raton Inlet and Jupiter Inlet. The number of sharks within the survey transect was directly counted from the video. Shark abundance peaked in the winter (January-March) with a maximum in 2011 of 12,128 individuals counted within the 75.6 km(-2) belt transect. This resulted in a maximum density of 803.2 sharks km(-2). By the late spring (April-May), shark abundance had sharply declined to 1.1% of its peak, where it remained until spiking again in January of the following year. Shark abundance was inversely correlated with water temperature and large numbers of sharks were found only when water temperatures were less than 25 °C. Shark abundance was also correlated with day of the year but not with barometric pressure. Although shark abundance was not correlated with photoperiod, the departure of the sharks from southeast Florida occurred around the vernal equinox. The shark migration along the United States eastern seaboard corresponds spatially and temporally with the spawning aggregations of various baitfish species. These baseline abundance data can be compared to future studies to determine if shark population size is changing and if sharks are restricting their southward

  18. Shark-bitten vertebrate coprolites from the Miocene of Maryland.

    PubMed

    Godfrey, Stephen J; Smith, Joshua B

    2010-05-01

    Coprolites (fossilized feces) preserve a wide range of biogenic components, from bacteria and spores to a variety of vertebrate tissues. Two coprolites from the Calvert Cliffs outcrop belt (Miocene-aged Chesapeake Group), MD, USA, preserve shark tooth impressions in the form of partial dental arcades. The specimens are the first known coprolites to preserve vertebrate tooth marks. They provide another example of trace fossils providing evidence of prehistoric animal behaviors that cannot be directly approached through the study of body fossils. Shark behaviors that could account for these impressions include: (1) aborted coprophagy, (2) benthic or nektonic exploration, or (3) predation.

  19. Global Cretaceous plate tectonics and paleogeography

    SciTech Connect

    Barron, E.J.; Beeson, D.; Chen, P.; Dingle, R.V.; Frakes, L.A; Funnell, B.M.; Kauffman, E.G.; Petri, S.; Reyment, R.A.; Riccardi, A.C.

    1985-01-01

    The International Geologic Correlation Program (IGCP) Project 191, The Cretaceous Paleoclimatic Atlas Project has compiled 89 Cretaceous paleogeographic maps representing ten regions or continents. The map resolution varies from stage by stage (e.g. North America, Europe, USSR, Australia) to four maps (e.g. China, Southern South America) to a compilation of localities (Antarctica). The paleogeography is plotted here on global plate tectonic reconstructions for each stage. The reconstructions include continental positions and latitude. In addition, the oceanic plates are reconstructed including bathymetry based on a thermal age-depth relationship. The compiled paleogeography and plate tectonic base maps represent the most comprehensive framework for plotting and analyzing sedimentologic, geochemical and paleontologic data with respect to geography and latitude for the Cretaceous time period.

  20. The last dicynodont: an Australian Cretaceous relict.

    PubMed Central

    Thulborn, Tony; Turner, Susan

    2003-01-01

    Some long-forgotten fossil evidence reveals that a dicynodont (mammal-like reptile of the infraorder Dicynodontia) inhabited Australia as recently as the Early Cretaceous, ca. 110 Myr after the supposed extinction of dicynodonts in the Late Triassic. This remarkably late occurrence more than doubles the known duration of dicynodont history (from ca. 63 Myr to ca. 170 Myr) and betrays the profound impact of geographical isolation on Australian terrestrial faunas through the Mesozoic. Australia's late-surviving dicynodont may be envisaged as a counterpart of the ceratopians (horned dinosaurs) in Cretaceous tetrapod faunas of Asia and North America. PMID:12803915

  1. An opilioacarid mite in Cretaceous Burmese amber

    NASA Astrophysics Data System (ADS)

    Dunlop, Jason A.; de Oliveira Bernardi, Leopoldo Ferreira

    2014-09-01

    A fossil opilioacarid mite (Parasitiformes: Opilioacarida) in Burmese amber is described as ? Opilioacarus groehni sp. nov. This ca. 99 Ma record (Upper Cretaceous: Cenomanian) represents only the third fossil example of this putatively basal mite lineage, the others originating from Eocene Baltic amber (ca. 44-49 Ma). Our new record is not only the oldest record of Opilioacarida, but it is also one of the oldest examples of the entire Parasitiformes clade. The presence of Opilioacarida—potentially Opiloacarus—in the Cretaceous of SE Asia suggests that some modern genus groups were formerly more widely distributed across the northern hemisphere, raising questions about previously suggested Gondwanan origins for these mites.

  2. Neoselachians and Chimaeriformes (Chondrichthyes) from the latest Cretaceous-Paleogene of Sierra Baguales, southernmost Chile. Chronostratigraphic, paleobiogeographic and paleoenvironmental implications

    NASA Astrophysics Data System (ADS)

    Otero, Rodrigo A.; Oyarzún, José Luis; Soto-Acuña, Sergio; Yury-Yáñez, Roberto E.; Gutierrez, Nestor M.; Le Roux, Jacobus P.; Torres, Teresa; Hervé, Francisco

    2013-12-01

    This paper discusses a well-represented fossil record of cartilaginous fishes (Chondrichthyes) from southern South America. The recovered samples allow the recognition of three assemblages with chronostratigraphic and paleogeographic value: i) typical Maastrichtian sharks and rays with affinities to eastern Pacific fauna, including the taxa Ischyrhiza chilensis, Serratolamna serrata, Centrophoroides sp. associated to Carcharias sp., and Dasyatidae indet.; ii) a scarce reworked assemblage of Paleocene-Early Eocene age including the taxa Otodus obliquus and Megascyliorhinus cooperi; iii) a rich assemblage with reworked taxa of Early to Middle Eocene age, together with autochthonous deposited Middle to Late Eocene taxa with close affinities to paleoichthyofaunas recovered from the North Atlantic, represented by Carcharias 'hopei', Odontaspis winkleri, Carcharoides catticus, Macrorhizodus praecursor, Carcharocles auriculatus, Striatolamia sp., Striatolamia macrota, Hexanchus agassizi, Notorhynchus sp., Myliobatis sp., Abdounia sp., Pristiophorus sp., Squatina sp., cf. Rhizoprionodon sp., Ischyodus sp., and one new species, Jaekelotodus bagualensis sp. nov. The studied samples include for the first time taxa with well established chronostratigraphic resolutions as well as taphonomic information that help clarifying the age of the fossil-bearing units. In addition, they provide relevant information about the evolution of the Magallanes (=Austral) Basin from the Upper Cretaceous to the Paleogene, suggesting a probable connection with the Quiriquina Basin of south-central Chile during the latest Cretaceous. Finally, the studied assemblages indicate a latitudinal pattern of distribution that provides valuable data on the environmental evolution and temperature of southern South America during the Paleogene.

  3. Using Ichthyoliths to Determine the Fish Response to the End-Cretaceous Mass Extinction

    NASA Astrophysics Data System (ADS)

    Sibert, E. C.; Norris, R. D.; Hull, P. M.

    2012-12-01

    Ichthyoliths are the small calcium phosphate fossil teeth, scales, and bone shards of fish and sharks. While it is extremely rare to find full body-fossils of fish, ichthyoliths are relatively abundant in oceanic sediments, with 10s to 100s of identifiable ichthyoliths in a few grams of sediment, most in the <100 μm size fraction. Ichthyolith accumulation rates and morphology, alone or in conjunction with more traditional microfossil and geochemical proxies, can be used to study the response of pelagic consumers and ecosystems to major events in Earth's history. As the only available high-resolution, continuous fossil record of vertebrates, ichthyoliths can be extremely valuable in understanding how higher order organisms respond to environmental forcing. Here we use this novel proxy to show that export flux of ichthyoliths to the deep North Pacific was stable across the K-Pg boundary despite major changes in flux of calcareous phytoplankton and foraminifera. Total consumer-level export production in the North Pacific remained at or above Cretaceous levels for at least 4 million years post-extinction. Similar studies across the extinction from the South Pacific and the Atlantic suggest that there is considerable regional geographic variation in the accumulation of ichthyoliths spanning the boundary, with the Pacific small fish seeming to fare better than their Atlantic counterparts in the post-extinction ecosystem. The regional differences in productivity of these post-disaster ecosystems suggest that the mass extinction did not produce a uniformly dead or microbially dominated surface ocean. Rather, despite widespread extinction and upheaval in lower trophic levels, the earliest Paleocene ocean, in some regions of the planet, appears to have had ecosystems capable of supporting levels of fish comparable to or even above those of the Late Cretaceous.

  4. The physiological tolerance of the grey carpet shark (Chiloscyllium punctatum) and the epaulette shark (Hemiscyllium ocellatum) to anoxic exposure at three seasonal temperatures.

    PubMed

    Chapman, Clint A; Harahush, Blake K; Renshaw, Gillian M C

    2011-09-01

    The epaulette shark (Hemiscyllium ocellatum) and the grey carpet shark (Chiloscyllium punctatum) are commonly found in periodically hypoxic environments. The ecophysiological time available for these animals to safely exploit these niches during different seasonal temperatures was examined. The time to loss of righting reflex (T (LRR)) was examined in response to an open ended anoxic challenge at three seasonal temperatures (23, 25 and 27°C). Ventilation rates were measured in an open ended anoxic challenge at 23°C and during 1.5 h of anoxia followed by 2 h of re-oxygenation at 23 and 25°C. The mean T (LRR) of epaulette and grey carpet sharks was inversely proportional to temperature. The T (LRR) was similar between species at 23°C; however, grey carpet sharks had significantly reduced T (LRR) at higher temperatures. During the standardised anoxic challenge, epaulette sharks entered into ventilatory depression significantly earlier at 25°C. During re-oxygenation, epaulette sharks exposed to anoxia at 23°C had no significant increase in ventilation rates. However, after anoxic challenge and re-oxygenation at 25°C, epaulette sharks showed a significant increase in ventilation rates during re-oxygenation. Grey carpet sharks displayed no evidence of ventilatory depression during anoxia. However, during re-oxygenation, grey carpet sharks had significantly elevated ventilation rates above pre-experimental levels and control animals. These data demonstrate that the anoxia tolerance times of both species were temperature dependent, with a significant reduction in the T (LRR) occurring at higher temperatures. Epaulette sharks had a significantly greater T (LRR) at higher temperatures than grey carpet sharks, which did not enter into a ventilatory depression.

  5. The Species and Origin of Shark Fins in Taiwan's Fishing Ports, Markets, and Customs Detention: A DNA Barcoding Analysis.

    PubMed

    Chuang, Po-Shun; Hung, Tzu-Chiao; Chang, Hung-An; Huang, Chien-Kang; Shiao, Jen-Chieh

    2016-01-01

    The increasing consumption of shark products, along with the shark's fishing vulnerabilities, has led to the decrease in certain shark populations. In this study we used a DNA barcoding method to identify the species of shark landings at fishing ports, shark fin products in retail stores, and shark fins detained by Taiwan customs. In total we identified 23, 24, and 14 species from 231 fishing landings, 316 fin products, and 113 detained shark fins, respectively. All the three sample sources were dominated by Prionace glauca, which accounted for more than 30% of the collected samples. Over 60% of the species identified in the fin products also appeared in the port landings, suggesting the domestic-dominance of shark fin products in Taiwan. However, international trade also contributes a certain proportion of the fin product markets, as four species identified from the shark fin products are not found in Taiwan's waters, and some domestic-available species were also found in the customs-detained sample. In addition to the species identification, we also found geographical differentiation in the cox1 gene of the common thresher sharks (Alopias vulpinus), the pelagic thresher shark (A. pelagicus), the smooth hammerhead shark (Sphyrna zygaena), and the scalloped hammerhead shark (S. lewini). This result might allow fishing authorities to more effectively trace the origins as well as enforce the management and conservation of these sharks.

  6. Utility of mesohabitat features for determining habitat associations of subadult sharks in Georgia’s estuaries

    USGS Publications Warehouse

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

    2010-01-01

    We examined the affects of selected water quality variables on the presence of subadult sharks in six of nine Georgia estuaries. During 231 longline sets, we captured 415 individuals representing nine species. Atlantic sharpnose shark (Rhizoprionodon terranovae), bonnethead (Sphyrna tiburo), blacktip shark (Carcharhinus limbatus) and sandbar shark (C. plumbeus) comprised 96.1% of the catch. Canonical correlation analysis (CCA) was used to assess environmental influences on the assemblage of the four common species. Results of the CCA indicated Bonnethead Shark and Sandbar Shark were correlated with each other and with a subset of environmental variables. When the species occurred singly, depth was the defining environmental variable; whereas, when the two co-occurred, dissolved oxygen and salinity were the defining variables. Discriminant analyses (DA) were used to assess environmental influences on individual species. Results of the discriminant analyses supported the general CCA findings that the presence of bonnethead and sandbar shark were the only two species that correlated with environmental variables. In addition to depth and dissolved oxygen, turbidity influenced the presence of sandbar shark. The presence of bonnethead shark was influenced primarily by salinity and turbidity. Significant relationships existed for both the CCA and DA analyses; however, environmental variables accounted for <16% of the total variation in each. Compared to the environmental variables we measured, macrohabitat features (e.g., substrate type), prey availability, and susceptibility to predation may have stronger influences on the presence and distribution of subadult shark species among sites.

  7. Preparation, anti-biofouling and drag-reduction properties of a biomimetic shark skin surface

    PubMed Central

    Pu, Xia; Li, Guangji; Huang, Hanlu

    2016-01-01

    ABSTRACT Shark skin surfaces show non-smoothness characteristics due to the presence of a riblet structure. In this study, biomimetic shark skin was prepared by using the polydimethylsiloxane (PDMS)-embedded elastomeric stamping (PEES) method. Scanning electron microscopy (SEM) was used to examine the surface microstructure and fine structure of shark skin and biomimetic shark skin. To analyse the hydrophobic mechanism of the shark skin surface microstructure, the effect of biomimetic shark skin surface microstructure on surface wettability was evaluated by recording water contact angle. Additionally, protein adhesion experiments and anti-algae adhesion performance testing experiments were used to investigate and evaluate the anti-biofouling properties of the surface microstructure of biomimetic shark skin. The recorded values of the water contact angle of differently microstructured surfaces revealed that specific microstructures have certain effects on surface wettability. The anti-biofouling properties of the biomimetic shark skin surface with microstructures were superior to a smooth surface using the same polymers as substrates. Moreover, the air layer fixed on the surface of the biomimetic shark skin was found to play a key role in their antibiont adhesion property. An experiment into drag reduction was also conducted. Based on the experimental results, the microstructured surface of the prepared biomimetic shark skin played a significant role in reducing drag. The maximum of drag reduction rate is 12.5%, which is higher than the corresponding maximum drag reduction rate of membrane material with a smooth surface. PMID:26941105

  8. Developmental origin of shark electrosensory organs.

    PubMed

    Freitas, Renata; Zhang, Guangjun; Albert, James S; Evans, David H; Cohn, Martin J

    2006-01-01

    Vertebrates have evolved electrosensory receptors that detect electrical stimuli on the surface of the skin and transmit them somatotopically to the brain. In chondrichthyans, the electrosensory system is composed of a cephalic network of ampullary organs, known as the ampullae of Lorenzini, that can detect extremely weak electric fields during hunting and navigation. Each ampullary organ consists of a gel-filled epidermal pit containing sensory hair cells, and synaptic connections with primary afferent neurons at the base of the pit that facilitate detection of voltage gradients over large regions of the body. The developmental origin of electroreceptors and the mechanisms that determine their spatial arrangement in the vertebrate head are not well understood. We have analyzed electroreceptor development in the lesser spotted catshark (Scyliorhinus canicula) and show that Sox8 and HNK1, two markers of the neural crest lineage, selectively mark sensory cells in ampullary organs. This represents the first evidence that the neural crest gives rise to electrosensory cells. We also show that pathfinding by cephalic mechanosensory and electrosensory axons follows the expression pattern of EphA4, a well-known guidance cue for axons and neural crest cells in osteichthyans. Expression of EphrinB2, which encodes a ligand for EphA4, marks the positions at which ampullary placodes are initiated in the epidermis, and EphA4 is expressed in surrounding mesenchyme. These results suggest that Eph-Ephrin signaling may establish an early molecular map for neural crest migration, axon guidance and placodal morphogenesis during development of the shark electrosensory system.

  9. Quantifying shark distribution patterns and species-habitat associations: implications of marine park zoning.

    PubMed

    Espinoza, Mario; Cappo, Mike; Heupel, Michelle R; Tobin, Andrew J; Simpfendorfer, Colin A

    2014-01-01

    Quantifying shark distribution patterns and species-specific habitat associations in response to geographic and environmental drivers is critical to assessing risk of exposure to fishing, habitat degradation, and the effects of climate change. The present study examined shark distribution patterns, species-habitat associations, and marine reserve use with baited remote underwater video stations (BRUVS) along the entire Great Barrier Reef Marine Park (GBRMP) over a ten year period. Overall, 21 species of sharks from five families and two orders were recorded. Grey reef Carcharhinus amblyrhynchos, silvertip C. albimarginatus, tiger Galeocerdo cuvier, and sliteye Loxodon macrorhinus sharks were the most abundant species (>64% of shark abundances). Multivariate regression trees showed that hard coral cover produced the primary split separating shark assemblages. Four indicator species had consistently higher abundances and contributed to explaining most of the differences in shark assemblages: C. amblyrhynchos, C. albimarginatus, G. cuvier, and whitetip reef Triaenodon obesus sharks. Relative distance along the GBRMP had the greatest influence on shark occurrence and species richness, which increased at both ends of the sampling range (southern and northern sites) relative to intermediate latitudes. Hard coral cover and distance across the shelf were also important predictors of shark distribution. The relative abundance of sharks was significantly higher in non-fished sites, highlighting the conservation value and benefits of the GBRMP zoning. However, our results also showed that hard coral cover had a large effect on the abundance of reef-associated shark species, indicating that coral reef health may be important for the success of marine protected areas. Therefore, understanding shark distribution patterns, species-habitat associations, and the drivers responsible for those patterns is essential for developing sound management and conservation approaches.

  10. Vertical Movement Patterns and Ontogenetic Niche Expansion in the Tiger Shark, Galeocerdo cuvier

    PubMed Central

    Afonso, André S.; Hazin, Fábio H. V.

    2015-01-01

    Sharks are top predators in many marine ecosystems and can impact community dynamics, yet many shark populations are undergoing severe declines primarily due to overfishing. Obtaining species-specific knowledge on shark spatial ecology is important to implement adequate management strategies for the effective conservation of these taxa. This is particularly relevant concerning highly-mobile species that use wide home ranges comprising coastal and oceanic habitats, such as tiger sharks, Galeocerdo cuvier. We deployed satellite tags in 20 juvenile tiger sharks off northeastern Brazil to assess the effect of intrinsic and extrinsic factors on depth and temperature usage. Sharks were tracked for a total of 1184 d and used waters up to 1112 m in depth. The minimum temperature recorded equaled 4°C. All sharks had a clear preference for surface (< 5 m) waters but variability in depth usage was observed as some sharks used mostly shallow (< 60 m) waters whereas others made frequent incursions into greater depths. A diel behavioral shift was detected, with sharks spending considerably more time in surface (< 10 m) waters during the night. Moreover, a clear ontogenetic expansion in the vertical range of tiger shark habitat was observed, with generalized linear models estimating a ~4-fold increase in maximum diving depth from 150- to 300-cm size-classes. The time spent in the upper 5 m of the water column did not vary ontogenetically but shark size was the most important factor explaining the utilization of deeper water layers. Young-of-the-year tiger sharks seem to associate with shallow, neritic habitats but they progressively move into deeper oceanic habitats as they grow larger. Such an early plasticity in habitat use could endow tiger sharks with access to previously unavailable prey, thus contributing to a wider ecological niche. PMID:25629732

  11. Big catch, little sharks: Insight into Peruvian small-scale longline fisheries

    PubMed Central

    Doherty, Philip D; Alfaro-Shigueto, Joanna; Hodgson, David J; Mangel, Jeffrey C; Witt, Matthew J; Godley, Brendan J

    2014-01-01

    Shark take, driven by vast demand for meat and fins, is increasing. We set out to gain insights into the impact of small-scale longline fisheries in Peru. Onboard observers were used to document catch from 145 longline fishing trips (1668 fishing days) originating from Ilo, southern Peru. Fishing effort is divided into two seasons: targeting dolphinfish (Coryphaena hippurus; December to February) and sharks (March to November). A total of 16,610 sharks were observed caught, with 11,166 identified to species level. Of these, 70.6% were blue sharks (Prionace glauca), 28.4% short-fin mako sharks (Isurus oxyrinchus), and 1% were other species (including thresher (Alopias vulpinus), hammerhead (Sphyrna zygaena), porbeagle (Lamnus nasus), and other Carcharhinidae species (Carcharhinus brachyurus, Carcharhinus falciformis, Galeorhinus galeus). Mean ± SD catch per unit effort of 33.6 ± 10.9 sharks per 1000 hooks was calculated for the shark season and 1.9 ± 3.1 sharks per 1000 hooks were caught in the dolphinfish season. An average of 83.7% of sharks caught (74.7% blue sharks; 93.3% mako sharks) were deemed sexually immature and under the legal minimum landing size, which for species exhibiting k-selected life history traits can result in susceptibility to over exploitation. As these growing fisheries operate along the entire Peruvian coast and may catch millions of sharks per annum, we conclude that their continued expansion, along with ineffective legislative approaches resulting in removal of immature individuals, has the potential to threaten the sustainability of the fishery, its target species, and ecosystem. There is a need for additional monitoring and research to inform novel management strategies for sharks while maintaining fisher livelihoods. PMID:25360274

  12. Vertical movement patterns and ontogenetic niche expansion in the tiger shark, Galeocerdo cuvier.

    PubMed

    Afonso, André S; Hazin, Fábio H V

    2015-01-01

    Sharks are top predators in many marine ecosystems and can impact community dynamics, yet many shark populations are undergoing severe declines primarily due to overfishing. Obtaining species-specific knowledge on shark spatial ecology is important to implement adequate management strategies for the effective conservation of these taxa. This is particularly relevant concerning highly-mobile species that use wide home ranges comprising coastal and oceanic habitats, such as tiger sharks, Galeocerdo cuvier. We deployed satellite tags in 20 juvenile tiger sharks off northeastern Brazil to assess the effect of intrinsic and extrinsic factors on depth and temperature usage. Sharks were tracked for a total of 1184 d and used waters up to 1112 m in depth. The minimum temperature recorded equaled 4°C. All sharks had a clear preference for surface (< 5 m) waters but variability in depth usage was observed as some sharks used mostly shallow (< 60 m) waters whereas others made frequent incursions into greater depths. A diel behavioral shift was detected, with sharks spending considerably more time in surface (< 10 m) waters during the night. Moreover, a clear ontogenetic expansion in the vertical range of tiger shark habitat was observed, with generalized linear models estimating a ~4-fold increase in maximum diving depth from 150- to 300-cm size-classes. The time spent in the upper 5 m of the water column did not vary ontogenetically but shark size was the most important factor explaining the utilization of deeper water layers. Young-of-the-year tiger sharks seem to associate with shallow, neritic habitats but they progressively move into deeper oceanic habitats as they grow larger. Such an early plasticity in habitat use could endow tiger sharks with access to previously unavailable prey, thus contributing to a wider ecological niche.

  13. Big catch, little sharks: Insight into Peruvian small-scale longline fisheries.

    PubMed

    Doherty, Philip D; Alfaro-Shigueto, Joanna; Hodgson, David J; Mangel, Jeffrey C; Witt, Matthew J; Godley, Brendan J

    2014-06-01

    Shark take, driven by vast demand for meat and fins, is increasing. We set out to gain insights into the impact of small-scale longline fisheries in Peru. Onboard observers were used to document catch from 145 longline fishing trips (1668 fishing days) originating from Ilo, southern Peru. Fishing effort is divided into two seasons: targeting dolphinfish (Coryphaena hippurus; December to February) and sharks (March to November). A total of 16,610 sharks were observed caught, with 11,166 identified to species level. Of these, 70.6% were blue sharks (Prionace glauca), 28.4% short-fin mako sharks (Isurus oxyrinchus), and 1% were other species (including thresher (Alopias vulpinus), hammerhead (Sphyrna zygaena), porbeagle (Lamnus nasus), and other Carcharhinidae species (Carcharhinus brachyurus, Carcharhinus falciformis, Galeorhinus galeus). Mean ± SD catch per unit effort of 33.6 ± 10.9 sharks per 1000 hooks was calculated for the shark season and 1.9 ± 3.1 sharks per 1000 hooks were caught in the dolphinfish season. An average of 83.7% of sharks caught (74.7% blue sharks; 93.3% mako sharks) were deemed sexually immature and under the legal minimum landing size, which for species exhibiting k-selected life history traits can result in susceptibility to over exploitation. As these growing fisheries operate along the entire Peruvian coast and may catch millions of sharks per annum, we conclude that their continued expansion, along with ineffective legislative approaches resulting in removal of immature individuals, has the potential to threaten the sustainability of the fishery, its target species, and ecosystem. There is a need for additional monitoring and research to inform novel management strategies for sharks while maintaining fisher livelihoods.

  14. Quantifying Shark Distribution Patterns and Species-Habitat Associations: Implications of Marine Park Zoning

    PubMed Central

    Espinoza, Mario; Cappo, Mike; Heupel, Michelle R.; Tobin, Andrew J.; Simpfendorfer, Colin A.

    2014-01-01

    Quantifying shark distribution patterns and species-specific habitat associations in response to geographic and environmental drivers is critical to assessing risk of exposure to fishing, habitat degradation, and the effects of climate change. The present study examined shark distribution patterns, species-habitat associations, and marine reserve use with baited remote underwater video stations (BRUVS) along the entire Great Barrier Reef Marine Park (GBRMP) over a ten year period. Overall, 21 species of sharks from five families and two orders were recorded. Grey reef Carcharhinus amblyrhynchos, silvertip C. albimarginatus, tiger Galeocerdo cuvier, and sliteye Loxodon macrorhinus sharks were the most abundant species (>64% of shark abundances). Multivariate regression trees showed that hard coral cover produced the primary split separating shark assemblages. Four indicator species had consistently higher abundances and contributed to explaining most of the differences in shark assemblages: C. amblyrhynchos, C. albimarginatus, G. cuvier, and whitetip reef Triaenodon obesus sharks. Relative distance along the GBRMP had the greatest influence on shark occurrence and species richness, which increased at both ends of the sampling range (southern and northern sites) relative to intermediate latitudes. Hard coral cover and distance across the shelf were also important predictors of shark distribution. The relative abundance of sharks was significantly higher in non-fished sites, highlighting the conservation value and benefits of the GBRMP zoning. However, our results also showed that hard coral cover had a large effect on the abundance of reef-associated shark species, indicating that coral reef health may be important for the success of marine protected areas. Therefore, understanding shark distribution patterns, species-habitat associations, and the drivers responsible for those patterns is essential for developing sound management and conservation approaches. PMID

  15. Biomarkers of whale shark health: a metabolomic approach.

    PubMed

    Dove, Alistair D M; Leisen, Johannes; Zhou, Manshui; Byrne, Jonathan J; Lim-Hing, Krista; Webb, Harry D; Gelbaum, Leslie; Viant, Mark R; Kubanek, Julia; Fernández, Facundo M

    2012-01-01

    In a search for biomarkers of health in whale sharks and as exploration of metabolomics as a modern tool for understanding animal physiology, the metabolite composition of serum in six whale sharks (Rhincodon typus) from an aquarium collection was explored using (1)H nuclear magnetic resonance (NMR) spectroscopy and direct analysis in real time (DART) mass spectrometry (MS). Principal components analysis (PCA) of spectral data showed that individual animals could be resolved based on the metabolite composition of their serum and that two unhealthy individuals could be discriminated from the remaining healthy animals. The major difference between healthy and unhealthy individuals was the concentration of homarine, here reported for the first time in an elasmobranch, which was present at substantially lower concentrations in unhealthy whale sharks, suggesting that this metabolite may be a useful biomarker of health status in this species. The function(s) of homarine in sharks remain uncertain but it likely plays a significant role as an osmolyte. The presence of trimethylamine oxide (TMAO), another well-known protective osmolyte of elasmobranchs, at 0.1-0.3 mol L(-1) was also confirmed using both NMR and MS. Twenty-three additional potential biomarkers were identified based on significant differences in the frequency of their occurrence between samples from healthy and unhealthy animals, as detected by DART MS. Overall, NMR and MS provided complementary data that showed that metabolomics is a useful approach for biomarker prospecting in poorly studied species like elasmobranchs.

  16. Biomarkers of Whale Shark Health: A Metabolomic Approach

    PubMed Central

    Dove, Alistair D. M.; Leisen, Johannes; Zhou, Manshui; Byrne, Jonathan J.; Lim-Hing, Krista; Webb, Harry D.; Gelbaum, Leslie; Viant, Mark R.; Kubanek, Julia; Fernández, Facundo M.

    2012-01-01

    In a search for biomarkers of health in whale sharks and as exploration of metabolomics as a modern tool for understanding animal physiology, the metabolite composition of serum in six whale sharks (Rhincodon typus) from an aquarium collection was explored using 1H nuclear magnetic resonance (NMR) spectroscopy and direct analysis in real time (DART) mass spectrometry (MS). Principal components analysis (PCA) of spectral data showed that individual animals could be resolved based on the metabolite composition of their serum and that two unhealthy individuals could be discriminated from the remaining healthy animals. The major difference between healthy and unhealthy individuals was the concentration of homarine, here reported for the first time in an elasmobranch, which was present at substantially lower concentrations in unhealthy whale sharks, suggesting that this metabolite may be a useful biomarker of health status in this species. The function(s) of homarine in sharks remain uncertain but it likely plays a significant role as an osmolyte. The presence of trimethylamine oxide (TMAO), another well-known protective osmolyte of elasmobranchs, at 0.1–0.3 mol L−1 was also confirmed using both NMR and MS. Twenty-three additional potential biomarkers were identified based on significant differences in the frequency of their occurrence between samples from healthy and unhealthy animals, as detected by DART MS. Overall, NMR and MS provided complementary data that showed that metabolomics is a useful approach for biomarker prospecting in poorly studied species like elasmobranchs. PMID:23166652

  17. Antarctic jaws: cephalopod prey of sharks in Kerguelen waters

    NASA Astrophysics Data System (ADS)

    Cherel, Yves; Duhamel, Guy

    2004-01-01

    Only five species of sharks have been recorded in the Southern Ocean, where their biology is essentially unknown. We investigated the feeding habits of the three commonest species from stomach content analysis of specimens taken as bycatches of the fishery targeting the Patagonian toothfish ( Dissostichus eleginoides) in upper slope waters of the Kerguelen Archipelago. The three species prey upon a diversity of fishes and cephalopods. They segregate by feeding on different species of squids of different sizes. The small lanternsharks ( Etmopterus cf. granulosus; 0.3 m on average) feed on small-sized Mastigoteuthis psychrophila, while the large porbeagles ( Lamna nasus; 1.9 m) feed on small-sized histioteuthids ( Histioteuthis atlantica and H. eltaninae) and on medium-sized juvenile ommastrephids of the genus Todarodes. Finally, the huge sleeper sharks ( Somniosus cf. microcephalus; 3.9 m) prey upon large-sized cephalopods ( Kondakovia longimana and Taningia danae) and giant squids ( Mesonychoteuthis hamiltoni and Architeuthis dux). Thus sleeper shark is a fish with sperm whale-like feeding habits and, hence, the second top predator known to science to rely significantly on giant squids. Prey species and biology indicate that porbeagles are pelagic predators in the entire water column, while sleeper sharks are mainly benthic top predators and scavengers. The present study also underlines the diversity and biomass of the poorly known cephalopod fauna, including giant squids, occurring in outer shelf and upper slope waters surrounding subantarctic islands.

  18. Mechanical properties of the hyomandibula in four shark species.

    PubMed

    Balaban, Jordan P; Summers, Adam P; Wilga, Cheryl A

    2015-01-01

    Sharks have cartilaginous elements that support the jaws and are subjected to variable loads. The aim of this study was to understand how these elements, the hyomandibulae, respond to compressive loads, and to describe the structural level mechanical properties of mineralized cartilage. Mechanical stiffness and effective Poisson's ratio of the hyomandibular cartilage were measured in four species of sharks (white-spotted bamboo, Chiloscyllium plagiosum; spiny dogfish, Squalus acanthias; sandbar, Carcharhinus plumbeus; and dusky smoothhound, Mustelus canis). The former two are suction feeders, while the latter two are bite feeders. The hyomandibulae of suction feeders were expected to be stiffer because of the increased loads on their hyomandibulae. Bamboo sharks, as the strongest suction feeders, have the stiffest hyomandibula with a stiffness of 106.12 MPa. The stiffness of spiny dogfish, sandbar sharks, and dusky smoothhounds were 41.58, 58.00, and 49.62 MPa, respectively. The proportion of the minerals found in the cross-section of the hyomandibula determines the elements stiffness. Effective Poisson's ratio was measured at low axial strains and was highly variable ranging from 2.3 × 10(-5) to 4.3 × 10(-1). This implies that the behavior of the hyomandibulae under load will be very different in different species. Furthermore, this wide range of values for the ratio has potential implications for modeling techniques, such as finite element modeling, which use Poisson's ratio as a fundamental input.

  19. 78 FR 77591 - Drawbridge Operation Regulation; Shark River, NJ

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-24

    ... SECURITY Coast Guard 33 CFR Part 117 Drawbridge Operation Regulation; Shark River, NJ AGENCY: Coast Guard, DHS. ACTION: Notice of deviation from drawbridge regulation. SUMMARY: The Coast Guard has issued a... Specialist, Coast Guard; telephone 757-398-6587, email Terrance.A.Knowles@uscg.mil . If you have questions...

  20. Swimming with Sharks: A Physical Educator's Guide to Effective Crowdsourcing

    ERIC Educational Resources Information Center

    Bulger, Sean M.; Jones, Emily M.; Katz, Nicole; Shrewsbury, Gentry; Wood, Justin

    2016-01-01

    The reality-competition television series Shark Tank affords up-and-coming entrepreneurs the opportunity to make a formal business presentation to a panel of potential investors. Adopting a similar framework, entrepreneurial teachers have started using web-based collaborative fundraising or crowdsourcing as a tool to build program capacity with…

  1. The spatial segregation patterns of sharks from Western Australia

    PubMed Central

    2016-01-01

    The extent to which sharks segregate by size and sex determines the population structure and the scale at which populations should be managed. We summarized 20 years of fisheries-dependent and independent sampling to define the spatial patterns of size and sexual segregation for sharks in Western Australia. Carcharhinus obscurus and C. plumbeus showed a large-scale (more than 1000 km) latitudinal gradient in size. Large individuals occurred predominantly in the northwest and north whereas smaller individuals occurred predominantly in the southwest and south. Mustelus antarcticus and Furgaleus macki showed strong sexual segregation at very large scales. Females occurred predominantly in the west and southwest whereas the proportion of males in catches substantially increased in the southeast. The populations of other shark species did not show sex and size segregation patterns at very large scales; most species, however, showed varying degrees of segregation when data were analysed at a smaller scale. These findings highlight the importance of matching the scale of observation to the scale of the phenomenon observed. As many shark species are highly mobile, if sampling is opportunistic and constrained both temporally and spatially, the observed segregation patterns may not be representative of those at the population level, leading to inaccurate scientific advice. PMID:27853609

  2. Loss of large predatory sharks from the Mediterranean Sea.

    PubMed

    Ferretti, Francesco; Myers, Ransom A; Serena, Fabrizio; Lotze, Heike K

    2008-08-01

    Evidence for severe declines in large predatory fishes is increasing around the world. Because of its long history of intense fishing, the Mediterranean Sea offers a unique perspective on fish population declines over historical timescales. We used a diverse set of records dating back to the early 19th and mid 20th century to reconstruct long-term population trends of large predatory sharks in the northwestern Mediterranean Sea. We compiled 9 time series of abundance indices from commercial and recreational fishery landings, scientific surveys, and sighting records. Generalized linear models were used to extract instantaneous rates of change from each data set, and a meta-analysis was conducted to compare population trends. Only 5 of the 20 species we considered had sufficient records for analysis. Hammerhead (Sphyrna spp.), blue (Prionace glauca), mackerel (Isurus oxyrinchus and Lamna nasus), and thresher sharks (Alopias vulpinus) declined between 96 and 99.99% relative to their former abundance. According to World Conservation Union (IUCN) criteria, these species would be considered critically endangered. So far, the lack of quantitative population assessments has impeded shark conservation in the Mediterranean Sea. Our study fills this critical information gap, suggesting that current levels of exploitation put large sharks at risk of extinction in the Mediterranean Sea. Possible ecosystem effects of these losses involve a disruption of top-down control and a release of midlevel consumers.

  3. Fine-Scale Movements of the Broadnose Sevengill Shark and Its Main Prey, the Gummy Shark

    PubMed Central

    Barnett, Adam; Abrantes, Kátya G.; Stevens, John D.; Bruce, Barry D.; Semmens, Jayson M.

    2010-01-01

    Information on the fine-scale movement of predators and their prey is important to interpret foraging behaviours and activity patterns. An understanding of these behaviours will help determine predator-prey relationships and their effects on community dynamics. For instance understanding a predator's movement behaviour may alter pre determined expectations of prey behaviour, as almost any aspect of the prey's decisions from foraging to mating can be influenced by the risk of predation. Acoustic telemetry was used to study the fine-scale movement patterns of the Broadnose Sevengill shark Notorynchus cepedianus and its main prey, the Gummy shark Mustelus antarcticus, in a coastal bay of southeast Tasmania. Notorynchus cepedianus displayed distinct diel differences in activity patterns. During the day they stayed close to the substrate (sea floor) and were frequently inactive. At night, however, their swimming behaviour continually oscillated through the water column from the substrate to near surface. In contrast, M. antarcticus remained close to the substrate for the entire diel cycle, and showed similar movement patterns for day and night. For both species, the possibility that movement is related to foraging behaviour is discussed. For M. antarcticus, movement may possibly be linked to a diet of predominantly slow benthic prey. On several occasions, N. cepedianus carried out a sequence of burst speed events (increased rates of movement) that could be related to chasing prey. All burst speed events during the day were across the substrate, while at night these occurred in the water column. Overall, diel differences in water column use, along with the presence of oscillatory behaviour and burst speed events suggest that N. cepedianus are nocturnal foragers, but may opportunistically attack prey they happen to encounter during the day. PMID:21151925

  4. A novel field method to distinguish between cryptic carcharhinid sharks, Australian blacktip shark Carcharhinus tilstoni and common blacktip shark C. limbatus, despite the presence of hybrids.

    PubMed

    Johnson, G J; Buckworth, R C; Lee, H; Morgan, J A T; Ovenden, J R; McMahon, C R

    2017-01-01

    Multivariate and machine-learning methods were used to develop field identification techniques for two species of cryptic blacktip shark. From 112 specimens, precaudal vertebrae (PCV) counts and molecular analysis identified 95 Australian blacktip sharks Carcharhinus tilstoni and 17 common blacktip sharks Carcharhinus limbatus. Molecular analysis also revealed 27 of the 112 were C. tilstoni × C. limbatus hybrids, of which 23 had C. tilstoni PCV counts and four had C. limbatus PCV counts. In the absence of further information about hybrid phenotypes, hybrids were assigned as either C. limbatus or C. tilstoni based on PCV counts. Discriminant analysis achieved 80% successful identification, but machine-learning models were better, achieving 100% successful identification, using six key measurements (fork length, caudal-fin peduncle height, interdorsal space, second dorsal-fin height, pelvic-fin length and pelvic-fin midpoint to first dorsal-fin insertion). Furthermore, pelvic-fin markings could be used for identification: C. limbatus has a distinct black mark >3% of the total pelvic-fin area, while C. tilstoni has markings with diffuse edges, or has smaller or no markings. Machine learning and pelvic-fin marking identification methods were field tested achieving 87 and 90% successful identification, respectively. With further refinement, the techniques developed here will form an important part of a multi-faceted approach to identification of C. tilstoni and C. limbatus and have a clear management and conservation application to these commercially important sharks. The methods developed here are broadly applicable and can be used to resolve species identities in many fisheries where cryptic species exist.

