Matthew Ajemian1, Philip Jose1, John Froeschke2, Gregory Stunz1
1Harte Research Institute for Gulf of Mexico Studies, Texas A&M University-Corpus Christi, Corpus Christi, TX, USA, 2Gulf of Mexico Fishery Management Council, Tampa, FL, USA
Trends and Characterization of the Land-based Recreational Shark Fishery off Texas
Most analyses of shark population trends use seasonally-limited fishery-independent data that generally neglect important nearshore coastal habitats (i.e.,<20m bottom depth). The Texas coast supports one of the largest year-round, land-based recreational shark fisheries in the United States. However, no studies have characterized the catch composition and overall trends in this fishery despite its beginnings several decades ago. We used fishery-dependent data from two distinct periods (historic = 1973-1986, and modern = 2008-2014) to assess the status of the nearshore shark community off Texas. Monthly catch records from both data sets were examined using multivariate techniques to examine seasonality in shark assemblages as well as potential shifts in catch composition over time. These fishery-dependent data revealed relatively distinct assemblages by season (ANOSIM Global R = 0.159; P = 0.0001) and period (ANOSIM Global R = 0.222; P = 0.0001). Similarity Percentange analysis showed a general shift in shark community assemblage from larger to smaller species. Most notably, Bull Shark (Carcharhinus leucas) dominance decreased over time while Blacktip Shark (Carcharhinus limbatus) contribution increased. Our analyses also identified a large decrease in mean total length (TL) of Bull Sharks from 232.8 cm to 175.1 cm and a modest increase in Blacktip Shark size from 125.1 cm to 127.9 cm TL. These findings document a significant change in the size and composition of Texas’ nearshore shark community potentially driven by overfishing and removal of large (>2 m) sharks. Future management decisions should account for these removals as stocks are rebuilt to historical levels.
Brenda Anderson1, Carolyn Belcher2, JoAnn Slack3, James Gelsleichter1
1University of North Florida, Jacksonville, FL, USA, 2Georgia Department of Natural Resources, Brunswick, GA, USA, 3University of Pennsylvania School of Veterinary Medicine, Kennett Square, PA, USA
The Use of Ultrasonic Imaging to Detect Reproductive Activity in Female Bonnetheads (Sphyrna tiburo)
Ultrasonography has become a widely used diagnostic tool in the veterinary field, following its introduction to obstetrics in humans in the 1960s. Traditional methods for investigating shark reproduction include euthanasia and dissection, which is not conducive to studying large or endangered sharks and are usually fatal to embryos. Ultrasound machines have not been widely used in shark research due to the machine’s fragile construction. The purpose of this study was to determine reproductive activity in female bonnetheads (Sphyrna tiburo) using a field-ready ultrasound machine and to compare the “gold standard” dissection method to ultrasound methods by determining their level of agreement. Female sharks (n = 71) were collected, euthanized, externally examined via ultrasound, and uteri dissected to determine reproductive activity. Presence and number of eggs and/or embryos were recorded using 8 MHz linear and 5 MHz curvilinear transducers. Contents of the uteri were dissected and counted. Kappa statistic was used to compare the level of agreement between the different methods: dissection to curvilinear transducer, dissection to linear transducer, and linear to curvilinear transducers. Dissection versus curvilinear transducer methods resulted in 88.9% agreement (Kappa coefficient = 0.7798). Dissection versus linear transducer methods resulted in 61.3% agreement (Kappa coefficient = 0.4192). Linear versus curvilinear transducer methods resulted in 97.3% agreement (Kappa coefficient = 0.9510). Overall, the ultrasound was a good indicator of presence of eggs/embryos in the bonnethead. Limitations of ultrasonography include image quality, gut content interference, and stacking of pups in utero.
James Anderson1, Kim Holland2
1University of Hawaii, Honolulu, HI, USA, 2Hawaii Institute of Marine Biology, Kaneohe, HI, USA
Holy Grail, Needle in a Haystack, or Wild-Goose Chase: Searching for a Shark Magnetoreceptor
The physical basis of magnetic field perception in both vertebrates and invertebrates has been the subject of debate for some time, with three hypotheses prevailing above others. The elasmobranch fishes (sharks, skates and rays) are the only class hypothesized to use their electrosensory capability in the perception of geo-magnetic stimuli. Other taxa argued to orient to or via the geomagnetic field have been hypothesized or demonstrated to use alternative mechanism. One such theory is the magnetite hypothesis, whereby intracellular crystals of the iron oxide magnetite (Fe3O4) are coupled to mechanosensitive channels that give rise to neuronal activity in specialized sensory cells. Efforts to find these primary sensory structures have failed to convincingly describe receptor locations, illustrating the need to develop new methods to test the magnetite hypothesis of magnetoreception. Here we describe an ongoing study that aims to identify and describe suitable candidate sensory cells in both the olfactory and vestibular organs of the Scalloped Hammerhead shark (Sphryna lewini). We report upon the efficacy of a novel approach to identify candidate cells, and in turn report efforts to both quantify and qualify cells with magnetic properties that could function in the perception of magnetic stimuli.
Allen Andrews1, Michelle Passerotti2, Lisa Kerr3, Lisa Natanson4, Sabine Wintner5
1NOAA Fisheries – PIFSC, HI, USA, 2NOAA Fisheries – SEFSC, FL, USA, 3Gulf of Maine Research Institute, ME, USA, 4NOAA Fisheries – NEFSC, RI, USA, 5KwaZuluNatal Sharks Board, Durban, South Africa
Maximum Age and Missing Time in Shark Vertebrae: The Limits and Validity of Age Estimates Using Bomb Radiocarbon Dating
Bomb radiocarbon dating has become a common tool in determining valid measures of age for large shark species. In most cases, estimates of age were made by counting growth-band pairs in vertebrae and usually in the corpus calcareum of vertebral cross-sections. These estimates of age have been either supported or refuted using measured radiocarbon values (reported as ∆14C) that are equated to a year-of-formation, and subsequently compared to an appropriate ∆14C reference record. While the approach seems straightforward, the application is not and an effective ageing project may require some significant assumptions that are sometimes overlooked. Two of the most important considerations are the sources of carbon available to the vertebrae and the use of a valid ∆14C reference to provide validated age estimates. Recent findings for some species indicate the vertebrae cease growth and as a consequence ages have been underestimated by decades (i.e. sand tiger shark, Carcharias taurus). However, proper alignment of the ∆14C measurements from vertebral samples to the ∆14C reference record does not always provide well-defined ages and many are still considered estimates that require some assumptions (i.e. white shark, Carcharodon carcharias). The aim of this presentation is to provide an overview of how bomb radiocarbon dating can work for shark vertebrae with some insight on how the method can fall short of expectations.
Csilla Ari1, 2, 3, Dominic D`Agostino1
1University of South Florida, FL, USA, 2Foundation for Oceans of the Future, Budapest, Hungary, 3Manta Pacific Research Foundation, HI, USA
Sensory and Cognitive Experiments on Giant Manta Rays
Large, complex and highly foliated brain of Mobulid species suggest good sensory abilities and complex social behavior. The largest brain of all fish species is possessed by manta rays with exceptionally large optic tectum and telencephalon among elasmobranchs. Visual accuracy and wavelength sensitivity were tested on two captive giant manta rays and evidence for visual threshold and wavelength discrimination abilities were found. Self-recognition is one of the more advanced cognitive skills, which has never been proven in any fish species so far. Manta rays have high encephalization quotient similarly to those species that passed the mirror self recognition test, therefore mirror exposure experiments were conducted on two captive giant manta rays to document their response to their mirror image. The present studies show contingency checking and self-directed behavior of manta rays when exposed to a mirror, implying higher order brain function, sophisticated cognitive and social skills.
Charles Bangley, Roger Rulifson
East Carolina University, Greenville, NC, USA
Is Pamlico Sound, North Carolina a “New” Nursery Habitat for the Bull Shark (Carcharhinus lecuas)?
The bull shark (Carcharhinus leucas) is a seasonal visitor to North Carolina nearshore and estuarine waters, but juveniles have historically been rare in the state’s waters. Catch and environmental data from North Carolina Division of Marine Fisheries gillnet and longline surveys were used to determine the suitability of Pamlico Sound as bull shark nursery habitat. All sharks were classified as adult, age 1+, or neonate based on recorded total length (mm). Generalized linear models were used to identify environmental and spatial factors related to the presence of each bull shark demographic. From 2007-2014, a total of 48 bull sharks were captured within the sound, of which 36 fell within age 1+ or neonate ranges. Bull sharks within juvenile length ranges were not captured prior to 2011, but were documented every year since. Environmental preferences did not differ significantly between age 1+ and neonate sharks, but adults were found at significantly greater depths and in closer proximity to inlets. Juvenile bull shark abundance was significantly related to temperature and salinity. Significant increases in mean water temperature and decreases in mean salinity occurred in Pamlico Sound from 2007-2014, particularly in May and June when parturition occurs in other bull shark nurseries. These environmental changes may have created favorable conditions for a bull shark nursery in Pamlico Sound.
Christine Bedore1, Nicholas Wegner2
1Georgia Southern University, Statesboro, GA, USA, 2Southwest Fisheries Science Center, National Marine Fisheries Service, La Jolla, CA, USA
Sensory Ecology of Elasmobranch Fishes
The sensory systems of chondrichthyan fishes are thought to represent the basal vertebrate condition from which more advanced modalities arose. Additionally, elasmobranch fishes inhabit nearly every marine environment and correspondingly represent a wide range of ecological adaptations. Therefore, elasmobranchs demonstrate an impressive array of sensory adaptations that correspond to their individual niches and provide ideal subjects for studying sensory adaptation to biological and physical environments. For example, most batoids possess duplex retinae comprised of rod and cone photoreceptors, although the potential for a species to have color vision varies with the spectral composition of the habitat. Cownose rays, Rhinoptera bonasus, have two cone pigments with color sensitivity that corresponds to their turbid, green-dominated, estuarine habitat. Similarly, yellow stingrays, Urobatis jamaicensis, have three cone pigments that correlate to their inhabitance in clear, spectrally rich reef-associated waters. Additionally, differences in visual temporal resolution, the ability to track moving objects, differs between these two species with the active, schooling cownose rays suffering a lower reduction in temporal resolution with decreases in ambient light levels and temperature. The reduced thermal sensitivity, combined with possession of a cranial rete, suggests that cownose rays may use cranial endothermy, or “brain warming”, to minimize reductions in nervous and sensory function when challenged with environmental temperature changes. Due to their small size relative to most cranial endotherms, as well as their ease of collection and maintenance in the laboratory, cownose rays make ideal models for testing unresolved hypotheses regarding sensorydriven evolution of cranial endothermy in fishes.
Joseph Bizzarro1, Simon Brown2, Heather Robinson2, David Ebert2, Adam Summers1
1University of Washington, Seattle, WA, USA, 2Pacific Shark Research Center, Moss Landing, CA, USA
How Can There Be So Many Skate Species?
