Triana Arguedas, Jim Gelsleichter
University of North Florida, 1 UNF Drive, Jacksonville FL 32224, USA
Trends in Abundance of Sharks in Northeast Florida Estuaries
Sharks are important components of many marine ecosystems, and play an important role in structuring community ecology. Because of this, it is important to examine their distribution and abundance, along with factors that influence their population dynamics. In 2012, we reported the results of the first 3 years (2009-2011) of a new, longterm survey of sharks in northeast Florida estuaries and bays, focusing on the species composition of sharks that use these areas as well as the abiotic factors that influence their habitat use patterns. These data indicated that inshore locations on northeast Florida provide critical habitat to up to 11 shark species, especially the Atlantic sharpnose (Rhizoprionodon terraenovae), blacktip (Carcharhinus limbatus), bonnethead (Sphyrna tiburo), and sandbar (Carcharhinus plumbeus) sharks, and that habitat use is significantly influenced by environmental factors, particularly temperature. In this presentation, we provide updated data on shark habitat use patterns in northeast Florida estuaries, along with the results of a now 7-year time-series on shark abundance in these locations. The overall goal of this research was to use time-series data to characterize trends in local shark populations for management purposes.
Emily Bradley, Jim Gelsleichter
University of North Florida, Jacksonville, Florida, USA
Variations in thyroid activity in Atlantic stingrays (Dasyatis sabina) with respect to reproductive cycle
Thyroid activity variations have been observed over many taxa. Previous studies have shown that thyroid activity can vary with respect to the reproductive cycle. However, very little published research to date has been focused thyroid activity and reproduction in elasmobranchs. Therefore, the purpose of this study was to examine the relationship between thyroid activity and reproduction in the Atlantic stingray, Dasyatis sabina, an animal for which reproductive biology has been well characterized. To address this goal, the histomorphology of the thyroid gland in both males and female Dasyatis sabina was examined. One measurement of thyroid activity, the height of epithelial cells (EH), displayed seasonal variations in both males and females. In males, EH was greatest in winter (Jan). During this time, after sperm storage has occurred, testes begin to regress and mating begins. In females, EH increased from early to late spring (Mar-May), the time of ovulation and early gestation. Female EH declined in June when yolk dependent embryos were present. These data were consistent with previous studies on females of the same species and with other vertebrates. This suggests a potential role for thyroid hormones during early gestation. The data for male stingrays is one of the first examinations of thyroid activity in relation to reproduction in male elasmobranchs. Other indicators of thyroid activity such as follicle diameter and histochemistry are discussed.
Alan Brooks1, Katie Vaccaro1, Dean Grubbs2, Toby Daly-Engel1
1University of West Florida, Pensacola, FL, USA, 2Florida State University, Tallahassee, FL, USA
Polyandry and Multiple Paternity in the Gulf Spurdog Shark, Squalus cf mitsukurii
Polyandry, a mating system where a female mates with multiple males during a single breeding season, is a common reproductive strategy among many species. It is suggested that polyandry may increase the genetic diversity of a population, increase fitness of offspring, and possibly increase reproductive output. As a result of polyandry, a litter of pups in a female can be sired by multiple males, which is a widespread phenomenon called multiple paternity. Multiple paternity has been shown to be common in sharks, with every species that has been studied using more than a single brood showing some evidence of multiple mating. Here we examine the frequency of multiple paternity in a newly-described species of dogfish shark, the Gulf spurdog Squalus cf mitsukurii (Squalus clarkae), using microsatellite fragment analysis. Microsatellites are short tandem repeats in DNA which are notable for a high rate of mutation, allowing for individuals in a population to be identified with a high degree of accuracy. In order to estimate the extent of multiple paternity in S. mitsukurii, 13 separate litters with mothers were analyzed, along with 50 unrelated individuals, using 12 previously-developed microsatellite loci. Initial results suggest that S. mitsukurii may be the first shark species to date that shows no evidence of multiple paternity, instead showing a predominance of genetic monogamy. Even though rates of multiple paternity are highly variable between species, this result is surprising and may have future implications on the diversity and extinction risk for deep-water sharks in the Gulf of Mexico.
Diego Cardeñosa1, Andrew Fields1, Stan Shea2, Maxwell Marsh1, Jessica Quinlan1, Elizabeth Babcock3, Kevin Feldheim4, Demian Chapman1
1Stony Brook University, Stony Brook, NY, USA, 2Bloom Association, Hong Kong, Hong Kong, 3University of Miami, Miami, FL, USA, 4Field Museum of Natural History, Chicago, IL, USA
Shark Species Composition and Proportion in the Guangzhou Dried-Seafood Market
Shark populations around the world are threatened by the high demand for their fins in Asian countries. The molecular identification of processed shark products has proven to be challenging, due to the level of degradation of the DNA. This lack of detailed speciesspecific data has hindered the adoption of management regulations of the shark trade on a global scale. Here, we describe the species composition and proportion of shark species in the Guangzhou dried-seafood market by using a novel multiplex PCR minibarcode assay and a Bayesian statistical model. The analyzed samples (n= 392) comprised 24 different chondrichthyan species with blue sharks (Prionace glauca; 36.22%), silky sharks (Carcharhinus falciformis; 11.73%), smooth hammerheads (Sphyrna zygaena; 9.44%) and scalloped hammerheads (S. lewini; 5.36%) being the most common species, representing 63% of the market. These results highlight the need of species-specific based regulation since the market is focused on a small subset of vulnerable species. As these highly vulnerable species become less abundant and more regulated, the market will likely keep shifting towards more productive and less regulated species such as blue sharks.
Lydia Crawford2, Faith Stone1, Ian Davenport1
1Xavier University of Louisiana, New Orleans, LA, USA, 2Tulane University, New Orleans, LA, USA
Follicle Cell Process, a shark thing?
Like many apex predators, chondrichthyan fishes tend to produce few offspring. To compensate for low fecundity their young are large and precocial at birth or hatching. Producing larger young requires more maternal investment to the embryo, either by producing larger eggs or by supplying nutrients to the developing embryo. The selective pressure to produce larger young has resulted in the transition from egg laying (oviparity) to live bearing (viviparity). Approximately 65% of chondrichthayns are viviparous. An early step in this transition was to increase egg size and keep them within the body cavity, ultimately until term. In some chondrichthyans, eggs can reach extreme sizes, i.e. greater that 10 cm in Centrophorus sp. This evokes several questions, how do enough nutrients get to the eggs and how do they maintain the integrity during ovulation and passage through the reproductive tract. Follicle cell processes (FCP) appear to answer to both questions. The FCP are a set of large tube-like structures that connect the follicle cells directly to the oocyte, thus facilitating the uptake of metabolites. They also contain the contractile, cytoskeletal protein actin, this combined with a change in orientation throughout oogenesis infers a supportive role. The FCP were first described in 2011 and associated with elasmobranchs, but recent data implies that they may be strictly a Selachian novelty; as they appear absent in the little skate Leucoraja erinacea (Batoids). This now raises the question, are FCP a chondrichthyan innovation which were lost in the Batoids, or exclusive to the Selachians.
Shelby Creager, Leif Carlsson, Erik Noonburg, Marianne Porter
Florida Atlantic University, Boca Raton, FL, USA
A Comparative Study on the Tensile Properties of Elasmobranch Skin
In sharks, the skin stiffens and acts as an exotendon modulated by changes in internal muscular pressures generated during swimming. Shark skin is embedded with dermal denticles which vary in morphology regionally along the body and among species. Denticles function to reduce drag, increase swimming performance, and may impact the mechanical properties of the skin. Our goals are to assess denticle density and differences in skin tensile properties regionally across three shark species (Carcharhinus limbatus, Sphyrna lewini, and Isurus oxyrinchus). We expected to see increased denticle density (denticles / mm2) in the dorsal and ventral regions and fewer denticles on lateral surfaces. We hypothesized that strength (maximum stress before failure), stiffness (resistance to tension), and toughness (ability to absorb energy without failing) will correlate with denticle density, and these properties will be greater on dorsal and ventral surfaces compared to lateral surfaces. The skin from juvenile sharks were dissected from the underlying fascia and muscle at twelve anatomical landmarks. A dogbone-shaped steel punch was used to extract the skin samples for mechanical testing. Skin samples were oriented longitudinally (cranial to caudal) and stretched at a strain rate of 2 mm/s until failure. A stress-strain curve was generated for each sample and maximum strength, stiffness, and toughness were calculated. Comparing the exotendon function among species will help us to better understand the extent to which sharks are conserving energy during swimming.
Simon Dedman1, Rick Officer1, Deirdre Brophy1, Maurice Clarke2, Dave Reid2
1Galway-Mayo Institute of Technology, Galway, Ireland, 2Marine Institute, Galway, Ireland
Gbm.auto – a Decision Support Tool automating Boosted Regression Tree modelling of data-poor species abundance using environmental and human inputs, mapping essential habitats, and designing MSY-based MPAs considering stakeholder priorities
The gbm.auto R package suite automates and greatly simplifies delta log-normal Boosted Regression Tree spatial modelling, removing the high technical barrier that prevents many potential users from reaping the benefits of this powerful statistical modelling technique. The package and its documentation allow users with very little experience of R to generate maps of predicted abundance, representativeness maps for those abundance maps, bar plots of the relative influence of explanatory variables, dot and line plots of the relationships between explanatory variables and response variables, databases of the processed model objects, and a report explaining all the steps taken within the model. This process can be used to map essential habitats such as nursery grounds and spawning areas, to produce areas of key conservation importance for multiple species. Escapement biomass – the percentage of the stock which must be retained each year to conserve it – is then combined with the predicted abundance maps to create a Decision Support Tool that generates location and size options for MPAs to protect the target stocks, based on stakeholder priorities, especially the minimisation of fishing effort displacement. In bridging the gap between advanced statistical mathematics and conservation science/management/policy, these tools can allow improved spatial abundance predictions, and therefore better management and better conservation. This poster demonstrates how the package is used and the outputs it produces.
