Daniel Abel1, Dean Grubbs2, Bryan Keller1, John Simcox1, Alexandra Dowlin1, Megan Novak1
1Coastal Carolina University, Conway, SC, USA, 2Florida State University, Tallahassee, FL, USA
Do Osmoregulatory Adaptations of Deep-Sea Sharks Represent a Paradigm Shift? Evidence from Rectal Glands of Hexanchus nakamurai and Other Species
A serendipitous observation of a smaller than expected rectal gland in a bigeye sixgill shark (Hexanchus nakamurai) led us to question whether smaller rectal glands were characteristic of deep-sea sharks and, if so, whether these differences were physiologically significant. We collected rectal glands from 6 shallow-water species [blacknose (Carcharhinus acronotus), finetooth (C. isodon), blacktip (C. limbatus), gulf smoothhound (M. sinusmexicanus), Atlantic sharpnose (Rhizoprionodon terraenovae), and bonnethead (Sphyrna tiburo)] and 4 mid- to deep-water species [little gulper (C. cf. uyato), dusky smoothhound (Mustelus canis), Cuban dogfish (Squalus cubensis), and shortspine spurdog (S. cf. mitsukuri)]. Mean dry rectal gland weight (x 1000)/body weight ratios ranged from 18.5 (C. acronotus) to > 40 (M. canis, S. tiburo, and S. cf. mitsukuri), and all were in the range of previous studies. Dry rectal gland mass/body mass ratios varied by genus and species (F8,77 = 55.44 and F4,81 = 40.55, respectively), but not by habitat [shallow: 28.90 ± 3.05 (µ ± SEM, N = 32); mid and deep: 31.50 ± 3.81 (N = 57)]. Although we have been unable to obtain rectal glands or blood samples from H. nakamurai or congeners/confamilials, these preliminary results suggest that both galeomorph and squalomorph deep-sea sharks operate by the long held osmoregulatory paradigm, and that our initial observation for H. nakamurai may obtain only for this species, genus, or family. Histological examination and blood chemistry are needed to understand the observed differences in the rectal glands and their physiological implications in the taxa we sampled.
Danielle Bailey1, Jill Hendon2, Andrew Evans1
1Department of Coastal Sciences, The University of Southern Mississippi, Ocean Springs, MS 39564, USA, 2Center for Fisheries Research and Development, The University of Southern Mississippi, Ocean Springs, MS 39564, USA
Species-specific Variation in Elasmobranch Interrenal Morphology, Histology, and Steroid Synthesis
Interrenal tissue in fish is homologous to the mammalian adrenal cortex, and is therefore composed of steroidogenic cells that secrete corticosteroids involved in critical physiological systems such as the stress response and hydromineral balance. In elasmobranchs, previous studies indicated that interrenal tissue is organized into discrete bodies that produce the dominant corticosteroid 1α-hydroxycorticosterone (1αB). However, studies in our laboratory revealed distinct differences in the size, abundance, color and distribution of putative interrenal bodies among several shark species including Finetooth (Carcharhinus isodon), Blacktip (Carcharhinus limbatus), Atlantic Sharpnose (Rhizoprionodon terraenovae), and Bonnethead (Sphyrna tiburo). In particular, the morphology of putative interrenal tissue in R. terraenovae and S. tiburo is distinct from the classic elasmobranch model, with a single pigmented body in R. terraenovae and a strip of interrenal tissue along the entire length of the kidney in S. tiburo. To validate the classification of interrenal tissue across these species, tissue was collected for histological examination and ex vivo incubations to verify corticosteroid production. Histological analysis revealed similarity in cell structure and organization across all species, and thin-layer chromatography demonstrated that 1α-B was the dominant corticosteroid produced by all putative interrenal tissues. Finally, morphometric analyses revealed differences in interrenal mass that may be related to corticosteorid output and therefore provide insight regarding species-specific differences in susceptibility to stress-induced mortality or reduced fitness.
Charles Bangley, Roger Rulifson
East Carolina University, Greenville, NC, USA
The Importance of Raleigh Bay as Overwintering Habitat for Juvenile Sandbar Sharks (Carcharhinus plumbeus)
Raleigh Bay, an area of the North Carolina coast between Cape Hatteras and Cape Lookout, has long been considered an important winter habitat for juvenile sandbar sharks, but this has largely been based on recaptures of tagged sharks originating from summer nurseries. In order to assess the importance of Raleigh Bay, juvenile sandbar sharks were tagged with acoustic transmitters and tracked using a stationary array deployed off of Cape Hatteras and other arrays along the U.S. east coast through the Atlantic Cooperative Telemetry Network from February 2013-October 2014. To delineate the spatial extent of potential sandbar shark habitat, daily sea surface temperature and chlorophyll-a concentration data recorded by the MODIS satellite were used to identify relationships between these environmental factors and shark presence at receiver locations. Boosted regression trees were used to identify environmental cut points between high and low likelihood of shark presence by season, which were then used to map areas of potential seasonal habitat. Projected juvenile sandbar shark habitat was more spatially restricted during winter than other seasons, and was focused in the area of Raleigh Bay and the Hatteras Bight. The unique geography of Cape Hatteras created an area where sharks could mitigate trade-offs between warmer temperatures and higher productivity. This may cause juvenile sharks from multiple primary nurseries to concentrate in Raleigh Bay, making this area critical habitat for the species.
Micah Barkenhaster1, Lauren Partridge1, Rachel Scharer2, Gregg Poulakis2
1Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, St. Petersburg, FL, USA, 2Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Charlotte Harbor Field Laboratory, Port Charlotte, FL, USA
Parasites as Indicators of Sawfish and Ecosystem Health: How "bad guys" can be Good News
Among parasites of fishes are those with inflexible fidelity to a single host species with which their fates are inherently entwined. Such is the case for some of the diminutive passengers of Smalltooth Sawfish, Pristis pectinata, co-evolved parasites that are almost certainly at greater risk of extinction than their host. In addition to their contribution to biological diversity, these organisms could serve as indicators of environmental and host population health. To evaluate the status of the P. pectinata parasite community in the Charlotte Harbor estuary, in 2005 we began to conduct routine screenings for ecto parasites during our routine sampling efforts for population monitoring and tagging. Also, to the greatest practical extent, we have opportunely conducted parasitological evaluations on recovered carcasses of freshly dead specimens. External parasites have included monogeneans, isopods, copepods, and leeches. Internal parasites have included digeneans and cestodes. These species include sawfish-specific parasites that have not been reported for decades and very likely undescribed species. One species of external monogenean, Dermophtherioides pristidis, is particularly common in our samples and may serve as a good biological indicator species.
Amanda Barker1, Bryan Frazier2, Douglas Adams3, Jim Gelsleichter4, David Portnoy1
1Texas A&M University Corpus Christi, Corpus Christi, TX, USA, 2South Carolina Department of Natural Resources, Charleston, SC, USA, 3Florida Fish and Wildlife Conservation Commission, Melbourne, FL, USA, 4University of North Florida, Jacksonville, FL, USA
Identification and Relative Abundance of Cryptic Hammerhead Sharks
Scalloped hammerheads (Sphyrna lewini) and Carolina hammerheads (Sphyrna gilberti) are cryptic species that are sympatrically distributed in the southeastern United States. The scalloped hammerhead employs a reproductive strategy in which parturition occurs in discrete coastal nursery habitats. Several nursery areas have been identified on the east coast of the United States, yet the extent to which Carolina hammerheads utilize the same nursery habitats is unknown. Because nursery utilization may not be equivalent between the species, one or more nurseries may be critical to the persistence of one or both species. In this study, we used double digest restriction-site associated DNA (ddRAD) sequencing to identify a panel of single nucleotide polymorphisms (SNPs) that can be used to reliably differentiate between the species of young-of-the-year sharks sampled in four locations (Bulls Bay, SC, Cape Canaveral, FL, Panama City, FL, and Corpus Christi, TX). Sixty-one out of 34,282 SNPs have been identified as diagnostic through preliminary analysis. Screening of 141 young of the year hammerhead sharks caught between 2012-2014 revealed a mix of scalloped, Carolina and great hammerhead sharks (101 S. lewini, 29 S. gilberti, 2 S. mokarran, 11 unidentified). Scalloped hammerheads were the most abundant hammerhead shark in all nurseries except Bulls Bay, SC where Carolina hammerheads comprised 61% of identified individuals.
Georgia Southern University, Statesboro, GA, USA
Evaluation of propofol immersion anesthesia in stingrays
Previous work has shown suppression of fish physiological responses to experimental stimuli while immobilized with the anesthetic tricaine. For example, temporal resolution (a measure of retinal integration speed) may be reduced by 50% in stingrays anesthetized with tricaine. Alternative anesthetic protocols have been evaluated for some fishes that may provide an adequate surgical plane of anesthesia, but yield accurate physiological data. Propofol is a dissociative-type anesthetic that produces rapid induction and recovery when administered intravenously in bamboo sharks. Propofol may provide more long-term immobilization for elasmobranchs when administered as an immersion anesthetic as in some teleosts. Immersion in propofol (1.25mg/L) induced a surgical plane of anesthesia in round stingrays (Urobatis halleri) slower than tricaine (100mg/L). Recovery from tricaine occurred within 30 minutes, whereas recovery from propofol took up to 3 hours. All stingrays recovered completely from both anesthetic regimens. These results suggest that propofol acts as an effective immersion anesthetic for stingrays and the effects of immersion in propofol are substantially longer lasting than tricaine (hours v. minutes). The long-lasting effects of propofol may warrant selection of propofol as an alternative anesthetic to tricaine when longer anesthetic periods are needed.
Dana Bethea1, John Carlson1, R. Dean Grubbs2, Gregg Poulakis3
1NOAA Fisheries Southeast Fisheries Science Center Panama City Laboratory, Panama City, FL, USA, 2Florida State University Coastal and Marine Laboratory, St. Teresa, FL, USA, 3Florida Fish and Wildlife Conservation Commission Port Charlotte Field Laboratory, Port Charlotte, FL, USA
Growth Rates of Smalltooth Sawfish, Pristis pectinata, Using Length-frequency and Tag-recapture Data
Predicting the recovery of an endangered species requires a clear understanding of its life history, including species-specific growth rates. To examine the growth rates of smalltooth sawfish, Pristis pectinata, we used length-frequency and tag-recapture data of animals collected 2009 to 2015 in southwest Florida USA. Stretched total length (STL) data from 621 captures (64 - 455 cm) and 137 recaptures (69 - 417 cm) were used for analyses. Length-frequency data showed modes at 80 - 85, 155 - 175, and 405 cm STL; however majority of the data were from animals less than 220 cm STL (n=580 captures, 134 recaptures). Animals were collected in all months, with 72% captured March to July. Data were analyzed using the ELEFAN II and PROJMAT methods to fit seasonal and non-seasonal von Bertalanffy growth functions. Growth parameters estimated from length-frequency data were Linf = 501 - 572 cm STL, k = 0.19 - 0.26 year-1, and t0 = -0.93 - -0.70 years, depending on the model used. Growth parameters for tag-recapture data were analyzed using the GROTAG method and were similar to that from lengthfrequency data (Linf = 424 cm STL, k = 0.23 year-1). This study supports published information for smalltooth sawfish and suggests this species has more rapid growth, especially during the first year, than has previously been reported.
Jennifer S. Bigman, Nicholas K. Dulvy
Simon Fraser University, Burnaby, BC, Canada
Body size and the speed of life
Elasmobranchs are among the most threatened groups of marine life and conservation efforts are lacking, likely due to the data-poor nature of this group (Dulvy et al. 2014). Understanding the intrinsic sensitivity to decline for threatened species and predicting the same for data-poor species is needed to prioritize management. As life history traits relate to intrinsic sensitivity to decline, they can be used to understand which species should be prioritized (Dulvy and Reynolds 2003, Hutchings et al. 2012). Many life history traits have been used as correlates of decline sensitivity, with population growth rate having one of the strongest relationships (Dulvy et al. 2004, Hutchings et al. 2012). Unfortunately, estimating population growth rates requires large, detailed demographic data sets resulting from many specimens, time, and funding. As population growth rates are constrained by metabolic function, measuring metabolic rate could be a possible tool for estimating the relative sensitivity to decline of an organism (Hennemann 1983). For elasmobranchs, measuring metabolic rate is often not feasible due to their large size, and some other trait that is easier to measure is needed. Here, we analyze the utility of a morphological trait, gill surface area, as a proxy for relative metabolic rate. Specifically, the relationship of metabolic rate, gill surface area, body size, and temperature will be explored for both elasmobranch and teleost fishes, as there is sparse data existing for elasmobranch metabolic rate and gill surface area. Results of this analysis will be presented along with the implications of this study.
Tara Boag1, Angela Cicia1, William Driggers III2, David Kulka3, Mark Simpson3, Carolyn Miri3, David Koester1, James Sulikowski1
1University of New England, Biddeford, ME, USA, 2National Marine Fisheries Center, Southeast Fisheries Science Center, Mississippi Laboratories, Pascagoula, MS, USA, 3Department of Fisheries and Oceans, Newfoundland, Canada
Utilizing histologically processed vertebrae to estimate age and size at sexual maturity of black dogfish (Centroscyllium fabricii) from the western north Atlantic
Aging deepwater elasmobranchs is challenging not only because they are difficult to capture, but also reduced calcification rates make discerning vertebral banding patterns problematic. As such, there is a need to modify traditional aging methodologies in order to help distinguish vertebral banding patterns in this group of fish. Previous work in skates suggests histological processing of vertebral cross-sections may help elucidate banding patterns in species that possess less-calcified skeletons. Building off this premise, the objective of this study was to modify and apply this technique to estimate age and size at sexual maturity of the black dogfish (males=266; females=211), a small, deepwater shark that is commonly caught as bycatch in Canadian trawl fishery. Maturity ogives suggest that 50% maturity in females occur at 6 years and 561mm total length (TL), whereas 50% maturity in males occurs at a younger age of 5.3 years and smaller size of 460mm TL. Age estimates were made from a subsample 186 dogfish (males=94; females=92) ranging in size from 170-720mm TL. The index of average percent error and age-bias plot indicate that the ageing method was precise and nonbiases. Additionally, marginal increment analysis, although incomplete, suggests seasonal growth and band disposition potentially occurs in winter or early spring. In conclusion, the present study indicates black dogfish exhibit characteristics that make other elasmobranchs population highly susceptible to overexploitation. Furthermore, our results suggest histological processing of vertebrae may be a useful technique in elucidating annual banding patterns, not only in black dogfish but other deepwater elasmobranchs.
Ramón Bonfil1, Melina Ricaño-Soriano1, Oscar Uriel Mendoza-Vargas2, Nataly Bolaño-Martínez3, Paola Yanira Palacios-Barreto3
1Océanos Vivientes AC, Mexico DF, Mexico, 2Posgrado en Ciencias Biologicas, UNAM, Mexico DF, Mexico, 3Posgrado en Ciencias del Mar y Limnología, UNAM, Mexico DF, Mexico
Gone right under our noses? - Conservation Status of ‘El Tiburón Sierra’ (Pristis ssp.) in México
Occurrence and abundance information of Critically Endangered smalltooth (Pristis pectinata) and largetooth (P. pristis) sawfishes across most of their former range is sorely needed for a comprehensive global conservation status assessment. The current presence of both species in Mexico and Latin America remains largely uncertain due to a void of reliable information based on focused studies. During August-November 2015, we performed the first-ever nation-wide study of sawfishes in Mexico. We developed specific materials to survey fishers, raise community awareness, and publicize sawfish conservation needs. We interviewed over 800 fishermen in 71 coastal towns along the entire Mexican coast of the Gulf of Mexico/Caribbean, and from the mouth of the Gulf of California to the southernmost State. Results indicate that both sawfish species are nearly extirpated from Mexico, but not quite so. Interviewees reported mean decadal dates of last sighting, as the 1980s for P. pectinata and P. pristis in the Gulf of Mexico/Caribbean coast, and as the 1970s for P. pristis in the Pacific coast. No confirmed reports of recent (<5 years) presence of either species were obtained during the survey anywhere in Mexico. However, a live juvenile smalltooth sawfish was caught and kept alive in the state of Veracruz just last January. Results also include the first historical relative abundance maps, records of former directed fisheries, former utilization, and main threats, among others. Both species must be re-categorized in conservation status in Mexican legislation. Our approach should be replicated along Central American countries and other parts of the world.
Darcy Bradley1, Yannis P. Papastamatiou2, Steven D. Gaines1, Jennifer E. Caselle1
1University of California, Santa Barbara, Santa Barbara, CA, USA, 2Florida International University, North Miami, FL, USA
Do SCUBA divers affect the long-term spatial behavior of reef sharks?
Humans play a significant predatory role in terrestrial and marine ecosystems and anthropogenic fear effects have been recorded in a suite of systems across the globe. An open question is whether the mere presence of SCUBA divers can have long-term effects on animal behavior in the marine environment. Using baited remote underwater video surveys (BRUVs), we examined the spatial distribution and abundance of reef sharks at heavily dived and undived sites at Palmyra atoll, a U.S. Wildlife Refuge that has a ban on extractive fishing. In recent years, researchers have reported seeing fewer and fewer reef sharks at Palmyra, and data from multiple SCUBA surveys resulted in contradictory trends in reported shark population abundance through time. However, a capture-recapture population study revealed that Palmyra’s reef shark population is stable. Failing to account for behavioral effects in monitoring studies may be problematic as in most places it is impossible to differentiate changes in estimated population abundance due to behavioral modifications and those resulting from fishing. In Palmyra, we can isolate and quantify the behavioral response of reef sharks to human activities in the absence of fishing. We hypothesized that sharks may be actively avoiding sites with substantial human activity. However, contrary to our prediction, we found no evidence that SCUBA divers affect the long-term spatial distribution of reef sharks at Palmyra. Therefore, the observation that sharks appear to be declining may be the result of habituation to human presence or short-term avoidance behavior.
Lauran Brewster1, Nicholas Whitney2, Samuel Gruber3, Tristan Guttridge3, Mike Elliott1, Ian Cowx1, Karissa Lear2, Adrian Gleiss5
1University of Hull, Hull, UK, 2Mote Marine Laboratory, Sarasota, Florida, USA, 3Bimini Biological Field Station Foundation, Bimini, Bahamas, 4Rosenstiel School of Marine and Atmospheric Science, Miami, Florida, USA, 5Murdoch University, Murdoch, Western Australia, Australia
Accelerating Understanding of Field Metabolic Rates in Elasmobranchs
Metabolism governs the rate at which organisms transform and use energy and consequently is often considered the most fundamental rate in biology. Ascertaining field metabolic rate (FMR) is essential for quantifying the impact of a species on its ecosystem and producing reliable bioenergetics models for use in fisheries management and ecosystem modelling. However, the validity of the model is dependent on its parameterization and the accuracy of its components, including metabolism. Determining FMR of free-swimming elasmobranchs has logistical constraints and difficulties, especially in reconciling laboratory-based studies with field studies. Activity-based energy expenditure is likely to be the largest and most variable component of metabolism in many species of sharks and so their fine-scale activity levels may be used as a proxy for metabolic rate. Here, we demonstrate the use of animal borne accelerometers for elucidating the activity and concurrent metabolic demands of the lemon shark, Negaprion brevirostris. The relationship between overall dynamic body acceleration (ODBA) and mass-specific oxygen consumption (MO2) was derived from lemon sharks exercised in a swim-tunnel respirometer. Trials were conducted over a range of temperatures to investigate the effect of temperature on the ODBA-MO2 relationship for consideration when determining FMR values, particularly between seasons. FMR was determined from free-living lemon sharks tagged at Bimini, Bahamas (n=10 during wet season, n=10 during dry season), where acceleration data was recorded at 30 Hz for 120 hours per individual.
NOAA Fisheries, Silver Spring, MD, USA
Recent changes in Atlantic Shark Management in the United States
The Highly Migratory Species Management Division of the National Marine Fisheries Service (NMFS) is responsible for the management of the U.S. federal shark fisheries in the Atlantic Ocean, including the Gulf of Mexico and Caribbean Sea. When federal management of sharks began in 1993, management was relatively simple, and included establishing three management groups for 39 species of sharks and requiring fishermen and dealers to follow certain regulations such as permitting and reporting. Over time, as shark science has improved and the public knowledge about the importance of sharks has increased, the regulations have become much more species- and regionally-based than the original regulations. In 2015, NMFS implemented several changes to federal shark management including the addition of three shark species to the management unit and the implementation of regulations that increase flexibility for commercial fishermen while continuing to rebuild overfished sharks. Potential changes coming in 2016 and beyond will continue to need strong scientific research and support.
Patrick Burke1, Maurits van Zinnicq Bergmann2, Mark Bond2, Samuel Gruber2, Simon Dedman2, Yannis Papastamatiou2, Tristan Guttridge2
1EMBC+, Ghent, Belgium, 2Bimini Biological Field Station, Bimini, Bahamas
Use of Baited Remote Underwater Video Surveys to Assess the Diversity and Distribution of Elasmobranchs and their Prey Species in Bimini, Bahamas
Establishing effective management and conservation policies for marine systems requires an understanding of the dynamic relationship between predators and their environment. There is currently a lack of understanding of how this relationship shapes natural communities and influences population dynamics. This study used baited remote underwater video surveys (BRUV) to investigate the influence of abiotic and biotic factors on elasmobranch distribution, relative abundance, and species-specific habitat associations around Bimini, Bahamas. To date, 31 BRUVs have been deployed during February with an additional 120 envisaged before June. BRUVs were deployed in multiple locations and habitat types around the island, with habitat categorized as sand flats, seagrass beds, coral reefs, and mangrove edge. These locations serve as representative habitat types for the greater Bimini ecosystem. Current assemblage observed 6 species of chondrichthyans, 19 families of osteichthyes, 1 species of marine reptile, and 4 species of invertebrates. Preliminary results suggest elasmobranch abundance and distribution is influenced by water depth, heterogeneous substrate, and high relative abundance of teleosts. The identification of significant factors influencing elasmobranch assemblage structure provides further insight into community dynamics that can contribute to effective management and conservation policies.
Cecily Burton1, Rachel Scharer1, Philip Stevens2, Gregg Poulakis1
1Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Charlotte Harbor Field Laboratory, Port Charlotte, FL, USA, 2Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, St. Petersburg, FL, USA
Diel Movements and Habitat Use of the Smalltooth Sawfish, Pristis pectinata, in the Peace River: Implications for Defining the Boundaries of a Nursery Hotspot
Movements and habitat use of endangered juvenile (<3 yr old) Smalltooth Sawfish (Pristis pectinata) were studied in the Peace River, Florida during 2014 using active manual tracking and passive acoustic monitoring to (1) document fine-scale habitat associations and (2) estimate the boundaries of the only known nursery hotspot in the river. A total of 23 sawfish were acoustically tagged on the north side of the river during the peak recruitment period in April and May. Subsequently, rather than following individuals for long periods of time, manual tracking was conducted during June and July using kayaks (day) and small boats (night) to determine position estimates of individuals relative to the shoreline and major habitat types (e.g., red mangroves, oyster reefs, canals) throughout the study area. During the day, juveniles remained along the northern shoreline and tended to be close (< 25 m) to red mangrove-dominated shorelines. At night, juveniles moved away from the northern shore, and made excursions to the south side of the river. These data suggest that the boundaries of the hotspot include both shorelines of a six river kilometer portion of the Peace River between the US 41 and I-75 bridges.
Michael Byrne1, Jeremy Vaudo1, Guy Harvey1, Bradley Wetherbee2, Mahmood Shivji1,3
1Guy Harvey Research Institute, Dania Beach, FL, USA, 2University of Rhode Island, Kingston, RI, USA, 3Save Our Seas Shark Research Center, Dania Beach, FL, USA
Using Satellite Telemetry to Quantify Fisheries Interactions and Survival of Shortfin Mako Sharks
Accurate measures of annual survival and fishing mortality are vital to successful fisheries management and conservation, however such parameters are notoriously difficult to measure for highly mobile pelagic species. Fin-mounted Argos transmitters (SPOT tags) may prove to be a valuable tool to gather information on survival and fisheries interactions. We tagged 42 shortfin mako sharks (Isurus oxyrinchus) off the U.S. east coast (EC; 27), and the Yucatan Peninsula (YP; 15) with SPOT tags which reported near daily location data for up to 628 days. We were able to identify fishing mortality events, capture locations, the fisher’s port of origin, and the fishery (i.e. commercial/recreational). Eight sharks tagged off the EC (29.6%), and four from the YP (26.7%) were confirmed harvested by fishers. This level of fishing mortality is above estimates derived from conventional tag data, and represents minimal estimates as additional transmitters may have been destroyed by fishers at sea. Makos were harvested by fishers from 5 countries: Canada (4), Mexico (3), U.S. (3), Cuba (1), and Spain (1), highlighting the need for international management. The majority of makos were captured by pelagic long-liners (83%). We used known-fate models for telemetry data to estimate an annual survival rate of 0.69 (0.54 – 0.81). This is best interpreted as a “maximum fishery survival” rate as it was not possible to detect natural mortality events. Our data suggests very high fishing pressure on makos in the western North Atlantic. Such estimates should prove valuable for incorporation into population models and stock assessments.
Hannah Calich, Neil Hammerschlag
University of Miami, Miami, Florida, USA
Quantifying Distribution and Environmental Preferences of Apex Predatory Sharks in the Western Atlantic Ocean
Great hammerhead, tiger, and bull sharks are either threatened with extinction or vulnerable to exploitation throughout their range due to interactions with commercial fisheries. Identifying critical habitats and environmental preferences of these species can provide important information for wildlife managers to implement regulations to reduce shark interactions with fishing gear. In the present study, we used spatial analysis to analyze data from over 100 great hammerhead, tiger, and bull sharks instrumented with satellite tags in the Western Atlantic Ocean and Gulf of Mexico. Using these data, we identified shark distribution patterns and correlated them with environmental data obtained through remote sensing. Habitat preferences were then overlapped with data on regional fishing intensity. This permitted us to identify areas and times where these sharks were vulnerable to fisheries interactions.
Sean Canfield, Brian Bowen
University of Hawaii at Manoa, Honolulu, HI, USA
Population Genetic Structure and Connectivity in the California Horn Shark (Heterodontus francisci)
The California horn shark (Heterodontus francisci) is a small, benthic shark inhabiting the East-Pacific coastline from California to Mexico. This species is known to maintain small home-ranges of approximately 1,000 square meters as adults and exhibit extremely high levels of site-fidelity. How these behaviors influence population-genetic structure is unknown, although there is some morphological evidence to indicate that the cohorts on the California mainland may be reproductively isolated from the Santa Catalina Island (CA) population - separated by only 20 kilometers of deep water. To assess population connectivity in this species, samples were collected from near-shore locations along the California mainland and from Santa Catalina Island. Using a genomic sampling technique called double-digest RADseq (ddRAD), hundreds of single-nucleotide polymorphisms from across the genome were identified and used to estimate connectivity and population structure between putative populations.
Aaron Carlisle1, Wade Smith2, Salvador Jorgenson3
1Stanford University, Pacific Grove, California, USA, 2University of British Columbia, Vancouver, British Columbia, Canada, 3Monterey Bay Aquarium, Monterey, California, USA
Insights into the natal origin and early life history of sharks from intrinsic chemical markers within vertebrae
Sharks, skates, and rays (elasmobranchs) exhibit complex patterns of movement and habitat use which often vary by sex, season and ontogenetic stage. As a result, there remain large gaps in our understanding of the life history of most species, particularly among more mobile and pelagic species. Migratory pathways, environmental history, and source populations have been successfully reconstructed from chemical markers in the otoliths of teleost fishes, but this approach has only recently been applied to studies of elasmobranchs. Electronic tagging has demonstrated that elasmobranchs often exhibit a high degree of site fidelity to feeding, breeding or nursery areas. Differences in environmental conditions and feeding among these areas can be reflected in the chemical composition of elasmobranch vertebrae, providing valuable markers of individual, age- and sex-specific differences in geographic origins and habitat use. Here, we discuss the utility of intrinsic chemical markers deposited in elasmobranch vertebrae and apply vertebral elemental and isotopic composition to infer patterns of maternal and juvenile habitat use in white sharks (Carcharodon carcharias). Analyses of vertebral chemistry offer a promising tool for the study and conservation of highly mobile shark and ray populations.
John Carlson, Enric Cortés
National Marine Fisheries Service, Panama City, FL, USA
Estimates of Maximum Rate of Population Increase for Sawfish: Do Sawfish have the Highest Risk of Extinction?
Sawfish are recognized as one of the world’s most endangered marine fish. All species are classified as highly threatened with extinction based on IUCN criteria. Sawfishes are captured as a target species and bycatch in a variety of fishing gears primarily due to their toothed rostra being easily entangled. In addition, they occur in shallow coastal waters associated with threatened mangrove habitats. Sawfish are currently considered to have low productivity and limited ability to rebound from exploitation. While productivity has been compared to exploited shark species, no comparison of extinction risk has been made among sympatric batoids. Acknowledging that many species of tropical and subtropical batoids are data poor, we estimated the extinction risk by calculating the maximum rate of population increase (rmax) using several variants of the Euler–Lotka model with different data requirements. Our results suggest sawfish have moderate levels of productivity, with one species, narrow sawfish, among the most productive batoids. Species with higher risks of extinction include pelagic batoids such as manta, mobulid and cownose ray. Larger dasayatid rays with low fecundity also exhibited low productivity. Sawfish have the ability to recover providing the availability of habitat and fishing-related mortality is low.