Skates (Rajiformes: Rajidae) are an extremely diverse group of cartilaginous, marine fishes; yet, they have historically been considered to occupy unconsolidated habitats and serve similar trophic roles. The hypothesis of ecological redundancy in skates was evaluated using diet composition data from two eastern North Pacific skate assemblages (central California, western Gulf of Alaska). Species-specific diet compositions differed significantly in both regions, supporting the alternative hypothesis of trophic separation in skates. The timing and location of hauls was the most important consideration in explaining the substantial dietary variability in each assemblage and reinforces the perception that skates are generalist predators. Dispersion analyses were highly significant, however, indicating additional extreme within-group variability in skate diet among these variables. Canonical correspondence analysis was used to associate specific variable factors with prey taxa and supported the general concept of greater piscivory and less reliance on small crustaceans with increasing total length. Diet composition and trophic level of Beringraja binoculata and Raja rhina differed considerably between regions and indicated a greater reliance on crustaceans in Alaska and fishes in California. These results, coupled with those of a complementary study of spatial relationships, demonstrate that skates are more ecologically diverse than previously reported. Pronounced differences in core resource use across broad, overlapping spectrums of trophic and spatial tolerances: 1) probably facilitate the coexistence of speciose skate assemblages, and 2) may explain the remarkable taxonomic diversity in this group. Ecological studies and fishery management plans that incorporate ecosystem considerations should incorporate species-specific data for skates.
Darcy Bradley1, Eric Conklin2, Yannis P. Papastamatiou3, Douglas J. McCauley4, Kydd Pollock2, Amanda Pollock5, Bruce E. Kendall1, Steve D. Gaines1, Jennifer E. Caselle6
1Bren School of Environmental Science and Management, University of California Santa Barbara, Santa Barbara, CA, USA, 2The Nature Conservancy, Hawai’i, Honolulu, HI, USA, 3School of Biology, Scottish Oceans Institute, University of St Andrews, St Andrews, Scotland, UK, 4Department of Ecology, Evolution, and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA, 5U.S. Fish and Wildlife Service, Honolulu, HI, USA, 6Marine Science Institute, University of California Santa Barbara, Santa Barbara, CA, USA
Managing a Moving Target: A Spatially Explicit Capture-recapture Reef Shark Population Density Estimate at an Unfished Coral Reef
Baseline population estimates are lacking for most species of reef shark. The grey reef shark (Carcharhinus amblyrhynchos), which is listed as Near Threatened on the IUCN Red List of Threatened Species, is highly mobile and therefore particularly difficult to monitor. At the same time, its mobility is precisely what has stymied its protection in much of the world – without understanding the spatial behavior of reef sharks, it is impossible to design spatial management strategies to protect them. Shark abundance through both space and time can be better estimated by directly accounting for reef shark movement in population estimates without the biases inherent in diver-based visual surveys. A spatio-temporal understanding of animal movement and abundance also allows managers to identify critical habitats, movement between habitats, and track changes to population size and structure. To directly address and incorporate animal movement in estimates of reef shark population size and density, we used a spatially explicit capture-recapture model from an eight year capture-recapture program augmented with telemetry data to produce the first baseline population density estimate of grey reef sharks and to further describe their spatial and temporal distribution at Palmyra atoll, a remote U.S. National Wildlife Refuge in the central Pacific Ocean. We found that diver based visual surveys had significantly over estimated shark density at an island wide scale. While our analysis revealed density ‘hot spots’, sharks also underwent regular excursions around the atoll, indicating that large scale spatial protection is necessary to recover reef shark populations globally.
Heather Brekke2, Nicholas Dulvy1
1Simon Fraser University, Vancouver, British Columbia, Canada, 2Royal Roads University, Victoria, British Columbia, Canada
Does it Matter How Many Sharks are Killed Each Year?
The number of elasmobranchs killed each year has become a key communication message used to raise public awareness of the plight of sharks, skates, and rays. The total number killed alone may divert attention from conservation success and the true problems, priorities, and actions. We illustrate this with an analysis of extent and pattern of catches of elasmobranchs within Canadian Pacific commercial fisheries over the past 30 years (1980–2013). In Canada, few elasmobranchs are subject to directed commercial fisheries, but some are incidentally caught in fisheries targeting teleosts. A total of 208,642 tonnes of elasmobranchs was recorded in Canadian Pacific waters over the thirty-year period, with most (93%) of weight comprised of the commercially valued elasmobranchs: Spotted Spiny Dogfish (Squalus suckleyi), Big Skate (Raja binoculata), and Longnose Skate (Raja rhina). Most (three-quarters) of the catch was retained and catch retention has changed little over the last 30 years. Overall, on average, nearly two million sharks, skates, and rays have been killed each year and there has been an 80% decline in catch over the last decade. While such statistics could be used to support what Hilborn has called the “litany of decline”, it seems instead that almost all of the recent catch has been sustainable and taken within scientifically set catch limits. Furthermore, the steep decline in catch is more likely to reflect a combination of declining market demand and improved management resulting in the emergence of sustainable elasmobranch fisheries.
Aaron Carlisle1, Mark Denny2, Nishad Jayasundara3, Adrian Gleiss4, Elliot Hazen1, Heidi Dewar1, Salvador Jorgensen5, Barbara Block2, Steven Bograd1
1NOAA Southwest Fisheries Science Center, Monterey, CA, USA, 2Stanford University, Pacific Grove, CA, USA, 3Duke University, Durham, NC, USA, 4University of Western Australia, Perth, WA, Australia, 5Monterey Bay Aquarium, Monterey, CA, USA
Linking Thermal Physiology with Habitat Availability in Juvenile Lamnid Sharks
Sharks in the family Lamnidae are unique in that they are endothermic, and maintain an elevated body temperature relative to ambient water temperature. An inability to maintain an elevated body temperature in response to thermal challenges can have serious consequences on the survival and fitness of these sharks. This is particularly relevant for neonates and small juveniles which may be thermally limited due to their low thermal inertia, potentially restricting them to moderate or warm water temperatures in which they are able to maintain elevated core temperatures. These potential thermal requirements provide us with a unique opportunity to explore the thermal niche of young juvenile lamnid sharks and model potential nursery habitats based on temperature. We created a biophysical heat-balance model for three species of lamnid shark (white, mako, and salmon sharks) to investigate the theoretical lower thermal limits of juvenile lamnid sharks and explore how this limit changes with size. Model results were compared to the observed thermal niche of juvenile lamnid sharks based on survey, bycatch and electronic tag data from their shared nursery area of the California Current. Understanding the mechanisms which may define thermal limits for these sharks allows us to investigate how physiology interacts with environmental conditions to influence habitat availability across spatial and temporal scales and through ontogeny.
Diana A. Churchill1, Michael R. Heithaus1, R. Dean Grubbs2
1Florida International University, Miami, FL, USA, 2Florida State University, Tallahassee, FL, USA
Estimating the Trophic Position of Deep-water Sharks and Associated Species Using Compound-specific Nitrogen Isotope Analysis of Amino Acids
The ability to estimate trophic position is an important step in understanding the ecological roles of deep-sea animals. Determining absolute trophic levels using whole tissue stable isotope analysis is often problematic because of the inter- and intra-specific variation associated with trophic discrimination factors. Some of this variability may be eliminated by using compound-specific nitrogen analysis of proteinaceous amino acids. Using this technique, we were able to estimate the trophic position of numerically abundant deep-sea organisms. Tissue samples were collected from demersal fish (sharks, hake, tilefish, and cutthroat eels) and benthic scavengers (giant isopods, hagfish, crabs and shrimp) captured at depths of 200-1500 m along the northern slope (NGS) and the west Florida slope (WFS) of the Gulf of Mexico during 2011 and 2012. Whole muscle tissue δ15N analyses reveal that these consumers span approximately 2 trophic levels, with the armed nylon shrimp (Heterocarpus ensifer) at the lowest relative trophic position and the little gulper shark (Centrophorus cf. uyato) at the highest. Compound-specific analyses will determine absolute trophic positions for the sampled deep-sea animals using source and trophic amino acid δ15N values as well as examine possible isotopic baseline differences between the NGS and WFS.
Christopher Clark1, Yukun Lin1, Jerry Hsiung1, Connor White2, Christopher Lowe2
1Harvey Mudd College, Claremont, CA, USA, 2California State University Long Beach, Long Beach, CA, USA
Planning, Control, and State Estimation for Animal Tracking with Autonomous Robots
The field of robotics has generated viable solutions to the planning, control and state estimation problems encountered when enabling mobile robots with autonomous capabilities. In this talk, such solutions are presented in the context of a particular application: the use of underwater robot systems for autonomous tracking of individual fish tagged with acoustic transmitters. Over the past 4 years, a multi-AUV (Autonomous Underwater Vehicle) system has been developed that is equipped with hydrophones and receivers to detect, localize, and autonomously follow tagged individuals. Experiments conducted in Big Fisherman’s Cove, CA demonstrate localization errors on the order of 6 meters when tracking tagged boats. When deployed to track tagged leopard sharks, the AUVs are able to track and follow the individuals for hours at a time, while simultaneously obtaining environment data, (e.g. bathymetry). AUV Path Planning is accomplished via graph search algorithms that ensure AUV paths do not intersect with obstacles or kelp beds. Decentralized AUV control laws enable the AUVs to circle a moving individual without affecting the animal’s behavior. Particle Filter state estimation algorithms are leveraged to successfully track the individual in real-time. Most recently, individuals have been tagged with a “smartTag” that houses an acoustic transmitter, video camera, automatic release system, and Inertial Measurement Unit. The use of this smartTag has decreased fish position estimation error by a factor of 2, and orientation estimation error by a factor of 4. Notably, the hardware and software techniques utilized are generalizable to a large class of tracking applications.
Paul J. Clerkin1, Jenny M. Kemper2, David A. Ebert1
1Pacific Shark Research Center, Moss Landing Marine Laboratories, Moss Landing, CA, USA, 2Hollings Marine Lab, Medical University of South Carolina, Charleston, SC, USA
Investigation and Taxonomy of Southwestern Indian Ocean Chimaeridae
Historically understudied, the Chimaeriformes (Chondrichthyes: Holocephali) has received increased attention over the past decade and half, with the expansion of deep-sea fisheries, with 19 species having been described. Despite this recent focus, 59% of all known chimaeras are data deficient as accessed by the IUCN. This lack of information is due to taxonomic uncertainty and the intrinsic complexities associated with sampling at great depth in remote areas. The Southwestern Indian Ocean (SWIO) offshore ecosystem is a poorly explored, remote region characterized by extreme topology that includes the massive Madagascar Ridge. This region is punctuated by seamounts that function as isolated underwater islands, supporting high abundance of fish, and a number of chimaera species. Currently, very little is known about SWIO Chimaeras, since only two species have been verified from the area, Hydrolagus africanus, and Chimaera notafricana. During two surveys (2012 and 2014) onboard a commercial deep-sea trawler in the SWIO offshore, six distinct species of Chimaeridae (4 Chimaera, 2 Hydrolagus) were collected. A comprehensive set of morphometric and meristic measurements, and genetic samples were collected from each specimen encountered. Comparisons with geographic congers using standard morphological methods along with comparative genetic samples were made between SWIO offshore chimaeras and those from South Africa, Australia, and New Zealand to investigate similarities and differences between these geographical regions. Taxonomic resolution of this enigmatic Chondrichthyan group will lead to improved species-specific identification.