Ariel N. Egan1, Toby S. Daly-Engel1, J. Marcus Drymon2
1University of West Florida, Pensacola, FL, USA, 2University of South Alabama, Mobile, AL, USA
Multiple Paternity of the Atlantic Sharpnose Shark (Rhizoprionodon terraenovae)
The Atlantic sharpnose shark (Rhizoprionodon terraenovae) is an abundant, small coastal shark found in temperate and tropical waters of the western Atlantic and Gulf of Mexico, where it is an important part of both artisanal and commercial elasmobranch fisheries. Life history characteristics in this species are generally established, but the occurrence of multiple mating by females (polyandry) as a reproductive strategy remains undocumented. Studies indicate that polyandry is common among sharks, but to date no small coastal sharks have been studied. For this study, muscle tissue samples from 20 R. terraenovae broods were collected off the coast of Alabama. DNA will be extracted from all samples and microsatellite markers applied for parentage analysis. With these data, we aim to discern the occurrence and frequency of multiple mating in R. terraenovae over several reproductive seasons to examine how this trait varies over time. The results and information from this study may provide additional information about genetic diversity of the R. terraenovae population in the Gulf of Mexico. Different reproductive strategies can influence genetic diversity and fitness, and are therefore of interest for conservation management. If multiple paternity proves to be common in R. terraenovae, potential population-level consequences of exploitation by fisheries may need to be assessed to understand how fisheries affect the genetic diversity of this species.
Nicole Enright, Gavin Naylor
College of Charleston, Charleston, South Carolina, USA
A Vicariance Model for Biogeography and Speciation in Elasmobranchs using Molecular Clocks
Understanding rates of molecular evolution and dates of divergence in different species can provide useful insights into phenomena such as adaptation and speciation, and may allow one to make inferences about population structure and biogeography. Barriers such as the Isthmus of Panama and the Suez Canal are relatively new vicariant barriers separating two bodies of water inhabited by elasmobranchs, where no gene flow can occur between the separated populations. Such structures provide opportunities to calibrate rates of molecular evolution across a diversity of marine taxa and to explore the influence of different life history parameters on estimated rates of molecular evolution. Elasmobranchs are well suited for such studies as they exhibit both a wide range of life history attributes and include several taxa whose populations have been separated by such vicariant events. In this study, rates of molecular evolution are contrasted for mitochondrial markers across a suite of elasmobranch sister taxa found on either side of vicariant barriers. Patterns of molecular evolution are examined for potential influence of different life history parameters including but not limited to ovipary versus vivipary, generation time, and effective population size.
Luara Falcão1, Matthew McDavitt2, Vicente Faria3
1Programa de Pós-graduação em Ciências Marinhas Tropicais, Instituto de Ciências do Mar – Labomar, Universidade Federal do Ceará, Fortaleza, Brazil, 2National Legal Research Group Inc., Charlottesville, VA, USA, 3Departamento de Ciências Biológicas, Universidade Federal do Ceará, Fortaleza, Brazil
International online trade of sawfish rostra
The sawfish are rays that belong to the family Pristidae. All five sawfish species are listed in Appendix I of CITES – Convention on International Trade in Endangered Species of Wild Fauna and Flora. International trade of species included in this appendix is prohibited, either whole animals or parts of them, with the exception of trade authorized by CITES for scientific purposes. Despite the risk of extinction and the urgent need for conservation, the sawfish is still a target for capture and trade. This trade consists mainly of isolated fins and rostra, which have great cultural value beyond their intrinsic commercial value. The present study aimed to monitor the online international sawfish trade. The data were obtained by searches on Google Images using key words about sawfish trade. The search was conducted between March 2015 and January 2016 with a frequency of 3 to 4 times per week. The following data were recorded for each offer of a sawfish specimen: (1) photo, (2) species, (3) URL, (4) price, (5) seller’s country, (6) delivery country, (7) size of rostra, (8) estimated rostra age (antique or recently collected), (9) product availability (whether it was already sold or not). A total of 403 isolated sawfish rostra available for trade were recorded. The result of this research is presented in the context of illegal sawfish trade as well as to highlight the need for monitoring of the online trade of such species.
Brittany Finucci1, Carlos Bustamante2, Emma Jones3, Matthew Dunn1
1Victoria University of Wellington, Wellington, New Zealand, 2Molecular Fisheries Laboratory, University of Queensland, Brisbane, Australia, 3National Institute of Water and Atmospheric Research (NIWA), Auckland, New Zealand
Specialized Diet of the Deep-sea Elasmobranch, the prickly dogfish (Oxynotus bruniensis)
Specialist diets have been identified amongst elasmobranch, although the degree of specialization can be subjected to individual specialists, competition, and fluctuations in spatial and temporal prey abundance and availability. Several examples of chondrichthyans playing a large role in diet of other chondrichthyans have been previously documented, although few are known from the deep-sea, and have included large bodied species. The prickly dogfish Oxynotus bruniensis is a small (<75 cm), little known deep-sea elasmobranch distributed on the outer continental and upper slope of southern Australia and New Zealand. Specimens (n = 53) were collected from research trawls surveys and fisheries observers from around New Zealand at depths from 400 to 1300 m. Stomach contents were dissected and prey items were identified to the lowest possible taxon. Findings included longnose chimaera Harriotta raleighana embryos and vitellus from unknown origin. The mitochondrial genes cox1 and nadh2 were sequenced from 24 samples of homogenized stomach content (including vitellus and egg cases). DNA sequences reveals that O. bruniensis preys exclusively on the egg cases of oviparous chondrichthyans, including Pacific spookfish Rhinochimaera pacifica and brown chimaera Chimaera carophila. These findings are the first evidence of a wild shark relying solely on egg cases from other chondrichthyans as a food source. In addition to its low reproductive output and high distribution overlap with fishing efforts, the reliance on a specialized diet may make O. bruniensis a particular vulnerable species to overfishing.
Austin Francis, Jr., Jay Hodgson, Aaron Schrey
Armstrong State University, Savannah, GA, USA
An Introductory Biology Laboratory on Form and Function Using Hammerhead Sharks
As part of an effort to improve student understanding and retention of evolution, a new introductory biology laboratory has been developed to illustrate how differences in form may result in differences in function. To accomplish this, students are asked to calculate drag force for different geometric shapes (with a known coefficient of drag) and generate hypotheses about how each shape will perform when moving through a fluid. Students are then provided with 3D printed versions of these geometric shapes for performance testing. With the width and mass standardized for all shapes, students determine the sinking rate (cm/s) for each shape as it descends in a fluid filled, 16 cm diameter, 120 cm tall cylindrical testing chamber. Each shape is tested three times and the average velocity used to evaluate performance (with shorter times reflecting reduced drag). These results are then used by students to generate hypotheses about how different hammerhead shark cephalofoils may be expected to perform. Computed tomography (CT) scans of three species of hammerhead shark (Sphyrna tudes, Sphyrna mokarran, and Eusphyra blochii) and one conical-shaped shark species (Rhizoprionodon terraenovae) were used to print 3D models of shark heads for performance testing. To test student derived hypotheses, the experimental design for geometric shapes was replicated with the average sinking velocity determined for each shark head. Initial results indicate greater student engagement in the lab, student comprehension of the basic principles of evolution, and motivation to learn more.
Joseph Aaron Frumkin, Kenshu Shimada
Depaul University, Chicago IL, USA
Morphological Differences in Placoid Scales among the Three Extant Species of Thresher Sharks (Lamniformes: Alopiidae) and Their Functional Implications
The thresher sharks (Alopiidae) are a group of lamniform sharks consisting of three extant species: Alopias pelagicus (pelagic thresher), A. superciliosus (bigeye thresher), and A. vulpinus (common thresher). They are characterized by a highly elongate caudal fin that is as long as the rest of the body, and at least A. pelagicus and A. vulpinus are documented to use their caudal fin to hunt for small fish prey by stunning them. On the other hand, the hunting behavior of A. superciliosus has not been observed in the wild, but it has been suggested that the species must be a faster swimmer relative to A. pelagicus and A. vulpinus based on the skeletal architecture of their caudal fins. We test this hypothesis by comparing placoid scale morphologies among the three species. Samples were taken from preserved museum specimens on their lateral side of the body above the pectoral fin immediately anterior to the first dorsal fin. Our preliminary study shows that all three species possess keeled scales consistent with most pelagic sharks. The average inter-keel distance is smaller for A. superciliosus (49.9 µm) compared to A. pelagicus (52.7 µm) and A. vulpinus (52.5 µm). The smaller inter-keel value in A. superciliosus suggests that the placoid scales of the species are better suited to reduce surface drag for faster swimming relative to scales of A. pelagicus and A. vulpinus. Therefore, our scale-based data support the hypothesis that A. superciliosus must be a faster swimming shark than A. pelagicus and A. vulpinus.