Jeffrey Carrier1, Jillian Morris3, Derek Burkholder4, Judith Gregoire5, Alena Ellerbee2, Sarah Maschal2
1Albion College, Albion, MI, USA, 2Monroe County Schools, Monroe County, FL, USA, 3Sharks4Kids, Ft. Lauderdale, FL, USA, 4Nova Southeastern University, Halmos College of Natural Sciences, Guy Harvey Research Inst., Dania Beach, FL, USA, 5Seacamp Association, Inc., Big Pine Key, FL, USA
Expanding Opportunities for Young Women in Shark Research: A STEM Initiative in the Florida Keys
Twelve sixth and seventh grade women from Monroe County Public Schools in the Florida Keys competed to participate in an on-going research project studying age, growth, and movement of nurse sharks (Ginglymostoma cirratum). Participants were selected by their teachers on the basis of an essay detailing their interest in shark biology and the role of such an experience in their perception of their eventual career goals. The program was developed to address the continuing need to attract women at an early age to the marine sciences by demonstrating the fundamental techniques for conducting basic research and familiarizing them with the capture, management, and release of large sharks. Five of the facilitators were men, and five, including the boat captains, were women, deliberately selected to demonstrate that the necessary skill sets were independent of sex. Following a lecture describing basic shark biology, tagging demonstrations were performed. Participants were then each given their own small nurse shark for tagging and release. The remaining days were spent capturing and tagging sharks from the Big Pine Key area. Twenty-four nurse sharks, four blacktips, two lemons, and one bull were captured. All were measured, tagged and were released. All work was done by participants. Immobilization was tasked to facilitators. A pre-test and post-test evaluation measured both learning and attitude changes during the experience and were overwhelmingly favorable: "This experience showed hands-on application to marine science (and) made me think of reasons why sharks are not scary and why there are so many misconceptions."
Jose I. Castro2, Keiichi Sato2, Ashby B. Bodine2
1NOAA/NMFS, St. Petersburg, Florida, USA, 2Okinawa Churashima Research Center, Okinawa, Japan
A Novel Mode of Embryonic Nutrition in the Tiger Shark, Galeocerdo cuvier
How are tiger shark embryos nourished to large size without a placental connection? Tiger sharks belong to the family Carcharhinidae, and all carcharhinid sharks are placental with the exception of the tiger shark. The aim of this study was to test the hypothesis that tiger shark embryos are nourished to large size by imbibing a clear uterine fluid found in their egg cases. Based on weights of fertilized eggs and of term embryos, the tiger shark is a matrotrophic species, and its embryos can reach gains of 2119% in wet weight and 1092% in dry weight during gestation. By measuring the total energy content of the fluid in the egg case by chemical oxygen demand (COD), the authors demonstrate that clear liquid in the tiger shark egg case is an energy-rich embryotrophe that nourishes the embryos to large size. The term embryotrophy is suggested for this process. The process appears to be an adaptation for producing large broods of up to 70 young of relatively large size.
Andrew Chin2, Michelle Heupel2, Colin Simpfendorfer1, William White3
1James Cook University, Townsville, QLD, Australia, 2Australian Institute of Marine Science, Townsville, QLD, Australia, 3CSIRO, Hobart, TAS, Australia
Crossing lines: a Multidisciplinary Framework for Migratory Hammerhead Sharks across Jurisdictional Boundaries
The conservation and management of migratory species is complex and challenging. International agreements such as CITES and CMS provide frameworks to manage highly migratory species, but management can be compromised by lack of data and tractable mechanisms to integrate disparate datasets. Hammerhead sharks (Sphyrna spp.) are highly migratory species taken in coastal and oceanic fisheries around the world and are listed in CITES and CMS. A large scale assessment of scalloped hammerhead (S. lewini) and great hammerhead (S. mokarran) populations across northern Australia, Indonesia and Papua New Guinea was conducted to inform management responses to CITES and CMS. A simple Integrative Assessment Framework for Migratory Species (IAFMS) was devised to systematically incorporate disparate data types across jurisdictions and create a regional synopsis. The IAF amalgamated data from fisheries catch records, fishery independent research, shark control programs, market surveys, BRUVS and citizen science data. Hammerhead populations are segregated by sex and size across the assessment area, with Australian populations dominated by juveniles and small sized adult males, while Indonesian and Papua New Guinean populations contained large adult females. The final IAF assessment stage introduced genetic and tagging data to produce conceptual models of regional hammerhead movement and stock structure. Several viable hypotheses for regional stock structure and movement patterns were produced, but more data are needed to identify the most plausible hypothesis. This work demonstrates a simple conceptual framework for assessing migratory species, and highlights priority areas for management and research of hammerheads in the Australasian region.
Francisco Concha1, Janine Caira1, Dave Ebert2
1University of Connecticut, Storrs, Connecticut, USA, 2Pacific Shark Research Center, Moss Landing, California, USA
On the identities and affinities of South American skates: Two case studies
Elasmobranch taxonomy has undergone remarkable transformations over the past several decades as a result of the identification and description of hundreds of new species-many from the waters of the Indo-Pacific region. Inspired by that earlier work, this study aimed to take a closer look at the identities of two intriguing South American batoids. The first was a small, deep-sea skate originally collected off Ecuador. Morphological and molecular investigations confirmed it represented a novel species of Notoraja, thereby extending the distribution of this genus across the Pacific Ocean to South America. The second case involved the commercially important skate Dipturus chilensis, which has traditionally been considered to occur throughout the coast of South America from Chile to the Falkland Islands. Preliminary molecular analyses called in to question the conspecificity of specimens from these disparate regions, in fact suggesting that D. chilensis from Chile was sister to D. nasutus from New Zealand, and that the taxon from the Falklands was the sister taxon to that clade. Additional morphological and molecular investigation confirmed the Falkland species to represent a distinct, and in fact, novel species of Dipturus; simultaneously that work also indicates that D. chilensis is endemic to Chile. These results have important conservation and management implications for they require that the species on the eastern and western coasts of South America be treated separately rather than as a single broadly distributed species. In combination, these results provide evidence of intriguing affinities between the elasmobranch faunas of the Western and Eastern Pacific Oceans.
Shannon Corrigan1, William White2, Lei Yang1, Aaron Henderson3, Gavin Naylor1
1Hollings Marine Laboratory, College of Charleston, Charleston, SC, USA, 2CSIRO Marine and Atmospheric Research, Hobart, TAS, Australia, 3The School for Field Studies, Center for Marine Resource Studies, South Caicos, Turks and Caicos Islands
Phylogeny of the manta and devilrays (Chondrichthyes: Mobulidae), with an updated taxonomic arrangement for the family
The manta and devilrays of the family Mobulidae are arguably the most charismatic ray group. They occur worldwide in tropical and temperate waters where they are also exploited to such an extent that there is now considerable concern regarding the conservation status of mobulid rays globally. Accurate taxonomy is recognised as the foundation of all other biological sciences and is crucially important for setting appropriate conservation management priorities. There has been progress toward characterizing the diversity and phylogeny of mobulid rays however, mobulid taxonomy remains largely unresolved due to a complex nomenclatural history and to poor representation of mobulids in biological collections. The Mobulidae is currently considered to comprise two genera, Manta and Mobula, encompassing two and nine nominal species respectively. Notable longstanding taxonomic uncertainties include the validity of the genus Manta, as well as distinguishing species boundaries from intraspecific variation within multiple lineages of Mobula. We provide an estimate of Mobulid phylogeny and present a revised taxonomy for the group based on analysis of DNA sequence data from whole mitochondrial genomes and more than 1000 protein coding, nuclear exons for a complete taxon sampling of mobulid rays. Any discordance between our molecular phylogenetic inferences and the previously recognised taxonomy were resolved by undertaking a detailed examination of morphological data and the nomenclatural history for the relevant taxa. We demonstrate that Manta is an invalid genus designation, provide evidence for multiple species level synonymies, and forward a new phylogeny for the group.
Enric Cortes1, Elizabeth Brooks2
1NOAA-NMFS-SEFSC, Panama City, FL, USA, 2NOAA-NMFS-NEFSC, Wood Hole, MA, USA
Predicting overfished and overfishing reference points with data-limited stock assessment methods and life history: application to shark stocks worldwide
We investigated whether reference points obtained from stock assessments could be replicated with simpler methods by comparing the overfished reference point obtained in stock assessments of a suite of shark stocks worldwide with predictions from a data-limited method that calculates biological reference points analytically based on life history data and an index of relative abundance. Predictions from this method agreed very well with those from the existing stock assessment models. We further tested the robustness of the method to assumptions about initial depletion of the population by identifying how much it would have to change to reverse the prediction on the state of the stock and assessed the plausability of that change. We found that the method was robust in 76% of the cases examined. We also compared the overfishing reference point from stock assessments to predictions based on two published relationships between FMSY and M for chondrichthyans. Additionally, we conducted a review of shark stock assessments to develop another benchmark of FMSY based on M against which we also compared results from stock assessments. Finally, we used simulation to generate ratios of FMSY/M for a range of M and steepness values for different relationships between median selectivity and age at maturity under different slopes of the selectivity and maturity curves. We found that FMSY<0.5M for low productivity stocks, and even lower values if immature individuals are harvested. Empirical evidence also suggests that for many shark species with comparatively low productivity, FMSY≈0.25M.
Lydia Crawford1, Ian Davenport2, Henry Bart1
1Tulane University, New Orleans, LA, USA, 2Xavier University, New Orleans, LA, USA
Association between Novel Ova Morphology and Chondrichthyan Reproduction
The reproductive biology of Chondrichthyan fishes evolved to produce larger, more precocious young with higher survival chances. To produce larger young, chondrichthyans must provide more nutrients to developing embryos. This can be performed through multiple methods, including larger oocytes, longer gestation, and uterogestation (consumption of nutrients within the uterus). Most chondrichthyans reproduce through vivipary (up to 65%). The first step in creating more developed young was an increase in egg size, accompanied by increasing the zona pellucida thickness. Typically nutrients enter the oocyte via diffusion from the follicle cell layer, which is important for transferring nourishment into the developing oocyte for storage, through the zona pellucida. However, diffusion is unlikely in chondrichthyans. It was unclear how oocytes in chondrichthyans receive nutrients and maintain integrity during transport within the female reproductive tract. Current work regarding Follicle Cell Processes (FCP) seeks to answer both these questions. FCP, first described in sharks in 2011, are unique structures that may transfer nutrients across the zona pellucida and provide structural support to developing oocytes. They are a series of tube-like structures that cross the zona pellucida, connecting the oocyte to the follicle cells. This direct connection suggests a role in nutrient transport. They also contain the cytoskeletal protein actin, which may play a role in structural support. FCP have been found in both carcharhiniform and saqualiform sharks, though recent work indicates they are not present in skates. I am studying follicles of modern chondrichthyans to understand the distribution, variation, and possible origin of these structures.
Dan Crear1, Jill Hendon2, Eric Hoffmayer3
1Virginia Institute of Marine Science, Gloucester Point, VA, USA, 2Center for Fisheries Research and Development, Gulf Coast Research Laboratory, Ocean Springs, MS, USA, 3National Marine Fisheries Service, Southeast Fisheries Science Center, Mississippi Laboratories, Pascagoula, MS, USA
Identifying the drivers of juvenile shark abundance and distribution within the Mississippi Sound
Shark nursery grounds are an important habitat that promotes young-of-year (YOY) and juvenile shark survivorship. Both abiotic and biotic variables play key roles in the abundance and distribution of individuals within these nursery grounds. From 2004 to 2014, 1,005 sampling sets using a 183-m gillnet (stretched mesh panels of 8.9 to 20.2 cm), a 152-m bottom longline (12/0 circle hook), or 1.85-km bottom longline (15/0 circle hook), were conducted in the Mississippi Sound by the Gulf Coast Research Laboratory’s Shark Research Program. The use of multiple gear types allowed for a more comprehensive look into the dominant species composition, including all developmental stages (i.e. YOY, juvenile, and adults). A two-step hurdle model was used to determine the effect the biotic and abiotic variables had on the distribution of multiple shark species caught in the Mississippi Sound. A multi-model inference approach was ultimately used for each step to determine the variables that strongly influenced the presence and abundance of each shark species. Atlantic sharpnose, blacktip, and finetooth sharks represented the three most abundant shark species encountered. In general, YOY and juvenile sharks were often present in more turbid, warmer waters. Interestingly, the presence of juvenile Atlantic sharpnose and blacktip sharks increased with increasing predator presence. Habitat suitability maps were created for each species by season within the Mississippi Sound to indicate areas of critical habitat.
Leanne Currey, Michelle Heupel
Australian Institute of Marine Science, Townsville, Queensland, Australia
Northern Great Barrier Reef: a Haven of Shark Diversity and Abundance
Australia's Great Barrier Reef (GBR) is world renowned for its diversity of marine life. Across a variety of habitats, 134 elasmobranch species occur in the GBR Marine Park (GBRMP), and likely fulfil a key role in ecosystem function. Baited Remote Underwater Video System (BRUVS) data collected along the entire GBR has revealed that shark abundance and species richness are most influenced by relative distance along and across the reef shelf and hard coral cover. Evidence suggests shark occurrence and species richness is higher in the Northern and Southern regions of the GBR compared to the Central GBR, while non-fished reefs support higher shark abundance. With a focus on coral reefs, the aim of this study was to assess the species composition and relative abundance of elasmobranchs sampled in the Northern GBR, and compare among management zones and with existing data. As part of the Global FinPrint Project, an initiative to assess shark and ray diversity and abundance in coral reef environments worldwide, BRUVS were deployed at two locations (n = 154), in no-take and fished reefs. Eighteen elasmobranch species were observed, with grey reef sharks Carcharhinus amblyrhynchos sighted on the majority of BRUVS. Abundance of elasmobranchs was high across the sites with similar numbers across zones, indicating a low influence of fishing pressure. This research highlights the exceptional diversity and abundance of species occurring in remote areas of the GBR, and contributes to our understanding of their distribution patterns and marine reserve use, which is essential for effective shark conservation.
Lindsay Davidson, Nicholas Dulvy
Simon Fraser University, Burnaby, Canada
Global Marine Protected Areas for Avoiding Extinctions
Target 11 of the Convention on Biological Diversity (CBD) outlines that 10% of global coastal oceans should be designated as a Marine Protected Areas (MPA) by 2020. This area goal has driven rapid gains in global MPA coverage but it remains unclear whether threatened species are being protected. We find the area-grabbing approach of MPA designations will fail to avert extinctions of sharks, rays, and chimaeras (Class Chondrichthyes). We find that only 10 of the 99 most vulnerable and irreplaceable chondrichthyans meet the minimum protection target of 10% of their range within a MPA and only one (Squalus raoulensis) is found in a Marine Reserve - those areas that are no-take and strictly protected. However, to protect chondrichthyans the solution is simple. Using a unique dataset we identify twelve countries that harbour over half of the world's vulnerable and irreplaceable chondrichthyans, as well as three-quarters of wideranging threatened species within an area of less than 1% of the world's ice-free oceans. These countries have much room for conservation and management action in terms of (i) adequate Shark-Plans, (ii) shark finning regulations, (iii) conserving migratory sharks and rays, (iv) commitments to eliminating Illegal Unreported and Unregulated fishing. Looking forward, an additional 3.5% of the global ice-free EEZ area would protect 50% of the global distribution of the 99 threatened endemics - well below the 10% target. Our analysis lays the foundation for marine biodiversity conservation goals beyond 2020.
Matthew Davis, Toby Daly-Engel
University of West Florida, Pensacola, FL, USA
Atlantic Sharpnose Shark (Rhizoprionodon terraenovae) Rangewide Genetic Stock Structure
The Atlantic Sharpnose shark (Rhizoprionodon terraenovae) is a small coastal species associated with the subtropical and tropical waters of the Gulf of Mexico (GoM) and northwest Atlantic. The members of the genus Rhizoprionodon are often utilized by smallscale fisheries as an important resource, and R. terraenovae alone represents 46% of annual artisanal elasmobranch catches in the southern GoM. Despite the species’ commonality in both artisanal and commercial fisheries, relatively little is known regarding its reproductive behavior, range limits, and movement patterns. We seek to characterize the fine-scale genetic connectivity of this species through statistical comparison of DNA sequences from both the mitochondrial and nuclear genome, including >650 base pairs of the control region and 10-12 microsatellite loci crossamplified from congener species. To date we have accumulated over 500 R. terraenovae tissue samples from 10 sites throughout its range from Rhode Island to Belize, and collections are ongoing. With these data we delineate the patterns of gene flow, philopatry, and dispersal in R. terraenovae, information that will enable managers and conservationists to better protect and manage this species in the future.
Simon Dedman1, Rick Officer1, Deirdre Brophy1, Maurice Clarke2, Dave Reid0
1Galway-Mayo Institute of Technology, Galway, Ireland, 2Marine Institute, Galway, Ireland
A flexible decision support tool for Maximum Sustainable Yield-based MPA design
Novel, spatial approaches have been called for to manage elasmobranchs, but existing techniques struggle to model abundance hotspots and essential habitats of data-poor stocks. When proposed MPA's are presented as definitive and singular solutions this can entrench an antagonistic relationship between fisherman and managers/scientists. We have used survey data and discarding records to develop Fmsy (fishing CPUE equating to Maximum Sustainable Yield) and Bpa (precautionary minimum total biomass to support a species) proxies for these populations, allowing us to estimate the proportion of population biomass that must be conserved annually to meet PA or MSY thresholds, i.e. escapement. We have then applied Boosted Regression Tree modelling of survey catch and environmental factors such as depth, substrate and flow, to map skate and ray abundance hotspots. The outputs are combined with international fishing effort data (VMS) and fed into a custom-built Decision Support Tool (DST), to identify the location and size of candidate MPAs that could protect the escapement PA biomass while minimizing the displacement of fishing effort. The DST allows fishermen, managers and scientists to use spatial management, underpinned by fisheries science, to explore MPAs which incorporate different and often conflicting priorities. The entirety of this work has been integrated into a simple R package which takes surveyed CPUE and environmental data and produces CPUE hotspot maps for a whole study area, including for sensitive subsets such as nursery areas, and an MPA-generating DST incorporating stakeholder priorities.
Erin Dillon, Aaron O'Dea
Smithsonian Tropical Research Institute, Panama City, Panama
Dermal Denticles as a Tool to Reveal Pre-exploitation Shark Communities
What were shark communities like before humans? Ecological surveys and historical records demonstrate significant declines in shark populations, yet pre-exploitation baselines are nonexistent. Fossil dermal denticles may offer insight into pre-human shark communities. Denticles are well-preserved in reef sediments, but their identification represents a major challenge. To address this problem, we built a large reference collection from museum and local collections comprising 215 denticles from 37 species within 16 elasmobranch families. Morphometric analysis revealed that denticle morphology is loosely tied to taxonomy, making species-level identification almost impossible. We found, however, that denticle traits are strongly correlated with life habit and feeding mode. Quantitative measurements of traits also corroborated existing qualitative functional groupings and refined the boundaries between them. For example, fast, predatory sharks possess thin, ridged 'drag reduction' denticles, whereas demersal sharks are characterized by thick 'abrasion strength' denticles. In a proof of concept, we extracted 254 denticles from a 7,000-year-old fossil reef and 602 denticles from comparable modern reefs in Bocas del Toro, Panama and classified them using the reference collection. Denticle assemblages in Holocene and modern sediments corresponded well with families documented in the region. We found a significant decrease in the relative abundance of 'drag reduction' denticles and an increase in 'abrasion strength' denticles over the last ~7,000 years. Denticles in modern sediments can therefore supplement survey data given the rarity of sharks, and denticles in the recent fossil record may shed light on shifts in shark community composition over time.
Pavel Dimens, David Portnoy
Texas A&M University - Corpus Christi, Corpus Christi, TX, USA
Population structure of a migratory small coastal shark, the blacknose shark Carcharhinus acronotus, across cryptic barriers to gene flow
For marine species existing along seemingly continuous habitat, identifying regional groups poses challenges because the ability to define a priori hypotheses with respect to population structure is limited. Further, in highly vagile species like the blacknose shark (Carcharhinus acronotus), individuals from independent populations may co-occur seasonally on feeding grounds. A recent study using microsatellite markers identified as many as five distinct populations spread across an area from South Carolina, USA to Campeche Banks, Mexico and the Bahamas but found ambiguity in the Florida Keys, an area that spans the divide between the U.S. Atlantic and eastern Gulf of Mexico populations, as well as their management units. This project used next-generation sequencing to identify single nucleotide polymorphisms (SNPs) across thousands of loci to distinguish between four possible scenarios of population structure and gene flow in the region: 1) the Keys are a zone of admixture between Atlantic and eastern Gulf of Mexico populations, 2) individuals from both populations are seasonally present in the Keys but there is no gene flow, 3) the Keys are a unique genetic unit, separate from Atlantic and Gulf of Mexico populations, 4) previous microsatellite markers were insufficient to resolve structure for the Keys and individuals there group distinctly with either Atlantic or Gulf populations.
Mareike Dornhege, Anne McDonald
Sophia University, Tokyo, Japan
Shifts in Shark Community Assemblage in the North Pacific Indicated by the Japanese Longline Fishery
Japan's oldest shark longline fishery dates back to the 18th century. According to the FAO, until the 1940s, Japan registered the highest elasmobranch landings worldwide and is currently the 9th largest shark fishery worldwide. The national longline fishery for sharks is concentrated in the port of Kesennuma in Northern Japan and since the collapse of the Pacific tuna fishery in 2003, blue shark and billfish are the main target species. The goal of this study is to present an analysis of this fishery and its effects on the ecosystem through an integrated approach. Three methods have been employed: 1) analysis of historical documents from libraries, museums and fisheries cooperatives on the historical use and fisheries of shark, with a focus on determining peaks in fisheries and most landed species over the past centuries; 2) interviews with fishermen, vessel owners, shark product processors and other stakeholders to identify any shifts in species landed over the past 60 years; and 3) analysis of landing and market data that recorded elasmobranchs to the species or family level over the past 20 years to calculate CPUEs and biodiversity indices. Results indicate that historically, a wide variety of sharks were used and preferred depending on the product created while today, only three species account for more than 95% of the landings and most products. Both fishermen and processors report steep declines in Squalus acanthias and the genus Charcharinus compared to the three dominant species, a trend which is confirmed by the CPUE and biodiversity analysis.
Kaitlin K Doucette1, Stephanie Mounaud2, William Neirman2, Andrew N Evans1
1Department of Coastal Sciences, The University of Southern Mississippi, Ocean Springs, MS 39564, USA, 2J. Craig Venter Institute, Rockville, MD 20850, USA
The Elasmobranch Microbiome: Changing Our Understanding of Vertebrate-Microbe Relationships
Communities of bacteria in digestive systems play a critical role in host physiology; however, the existence of non-pathogenic bacteria in other healthy tissues is unusual. Previous studies suggested that elasmobranch fishes, unique in numerous aspects of physiology, possess endogenous bacteria in tissues that are sterile in other vertebrates such as kidney, liver and blood. Surprisingly, this phenomenon has not been explored since initial publications in the late 1980s, which employed culture-based approaches to microbial characterization. Using modern methods (16S rRNA gene sequencing via the Illumina MiSEQ platform), we identified a diverse array of bacteria present in intestinal, hepatic and renal tissues of Dasyatis sabina (Atlantic stingray) and Rhizoprionodon terraenovae (Atlantic sharpnose shark) from the Gulf of Mexico. Using this preliminary data, we hope to elucidate the costs and benefits of symbiont bacteria to elasmobranch hosts. The results of this study suggest an unprecedented relationship between microbes and vertebrate hosts and raise compelling questions about the importance of resident bacteria to elasmobranch physiology, as well as the possible implications of differences in microbial diversity across individuals.
Alistair Dove1, Harry Webb1, Rafael De la Parra-Venegas3, Christian Schreiber1, Jeffrey Reid1, Simon Pierce5, Robert Hueter4, Katie Hindle2, LeeAnn Henry2, Annalea Beard2, Ross Leo2, Elizabeth Clingham2
1Georgia Aquarium, Atlanta, Georgia, USA, 2St Helena Government, Jamestown, St Helena, UK, 3Ch'ooj Ajauil AC, Cancun, Quintana Roo, Mexico, 4Mote Marine Laboratory, Sarasota, Florida, USA, 5Marine Megafauna Foundation, Tofo, Mozambique
St Helena Island provides important habitat for whale sharks
Studies of whale sharks in recent years have focused on near-coastal aggregations, but this approach does not tell the whole demographic story because these events are typically dominated by immature males. Remote oceanic islands have been hypothesized to be the site of mating or pupping in whale sharks, which are activities affiliated by definition with adults. One such island is St Helena in the South Atlantic, which was recently discovered to play host to a seasonally predictable population of adult whale sharks. Two collaborative expeditions have been conducted in 2015 and 2016 to document whale shark abundance and population composition, to characterize behavior and habitat use around the island, and to determine regional scale movement patterns using satellite telemetry. The whale shark population observed at St Helena consisted of an approximately equal mix of mature males and females that were larger than the sub-adults seen in most coastal aggregation sites, but smaller than the large female animals seen regularly in the Galapagos. Two eyewitness accounts of mating behavior have been recorded at St Helena, but this behavior was not directly observed during the expeditions. Preliminary PAT telemetry data are showing a pattern of extraordinary deep diving in the vicinity of the island. A single useful track from the 2015 expedition suggests that St Helena whale sharks are connected to the west coast of Africa. We propose a regional movement pattern with animals feeding in coastal upwelling zones, and travelling to remote oceanic islands to fulfill aspects of the reproductive cycle.
Rachel Dreyer, Kim Bassos-Hull, Krystan Wilkinson, Breanna DeGroot
Mote Marine Laboratory, Sarasota, FL, USA
When the Shark Bites and the Remora Sucks: Incidence of Injury on Spotted Eagle Rays (Aetobatus narinari) and Lesser Devil Rays (Mobula hypostoma)
The spotted eagle ray, Aetobatus narinari, and the lesser devil ray, Mobula hypostoma, have been the subjects of capture-tag-release studies off southwest Florida from 2009-2015. We analyzed data and photographs of A. narinari (2009 - 2015, n=518) and M. hypostoma (2013 - 2015, n=97) to determine incidence of injury inflicted by shark predators, other species such as remoras and marine mammals, and human activity. While predation was not actively observed by researchers, shark bite wounds and scars were documented in both A. narinari (n=45) and M. hypostoma (n=26). Remoras attach to the smooth, mucous-coated skin of rays and attachment sites are recognized by the pattern created by the remora's modified dorsal fin. Many A. narinari (n=390) and M. hypostoma (n=68) displayed recent wounds or healed scars from remora attachment. Of these animals, 23 and 12, respectively, had open wounds with bloody and/or reddened tissue. Recaptured A. narinari with remora scars on the first capture (n=25) displayed rapid healing, including one individual that displayed no remora attachment sites after 225 days at liberty. No M. hypostoma individuals were recaptured during this study; however, one individual held at our facility for 21 days showed near-complete healing from a shark bite wound observed at capture. Injuries inflicted by anthropogenic sources including boat scars, fishing line entanglement, and fishing hook embedment were observed on A. narinari (n=15) and M. hypostoma (n=3). This study confirms that A. narinari and M. hypostoma displayed significant healing abilities after non-fatal injuries.
J. Marcus Drymon1, John Froeschke2, Andrea Kroetz3, John Mareska4, Sean Powers1
1University of South Alabama, Dauphin Island, AL, USA, 2Gulf of Mexico Fishery Management Council, Tampa, FL, USA, 3NOAA Fisheries, Panama City, FL, USA, 4Alabama Department of Conservation and Natural Resources, Marine Resources Division, Dauphin Island, AL, USA
Sex-specific seasonal changes in community dynamics of a northern Gulf of Mexico coastal shark assemblage
Abiotic factors are known to influence the distribution of marine organisms; however, the relative importance of abiotic drivers is often species and sex-specific. Understanding how species respond to changes in abiotic conditions is critical for successful conservation and management plans, and in light of future climate change. To investigate species and sex-specific seasonal changes in the community dynamics of coastal shark assemblage, we analyzed catch data from two concurrent bottom longline surveys. A combination of multivariate (PERMANOVA) and univariate (boosted regression trees) approaches was used to examine differences in the assemblage as a function of season and depth, and further explore the factors influencing the sex-specific probability of capture. From February 2011 through May 2013, 126 bottom longline sets were conducted, resulting in the capture of 1844 individuals across 19 elasmobranch taxa. Multivariate analysis revealed a community structured by season and depth. Boosted regression trees further revealed species and sex-specific differences in the factors driving species’ distributions. For females, depth had the highest relative influence on the distribution of Atlantic sharpnose (Rhizoprionodon terraenovae), blacknose (Carcharhinus acronotus), and bull sharks (C. leucas), whereas bottom temperature and longitude had a larger relative influence on the distribution of male Atlantic sharpnose and blacktip sharks (C. limbatus). These results support the counterintuitive notion that despite having relatively small size at birth, Atlantic sharpnose and blacknose sharks may be using open waters for parturition. Our findings underscore the importance of quantifying species-specific abiotic drivers of shark distribution, particularly in light of impending climate change.
Nicholas Dulvy1, Will Stein1, Chris Mull1, Tyler Kuhn2, Neil Aschliman3, Lindsay Davidson1, Jeff Joy4, Gordon Smith1, Arne Moers1
1Simon Fraser University, Vancouver, Canada, 2Yukon Beringia Interpretive Centre, Whitehorse, Canada, 3St Ambrose University, Iowa, USA, 4C Centre of Excellence HIV/AIDS, Vancouver, Canada
Using trees to save sharks and rays
Inevitably, greatest conservation attention is given to the most charismatic or distinctive species while others equally deserving get left behind. How do we ensure that the lesscharismatic underworld of chondrichthyans is prioritised for conservation action in an objective manner? We take advantage of recent advances in phylogenetic methods for combining genetic and taxonomic information to produce taxon-complete phylogenies to rank all 1192 chondrichthyan species by their evolutionary distinctiveness. First, we recovered a molecular phylogeny of 624 species based on 13 mitochondrial and 2 nuclear loci from GenBank and Barcode of Life. Second, this time-calibrated tree was infilled with the remaining species for which there were no molecular data based on their known taxonomic affinities. We generated a distribution of 10,000 fully resolved, taxoncomplete phylogenies. We describe the depths, habitats, and geographic locations with the greatest and least amount of evolutionary distinctiveness. We combined Evolutionary Distinctiveness information with known and inferred Global Endangerment scores to identify EDGE species and locations that embody the highest conservation priorities to mitigate the loss of chondrichthyans' unique evolutionary history.