Daniel Coffey, Kim Holland
Hawaii Institute of Marine Biology, University of Hawaii at Manoa, Kaneohe, HI, USA
In Situ Measurements of Dissolved Oxygen from a Vertically Migrating Deepwater Shark, the Bluntnose Sixgill (Hexanchus griseus)
Advances in biologging technology have enhanced our understanding of the ecology of marine animals and have been central to identifying how contemporary oceanographic conditions establish patterns in their distribution and behavior. In particular, the impact of dissolved oxygen on the vertical distribution of marine animals is becoming increasingly recognized. Insights into the impact of oxygen on vertical movements would be advanced by in situ measurements of dissolved oxygen from animal-borne sensors instead of relying on model-derived, climatological data. Here we demonstrate the capabilities of a novel dissolved oxygen pop-up satellite archival tag (DO-PAT) by presenting the results from calibration experiments and trial deployments on bluntnose sixgill sharks (Hexanchus griseus). The DO-PATs provided fast, accurate, and stable measurements in calibration trials and conductivity-temperature-depth (CTD) vertical profiles. In addition, initial deployments on H. griseus effectively captured the oceanography of the region when compared with World Ocean Atlas 2013 values. This is the first study to demonstrate the use of an animal-borne device for measuring in situ dissolved oxygen saturation. The information returned from DO-PATs is relevant not only to the study of the ecology of marine animals but will also become a useful new tool for investigating the physical structure of the oceans.
Toby Daly-Engel1, Dean Grubbs2, Rebecca Varney1, Erin Pereira1, Shawn Larson3
1University of West Florida, Pensacola, FL, USA, 2Florida State University, Tallahassee, FL, USA, 3Seattle Aquarium, Seattle, WA, USA
Strange Things Happen When You Turn Back the Molecular Clock: Evolution and Speciation in Sixgill Sharks (Genus Hexanchus)
It is largely unknown what selective forces impact evolution and speciation in the deep ocean, though this ecosystem is thought to be largely unchallenged by climatic change relative to shelf and coastal habitat. Fossil records and recent genetic analyses indicate that sixgill sharks (Hexanchus, Hexanchidae) are members of the first extant shark taxon to emerge following the shark batoid-split approximately 300 MYA. Unlike other Squalomorph lineages, many of which moved inshore to shallower shelf habitat and consequently diversified widely over evolutionary time, sixgills remain a primarily deep-water group, which may have contributed to their low speciation rates. Here we explore the factors that shape sixgill shark diversification in the deep ocean. DNA was collected from 130 Hexanchus griseus and 9 H. nakamurai from 13 collection sites across a global range. We sequenced four mitochondrial and nuclear genes plus 11 microsatellite loci, and found low molecular diversity across the genome relative to other shark species of a similar size. Coalescent analysis indicates a deep evolutionary split within H. griseus resulting in multiple well-defined global clades, one Indo-Atlantic and one restricted to the Pacific. We also show a deeper split within H. nakamurai that has resulted in at least one previously-unknown cryptic species, located in the West Indian Ocean. A molecular clock for the mtDNA control region and calibrated to the emergence of the Isthmus of Panama confirmed that rates of evolution in sixgills is dramatically lower than that of other shark taxa.
Lindsay Davidson, Nicholas Dulvy
Simon Fraser University, Burnaby, Canada
Conservation Priorities and Political Responsibilities for Chondrichthyans
Global areas with concentrations of biodiversity (hotspots) are often prioritized for conservation and management action. The first hotspot analysis found that 1.5% of the earth’s land surface area contained almost half of the world’s threatened endemic plants and 30% of threatened vertebrates. The term hotspot has heretofore become a blanket term for finding concentrations of biodiversity using a variety of measurements. For example, the majority of marine analyses have described hotspots based on species richness patterns. Species richness patterns, however, are driven by common species. Therefore basing conservation and management actions on species richness patterns would not protect the most rare or vulnerable species. Here, we use a systematic conservation planning approach to determine the location of global marine hotspots as originally defined by Myers (2000). We define hotspots as global marine areas with concentrations of threatened, endemic chondrichthyans. We found the highest counts of threatened endemics in the national marine waters of, in descending order, Brazil, Taiwan, Uruguay, Argentina, and South Africa. Just over half of the 13 countries with the greatest number of threatened endemics in their national waters have a National Plan of Action (NPOA) for Sharks or finning regulation in place. Only one of the countries, Australia, has a NPOA that meets >65% of the objectives of sustainable fishing. This information can be used to inform the use of limited resources for the conservation of marine threatened species.
Texas Parks and Wildlife Dept, Pleasure Island, TX, USA
Plasma Solute Properties, Movements, and Structure of Bull Shark, Carcharhinus leucas, Populations in Sabine Lake and Lake Pontchartrain: A Comparative Study
The euryhaline bull shark, Carcharhinus leucas, is found in many coastal habitats throughout the Gulf of Mexico. The C. leucas populations were sampled in two estuarine systems to assess structure, movements, and osmoregulatory parameters: Lake Pontchartrain, Louisiana and Sabine Lake, Texas. The population structures were similar in both locations with mean size and sex not being significantly different through analysis of University of New Orlean’s Nekton Research Laboratory data from 2000-2013 and Texas Parks and Wildlife Coastal Fisheries data from 1986-2015. The C. leucas movements were seasonally influenced based on temperature in both areas according to an acoustic receiver monitoring array and seasonal collections. The plasma solute concentrations were determined from blood taken during the last year in each location. The Na+, K+, Cl–, Mg2+, Ca2+, urea and TMAO concentrations were significantly different between locations. Lake Pontchartrain is more stable in regards to salinity than Sabine Lake and as a result Sabine Lake bull sharks exhibited more fluctuation in these solute concentrations throughout the seasons. In summary, comparisons of two C. leucas populations from two distinct coastal habitats resulted in similar movements and structure while revealing a fluctuation in plasma solute concentrations due to variable salinity levels.
Melissa Gonzalez De Acevedo, Jim Gelsleichter
University of North Florida, Jacksonville, FL, USA
Hormone Regulation of Sperm Storage in Female Bonnethead Sharks (Sphyrna tiburo)
Female sperm storage is a phenomenon that has evolved in many different taxa, allowing viable sperm to be retained in the reproductive tract for an extended time period. Previous studies have determined that reproductive hormone may play an important role in regulating various aspects of sperm storage in certain vertebrates, including the long-term survival of sperm and its release near the end of the storage period. However, to date, no published studies have investigated the hormone regulation of sperm storage in the reproductive tract of female elasmobranchs despite evidence for this phenomenon in several shark species. Therefore, the purpose of this study was to investigate if gonadal steroid hormones such as 17β-estradiol, androgens, and progesterone, which have been shown to increase in circulation during various periods of sperm storage, may play in regulating this poorly understood process. To accomplish this, circulating concentrations of gonadal sex hormones and the distribution of sex steroid receptors in the oviducal gland, the sperm storage organ of female sharks, were examined in the bonnethead (Sphyrna tiburo), an annually-reproducing species known to store sperm for a 3-6 month period between copulation and ovulation/fertilization. As demonstrated in previous studies, female bonnetheads exhibited increases in circulating steroid concentrations both during (testosterone, 17βestradiol) as well as near the end (progesterone) of the sperm storage period. Immunocytochemical analysis of androgen, estrogen, and progesterone receptors in the oviducal gland demonstrated that epithelial cells of sperm-storage tubules and spermatozoa itself are direct targets for these hormones.
Simon Dedman1, Rick Officer1, Deirdre Brophy1, Maurice Clarke2, David Reid2
1Galway-Mayo Institute of Technology, Galway, Co. Galway, Ireland, 2Marine Institute, Rinville, Co. Galway, Ireland
Modelling Abundance Hotspots for Data-poor Irish Sea Rays
Skates and rays represent one of the most vulnerable components of the fish community in temperate demersal fisheries such as the Irish Sea. They also tend to be data poor in comparison to commercially exploited teleost fish. Spatial management has been suggested as an important tool in protecting these species, but requires an understanding of the abundance distribution, and its relationship with the environment at both adult and juvenile life history stages. In this analysis, delta log-normal boosted regression tree models were used with bottom trawl survey data to derive rays’ spatial abundance, and environmental links. The modelling approach allowed the development of detailed predictive maps of abundance of four common and rare skate and ray species implicated in the fishery: thornback, spotted, cuckoo and blonde rays. The distributions were driven by a general preference for sand and courser substrates, higher salinities, temperatures and currents speeds. The abundance distribution maps were examined together with maps of skate and ray commercial landings, suggesting that the main hotspots for the species were away from the main commercial fishing areas. The maps were also compared to potential MPAs proposed for wider ecosystem protection, and the main hotspots were well covered by the proposed MPAs. This combination of the main abundance hotspots in areas of low fishing, and wider potential ecosystem protection, suggests good potential for spatial management measures to protect these species in the Irish Sea.
Hayley DeHart1, Gavin Naylor1, Bryan Frazier2
1College of Charleston, Charleston, SC, USA, 2South Carolina Department of Natural Resources, Charleston, SC, USA
Comparing Demographic and Genetic Estimates of Population Sizes in Three Coastal Shark Species
Sharks are widely held by the scientific community to be threatened with extinction, and yet they remain some of the most poorly understood marine vertebrate organisms. There is belief among marine conservation biologists that population genetics based approaches can be used to distinguish species, populations, and even population sizes for these threatened animals. Estimating population sizes using multiple estimates, as well as multiple species, is critical to understanding true population sizes and life history traits that affect these estimates. This study aims to estimate census population size (Nc) and compare this demographic value to the genetically determined effective number of breeders (Nb). Census size will be estimated from an on-going demographic mark and recapture study conducted by South Carolina Department of Natural Resources and estimated using the program MARK. Effective number of breeders will be estimated using a cross-species gene capture method and variability will detected in these data to estimate effective number of breeders using the program NeEstimator. These methods will be deployed on three separate shark species: bonnetheads (Sphyrna tiburo), finetooth sharks (Carcharhinus isodon), and sandbar sharks (Carcharhinus plumbeus). These species all exhibit different population structure, life history, and recapture rates, which may in turn affect their Nb/Nc ratio, a value that may be used for future conservation regulation. It is believed that the comparisons between these estimates and species may be used for population assessment and management of coastal shark species.
Michael Doane, Elizabeth Dinsdale
San Diego State University, San Diego, CA, USA
Revealing a Physiological Role of Shark Skin Through Microbial Community Analysis
Sharks are apex predators that support an unnoticed yet diverse consortia of microbial organisms. Microbial life is inherently involved in the health of sharks but little is known of baseline composition of the shark microbiota. Shark skin is the first line of defense against pathogenic environmental microbiota. We hypothesized the boundary layer would yield structured microbial communities that were distinct from the water column microbiota. Microbes were collected from the base of the first dorsal fin of 6 Common thresher sharks (Alopias vulpinus) in the California Bight using a “supersucker” method. DNA was processed for shot-gun metagenomics and sequenced using Ion Torrent technology. The MG-RAST platform was used to annotate the resulting genomic data, which yielded an average of 936,614 high quality sequences having an average sequence length of 180 base-pairs. Each metagenome yielded an average of 577,797 sequences with protein coding motifs but of those only 2.9 to 8.2% matched known protein sequences in the SEED database. Microbial communities were more similar within shark samples than the water column microbial communities (PERMANOVA, p=0.003). Potential functional composition of microbial communities was also more similar to other shark samples than to the water column (PERMANOVA, p<0.001). Highly structured, distinct microbial communities on the skin surface suggest sharks possess physiological processes that are selective on microbial associates. Sharks produce a thin integument mucus layer that likely acts to regulate microbial activity, similar to that of teleost fishes. Our findings build on the understanding of shark interactions with their surrounding environment.