Jim Gelsleichter, Morgan Eason
University of North Florida, Jacksonville, FL, USA
Localization of progesterone receptors in reproductive organs of female bonnetheads (Sphyrna tiburo)
Previous studies on sharks have examined plasma concentrations of the gonadal steroids estradiol (E2), testosterone (T), and progesterone (P4) in elasmobranchs, and have provided strong evidence for their involvement in regulating various stages of reproduction. P4 in particular has been shown to be elevated during two specific periods of female reproduction in some sharks, ovulation and early gestation. However, while logical roles for P4 during these stages have been presented, virtually no published studies to date have examined the location of P4 receptors (PRs) in elasmobranch reproductive organs; this is generally needed to identify possible target organs and clarify potential roles for this hormone. Therefore, the goal of this study was to examine the location of PRs to identify possible targets in elasmobranchs. We examined the presence of PRs in histological sections of reproductive organs of female bonnetheads (Sphyrna tiburo) via immunocytochemistry using mouse monoclonal antibodies against PRs. Progesterone receptors were detected in multiple reproductive organs including the uterus, oviducal gland, and ovary. These data indicate multifaceted roles for P4 in elasmobranch reproduction. Data from other species of elasmobranchs will also be discussed to consider possible broad roles for P4 in elasmobranchs.
Elitza Germanov1, Andrea Marshall2, I Gede Hendrawan3, Neil Loneragan1
1Murdoch University, Perth, WA, Australia, 2Marine Megafauna Foundation, Truckee, CA, USA, 3Udayana University, Denpassar, Bali, Indonesia
Plastics on the Menu: Microplastics are Present in the Feeding Habitats of Manta Rays
Microplastic marine debris is a ubiquitous, multi-facetted environmental issue. Recent advances in research have shed light on global microplastics estimates, threats to biodiversity and key focal regions for intervention. Yet there is limited knowledge of the potential for microplastic ingestion by threatened large filter feeders, such as manta rays, in regions highly implicated with plastic pollution. Here, we characterize microplastics concentrations in critical feeding habitats for manta rays (Manta alfredi), in Nusa Penida, Indonesia, an area fraught with marine plastic pollution. Using a 200micron plankton net, we evaluated micro (<5mm) and meso (5-200mm) plastic pollution in top 0.5m of the water column during twelve individual feeding events. The majority of plastic pieces were in the 1-5mm size range (74.2%). Plastic pieces were comprised of soft (48.9%) or hard (38.8%) secondary micro and mesoplastics, with polystyrene beads and nylon fibers comprising the rest. Overall, the average concentration of plastic pieces in the feeding location was 1.12 X 10-4 pieces per cubic meter. Given the large quantities of water manta rays must filter to meet their daily energy demands, feeding activity in the study location will likely result in microplastic ingestion. We recommend that plastic waste cleanup and prevention be prioritized for critical feeding habitats for manta rays and other resident or seasonal large filter feeders.
Leonardo Guida, Terence I. Walker, Richard D. Reina
Monash University, Clayton, Victoria, Australia
Just chill & survive – How the Behaviour of the Gummy Shark During Longline Capture Reduces the Physiological Stress Response
Many factors influence the physiological stress response to fisheries capture in elasmobranchs. However, the influence of sea surface temperatures (SST) and behaviour are unknown and crucial considering global fishing pressures. We investigated the effect of SST and behaviour on the physiological stress response to capture of the gummy shark, Mustelus antarcticus. Capture time for 23 M. antarcticus ranged 32-241 min as measured by hook timers or time depth recorders (TDR) in SSTs ranging 12-20°C. TDR data from 13 M. antarcticus were analysed to quantify capture behaviour as the percentage of time spent moving during capture. Several physiological variables measured from blood samples obtained immediately upon the animals’ landing indicated that although warmer SSTs increased metabolic rate, the stress response to capture was not exacerbated by capture duration. During capture, movement occurred for an average of 10% of the time and since M. antarcticus can respire whilst stationary, restricted movement probably mitigated potential influences of increased SSTs and capture duration on the stress response. We highlight the importance of seasonal water temperatures and capture behaviour when assessing the resilience to fisheries capture and the implementation of appropriate fisheries management strategies.
Theresa Gunn, Christine Bedore
Georgia Southern University, Statesboro, Georgia, USA
Environmental control of yellow stingray camouflage
Many reef fishes exhibit dynamic coloration and body patterns that can change under nervous control. Lowe et al (1996) showed that hammerheads in high UV environments have higher skin melanin concentrations, which likely functions as a protective mechanism against UV damage. However, several species of benthic sharks and rays likely alter melanin concentrations in the skin to provide background matching for camouflage. The yellow stingray (Urobatis jamaicensis) is a small, reef-dwelling elasmobranch with elaborate spot patterns that differs dramatically from other local stingrays, which are primarily uniformly drab. Because yellow stingrays likely match their environment as a predator avoidance strategy, melanin responses to UV may also be controlled by other environmental mechanisms such as background (e.g. sand, reef) color. To investigate the environmental parameters that induce changes in melanin concentration of yellow stingrays, we housed rays in one of four color environments: completely white, completely black, black walls and a white bottom, and white walls and a black bottom and one of two light environments: 24h light (UV present) and 24h dark (UV absent). We observed that the rays changed the brightness of their skin to match that of the bottom of their experimental tanks, regardless of presence or absence of UV light. We plan to further examine the underlying visual and physiological mechanisms that control color change in the yellow stingray.
Alexander Hansell1, Janne Haugen1, Sofia Gabriel1, Kim Friedman2, Steven Cadrin2
1Department of Fisheries Oceanography, School for Marine Science and Technology, University of Massachusetts – Dartmouth, Fairhaven, MA, USA, 2Marine and Inland Fisheries Branch, Food and Agriculture Organization of the United Nations (FAO), Rome, Italy
Impact of CITES Listing, Cop16, on the Scalloped Hammerhead, Sphyrna lewini, in Brazil
The Convention on International Trade in Endangered Species (CITES) is an international regulatory agreement between 181 countries that aims to ensure international trade does not threaten the survival of endangered species. In 2013, at the Conference of Parties to CITES (CoP16) the scalloped hammerhead (Sphyrna lewini) was listed in Appendix II, with a deferred activation date of 2014. To evaluate the effectiveness and impacts of this listing, a fishery assessment framework was created, to assess 5 key categories of the fishery i) governance, ii) fishers, iii) stocks, iv) trade and v) socio-cultural issues. This framework was applied to scalloped hammerhead fisheries in Brazil, as hammerhead captures in Brazil were noted as globally high before the CoP16 legislation. Changes across three subsections for each category and gaps in implementation, with suggestions for activities to address deficiencies, were documented. Information was obtained from reports and interviews from the United Nations Food and Agriculture Organization and Brazilian fisheries. This case study demonstrates the utility of a new fishery assessment framework to determine ‘what is’ and ‘what isn’t’ working in managing a fishery for a CITES Appendix II listed species. Preliminary results reveal changes in all five categories and highlights growing artisanal fisheries and shark meat trade. Highlighting and monitoring a broad range of CITES related impacts on the Brazilian scalloped hammerhead fishery offers valuable feedback to management to evaluate current policy initiatives and drive adaptive management.
Matthew Jew, David A. Ebert, Paul J. Clerkin, Justin A. Cordova, Jessica Jang, Breanna Machuca, Melissa C. Nehmens, Catarina Pien, Amber Reichert, Victoria E. Vásquez, Kristin A. Walovich
Moss Landing Marine Laboratories, Moss Landing, CA, USA
Looking for “Lost Sharks”
Sharks, and their relatives the batoids and chimaeras, come in a variety of sizes and shapes, from the whale shark (Rhincodon typus), the world’s largest fish, to the dwarf pygmy sharks (Squaliolus spp.), and occupy most marine and some freshwater habitats. There are more than 500 species of sharks, along with nearly 650 batoid and 50 chimaera species, bringing the overall total to about 1200 species of sharks and shark-like fishes. The diversity of sharks and their relatives has increased exponentially over the past decade with more than 230 new species having been described over the past decade. This represents nearly 20% of all shark species that have been described. Most of these new discoveries have come from the Indo-Australian region, followed by the Western Indian Ocean and Western North Pacific regions. However, a review of the Red List status of Chondrichthyans indicates that 17.4% are threatened and nearly half (46.8%) are Data Deficient or have not been assessed. Despite such a rich and diverse fauna, the majority of sharks and their relatives have largely been “lost”, having been overshadowed by a few large charismatic media mega-stars, such the White Shark (Carcharodon carcharias). In an effort to highlight and assess these little known, or unknown, species we have initiated a global program “Looking for Lost Sharks” to find and discover these lost sharks.
Bryan Keller, Chip Cotton, Dean Grubbs
Florida State University Coastal and Marine Laboratory, Tallahassee, FL, USA
Reproductive biology and embryonic development in two common deep-water dogfishes (Squalus cubensis and S. cf. mitsukurii) from the northern Gulf of Mexico
Little is known about the reproductive biology of most deep-sea sharks (>200m), despite comprising over half of all identified shark species. In conjunction with a project to examine the ecological effects of the 2010 Deepwater Horizon oil spill (Deep-C; www.deep-c.org), sharks were collected near Desoto Canyon in the northern Gulf of Mexico using demersal longlines in depths ranging from approximately 200-600m. Samples and data from 243 Cuban dogfish (Squalus cubensis) and 323 undescribed dogfish (S. cf. mitsukurii) (sexes combined) were collected to determine reproductive parameters. Modes of reproductive development, and hence maternal-embryonic nutritional relationships, vary greatly among elasmobranchs, and literature suggests lecithotrophic species experience a 20% (or more) loss in organic matter during embryogenesis, whereas matrotrophic species exhibit a lesser reduction, or in many cases an increase in organic matter. These changes in biomass reflect the net balance of metabolic losses of embryogenesis and any maternal nutritional supplementation during gestation. In this ongoing study, we are measuring wet, dry, and ash weights of eggs and embryos in over 70 gravid uteri to determine changes in organic matter during gestation and hence reveal the maternal-embryonic nutritional relationships for both species. Our results will suggest whether these species exhibit a lecithotrophic or matrotrophic mode of reproduction. Additionally, we also report size-related fecundity, ovarian cycle, and seasonality of mating. Such reproductive parameters, as well as the maternal-embryonic relationships among our study species, have not previously been reported and these results will shed light on the bioenergetics and scope for growth of these species.