Robert Edman1, Gorka Sancho1, Bryan Frazier2, Wally Bubley2, John Kucklick3
1College of Charleston, Charleston, SC, USA, 2South Carolina Department of Natural Resources, Charleston, SC, USA, 3National Institute of Standards and Technology, Charleston, SC, USA
Movement Patterns and Trophic Ecology of Tiger Sharks (Galeocerdo cuvier) Caught off the Southeast Coast of the United States
Exploitation of sharks has markedly increased in the past three decades, and this exploitation, coupled with degradation of essential habitats, can contribute to declining species abundance. Understanding the movement patterns and diet composition of sharks is central to creating and enacting appropriate management actions to preserve these animals and their habitats. The present study seeks to analyze the movement patterns and diet of Tiger Sharks caught in coastal waters of the southeast United States utilizing passive acoustic telemetry, satellite telemetry, and stable isotope analysis. Results show Tiger Sharks tagged in South Carolina during spring months move extensively in coastal and shelf waters. These movement patterns appear to differ from Tiger Sharks tagged in the Bahamas and Bermuda, which move primarily through shelf and offshore waters. Results of Tiger Sharks tagged during autumn months indicate that these sharks may overwinter in offshore waters and in the Bahamas. Stable isotope analyses on multiple tissue types (blood, muscle, skin, and plasma) from captured Tiger Sharks confirm that smaller Tiger Sharks occupy a lower trophic level, and that this species undergoes an ontogenetic diet shift. Results of a Bayesian mixing model will be used to determine the proportions of different prey items in the diet of Tiger Sharks caught in South Carolina. Satellite and acoustic tracking of tagged sharks is ongoing, and the third year of tagging and collecting samples from Tiger Sharks is currently underway.
Samantha Ehnert, Jim Gelsleichter
University of North Florida, Jacksonville, FL, USA
Mercury Accumulation and Effects in the Brain of Atlantic Sharpnose Sharks (Rhizoprionodon terraenovae)
Sharks often bioaccumulate mercury (Hg) in muscle to levels that threaten human health. However, few published studies have examined if the high Hg levels seen in shark muscle also occur in the shark brain, or if Hg accumulation affects shark neurophysiology. Therefore, this study examined if shark brains accumulate significant levels of Hg, if Hg accumulation occurs in certain subcomponent of the brain, and if Hg accumulation is associated with effects on the shark nervous system, with special focus on the Atlantic sharpnose shark (Rhizoprionodon terraenovae). Sharks were collected along the southeast U.S. coast. Muscle and brain Hg concentrations were determined using a Direct Mercury Analyzer. Correlations between brain Hg concentrations and levels of known biomarkers of Hg-induced neurological effects (e.g., levels of a protein biomarker of glial cell damage, S100b, and markers of oxidative stress) in shark cerebrospinal fluid (CSF) were examined. Brain Hg levels were correlated with muscle Hg levels, but were significantly lower and did not exceed most known thresholds for neurological effects, suggesting limited potential for such responses. Data on CSF biomarker levels support this premise, because they were not correlated with brain Hg levels. Higher Hg levels were measured in the forebrain of shark in comparison with the hindbrain, but levels in both were below threshold levels for effects. This study is the most extensive analysis of Hg in a single shark species, spanning most of its Atlantic range. It is also the first to examine neurological effects of Hg exposure in these animals.
University of Bahri, Khartoum, Sudan
The Occurrence of the Green Sawfish (Pristis zijsron) along the Sudanese Red Sea with Observations on Some Reproductive Parameters
The aim of the study is to identify the species of sawfish in the Sudanese Red Sea and to assess its current status. Collection of data has been carried out since 2001 by the author. Data from fieldwork was compiled for the period 2001 to 2016, and during Oct 2015 to March 2016 data have been collected from bottom trawling in the southern Sudanese Red Sea Coast. Data have also been collected since 2011 through standard questioner and interviews with fishermen along the Sudanese Red Coast (Age 15 to 90). Identification of 21 rostra of adult sawfish (from 1978 to 2016), two adult sawfishes and juvenile sawfish were Pristis zijsron. The result of the questioners and the interviews showed that the sawfish were abundant along all the coastal lagoons (mersas) of the Sudanese Red Sea coast until the 1980s. Larger sizes of sawfish were from the north coast (about 6 m) while the maximum size recorded from the South coast was 375 cm. Current nursery areas of P. zijsron along the Sudanese Red seacoast were identified. Based on few specimens (four females) and reports from the fishers, birth dates are from early January to late April. The size of pregnant females ranges from 350 to 375 cm. The maximum numbers of the pups encountered were 8 while the minimum number of pups encountered were 6. Fishers reported 2. Size at birth ranges from 80 to 84 cm. The project is continuing.
Daniel Fahy, Richard Spieler, William Hamlett
Nova Southeastern University, Halmos College of Natural Sciences and Oceanography, Guy Harvey Oceanographic Center, Dania Beach, Florida, USA
Synchrony of Male and Female Reproductive Parameters during the Biannual Reproductive Cycle of the Yellow Stingray, Urobatis jamaicensis (Myliobatiformes: Urotrygonidae)
A definitive, biannual reproductive cycle with mature females capable of producing two broods annually was documented for the yellow stingray (Urobatis jamaicensis) in southeast Florida. Pregnant females were collected during all months throughout the year, but exhibited two discretely overlapping periods of reproduction. The first cycle extended from January to August and the second cycle from July to February. Male and female stingrays each demonstrated mutual synchrony with consistent bimodal patterns measured for nearly all reproductive parameters. Combining data from individuals on: follicle development, ovulation, embryonic growth, and parturition identified the periodicities of the repetitive female cycles with ovulation and parturition coinciding from January through April (Feb-Mar peak), and July through October (Aug-Sep peak). Sequential patterns of follicle development, with concurrent vitellogenesis and limited reproductive intervals, enabled females to breed immediately following or shortly after parturition of the previous cycle. Gestational periods overlapped during the transition between consecutive cycles (Jan-Feb & Jul-Aug). Thus these periods often displayed the simultaneous occurrence of either term stage females completing the previous cycle, or post-ovulatory females at the onset of the subsequent cycle. Gestation rates of ca. 5 months were estimated from the timing between peak ovulation, and observations of both postpartum females and free swimming neonates. Bimodal patterns of spermatogenesis and male sperm storage maintained appropriate levels of synchrony between male and female biannual cycles. Additional support of a biannual cycle was provided by significant differences between fecundity and lateralization of uterine function during each reproductive cycle.
Vicente Faria1, João Eduardo Freitas2, Bruno Macena3, Andrey Castro4, Pedro Afonso5, Jorge Miguel Fontes5, Simon Thorrold6, Patricia Bordallo7, Fábio Hazin8, Tito Lotufo9
1Departamento de Ciências Biológicas, Universidade Federal do Ceará, Fortaleza, Brazil, 2Programa de Pós-graduação em Ciências Marinhas Tropicais, Instituto de Ciências do Mar - Labomar, Universidade Federal do Ceará, Fortaleza, Brazil, 3Programa de Pósgraduação em Oceanografia, Departamento de Oceanografia, Universidade Federal de Pernambuco, Recife, Brazil, 4Departamento de Ciências Naturais, Universidade Federal de São João del Rei, São João del Rei, Brazil, 5MARE – Marine and Environmental Sciences Centre, University of the Azores, Azores, Portugal, 6Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA, 7Embrapa Agroindústria Tropical, Fortaleza, Brazil, 8Departamento de Pesca e Aquicultura, Universidade Federal Rural de Pernambuco, Recife, Brazil, 9Instituto Oceanográfico, Universidade de São Paulo, São Paulo, Brazil
Population genetic structure of the whale shark, Rhincodon typus, in the Atlantic Ocean
Currently, there is no consensus about whale shark population genetic structure at a global scale. Proposed models based on the mitochondrial DNA control region and microsatellites include (a) a single circumtropical population with low geographic differentiation (mainly between Atlantic and Indian Oceans), and (b) two populations that rarely mix: Atlantic and Indo-Pacific. In both cases, genetic data about the whale shark in the Atlantic has been obtained from specimens sampled in the Gulf of Mexico/Caribbean. The goal of this study was to further describe the population genetics of whale sharks by sequencing the mitochondrial DNA control region (1,344 to 1,388 base pairs) from specimens sampled along previously unsampled Atlantic areas including the following regions and localities: southwest (Ceará, Bahia, and Santa Catarina, in the Brazilian coast; n=3), central (Saint Peter and Saint Paul Archipelago; n=4), and northwest (Azores Archipelago; n=3). We will present a network to describe the relationships among Atlantic whale shark mtDNA haplotypes. The Atlantic network will also be presented in a global context based on publicly available DNA sequences. Further analysis of the dataset will include an analysis of molecular variance to assess whale shark population genetic structure between Atlantic, Indian, and Pacific Oceans.
Thomas Farrugia, Andrew Seitz
University of Alaska Fairbanks, Fairbanks, AK, USA
Developing the First Stock Assessment for Skates in Alaska: What Harvest Level is Sustainable?
Skates are in growing demand worldwide, specifically in European and Asian markets. Big (Beringraja binoculata) and longnose (Raja rhina) skates are the most commonly landed skates in Alaska and currently, these species are landed as non-target catch, partly because of a lack of information and formal stock assessments. Because skates are long-lived, slow-growing and late-maturing, they are vulnerable to overfishing, and management is unlikely to allow additional skate landings until skate populations are shown to be capable of sustaining increased harvest pressures. Recently, more species-specific information on these skates has made it possible to develop full stock assessments. Through cooperation with the National Marine Fisheries Service (NMFS), we developed the first stock assessment for big skates in Alaska, using Stock Synthesis (SS3), a powerful software package flexible enough to handle data-poor assessments. This single-sex model divides the fishery into longline and trawl fleets, and incorporates two survey data sets. The model shows that the big skate population in the Gulf of Alaska has declined since 2004, and suggests that the initial depletion of the stock has not yet pushed the population to the biomass at maximum sustainable yield. It is unlikely that skate landings could be substantially increased without jeopardizing the sustainability of the stock. A parallel model for longnose skates will also be developed and these models will be shared with NMFS, and used to evaluate the feasibility of expanding harvest opportunities and prosecuting directed fisheries for skates in Alaska.
Luciana C Ferreira1, Michele Thums2, Andre Afonso5, Adam Barnett3, Richard Fitzpatrick3, Neil Hammerschlag4, Fabio Hazin5, Michael Heithaus6, Rory McAuley7, Jessica Meeuwig9, Mahmood Shivji10, John Stevens8, Ben Radford2, Mark Meekan2
1University of Western Australia/Australian Institute of Marine Science, Perth, WA, Australia, 2Australian Institute of Marine Science, Perth, WA, Australia, 3James Cook University, Cairns, QLD, Australia, 4University of Miami, Miami, FL, USA, 5Universidade Federal Rural de Pernambuco, Recife, PE, Brazil, 6Florida International University, Miami, FL, USA, 7Department of Fisheries, Government of Western Australia, Perth, WA, Australia, 8CSIRO Marine and Atmospheric Research, Hobart, TAS, Australia, 9University of Western Australia, Perth, WA, Australia, 10Nova Southeastern University, Fort Lauderdale, FL, USA
Global Patterns in the Movements and Habitat Use of tiger sharks
The expense and difficulties of capturing and tagging large apex predators such as tiger sharks means that most studies report movement and habitat use data for only a few individuals. This hampers our understanding of the ecological and environmental drivers of movement at both stock and population scales. To address this issue, we pooled data among tracking studies to create a database of tracks of 104 tiger sharks that were tagged in the Indian (Ningaloo Reef, Australia), the Pacific (Great Barrier Reef and Hawaii), and the Atlantic (Recife, Fernando de Noronha Brazil, Florida and Bahamas) Oceans. Monthly utilization distributions were calculated for each track using the Biased Random Bridge kernel method. Tracks were divided into periods of migration and residency and the migration section was analysed separately with a Step Selection Function. This method generates random steps around each location based on the real distribution of angles and steps as a way to estimate resource selection by comparing observed habitat used with available structures. We then modelled the resulting dataset with a binomial distribution using generalized additive mixed models with a range of environmental variables (SST, bathymetry, currents). Utilization distributions were also used as a response variable to identify the major drivers of movement and habitat use for the species. We only found weak trends in migratory movements, suggesting high plasticity in spatial ecology of tiger sharks a trait that might be important in the success of the species as a top order predator in tropical oceans worldwide.
Andrew Fields1, Kevin Feldheim2, Gregg Poulakis3, Rachel Scharer3, Demian Chapman1
1Stony Brook University, Stony Brook, NY, USA, 2The Field Museum, Chicago, IL, USA, 3Florida Fish and Wildlife Conservation Commission, Port Charlotte, FL, USA
Insights on Smalltooth Sawfish, Pristis pectinata, Biology and Life History from Over a Decade of Genetic Sampling
Florida populations of smalltooth sawfish (Pristis pectinata) have declined up to 99% over the past several decades. Despite this, these populations are relatively robust genetically, exhibiting high levels of allelic richness and heterozygosity at microsatellite loci. Using this suite of microsatellite markers, we examined the mating system and potential reproductive philopatry at two sites in Florida: the Caloosahatchee River and the Peace River. Preliminary results have shown a biennial reproductive cycle and interannual site fidelity of mature females to these sites. Additionally, we describe the first documented cases of parthenogenesis in a normally sexually reproducing wild vertebrate. These results will be instrumental in guiding the recovery planning process for this species.
Andrew Fields1, Gunter Fisher2, Stanley Shea3, Huarong Zhang3, Debra Abercrombie4, Kevin Feldheim5, Elizabeth Babcock6, Demian Chapman1
1Stony Brook University, Stony Brook, NY, USA, 2Kadoorie Farm and Botanic Garden, Tai Po, Hong Kong, 3BLOOM association, Central, Hong Kong, 4Abercrombie and Fish, Port Jefferson Station, NY, USA, 5Pritzker Laboratory for Molecular Systematics and Evolution, The Field Museum, Chicago, IL, USA, 6Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA
Species composition of the global shark fin trade assessed by a genetics-based survey of the retail market
Fisheries supplying the demand for the Cantonese delicacy shark fin soup are a major driver in the depletion of shark populations all over the world, prompting strong public support for new investments to address this global environmental problem. Understanding the species composition of the global dried shark fin trade will be an essential component of emerging efforts to improve the sustainability of these fisheries. We estimate the contemporary species composition of the fin trade by genetically surveying randomly collected samples (N=4,800) from the retail market of the Hong Kong Special Administrative Region (SAR), one of the world’s largest shark fin trading and consumption centers. We estimate that at least 81-99 species of sharks, rays and chimeras occur in the fin trade yet the trade has become very focused on a small subset of the sharks. The blue shark (Prionace glauca), a productive epipelagic species, has become the foundation of the trade (40.73-57.56%) as the importance of certain less prolific species has declined. The supplies of many of the other commonly traded species are likely to decline in the future due to overfishing and increasing regulation, while one third of all of the traded species are assessed by the International Union for the Conservation of Nature (IUCN) to be at high risk of extinction.
Brittany Finucci1, Matthew Dunn1, Emma Jones2
1Victoria University of Wellington, Wellington, New Zealand, 2National Institute of Water and Atmospheric Research (NIWA), Auckland, New Zealand
Aggregative Behaviour and Social Structure in Deep-sea Chondrichthyans
A wide range of Chondrichthyans are known to form aggregations, associations or groupings. The motivation for these interactions have been attributed to foraging, reproduction, energy conservation, and social preference. Due to the highly mobile nature of sharks, in addition to the difficulty of following individuals in the open sea, most research on social interactions or associations has been limited to temperate, inshore species, with some degree of site fidelity. However, some of the earliest insights into the structure of shark groupings were gained from analysing commercial trawl catches. We evaluate the occurrence of social grouping in a range of common and infrequently caught deep-sea chondrichthyans (6 holocephalans, 10 elasmobranchs), including the estimation of companion preferences across sex and size classes, using a large data set from fisheries-independent research trawl surveys. Only a few species were found to engage in aggregative behaviour, and those that did had companion preferences that varied with sex, and fish density. Group composition changed with depth and density, and for some species, aggregations were repeatedly found in discreet locations. Most often, aggregations consisted largely of juveniles, and mature females were the least likely to form aggregations. However, this pattern was not true of all species. The existence and nature of aggregations will influence species relative vulnerability to fishing.
Cristín Keelin Fitzpatrick1, Andrea Bernard1, Filip Osaer2, Krupskaya Narváez2, Mahmood Shivji1
1Save Our Seas Shark Research Center and Guy Harvey Research Institute, Nova Southeastern University, Dania Beach, Florida, USA, 2ElasmoCan, Las Palmas de Gran Canaria, Spain
A Genetic Exploration in a Last Refuge: The Common Angelshark (Squatina squatina) in the Canary Islands
The common angelshark (Squatina squatina) has been extirpated from nearly the entirety of its historical eastern North Atlantic and Mediterranean range and is listed as ‘Critically Endangered’ by the IUCN Red List of Threatened Species. Currently, only a single known remnant population of any abundance exists, occurring within the waters surrounding the Canary Islands. Nothing is known about the genetic population dynamics of this species. To assess the common angelshark’s genetic connectivity and diversity, tissue samples (n = 509) were collected between 2009-2016 from three separate islands within the archipelago: Gran Canaria and Tenerife – which are separated by a deep ocean channel (~3000 m) which potentially serves as a barrier to dispersal for this benthic species, and Lanzarote. To date, DNA sequences have been obtained from four mitochondrial loci [control region (CR) (n = 233), Cytochrome c oxidase subunit 1 (COI) (n = 16), NADH dehydrogenase subunit 4 (ND4) (n =28), and NADH dehydrogenase subunit 2 (ND2) (n =4)] revealing exceptionally low genetic diversity across all regions, as identical haplotypes were found in nearly all analyzed individuals. Additionally, next-generation sequencing has been used to develop a species-specific library for novel microsatellites and preliminary screening of each of 18 markers has shown these loci to be monomorphic across 16 individuals. Further screening of additional loci (mitochondrial and microsatellite) and individuals is ongoing. Such potentially low levels of genetic diversity may have far reaching implications for the persistence of this species and ultimately underscore the common angelsharks’ highly vulnerable state.
Shark Advocates International, Washington, DC, USA
Saving Sawfish: Progress and Priorities for Preventing Extinction and Promoting Recovery
The exceptionally high extinction risk for the world’s sawfishes (family Pristidae), after decades of going largely unnoticed, has in recent years received significant attention. While resulting actions include the strongest possible commitments under global wildlife agreements, basic safeguards remain urgently needed in many key regions where sawfish are highly endangered. In 2013, the last of the sawfish species was listed under Appendix I of the Convention on International Trade in Endangered Species (CITES), thereby essentially banning commercial, international trade in all sawfishes and their parts. Additional sawfish conservation needs were explored and prioritized during the development of the 2014 International Union for Conservation of Nature (IUCN) Global Sawfish Conservation Strategy. All five sawfish species were listed on Appendix I and II of the Convention on Migratory Species (CMS) later in 2014, bringing obligations for strict national protection and commitments to collaborate on regional conservation. In 2016, the sawfishes were also added to the scope of the CMS Memorandum of Understanding for Migratory Sharks, an agreement that is, on one hand, voluntary without mechanisms to ensure compliance, and, on the other, unique in the world with great promise for benefits. These advances, as well as the relatively effective US Recovery Plan for Smalltooth Sawfish (Pristis pectinata) under the Endangered Species Act, have sparked increased opportunities for researching and safeguarding sawfish in previously under-studied regions, including several developing countries. Implementation of these initiatives will be reviewed. Recommendations for priority next steps to prevent sawfish extinction and promote recovery will be offered.
Lauren Fuller, Glenn Parsons
University of Mississippi, Oxford, MS, USA
Sedation as a Means to Reduce Capture Stress of Sharks
Capture stress is a significant problem in fisheries biology and may lead to reduced survivorship of bycaptured species. In some fisheries, sedation may be useful for capture stress reduction. In this study, we provide preliminary data regarding the effect of iso-eugenol (clove oil) sedation on the stress response of sharks via measurement of lactate and respiration rate. Sharks caught by hook-and-line (Rhizoprionodon terraenovae, Carcharhinus isodon, and Carcharhinus limbatus) were placed into a sealed respiration chamber in-situ containing iso-eugenol (treatment) or seawater (control) from which dissolved oxygen was continuously monitored to determine the respiration rate. Blood samples were taken at 0, 10, 20 and 30 minute intervals and later analyzed for lactate. The results indicate that treatment has a significant effect on overall respiration rate in R. terraenovae. There is no significant difference in shark lactate levels between treatments, but the proposed sample size has not yet been achieved. These preliminary results suggest that iso-eugenol sedation may be useful for stress reduction in bycaptured sharks, thereby increasing survivorship after release.
Tony Gamble1, Martin Cohn2, David Zarkower3
1Marquette University, Milwaukee, WI, USA, 2University of Florida, Gainesville, FL, USA, 3University of Minnesota, Minneapolis, MN, USA
Sex-specific genetic markers and sex chromosomes in the Little Skate (Leucoraja erinacea)
The Little Skate (Leucoraja erinacea) is an emerging model in the study of developmental biology and human disease. The ability to accurately sex individuals is vital to this research, particularly as it relates to gonadal development and other sex differences. Adults and advanced embryos can be sexed via examination of sexually dimorphic traits such as presence of claspers on male pelvic fins or differentiated gonads. However, early embryos cannot be morphologically sexed and there is no molecular test to differentiate males from females prior to sex determination. PCR sex tests have proven invaluable in other vertebrate model organisms such as mouse and chicken and a skate molecular sex test would aid the study of sexually dimorphic traits in early development. We developed a PCR-based assay to sex L. erinacea using data from restriction site associated DNA sequencing, or RAD-seq. RAD-seq sequences restriction-digested DNA and can generate tens of thousands of molecular markers for analysis. We identified and validated three male-specific genetic markers by comparing RAD-seq data from ten male and nine female L. erinacea. These markers can identify the genetic sex of L. erinacea at all developmental stages and will significantly enhance developmental studies of this emerging vertebrate model. Furthermore, male-specific markers confirm an XY sex chromosome system in L. erinacea. We will discuss the implications of L. erinacea sex chromosomes on elasmobranch sex chromosome evolution and identify opportunities for further study.
Jim Gelsleichter1, R. Dean Grubbs2, John Carlson3
1University of North Florida, Jacksonville, FL, USA, 2Florida State University Coastal and Marine Laboratory, St. Teresa, FL, USA, 3NOAA Fisheries Service, Panama City, FL, USA
Updated information on the reproductive biology of the smalltooth sawfish Pristis pectinata
Due to overfishing and human destruction of its habitat, the smalltooth sawfish (Pristis pectinata) became listed as “endangered” under the U.S. Endangered Species Act in 2003 and it remains one of very few U.S. domestic marine fish to hold this undesirable designation. Because of this, conservation measures have been established to allow remnant U.S. sawfish populations to rebuild, but these efforts are hampered by a lack of information on sawfish life history, including reproduction. This study examined reproduction in adult male and female smalltooth sawfish using nonlethal approaches such as the analysis of circulating sex hormones and ultrasonography. Additional data were obtained from necropsies of sawfish that died unintentionally as a result of cold stress or fishery interactions. Based on necropsy and hormone data, male sawfish appear to undergo spermatogenesis between fall and winter, after which they may exhibit male sperm storage and protracted mating activity until late spring. Based on necropsy data and ultrasonography, female sawfish appear to reproduce following a biennial cycle that includes follicular development from fall to spring, presumably followed by ovulation and mating in late spring, and a one-year gestation period from early summer to the subsequent spring. However, to date, sex hormone data has not been useful for clarifying female reproductive patterns. A hypothesized schedule for smalltooth sawfish reproduction is presented based on these multifaceted observations for use in management and conservation.
Texas A&M University, College Station, TX, USA
One Mustelus, two Mustelus, three Mustelus, more; assessing biodiversity of smoothhound sharks in the western Atlantic
Taxonomic difficulties in distinguishing among species of smoothhound sharks present challenges in estimating biodiversity and in developing management plans that are in-line with species-specific sustainability. First, I will discuss the current state of knowledge of smoothhounds in the western Atlantic, including species composition, the availability of type specimens, species ranges, and conservation status for each of the species currently described from the region. Issues with species accounts and research gaps will be noted. Next, I will discuss assessments of genetic divergence among smoothhound species, including initial analyses showing that there may be undescribed species in the western Atlantic. Lastly, I will describe a collaborative effort to collect voucher specimens and genetic samples from countries throughout the western Atlantic with the goal to accurately determine the species composition/biodiversity of smoothhound sharks in the western Atlantic.
Mark Grace1, Laura Dias2, Lance Garrison3, Keith Mullin1, Kathy Maze-Foley4, Carrie Sinclair1
1NOAA/NMFS/SEFSC/Mississippi Laboratories, Pascagoula, MS, USA, 2Cooperative Institute for Marine and Atmospheric Studies, Univ. of Miami, Miami, FL, USA, 3NOAA/NMFS/SEFSC/Miami Laboratory, Miami, FL, USA, 4NOAA/NMFS/SEFSC Beaufort Laboratory Affiliate, Beaufort, NC, USA
Ectoparasitic Predators; Cookie Cutter Shark Bite Wounds on Cetaceans of the Gulf of Mexico
Cookie cutter sharks (Dalatiidae, Squaliformes) are often described as ectoparasitic predators of a variety of high trophic level prey species including cetaceans, tunas, billfishes, and squids. These sharks employ a unique feeding behavior that allows them to use their cookie-cutter like teeth to excise a nearly symmetrical oval flesh plug from the body of their prey. A data element of NOAA/NMFS/SEFSC surveys of Gulf of Mexico cetaceans is the documentation of the fresh wounds or scars that can be observed on cetaceans that approach vessels to bow ride or if they are otherwise close enough to allow observation. Cookie-cutter bite wounds were observed on eight percent of sightings (solitary or groups) represented by 11 dolphin species and two whale species. Pantropical spotted dolphin sightings (Stenella attenuata Gray 1846) had the most records of cookie cutter bite wounds (40%). In addition, during a Gulf of Mexico midwater trawling study targeting cetacean prey aggregations (fish and invertebrates), two cookie cutter sharks were sampled for stable isotopes (Isistius brasilensis Quoy & Gaimard 1824 and I. plutodus Garrick & Springer 1964). The ratio analysis of 13C and 15N positions these ectoparasitic sharks in a high trophic level and provides verification that they feed on other high trophic level species.
Rachel Graham1, Ivy Baremore1, Samantha Strindberg2
1MarAlliance, San Pedro, Belize, 2Wildlife Conservation Society, California, USA
A Tale of Two Atolls: Differences in Elasmobranch Abundance and Density Between Two Offshore Atolls in Belize
Turneffe and Lighthouse Reef Atolls are two of the Atlantic Ocean’s four atolls, forming part of the Meso-American Barrier Reef in Belize, with sharply contrasting protection status. Located approximately 50 km east of Belize City, Turneffe Atoll was recently declared a multi-zoned marine protected area; although gear types are restricted, it is still easily accessible to fishers. Lighthouse Reef Atoll is more remote and provides open access to fishing, bar two fully protected sites. The study examined the status of elasmofauna using three methods: longlines, Baited Remote Underwater Video (BRUV), and in water Distance Sampling (DS). Surveys were conducted at fixed stations from 2014-2016. Stations were randomly positioned at evenly-spaced locations throughout three habitat types: forereef, backreef, and lagoon. Data analyses included: catch-per-unit-effort (CPUE) for longline, MaxN and frequency of occurrence for BRUVs, and population size and density estimates from DS data. Generalized Linear Models (GLM) were used to assess differences in abundance by year, habitat, location, protection status, depth and environmental parameters. Results from the three consecutive survey years indicate that Lighthouse Reef Atoll, though much smaller, has significantly higher abundance and occurrence of shark species than Turneffe Atoll. Density and population size estimates of rays were similar between atolls. CPUE and MaxN were highest at both atolls for sharks on the windward forereef habitats. This study suggests high historic fishing mortality at Turneffe Atoll, where proximity to population centers negatively affects shark populations. Continued monitoring will help to determine the effectiveness of Turneffe Atoll in protecting elasmobranchs.
Madeline Green2, Blanche D'Anastasi3, Jean-Paul Hobbs4, Kevin Feldheim5, Rory McAuly6, Sterling Peverell7, Jason Stapley7, Sharon Appleyard8, William White8, Colin Simpfendorfer1, Lynne van Herwerden3
1Centre for Sustainable Tropical Fisheries and Aquaculture, James Cook University, Queensland, Australia, 2Institute for Marine and Antarctic Studies, University of Tasmania, Tasmania, Australia, 3College of Marine and Environmental Sciences, James Cook University, Queensland, Australia, 4Department of Environment and Agriculture, Curtin University, Western Australia, Australia, 5Laboratory for Systematics and Evolution, the Field Museum, Chicago, IL, USA, 6Western Australian Government, Department of Fisheries, Western Australia, Australia, 7Queensland Department of Primary Industries and Fisheries, Northern Fisheries Centre, Queensland, Australia, 8National Research Collections Australia, CSIRO, Tasmania, Australia
Population Connectivity of Narrow Sawfish (Anoxypristis cuspidata) in Australia and Papua New Guinea using genetic markers
The Narrow or Knifetooth sawfish (Anoxypristis cuspidata) belongs to the most endangered family within the Class Chondrichthyes; the sawfishes. This species has undergone significant declines in range and abundance due to anthropogenic activities including fishing and habitat loss. Very little is known of adult movements and sex-biased behaviour that may be exhibited by Indo-Pacific populations. In order to better manage and protect this threatened species, understanding habitat usage and behaviour is critical. Using a combination of mitochondrial and nuclear (microsatellites) markers, this study identified the population structure of A. cuspidata in Australia and Papua New Guinea (PNG). Significant mitochondrial structuring was found for the east Australian coast population and other sampled locations both in northern Australia and PNG. Suggesting residency or philopatric behaviours are likely for females specifically on the east coast of Australia. Similarly, microsatellite markers identified a lack of connectivity between the east coast and all other locations across northern Australia (microsatellite markers were unavailable for PNG populations). Results from this work show the east Australian population of A. cuspidata have no genetic connectivity with other sampled Australian and PNG locations. Consequently, the east Australian population is likely to be less resilient than others if localised anthropogenic pressures remain. Microsatellite results require further investigation due to the low number of suitable markers available for the species. However, given the endangered status and lack of knowledge for A. cuspidata this study presents important findings, which can be used to improve management outcomes.