Drew Duckett, Gavin Naylor
College of Charleston, Charleston, SC, USA
Maximizing Statistical Power in Shark Population Structure Analyses
Next Generation Sequencing technologies developed in recent years allow for the collection of substantially more DNA sequence data than has previously been possible. However, the comparative utility of the various kinds of molecular markers now available for exploring population genetic questions has not yet been thoroughly evaluated. Few population genetics studies test the statistical power of the marker types used or the sampling schemes employed for answering the question posed. Using too few loci, the incorrect marker type, or inadequate sampling can severely compromise the statistical significance of research findings obtained. The present study explores the differences in statistical power associated with different molecular marker types, different numbers of marker loci, and different sampling schemes for analyzing population structure. These issues are addressed through both computer simulation and empirical data sets of three shark species with different life history characteristics. The results of the present study will serve to guide researchers as to which markers are most appropriate for different kinds of questions and increase knowledge of the population structures of the shark species evaluated.
New Jersey Institute of Technology, Newark, NJ, USA
Biomechanics of Shark Swimming
The mechanics of the heterocercal tail in sharks is a classic problem in functional vertebrate biology. Because sharks lack a buoyant swim bladder, their ability to produce lift and balance torques while swimming has long been a subject of research and debate in the field of vertebrate locomotion. Just as understanding the kinematic motions of the shark tail required three-dimensional analysis, new three-dimensional fluid dynamics tools allow us to view complex swimming instantaneously without trying to assimilate data from multiple two-dimensional data sets. Recently, I have discovered not only how sharks are able to produce lift, but also how they are able to modulate their tail stiffness to generate nearly continuous thrust.
Shark Advocates International, Washington, DC, USA
Spotlight on the Small and Flat: Conservation Status Updates for Select U.S. Atlantic Dogfish, Skates, and Rays
While large sharks continue to be a popular focus for conservation attention, smaller, flatter species actually hold the national titles for elasmobranch depletion, recovery, and landings, as well as most and least protected species. As the most commercially important U.S. shark, the spiny dogfish (Squalus acanthias) has been to driven to depletion and back, regulated through quotas that once severely restricted fishing yet now grossly exceed demand. Lagging more than a decade behind in basic assessment and management is the similarly sized Atlantic smoothhound or “smooth dogfish” (Mustelus canis), which feeds poorly understood markets and is the nation’s sole subject of the world’s weakest ban on shark “finning.” A complex of Northwest Atlantic skates (Family Rajidae), used for food and bait, supports the country’s largest elasmobranch fishery, yet the American public’s concern for the overfished species is outweighed by growing appreciation for eating skate wing, thereby allowing for less than rigorous recovery actions. Despite the now notorious “Save the Bay, Eat a Ray” industry campaign, Americans appear more interested in appreciating cownose rays (Rhinoptera bonasus) in touch tanks than on their plates. Still, this exceptionally vulnerable, unassessed species continues to be taken without limit as bycatch and in tournaments. The focus for ensuring the recovery of Florida’s Endangered Smalltooth Sawfish (Pristis pectinata) has shifted from securing legal safeguards to restoring adequate funding for implementing the recovery plan, particularly programs to prevent mishandling. Following the latest conservation status updates, recommendations for improvement will be offered.
Dewayne Fox1, Bradley Wetherbee2, Symone Johnson1, James Kilfoil1
1Delaware State University, Dover, DE, USA, 2University of Rhode Island, Kingston, RI, USA
Development of a Multifaceted Conservation Plan for Sand Tigers (Carcharias taurus) in the Delaware Bay and Nearshore Coastal Waters
Due to their large size, feeding habits, abundance, and prolonged periods of occurrence, Sand Tigers (Carcharias taurus) serve as apex predators for the Delaware Bay and much of the surrounding nearshore coastal waters. Likely a result of their restricted summer movements and overlap with humans, they unfortunately suffer the consequences of intentional and accidental takes in fisheries. Most problematic is the recently developed and apparently increasing recreational sector targeting this prohibited species. Adding to our concerns is the fact that the fishery has increased in size and popularity after Sand Tigers were listed as a Species of Concern by NOAA-NMFS. Facing a growing problem, the State of Delaware implemented regulatory changes in 2011 in an effort to increase survival of recreationally landed Sand Tigers. While these changes have likely led to reductions in angling pressure, a more unified approach is required to conserve and recover this species. Our plan includes enhanced protection of core Sand Tiger habitats, working with anglers to change practices and/or implement use of conservation engineering approaches, as well changes in cooperative tagging programs and scientific/aquaria collections. While the State of Delaware has taken large steps to educate the public on the need for improved angling practices, the lack of higher level support cannot help but undermine the state’s efforts. Ultimately, to be successful and applicable to the US northwest Atlantic Sand Tiger population as a whole, a number of state and federal agencies, as well as local stakeholders must cooperate.
Bryan Frazier1, Dana Bethea2, William Driggers3, Robert Hueter4, John Tyminski4
1South Carolina Department of Natural Resources, Charleston, SC, USA, 2NOAA Southeast Fisheries Science Center, Panama City, FL, USA, 3NOAA Southeast Fisheries Science Center, Pascagoula, MS, USA, 4Mote Marine Laboratory, Pensacola, FL, USA
Growth Rates of Bonnetheads (Sphyrna tiburo) from the Western North Atlantic Ocean Estimated from Tag-Recapture Data
Regional variation in growth has been observed for multiple species of elasmobranches. Recently, published age and growth models for bonnetheads (Sphyrna tiburo) reported larger than expected life history differences between sharks from the eastern Gulf of Mexico and off the coast of South Carolina. Growth can be estimated independent of age by using length based growth models. A maximum likelihood approach (GROTAG) was used to analyze direct growth estimates from tag-recapture derived data. Region and sex-specific models were generated allowing investigation of regional growth, and likelihood ratio tests were used to determine optimal parameterization of the models. Parameters explored included individual growth variability, seasonal growth, measurement error and outliers for each data set. A comparison of region-specific length based models to published age-based models for bonnetheads will be discussed.
Mark Grace1, Michael Doosey2, Henry Bart2, Gavin Naylor3
1NOAA/NMFS, Pascagoula, MS, USA, 2Tulane University Biodiversity Research Institute, Belle Chasse, LA, USA, 3Hollings Marine Institute, Charleston, SC, USA
First Record of a Pocket Shark (Mollisquama sp.) from the Gulf of Mexico
Kitefin sharks of the family Dalatiidae (Squaliformes) comprise 7 genera of which five are monotypic; the highest percentage of monotypic genera for any family in the order Squaliformes. One of the rarest monotypic dalatiids, Mollisquama parini Dolganov, 1984 was described from a single female specimen collected from the Nazca Submarine Ridge in the southeast Pacific Ocean. A second Mollisquama specimen was captured during a 2010 midwater trawl survey of the northern Gulf of Mexico conducted by NOAA/NMFS Southeast Fisheries Science Center, Mississippi Laboratories. Both the holotype of M. parini and the Gulf of Mexico specimen possess the remarkable pocket gland with its large slit-like external opening located just above the pectoral fin. Features found on the Gulf of Mexico specimen that were not noted in the description of M. parini include a series of ventral photophore agglomerations and a modified dermal denticle surrounded by a radiating arrangement of denticles just posterior to the mouth. Phylogenetic analysis of NADH2 gene sequences places Mollisquama sister to Dalatias plus Isistius within the family Dalatiidae.
Alexander Hansell1, Steve Kessel3, Lauran Brewster4, Steve Cadrin1, Greg Skomal5, Samuel Gruber6, Tristan Guttridge2
1University of Massachusetts – Dartmouth, Fairhaven, MA, USA, 2Bimini, Biological Field Station, Bimini, Bahamas, 3University of Windsor, Windsor, Canada, 4University of Hull, Hull, UK, 5Massachusetts Division of Marine Fisheries, New Bedford, MA, USA, 6Rosenstiel School of Marine and Atmospheric Science, Miami, FL, USA
Coastal Shark Assemblage, 11 – Year Fishery-Independent Shallow Water Longline Survey in 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. An 11-year (2004-2014) standardized, shallow water longline assessment was conducted monthly in the eastern coastal waters of Bimini, Bahamas. Each survey was comprised of five longline sets of 15 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. Seasonal trends indicate an abundance of nurse, blacktip, and lemon sharks during the warmer months. Over the course of the study, there was an increase in the tiger shark population. Nurse, blacktip, and lemon shark numbers were relatively stable. Preliminary general additive models indicate that catch rates are influenced by month, year, temperature, tide, soak time, and lunar cycle.
Hannah Hart1, Andrew Evans2, Jim Gelsleichter1, Greg Ahearn1
1University of North Florida, Jacksonville, FL, USA, 2University of Southern Mississippi Gulf Coast Research Lab, Ocean Springs, MS, USA
Molecular Identification and Functional Characteristics of Peptide Transporter 1 (PEPT1) in the Bonnethead Shark (Sphyrna tiburo)
Elasmobranchs are considered top predators with worldwide distribution, and in general these fish play an important role in the transfer of energy from the lower to the upper trophic levels within marine ecosystem. Despite this, little research regarding the rates of prey ingestion, digestion, and processes of energy and nutrient absorption have been explored. Specifically understudied is enzymatic digestion within the intestinal brush border that functions to break down macromolecules into smaller subunits for luminal absorption across the gastrointestinal epithelium. Given their carnivorous diet, the present study sought to expand knowledge on nutrient intake in elasmobranchs by focusing on the uptake of products of protein metabolism. To accomplish this, Peptide Transporter 1 (PEPT1), a protein found within the brush border membrane (BBM) of higher vertebrates that is responsible for the translocation and absorption of small peptides released during digestion by luminal and membrane- bound proteases, was molecularly identified in the bonnethead shark (Sphyrna tiburo) using degenerate primers based on conserved portions of known PEPT1 sequence in Atlantic stingray. The transporter was also localized by immunocytochemistry with rabbit polyclonal antirat PEPT1 and the Vector ImmPRESS anti-rabbit kit in all the same organs. Vesicle studies were used to identify the affinity of the transporter, and to quantify the rate of uptake using 3H-glycylsarcosine. Such results provide insight into the rate and properties of food passage within S. tiburo, and can lead to topics such as physiological regulation of protein metabolism, and how it may vary in elasmobranchs that exhibit different feeding strategies.
Eric Hoffmayer1, Jennifer McKinney2, Jill Hendon3, James Franks3, Brett Falterman2, William Driggers1
1National Marine Fisheries Service, Pascagoula, MS, USA, 2Louisiana Department of Wildlife and Fisheries, Baton Rouge, LA, USA, 3Gulf Coast Research Laboratory, Ocean Springs, MS, USA
Northern Gulf of Mexico Whale Shark Research Program: What We Have Learned about Whale Shark Aggregations in the Northern Gulf of Mexico
The Northern Gulf of Mexico Whale Shark Research Program was initiated in 2003 to increase our knowledge of whale shark occurrence and distribution within the region. A primary component of this program is a whale shark sighting website, which accommodates reports of regional sightings by “citizen scientists.” Whale sharks aggregate in areas of high prey abundance and our hope was to examine factors driving this behavior in the northern Gulf of Mexico. To date, over 600 whale shark sighting reports have been received. Reports were provided by a number of groups, including recreational anglers, divers, helicopter pilots and petroleum industry personnel and were categorized as sightings of solitary individuals, small aggregations (2-9 individuals) or large aggregations (10 or more individuals). Whale shark aggregations represented 190 (31%) of reported sightings, 47 (25%) of which were large aggregations between 10-150 individuals. All of the reported large aggregations occurred during summer, almost exclusively along the continental shelf edge, with 19 (41%) occurring at Ewing Bank off Louisiana. Directed research efforts were made to encounter aggregations to determine the size and sex of the sharks within the aggregation and to identify the primary prey source(s) by collecting plankton samples. Five aggregations were encountered and appeared to consist of largely juvenile males that were feeding on little tunny (Euthynnus alletteratus) eggs. The use of sightings data provided by “citizen scientists” has proven to be an inexpensive and effective technique for characterizing whale shark distribution, seasonality and aggregation locations in the northern Gulf of Mexico.