Matthew Kolmann1, Swara Shah1, Henil Patel1, Dean Grubbs2, Nathan Lovejoy1
1University of Toronto Scarborough, Toronto, ON, Canada, 2Florida State University Coastal and Marine Laboratory, St. Teresa, FL, USA
Ecological consequences of alternative muscle scaling in durophagous stingrays
Large jaw adductor muscles, robust jaws, and force-efficient jaw lever systems are hallmarks of durophagous vertebrates. Positive allometry of feeding performance is generally assumed for durophagous predators, for when juveniles compete with adults, earlier access to prey is necessitated. Bullnose rays represent a parallel evolutionary lineage (Myliobatinae) of durophagous stingrays, found in sympatry with related cownose rays (Rhinopterinae). The cranial anatomy of 15 bullnose rays (Myliobatis freminvillei) were analyzed using a biomechanical model which estimates bite force over ontogeny. Bullnose ray bite force scaling patterns were compared to those of two separate populations of cownose rays (Rhinoptera bonasus) from the Gulf of Mexico and Virginia, which have more catholic and more molluscivorous diets, respectively. Bullnose and cownose ray feeding apparatuses are both characterized by isometric conservation of jaw leverage (mechanical advantage) across their ontogeny, while most jaw adductor muscles grow with positive allometry. In contrast to cownose rays, bite force generation scaled isometrically in bullnose rays. In three lineages of durophagous stingrays, we find subtly different muscle scaling patterns, little evidence of skeletal remodeling facilitating increased jaw leverage, but clear differences in overall feeding performance over ontogeny. Ecologically, despite an earlier advantage in absolute jaw leverage, bullnose rays are eventually out-performed by sympatric cownose rays in Chesapeake Bay, despite the former preying on comparably stiffer prey (gastropods). Although the diet of bullnose rays may require greater crushing forces, cownose ray aggregations exposes these migratory, gregarious fishes to greater levels of interspecific competition than solitary bullnose rays.
Kady Lyons1, Aaron Carlisle2, Christopher G. Lowe1
1CSULB, Long Beach, CA, USA, 2Stanford, Pacific Grove, CA, USA
Influence of maturity on mercury accumulation over ontogeny in muscle and liver of male round stingrays
Mercury is naturally available in the environment and can readily bioaccumulate in marine animals. While mercury is known to accumulate in multiple tissues, distribution of this contaminant within different tissues and its dynamics are poorly understood in elasmobranchs. The round stingray (Urobatis halleri) is a locally abundant elasmobranch in southern California that represents an appropriate model to investigate patterns of mercury tissue distribution across age classes. Total mercury was measured in liver and muscle of male stingrays from Seal Beach, California, as well as from individuals from the offshore island of Santa Catalina. Stable isotope analysis was also performed on the muscle and plasma of a subset of rays over a range of age classes to investigate mercury accumulation with respect to trophic ecology. Mercury in both tissues was found to significantly increase with size, however, mercury accumulation was found to drastically increase after maturity. There were no patterns in δ15N or δ13C with size, although δ15N was found to significantly increase with ontogeny in stingray whole blood, which reflects recent diet. Since SIA values were indistinguishable between adult and juvenile stingrays for muscle, it is unlikely that any ontogenetic changes in overall trophic ecology account for the substantial ontogenetic increases found in mercury with size. Rather, the strong accumulation pattern observed after maturity, and concomitant increase in δ15N in whole blood, is likely due to factors that are influenced by reproduction (e.g. reproductive behavior, growth rate and biochemical changes in tissues) or mercury dynamics (e.g. tissue redistribution of mercury).
Nicholas J. Marra1,2, Minghui Wang3, Paulina Pavinski Bitar2, Qi Sun3, Aleksey Komissarov4, Stephen J. O’Brien1,4, Michael J. Stanhope2, Mahmood Shivji1
1Save Our Seas Foundation Shark Research Center, Nova Southeastern University, Dania Beach, FL, USA, 2Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, NY, USA, 3Bioinformatics Facility, Cornell University, Ithaca, NY, USA, 4Theodosius Dobzhansky Center for Genome Bioinformatics St. Petersburg State University, St. Petersburg, Russia
Genome Sequence of the White Shark (Carcharodon carcharias): Insights into Genome Size Evolution, Life History Characters, and a Primitive Adaptive Immune System
The white shark, Carcharodon carcharias, is a species of great interest to the public, shark biologists, and geneticists alike. Several of its life history characteristics are of evolutionary and/or ecological interest such as regional endothermy, its role as a large apex predator, long lifespan, and a primitive adaptive immune system. We have utilized a combination of quality trimmed single-end, paired-end, overlapping paired-end, and mate-paired Illumina sequencing data to obtain 104x coverage of the white shark genome, the largest chondrichthyan genome yet sequenced. In addition to estimating genome size (roughly 5 gbp) and repeat content (roughly 60% is comprised of repetitive content), we have employed the MAKER pipeline on the assembled data to provide annotations, resulting in about 34,000 predicted genes with an average size of 20.6 kbp. From these annotated loci we were able to gain insights into the genetics behind several aspects of white shark biology. For example, sharks are thought to lack color vision. Accordingly, we were unable to identify the full complement of 5 traditional opsin genes needed for full color vision. However, genes for two possible color-absorbing opsins were identified and point to the possibility of limited color vision in this species. We also identified 193,576 microsatellites (23,586 perfect repeats) that could be adapted for conservation genetics studies in this and other lamnid species. Ongoing study of these genes, those encoding aspects of the adaptive immune system, and telomere length in this species, include some of the current efforts underway with this genome assembly and characterization.
Jonathan McKenzie1, Hannah Medd0
1Florida SouthWestern State College, Ft. Myers, FL, USA, 2American Shark Conservancy, Delray Beach, FL, USA
Preliminary Investigation on the Structure and Dynamics of Near-Shore Coastal Shark Assemblages off Southeast Florida
The Florida marine ecoregion satisfies provisions as Essential Fish Habitat for sharks with many species utilizing the nearby, productive pelagic waters, tropical coral reefs, and estuaries during different stages of their life history. However, biologically vulnerable shark species in Florida are subjected to fishing mortality through directed efforts and as bycatch by both commercial and recreational fishers. Using baited and un-baited video/photographic surveys we aim to provide spatial and temporal patterns of shark assemblages and identify possible environmental linkages. This project will use non-invasive techniques to collect data instead of using fishery-dependent or independent catch records to provide useful data for the management and conservation of regional shark species. Diver Operated Video Systems and Baited Remote Underwater Video Systems are cost-effective, non-destructive methodologies that have been used to describe shark assemblages and can contribute to community education and awareness programs. This is the first attempt to survey shark assemblages using underwater video/photography survey techniques in multi-use areas along southeast Florida.
Alexandra Meyer, Larry G. Allen
California State University, Northridge, Northridge, California, USA
Identification of SNP Loci in the Shovelnose Guitarfish, Rhinobatos productus Using Next-Generation Sequencing
The use of single nucleotide polymorphism (SNP) data from Restriction Site Associated DNA sequencing (RAD-seq) is rapidly taking the place of microsatellites in studies of population connectivity using nuclear DNA. In general, SNP loci reveal more fine-scale genetic structure than microsatellites, given the relative abundance of SNPs within the genome and their relatively low mutation rate, leading to more stability over microevolutionary time (Coates et al. 2009). Despite these advantages, the application of RAD-seq and SNP comparison to the genetic analysis of elasmobranch fishes remains largely untried. In a pilot study, DNA was extracted from tissue collected from Rhinobatos productus (shovelnose guitarfish, Ayres 1854) and genomic libraries were extracted from the DNA using the 2bRAD sequencing protocol (Wang et al. 2012). Libraries were successfully extracted from 10 individuals, with varying degrees of product concentration. R. productus is an especially viable candidate for population genetic studies as the species is easily accessible and has a relatively small geographic range, from the Gulf of California to Central California. Prior studies have indicated that R. productus is restricted by known phylogeographic barriers, particularly the tip of Baja California Sur, as evidenced by low population connectivity at the mitochondrial level (Sandoval-Castillo et al. 2004). Though no studies have been produced studying the nuclear population genetic structure, R. productus seems to be a viable candidate for the use of 2bRAD sequencing for the detection and analysis of SNP loci in order to describe the overall population structure.
Lauren Meyer1, Charlie Huveneers1, Peter Nichols2, Heidi Pethybridge2, Barry Bruce2, Crystal Beckman3
1Flinders University, Adelaide, South Australia, Australia, 2CSIRO, Hobart, Tasmania, Australia, 3SARDI, Adelaide, South Australia, Australia
Bait, Berley and Biochemistry – Using Biochemistry to Assess the Impact of South Australia’s Cage-Diving Industry on Local White Sharks Carcharodon carcharias
Wildlife tourism is considered the fastest growing sector of the tourism industry, bringing in billions of dollars around the world and with it, a myriad of management and conservation challenges. In Australia, the Neptune Islands Group Marine Park is home to nation’s largest aggregation of adult white shark (Carcharodon carcharias) and Australia’s only white shark cage-diving industry. Previous studies have shown that the industry here has induced changes to white shark swimming patterns and residency and therefore has been identified as a potential threat to the recovery of the species. Yet, there have not been any studies investigating the nutritional effects of interacting with the cage-diving industry. For example, the time spent interacting with tethered bait (tuna heads, gills and guts) and around cage-diving vessels might disrupt the natural foraging behaviour of white sharks and their ability to feed on seals, which is presumably the primary reason for white shark visiting and residing at seal colonies. Using stable isotopes and lipid signatures to evaluate dietary sources and trophic niche, we investigate the impact of tourism on the feeding ecology of white sharks.