R. Dean Grubbs1, John Carlson2, Mark Bond3, Bianca Prohaska4, Johanna Imhoff4
1Florida State University Coastal and Marine Lab, St. Teresa, FL, USA, 2NOAA Fisheries - SEFSC, Panama City, FL, USA, 3Florida International University, Miami, FL, USA, 4Florida State University, Tallahassee, FL, USA
Smalltooth Sawfish in Florida and the Bahamas – National Parks as Potential “Lifeboats” for Recovery
The smalltooth sawfish (Pristis pectinata) is listed as Critically Endangered in the IUCN Red List of Threatened Species and Endangered under the United States’ Endangered Species Act. The species is restricted to the Atlantic Ocean and populations declined throughout the range due to overfishing and habitat loss. Bycatch remains the largest source of direct mortality and continued habitat loss from urban development, agriculture, and freshwater diversion likely hinders recovery. Southwest Florida in the U.S. and the west side of Andros Island in the Bahamas are the only known regions where significant numbers of smalltooth sawfish remain. Both systems are characterized by extensive mangrove estuaries with highly variable salinity and proximity to relatively deep shelf-edge habitats that are buffered from seasonal temperature extremes. Both systems also include substantial national parks that offer habitat protection (Everglades National Park – ENP; Andros West Side National Park - AWSNP) and telemetry data suggest there is little movement of sawfish between them. The human population density in southwest Florida is orders of magnitude higher than around Andros which influences water quality as well as fishing mortality risk. Recreational and charter fishing effort is very high in ENP, but very low in AWSNP. Similarly, commercial longline, trawl, and trap fisheries exploit the deeper shelf-edge habitats occupied by sawfish off Florida but similar habitats off the Bahamas are exposed to few commercial fishers. Florida and Andros Island may be critical to smalltooth sawfish recovery, therefore habitat quality and bycatch risk should be monitored closely.
Leonardo Guida1, Terence I. Walker1, Cynthia Awruch2, Richard D. Reina1
1Monash University, Clayton, Victoria, Australia, 2University of Tasmania, Hobart, Tasmania, Australia
Physiological Responses to the Pre-natal Stress of Fisheries Capture in Pregnant Southern Fiddler Rays (Trygonorrhina dumerilii) and Their Neonates
Assessing fisheries impacts on elasmobranch populations has largely focused on quantifying both immediate and delayed mortality rates. However, very little is known about the sub-lethal effects of capture stress, particularly in pregnant females. Our study is the first to investigate the consequences of capture on a pregnant elasmobranch species, the southern fiddler ray (Trygonorrhina dumerilii). Nineteen pregnant females were collected by hand in Swan Bay, Australia, and transported to aquaria where nine females were subjected to trawl capture (8 hr) followed immediately by air exposure (30 min). Immediately prior to, and for up to 28 days post trawling, all females were routinely sampled to monitor changes in total body mass (TBM), sex-steroid levels (17beta-estradiol, progesterone, testosterone) and granulocyte to lymphocyte ratio (G:L). At parturition, neonates were measured for total length (TL), TBM and where possible, G:L was also calculated. Trawling reduced maternal TBM and elevated the G:L for up to 28 days post trawling. Trawling did not significantly affect any sex-steroid titers, however all females reported lower than expected concentrations in all sex-steroids at 28 days post trawling. Neonates who experienced pre-natal stress were lower in TBM and TL, and had an elevated G:L. Our results suggest that depending on the magnitude of environmental stress experienced by a pregnant female, a single capture event (or multiple) is sufficient to influence current and future reproductive efforts.
Tristan Guttridge1, Lucy Howey-Jordan3, Maurits Van Zinnicq Bergmann1, Jean-Sebastien Finger2, Steven Kessel5, Jill Brooks6, William Winram7, Mark Bond4, Lance Jordan3, Christopher Bolte1, Rachael Cashman1, Nathaniel Grimes1, Emily Tolentino2, Samuel Gruber8
1Bimini Biological Field Station Foundation, Bimini, Bahamas, 2Humboldt University, Berlin, Germany, 3Microwave Telemetry, MD, USA, 4Florida International University, Miami, FL, USA, 5Windsor University, Windsor, Canada, 6Carleton University, Ottawa, Canada, 7Watermen Project, Geneva, Switzerland, 8University of Miami, FL, USA
Better in the Bahamas? Regional connectivity and seasonal residency of the great hammerhead shark in the U.S.A. and the Bahamas
The great hammerhead shark Sphyrna mokarran, is a large bodied, broadly distributed tropical shark typically restricted to coastal and shelf habitats. It is highly valued for its fins (in target and incidental fisheries), suffers high bycatch mortality coupled with low fecundity, and as a result is considered vulnerable to over-exploitation and population depletion. Although there is very little species specific data available, the absence of recent catch records give cause to suspect 25-year population declines across its range. Here, using a combination of satellite and acoustic telemetry we assessed the movement patterns and habitat use of the Endangered (IUCN Redlist) S. mokarran tagged in Bimini, The Bahamas, and Jupiter, Florida, USA. Since 2011, ten individuals were implanted with V16 acoustic transmitters and tracked through an acoustic array data share consortium off the coast of Jupiter. In January 2014 and 2015 in Bimini, 18 S. mokarran were fitted with V16 acoustic tags and four were tagged with high rate pop-off archival satellite tags. A receiver array was established in various habitats in Bimini to monitor their local movements. Results revealed large scale return migrations (up to 1200 km), seasonal residency to local areas (some for 5 months), site fidelity (annual return to Bimini and Jupiter for many individuals) and numerous international movements. These findings significantly enhance our understanding of the movement ecology of S. mokarran and will contribute to their improved conservation and management.
Neil Hammerschlag1, Shanta Barley2, Duncan Irschick3, Jessica Meeuwig2, Emily Nelson1, Mark Meekan4
1University of Miami, Miami, Florida, USA, 2University of Western Australia, Perth, Western Australia, Australia, 3University of Massachusetts at Amherst, Amherst, Massachusetts, USA, 4Australian Institute of Marine Science, Perth, Western Australia, Australia
Fishery depletion of sharks cause morphological changes in prey
The ecological and evolutionary consequences of shark population declines on ecosystems are of scientific and conservation concern. Here, we examine the indirect effects of humans on ecological communities via the depletion of sharks in large ecosystems spanning hundreds of kilometers. We provide evidence that the removal of sharks drives changes in the morphological traits of seven different prey fishes that vary in behavior, body type, diet and trophic guild. On coral reefs that have experienced the selective removal of sharks, fishes have significantly smaller caudal fins and eyes compared to similar reefs with relatively intact shark populations. We suggest that these morphological changes represent a case of rapid evolution due to predator removals. Our findings further demonstrate the ecological and evolutionary importance of sharks and their need for effective and timely conservation.
Alexander Hansell1, Steven Kessel3, Steven Cadrin1, Gregory Skomal4, Samuel Gruber5, Tristan Guttridge2
1Department of Fisheries Oceanography, School for Marine Science and Technology, University of Massachusetts - Dartmouth, Fairhaven, MA, USA, 2Bimini Biological Filed Station, South, Bimini, Bahamas, 3University of Windsor, Great Lakes Institute for Environmental Research, Windsor, ON, Canada, 4Massachusetts Division of Marine Fisheries, New Bedford, MA, USA, 5Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, Miami, FL, USA
Demographics and Local Abundance Trends for the Coastal Shark Assemblage of Bimini, Bahamas
Understanding population dynamics is essential for implementing effective conservation and management of coastal sharks. Fishery-independent surveys can offer valuable information for data-limited situations. A 12-year (2004-2015) standardized, shallow water longline assessment was conducted monthly in the eastern coastal waters of Bimini, Bahamas. Each survey was comprised of five longline sets, totaling 75 hooks, with a soak time of 24 hours. A total of 684 sharks from nine species were caught over the course of the study with tiger (Galeocerdo cuvier), nurse (Ginglymostoma cirratum), blacktip (Carcharhinus limbatus) and lemon (Negaprion brevirostris) sharks comprising 94.9% of the catch. Based on total length, the majority of tiger (91.3%), nurse (54.4%), and lemon (81%) sharks were immature, while most blacktip sharks (84.6%) were mature. A sexual bias was noted in the data. The tiger (77.3%) and blacktip (58.3%) sharks were more often female, while the majority of lemon (73%) and nurse (56.8%) sharks were male. Furthermore, seasonal trends indicate an abundance of nurse, blacktip, and lemon sharks during the summer. Annual trends indicate an increasing tiger shark population and stable nurse, blacktip, and lemon shark populations. General additive models indicate that catch rates are influenced by month, year, temperature, tide, soak time, and lunar cycle.
Janne B. Haugen1, Steven X. Cadrin1, Alexander C. Hansell1, Sofia M. Gabriel1, Cate O'Keefe1, Tobey H. Curtis2, Kim Friedman3
1Department of Fisheries Oceanography, School for Marine Science and Technology, University of Massachusetts - Dartmouth, Fairhaven, MA, USA, 2National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Greater Atlantic Regional Fisheries Office, Gloucester, MA, USA, 3Marine and Inland Fisheries Branch, Food and Agriculture Organization of the United Nations, Rome, Italy
Evaluating the Impacts of CITES on the Northeast Atlantic Porbeagle (Lamna nasus) Stock
The porbeagle shark (Lamna nasus) was listed in the Convention on International Trade in Endangered Species (CITES) Appendix II in 2013, with the effective date in 2014. To evaluate the effectiveness of the adoption of porbeagle sharks into CITES, we created a broad fishery assessment framework to review and monitor impacts of this recent trade regulation. Information and data were collected for five sections of the framework: i) Governance, ii) Fishers, iii) Stocks, iv) Trade and v) Socio-Cultural issues, from the Food and Agriculture Organization and European fishery sources. Workshops and interviews with local communities and fishery managers were organized to generate feedback and input on the design and indicators used in the framework. We identified changes under three subsections of each of the five sections of the framework, and assessed the effectiveness and impacts of these changes, as well as the need for future support. Most of the impacts of the CITES listing, such as changes in policy and management, landings and handling of by-catch, were under sections i-iii in the framework, with less information available on the trade value chain, livelihoods and community awareness. Determining CITES related impacts on porbeagle shark stocks through time offers feedback to policy and management on what is and is not working, to ensure productive and sustainable management of porbeagle fisheries. This case study may serve as a demonstration of how a fishery assessment framework can be used for evaluation of other CITES listed species, including more data-limited elasmobranchs.
Michelle Heupel1, Colin Simpfendorfer2
1Australian Institute of Marine Science, Townsville, Qld, Australia, 2James Cook University, Townsville, Qld, Australia
Drivers of reef shark movement: what's most important?
Predator presence has been reported to influence the movement and behaviour patterns of prey species in various ecosystems. The movement of predators is thus key to the behaviour patterns of prey populations and defining their corresponding movements. However, the drivers of movement patterns in predators are much more difficult to define, especially in aquatic environments. Here we explore the movement patterns of reef sharks as a case study in drivers of marine predator movement. Long-term acoustic telemetry data collected from reef sharks (grey reef, blacktip reef, silvertip, tiger and bull sharks) within the Great Barrier Reef over a five year period were examined to determine potential drivers of movement. Telemetry data revealed complex movement patterns of reef sharks that vary by size, sex, species and habitat type. Some of the common drivers for coastal species, such as environmental conditions, appear to be irrelevant to most reef shark movements. This indicates biological drivers are more important in the movement patterns of these individuals. This talk will consider the importance of various drivers of reef shark movements and the implications of these drivers for defining ecosystem dynamics and within the context of conservation management.
Jeremy M. Higgs1, Jill M. Hendon1, Dana M. Bethea2, James A. Sulikowski3, Eric R. Hoffmayer4, William B. Driggers4
1The University of Southern Mississippi, Gulf Coast Research Laboratory, Center for Fisheries Research and Development, Ocean Springs, MS, USA, 2National Marine Fisheries Service, Southeast Fisheries Science Center, Panama City Laboratory, Panama City, FL, USA, 3University of New England, Department of Marine Sciences, Marine Science Education and Research Center, Biddeford, ME, USA, 4National Marine Fisheries Service, Southeast Fisheries Science Center, Mississippi Laboratories, Pascagoula, MS, USA
Age and growth of the finetooth shark, Carcharhinus isodon, in the northern Gulf of Mexico: a multi-model approach
Age, growth, and size and age at maturity estimates were examined for finetooth sharks (Carcharhinus isodon) in the northern Gulf of Mexico (GOM). Life history data were examined from a total of 711 finetooth sharks (424 female; 287 male) collected in coastal waters between Apalachicola Bay, Florida and East Bay, Louisiana from April 2007 through September 2013. Size and age at which 50% of the finetooth population was estimated to be mature was 1032 and 962 mm fork length (FL) and 4.1 and 3.6 years for females and males, respectively. The observed maximum size and age was 1384 and 1130-mm FL and 9.4 and 6.5 years for females and males, respectively. Sex-specific, two and three parameter von Bertalanffy, Gompertz, and logistic growth models were fitted to the size-at-age data and were found to be statistically significant p < 0.05. Examination of models of best fit to the data indicated female growth was best described by the logistic model and male growth was best described by the three parameter von Bertalanffy. Three parameter von Bertalanffy model estimates for females and males were: L∞ = 1308-mm FL and k = 0.26/yr and L∞ = 1164-mm FL and k = 0.32/yr, respectively. The findings of this study further expand knowledge of the life history estimates of finetooth sharks in the nGOM.
Eric Hoffmayer, Adam Pollack, William Driggers, Christian Jones, Matthew Campbell
National Marine Fisheries Service, Southeast Fisheries Science Center, Mississippi Laboratories, Pascagoula, MS, USA
Neritic distribution of bonnetheads, Sphyrna tiburo, indicates limited use of inshore nurseries in the western Gulf of Mexico
The bonnethead, Sphyrna tiburo, is a small coastal shark species known to inhabit coastal waters of the northern Gulf of Mexico during spring, summer and fall. Despite showing a clear preference for shallow waters (10-25 m) during warm months, bonnetheads migrate to offshore deeper waters during winter; however, little is known about these seasonal movements or utilization of neritic waters. The objective of this study was to use fishery-independent bottom trawl data to describe the spatial distribution of bonnetheads in the northern Gulf of Mexico. From 1987-2014, 645 bonnetheads (274– 1220 mm STL) were captured at 362 stations, with the majority of individuals collected (61%) being young-of-the-year. Catch rates of bonnetheads were higher in the western Gulf of Mexico and their occurrence was relatively rare in neritic waters east of Mobile Bay. Sharks were captured in depths ranging from 5 to 71 m, with the majority of the sharks captured between 10 and 30 m. Despite their reported preference for shallow waters, 40% of bonnetheads were captured in waters deeper than 25 m. Furthermore, the use of deeper waters (25-55 m) by 46.4% of the young-of-the-year sharks suggests that nursery areas may not be as discrete as previously thought. It is widely stated that blue crabs are the primary prey of bonnetheads; however, stomach content analysis of 25 young-of-the-year individuals collected during the 2015 fall trawl survey indicated that mantis shrimp (Squilla sp.) was their primary prey and spatial analysis revealed that the distribution of the two species were highly correlated.
Lisa Hollensead1, Dean Grubbs1, John Carlson2, Dana Bethea2
1Florida State University, Tallahassee, FL, USA, 2NOAA NMFS, Panama City, FL, USA
Assessing Residence Time and Habitat Use of Juvenile Pristis pectinata Using Acoustic Monitoring in a Nursery
Highly productive estuaries have been shown to serve as nurseries for many marine fishes. However, few studies quantitatively measure the biotic characteristics that often drive a habitat's function as a nursery. This information is critical when developing recovery plans for endangered species, such as the smalltooth sawfish (Pristis pectinata). This study incorporated a combination of acoustic telemetry monitoring and quantification of biotic attributes in order to assess nursery habitat use of juvenile smalltooth sawfish. In order to monitor movements, thirty-two VEMCO VR2w receivers were deployed within Everglades National Park during 2011. The array was used to quantify seasonal residency, determine emigration timing, and identify migration corridors. Benthic grain size and organic content along with mangrove prop root density and limb overhang were quantified throughout the study area. These habitat variables were used to construct logistic models in order to test for any relationship between habitat attributes and presence of tagged sawfish. Monitoring results of twenty sawfish were variable. Observed residency within the backcountry nursery ranged from days to several months with overwintering (N=5) occurring along Chokoloskee Island. Three individuals tagged in the backcountry exhibited directed emigration into Chokoloskee Bay in summer via the Lopez River which may be a migration corridor. Results also indicated that sawfish quickly moved through deep-water, narrow creeks and rivers between shallow tidally-influenced bays. A step wise regression analysis of hits per hour incorporating all habitat variables indicated that sawfish had an increased probability of being encountered in areas with high prop root density.
Md Anwar Hossain1, Benjamin S. Thompson2, Gawsia Wahidunnesssa Chowdhury1, Samiul Mohsanin2, Zubair H. Fahad2, Heather J. Koldewey3, Md Anwarul Islam1
1Department of Zoology, University of Dhaka, Dhaka, Bangladesh, 2WildTeam, Dhaka, Bangladesh, 3Zoological Society of London, London, UK
Sawfish exploitation and status in Bangladesh
Sawfish are among the world's most threatened and understudied marine fishes. There are few studies on sawfish from outside Australian and USA waters - a significant knowledge gap considering their circumtropical distribution and migratory nature. This paper presents the first assessment of sawfish exploitation and status in Bangladesh. A countrywide rapid assessment was undertaken between December 2011 and November 2012, using an interdisciplinary methodology. Fish landing stations, dry fish markets, and fishing villages were visited and a sawfish medicine maker was found and interviewed. In addition, interviews with national specialists at academic and fisheries institutions were undertaken. In total, 203 questionnaire surveys were conducted with fishers and traders in order to understand the extent of decline, potential drivers of declines, and local perceptions and uses of sawfish. Eighteen rostra were documented from museum archives and private collections, and unpublished data were sourced. Two sawfish species, Pristis pristis and Anoxypristis cuspidata were confirmed to be present in Bangladesh. General population declines were revealed. The average annual sawfish encounter rate (observations and catches) declined from 3.7 individuals using lifetime recall data (~22-year), to 1.5 using 5-year recall data, and further to 0.7 using 1-year recall data. The consensus from social research methods was that sawfish were caught as bycatch, with drift gill nets being cited as the most damaging gear type. Every respondent perceived sawfish as a useful animal. Conservation measures are proposed, including a local education and outreach programme to seek behavioural changes - primarily to release live sawfish.
Jeanette Huber1, Gavin Naylor1, Tanya Darden2
1University of Charleston, South Carolina, Charleston, South Carolina, USA, 2South Carolina Department of Natural Resources, Charleston, South Carolina, USA
From past to present: A global population structure and genetic diversity study of a critically endangered fish using historical specimens
The largetooth sawfish Pristis pristis (Linnaeus, 1758) is among the most critically endangered marine vertebrate species primarily due to anthropogenic effects compounded by their low intrinsic growth rates. Once globally abundant, they have been locally extirpated from much of their historical range over the last 200 years. However, due to their iconic and unique appearance, sawfish rostra are often well represented in museum collections around the world. Archival sawfish tissues can supplement contemporary samples in population genetic studies as well as assess the susceptibility of this coastal elasmobranch to genetic erosion. This study will take advantage of DNA hybridization gene capture and next generation sequencing (NGS) techniques that are optimal for obtaining whole mitochondrial genome sequences from even degraded tissues typical of historical specimens. A total of 163 samples representing 5 ocean basins will be used to examine, characterize and contrast genetic variation in historical and contemporary sawfish populations. Results will be used to identify contemporary management units and provide a historical baseline to guide global and regional sawfish conservation strategies.
Johanna Imhoff, R. Dean Grubbs
Florida State University, Tallahassee, Florida, USA
Comparative Mercury Contamination in Demersal Deep Sea Sharks in the Gulf of Mexico
As mid to upper trophic level predators, elasmobranchs are at risk of carrying high loads of bioaccumulating toxicants. Methylmercury (MeHg) is of particular concern in fishes because high levels of contamination can put humans at risk for reproductive and neurological problems via fish consumption. Research on MeHg contamination in deep sea sharks has shown that MeHg concentration increases with the size of the shark, often exceeds recommended values for safe human consumption and generally increases with increasing trophic level and with dependence on benthic versus pelagic food webs. MeHg is one of several pollutants that are of particular concern after an oil spill. It has been hypothesized that oil spills create ideal conditions for blooms in the bacteria that methylate mercury. As mid to upper trophic level predators, deep sea sharks have the potential to bioaccumulate high concentrations of MeHg and their high longevity may facilitate the persistence of high levels of MeHg in the system for long periods of time. Therefore mercury analysis of coexisting deep sea sharks in a habitat near a source of anthropogenic pollution (i.e. the Deepwater Horizon Oil spill) could provide useful information on the roles of taxonomy and depth habitat in toxicological response of mesopredators after an oil spill. Methylmercury speciation and concentrations will be analyzed in six shark species that range from the continental shelf edge to the mid-slope and include both Carcarhiniformes (Mustelus canis, M. sinusmexicanus) and Squaliformes (Squalus cubensis, S. cf. mitsukurii, Centrophorus uyato, C. granulosus).
Rima Jabado, Reem Al Baharna, Sultan Al Ali, Mohsin Al Ameri, Ayesha Al Blooshi
Environment Agency Abu Dhabi, Abu Dhabi, United Arab Emirates
The Last Stand of the Critically Endangered Green Sawfish, Pristis zijsron, in the Arabian Gulf?
Sawfishes represent one the most threatened group of marine fishes around the world. Historical declines have been documented throughout the geographic distribution of all five species and it has been suggested that they might be extinct as a functional component in Arabian Gulf coastal ecosystems. Interviews with fishermen were conducted across the United Arab Emirates (UAE) between November 2015-April 2016 to determine the national status of sawfishes, gather information on encounters and abundance, as well as identify locations where populations might still be found. Based on pictures and rostra from various sources, the only species recorded in UAE waters is the green sawfish, Pristis zijsron. Fishermen confirmed sawfishes had drastically declined in the last 20 years yet the majority of respondents reported encounters in the last five to ten years. Sawfishes were not perceived to be a culturally significant resource and when caught were mainly used as a source of food, with their high value fins sold to traders and rostra retained as decorations in houses. The consensus was that sawfish used to be targeted but are now only caught as incidental catch primarily with gillnets and hook and line. While results of this study provide evidence of a large decline in sawfishes in the past 20 years, they highlight the importance of Abu Dhabi waters as a region where sawfishes are still encountered and provide an area where research, monitoring, as well as conservation and recovery efforts should be focused to avoid local extinction and restore robust populations.
Jacob Jerome, Austin Gallagher, Neil Hammerschlag
University of Miami, Miami, Florida, USA
Integrating Physiological and Behavioral Biomarkers of Fishing Capture Stress in Coastal Shark Species
In both commercial and recreational fisheries, many sharks are captured and released alive but may suffer post-release fitness loss or even mortality due to capture stress. Thus, understanding behavioral and physiological responses of sharks to capture stress is important for determining best fishing practices and for establishing effective management strategies. In this study, we quantified sub-lethal effects of capture through monitoring blood glucose, hematocrit and reflex impairment on 5 species of coastal sharks: great hammerhead (Sphyrna mokarran), bull (Carcharhinus leucas), blacktip (Carcharhinus limbatus), nurse (Ginglymostoma cirratum) and tiger (Galeocerdo cuvier). We further evaluated inter- and intra- specific relationships between these parameters and fight time, sea surface temperature, dissolved oxygen, and season.
Christian Jones1, Eric Hoffmayer1, Jill Hendon2, Joseph Quattro3, Justin Lewandowski3, Mark Roberts3, Gregg Poulakis4, Matthew Ajemian5, William Driggers1, Marcelo de Carvalho6, Mariana Rêgo7, Fábio Hazin7, J. Fernando Márquez-Farías8
1National Marine Fisheries Service, Southeast Fisheries Science Center, Mississippi Laboratories, Pascagoula, MS, USA, 2University of Southern Mississippi, Gulf Coast Research Laboratory, Ocean Springs, MS, USA, 3University of South Carolina, Department of Biology, Columbia, SC, USA, 4Florida Fish and Wildlife Commission, Fish and Wildlife Research Institute, Port Charlotte, FL, USA, 5Florida Atlantic University, Harbor Branch Oceanographic Institute, Fort Pierce, FL, USA, 6Universidade de São Paulo, Instituto de Biociências, Departamento de Zoologia, São Paulo, SP, Brazil, 7Universidade Federal Rural de Pernambuco, Departamento de Pesca, Recife, PE, Brazil, 8Universidad Autónoma de Sinaloa, Facultad de Ciencias del Mar, Mazatlán, SIN, Mexico
Rhinoptera brasiliensis Müller, 1836 in the northern Gulf of Mexico
In 2007, three rays identified as Rhinoptera brasiliensis Müller, 1836, based on tooth series counts, were captured in the northern Gulf of Mexico (GOM), a region far outside their accepted range of the coastal waters of southern Brazil. Genetic analyses confirmed that these individuals were distinct from Rhinoptera bonasus (Mitchill, 1815), the only recognized indigenous species. Further analyses of over 300 specimens, including reference mitochondrial DNA sequences from voucher specimens, confirmed the widespread occurrence of two species of cownose rays in the northern GOM. Genetic analyses indicated the second species relates most closely to R. brasiliensis. The distributions of the two species differed, with R. bonasus being more prevalent in the eastern GOM, and R. brasiliensis in the western GOM. There was an approximately 90% rate of agreement between identifications based on tooth series counts (R. bonasus = 5 to 13, R. brasiliensis = 7 to 15), which have been the standard for differentiating among rhinopterids, and those based on mitochondrial DNA sequences. Analyses of morphological and skeletal data identified several discriminating characters. The shapes of several skeletal elements and spiral valve lamellae counts (R. bonasus = 26 to 28, R. brasiliensis = 29 to 31) also appeared to be consistently reliable in differentiating between the two species. This is the first study to verify the occurrence and distribution of R. brasiliensis in the northern GOM; however, the close genetic relationships to other rhinopterid species, as well as the morphological similarity of the group as a whole, require additional research.
Elizabeth R. Jones, Andrew N. Evans
Department of Coastal Sciences, The University of Southern Mississippi, Ocean Springs, MS 39564, USA
Corticosteroid Receptors in the Atlantic Stingray, Dasyatis sabina: Sequence, Expression, and Physiological Implications
Elasmobranchs possess a unique corticosteroid called 1α-hydroxycorticosterone, or 1αB, which is thought to mediate energy availability during stress (as a glucocorticoid hormone) and hydromineral balance during osmoregulation (as a mineralocorticoid hormone). The mechanisms underlying regulation of 1α-B’s dual roles are poorly understood, however differentiation of these functions could occur via interaction with different receptor types. Elasmobranchs have two receptors capable of binding 1α-B: a glucocorticoid receptor (GR) and a mineralocorticoid receptor (MR). In other vertebrates, these receptors act by binding their corticosteroid ligand then migrating to the nucleus where they alter transcription of target genes. To investigate the role of elasmobranch corticosteroid receptors in 1α-B actions, we used degenerate PCR coupled with rapid amplification of cDNA ends (RACE) to isolate mRNAs encoding the GR and MR of the Atlantic stingray, Dasyatis sabina. Alignment of D. sabina GR and MR protein sequences with those of other vertebrate taxa revealed a high level of conservation in the DNA binding domain of the receptors and in amino acid residues involved in binding the steroid ligand (1α-B). Additionally, we used qPCR to examine the mRNA expression and abundance of GR and MR in a variety of tissues and found them to be ubiquitously expressed. These combined results indicate that the receptors for 1α-B function similarly to other vertebrate steroid receptors, and further support the hypothesis that 1α-B plays a central role in governing the stress and osmoregulatory physiology of elasmobranchs.
Armelle Jung1, Mohamed Kamara2, Salatou Sambou3, Inluta Incom4, Aissa Regalla5, Amadeu Almeida4, Ceuna Quade4, Moussa Silla6, Framoudou Doumbouya6, Ebou Mbye7, Gibril Gabis7, Abdoulaye Diedhiou8, Lamine Camara9, Cécile Brigaudeau1, Mika Diop10, George Burgess11
1Des Requins et Des Hommes (DRDH), Brest, France, 2Ministry of Fisheries and Marine Ressources, Freetown, Sierra Leone, 3Des Requins et Des Hommes (DRDH), Casamance, Senegal, 4Centro de Investigaçao Pesqueira Aplicada (CIPA), Bissau, Guinea-Bissau, 5Instituto da Biodiversidade e das Áreas Protegidas (IBAP), Bissau, Guinea-Bissau, 6Centre National des Sciences Halieutiques de Boussoura (CNSHB), Conakry, Guinea, 7Ministry of Fisheries and Water Ressources, Banjul, Gambia, 8Direction des Pêches Maritimes, Dakar, Senegal, 9Ministère des Pêches et de l'Economie Maritime (MPEM), Nouakchott, Mauritania, 10Commission Sous Régionale des Pêches (CSRP), Dakar, Senegal, 11Museum of Natural History, University of Florida, Gainesville, FL, USA
Sawfishes in Northwestern Africa
Sawfishes historically were regarded as common in northwestern Africa, even being depicted on the banknotes and coins of the regional. Listed as critically endangered (IUCN Red List), Pristis pristis and P. pectinata are still encountered in the area but are poorly reported. The Africasaw project has developed a regional alert network for sawfishes in cooperation with national authorities and fisheries communities of the five countries of the area. The network allows us to collect field data on past and present distribution and biology of native sawfishes. Data from 705 sawfish encounters from 1865-2015 were gathered and analyzed. Capture gear most often involved seines/set nets (60% of the by-catches) followed by longlines and trawl nets. Sawfishes are encountered year-round, and all sizes are represented. Most neonates are caught just after the rainy season while actively mature animals are found during the transition season in the estuarine habitats. Our recent (post 2010, n=45) data identifies crucial hot spots in Guinea Bissau, Sierra Leone and Senegal that will be decisive for the future of the species. Sawfishes were alive at capture in 76% of the fully-documented catches (n=131), underscoring the major role of fishermen in release choice and the urgency to pursue sensitization actions with this user group. These elements are discussed within the perspective of the global sawfish conservation strategy.