Johanna Imhoff1, R. Dean Grubbs2
1Florida State University, Tallahassee, FL, USA, 2FSU Coastal and Marine Laboratory, St. Teresa, FL, USA
Methylmercury Contamination in Six Species of Deepwater Sharks in the Northeastern 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 deepwater 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 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, deepwater 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 deepwater 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 levels will be analyzed in six shark species that range from the continental shelf edge to the mid-slope and include both Carcharhiniformes (Mustelus canis, M. sinusmexicanus) and Squaliformes (Squalus cubensis, S. cf. mitsukurii, Centrophorus uyato, C. granulosus).
Matthew Jew, David A. Ebert
Moss Landing Marine Laboratories, Moss Landing, CA, USA
Redescription of the Bigeye Chimaera, Hydrolagus macrophthalmus, de Buen, 1959, (Chimaeriformes: Chimaeridae), with Comments on the Family Chimaeridae from the Southeastern Pacific Ocean
Hydrolagus macrophthalmus de Buen, 1959 is a little known chimaeroid species from the Southeastern Pacific Ocean. It was described based on two specimens by Fernando de Buen, and at the time it was the only chimaeroid species, other than Callorhinchus callorynchus (Linnaeus, 1758) known from the region. At least four other species are now known to occur in the area therefore making improved identification between species all the more important. Hydrolagus macrophthalmus can be distinguished from the other regional species by a combination of uniform height of the elongated second dorsal fin, a long curved first dorsal fin spine that extends past the origin of the second dorsal fin when laid flat and uniform dark brown coloration with no light markings or spots laterally on the body. The species is compared to four other species reported to occur in the Southeastern Pacific Ocean: H. alphus, H. melanophasma, H. mccoskeri and H. trolli. Improved identification of Southeastern Pacific Ocean chimaeras will help in developing better management practices and conservation of these little known Chondrichthyans.
Stephen Kajiura, Shari Tellman
Florida Atlantic University, Boca Raton, FL, USA
Seasonal Shark Abundance in South Florida
Southeast Florida experiences an enormous seasonal influx of upper trophic level marine predators each year as blacktip sharks (Carcharhinus limbatus) form massive aggregations in nearshore waters. The narrow shelf and close proximity of the Gulf Stream Current to the Palm Beach County (PBC) shoreline constrain tens of thousands of sharks to the shallow, coastal environment. This natural bottleneck provides a unique opportunity to estimate abundance. Over a four year period, a biweekly aerial survey was flown along the length of PBC and the number of sharks within 200m of shore was directly counted. Shark abundance peaked in the winter (January-March) at over 12,000 individuals, and declined to nearly zero in the summer months. This corresponds to a maximum density of over 800 sharks km-2. Because these numbers represent only the sharks immediately adjacent to the shoreline, they are a gross underestimate of the total number of sharks present. Shark abundance was inversely correlated with water temperature with sharks found in large numbers only when water temperatures were less than 25°C. These baseline abundance data can be compared to future studies to determine if shark population size is changing and if sharks are restricting their southward migration as global water temperatures increase.
Bryan Keller1, Jean-Sebastien Finger2, Tristan Guttridge2, Samuel Gruber2
1Coastal Carolina University, Conway, SC, USA, 2Bimini Biological Field Station, Bimini, Bahamas, Bahamas
Energetic Savings During Group Participation and the Influence of Swimming Speed on Partner Preference in the Juvenile Lemon Shark, Negaprion brevirostris
Grouping in sharks is well-known, however, there are few quantitative analyses on the mechanisms that drive their formation. In this study we use controlled semi-captive behavioral experiments to assess the potential role that swimming speed and energetic efficiency plays in the group formation and social behavior of a large marine vertebrate. Juvenile lemon sharks, Negaprion brevirostris, in Bimini, Bahamas were captured, measured, tagged with external color codes for individual recognition, and housed in pens that exposed them to ambient conditions. Sharks were introduced into a social network pen while an overhead video system recorded behaviors for one hour. Tracking software transformed their movement patterns into a coordinate system. Multiple algorithms were used to analyze these coordinates, and a matrix of interactions was produced demonstrating when sharks were following or paralleling other individuals. When individuals were engaged in a following behavior, swimming speed was calculated for both animals while ensuring the distance between the two was constant. Similarly, an investigation was conducted to determine if interacting sharks select each other based upon swimming speed. Preliminary results suggest that juvenile lemon sharks show an active partner preference for animals with a similar swimming speed and that energy is conserved while closely following a conspecific. This research advances our understanding of the mechanisms driving group formation in lemon sharks, a model species for large marine predators.
Steven Kessel1, Alexander Hansell4, Samuel Gruber1, Tristan Guttridge1, Nigel Hussey2, Rupert Perkins3
1Bimini Biological Field Station Foundation, Bimini, Bahamas, 2University of Windsor, Windsor, Canada, 3Cardiff University, Cardiff, UK, 4University of Massachusetts, Fairhaven, MA, USA
Lemon Shark (Negaprion brevirostris) Catch Per Unit Effort (CPUE) Trends, Bimini, Bahamas, Derived from a Fishery Independent, 32-year Shallow Water Longline Survey
Long-term population assessments are necessary to determine species specific trends and inform management decisions. The waters surrounding the Bimini Islands, Bahamas, are rich in elasmobranch fauna. This study assessed three shallow water longline research campaigns at this location, 1982 – 1992, 1993 – 2003 and 2004 – 2014, with the aim to determine annual catch per unit effort (CPUE) trends for an IUCN listed near threatened species, the lemon shark (Negaprion brevirostris). A general additive model (GAM) was used to analyse the non-linear annual CPUE values over the entire 32 year research period. The GAM displayed high variability of annual CPUE, with a peak value of 0.026 in 2000. The 1982-1992 campaign saw highest portion of mature individuals (19.8%) and the smallest average pre-caudal length [PCL] (198 cm). The 1993 – 2003 campaign had the highest average annual CPUE (0.018) and percentage of total capture (32.3%). The 2004 – 2014 research period saw largest average PCL size (134.8 cm) and the lowest average CPUE values (0.009) of the entire research period. Long-term trends of this study highlight annual variability, and provide a baseline for future assessment of the Bahamas shark sanctuary relative to lemon shark abundance.
Peter Klimley1, David Acuna2, Randall Arauz3, Sandra Bessudo4, Eduardo Espinosa5, Hector Guzman6, Alex Hearn7, Mauricio Hoyos8, James Ketchum8, Cesar Penaherrera9, George Shillinger10, German Soler4
1University of California, Davis, CA, USA, 2Charles Darwin Foundation, Puerto Ayora, Santa Cruz Island Galapagos, Ecuador, 3Programa Restauracion Tortugas Marinas, San Jose, Costa Rica, 4Fundacion Malpelo, Bogota, Colombia, 5Parque Nacional Galapagos, Puerto Ayora, Santa Cruz Island, Ecuador, 6Smithsonian Tropical Research Institute, Panama City, Panama, 7Turtle Island Restoration Network, Forest Knolls, CA, USA, 8Pelagios Kakunja, La Paz, Baja California Sur, Mexico, 9University of Tasmania, Hobart, Tasmania, Australia, 10Hopkins Marine Station, Stanford University, Pacific Grove, CA, USA
The Role of Geology and the Design of Marine Reserves for Sharks in the Eastern Pacific
Nine species of sharks are commonly are present at “hot spots”, at seamounts and islands in the Eastern Pacific. The movements of these species have been described at the Espiritu Santo Seamount and Revillagigedos, Cocos, Coiba, Malpelo, and Galapagos Islands by (1) shipboard tracking, (2) satellite tracking, and (3) coded beacon detection by autonomous receivers. The whitetip reef, silvertip, blacktip, and tiger sharks are seasonally insular, staying most of the time close to shore. The Galapagos, scalloped hammerhead, silky, and small-tooth sandtiger sharks are seasonally insular-pelagic, making daytime or nighttime foraging migrations into the pelagic environment. The whale shark is truly pelagic, moving widely throughout the ocean while only briefly visiting these hot spots. These sites are of volcanic origin, being formed by the extrusion of basalt containing single-domain particles of magnetite from the earth’s lithosphere that align to the polarity of the earth’s field as the basalt cools after eruptions. The polarity of the earth’s main field rotates periodically over geological time so the lava flows contain magnetite aligned parallel and anti-parallel to the current earth’s field forming maxima (“ridges”) and minima (“valleys”) in the earth’s field to which sharks may orient using magnetic “topotaxis”. It is suggested that these magnetic features limit extent of the feeding excursions of these species, and knowledge of their extent can be used to specify zones of enforcement of fishing prohibitions at these sites so that they can continue to generate revenue as “shark parks”.
Matthew Kolmann, Nathan Lovejoy
University of Toronto Scarborough, Toronto, Ontario, Canada
Feeding Kinematics of the Ocellate River Ray, Potamotrygon motoro
Marine to freshwater incursions are comparably rare events, although several fish lineages have bridged the ecological and physiological boundaries inherent to these transitions. The South American river rays, Potamotrygonidae, invaded freshwater at least 14 mya and have subsequently diversified into nearly 30+ species. From a generalist invertivore ancestor, several instances of piscivory, mulloscivory, and insectivory have arisen independently in this clade of stingrays. For dietary generalists like Potamotrygon motoro, considerable behavioral modulation is assumed to be necessary to consume such a wide swath of prey taxa and prey materials. Here we present data on prey-handling in P. motoro filmed on bare-bottom enclosures using highspeed videography. We report the degree of asymmetrical jaw protrusion, relevant for processing large or tough prey as well as the general behavioral routines involving prey capture, prey processing, and overall handling time. We find that these rays utilize an initial “pounce” to apprehend prey, followed by repeated jaw protrusion and retraction, during which indigestible prey material is ejected from the spiracles. Prey-handling times increase for larger prey items as well as the degree to which jaw asymmetrical protrusion is observed. Based on prior myological studies, we hypothesize then that the coracohyomandibularis and levator hyomandibularis aid in hyoid depression and retraction (respectively), and when coupled with the coracomandibularis, protrude the jaws. These muscles in particular may be relevant to further study of functional feeding trait evolution in the Potamotrygonidae.
Christopher Lowe1, Connor White1, Diego Bernal2
1California State Univ. Long Beach, Long Beach, CA, USA, 2Univ. Mass. Dartmouth, Dartmouth, MA, USA
Behavioral Thermoregulation in Elasmobranch Fishes: What Do We Know and Where Do We Go from Here?
There is a growing number of telemetry-based movement studies across a range of ectothermic elasmobranch species suggesting that individuals exhibit some form of behavioral thermoregulation. In addition, there is considerable speculation as to the benefits of this behavior and what potentially drives movements relative to changing water temperatures. Fewer studies have focused on quantifying the actual physiological cost/benefits of changing body temperatures and how these changes may influence behavior. Unfortunately, in a vast majority of cases there is little physiological and behavioral data for the same species to allow for realistic assessment of potential behavioral thermoregulation. Cases where there are comparable physiological and behavioral data have focused primarily on smaller species that are easier to keep in captive settings. As a result, our understanding of how behavioral thermoregulation scales with body size is sorely lacking. New technology, experimental designs, and modeling tools may allow for a better assessment of behavioral thermoregulation. New movement (accelerometer, temp and depth dataloggers) and tracking tools (VRAP, MAP600, AUVs) can allow for simultaneous, fine-scale assessment of movements relative to environmental conditions, especially if accompanied with internal body temperature sensors (e.g., gastric or IP temperature sensors). Use of field-based translocation experiments across thermal gradients may allow for experimental assessment of body temperature and movement predictions. Lastly, better physiological, behavioral and related environmental data will allow for more sophisticated modelling to predict movement patterns as ocean temperatures continue to warm.