  5. Detection of piRNAs in whitespotted bamboo shark liver.

    PubMed

    Yang, Lingrong; Ge, Yinghua; Cheng, Dandan; Nie, Zuoming; Lv, Zhengbing

    2016-09-15

    Piwi-interacting RNAs (piRNAs) are 26 to 31-nt small non-coding RNAs that have been reported mostly in germ-line cells and cancer cells. However, the presence of piRNAs in the whitespotted bamboo shark liver has not yet been reported. In a previous study of microRNAs in shark liver, some piRNAs were detected from small RNAs sequenced by Solexa technology. A total of 4857 piRNAs were predicted and found in shark liver. We further selected 17 piRNAs with high and significantly differential expression between normal and regenerative liver tissues for subsequent verification by Northern blotting. Ten piRNAs were further identified, and six of these were matched to known piRNAs in piRNABank. The actual expression of six known and four novel piRNAs was validated by qRT-PCR. In addition, a total of 401 target genes of the 10 piRNAs were predicted by miRanda. Through GO and pathway function analyses, only five piRNAs could be annotated with eighteen GO annotations. The results indicated that the identified piRNAs are involved in many important biological responses, including immune inflammation, cell-specific differentiation and development, and angiogenesis. This manuscript provides the first identification of piRNAs in the liver of whitespotted bamboo shark using Solexa technology as well as further elucidation of the regulatory role of piRNAs in whitespotted bamboo shark liver. These findings may provide a useful resource and may facilitate the development of therapeutic strategies against liver damage.

  6. DNA capture reveals transoceanic gene flow in endangered river sharks

    PubMed Central

    Li, Chenhong; Corrigan, Shannon; Yang, Lei; Straube, Nicolas; Harris, Mark; Hofreiter, Michael; White, William T.; Naylor, Gavin J. P.

    2015-01-01

    For over a hundred years, the “river sharks” of the genus Glyphis were only known from the type specimens of species that had been collected in the 19th century. They were widely considered extinct until populations of Glyphis-like sharks were rediscovered in remote regions of Borneo and Northern Australia at the end of the 20th century. However, the genetic affinities between the newly discovered Glyphis-like populations and the poorly preserved, original museum-type specimens have never been established. Here, we present the first (to our knowledge) fully resolved, complete phylogeny of Glyphis that includes both archival-type specimens and modern material. We used a sensitive DNA hybridization capture method to obtain complete mitochondrial genomes from all of our samples and show that three of the five described river shark species are probably conspecific and widely distributed in Southeast Asia. Furthermore we show that there has been recent gene flow between locations that are separated by large oceanic expanses. Our data strongly suggest marine dispersal in these species, overturning the widely held notion that river sharks are restricted to freshwater. It seems that species in the genus Glyphis are euryhaline with an ecology similar to the bull shark, in which adult individuals live in the ocean while the young grow up in river habitats with reduced predation pressure. Finally, we discovered a previously unidentified species within the genus Glyphis that is deeply divergent from all other lineages, underscoring the current lack of knowledge about the biodiversity and ecology of these mysterious sharks. PMID:26460025

  7. Labial cartilages in the smalltooth sandtiger shark, Odontaspis ferox (lamniformes: odontaspididae) and their significance to the phylogeny of lamniform sharks.

    PubMed

    Shimada, Kenshu; Rigsby, Cynthia K; Kim, Sun H

    2009-06-01

    Using computed tomography, we discovered labial cartilages (splanchnocranial components) in an enigmatic lamniform shark, Odontaspis ferox (smalltooth sandtiger). We demonstrate that the presence of labial cartilages is plesiomorphic in Lamniformes, affirming that their "reduction" cannot be used as a synapomorphy for the order. Rather, their loss occurred through lamniform phylogeny.

  8. Modelling tooth–prey interactions in sharks: the importance of dynamic testing

    PubMed Central

    Farina, Stacy C.; Brash, Jeffrey; Summers, Adam P.

    2016-01-01

    The shape of shark teeth varies among species, but traditional testing protocols have revealed no predictive relationship between shark tooth morphology and performance. We developed a dynamic testing device to quantify cutting performance of teeth. We mimicked head-shaking behaviour in feeding large sharks by attaching teeth to the blade of a reciprocating power saw fixed in a custom-built frame. We tested three tooth types at biologically relevant speeds and found differences in tooth cutting ability and wear. Teeth from the bluntnose sixgill (Hexanchus griseus) showed poor cutting ability compared with tiger (Galeocerdo cuvier), sandbar (Carcharhinus plumbeus) and silky (C. falciformis) sharks, but they also showed no wear with repeated use. Some shark teeth are very sharp at the expense of quickly dulling, while others are less sharp but dull more slowly. This demonstrates that dynamic testing is vital to understanding the performance of shark teeth. PMID:27853592

  9. Growth and Maximum Size of Tiger Sharks (Galeocerdo cuvier) in Hawaii

    PubMed Central

    Meyer, Carl G.; O'Malley, Joseph M.; Papastamatiou, Yannis P.; Dale, Jonathan J.; Hutchinson, Melanie R.; Anderson, James M.; Royer, Mark A.; Holland, Kim N.

    2014-01-01

    Tiger sharks (Galecerdo cuvier) are apex predators characterized by their broad diet, large size and rapid growth. Tiger shark maximum size is typically between 380 & 450 cm Total Length (TL), with a few individuals reaching 550 cm TL, but the maximum size of tiger sharks in Hawaii waters remains uncertain. A previous study suggested tiger sharks grow rather slowly in Hawaii compared to other regions, but this may have been an artifact of the method used to estimate growth (unvalidated vertebral ring counts) compounded by small sample size and narrow size range. Since 1993, the University of Hawaii has conducted a research program aimed at elucidating tiger shark biology, and to date 420 tiger sharks have been tagged and 50 recaptured. All recaptures were from Hawaii except a single shark recaptured off Isla Jacques Cousteau (24°13′17″N 109°52′14″W), in the southern Gulf of California (minimum distance between tag and recapture sites  =  approximately 5,000 km), after 366 days at liberty (DAL). We used these empirical mark-recapture data to estimate growth rates and maximum size for tiger sharks in Hawaii. We found that tiger sharks in Hawaii grow twice as fast as previously thought, on average reaching 340 cm TL by age 5, and attaining a maximum size of 403 cm TL. Our model indicates the fastest growing individuals attain 400 cm TL by age 5, and the largest reach a maximum size of 444 cm TL. The largest shark captured during our study was 464 cm TL but individuals >450 cm TL were extremely rare (0.005% of sharks captured). We conclude that tiger shark growth rates and maximum sizes in Hawaii are generally consistent with those in other regions, and hypothesize that a broad diet may help them to achieve this rapid growth by maximizing prey consumption rates. PMID:24416287

  10. Growth and maximum size of tiger sharks (Galeocerdo cuvier) in Hawaii.

    PubMed

    Meyer, Carl G; O'Malley, Joseph M; Papastamatiou, Yannis P; Dale, Jonathan J; Hutchinson, Melanie R; Anderson, James M; Royer, Mark A; Holland, Kim N

    2014-01-01

    Tiger sharks (Galecerdo cuvier) are apex predators characterized by their broad diet, large size and rapid growth. Tiger shark maximum size is typically between 380 & 450 cm Total Length (TL), with a few individuals reaching 550 cm TL, but the maximum size of tiger sharks in Hawaii waters remains uncertain. A previous study suggested tiger sharks grow rather slowly in Hawaii compared to other regions, but this may have been an artifact of the method used to estimate growth (unvalidated vertebral ring counts) compounded by small sample size and narrow size range. Since 1993, the University of Hawaii has conducted a research program aimed at elucidating tiger shark biology, and to date 420 tiger sharks have been tagged and 50 recaptured. All recaptures were from Hawaii except a single shark recaptured off Isla Jacques Cousteau (24°13'17″N 109°52'14″W), in the southern Gulf of California (minimum distance between tag and recapture sites  =  approximately 5,000 km), after 366 days at liberty (DAL). We used these empirical mark-recapture data to estimate growth rates and maximum size for tiger sharks in Hawaii. We found that tiger sharks in Hawaii grow twice as fast as previously thought, on average reaching 340 cm TL by age 5, and attaining a maximum size of 403 cm TL. Our model indicates the fastest growing individuals attain 400 cm TL by age 5, and the largest reach a maximum size of 444 cm TL. The largest shark captured during our study was 464 cm TL but individuals >450 cm TL were extremely rare (0.005% of sharks captured). We conclude that tiger shark growth rates and maximum sizes in Hawaii are generally consistent with those in other regions, and hypothesize that a broad diet may help them to achieve this rapid growth by maximizing prey consumption rates.

  11. Widespread utility of highly informative AFLP molecular markers across divergent shark species.

    PubMed

    Zenger, Kyall R; Stow, Adam J; Peddemors, Victor; Briscoe, David A; Harcourt, Robert G

    2006-01-01

    Population numbers of many shark species are declining rapidly around the world. Despite the commercial and conservation significance, little is known on even the most fundamental aspects of their population biology. Data collection that relies on direct observation can be logistically challenging with sharks. Consequently, molecular methods are becoming increasingly important to obtain knowledge that is critical for conservation and management. Here we describe an amplified fragment length polymorphism method that can be applied universally to sharks to identify highly informative genome-wide polymorphisms from 12 primer pairs. We demonstrate the value of our method on 15 divergent shark species within the superorder Galeomorphii, including endangered species which are notorious for low levels of genetic diversity. Both the endangered sand tiger shark (Carcharodon taurus, N = 18) and the great white shark (Carcharodon carcharias, N = 7) displayed relatively high levels of allelic diversity. A total of 59 polymorphic loci (H(e) = 0.373) and 78 polymorphic loci (H(e) = 0.316) were resolved in C. taurus and C. carcharias, respectively. Results from other sharks (e.g., Orectolobus ornatus, Orectolobus sp., and Galeocerdo cuvier) produced remarkably high numbers of polymorphic loci (106, 94, and 86, respectively) from a limited sample size of only 2. A major constraint to obtaining much needed genetic data from sharks is the time-consuming process of developing molecular markers. Here we demonstrate the general utility of a technique that provides large numbers of informative loci in sharks.

  12. Structure and dynamics of the shark assemblage off Recife, Northeastern Brazil.

    PubMed

    Afonso, André S; Andrade, Humber A; Hazin, Fábio H V

    2014-01-01

    Understanding the ecological factors that regulate elasmobranch abundance in nearshore waters is essential to effectively manage coastal ecosystems and promote conservation. However, little is known about elasmobranch populations in the western South Atlantic Ocean. An 8-year, standardized longline and drumline survey conducted in nearshore waters off Recife, northeastern Brazil, allowed us to describe the shark assemblage and to monitor abundance dynamics using zero-inflated generalized additive models. This region is mostly used by several carcharhinids and one ginglymostomid, but sphyrnids are also present. Blacknose sharks, Carcharhinus acronotus, were mostly mature individuals and declined in abundance throughout the survey, contrasting with nurse sharks, Ginglymostoma cirratum, which proliferated possibly due to this species being prohibited from all harvest since 2004 in this region. Tiger sharks, Galeocerdo cuvier, were mostly juveniles smaller than 200 cm and seem to use nearshore waters off Recife between January and September. No long-term trend in tiger shark abundance was discernible. Spatial distribution was similar in true coastal species (i.e. blacknose and nurse sharks) whereas tiger sharks were most abundant at the middle continental shelf. The sea surface temperature, tidal amplitude, wind direction, water turbidity, and pluviosity were all selected to predict shark abundance off Recife. Interspecific variability in abundance dynamics across spatiotemporal and environmental gradients suggest that the ecological processes regulating shark abundance are generally independent between species, which could add complexity to multi-species fisheries management frameworks. Yet, further research is warranted to ascertain trends at population levels in the South Atlantic Ocean.

  13. Ultrastructure Organization of Collagen Fibrils and Proteoglycans of Stingray and Shark Corneal Stroma

    PubMed Central

    Alanazi, Saud A.; Almubrad, Turki; AlIbrahim, Ahmad I. A.; Khan, Adnan A.; Akhtar, Saeed

    2015-01-01

    We report here the ultrastructural organization of collagen fibrils (CF) and proteoglycans (PGs) of the corneal stroma of both the stingray and the shark. Three corneas from three stingrays and three corneas from three sharks were processed for electron microscopy. Tissues were embedded in TAAB 031 resin. The corneal stroma of both the stingray and shark consisted of parallel running lamellae of CFs which were decorated with PGs. In the stingray, the mean area of PGs in the posterior stroma was significantly larger than the PGs of the anterior and middle stroma, whereas, in the shark, the mean area of PGs was similar throughout the stroma. The mean area of PGs of the stingray was significantly larger compared to the PGs, mean area of the shark corneal stroma. The CF diameter of the stingray was significantly smaller compared to the CF diameter in the shark. The ultrastructural features of the corneal stroma of both the stingray and the shark were similar to each other except for the CFs and PGs. The PGs in the stingray and shark might be composed of chondroitin sulfate (CS)/dermatan sulfate (DS) PGs and these PGs with sutures might contribute to the nonswelling properties of the cornea of the stingray and shark. PMID:26167294

  14. Reconstruction of parental microsatellite genotypes reveals female polyandry and philopatry in the lemon shark, Negaprion brevirostris.

    PubMed

    Feldheim, Kevin A; Gruber, Samuel H; Ashley, Mary V

    2004-10-01

    Because sharks possess an unusual suite of reproductive characteristics, including internal fertilization, sperm storage, relatively low fecundity, and reproductive modes that range from oviparity to viviparity, they can provide important insight into the evolution of mating systems and sexual selection. Yet, to date, few studies have characterized behavioral and genetic mating systems in natural populations of sharks or other elasmobranchs. In this study, highly polymorphic microsatellite loci were used to examine breeding biology of a large coastal shark, the lemon shark, Negaprion brevirostris, at a tropical lagoon nursery. Over six years, 910 lemon sharks were sampled and genotyped. Young were assigned into sibling groups that were then used to reconstruct genotypes of unsampled adults. We assigned 707 of 735 young sharks to one of 45 female genotypes (96.2%), and 485 (66.0%) were assigned to a male genotype. Adult female sharks consistently returned to Bimini on a biennial cycle to give birth. Over 86% of litters had multiple sires. Such high levels of polyandry raise the possibility that polyandry evolved in viviparous sharks to reduce genetic incompatibilities between mother and embryos. We did not find a relationship between relatedness of mates and the number of offspring produced, indicating that inbreeding avoidance was probably not driving pre- or postcopulatory mate choice. Adult male sharks rarely sired more than one litter at Bimini and may mate over a broader geographic area.

  15. Structure and Dynamics of the Shark Assemblage off Recife, Northeastern Brazil

    PubMed Central

    Afonso, André S.; Andrade, Humber A.; Hazin, Fábio H. V.

    2014-01-01

    Understanding the ecological factors that regulate elasmobranch abundance in nearshore waters is essential to effectively manage coastal ecosystems and promote conservation. However, little is known about elasmobranch populations in the western South Atlantic Ocean. An 8-year, standardized longline and drumline survey conducted in nearshore waters off Recife, northeastern Brazil, allowed us to describe the shark assemblage and to monitor abundance dynamics using zero-inflated generalized additive models. This region is mostly used by several carcharhinids and one ginglymostomid, but sphyrnids are also present. Blacknose sharks, Carcharhinus acronotus, were mostly mature individuals and declined in abundance throughout the survey, contrasting with nurse sharks, Ginglymostoma cirratum, which proliferated possibly due to this species being prohibited from all harvest since 2004 in this region. Tiger sharks, Galeocerdo cuvier, were mostly juveniles smaller than 200 cm and seem to use nearshore waters off Recife between January and September. No long-term trend in tiger shark abundance was discernible. Spatial distribution was similar in true coastal species (i.e. blacknose and nurse sharks) whereas tiger sharks were most abundant at the middle continental shelf. The sea surface temperature, tidal amplitude, wind direction, water turbidity, and pluviosity were all selected to predict shark abundance off Recife. Interspecific variability in abundance dynamics across spatiotemporal and environmental gradients suggest that the ecological processes regulating shark abundance are generally independent between species, which could add complexity to multi-species fisheries management frameworks. Yet, further research is warranted to ascertain trends at population levels in the South Atlantic Ocean. PMID:25010514

  16. Acoustic telemetry validates a citizen science approach for monitoring sharks on coral reefs.

    PubMed

    Vianna, Gabriel M S; Meekan, Mark G; Bornovski, Tova H; Meeuwig, Jessica J

    2014-01-01

    Citizen science is promoted as a simple and cost-effective alternative to traditional approaches for the monitoring of populations of marine megafauna. However, the reliability of datasets collected by these initiatives often remains poorly quantified. We compared datasets of shark counts collected by professional dive guides with acoustic telemetry data from tagged sharks collected at the same coral reef sites over a period of five years. There was a strong correlation between the number of grey reef sharks (Carcharhinus amblyrhynchos) observed by dive guides and the telemetry data at both daily and monthly intervals, suggesting that variation in relative abundance of sharks was detectable in datasets collected by dive guides in a similar manner to data derived from telemetry at these time scales. There was no correlation between the number or mean depth of sharks recorded by telemetry and the presence of tourist divers, suggesting that the behaviour of sharks was not affected by the presence of divers during our study. Data recorded by dive guides showed that current strength and temperature were important drivers of the relative abundance of sharks at monitored sites. Our study validates the use of datasets of shark abundance collected by professional dive guides in frequently-visited dive sites in Palau, and supports the participation of experienced recreational divers as contributors to long-term monitoring programs of shark populations.

  17. Australian and U.S. news media portrayal of sharks and their conservation.

    PubMed

    Muter, Bret A; Gore, Meredith L; Gledhill, Katie S; Lamont, Christopher; Huveneers, Charlie

    2013-02-01

    Investigation of the social framing of human-shark interactions may provide useful strategies for integrating social, biological, and ecological knowledge into national and international policy discussions about shark conservation. One way to investigate social opinion and forces related to sharks and their conservation is through the media's coverage of sharks. We conducted a content analysis of 300 shark-related articles published in 20 major Australian and U.S. newspapers from 2000 to 2010. Shark attacks were the emphasis of over half the articles analyzed, and shark conservation was the primary topic of 11% of articles. Significantly more Australian articles than U.S. articles treated shark attacks (χ(2) = 3.862; Australian 58% vs. U.S. 47%) and shark conservation issues (χ(2) = 6.856; Australian 15% vs. U.S. 11%) as the primary article topic and used politicians as the primary risk messenger (i.e., primary person or authority sourced in the article) (χ(2) = 7.493; Australian 8% vs. U.S. 1%). However, significantly more U.S. articles than Australian articles discussed sharks as entertainment (e.g., subjects in movies, books, and television; χ(2) = 15.130; U.S. 6% vs. Australian 1%) and used scientists as the primary risk messenger (χ(2) = 5.333; U.S. 25% vs. Australian 15%). Despite evidence that many shark species are at risk of extinction, we found that most media coverage emphasized the risks sharks pose to people. To the extent that media reflects social opinion, our results highlight problems for shark conservation. We suggest that conservation professionals purposefully and frequently engage with the media to highlight the rarity of shark attacks, discuss preventative measures water users can take to reduce their vulnerability to shark encounters, and discuss conservation issues related to local and threatened species of sharks. When integrated with biological and ecological data, social-science data may help generate a more comprehensive perspective

  18. Acoustic Telemetry Validates a Citizen Science Approach for Monitoring Sharks on Coral Reefs

    PubMed Central

    Vianna, Gabriel M. S.; Meekan, Mark G.; Bornovski, Tova H.; Meeuwig, Jessica J.

    2014-01-01

    Citizen science is promoted as a simple and cost-effective alternative to traditional approaches for the monitoring of populations of marine megafauna. However, the reliability of datasets collected by these initiatives often remains poorly quantified. We compared datasets of shark counts collected by professional dive guides with acoustic telemetry data from tagged sharks collected at the same coral reef sites over a period of five years. There was a strong correlation between the number of grey reef sharks (Carcharhinus amblyrhynchos) observed by dive guides and the telemetry data at both daily and monthly intervals, suggesting that variation in relative abundance of sharks was detectable in datasets collected by dive guides in a similar manner to data derived from telemetry at these time scales. There was no correlation between the number or mean depth of sharks recorded by telemetry and the presence of tourist divers, suggesting that the behaviour of sharks was not affected by the presence of divers during our study. Data recorded by dive guides showed that current strength and temperature were important drivers of the relative abundance of sharks at monitored sites. Our study validates the use of datasets of shark abundance collected by professional dive guides in frequently-visited dive sites in Palau, and supports the participation of experienced recreational divers as contributors to long-term monitoring programs of shark populations. PMID:24760081

  19. Plastic debris collars on juvenile carcharhinid sharks (Rhizoprionodon lalandii) in southwest Atlantic.

    PubMed

    Sazima, Ivan; Gadig, Otto B F; Namora, Rafael C; Motta, Fábio S

    2002-10-01

    Three juvenile Brazilian sharpnose sharks (Rhizoprionodon lalandii) caught in gillnets in southeast Brazil, southwest Atlantic, were found with plastic debris rings around their gill or mouth region. The rings caused severe abrasion on the sharks' tissues as the animal grew, the collars probably hampering normal feeding and/or ventilation since two of the collared individuals were emaciated. The rings were identified as detachable lid parts from plastic bottles, likely thrown overboard by fishery and/or recreation boats. As several carcharhinid shark species dwells and reproduce in shallow waters, the impact of discarded plastic debris likely is greater on this shark type.

  20. Survey Sequencing and Comparative Analysis of the Elephant Shark (Callorhinchus milii) Genome

    PubMed Central

    Venkatesh, Byrappa; Kirkness, Ewen F; Loh, Yong-Hwee; Halpern, Aaron L; Lee, Alison P; Johnson, Justin; Dandona, Nidhi; Viswanathan, Lakshmi D; Tay, Alice; Venter, J. Craig; Strausberg, Robert L; Brenner, Sydney

    2007-01-01

    Owing to their phylogenetic position, cartilaginous fishes (sharks, rays, skates, and chimaeras) provide a critical reference for our understanding of vertebrate genome evolution. The relatively small genome of the elephant shark, Callorhinchus milii, a chimaera, makes it an attractive model cartilaginous fish genome for whole-genome sequencing and comparative analysis. Here, the authors describe survey sequencing (1.4× coverage) and comparative analysis of the elephant shark genome, one of the first cartilaginous fish genomes to be sequenced to this depth. Repetitive sequences, represented mainly by a novel family of short interspersed element–like and long interspersed element–like sequences, account for about 28% of the elephant shark genome. Fragments of approximately 15,000 elephant shark genes reveal specific examples of genes that have been lost differentially during the evolution of tetrapod and teleost fish lineages. Interestingly, the degree of conserved synteny and conserved sequences between the human and elephant shark genomes are higher than that between human and teleost fish genomes. Elephant shark contains putative four Hox clusters indicating that, unlike teleost fish genomes, the elephant shark genome has not experienced an additional whole-genome duplication. These findings underscore the importance of the elephant shark as a critical reference vertebrate genome for comparative analysis of the human and other vertebrate genomes. This study also demonstrates that a survey-sequencing approach can be applied productively for comparative analysis of distantly related vertebrate genomes. PMID:17407382

  1. A streamlined DNA tool for global identification of heavily exploited coastal shark species (genus Rhizoprionodon).

    PubMed

    Pinhal, Danillo; Shivji, Mahmood S; Nachtigall, Pedro G; Chapman, Demian D; Martins, Cesar

    2012-01-01

    Obtaining accurate species-specific landings data is an essential step toward achieving sustainable shark fisheries. Globally distributed sharpnose sharks (genus Rhizoprionodon) exhibit life-history characteristics (rapid growth, early maturity, annual reproduction) that suggests that they could be fished in a sustainable manner assuming an investment in monitoring, assessment and careful management. However, obtaining species-specific landings data for sharpnose sharks is problematic because they are morphologically very similar to one another. Moreover, sharpnose sharks may also be confused with other small sharks (either small species or juveniles of large species) once they are processed (i.e., the head and fins are removed). Here we present a highly streamlined molecular genetics approach based on seven species-specific PCR primers in a multiplex format that can simultaneously discriminate body parts from the seven described sharpnose shark species commonly occurring in coastal fisheries worldwide. The species-specific primers are based on nucleotide sequence differences among species in the nuclear ribosomal internal transcribed spacer 2 locus (ITS2). This approach also distinguishes sharpnose sharks from a wide range of other sharks (52 species) and can therefore assist in the regulation of coastal shark fisheries around the world.

  2. Ultrastructure Organization of Collagen Fibrils and Proteoglycans of Stingray and Shark Corneal Stroma.

    PubMed

    Alanazi, Saud A; Almubrad, Turki; AlIbrahim, Ahmad I A; Khan, Adnan A; Akhtar, Saeed

    2015-01-01

    We report here the ultrastructural organization of collagen fibrils (CF) and proteoglycans (PGs) of the corneal stroma of both the stingray and the shark. Three corneas from three stingrays and three corneas from three sharks were processed for electron microscopy. Tissues were embedded in TAAB 031 resin. The corneal stroma of both the stingray and shark consisted of parallel running lamellae of CFs which were decorated with PGs. In the stingray, the mean area of PGs in the posterior stroma was significantly larger than the PGs of the anterior and middle stroma, whereas, in the shark, the mean area of PGs was similar throughout the stroma. The mean area of PGs of the stingray was significantly larger compared to the PGs, mean area of the shark corneal stroma. The CF diameter of the stingray was significantly smaller compared to the CF diameter in the shark. The ultrastructural features of the corneal stroma of both the stingray and the shark were similar to each other except for the CFs and PGs. The PGs in the stingray and shark might be composed of chondroitin sulfate (CS)/dermatan sulfate (DS) PGs and these PGs with sutures might contribute to the nonswelling properties of the cornea of the stingray and shark.

  3. An Astronomical Pattern-Matching Algorithm for Automated Identification of Whale Sharks

    NASA Technical Reports Server (NTRS)

    Arzoumanian, Z.; Holmberg, J.; Norman, B.

    2005-01-01

    The largest shark species alive today, whale sharks (Rhincodon typus) are rare and poorly studied. Directed fisheries, high value in international trade, a highly migratory nature, and generally low abundance make this species vulnerable to exploitation. Mark- and-recapture studies have provided our current understanding of whale shark demographics and life history, but conventional tagging has met with limited success. To aid in conservation and management efforts, and to further our knowledge of whale shark biology, an identification technology that maximizes the scientific value of individual sighting is needed.

  4. Mitochondrial proton leak rates in the slow, oxidative myotomal muscle and liver of the endothermic shortfin mako shark (Isurus oxyrinchus) and the ectothermic blue shark (Prionace glauca) and leopard shark (Triakis semifasciata).

    PubMed

    Duong, Cindy A; Sepulveda, Chugey A; Graham, Jeffrey B; Dickson, Kathryn A

    2006-07-01

    Mitochondrial proton leak was assessed as a potential heat source in the slow, oxidative (red) locomotor muscle and liver of the shortfin mako shark (Isurus oxyrinchus), a regional endotherm that maintains the temperature of both tissues elevated above ambient seawater temperature. We hypothesized that basal proton leak rates in red muscle and liver mitochondria of the endothermic shortfin mako shark would be greater than those of the ectothermic blue shark (Prionace glauca) and leopard shark (Triakis semifasciata). Respiration rate and membrane potential in isolated mitochondria were measured simultaneously at 20 degrees C using a Clark-type oxygen electrode and a lipophilic probe (triphenylmethylphosphonium, TPMP(+)). Succinate-stimulated respiration was titrated with inhibitors of the electron transport chain, and the non-linear relationship between respiration rate and membrane potential was quantified. Mitochondrial densities of both tissues were measured by applying the point-contact method to electron micrographs so that proton leak activity of the entire tissue could be assessed. In all three shark species, proton leak occurred at a higher rate in red muscle mitochondria than in liver mitochondria. For each tissue, the proton leak curves of the three species overlapped and, at a membrane potential of 160 mV, mitochondrial proton leak rate (nmol H(+) min(-1) mg(-1) protein) did not differ significantly between the endothermic and ectothermic sharks. This finding indicates that red muscle and liver mitochondria of the shortfin mako shark are not specialized for thermogenesis by having a higher proton conductance. However, mako mitochondria did have higher succinate-stimulated respiration rates and membrane potentials than those of the two ectothermic sharks. This means that under in vivo conditions mitochondrial proton leak rates may be higher in the mako than in the ectothermic species, due to greater electron transport activity and a larger proton gradient

  5. Migration of a Late Cretaceous fish.

    PubMed

    Carpenter, Scott J; Erickson, J Mark; Holland, F D

    2003-05-01

    Late Cretaceous sediments from the Western Interior of North America yield exceptionally well preserved fossils that serve as proxies for the rapidly changing climate preceding the Cretaceous/Tertiary boundary (about 67-65 Myr ago). Here we reconstruct the ontogenetic history of a Maastrichtian-age fish, Vorhisia vulpes, by using the carbon, oxygen and strontium isotope ratios of four aragonite otoliths collected from the Fox Hills Formation of South Dakota. Individuals of V. vulpes spawned in brackish water (about 70-80% seawater) and during their first year migrated to open marine waters of the Western Interior Seaway, where they remained for 3 years before returning to the estuary, presumably to spawn and die. The mean delta(18)O from the marine growth phase of V. vulpes yields a seawater temperature of 18 degrees C, which is consistent with leaf physiognomy and general-circulation-model temperature estimates for the Western Interior during the latest Maastrichtian.

  6. Palaeontology: pterosaur embryo from the Early Cretaceous.

    PubMed

    Wang, Xiaolin; Zhou, Zhonghe

    2004-06-10

    Dinosaur embryos have been discovered all over the world, but so far no pterosaur embryos have been reported. Here we describe a Chinese fossil from the Early Cretaceous period containing an embryo that is unambiguously a pterosaur. The embryonic skeleton, which is exquisitely preserved in its egg, is associated with eggshell fragments, wing membranes and skin imprints. This discovery confirms that pterosaurs were egg-layers and sheds new light on our understanding of pterosaur development.

  7. Anomalous paleointensity variation in the Late Cretaceous

    NASA Astrophysics Data System (ADS)

    Chang, B.; Doh, S.; Yu, Y.; Kim, W.

    2010-12-01

    A successive paleointensity variation of the Late Cretaceous (~73.1 Ma) was obtained from the six consecutive lava flows at Jeon-gok Volcanic Complex (JVC) in Korea. A total of 283 samples were collected vertically from the bottom of the flow exposures. For the paleointensity determination, over 200 samples were subjected to the Thellier-type IZZI method with systematic alteration checks. Seventy-nine samples passed conventional reliable criteria, yielding a success rate of 38.7%. The paleofield carrier was found as a magnetite, based on the thermomagnetic analysis. Additional rock magnetic experiments revealed a predominance of single-domain magnetite with partial contribution from superparamagnetic grains. Temporally, the estimated paleointensities (2.7-51.1 μT) displayed distinctive half-sinusoidal fluctuation. The corresponding virtual axial dipole moments range from 4.7 to 90.1 ZAm2 (Z = 1021). Such enormous paleointensity variation with extremely low to high intensity might indicate the period of the geomagnetic field transition or excursion in the Late Cretaceous. Perhaps this ancient geomagnetic field intensity fluctuation reflects the geomagnetic secular variation in late Cretaceous.

  8. The complete mitochondrial genome sequence of the world's largest fish, the whale shark (Rhincodon typus), and its comparison with those of related shark species.

    PubMed

    Alam, Md Tauqeer; Petit, Robert A; Read, Timothy D; Dove, Alistair D M

    2014-04-10

    The whale shark (Rhincodon typus) is the largest extant species of fish, belonging to the order Orectolobiformes. It is listed as a "vulnerable" species on the International Union for Conservation of Nature (IUCN)'s Red List of Threatened Species, which makes it an important species for conservation efforts. We report here the first complete sequence of the mitochondrial genome (mitogenome) of the whale shark obtained by next-generation sequencing methods. The assembled mitogenome is a 16,875 bp circle, comprising of 13 protein-coding genes, two rRNA genes, 22 tRNA genes and a control region. We also performed comparative analysis of the whale shark mitogenome to the available mitogenome sequences of 17 other shark species, four from the order Orectolobiformes, five from Lamniformes and eight from Carcharhiniformes. The nucleotide composition, number and arrangement of the genes in whale shark mitogenome are the same as found in the mitogenomes of the other members of the order Orectolobiformes and its closest orders Lamniformes and Carcharhiniformes, although the whale shark mitogenome had a slightly longer control region. The availability of mitogenome sequence of whale shark will aid studies of molecular systematics, biogeography, genetic differentiation, and conservation genetics in this species.

  9. Cone monochromacy and visual pigment spectral tuning in wobbegong sharks.

    PubMed

    Theiss, Susan M; Davies, Wayne I L; Collin, Shaun P; Hunt, David M; Hart, Nathan S

    2012-12-23

    Much is known regarding the evolution of colour vision in nearly every vertebrate class, with the notable exception of the elasmobranchs. While multiple spectrally distinct cone types are found in some rays, sharks appear to possess only a single class of cone and, therefore, may be colour blind. In this study, the visual opsin genes of two wobbegong species, Orectolobus maculatus and Orectolobus ornatus, were isolated to verify the molecular basis of their monochromacy. In both species, only two opsin genes are present, RH1 (rod) and LWS (cone), which provide further evidence to support the concept that sharks possess only a single cone type. Examination of the coding sequences revealed substitutions that account for interspecific variation in the photopigment absorbance spectra, which may reflect the difference in visual ecology between these species.

  10. Was everything bigger in Texas? Characterization and trends of a land-based recreational shark fishery

    USGS Publications Warehouse

    Ajemian, Matthew J.; Jose, Philip D.; Froeschke, John T.; Wildhaber, Mark L.; Stunz, Gregory W.

    2016-01-01

    Although current assessments of shark population trends involve both fishery-independent and fishery-dependent data, the latter are generally limited to commercial landings that may neglect nearshore coastal habitats. Texas has supported the longest organized land-based recreational shark fishery in the United States, yet no studies have used this “non-traditional” data source to characterize the catch composition or trends in this multidecadal fishery. We analyzed catch records from two distinct periods straddling heavy commercial exploitation of sharks in the Gulf of Mexico (historical period = 1973–1986; modern period = 2008–2015) to highlight and make available the current status and historical trends in Texas’ land-based shark fishery. Catch records describing large coastal species (>1,800 mm stretched total length [STL]) were examined using multivariate techniques to assess catch seasonality and potential temporal shifts in species composition. These fishery-dependent data revealed consistent seasonality that was independent of the data set examined, although distinct shark assemblages were evident between the two periods. Similarity percentage analysis suggested decreased contributions of Lemon Shark Negaprion brevirostris over time and a general shift toward the dominance of Bull Shark Carcharhinus leucas and Blacktip Shark C. limbatus. Comparisons of mean STL for species captured in historical and modern periods further identified significant decreases for both Bull Sharks and Lemon Sharks. Size structure analysis showed a distinct paucity of landed individuals over 2,000 mm STL in recent years. Although inherent biases in reporting and potential gear-related inconsistencies undoubtedly influenced this fishery-dependent data set, the patterns in our findings documented potential declines in the size and occurrence of select large coastal shark species off Texas, consistent with declines reported in the Gulf of Mexico. Future management efforts

  11. Impacts of food web structure and feeding behavior on mercury exposure in Greenland Sharks (Somniosus microcephalus).

    PubMed

    McMeans, Bailey C; Arts, Michael T; Fisk, Aaron T

    2015-03-15

    Benthic and pelagic food web components in Cumberland Sound, Canada were explored as sources of total mercury (THg) to Greenland Sharks (Somniosus microcephalus) via both bottom-up food web transfer and top-down shark feeding behavior. Log10THg increased significantly with δ(15)N and trophic position from invertebrates (0.01 ± 0.01 μg · g(-1) [113 ± 1 ng · g(-1)] dw in copepods) to Greenland Sharks (3.54 ± 1.02 μg · g(-1)). The slope of the log10THg vs. δ(15)N linear regression was higher for pelagic compared to benthic food web components (excluding Greenland Sharks, which could not be assigned to either food web), which resulted from THg concentrations being higher at the base of the benthic food web (i.e., in benthic than pelagic primary consumers). However, feeding habitat is unlikely to consistently influence shark THg exposure in Cumberland Sound because THg concentrations did not consistently differ between benthic and pelagic shark prey. Further, size, gender and feeding behavior (inferred from stable isotopes and fatty acids) were unable to significantly explain THg variability among individual Greenland Sharks. Possible reasons for this result include: 1) individual sharks feeding as generalists, 2) high overlap in THg among shark prey, and 3) differences in turnover time between ecological tracers and THg. This first assessment of Greenland Shark THg within an Arctic food web revealed high concentrations consistent with biomagnification, but low ability to explain intra-specific THg variability. Our findings of high THg levels and consumption of multiple prey types, however, suggest that Greenland Sharks acquire THg through a variety of trophic pathways and are a significant contributor to the total biotic THg pool in northern seas.

  12. Reef-fidelity and migration of tiger sharks, Galeocerdo cuvier, across the Coral Sea.

    PubMed

    Werry, Jonathan M; Planes, Serge; Berumen, Michael L; Lee, Kate A; Braun, Camrin D; Clua, Eric

    2014-01-01

    Knowledge of the habitat use and migration patterns of large sharks is important for assessing the effectiveness of large predator Marine Protected Areas (MPAs), vulnerability to fisheries and environmental influences, and management of shark-human interactions. Here we compare movement, reef-fidelity, and ocean migration for tiger sharks, Galeocerdo cuvier, across the Coral Sea, with an emphasis on New Caledonia. Thirty-three tiger sharks (1.54 to 3.9 m total length) were tagged with passive acoustic transmitters and their localised movements monitored on receiver arrays in New Caledonia, the Chesterfield and Lord Howe Islands in the Coral Sea, and the east coast of Queensland, Australia. Satellite tags were also used to determine habitat use and movements among habitats across the Coral Sea. Sub-adults and one male adult tiger shark displayed year-round residency in the Chesterfields with two females tagged in the Chesterfields and detected on the Great Barrier Reef, Australia, after 591 and 842 days respectively. In coastal barrier reefs, tiger sharks were transient at acoustic arrays and each individual demonstrated a unique pattern of occurrence. From 2009 to 2013, fourteen sharks with satellite and acoustic tags undertook wide-ranging movements up to 1114 km across the Coral Sea with eight detected back on acoustic arrays up to 405 days after being tagged. Tiger sharks dove 1136 m and utilised three-dimensional activity spaces averaged at 2360 km³. The Chesterfield Islands appear to be important habitat for sub-adults and adult male tiger sharks. Management strategies need to consider the wide-ranging movements of large (sub-adult and adult) male and female tiger sharks at the individual level, whereas fidelity to specific coastal reefs may be consistent across groups of individuals. Coastal barrier reef MPAs, however, only afford brief protection for large tiger sharks, therefore determining the importance of other oceanic Coral Sea reefs should be a

  13. Environmental neurotoxins β-N-methylamino-l-alanine (BMAA) and mercury in shark cartilage dietary supplements.

    PubMed

    Mondo, Kiyo; Broc Glover, W; Murch, Susan J; Liu, Guangliang; Cai, Yong; Davis, David A; Mash, Deborah C

    2014-08-01

    Shark cartilage products are marketed as dietary supplements with claimed health benefits for animal and human use. Shark fin and cartilage products sold as extracts, dry powders and in capsules are marketed based on traditional Chinese medicine claims that it nourishes the blood, enhances appetite, and energizes multiple internal organs. Shark cartilage contains a mixture of chondroitin and glucosamine, a popular nutritional supplement ingested to improve cartilage function. Sharks are long-lived apex predators, that bioaccumulate environmental marine toxins and methylmercury from dietary exposures. We recently reported detection of the cyanobacterial toxin β-N-methylamino-l-alanine (BMAA) in the fins of seven different species of sharks from South Florida coastal waters. Since BMAA has been linked to degenerative brain diseases, the consumption of shark products may pose a human risk for BMAA exposures. In this report, we tested sixteen commercial shark cartilage supplements for BMAA by high performance liquid chromatography (HPLC-FD) with fluorescence detection and ultra performance liquid chromatography/mass spectrometry/mass spectrometry (UPLC-MS/MS). Total mercury (Hg) levels were measured in the same shark cartilage products by cold vapor atomic fluorescence spectrometry (CVAFS). We report here that BMAA was detected in fifteen out of sixteen products with concentrations ranging from 86 to 265μg/g (dry weight). All of the shark fin products contained low concentrations of Hg. While Hg contamination is a known risk, the results of the present study demonstrate that shark cartilage products also may contain the neurotoxin BMAA. Although the neurotoxic potential of dietary exposure to BMAA is currently unknown, the results demonstrate that shark cartilage products may contain two environmental neurotoxins that have synergistic toxicities.

  14. Tidal influence on spatial dynamics of leopard sharks, Triakis semifasciata, in Tomales Bay, California

    USGS Publications Warehouse

    Ackerman, Joshua T.; Kondratieff, Matthew C.; Matern, Scott A.; Cech, Joseph J. Jr.