Stephen Kajiura1, Rachel Berquist2, Tricia Meredith1, Lawrence Frank2
1Florida Atlantic University, Boca Raton, Florida, USA, 2University of California San Diego, La Jolla, California, USA
Diffusion Tensor Magnetic Resonance Microscopy Reveals Novel Olfactory System Neural Organization in the Atlantic Stingray, Dasyatis sabina
All life on earth exhibits some degree of chemical sensitivity. Within the vertebrate clade, the organization of the olfactory system is largely conserved, despite their morphological diversity. Histological evidence suggests that the elasmobranch fishes demonstrate a remarkably different olfactory bulb organization than other vertebrates, including the teleost fishes. However, conventional histology is laborious, destroys intact structure, results in disjointed samples which must be reconstituted to elucidate three dimensional organization, and thus is inherently prone to tissue damage and registration errors. Here we show that Diffusion Tensor Microscopy (DTM) can be applied to facilitate Fiber Tract Mapping (FTM) of complex peripheral and central neural pathways. Using this non-invasive 3D digital imaging methodology, we imaged the olfactory organ and olfactory bulb of a basal vertebrate, the Atlantic stingray, Dasyatis sabina. We found that Olfactory Receptor Neurons (ORNs) project from the olfactory epithelium through the secondary and primary olfactory lamellae to the olfactory bulb. Within the bulb, the ORNs maintain their spatial integrity by projecting to glomeruli situated within one to two lamella widths of their point of origin producing a somatotopic bulbar organization. This contrasts with teleost fishes which possess a chemotopic organization whereby olfactory receptor neurons that share similar chemical sensitivity converge in glomeruli regardless of their point of origin within the olfactory epithelium. Our results illustrate the utility of DTM and FTM to efficiently inform us about intact neuronal structure by revealing a three dimensional bulbar organization that we believe may be fundamentally different from all other vertebrates.
Jenny Kemper, Gavin Naylor
Medical University of South Carolina, Charleston, SC, USA
A Species-Level Phylogeny of Chimaeroids Using Genomic Comparisons
Chimaeroids are a small and once diverse group of cartilaginous fishes with origins dating back at least 420 million years. Extant chimaeras, with 49 currently described species, represent the sister group to the sharks, skates and rays, and are also closely related to the extinct iniopterygians. While cartilaginous fishes as a whole are considered to be the oldest living group of jawed vertebrates and provide a unique reference for vertebrate evolution, the Chimaeriformes occupy the most basal position within this group. However, most molecular studies have focused on sharks and rays, and only used chimaeras as an outgroup. The few molecular studies that have attempted to address intra-relationships among chimaeras have used only a few species, or do not include all the genera. To date, there have been no comprehensive molecular studies that have estimated the intra-relationships within these fishes. It is necessary to reconstruct the phylogenetic relationships among all the extant members in order to better estimate the ancestral state and predict how changes in genetic architecture may have evolved over time within the chimaeras and across vertebrates. Our objective in the current study was to estimate a species-level phylogeny of extant chimaeroids. We used a new method of DNA hybridization capture in which approximately 1265 nuclear, single-copy exons were captured, followed by next-generation sequencing. Additionally, whole mitochondrial genomes were captured by similar methods. The two datasets will be subjected to phylogenetic analyses to estimate a species-level phylogeny and topologies will be compared between datasets.
Steven Kessel1, David Yurkowski1, Tarik Chekchak2, Graham Hill3, Rebecca Klaus2, Ryan Walter1, Nigel Hussey1
1University of Windsor, Windsor, Canada, 2Equipe Cousteau, Paris, France, 3The Deep Aquarium, Hull, UK
Spatial use of coastal manta rays (Manta alfredi) in Sudan relative to marine reserve boundaries, and proximity to a proposed coastal development
Large coastal manta ray aggregations have been regularly observed off the north Sudanese coast of the Red Sea, yet almost no focused research has been conducted on these animals. The majority of sightings have occurred within the boundaries of the Dungonab Bay marine reserve, however, an island development within these boundaries has been proposed. Wildlife Computers® SPOT 4 tags were secured to the dorsal fins of three coastal manta rays. A two-state switching Bayesian State Space Model (BSSM), that allows movement parameters to switch between behavioural states, was fit to the recorded locations. Locations were then used to calculate home ranges at 50% and 95% Kernel Utilization Distributions (KUD). A total of 682 BSSM locations were recorded between 30 October 2012 and 6 November 2013. Of these, 98.5% fell within the reserve boundaries, 99.5% for manta 1, 91.5% for manta 2, and 100% for manta 3. The BSSM identified that all three mantas were resident/foraging during 99% of transmissions, with 50% and 95% KUD home ranges falling mainly within reserve boundaries. For all three manta rays combined (88.4%), and all individuals (manta 1 - 92.4%, manta 2 - 64.9%, manta 3 - 91.9%), the majority of locations occurred with 15 km of the proposed development. The distribution of recoded locations indicated that the established reserve boundary is spatially appropriate for protecting manta rays in the region. The close proximity of locations/home ranges to the proposed development highlights the potential threat of disruption to the local coastal manta ray population.
Michael Kinney1, Dovi Kacev1, Suzanne Kohin2, Tomoharu Eguchi2
1Ocean Associates; Under Contract to Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, California, USA, 2Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, California, USA
Quantitative approach for analyzing telemetry data in data-limited situations
Horizontal behavior of highly migratory marine species is difficult to study due to numerous factors including wide-ranging movements, minimal surface time, and remoteness of their habitats. Satellite telemetry enables researchers to track individual movements, but population level inferences are rare, in many cases due to data limitations. We introduce a Bayesian modeling framework to address population level questions about traditionally data-limited species. We tested the framework using a large telemetry dataset for Isurus oxyrinchus. First, a permuted random forest analysis is implemented to determine which variables are statistically important. Next, a generalized additive mixed model is used to test that the remaining variables have a linear relationship with the response variable. Using rjags, an R package for analysis of Bayesian hierarchical models using Markov Chain Monte Carlo simulation, we then developed a movement model to generate parameter estimates for each of the variables of interest. We also demonstrate how two commonly used maximum likelihood (MLE) mixed models can be similarly applied. By randomly reducing the tagging dataset by 25, 50, 75, and 90 percent and recalculating the parameter estimates, we demonstrate that this approach can be applied in data-limited situations. Lastly, the models are used to make forward predictions on novel data. Despite performing similarly, we advocate using the Bayesian approach over the MLE models due to the ability for later studies to easily utilize results of past study to inform working models, and the ability to use prior knowledge via informed priors in systems where such information is available.
Melanie Kolacy, James Sulikowski, Teresa Dzieweczynski
University of New England, Biddeford, Maine, USA
Effects of Temperature on Behavior and Brain Development of the Little Skate
Over the last 10 years the Gulf of Maine (GOM), has experienced unprecedented warming trends. Research regarding the effects of climate change has primarily focused on bony fish, with minimal knowledge of the effects on elasmobranchs, particularly oviparous species. Recent research on the oviparous little skate has indicated that eggs deposited and incubated in warmer temperatures have shorter gestations and higher mortality rates before and after hatching. In order to better understand this observed mortality in neonate little skates, a series of behavioral tests were implemented to exam the possible linkage between increased ambient temperature and survivability. Here, oviposited eggs from a captive breeding stock were equally divided into two separate conditions. One group of egg cases (N=146) was held at ambient temperature conditions, while the second condition (N=130) simulated an elevated temperature condition of 5˚C above the ambient temperature. After hatching in these conditions, each little skate was measured, tagged, and returned to their respective temperature conditions. Possible differences in behavior were assessed using three assays; foraging, tapstartle responses, and activity levels. Preliminary results suggest higher foraging in all skates raised in ambient temperatures (N=19), while skates raised in elevated temperatures (N=14) fed minimally (14.3%) or not at all (85.7%). 50% of elevated skates displayed a delayed response and appeared to swim shorter distances when startled. However, both elevated and ambient skates seemed to display similar activity levels. These results are currently being analyzed and will be discussed at the AES Conference.
Matthew Kolmann1, Kenneth Welch1, Adam Summers2, Nathan Lovejoy1
1University of Toronto Scarborough, Toronto, ON, Canada, 2University of Washington, Seattle, WA, USA
Goats of the sea - bilaterally asymmetric chewing in an elasmobranch
Freshwater stingrays invaded the prehistoric Amazonian mega-lagoon around 14-28 mya, and now number 30+ species. They have diversified to fill an array of trophic niches across South American river basins though they lack the prey-processing pharyngeal jaws of teleosts. Several freshwater rays (Potamotrygonidae) are the only insectivorous elasmobranchs, specializing on aquatic insect larva in particular. Concurrent with insectivory, in these rays we see asymmetrical jaw motion (chewing) during prey processing. A mainstay of mammalian feeding, asymmetric chewing has never been described in a cartilaginous or actinopterygian fish. We will present kinematic data on prey-processing in an insect-feeding freshwater stingray, Potamotrygon motoro. Asymmetrical jaw protrusion and substantial lateral movement of the jaws occurs when feeding on tough prey items like insects, presumably shearing the chitinous exoskeleton. Aiding in this, insectivorous rays can behaviorally reorient their teeth from a flattened surface to occluding cusps when feeding on tough prey, as the dental ligament is flexed at the medial jaw symphyses. Despite a simple jaw morphology, potamotrygonids accomplish impressive post-capture prey manipulation and processing by combining hydrodynamic forces with complex movements of the jaws. The impetus for kinematic flexibility of the oral jaws in stingrays may be the batoid penchant for de-coupling prey processing from prey capture: stingrays use their whole body to generate suction and apprehend prey. The de-coupled nature of the jaws from the cranium (euhyostyly), tethered and supported by muscles rather than articulated skeletal elements, may also play a role in explaining the highly-kinetic and adaptable stingray feeding apparatus.
Andrea Kroetz, Dana Bethea, John Carlson
NOAA Southeast Fisheries Science Center, Panama City, FL, USA
Predictive modeling of habitat use by juvenile smalltooth sawfish (Pristis pectinata)
Smalltooth sawfish, Pristis pectinata, like all species of sawfish, are among the most endangered of marine fishes. Successful recovery of sawfish populations requires juvenile recruitment success and initiatives now strive to include the protection of areas used by juveniles in order to promote survivorship. Initial studies using public encounter data have identified sheltered, shallow, mangrove areas as potential nursery habitat with subsequent studies finding warmer water temperatures and variable salinity associated with the capture of juvenile sawfish. However, further refinement is required to fully predict the essential features smalltooth sawfish require as juveniles. We analyzed data from fisheries independent gillnet surveys in south Florida to identify relationships between environmental predictors and juvenile smalltooth sawfish abundance and distribution. Boosted regression trees (BRT) were used to predict these relationships and identified environmental factors influencing juvenile smalltooth sawfish distribution. Model performance of the BRTs were high and identified salinity, water temperature, and presence of mangrove pneumatophores as the three factors having the most influence on juvenile smalltooth sawfish distribution. Probability of occurrence was determined by interpolating the BRT models to maps of south Florida using ordinary kriging. Depending on the predictor variable analyzed, predictability of juvenile smalltooth sawfish occurrence varied throughout the Everglades National Park. Results from our study will be essential to further refine this species' use of critical habitat. The construction of habitat models to identify potential nursery habitats will greatly add to the improvement of the smalltooth sawfish recovery plan.
Takahiro Kusaka1, Koujirou Hara2, Keisuke Furumitsu2, Shinji Uehara3, Yuta Yagi3, Atsuko Yamaguchi2, Naoki Yagishita2
1Graduate school of Agriculture, Kinki University, Nara, Japan, 2Graduate School of Fisheries and Environmental Sciences, Nagasaki University, Nagasaki, Japan, 3Japan Sea National Fisheries Research Institute, Niigata, Japan
Genetic population structure of a Japanese common skate Dipturus cf. kwangtungensis in Japan inferred from mitochondrial cytochrome b gene
The genetic population structure of a Japanese common skate Dipturus cf. kwangtungensis in Japan was examined based on partial sequences of the mitochondrial (mt) cytochrome (cyt) b gene. We obtained 931 base pairs of the mt cyt b gene from 226 individuals around Japan, and revealed 59 polymorphic sites that defined 35 haplotypes. Neighbor-joining (NJ) tree and the minimum spanning network (MSN) of the haplotypes revealed two lineages: the first lineage contained populations in the Sea of Japan and the East China Sea, and the second lineage contained populations in the Pacific coast. Moreover, the second lineage were subdivided into two populations (northern part of Honshu and Kochi populations). Significant genetic differentiation was detected between northern part of Honshu population, Kochi population, and the group containing geographic populations in the Sea of Japan and the East China Sea by both hierarchical molecular variance analysis and pairwise FST, which correspond to the results of both NJ tree and MSN. Haplotype diversity was high in each geographic population (0.521－0.884) except Kochi population (0.245). Nucleotide diversity was low in all geographic populations (0.0005－0.0031). The demographic history of D. cf. kwangtungensis estimated by mismatch distribution analyses and neutrality tests suggested a sudden population expansion occurred 88,000－141,000 years ago. The fall in sea level during glaciations in the Pleistocene may have caused the habitats of D. cf. kwangtungensis to deteriorate and that the rapid population expansions must have occurred during interglacial periods.
Peter Kyne1, Pierre Feutry2, Rob Lindsay3, Amos Shields3, Albert Myoung3, Rita Purack3, Francis Miljat3, Aaron Green3, Theresa Lemon3, Travis Maloney3, Richard Pillans4, Grant Johnson5, Thor Saunders5, Christy Davies6, Richard Hillary2, Mark Bravington2
1Charles Darwin University, Darwin, Northern Territory, Australia, 2CSIRO, Hobart, Tasmania, Australia, 3Malak Malak Ranger Group, Daly River, Northern Territory, Australia, 4CSIRO, Brisbane, Queensland, Australia, 5Northern Territory Fisheries, Darwin, Northern Territory, Australia, 6North Australian Indigenous Land and Sea Management Alliance, Darwin, Northern Territory, Australia
Floodplain Waterholes as High Risk Nursery Habitat for the Critically Endangered Largetooth Sawfish in Northern Australia
Northern Australia is a global hotspot for the Critically Endangered Largetooth Sawfish Pristis pristis. The region is characterized by a dynamic monsoonal wet-dry cycle with intense rainfall and freshwater flow in large river systems during the wet season and minimal rainfall during the dry season. The wet season results in inundation of river floodplains but as water retracts during the dry season, aquatic fauna is forced into remaining waterholes. Juvenile (0+ age class) sawfish were located in floodplain waterholes of the Daly River in Australia's Northern Territory. Sawfish occurred in both large and very small waterholes; in one case, a number of sawfish had to be relocated to the main river channel as their waterhole was close to drying out. A risk management protocol has been established for local Indigenous rangers to patrol floodplains annually to search for isolated sawfish at risk of mortality. All individuals were genotyped at thousands of loci allowing for full and half sibling inference. Combining kinship information with mitogenome haplotypes we were able to determine the minimum number of adult females responsible for one annual cohort. Although sample size was low, full sibling relationships amongst Daly River floodplain sawfish suggest dispersal of individuals of a litter across the floodplain. When considering samples from several rivers across northern Australia, full siblings were always identified from the same river. On the other hand, half-sibling pairs were also identified from different, often widely-dispersed rivers suggesting adults can disperse from one river to another to reproduce.
Julia Lawson1, Rachel Walls1, Sonja Fordham2, Mary O'Malley3, Michelle Heupel5, Guy Stevens4, Daniel Fernando10, Ania Budziak6, Colin Simpfendorfer7, Lindsay Davidson1, Isabel Ender4, Malcolm Francis8, Giuseppe Notarbartolo di Sciara9, Nicholas Dulvy1
1Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada, 2Shark Advocates International, The Ocean Foundation, Washington, DC, USA, 3WildAid, San Francisco, CA, USA, 4Manta Trust, Dorchester, Dorset, UK, 5Australian Institute of Marine Science, Townsville, Queensland, Australia, 6Project AWARE Foundation, Rancho Santa Margarita, CA, USA, 7Centre for Sustainable Tropical Fisheries and Aquaculture & College of Marine and 20 Environmental Sciences, James Cook University, Townsville, Queensland, Australia, 8National Institute of Water and Atmospheric Research, Wellington, New Zealand, 9Tethys Research Institute, Milano, Italy, 10Linnaeus University, Kalmar, Sweden
Sympathy for the devil: a conservation strategy for devil and manta rays
Increased interest in luxury products and Traditional Chinese Medicine has been linked to depletion of both terrestrial and marine wildlife. Among the most rapidly emerging concerns with respect to these markets is the relatively new demand for gill plates, or Peng Yu Sai ("Fish Gills"), from devil and manta rays (subfamily Mobulinae). High value gill plates drive international trade supplied by largely unmonitored and unregulated bycatch and target fisheries around the world. Devil and manta rays are sensitive to overexploitation because of their exceptionally low productivity. Scientific research, conservation campaigns, and international and national protections that restrict fishing or trade have increased in recent years. Many key protections, however, apply only to manta rays. We review the state of scientific knowledge for these species, and summarize the geographic ranges, fisheries and national and international protections for these species. We use a conservation planning approach to develop the Global Devil and Manta Ray Conservation Strategy, specifying a vision, goals, objectives, and actions to advance the conservation of both devil and manta rays. Generally, there is greater scientific attention and conservation focused on manta compared to devil Rays. We discuss how the successes in manta ray conservation can be expanded to benefit devil rays. We also examine solutions for the two leading threats to both devil and manta rays - bycatch and target fisheries. Our paper suggests that given similarities in sensitivity and appearance, particularly of the dried gill plate product, some conservation measures should be expanded to include devil rays.
Ruth Leeney1, Nick Dulvy1, Frances Humber2, Aude Carro2
1Simon Fraser University, Burnaby, VA, Canada, 2Blue Ventures, London, UK
Madagascar and Mozambique - the last hope for Africa's sawfishes?
Sawfishes are critically endangered worldwide, but in many parts of their former range, current data on their continued existence, or extirpation, are lacking. This seriously hinders conservation efforts. Sawfishes are known to have been present historically in the western Indian Ocean but until recently, their current status in this region was unknown. Interview surveys were carried out in Mozambique in 2014, and Madagascar in 2015, to collect information on sawfish distribution, recent catches, socio-economic value and cultural importance. Several sites were identified in both countries where recent captures (in the same year in which interviews were conducted) were reported and where sawfishes are likely still present. Rostra from Green and Largetooth sawfishes were found in Mozambique, but only Largetooth Sawfish rostra were encountered in Madagascar. Gill nets were the fishing gear most commonly attributed to sawfish catches, and sawfishes had been encountered by both artisanal and industrial fishers. Sawfishes did not hold any cultural importance in Mozambique or for most of the communities visited in Madagascar, but have some socio-economic importance to fishers, primarily through the sale of their fins. The continued presence of sawfishes in these two WIO countries offers some hope that populations might recover throughout the region, if the appropriate conservation and management measures are rapidly put in place. These findings provide a baseline from which directed research and conservation efforts for sawfishes can be developed. A workshop was held in Mozambique in 2015 to encourage the development of a national conservation strategy for sawfishes.
Agostino Leone1, Gregory Neils Puncher1, Francesco Ferretti2, Emilio Sperone3, Sandro Tripepi3, Primo Micarelli4, Andrea Gambarelli5, Maurizio Sarà6, Marco Arculeo6, Giuliano Doria7, Fulvio Garibaldi8, Andrea Dall'Asta9, Daniela Minelli10, Elisabetta Cilli11, Stefano Vanni12, Fabrizio Serena13, Alessia Cariani1, Fausto Tinti1
1Department of Biological, Geological & Environmental Sciences (BiGeA), University of Bologna, Bologna, Italy, 2Hopkins Marine Station, Department of Biology, Stanford University, Monterey, CA, USA, 3DiBEST Department of Biology, Ecology and earth Science, University of Calabria, Arcavacata di Rende, Italy, 4Centro Studi Squali, Aquarium Mondo Marino, Massa Marittima, Italy, 5Museum of Zoology and Comparative Anatomy of Modena, University of Modena, Modena, Italy, 6Department of Environmental Biology and Biodiversity, University of Palermo, Palermo, Italy, 7Civic Museum of Natural History "Giacomo Doria", Genova, Italy, 8Department of Earth Sciences, Environmental and Life, University of Genova, Genova, Italy, 9Civic Museum of Natural History of Trieste, Trieste, Italy, 10Museum of Comparative Anatomy, University of Bologna, Bologna, Italy, 11Department of Cultural Heritage, University of Bologna, Ravenna, Italy, 12Museum of Natural History of Firenze “La Specola”, Firenze, Italy, 13Regional Agency for Environmental Protection of Tuscany, ARPAT, Livorno, Italy
Mediterranean Jaws: Origin of the Mediterranean Population of Great White Shark, Carcharodon carcharias, Inferred from aDNA variation
The origin of the Mediterranean great white shark (GWS) population has remained uncertain for a long time. Recently, comparative mtDNA analyses, based on four Mediterranean samples, indicated that Mediterranean GWS showed little genetic differentiation from Indo Pacific lineages and strong separation from closer Atlantic haplotypes. It was suggested that Mediterranean white sharks originated in the Pleistocene (~400Kya) from a long distance dispersal of individuals from Australia via South Africa. However, this hypothesis is incongruent with the presence of Mediterranean GWS fossils older than the Pleistocene. We addressed this data gap by analysing control region and COI gene fragments from mtDNA extracted from 18 historical specimens (30-193 years old) collected from Italian museums, research institutes and private collections. Phylogenetic analyses confirmed that the Mediterranean and Pacific populations have a closer evolutionary relationship rather than South-African and North Western Atlantic populations. Comparisons of genetic diversity across global populations highlighted that Mediterranean GWS have low haplotype and nucleotide diversity, while the Australian population has the highest values, suggesting a founder effect in the Mediterranean and a stable population in Australia with a long evolutionary history. Combined divergence time analyses, carried out using internal calibrations with fossil and paleo-geographical data or an estimated evolutionary rate, suggested that Mediterranean GWS originated in the early Pliocene (~5.3MYA). These results suggest a GWS historical long-dispersal and paleo-colonization of the Mediterranean via a possible stepping stone model of eastward migration, from the Pacific through Central America, before the closure of the Central America Seaway.
Christopher G. Lowe1, Connor White1, Ryan Logan1, Armand Barillotti1, Chuck Winkler2, Sal Jorgensen3, John O'Sullivan3
1California State University Long Beach, Long Beach, CA, USA, 2Southern California Marine Institute, Terminal Island, CA, USA, 3Monterey Bay Aquarium, Monterey, CA, USA
Nearshore movements of juvenile white sharks off southern California
Over the last 10 years, there has been an increase in juvenile white sharks (< 2 m TL) caught and observed along the southern California (CA) coastline, with many animals observed within 100 m of the shoreline. Over the past 7 years we have tagged 32 juvenile white sharks with coded acoustic transmitters to track their long-term (multiple year) movements and site fidelity to nearshore locations throughout southern CA. Telemetry, catch and observation data have indicated that juvenile white sharks typically leave southern CA water and migrate south during the winter. However, in 2013 (n=1), 2014 (n=5) and 2015 (n=1) individuals were detected throughout the year in nearshore southern CA waters, due to the warmer than average water temperatures during those winters. In 2015 most detections came from two 7 km stretches of beach in southern Santa Monica Bay (SMB) (29.5% of Total Detections) and North Orange County (64.3% of Total Detections). Five Individuals tagged in SMB displayed high site fidelity to that area being detected for 88 to 163 days, with one up to 113 consecutive days. Similar patterns were observed along North Orange County with tagged individuals detected up to 135 days detected at that location. Three individuals moved between these two hotspots. These data suggests that individuals are spending large amounts of time in shallow coastal habitats and appear to have high fidelity to small spatial areas.
Sarah Luongo, Christopher G. Lowe
California State University Long Beach, Long Beach, CA, USA
Feelin’ the Heat, Seasonally Acclimated Metabolic Q10 of the California Horn Shark, Heterodontus francisci
With global sea temperature rise, it is unclear how many marine ectothermic organisms will react, particularly elasmobranchs. A better understanding of their metabolic Q10, temperature sensitivity, is needed in order to make realistic predictions as to how some populations will react over time. Oxygen consumption was used as a proxy to measure acclimated metabolic rates of the horn shark, Heterodontus francisci, at winter and summer temperatures (16 °C and 20 °C, respectively) typically experienced in a given year and to measure metabolic Q10. Sharks were kept in a large holding tank at one of the desired temperatures for two weeks prior to the trial to allow for physiological acclimation. Trial duration varied among individuals and temperature, trials took up to 12 hours with re-saturation of oxygen occurring when levels reached 80% of starting saturation. Sharks tested to date have ranged in size (37-45cm TL) and weight (0.410.679 kg) (n = 8). The resting, pre-prandial metabolic rates of the horn shark at 16°C and 20°C were 32.6 ± 9.5 mg O2 kg-1 hr-1 and 44.4 ± 8.8 mg O2 kg-1 hr-1, respectively. Of the eight horn sharks that we have tested, we estimate a metabolic Q10 of 2.31. These data provide a baseline for understanding the current physiological state of these organisms relative to present sea conditions, but can be modeled to help predict and manage behavioral responses associated with increased sea temperature.
Kady Lyons1, Douglas H Adams0
1CSULB, Long Beach, CA, USA, 2Florida Fish & Wildlife Conservation Commission Fish & Wildlife Research Institute, Melbourne, FL, USA
Tissue distribution, accumulation, and maternal offloading of organochlorine contaminants in Bonnethead Sharks
Legacy organochlorine contaminants (e.g. DDT, PCBs) continue to persist in the environment and accumulate in fish and wildlife long after use and production have ceased. Since these contaminants also biomagnify with trophic level they can be used as a tool for examining ecological relationships within and among related species. Organochlorine contaminants were measured in the liver, muscle and brain tissue of Bonnetheads (Sphyrna tiburo) from the southeastern U.S. over a range of size classes to determine patterns of accumulation as well as the extent of maternal offloading in a pseudo-placental elasmobranch. We found that a vast majority of organic contaminants accumulated in the livers of sharks of all stages, with brains having the next highest concentration followed by muscle tissue. Hepatic contaminant concentrations increased with size, however, male Bonnetheads were found to have greater concentrations than similarly-sized females. Adult females were found to be more efficient at transferring contaminants via ovulated eggs rather than across the placental structure during gestation. Nevertheless, the still developing embryos were exposed to substantial concentrations of contaminants during development. These findings warrant further investigation into the potential health impacts of this early-stage exposure as well as the influence of organic contaminants on brain development and neurological functioning in elasmobranchs.
Kady Lyons1, Chris L. Chabot2, Corinne N. Paterson2, Christopher G. Lowe1
1California State University, Long Beach, Long Beach, California, USA, 2California State University, Northridge, Northridge, California, USA
Who’s My Daddy? Multiple Paternity and Evidence of Cryptic Female Choice in the Round Stingray (Urobatis halleri)
Polyandry resulting in multiply-sired litters has been documented in the majority of elasmobranch species examined to date. Although commonly observed, reasons for this mating system remain relatively obscured due to the logistical difficulty in sampling animals and the lack of a detailed understanding of many species’ reproductive biology and ecology, especially in batoids and rays in particular. The round stingray (Urobatis halleri) is an abundant, well-studied elasmobranch distributed throughout the northeastern Pacific that is an excellent model for the testing of hypotheses regarding multiple paternity in elasmobranchs. Twenty mid- to late-term pregnant females were sampled off the coast of Seal Beach California and their litters analyzed for the occurrence of multiple paternity using five nuclear microsatellite loci. We observed that two or more fathers sired 90% of litters and that reproductive skew was relatively low in 61% of the litters. Our data suggests that females have two distinct ovulating patterns that contribute to the high rates of multiple paternity and relatively even skew. In addition, we found no evidence of paternal genetic benefits; further suggesting that cryptic female choice through sequential ovulation is a mechanism by which a high rate of multiple paternity is maintained.
M Aaron MacNeil1, Christopher J Fonnesbeck2
1Australian Institute of Marine Science, Townsville, Australia, 2Vanderbilt University, Nashville, TN, USA
BRUVS relative abundance estimation for global shark surveys
The use of baited remote underwater visual surveys (BRUVS) for quantifying marine species and communities that are otherwise difficult to observe has become widespread. Yet inherent sampling biases confound naive comparisons of abundance or diversity that have been well-studied for passive sampling methods that do not attract individuals to bait. Here we outline various sources of sampling bias for BRUVS as they relate to estimating the relative abundance of reef-associated sharks around the world. We develop a modelling framework to overcome BRUVS sampling biases and demonstrate its potential impact on real-world data. We conclude that, while remote sampling methods have great potential to catalyze understanding of the world's oceans, thoughtful models must be developed to ensure accurate interpretation of what are ultimately second-hand observations.
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
Comparative Genomics and Transcriptomics of Elasmobranchs: Insights into a Primitive Adaptive Immune System
The Elasmobranchii and Holocephali comprise the class Chondrichthyes and as a group represent the most basal vertebrate lineage with an adaptive immune system. To date, studies of immune genes in elasmobranchs have been restricted to single species studies or to select loci. Here we report the results of our comparative transcriptomic and genomic analyses involving several elasmobranch species, focusing on characterization of the immunome. We present our RNA-seq analysis of heart tissue, revealing several striking immunogenetic differences between the four elasmobranchs and three teleost fishes included in our study. These differences included enrichment within the elasmobranchs of genes associated with adaptive immunity Genome Ontology terms, such as “antigen processing and presentation of exogenous peptide antigen via MHC class II”, as well as evidence of positive selection of elasmobranch genes (e.g. legumain) classified within this same functional category. This in turn suggests that this particular immunological function may underlie some of the distinctive capabilities of the elasmobranch immune system. In regards to genomics, we report our updated and annotated assembly of the approximately 5 Gbp white shark genome, with over 100x sequencing coverage, and a gap percentage of 7%. We also report here for the first time, our assembled and annotated 3 Gbp great hammerhead genome. These completed shark genomes facilitate a thorough comparison of the immune gene content of two elasmobranch representatives to model vertebrates and the holocephalan, elephant shark, providing insights into shared features of elasmobranch genomes that drive functional and adaptive differences of their unique immune systems.