Muhammad Moazzam, Rab Nawaz, Saba Ayub WWF-Pakistan, Karachi, Pakistan
Shark in the bycatch of tuna gillnet fisheries of Pakistan: A serious threats to their vulnerable population
Pakistan has a substantially large tuna gillnet fleet consisting of about 700 large wooden fishing boats which ply in the offshore waters of Pakistan and in the Area Beyond National Jurisdiction adjacent to its Exclusive Economic Zone. These vessels use long gillnets having a length of more than 7 km. Shark, pelagic rays, whale shark and mobulids are among the major bycatch of the tuna gillnet operations. Shortfin mako, (Isurus oxyrinchus) and pelagic thresher (Alopias pelagicus) are among the most common sharks whereas silky (Carcharhinus falciformis), oceanic whitetip (Carcharhinus longimanus) and scalloped hammerhead (Sphyrna lewini) are also represented in the catches. Among rays, pelagic stingray (Pteroplatytrygon violacea) is occasionally caught whereas mobulids are represented by 6 species; of which spinetail mobula (Mobula japonica) is the most common species. Whale sharks are also found to be entangled in gillnet fishing gears on many occasions. This is for the first time quantitative and qualitative data about elasmobranch catches in the pelagic gillnets being used in the Arabian Sea is documented. In the paper, information about seasonal abundance and spatial distribution of various elasmobranchs is also presented. For the protection of some of the important elasmobranchs including whale shark (Rhincodon typus) and mobulids which are commonly entangled in the gillnets, a program for their safe release was initiated. Through this program, 25 whale sharks, 10 mobulids and 1 pelagic stingray were successfully released in a period of about 20 months.
Brian Moe1, Charles Cotton2
1Florida State University, Department of Biological Science, Tallahassee, FL, USA, 2Florida State University, Coastal and Marine Laboratory, St. Teresa, FL, USA
Estimating length-at-age for the little gulper shark Centrophorus cf. uyato in the Gulf of Mexico: an evaluation of alternative aging techniques
Basic life history information is necessary for the proper development of stock assessments and appropriate management plans. However, life history parameters for many deep-water species of sharks are lacking or entirely absent. Though deep-water sharks in general are presumed to be less resilient to population depletion than their shallow-water counterparts, resource managers require basic, species-specific life history information to impose appropriate harvest limits and prevent overfishing. This study is intended to provide the first length-at-age estimates for the little gulper shark Centrophorus cf. uyato, a species for which basic life history information is mostly lacking. Dorsal fin spines will be aged using standard methods (transverse sectioning, staining, polishing), as well as emerging methods (computed tomography scanning and near-infrared spectroscopy). This study will determine the most effective method of age determination for this species and provide the first age estimates for C. cf. uyato in the Gulf of Mexico. The results of this study will lead to a full age and growth study for this population.
Clark Morgan, Jim Gelsleichter
University of North Florida, Jacksonville, Florida, USA
A Survey of Shark Abundance on Northeast Florida Beaches
Long-term abundance surveys are necessary for identifying trends in the status of fish populations that are the target of commercial and/or recreational fisheries. This is especially the case for populations of certain fish like sharks and their relatives, which grow slowly and often take a long period of time to rebuild from fishery-associated declines. In this presentation, we provide preliminary data on the species composition and abundance of shark populations that use nearshore waters on the northeast Florida coast from the initial years of a new survey focusing on shark abundance in coastal habitats. The overall goal of this survey is to examine long-term patterns in large and small coastal shark abundance on northeast Florida beaches along with conducting more comprehensive assessments of shark life history, especially reproduction, so that still-unclear questions about certain commercially- and/or recreationally-important shark species can be addressed. These questions include but are not limited to: the status of state-protected, but largely unsurveyed species such as the lemon shark (Negaprion brevirostris) and tiger shark (Galeocerdo cuvier), the current status of aggressively managed large and small coastal shark species that have traditionally made up a significant contribution of commercial or recreational shark landings, and the reproductive biology of still-poorly studied species such as N. brevirostris.
Kat Mowle, Jim Gelsleichter
University of North Florida, Jacksonville, FL, USA
Characterization of the Vitellogenin Cycle in the Bonnethead Shark Sphyrna tiburo
Vitellogenin (Vtg) is a precursor to yolk-proteins that is known to be produced in the liver under the control of the hormone estradiol (E2) in reproductively active females of most non-mammalian vertebrates. Previous studies have examined Vtg production in a wide variety of fishes, but no studies to date have done so in a placental viviparous elasmobranch. Therefore, the purpose of this study is to examine Vtg production in a viviparous shark species, the yolk-sac placental bonnethead shark Sphyrna tiburo. Specifically, this study focuses on determining where Vtg is produced in S. tiburo, how reproductive steroid hormones influence Vtg production, and what temporal patterns occur in Vtg levels throughout the species’ reproductive cycle. In this preliminary stage of this study, Vtg presence in the plasma of S. tiburo individuals from all reproductive stages was analyzed using immunoblotting techniques. So far, Vtg has been detected in the plasma of S. tiburo individuals collected in the fall postpartum/mating stage of their reproductive cycle. Additional work will examine Vtg presence in S. tiburo liver and ovaries, and the presence of receptors for hormones likely involved in regulating Vtg production, including estradiol and progesterone, using immunocytochemistry and in situ hybridization.
Cody Nash1, Jill Hendon2, Toby Daly-Engel1
1University of West Florida, Pensacola, FL, USA, 2Center for Fisheries Research and Development, Gulf Coast Research Laboratory, The University of Southern Mississippi, Ocean Springs, MS, USA
Frequency of multiple paternity in the finetooth shark, Carcharhinus isodon, in the Northern Gulf of Mexico
The finetooth shark, Carcharhinus isodon, is a poorly understood shark species inhabiting the coastal waters of the Southeastern U.S. They are a common shallow-water species found in the Atlantic Ocean from South Carolina to Florida as well as in the Gulf of Mexico (GoM). In the GoM, C. isodon is targeted by some artisanal and commercial fisheries and is regularly caught in others as by-catch. It is thought that they are currently being overfished in the GoM. Despite their ubiquity, little is known about their life history and reproductive biology. We seek to gain a better understanding of the reproductive biology of this species by determining the frequency of multiple paternity within a Northern GoM population. Samples have been collected off of the Mississippi coast from nearly 100 females and their litters over a period of three years. Ten or more species-specific and cross-amplified microsatellite loci will be used to estimate the number of non-maternal alleles within each litter. This will allow us to infer the frequency of multiple paternity in this population. Multiple paternity is common in sharks, and could have a significant impact on their genetic diversity. The evolution of this behavior is poorly understood, and further study could lead to deeper knowledge of its adaptive advantage. This, in turn, will allow for improved management decisions regarding C. isodon and other sharks.
Melissa Nehmens1, Kevin Feldheim2, David Ebert1
1Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Rd., Moss Landing, CA 95039, USA, 2Field Museum, Pritzker Laboratory for Molecular Systematics and Evolution, Chicago, IL, USA
What Are They Doing Down There: An Investigation of Multiple Paternity in a Deep-Sea Shark
The Southern Lanternshark, Etmopterus granulosus, is a deep-sea shark commonly found throughout the southern oceans and frequently caught as bycatch in deep-sea fisheries. Outside of Australian and New Zealand waters little information is available on its reproductive biology, including multiple paternity. To date, few studies have been undertaken to determine whether multiple paternity occurs in deep-sea species such as E. granulosus. In this study, 18 litters of E. granulosus were opportunistically collected as bycatch along the Madagascar Ridge and Walter Shoal in the Southwestern Indian Ocean and examined for multiple paternity. Novel microsatellite markers were developed to test for the presence and frequency of multiple paternity. Additionally, litter size and polyandry as they relate to female size were examined to determine if a relationship exists between these parameters. As a reproductive strategy, multiple paternity may greatly benefit the overall fitness of the population and individual females by increasing genetic diversity. Examination of the mating system in this common deep-sea species will improve our understanding of its life history, and may have important conservation and fisheries management implications.
Emily Peele1, Thomas Lankford1, Paul Barrington2, Jennifer Wyffels3
1University of North Carolina, Wilmington, Wilmington, NC, USA, 2North Carolina Aquarium at Fort Fisher, Kure Beach, NC, USA, 3South-East Zoo Alliance for Reproduction & Conservation, Yulee, FL, USA
Ageing bonnethead shark (Sphyrna tiburo) pups using umbilicus morphology
Wound healing at the umbilicus or site of placental connection for neonate bonnethead sharks, Sphyrna tiburo, was studied for two litters born and maintained at the North Carolina Aquarium, Fort Fisher. Photographic images of the abdomen were taken at weekly intervals beginning at parturition and area of open ‘wound’ was isolated and calculated digitally. For non-surviving pups, the umbilicus was preserved and examined using scanning electron microscopy. Umbilicus healing pattern was characterized into one of 6 stages: (1) umbilical stump present (2) closed wound with denticle-free epidermis (3) contraction and bridging of denticle covered epidermis near the middle of the umbilicus (4) anterior terminus of umbilicus remains denticle free (5) complete covering of scar with denticles varying in morphology and distribution and (6) uniform denticle orientation and morphology over umbilicus. Complete epithelialization or wound closure occurs shortly after parturition, following the loss of umbilical stump (4 ± 1 SD days). Visible umbilical scar healing is dominated by the final, or maturation stage of wound healing as represented by eruption and orientation of dermal denticles. Rate of wound healing was dependent on initial wound area, but progressed to stage 4 for all sharks after 3 weeks. No pups advanced to stage 6 during the timeframe of this study (150 days). Through detailed study of temporal changes in appearance of the umbilical wound, a more accurate aging technique for wild caught neonatal sharks is possible. Determining age of pups helps identify and improve the management of nursery habitats for coastal shark species.