    2000-01-01

    We used ultrasonic telemetry to determine the movement directions and movement rates of leopard sharks, Triakis semifasciata, in Tomales Bay, California. To analyze tide and time of day effects, we surgically implanted transmitters in the peritoneal cavities of one male and five female leopard sharks, which we located during summer for three to five sampling sessions lasting 12 to 24 h each. All leopard sharks showed strong movement direction patterns with tide. During incoming tides, sharks moved significantly (p<0.0001) towards the inner bay, apparently to exploit the extensive inner bay muddy littoral zones' food resources. On outgoing tides, sharks showed significant (p<0.0001) movements towards the outer bay. During high tide, there was no discernible pattern to their movements (p=0.092). Shark movement rates were significantly (p<0.0001) greater during dark periods (mean±SE: 10.5±1.0 m min−1), compared with fully lighted ones (6.7±0.5 m min−1). Movement rates of longer sharks tended to be greater than those of shorter ones (range means±SE: 5.8±0.6 m min−1 for the 91 cm shark, to 12.8±1.6 m min−1 for the 119 cm shark), but the leopard sharks' overall mean movement rate (8.1±0.5 m min−1) was slower than other (more pelagic) sharks.

  15. 50 CFR 300.209 - Alternative procedures for nations identified as having vessels engaged in shark catch that are...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... identified as having vessels engaged in shark catch that are not certified in this subpart. 300.209 Section... identified as having vessels engaged in shark catch that are not certified in this subpart. (a) These... not target or incidentally catch sharks, or were harvested by practices that— (1) Are comparable...

  16. 76 FR 53840 - Fisheries of the Exclusive Economic Zone Off Alaska; Other Rockfish, Other Flatfish, Sharks, and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-30

    ... Aleutian Islands (AI) other rockfish, BSAI other flatfish, BSAI sharks, and BSAI skates was established as... the ITACs for AI other rockfish, BSAI other flatfish, BSAI sharks, and BSAI skates in the BSAI need to... 2,475 mt to the AI other rockfish, BSAI other flatfish, BSAI sharks, and BSAI skates...

  17. 76 FR 59924 - Fisheries of the Exclusive Economic Zone Off Alaska; Sharks in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-28

    ... Economic Zone Off Alaska; Sharks in the Bering Sea and Aleutian Islands Management Area AGENCY: National...: Temporary rule; closure. SUMMARY: NMFS is prohibiting retention of sharks in the Bering Sea and Aleutian... sharks in the BSAI has been reached. DATES: Effective 1200 hrs, Alaska local time (A.l.t.), September...

  18. 78 FR 57097 - Fisheries of the Exclusive Economic Zone Off Alaska; Sharks in the Bering Sea and Aleutian...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-17

    ... Economic Zone Off Alaska; Sharks in the Bering Sea and Aleutian Islands Management Area AGENCY: National...: Temporary rule; closure. SUMMARY: NMFS is prohibiting retention of sharks in the Bering Sea and Aleutian... sharks in the BSAI has been reached. DATES: Effective 1200 hrs, Alaska local time (A.l.t.), September...

  19. Cestodes from deep-water squaliform sharks in the Azores

    NASA Astrophysics Data System (ADS)

    Caira, Janine N.; Pickering, Maria

    2013-12-01

    The majority of our knowledge on marine tapeworms (cestodes) is limited to taxa that are relatively easy to obtain (i.e., those that parasitize shallower-water species). The invitation to participate in a deep-water research survey off the Condor seamount in the Azores offered the opportunity to gain information regarding parasites of the less often studied sharks of the mesopelagic and bathypelagic zone. All tapeworms (Platyhelminthes: Cestoda) found parasitizing the spiral intestine of squaliform shark species (Elasmobranchii: Squaliformes) encountered as part of this survey, as well as some additional Azorean sampling from previous years obtained from local fishermen are reported. In total, 112 shark specimens of 12 species of squaliform sharks representing 4 different families from depths ranging between 400 and 1290 m were examined. Cestodes were found in the spiral intestines from 11 of the 12 squaliform species examined: Deania calcea, D. cf. profundorum, D. profundorum, Etmopterus princeps, E. pusillus, E. spinax, Centroscyllium fabricii, Centroscymnus coelolepis, C. cryptacanthus, C. crepidater, and Dalatias licha. No cestodes were found in the spiral intestines of Centrophorus squamosus. Light microscopy and scanning electron microscopy revealed several potentially novel trypanorhynch and biloculated tetraphyllidean species. Aporhynchid and gilquiniid trypanorhynchs dominated the adult cestode fauna of Etmopterus and Deania host species, respectively, while larval phyllobothriids were found across several host genera, including, Deania, Centroscyllium, and Centroscymnus. These results corroborate previous findings that deep-water cestode faunas are relatively depauperate and consist primarily of trypanorhynchs of the families Gilquiniidae and Aporhynchidae and larval tetraphyllideans. A subset of specimens of most cestode species was preserved in ethanol for future molecular analysis to allow more definitive determinations of the identification of the

  20. Algae Reefs in Shark Bay, Western Australia, Australia

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Numerous algae reefs are seen in Shark Bay, Western Australia, Australia (26.0S, 113.5E) especially in the southern portions of the bay. The south end is more saline because tidal flow in and out of the bay is restricted by sediment deposited at the north and central end of the bay opposite the mouth of the Wooramel River. This extremely arid region produces little sediment runoff so that the waters are very clear, saline and rich in algae.

  1. Seasonal and Ontogenetic Changes in Movement Patterns of Sixgill Sharks

    PubMed Central

    Andrews, Kelly S.; Williams, Greg D.; Levin, Phillip S.

    2010-01-01

    Background Understanding movement patterns is fundamental to population and conservation biology. The way an animal moves through its environment influences the dynamics of local populations and will determine how susceptible it is to natural or anthropogenic perturbations. It is of particular interest to understand the patterns of movement for species which are susceptible to human activities (e.g. fishing), or that exert a large influence on community structure, such as sharks. Methodology/Principal Findings We monitored the patterns of movement of 34 sixgill sharks Hexanchus griseus using two large-scale acoustic arrays inside and outside Puget Sound, Washington, USA. Sixgill sharks were residents in Puget Sound for up to at least four years before making large movements out of the estuary. Within Puget Sound, sixgills inhabited sites for several weeks at a time and returned to the same sites annually. Across four years, sixgills had consistent seasonal movements in which they moved to the north from winter to spring and moved to the south from summer to fall. Just prior to leaving Puget Sound, sixgills altered their behavior and moved twice as fast among sites. Nineteen of the thirty-four sixgills were detected leaving Puget Sound for the outer coast. Three of these sharks returned to Puget Sound. Conclusions/Significance For most large marine predators, we have a limited understanding of how they move through their environment, and this clouds our ability to successfully manage their populations and their communities. With detailed movement information, such as that being uncovered with acoustic monitoring, we can begin to quantify the spatial and temporal impacts of large predators within the framework of their ecosystems. PMID:20838617

  2. The characterization of angiogenesis inhibitor from shark cartilage.

    PubMed

    Liang, J H; Wong, K P

    2000-01-01

    An angiogenesis inhibitor isolated from shark cartilage, SCF2, has been characterized. SCF2 was shown to have specific angiogenesis-inhibiting activity in endothelial cell culture assays. Results of structural and functional studies indicate that the inhibitor is not a typical protein. It is a heat-stable proteoglycan, which contains keratan sulfate units and peptide. Gel filtration chromatography shows that the molecular weight of the angiogenesis inhibitor is about 10 kd.

  3. Predicting current and future global distributions of whale sharks.

    PubMed

    Sequeira, Ana M M; Mellin, Camille; Fordham, Damien A; Meekan, Mark G; Bradshaw, Corey J A

    2014-03-01

    The Vulnerable (IUCN) whale shark spans warm and temperate waters around the globe. However, their present-day and possible future global distribution has never been predicted. Using 30 years (1980-2010) of whale shark observations recorded by tuna purse-seiners fishing in the Atlantic, Indian and Pacific Oceans, we applied generalized linear mixed-effects models to test the hypothesis that similar environmental covariates predict whale shark occurrence in all major ocean basins. We derived global predictors from satellite images for chlorophyll a and sea surface temperature, and bathymetric charts for depth, bottom slope and distance to shore. We randomly generated pseudo-absences within the area covered by the fisheries, and included fishing effort as an offset to account for potential sampling bias. We predicted sea surface temperatures for 2070 using an ensemble of five global circulation models under a no climate-policy reference scenario, and used these to predict changes in distribution. The full model (excluding standard deviation of sea surface temperature) had the highest relative statistical support (wAICc  = 0.99) and explained ca. 60% of the deviance. Habitat suitability was mainly driven by spatial variation in bathymetry and sea surface temperature among oceans, although these effects differed slightly among oceans. Predicted changes in sea surface temperature resulted in a slight shift of suitable habitat towards the poles in both the Atlantic and Indian Oceans (ca. 5°N and 3-8°S, respectively) accompanied by an overall range contraction (2.5-7.4% and 1.1-6.3%, respectively). Predicted changes in the Pacific Ocean were small. Assuming that whale shark environmental requirements and human disturbances (i.e. no stabilization of greenhouse gas emissions) remain similar, we show that warming sea surface temperatures might promote a net retreat from current aggregation areas and an overall redistribution of the species.

  4. The V-SHARK high contrast imager at LBT

    NASA Astrophysics Data System (ADS)

    Pedichini, F.; Ambrosino, F.; Centrone, M.; Farinato, J.; Li Causi, G.; Pinna, E.; Puglisi, A.; Stangalini, M.; Testa, V.

    2016-08-01

    In the framework of the SHARK project the visible channel is a novel instrument synergic to the NIR channel and exploiting the performances of the LBT XAO at visible wavelengths. The status of the project is presented together with the design study of this innovative instrument optimized for high contrast imaging by means of high frame rate. Its expected results will be presented comparing the simulations with the real data of the "Forerunner" experiment taken at 630nm.

  5. Annually recurring parthenogenesis in a zebra shark Stegostoma fasciatum.

    PubMed

    Robinson, D P; Baverstock, W; Al-Jaru, A; Hyland, K; Khazanehdari, K A

    2011-11-01

    A zebra shark, Stegostoma fasciatum, held in captivity at the Burj Al Arab aquarium, produced embryos and pups in the absence of a male. A total of 15 pups were produced from eggs laid within the aquarium over a period of four consecutive years commencing 2007. Parthenogenesis was confirmed through DNA analysis for three pups sampled during the first two consecutive egg cycles and is presumed to be the method of reproduction responsible thereafter.

  6. Cretaceous gastropods: contrasts between tethys and the temperate provinces.

    USGS Publications Warehouse

    Sohl, N.F.

    1987-01-01

    During the Cretaceous Period, gastropod faunas show considerable differences in their evolution between the Tethyan Realm (tropical) and the Temperate Realms to the north and south. Like Holocene faunas, prosobranch, gastropods constitute the dominant part of Cretaceous marine snail faunas. Entomotaeneata and opisthobranchs usually form all of the remainder. In Tethyan faunas the Archaeogastropoda form a consistent high proportion of total taxa but less than the Mesogastropoda throughout the period. In contrast, the Temperate faunas beginning in Albian times show a decline in percentages of archaeogastropod taxa and a significant increase in the Neogastropoda, until they constitute over 50 percent of the taxa in some faunas. The neogastropods never attain high diversity in the Cretaceous of the Tethyan Realm and are judged to be of Temperate Realm origin. Cretaceous Tethyan gastropod faunas are closely allied to those of the 'corallien facies' of the Jurassic and begin the period evolutionarily mature and well diversified. Three categories of Tethyan gastropods are analyzed. The first group consists of those of Jurassic ancestry. The second group orginates mainly during the Barremian and Aptian, reaches a climax in diversification during middle Cretaceous time, and usually declines during the latest Cretaceous. The third group originates late in the Cretaceous and consists of taxa that manage to either survive the Cretaceous-Tertiary crisis or give rise to forms of prominence among Tertiary warm water faunas. Temperate Realm gastropod faunas are less diverse than those of Tethys during the Early Cretaceous. They show a steady increase in diversity, primarily among the Mesogastropoda and Neogastropoda. This trend culminates in latest Cretaceous times when the gastropod assemblages of the clastic provinces of the inner shelf contain an abundance of taxa outstripping that of any other part of the Cretaceous of either realm. Extinction at the Cretaceous

  7. Significance of Tocopherols during Cretaceous Oae

    NASA Astrophysics Data System (ADS)

    Brassell, S. C.

    2013-12-01

    Most biomarker studies of Cretaceous OAE have tended to focus on investigations of hydrocarbon constituents, which means that evidence of environmental conditions contained in the distributions and abundance of more polar components has rarely been utilized with the notable exception of GDGTs as paleotemperature proxies. One group of functionalized lipids, tocopherols, fulfills various critical functions in plants and bacteria, including optimization of photosynthetic activity and macronutrient homeostasis in cyanobacteria. These compounds are often prevalent constituents of immature Cretaceous sediments rich in organic matter (OM) in those instances where analytical protocols have assessed their presence. They occur in Cenomanian-Turonian (OAE2), early Aptian (OAE1a), Valanginian, and other Cretaceous sediments, and their concentrations can exceed 2-5 mg/g dry sediment. One possible explanation for the abundance of tocopherols is that environmental conditions prevailing during OAE led to enhanced biochemical production of these components by phytoplankton, given their key biophysiochemical role of protecting lipids and membranes against oxidative stress. High concentrations of tocopherols (>250 mg/g dry weight) have been reported in haptophytes and marine green algae, and their production in cyanobacteria increases under high light intensity. Hence, environmental conditions during Cretaceous OAE may have been conducive to production of copious amounts of tocopherols by phytoplankton in response to environment stresses. Previous work in contemporary systems has suggested that the propensity of tocopherols to autooxidation would make their survival in sediments unlikely. However, this scenario and interpretation is clearly not applicable during Cretaceous episodes of enhanced OM sequestration and/or dysoxia. Since tocopherols serve to protect plant cells from oxidative damage it seems plausible that they might fulfill a similar function in settling, particulate, and

  8. Comparative studies of high performance swimming in sharks II. Metabolic biochemistry of locomotor and myocardial muscle in endothermic and ectothermic sharks.

    PubMed

    Bernal, D; Smith, D; Lopez, G; Weitz, D; Grimminger, T; Dickson, K; Graham, J B

    2003-08-01

    Metabolic enzyme activities in red (RM) and white (WM) myotomal muscle and in the heart ventricle (HV) were compared in two lamnid sharks (shortfin mako and salmon shark), the common thresher shark and several other actively swimming shark species. The metabolic enzymes measured were citrate synthase (CS), an index of aerobic capacity, and lactate dehydrogenase (LDH), an index of anaerobic capacity. WM creatine phosphokinase (CPK) activity, an index of rapid ATP production during burst swimming, was also quantified. Enzyme activities in RM, WM and HV were similar in the two lamnid species. Interspecific comparisons of enzyme activities at a common reference temperature (20 degrees C) show no significant differences in RM CS activity but higher CS activity in the WM and HV of the lamnid sharks compared with the other species. For the other enzymes, activities in lamnids overlapped with those of other shark species. Comparison of the HV spongy and compact myocardial layers in mako, salmon and thresher sharks reveals a significantly greater spongy CS activity in all three species but no differences in LDH activity. Adjustment of enzyme activities to in vivo RM and WM temperatures in the endothermic lamnids elevates CS and LDH in both tissues relative to the ectothermic sharks. Thus, through its enhancement of both RM and WM enzyme activity, endothermy may be an important determinant of energy supply for sustained and burst swimming in the lamnids. Although lamnid WM is differentially warmed as a result of RM endothermy, regional differences in WM CS and LDH activities and thermal sensitivities (Q(10) values) were not found. The general pattern of the endothermic myotomal and ectothermic HV muscle metabolic enzyme activities in the endothermic lamnids relative to other active, ectothermic sharks parallels the general pattern demonstrated for the endothermic tunas relative to their ectothermic sister species. However, the activities of all enzymes measured are lower in

  9. Thermodynamic analysis of shark skin texture surfaces for microchannel flow

    NASA Astrophysics Data System (ADS)

    Yu, Hai-Yan; Zhang, Hao-Chun; Guo, Yang-Yu; Tan, He-Ping; Li, Yao; Xie, Gong-Nan

    2016-09-01

    The studies of shark skin textured surfaces in flow drag reduction provide inspiration to researchers overcoming technical challenges from actual production application. In this paper, three kinds of infinite parallel plate flow models with microstructure inspired by shark skin were established, namely blade model, wedge model and the smooth model, according to cross-sectional shape of microstructure. Simulation was carried out by using FLUENT, which simplified the computation process associated with direct numeric simulations. To get the best performance from simulation results, shear-stress transport k-omega turbulence model was chosen during the simulation. Since drag reduction mechanism is generally discussed from kinetics point of view, which cannot interpret the cause of these losses directly, a drag reduction rate was established based on the second law of thermodynamics. Considering abrasion and fabrication precision in practical applications, three kinds of abraded geometry models were constructed and tested, and the ideal microstructure was found to achieve best performance suited to manufacturing production on the basis of drag reduction rate. It was also believed that bionic shark skin surfaces with mechanical abrasion may draw more attention from industrial designers and gain wide applications with drag-reducing characteristics.

  10. Hydrodynamics of prey capture in sharks: effects of substrate.

    PubMed

    Nauwelaerts, Sandra; Wilga, Cheryl; Sanford, Christopher; Lauder, George

    2007-04-22

    In suction feeding, a volume of water is drawn into the mouth of a predator. Previous studies of suction feeding in fishes have shown that significant fluid velocities are confined to a region within one mouth width from the mouth. Therefore, the predator must be relatively close to the prey to ensure capture success. Here, theoretical modelling is combined with empirical data to unravel the mechanism behind feeding on a substrate. First, we approached the problem theoretically by combining the stream functions of two sinks. Computational fluid dynamics modelling is then applied to make quantitative predictions regarding the effects of substrate proximity on the feeding hydrodynamics of a benthic shark. An oblique circular cylinder and a shark head model were used. To test the models, we used digital particle image velocimetry to record fluid flow around the mouth of white-spotted bamboo sharks, Chiloscyllium plagiosum, during suction feeding on the substrate and in the water column. Empirical results confirmed the modelling predictions: the length of the flow field can be doubled due to passive substrate effects during prey capture. Feeding near a substrate extends the distance over which suction is effective and a predator strike can be effective further from the prey.

  11. Shark cartilage-containing preparation: protection against reactive oxygen species.

    PubMed

    Felzenszwalb, I; Pelielo de Mattos, J C; Bernardo-Filho, M; Caldeira-de-Araújo, A

    1998-12-01

    There is overwhelming evidence to indicate that free radicals cause oxidative damage to lipids, proteins and nucleic acids and are involved in the pathogenesis of several degenerative diseases. Therefore, antioxidants, which can neutralize free radicals, may be of central importance in the prevention of these disease states. The protection that fruits and vegetables provide against disease has been attributed to the various antioxidants contained in them. Recently, an anti-inflammatory and analgesic activity of a water-soluble fraction from shark cartilage has been described. Using electrophoretical assays, bacteria survival and transformation and the Salmonella/mammalian-microsome assay, we investigated the putative role of shark cartilage-containing preparation in protecting cells against reactive oxygen species induced DNA damage and mutagenesis. If antimutagens are to have any impact on human disease, it is essential that they are specifically directed against the most common mutagens in daily life. Our data suggest that shark cartilage-containing preparation can play a scavenger role for reactive oxygen species and protects cells against inactivation and mutagenesis.

  12. Convergent evolution in mechanical design of lamnid sharks and tunas.

    PubMed

    Donley, Jeanine M; Sepulveda, Chugey A; Konstantinidis, Peter; Gemballa, Sven; Shadwick, Robert E

    2004-05-06

    The evolution of 'thunniform' body shapes in several different groups of vertebrates, including whales, ichthyosaurs and several species of large pelagic fishes supports the view that physical and hydromechanical demands provided important selection pressures to optimize body design for locomotion during vertebrate evolution. Recognition of morphological similarities between lamnid sharks (the most well known being the great white and the mako) and tunas has led to a general expectation that they also have converged in their functional design; however, no quantitative data exist on the mechanical performance of the locomotor system in lamnid sharks. Here we examine the swimming kinematics, in vivo muscle dynamics and functional morphology of the force-transmission system in a lamnid shark, and show that the evolutionary convergence in body shape and mechanical design between the distantly related lamnids and tunas is much more than skin deep; it extends to the depths of the myotendinous architecture and the mechanical basis for propulsive movements. We demonstrate that not only have lamnids and tunas converged to a much greater extent than previously known, but they have also developed morphological and functional adaptations in their locomotor systems that are unlike virtually all other fishes.

  13. Convergence in Thunniform Anatomy in Lamnid Sharks and Jurassic Ichthyosaurs.

    PubMed

    Lingham-Soliar, Theagarten

    2016-12-01

    Among extinct ichthyosaurs the Jurassic forms Ichthyosaurus and Stenopterygius share a number of anatomical specializations with lamnid sharks, characterized in the white shark, Carcharodon carcharias These features allow their inclusion within the mode of high-speed thunniform swimming to which only two other equally distinctive phylogenetic groups belong, tuna and dolphins-a striking testaments to evolutionary convergence. Jurassic ichthyosaurs evolved from reptiles that had returned to the sea (secondarily adapted) about 250 million years ago (MYA) while lamnid sharks evolved about 50 MYA from early cartilaginous fishes (originating ca. 400 MYA). Their shared independently evolved anatomical characteristics are discussed. These include a deep tear-drop body shape that helped initially define members as thunniform swimmers. Later, other critical structural characteristics were discovered such as the crossed-fiber architecture of the skin, high-speed adapted dorsal and caudal fins, a caudal peduncle and series of ligaments to enable transmission of power from the musculature located anteriorly to the caudal fin. Both groups also share a similar chemistry of the dermal fibers, i.e., the scleroprotein collagen.

  14. Relations between morphology, buoyancy and energetics of requiem sharks

    PubMed Central

    Papastamatiou, Yannis P.

    2016-01-01

    Sharks have a distinctive shape that remained practically unchanged through hundreds of millions of years of evolution. Nonetheless, there are variations of this shape that vary between and within species. We attempt to explain these variations by examining the partial derivatives of the cost of transport of a generic shark with respect to buoyancy, span and chord of its pectoral fins, length, girth and body temperature. Our analysis predicts an intricate relation between these parameters, suggesting that ectothermic species residing in cooler temperatures must either have longer pectoral fins and/or be more buoyant in order to maintain swimming performance. It also suggests that, in general, the buoyancy must increase with size, and therefore, there must be ontogenetic changes within a species, with individuals getting more buoyant as they grow. Pelagic species seem to have near optimally sized fins (which minimize the cost of transport), but the majority of reef sharks could have reduced the cost of transport by increasing the size of their fins. The fact that they do not implies negative selection, probably owing to decreased manoeuvrability in confined spaces (e.g. foraging on a reef). PMID:27853556

  15. Relations between morphology, buoyancy and energetics of requiem sharks.

    PubMed

    Iosilevskii, Gil; Papastamatiou, Yannis P

    2016-10-01

    Sharks have a distinctive shape that remained practically unchanged through hundreds of millions of years of evolution. Nonetheless, there are variations of this shape that vary between and within species. We attempt to explain these variations by examining the partial derivatives of the cost of transport of a generic shark with respect to buoyancy, span and chord of its pectoral fins, length, girth and body temperature. Our analysis predicts an intricate relation between these parameters, suggesting that ectothermic species residing in cooler temperatures must either have longer pectoral fins and/or be more buoyant in order to maintain swimming performance. It also suggests that, in general, the buoyancy must increase with size, and therefore, there must be ontogenetic changes within a species, with individuals getting more buoyant as they grow. Pelagic species seem to have near optimally sized fins (which minimize the cost of transport), but the majority of reef sharks could have reduced the cost of transport by increasing the size of their fins. The fact that they do not implies negative selection, probably owing to decreased manoeuvrability in confined spaces (e.g. foraging on a reef).

  16. Ecological drivers of shark distributions along a tropical coastline.

    PubMed

    Yates, Peter M; Heupel, Michelle R; Tobin, Andrew J; Simpfendorfer, Colin A

    2015-01-01

    As coastal species experience increasing anthropogenic pressures there is a growing need to characterise the ecological drivers of their abundance and habitat use, and understand how they may respond to changes in their environment. Accordingly, fishery-independent surveys were undertaken to investigate shark abundance along approximately 400 km of the tropical east coast of Australia. Generalised linear models were used to identify ecological drivers of the abundance of immature blacktip Carcharhinus tilstoni/Carcharhinus limbatus, pigeye Carcharhinus amboinensis, and scalloped hammerhead Sphyrna lewini sharks. Results indicated general and species-specific patterns in abundance that were characterised by a range of abiotic and biotic variables. Relationships with turbidity and salinity were similar across multiple species, highlighting the importance of these variables in the functioning of communal shark nurseries. In particular, turbid environments were especially important for all species at typical oceanic salinities. Mangrove proximity, depth, and water temperature were also important; however, their influence varied between species. Ecological drivers may promote spatial diversity in habitat use along environmentally heterogeneous coastlines and may therefore have important implications for population resilience.

  17. Disseminated fungal infection in two species of captive sharks.

    PubMed

    Marancik, David P; Berliner, Aimee L; Cavin, Julie M; Clauss, Tonya M; Dove, Alistair D M; Sutton, Deanna A; Wickes, Brian L; Camus, Alvin C

    2011-12-01

    In this report, two cases of systemic mycosis in captive sharks are characterized. These cases were progressive and ultimately culminated in terminal disease. Paecilomyces lilacinus, an uncommon pathogen in human and veterinary medicine, was associated with areas of necrosis in the liver, heart, and gill in a great hammerhead shark (Sphyrna mokarran). Fungal growth was observed from samples of kidney, spleen, spinal fluid, and coelomic cavity swabs. Dual fungal infection by Exophiala pisciphila and Mucor circinelloides was diagnosed in a juvenile zebra shark (Stegostoma fasciatum). Both fungi were present in the liver, with more severe tissue destruction associated with E. pisciphila. E. pisciphila also produced significant necrosis in the spleen and gill, while M. circinelloides was associated with only minimal tissue changes in the heart. Fungal cultures from liver, kidney, and spleen were positive for both E. pisciphila and M. circinelloides. Identification of P. lilacinus and M. circinelloides was based on colonial and hyphal morphology. E. pisciphila was identified by sequence analysis of the 28S rRNA D1/D2 region and the internal transcribed spacer (ITS) region between the 18S and 28S rRNA subunit. These cases, and a lack of information in the literature, highlight the need for further research and diagnostic sampling to further characterize the host-pathogen interaction between elasmobranchs and fungi.

  18. Ecological Drivers of Shark Distributions along a Tropical Coastline

    PubMed Central

    Yates, Peter M.; Heupel, Michelle R.; Tobin, Andrew J.; Simpfendorfer, Colin A.

    2015-01-01

    As coastal species experience increasing anthropogenic pressures there is a growing need to characterise the ecological drivers of their abundance and habitat use, and understand how they may respond to changes in their environment. Accordingly, fishery-independent surveys were undertaken to investigate shark abundance along approximately 400 km of the tropical east coast of Australia. Generalised linear models were used to identify ecological drivers of the abundance of immature blacktip Carcharhinus tilstoni/Carcharhinus limbatus, pigeye Carcharhinus amboinensis, and scalloped hammerhead Sphyrna lewini sharks. Results indicated general and species-specific patterns in abundance that were characterised by a range of abiotic and biotic variables. Relationships with turbidity and salinity were similar across multiple species, highlighting the importance of these variables in the functioning of communal shark nurseries. In particular, turbid environments were especially important for all species at typical oceanic salinities. Mangrove proximity, depth, and water temperature were also important; however, their influence varied between species. Ecological drivers may promote spatial diversity in habitat use along environmentally heterogeneous coastlines and may therefore have important implications for population resilience. PMID:25853657

  19. Functional morphology of the nasal region of a hammerhead shark.

    PubMed

    Abel, Richard L; Maclaine, James S; Cotton, Ross; Xuan, Viet Bui; Nickels, Timothy B; Clark, Thomas H; Wang, Zhijin; Cox, Jonathan P L

    2010-04-01

    We describe several novel morphological features in the nasal region of the hammerhead shark Sphyrna tudes. Unlike the open, rounded incurrent nostril of non-hammerhead shark species, the incurrent nostril of S. tudes is a thin keyhole-like aperture. We discovered a groove running anterior and parallel to the incurrent nostril. This groove, dubbed the minor nasal groove to distinguish it from the larger, previously described, (major) nasal groove, is common to all eight hammerhead species. Using life-sized plastic models generated at 200 microm resolution from an X-ray scan, we also investigated flow in the nasal region. Even modest oncoming flow speeds stimulate extensive, but not complete, circulation within the model olfactory chamber, with flow passing through the two main olfactory channels. Flow crossed from one channel to another via a gap in the olfactory array, sometimes guided by the interlamellar channels. Major and minor nasal grooves, as well as directing flow into the olfactory chamber, can, in conjunction with the nasal bridge separating incurrent and excurrent nostrils, limit flow passing into the olfactory chamber, possibly to protect the delicate nasal structures. This is the first simulation of internal flow within the olfactory chamber of a shark.

  20. Cretaceous stratigraphic sequences of north-central California suggest a discontinuity in the Late Cretaceous forearc basin

    SciTech Connect

    Haggart, J.W.

    1986-10-01

    The Cretaceous sedimentary succession preserved east of Redding, at the northern end of California's Great Valley, indicates that marine deposition was widespread in the region for only two periods during the Late Cretaceous. If it is assumed that there was minimal Cenozoic offset between the northern Sierra Nevada and eastern Klamath Mountains terranes, Cretaceous sedimentation in this region was most likely restricted to a narrow trough and was not a continuation of the wide, Cretaceous forearc basin of central California. The dissimilar depositional histories of the Redding basin and the Hornbrook basin of north-central California suggest that the basins were not linked continuously during the Late Cretaceous. A thick section of Cretaceous strata beneath the southwestern Modoc Plateau is considered unlikely.

  1. Plastic toy shark drifts through airlock in front of EMU suited MS Lenoir

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Plastic toy shark drifts through airlock and around fully extravehicular mobility unit (EMU) suited Mission Specialist (MS) Lenoir. Lenoir watches as shark drifts pass his left hand. Lenoir donned the EMU in preparation for a scheduled extravehicular activity (EVA) which was cancelled due to EMU problems.

  2. Variation in depth of whitetip reef sharks: does provisioning ecotourism change their behaviour?

    NASA Astrophysics Data System (ADS)

    Fitzpatrick, Richard; Abrantes, Kátya G.; Seymour, Jamie; Barnett, Adam

    2011-09-01

    In the dive tourism industry, shark provisioning has become increasingly popular in many places around the world. It is therefore important to determine the impacts that provisioning may have on shark behaviour. In this study, eight adult whitetip reef sharks Triaenodon obesus were tagged with time-depth recorders at Osprey Reef in the Coral Sea, Australia. Tags collected time and depth data every 30 s. The absolute change in depth over 5-min blocks was considered as a proxy for vertical activity level. Daily variations in vertical activity levels were analysed to determine the effects of time of day on whitetip reef shark behaviour. This was done for days when dive boats were absent from the area, and for days when dive boats were present, conducting shark provisioning. Vertical activity levels varied between day and night, and with the presence of boats. In natural conditions (no boats present), sharks remained at more constant depths during the day, while at night animals continuously moved up and down the water column, showing that whitetip reef sharks are nocturnally active. When boats were present, however, there were also long periods of vertical activity during the day. If resting periods during the day are important for energy budgets, then shark provisioning may affect their health. So, if this behaviour alteration occurs frequently, e.g., daily, this has the potential to have significant negative effects on the animals' metabolic rates, net energy gain and overall health, reproduction and fitness.

  3. Whale sharks target dense prey patches of sergestid shrimp off Tanzania

    PubMed Central

    Rohner, Christoph A.; Armstrong, Amelia J.; Pierce, Simon J.; Prebble, Clare E. M.; Cagua, E. Fernando; Cochran, Jesse E. M.; Berumen, Michael L.; Richardson, Anthony J.

    2015-01-01

    Large planktivores require high-density prey patches to make feeding energetically viable. This is a major challenge for species living in tropical and subtropical seas, such as whale sharks Rhincodon typus. Here, we characterize zooplankton biomass, size structure and taxonomic composition from whale shark feeding events and background samples at Mafia Island, Tanzania. The majority of whale sharks were feeding (73%, 380 of 524 observations), with the most common behaviour being active surface feeding (87%). We used 20 samples collected from immediately adjacent to feeding sharks and an additional 202 background samples for comparison to show that plankton biomass was ∼10 times higher in patches where whale sharks were feeding (25 vs. 2.6 mg m−3). Taxonomic analyses of samples showed that the large sergestid Lucifer hanseni (∼10 mm) dominated while sharks were feeding, accounting for ∼50% of identified items, while copepods (<2 mm) dominated background samples. The size structure was skewed towards larger animals representative of L.hanseni in feeding samples. Thus, whale sharks at Mafia Island target patches of dense, large, zooplankton dominated by sergestids. Large planktivores, such as whale sharks, which generally inhabit warm oligotrophic waters, aggregate in areas where they can feed on dense prey to obtain sufficient energy. PMID:25814777

  4. 78 FR 24148 - Atlantic Highly Migratory Species; Atlantic Shark Management Measures

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-24

    ... still overfished and still experiencing overfishing (i.e., their stock status has not changed). On... analyses and explore management options specific to rebuilding and ending overfishing of dusky sharks. This... overfishing of the dusky shark stock, consistent with the Magnuson-Stevens Fishery Conservation and...

  5. Complete mitochondrial genome of the megamouth shark Megachasma pelagios (Chondrichthyes, Megachasmidae).

    PubMed

    Chang, Chia-Hao; Shao, Kwang-Tsao; Lin, Yeong-Shin; Chiang, Wei-Chuan; Jang-Liaw, Nian-Hong

    2014-06-01

    Here we describe the complete mitochondrial genome sequence of the megamouth shark, Megachasma pelagios, which is an extremely rare species of deepwater shark. The circle genome (16,694 bp) consists of 13 protein coding, 22 tRNA, 2 rRNA genes and 1 control region. It has the typical vertebrate mitochondrial gene arrangement.

  6. How Full Is Your Luggage? Background Knowledge of Zoo Visitors Regarding Sharks

    ERIC Educational Resources Information Center

    das Neves, João Pedro Correia; Monteiro, Rute Cristina Rocha

    2013-01-01

    For the general population, sharks have a reputation that does not really fit with their biological and ecological nature. Informal surveys often classify sharks as dangerous, aggressive and/or man-eaters. This apparent common knowledge seems difficult to detach from the conscience of many worldwide zoo visitors, even with the help of…

  7. Age-related polychlorinated biphenyl dynamics in immature bull sharks (Carcharhinus leucas).

    PubMed

    Olin, Jill A; Beaudry, Marina; Fisk, Aaron T; Paterson, Gordon

    2014-01-01

    Polychlorinated biphenyls (PCBs) were quantified in liver tissues of bull sharks (Carcharhinus leucas) ranging in age from <4 wk to >3 yr. Summed values of PCBs (ΣPCBs) ranged from 310 ng/g to 22 070 ng/g (lipid wt) across age classes with ΣPCB concentrations for the youngest sharks in the present study (<4 wk; 5230 ± 2170 ng/g lipid wt) determined to not significantly differ from those quantified in >3-yr-old sharks, highlighting the extent of exposure of this young life stage to this class of persistent organic pollutants (POPs). Age normalization of PCB congener concentrations to those measured for the youngest sharks demonstrated a significant hydrophobicity (log octanol/water partition coefficient [KOW ]) effect that was indicative of maternal offloading of highly hydrophobic (log KOW ≥6.5) congeners to the youngest individuals. A distinct shift in the PCB congener profiles was also observed as these young sharks grew in size. This shift was consistent with a transition from the maternally offloaded signal to the initiation of exogenous feeding and the contributions of mechanisms including growth dilution and whole-body elimination. These results add to the growing pool of literature documenting substantially high concentrations of POPs in juvenile sharks that are most likely attributable to maternal offloading. Collectively, such results underscore the potential vulnerability of young sharks to POP exposure and pose additional concerns for shark-conservation efforts.

  8. Whale sharks target dense prey patches of sergestid shrimp off Tanzania.

    PubMed

    Rohner, Christoph A; Armstrong, Amelia J; Pierce, Simon J; Prebble, Clare E M; Cagua, E Fernando; Cochran, Jesse E M; Berumen, Michael L; Richardson, Anthony J

    2015-03-01

    Large planktivores require high-density prey patches to make feeding energetically viable. This is a major challenge for species living in tropical and subtropical seas, such as whale sharks Rhincodon typus. Here, we characterize zooplankton biomass, size structure and taxonomic composition from whale shark feeding events and background samples at Mafia Island, Tanzania. The majority of whale sharks were feeding (73%, 380 of 524 observations), with the most common behaviour being active surface feeding (87%). We used 20 samples collected from immediately adjacent to feeding sharks and an additional 202 background samples for comparison to show that plankton biomass was ∼10 times higher in patches where whale sharks were feeding (25 vs. 2.6 mg m(-3)). Taxonomic analyses of samples showed that the large sergestid Lucifer hanseni (∼10 mm) dominated while sharks were feeding, accounting for ∼50% of identified items, while copepods (<2 mm) dominated background samples. The size structure was skewed towards larger animals representative of L.hanseni in feeding samples. Thus, whale sharks at Mafia Island target patches of dense, large, zooplankton dominated by sergestids. Large planktivores, such as whale sharks, which generally inhabit warm oligotrophic waters, aggregate in areas where they can feed on dense prey to obtain sufficient energy.

  9. Children's Perceptions of Sharks and Understanding of Its Ecological Significance for Educational Implications

    ERIC Educational Resources Information Center

    Tsoi, Kwok Ho

    2011-01-01

    Global shark populations are seriously declining and many species are now threatened by anthropogenic stresses. Their extinction would cause devastating consequences to the marine biodiversity and ecosystems. However some children describe the sharks as bad guys, "we should kill them all!" Such children's view motivates my study…

  10. 77 FR 75896 - Atlantic Highly Migratory Species; 2013 Atlantic Shark Commercial Fishing Season

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-26

    ... 2 to the 2006 Consolidated HMS FMP, we established a shark research fishery to maintain time series... time-series of wintertime abundance for shark species or collecting vital biological and regional data... the first time NMFS anticipates using the inseason adjustments. The October 2012 proposed...

  11. 75 FR 57259 - Atlantic Highly Migratory Species; Atlantic Shark Management Measures; 2011 Research Fishery

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-20

    ..., July 15, 2008) established, among other things, a shark research fishery to maintain time series data... stock structure; Maintain time-series of abundance from previously derived indices for the shark BLL... must be received no later than 5 p.m., local time, on October 20, 2010. ADDRESSES: Please...

  12. The Drosophila Shark tyrosine kinase is required for embryonic dorsal closure

    PubMed Central

    Fernandez, Rafael; Takahashi, Fumitaka; Liu, Zhao; Steward, Ruth; Stein, David; Stanley, E. Richard

    2000-01-01

    Dorsal closure (DC) in the Drosophila embryo requires the coordinated interaction of two different functional domains of the epidermal cell layer—the leading edge (LE) and the lateral epidermis. In response to activation of a conserved c-Jun amino-terminal kinase (JNK) signaling module, the dorsal-most layer of cells, which constitute the LE of the stretching epithelial sheet, secrete Dpp, a member of the TGFβ superfamily. Dpp and other LE cell-derived signaling molecules stimulate the bilateral dorsal elongation of cells of the dorsolateral epidermis over the underlaying amnioserosa and the eventual fusion of their LEs along the dorsal midline. We have found that flies bearing a Shark tyrosine kinase gene mutation, shark1, exhibit a DC-defective phenotype. Dpp fails to be expressed in shark1 mutant LE cells. Consistent with these observations, epidermal-specific reconstitution of shark function or overexpression of an activated form of c-Jun in the shark1 mutant background, rescues the DC defect. Thus, Shark regulates the JNK signaling pathway leading to Dpp expression in LE cells. Furthermore, constitutive activation of the Dpp pathway throughout the epidermis fails to rescue the shark1 DC defect, suggesting that Shark may function in additional pathways in the LE and/or lateral epithelium. PMID:10716948

  13. Blacktip reef sharks (Carcharhinus melanopterus) show high capacity for wound healing and recovery following injury.

    PubMed

    Chin, Andrew; Mourier, Johann; Rummer, Jodie L

    2015-01-01

    Wound healing is important for sharks from the earliest life stages, for example, as the 'umbilical scar' in viviparous species heals, and throughout adulthood, when sharks can incur a range of external injuries from natural and anthropogenic sources. Despite anecdotal accounts of rapid healing in elasmobranchs, data regarding recovery and survival of individuals from different wound or injury types has not been systematically collected. The present study documented: (i) 'umbilical scar' healing in wild-caught, neonatal blacktip reef sharks while being reared for 30 days in flow-through laboratory aquaria in French Polynesia; (ii) survival and recovery of free-swimming blacktip reef sharks in Australia and French Polynesia following a range of injuries; and (iii) long-term survival following suspected shark-finning activities. Laboratory monitoring, tag-recapture records, telemetry data and photo-identification records suggest that blacktip reef sharks have a high capacity to survive and recover from small or even large and severe wounds. Healing rates, recovery and survival are important factors to consider when assessing impacts of habitat degradation and fishing stress on shark populations. The present study suggests that individual survival may depend more on handling practices and physiological stress rather than the extent of physical injury. These observations also contribute to discussions regarding the ethics of tagging practices used in elasmobranch research and provide baseline healing rates that may increase the accuracy in estimating reproductive timing inferred from mating scars and birth dates for neonatal sharks based on umbilical scar healing status.