Carl Luer1, Cathy Walsh1, Laura Edsberg2, Jennifer Wyffels2
1Mote Marine Laboratory, Sarasota, FL, USA, 2Daemen College Center for Wound Healing Research, Amherst, NY, USA
Experimental Wounding of Atlantic Stingrays, Dasyatis sabina: Role of Epidermal Mucus in Protection of Early Stage Wound Beds
Anecdotal reports of relatively rapid and infection-free healing of wounds in sharks and rays are common, yet controlled experimental wounding studies to characterize the healing process are rare. Experimental wounds were inflicted on pectoral fins of Atlantic stingrays, Dasyatis sabina, by excising the epidermal and dermal layers of skin and exposing the epaxial musculature. While the gross physical appearance suggests that wound beds are covered by blood and/or blood clots for at least the first 4 days, histology has shown that migration of epidermal cells from the wound margin onto the bed is well underway by 16-24 hours. By 48 hours, the wound bed is completely covered with a thin epidermal layer containing mucus cells and a clearly identifiable basal layer. Wound biopsy samples were examined using scanning electron microscopy (SEM) and post-fixation to preserve secreted epidermal mucus. Resulting SEM images of 8, 16, and 24 hour wounds demonstrate that wounds are covered with mucus before re-epithelialization. The 24 and 16 hour wound beds are obscured almost completely by mucus, while much of the 8 hour wound bed surface, particularly near the wound bed margins, is also covered by mucus. Studies are underway to investigate the extent of mucus coverage on wounds at times earlier than 8 hours. Epidermal mucus secretions isolate the wound from the environment and may represent the first line of defense for wound healing in D. sabina.
Kady Lyons, Matt Vijayan
University of Calgary, Calgary, Alberta, Canada
Compromised Stress Response in Round Stingrays Exposed to PCBs along the Southern California Coast
Stress response impairment due to environmental contaminant exposure has been documented in a variety of organisms; however, little research has investigated these types of effects in elasmobranch fishes. The objective of this study was to examine the primary and secondary stress response in round stingrays (Urobatis halleri) that have been exposed to different levels of environmental organochlorine contaminants, primarily polychlorinated biphenyls (PCBs). Our hypothesis was that higher PCBs body burden would compromise the stress response in this species. To test this, stingrays were sampled from two locations (mainland California, Long Beach, and a nearby offshore island, Catalina) and subjected to two treatments (“stressed” and “unstressed”). Stingrays were collected by hook and line from these two locations and plasma was sampled either immediately (unstressed) or 15 min after handling and confinement (stressed) to examine changes in liver and plasma parameters. Stingrays sampled from Long Beach had significantly higher hepatic PCB levels compared to stingrays Catalina. Our results support the hypothesis that higher PCB body burden suppresses the highly conserved corticosteroid stress response in these animals. Also, liver glucose and glycogen content were lower in the stressed Long Beach stingrays compared to the Catalina rays. Overall, PCB contamination reduces the capacity to elicit a physiological stress response in the round stingrays.
Heather Marshall1, Diego Bernal2, Gregory Skomal3, Richard Brill4, Peter Bushnell5, Nick Whitney1
1Mote Marine Laboratory, Sarasota, FL, USA, 2University of Massachusetts Dartmouth, North Dartmouth, MA, USA, 3Massachusetts Division of Marine Fisheries, New Bedford, MA, USA, 4National Marine Fisheries Service, NOAA, Gloucester Point, VA, USA, 5Indiana University South Bend, South Bend, IN, USA
The Importance of Physiology in Shark Mortality Assessments and Fisheries Management
The National Marine Fisheries Service recently released the Atlantic Highly Migratory Species Management-Based Research Needs and Priorities, with research needs including establishing post-release mortality rates for commercially caught sharks. Published at-vessel mortality rates indicate that capture-associated mortality is species-specific. Through assessments using various types of electronic tags (e.g., pop-up satellite archiving tags and accelerometer tags), such species-specific responses appear to carry over to post-release mortality rates as well, with rates ranging from 0% (Galeocerdo cuvier, and Carcharhinus leucas) to 75% (C. brevipinna). Research assessing interspecific mortality rates is critical, but it is also imperative to understand the physiology underlying such mortality events. The physiological upset sharks experience while captured on fishing gear can result in irreversible cellular damage, resulting in immediate or delayed mortality. Previous research on shark stress physiology has found that changes in various blood stress indicators (e.g., lactate) are correlated with magnitude of the capture stress, and that blood potassium levels are significant (p<0.05) predictors of both at-vessel and post-release mortality. The future of such research lies in pointed physiological studies to understand how stress indicators and mortality are linked, and how such information can be used to understand the capture-related stress response in teleosts as well. The further elucidation of mortality indicators, and what is driving such mortality events, can be used on various scales in the future to predict mortality rates, and develop mitigation measures for fisheries management.
Rui Matsumoto1, Miwa Suzuki2, Kiyoshi Asahina2, Kiyomi Murakumo1, Yosuke Matsumoto1, Keiichi Ueda1, Keiichi Sato3
1Okinawa Churaumi Aquarium, Okinawa, Japan, 2Nihon University, Kanagawa, Japan, 3Okinawa Churashima Research Center, Okinawa, Japan
Long-term Observation of the Behavioral and Hormonal Trends in Male Whale Shark in the Okinawa Churaumi Aquarium
The maturation cycle of a male whale shark kept in the Okinawa Churaumi Aquarium for 20 years was recorded. This shark (total length [TL], 4.6 m) was accidentally caught by local fishermen in March 1995. In order to determine the exact size of this shark at maturation, we have monitored the clasper elongation; the elongation was defined as the ratio of the outer length (COL) of the clasper to the length of the inner pelvic margin (P2I). Analysis revealed that this ratio increased rapidly from 1.09 (August 2011) to 1.60 (July 2012), and the shark attained a length of 8.5 m TL. A high plasma testosterone level was maintained at 21.49 ng/mL (June 2011-June 2012) during rapid clasper elongation. Additionally, we observed a behavioral change where the whale shark began to rotate its entire body laterally, while crossing both claspers (April 2012) and simultaneously discharged white turbid fluid from its clasper tips (August 2012). We continued to monitor the behavioral and hormonal changes in the shark. In May 2014, the male began demonstrating sexual behavior by pursuing two immature female sharks (7.5 m and 7.4 m TL). In June 2014, we continued to monitor this pursuing behavior and began counting the number of clasper rotating actions as well as measured the hormone levels and water temperature. Current observations indicate that the clasper rotation and pursuing action increased in frequency at higher water temperatures (25-28°C) from June to early August and did not occur in lower temperature waters.
Emily Meese, Christopher G. Lowe
CSU Long Beach, Long Beach, CA, USA
Finding a Resting Place: How Environmental Conditions Affect the Spatial Distribution of Benthic Elasmobranchs at Big Fisherman’s Cove, Santa Catalina Island
Ectothermic elasmobranchs are known to seek out habitats and environmental conditions to optimize their energetic requirements. Spatial distribution patterns of three species, bat rays (Myliobatis californica), shovelnose guitarfish (Rhinobatos productus), and round stingrays (Urobatis halleri) were used to determine resting habitat within Big Fisherman’s Cove (BFC), Santa Catalina Island. Distribution patterns of individuals were determined via field observation surveys and related to detailed georeferenced habitat maps. All species were found associated with sand and vegetated/sand substrata; however, all three species selected their substrata disproportionally from what was available in the survey area within the cove (p < 0.001). Seafloor water temperatures were stratified by distance to the shoreline (range: 17-21 ºC), and differed between two survey periods (fall 2013 and summer 2014). In the fall, there was a significantly higher density of all three species in areas with water temperatures ~18 ºC (range: 17.0 – 20.75) (p < 0.001). Bat ray density increased in the summer around areas with temperatures between 20.25 – 20.75 ºC in BFC, while they had a more random spatial distribution in the fall. All three species demonstrated a hierarchical habitat selection by prioritizing either substrata type or temperature ranges. Aggregating elasmobranchs can potentially be more susceptible to exploitation when at these sites. Therefore, understanding how individuals select their resting habitat and environmental conditions may provide managers with opportunities to provide better protection for these species.
Joshua K. Moyer, William E. Bemis
Cornell University, Ithaca, NY, USA
Comparisons of Tooth Structure and Replacement in the Blue Shark (Prionace glauca) and the Great White Shark (Carcharodon carcharias)
Elasmobranchs exhibit two distinct arrangements of mineralized tissues in the teeth that are known as orthodont and osteodont histotypes. Traditionally, it has been said that orthodont teeth maintain a pulp cavity throughout tooth development whereas osteodont teeth are filled with osteodentine and lack a pulp cavity when fully developed. We used light microscopy, scanning electron microscopy, and high-resolution micro-computed tomography to compare the structure and development of elasmobranch teeth representing the two histotypes. As an example of the orthodont histotype, we studied teeth of the Blue Shark, Prionace glauca (Carcharhiniformes: Carcharhinidae). For the osteodont histotype, we studied teeth of the Great White Shark, Carcharodon carcharias (Lamniformes: Lamnidae). We document similarities and differences in tooth development and the microstructure of tissues in these two species and review the history of definitions and interpretations of elasmobranch tooth histotypes. We discuss a possible correlation between tooth histotype and tooth replacement and review the history of histotype differentiation in sharks. We find that contrary to a long held misconception, there is no orthodentine in the osteodont teeth of C. carcharias.
Emily Nelson1, Neil Hammerschlag1, 2, Duncan Irschick3
1Rosenstiel School of Marine and Atmospheric Science, Miami, FL, USA, 2Leonard and Jayne Abess Center for Ecosystem, Science and Policy, Coral Gables, FL, USA, 3Department of Biology, University of Massachusetts at Amherst, Amherst, MA, USA
Variation in Body Form Influences Broad Scale Movement Patterns and Ecological Locomotor Performance by an Apex Predator
Throughout the long evolutionary history of sharks, physical, hydro-dynamical, and ecological demands have created considerable selection pressure to create the most efficient design for locomotion. Variation in body shape can impact an individual’s ability to move effectively through the water and variation in body condition can influence the timing, length, and nature of migrations. Here we present a functional approach toward movement. We integrate functional morphology, physiology, and ecology to determine how variation in body form influences broad scale movement patterns and ecological locomotor performance of a marine apex predator (the tiger shark, Galeocerdo cuvier). Fourteen tiger sharks, ranging in size from 180 cm to 357 cm (total length) were captured. For each individual, 13 morphological measurements were taken and sharks were tagged with satellite transmitters to track their movement patterns. Using these data we evaluated how variation among individuals in movement (maximum distance moved, dispersion rate, rate of movement, kernels density, activity space, and area used per day) is influenced by morphology (caudal fin area, caudal fin aspect ratio, total length, and body condition). Our results help to understand the mechanisms underlying of the ecological and evolutionary implications of variation in morphological adaptations on marine apex predator movement and behavior.
Florida Atlantic University, Boca Raton, FL, USA
The Yellow Stingray, Urobatis jamaicensis, Has a Magnetic Sense but Can It Use the Geomagnetic Field to Derive a Sense of Location?