Catarina Pien, David Ebert
Moss Landing Marine Laboratories, Moss Landing, CA, USA
Characterization of the elasmobranch assemblage in Elkhorn Slough, CA
Elkhorn Slough is an estuarine embayment that drains directly into the Monterey Bay. Over the last few decades, Elkhorn Slough has undergone several natural and anthropogenic changes, the most significant being the building of Moss Landing Harbor, which greatly altered the environment to become more marine, with higher current, tidal prism, and rates of erosion. Along with these physical changes, the biological composition of elasmobranchs has also changed over time. Certain species such as the Thornback Ray Platyrhinoidis triseriata have increased in abundance, while others such as the Shovelnose Guitarfish Rhinobatos productus and Grey Smoothhound Mustelus californicus have become scarce in Elkhorn Slough. This study aims to create a baseline for the elasmobranch species currently using Elkhorn Slough, and to understand which variables influence their presence, as well as their abundance. Between April 2015 and July 2016, longlines and gillnets were used to sample elasmobranchs. Specimens were measured, sexed, and their locations were recorded. Temperature, salinity, oxygen, and turbidity were also recorded. Spatial and statistical analyses will be used to determine which species are most abundant, where they are most densely located, whether segregation (sex, size, species) occurs, when species are seasonally migrating, and which factors are playing an important role in the presence and abundance of these species in an important California estuary. Attaining a better understanding of what attracts these species to Elkhorn Slough will allow for better management of these species, which play an important role in the dynamics of California estuaries.
Jeffrey Plumlee, David Wells
Texas A&M University at Galveston, Galveston, TX, USA
Feeding ecology of three coastal sharks in the northwest Gulf of Mexico
The feeding ecology of three coastal shark species, Atlantic sharpnose (Rhizoprionodon terraenovae), bonnethead (Sphyrna tiburo), and blacktip (Carcharhinus limbatus) sharks were examined in the northwest Gulf of Mexico (GOM). A total of 601 (305 Atlantic sharpnose, 239 bonnethead, and 57 blacktip) sharks were collected over two years via dockside sampling from recreational anglers in Galveston, Texas. All individuals had stomach contents examined, and a subset (50 Atlantic sharpnose, 50 bonnethead, and 36 blacktip) were analyzed for stable isotopes (carbon, nitrogen, and sulfur) in muscle tissue, revealing short-term and long-term feeding strategies. Both blacktip and Atlantic sharpnose stomach contents consisted of teleost fish with % index of relative importance (IRIs) of 98.95 and 91.16% respectively, whereas bonnethead diets were dominated by crustaceans (%IRI = 87.20). Stable isotope analysis revealed bonnetheads had higher mean carbon (δ13C) and lower sulfur (δ34S) values, indicating inshore feeding and a preference for benthic invertebrates. Atlantic sharpnose and blacktips were shown to feed on similar prey using stomach content analysis, yet Atlantic sharpnose had a broader diet including cephalopods and crustaceans in addition to teleost fishes. Differences were further established using nitrogen (δ15N) values, which were significantly lower for Atlantic sharpnose than blacktips. Collectively, stomach contents and stable isotope analyses support different feeding strategies of three common shark species. Sulfur (δ34S), in addition, appears to serve as a natural tracer, distinguishing benthic versus pelagic feeding patterns in elasmobranchs. This study provides important ecosystem-based feeding information of upper trophic-level predators in coastal waters of the northwestern GOM.
Amber Reichert1, Lonny Lundsten2, David Ebert1
1Moss Landing Marine Laboratories, Moss Landing, CA, USA, 2Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA, 3California Academy of Sciences, San Francisco, CA, USA
First North Pacific records of the pointy nosed blue chimaera, Hydrolagus cf. trolli (Chondrichthyes: Chimaeriformes: Chimaeridae)
The occurrence of Hydrolagus cf. trolli is reported for the first time from the central and eastern North Pacific Ocean. Using video taken during ROV surveys, specimens were identified using MBARI’s Video Annotation and Reference System database (VARS). This is a geographic range extension for this species, as it was previously only known to occur in the southern Pacific Ocean off of Australia, New Zealand, New Caledonia, and Chile.
Katherine E. Schweiss1, Jill M. Hendon2, Nicole M. Phillips1
1The University of Southern Mississippi, Hattiesburg, Mississippi, USA, 2The University of Southern Mississippi Gulf Coast Research Lab, Ocean Springs, Mississippi, USA
A simplified approach to genetically sexing elasmobranchs using qualitative PCR
Determining a sex for elasmobranchs is typically done visually, by looking for the presence or absence of male claspers. While this method is easy and reliable, many current research endeavors are based on samples that are not associated with a source animal (i.e., dried fins, sawfish saws), making visual assessments impossible. Having a method to determine or verify sex data for such samples would be a useful tool for increasing the value of the sample and enhancing the resultant assessments. Male heterogamety predominates in elasmobranchs; therefore, males are typically XY and females are XX. The aim of the current study was to develop a multiplex polymerase chain reaction (PCR) to amplify a portion of each of the X and Y chromosome in elasmobranchs. Primers were developed and tested for representative shark and ray species using a qualitative PCR (qPCR) approach. Resultant dissociation peaks are produced during qPCR, where males produce two peaks (corresponding to amplicons for both the X and Y chromosomes) and females produce one peak (corresponding to an amplicon for the X chromosome). Application of qPCR for genetically sexing elasmobranchs is faster and more accurate than the conventional PCR and gel electrophoresis methods commonly employed in sexing other organisms. In addition, this method is more likely to be successful for samples with low quantity or quality DNA.
Gail Schwieterman1, Karissa Lear1, Heather Marshall1, Jack Morris1, Connor White2, Robert Hueter1, Gregory Skomal3, Nicholas Whitney1
1Mote Marine Laboratory, Sarasota, FL, USA, 2California State University Long Beach, Long Beach, CA, USA, 3Massachusetts Division of Marine Fisheries, New Bedford, MA, USA
Post-Release Mortality of Coastal Sharks in a Commercial Longline Fishery
Estimating post-release mortality rates is essential to understanding the impact of fishing and properly informing management measures. However, logistical difficulties have resulted in relatively few post-release studies, typically with small sample sizes. Here, we quantify post-release mortality of large coastal sharks in the Florida commercial longline fishery using acceleration data loggers (ADLs) to infer mortality. We recorded hook times, capture measures (e.g. animal condition), took blood samples, and applied ADLs to longline-caught sharks. Between December 2013 and January 2016 we tagged 229 sharks with ADLs with a 90.8% tag recovery rate. Shark species tagged included blacktip (C. limbatus), sandbar (C. plumbeus), tiger (Galeocerdo cuvier), spinner (C. brevipinna), bull (C. leucas), blacknose (C. acronotus), great hammerhead (Sphyrna mokarran), scalloped hammerhead (S. lewini), and dusky sharks (C. obscurus). Species-specific post-release mortality rates ranged from 2.04% (G. cuvier) to 75% (C. brevipinna). Surviving sharks were monitored for an average of 24.9 ± 22.3 h (mean ± SD), and up to 204.5 h post-release. Mixed modeling of blood stress indicators and capture metrics show several variables significantly correlate with post-release outcome.
Ashley Shaw1, Bryan Frazier1, Amanda Barker2, David Portnoy2, Doug Adams3
1South Carolina Department of Natural Resources, Marine Resources Research Institute, Charleston, SC, USA, 2Marine Genomics Laboratory, Department of Life Sciences, Harte Research Institute, Texas A&M University-Corpus Christi, Corpus Christi, TX, USA, 3Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, Melbourne, FL, USA
Diet analysis of two cryptic Hammerhead species off the Southeastern United States
Two sympatric species, Sphyrna lewini, Scalloped Hammerhead and the recently described Sphyrna gilberti, Carolina Hammerhead, inhabit nursery areas as young-ofyear along the southeastern United States. As part of ongoing research to determine spatial and temporal distribution of the two species, trophic ecology will also be examined. The diet of Hammerhead species, particularly young-of-year sharks, has not been examined in the waters off of the southeastern United States. This study examines stomach contents as well as stable isotope analyses to determine the dietary habits of the Scalloped and Carolina Hammerheads. Comparisons will be made among and between Hammerheads from two distinct habitats, Bulls Bay, an estuarine nursery in SC, and Cape Canaveral, a neritic nursery in FL.
Chelsea Shields, James Gelsleichter
University of North Florida, Jacksonville, Florida, USA
Potential Associations between Gonadotropins and Reproduction in Female Stingrays
Follicle Stimulating hormone (FSH) and luteinizing hormone (LH) are glycoproteins that are responsible for regulating gametogenesis and gamete maturation in all vertebrates. However, although these hormones have been detected in some elasmobranchs, no studies have examined temporal associations with reproduction in these fishes. The goal of this study was to examine temporal changes in circulating FSH and LH concentrations in relation to the reproductive cycle of the Atlantic stingray (Dasyatis sabina), an elasmobranch species with a well characterized breeding cycle. Plasma samples were collected from mature female D. sabina from all reproductive stages. FSH- and LH-like immunoreactivity was examined using Western Blot. Dot blot analysis was used to obtain semi-quantitative data on hormone concentrations. FSH-like immunoreactivity was observed in female stingrays from all reproductive stages except late pregnancy, when females nourish developing embryos with uterine histotroph. Changes in FSH-like immunoreactivity was determined during other reproductive stages. LH-immunoreactivity was detected in plasma from female stingrays, but results were poor and did not provide a clear understanding of temporal changes in this hormone. Potential associations between gonadotropins and reproduction in female stingrays will be discussed along with preliminary observations on levels of these hormones in male stingrays.