  14. The Shark Assemblage at French Frigate Shoals Atoll, Hawai‘i: Species Composition, Abundance and Habitat Use

    PubMed Central

    Dale, Jonathan J.; Stankus, Austin M.; Burns, Michael S.; Meyer, Carl G.

    2011-01-01

    Empirical data on the abundance and habitat preferences of coral reef top predators are needed to evaluate their ecological impacts and guide management decisions. We used longline surveys to quantify the shark assemblage at French Frigate Shoals (FFS) atoll from May to August 2009. Fishing effort consisted of 189 longline sets totaling 6,862 hook hours of soak time. A total of 221 sharks from 7 species were captured, among which Galapagos (Carcharhinus galapagensis, 36.2%), gray reef (Carcharhinus amblyrhynchos, 25.8%) and tiger (Galeocerdo cuvier, 20.4%) sharks were numerically dominant. A lack of blacktip reef sharks (Carcharhinus melanopterus) distinguished the FFS shark assemblage from those at many other atolls in the Indo-Pacific. Compared to prior underwater visual survey estimates, longline methods more accurately represented species abundance and composition for the majority of shark species. Sharks were significantly less abundant in the shallow lagoon than adjacent habitats. Recaptures of Galapagos sharks provided the first empirical estimate of population size for any Galapagos shark population. The overall recapture rate was 5.4%. Multiple closed population models were evaluated, with Chao Mh ranking best in model performance and yielding a population estimate of 668 sharks with 95% confidence intervals ranging from 289–1720. Low shark abundance in the shallow lagoon habitats suggests removal of a small number of sharks from the immediate vicinity of lagoonal islets may reduce short-term predation on endangered monk seal (Monachus schauinslandi) pups, but considerable fishing effort would be required to catch even a small number of sharks. Additional data on long-term movements and habitat use of sharks at FFS are required to better assess the likely ecological impacts of shark culling. PMID:21347321

  15. The shark assemblage at French Frigate Shoals atoll, Hawai'i: species composition, abundance and habitat use.

    PubMed

    Dale, Jonathan J; Stankus, Austin M; Burns, Michael S; Meyer, Carl G

    2011-02-10

    Empirical data on the abundance and habitat preferences of coral reef top predators are needed to evaluate their ecological impacts and guide management decisions. We used longline surveys to quantify the shark assemblage at French Frigate Shoals (FFS) atoll from May to August 2009. Fishing effort consisted of 189 longline sets totaling 6,862 hook hours of soak time. A total of 221 sharks from 7 species were captured, among which Galapagos (Carcharhinus galapagensis, 36.2%), gray reef (Carcharhinus amblyrhynchos, 25.8%) and tiger (Galeocerdo cuvier, 20.4%) sharks were numerically dominant. A lack of blacktip reef sharks (Carcharhinus melanopterus) distinguished the FFS shark assemblage from those at many other atolls in the Indo-Pacific. Compared to prior underwater visual survey estimates, longline methods more accurately represented species abundance and composition for the majority of shark species. Sharks were significantly less abundant in the shallow lagoon than adjacent habitats. Recaptures of Galapagos sharks provided the first empirical estimate of population size for any Galapagos shark population. The overall recapture rate was 5.4%. Multiple closed population models were evaluated, with Chao M(h) ranking best in model performance and yielding a population estimate of 668 sharks with 95% confidence intervals ranging from 289-1720. Low shark abundance in the shallow lagoon habitats suggests removal of a small number of sharks from the immediate vicinity of lagoonal islets may reduce short-term predation on endangered monk seal (Monachus schauinslandi) pups, but considerable fishing effort would be required to catch even a small number of sharks. Additional data on long-term movements and habitat use of sharks at FFS are required to better assess the likely ecological impacts of shark culling.

  16. Shark Attack: high affinity binding proteins derived from shark vNAR domains by stepwise in vitro affinity maturation.

    PubMed

    Zielonka, Stefan; Weber, Niklas; Becker, Stefan; Doerner, Achim; Christmann, Andreas; Christmann, Christine; Uth, Christina; Fritz, Janine; Schäfer, Elena; Steinmann, Björn; Empting, Martin; Ockelmann, Pia; Lierz, Michael; Kolmar, Harald

    2014-12-10

    A novel method for stepwise in vitro affinity maturation of antigen-specific shark vNAR domains is described that exclusively relies on semi-synthetic repertoires derived from non-immunized sharks. Target-specific molecules were selected from a CDR3-randomized bamboo shark (Chiloscyllium plagiosum) vNAR library using yeast surface display as platform technology. Various antigen-binding vNAR domains were easily isolated by screening against several therapeutically relevant antigens, including the epithelial cell adhesion molecule (EpCAM), the Ephrin type-A receptor 2 (EphA2), and the human serine protease HTRA1. Affinity maturation was demonstrated for EpCAM and HTRA1 by diversifying CDR1 of target-enriched populations which allowed for the rapid selection of nanomolar binders. EpCAM-specific vNAR molecules were produced as soluble proteins and more extensively characterized via thermal shift assays and biolayer interferometry. Essentially, we demonstrate that high-affinity binders can be generated in vitro without largely compromising the desirable high thermostability of the vNAR scaffold.

  17. Quantification of massive seasonal aggregations of blacktip sharks (Carcharhinus limbatus) in Southeast Florida

    DOE PAGES

    Kajiura, Stephen M.; Tellman, Shari L.; Patterson, Heather M.

    2016-03-30

    Southeast Florida witnesses an enormous seasonal influx of upper trophic level marine predators each year as massive aggregations of migrating blacktip sharks (Carcharhinus limbatus) overwinter in nearshore waters. The narrow shelf and close proximity of the Gulf Stream current to the Palm Beach County shoreline drive tens of thousands of sharks to the shallow, coastal environment. This natural bottleneck provides a unique opportunity to estimate relative abundance. Over a four year period from 2011–2014, an aerial survey was flown approximately biweekly along the length of Palm Beach County. A high definition video camera and digital still camera mounted out ofmore » the airplane window provided a continuous record of the belt transect which extended 200 m seaward from the shoreline between Boca Raton Inlet and Jupiter Inlet. The number of sharks within the survey transect was directly counted from the video. Shark abundance peaked in the winter (January-March) with a maximum in 2011 of 12,128 individuals counted within the 75.6 km-2 belt transect. This resulted in a maximum density of 803.2 sharks km-2. By the late spring (April-May), shark abundance had sharply declined to 1.1% of its peak, where it remained until spiking again in January of the following year. Shark abundance was inversely correlated with water temperature and large numbers of sharks were found only when water temperatures were less than 25°C. Shark abundance was also correlated with day of the year but not with barometric pressure. Although shark abundance was not correlated with photoperiod, the departure of the sharks from southeast Florida occurred around the vernal equinox. The shark migration along the United States eastern seaboard corresponds spatially and temporally with the spawning aggregations of various baitfish species. As a result, these baseline abundance data can be compared to future studies to determine if shark population size is changing and if sharks are restricting

  18. Shark myelin basic protein: amino acid sequence, secondary structure, and self-association.

    PubMed

    Milne, T J; Atkins, A R; Warren, J A; Auton, W P; Smith, R

    1990-09-01

    Myelin basic protein (MBP) from the Whaler shark (Carcharhinus obscurus) has been purified from acid extracts of a chloroform/methanol pellet from whole brains. The amino acid sequence of the majority of the protein has been determined and compared with the sequences of other MBPs. The shark protein has only 44% homology with the bovine protein, but, in common with other MBPs, it has basic residues distributed throughout the sequence and no extensive segments that are predicted to have an ordered secondary structure in solution. Shark MBP lacks the triproline sequence previously postulated to form a hairpin bend in the molecule. The region containing the putative consensus sequence for encephalitogenicity in the guinea pig contains several substitutions, thus accounting for the lack of activity of the shark protein. Studies of the secondary structure and self-association have shown that shark MBP possesses solution properties similar to those of the bovine protein, despite the extensive differences in primary structure.

  19. Pharmacokinetics of cefovecin (Convenia) in white bamboo sharks (Chiloscyllium plagiosum) and Atlantic horseshoe crabs (Limulus polyphemus).

    PubMed

    Steeil, James C; Schumacher, Juergen; George, Robert H; Bulman, Frank; Baine, Katherine; Cox, Sherry

    2014-06-01

    Cefovecin was administered to six healthy adult white bamboo sharks (Chiloscyllium plagiosum) and six healthy adult Atlantic horseshoe crabs (Limulus polyphemus) to determine its pharmacokinetics in these species. A single dose of cefovecin at 8 mg/kg was administered subcutaneously in the epaxial region of the bamboo sharks and in the proximal articulation of the lateral leg of the horseshoe crabs. Blood and hemolymph samples were collected at various time points from bamboo sharks and Atlantic horseshoe crabs. High performance liquid chromatography was performed to determine plasma levels of cefovecin. The terminal halflife of cefovecin in Atlantic horseshoe crabs was 37.70 +/- 9.04 hr and in white bamboo sharks was 2.02 +/- 4.62 hr. Cefovecin concentrations were detected for 4 days in white bamboo sharks and for 14 days in Atlantic horseshoe crabs. No adverse effects associated with cefovecin administration were seen in either species.

  20. Eye lens radiocarbon reveals centuries of longevity in the Greenland shark (Somniosus microcephalus).

    PubMed

    Nielsen, Julius; Hedeholm, Rasmus B; Heinemeier, Jan; Bushnell, Peter G; Christiansen, Jørgen S; Olsen, Jesper; Ramsey, Christopher Bronk; Brill, Richard W; Simon, Malene; Steffensen, Kirstine F; Steffensen, John F

    2016-08-12

    The Greenland shark (Somniosus microcephalus), an iconic species of the Arctic Seas, grows slowly and reaches >500 centimeters (cm) in total length, suggesting a life span well beyond those of other vertebrates. Radiocarbon dating of eye lens nuclei from 28 female Greenland sharks (81 to 502 cm in total length) revealed a life span of at least 272 years. Only the smallest sharks (220 cm or less) showed signs of the radiocarbon bomb pulse, a time marker of the early 1960s. The age ranges of prebomb sharks (reported as midpoint and extent of the 95.4% probability range) revealed the age at sexual maturity to be at least 156 ± 22 years, and the largest animal (502 cm) to be 392 ± 120 years old. Our results show that the Greenland shark is the longest-lived vertebrate known, and they raise concerns about species conservation.

  1. Slingshot feeding of the goblin shark Mitsukurina owstoni (Pisces: Lamniformes: Mitsukurinidae)

    PubMed Central

    Nakaya, Kazuhiro; Tomita, Taketeru; Suda, Kenta; Sato, Keiichi; Ogimoto, Keisuke; Chappell, Anthony; Sato, Toshihiko; Takano, Katsuhiko; Yuki, Yoshio

    2016-01-01

    Five striking and prey capture events of two goblin sharks were videotaped at sea for the first time, showing their extraordinary biting process. The goblin sharks swung their lower jaw downward and backward to attain a huge gape and then rapidly protruded the jaws forward a considerable distance. The jaws were projected at a maximum velocity of 3.1 m/s to 8.6–9.4% of the total length of the shark, which is by far the fastest and greatest jaw protrusion among sharks. While the jaws were being retracted, the mouth opened and closed again, which was considered a novel feeding event for sharks. Phylogenetic evidence suggested that their feeding behavior has evolved as an adaptation to food-poor deep-sea environments, possibly as a trade-off for the loss of strong swimming ability. PMID:27282933

  2. Shark fisheries in the Southeast Pacific: A 61-year analysis from Peru

    PubMed Central

    Gonzalez-Pestana, Adriana; Kouri J., Carlos; Velez-Zuazo, Ximena

    2016-01-01

    Peruvian waters exhibit high conservation value for sharks. This contrasts with a lag in initiatives for their management and a lack of studies about their biology, ecology and fishery. We investigated the dynamics of Peruvian shark fishery and its legal framework identifying information gaps for recommending actions to improve management. Further, we investigated the importance of the Peruvian shark fishery from a regional perspective. From 1950 to 2010, 372,015 tons of sharks were landed in Peru. From 1950 to 1969, we detected a significant increase in landings; but from 2000 to 2011 there was a significant decrease in landings, estimated at 3.5% per year. Six species represented 94% of landings: blue shark ( Prionace glauca), shortfin mako ( Isurus oxyrinchus), smooth hammerhead ( Sphyrna zygaena), common thresher ( Alopias vulpinus), smooth-hound ( Mustelus whitneyi) and angel shark ( Squatina californica). Of these, the angel shark exhibits a strong and significant decrease in landings: 18.9% per year from 2000 to 2010. Peru reports the highest accumulated historical landings in the Pacific Ocean; but its contribution to annual landings has decreased since 1968. Still, Peru is among the top 12 countries exporting shark fins to the Hong Kong market. Although the government collects total weight by species, the number of specimens landed as well as population parameters (e.g. sex, size and weight) are not reported. Further, for some genera, species-level identification is deficient and so overestimates the biomass landed by species and underestimates the species diversity. Recently, regional efforts to regulate shark fishery have been implemented to support the conservation of sharks but in Peru work remains to be done. PMID:27635216

  3. Scale morphology and flexibility in the shortfin mako Isurus oxyrinchus and the blacktip shark Carcharhinus limbatus.

    PubMed

    Motta, Philip; Habegger, Maria Laura; Lang, Amy; Hueter, Robert; Davis, Jessica

    2012-10-01

    We quantified placoid scale morphology and flexibility in the shortfin mako Isurus oxyrinchus and the blacktip shark Carcharhinus limbatus. The shortfin mako shark has shorter scales than the blacktip shark. The majority of the shortfin mako shark scales have three longitudinal riblets with narrow spacing and shallow grooves. In comparison, the blacktip shark scales have five to seven longitudinal riblets with wider spacing and deeper grooves. Manual manipulation of the scales at 16 regions on the body and fins revealed a range of scale flexibility, from regions of nonerectable scales such as on the leading edge of the fins to highly erectable scales along the flank of the shortfin mako shark body. The flank scales of the shortfin mako shark can be erected to a greater angle than the flank scales of the blacktip shark. The shortfin mako shark has a region of highly flexible scales on the lateral flank that can be erected to at least 50°. The scales of the two species are anchored in the stratum laxum of the dermis. The attachment fibers of the scales in both species appear to be almost exclusively collagen, with elastin fibers visible in the stratum laxum of both species. The most erectable scales of the shortfin mako shark have long crowns and relatively short bases that are wider than long. The combination of a long crown length to short base length facilitates pivoting of the scales. Erection of flank scales and resulting drag reduction is hypothesized to be passively driven by localized flow patterns over the skin.

  4. Foraging mode of the grey reef shark, Carcharhinus amblyrhynchos, under two different scenarios

    NASA Astrophysics Data System (ADS)

    Robbins, W. D.; Renaud, P.

    2016-03-01

    Knowledge of an animal's predatory interactions provides insight into its ecological role. Until now, investigation of reef shark predation has relied on artificial stimuli to facilitate feeding events, with few sightings of natural predation events. Here we document two different foraging modes of the grey reef shark, Carcharhinus amblyrhynchos (f. Carcharhinidae), recorded without the influence of baits or burley. The first mode saw an aggregation of sharks targeting a morning mass spawning event of marbled grouper (f. Serranidae). We observed 120 separate grouper spawns over a 104-min period. Detailed analysis of 52 spawns showed an average of five groupers and 2.7 sharks involved in each spawn, with sharks usually on site within 1.29 s of spawn initiation. The success rate of investigating sharks was relatively low (8.1 %), and conspecific competition, rather than cooperative behaviour, was repeatedly observed among sharks. The second foraging mode documented was the nocturnal predation of individual fishes in the same reef pass 2 weeks later. Here, 128 separate fish pursuits were observed, with fusiliers (f. Caesionidae) comprising 88 % of targeted individuals. Multiple sharks usually investigated each fish, with over 300 interaction events recorded. Over 100 bite attempts were observed, and again the rate of predation was low, with fish taken in only 5.3 % of investigations (16 % of attempted bites). Our findings show that grey reef sharks naturally prey on species across a range of trophic levels, employing foraging techniques optimised for prey species and circumstance. Although a high-order mesopredator, the low rates of predation success observed suggest that grey reef sharks may have limited direct impact on lower-trophic-order species; however, this remains to be verified.

  5. Reef-Fidelity and Migration of Tiger Sharks, Galeocerdo cuvier, across the Coral Sea

    PubMed Central

    Werry, Jonathan M.; Planes, Serge; Berumen, Michael L.; Lee, Kate A.; Braun, Camrin D.; Clua, Eric

    2014-01-01

    Knowledge of the habitat use and migration patterns of large sharks is important for assessing the effectiveness of large predator Marine Protected Areas (MPAs), vulnerability to fisheries and environmental influences, and management of shark–human interactions. Here we compare movement, reef-fidelity, and ocean migration for tiger sharks, Galeocerdo cuvier, across the Coral Sea, with an emphasis on New Caledonia. Thirty-three tiger sharks (1.54 to 3.9 m total length) were tagged with passive acoustic transmitters and their localised movements monitored on receiver arrays in New Caledonia, the Chesterfield and Lord Howe Islands in the Coral Sea, and the east coast of Queensland, Australia. Satellite tags were also used to determine habitat use and movements among habitats across the Coral Sea. Sub-adults and one male adult tiger shark displayed year-round residency in the Chesterfields with two females tagged in the Chesterfields and detected on the Great Barrier Reef, Australia, after 591 and 842 days respectively. In coastal barrier reefs, tiger sharks were transient at acoustic arrays and each individual demonstrated a unique pattern of occurrence. From 2009 to 2013, fourteen sharks with satellite and acoustic tags undertook wide-ranging movements up to 1114 km across the Coral Sea with eight detected back on acoustic arrays up to 405 days after being tagged. Tiger sharks dove 1136 m and utilised three-dimensional activity spaces averaged at 2360 km3. The Chesterfield Islands appear to be important habitat for sub-adults and adult male tiger sharks. Management strategies need to consider the wide-ranging movements of large (sub-adult and adult) male and female tiger sharks at the individual level, whereas fidelity to specific coastal reefs may be consistent across groups of individuals. Coastal barrier reef MPAs, however, only afford brief protection for large tiger sharks, therefore determining the importance of other oceanic Coral Sea reefs should be a

  6. Residency, habitat use and sexual segregation of white sharks, Carcharodon carcharias in False Bay, South Africa.

    PubMed

    Kock, Alison; O'Riain, M Justin; Mauff, Katya; Meÿer, Michael; Kotze, Deon; Griffiths, Charles

    2013-01-01

    White sharks (Carcharodon carcharias) are threatened apex predators and identification of their critical habitats and how these are used are essential to ensuring improved local and ultimately global white shark protection. In this study we investigated habitat use by white sharks in False Bay, South Africa, using acoustic telemetry. 56 sharks (39 female, 17 male), ranging in size from 1.7-5 m TL, were tagged with acoustic transmitters and monitored on an array of 30 receivers for 975 days. To investigate the effects of season, sex and size on habitat use we used a generalized linear mixed effects model. Tagged sharks were detected in the Bay in all months and across all years, but their use of the Bay varied significantly with the season and the sex of the shark. In autumn and winter males and females aggregated around the Cape fur seal colony at Seal Island, where they fed predominantly on young of the year seals. In spring and summer there was marked sexual segregation, with females frequenting the Inshore areas and males seldom being detected. The shift from the Island in autumn and winter to the Inshore region in spring and summer by females mirrors the seasonal peak in abundance of juvenile seals and of migratory teleost and elasmobranch species respectively. This study provides the first evidence of sexual segregation at a fine spatial scale and demonstrates that sexual segregation in white sharks is not restricted to adults, but is apparent for juveniles and sub-adults too. Overall, the results confirm False Bay as a critical area for white shark conservation as both sexes, across a range of sizes, frequent the Bay on an annual basis. The finding that female sharks aggregate in the Inshore regions when recreational use peaks highlights the need for ongoing shark-human conflict mitigation strategies.

  7. Modulation of shark prey capture kinematics in response to sensory deprivation.

    PubMed

    Gardiner, Jayne M; Atema, Jelle; Hueter, Robert E; Motta, Philip J

    2017-02-01

    The ability of predators to modulate prey capture in response to the size, location, and behavior of prey is critical to successful feeding on a variety of prey types. Modulating in response to changes in sensory information may be critical to successful foraging in a variety of environments. Three shark species with different feeding morphologies and behaviors were filmed using high-speed videography while capturing live prey: the ram-feeding blacktip shark, the ram-biting bonnethead, and the suction-feeding nurse shark. Sharks were examined intact and after sensory information was blocked (olfaction, vision, mechanoreception, and electroreception, alone and in combination), to elucidate the contribution of the senses to the kinematics of prey capture. In response to sensory deprivation, the blacktip shark demonstrated the greatest amount of modulation, followed by the nurse shark. In the absence of olfaction, blacktip sharks open the jaws slowly, suggestive of less motivation. Without lateral line cues, blacktip sharks capture prey from greater horizontal angles using increased ram. When visual cues are absent, blacktip sharks elevate the head earlier and to a greater degree, allowing them to overcome imprecise position of the prey relative to the mouth, and capture prey using decreased ram, while suction remains unchanged. When visual cues are absent, nurse sharks open the mouth wider, extend the labial cartilages further, and increase suction while simultaneously decreasing ram. Unlike some bony fish, neither species switches feeding modalities (i.e. from ram to suction or vice versa). Bonnetheads failed to open the mouth when electrosensory cues were blocked, but otherwise little to no modulation was found in this species. These results suggest that prey capture may be less plastic in elasmobranchs than in bony fishes, possibly due to anatomical differences, and that the ability to modulate feeding kinematics in response to available sensory information varies

  8. Natural or Artificial? Habitat-Use by the Bull Shark, Carcharhinus leucas

    PubMed Central

    Werry, Jonathan M.; Lee, Shing Y.; Lemckert, Charles J.; Otway, Nicholas M.

    2012-01-01

    Background Despite accelerated global population declines due to targeted and illegal fishing pressure for many top-level shark species, the impacts of coastal habitat modification have been largely overlooked. We present the first direct comparison of the use of natural versus artificial habitats for the bull shark, Carcharhinus leucas, an IUCN ‘Near-threatened’ species - one of the few truly euryhaline sharks that utilises natural rivers and estuaries as nursery grounds before migrating offshore as adults. Understanding the value of alternate artificial coastal habitats to the lifecycle of the bull shark is crucial for determining the impact of coastal development on this threatened but potentially dangerous species. Methodology/Findings We used longline surveys and long-term passive acoustic tracking of neonate and juvenile bull sharks to determine the ontogenetic value of natural and artificial habitats to bull sharks associated with the Nerang River and adjoining canals on the Gold Coast, Australia. Long-term movements of tagged sharks suggested a preference for the natural river over artificial habitat (canals). Neonates and juveniles spent the majority of their time in the upper tidal reaches of the Nerang River and undertook excursions into adjoining canals. Larger bull sharks ranged further and frequented the canals closer to the river mouth. Conclusions/Significance Our work suggests with increased destruction of natural habitats, artificial coastal habitat may become increasingly important to large juvenile bull sharks with associated risk of attack on humans. In this system, neonate and juvenile bull sharks utilised the natural and artificial habitats, but the latter was not the preferred habitat of neonates. The upper reaches of tidal rivers, often under significant modification pressure, serve as nursery sites for neonates. Analogous studies are needed in similar systems elsewhere to assess the spatial and temporal generality of this research

  9. Quantifying movement patterns for shark conservation at remote coral atolls in the Indian Ocean

    NASA Astrophysics Data System (ADS)

    Field, I. C.; Meekan, M. G.; Speed, C. W.; White, W.; Bradshaw, C. J. A.

    2011-03-01

    Grey reef sharks ( Carcharhinus amblyrhynchos) are apex predators found on many Indo-Pacific coral reefs, but little is known about their movement patterns and habitat requirements. We used acoustic telemetry to determine movements and habitat use of these sharks at the isolated Rowley Shoals atolls, 250 km off the coast of north-western Australia. We equipped 12 male and 14 female sharks ranging from 0.79 to 1.69 m in total length with transmitters that were detected by an array of 11 strategically placed receivers on two atoll reefs. Over 26,000 detections were recorded over the 325 days of receiver deployment. No sharks were observed to move between reefs. Receivers on the outer slopes of reefs provided nearly all (99%) of the detections. We found no differences in general attendance parameters due to size, sex or reef, except for maximum period of detection where larger sharks were detected over a longer period than smaller sharks. Male and female sharks were often detected at separate receivers at the outer slope habitat of one reef, suggesting sexual segregation, but this pattern did not occur at the second reef where males and females were detected at similar frequencies. We identified two patterns of daily behaviour: (1) sharks were present at the reef both day and night or (2) sharks spent more time in attendance during day than at night. Fast Fourier transforms identified 24-h cycles of attendance at the reef and a secondary peak of attendance at 12 h for most sharks, although no individuals shared the same attendance patterns. Our study provides baseline data that can be used to optimise the minimum area and habitat requirements for conservation of these apex predators.

  10. Residency, Habitat Use and Sexual Segregation of White Sharks, Carcharodon carcharias in False Bay, South Africa

    PubMed Central

    Kock, Alison; O’Riain, M. Justin; Mauff, Katya; Meÿer, Michael; Kotze, Deon; Griffiths, Charles

    2013-01-01

    White sharks (Carcharodon carcharias) are threatened apex predators and identification of their critical habitats and how these are used are essential to ensuring improved local and ultimately global white shark protection. In this study we investigated habitat use by white sharks in False Bay, South Africa, using acoustic telemetry. 56 sharks (39 female, 17 male), ranging in size from 1.7–5 m TL, were tagged with acoustic transmitters and monitored on an array of 30 receivers for 975 days. To investigate the effects of season, sex and size on habitat use we used a generalized linear mixed effects model. Tagged sharks were detected in the Bay in all months and across all years, but their use of the Bay varied significantly with the season and the sex of the shark. In autumn and winter males and females aggregated around the Cape fur seal colony at Seal Island, where they fed predominantly on young of the year seals. In spring and summer there was marked sexual segregation, with females frequenting the Inshore areas and males seldom being detected. The shift from the Island in autumn and winter to the Inshore region in spring and summer by females mirrors the seasonal peak in abundance of juvenile seals and of migratory teleost and elasmobranch species respectively. This study provides the first evidence of sexual segregation at a fine spatial scale and demonstrates that sexual segregation in white sharks is not restricted to adults, but is apparent for juveniles and sub-adults too. Overall, the results confirm False Bay as a critical area for white shark conservation as both sexes, across a range of sizes, frequent the Bay on an annual basis. The finding that female sharks aggregate in the Inshore regions when recreational use peaks highlights the need for ongoing shark-human conflict mitigation strategies. PMID:23383052

  11. Shark fisheries in the Southeast Pacific: A 61-year analysis from Peru.

    PubMed

    Gonzalez-Pestana, Adriana; Kouri J, Carlos; Velez-Zuazo, Ximena

    2014-01-01

    Peruvian waters exhibit high conservation value for sharks. This contrasts with a lag in initiatives for their management and a lack of studies about their biology, ecology and fishery. We investigated the dynamics of Peruvian shark fishery and its legal framework identifying information gaps for recommending actions to improve management. Further, we investigated the importance of the Peruvian shark fishery from a regional perspective. From 1950 to 2010, 372,015 tons of sharks were landed in Peru. From 1950 to 1969, we detected a significant increase in landings; but from 2000 to 2011 there was a significant decrease in landings, estimated at 3.5% per year. Six species represented 94% of landings: blue shark ( Prionace glauca), shortfin mako ( Isurus oxyrinchus), smooth hammerhead ( Sphyrna zygaena), common thresher ( Alopias vulpinus), smooth-hound ( Mustelus whitneyi) and angel shark ( Squatina californica). Of these, the angel shark exhibits a strong and significant decrease in landings: 18.9% per year from 2000 to 2010. Peru reports the highest accumulated historical landings in the Pacific Ocean; but its contribution to annual landings has decreased since 1968. Still, Peru is among the top 12 countries exporting shark fins to the Hong Kong market. Although the government collects total weight by species, the number of specimens landed as well as population parameters (e.g. sex, size and weight) are not reported. Further, for some genera, species-level identification is deficient and so overestimates the biomass landed by species and underestimates the species diversity. Recently, regional efforts to regulate shark fishery have been implemented to support the conservation of sharks but in Peru work remains to be done.

  12. New depositional models for Cretaceous source rocks

    SciTech Connect

    Kauffman, E.G.; Villamil, T. )

    1993-02-01

    The Cretaceous marks one of the greatest periods of source rock development in geologic history, especially in coastal and epi-continental marine basins where the number, duration, and geographic extent of Corg-rich intervals exceeds that of oceanic basins. Large-scale factors regulating Cretaceous source rocks include sealevel, sedimentation rate/type, paleoclimate and marine thermal gradients, paleoceanography (circulation, stratification, chemistry, upwelling, nutrient supply), and surface water productivity. Marine dispositional settings favored as models for Corg concentration include silled and tectonically depressed basins, intersection of OMZ's with shallow continental seas, coastal upwelling, highly stratified shallow seas, and oceanic anoxic events (OAE's). All of these settings are thought to be characterized by stagnant, anoxic/highly dysoxic water masses above the sediment-water interface, and highly stressed benthic environments. This seemingly supported by fine lamination, spare bioturbation, high pyrite and Corg content of most source rocks. But high-resolution (cm-scale) sedimentologic, paleobiologic, and geochemical analyses of Jurassic-Cretaceous source rocks reveal, instead, dynamic benthic environments with active currents, episodically crowded with diverse life in event communities, and persistently characterized by longer term, low diversity resident benthic communities. These characteristics indicate rapidly fluctuating, predominantly dysoxic to oxic waters at and above the sediment-water interface for most Corg-rich black shales. A new model for source rock generation is proposed which retains the redox boundary at or near the sediment-water interface over large areas of seafloor, in part aided by extensive development of benthic microbial mats which may contribute up to 30% of the Corg to marine source rocks.

  13. DNA sequence from Cretaceous period bone fragments.

    PubMed

    Woodward, S R; Weyand, N J; Bunnell, M

    1994-11-18

    DNA was extracted from 80-million-year-old bone fragments found in strata of the Upper Cretaceous Blackhawk Formation in the roof of an underground coal mine in eastern Utah. This DNA was used as the template in a polymerase chain reaction that amplified and sequenced a portion of the gene encoding mitochondrial cytochrome b. These sequences differ from all other cytochrome b sequences investigated, including those in the GenBank and European Molecular Biology Laboratory databases. DNA isolated from these bone fragments and the resulting gene sequences demonstrate that small fragments of DNA may survive in bone for millions of years.

  14. Multi-Year Impacts of Ecotourism on Whale Shark (Rhincodon typus) Visitation at Ningaloo Reef, Western Australia

    PubMed Central

    Sanzogni, R. L.; Meekan, M. G.; Meeuwig, J. J.

    2015-01-01

    In-water viewing of sharks by tourists has become a popular and lucrative industry. There is some concern that interactions with tourists with ecotourism operations might harm sharks through disruption of behaviours. Here, we analysed five years of whale shark (Rhincodon typus) encounter data by an ecotourism industry at Ningaloo Reef, Western Australia, to assess the impact of ecotourism interactions on shark visitation, within the context of the biological and physical oceanography of the region. Our data base consisted of 2823 encounter records for 951 individual whale sharks collected by ecotourism operators between 2007 and 2011. We found that total encounters per whale shark and encounters per boat trip increased through time. On average, whale sharks re-encountered in subsequent years were encountered earlier, stayed longer and tended to be encountered more often within a season than sharks that were only encountered in a single year. Sequential comparisons between years did not show any patterns consistent with disturbance and the rate of departure of whale sharks from the aggregation was negatively correlated to the number of operator trips. Overall, our analysis of this multi-year data base found no evidence that interactions with tourists affected the likelihood of whale shark re-encounters and that instead, physical and biological environmental factors had a far greater influence on whale shark visitation rates. Our approach provides a template for assessing the effects of ecotourism interactions and environmental factors on the visitation patterns of marine megafauna over multiple years. PMID:26398338

  15. Multi-Year Impacts of Ecotourism on Whale Shark (Rhincodon typus) Visitation at Ningaloo Reef, Western Australia.

    PubMed

    Sanzogni, R L; Meekan, M G; Meeuwig, J J

    2015-01-01

    In-water viewing of sharks by tourists has become a popular and lucrative industry. There is some concern that interactions with tourists with ecotourism operations might harm sharks through disruption of behaviours. Here, we analysed five years of whale shark (Rhincodon typus) encounter data by an ecotourism industry at Ningaloo Reef, Western Australia, to assess the impact of ecotourism interactions on shark visitation, within the context of the biological and physical oceanography of the region. Our data base consisted of 2823 encounter records for 951 individual whale sharks collected by ecotourism operators between 2007 and 2011. We found that total encounters per whale shark and encounters per boat trip increased through time. On average, whale sharks re-encountered in subsequent years were encountered earlier, stayed longer and tended to be encountered more often within a season than sharks that were only encountered in a single year. Sequential comparisons between years did not show any patterns consistent with disturbance and the rate of departure of whale sharks from the aggregation was negatively correlated to the number of operator trips. Overall, our analysis of this multi-year data base found no evidence that interactions with tourists affected the likelihood of whale shark re-encounters and that instead, physical and biological environmental factors had a far greater influence on whale shark visitation rates. Our approach provides a template for assessing the effects of ecotourism interactions and environmental factors on the visitation patterns of marine megafauna over multiple years.

  16. Long-term natal site-fidelity by immature lemon sharks (Negaprion brevirostris) at a subtropical island.

    PubMed

    Chapman, Demian D; Babcock, Elizabeth A; Gruber, Samuel H; Dibattista, Joseph D; Franks, Bryan R; Kessel, Steven A; Guttridge, Tristan; Pikitch, Ellen K; Feldheim, Kevin A

    2009-08-01

    Although many sharks begin their life confined in nursery habitats, it is unknown how rapidly they disperse away from their natal area once they leave the nursery. We examine this issue in immature lemon sharks (Negaprion brevirostris) from the time they leave the nursery (approximately age 3) at a subtropical island (Bimini, Bahamas), through to the onset of sexual maturity (approximately age 12). From 1995 to 2007 we tagged and genotyped a large fraction of the nursery-bound sharks at this location (0-3 years of age, N = 1776 individuals). From 2003 to 2007 we sampled immature sharks aged from 3 to 11 years (N = 150) living around the island and used physical/genetic tag recaptures coupled with kinship analysis to determine whether or not each of these 'large immature sharks' was locally born. We show that many island-born lemon sharks remain close to their natal area for long periods (years) after leaving the nursery; more than half of the sampled sharks up to 135 cm total length ( approximately 6 years old) were locally born. The fraction of locally born sharks gradually declined with increasing shark size, indicating that dispersal is relatively slow and does not primarily occur after sharks reach a threshold size. Local conservation measures (e.g. localized fishery closures, marine protected areas) can therefore help protect island-born lemon sharks even after they leave the nursery habitat.

  17. 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.

  18. Cretaceous - Tertiary Hoploparia species: Occurrence, paleobiogeography and predation context

    NASA Astrophysics Data System (ADS)

    El-Shazly, Soheir

    2015-12-01

    The study of Hoploparia species in 25 localities in Northern and Southern Hemispheres from Early Cretaceous to Early Miocene reveals the appearance of 51 species in Early Cretaceous, mostly in Northern Hemisphere, 46 species from Late Cretaceous (42 and 4 carryover from the Early Cretaceous), 7 species from Danian (4 plus 3 carryover from the Late Cretaceous), 7 species from Eocene (6 plus one from the Early Cretaceous), 2 species from Lower Oligocene and the last recorded species Hoploparia persisted in the Early Miocene of Antarctica. The oldest Hoploparia was recorded from Europe and distributed through the Northern and Southern Hemispheres with the facilitation of the Indo-Madagascar sea-way and Hispanic corridor. The tolerance for temperature and water depth as well as the morphological changes in genus Hoploparia in the Late Cretaceous and Tertiary periods, helped some species to survive the K/T event. Drill-hole predation in Hoploparia longimana (Sowerby, 1826) was recorded for the first time from the Lower Cretaceous (Albian) of Egypt.

  19. Re-Creating Missing Population Baselines for Pacific Reef Sharks

    PubMed Central

    Nadon, Marc O; Baum, Julia K; Williams, Ivor D; Mcpherson, Jana M; Zgliczynski, Brian J; Richards, Benjamin L; Schroeder, Robert E; Brainard, Russell E

    2012-01-01

    Summary Abstract Sharks and other large predators are scarce on most coral reefs, but studies of their historical ecology provide qualitative evidence that predators were once numerous in these ecosystems. Quantifying density of sharks in the absence of humans (baseline) is, however, hindered by a paucity of pertinent time-series data. Recently researchers have used underwater visual surveys, primarily of limited spatial extent or nonstandard design, to infer negative associations between reef shark abundance and human populations. We analyzed data from 1607 towed-diver surveys (>1 ha transects surveyed by observers towed behind a boat) conducted at 46 reefs in the central-western Pacific Ocean, reefs that included some of the world's most pristine coral reefs. Estimates of shark density from towed-diver surveys were substantially lower (<10%) than published estimates from surveys along small transects (<0.02 ha), which is not consistent with inverted biomass pyramids (predator biomass greater than prey biomass) reported by other researchers for pristine reefs. We examined the relation between the density of reef sharks observed in towed-diver surveys and human population in models that accounted for the influence of oceanic primary productivity, sea surface temperature, reef area, and reef physical complexity. We used these models to estimate the density of sharks in the absence of humans. Densities of gray reef sharks (Carcharhinus amblyrhynchos), whitetip reef sharks (Triaenodon obesus), and the group “all reef sharks” increased substantially as human population decreased and as primary productivity and minimum sea surface temperature (or reef area, which was highly correlated with temperature) increased. Simulated baseline densities of reef sharks under the absence of humans were 1.1–2.4/ha for the main Hawaiian Islands, 1.2–2.4/ha for inhabited islands of American Samoa, and 0.9–2.1/ha for inhabited islands in the Mariana Archipelago, which suggests

  20. Cretaceous-Palaeogene experiments in Biogeochemical Resilience

    NASA Astrophysics Data System (ADS)

    Penman, D. E.; Henehan, M. J.; Hull, P. M.; Planavsky, N.; Schmidt, D. N.; Rae, J. W. B.; Thomas, E.; Huber, B. T.

    2015-12-01

    Human activity is altering biogeochemical cycles in the ocean. While ultimately anthropogenic forcings may be brought under control, it is still unclear whether tipping points may exist beyond which human-induced changes to biogeochemical cycles become irreversible. We use the Late Cretaceous and the Cretaceous-Palaeogene (K-Pg) boundary interval as an informative case study. Over this interval, two carbon cycle perturbations (gradual flood basalt volcanism and abrupt bolide impact) occurred within a short time window, allowing us to investigate the resilience of biogeochemical cycles to different pressures applied to the same initial boundary conditions on very different time scales. We demonstrate that relatively gradual emission of CO2 from the Deccan large igneous province was efficiently mitigated within the limits of existing biogeochemical processes. However, the rapid extinction of pelagic calcifying organisms at the K-Pg boundary due to the Chicxulub bolide impact had more profound effects, and caused lasting (> 1 million years) changes to biogeochemical cycles. By combining sedimentological observations with boron isotope-based pH reconstructions over these events, we document two potentially useful partial analogues for best and worst case scenarios for anthropogenic global change. We suggest that if current ocean acidification results in the mass extinction of marine pelagic calcifiers, we may cause profound changes to the Earth system that will persist for 100,000s to millions of years.