Heather Marshall1, Nicholas Whitney1, Connor White2, Diego Bernal3, Enrico Gennari4, Ryan Johnson4, Christopher Fischer5, Gregory Skomal6
1Mote Marine Laboratory, Sarasota, FL, USA, 2California State University Long Beach, Long Beach, CA, USA, 3University of Massachusetts Dartmouth, North Dartmouth, MA, USA, 4Oceans Research, Mossel Bay, South Africa, 5OCEARCH, Park City, UT, USA, 6Massachusetts Division of Marine Fisheries, New Bedford, MA, USA
The stress response and recovery behavior of the white shark (Carcharodon carcharias) after capture on handline gear
With a growing white shark (Carcharodon carcharias) population in the western North Atlantic, incidental capture of this species has increased in recent years. Given the importance of post-release survivorship to population growth, a detailed assessment of the physiological effects of capture and their subsequent impacts on survivorship is warranted. The objectives of this research were to quantify relative acid-base, electrolyte, and metabolite disturbances in the blood of white sharks exposed to handline capture, air exposure, and handling, to examine immediate and delayed post-release mortality with satellite tracking, and to characterize post-release recovery in this species using accelerometry. For capture times ranging from 10-123 minutes, we did not find significant changes in blood stress parameters, which were consistent across individuals (n=29). Three individuals blood sampled multiple times during tagging exhibited no significant changes in blood biochemistry while out of the water, thereby indicating that the tagging event (i.e., time out of water) did not exacerbate the stress of capture. Individuals from which accelerometer data were obtained (N=4) showed a gradual increase in tailbeat frequency and amplitude in the first few hours after release, with three individuals exhibiting repetitive swim-glide (“yo-yo”) diving behavior. Satellite tag data indicate survivorship for several months or years for most individuals. Overall, the white shark appears to be a robust species when exposed to hook-and-line capture stress.
Christopher Martinez1, F. James Rohlf2, Michael Frisk2
1American Museum of Natural History, New York, NY, USA, 2Stony Brook University, Stony Brook, NY, USA
Have We Been Underrepresenting the Morphological and Ecological Diversity of Skates?
Skates (Batoidea: Rajoidei) are often characterized as a morphologically conserved clade. At some levels this is certainly true, but a strict adherence to this view may result in underrepresentation of morphological and associated ecological variation in skates. In order to assess the relative diversity of forms in rajoids, we used geometric morphometrics to compare shape variation in an important feature of all batoids; their anteroposteriorly expanded pectoral fins. We found that while overall shape disparity (variance) was greater in stingrays (Batoidea: Myliobatoidei) than skates, the degree to which it was larger is slightly misleading due to a gap between strongly bimodal stingray morphotypes. The observed diversity of skate pectoral fins, as indicated by the relative location and distribution of shapes in batoid morphospace, points to marked variation in fin performance that also implies ecological variation of skates may be larger than it is sometimes credited for. Additionally, intraspecific variation within skates, in the form of sexually dimorphic pectoral fins, adds another dimension to shape diversity within this clade, which may also have ecological consequences of its own. Given these results, we advocate an updated and nuanced paradigm regarding the morphologically conserved skate clade that accommodates the level of body shape variation observed and the ecological implications thereof.
Mark Meekan1, Lauren Fear2, Andy Radford2, Steve Simpson3
1Australian Institute of Marine Science, WA, Australia, 2School of Biological Sciences, University of Bristol, Bristol, UK, 3Biosciences, College of Life & Environmental Sciences, University of Exeter, Exeter, UK
A Model Predator: The Influence of Predation Threat on the Behaviour, Abundance and Diversity of Coral Reef Fishes
Predators influence prey both directly, through consumption and indirectly, via effects on their behaviour. Behavioural impacts (termed "risk effects") on prey are sometimes subtle and difficult to measure, particularly in coral reef ecosystems, where attempts at predation by large meso- and apex predators such as sharks are rarely witnessed. Here, we used an experimental approach to explore the effects of the presence of sharks and large meso-predators on reef fishes. We examined the behaviour, size, identity, abundance and diversity of fishes visiting baited video camera systems (BRUVS) in the presence of life-size models of reef sharks (1.3 m Total Length, TL), large coral trout (1 m TL) small coral trout (0.4 m TL) and a plastic pipe control. We found evidence for risk effects in coral reef fishes whereby the presence of the model shark and large trout was correlated with lower mean and maximum numbers of smaller, meso-predatory species visiting the bait bag. The presence of these models was also correlated with a lower species diversity of fish visiting the bait. Fish spent significantly greater periods of time around the bait (in the field of vision of the camera) in the presence of the small trout than when there was either a large trout or a shark model. Our approach shows how models can be used to manipulate and reveal risk effects of large predators in complex reef environments and demonstrates clear impacts of predation risk on coral reef fish communities.
Carl Meyer2, Kim Holland1, Melanie Hutchinson2, James Anderson1, Mark Royer1, Danny Coffey1
1University of Hawaii, Honolulu, HI, USA, 2Hawaii Institute of Marine Biology, Kaneohe, HI, USA
New Insights into Coastal Habitat Use By Tiger Sharks In Hawaii
An anomalous increase in shark bites around Maui in 2012 and 2013 highlighted gaps in our understanding of tiger shark movements in these waters. We used satellite and acoustic telemetry to quantify tiger shark spatial dynamics around Maui, and to determine their presence in near shore areas used for ocean recreation. Each shark had unique home range characteristics but there were several common themes of space and habitat use among individuals. For example, tiger shark home ranges typically included waters around several adjacent islands, and sharks were most frequently detected over coastal shelf habitat within the 200 m isobath. Most individuals utilized clearly-defined core areas associated with relatively wide areas of shelf and strong currents. Core use areas around Maui were often adjacent to ocean recreation beaches. Coastal shelf habitats around Maui are considerably more extensive than around any other Main Hawaiian Island (MHI), suggesting Maui waters might support more sharks than other neighboring islands, and may perhaps be an important feeding or reproductive habitat for tiger sharks from throughout the MHI. Collectively, these factors may partly explain higher long-term shark bite incident rates in Maui waters compared to other Hawaiian Islands.
Lauren Meyer, Madeline Green
Shark Share Global, Hobart, Tasmania, Australia
Shark Share Global: a virtual tissue bank for collaborative elasmobranch research
With more than a quarter of elasmobranchs considered endangered and another 47 per cent lacking basic biological data, there has never been a more crucial time for shark and ray scientists to work collaboratively and efficiently to understand the biology, ecology and physiology of elasmobranchs. Although opportunistic tissue collection occurs often in the field, in many cases not all potential samples are collected, samples are disposed of due to a lack of institutional storage, or they are left in freezers for potential future projects, which may not materialize. Additionally, sourcing samples for research projects remains challenging without broad global connections. Here, we propose an online database (Shark Share Global) to help overcome sampling inefficiencies and provide a user-friendly platform for sharing elasmobranch tissues. By creating a virtual global tissue bank, Shark Share Global is able to facilitate collaborative efforts, increasing multidisciplinary research without drastically increasing project costs. Here, we will introduce the database, its functionality and expected outcomes for the greater elasmobranch research community.
Muhammad Moazzam, Hamid Badar Osmany
Marine Fisheries Department, Government of Pakistan, Karachi, Pakistan
Are sawfishes locally extinct in Pakistan? Recent evidences suggest otherwise!
Three species of sawfishes were known to occur in Pakistan including knifetooth sawfish (Anoxypristis cuspidatus), common sawfish (Pristis pristis) and largecomb sawfish (P. zijsron). Of these, P. pristis was reported to be the most common species occurring in the lower reaches of the River Indus, associated estuarine areas, lagoons and shallow coastal waters.. There used to an important fisheries for sawfishes along the coast of Pakistan. Introduction of nylon net and proliferation of bottom set gillnetting in 1960s and 1970s respectively led to the decline in the catches and by 1980 the target fishery for sawfish collapsed. Although some specimens were occasionally caught but it was generally believed that sawfishes are locally extinct in Pakistan. A study was initiated in 2013 to record any sawfish caught by fishermen along the coast of Pakistan. During last three years only five authentic records of their occurrence were made. One specimen of A. cuspidatus was caught in the Khajar Creek (Indus Delta) whereas remaining 4 specimens collected from shallow coastal waters were identified as P. pristis. There are another 5 records of sawfishes during this period in which species could not be identified and there are some uncertainly associated with these records. In the paper, a review of the status of sawfishes is made. The collected data indicates that sawfishes are not extinct in Pakistan although they are very rare in occurrence. Considering their rarity the need for the conservation of sawfishes in Pakistan cannot be over-emphasized.
Brian Moe1, Paul Venturelli2
1Florida State University, Department of Biological Science, Tallahassee, FL, USA, 2University of Minnesota, Department of Fisheries, Wildlife and Conservation Biology, St. Paul, MN, USA
Modeling elasmobranch growth: an application of biphasic growth theory
The von Bertalanffy growth model is the most commonly used growth model in elasmobranch literature. However, this model has been criticized for its failure to account for the change in energy allocation at the onset of maturity, and therefore growth that occurs after a fish matures. The Lester growth model (LGM) is a biphasic alternative to the von Bertalanffy growth model that incorporates life history trade-offs between reproduction, growth, and survival to describe lifetime growth as a straight line (immature phase) and a curve (mature phase). We used 52 datasets from 29 elasmobranch species to compare the performance of the LGM to four conventional growth models (von Bertalanffy, Gompertz, logistic, and a two-phase von Bertalanffy). According to Akaike Information Criterion (AICc), the LGM was the best fitting model for 80.8% of datasets. Our results show clear support for the LGM as a means of describing lifetime growth of some of the world's most common, endangered, and economically important elasmobranchs; and bring into question the default status of conventional growth models in the elasmobranch literature.
IUCN Shark Specialist Group/Bangor University, Bangor, UK
Guitarfishes: can learning from the sawfish disaster prevent a similar fate?
Sawfishes (Pristidae) and guitarfishes (Rhynchobatidae, Rhinobatidae, Rhinidae) share numerous characteristics: they are large, distinctive shark-like rays found in shallow water close to humans that are vulnerable to capture and economically valuable. For the sawfishes, scientists and managers largely failed to recognise, document, and prevent catastrophic global declines, making realistic attempts at their recovery impossible or extraordinarily difficult in most cases. However, this experience can provide valuable lessons to try and ensure the same mistakes are not made for guitarfishes: a group that remains poorly researched with alarming declines reported for some species. Drawing on first-hand experiences with fisheries in Arabia and West Africa, information on guitarfish taxonomy, fisheries, utilisation and research is reviewed in order to identify priorities for scientists, managers, and conservationists.
David Morgan1, Jeff Whitty1, Adrian Gleiss1, Nicole Phillips2, Mark Allen1, Brendan Ebner3, Karissa Lear1, Stephen Beatty1
1Murdoch University, Murdoch, Western Australia, Australia, 2The University of Southern Mississippi, Hattiesburg, Mississippi, USA, 3James Cook University, Townsville, Queensland, Australia
Sawfish Research and Conservation in Western Australia: Current and Future Research Priorities
Western Australia is an important global refuge for four species of sawfish. Researchers from Murdoch University have been investigating the ecology of the three Pristis spp. found here, including the Dwarf Sawfish (Pristis clavata), the Freshwater (or Largetooth) Sawfish (Pristis pristis) and the Green Sawfish (Pristis zijsron). The main focus of our research has been to investigate the habitat utilization of nursery areas for these species using mark/recapture and acoustic telemetry and simple catch data from fishery independent surveys for each species in the north of the State. The catch rates of each of these species are some of the highest reported, and interactions with recreational and commercial fisheries is thus inevitable. Through targeted surveys, including site specific biannual surveys over 15 years and engagement with traditional ranger and public awareness programs, Western Australian's are becoming increasingly aware of the global decline of these species. The sheer size of the Western Australian coastline (sawfish habitats span some 6000 km) and small human population present challenges for monitoring these species, but are also factors making Western Australia a critical global refuge for these species. Despite the remote nature of the areas where sawfish occur, increasing industrialization of Australia's north-west in conjunction with the predicted severe impacts of climate change in this area may see the quality of these refuges change drastically in the near future.
Joshua Moyer, William Bemis
Cornell University, Ithaca, NY, USA
Shark Teeth as Edged Weapons: Serrated Teeth of Three Species of Selachians
Prior to European contact, South Pacific islanders used serrated shark teeth as components of tools and weapons. They did this because serrated shark teeth are remarkably effective at slicing through soft tissues. To understand more about the forms and functions of serrated shark teeth, we examined the morphology and histology of tooth serrations in three species: the Tiger Shark (Galeocerdo cuvier), Blue Shark (Prionace glauca), and White Shark (Carcharodon carcharias). We show that there are two basic types of serrations. Primary serrations consist of three layers of enameloid with underlying dentine filling the serration’s base. All three species studied have primary serrations, although the dentine component differs (orthodentine in Tiger and Blue sharks; osteodentine in the White Shark). Smaller secondary serrations are found in the Tiger Shark, formed solely by enameloid with no contribution from underlying dentine. Secondary serrations are effectively “serrations within serrations” that allow teeth to cut at different scales. We propose that the cutting edges of Tiger Shark teeth, equipped with serrations at different scales, are linked to a diet that includes large, hard-shelled prey (e.g., sea turtles) as well as smaller, softer prey such as fishes. We discuss other aspects of serration form and function by making analogies to man-made cutting implements, such as knives and saws.
Christopher Mull, Nicholas Dulvy
Simon Fraser University, Burnaby, BC, Canada
Size doesn’t matter: offspring production scales across sharks, skates, rays and chimaeras
Chondrichthyans are a unique clade that exhibits every described form of reproductive mode found in vertebrates, with large variation in reproductive traits (e.g. age at maturity, reproductive lifespan, fecundity). Measurements of offspring production are critical for addressing ecological and evolutionary hypotheses about life histories. Here we examine how total offspring production (biomass of offspring yr-1) and maternal investment (biomass of individual pups) vary with maternal body size across 624 chondrichthyan species. Total offspring production scales with maternal body mass across all species with mothers producing ~10% of their body mass in offspring yr-1. Around this scaling, variation is attributed predominantly to reproductive mode with live-bearing matrotrophs, specifically placental and lipid histotrophic species, exhibiting higher total offspring production. In contrast maternal investment did not scale with maternal mass and all variation was attributable to reproductive mode, with matrotrophic species exhibiting larger offspring relative to maternal size. Because much life history data in chondrichthyans is not complete and patterns of missing information are not completely random, observed patterns may be biased by the available data. To address this we also examine these same patterns using phylogenetically imputed life history traits. Incorporating phylogenetic information reduced the error rate of imputed missing values and observed patterns did not change. Phylogenetic imputation provides a potentially useful tool for generating reliable estimates of life history traits based on morphology, ecology and shared evolutionary history in lieu of difficult to obtain empirical measurements.
Gavin Naylor1, Jason Davies2
1College of Charleston, Charleston, SC, USA, 2Jason Davies Ltd, London, UK
An Interactive Online Database About the Biology of Sharks, Skates, Rays and Chimaeras
We have assembled an online database that, when completed, will provide information on all described extant species of sharks rays and chimaeras. Scientific illustrations and distribution maps will be provided for all currently described species, while interactive CT scans of skeletal elements will be included for representatives of most chondrichthyan families. The information is presented in an evolutionary framework derived from an analysis of genome scale DNA sequence data. We will demonstrate some of the key features and tools associated with the database during the presentation.
Kyle Newton, Stephen Kajiura
Florida Atlantic University, Boca Raton, FL, USA
I Knew I Should’ve Taken That Left Turn in Albuquerque: Using Magnetic Field Polarity to Solve a Navigational Task in the Yellow Stingray, Urobatis jamaicensis
Our previous work has demonstrated that yellow stingrays can detect changes in magnetic field strength and inclination angle, learn a behavioral task and remember it for up to six months. This study tests the hypothesis that stingrays can use magnetic cues to solve a navigational task. Yellow stingrays were held in a flow through seawater tank under a 12:12 hour light-dark cycle, fed every two days, and allowed to acclimate to the experimental apparatus for seven days. Prior to training the stingrays were fasted to increase motivation. Training sessions occurred every two days and consisted of 10 two-minute trails per session. Each magnetic stimulus training trial consisted of placing an individual stingray into a T-maze with the starting arm aligned with the axis of the local geomagnetic field. The magnetic field polarity at intersection of the T-maze was randomly manipulated 90 degrees to the left or right such that north always indicated the correct, and south indicated the incorrect, arm to receive the food reward. The learning criterion was defined as the stingray making the correct choice ≥70% during a training session for three consecutive sessions. Once the criterion was met the training stopped and the stingrays were reverse trained to associate south with the food reward. Stingrays were exposed to progressively smaller changes in stimuli to determine the threshold for a behavioral response. Threshold responses were used to determine the feasibility of a stingray using the geomagnetic field polarity as a cue during a biologically relevant navigational task.
Andrew Nosal1, Daniel Cartamil1, Chi Lam2, Philip Hastings1
1Scripps Institution of Oceanography, La Jolla, CA, USA, 2University of Massachusetts - Boston, Boston, MA, USA
Movement Ecology of Juvenile Blue (Prionace glauca) and Mako Sharks (Isurus oxyrinchus) off Southern California and Baja California, Mexico
The movements of juvenile Blue (Prionace glauca) and Mako Sharks (Isurus oxyrinchus) were quantified off southern California and Baja California, Mexico. Five Blues (mean FL=77±11 cm; range: 67-95 cm) and five Makos (mean FL=80±9 cm; range: 70-89 cm were tagged with pop-up archival X-Tags (Microwave Telemetry). The tracking periods ranged from 13 to 86 d (mean=45±24 d) with net displacement between tagging and pop-up locations averaging 259±90 km for Blues (range: 167-375 km) and 265±164 km for Makos (range: 95-501 km). Based on geolocation estimates, horizontal movements occupied an area from the continental slope to approximately 400 km offshore. Both species spent the majority of their time just below the surface with only occasional dives below 50 m (Blue max depth: 224 m; Mako max depth: 194 m). Both species exhibited diel vertical migration, with that of Blues being particularly pronounced, generally occupying deeper water at night (day: 77.3% of time spent at <2 m and 21.3% at 2-50 m; night: 45.8% at 0-2 m and 52.5% at 2-50 m). In contrast, Makos generally occupied shallower water at night (day: 19.7% of time spent at <2 m and 77.8% at 2-50 m; night: 31.4% at 0-2 m and 67.3% at 2-50 m). Unique to Makos was a conspicuous avoidance of surface waters between approximately 0900 and 1500 h, which may be related to thermoregulation. This is the first study to track such small Mako and Blue Sharks and offers insight into nursery habitat and niche partitioning amongst juvenile pelagic sharks.
Robert Nowicki, Michael Heithaus
Florida International University, Miami, FL, USA
Response of an apex predator, the tiger shark, Galeocerdo cuvier, to widespread seagrass decline
Seagrasses support a wide variety of taxa through their extensive ecosystem functions. These functions include provisioning of food as well as habitat. Despite their functional importance, seagrasses are declining worldwide at a rapid and accelerating rate. These declines have strong implications for seagrass associated communities which rely on them. While the effects of seagrass loss have been documented on some megafauna like green turtles (Chelonia mydas), there is relatively little information on how such declines impact highly mobile apex predators like large sharks. Because of their trophic removal from seagrasses and the variability of loss effects on shark prey, large sharks may exhibit different responses to resource decline than anticipated. Here we use a long term dataset of prey abundance and shark catch data to assess the effects of a widespread seagrass decline on the tiger shark community of Shark Bay, Western Australia. We find that though some shark prey appear less abundant, tiger sharks themselves may exhibit resilience to resource loss. We further discuss what may drive the observed patterns and what this may mean more generally.
Owen O'Shea1, Elizabeth Wallace2
1Cape Eleuthera Insitute, Eleuthera, Bahamas, 2Florida Fish and Wildlife Conservation Commision, Florida, USA
Gene flow and connectivity in an elusive batoid from The Bahamas
Anthropogenic incursions to coastal habitats have the potential to disrupt residency patterns and connectivity among stingray populations. Furthermore, these impacts may disrupt migratory pathways, particularly in island nations where deep ocean troughs provide challenges to dispersal and potentially, population renewal. The Caribbean whiptail stingray (Himantura schmardae) is an elusive dasyatid, popular in anecdote, rare in its known range, only recorded in The Bahamas from one sighting in 1968 and which taxonomic placement remains to be fully evaluated. This research aims to determine genetic connectivity of seemingly isolated populations of this ray across multiple spatial scales within the Exuma Sound, central Bahamas. Genomic DNA will be obtained from wild rays across three locations spanning from south Eleuthera to Great Exuma including The Exuma island chain. Genetic samples will be analysed by amplifying the mitochondrial cytochrome b gene to verify species, before all individuals are screened for a large array of single nucleotide polymorphisms (SNPs) to determine genetic population structure and familial relationships. The novel SNP array will be developed using advanced next generation sequencing technology. This next-generation methodology will allow for the determination of high-resolution genetic relatedness over restricted temporal scales highlighting potential migratory pathways across just one or two generations, instead of traditional historical radiation. These data can be used to directly create frameworks for management and conservation initiatives in The Bahamas for coastal and nearshore environments, but also provide much needed data on this cryptic species in the northern portion of its range.
Geoffrey Osgood1, Easton White2, Julia Baum1
1University of Victoria, Victoria, BC, Canada, 2University of California, Davis, Davis, CA, USA
The influence of shark population characteristics on statistical inference of population trends
Analyses of abundance data are critically important for understanding shark population trends. Shark abundance time series are typically short, highly variable, and with a high proportion of zeros - all properties that make typical analytical methods challenging or potentially unreliable. Shark behavior such as schooling and mobility also can complicate estimates of trends in abundance. We evaluated how analytical methods influence estimates of shark population trends by applying different statistical models to both simulated and empirical shark population data. We assessed the effects of the magnitude of changes in population abundance (trend strength), variability in population abundance, and the degree of zero inflation on the ability of different types of generalized linear models (GLMs) to make accurate inferences about population trends for common, rare, and schooling model shark species, as well as for populations with different movement patterns. We then compared the results of different GLMs fit on a long-term time series of shark and ray observations at Cocos Island off Costa Rica. Stronger trends, higher variability, zero inflation, and mobile behavior result in less reliable conclusions about declines, especially for rare sharks. Overall, the conclusions from different models do not differ substantially, particularly when declines are not severe, although binomial models and linear regressions are often inaccurate on both simulated and real data. Monitoring decisions require reliable information on trends and so dispersion in real shark populations should be carefully considered in data collection and the choice of appropriate GLMs.
Sebastián Pardo1, Holly Kindsvater1, Elizabeth Cuevas-Zimbrón2, Oscar SosaNishizaki2, Juan Carlos Pérez-Jiménez3, Nicholas Dulvy1
1Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada, 2Laboratorio de Ecología Pesquera, Departamento de Oceanografía Biológica, CICESE, Ensenada, Baja California, Mexico, 3iencias de la Sustentabilidad, El Colegio de la Frontera Sur, Lerma, Campeche, Mexico
Devil in the Details: Growth, Productivity, and Extinction Risk of a Data-sparse Devil Ray
Devil rays (Mobula spp.) face rapidly intensifying fishing pressure to meet the ongoing international trade and demand for their gill plates. This has been exacerbated by trade regulation of manta ray gill plates following their 2014 CITES listing. Furthermore, the paucity of information on growth, mortality, and fishing effort for devil rays make quantifying population growth rates and extinction risk challenging. Here, we use a published size-at-age dataset for a large-bodied devil ray species, the Spinetail Devil Ray (Mobula japanica), to estimate somatic growth rates, age at maturity, maximum age and natural and fishing mortality. From these estimates, we go on to calculate a plausible distribution of the maximum intrinsic population growth rate (rmax) and place the productivity of this large devil ray in context by comparing it to 95 other chondrichthyan species. We find evidence that larger devil rays have low somatic growth rate, low annual reproductive output, and low maximum population growth rates, suggesting they have low productivity. Devil ray maximum intrinsic population growth rate is very similar to that of manta rays, indicating devil rays can potentially be driven to local extinction at low levels of fishing mortality. We show that fishing rates of a small-scale artisanal Mexican fishery were up to three times greater than the natural mortality rate, and twice as high as our estimate of rmax, and therefore unsustainable. Our approach can be applied to assess the limits of fishing and extinction risk of any species with indeterminate growth, even with sparse size-at-age data.
Kristene Parsons, Jan McDowell, Heidi Brightman, Eric Hilton, Robert Latour
Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, VA, USA
Review of the Smooth Butterfly Ray, Gymnura micrura (Myliobatiformes: Gymnuridae) Reveals a Species Complex in the Western North Atlantic Ocean
The Smooth Butterfly Ray, Gymnura micrura Bloch & Schneider 1801, is considered a wide-ranging species that occurs in warm temperate and tropical Atlantic waters from the U.S. to Brazil. In shallow coastal regions, G. micrura is common bycatch in demersal fisheries due to habitat overlap with commercially valuable marine resources. However, incidental catch data and life history parameters are lacking for this species in U.S. waters, and the identification of G. micrura has been complicated by morphological variation in this species. Previous taxonomic descriptions do not fully account for sexual dimorphism or other variations in the morphology and life history observed throughout its range, and type material is not available. Resolving the taxonomy of G. micrura is crucial for the assessment of populations and their vulnerability to fisheries interactions. In this study, we revised the taxonomy of G. micrura based on morphological characters, genetics, and life history of specimens from Suriname (type locality) and the Atlantic and Gulf coasts of the U.S. Multivariate ordination (non-metric multidimensional scaling) analyses of morphometric data, discrete morphological characters (e.g. color patterns), and genetic analyses using mitochondrial (ND2, ND4, CO1, Cytb) and nuclear (RAG1) gene sequences revealed a complex of three distinct species across the western Central and North Atlantic. Taxonomic descriptions and life history aspects of G. micrura and the two new species from U.S. waters will be presented, and implications for future assessments of populations will be discussed.
Cassidy Peterson, Robert Latour
Virginia Institute of Marine Science, Gloucester Point, VA, USA
Abundance and Community Interactions of Atlantic Coastal Sharks
Broad-scale analyses of shark population and community dynamics are particularly challenging given the complex life history strategies employed and their vast migratory patterns. Consequently, studies are generally limited to analyzing small-scale, localized dynamics that can be examined from easily accessible, nearshore environments. Survey-based trends in abundance frequently display data conflict, and shark interspecies interactions have never been assessed at a wide geographic scale. We used generalized linear models (GLMs) to estimate annual indices of abundance from eight species of Atlantic coastal sharks from six fishery-independent surveys along the U.S. east coast and within the Gulf of Mexico. These conflicting indices of abundance were input into a dynamic factor analysis (DFA) model with large-scale climatic indices and anthropogenic forces as covariates to produce simplified species-specific trends of abundance for each species throughout the sampled distribution. We input common trends into a multivariate, first-order autoregressive, state-space (MARSS-1) model to estimate interspecies interactions and density dependence. Broad-scale interactions were compared to localized interactions generated from MARSS-1 analyses on GLM-based indices of abundance calculated from individual surveys. Large coastal species showed similar patterns of abundance since 1975, while small coastal species showed more regional variability in abundance. We have been able to quantitatively show density dependence in seven species and seven broad-scale (and three localized) interspecies interactions. These results may assist in assessment efforts by reducing conflicting information input into stock assessment models, and accounting for community relationships that may affect population growth rate of various species.
Nicole Phillips1, David Morgan2
1University of Southern Mississippi, Hattiesburg, Mississippi, USA, 2Murdoch University, Murdoch, Western Australia, Australia
Genetic Bottlenecks in Pristis Sawfishes in Australia
Australia is recognized as the last stronghold for three of the four Pristis sawfishes. This study examined patterns of genetic diversity in Australian Pristis sawfishes to assess their genetic ‘health’ and whether there was evidence of genetic bottlenecks in these populations. Based on data for a portion of the mitochondrial DNA and microsatellite loci, the overall levels of genetic diversity for each of P. pristis, P. zijsron and P. clavata were moderate. However, the assemblages of P. zijsron and P. clavata in northeast Australia appear to have lower levels of genetic diversity than those in the northwest. Furthermore, there is a signature of a genetic bottleneck in all three species that is especially pronounced in P. clavata in northeast Australia. Demographic analyses and preliminary genetic data generated from historic sawfish rostra were used to evaluate whether these declines in genetic diversity were the result of recent bottlenecks or historic founder effects. Understanding temporal patterns of genetic diversity is important in the conservation of critically endangered and endangered sawfishes because it informs on whether the levels of genetic diversity observed in contemporary populations have been sustained for long periods of time or whether they are the result of more recent anthropogenic activities.
Gregg Poulakis1, Karissa Lear3, Rachel Scharer1, Nicholas Whitney2
1Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Charlotte Harbor Field Laboratory, Port Charlotte, FL, USA, 2Behavioral Ecology and Physiology Program, Mote Marine Laboratory, Sarasota, FL, USA, 3Freshwater Fish Group and Fish Health Unit, Centre for Fish and Fisheries Research, School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA, Australia
Where and How do Smalltooth Sawfish, Pristis pectinata, Spend Time in their Nurseries? Insights from Acoustic and Accelerometer Data
In recent decades, use of telemetry to determine general locations of many fish species has improved our understanding of broad habitat use patterns. However, these studies are limited in their ability to provide insights into specific behaviors or reasons for using specific habitats. Recently, acceleration data loggers (ADLs) have been developed to quantify behavioral parameters (e.g., % time active, resting, feeding, mating) based on the animal's movements. Although ADLs provide data on behavior and physiology they do not provide information on animal location. For this reason, we used acoustic and ADL tags concurrently to improve our understanding of endangered Smalltooth Sawfish (Pristis pectinata) ecology in the Peace River, Florida. In 2014 and 2015, seven juveniles (808-1831 mm stretch total length; <2 yr old) were double tagged and one was double tagged twice. Preliminary ADL data analyses have indicated a diel pattern of hourly activity with juveniles more active at night (mean = 77.5% ± 26.5 SE) than during the day (mean = 63.1% ± 31.3 SE). Acoustic data showed that juveniles resided in protected backwater habitats near red mangrove shorelines during the day and moved into open water habitats away from shore at night. Brief events of high acceleration amplitude and frequency, which may be indicative of foraging, occurred during day and night. This suggests that the diel patterns of activity and location within the nursery were not solely related to foraging. Water temperature, depth, and tide will be examined to determine how they may have influenced habitat use.