Diana Lorena Silva-Garay1, Ximena Vélez-Zuazo1, John G. Ramírez2, Aldo S. Pacheco3
1Center for Conservation and Sustainability, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, D.C., USA, 2Instituto de Ciencias del Mar de Barcelona CSIC-ICM, Barcelona, Spain, 3CENSOR Laboratory, Instituto de Ciencias Naturales Alexander von Humboldt, Universidad de Antofagasta, Antofagasta, Chile
Feeding Partitioning in an Assemblage of Demersal-Neritic Elasmobranchs in the Southeastern Pacific
Elasmobranchs play a regulatory role over prey populations; however, this is less understood for demersal-neritic species, which are facing numerous threats in coastal ecosystems. Dietary studies are a useful tool for understanding species role and their trophic interactions. To this purpose, we investigated the diet from stomach contents of four stingrays (Dasyatis dipterura, Myliobatis peruvianus, M. chilensis, Urotrygon chilensis), a guitarfish (Rhinobatos planiceps), a shark (Mustelus mento), and a chimaera (Callorhinchus callorhynchus) collected around an artificial reef along the central coast of Peru from 2012 to 2014. We investigated (1) their diet composition, trophic interactions, trophic level (TL) and niche breadth, and (2) the likely influence of the artificial reef in their feeding dynamics. We used the index of relative importance (IRI%) and PERMANOVA-test to this analysis. All species exhibited a high feeding specialization (Levin<0.3) and dietary separation (p<0.05). While stingrays preferred soft bottom polychaetes and pelagic teleost fish (p>0.09), the shark and guitarfish fed on crabs (p>0.06) and the chimaera consumed mostly mollusks. The species which diet included bivalve mollusks were more associated with the artificial reef, an important hard-bottom food supply for species that feed on hard bottom prey items. The results highlight the relevance of the assemblage predatory activity (mean TL=2.85 ± 0.47) on a broad group of prey taxa and their predation over pelagic and benthic fauna gives insights of their feeding dynamic in this rich upwelling coastal ecosystem.
Katherine St. Clair, Tasha Metz, David Wells
Texas A&M University – Galveston Campus, Galveston, TX, USA
Stable isotope variability in cownose rays (Rhinoptera bonasus) within the northwestern Gulf of Mexico
The trophic ecology of cownose rays (Rhinoptera bonasus) has been studied extensively along the Atlantic coast and eastern Gulf of Mexico, but is not well described in the northwestern Gulf of Mexico. Therefore, this study examined spatial and temporal trends in carbon (δ13C) and nitrogen (δ15N) stable isotopes along the Texas coast, as well as the influence of size and sex of individuals on stable isotopes by quantifying isotopic niches via Bayesian ellipses created within the R package ‘Stable Isotope Bayesian Ellipses in R’ (Jackson et al. 2011). Epidermal samples, from the trailing edge of the pectoral fin, were collected for isotopic analysis during in-water entanglement netting surveys conducted along the Texas coast from 2009 – 2012. Isotopic niche size was comparable across Texas bay systems in 2012, with only the lower Laguna Madre (spring) significantly different. However, mean δ13C and δ15N signatures varied spatially across bay systems. Isotopic niche size varied seasonally within the lower Laguna Madre, with summer 2012 significantly different than all other sampling periods. Additionally, female mean δ13C signatures were significantly enriched compared to those of males, indicating female rays are foraging over longer periods of time within inshore habitats. There was also evidence of differential foraging between life history stages, with mean δ13C signatures of subadults differing significantly from adult rays in Aransas Bay. Future studies should utilize a multi-tissue approach to enable comparisons of trophic ecology over both short- and long-term timescales, as well as incorporate stomach content analysis to identify prey species consumed.
Duane Stevenson, Gerald Hoff, James Orr, Ingrid Spies, Chris Rooper
NOAA/National Marine Fisheries Service, Alaska Fisheries Science Center, Seattle, WA, USA
Fishery Interactions with Skate Nursery Areas in the Eastern Bering Sea
Since early 2015, fishery observers in the North Pacific Groundfish and Halibut Observer Program have been receiving training in the identification and sampling of skate egg cases. The goal of this training has been to support an NPRB project examining the unique properties of skate nursery sites in the eastern Bering Sea and the interactions of fisheries with skate egg cases. During the 2015 training year, over 230 observers received training in egg case identification and sampling, and recorded data on over 1000 skate egg cases. A total of 11 skate taxa were identified from egg cases, and over half (58%) of the egg cases were identified as Alaska skate (Bathyraja parmifera). Observers scored each egg case as either “viable”, meaning it contained an intact egg or embryo in some stage of development, or “non-viable”, meaning it was either empty or full of mud. Approximately 33% of the egg cases sampled by observers were classified as viable. Program wide, over 10,000 skate egg cases were encountered by observers. The majority of those egg cases (87%) were encountered on longliners targeting Pacific cod in the Bering Sea. Egg case encounters were concentrated on the outer shelf of the eastern Bering Sea, and over half of all egg cases reported were encountered in the area of Bering Canyon. Data collection for this project will continue through 2017, by which time we hope to have a comprehensive overview of fishery interactions with skate nursery areas in the eastern Bering Sea.
Dominic Swift, David Portnoy
Texas A&M University-Corpus Christi, Corpus Christi, TX, USA
High-throughput Sequencing for Genetic Monitoring and Stock Structure Assessment of Blacktip Sharks (Carcharhinus limbatus)
Blacktip sharks (Carcharhinus limbatus) are one of the dominant large coastal species landed by commercial and recreational fisheries in the U.S. Atlantic and Gulf of Mexico. Blacktips give birth in nursery areas which are vital for juvenile survival and are considered essential fish habitat. In blacktips and other large coastal sharks, females may show philopatry to these nurseries and this may result in substructure, making these sharks more vulnerable to localized overfishing. Further, nurseries along the U.S. Atlantic and Gulf of Mexico coasts differ in environmental conditions which may lead to localized adaption, important for population viability when the environment is heterogeneous in space and time. We will sample 500-600 young-of-the-year and mature blacktip sharks across the U.S. Atlantic and Gulf of Mexico. We will use double digest restriction-site associated DNA (ddRAD) sequencing to (i) establish baseline genetic monitoring data for blacktips, (ii) provide high-resolution genetic data for blacktip stock assessment, (iii) develop replicable methods for genetic monitoring and stock structure assessment of other shark species. Genomic monitoring will involve estimating the effective number of breeders (Nb) and the minimum number of female breeders (Nmf) at each nursery area, as well as characterizing baseline genetic diversity of the breeding stock. We also will investigate the potential for localized adaptation associated with nurseries and develop fine-scale genetic tags to be used in future mark-and-recapture studies.
Victoria Elena Vásquez, David A Ebert
Moss Landing Marine Laboratories, Moss Landing, CA, USA
‘IT’S HAMMERTIME!’: Uncovering the Secrets of an Iconic Shark with Citizen Science
Hammerhead sharks (Sphyrna spp.) are distinctive, and rather iconic, among shark species, with their “hammer-shaped” head. Two species are known to occur in the Northeast Pacific off southern California; the Scalloped (Sphyrna lewini) and Smooth (S. zygaena). Of these two species, the Smooth Hammerhead is the more temperate occurring species and is not uncommon off southern California. However, the extent of its occurrence is poorly known. The Scalloped Hammerhead is less common to rare in this area, typically only observed during warm water years usually associated with El Niño events. In recent years the use of mobile devices and through social media the general public and media has captured and informally documented images of Hammerhead Sharks, prompting interest from the public. The public’s perception is that they are increasing in abundance. Therefore, in an effort to better document and identify the Hammerhead species involved, a citizen science project was initiated in 2014 called ‘Hammertime’. Information is gathered through a web-based survey designed and monitored by the Pacific Shark Research Center. Basic, or more detailed, observational information, such as date and time of sightings, can be entered through a portal. Data collected overtime will allow researchers to evaluate long-term trends. This knowledge is of particular importance for Smooth and Scalloped Hammerhead Sharks since little is known about their use of Southern California waters. A better understanding of abundance, distribution and seasonality of Hammerhead Sharks in Southern California waters will help to better inform conservation and fishery management practices.
Jeremy Vaudo1, Bradley Wetherbee2, Jessica Harvey3, Alexandra Prebble1, Keith Bruni2, Mark Corcoran1, Matt Potenski1, Guy Harvey1, Mahmood Shivji1
1Guy Harvey Research Institute, Nova Southeastern University, Dania Beach, FL, USA, 2University of Rhode Island, Kingston, RI, USA, 3Cayman Islands Department of Environment, George Town, Grand Cayman, Cayman Islands
Characterization and monitoring of one of the world’s most valuable ecotourism animals, the southern stingray, Dasyatis americana, at Stingray City, Grand Cayman
Marine wildlife-oriented ecotourism often involves the provisioning of animals to increase the reliability of human-animal interactions. While these practices may increase the enjoyment of tourists, the long-term effects on wildlife are often unclear. The Stingray City Sandbar (SCS), Grand Cayman, is a location where southern stingrays, Dasyatis americana, are provisioned for ecotourism, resulting in behavioral and physiological changes. Recently, tourist operators have claimed that the number of stingrays at SCS has decreased substantially, however, there has never been a formal survey of stingrays at SCS. We examined over 13 years of southern stingray tagging data and enacted a structured census of the SCS aggregation to provide a formal characterization of the aggregation, establish a baseline for future monitoring, and provide some basic biological information on southern stingrays. Mature females dominated the SCS aggregation across years, and confirming operator fears, the size of the SCS declined between 2008 and 2012 from >100 to ~60 stingrays. Since 2012, stingray numbers have increased and appear to have stabilized at ~90 stingrays, which is still lower than historical levels. Females tended to be recaptured over much longer periods of time than males, with ~20% of recaptured females present for 10+ years, while male recaptures typically occurred within 3 years. As a result, there was more consistency of females over time, while males turned over more quickly. Our results suggest the SCS aggregation is highly dependent on recruitment from the general population and highlight the importance of regular monitoring for successful management of ecotourism activities.