  1. Cretaceous African life captured in amber

    PubMed Central

    Schmidt, Alexander R.; Perrichot, Vincent; Svojtka, Matthias; Anderson, Ken B.; Belete, Kebede H.; Bussert, Robert; Dörfelt, Heinrich; Jancke, Saskia; Mohr, Barbara; Mohrmann, Eva; Nascimbene, Paul C.; Nel, André; Nel, Patricia; Ragazzi, Eugenio; Roghi, Guido; Saupe, Erin E.; Schmidt, Kerstin; Schneider, Harald; Selden, Paul A.; Vávra, Norbert

    2010-01-01

    Amber is of great paleontological importance because it preserves a diverse array of organisms and associated remains from different habitats in and close to the amber-producing forests. Therefore, the discovery of amber inclusions is important not only for tracing the evolutionary history of lineages with otherwise poor fossil records, but also for elucidating the composition, diversity, and ecology of terrestrial paleoecosystems. Here, we report a unique find of African amber with inclusions, from the Cretaceous of Ethiopia. Ancient arthropods belonging to the ants, wasps, thrips, zorapterans, and spiders are the earliest African records of these ecologically important groups and constitute significant discoveries providing insight into the temporal and geographical origins of these lineages. Together with diverse microscopic inclusions, these findings reveal the interactions of plants, fungi and arthropods during an epoch of major change in terrestrial ecosystems, which was caused by the initial radiation of the angiosperms. Because of its age, paleogeographic location and the exceptional preservation of the inclusions, this fossil resin broadens our understanding of the ecology of Cretaceous woodlands. PMID:20368427

  2. Low ecological disparity in Early Cretaceous birds.

    PubMed

    Mitchell, Jonathan S; Makovicky, Peter J

    2014-07-22

    Ecological divergence is thought to be coupled with evolutionary radiations, yet the strength of this coupling is unclear. When birds diversified ecologically has received much less attention than their hotly debated crown divergence time. Here, we quantify how accurately skeletal morphology can predict ecology in living and extinct birds, and show that the earliest known assemblage of birds (=pygostylians) from the Jehol Biota (≈125 Ma) was substantially impoverished ecologically. The Jehol avifauna has few representatives of highly preservable ecomorphs (e.g. aquatic forms) and a notable lack of ecomorphological overlap with the pterosaur assemblage (e.g. no large or aerially foraging pygostylians). Comparisons of the Jehol functional diversity with modern and subfossil avian assemblages show that taphonomic bias alone cannot explain the ecomorphological impoverishment. However, evolutionary simulations suggest that the constrained ecological diversity of the Early Cretaceous pygostylians is consistent with what is expected from a relatively young radiation. Regardless of the proximate biological explanation, the anomalously low functional diversity of the Jehol birds is evidence both for ecological vacancies in Cretaceous ecosystems, which were subsequently filled by the radiation of crown Aves, and for discordance between taxonomic richness and ecological diversity in the best-known Mesozoic ecosystem.

  3. Low ecological disparity in Early Cretaceous birds

    PubMed Central

    Mitchell, Jonathan S.; Makovicky, Peter J.

    2014-01-01

    Ecological divergence is thought to be coupled with evolutionary radiations, yet the strength of this coupling is unclear. When birds diversified ecologically has received much less attention than their hotly debated crown divergence time. Here, we quantify how accurately skeletal morphology can predict ecology in living and extinct birds, and show that the earliest known assemblage of birds (= pygostylians) from the Jehol Biota (≈ 125 Ma) was substantially impoverished ecologically. The Jehol avifauna has few representatives of highly preservable ecomorphs (e.g. aquatic forms) and a notable lack of ecomorphological overlap with the pterosaur assemblage (e.g. no large or aerially foraging pygostylians). Comparisons of the Jehol functional diversity with modern and subfossil avian assemblages show that taphonomic bias alone cannot explain the ecomorphological impoverishment. However, evolutionary simulations suggest that the constrained ecological diversity of the Early Cretaceous pygostylians is consistent with what is expected from a relatively young radiation. Regardless of the proximate biological explanation, the anomalously low functional diversity of the Jehol birds is evidence both for ecological vacancies in Cretaceous ecosystems, which were subsequently filled by the radiation of crown Aves, and for discordance between taxonomic richness and ecological diversity in the best-known Mesozoic ecosystem. PMID:24870044

  4. How did the Cretaceous world end?

    NASA Astrophysics Data System (ADS)

    Bell, Peter M.

    Factors related to evidence of a major impact on the earth by an extraterrestrial body, at about the time of the close of the Cretaceous period, have been the center of discussion at a number of recent symposia. An example is the one entitled ‘Terminal Cretaceous Extinction: A Comparative Assessment of Causes,’ held at the annual meeting of the American Association for the Advancement of Science, Washington, D.C., in January 1982. Another was simply ‘Terrestrial Impacts and C-T Extinctions,’ held at the Thirteenth Lunar and Planetary Science Conference, Houston, Tex., March 1982.The possibility that an impact may have caused global-scale extinctions of terrestrial and marine life was the main reason for organizing the conferences, but the focus that emerged was on the geochemistry and geophysics of the impacts themselves. A possibility is that the impact occurred in an ocean, resulting in some rather major consequences, including oceanic temperature changes of several degrees Centigrade, an earthquake that would rate magnitude 12 on the Richter scale, and a tsunami, initially about 5 km high, that would have traversed the globe, inundating all low-lying continental areas on the earth within 27 hours.

  5. The Darwin Rise: A Cretaceous superswell?

    NASA Astrophysics Data System (ADS)

    McNutt, M. K.; Winterer, E. L.; Sager, W. W.; Natland, J. H.; Ito, G.

    1990-07-01

    The Japanese Guyots, Wake Guyots, and Mid-Pacific Mountains are part of a broad area of Cretaceous volcanism in the western Pacific termed the “Darwin Rise.” Based on Seabeam bathymetric data we classify these drowned volcanic islands as: type “A,” those that advanced to the atoll stage before final submergence; type “B,” those that drowned at the barrier reef stage; and type “V,” those with little or no reef material on their volcanic summits. Widespread evidence for karst topography extending to depths of 200 m on the summits of A and B guyots sheds new light on events leading to the synchronous extinction of reefs on the Darwin Rise in the mid-Cretaceous. We propose that after the formation of the reefs on the A and B guyots, the entire region was elevated at approximately the Aptian-Albian boundary (113 Ma) to form a superswell similar to that existing now in French Polynesia. The type V guyots formed on this anomalously shallow lithosphere. The demise of the reefs was the direct result of the rise of this superswell, although climate factors may have prevented reef recolonization following its later subsidence.

  6. Cretaceous African life captured in amber.

    PubMed

    Schmidt, Alexander R; Perrichot, Vincent; Svojtka, Matthias; Anderson, Ken B; Belete, Kebede H; Bussert, Robert; Dörfelt, Heinrich; Jancke, Saskia; Mohr, Barbara; Mohrmann, Eva; Nascimbene, Paul C; Nel, André; Nel, Patricia; Ragazzi, Eugenio; Roghi, Guido; Saupe, Erin E; Schmidt, Kerstin; Schneider, Harald; Selden, Paul A; Vávra, Norbert

    2010-04-20

    Amber is of great paleontological importance because it preserves a diverse array of organisms and associated remains from different habitats in and close to the amber-producing forests. Therefore, the discovery of amber inclusions is important not only for tracing the evolutionary history of lineages with otherwise poor fossil records, but also for elucidating the composition, diversity, and ecology of terrestrial paleoecosystems. Here, we report a unique find of African amber with inclusions, from the Cretaceous of Ethiopia. Ancient arthropods belonging to the ants, wasps, thrips, zorapterans, and spiders are the earliest African records of these ecologically important groups and constitute significant discoveries providing insight into the temporal and geographical origins of these lineages. Together with diverse microscopic inclusions, these findings reveal the interactions of plants, fungi and arthropods during an epoch of major change in terrestrial ecosystems, which was caused by the initial radiation of the angiosperms. Because of its age, paleogeographic location and the exceptional preservation of the inclusions, this fossil resin broadens our understanding of the ecology of Cretaceous woodlands.

  7. Mechanical challenges to freshwater residency in sharks and rays.

    PubMed

    Gleiss, Adrian C; Potvin, Jean; Keleher, James J; Whitty, Jeff M; Morgan, David L; Goldbogen, Jeremy A

    2015-04-01

    Major transitions between marine and freshwater habitats are relatively infrequent, primarily as a result of major physiological and ecological challenges. Few species of cartilaginous fish have evolved to occupy freshwater habitats. Current thought suggests that the metabolic physiology of sharks has remained a barrier to the diversification of this taxon in freshwater ecosystems. Here, we demonstrate that the physical properties of water provide an additional constraint for this species-rich group to occupy freshwater systems. Using hydromechanical modeling, we show that occurrence in fresh water results in a two- to three-fold increase in negative buoyancy for sharks and rays. This carries the energetic cost of lift production and results in increased buoyancy-dependent mechanical power requirements for swimming and increased optimal swim speeds. The primary source of buoyancy, the lipid-rich liver, offers only limited compensation for increased negative buoyancy as a result of decreasing water density; maintaining the same submerged weight would involve increasing the liver volume by very large amounts: 3- to 4-fold in scenarios where liver density is also reduced to currently observed minimal levels and 8-fold without any changes in liver density. The first data on body density from two species of elasmobranch occurring in freshwater (the bull shark Carcharhinus leucas, Müller and Henle 1839, and the largetooth sawfish Pristis pristis, Linnaeus 1758) support this hypothesis, showing similar liver sizes as marine forms but lower liver densities, but the greatest negative buoyancies of any elasmobranch studied to date. Our data suggest that the mechanical challenges associated with buoyancy control may have hampered the invasion of freshwater habitats in elasmobranchs, highlighting an additional key factor that may govern the predisposition of marine organisms to successfully establish in freshwater habitats.

  8. Constructional morphology within the head of hammerhead sharks (sphyrnidae).

    PubMed

    Mara, Kyle R; Motta, Philip J; Martin, Andrew P; Hueter, Robert E

    2015-05-01

    The study of functional trade-offs is important if a structure, such as the cranium, serves multiple biological roles, and is, therefore, shaped by multiple selective pressures. The sphyrnid cephalofoil presents an excellent model for investigating potential trade-offs among sensory, neural, and feeding structures. In this study, hammerhead shark species were chosen to represent differences in head form through phylogeny. A combination of surface-based geometric morphometrics, computed tomography (CT) volumetric analysis, and phylogenetic analyses were utilized to investigate potential trade-offs within the head. Hammerhead sharks display a diversity of cranial morphologies where the position of the eyes and nares vary among species, with only minor changes in shape, position, and volume of the feeding apparatus through phylogeny. The basal winghead shark, Eusphyra blochii, has small anteriorly positioned eyes. Through phylogeny, the relative size and position of the eyes change, such that derived species have larger, more medially positioned eyes. The lateral position of the external nares is highly variable, showing no phylogenetic trend. Mouth size and position are conserved, remaining relatively unchanged. Volumetric CT analyses reveal no trade-offs between the feeding apparatus and the remaining cranial structures. The few trade-offs were isolated to the nasal capsule volume's inverse correlation with braincase, chondrocranial, and total cephalofoil volume. Eye volume also decreased as cephalofoil width increased. These data indicate that despite considerable changes in head shape, much of the head is morphologically conserved through sphyrnid phylogeny, particularly the jaw cartilages and their associated feeding muscles, with shape change and morphological trade-offs being primarily confined to the lateral wings of the cephalofoil and their associated sensory structures.

  9. Cyanobacterial Neurotoxin β-N-Methylamino-L-alanine (BMAA) in Shark Fins

    PubMed Central

    Mondo, Kiyo; Hammerschlag, Neil; Basile, Margaret; Pablo, John; Banack, Sandra A.; Mash, Deborah C.

    2012-01-01

    Sharks are among the most threatened groups of marine species. Populations are declining globally to support the growing demand for shark fin soup. Sharks are known to bioaccumulate toxins that may pose health risks to consumers of shark products. The feeding habits of sharks are varied, including fish, mammals, crustaceans and plankton. The cyanobacterial neurotoxin β-N-methylamino-L-alanine (BMAA) has been detected in species of free-living marine cyanobacteria and may bioaccumulate in the marine food web. In this study, we sampled fin clips from seven different species of sharks in South Florida to survey the occurrence of BMAA using HPLC-FD and Triple Quadrupole LC/MS/MS methods. BMAA was detected in the fins of all species examined with concentrations ranging from 144 to 1836 ng/mg wet weight. Since BMAA has been linked to neurodegenerative diseases, these results may have important relevance to human health. We suggest that consumption of shark fins may increase the risk for human exposure to the cyanobacterial neurotoxin BMAA. PMID:22412816

  10. Evidence of Maternal Offloading of Organic Contaminants in White Sharks (Carcharodon carcharias)

    PubMed Central

    Mull, Christopher G.; Lyons, Kady; Blasius, Mary E.; Winkler, Chuck; O’Sullivan, John B.; Lowe, Christopher G.

    2013-01-01

    Organic contaminants were measured in young of the year (YOY) white sharks (Carcharodon carcharias) incidentally caught in southern California between 2005 and 2012 (n = 20) and were found to be unexpectedly high considering the young age and dietary preferences of young white sharks, suggesting these levels may be due to exposure in utero. To assess the potential contributions of dietary exposure to the observed levels, a five-parameter bioaccumulation model was used to estimate the total loads a newborn shark would potentially accumulate in one year from consuming contaminated prey from southern California. Maximum simulated dietary accumulation of DDTs and PCBs were 25.1 and 4.73 µg/g wet weight (ww) liver, respectively. Observed ΣDDT and ΣPCB concentrations (95±91 µg/g and 16±10 µg/g ww, respectively) in a majority of YOY sharks were substantially higher than the model predictions suggesting an additional source of contaminant exposure beyond foraging. Maternal offloading of organic contaminants during reproduction has been noted in other apex predators, but this is the first evidence of transfer in a matrotrophic shark. While there are signs of white shark population recovery in the eastern Pacific, the long-term physiological and population level consequences of biomagnification and maternal offloading of environmental contaminants in white sharks is unclear. PMID:23646154

  11. Evidence of maternal offloading of organic contaminants in white sharks (Carcharodon carcharias).

    PubMed

    Mull, Christopher G; Lyons, Kady; Blasius, Mary E; Winkler, Chuck; O'Sullivan, John B; Lowe, Christopher G

    2013-01-01

    Organic contaminants were measured in young of the year (YOY) white sharks (Carcharodon carcharias) incidentally caught in southern California between 2005 and 2012 (n = 20) and were found to be unexpectedly high considering the young age and dietary preferences of young white sharks, suggesting these levels may be due to exposure in utero. To assess the potential contributions of dietary exposure to the observed levels, a five-parameter bioaccumulation model was used to estimate the total loads a newborn shark would potentially accumulate in one year from consuming contaminated prey from southern California. Maximum simulated dietary accumulation of DDTs and PCBs were 25.1 and 4.73 µg/g wet weight (ww) liver, respectively. Observed ΣDDT and ΣPCB concentrations (95±91 µg/g and 16±10 µg/g ww, respectively) in a majority of YOY sharks were substantially higher than the model predictions suggesting an additional source of contaminant exposure beyond foraging. Maternal offloading of organic contaminants during reproduction has been noted in other apex predators, but this is the first evidence of transfer in a matrotrophic shark. While there are signs of white shark population recovery in the eastern Pacific, the long-term physiological and population level consequences of biomagnification and maternal offloading of environmental contaminants in white sharks is unclear.

  12. Meningoencephalitis associated with Carnobacterium maltaromaticum-like bacteria in stranded juvenile salmon sharks (Lamna ditropis).

    PubMed

    Schaffer, P A; Lifland, B; Van Sommeran, S; Casper, D R; Davis, C R

    2013-05-01

    Juvenile salmon sharks beach yearly along the California coast, primarily during late summer and early fall. Fresh, frozen, and formalin-fixed tissues from 19 stranded salmon sharks were collected for examination. Histopathology revealed meningitis or meningoencephalitis in 18 of 19 shark brains with intralesional bacteria observed in 6 of the affected brains. Bacterial culture of fresh or frozen brain, liver, and/or heart blood from 13 sharks yielded pure cultures characterized molecularly and/or biochemically as belonging to the genus Carnobacterium. The 16s ribosomal DNA sequence of 7 tissue isolates from 7 separate sharks was 99% homologous to C. maltaromaticum (GenBank FJ656722.1). Sequence of the large ribosomal DNA intergenic spacer region (ISR) was 97% homologous to C. maltaromaticum (AF374295.1). This is the first report of Carnobacterium infection in any shark species, and the authors posit that brain infection caused by Carnobacterium is a significant cause of morbidity and mortality in juvenile salmon sharks found stranded along the Pacific coast of California.

  13. Cyanobacterial neurotoxin β-N-methylamino-L-alanine (BMAA) in shark fins.

    PubMed

    Mondo, Kiyo; Hammerschlag, Neil; Basile, Margaret; Pablo, John; Banack, Sandra A; Mash, Deborah C

    2012-02-01

    Sharks are among the most threatened groups of marine species. Populations are declining globally to support the growing demand for shark fin soup. Sharks are known to bioaccumulate toxins that may pose health risks to consumers of shark products. The feeding habits of sharks are varied, including fish, mammals, crustaceans and plankton. The cyanobacterial neurotoxin β-N-methylamino-L-alanine (BMAA) has been detected in species of free-living marine cyanobacteria and may bioaccumulate in the marine food web. In this study, we sampled fin clips from seven different species of sharks in South Florida to survey the occurrence of BMAA using HPLC-FD and Triple Quadrupole LC/MS/MS methods. BMAA was detected in the fins of all species examined with concentrations ranging from 144 to 1836 ng/mg wet weight. Since BMAA has been linked to neurodegenerative diseases, these results may have important relevance to human health. We suggest that consumption of shark fins may increase the risk for human exposure to the cyanobacterial neurotoxin BMAA.

  14. Biological aspects of sharks caught off the Coast of Pernambuco, Northeast Brazil.

    PubMed

    Fischer, A F; Hazin, F H V; Carvalho, F; Viana, D L; Rêgo, M G; Wor, C

    2009-11-01

    One hundred seventeen specimens of sharks were caught along the coast of Pernambuco State, Northern Brazil, between May 2004 and May 2007, among which 86 were blacknose sharks, Carcharhinus acronotus, enabling a more detailed study of the species. Blacknose sharks were caught in the 2 study areas along the Boa Viagem/Piedade and Paiva beaches, accounting for the highest relative abundance among the species caught (73.5% of total). Potentially dangerous sharks, tiger and bull sharks, were also caught in the same areas, whereas hammerhead and blacktip sharks were only captured off Boa Viagem/Piedade. Concerning the blacknose shark, the total length (TL) ranged from 39.0 to 180.0 cm. Among the 38 females analysed, 32 were juveniles, 11 were maturing, 2 were pre-ovulatory and 21 were pregnant. Sexing was possible for 75 of the 83 embryos, 38 of which were males and 37 were females, with a sex proportion of 1:0.9 and total length ranging between 6.4 and 63.5 cm. Ovarian fecundity ranged from 5 to 10 and uterine fecundity from 1 to 3, with an estimated gestational period of 9 months. Among the 48 males, 6 were juveniles and 42 were adults. Both males and females seem to reach sexual maturity at about 105.0 cm TL. Among the 86 stomachs analysed, only 22.1% had contents, with teleosts as the most frequent item.

  15. Global pattern of phylogenetic species composition of shark and its conservation priority.

    PubMed

    Chen, Hungyen; Kishino, Hirohisa

    2015-10-01

    The diversity of marine communities is in striking contrast with the diversity of terrestrial communities. In all oceans, species richness is low in tropical areas and high at latitudes between 20 and 40°. While species richness is a primary metric used in conservation and management strategies, it is important to take into account the complex phylogenetic patterns of species compositions within communities. We measured the phylogenetic skew and diversity of shark communities throughout the world. We found that shark communities in tropical seas were highly phylogenetically skewed, whereas temperate sea communities had phylogenetically diversified species compositions. Interestingly, although geographically distant from one another, tropical sea communities were all highly skewed toward requiem sharks (Carcharhinidae), hammerhead sharks (Sphyrnidae), and whale sharks (Rhincodon typus). Worldwide, the greatest phylogenetic evenness in terms of clades was found in the North Sea and coastal regions of countries in temperate zones, such as the United Kingdom, Ireland, southern Australia, and Chile. This study is the first to examine patterns of phylogenetic diversity of shark communities on a global scale. Our findings suggest that when establishing conservation activities, it is important to take full account of phylogenetic patterns of species composition and not solely use species richness as a target. Protecting areas of high phylogenetic diversity in sharks, which were identified in this study, could form a broader strategy for protecting other threatened marine species.

  16. F-5F Shark Nose radome lightning test

    NASA Technical Reports Server (NTRS)

    Scott, G. W.

    1980-01-01

    A unique F-5F radome wtih a geometry similar to a Shark Nose profile was tested with a high voltage Marx generator, 1,200,000 volts in order to demonstrate the effectiveness of the lightning protection system with currents from 5,000 amperes or greater. An edge discontinuity configuration is a characteristic feature in the forward region of the radome and occasionally serves as an attachment point. The results of nineteen attachment tests at various aspect angles with an air gap of one meter indicated that no damage occurred to the dielectric material of the radom. The test proved the effectiveness of the lightning protection system.

  17. A conservative approach to parallelizing the Sharks World simulation

    NASA Technical Reports Server (NTRS)

    Nicol, David M.; Riffe, Scott E.

    1990-01-01

    Parallelizing a benchmark problem for parallel simulation, the Sharks World, is described. The described solution is conservative, in the sense that no state information is saved, and no 'rollbacks' occur. The used approach illustrates both the principal advantage and principal disadvantage of conservative parallel simulation. The advantage is that by exploiting lookahead an approach was found that dramatically improves the serial execution time, and also achieves excellent speedups. The disadvantage is that if the model rules are changed in such a way that the lookahead is destroyed, it is difficult to modify the solution to accommodate the changes.

  18. Plastic debris straps on threatened blue shark Prionace glauca.

    PubMed

    Colmenero, Ana I; Barría, Claudio; Broglio, Elisabetta; García-Barcelona, Salvador

    2017-02-15

    Juveniles of blue shark Prionace glauca caught in pelagic longlines targeting tuna and swordfish in the Atlantic Ocean and the Mediterranean Sea were found entangled with plastic straps around their gill region. The plastic debris were identified as strapping bands and caused several degrees of injuries on the dorsal musculature and pectoral fins. They were also obstructing the gill slits probably causing breathing issues. These records were uploaded in the web site seawatchers.org, and highlight the potential of citizen science in revealing the occurrence of such problems which could help to measure the effects of plastic debris on marine life.

  19. Shark: Fast Data Analysis Using Coarse-grained Distributed Memory

    DTIC Science & Technology

    2013-05-01

    18. NUMBER OF PAGES 31 19a. NAME OF RESPONSIBLE PERSON a . REPORT unclassified b . ABSTRACT unclassified c. THIS PAGE unclassified Standard...descending order. We could execute the following query in Shark: FROM (SELECT * FROM messages a JOIN profiles b ON (a.user_id = b.user_id and a.ds=’2011-12...TableScan:% a partition:% 2011=12=07 TableScan:% b Stage&1 Group%By Select columns:%all Join Reduce Map Stage&2 Reduce%Output sort:%user_id sort%order

  20. Extreme Inverted Trophic Pyramid of Reef Sharks Supported by Spawning Groupers.

    PubMed

    Mourier, Johann; Maynard, Jeffrey; Parravicini, Valeriano; Ballesta, Laurent; Clua, Eric; Domeier, Michael L; Planes, Serge

    2016-08-08

    The extent of the global human footprint [1] limits our understanding of what is natural in the marine environment. Remote, near-pristine areas provide some baseline expectations for biomass [2, 3] and suggest that predators dominate, producing an inverted biomass pyramid. The southern pass of Fakarava atoll-a biosphere reserve in French Polynesia-hosts an average of 600 reef sharks, two to three times the biomass per hectare documented for any other reef shark aggregations [4]. This huge biomass of predators makes the trophic pyramid inverted. Bioenergetics models indicate that the sharks require ∼90 tons of fish per year, whereas the total fish production in the pass is ∼17 tons per year. Energetic theory shows that such trophic structure is maintained through subsidies [5-9], and empirical evidence suggests that sharks must engage in wide-ranging foraging excursions to meet energy needs [9, 10]. We used underwater surveys and acoustic telemetry to assess shark residency in the pass and feeding behavior and used bioenergetics models to understand energy flow. Contrary to previous findings, our results highlight that sharks may overcome low local energy availability by feeding on fish spawning aggregations, which concentrate energy from other local trophic pyramids. Fish spawning aggregations are known to be targeted by sharks, but they were previously believed to play a minor role representing occasional opportunistic supplements. This research demonstrates that fish spawning aggregations can play a significant role in the maintenance of local inverted pyramids in pristine marine areas. Conservation of fish spawning aggregations can help conserve shark populations, especially if combined with shark fishing bans.

  1. Early-life exposure to climate change impairs tropical shark survival.

    PubMed

    Rosa, Rui; Baptista, Miguel; Lopes, Vanessa M; Pegado, Maria Rita; Paula, José Ricardo; Trübenbach, Katja; Leal, Miguel Costa; Calado, Ricardo; Repolho, Tiago

    2014-10-22

    Sharks are one of the most threatened groups of marine animals worldwide, mostly owing to overfishing and habitat degradation/loss. Although these cartilaginous fish have evolved to fill many ecological niches across a wide range of habitats, they have limited capability to rapidly adapt to human-induced changes in their environments. Contrary to global warming, ocean acidification was not considered as a direct climate-related threat to sharks. Here we show, for the first time, that an early ontogenetic acclimation process of a tropical shark (Chiloscyllium punctatum) to the projected scenarios of ocean acidification (ΔpH = 0.5) and warming (+4°C; 30°C) for 2100 elicited significant impairments on juvenile shark condition and survival. The mortality of shark embryos at the present-day thermal scenarios was 0% both at normocapnic and hypercapnic conditions. Yet routine metabolic rates (RMRs) were significantly affected by temperature, pH and embryonic stage. Immediately after hatching, the Fulton condition of juvenile bamboo sharks was significantly different in individuals that experienced future warming and hypercapnia; 30 days after hatching, survival rapidly declined in individuals experiencing both ocean warming and acidification (up to 44%). The RMR of juvenile sharks was also significantly affected by temperature and pH. The impact of low pH on ventilation rates was significant only under the higher thermal scenario. This study highlights the need of experimental-based risk assessments of sharks to climate change. In other words, it is critical to directly assess risk and vulnerability of sharks to ocean acidification and warming, and such effort can ultimately help managers and policy-makers to take proactive measures targeting most endangered species.

  2. The last frontier: catch records of white sharks (Carcharodon carcharias) in the Northwest Pacific Ocean.

    PubMed

    Christiansen, Heather M; Lin, Victor; Tanaka, Sho; Velikanov, Anatoly; Mollet, Henry F; Wintner, Sabine P; Fordham, Sonja V; Fisk, Aaron T; Hussey, Nigel E

    2014-01-01

    White sharks are highly migratory apex predators, globally distributed in temperate, sub-tropical, and tropical waters. Knowledge of white shark biology and ecology has increased recently based on research at known aggregation sites in the Indian, Atlantic, and Northeast Pacific Oceans; however, few data are available for the Northwest Pacific Ocean. This study provides a meta-analysis of 240 observations of white sharks from the Northwest Pacific Ocean between 1951 and 2012. Records comprise reports of bycatch in commercial fisheries, media accounts, personal communications, and documentation of shark-human interactions from Russia (n = 8), Republic of Korea (22), Japan (129), China (32), Taiwan (45), Philippines (1) and Vietnam (3). Observations occurred in all months, excluding October-January in the north (Russia and Republic of Korea) and July-August in the south (China, Taiwan, Philippines, and Vietnam). Population trend analysis indicated that the relative abundance of white sharks in the region has remained relatively stable, but parameterization of a 75% increase in observer effort found evidence of a minor decline since 2002. Reliably measured sharks ranged from 126-602 cm total length (TL) and 16-2530 kg total weight. The largest shark in this study (602 cm TL) represents the largest measured shark on record worldwide. For all countries combined the sex ratio was non-significantly biased towards females (1∶1.1; n = 113). Of 60 females examined, 11 were confirmed pregnant ranging from the beginning stages of pregnancy (egg cases) to near term (140 cm TL embryos). On average, 6.0±2.2 embryos were found per litter (maximum of 10) and gestation period was estimated to be 20 months. These observations confirm that white sharks are present in the Northwest Pacific Ocean year-round. While acknowledging the difficulties of studying little known populations of a naturally low abundance species, these results highlight the need for dedicated research to

  3. Early-life exposure to climate change impairs tropical shark survival

    PubMed Central

    Rosa, Rui; Baptista, Miguel; Lopes, Vanessa M.; Pegado, Maria Rita; Ricardo Paula, José; Trübenbach, Katja; Leal, Miguel Costa; Calado, Ricardo; Repolho, Tiago

    2014-01-01

    Sharks are one of the most threatened groups of marine animals worldwide, mostly owing to overfishing and habitat degradation/loss. Although these cartilaginous fish have evolved to fill many ecological niches across a wide range of habitats, they have limited capability to rapidly adapt to human-induced changes in their environments. Contrary to global warming, ocean acidification was not considered as a direct climate-related threat to sharks. Here we show, for the first time, that an early ontogenetic acclimation process of a tropical shark (Chiloscyllium punctatum) to the projected scenarios of ocean acidification (ΔpH = 0.5) and warming (+4°C; 30°C) for 2100 elicited significant impairments on juvenile shark condition and survival. The mortality of shark embryos at the present-day thermal scenarios was 0% both at normocapnic and hypercapnic conditions. Yet routine metabolic rates (RMRs) were significantly affected by temperature, pH and embryonic stage. Immediately after hatching, the Fulton condition of juvenile bamboo sharks was significantly different in individuals that experienced future warming and hypercapnia; 30 days after hatching, survival rapidly declined in individuals experiencing both ocean warming and acidification (up to 44%). The RMR of juvenile sharks was also significantly affected by temperature and pH. The impact of low pH on ventilation rates was significant only under the higher thermal scenario. This study highlights the need of experimental-based risk assessments of sharks to climate change. In other words, it is critical to directly assess risk and vulnerability of sharks to ocean acidification and warming, and such effort can ultimately help managers and policy-makers to take proactive measures targeting most endangered species. PMID:25209942

  4. How great white sharks nourish their embryos to a large size: evidence of lipid histotrophy in lamnoid shark reproduction.

    PubMed

    Sato, Keiichi; Nakamura, Masaru; Tomita, Taketeru; Toda, Minoru; Miyamoto, Kei; Nozu, Ryo

    2016-09-15

    The great white shark (Carcharodon carcharias) exhibits viviparous and oophagous reproduction. A 4950 mm total length (TL) gravid female accidentally caught by fishermen in the Okinawa Prefecture, Southern Japan carried six embryos (543-624 mm TL, three in each uterus). Both uteri contained copious amounts of yellowish viscous uterine fluid (over 79.2 litres in the left uterus), nutrient eggs and broken egg cases. The embryos had yolk stomachs that had ruptured, the mean volume of which was approximately 197.9 ml. Embryos had about 20 rows of potentially functional teeth in the upper and lower jaws. Periodic acid Schiff (PAS)-positive substances were observed on the surface and in the cytoplasm of the epithelial cells, and large, secretory, OsO4-oxidized lipid droplets of various sizes were distributed on the surface of the villous string epithelium on the uterine wall. Histological examination of the uterine wall showed it to consist of villi, similar to the trophonemata of Dasyatidae rays, suggesting that the large amount of fluid found in the uterus of the white shark was likely required for embryo nutrition. We conclude that: (1) the lipid-rich fluid is secreted from the uterine epithelium only in early gestation before the onset of oophagy, (2) the embryos probably use the abundant uterine fluid and encased nutrient eggs for nutrition at this stage of their development, and (3) the uterine fluid is the major source of embryonic nutrition before oophagy onset. This is the first record of the lipid histotrophy of reproduction among all shark species.

  5. How great white sharks nourish their embryos to a large size: evidence of lipid histotrophy in lamnoid shark reproduction

    PubMed Central

    Sato, Keiichi; Nakamura, Masaru; Tomita, Taketeru; Toda, Minoru; Miyamoto, Kei; Nozu, Ryo

    2016-01-01

    ABSTRACT The great white shark (Carcharodon carcharias) exhibits viviparous and oophagous reproduction. A 4950 mm total length (TL) gravid female accidentally caught by fishermen in the Okinawa Prefecture, Southern Japan carried six embryos (543-624 mm TL, three in each uterus). Both uteri contained copious amounts of yellowish viscous uterine fluid (over 79.2 litres in the left uterus), nutrient eggs and broken egg cases. The embryos had yolk stomachs that had ruptured, the mean volume of which was approximately 197.9 ml. Embryos had about 20 rows of potentially functional teeth in the upper and lower jaws. Periodic acid Schiff (PAS)-positive substances were observed on the surface and in the cytoplasm of the epithelial cells, and large, secretory, OsO4-oxidized lipid droplets of various sizes were distributed on the surface of the villous string epithelium on the uterine wall. Histological examination of the uterine wall showed it to consist of villi, similar to the trophonemata of Dasyatidae rays, suggesting that the large amount of fluid found in the uterus of the white shark was likely required for embryo nutrition. We conclude that: (1) the lipid-rich fluid is secreted from the uterine epithelium only in early gestation before the onset of oophagy, (2) the embryos probably use the abundant uterine fluid and encased nutrient eggs for nutrition at this stage of their development, and (3) the uterine fluid is the major source of embryonic nutrition before oophagy onset. This is the first record of the lipid histotrophy of reproduction among all shark species. PMID:27635035

  6. Late Cretaceous restructuring of terrestrial communities facilitated the end-Cretaceous mass extinction in North America

    NASA Astrophysics Data System (ADS)

    Mitchell, Jonathan S.; Roopnarine, Peter D.; Angielczyk, Kenneth D.

    2012-11-01

    The sudden environmental catastrophe in the wake of the end-Cretaceous asteroid impact had drastic effects that rippled through animal communities. To explore how these effects may have been exacerbated by prior ecological changes, we used a food-web model to simulate the effects of primary productivity disruptions, such as those predicted to result from an asteroid impact, on ten Campanian and seven Maastrichtian terrestrial localities in North America. Our analysis documents that a shift in trophic structure between Campanian and Maastrichtian communities in North America led Maastrichtian communities to experience more secondary extinction at lower levels of primary production shutdown and possess a lower collapse threshold than Campanian communities. Of particular note is the fact that changes in dinosaur richness had a negative impact on the robustness of Maastrichtian ecosystems against environmental perturbations. Therefore, earlier ecological restructuring may have exacerbated the impact and severity of the end-Cretaceous extinction, at least in North America.

  7. Late Cretaceous restructuring of terrestrial communities facilitated the end-Cretaceous mass extinction in North America.

    PubMed

    Mitchell, Jonathan S; Roopnarine, Peter D; Angielczyk, Kenneth D

    2012-11-13

    The sudden environmental catastrophe in the wake of the end-Cretaceous asteroid impact had drastic effects that rippled through animal communities. To explore how these effects may have been exacerbated by prior ecological changes, we used a food-web model to simulate the effects of primary productivity disruptions, such as those predicted to result from an asteroid impact, on ten Campanian and seven Maastrichtian terrestrial localities in North America. Our analysis documents that a shift in trophic structure between Campanian and Maastrichtian communities in North America led Maastrichtian communities to experience more secondary extinction at lower levels of primary production shutdown and possess a lower collapse threshold than Campanian communities. Of particular note is the fact that changes in dinosaur richness had a negative impact on the robustness of Maastrichtian ecosystems against environmental perturbations. Therefore, earlier ecological restructuring may have exacerbated the impact and severity of the end-Cretaceous extinction, at least in North America.

  8. Late Cretaceous restructuring of terrestrial communities facilitated the end-Cretaceous mass extinction in North America

    PubMed Central

    Roopnarine, Peter D.; Angielczyk, Kenneth D.

    2012-01-01

    The sudden environmental catastrophe in the wake of the end-Cretaceous asteroid impact had drastic effects that rippled through animal communities. To explore how these effects may have been exacerbated by prior ecological changes, we used a food-web model to simulate the effects of primary productivity disruptions, such as those predicted to result from an asteroid impact, on ten Campanian and seven Maastrichtian terrestrial localities in North America. Our analysis documents that a shift in trophic structure between Campanian and Maastrichtian communities in North America led Maastrichtian communities to experience more secondary extinction at lower levels of primary production shutdown and possess a lower collapse threshold than Campanian communities. Of particular note is the fact that changes in dinosaur richness had a negative impact on the robustness of Maastrichtian ecosystems against environmental perturbations. Therefore, earlier ecological restructuring may have exacerbated the impact and severity of the end-Cretaceous extinction, at least in North America. PMID:23112149

  9. New Australian sauropods shed light on Cretaceous dinosaur palaeobiogeography

    PubMed Central

    Poropat, Stephen F.; Mannion, Philip D.; Upchurch, Paul; Hocknull, Scott A.; Kear, Benjamin P.; Kundrát, Martin; Tischler, Travis R.; Sloan, Trish; Sinapius, George H. K.; Elliott, Judy A.; Elliott, David A.

    2016-01-01

    Australian dinosaurs have played a rare but controversial role in the debate surrounding the effect of Gondwanan break-up on Cretaceous dinosaur distribution. Major spatiotemporal gaps in the Gondwanan Cretaceous fossil record, coupled with taxon incompleteness, have hindered research on this effect, especially in Australia. Here we report on two new sauropod specimens from the early Late Cretaceous of Queensland, Australia, that have important implications for Cretaceous dinosaur palaeobiogeography. Savannasaurus elliottorum gen. et sp. nov. comprises one of the most complete Cretaceous sauropod skeletons ever found in Australia, whereas a new specimen of Diamantinasaurus matildae includes the first ever cranial remains of an Australian sauropod. The results of a new phylogenetic analysis, in which both Savannasaurus and Diamantinasaurus are recovered within Titanosauria, were used as the basis for a quantitative palaeobiogeographical analysis of macronarian sauropods. Titanosaurs achieved a worldwide distribution by at least 125 million years ago, suggesting that mid-Cretaceous Australian sauropods represent remnants of clades which were widespread during the Early Cretaceous. These lineages would have entered Australasia via dispersal from South America, presumably across Antarctica. High latitude sauropod dispersal might have been facilitated by Albian–Turonian warming that lifted a palaeoclimatic dispersal barrier between Antarctica and South America. PMID:27763598

  10. Fossil evidence for Cretaceous escalation in angiosperm leaf vein evolution.

    PubMed

    Feild, Taylor S; Brodribb, Timothy J; Iglesias, Ari; Chatelet, David S; Baresch, Andres; Upchurch, Garland R; Gomez, Bernard; Mohr, Barbara A R; Coiffard, Clement; Kvacek, Jiri; Jaramillo, Carlos

    2011-05-17

    The flowering plants that dominate modern vegetation possess leaf gas exchange potentials that far exceed those of all other living or extinct plants. The great divide in maximal ability to exchange CO(2) for water between leaves of nonangiosperms and angiosperms forms the mechanistic foundation for speculation about how angiosperms drove sweeping ecological and biogeochemical change during the Cretaceous. However, there is no empirical evidence that angiosperms evolved highly photosynthetically active leaves during the Cretaceous. Using vein density (D(V)) measurements of fossil angiosperm leaves, we show that the leaf hydraulic capacities of angiosperms escalated several-fold during the Cretaceous. During the first 30 million years of angiosperm leaf evolution, angiosperm leaves exhibited uniformly low vein D(V) that overlapped the D(V) range of dominant Early Cretaceous ferns and gymnosperms. Fossil angiosperm vein densities reveal a subsequent biphasic increase in D(V). During the first mid-Cretaceous surge, angiosperm D(V) first surpassed the upper bound of D(V) limits for nonangiosperms. However, the upper limits of D(V) typical of modern megathermal rainforest trees first appear during a second wave of increased D(V) during the Cretaceous-Tertiary transition. Thus, our findings provide fossil evidence for the hypothesis that significant ecosystem change brought about by angiosperms lagged behind the Early Cretaceous taxonomic diversification of angiosperms.

  11. Climate-mediated diversification of turtles in the Cretaceous

    PubMed Central

    Nicholson, David B.; Holroyd, Patricia A.; Benson, Roger B. J.; Barrett, Paul M.