The strength and inclination angle of the geomagnetic field vary predictably with latitude and magnetically sensitive animals can use these cues to derive a sense of location during migrations. Our previous work has demonstrated that the yellow stingray, Urobatis jamaicensis, can detect magnetic fields from permanent magnets. However, it is unknown if elasmobranchs can detect changes in the strength or inclination angle of a magnetic field. Stingrays were placed into two treatment groups that experienced magnetic stimuli that were 2.5X the range of possible magnetic field values that this species might encounter across its distribution. Stimuli were generated by a Merritt four-coil electromagnet system and the initial response of naive rays to stimuli served as a control. Individual stingrays were trained to swim to a feeding station when the magnetic field strength was increased by 45 μT or the inclination angle was shifted vertically by 75°. Once the rays learned the task the stimulus intensity was gradually reduced in order to determine the threshold for a behavioral response. Rays were then subjected to stimuli from the other treatment group to determine if the rays could discriminate between the two stimuli.
Robert J. Nowicki, Jordan A. Thomson, James W. Fourqurean, Michael R. Heithaus
Florida International University, Miami, FL, USA
Effects of Predation Risk from Tiger Sharks (Galeocerdo cuvier) on Resilience of an Iconic Seagrass Ecosystem Following a Widespread Climate Driven Disturbance
Ecological resilience will play an important role as anthropogenic ecosystem disturbance continues. Understanding how marine apex marine predators contribute to resilience is important in the context of global overfishing and increased disturbance potential from climate change. Here I present a 16 month field experiment to determine whether a dominant apex predator, the tiger shark (Galeocerdo cuvier), contributes to the stability of the recently disturbed seagrass community of Shark Bay, Australia. Shark loss was mimicked by simulating shifts in risk-sensitive habitat use and foraging patterns of dugong mega-grazers. Different levels of dugong excavation grazing, imitated by divers, were applied to plots to characterize these shifts. Excavation is energetically profitable to dugongs but destructive to seagrass beds, removing both target and non-target seagrass; it also increases risk of predation and is rarely used when predators are abundant. Mixed effects modeling was used to determine the importance of grazing treatments to the change in percent cover of the dominant climax seagrass (Amphibolis antarctica) and an herbivore-preferred pioneer seagrass (Halodule uninervis). A. antarctica cover declined with shark loss and subsequent increased grazing, though the effects were site-dependent. H. uninervis also declined but was more variable. Results indicate the current, fragile state of Shark Bay and the likelihood for a phase shift to an A. antarctica depauperate ecosystem if tiger sharks were removed from the ecosystem. This work highlights the contribution apex predators can make to the resilience of marine ecosystems, as they become exposed to more frequent and intense disturbances through climate change.
E.W. Misty Paig-Tran1, Lara Ferry1
1CSU Fullerton, Fullerton, CA, USA, 2Arizona State University West, Phoenix, AZ, USA
Integrative Elasmobranch Biology for the 21st Century
The current climate at granting institutions requires new research proposals to be truly interdisciplinary between two or more fields to be competitive for funding. NSF now has an entire division (Integrative Organismal Systems) dedicated to supporting research that is inherently integrative and asks us to identify “Grand Challenges in Organismal Biology”. We argue in this symposium that elasmobranchs are excellent candidates for integrative research for numerous reasons, the most compelling of which are that: 1) they are ideal for asking large scale evolutionary questions (ex. evolution of endothermy) as they are a basal vertebrate on the tree of life and have survived with essentially the same features as they had 450 million years ago; 2) they are ecologically unusual in that they are the apex predators in nearly every system where they are present and thus play an important and possibly unmatched role in most trophic systems; and, 3) they are functionally important in that they possess an entirely cartilaginous skeleton, they are the first lineage to develop a true set of jaws, and they have the complex sensory system we typically associate with all vertebrates. Here we present a review of the history of integrative elasmobranch research and touch upon how the future of elasmobranch research is driving a variety of scientific fields of study highlighting how elasmobranchs were an essential part of the research, that elasmobranchs were the ideal organism for the research, and how the research is truly interdisciplinary between two or more fields of study.
University of St Andrews, St Andrews, UK
A Day in the Life: Combining Biologging and Modelling to Understand Shark Behaviour and Physiology
Sharks represent an important ecological group as many species are meso or upper level predators. They are also an excellent study animal for ecological and behavioural studies as their larger size allows them to retain and carry a variety of sensors that record behavioural and physiological data in real time. With the current iterations of sensors we can measure the horizontal and vertical movements, activity, habitat selection, digestive physiology, and biomechanics of free-ranging animals. However, these tools are producing large datasets, and we need the appropriate statistical and modelling tools to appropriately analyse them. Analytical tools such as Hidden Markov Models allow us to identify switching behaviours and determine the covariates that drive these switches, and can be applied to a variety of time-series data including animal step lengths and turning angles, swimming depths, and activity. I will illustrate these methods using tracking data from white sharks, and behavioural/physiological data from reef (grey reef and blacktip reef sharks) and pelagic (oceanic whitetips) sharks. By combining these methods we can start to move beyond just describing shark movements, but also focus on the drivers of these movements.
Sebastian Pardo1, Marc Dando2, Nick Dulvy1
1Simon Fraser University, Vancouver, BC, Canada, 2FlukeArt, Plymouth, UK
Can Fin Shape Explain Variation in Somatic Growth Among Shark Species?
Across vertebrate taxa, morphology is related to function. An example from fishes is that caudal fin shape relates with swimming speed and activity level, with more elongated fins indicative of fast, active species and rounded fins slower, inactive ones. There is evidence that activity levels correlate with food consumption (more active fish eat more prey), and given that food consumption is relative to somatic growth rate (the more you eat the faster you grow), it might be possible to explain observed variation in growth among species based on a simple measure of fin morphology: caudal fin aspect ratio. Here we present a framework for exploring the relationship between somatic growth rate, maximum size, ocean temperature, and aspect ratio among a range of shark species, and discuss preliminary findings.
Cheston Peterson1, R. Dean Grubbs1, 2
1Florida State University, Tallahassee, FL, USA, 2FSU Coastal and Marine Laboratory, St. Teresa, FL, USA
Investigating Trophic Relationships Between Sharksuckers (Echeneis naucrates) and Their Elasmobranch Hosts Using Stable Isotope Analysis
Despite the ubiquity of the symbiotic relationships of diskfishes (Echeneidae) and their hosts in marine ecology, the nature of the symbioses between individual species and their hosts is poorly understood – especially among the facultative symbionts (Echeneis sp.). We used carbon and nitrogen stable isotope analysis of white muscle biopsies from both free-living and commensal sharksuckers (Echeneis naucrates), as well as their hosts, to evaluate the suggestion that commensal sharksuckers feed heavily on scraps of their hosts’ prey. We also used these data to evaluate among-host differences in pairwise similarity of individual sharksucker and host isotopic signatures, which we hypothesize could be indicative of long-term commensalism or high quality hosts. Mean pairwise differences of both δ13C and δ15N were lowest in bull (Carcharhinus leucas) and lemon (Negaprion brevirostris) sharks, and highest in nurse (Ginglymostoma cirratum) and tiger sharks (Galeocerdo cuvier). There was no effect of host taxon on pairwise δ13C differences, but there was a significant effect of host taxon on pairwise δ15N differences. Similarly, there was not an effect of commensalism on δ13C, accounting for variation in sharksucker size and collection location; however, there was an effect of commensalism on δ15N, accounting for variation in sharksucker size and collection location. Despite being larger in size, free-living sharksuckers had lower δ15N values, and therefore relative trophic position, than commensal sharksuckers. Our results suggest relative trophic levels of sharksuckers drop when they are free-living and that there may be an ontogenetic shift in both dependency on commensalism and trophic level.
Mariah O. Pfleger1, R. Dean Grubbs2, Toby S. Daly-Engel1
1University of West Florida, Pensacola, FL, USA, 2Florida State University, Tallahassee, FL, USA
The Dogfish Formerly Known as Mitsukurii: A New Deep-water Shark Species from the Gulf of Mexico
The shortspine spurdog shark (Squalus mitsukurii) is a putative circumglobal deep-water shark that was originally described from Japanese waters. Sharks of the genus Squalus are easily misidentified due to the high degree of morphological similarity with their congeners. Recent taxonomic research on this species from the Pacific has indicated that S. mitsukurii may actually comprise a species complex, a group of separate but closely related species. Using approximately 680 bp of mitochondrial cytochrome c oxidase 1 (barcoding gene) we found 99.61% bootstrap support for the separation of the Gulf of Mexico Squalus cf mitsukurii from Squalus mitsukurii in Japan. We found similar support using 595 bp of mitochondrial NADH dehydrogenase 2 (ND2), as well as morphological characters. The new species in the Gulf of Mexico is named Squalus clarkae in honor of Dr. Eugenie Clark.
David Portnoy1, Jonathan Puritz2, Christopher Hollenbeck2, John Gold2
1Texas A&M University – Corpus Christi, Corpus Christi, TX, USA, 2Harte Research Institute, Corpus Christi, TX, USA
Adaptive Genetic Variation and Male-mediated Gene Flow in the Bonnethead
The combination of male-biased dispersal and female philopatry, common in sharks, is expected to homogenize genetic variation in nuclear sequences across geographic space relative to variation in mitochondrial (mt)DNA sequences. However, when site-fidelity occurs across a heterogeneous environment, local selective regimes may add complexity to this pattern and on a genome-wide scale. We examined this possibility in bonnetheads, a species known to exhibit site fidelity. We obtained samples of bonnetheads from three areas along the west (Gulf) coast of Florida and one area off North Carolina on the U.S. Atlantic coast. We assessed patterns of variation in each sample in sequences of mtDNA and in 5,914 nuclear-encoded single nucleotide polymorphisms (SNPs). Sequences of mtDNA and putatively neutral SNPs revealed male-mediated gene flow and female philopatry among the samples from the Gulf. A total of 45 ‘outlier’ SNPs (O-SNPs) were identified, and allele frequencies for 20 O-SNPs were correlated significantly with latitude, suggesting localized adaptation. There were no fixed differences in allele frequencies at any O-SNP locus; combinations of alleles common in one sample were present in low frequencies in other samples. There also was a significant correlation between estimates of genetic divergence based on O-SNPS and mtDNA sequences, but not between mtDNA sequences and either O-SNPs or putatively neutral SNPs. These results indicate that localized adaptive variation may sort primarily through the philopatric sex (females), with the dispersing sex (males) facilitating movement of potentially adaptive variation among locations and/or environments.
Gregg Poulakis, Philip Stevens, Rachel Scharer
Florida Fish and Wildlife Conservation Commission, Port Charlotte, FL, USA
A Comparison of Movement Patterns in Two Smalltooth Sawfish, Pristis pectinata, Nursery Areas
Movements of endangered juvenile (<3 yr old) Smalltooth Sawfish (Pristis pectinata) were monitored in the highly human-altered, freshwater inflow-managed Caloosahatchee River (2005-2013) and in the more natural Peace River, Florida (20102013) using 63 acoustic listening stations. A total of 133 sawfish (76 in the Caloosahatchee River; 57 in the Peace River) were monitored in main-stem river habitats and non-main-stem habitats (i.e., natural mangrove-lined creeks, semi-natural creeks, seawall-lined canals) of both river systems. 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 that contained natural shoreline habitats along a 25 river kilometer (rkm) stretch of the nursery. They moved upriver during dry, low freshwater inflow conditions and downriver during wet, high inflow conditions. In contrast, in the Peace River, sawfish tended to remain in only a 6 rkm portion of the nursery during all freshwater inflow conditions. This portion of the nursery includes the only hotspot that has been identified in the Peace River. Possible reasons for these observations relate to differences in geomorphology and freshwater inflow regimes between the rivers.