Bianca Prohaska1, R. Dean Grubbs1, Dana Bethea2, Gregg Poulakis3, Rachel Scharer3
1Florida State University, Tallahassee, FL, USA, 2NOAA Fisheries Panama City Lab, Panama City, FL, USA, 3FWC, Port Charlotte, FL, USA
Physiological Ecology of Smalltooth Sawfish (Pristis pectinata) in Florida Waters
Similar to other species of elasmobranchs, smalltooth sawfish are slow growing, mature late in life, and produce relatively few young, all factors which have contributed to the sensitivity of smalltooth sawfish to dramatic population declines from overfishing, bycatch in commercial fisheries, recreational fishing, and habitat loss. Currently, nothing is known regarding the physiological stress response of these fish to capture or to other physiological challenges such as habitat loss, and in the absence of basic biological data, effective conservation plans cannot be formulated, making populations highly susceptible to further declines. We plan to elucidate the basic stress physiology of these fish over ontogeny, determine the implications of recreational fishing pressures in light of their physiology, and determine if habitat loss has resulted in chronic stress in these fishes. To address these research interests, a blood sample will be immediately collected from the caudal vein of each smalltooth sawfish upon capture to attain a suite of blood chemical parameters that will include: pH, lactate, pCO2, HCO3, K+, glucose, and hematocrit. Preliminary results suggest that the stress response to fishing capture in smalltooth sawfish is relatively low compared to other elasmobranchs examined to date. Additionally, preliminary results indicate that young of the year smalltooth sawfish have a higher stress response to capture than that of juveniles or adults, but this response is still relatively low compared to other elasmobranchs studied to date.
Danielle Quinn1, Julia Whidden2, Trevor Avery1
1Acadia University, Wolfville, Nova Scotia, Canada, 2University of Miami, Miami, Florida, USA
Quantifying and Interpreting Evidence of School and Site Fidelity of Little Skate (Leucoraja erinacea) and Winter Skate (Leucoraja ocellata) in a Spatially Confined Area in the Bay of Fundy, Canada
The overarching goal was to provide a general overview of at-risk species in spatially confined areas, including the identification of potential approaches to analyze movement patterns, and school/site fidelity. The Inner Bay of Fundy is home to several at-risk fish species, including Little skate (Leucoraja erinacea; Near Threatened, IUCN 2009), and Winter skate (Leucoraja ocellata; Endangered, IUCN 2009). These sibling species are sympatric, and inhabit a region with the highest tides in the world, fluctuating nearly 16 m twice daily. Skate movement patterns are poorly understood, particularly when compared to the body of literature that exists on the small and largescale movements of rays and sharks. Uniquely-numbered dart tags were applied to over 2800 little and winter skate at a fixed tagging site from 2012 – 2015, and 5 – 10 % were recaptured. The high frequency of recaptures and temporal span over which these recaptures occurred provide valuable data regarding movement patterns. There was a high frequency of individuals tagged together being caught together, up to three years later. A novel approach to quantifying school and site fidelity was used to describe these patterns. These observations provide insight into the schooling and movement behavior of these at-risk species of skate in the confines of the Inner Bay of Fundy.
Amy Rowley1, Toby Daly-Engel3, Mariana Rego4, Francisco Garcia-Gonzalez5, John Fitzpatrick2
1University of Manchester, Manchester, UK, 2Stockholm University, Stockholm, Sweden, 3University of West Florida, Pensacola, FL, USA, 4Universidade Federal de Pernambuco, Recife, Pernambuco, Brazil, 5Doñana Biological Station, Sevilla, Spain
Sexual Selection and the Evolution of Reproductive Traits in Sharks and Rays
When females mate with multiple males in a single reproductive cycle, sexually selected processes of female mate choice and competition among males can continue after mating has taken place. While genetic analyses have confirmed that female promiscuity is widespread among sharks and rays, the extent of this multiple mating - and thus the intensity of sexual selection - varies considerably among species. Here we consider how post-mating sexual selection drives the evolution of male reproductive traits across elasmobranch species. Males of species in which females mate promiscuously invest more in sperm producing tissue and produce sperm with longer flagella. These findings shed light on evolutionary responses to sexual selection in a basal vertebrate group and provide valuable insights into the breeding biology of this enigmatic group of fishes.
Cassandra Ruck1, Andrea Bernard1, Fabio Hazin2, Rima Jabado3, Mahmood Shivji1
1Save Our Seas Shark Research Center USA, Nova Southeastern University, 8000 N Ocean Drive, Dania Beach, FL, USA, 2Universidade Federal Rural de Pernambuco, Recife, PE 52171-032, Brazil, 3Gulf Elasmo Project, P.O Box 29588, Dubai, United Arab Emirates
Global-Scale Genetic Population Structure and Diversity in the Oceanic Whitetip Shark, Carcharhinus longimanus
The oceanic whitetip, Carcharhinus longimanus, is a circumtropical, pelagic shark of high conservation concern (IUCN Red List: "Critically Endangered" in the W North and W Central Atlantic and "Vulnerable" globally). We present an updated assessment of the global population structure, genetic diversity, and demographic history of this shark based on analysis of two mitochondrial genome regions (whole control region and partial NADH dehydrogenase subunit 4 (ND4) gene) and nine nuclear microsatellite loci. No population differentiation was detected between the north and south Atlantic. However, significant structure was consistently detected between the Western Atlantic and Indo-Pacific Oceans across both mitochondrial and nuclear markers. This population structure was coupled with deep geographic mitochondrial haplotype mixing and evidence of contemporary migration between the Western Atlantic and Indo-Pacific Oceans. We theorize that semi-permeable thermal barriers are responsible for the differentiation between the Western Atlantic and Indo-Pacific. Additionally, a signal of matrilineal structure between the Indian and the Pacific Oceans was detected with AMOVA and pairwise analyses of the ND4 gene (pairwise ΦST = 0.051, P = 0.046; pairwise Jost's D = 0.311, 95% CI = 0.020, 0.061). Relatively low mtDNA genetic diversity (concatenated mtCR-ND4: π = 0.32% ± 0.17%) compared to other globally distributed elasmobranch species raises concern for the future genetic health of these populations. Overall, despite the global distribution and high mobility of C. longimanus, significant population structure exists between the Western Atlantic and Indo-Pacific Oceans, and effective management strategies must take this into consideration.
Jillian Sawyna, Weston Spivia, Kelly Radecki, Deborah Fraser, Christopher Lowe
California State University, Long Beach, Long Beach, CA, USA
Examination of the Potential Association Between Chronic Organochlorine Exposure and Immunotoxicity in the Round Stingray (Urobatis halleri)
Chronic organochlorine (OC) exposure has been shown to cause immune impairment in numerous vertebrate species. To determine if local elasmobranchs exhibited a similar effect due to high OC contamination found along the coastal southern California mainland, innate immune function was compared in round stingrays (U. halleri) collected from the mainland and Santa Catalina Island, a reference site. Microscopy and flow cytometry were used to assess proliferation and phagocytosis in splenic and peripheral blood leukocytes. Percent phagocytosis, and mean fluorescence index (MFI) were evaluated by quantifying % leukocytes positive for, and relative amounts of ingested fluorescent E. coli BioParticles. Total cell proliferation differed between sites, with mainland rays having a higher concentration of cells in whole blood. Splenic mean (± SE) % phagocytosis (24.7 ± 4.98 %) was significantly higher in mainland rays compared to Catalina (9.96 ± 1.18 %). MFI was also greater among the mainland population (2681.74 ± 410.06 and 1197.1 ± 146.97). In blood, mainland rays had a significantly higher % phagocytosis (23.44 ± 2.887 %) compared to Catalina (12.98 ± 1.58 %), yet no difference was found in MFI. ∑PCB and ∑pesticide loads were the most influential factors describing increasing splenic % phagocytosis and MFI, while ∑PCB load alone explained increasing % phagocytosis in blood. Data suggests OC-correlated immunostimulation; however, other site-specific environmental variables may be contributing to the observed effects.
Rachel Scharer1, Philip Stevens2, Gregg Poulakis1
1Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Charlotte Harbor Field Laboratory, Port Charlotte, FL, USA, 2Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, St. Petersburg, FL, USA
Not All Nurseries are Created Equal: Differences in Large-scale Habitat Use Patterns between Two Smalltooth Sawfish, Pristis pectinata, Nursery Areas
Endangered Smalltooth Sawfish (Pristis pectinata) are known to use multiple southwest Florida estuaries during their first 2-3 years of life and understanding region-specific habitat use patterns has become important for effective management. Our research in the Charlotte Harbor estuarine system, was initially focused in the Caloosahatchee River, a highly human-altered river system, and we have now expanded sampling into a more natural area, the Peace River. A total of 238 juveniles ranging from 708 to 2,640 mm stretch total length were captured, tagged, and released between 2010 and 2015. Electivity analyses showed that sawfish in both rivers had affinities for water <1 m deep, water >24°C, moderate to high dissolved oxygen levels (>4 mg l-1), and salinities between 12 and 27. Movements were monitored in main-stem river habitats and non-main-stem habitats (i.e., natural mangrove-lined creeks, semi-natural creeks, seawall-lined canals) using acoustic listening stations. Sawfish used all of the habitats available to them in both rivers, but tended to reside in specific regions of the nurseries. In the Caloosahatchee River, sawfish were usually associated with five hotspots along a 25 river kilometer (rkm) stretch of the river. They moved upriver during dry, low freshwater inflow conditions and downriver during wet, high inflow conditions. In contrast sawfish tended to remain in only a six rkm portion of the Peace River during all freshwater inflow conditions. Possible reasons for these observations relate to differences in geomorphology and freshwater inflow regimes between the rivers.
Institute of Zoology, University of Bonn, Bonn, Germany
Sharks don't just have Sharp Teeth but are also Sharp Thinkers - Cognition in Elasmobranchs
While there has been an upsurge in behavioural studies on fish and even shark cognition in recent years, comparatively few studies have tried to uncover the relevant neuronal substrates involved. Here, learning and memory functions were assessed in bamboo sharks (Chiloscyllium griseum) and freshwater stingrays (Potamotrygon motoro) on a behavioural and neuronal level. Most behavioural studies were performed as two-alternative forced choice experiments, in which the positive stimulus was reinforced by a food reward. Selected spatial and visual discrimination experiments in sharks were complemented by lesion experiments or immediate-early gene expression studies using egr-1 and c-fos to determine involvement of selected brain structures. Sharks and rays successfully mastered selected object recognition and categorization tasks and showed visual perception of illusionary contours, symmetry, and movement, as well as spatial orientation and memory retention capabilities. Both lesion and gene expression studies in sharks indicate that even in the absence of a neocortex, selected cognitive functions are processed in the telencephalon, with some pallial regions matching potentially homologous areas in other vertebrates where similar functions are being processed. Results of these studies indicate that the here assessed cognitive abilities in bamboo sharks and freshwater stingrays are as well developed as in many other vertebrates, aiding them in activities such as food retrieval, predator avoidance, mate choice and habitat selection.
Jason C. Seitz1, Jan Jeffrey Hoover2
1ANAMAR Environmental Consulting, Inc., Gainesville, FL, USA, 2US Army Engineer Research and Development Center, Vicksburg, MS, USA
Taxonomic Resolution of Sawfish Rostra from a Private Collection
Management and recovery of endangered sawfishes worldwide is challenged by unreliability of species determination. Often, dried rostra (saws) are the only vouchered material available to represent an historical occurrence, yet traditional methods of species identification of rostra (rostral tooth counts) are fallible. We evaluated the utility of rostral morphometric characters on classification of specimens from a private collection of 25 old rostra. All rostra available from collectors and donated by fishers were obtained by a single individual (logistics permitting) so we believe the collection is representative of sawfishes globally. Rostrum data consisted of: overall length (used to standardize data), standard length, standard width, distal width, gap between right proximal teeth, gap between right distal teeth, number of teeth on each side (used for species assignments). Principal component analysis (PCA) of morphometric characters was informative. PC1 (x-axis) accounted for 74% variance and was associated with 4 variables (loadings = |0.36−0.43|), PC2 (y-axis) amounted for 14% variance and was associated with a single variable (loading = |0.70|). Point clusters were consistent with putative identifications. On PC1, Anoxypristis cuspidata (Knifetooth Sawfish) plotted low, Pristis pectinata and P. zijsron (smalltooth complex) at intermediate values, and P. microdon and P. perotteti (largetooth complex) at high values. P. pectinata and P. zijsron were separated from each other along PC2, as were P. microdon and P. perotteti. Results demonstrate utility of analyzing smaller collections (N < 40) and suggest that pooled data from private collections can characterize phenotypic variation in sawfish interspecifically and intraspecifically.
Jason Seitz1, John Waters2
1ANAMAR Environmental Consulting, Inc., Gainesville, Florida, USA, 2Aquatic Research & Conservation Society, Inc., Little Canada, Minnesota, USA
Should Florida really be considered part of the historic range for the endangered Largetooth Sawfish (Pristis pristis)?
The U.S. population of the endangered Largetooth Sawfish, Pristis pristis, is among those populations with the highest probability of extinction. Identifying areas with valid historical records of this species is therefore critical as these areas may be important to the eventual recovery of the species. The eastern extent of the U.S. range of P. pristis is reported to include Florida based on only four historical records purported to be from the state: one from southern Florida based on a dried rostrum held at the American Museum of Natural History (AMNH), one from near Clearwater based on a dried whole specimen seen on display, one each from Salerno and Key West based on dried rostra. Three of these records only presume a local capture location, as the capture or landing of each specimen was not observed by the researcher. The AMNH specimen was only presumed to have been collected during the spring 1910 Tecla expedition to southern Florida but evidence indicates to the contrary. This paper discusses more likely scenarios for the appearance of these dried specimens in Florida and the most plausible scenarios as to the source of the AMNH specimen. Given the dubious nature of the four P. pristis accounts purported to be from Florida and the lack of verified vouchered specimens or catches in the state, Florida should be omitted from the range of this species. Texas, or possibly Louisiana, should be considered the eastern-most extent of the species in the United States.
Emily Seubert, Marcus Drymon
University of South Alabama, Mobile, AL, USA
Species and functional biodiversity of apex and mesopredators in the northern Gulf of Mexico
High biodiversity can enhance the resiliency of an ecosystem and hasten the recovery of collapsed populations. Apex and mesopredators often overlap trophic niches, and thus can facilitate the ability of an ecosystem to rebound from a disturbance. To investigate the species and functional diversity of apex and mesopredators across the northern Gulf of Mexico, we plan to analyze catch data from two years of bottom longline surveys conducted in both inshore and offshore waters. Species diversity will be calculated from catch data using standard diversity indices while functional biodiversity will be determined through stable isotope analysis of carbon, nitrogen, and sulfur sampled from two distinct tissue types, white muscle and blood plasma. During the first year of sampling in 2015, 24 bottom longline sets were conducted and 314 individuals from 17 different species were landed. Preliminary results show that overall, offshore sites in Louisiana have the highest diversity while offshore sites in Mississippi contain the lowest diversity. Inshore sites in Alabama had the highest number of species whereas offshore Alabama sites contained the fewest number of species per region. The addition of data collected in 2016 will elucidate the trends from Year 1. Early evidence of high predator diversity across a small spatial scale indicates that the ecosystem may be resilient in the face of environmental disturbances, which are not uncommon in the northern Gulf of Mexico. Investigating the potential for this system to recover from environmental disasters is critical for both preemptive management and post-disaster mitigation strategies.
C. Samantha Sherman1, Andrew Chin1, Michelle R. Heupel2, Colin A. Simpfendorfer1
1James Cook University, Townsville, Queensland, Australia, 2Australian Institute of Marine Science, Townsville, Queensland, Australia
Encountering batoids on coral reefs in Malaysian Borneo
Batoids are emerging as a conservation concern, especially in locations such as South East Asia where fishing pressure is high. In this region, batoids are caught for their meat and skin. Although there is a high diversity of batoids in the region, little is known about their abundances in coral reef ecosystems. The Global FinPrint Project is the first global-scale survey of elasmobranchs in coral reef ecosystems. The project uses baited remote underwater video systems (BRUVS) to determine relative diversity and abundance of coral reef sharks and rays. These data form an important baseline for future studies, and provide data about diversity, abundance and distribution patterns that can inform fisheries and marine park management. In 2015, over 300 BRUVS were set at three sites in Malaysian Borneo in the Tunku Abdul Rahman Park near Kota Kinabalu and in the islands off of Semporna. Preliminary analyses from these Malaysian locations will be presented. Two species were seen most often: the bluespotted maskray (Neotrygon kuhlii) and the blue-spotted ribbontailed ray (Taeniura lymma). Other species were rarely observed, showing that while there is high diversity, many of those species may be quite rare, or perhaps difficult to sample using BRUVS. A cursory inspection of fish markets and of wholesale websites suggests that the bluespotted maskray and blue-spotted ribbontailed ray are amongst the most common batoid species in local markets.
David Shiffman, Neil Hammerschlag
University of Miami, Miami, FL, USA
Intraspecific Variation in the Relative Diet Breadth and Overlap of Coastal Sharks Revealed Through Stable Isotope Analysis
Determination of the diet and ecosystem role of sharks is a research priority that is important for understanding the potential consequences of population declines. Interactions between shark species can vary widely, with documented cases of both resource partitioning and significant diet overlap. We used stable isotope analysis to assess the relative diet breadth and overlap between eleven mesopredatory and apex predatory species of sharks in three distinct South Florida coastal habitats, testing whether the ecological interactions between species remained constant. The relative diet breadth and overlap between shark species was not constant between habitats. The diet of some species pairs overlapped almost 100% in one habitat, but didn’t overlap at all in other habitats. The species with the widest relative diet breadth varied from one habitat to another, as did the species with the highest trophic level. This intraspecific variation between the diet breadth and diet overlap of shark species suggests that the ecosystem role of a marine predator in one environment cannot be reliably inferred from studies in a different environment, and that habitat-specific studies are required.
Oliver Shipley1, Emily Tolentino2, Lucy Howey-Jordan2, Lance Jordan2, Edward Brooks1
1Shark Research and Conservation Program, The Cape Eleuthera Institute, Eleuthera, Bahamas, 2Microwave Telemetry Inc, Columbia, Maryland, USA
Pop-up satellite archival tags reveal the extent of post-release survivorship and vertical habitat use in a data-deficient, deep-water chondrichthyan, the Cuban dogfish (Squalus cubensis)
Pop-up satellite archival tags have proven a valuable method to quantify behavioral modification and the extent of post-release survivorship in large fishes, which are ubiquitously caught in commercial fisheries worldwide. The need to assess these parameters is required within deep-water species, where the effects of fisheries exploitation are exacerbated by extreme K-selected life-history traits. We deployed 7 High Rate pop-up satellite archival tags (PSATs) on the data-deficient (IUCN), medium-bodied, deep-sea shark, the Cuban dogfish (Squalus cubensis), to investigate how experimental capture may affect susceptibility to post-release mortality. We examined: post-release recovery behavior, subsequent vertical movement, and incidents of predation. Data were retrieved from 6 individuals with deployment durations ranging from 5 to 14 days. Recovery periods (defined by <5m vertical movement between consecutive depth records, once individuals had returned to depth) ranged from 0 to 1.5 days among individuals, suggesting some animals required re-acclimatization before becoming active. Half of the tagged animals were consumed by predators within 24 hours of release during the active phase and after the initial recovery period. The three surviving individuals exhibited clear diel-vertical behavior (ca. 24 hour cycle) such that shallower depths were occupied during the night. Animals occupied depths between 903.8 m and 324.1 m and experienced temperatures between 5.83 to 18.26 °C. PSAT data suggest Cuban dogfish may be highly susceptible to post-release mortality, primarily through predation, after being released from longlines. Depth data also suggest this species may be highly susceptible to commercial fisheries capture, through movement across a broad depth range.
Colin Simpfendorfer1, Peter Kyne2, Tansyn Noble1, Julie Goldsbury1, Rose Basiita1, Rob Lindsay3, Amos Shields3, Camillus Perry4, Dean Jerry1
1James Cook University, Townsville, Queensland, Australia, 2Charles Darwin University, Darwin, Northern Territory, Australia, 3Malak Malak Ranger Group, Darwin, Northern Territory, Australia, 4Wudikupildiyerr Ranger Group, Darwin, Northern Territory, Australia
Environmental DNA detects Critically Endangered largetooth sawfish in the wild
Environmental DNA (eDNA) is a relatively new tool for the detection of rare, threatened and invasive species in water bodies. In this study we investigated the utility of an eDNA approach in detecting the Critically Endangered largetooth sawfish, Pristis pristis, in freshwater habitats in northern Australia. Water samples were collected from a large aquaria mesocosm containing sawfish and other aquatic species, and floodplain waterholes and the main river channel of the Daly River, Northern Territory. Water samples were filtered using a 20 µm nylon filter. DNA was extracted from filters and analysed with PCR using species -specific mitochondrial cytochrome oxidase subunit 1 (COI) primers designed to amplify only largetooth sawfish DNA. PCR products were cleaned and the COI gene sequenced to confirm the species identity. Testing this method using three aquaria, one containing a largetooth sawfish, positively identified sawfish only in the correct aquarium. In the field water samples, seven of eight floodplain waterholes produced a sawfish eDNA PCR product, while eDNA was not detected in the main river channel. Based on gillnet sampling and traditional ecological knowledge, sawfish were known to occur at half of the waterhole and floodplain sites that tested positive for sawfish eDNA. These results demonstrated that an eDNA approach to detecting largetooth sawfish can produce reliable results and can be used as a survey tool to help with conservation efforts for this and other threatened elasmobranchs.
Rachel Skubel, Neil Hammerschlag
University of Miami, Miami, FL, USA
Estimates of apex predatory sharks' energetic scope from long-term multi-sensor tags, and applications to climate change
All animals’ performance is inherently limited by temperature. Quantifying a species’ optimal thermal environment, particularly for ectothermic fish whose body temperature is dictated by that of the surrounding water, is necessary in order to project their behaviors with respect to climate change. Here, we demonstrate a novel application of estimation of pop-up satellite archival tag (PSAT) acceleration data to estimate temperature preferences of apex predatory sharks in the wild, including the longest accelerometry record for any organism to date (378 days). For three tiger sharks (Galeocerdo cuvier) and two great hammerhead sharks (Sphyrna mokarran), vectorial dynamic body acceleration (a proxy for oxygen consumption) was calculated from acceleration along three axes, and then related to ambient water temperature to approximate scope for oxygen consumption over a temperature range. Tiger sharks, tracked for 31, 22, and 378 days had greatest oxygen consumption in cooler waters (~1020°C). Great hammerhead sharks, tracked for 8 and 10 days, consistently exploited warm shallow waters. Tiger sharks’ scope for oxygen consumption declined sharply between 30 and 31°C, while great hammerhead sharks appeared not to reach waters warm enough to result in a significant decline. These results (a) suggest that tiger sharks spend most of their time in waters warmer than optimal for oxygen consumption, as a possible tradeoff for foraging and reproduction opportunities, and (b) demonstrate the feasibility of using long-term accelerometry records to obtain physiologically relevant estimates of thermal preferences.
Kelcee Smith1, Sabrina Taylor1, William Kelso1, Michael Kaller1, John Carlson2, Dana Bethea2
1Louisiana State University, Baton Rouge, LA, USA, 2NOAA Fisheries Service - Southeast Fisheries Science Center, Panama City, FL, USA
Estimating Abundance of Smalltooth Sawfish (Pristis pectinata) with Capture-Mark-Recapture Data
In the United States, the Smalltooth Sawfish (Pristis pectinata) is an endangered elasmobranch currently comprising a single population restricted to southwestern Florida. The population has been drastically reduced and fragmented during the 20th century due to overfishing and habitat loss and was listed federally as endangered in 2003. Although habitat use and migration, age and growth, and other life history characteristics have been studied, current abundance remains unknown. Capture-mark-recapture data collected in southwestern Florida from 2009-2015 was used to determine a contemporary census size of juvenile P. pectinata. Data were separated into two cohorts (spring/summer & fall/winter) based on length-frequency distribution in order to minimize zeroes in the dataset. Program MARK was used to estimate recapture probabilities and apparent survival from individual capture histories, assuming a closed population. Models with time dependent capture probability and constant recapture probability estimated 181 and 79 individuals in the spring/summer and fall/winter cohorts, respectively. Estimates of population size largely determine risk of extinction in population viability analysis; therefore, historic population estimates will be compared to contemporary estimates of abundance to assess the extent of the population decline and extinction risk, allowing for more direct and effective management, conservation, and recovery efforts for the species.
Conrad Speed1, Mark Meekan1, Mike Cappo2
1Australian Institute of Marine Science, Perth, Western Australia, Australia, 2Australian Institute of Marine Science, Townsville, Queensland, Australia
Evidence of recovery of shark and ray populations at a remote Marine Reserve in north Western Australia
There is an ongoing debate about the efficacy of Marine Reserves to protect large and highly mobile organisms. Using Baited Underwater Video Stations (BRUVS) as part of the Global FinPrint Project, we assessed whether elasmobranch abundance and diversity has changed with Marine Reserve enforcement at Ashmore Reef, Western Australia. Ashmore Reef is an emergent continental shelf-edge reef in the Indian Ocean, located 800 km west of Darwin and 140 km south of Indonesia. A Commonwealth Marine Reserve was established in 1983, although historically this area was fished by traditional Indonesian fishers. Illegal fishing has since been observed at Ashmore; however Australian Customs have had an ongoing permanent presence at the reef since 2000. We compare archival data from a 2004 BRUVS survey with a recent survey in 2016. We deployed over 100 BRUVS during 2016 around the shallow (0-40 m) reef slope and backreef habitats within the Marine Reserve. The shark assemblage was dominated by Carcharhinus amblyrhynchos in the current and previous surveys. The current survey showed numerous species that were not observed in 2004, such as: Galeocerdo cuvier, Nebrius ferrugineus, Stegostoma fasciatum, and Himantura granulata. Members of the Rhynchobatidae family were also observed more frequently in the current survey. Our results might have been due to a greater extent of spatial sampling in 2016, or seasonal differences in species distribution between the two surveys. We assess how species distribution and abundance varies across habitats, depth, and through time and discuss whether changes to border enforcement have affected elasmobranch populations.
Ashley Stoehr1, Jeanine Donley2, Scott Aalbers3, Doug Syme4, Chugey Sepulveda3, Diego Bernal1
1University of Massachusetts Dartmouth, Dartmouth, MA, USA, 2MiraCosta College, Oceanside, CA, USA, 3Pfleger Institute of Environmental Research, Oceanside, CA, USA, 4University of Calgary, Calgary, Alberta, Canada
Thermal sensitivity of red muscle function in a deep-diving shark
Amongst pelagic elasmobranchs, bigeye thresher sharks (Alopias supercilious) exhibit robust vertical mobility, undertaking routine long-duration dives from the surface (1820˚C) to beneath the thermocline (5-10˚C). Unlike pelagic fishes capable of regional endothermy (e.g., common thresher sharks, swordfish), the subcutaneous red muscle (RM) morphology of bigeye threshers precludes heat retention and results in large RM temperature fluctuations during prolonged dives. This study used the work loop technique to determine if bigeye thresher RM was impaired at cool temperatures or functioned across naturally-occurring temperatures (8, 16, 24˚C). Bigeye thresher RM did not produce positive power above a presumed tail beat frequency of 0.5 Hz, even when warmed to 24˚C. However, RM produced positive power at 8-24˚C and 0.25-0.5 Hz. The lower thermal sensitivity of bigeye thresher RM suggests that fishes lacking RM endothermy exhibit greater thermal independence. This thermal strategy may provide a cost-effective mechanism to facilitate sustained swimming in disparate thermal environments, but may compromise swimming speeds during prolonged cold exposure.
James Sulikowski1, Carolyn Wheeler1, Bianca Prohaska2, Neil Hammerschlag3
1University of New England, Biddeford, Maine, USA, 2Florida State University, Tallahassee, Florida, USA, 3University of Miami, Miami, Florida, USA
Stick it where the sun don’t shine: Advances in the non lethal study of elasmobranch reproductive biology for conservation management
Data on maturity state, gestation period, and fecundity are essential for proper conservation and management of elasmobranchs. Historically, this information has been collected by lethal sampling, an approach that is problematic for threatened and endangered species. Recent studies have demonstrated that non-lethal approaches can be as effective as lethal ones for assessment of the reproductive status of elasmobranchs. Using examples from various species and reproductive modes, this study summarizes our current knowledge of several techniques: 1) analysis of circulating plasma hormones; 2) concentrations of steroid hormones from skeletal muscle tissue; and 3) the use of ultrasonography to discern pregnancy and follicular development and their use as reliable indicators of reproductive status in elasmobranchs.
John Swenson, Karen Crow
San Francisco State University, San Francisco, CA, USA
How the Devil Ray Got Its Horns: The Evolution and Development of Cephalic Lobes
Devil rays and their relatives (Family: Myliobatidae) are derived and highly divergent batoids, with some taxa considered the only living vertebrates with three functional paired appendages. The third set of appendages, termed "cephalic lobes", are modifications of the anterior pectoral fin that evolved to assist with feeding as the myliobatids transitioned from a benthic to a more pelagic lifestyle. To investigate the genetic underpinnings of these unique appendages, we collected embryos from the cownose ray (Rhinoptera bonasus) and will sequence the transcriptome of developing cephalic lobes for comparison with pectoral fin. Preliminary data indicate previously underappreciated genetic pathways may be responsible for modifying multiple regions of the body in this taxon.