    2015-01-01

    Chelonians are ectothermic, with an extensive fossil record preserved in diverse palaeoenvironmental settings: consequently, they represent excellent models for investigating organismal response to long-term environmental change. We present the first Mesozoic chelonian taxic richness curve, subsampled to remove geological/collection biases, and demonstrate that their palaeolatitudinal distributions were climate mediated. At the Jurassic/Cretaceous transition, marine taxa exhibit minimal diversity change, whereas non-marine diversity increases. A Late Cretaceous peak in ‘global' non-marine subsampled richness coincides with high palaeolatitude occurrences and the Cretaceous thermal maximum (CTM): however, this peak also records increased geographic sampling and is not recovered in continental-scale diversity patterns. Nevertheless, a model-detrended richness series (insensitive to geographic sampling) also recovers a Late Cretaceous peak, suggesting genuine geographic range expansion among non-marine turtles during the CTM. Increased Late Cretaceous diversity derives from intensive North American sampling, but subsampling indicates that Early Cretaceous European/Asian diversity may have exceeded that of Late Cretaceous North America. PMID:26234913

  12. Fossil evidence for Cretaceous escalation in angiosperm leaf vein evolution

    PubMed Central

    Feild, Taylor S.; Brodribb, Timothy J.; Iglesias, Ari; Chatelet, David S.; Baresch, Andres; Upchurch, Garland R.; Gomez, Bernard; Mohr, Barbara A. R.; Coiffard, Clement; Kvacek, Jiri; Jaramillo, Carlos

    2011-01-01

    The flowering plants that dominate modern vegetation possess leaf gas exchange potentials that far exceed those of all other living or extinct plants. The great divide in maximal ability to exchange CO2 for water between leaves of nonangiosperms and angiosperms forms the mechanistic foundation for speculation about how angiosperms drove sweeping ecological and biogeochemical change during the Cretaceous. However, there is no empirical evidence that angiosperms evolved highly photosynthetically active leaves during the Cretaceous. Using vein density (DV) measurements of fossil angiosperm leaves, we show that the leaf hydraulic capacities of angiosperms escalated several-fold during the Cretaceous. During the first 30 million years of angiosperm leaf evolution, angiosperm leaves exhibited uniformly low vein DV that overlapped the DV range of dominant Early Cretaceous ferns and gymnosperms. Fossil angiosperm vein densities reveal a subsequent biphasic increase in DV. During the first mid-Cretaceous surge, angiosperm DV first surpassed the upper bound of DV limits for nonangiosperms. However, the upper limits of DV typical of modern megathermal rainforest trees first appear during a second wave of increased DV during the Cretaceous-Tertiary transition. Thus, our findings provide fossil evidence for the hypothesis that significant ecosystem change brought about by angiosperms lagged behind the Early Cretaceous taxonomic diversification of angiosperms. PMID:21536892

  13. Co-occurrence of Pacific sleeper sharks Somniosus pacificus and harbor seals Phoca vitulina in Glacier Bay

    USGS Publications Warehouse

    Taggart, S.J.; Andrews, A.G.; Mondragon, Jennifer; Mathews, E.A.

    2005-01-01

    We present evidence that Pacific sleeper sharks Somniosus pacificus co-occur with harbor seals Phoca vitulina in Glacier Bay, Alaska, and that these sharks scavenge or prey on marine mammals. In 2002, 415 stations were fished throughout Glacier Bay on a systematic sampling grid. Pacific sleeper sharks were caught at 3 of the 415 stations, and at one station a Pacific halibut Hippoglossus stenolepis was caught with a fresh bite, identified as the bite of a sleeper shark. All 3 sharks and the shark-bitten halibut were caught at stations near the mouth of Johns Hopkins Inlet, a glacial fjord with the highest concentration of seals in Glacier Bay. Using a bootstrap technique, we estimated the probability of sampling the sharks (and the shark-bitten halibut) in the vicinity of Johns Hopkins Inlet. If sharks were randomly distributed in Glacier Bay, the probability of sampling all 4 pots at the mouth of Johns Hopkins Inlet was very low (P = 0.00002). The highly non-random distribution of the sleeper sharks located near the largest harbor seal pupping and breeding colony in Glacier Bay suggests that these 2 species co-occur and may interact ecologically in or near Johns Hopkins Inlet.

  14. Cretaceous-Tertiary findings, paradigms and problems

    NASA Technical Reports Server (NTRS)

    Officer, C. B.; Drake, C. L.

    1988-01-01

    The asteroid hypothesis has stimulated numerous studies of the paleontological record at Cretaceous/Tertiary time as well as of geological indicators of environmental crisis preserved in the rock record. Both extinctions and geological anomalies often occur at times that do not appear to be synchronous or instantaneous. The record includes paleontological indicators of dinosaurs, terrestrial flora, marine planktonic organisms, and shallow water marine macrofauna and geological phenomena include occurrences of iridium and other platinum metals, trace elements, clay mineralogy, shocked minerals, soot, microspherules, and isotopes of osmium, strontium and carbon. These findings are reviewed in the context of the alternate hypotheses of an exogenic cause, involving either a single asteroid impact or multiple commentary impacts, and an endogenic cause, involving intense global volcanism and major sea level regression.

  15. Excretory transport of xenobiotics by dogfish shark rectal gland tubules.

    PubMed

    Miller, D S; Masereeuw, R; Henson, J; Karnaky, K J

    1998-09-01

    Marine elasmobranch rectal gland is a specialized, osmoregulatory organ composed of numerous blind-ended, branched tubules emptying into a central duct. To date, NaCl excretion has been its only described function. Here we use isolated rectal gland tubule fragments from dogfish shark (Squalus acanthias), fluorescent xenobiotics, and confocal microscopy to describe a second function, xenobiotic excretion. Isolated rectal gland tubules rapidly transported the fluorescent organic anion sulforhodamine 101 from bath to lumen. Luminal accumulation was concentrative, saturable, and inhibited by cyclosporin A (CSA), chlorodinitrobenzene, leukotriene C4, and KCN. Inhibitors of renal organic anion transport (probenecid, p-aminohippurate), organic cation transport (tetraethylammonium and verapamil), and P-glycoprotein (verapamil) were without effect. Cellular accumulation of sulforhodamine 101 was not concentrative, saturable, or inhibitable. Rectal gland tubules did not secrete fluorescein, daunomycin, or a fluorescent CSA derivative. Finally, frozen rectal gland sections stained with an antibody to a hepatic canalicular multispecific organic anion transporter (cMOAT or MRP2) showed heavy and specific staining on the luminal membrane of the epithelial cells. We conclude that rectal gland is capable of active and specific excretion of xenobiotics and that such transport is mediated by a shark analog of MRP2, an ATP-driven xenobiotic transporter, but not by P-glycoprotein.

  16. Anatomy and evolution of heterocercal tail in lamniform sharks.

    PubMed

    Kim, Sun H; Shimada, Kenshu; Rigsby, Cynthia K

    2013-03-01

    Lamniformes is a small shark group consisting of 15 extant species with remarkably diverse lifestyles and a wide range in heterocercal tail morphology. The caudal fin morphology must be related to their lifestyle because the tail is a main locomotive structure in sharks, but such relationships have remained largely uninvestigated. Here, the morphology-lifestyle relationship in lamniforms is examined through phylogenetic mapping. This study suggests that, within Lamniformes, caudal fins with a more horizontally directed curvature of the vertebral column are plesiomorphic, whereas those with a large dorsally directed curvature of the vertebral column are apomorphic. It also shows that caudal fins with posteriorly directed hypochordal rays are plesiomorphic, and that those with ventrally directed hypochordal rays are apomorphic within Lamniformes. Four basic caudal fin types are recognized in lamniforms on the basis of these skeletal variables in which one corollary is that the evolution of external morphology of caudal fin does not necessarily correspond to the evolution of its skeletal anatomy. This study also demonstrates that specific lifestyles seen in different lamniforms are indeed correlative with different caudal fin types in which a less asymmetrical heterocercal tail is a derived feature in lamniforms that evolved for fast swimming to capture fast swimming prey.

  17. Angiogenic inhibitor protein fractions derived from shark cartilage.

    PubMed

    Bargahi, Afshar; Rabbani-Chadegani, Azra

    2008-02-01

    Development of therapies based on the growth inhibition of new blood vessels is among the most intensively studied approaches to the treatment of cancer and other angiogenesis-related diseases. Shark cartilage has been proven to have inhibitory effects on the endothelial cell angiogenesis, metastasis, cell adhesion and MMP (matrix metalloprotease) activity. In the present study, we have used a chromatography-based procedure for the isolation and partial purification of a shark cartilage protein fraction containing anti-angiogenesis activity. Proteins were extracted in 4 M guanidinium chloride, followed by sequential anion- and cation-exchange column chromatography. Angiogenesis assays were performed using the rat aortic ring and chick CAM (chorioallantoic membrane) assay models. The results show that the final fraction contains two proteins with molecular masses of 14.7 and 16 kDa. The protein fraction is able to block microvessel sprouting in the collagen-embedded rat aortic ring assay in vitro and inhibition of capillary sprouting in the CAM assay in vivo. It is suggested that these are partially purified anti-angiogenesis proteins, which have further biotechnological or biomedical applications.

  18. A Palaeozoic shark with osteichthyan-like branchial arches.

    PubMed

    Pradel, Alan; Maisey, John G; Tafforeau, Paul; Mapes, Royal H; Mallatt, Jon

    2014-05-29

    The evolution of serially arranged, jointed endoskeletal supports internal to the gills--the visceral branchial arches--represents one of the key events in early jawed vertebrate (gnathostome) history, because it provided the morphological basis for the subsequent evolution of jaws. However, until now little was known about visceral arches in early gnathostomes, and theories about gill arch evolution were driven by information gleaned mostly from both modern cartilaginous (chondrichthyan) and bony (osteichthyan) fishes. New fossil discoveries can profoundly affect our understanding of evolutionary history, by revealing hitherto unseen combinations of primitive and derived characters. Here we describe a 325 million year (Myr)-old Palaeozoic shark-like fossil that represents, to our knowledge, the earliest identified chondrichthyan in which the complete gill skeleton is three-dimensionally preserved in its natural position. Its visceral arch arrangement is remarkably osteichthyan-like, suggesting that this may represent the common ancestral condition for crown gnathostomes. Our findings thus reinterpret the polarity of some arch features of the crown jawed vertebrates and invert the classic hypothesis, in which modern sharks retain the ancestral condition. This study underscores the importance of early chondrichthyans in resolving the evolutionary history of jawed vertebrates.

  19. Energetics of the yo-yo dives of predatory sharks.

    PubMed

    Iosilevskii, Gil; Papastamatiou, Yannis P; Meyer, Carl G; Holland, Kim N

    2012-02-07

    Sharks zigzag vertically through the water in a series of alternating ascending and descending segments, changing depth by a few tens of meters over a period of a few hundred seconds. This 'yo-yo' like behavior has several characteristic patterns, identifiable by the way the swimming and vertical velocities vary along the dive. We suggest that these patterns represent different optimal strategies minimizing the cost of locomotion under different constraints; moreover, these constraints can be inferred by matching the pattern of a dive with a (standard) optimal swimming strategy for which the constraints are known. We used three sets of constraints and two definitions of the 'cost of locomotion' to analytically generate four standard optimal strategies; we have used high resolution tracking data from four tiger sharks to identify two different yo-yo diving patterns. These patterns seem to match two of the standard strategies: one that maximizes range, given an alternating power supply (e.g., swimming actively on ascents and lazily on descents); and the other that maximizes range, given an alternating vertical velocity (implying an 'intentional' up-and-down motion).

  20. Molecular Phylogeny of the Bamboo Sharks (Chiloscyllium spp.)

    PubMed Central

    Masstor, Noor Haslina; Samat, Abdullah; Nor, Shukor Md; Md-Zain, Badrul Munir

    2014-01-01

    Chiloscyllium, commonly called bamboo shark, can be found inhabiting the waters of the Indo-West Pacific around East Asian countries such as Malaysia, Myanmar, Thailand, Singapore, and Indonesia. The International Union for Conservation of Nature (IUCN) Red List has categorized them as nearly threatened sharks out of their declining population status due to overexploitation. A molecular study was carried out to portray the systematic relationships within Chiloscyllium species using 12S rRNA and cytochrome b gene sequences. Maximum parsimony and Bayesian were used to reconstruct their phylogeny trees. A total of 381 bp sequences' lengths were successfully aligned in the 12S rRNA region, with 41 bp sites being parsimony-informative. In the cytochrome b region, a total of 1120 bp sites were aligned, with 352 parsimony-informative characters. All analyses yield phylogeny trees on which C. indicum has close relationships with C. plagiosum. C. punctatum is sister taxon to both C. indicum and C. plagiosum while C. griseum and C. hasseltii formed their own clade as sister taxa. These Chiloscyllium classifications can be supported by some morphological characters (lateral dermal ridges on the body, coloring patterns, and appearance of hypobranchials and basibranchial plate) that can clearly be used to differentiate each species. PMID:25013766

  1. Geography of cretaceous extinctions: Data base development

    NASA Technical Reports Server (NTRS)

    Raup, D. M.

    1991-01-01

    Data bases built from the source literature are plagued by problems of data quality. Unless the data acquisition is done by experts, working slowly, the data base may contain so much garbage that true signals and patterns cannot be detected. On the other hand, high quality data bases develop so slowly that satisfactory statistical analysis may never be possible due to the small sample sizes. Results of a test are presented of the opposite strategy: rapid data acquisition by non-experts with minimal control on data quality. A published list of 186 species and genera of fossil invertibrates of the latest Cretaceous Age (Maestrichtian) were located through a random search of the paleobiological and geological literature. The geographic location for each faunal list was then transformed electronically to Maestrichtian latitude and longitude and the lists were further digested to identify the genera occurring in each ten-degree, latitude-longitude block. The geographical lists were clustered using the Otsuka similarity coefficient and a standard unweight-pair-group method. The resulting clusters are remarkably consistent geographically, indicating that a strong biogeographic signal is visible despite low-quality data. A further test evaluated the geographic pattern of end-Cretaceaous extinctions. All genera in the data base were compared with Sepkoski's compendium of time ranges of genera to determine which of the reported genera survived the Cretaceous mass extinction. In turn, extinction rates for the ten-degree, latitude-longitude blocks were mapped. The resulting distribution is readily interpretable as a robust pattern of the geography of the mass extinction. The study demonstrates that a low-quality data base, built rapidly, can provide a basis for meaningful analysis of past biotic events.

  2. Latest Cretaceous sedimentation on Peninsular Ranges block

    SciTech Connect

    Abbott, P.L.

    1986-04-01

    The Peninsular Ranges block is dominated by a Late Jurassic-middle Cretaceous batholithic belt that extends from the Santa Ana Mountains in southern California southward through the state of Baja California. From paleomagnetic evidence, the block appears to have moved north about 11/sup 0/ with respect to the North American craton since the Late Cretaceous. The Campanian-Maestrichtian sedimentary record along the western side of the block shows that sedimentation occurred contemporaneously with faulting. Dominantly coarse sediments were stripped off the batholithic complex, carried westward relatively short distances, and deposited in alluvial-fan, fluvial, fan-delta, and shelf environments as well as in submarine fans built into local, fault-created basins. The Peninsular Ranges block apparently moved northward in response to oblique subduction of the Farallon plate; it seemingly rode along on a reasonably even keel as transcurrent faulting wrenched pieces off its western side. The steady keel allowed the sedimentary record to reflect eustatic changes. Along the west side of the Peninsular Ranges block, the Campanian column typically has a retrogradational sequence lower in the section that is overlain by a progradational sequence. This pattern holds for the Santa Ana Mountains, San Diego, California, and Descanso, Salsipuedes, and El Rosario, Baja California. Eustatic sea level changes left a dominant imprint on the entire stratigraphic column, although local facies may be distinctly different because basins were created by contemporaneous faulting. The fault basins may have had a borderland-style topography, judging from their relatively small size, discontinuous and sporadic development, and apparently linear margins.

  3. Lower Cretaceous lacustrine deposits and paleosol development

    SciTech Connect

    Mantzios, C.; Vondra, C.F.

    1987-05-01

    The Little Sheep Mudstone Member of the Lower Cretaceous Cloverly Formation in the Big Horn basin, Wyoming, is predominantly a montmorillonite-rich lacustrine deposit. It is informally subdivided into lower and upper units. The lower unit is a playa-lake deposit rich in bentonite derived from the alteration of volcanic ash which had its origin to the west. Horizons of silcretes and septarian nodules are common. The latter show irregular lenticular cracks and are filled with coarse calcite and barite crystals. They formed by desiccation of a clay-gel during dry periods. Silcretes are diagenetic products that formed due to the lowering of silica solubility along with decreasing of the pH value. Desiccation cracks on the playa surface were filled with chalcedony which later underwent replacement by calcite. The upper unit is a perennial saline lake deposit similar to that accumulating in Lake Magadi of the Eastern Rift Valley, Kenya, Chert nodules covered with calcium carbonate form stratigraphically persistent horizons. This chert is the product of the magadiite-kenyaite-chert transformation of Hay. Lenticular devitrified tuffs occurring at various stratigraphic positions up to 3 m thick were deposited in depressions or swales. Locally the tuffs show evidence of mass movement. Pedogenic features in both units indicate paleosol development. Tree trunks, plant roots, burrows, clay-rich zones, and organic-rich A and more iron-rich B master horizons are recognized. These paleosols resemble modern-day Vertisols. The lower unit is not as extensive areally as the upper unit which is present throughout the Big Horn basin, indicating that extensive lakes occurred during the Early Cretaceous in the Sevier foreland basin.

  4. Cretaceous Vertebrate Tracksites - Korean Cretaceous Dinosaur Coast World Heritage Nomination Site

    NASA Astrophysics Data System (ADS)

    Huh, M.; Woo, K. S.; Lim, J. D.; Paik, I. S.

    2009-04-01

    South Korea is one of the best known regions in the world for Cretaceous fossil footprints, which are also world-renowned. Korea has produced more scientifically named bird tracks (ichnotaxa) than any other region in the world. It has also produced the world's largest pterosaur tracks. Dinosaur tracksites also have the highest frequency of vertebrate track-bearing levels currently known in any stratigraphic sequence. Among the areas that have the best track records, and the greatest scientific significance with best documentation, Korea ranks very highly. Objective analysis of important individual tracksites and tracksite regions must be based on multiple criteria including: size of site, number of tracks, trackways and track bearing levels, number of valid named ichnotaxa including types, number of scientific publications, quality of preservation. The unique and distinctive dinosaur tracksites are known as one of the world's most important dinosaur track localities. In particular, the dinosaur track sites in southern coastal area of Korea are very unique. In the sites, we have excavated over 10,000 dinosaur tracks. The Hwasun sites show diverse gaits with unusual walking patterns and postures in some tracks. The pterosaur tracks are the most immense in the world. The longest pterosaur trackway yet known from any track sites suggests that pterosaurs were competent terrestrial locomotors. This ichnofauna contains the first pterosaur tracks reported from Asia. The Haenam Uhangri pterosaur assigns to a new genus Haenamichnus which accomodates the new ichnospecies, Haenamichnus uhangriensis. At least 12 track types have been reported from the Haman and Jindong Formations (probably late Lower Cretaceous). These include the types of bird tracks assigned to Koreanornis, Jindongornipes, Ignotornis and Goseongornipes. In addition the bird tracks Hwangsanipes, Uhangrichnus, the pterosaur track Haenamichnus and the dinosaur tracks, Brontopodus, Caririchnium, Minisauripus and

  5. 75 FR 9158 - Atlantic Coastal Fisheries Cooperative Management Act Provisions; Coastal Sharks Fishery

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-01

    ... National Oceanic and Atmospheric Administration RIN 0648-XU54 Atlantic Coastal Fisheries Cooperative Management Act Provisions; Coastal Sharks Fishery AGENCY: National Marine Fisheries Service (NMFS), National.... SUMMARY: NMFS announces that on February 4, 2010, the Atlantic States Marine Fisheries...

  6. 76 FR 65673 - Atlantic Highly Migratory Species; Atlantic Shark Management Measures; Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-24

    ... end overfishing, as necessary. The notice provided an incorrect date for a scoping meeting held in... rulemaking to rebuild and/or end overfishing of these Atlantic shark stocks and to prepare an...

  7. Pectoral Fin of the Megamouth Shark: Skeletal and Muscular Systems, Skin Histology, and Functional Morphology

    PubMed Central

    Tomita, Taketeru; Tanaka, Sho; Sato, Keiichi; Nakaya, Kazuhiro

    2014-01-01

    This is the first known report on the skeletal and muscular systems, and the skin histology, of the pectoral fin of the rare planktivorous megamouth shark Megachasma pelagios. The pectoral fin is characterized by three features: 1) a large number of segments in the radial cartilages; 2) highly elastic pectoral fin skin; and 3) a vertically-rotated hinge joint at the pectoral fin base. These features suggest that the pectoral fin of the megamouth shark is remarkably flexible and mobile, and that this flexibility and mobility enhance dynamic lift control, thus allowing for stable swimming at slow speeds. The flexibility and mobility of the megamouth shark pectoral fin contrasts with that of fast-swimming sharks, such as Isurus oxyrhinchus and Lamna ditropis, in which the pectoral fin is stiff and relatively immobile. PMID:24465959

  8. Is the scaling of swim speed in sharks driven by metabolism?

    PubMed

    Jacoby, David M P; Siriwat, Penthai; Freeman, Robin; Carbone, Chris

    2015-12-01

    The movement rates of sharks are intrinsically linked to foraging ecology, predator-prey dynamics and wider ecosystem functioning in marine systems. During ram ventilation, however, shark movement rates are linked not only to ecological parameters, but also to physiology, as minimum speeds are required to provide sufficient water flow across the gills to maintain metabolism. We develop a geometric model predicting a positive scaling relationship between swim speeds in relation to body size and ultimately shark metabolism, taking into account estimates for the scaling of gill dimensions. Empirical data from 64 studies (26 species) were compiled to test our model while controlling for the influence of phylogenetic similarity between related species. Our model predictions were found to closely resemble the observed relationships from tracked sharks, providing a means to infer mobility in particularly intractable species.

  9. Cloning and characterization of tissue inhibitor of metalloproteinase-3 (TIMP-3) from shark, Scyliorhinus torazame.

    PubMed

    Kim, J T; Kim, M S; Bae, M K; Song, H S; Ahn, M Y; Kim, Y J; Lee, S J; Kim, K W

    2001-01-26

    We cloned the full-length cDNA encoding TIMP-3 from the cartilage of cloudy dogfish, Scyliorhinus torazame. The entire open reading frame was composed of 645 nucleotides and 214 residues including 12 conserved cysteines and asparagine-184, a putative site for N-linked sugars. It showed about 72% identity to those of other species based on the deduced amino acid sequence. The mRNA of shark TIMP-3 were expressed abundantly in brain and cartilage tissues. To investigate the roles of shark TIMP-3, an expression vector was constructed and transfected into HT1080 human fibrosarcoma cells. Overexpression of shark TIMP-3 reduced the activity of MMP-2 in gelatin zymography. Through human Alu PCR based CAM assay, we also confirmed that shark TIMP-3 transfected HT1080 cells had less intravasation effects.

  10. Shark-cartilage containing preparation protects cells against hydrogen peroxide induced damage and mutagenesis.

    PubMed

    Gomes, E M; Souto, P R; Felzenszwalb, I

    1996-04-06

    Natural products from flora and fauna are frequently used as nutritional supplements and medicaments. Two short-term assays were carried out and negative results were obtained for shark-cartilage containing preparation. The tests employed were the Salmonella/mammalian microsome assay using tester strains TA97, TA98, TA100, TA102 and TA1535 with or without S9 mix and the SOS-Chromotest with Escherichia coli strain PQ37. Evidence for shark-cartilage containing preparation functioning as an antimutagen was detected. Using bacterial survival assays with Escherichia coli fpg (BH20) and xthA (BW9091), we investigated the putative role of shark-cartilage containing preparation in protecting cells against lesions induced by hydrogen peroxide in normal and low iron level conditions. Our data suggest that shark-cartilage containing preparation can play a scavenger role for reactive oxygen species and protect against DNA lesions in both conditions.

  11. Evaluation of dredged material proposed for ocean disposal from Shark River Project area

    SciTech Connect

    Antrim, L.D.; Gardiner, W.W.; Barrows, E.S.; Borde, A.B.

    1996-09-01

    The objective of the Shark River Project was to evaluate proposed dredged material to determine its suitability for unconfined ocean disposal at the Mud Dump Site. Tests and analyses were conducted on the Shark River sediments. The evaluation of proposed dredged material consisted of bulk sediment chemical and physical analysis, chemical analyses of dredging site water and elutriate, water-column and benthic acute toxicity tests, and bioaccumulation tests. Individual sediment core samples collected from the Shark River were analyzed for grain size, moisture content, and total organic carbon (TOC). One sediment composite was analyzed for bulk density, specific gravity, metals, chlorinated pesticides, polychlorinated biphenyl (PCB) congeners, polynuclear aromatic hydrocarbons (PAHs), and 1,4- dichlorobenzene. Dredging site water and elutriate, prepared from suspended-particulate phase (SPP) of the Shark River sediment composite, were analyzed for metals, pesticides, and PCBs. Benthic acute toxicity tests and bioaccumulation tests were performed.

  12. Is the scaling of swim speed in sharks driven by metabolism?

    PubMed Central

    Jacoby, David M. P.; Siriwat, Penthai; Freeman, Robin; Carbone, Chris

    2015-01-01

    The movement rates of sharks are intrinsically linked to foraging ecology, predator–prey dynamics and wider ecosystem functioning in marine systems. During ram ventilation, however, shark movement rates are linked not only to ecological parameters, but also to physiology, as minimum speeds are required to provide sufficient water flow across the gills to maintain metabolism. We develop a geometric model predicting a positive scaling relationship between swim speeds in relation to body size and ultimately shark metabolism, taking into account estimates for the scaling of gill dimensions. Empirical data from 64 studies (26 species) were compiled to test our model while controlling for the influence of phylogenetic similarity between related species. Our model predictions were found to closely resemble the observed relationships from tracked sharks, providing a means to infer mobility in particularly intractable species. PMID:26631246

  13. 77 FR 8218 - Atlantic Highly Migratory Species; Atlantic Shark Management Measures; 2012 Research Fishery

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-14

    ... maintain time series data for stock assessments and to meet NMFS' research objectives. The shark research... meeting for selected participants. In this notice, NMFS announces the date and time of that meeting....

  14. 78 FR 14515 - Atlantic Highly Migratory Species; Atlantic Shark Management Measures; 2012 Research Fishery

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-06

    ..., a shark research fishery to maintain time series data for stock assessments and to meet NMFS... participants. In this notice, we announce the date and time of that meeting. DATES: A conference call will...

  15. First case of synophthalmia and albinism in the Pacific angel shark Squatina californica.

    PubMed

    Escobar-Sánchez, O; Moreno-Sánchez, X G; Aguilar-Cruz, C A; Abitia-Cárdenas, L A

    2014-08-01

    The first record in Mexican waters of albinism and synophthalmia (partial cyclopia) in the Pacific angel shark, Squatina californica is presented. Albinism is not lethal, but synophthalmia may cause the death of the individual immediately after birth.

  16. Great hammerhead sharks swim on their side to reduce transport costs

    PubMed Central

    Payne, Nicholas L.; Iosilevskii, Gil; Barnett, Adam; Fischer, Chris; Graham, Rachel T.; Gleiss, Adrian C.; Watanabe, Yuuki Y.

    2016-01-01

    Animals exhibit various physiological and behavioural strategies for minimizing travel costs. Fins of aquatic animals play key roles in efficient travel and, for sharks, the functions of dorsal and pectoral fins are considered well divided: the former assists propulsion and generates lateral hydrodynamic forces during turns and the latter generates vertical forces that offset sharks' negative buoyancy. Here we show that great hammerhead sharks drastically reconfigure the function of these structures, using an exaggerated dorsal fin to generate lift by swimming rolled on their side. Tagged wild sharks spend up to 90% of time swimming at roll angles between 50° and 75°, and hydrodynamic modelling shows that doing so reduces drag—and in turn, the cost of transport—by around 10% compared with traditional upright swimming. Employment of such a strongly selected feature for such a unique purpose raises interesting questions about evolutionary pathways to hydrodynamic adaptations, and our perception of form and function. PMID:27457414

  17. 77 FR 3393 - Atlantic Highly Migratory Species; 2012 Atlantic Shark Commercial Fishing Season

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-24

    ... blue sharks) in the northwestern Atlantic Ocean, including the Gulf of Mexico and the Caribbean Sea... northwestern Atlantic, including the Gulf of Mexico and Caribbean. DATES: The 2012 Atlantic commercial...

  18. The lantern shark's light switch: turning shallow water crypsis into midwater camouflage

    PubMed Central

    Claes, Julien M.; Mallefet, Jérôme

    2010-01-01

    Bioluminescence is a common feature in the permanent darkness of the deep-sea. In fishes, light is emitted by organs containing either photogenic cells (intrinsic photophores), which are under direct nervous control, or symbiotic luminous bacteria (symbiotic photophores), whose light is controlled by secondary means such as mechanical occlusion or physiological suppression. The intrinsic photophores of the lantern shark Etmopterus spinax were recently shown as an exception to this rule since they appear to be under hormonal control. Here, we show that hormones operate what amounts to a unique light switch, by acting on a chromatophore iris, which regulates light emission by pigment translocation. This result strongly suggests that this shark's luminescence control originates from the mechanism for physiological colour change found in shallow water sharks that also involves hormonally controlled chromatophores: the lantern shark would have turned the initial shallow water crypsis mechanism into a midwater luminous camouflage, more efficient in the deep-sea environment. PMID:20410033

  19. 78 FR 73500 - Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-06

    ... National Oceanic and Atmospheric Administration RIN 0648-XC997 Schedules for Atlantic Shark Identification Workshops and Protected Species Safe Handling, Release, and Identification Workshops AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce. ACTION:...

  20. Great hammerhead sharks swim on their side to reduce transport costs.

    PubMed

    Payne, Nicholas L; Iosilevskii, Gil; Barnett, Adam; Fischer, Chris; Graham, Rachel T; Gleiss, Adrian C; Watanabe, Yuuki Y

    2016-07-26

    Animals exhibit various physiological and behavioural strategies for minimizing travel costs. Fins of aquatic animals play key roles in efficient travel and, for sharks, the functions of dorsal and pectoral fins are considered well divided: the former assists propulsion and generates lateral hydrodynamic forces during turns and the latter generates vertical forces that offset sharks' negative buoyancy. Here we show that great hammerhead sharks drastically reconfigure the function of these structures, using an exaggerated dorsal fin to generate lift by swimming rolled on their side. Tagged wild sharks spend up to 90% of time swimming at roll angles between 50° and 75°, and hydrodynamic modelling shows that doing so reduces drag-and in turn, the cost of transport-by around 10% compared with traditional upright swimming. Employment of such a strongly selected feature for such a unique purpose raises interesting questions about evolutionary pathways to hydrodynamic adaptations, and our perception of form and function.

  1. A New Method to Calibrate Attachment Angles of Data Loggers in Swimming Sharks

    NASA Astrophysics Data System (ADS)

    Kawatsu, Shizuka; Sato, Katsufumi; Watanabe, Yuuki; Hyodo, Susumu; Breves, Jason P.; Fox, Bradley K.; Grau, E. Gordon; Miyazaki, Nobuyuki

    2009-12-01

    Recently, animal-borne accelerometers have been used to record the pitch angle of aquatic animals during swimming. When evaluating pitch angle, it is necessary to consider a discrepancy between the angle of an accelerometer and the long axis of an animal. In this study, we attached accelerometers to 17 free-ranging scalloped hammerhead shark ( Sphyrna lewini) pups from Kaneohe Bay, Hawaii. Although there are methods to calibrate attachment angles of accelerometers, we confirmed that previous methods were not applicable for hammerhead pups. According to raw data, some sharks ascended with a negative angle, which differs from tank observations of captive sharks. In turn, we developed a new method to account for this discrepancy in swimming sharks by estimating the attachment angle from the relationship between vertical speed (m/s) and pitch angle obtained by each accelerometer. The new method can be utilized for field observation of a wide range of species.

  2. Scalloped hammerhead shark Sphyrna lewini, utilizes deep-water, hypoxic zone in the Gulf of California.

    PubMed

    Jorgensen, S J; Klimley, A P; Muhlia-Melo, A F

    2009-05-01

    A hammerhead shark Sphyrna lewini tracked for 74 days revealed an expansion of the range of vertical distribution for the species to include the extreme hypoxic environment of the oxygen minimum layer in the Gulf of California.

  3. Low Genetic Differentiation across Three Major Ocean Populations of the Whale Shark, Rhincodon typus

    PubMed Central

    Schmidt, Jennifer V.; Schmidt, Claudia L.; Ozer, Fusun; Ernst, Robin E.; Feldheim, Kevin A.; Ashley, Mary V.; Levine, Marie

    2009-01-01

    Background Whale sharks are a declining species for which little biological data is available. While these animals are protected in many parts of their range, they are fished legally and illegally in some countries. Baseline biological and ecological data are needed to allow the formulation of an effective conservation plan for whale sharks. It is not known, for example, whether the whale shark is represented by a single worldwide panmictic population or by numerous, reproductively isolated populations. Genetic analysis of population structure is one essential component of the baseline data required for whale shark conservation. Methodology/Principal Findings We have identified 8 polymorphic microsatellites in the whale shark and used these markers to assess genetic variation and population structure in a panel of whale sharks covering a broad geographic region. This is the first record of microsatellite loci in the whale shark, which displayed an average of 9 alleles per locus and mean Ho = 0.66 and He = 0.69. All but one of the eight loci meet the expectations of Hardy-Weinberg equilibrium. Analysis of these loci in whale sharks representing three major portions of their range, the Pacific (P), Caribbean (C), and Indian (I) Oceans, determined that there is little population differentiation between animals sampled in different geographic regions, indicating historical gene flow between populations. FST values for inter-ocean comparisons were low (P×C = 0.0387, C×I = 0.0296 and P×I = −0.0022), and only C×I approached statistical significance (p = 0.0495). Conclusions/Significance We have shown only low levels of genetic differentiation between geographically distinct whale shark populations. Existing satellite tracking data have revealed both regional and long-range migration of whale sharks throughout their range, which supports the finding of gene flow between populations. Whale sharks traverse geographic and political boundaries

  4. Dinosaur morphological diversity and the end-Cretaceous extinction.

    PubMed

    Brusatte, Stephen L; Butler, Richard J; Prieto-Márquez, Albert; Norell, Mark A

    2012-05-01

    The extinction of non-avian dinosaurs 65 million years ago is a perpetual topic of fascination, and lasting debate has focused on whether dinosaur biodiversity was in decline before end-Cretaceous volcanism and bolide impact. Here we calculate the morphological disparity (anatomical variability) exhibited by seven major dinosaur subgroups during the latest Cretaceous, at both global and regional scales. Our results demonstrate both geographic and clade-specific heterogeneity. Large-bodied bulk-feeding herbivores (ceratopsids and hadrosauroids) and some North American taxa declined in disparity during the final two stages of the Cretaceous, whereas carnivorous dinosaurs, mid-sized herbivores, and some Asian taxa did not. Late Cretaceous dinosaur evolution, therefore, was complex: there was no universal biodiversity trend and the intensively studied North American record may reveal primarily local patterns. At least some dinosaur groups, however, did endure long-term declines in morphological variability before their extinction.

  5. Colombian late cretaceous tropical planktonic foraminifera: Redressing the imbalance

    SciTech Connect

    McCarthy, L.D.

    1993-02-01

    Recent work involving Late Cretaceous planktonic foraminifera has concentrated on European and other areas in the Northern Hemisphere. Many of the biostratigraphical and evolutionary models reflect this geographical restriction and ignore earlier studies from tropical areas. In 1955 Rolando Gandolfi described many new species and subspecies from Colombia and provided a different view of the evolutionary development of planktonic foraminifera. A re-examination of the Gandolfi type collection using Scanning Electron Micrography (Environmental Chamber technique) integrated with Colombian well samples from onshore Guajira area, Middle and Upper Magdalena Valley and Putumayo Basin has given a new view into the evolutionary development of Late Cretaceous planktonic foraminifera. This has enabled a modified globigerine Late Cretaceous biostratigraphy to be constructed for Colombia. This work redresses the imbalance between studies of tropical and northern high latitude Late Cretaceous planktonic foraminifera and provides an insight into the paleoenvironmental and paleoclimatological factors influencing the Colombian region at the time.

  6. Patterns of Occurrence of Sharks in Sydney Harbour, a Large Urbanised Estuary

    PubMed Central

    Smoothey, Amy F.; Gray, Charles A.; Kennelly, Steve J.; Masens, Oliver J.; Peddemors, Victor M.; Robinson, Wayne A.

    2016-01-01

    Information about spatial and temporal variability in the distribution and abundance of shark-populations are required for their conservation, management and to update measures designed to mitigate human-shark interactions. However, because some species of sharks are mobile, migratory and occur in relatively small numbers, estimating their patterns of distribution and abundance can be very difficult. In this study, we used a hierarchical sampling design to examine differences in the composition of species, size- and sex-structures of sharks sampled with bottom-set longlines in three different areas with increasing distance from the entrance of Sydney Harbour, a large urbanised estuary. During two years of sampling, we obtained data for four species of sharks (Port Jackson, Heterodontus portusjacksoni; wobbegong, Orectolobus maculatus; dusky whaler, Carcharhinus obscurus and bull shark, Carcharhinus leucas). Only a few O. maculatus and C. obscurus were caught, all in the area closest to the entrance of the Harbour. O. maculatus were caught in all seasons, except summer, while C. obscurus was only caught in summer. Heterodontus portusjacksoni were the most abundant species, caught in the entrance location mostly between July to November, when water temperature was below 21.5°C. This pattern was consistent across both years. C. leucas, the second most abundant species, were captured in all areas of Sydney Harbour but only in summer and autumn when water temperatures were above 23°C. This study quantified, for this first time, how different species utilise different areas of Sydney Harbour, at different times of the year. This information has implications for the management of human-shark interactions, by enabling creation of education programs to modify human behaviour in times of increased risk of potentially dangerous sharks. PMID:26824349

  7. The complete mitochondrial genome of the sand tiger shark, Carcharias taurus (Chondrichthyes, Odontaspididae).

    PubMed

    Chang, Chia-Hao; Jabado, Rima W; Lin, Yeong-Shin; Shao, Kwang-Tsao

    2015-01-01

    The complete mitochondrial genome of the sand tiger shark consists of 16,773 bp and including 13 protein-coding genes, 2 ribosomal RNA, 22 transfer RNA genes, 1 replication origin region and 1 control region. The mitochondrial gene arrangement of the sand tiger shark is the same as the one observed in most vertebrates. Base composition of the genome is A (31.8%), T (28.7%), C (26.3%) and G (13.2%).

  8. The complete mitochondrial genome of the great white shark, Carcharodon carcharias (Chondrichthyes, Lamnidae).

    PubMed

    Chang, Chia-Hao; Shao, Kwang-Tsao; Lin, Yeong-Shin; Fang, Yi-Chiao; Ho, Hsuan-Ching

    2014-10-01

    The complete mitochondrial genome of the great white shark having 16,744 bp and including 13 protein-coding genes, 2 ribosomal RNA, 22 transfer RNA genes, 1 replication origin region and 1 control region. The mitochondrial gene arrangement of the great white shark is the same as the one observed in the most vertebrates. Base composition of the genome is A (30.6%), T (28.7%), C (26.9%) and G (13.9%).

  9. The complete mitochondrial genome of the salmon shark, Lamna ditropis (Chondrichthyes, Lamnidae).

    PubMed

    Chang, Chia-Hao; Jang-Liaw, Nian-Hong; Lin, Yeong-Shin; Carlisle, Aaron; Hsu, Hua Hsun; Liao, Yun-Chih; Shao, Kwang-Tsao

    2016-01-01

    The complete mitochondrial genome of the salmon shark consists of 16,699 bp and includes 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes, 1 replication origin region and 1 control region. The mitochondrial gene arrangement of the salmon shark is the same as that of most vertebrates. Base composition of the genome is A (29.6%), T (28.6%), C (27.1%), and G (14.8%).

  10. Patterns of Occurrence of Sharks in Sydney Harbour, a Large Urbanised Estuary.

    PubMed

    Smoothey, Amy F; Gray, Charles A; Kennelly, Steve J; Masens, Oliver J; Peddemors, Victor M; Robinson, Wayne A

    2016-01-01

    Information about spatial and temporal variability in the distribution and abundance of shark-populations are required for their conservation, management and to update measures designed to mitigate human-shark interactions. However, because some species of sharks are mobile, migratory and occur in relatively small numbers, estimating their patterns of distribution and abundance can be very difficult. In this study, we used a hierarchical sampling design to examine differences in the composition of species, size- and sex-structures of sharks sampled with bottom-set longlines in three different areas with increasing distance from the entrance of Sydney Harbour, a large urbanised estuary. During two years of sampling, we obtained data for four species of sharks (Port Jackson, Heterodontus portusjacksoni; wobbegong, Orectolobus maculatus; dusky whaler, Carcharhinus obscurus and bull shark, Carcharhinus leucas). Only a few O. maculatus and C. obscurus were caught, all in the area closest to the entrance of the Harbour. O. maculatus were caught in all seasons, except summer, while C. obscurus was only caught in summer. Heterodontus portusjacksoni were the most abundant species, caught in the entrance location mostly between July to November, when water temperature was below 21.5°C. This pattern was consistent across both years. C. leucas, the second most abundant species, were captured in all areas of Sydney Harbour but only in summer and autumn when water temperatures were above 23°C. This study quantified, for this first time, how different species utilise different areas of Sydney Harbour, at different times of the year. This information has implications for the management of human-shark interactions, by enabling creation of education programs to modify human behaviour in times of increased risk of potentially dangerous sharks.