Mao Watanabe, Keisuke Furumitsu, Yu Umezawa, Naoki Yagishita, Atsuko Yamaguchi
Nagasaki University, Nagasaki, Nagasaki, Japan
Stable isotope and stomach contents analyses of Aetobatus narutobiei to clarify its feeding ecology and foraging impact on bivalve fisheries in Ariake Bay
The naru eagle ray Aetobatus narutobiei, inhabiting the southwestern coastal areas of Japan, has increased in numbers since 1990s. A. narutobiei feeds on bivalves and is considered to be responsible for the decrease in bivalve catches in coastal areas such as Ariake Bay. Our previous studies showed that A. narutobiei is a seasonal resident of Ariake Bay, however, detailed information on the feeding ecology and foraging impact of this species on bivalve fisheries, including bivalve cultures, is limited. In the present study, A. narutobiei (n = 188) were collected from Ariake Bay. Recognizable stomach contents were analyzed based on the mean weight percentage of each prey item. Muscle tissue samples of A. narutobiei and mollusk samples identified as prey items were analyzed for carbon (δ13C) and nitrogen (δ15N) isotopes. The main prey items identified by stomach contents analysis were bivalves such as Scapharca kagoshimensiss, Crassostrea gigas, and Ruditapes philippinarum. There was no significant difference in isotopes between sexes and among months; however, significant differences were found among size classes for both δ13C and δ15N. The results of isotope analysis suggested that Scapharca kagoshimensiss accounts for the largest proportion of the A. narutobiei diet. Moreover, comparative analysis of the stable isotopes in Scapharca kagoshimensisss collected from cultured and wild areas showed that A. narutobiei likely feeds predominantly on the wild Scapharca kagoshimensiss. This study demonstrates the possibility of using stable isotope analysis as a tool to determine both the feeding ecology and foraging impact of a predator species on bivalve cultures.
Nicholas Whitney1, Karissa Lear1, Lindsay Gaskins1, Adrian Gleiss2
1Behavioral Ecology and Physiology Program, Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, FL 34236, USA, 2Centre for Fish and Fisheries Research, Murdoch University, 90 South Street, WA 6150, Australia
The effects of temperature and swimming speed on the metabolic rate of the nurse shark (Ginglymostoma cirratum, Bonaterre)
Sharks and other top predators have a substantial impact on their ecosystems through trophically mediated effects, and understanding the scope of this impact is essential to forming an accurate picture of energy flow within an ecosystem. One of the most important factors to consider when assessing a predator’s impact is metabolic rate, which is dependent on a number of environmental, physiological, and anatomical characteristics. Standard (SMR) and routine metabolic rates (RMR) and swimming dynamics of the nurse shark (Ginglymostoma cirratum, Bonaterre) were assessed using a static respirometer over two experimental temperatures (23 and 30 °C). The metabolic rates measured here represent the lowest reported for any shark species to date. Mean (± SD) SMRs at 23 °C and 30 °C were 36 ± 8 and 60 ± 17 mg O2 kg– 1
h– 1, and mean RMRs were 95 ± 15 and 138 ± 21 mg O2 kg– 1 h– 1, respectively. The Q10 for SMR was 2.42 between 23 and 30 °C. Minimum cost of transport (COTmin) at 23 °C was 68 mg O2
kg– 1 km– 1, where swimming speed was 0.33 BL s– 1. The COTmin increased to 81 mg O2 kg– 1
km– 1at 30 °C, where swimming speed was 0.44 BL s– 1. The proportional cost of activity was greater compared to other elasmobranchs, and nearly twice that of most ram ventilating shark species. These results highlight the sedentary nature of nurse sharks and suggest that they are energetically suited for a minimally active lifestyle.
Naoki Yagishita1, Takahiro Kusaka2, Hara Koujirou1, Keisuke Furumitsu1, Shinji Uehara3, Yuta Yagi3, Atsuko Yamaguchi1
1Graduate School of Fisheries and Environmental Sciences, Nagasaki University, Nagasaki, Japan, 2Graduate School of Agriculture, Kinki University, Nara, Japan, 3Japan Sea National Fisheries Research Institute, Niigata, Japan
Microsatellite DNA analysis of population structure of a Japanese common skate Dipturus cf. kwangtungensis in Japan
A Japanese common skate Dipturus cf. kwangtungensis is distributed in the coast of Japan from Hokkaido southward to Kyushu, the East China Sea, Korean Peninsula, and Taiwan, inhabiting depth of 20 to 320 m. The populations around Japan of the species are indicated to be structured by mitochondrial DNA analyses. We investigated population structure of D. cf. kwangtungensis based on polymorphism of microsatellite (simple sequence repeat: SSR). Samples of D. cf. kwangtungensis were collected from the Pacific Ocean (northern part of Honshu), the Sea of Japan (Niigata and Kyoto Prefs.), the East China Sea (Goto Islands and Danjo-gunto Islands). Polymerase chain reactions were carried out to amplify four SSR loci (LERI21, 34, 44, 50; El Nagar et al. 2010). The number of alleles per SSR locus within samples varied from 2 to 13 with a mean of 5.5. The Ho ranged from 0.182 to 0.909 with a mean of 0.611, and the He ranged from 0.385 to 0.939 with a mean of 0.703. The pairwise Fst values between northern part of Honshu and each of the other four geographic populations were high (0.1570.252) and significant after Bonferroni correction (P < 0.001), while the values between each of the geographic populations in the Sea of Japan and the East China Sea were low (from -0.026 to 0.013) and not significant (P > 0.05). The genetic differentiation was suggested between population in the Pacific Ocean and the group containing populations in the Sea of Japan and the East China Sea.
Atsuko Yamaguchi, Kojiro Hara, Noriko Omori, Keisuke Furumitsu
Nagasaki University, Nagasaki, Japan
Two hammerhead sharks, Sphyrna lewini and S. zygaena in Ariake Bay, Japan: size and age composition, feeding habits, and migration
Hammerhead sharks of the genus Sphyrna play an important role as predators in ecosystems. However, very few studies exist on the species of Sphyrna in Japan, including Ariake Bay, the largest bay in Kyushu. Here, we report the assessment of biological and behavioral aspects of two hammerhead sharks, S. lewini and S. zygaena, such as age composition, feeding habits, and migration, based on the specimens collected in Ariake Bay from 2006 to 2016. S. lewini specimens collected were 429-3290 mm in total length (TL) with aged 0-33; however, specimens aged 2-8 were not collected. S. zygaena specimens collected were 548-1590 mm TL; however, specimens of mature animals were not collected. The stomach contents of both species comprised primarily teleosts, cephalopods, and crustaceans. Of those, teleosts were predominant; the two Sphyrna spp. were therefore considered to feed primarily on teleosts in Ariake Bay. The investigation of movement and migration revealed that small S. zygaena individuals enter the bay incidentally. In contrast, S. lewini was considered to visit the bay to breed in early summer and leave after giving birth and mating. Juvenile S. lewini appeared to move to the open sea in autumn after inhabiting the shallow areas of the bay through the summer. We estimate that they inhabit the open sea and do not return to the bay until they reach sexual maturity. Ariake Bay was thus regarded as playing an important role as a nursery ground for S. lewini.
Toshikazu Yano1, Seiji Ohshimo2, Minoru Kanaiwa3, Tsutomu Hattori1, Masa-aki Fukuwaka4, Toru Nagasawa5, Sho Tanaka6
1Tohoku National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Aomori, Japan, 2National Research Institute of Far Seas Fisheries, Japan Fisheries Research and Education Agency, Shizuoka, Japan, 3Tokyo University of Agriculture, Hokkaido, Japan, 4Seikai National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Nagasaki, Japan, 5Hokkaido National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Hokkaido, Japan, 6Tokai University, Shizuoka, Japan
Estimation of Spatial Distribution of North Pacific Spiny Dogfish Squalus suckleyi using Generalized Additive Models
The distribution of North Pacific spiny dogfish Squalus suckleyi is not well known in the whole North Pacific, in particular around Japan. Our objective is to demonstrate the dogfish habitat in the North Pacific and to evaluate the effect of sea surface temperature (SST) and prey availability. A total of 14,893 gillnet operations were conducted in the North Pacific from 1972–2011 and the presence/absence of dogfish in each gillnet were analyzed by the generalized additive models with a binomial error distribution. Our results supported the previous study that the probability of dogfish presence was highest around the Gulf of Alaska and presented the following new findings; (1) the area with a high probability of presence also exists off Japan, (2) the distribution is continuous between two areas. Though the waters in the Tsugaru Strait has been considered as a primary habitat area for this species, our results showed that the area with higher probability located in the Sea of Japan off Hokkaido Island than the Tsugaru Strait. The spiny dogfish probability of the presence was high ranging 6 to 12 °C in SST, and the probability was higher if the prey co-exist. These results indicate that the factors both distribution of prey species and SST affect to the dogfish habitat, and the evaluating the habitat of this species could be available for rational management.