Jordan Taylor, Gavin Naylor
College of Charleston, Charleston, SC, USA
A Morphometric approach for assessing the Elasmobranch Fishes from the Late Eocene of South Carolina
Isolated chondrichthyan teeth are the most abundant vertebrate fossils represented in the fossil record, and are widely distributed along the southeastern United States. The coastal plain in South Carolina contains an abundance of chondrichthyan remains from the Eocene epoch. It is distinguishable from other epochs by the presence of distinct, calcareous nannofossil assemblages and levels of dissolved carbon. The Eocene lasted from 55.8 to 33.9 million years ago and is characterized by accelerated global cooling, changes in ocean circulation, and a drop in global temperature of about 2°C. The effects of this climatic transition on fauna diversity have been observed in the calcareous nannofossil assemblage, but have yet to be observed in vertebrate macrofauna, specifically elasmobranchs. The present study aims to identify the diversity and distribution of the elasmobranch fauna using isolated teeth found in the Parkers Ferry formation (33.239068° N, -80.425665°W), which represents a period of cooling in South Carolina. Many extant sharks can be identified on the basis of tooth morphology, which has been typically qualitative in nature. This sorting "technique" has led to taxonomic problems in the fossil record, because there are several patterns of heterodonty that influence tooth shape. In this study, a geometric morphometric technique will be applied to extant and fossil teeth as a quantitative approach to identify the elasmobranch taxa from the late Eocene. The results of the present study will provide a reliable and unbiased method to identifying sharks' teeth.
Thomas TinHan, R.J. David Wells
Texas A&M University at Galveston, Galveston, Texas, USA
Feeding Ecology of Juvenile Bull Sharks in the Northwest Gulf of Mexico
Estuaries along the Gulf coast provide valuable nursery habitat for juveniles of several species of elasmobranchs (e.g. Bull Sharks), but questions remain as to how young sharks exploit resources along the marine-freshwater continuum. In this study, we examine spatial and temporal patterns in the feeding ecology of juvenile (<210 cm total length) Bull Sharks in estuaries along the Texas coast. Juvenile sharks (N = 142) were collected opportunistically from five estuarine complexes along the Texas coast over a two-year period. Stomach contents from all individuals were identified to the lowest possible taxon, and four metrics of dietary composition were calculated: 1) percent number, 2) percent weight, 3) percent frequency of occurrence, and 4) index of relative importance (IRI and % IRI) as an omnibus metric of dietary composition. Stomach contents were dominated by teleost prey, particularly drums/croakers (45% IRI), mullets (25% IRI), and catfishes (13% IRI), and taxonomic contributions to dietary composition were consistent across multiple metrics. Stable isotopes of carbon (δ13C), nitrogen (δ15N) and sulfur (δ34S) obtained from epaxial tissue of juvenile sharks were used to infer trophic position and sources of organic matter in Bull Shark diets. In addition, we examined differences in feeding ecology among sharks from distinct estuarine complexes, and the shifts in diet or trophic position occurring with respect to season or ontogeny. Here we present the results of these analyses and discuss the role Bull Sharks may play in the trophic connectivity of Texas nearshore systems.
Taketeru Tomita1, Chip Cotton2, Minoru Toda3
1Okinawa Churashima Research Center, Motobu, Okinawa, Japan, 2Florida State University Coastal and Marine Laboratory, St. Teresa, FL, USA, 3Okinawa Churaumi Aquarium, Motobu, Okinawa, Japan
Gas diffusion model indicates that oxygen diffusion through uterine wall is insufficient to sustain dogfish embryo
Unlike mammals or some "placental viviparous" sharks, most viviparous elasmobranchs lack connection with the mother, and thus, the embryos must acquire oxygen from the surrounding uterine fluid for a period ranging from several months to more than a year. However, the mechanisms underlying oxygen delivery and uptake in elasmobranchs remain largely unknown. Diagnostic sonography performed on a captive Japanese dogfish (Squalus japonicus) at the Okinawa Churaumi Aquarium demonstrated that a late-stage embryo used buccal movement to pump uterine fluid, suggesting that the embryo acquires oxygen from uterine fluid via gill ventilation. A previous study hypothesized that embryonic respiration in aplacental elasmobranchs depends on oxygen supplied by the uterine wall. To test this hypothesis, the rate of oxygen supply from the uterus was estimated by applying a "gas diffusion model" to the uterine wall of two dogfish species (Squalus cf. mitsukurii and Squalus cubensis). Our model calculations suggested that the supply of oxygen via diffusion through the uterine wall contributes less than 15-30% of the total oxygen demand of late-stage embryos, indicating that uterine wall is not the main source of oxygen for embryonic respiration. Previously, some authors have suggested that pregnant dogfish intermittently exchange uterine fluid with external seawater during late gestation. Thus, late-stage embryos may acquire oxygen primarily from uterine seawater introduced from the external environment.
Maurits van Zinnicq Bergmann1, Tristan Guttridge1, Mark Bond2, Samuel Gruber1, Yannis Papastamatiou2
1Bimini Biological Field Station, South Bimini, Bahamas, 2Florida International University, Miami, Florida, USA
Movement Networks and Habitat Preferences of a Multi-Species Elasmobranch Assemblage in Bimini, Bahamas
Describing the ecological role of a species is contingent upon a holistic understanding of the relationships between animal movement, physical environment, and interactions with con-/heterospecifics. Such interactions define the structure and dynamics of populations and communities. How large predators influence these processes in marine systems, however, remains poorly understood. Here, a combination of passive acoustic telemetry, baited remote underwater video system (BRUVS) and fixed environmental data loggers in an island system in Bimini, The Bahamas, to identify physical (water temperature, depth) and biological drivers (competition, prey availability) of movement, habitat and space use, habitat specificity and spatial hotspots of lemon Negaprion brevirostris (n=14), great hammerhead Sphyrna mokarran (n=20), tiger Galeocerdo cuvier (n=12), nurse Ginglymostoma cirratum (n=14), bull Carcharhinus leucas (n=7), blacktip C. limbatus (n=7), Caribbean reef C. perezi sharks (n=6), and southern stingray Dasyatis americana (n=6). A multi-habitat acoustic array monitored localized movements and residencies, while a data share collaboration of acoustic arrays monitored long-distance movements. BRUV surveys assessed relative abundance and distribution of elasmobranch and prey species for each habitat type that were representative of the Bimini array. Preliminary results revealed singular and diverse habitat use (Caribbean reef and nurse/great hammerhead, respectively), spatial hotspots and concentrated movements (around coral reefs/deep-water drop-off), numerous (trans-national boundary) migrations (nurse, lemon, hammerhead) and long-term, seasonal site fidelity. The creation of mechanistic home range models, through quantification of elasmobranch habitat associations and movement networks, will be vital to delineate key areas for protection and predict home range size and the impacts of anthropogenic perturbations.
Eduardo Villalobos1, Héctor Espinosa1, Paulo Brito3, Jesús Alvarado2
1Instituto de Biología, UNAM, Ciudad de México, Mexico, 2Instituto de Geologia, UNAM, Ciudad de México, Mexico, 3Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
Morphological analysis of the genus Zapteryx (Rhinobatidae: Batoidea) and its phylogenetic implications
The genus Zapteryx is composed of three species, which are distributed in the coasts of the American continent: in the Pacific side Z. exasperata and Z. xyster and in the Atlantic coast Z. brevirostris. This genus poorly studied from the phylogenetic perspective and its phylogenetic relations with other members of the family Rhinobatidae (Aptychotrema, Rhinobatos and Trygonorrhina) are uncertain. Using a parsimony phylogenetic analysis with chondroskeleton characters, the present study seeks to determine the phylogenetic topology of the genus Zapteryx and its phylogenetic relations with the family Rhinobatidae. The phylogenetic analysis included several species from the guitar fishes sensu (Compagno, 1977) and five fossil species of guitar fishes from de Upper Cretaceous. The character review was made via dissections or using images from x-rays and tomographys from specimens kept in the Colección Nacional de Peces, del Instituto de Biología UNAM, the Colección Nacional de Paleontología del Instituto de Geología UNAM, the Ichthyology Collection of the University of the State of Rio du Janeiro and from bibliographical reviews. The matrix for the phylogenetic analysis was elaborated using the program WINCLADA and analyzed using the algorithms of TBR and Ratchet in the program TNT. The results of these analyses show that the genus Zapteryx has not immediate phylogenetic affiliations with the genus Rhinobatos and Aptychotrema and that the family Rhinobatidae could be divided in at least two taxonomic entities of the same hierarchy.
Elizabeth Vinyard1, Walter Bubley2, Bryan Frazier2, Marcus Drymon3, Jim Gelsleichter4
1The Graduate School at the University of Charleston, South Carolina, Charleston, SC, USA, 2South Carolina Department of Natural Resources, Charleston, SC, USA, 3University of South Alabama, Mobile, AL, USA, 4University of North Florida, Jacksonville, FL, USA
Age, growth, and maturation of the Finetooth Shark, Carcharhinus isodon, in coastal waters of the western North Atlantic Ocean
Age, growth, and maturity was examined for Finetooth Sharks, Carcharhinus isodon, in coastal waters of the western North Atlantic Ocean (WNA) from Winyah Bay, South Carolina to Cape Canaveral, Florida. Vertebrae from 190 males and 217 females were aged, and the maximum observed age for males and females was 21.9 years and 22.3 years, respectively. Sizes ranged from 376 mm to 1174 mm FL for males and 380 mm to 1282 mm FL for females. Significant differences were detected between the sexes necessitating sex-specific von Bertalanffy growth models. These models yielded the following equations: Lt = 1141 mm FL - (1 - e -0.279(t-(-1.857))) for males and Lt = 1257 mm FL - (1 - e -0.197(t-(-2.335))) for females. Median length (L50) and age (A50) where 50% of the population is mature were 999 mm FL for males and 1041 mm FL for females corresponding to 6.4 years and 6.9 years, respectively. Significant differences in growth were detected between the current study and previously published parameters for the WNA. The current study found greater observed maximum ages, A50, t0, and L0 for both sexes and greater L50 for females. Both sexes were found to have lower L∞ parameters and males displayed lower L50 and lower k compared to the previous study. Previously no significant differences were detected in growth models from the WNA and Gulf of Mexico (GOM); however, results from the current study as well as reproductive, tagging and genetic studies suggest separate stocks in the WNA and GOM.
Paddy Walker, Irene Kingma
Dutch Elasmobranch Society, Amsterdam, The Netherlands
Baseline Study for Underpinning of the Management of Sharks and Rays in the Dutch Caribbean
In August 2015 the Save our Sharks project was launched in the Netherlands and the Dutch Caribbean. This is a 3 year campaign which aims to stop the decline of sharks and rays in the Dutch Caribbean. During the project dedicated research, stakeholder involvement and participatory development of management measures should ultimately lead to better protection of the elasmobranchs around the islands. The project will focus on: education on the importance of sharks in the marine ecosystem; working with local fishermen to find solutions workable solutions to stop shark (by)catches; working with government to realise effective management and control of shark populations; and enhancing the scientific knowledge needed for conservation and management. In this talk we will present the first results of the project, including baseline studies carried out around the islands of Saba and St Maarten using Baited Remote Underwater Videos (BRUVs) and tagging studies carried out using acoustic tags. The results will be put into the context of broader conservation and management measures and the need for international collaboration.
Ornella Celine Weideli1,4, Yannis Papastamatiou2, Mahmood Shivji3, Michael Heithaus2, Rainer von Brandis4, Serge Planes1
1CRIOBE USR3278-EPHE-CNRS-UPVD, Perpignan, France, 2Florida International University (FIU), North Miami, FL, USA, 3Save Our Seas Shark Research Center (SOSSRC) NOVA University, Dania Beach, FL, USA, 4Save Our Seas Foundation D'Arros Research Centre (SOSF-DRC), D'Arros Island, Seychelles
Resource Partitioning and Competition in a Mutually Used Shark Nursery
Traditional theoretical approaches predict that resource partitioning is crucial to the coexistence of ecologically and morphologically similar species, as it minimizes competition among sympatric species. This partitioning may occur through divergence in resource use or through differences in spatial and temporal habitat use. Coastal reef sharks often use lagoons as nursery areas for their young, where inter-specific competition may be particularly high. At St. Joseph Atoll, Seychelles, two sympatric juvenile shark species, the sicklefin lemon shark, Negaprion acutidens, and the blacktip reef shark, Carchahinus melanopterus, use shallow flats as a communal nursery. Both shark species are viviparous with no maternal care, therefore inexperienced and opportunistic behaviour is assumed to lead to niche overlaps and competition. Investigation of competition within shark nurseries at fine spatial scales are lacking, despite its importance for coastal nursery management. We investigated spatial and temporal niche partitioning using active tracking. We quantified dietary overlap using visual and molecular analysis of stomach contents (DNA barcoding), and analysis of stable isotopes (SIA) of red blood and plasma tissues. Preliminary results show various degrees of spatial and trophic segregation between the two species. If niche partition results through the avoidance of competition, or if it is shaped by species-specific food or habitat preferences, remains to be proven.
Monique Welten1, Moya Meredith Smith3, Charlie Underwood4, Zerina Johanson2
1University of Bristol, Bristol, UK, 2Natural History Museum, London, UK, 3King's College, London, UK, 4Birkbeck University of London, London, UK
Teeth inside and outside the mouth: an X_CT analysis of topographic relationships in sawshark and sawfish dentitions (Elasmobranchii; Chondrichthyes)
The origin and evolution of teeth is still under debate, with competing hypotheses seeking to explain their evolutionary origins. Teeth and tooth-like structures, odontodes, are present both externally (skin denticles, scales) and internally (oropharyngeal teeth). Sharks and rays have been studied intensively to address evolutionary origins of teeth, since their dermal scales show great similarity to their oral teeth. According to the ‘'Outside in'' theory, teeth evolved from skin denticles after the ancestral mouth cavity evolved by invagination of the skin. The 'Inside out'' hypothesis however, suggests that teeth evolved independently from skin denticles. Tooth-like structures are also found on the elongate ‘saw' in three chondrichthyan groups: the sawfish, the fossil Scelorhynchidae; and the sawsharks. These ‘'teeth'' differ from oral teeth and skin denticles, presenting a challenge in understanding their morphology and patterning, and relation to either skin denticles or oral teeth. We used Computed Tomography to study growth and replacement patterns of ‘'saw -teeth'' in embryos, adults and fossils of these groups, to compare with their skin denticles and jaw teeth. Our results showed that in the sawfish ‘'saw-teeth'' are of equal size and retained during life. By contrast, in sawsharks, the ‘'saw-teeth" are of various sizes; and are replaced irregularly, but in a size-specific manner. Strikingly, saw-teeth in the fossil sawfish Sclerorhynchus show many similarities in morphology to those of sawsharks, despite the lack of close phylogenetic relationships. We conclude that the saw ‘'teeth'' are specialized skin denticles, functioning as feeding and prey-obtaining structures.
John Whalen, Jim Gelsleichter
University of North Florida, Jacksonville, FL, USA
Multibiomarker evaluation of pollutant effects in Atlantic stingray (Dasyatis sabina) populations in Florida's St. Johns River
The goal of this study was to examine the potential health effects of polychlorinated biphenyl (PCB) and polycyclic aromatic hydrocarbon (PAH) exposure on Atlantic stingray populations in Florida’s St. Johns River (SJR). Special emphasis was placed on identifying PAH- and/or PCB-related effects in stingrays from areas of the lower SJR basin that have been shown to possess elevated levels of these compounds, as well as characterizing baseline levels of pollutant exposure in other areas that may be subjected to dredging in the near future, potentially resuspending contaminated sediments and increasing pollutant associated effects. To accomplish this, we measured PCB and PAH biomarker levels in D. sabina collected from contaminated sites and reference locations. We specifically examined the biomarkers cytochrome P4501a1 (CYP1a1), a Phase I detoxification enzyme; glutathione-S-transferase (GST), a Phase II detoxification enzyme; fluorescent aromatic compounds (FACs), PAH bile metabolites; lipid peroxidation (LPO), cell membrane damage; and thyroid epithelial height (TEH), an assessment of endocrine disruption-induced hypothyroidism. Enzymatic activity of CYP1a1 and GST was measured using the EROD assay and a GST Assay Kit, while LPO was measured with an OxiSelect TBARS Assay Kit. FACs were measured using fixed wavelength fluorescence and TEH was analyzed histologically. Biomarker levels of individuals collected from contaminated sites were compared to individuals collected from reference sites. The data suggest that pollutant biomarker levels in SJR D. sabina did not differ significantly from those measured in individuals from reference locations. However, the close proximity of high biomarker levels to known contaminated areas suggests continuous exposure.
Catharine J. Wheaton1, Andrew N. Evans2, John M. Rimoldi3, Rama S. V. Gadepalli3, Bobbi R. O’Hara4, Natalie D. Mylniczenko1
1Animals, Science and Environment, Disney’s Animal Kingdom® and The SEAS with Nemo and Friends®, Lake Buena Vista, FL, 32830, USA, 2Department of Coastal Sciences, University of Southern Mississippi, Ocean Springs, MS 39564, USA, 3Department of Medicinal Chemistry, University of Mississippi, University, MS 38677, USA, 4Research and Development, Arbor Assays L.L.C., Ann Arbor, MI, 48108, USA
Development and Preliminary Validation of a Monoclonal Antibody for Enzyme Immunoassay of the Steroid 1α-hydroxycorticosterone in Selected Elasmobranch Species
Measurement of 1α-hydroxycorticosterone (1αOH-B), the putative primary stress and ionoregulatory hormone for shark and ray species has been of significant biological interest and a major scientific challenge for over 50 years. Previous research relied on measurements using techniques such as thin-layer chromatography, ultraviolet absorption spectra, or high-performance liquid chromatography of incubates from interrenal glands or large volumes of blood, often pooled from multiple individuals. Although commercial enzyme immunoassays (EIA) are available for corticosterone, those tested exhibit only low relative cross-reactivity to 1αOH-B (3-5%). To improve measurement of 1αOH-B, we developed a monoclonal antibody using a synthesized 1αOH-B derivative for testing in a double-antibody EIA system. Relative displacements of cross-reactant compounds showed good sensitivity for 1αOH-B and 11-dehydrocorticosterone with low reactivity to related steroids including corticosterone. Adjustment of incubation times and titration of the antibody and conjugate concentrations increased sensitivity of the EIA for 1αOH-B (range 4-12 ng/ml, 90% binding). Banked serum and plasma samples from selected elasmobranch species managed at The SEAS with Nemo and Friends® were used to validate sample treatment and extraction protocols to optimize measurement of 1αOH-B in <1 ml of sample. Improved measurement of 1αOH-B in sharks and rays will be important for many aspects of collection, transport, medical treatment, and aquaria and conservation management of these charismatic and ecologically important species.
Connor White1, Kady Lyon1, Kevin Weng3, Chuck Winkler2, Salvador Jorgensen3, John O'Sullivan3
1California State University Long Beach, Long Beach, CA, USA, 2Southern California Marine Institute, Terminal Island, CA, USA, 3Monterey Bay Aquarium, Monterey, CA, USA
Movement of Juvenile White Sharks in Southern California: Predicting Future Nursery Habitat
The white shark, Carcharodon carcharias, is an apex predator with a circumglobal distribution and a low intrinsic growth rate that is listed as vulnerable by the IUCN. While considerable information is known for adults, there is limited information on the movements, environments, and distributions of juvenile white sharks (JWS). Understanding this life stage is important as JWS experience considerable overlap with human activities and juveniles often have the highest mortality of any life stage. In an effort to quantify JWS movements and understand their distribution in the Southern California Bight, JWS were captured and outfitted with satellite transmitters (SPOT tags: n=20). There was a large amount of variability in number of geopositions rendered (Class 0-3: 645 locations; mean: 36, range: 0-130), with individuals having a higher probability of detection later in the day (1700-2000). Some individuals (n=9) displayed movements south of the United States border into Baja California, Mexico. A generalized linear model with a binomial distribution was used as a resource selection function to predict presence of individuals based on depth, distance to shoreline, and daily sea surface temperature (SST). Sharks were found to significantly select shallow habitats (<2500 m) close to land (<50km) at temperatures between 15.6 and 24.3C. The model predicts sharks to move to Baja California during winter and a higher probability of JWS in southern California during El Niño years.
Stacia White1, Katy Duke2, Paula Carlson3, Alan Henningsen4, Katherine Hunter5, Richard Preziosi5, Jennifer Rountree5, Graham Hill2, John Fitzpatrick6
1Ripley's Aquariums, Inc., Myrtle Beach, SC, USA, 2The Deep, Hull, East Yorkshire, UK, 3Dallas World Aquarium, Dallas, TX, USA, 4National Aquarium, Baltimore, MD, USA, 5The University of Manchester, Manchester, UK, 6Stockholm University, Stockholm, Sweden
Making Connections for Sawfish: The Role of Public Aquaria in Sawfish Biology and Conservation
Aquaria are important partners in sawfish science and conservation. Important messages are communicated to millions of aquarium visitors by providing face – to - face encounters with living sawfish in a unique educational setting. The global decline of sawfishes is increasing the need for conservation of fragile coastal habitats. Public aquaria can build on these connections, to promote conservation solutions. Collaboration across many disciplines is vital for successful conservation of sawfishes, and aquaria can contribute alongside with academic institutions, conservation organizations, field research groups, government agencies and the local populations. All stakeholders can benefit from information exchange, and the implementation of knowledge on sawfish biology, ecology, and conservation. The IUCN Shark Specialist Group’s Global Strategy for Sawfish Conservation provides a framework for collaborative sawfish conservation, including opportunities for aquaria to participate in conservation education, research and public awareness. The Association of Zoos and Aquariums’ (AZA) Species Survival Plan and the European Association of Zoos and Aquaria (EAZA) Studbook, population management programs for pristids, provide member facilities a forum in which to share important data collected about their animals, and work collaboratively on sawfish husbandry, research and conservation. Current research at The Deep is developing non-invasive methods of DNA collection from elasmobranch species in collaboration with the University of Manchester. These methods have produced usable quantities of material for DNA analysis which the way forward for the establishment of a central identification DNA database of captive Pristis as proposed in the IUCN Strategy. These programs provide additional platforms for communication and collaboration with other stakeholders to promote sawfish science and conservation. Although the focus is on how aquaria have and can contribute to sawfish research and conservation, the greatest opportunity and need is for future collaboration with aquaria worldwide and other important stakeholders through existing as well as new programs and strategies.
William White1, Sharon Appleyard1, Leontine Baje2, Benthly Sabub2
1CSIRO National Research Collections Australia, Hobart, Australia, 2National Fisheries Authority, Port Moresby, Papua New Guinea
Preliminary Investigation into Sawfish Catches in Papua New Guinea
During a larger project on the shark and ray fisheries of Papua New Guinea which commenced in 2014, records of sawfish catches were collated and anecdotal information from fishers collected. Tissue samples, photographs and morphometric measurements from dried rostra and/or fins were taken from any sawfish observed during artisanal surveys. Also, an observer program on prawn trawlers in the Gulf of Papua collected data and samples from any sawfish captures. All four species known to occur in the area (Anoxypristis cuspidata, Pristis clavata, P. pristis and P. zijsron) were recorded in the fishery catches. Anoxypristis cuspidata was by far the most abundant species caught. Most records were from the Gulf of Papua but records also taken from Manus, Rabaul and Bougainville. The difficulties in collecting such data in Papua New Guinea and the best way to continue acquiring good data and providing capacity building tools are discussed.
Jeff Whitty1, James Keleher1, Adrian Gleiss1, Brendan Ebner2, Colin Simpfendorfer3, David Morgan1
1Murdoch University, Perth, Western Australia, Australia, 2CSIRO, Atherton, Queensland, Australia, 3James Cook University, Townsville, Queensland, Australia
Heterogeneous habitat use of the critically endangered largetooth sawfish (Pristis pristis) in a riverine nursery
Understanding the habit use and selection of a species is important for identifying environments and resources that it is dependent upon. However, these subjects can be complex and often involve a balance of multiple abiotic and biotic rewards and risks. This study used acoustic monitoring to assess the movements of 32 juvenile largetooth sawfish (Pristis pristis) in association with various abiotic and biotic variables in the Fitzroy River, Western Australia between 2008 and 2015, in order to determine which nursery habitats and resources are important to this critically endangered species. Pristis pristis demonstrated an affinity for deep-water runs and pools with high concentrations of large woody debris in the day-time, when activity was lowest, and for shallow-water habitats, such as glides, in the night-time, when movement and distance travelled significantly increased. Depth selection changed in response to the time of day, with individuals occupying deeper depths in the day-time and shallower depths in the nighttime, moving between these depths in accordance with light intensity, regardless of the habitat type. Mean hourly depth of P. pristis also decreased through the dry season as temperatures increased and river stage height decreased. These results highlight that habitat use and selection of juvenile P. pristis are not static and that the species uses a range of riverine microhabitats. Given the threatened status of P. pristis, these habitats, which are largely unprotected in Australia, need to be strategically managed to promote juvenile survivorship and conservation of this species.
Tonya Wiley-Lescher1, Adam Brame2
1Haven Worth Consulting, Palmetto, Florida, USA, 2NOAA Fisheries Service Southeast Regional Office Protected Resources Division, St. Petersburg, Florida, USA
Endangered Species Act Five-year Review and Recovery Plan Updates for US Smalltooth Sawfish, Pristis pectinata
The United States distinct population segment (DPS) of smalltooth sawfish (Pristis pectinata) was classified as Endangered under the US Endangered Species Act (ESA) in 2003. A recovery plan for the US DPS of smalltooth sawfish was published in 2009 detailing goals and actions necessary to meet identified recovery criteria. To monitor recovery efforts and ongoing threats to the species, the ESA requires the status of the species be assessed through regular 5-year reviews. The first review was completed in 2010 and, based on criteria established in the recovery plan, determined the species still warranted protections afforded by an Endangered classification. Recently a second ESA 5-year review was commenced and will determine if the listing classification of Endangered under the ESA is still appropriate. Changes to the recovery plan, including revised recovery goals and criteria, are also underway. Updating the plan, and the recovery criteria it contains, will help scientists and managers work toward restoring the sawfish population in the US to the point where it is a secure part of its ecosystem and protections under the ESA are no longer needed. Results of the second 5-year review and updated recovery plan will be presented.
Barbara Wueringer1, Teagan Marzullo1, Vera Schluessel2
1Sharks And Rays Australia, Bungalow, Queensland, Australia, 2University of Bonn, Institute of Zoology, Bonn, Germany
Sawfish research in Queensland, Australia
For four species of sawfish, i.e. the green sawfish Pristis zijsron, the dwarf sawfish Pristis clavata, the freshwater sawfish P. pristis and the narrow sawfish Anoxypristis cuspidata, the waters of Northern Australia are likely to represent their last global stronghold. The organization Sharks And Rays Australia is currently undertaking a project assessing the distribution and abundance of these four sawfish species in Northern Queensland, focusing on Far North Queensland, the Cape York region and the coastline of the Gulf of Carpenteria. The region north of Cairns is only sparsely populated by approximately 28,000 people. A large percentage of the 2500 km coastline and rivers are believed to be an important habitat for sawfish. The aim of Sharks and Rays Australia will be to determine the status quo and review the limitations of the current knowledge on the occurrences of sawfish within this region. The methods of our study, including a tagging study, collaborations with local indigenous rangers and the involvement of the public, will be presented together with preliminary results and future aims for the expansion of this study.
Jennifer Wyffels, Linda M. Penfold
South-East Zoo Alliance for Reproduction & Conservation, Yulee, FL, USA
Comparative Morphology of Shark Sperm Using Light and Electron Microscopy
Elasmobranch spermatozoa studied so far are characterized by a conical acrosome, helical nucleus, long mitochondria-rich midpiece, and helical tail. Semen was collected from 5 sharks (Carcharias taurus, Chiloscyllium plagiosum, Chiloscyllium punctatum, Mustelus canis, and Carcharhinus limbatus) for comparative light and scanning and transmission electron microscopy. Spermatozoa had a species-specific number of gyres or twists (C. plagiosum 32, C. taurus 17, M. canis 11, and C. limbatus 5) that continued into part of the midpiece for C. plagiosum, C. punctatum, and M. canis. The midpiece was composed of glycogen granules and mitochondria with concentric cristae. A cytoplasmic sleeve, analogous to the cytoplasmic droplet of other vertebrates, was located at the junction of the midpiece and flagellum and was shed via movement down the flagellum over time after semen collection. For all species the flagellum contained two ovoid longitudinal columns adjacent to the axoneme at doublets 3 and 8. In contrast to the other sharks, the nucleus of C. limbatus underwent changes with cell death that manifested as foci of nuclear expansion from DNA decondensation. C. punctatum and C. plagiosum spermatozoa were observed to be capable of both forward and backward motility. Reverse motility for spermatozoa is a remarkable feature not reported for other species.
Kara Yopak1, Barbara Wueringer2, Kirk Feindel3, Shaun Collin1
1University of Western Australia, Crawley, WA, Australia, 2Sharks And Rays Australia, Bungalow, Qld, Australia, 3Center for Microscopy Characterisation and Analysis, UWA, Crawley, WA, Australia
What you Saw Isn’t always What you Get: Patterns of Brain Organization in Sawfishes
Broad variability has been documented within cartilaginous fishes regarding the size and complexity of the brain and its major components (olfactory bulbs, telencephalon, diencephalon, mesencephalon, cerebellum and medulla). This variability is often associated with habitat or specific behavior patterns, even in phylogenetically unrelated species that share certain lifestyle characteristics. However, few studies to date have examined the brain in species that have convergently evolved morphological specializations, such as the protruded “saw” rostrum of sawfishes and sawsharks, which is used for detecting and/or manipulating prey. This study examined the brains of four species of sawfishes, including representatives from the Anoxypristis and Pristis genera, in comparison to the sawshark Pristiophorus cirratus and an existing dataset of approximately 100 other chondrichthyan species, which differed with respect to their phylogeny and ecology. Brains were assessed in these critically endangered species using magnetic resonance imaging (MRI), which allowed for non-invasive interrogation of the organization of the central nervous system and the quantification of different brain regions. Results show dramatic differences in both relative brain size and brain morphology between sawfishes and sawsharks, which reflect their phylogenetic and ecological divergence. Of particular note is the variation in size and complexity of the corpus cerebellum, a region of the brain thought to be responsible for executing fast and efficient movement in these ancient predators. Results support the assertion that the saw-like rostrum may serve different functions in these two divergent taxa and that their brain organization may reflect a range of behavioral and ecological specializations.