  11. Unexpected Positive Buoyancy in Deep Sea Sharks, Hexanchus griseus, and a Echinorhinus cookei.

    PubMed

    Nakamura, Itsumi; Meyer, Carl G; Sato, Katsufumi

    2015-01-01

    We do not expect non air-breathing aquatic animals to exhibit positive buoyancy. Sharks, for example, rely on oil-filled livers instead of gas-filled swim bladders to increase their buoyancy, but are nonetheless ubiquitously regarded as either negatively or neutrally buoyant. Deep-sea sharks have particularly large, oil-filled livers, and are believed to be neutrally buoyant in their natural habitat, but this has never been confirmed. To empirically determine the buoyancy status of two species of deep-sea sharks (bluntnose sixgill sharks, Hexanchus griseus, and a prickly shark, Echinorhinus cookei) in their natural habitat, we used accelerometer-magnetometer data loggers to measure their swimming performance. Both species of deep-sea sharks showed similar diel vertical migrations: they swam at depths of 200-300 m at night and deeper than 500 m during the day. Ambient water temperature was around 15°C at 200-300 m but below 7°C at depths greater than 500 m. During vertical movements, all deep-sea sharks showed higher swimming efforts during descent than ascent to maintain a given swimming speed, and were able to glide uphill for extended periods (several minutes), indicating that these deep-sea sharks are in fact positively buoyant in their natural habitats. This positive buoyancy may adaptive for stealthy hunting (i.e. upward gliding to surprise prey from underneath) or may facilitate evening upward migrations when muscle temperatures are coolest, and swimming most sluggish, after spending the day in deep, cold water. Positive buoyancy could potentially be widespread in fish conducting daily vertical migration in deep-sea habitats.

  12. Migration pathways, behavioural thermoregulation and overwintering grounds of blue sharks in the Northwest Atlantic.

    PubMed

    Campana, Steven E; Dorey, Anna; Fowler, Mark; Joyce, Warren; Wang, Zeliang; Wright, Dan; Yashayaev, Igor

    2011-02-23

    The blue shark Prionace glauca is the most abundant large pelagic shark in the Atlantic Ocean. Although recaptures of tagged sharks have shown that the species is highly migratory, migration pathways towards the overwintering grounds remain poorly understood. We used archival satellite pop-up tags to track 23 blue sharks over a mean period of 88 days as they departed the coastal waters of North America in the autumn. Within 1-2 days of entering the Gulf Stream (median date of 21 Oct), all sharks initiated a striking diel vertical migration, taking them from a mean nighttime depth of 74 m to a mean depth of 412 m during the day as they appeared to pursue vertically migrating squid and fish prey. Although functionally blind at depth, calculations suggest that there would be a ~2.5-fold thermoregulatory advantage to swimming and feeding in the markedly cooler deep waters, even if there was any reduced foraging success associated with the extreme depth. Noting that the Gulf Stream current speeds are reduced at depth, we used a detailed circulation model of the North Atlantic to examine the influence of the diving behaviour on the advection experienced by the sharks. However, there was no indication that the shark diving resulted in a significant modification of their net migratory pathway. The relative abundance of deep-diving sharks, swordfish, and sperm whales in the Gulf Stream and adjacent waters suggests that it may serve as a key winter feeding ground for large pelagic predators in the North Atlantic.

  13. Unexpected Positive Buoyancy in Deep Sea Sharks, Hexanchus griseus, and a Echinorhinus cookei

    PubMed Central

    Nakamura, Itsumi; Meyer, Carl G.; Sato, Katsufumi

    2015-01-01

    We do not expect non air-breathing aquatic animals to exhibit positive buoyancy. Sharks, for example, rely on oil-filled livers instead of gas-filled swim bladders to increase their buoyancy, but are nonetheless ubiquitously regarded as either negatively or neutrally buoyant. Deep-sea sharks have particularly large, oil-filled livers, and are believed to be neutrally buoyant in their natural habitat, but this has never been confirmed. To empirically determine the buoyancy status of two species of deep-sea sharks (bluntnose sixgill sharks, Hexanchus griseus, and a prickly shark, Echinorhinus cookei) in their natural habitat, we used accelerometer-magnetometer data loggers to measure their swimming performance. Both species of deep-sea sharks showed similar diel vertical migrations: they swam at depths of 200–300 m at night and deeper than 500 m during the day. Ambient water temperature was around 15°C at 200–300 m but below 7°C at depths greater than 500 m. During vertical movements, all deep-sea sharks showed higher swimming efforts during descent than ascent to maintain a given swimming speed, and were able to glide uphill for extended periods (several minutes), indicating that these deep-sea sharks are in fact positively buoyant in their natural habitats. This positive buoyancy may adaptive for stealthy hunting (i.e. upward gliding to surprise prey from underneath) or may facilitate evening upward migrations when muscle temperatures are coolest, and swimming most sluggish, after spending the day in deep, cold water. Positive buoyancy could potentially be widespread in fish conducting daily vertical migration in deep-sea habitats. PMID:26061525

  14. Migration Pathways, Behavioural Thermoregulation and Overwintering Grounds of Blue Sharks in the Northwest Atlantic

    PubMed Central

    Campana, Steven E.; Dorey, Anna; Fowler, Mark; Joyce, Warren; Wang, Zeliang; Yashayaev, Igor

    2011-01-01

    The blue shark Prionace glauca is the most abundant large pelagic shark in the Atlantic Ocean. Although recaptures of tagged sharks have shown that the species is highly migratory, migration pathways towards the overwintering grounds remain poorly understood. We used archival satellite pop-up tags to track 23 blue sharks over a mean period of 88 days as they departed the coastal waters of North America in the autumn. Within 1–2 days of entering the Gulf Stream (median date of 21 Oct), all sharks initiated a striking diel vertical migration, taking them from a mean nighttime depth of 74 m to a mean depth of 412 m during the day as they appeared to pursue vertically migrating squid and fish prey. Although functionally blind at depth, calculations suggest that there would be a ∼2.5-fold thermoregulatory advantage to swimming and feeding in the markedly cooler deep waters, even if there was any reduced foraging success associated with the extreme depth. Noting that the Gulf Stream current speeds are reduced at depth, we used a detailed circulation model of the North Atlantic to examine the influence of the diving behaviour on the advection experienced by the sharks. However, there was no indication that the shark diving resulted in a significant modification of their net migratory pathway. The relative abundance of deep-diving sharks, swordfish, and sperm whales in the Gulf Stream and adjacent waters suggests that it may serve as a key winter feeding ground for large pelagic predators in the North Atlantic. PMID:21373198

  15. Shark River Inlet, New Jersey, Entrance Shoaling: Report 2, Analysis With Coastal Modeling System

    DTIC Science & Technology

    2010-07-01

    benefits and possible solutions Advance dredging is a possible interim solution that can be implemented at modest cost and examined for performance...ER D C/ CH L TR -1 0- 4 Coastal Inlets Research Program Shark River Inlet, New Jersey, Entrance Shoaling: Report 2, Analysis with...Program ERDC/CHL TR-10-4 July 2010 Shark River Inlet, New Jersey, Entrance Shoaling: Report 2, Analysis with Coastal Modeling System Tanya M. Beck

  16. Intraspecific variation in vertical habitat use by tiger sharks (Galeocerdo cuvier) in the western North Atlantic

    PubMed Central

    Vaudo, Jeremy J; Wetherbee, Bradley M; Harvey, Guy; Nemeth, Richard S; Aming, Choy; Burnie, Neil; Howey-Jordan, Lucy A; Shivji, Mahmood S

    2014-01-01

    Tiger sharks (Galeocerdo cuvier) are a wide ranging, potentially keystone predator species that display a variety of horizontal movement patterns, making use of coastal and pelagic waters. Far less, however, is known about their vertical movements and use of the water column. We used pop-up satellite archival tags with two data sampling rates (high rate and standard rate tags) to investigate the vertical habitat use and diving behavior of tiger sharks tagged on the Puerto Rico–Virgin Islands platform and off Bermuda between 2008 and 2009. Useable data were received from nine of 14 sharks tagged, tracked over a total of 529 days. Sharks spent the majority of their time making yo-yo dives within the upper 50 m of the water column and considerable time within the upper 5 m of the water column. As a result, sharks typically occupied a narrow daily temperature range (∼2°C). Dives to greater than 200 m were common, and all sharks made dives to at least 250 m, with one shark reaching a depth of 828 m. Despite some similarities among individuals, a great deal of intraspecific variability in vertical habit use was observed. Four distinct depth distributions that were not related to tagging location, horizontal movements, sex, or size were detected. In addition, similar depth distributions did not necessitate similar dive patterns among sharks. Recognition of intraspecific variability in habitat use of top predators can be crucial for effective management of these species and for understanding their influence on ecosystem dynamics. PMID:24963376

  17. Blacktip reef sharks (Carcharhinus melanopterus) show high capacity for wound healing and recovery following injury

    PubMed Central

    Chin, Andrew; Mourier, Johann; Rummer, Jodie L.

    2015-01-01

    Wound healing is important for sharks from the earliest life stages, for example, as the ‘umbilical scar’ in viviparous species heals, and throughout adulthood, when sharks can incur a range of external injuries from natural and anthropogenic sources. Despite anecdotal accounts of rapid healing in elasmobranchs, data regarding recovery and survival of individuals from different wound or injury types has not been systematically collected. The present study documented: (i) ‘umbilical scar’ healing in wild-caught, neonatal blacktip reef sharks while being reared for 30 days in flow-through laboratory aquaria in French Polynesia; (ii) survival and recovery of free-swimming blacktip reef sharks in Australia and French Polynesia following a range of injuries; and (iii) long-term survival following suspected shark-finning activities. Laboratory monitoring, tag-recapture records, telemetry data and photo-identification records suggest that blacktip reef sharks have a high capacity to survive and recover from small or even large and severe wounds. Healing rates, recovery and survival are important factors to consider when assessing impacts of habitat degradation and fishing stress on shark populations. The present study suggests that individual survival may depend more on handling practices and physiological stress rather than the extent of physical injury. These observations also contribute to discussions regarding the ethics of tagging practices used in elasmobranch research and provide baseline healing rates that may increase the accuracy in estimating reproductive timing inferred from mating scars and birth dates for neonatal sharks based on umbilical scar healing status. PMID:27293741

  18. The Species and Origin of Shark Fins in Taiwan’s Fishing Ports, Markets, and Customs Detention: A DNA Barcoding Analysis

    PubMed Central

    Chuang, Po-Shun; Hung, Tzu-Chiao; Chang, Hung-An; Huang, Chien-Kang; Shiao, Jen-Chieh

    2016-01-01

    The increasing consumption of shark products, along with the shark’s fishing vulnerabilities, has led to the decrease in certain shark populations. In this study we used a DNA barcoding method to identify the species of shark landings at fishing ports, shark fin products in retail stores, and shark fins detained by Taiwan customs. In total we identified 23, 24, and 14 species from 231 fishing landings, 316 fin products, and 113 detained shark fins, respectively. All the three sample sources were dominated by Prionace glauca, which accounted for more than 30% of the collected samples. Over 60% of the species identified in the fin products also appeared in the port landings, suggesting the domestic-dominance of shark fin products in Taiwan. However, international trade also contributes a certain proportion of the fin product markets, as four species identified from the shark fin products are not found in Taiwan’s waters, and some domestic-available species were also found in the customs-detained sample. In addition to the species identification, we also found geographical differentiation in the cox1 gene of the common thresher sharks (Alopias vulpinus), the pelagic thresher shark (A. pelagicus), the smooth hammerhead shark (Sphyrna zygaena), and the scalloped hammerhead shark (S. lewini). This result might allow fishing authorities to more effectively trace the origins as well as enforce the management and conservation of these sharks. PMID:26799827

  19. A Comparison of Spatial and Movement Patterns between Sympatric Predators: Bull Sharks (Carcharhinus leucas) and Atlantic Tarpon (Megalops atlanticus)

    PubMed Central

    Hammerschlag, Neil; Luo, Jiangang; Irschick, Duncan J.; Ault, Jerald S.

    2012-01-01

    Background Predators can impact ecosystems through trophic cascades such that differential patterns in habitat use can lead to spatiotemporal variation in top down forcing on community dynamics. Thus, improved understanding of predator movements is important for evaluating the potential ecosystem effects of their declines. Methodology/Principal Findings We satellite-tagged an apex predator (bull sharks, Carcharhinus leucas) and a sympatric mesopredator (Atlantic tarpon, Megalops atlanticus) in southern Florida waters to describe their habitat use, abundance and movement patterns. We asked four questions: (1) How do the seasonal abundance patterns of bull sharks and tarpon compare? (2) How do the movement patterns of bull sharks and tarpon compare, and what proportion of time do their respective primary ranges overlap? (3) Do tarpon movement patterns (e.g., straight versus convoluted paths) and/or their rates of movement (ROM) differ in areas of low versus high bull shark abundance? and (4) Can any general conclusions be reached concerning whether tarpon may mitigate risk of predation by sharks when they are in areas of high bull shark abundance? Conclusions/Significance Despite similarities in diet, bull sharks and tarpon showed little overlap in habitat use. Bull shark abundance was high year-round, but peaked in winter; while tarpon abundance and fishery catches were highest in late spring. However, presence of the largest sharks (>230 cm) coincided with peak tarpon abundance. When moving over deep open waters (areas of high shark abundance and high food availability) tarpon maintained relatively high ROM in directed lines until reaching shallow structurally-complex areas. At such locations, tarpon exhibited slow tortuous movements over relatively long time periods indicative of foraging. Tarpon periodically concentrated up rivers, where tracked bull sharks were absent. We propose that tarpon trade-off energetic costs of both food assimilation and osmoregulation

  20. Identification of factors influencing shark catch and mortality in the Marshall Islands tuna longline fishery and management implications.

    PubMed

    Bromhead, D; Clarke, S; Hoyle, S; Muller, B; Sharples, P; Harley, S

    2012-04-01

    Recent average annual catches of sharks by tuna longline vessels fishing in the Republic of the Marshall Islands (RMI) are estimated to be between 1583 and 2274 t. Although 22 shark species have been recorded by the observer programme for this fishery, 80% of the annual catch comprises only five species: blue shark Prionace glauca, silky shark Carcharhinus falciformis, bigeye thresher shark Alopias superciliosus, pelagic thresher shark Alopias pelagicus and oceanic whitetip shark Carcharhinus longimanus. Wire leaders (i.e. branch lines or traces) were also used by nearly all observed vessels. Generalized additive model (GAM)-based analyses of catch rates indicated that P. glauca and A. superciliosus are caught in higher numbers when vessels fish in relatively cooler waters, at night, close to the full moon, when the 27° C thermocline is close to the surface and during El Niño conditions. In contrast, C. falciformis, A. pelagicus and C. longimanus are caught in higher numbers when shark lines are used (all three species) or hooks are set at a shallow depth (A. pelagicus and C. longimanus and, also, P. glauca). These findings are generally consistent with current knowledge of these species' habitat preferences, movement and distribution. The results of these analyses were combined with information pertaining to shark condition and fate upon capture to compare the likely effectiveness of a range of potential measures for reducing shark mortality in the longline fishery. Of the options considered, the most effective would be to combine measures that reduce the catch rate (e.g. restrictions on the use of wire leaders, shark baits and shark lines) with measures that increase survival rates after post-capture release (e.g. finning bans).

  1. Ultrasound examination and behavior scoring of captive broadnose sevengill sharks, Notorynchus cepedianus (Peron, 1807).

    PubMed

    Daly, Jonathan; Gunn, Ian; Kirby, Nick; Jones, Robert; Galloway, David

    2007-09-01

    Serial ultrasound examination of four mature female sevengill sharks (Notorynchus cepedianus) was carried out over 18 months. Monitoring the reproductive cycle and development of follicles and fetuses in sharks in a noninvasive manner using this technique has not been reported previously. Sharks were caught out of the "Oceanarium" tank by divers using a specially made catch-out bag, and brought to a holding area for examination. A behavior scoring system was used to monitor the impact of regular handling on the well-being of the animals. Ultrasound showed the growth and regression of follicles in sevengill ovaries, and allowed an approximation of the reproductive stage of these sharks. Monitoring behavior at five time points during the procedure showed that regular handling of sharks for clinical studies could be done with minimal impact on animal welfare. The ability to follow reproductive events in elasmobranches using ultrasonography is an important step in the application of assisted reproductive technology in these species. Assisted reproductive technology, such as monitoring female reproductive cycles and artificial insemination, could potentially be used to maintain genetic diversity and compliment aquaria-based breeding programs for endangered species such as the gray nurse shark (Carcharias taurus). Zoo Biol 26:383-395, 2007. (c) 2007 Wiley-Liss, Inc.

  2. Large-proportional shrunken bio-replication of shark skin based on UV-curing shrinkage

    NASA Astrophysics Data System (ADS)

    Chen, Huawei; Che, Da; Zhang, Xin; Yue, Yue; Zhang, Deyuan

    2015-01-01

    The shark skin effect has attracted worldwide attention because of its superior drag reduction. As the product of natural selection, the maximum drag reduction of shark skin is found in its normal living environment. Large-proportional shrinkage of shark skin morphology is greatly anticipated for its adaptation to faster fluid flow. One novel approach, large-proportional shrunken bio-replication, is proposed as a method to adjust the optimal drag reduction region of shark skin based on the shrinkage of UV-cured material. The shark skin is taken as a replica template to allow large-proportional shrinking in the drag reduction morphology by taking advantage of the shrinkage of UV-curable material. The accuracy of the large-proportional shrunken bio-replication approach is verified by a comparison between original and shrunken bio-replicated shark skin, which shows that the shrinking ratio can reach 23% and the bio-replication accuracy is higher than 95%. In addition, the translation of the optimum drag reduction peak of natural surface function to various applications and environments is proved by drag reduction experiments.

  3. Expression of Wnt signaling skeletal development genes in the cartilaginous fish, elephant shark (Callorhinchus milii).

    PubMed

    D'Souza, Damian G; Rana, Kesha; Milley, Kristi M; MacLean, Helen E; Zajac, Jeffrey D; Bell, Justin; Brenner, Sydney; Venkatesh, Byrappa; Richardson, Samantha J; Danks, Janine A

    2013-11-01

    Jawed vertebrates (Gnasthostomes) are broadly separated into cartilaginous fishes (Chondricthyes) and bony vertebrates (Osteichthyes). Cartilaginous fishes are divided into chimaeras (e.g. ratfish, rabbit fish and elephant shark) and elasmobranchs (e.g. sharks, rays and skates). Both cartilaginous fish and bony vertebrates are believed to have a common armoured bony ancestor (Class Placodermi), however cartilaginous fish are believed to have lost bone. This study has identified and investigated genes involved in skeletal development in vertebrates, in the cartilaginous fish, elephant shark (Callorhinchus milii). Ctnnb1 (β-catenin), Sfrp (secreted frizzled protein) and a single Sost or Sostdc1 gene (sclerostin or sclerostin domain-containing protein 1) were identified in the elephant shark genome and found to be expressed in a number of tissues, including cartilage. β-catenin was also localized in several elephant shark tissues. The expression of these genes, which belong to the Wnt/β-catenin pathway, is required for normal bone formation in mammals. These findings in the cartilaginous skeleton of elephant shark support the hypothesis that the common ancestor of cartilaginous fishes and bony vertebrates had the potential for making bone.

  4. Effects of an Electric Field on White Sharks: In Situ Testing of an Electric Deterrent

    PubMed Central

    Huveneers, Charlie; Rogers, Paul J.; Semmens, Jayson M.; Beckmann, Crystal; Kock, Alison A.; Page, Brad; Goldsworthy, Simon D.

    2013-01-01

    Elasmobranchs can detect minute electromagnetic fields, <1 nVcm–1, using their ampullae of Lorenzini. Behavioural responses to electric fields have been investigated in various species, sometimes with the aim to develop shark deterrents to improve human safety. The present study tested the effects of the Shark Shield Freedom7™ electric deterrent on (1) the behaviour of 18 white sharks (Carcharodon carcharias) near a static bait, and (2) the rates of attacks on a towed seal decoy. In the first experiment, 116 trials using a static bait were performed at the Neptune Islands, South Australia. The proportion of baits taken during static bait trials was not affected by the electric field. The electric field, however, increased the time it took them to consume the bait, the number of interactions per approach, and decreased the proportion of interactions within two metres of the field source. The effect of the electric field was not uniform across all sharks. In the second experiment, 189 tows using a seal decoy were conducted near Seal Island, South Africa. No breaches and only two surface interactions were observed during the tows when the electric field was activated, compared with 16 breaches and 27 surface interactions without the electric field. The present study suggests that the behavioural response of white sharks and the level of risk reduction resulting from the electric field is contextually specific, and depends on the motivational state of sharks. PMID:23658766

  5. An unprecedented aggregation of whale sharks, Rhincodon typus, in Mexican coastal waters of the Caribbean Sea.

    PubMed

    de la Parra Venegas, Rafael; Hueter, Robert; González Cano, Jaime; Tyminski, John; Gregorio Remolina, José; Maslanka, Mike; Ormos, Andrea; Weigt, Lee; Carlson, Bruce; Dove, Alistair

    2011-04-29

    Whale sharks, Rhincodon typus, are often perceived as solitary behemoths that live and feed in the open ocean. To the contrary, evidence is accumulating that they are gregarious and form seasonal aggregations in some coastal waters. One such aggregation occurs annually north of Cabo Catoche, off Isla Holbox on the Yucatán Peninsula of Mexico. Here we report a second, much denser aggregation of whale sharks (dubbed "the Afuera") that occurs east of the tip of the Yucatán Peninsula in the Caribbean Sea. The 2009 Afuera event comprised the largest aggregation of whale sharks ever reported, with up to 420 whale sharks observed in a single aerial survey, all gathered in an elliptical patch of ocean approximately 18 km(2). Plankton studies indicated that the sharks were feeding on dense homogenous patches of fish eggs, which DNA barcoding analysis identified as belonging to little tunny, Euthynnus alletteratus. This contrasts with the annual Cabo Catoche aggregation nearby, where prey consists mostly of copepods and sergestid shrimp. Increased sightings at the Afuera coincide with decreased sightings at Cabo Catoche, and both groups have the same sex ratio, implying that the same animals are likely involved in both aggregations; tagging data support this idea. With two whale shark aggregation areas, high coastal productivity and a previously-unknown scombrid spawning ground, the northeastern Yucatán marine region is a critical habitat that deserves more concerted conservation efforts.

  6. Odor tracking in sharks is reduced under future ocean acidification conditions.

    PubMed

    Dixson, Danielle L; Jennings, Ashley R; Atema, Jelle; Munday, Philip L

    2015-04-01

    Recent studies show that ocean acidification impairs sensory functions and alters the behavior of teleost fishes. If sharks and other elasmobranchs are similarly affected, this could have significant consequences for marine ecosystems globally. Here, we show that projected future CO2 levels impair odor tracking behavior of the smooth dogfish (Mustelus canis). Adult M. canis were held for 5 days in a current-day control (405 ± 26 μatm) and mid (741 ± 22 μatm) or high CO2 (1064 ± 17 μatm) treatments consistent with the projections for the year 2100 on a 'business as usual' scenario. Both control and mid CO2 -treated individuals maintained normal odor tracking behavior, whereas high CO2 -treated sharks significantly avoided the odor cues indicative of food. Control sharks spent >60% of their time in the water stream containing the food stimulus, but this value fell below 15% in high CO2 -treated sharks. In addition, sharks treated under mid and high CO2 conditions reduced attack behavior compared to the control individuals. Our findings show that shark feeding could be affected by changes in seawater chemistry projected for the end of this century. Understanding the effects of ocean acidification on critical behaviors, such as prey tracking in large predators, can help determine the potential impacts of future ocean acidification on ecosystem function.

  7. Movement Patterns of Juvenile Whale Sharks Tagged at an Aggregation Site in the Red Sea

    PubMed Central

    Berumen, Michael L.; Braun, Camrin D.; Cochran, Jesse E. M.; Skomal, Gregory B.; Thorrold, Simon R.

    2014-01-01

    Conservation efforts aimed at the whale shark, Rhincodon typus, remain limited by a lack of basic information on most aspects of its ecology, including global population structure, population sizes and movement patterns. Here we report on the movements of 47 Red Sea whale sharks fitted with three types of satellite transmitting tags from 2009–2011. Most of these sharks were tagged at a single aggregation site near Al-Lith, on the central coast of the Saudi Arabian Red Sea. Individuals encountered at this site were all juveniles based on size estimates ranging from 2.5–7 m total length with a sex ratio of approximately 1∶1. All other known aggregation sites for juvenile whale sharks are dominated by males. Results from tagging efforts showed that most individuals remained in the southern Red Sea and that some sharks returned to the same location in subsequent years. Diving data were recorded by 37 tags, revealing frequent deep dives to at least 500 m and as deep as 1360 m. The unique temperature-depth profiles of the Red Sea confirmed that several whale sharks moved out of the Red Sea while tagged. The wide-ranging horizontal movements of these individuals highlight the need for multinational, cooperative efforts to conserve R. typus populations in the Red Sea and Indian Ocean. PMID:25076407

  8. The breeding biology of lemon sharks at a tropical nursery lagoon.

    PubMed Central

    Feldheim, Kevin A; Gruber, Samuel H; Ashley, Mary V

    2002-01-01

    Surprisingly little is known about the reproductive behaviour and breeding biology of most shark species, especially in natural populations. Here, we characterize reproductive patterns and use of a natal nursery at Bimini, Bahamas by lemon sharks, Negaprion brevirostris. We systematically and exhaustively sampled young lemon sharks at Bimini annually from 1995 to 2000 and opportunistically sampled adults over the same period. Out of the 897 young sharks sampled, 119 could be assigned to five sampled mothers using microsatellite genotyping. Reproductive females showed strong philopatry to the nursery, returning to Bimini every two years to give birth. Each of these females may rely entirely on the Bimini nursery for recruitment. The protection of known nursery grounds should therefore figure prominently in conservation efforts for large coastal shark species. The reconstruction of paternal genotypes indicates that litters are sired by multiple males, and females mate with different males nearly every breeding cycle. The ubiquitous polyandry reported here raises the possibility that genetic incompatibility and post-copulatory paternity-biasing mechanisms may operate in viviparous sharks. PMID:12204125

  9. The breeding biology of lemon sharks at a tropical nursery lagoon.

    PubMed

    Feldheim, Kevin A; Gruber, Samuel H; Ashley, Mary V

    2002-08-22

    Surprisingly little is known about the reproductive behaviour and breeding biology of most shark species, especially in natural populations. Here, we characterize reproductive patterns and use of a natal nursery at Bimini, Bahamas by lemon sharks, Negaprion brevirostris. We systematically and exhaustively sampled young lemon sharks at Bimini annually from 1995 to 2000 and opportunistically sampled adults over the same period. Out of the 897 young sharks sampled, 119 could be assigned to five sampled mothers using microsatellite genotyping. Reproductive females showed strong philopatry to the nursery, returning to Bimini every two years to give birth. Each of these females may rely entirely on the Bimini nursery for recruitment. The protection of known nursery grounds should therefore figure prominently in conservation efforts for large coastal shark species. The reconstruction of paternal genotypes indicates that litters are sired by multiple males, and females mate with different males nearly every breeding cycle. The ubiquitous polyandry reported here raises the possibility that genetic incompatibility and post-copulatory paternity-biasing mechanisms may operate in viviparous sharks.

  10. Novel Acoustic Technology for Studying Free-Ranging Shark Social Behaviour by Recording Individuals' Interactions

    PubMed Central

    Guttridge, Tristan L.; Gruber, Samuel H.; Krause, Jens; Sims, David W.

    2010-01-01

    Group behaviours are widespread among fish but comparatively little is known about the interactions between free-ranging individuals and how these might change across different spatio-temporal scales. This is largely due to the difficulty of observing wild fish groups directly underwater over long enough time periods to quantify group structure and individual associations. Here we describe the use of a novel technology, an animal-borne acoustic proximity receiver that records close-spatial associations between free-ranging fish by detection of acoustic signals emitted from transmitters on other individuals. Validation trials, held within enclosures in the natural environment, on juvenile lemon sharks Negaprion brevirostris fitted with external receivers and transmitters, showed receivers logged interactions between individuals regularly when sharks were within 4 m (∼4 body lengths) of each other, but rarely when at 10 m distance. A field trial lasting 17 days with 5 juvenile lemon sharks implanted with proximity receivers showed one receiver successfully recorded association data, demonstrating this shark associated with 9 other juvenile lemon sharks on 128 occasions. This study describes the use of acoustic underwater proximity receivers to quantify interactions among wild sharks, setting the scene for new advances in understanding the social behaviours of marine animals. PMID:20174465

  11. Runx Family Genes in a Cartilaginous Fish, the Elephant Shark (Callorhinchus milii)

    PubMed Central

    Nah, Giselle Sek Suan; Lim, Zhi Wei; Tay, Boon-Hui; Osato, Motomi; Venkatesh, Byrappa

    2014-01-01

    The Runx family genes encode transcription factors that play key roles in hematopoiesis, skeletogenesis and neurogenesis and are often implicated in diseases. We describe here the cloning and characterization of Runx1, Runx2, Runx3 and Runxb genes in the elephant shark (Callorhinchus milii), a member of Chondrichthyes, the oldest living group of jawed vertebrates. Through the use of alternative promoters and/or alternative splicing, each of the elephant shark Runx genes expresses multiple isoforms similar to their orthologs in human and other bony vertebrates. The expression profiles of elephant shark Runx genes are similar to those of mammalian Runx genes. The syntenic blocks of genes at the elephant shark Runx gene loci are highly conserved in human, but represented by shorter conserved blocks in zebrafish indicating a higher degree of rearrangements in this teleost fish. Analysis of promoter regions revealed conservation of binding sites for transcription factors, including two tandem binding sites for Runx that are totally conserved in the distal promoter regions of elephant shark Runx1-3. Several conserved noncoding elements (CNEs), which are putative cis-regulatory elements, and miRNA binding sites were identified in the elephant shark and human Runx gene loci. Some of these CNEs and miRNA binding sites are absent in teleost fishes such as zebrafish and fugu. In summary, our analysis reveals that the genomic organization and expression profiles of Runx genes were already complex in the common ancestor of jawed vertebrates. PMID:24699678

  12. Bioaccumulation of organohalogenated compounds in sharks and rays from the southeastern USA.

    PubMed

    Weijs, Liesbeth; Briels, Nathalie; Adams, Douglas H; Lepoint, Gilles; Das, Krishna; Blust, Ronny; Covaci, Adrian

    2015-02-01

    Organohalogenated compounds are widespread in the marine environment and can be a serious threat to organisms in all levels of aquatic food webs, including elasmobranch species. Information about the concentrations of POPs (persistent organic pollutants) and of MeO-PBDEs (methoxylated polybrominated diphenyl ethers) in elasmobranchs is scarce and potential toxic effects are poorly understood. The aims of the present study were therefore to investigate the occurrence of multiple POP classes (PCBs, PBDEs, DDXs, HCB, CHLs) and of MeO-PBDEs in various elasmobranch species from different trophic levels in estuarine and marine waters of the southeastern United States. Overall, levels and patterns of PCBs, PBDEs, DDXs, HCB, CHLs and of MeO-PBDEs varied according to the species, maturity stage, gender and habitat type. The lowest levels of POPs were found in Atlantic stingrays and the highest levels were found in bull sharks. As both species are respectively near the bottom and at top of the trophic web, with juvenile bull sharks frequently feeding on Atlantic stingrays, these findings further suggest a bioaccumulation and biomagnification process with trophic position. MeO-PBDEs were not detected in Atlantic stingrays, but were found in all shark species. HCB was not found in Atlantic stingrays, bonnetheads or lemon sharks, but was detected in the majority of bull sharks examined. Comparison with previous studies suggests that Atlantic stingrays may be experiencing toxic effects of PCBs and DDXs on their immune system. However, the effect of these compounds on the health of shark species remains unclear.

  13. Uptake of human pharmaceuticals in bull sharks (Carcharhinus leucas) inhabiting a wastewater-impacted river.

    PubMed

    Gelsleichter, James; Szabo, Nancy J

    2013-07-01

    The presence of human pharmaceuticals in sewage-impacted ecosystems is a growing concern that poses health risks to aquatic wildlife. Despite this, few studies have investigated the uptake of active pharmaceutical ingredients (APIs) in aquatic organisms. In this study, the uptake of 9 APIs from human drugs was examined and compared in neonate bull sharks (Carcharhinus leucas) residing in pristine (Myakka River) and wastewater-impacted (Caloosahatchee River) tributaries of Florida's Charlotte Harbor estuary. The synthetic estrogen used in human contraceptives (17α-ethynylestradiol) and 6 of the selective serotonin/norepinephrine reuptake inhibitors (citalopram, fluoxetine, fluvoxamine, paroxetine, sertraline, venlafaxine) used in human antidepressants were observed at detectable and, in some cases, quantifiable levels in plasma of Caloosahatchee River sharks. Comparatively, only venlafaxine was detected in the plasma of a single Myakka River shark at a level below the limit of quantitation. These results suggest that sharks residing in wastewater-impacted habitats accumulate APIs, a factor that may pose special risks to C. leucas since it is one of few shark species to regularly occupy freshwater systems. Further research is needed to determine if the low levels of API uptake observed in Caloosahatchee River bull sharks pose health risks to these animals.

  14. Movement patterns of juvenile whale sharks tagged at an aggregation site in the Red Sea.

    PubMed

    Berumen, Michael L; Braun, Camrin D; Cochran, Jesse E M; Skomal, Gregory B; Thorrold, Simon R

    2014-01-01

    Conservation efforts aimed at the whale shark, Rhincodon typus, remain limited by a lack of basic information on most aspects of its ecology, including global population structure, population sizes and movement patterns. Here we report on the movements of 47 Red Sea whale sharks fitted with three types of satellite transmitting tags from 2009-2011. Most of these sharks were tagged at a single aggregation site near Al-Lith, on the central coast of the Saudi Arabian Red Sea. Individuals encountered at this site were all juveniles based on size estimates ranging from 2.5-7 m total length with a sex ratio of approximately 1∶1. All other known aggregation sites for juvenile whale sharks are dominated by males. Results from tagging efforts showed that most individuals remained in the southern Red Sea and that some sharks returned to the same location in subsequent years. Diving data were recorded by 37 tags, revealing frequent deep dives to at least 500 m and as deep as 1360 m. The unique temperature-depth profiles of the Red Sea confirmed that several whale sharks moved out of the Red Sea while tagged. The wide-ranging horizontal movements of these individuals highlight the need for multinational, cooperative efforts to conserve R. typus populations in the Red Sea and Indian Ocean.

  15. Effects of an electric field on white sharks: in situ testing of an electric deterrent.

    PubMed

    Huveneers, Charlie; Rogers, Paul J; Semmens, Jayson M; Beckmann, Crystal; Kock, Alison A; Page, Brad; Goldsworthy, Simon D

    2013-01-01

    Elasmobranchs can detect minute electromagnetic fields, <1 nV cm(-1), using their ampullae of Lorenzini. Behavioural responses to electric fields have been investigated in various species, sometimes with the aim to develop shark deterrents to improve human safety. The present study tested the effects of the Shark Shield Freedom7™ electric deterrent on (1) the behaviour of 18 white sharks (Carcharodon carcharias) near a static bait, and (2) the rates of attacks on a towed seal decoy. In the first experiment, 116 trials using a static bait were performed at the Neptune Islands, South Australia. The proportion of baits taken during static bait trials was not affected by the electric field. The electric field, however, increased the time it took them to consume the bait, the number of interactions per approach, and decreased the proportion of interactions within two metres of the field source. The effect of the electric field was not uniform across all sharks. In the second experiment, 189 tows using a seal decoy were conducted near Seal Island, South Africa. No breaches and only two surface interactions were observed during the tows when the electric field was activated, compared with 16 breaches and 27 surface interactions without the electric field. The present study suggests that the behavioural response of white sharks and the level of risk reduction resulting from the electric field is contextually specific, and depends on the motivational state of sharks.

  16. Sharks modulate their escape behavior in response to predator size, speed and approach orientation.

    PubMed

    Seamone, Scott; Blaine, Tristan; Higham, Timothy E

    2014-12-01

    Escape responses are often critical for surviving predator-prey interactions. Nevertheless, little is known about how predator size, speed and approach orientation impact escape performance, especially in larger prey that are primarily viewed as predators. We used realistic shark models to examine how altering predatory behavior and morphology (size, speed and approach orientation) influences escape behavior and performance in Squalus acanthias, a shark that is preyed upon by apex marine predators. Predator models induced C-start escape responses, and increasing the size and speed of the models triggered a more intense response (increased escape turning rate and acceleration). In addition, increased predator size resulted in greater responsiveness from the sharks. Among the responses, predator approach orientation had the most significant impact on escapes, such that the head-on approach, as compared to the tail-on approach, induced greater reaction distances and increased escape turning rate, speed and acceleration. Thus, the anterior binocular vision in sharks renders them less effective at detecting predators approaching from behind. However, it appears that sharks compensate by performing high-intensity escapes, likely induced by the lateral line system, or by a sudden visual flash of the predator entering their field of view. Our study reveals key aspects of escape behavior in sharks, highlighting the modulation of performance in response to predator approach.

  17. The actuation of microflaps inspired by shark scales deeply embedded in a boundary layer

    NASA Astrophysics Data System (ADS)

    Morris, Jackson; Lang, Amy; Hubner, Paul

    2016-11-01

    Thanks to millions of years of natural selection, sharks have evolved to become quick apex predators. Shark skin is made up of microscopic scales on the order of 0.2 mm in size. This array of scales is hypothesized to be a flow control mechanism where individual scales are capable of being passively actuated by reversed flow in water due to their preferential orientation to attached flow. Previous research has proven shark skin to reduce flow separation in water, which would result in lower pressure drag. We believe shark scales are strategically sized to interact with the lower 5 percent of the boundary layer, where reversed flow occurs close to the wall. To test the capability of micro-flaps to be actuated in air various sets of flaps, inspired by shark scale geometry, were rapidly prototyped. These microflaps were tested in a low-speed wind tunnel at various flow speeds and boundary layer thicknesses. Boundary layer flow conditions were measured using a hot-wire probe and microflap actuation was observed. Microflap actuation in airflow would mean that this bio-inspired separation control mechanism found on shark skin has potential application for aircraft. Boeing.

  18. Gonadal Morphology, Histology, and Endocrinological Characteristics of Immature Female Whale Sharks, Rhincodon typus.

    PubMed

    Nozu, Ryo; Murakumo, Kiyomi; Matsumoto, Rui; Nakamura, Masaru; Ueda, Keiichi; Sato, Keiichi

    2015-10-01

    Captive breeding of whale sharks is one of the great challenges for aquariums. However, there is limited information available related to reproductive physiology due to the difficulty of sampling and long-term observation. In the present report, we provide information on the reproductive physiology of female whale sharks, which were incidentally captured as bycatch in a set-net off the coast of Okinawa, Japan. Total lengths of three captured female whale sharks were 403, 665, and 761 cm, respectively, at the time of their death. Collected paired ovaries differed in size between right and left. However, it seems not to determine which side of ovary becomes developed. Histological observations revealed that oocytes surrounded by follicle cell layers localized in the developed ovary, and most developed oocytes exhibited yolk vesicle stage. Additionally, in the largest specimen, there were low levels of three steroid hormones (Testosterone, Dihydrotestosterone, and Estradiol-17ß) that did not show seasonal variation. The present results indicate that even the whale shark over 7 m in TL are still histologically and endocrinologically immature. We expect that the present data will provide fundamental information related to reproductive physiology of female whale sharks, and will contribute to protection activities and increased success in captive breeding of whale sharks.

  19. The effect of shark cartilage extracts on the growth and metastatic spread of the SCCVII carcinoma.

    PubMed

    Horsman, M R; Alsner, J; Overgaard, J

    1998-01-01

    This study was designed to investigate the potential of shark cartilage extracts to inhibit the growth and metastatic spread of a murine solid tumour. The SCCVII carcinoma, implanted in the right rear foot of C3H mice, was used. Following tumour implantation, two different commercially available extracts of shark cartilage (Sharkilage and MIA Shark Powder) were dissolved in water and orally administered to the mice at doses that ranged from 5 to 100 mg per mouse. These injections were repeated on a daily basis for up to 25 days post-implantation of the primary tumour. Compared to non-drug-treated animals, daily administration of the shark cartilage extracts did not show any adverse toxicity (as measured by changes in body weight and lethality). More importantly, none of the shark cartilage doses tested had any retarding effect on the growth of the primary tumour, nor did they inhibit the development of metastases seen in the lungs of the tumour-bearing mice at autopsy. In conclusion, our results offer no support for the proposed use of shark cartilage extracts as an anti-cancer therapy.

  20. An Experimental Study of Flow Separation Control by Shortfin Mako Shark Skin

    NASA Astrophysics Data System (ADS)

    Afroz, Farhana; Lang, Amy; Motta, Philip; Habegger, Maria

    2013-11-01

    The shortfin mako shark (Isurus oxyrinchus) is a fast swimmer and has incredible turning agility. Shark skin is covered with flexible scales and this bristling capability may result in a unique Boundary Layer Control (BLC) method to reduce drag. It is hypothesized that scales bristle when the flow above it is reversed, and between the bristled scales embedded micro-vortices form in the cavities which induce boundary layer mixing and aid in delaying flow separation. To testify this hypothesis, samples of mako shark skin have been tested in a water tunnel under various strengths of adverse pressure gradient (APG). Laminar and turbulent separation over shark skin was studied experimentally using Time-Resolved Digital Particle Image Velocimetry (TR-DPIV) system, where the APG was generated and varied using a rotating cylinder. Then shark skin results were compared with that of a flat plate data for a given amount of APG. The study reveals that shark skin is capable of controlling both laminar and turbulent flow separation. Support under NSF grant 0932352 is gratefully acknowledged. First author Farhana Afroz was also supported by a scholarship through the Alabama EPSCoR Graduate Research Scholars Program.

  1. Biomagnification of mercury and selenium in blue shark Prionace glauca from the Pacific Ocean off Mexico.

    PubMed

    Escobar-Sánchez, Ofelia; Galván-Magaña, Felipe; Rosíles-Martínez, René

    2011-12-01

    The aim of this study was to determine the biomagnification of mercury through the principal prey of the blue shark, Prionace glauca, off the western coast of Baja California Sur, Mexico, as well as the relationship between mercury and selenium in blue sharks. High levels of mercury were found in shark muscle tissues (1.39 ± 1.58 μg/g wet weight); these values are above the allowed 1.0 μg/g for human consumption. The mercury to selenium molar ratio was 1:0.2. We found a low correlation between mercury bioaccumulation and shark size. Juveniles have lower concentrations of mercury than adults. Regarding the analyzed prey, the main prey of the blue shark, pelagic red crab, Pleuroncodes planipes, bioaccumulated 0.04 ± 0.01 μg/g Hg wet weight, but the prey with higher bioaccumulation was the bullet fish Auxis spp. (0.20 ± 0.02 μg/g wet weight). In terms of volume, the red crab P. planipes can be the prey that provides high levels of mercury to the blue shark.

  2. Evaluating the performance of methods for estimating the abundance of rapidly declining coastal shark populations.

    PubMed

    McCauley, Douglas J; McLean, Kevin A; Bauer, John; Young, Hillary S; Micheli, Fiorenza

    2012-03-01

    Accurately surveying shark populations is critical to monitoring precipitous ongoing declines in shark abundance and interpreting the effects that these reductions are having on ecosystems. To evaluate the effectiveness of existing survey tools, we used field trials and computer simulations to critically examine the operation of four common methods for counting coastal sharks: stationary point counts, belt transects, video surveys, and mark and recapture abundance estimators. Empirical and theoretical results suggest that (1) survey method selection has a strong impact on the estimates of shark density that are produced, (2) standardizations by survey duration are needed to properly interpret and compare survey outputs, (3) increasing survey size does not necessarily increase survey precision, and (4) methods that yield the highest density estimates are not always the most accurate. These findings challenge some of the assumptions traditionally associated with surveying mobile marine animals. Of the methods we trialed, 8 x 50 m belt transects and a 20 m radius point count produced the most accurate estimates of shark density. These findings can help to improve the ways we monitor, manage, and understand the ecology of globally imperiled coastal shark populations.

  3. An Unprecedented Aggregation of Whale Sharks, Rhincodon typus, in Mexican Coastal Waters of the Caribbean Sea

    PubMed Central

    de la Parra Venegas, Rafael; Hueter, Robert; González Cano, Jaime; Tyminski, John; Gregorio Remolina, José; Maslanka, Mike; Ormos, Andrea; Weigt, Lee; Carlson, Bruce; Dove, Alistair

    2011-01-01

    Whale sharks, Rhincodon typus, are often perceived as solitary behemoths that live and feed in the open ocean. To the contrary, evidence is accumulating that they are gregarious and form seasonal aggregations in some coastal waters. One such aggregation occurs annually north of Cabo Catoche, off Isla Holbox on the Yucatán Peninsula of Mexico. Here we report a second, much denser aggregation of whale sharks (dubbed “the Afuera”) that occurs east of the tip of the Yucatán Peninsula in the Caribbean Sea. The 2009 Afuera event comprised the largest aggregation of whale sharks ever reported, with up to 420 whale sharks observed in a single aerial survey, all gathered in an elliptical patch of ocean approximately 18 km2. Plankton studies indicated that the sharks were feeding on dense homogenous patches of fish eggs, which DNA barcoding analysis identified as belonging to little tunny, Euthynnus alletteratus. This contrasts with the annual Cabo Catoche aggregation nearby, where prey consists mostly of copepods and sergestid shrimp. Increased sightings at the Afuera coincide with decreased sightings at Cabo Catoche, and both groups have the same sex ratio, implying that the same animals are likely involved in both aggregations; tagging data support this idea. With two whale shark aggregation areas, high coastal productivity and a previously-unknown scombrid spawning ground, the northeastern Yucatán marine region is a critical habitat that deserves more concerted conservation efforts. PMID:21559508

  4. [Demographic analysis of the blue shark, Prionace glauca, in the North Atlantic Ocean].

    PubMed

    Gao, Chun-xia; Dai, Xiao-jie; Tian, Si-quan; Wu, Feng; Zhu, Jiang-feng

    2016-02-01

    The blue shark, Prionace glauca, is the main by-catch species in tuna longline fishery. As one of top species in the oceanic food webs, the blue shark plays an important role in the marine ecosystem. Traditional stock assessment methods are difficult to accurately evaluate the population dynamic for this shark because of limited data. Based on life-history parameters of the blue shark in the North Atlantic, demographic analysis was employed to estimate the demographic parameters and evaluate the potential exploitation for the blue shark. Moreover, we discussed the relationship between age at first capture and critical value of fishing mortality corresponding to the value of intrinsic rate of natural increase 0. The results showed that the survival rate (S) of blue shark from 0.719 to 0.820, intrinsic rate of natural increase (r0) from 0.250 to 0.381, time of population doubling (tx2) from 1.819 to 2.773 years, reproduction rate per generation (R0) from 6.600 to 22.255, and generation time (G) from 8.498 to 10.162 years. The sensitivity analysis for the life history parameters revealed that the uncertainties of natural mortality existed in the first age class, age at maturity and maximum age had slight influence on the demographic parameters. Fishing mortality (Fc) increased with the age at first capture. When the age at first capture (tc) was more than five, there was no obvious relationship between Fc and tc.

  5. High connectivity of the crocodile shark between the Atlantic and Southwest Indian Oceans: highlights for conservation.

    PubMed

    da Silva Ferrette, Bruno Lopes; Mendonça, Fernando Fernandes; Coelho, Rui; de Oliveira, Paulo Guilherme Vasconcelos; Hazin, Fábio Hissa Vieira; Romanov, Evgeny V; Oliveira, Claudio; Santos, Miguel Neves; Foresti, Fausto

    2015-01-01

    Among the various shark species that are captured as bycatch in commercial fishing operations, the group of pelagic sharks is still one of the least studied and known. Within those, the crocodile shark, Pseudocarcharias kamoharai, a small-sized lamnid shark, is occasionally caught by longline vessels in certain regions of the tropical oceans worldwide. However, the population dynamics of this species, as well as the impact of fishing mortality on its stocks, are still unknown, with the crocodile shark currently one of the least studied of all pelagic sharks. Given this, the present study aimed to assess the population structure of P. kamoharai in several regions of the Atlantic and Indian Oceans using genetic molecular markers. The nucleotide composition of the mitochondrial DNA control region of 255 individuals was analyzed, and 31 haplotypes were found, with an estimated diversity Hd = 0.627, and a nucleotide diversity π = 0.00167. An analysis of molecular variance (AMOVA) revealed a fixation index ΦST = -0.01118, representing an absence of population structure among the sampled regions of the Atlantic Ocean, and between the Atlantic and Indian Oceans. These results show a high degree of gene flow between the studied areas, with a single genetic stock and reduced population variability. In panmictic populations, conservation efforts can be concentrated in more restricted areas, being these representative of the total biodiversity of the species. When necessary, this strategy could be applied to the genetic maintenance of P. kamoharai.

  6. High Connectivity of the Crocodile Shark between the Atlantic and Southwest Indian Oceans: Highlights for Conservation

    PubMed Central

    da Silva Ferrette, Bruno Lopes; Mendonça, Fernando Fernandes; Coelho, Rui; de Oliveira, Paulo Guilherme Vasconcelos; Hazin, Fábio Hissa Vieira; Romanov, Evgeny V.; Oliveira, Claudio; Santos, Miguel Neves; Foresti, Fausto

    2015-01-01

    Among the various shark species that are captured as bycatch in commercial fishing operations, the group of pelagic sharks is still one of the least studied and known. Within those, the crocodile shark, Pseudocarcharias kamoharai, a small-sized lamnid shark, is occasionally caught by longline vessels in certain regions of the tropical oceans worldwide. However, the population dynamics of this species, as well as the impact of fishing mortality on its stocks, are still unknown, with the crocodile shark currently one of the least studied of all pelagic sharks. Given this, the present study aimed to assess the population structure of P. kamoharai in several regions of the Atlantic and Indian Oceans using genetic molecular markers. The nucleotide composition of the mitochondrial DNA control region of 255 individuals was analyzed, and 31 haplotypes were found, with an estimated diversity Hd = 0.627, and a nucleotide diversity π = 0.00167. An analysis of molecular variance (AMOVA) revealed a fixation index ΦST = -0.01118, representing an absence of population structure among the sampled regions of the Atlantic Ocean, and between the Atlantic and Indian Oceans. These results show a high degree of gene flow between the studied areas, with a single genetic stock and reduced population variability. In panmictic populations, conservation efforts can be concentrated in more restricted areas, being these representative of the total biodiversity of the species. When necessary, this strategy could be applied to the genetic maintenance of P. kamoharai. PMID:25689742

  7. A novel mini-DNA barcoding assay to identify processed fins from internationally protected shark species.

    PubMed

    Fields, Andrew T; Abercrombie, Debra L; Eng, Rowena; Feldheim, Kevin; Chapman, Demian D

    2015-01-01

    There is a growing need to identify shark products in trade, in part due to the recent listing of five commercially important species on the Appendices of the Convention on International Trade in Endangered Species (CITES; porbeagle, Lamna nasus, oceanic whitetip, Carcharhinus longimanus scalloped hammerhead, Sphyrna lewini, smooth hammerhead, S. zygaena and great hammerhead S. mokarran) in addition to three species listed in the early part of this century (whale, Rhincodon typus, basking, Cetorhinus maximus, and white, Carcharodon carcharias). Shark fins are traded internationally to supply the Asian dried seafood market, in which they are used to make the luxury dish shark fin soup. Shark fins usually enter international trade with their skin still intact and can be identified using morphological characters or standard DNA-barcoding approaches. Once they reach Asia and are traded in this region the skin is removed and they are treated with chemicals that eliminate many key diagnostic characters and degrade their DNA ("processed fins"). Here, we present a validated mini-barcode assay based on partial sequences of the cytochrome oxidase I gene that can reliably identify the processed fins of seven of the eight CITES listed shark species. We also demonstrate that the assay can even frequently identify the species or genus of origin of shark fin soup (31 out of 50 samples).

  8. A Novel Mini-DNA Barcoding Assay to Identify Processed Fins from Internationally Protected Shark Species

    PubMed Central

    Fields, Andrew T.; Abercrombie, Debra L.; Eng, Rowena; Feldheim, Kevin; Chapman, Demian D.

    2015-01-01

    There is a growing need to identify shark products in trade, in part due to the recent listing of five commercially important species on the Appendices of the Convention on International Trade in Endangered Species (CITES; porbeagle, Lamna nasus, oceanic whitetip, Carcharhinus longimanus scalloped hammerhead, Sphyrna lewini, smooth hammerhead, S. zygaena and great hammerhead S. mokarran) in addition to three species listed in the early part of this century (whale, Rhincodon typus, basking, Cetorhinus maximus, and white, Carcharodon carcharias). Shark fins are traded internationally to supply the Asian dried seafood market, in which they are used to make the luxury dish shark fin soup. Shark fins usually enter international trade with their skin still intact and can be identified using morphological characters or standard DNA-barcoding approaches. Once they reach Asia and are traded in this region the skin is removed and they are treated with chemicals that eliminate many key diagnostic characters and degrade their DNA (“processed fins”). Here, we present a validated mini-barcode assay based on partial sequences of the cytochrome oxidase I gene that can reliably identify the processed fins of seven of the eight CITES listed shark species. We also demonstrate that the assay can even frequently identify the species or genus of origin of shark fin soup (31 out of 50 samples). PMID:25646789

  9. Stratigraphy and paleogeography of the Cretaceous in Arabian Peninsula

    SciTech Connect

    Alsharhan, A.S.; Nairn, A.E.M.

    1986-05-01

    The Cretaceous of the Arabian Peninsula is divided into three major units by regional unconformities: Lower Cretaceous Thamama Group (Berriasian-middle Aptian), middle Cretaceous Wasia Group (Albian-Turonian), and Upper Cretaceous Aruma Group (Coniacian-Maestrichtian). The profusion of named stratigraphic units in the area reflects not only the lithologic variation resulting from facies changes, but also terminologies adopted by different companies. The authors provide a stratigraphic nomenclature defining standard type sections and indicate synonymies, which follow the recommendation of 10th Geological Liaison Meeting and hence are acceptable to operators in the area. The sedimentologic history of the area was presented in a series of paleogeographic maps, which they relate to the regional tectonic framework. The maps show a predominantly carbonate shelf ramp bordering a land area to the north and west. The principal change in depositional environment occurs during the Upper Cretaceous, as a result of tectonic activity. Less significant changes are attributed to eustatic sea level fluctuations, on which tilting caused by tectonic movement may be superposed during the Lower and middle Cretaceous. The major producing horizons lie below the regional unconformities; secondary porosity in the shelf reefal buildups was developed during subaerial exposure in the Shuaiba Formation (early-middle Aptian), in the Mishrif Formation (late Cenomanian), and in the Simsima Formation (Maestrichtian).

  10. A Late Cretaceous ceratopsian dinosaur from Europe with Asian affinities.

    PubMed

    Osi, Attila; Butler, Richard J; Weishampel, David B

    2010-05-27

    Ceratopsians (horned dinosaurs) represent a highly diverse and abundant radiation of non-avian dinosaurs known primarily from the Cretaceous period (65-145 million years ago). This radiation has been considered to be geographically limited to Asia and western North America, with only controversial remains reported from other continents. Here we describe new ceratopsian cranial material from the Late Cretaceous of Iharkút, Hungary, from a coronosaurian ceratopsian, Ajkaceratops kozmai. Ajkaceratops is most similar to 'bagaceratopsids' such as Bagaceratops and Magnirostris, previously known only from Late Cretaceous east Asia. The new material unambiguously demonstrates that ceratopsians occupied Late Cretaceous Europe and, when considered with the recent discovery of possible leptoceratopsid teeth from Sweden, indicates that the clade may have reached Europe on at least two independent occasions. European Late Cretaceous dinosaur faunas have been characterized as consisting of a mix of endemic 'relictual' taxa and 'Gondwanan' taxa, with typical Asian and North American groups largely absent. Ajkaceratops demonstrates that this prevailing biogeographical hypothesis is overly simplified and requires reassessment. Iharkút was part of the western Tethyan archipelago, a tectonically complex series of island chains between Africa and Europe, and the occurrence of a coronosaurian ceratopsian in this locality may represent an early Late Cretaceous 'island-hopping' dispersal across the Tethys Ocean.

  11. Fire and the spread of flowering plants in the Cretaceous.

    PubMed

    Bond, William J; Scott, Andrew C

    2010-12-01

    We suggest that the spread of angiosperms in the Cretaceous was facilitated by novel fire regimes. Angiosperms were capable of high productivity and therefore accumulated flammable biomass ('fuel') more rapidly than their predecessors. They were capable of rapid reproduction, allowing populations to spread despite frequent disturbance. We evaluate the evidence for physical conditions conducive to fires in the Cretaceous. These included high temperatures, seasonally dry climate and higher atmospheric oxygen than current levels. We evaluate novel properties of angiosperms that contributed to rapid biomass accumulation, and to their ability to thrive in frequently disturbed environments. We also review direct evidence for Cretaceous fires. Charcoal mesofossils are common in Cretaceous deposits of the Northern Hemisphere. Inertinite, the charcoal component of coal, is common throughout the Cretaceous and into the Palaeocene, but declined steeply from the Eocene when angiosperm-dominated forests became widespread. Direct and indirect evidence is consistent with angiosperms initiating novel fire regimes, promoting angiosperm spread in the Cretaceous. Several traits are consistent with frequent surface fires. We suggest that forest was slow to develop until the Eocene, when fire activity dropped to very low levels. The causes and consequences of fires in the deep past warrant greater attention.

  12. Groundwater from Lower Cretaceous rocks in Kansas

    USGS Publications Warehouse

    Keene, Katherine M.; Bayne, Charles Knight

    1976-01-01

    Sandstones in Lower Cretaceous rocks contain supplies, of water that may be adequate to meet increasing present and future demands for supplemental municipal and domestic use in central and western Kansas. An estimated 70 to 80 million acre-feet (86,000 to 99,000 cubic hectometers) of water containing less than 1,000 milligrams per liter dissolved solids may be acceptable for use at the present (1976). An additional 10 to 15 million acre-feet (12,000 to 18,000 cubic hectometers) containing 1,000 to 3,000 milligrams per liter dissolved solids is estimated to be available for use in the future with appropriate desalinization. Lower Cretaceous rocks crop out from Washington County on the north to Comanche County on-the south. The rocks dip from a structural high in the southwest part of the State to structural lows in the northwest and north-central part. Depth below land surface increases generally northwestward to about 2,600 feet (790 meters); thickness of the rocks increases westward, nearly zero to about 850 feet (260 meters). The rocks consist chiefly of marine to nonmarine shale and silt- stone interbedded with coastal to deltaic sandstone. The interbedded sandstone, which composes about one-third of the rocks, consists of one or more lenses that thicken westward to about 400 feet (120 meters) in the central part of western Kansas. The yield of water to individual wells is related to areal extent, thickness, and interconnection of the sand lenses and to grain size and cementation of the sand. Large amounts of water may be pumped by wells where loosely cemented sand lenses are interconnected. Wells commonly yield adequate supplies for domestic and stock use; reported yields from municipal and irrigation wells range from about 100 to 2,000 gallons per minute (6 to 125 liters per second). Recharge to the Lower Cretaceous-rocks occurs in the area of outcrop and from hydraulically connected saturated Cenozoic rocks, especially in the southern part of the State

  13. Late Cretaceous Volcaniclastics in NW Turkey

    NASA Astrophysics Data System (ADS)

    Boehm, Katharina; Wolfgring, Erik; Omer Yilmaz, Ismail; Tüysüz, Okan; Wagreich, Michael

    2015-04-01

    On the southwestern coast of the Black Sea, in the western Pontides Upper Cretaceous tuff layers are present. The tuffs are intercalated with limestones, marls and turbidites and were investigated with focus on their geochemistry, to get new insights to the arrangement of terranes and ocean basins at this time. In the region two Upper Cretaceous volcanic units can be distinguished, separated by distinct red pelagic limestone successions, belonging to the Unaz Formation. The lower volcanic unit is named Dereköy Formation and is Turonian to Santonian in age. It is thought to be deposited within extension structures, contemporaneously with rifting in the western Black Sea basin. The upper volcanic unit is called Cambu Formation. According to biostratigraphic data it is deposited throughout Campanian, when spreading in the western Black Sea basin started. Interpreted as submarine deposits, element mobility has to be taken into account when interpreting geochemical ICP-MS data of the volcaniclastics. Multiple discrimination diagrams with suitable proxies elucidate the type of volcanism and contribute to reconstruction of the tectonic setting. The classified rock types range from basaltic to rhyodacitic in both volcanic formations. Basically degree of differentiation and alkalinity are the parameters looked at, when determining rock types of the volcanic eruption. Further volcanic series are specified as calc-alkaline to shoshonitic. Moreover, a volcanic arc setting seems to be the most likely case, following several discrimination diagrams, as well as normalized multi-element plots. This tectonic setting can be discussed in connection with paleo-tectonic reconstructions. Most cited in literature nowadays are models favoring a northward subduction of the northern branch of Neotethys, creating an extensional setting north of the Pontides. This kind of back arc extension is interpreted as the reason of a southward drift of the Istanbul continental fragment from Eurasia

  14. Environmental Influences on the Abundance and Sexual Composition of White Sharks Carcharodon carcharias in Gansbaai, South Africa

    PubMed Central

    Towner, Alison V.; Underhill, Les G.; Jewell, Oliver J. D.; Smale, Malcolm J.

    2013-01-01

    The seasonal occurrence of white sharks visiting Gansbaai, South Africa was investigated from 2007 to 2011 using sightings from white shark cage diving boats. Generalized linear models were used to investigate the number of great white sharks sighted per trip in relation to sex, month, sea surface temperature and Multivariate El Niño/Southern Oscillation (ENSO) Indices (MEI). Water conditions are more variable in summer than winter due to wind-driven cold water upwelling and thermocline displacement, culminating in colder water temperatures, and shark sightings of both sexes were higher during the autumn and winter months (March–August). MEI, an index to quantify the strength of Southern Oscillation, differed in its effect on the recorded numbers of male and female white sharks, with highly significant interannual trends. This data suggests that water temperature and climatic phenomena influence the abundance of white sharks at this coastal site. In this study, more females were seen in Gansbaai overall in warmer water/positive MEI years. Conversely, the opposite trend was observed for males. In cool water years (2010 to 2011) sightings of male sharks were significantly higher than in previous years. The influence of environmental factors on the physiology of sharks in terms of their size and sex is discussed. The findings of this study could contribute to bather safety programmes because the incorporation of environmental parameters into predictive models may help identify times and localities of higher risk to bathers and help mitigate human-white shark interactions. PMID:23951111

  15. Place learning prior to and after telencephalon ablation in bamboo and coral cat sharks (Chiloscyllium griseum and Atelomycterus marmoratus).

    PubMed

    Fuss, Theodora; Bleckmann, Horst; Schluessel, Vera

    2014-01-01

    This study assessed complex spatial learning and memory in two species of shark, the grey bamboo shark (Chiloscyllium griseum) and the coral cat shark (Atelomycterus marmoratus). It was hypothesized that sharks can learn and apply an allocentric orientation strategy. Eight out of ten sharks successfully completed the initial training phase (by locating a fixed goal position in a diamond maze from two possible start points) within 14.9 ± 7.6 sessions and proceeded to seven sets of transfer tests, in which sharks had to perform under altered environmental conditions. Transfer tests revealed that sharks had oriented and solved the tasks visually, using all of the provided environmental cues. Unintentional cueing did not occur. Results correspond to earlier studies on spatial memory and cognitive mapping in other vertebrates. Future experiments should investigate whether sharks possess a cognitive spatial mapping system as has already been found in several teleosts and stingrays. Following the completion of transfer tests, sharks were subjected to ablation of most of the pallium, which compromised their previously acquired place learning abilities. These results indicate that the telencephalon plays a crucial role in the processing of information on place learning and allocentric orientation strategies.

  16. 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.

  17. Environmental influences on the abundance and sexual composition of white sharks Carcharodon carcharias in Gansbaai, South Africa.

    PubMed

    Towner, Alison V; Underhill, Les G; Jewell, Oliver J D; Smale, Malcolm J

    2013-01-01

    The seasonal occurrence of white sharks visiting Gansbaai, South Africa was investigated from 2007 to 2011 using sightings from white shark cage diving boats. Generalized linear models were used to investigate the number of great white sharks sighted per trip in relation to sex, month, sea surface temperature and Multivariate El Niño/Southern Oscillation (ENSO) Indices (MEI). Water conditions are more variable in summer than winter due to wind-driven cold water upwelling and thermocline displacement, culminating in colder water temperatures, and shark sightings of both sexes were higher during the autumn and winter months (March-August). MEI, an index to quantify the strength of Southern Oscillation, differed in its effect on the recorded numbers of male and female white sharks, with highly significant interannual trends. This data suggests that water temperature and climatic phenomena influence the abundance of white sharks at this coastal site. In this study, more females were seen in Gansbaai overall in warmer water/positive MEI years. Conversely, the opposite trend was observed for males. In cool water years (2010 to 2011) sightings of male sharks were significantly higher than in previous years. The influence of environmental factors on the physiology of sharks in terms of their size and sex is discussed. The findings of this study could contribute to bather safety programmes because the incorporation of environmental parameters into predictive models may help identify times and localities of higher risk to bathers and help mitigate human-white shark interactions.

  18. Pass the salt: physiological consequences of ecologically relevant hyposmotic exposure in juvenile gummy sharks (Mustelus antarcticus) and school sharks (Galeorhinus galeus)

    PubMed Central

    Morash, Andrea J.; Mackellar, Sara R. C.; Tunnah, Louise; Barnett, David A.; Stehfest, Kilian M.; Semmens, Jayson M.; Currie, Suzanne

    2016-01-01

    Estuarine habitats are frequently used as nurseries by elasmobranch species for their protection and abundant resources; however, global climate change is increasing the frequency and severity of environmental challenges in these estuaries that may negatively affect elasmobranch physiology. Hyposmotic events are particularly challenging for marine sharks that osmoconform, and species-specific tolerances are not well known. Therefore, we sought to determine the effects of an acute (48 h) ecologically relevant hyposmotic event (25.8 ppt) on the physiology of two juvenile shark species, namely the school shark (Galeorhinus galeus), listed by the Australian Environmental Protection and Biodiversity Conservation Act as ‘conservation dependent’, and the gummy shark (Mustelus antarcticus), from the Pittwater Estuary (Australia). In both species, we observed a decrease in plasma osmolality brought about by selective losses of NaCl, urea and trimethylamine N-oxide, as well as decreases in haemoglobin, haematocrit and routine oxygen consumption. Heat-shock protein levels varied between species during the exposure, but we found no evidence of protein damage in any of the tissues tested. Although both species seemed to be able to cope with this level of osmotic challenge, overall the school sharks exhibited higher gill Na+/K+-ATPase activity and ubiquitin concentrations in routine and experimental conditions, a larger heat-shock protein response and a smaller decrease in routine oxygen consumption during the hyposmotic exposure, suggesting that there are species-specific responses that could potentially affect their ability to withstand longer or more severe changes in salinity. Emerging evidence from acoustic monitoring of sharks has indicated variability in the species found in the Pittwater Estuary during hyposmotic events, and together, our data may help to predict species abundance and distribution in the face of future global climate change. PMID:27757235

  19. Identification of shark species composition and proportion in the Hong Kong shark fin market based on molecular genetics and trade records.

    PubMed

    Clarke, Shelley C; Magnussen, Jennifer E; Abercrombie, Debra L; McAllister, Murdoch K; Shivji, Mahmood S

    2006-02-01

    The burgeoning and largely unregulated trade in shark fins represents one of the most serious threats to shark populations worldwide. In Hong Kong, the world's largest shark fin market, fins are classified by traders into Chinese-name categories on the basis of market value, but the relationship between market category and shark species is unclear preventing identification of species that are the most heavily traded. To delineate these relationships, we designed a sampling strategy for collecting statistically sufficient numbers of fins from traders and categories under conditions of limited market access because of heightened trader sensitivities. Based on information from traders and morphological inspection, we hypothesized matches between market names and shark taxa for fins within 11 common trade categories. These hypotheses were tested using DNA-based species identification techniques to determine the concordance between market category and species. Only 14 species made up approximately 40% of the auctioned fin weight. The proportion of samples confirming the hypothesized match, or concordance, varied from 0.64 to 1 across the market categories. We incorporated the concordance information and available market auction records for these categories into stochastic models to estimate the contribution of each taxon by weight to the fin trade. Auctioned fin weight was dominated by the blue shark (Prionace glauca), which was 17% of the overall market. Other taxa, including the shortfin mako (Isurus oxyrinchus), silky (Carcharhinus falciformis), sandbar (C. obscurus), bull (C. leucas), hammerhead (Sphyrna spp.), and thresher (Alopias spp.), were at least 2-6% of the trade. Our approach to marketplace monitoring of wildlife products isparticularly applicable to situations in which quantitative data at the source of resource extraction are sparse and large-scale genetic testing is limited by budgetary or other market access constraints.

  20. Molecular systematics and global phylogeography of angel sharks (genus Squatina).

    PubMed

    Stelbrink, Björn; von Rintelen, Thomas; Cliff, Geremy; Kriwet, Jürgen

    2010-02-01

    Angel sharks of the genus Squatina represent a group comprising 22 extant benthic species inhabiting continental shelves and upper slopes. In the present study, a comprehensive phylogenetic reconstruction of 17 Squatina species based on two mitochondrial markers (COI and 16S rRNA) is provided. The phylogenetic reconstructions are used to test biogeographic patterns. In addition, a molecular clock analysis is conducted to estimate divergence times of the emerged clades. All analyses show Squatina to be monophyletic. Four geographic clades are recognized, of which the Europe-North Africa-Asia clade is probably a result of the Tethys Sea closure. A second sister group relationship emerged in the analyses, including S. californica (eastern North Pacific) and S. dumeril (western North Atlantic), probably related to the rise of the Panamanian isthmus. The molecular clock analysis show that both lineage divergences coincide with the estimated time of these two geological events.

  1. Occurrence of the megatoothed sharks (Lamniformes: Otodontidae) in Alabama, USA

    PubMed Central

    Ebersole, Jun

    2014-01-01

    The Otodontidae include some of the largest sharks to ever live in the world’s oceans (i.e., Carcharocles megalodon). Here we report on Paleocene and Eocene occurrences of Otodus obliquus and Carcharocles auriculatus from Alabama, USA. Teeth of Otodus are rarely encountered in the Gulf Coastal Plain and this report is one of the first records for Alabama. Carcharocles auriculatus is more common in the Eocene deposits of Alabama, but its occurrence has been largely overlooked in the literature. We also refute the occurrence of the Oligocene Carcharocles angustidens in the state. Raised awareness and increased collecting of under-sampled geologic formations in Alabama will likely increase sample sizes of O. obliquus and C. auriculatus and also might unearth other otodontids, such as C. megalodon and C. chubutensis. PMID:25332848

  2. Microbial mats and modern stromatolites in Shark Bay, Western Australia

    NASA Technical Reports Server (NTRS)

    Golubic, S.

    1985-01-01

    Distribution, external morphology, texture, and microbial composition of microbial mats in Hamelin Pool, Shark Bay, Western Australia, have been studied and reviewed along a composite representative profile starting from the permanently submerged zone, across the zones of periodic flooding, toward permanently emerged land and coastal dunes. The following nine types of algal mats have been recognized: colloform, gelatinous, smooth, pincushion, tufted, mamillate, film, reticulate, and blister. Solar ponds represent a particular environment. The mat types represent microbial communities that are characterized by one or more dominant microorganisms. The colonization and stabilization of loose sediment is carried out by a microbial assemblage of generalists that prepare the ground for later replacement and succession by specialized microflora. Lithification of microbial mats takes place periodically, mainly during the austral summer. This process is destructive for the microbial community but increases the preservation potential of the stromatolitic structures.

  3. Sojourner Rover View of Shark and Half Dome

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The rounded knobs (arrows) up to 3 or 4 cm wide on Shark (left; approximately 70 cm wide)) and Half Dome (upper right) and in the foreground could be pebbles in a cemented matrix of clays, silts, and sands; such rocks are called conglomerates. Well-rounded objects like these were not seen at the Viking sites.

    NOTE: original caption as published in Science Magazine.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

  4. High hemoglobin mixed disulfide content in hemolysates from stressed shark.

    PubMed

    Dafré, A L; Reischl, E

    1990-01-01

    1. Hemolysate from heavily stressed smooth hammerhead shark, Sphyrna zygaena, shows three electrophoretic components, SZ I, SZ II and SZ III, whose relative concentrations are 36.4 +/- 6.8, 36.4 +/- 5.0 and 20.8 +/- 5.7%, respectively. After reduction with DTE only SZ I remained. 2. SZ I reacted with glutathione disulfide reconstitute SZ II and SZ III. 3. Non-reduced, DTE-reduced, and denatured hemoglobin were found to have 2.0 +/- 0.4, 3.7 +/- 0.6, and 9.4 +/- 0.7-SH groups, respectively. 4. Erythrocyte non-protein--SH (NPSH), including glutathione present as mixed disulfide with SZ II and SZ III, is 1.7 NPSH/Hb.

  5. Alternative adaptive immunity strategies: coelacanth, cod and shark immunity.

    PubMed

    Buonocore, Francesco; Gerdol, Marco

    2016-01-01

    The advent of high throughput sequencing has permitted to investigate the genome and the transcriptome of novel non-model species with unprecedented depth. This technological advance provided a better understanding of the evolution of adaptive immune genes in gnathostomes, revealing several unexpected features in different fish species which are of particular interest. In the present paper, we review the current understanding of the adaptive immune system of the coelacanth, the elephant shark and the Atlantic cod. The study of coelacanth, the only living extant of the long thought to be extinct Sarcopterygian lineage, is fundamental to bring new insights on the evolution of the immune system in higher vertebrates. Surprisingly, coelacanths are the only known jawed vertebrates to lack IgM, whereas two IgD/W loci are present. Cartilaginous fish are of great interest due to their basal position in the vertebrate tree of life; the genome of the elephant shark revealed the lack of several important immune genes related to T cell functions, which suggest the existence of a primordial set of TH1-like cells. Finally, the Atlantic cod lacks a functional major histocompatibility II complex, but balances this evolutionary loss with the expansion of specific gene families, including MHC I, Toll-like receptors and antimicrobial peptides. Overall, these data point out that several fish species present an unconventional adaptive immune system, but the loss of important immune genes is balanced by adaptive evolutionary strategies which still guarantee the establishment of an efficient immune response against the pathogens they have to fight during their life.

  6. Durophagy in sharks: feeding mechanics of the hammerhead Sphyrna tiburo.

    PubMed

    Wilga, C D; Motta, P J

    2000-09-01

    This study investigates the motor pattern and head movements during feeding of a durophagus shark, the bonnethead Sphyrna tiburo, using electromyography and simultaneous high-speed video. Sphyrna tiburo feeds almost exclusively on hard-shelled crabs, with shrimp and fish taken occasionally. It captures crabs by ram feeding, then processes or reduces the prey by crushing it between molariform teeth, finally transporting the prey by suction for swallowing. The prey-crushing mechanism is distinct from that of ram or bite capture and suction transport. This crushing mechanism is accomplished by altering the duration of jaw adductor muscle activity and modifying jaw kinematics by the addition of a second jaw-closing phase. In crushing events, motor activity of the jaw adductor muscles continues (biting of the prey occurs as the jaws close and continues after the jaws have closed) throughout a second jaw-closing phase, unlike capture and transport events during which motor activity (biting) ceases at jaw closure. Sphyrna tiburo is able to take advantage of a resource (hard prey) that is not readily available to most sharks by utilizing a suite of durophagous characteristics: molariform teeth, a modified jaw protrusor muscle, altered jaw adductor activity and modified jaw kinematics. Sphyrna tiburo is a specialist feeder on crab prey as demonstrated by the lack of differences in kinematic or motor patterns when offered prey of differing hardness and its apparent lack of ability to modulate its behavior when feeding on other prey. Functional patterns are altered and coupled with modifications in dental and jaw morphology to produce diverse crushing behaviors in elasmobranchs.

  7. Inferences on the Cretaceous Superchron geodynamo

    NASA Astrophysics Data System (ADS)

    Cottrell, R. D.; Tarduno, J. A.; Smirnov, A. V.

    2002-12-01

    Superchrons provide an opportunity to view the geomagnetic field in its extreme, when reversals are rare, or absent altogether. They represent robust features that are useful for the affirmation of theoretical and numerical models of the geodynamo. However, to gain a complete picture of the geodynamo, we must move beyond polarity to characterize the morphology, secular variation and intensity of the field. Unfortunately, geologic and associated experimental alteration often prohibits the simultaneous definition of paleofield directions and intensities. Recently we developed a method for the measurement of paleointensity that utilizes single plagioclase crystals separated from basaltic lava flows. These crystals, which contain sub-micron sized titanomagnetite and magnetite inclusions, are less susceptible to alteration during the laboratory heatings required by paleointensity analysis. This method provides a means to obtain high resolution paleointensity data from sequences of basalt flows, which can in turn be used to characterize secular variation. Paleomagnetic and paleointensity data collected using this approach from lavas of the Rajmahal Traps (113-116 Ma) and the high Arctic (~95 Ma) indicate that the time-averaged Cretaceous Normal Polarity Superchron field was remarkably strong and stable. When compared with global results available at lower latitudes, these data define a time-averaged field that is overwhelmingly dominated by the axial dipole (octupole components are insignificant). Superchrons may reflect times when the nature of core-boundary heat flux allows the geodynamo to operate at peak efficiency.

  8. Using Fossil Shark Teeth to Illustrate Evolution and Introduce Basic Geologic Concepts in a High School Biology Classroom

    NASA Astrophysics Data System (ADS)

    Agnew, J. G.; Nunn, J. A.

    2007-12-01

    Shell Foundation sponsors a program at Louisiana State University called Shell Undergraduate Recruitment and Geoscience Education (SURGE). The purpose of SURGE is to help local high school science teachers incorporate geology into their classrooms by providing resources and training. As part of this program, a workshop for high school biology teachers was held at Louisiana State University in Baton Rouge on June 3-5, 2007. We had the teachers do a series of activities on fossil shark teeth to illustrate evolution and introduce basic earth science concepts such as geologic time, superposition, and faunal succession and provided the teachers with lesson plans and materials. As an example, one of our exercises explores the evolution of the megatoothed shark lineage leading to Carcharocles megalodon, the largest predatory shark in history with teeth up to 17 cm long. Megatoothed shark teeth make excellent evolutionary subjects because they have a good fossil record and show continuous transitions in morphology from the Eocene to Pliocene. Our activity follows the learning cycle model. We take advantage of the curiosity of sharks shared by most people, and allow students to explore the variations among different shark teeth and explain the causes of those variations. The objectives of this exercise are to have the students: 1) sort fossil shark teeth into biologically reasonable species; 2) form hypotheses about evolutionary relationships among fossil shark teeth; and 3) describe and interpret evolutionary trends in the fossil Megatoothed lineage. To do the activity, students are divided into groups of 2-3 and given a shuffled set of 72 shark tooth cards with different images of megatoothed shark teeth. They are instructed to group the shark tooth cards into separate species of sharks. After sorting the cards, students are asked to consider the evolutionary relationships among their species and arrange their species chronologically according to the species first

  9. Comparative Use of a Caribbean Mesophotic Coral Ecosystem and Association with Fish Spawning Aggregations by Three Species of Shark.

    PubMed

    Pickard, Alexandria E; Vaudo, Jeremy J; Wetherbee, Bradley M; Nemeth, Richard S; Blondeau, Jeremiah B; Kadison, Elizabeth A; Shivji, Mahmood S

    2016-01-01

    Understanding of species interactions within mesophotic coral ecosystems (MCEs; ~ 30-150 m) lags well behind that for shallow coral reefs. MCEs are often sites of fish spawning aggregations (FSAs) for a variety of species, including many groupers. Such reproductive fish aggregations represent temporal concentrations of potential prey that may be drivers of habitat use by predatory species, including sharks. We investigated movements of three species of sharks within a MCE and in relation to FSAs located on the shelf edge south of St. Thomas, United States Virgin Islands. Movements of 17 tiger (Galeocerdo cuvier), seven lemon (Negaprion brevirostris), and six Caribbean reef (Carcharhinus perezi) sharks tagged with acoustic transmitters were monitored within the MCE using an array of acoustic receivers spanning an area of 1,060 km2 over a five year period. Receivers were concentrated around prominent grouper FSAs to monitor movements of sharks in relation to these temporally transient aggregations. Over 130,000 detections of telemetered sharks were recorded, with four sharks tracked in excess of 3 years. All three shark species were present within the MCE over long periods of time and detected frequently at FSAs, but patterns of MCE use and orientation towards FSAs varied both spatially and temporally among species. Lemon sharks