Cassandra Ruck1, 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 Genetic Connectivity in a Shark of High Conservation Concern, the Oceanic Whitetip, Carcharhinus longimanus
The oceanic whitetip shark, Carcharhinus longimanus, is globally distributed in warm waters and has suffered drastic declines in recent history due to high bycatch in diverse pelagic fisheries and demand for its large fins in international trade. Due to these declines, the once common oceanic whitetip is now listed as “Critically Endangered” in the Western North and Western Central Atlantic and “Vulnerable” to extinction globally by the IUCN Red List. Thus, there are urgent calls for improved data collection and management strategies to conserve this enigmatic species. However, there exist no data on the population genetics of oceanic whitetip sharks. We report an assessment of the global population structure and demographic history of this shark based on analysis of two mitochondrial DNA region sequences (entire control region (1067 bp) and part of the NADH dehydrogenase subunit 4 gene (682 bp) and nuclear microsatellite markers. Pairwise analysis of concatenated mitochondrial data with ARLEQUIN v. 184.108.40.206 indicates significant differentiation between the western Atlantic (n=93) and Indo-Pacific (n=72) populations (ΦST = 0.0757, P<0.001). Furthermore, analysis of only the 682 bp ND4 fragment, a more variable locus than the control region in this species, indicates differentiation between all three ocean basins: Atlantic vs. Pacific (n=40) (ΦST = 0.0804 , P< 0.001), Atlantic vs. Indian (n=32) (ΦST = 0.0508, P=0.0108), Indian vs. Pacific (ΦST =0.0509, P=0.033). Despite the global distribution and presumably high vagility of C. longimanus, significant population structure exists and effective management strategies must take this into consideration.
Keiichi Sato1, Masaru Nakamura1, Taketeru Tomita2
1Okinawa Churashima Research Center, Motobu, Okinawa, Japan, 2FSU Coastal and Marine Laboratory, St. Teresa, FL, USA
Nourishment of White Shark Embryos with Uterine Milk during the Early Gestation Period
The white shark, Carcharodon carcharias, demonstrates viviparous and oophagous modes of reproduction. Morphological and histological observations of a 4,950mmTL gravid female accidentally caught by fishermen in the Okinawa Prefecture, Southern Japan revealed that the shark had conceived six embryos (543-624 mm), and also contained copious amounts of yellowish viscoid uterine fluid as well encased nutrient eggs and broken egg cases in both uteri. Although ruptured, the six embryos had large stomachs, and the mean volume of the stomachs was approximately 197.9mL. About 20 rows of potentially functional teeth were present in the upper and lower jaws. Periodic Acid Schiff-positive substances were observed on the surface and in the cytoplasm of the epithelial cells, and large, secretory, OsO4-oxidized lipoid droplets of various sizes were distributed on the surface of the villous string epithelium on the uterine wall. These histological observations demonstrated that the uterine wall was comprised of villous structures, similar to the trophonemata of nourishing embryos of dasyatid rays, thereby suggesting that the large amount of fluid found in the uterus of the white shark was required for embryo nutrition. Hence, the following conclusions were drawn: (1) the uterine fluid is secreted from the uterine villi, (2) the embryos are able to use abundant uterine fluid and encased nutrient eggs for nutrition at this stage, and (3) the uterine fluid is the major source of embryonic nutrition before oophagy onset.
Rachel Scharer, Philip Stevens, Gregg Poulakis
Florida Fish and Wildlife Conservation Commission, Port Charlotte, FL, USA
A Comparison of Abiotic Affinities and Spatiotemporal Distribution Patterns in Two Smalltooth Sawfish, Pristis pectinata, Nursery Areas
Research on the endangered Smalltooth Sawfish (Pristis pectinata) in the Charlotte Harbor estuarine system in southwest Florida has been ongoing for about a decade and we have begun to understand the life history, ecology, and habitat use patterns of this species. Sawfish are known to use multiple southwest Florida estuaries during the first 2-3 years of life and preliminary genetics analyses have indicated that adult females are returning to the same regions (e.g., major rivers) for parturition. Thus, understanding region-specific habitat use patterns has become important for effective management. Our initial research (2005-2009) was focused in the Caloosahatchee River; a highly human-altered river system within the federally designated Critical Habitat for juveniles. Most recently (2010-2013), we continued research in the Caloosahatchee and expanded sampling into a more natural area, the Peace River. A total of 135 juveniles ranging from 708 to 2,640 mm stretch total length were captured, tagged, and released between February and September. Annual recruitment peaked during April and May in both river systems. Logistic regression models identified combinations of water depth, water temperature, dissolved oxygen, and salinity as influencing the probability of catching a sawfish. 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. Possible reasons for differences in dissolved oxygen and salinity affinities between the rivers relate to differences in their geomorphology and freshwater inflow regimes.
Ronald Seidel1, David Knoetel2, Merlind Schotte2, Daniel Baum2, Daniel Huber3, Michael Blumer4, James Weaver5, Mason Dean1
1Max Planck Institute, Potsdam, Germany, 2Zuse Institute, Berlin, Germany, 3University of Tampa, Tampa, FL, USA, 4Medizinische Universitaet, Innsbruck, Austria, 5Wyss Institute for Biologically Inspired Engineering, Cambridge, MA, USA
Interdisciplinary Approaches to Skeletal Biology and Mechanics: Design Lessons from Shark Skeletons
Fish skeletal tissues are far more diverse than those of mammals, providing unique windows into skeletal biology, development and form-function relationships in general, but also the evolutionary and environmental pressures that shape anatomy. We investigate the materials, structure and mechanics of elasmobranch cartilage, comprised of unmineralized cartilage wrapped in a layer of geometric, sub-millimeter, mineralized tiles (tesserae). Our interdisciplinary collaboration ties together high-resolution material and ultrastructure data with analyses of skeletal form to build bio-realistic and bioinspired 3d-printed models for hypothesis testing and comparison with native tissues. We’ve learned that tesserae begin from isolated mineralization zones, employing a similar mineralization regulation pathway to bone, but being patterned on a wider diversity of collagens. As tesserae grow into contact, striking patterns of structural reinforcement appear, developing mineral density and tissue stiffness comparable to (and sometimes higher than) mammalian mineralized cartilage or bone. Using custom, quantitative shape analyses of high-resolution CT scans, we map the massive network of tesserae on skeletal elements, allowing derivation of tissue growth and tiling laws and comparison with theoretical tilings. These data act as inputs into physical and theoretical models of tessellated cartilage, developed using new multi-material 3D printing techniques for high-resolution model fabrication. Combined with quantitative shape and mechanics analyses of whole jaws from shark species with different diets, we draw together multiple size scales to build holistic understandings of skeletal biology, learning fundamental design rules for this and other skeletal tissues, as well as layered, low-density composite materials in general.
David Shiffman, Catherine Macdonald, Harry Ganz, Neil Hammerschlag
University of Miami, Miami, FL, USA
Initial Assessment of the Scale, Practices and Conservation Implications of Land-Based Shark Fishing in South Florida
Angling for sharks from beaches is a popular recreational activity in Florida, but the scale, practices, and conservation implications remain unknown. Here we analyze thousands of posts made by land-based shark anglers on the public online discussion board of a local fishing club in order to assess angler attitudes, perceptions and practices. We found that land-based shark anglers are generally young (under 30) and male, a demographic different from most recreational anglers. These anglers enjoy land-based shark fishing because it is more affordable than boat-based fishing, but still allows people to catch and interact with large and exciting fish. Though there is some skepticism of government-led scientific population estimates, land-based shark anglers are aware of and concerned by global shark population declines. Conflicts between beach stakeholders (swimmers and anglers) are frequently discussed. These anglers believe that regulations which restrict recreational angling for overfished species are unjust because they believe commercial fishing is what caused the population declines. Land-based shark anglers also frequently discuss how laws that restrict land-based fishing, but not boat-based fishing (including beaches that ban fishing, and restrictions within state waters but not adjacent Federal waters), discriminate against lower income anglers. Land-based shark fishing raises some conservation concerns because of the increased physiological stress caused by the sharks being brought onto land. Additionally, there are numerous interactions with protected species like the physiologically sensitive great hammerhead. Potential policy and education solutions that minimize these conservation concerns and stakeholder conflicts while still allowing recreational anglers to fish are proposed.
Brendan Talwar1, Edward Brooks2, Alp Gokgoz2, John Mandelman3, Dean Grubbs1
1Florida State University, St. Teresa, FL, USA, 2Cape Eleuthera Institute, Rock Sound, Eleuthera, Bahamas, 3New England Aquarium, Boston, MA, USA
Stress Physiology and Post-release Survivorship of Cuban Dogfish and Gulper Sharks Caught on Longlines
Cuban dogfish (Squalus cubensis) and gulper sharks (Centrophorus cf. uyato) are common bycatch in deepwater longline fisheries, yet their fate after release is entirely unknown. Given the highly variable nature of a deepwater longline haul and the documented interspecific differences in the elasmobranch stress response, this research investigates (i) the 24hr post-release survivorship rates of S. cubensis and C. cf. uyato, (ii) the potential factors contributing to mortality, and (iii) the suitability of caging as a method to address these aims. To meet these objectives, individuals were caught on longlines in Exuma Sound, The Bahamas, and lowered to their respective capture depths (450-900m) in a video-monitored cage. Squalus cubensis experienced a 43.8±0.73% 24hr post-release survivorship rate whereas C. cf. uyato experienced 100% mortality. A logistic regression analysis showed that at-vessel blood pH and release condition could predict survivorship for S. cubensis, whereas glucose and lactate could not. Caging had no significant effect on S. cubensis mortality; in comparison, C. cf. uyato commonly lost the ability to orient within the cage prior to mortality. The exact drivers of this trend are unclear. This study greatly improves our understanding of discard mortality for deep sea sharks and offers a first characterization of the stress response for two common bycatch species. It also suggests that containment studies may not be appropriate for the genus Centrophorus.
Taketeru Tomita1, Masaru Nakamura2, Keiichi Sato2, Hiroko Takaoka3, Minoru Toda2, Junro Kawauchi4, Kazuhiro Nakaya4
1Florida State University Coastal and Marine Laboratory, St Teresa, FL, USA, 2Okinawa Churashima Research Center, Motobu, Okinawa, Japan, 3Okinawa Churaumi Aquarium, Motobu, Okinawa, Japan, 4Hokkaido University, Hakodate, Hokkaido, Japan
Changes in Catshark Embryo Respiratory Mode During Mid-embryonic Period
Elasmobranchs are unique among fishes in producing extremely large embryos. Such a large embryo, with low body surface-volume ratio, may present respiratory challenges in utero. This is because gas diffusion solely through the body surface does not meet the oxygen demand for large embryos. Thus, some specific respiratory mechanisms are expected. Morphological and kinematical observations on captive catshark embryos have suggested that the embryo switches its respiratory mode just before the respiratory slits open on the egg capsule. During the pre-opening period, the embryo acquires oxygen mainly via diffusion in the external gill filaments. After slit opening, embryo starts buccal pumping to pass water over the internal gills. Some structural modifications (e.g., development of blood vessels in internal gills, development of oral valve, and establishment of pharyngeal skeletons and associated muscles) occur at the same time. It is known that the oxygen tension in the egg capsule is quite unstable after slit opening. The ability of buccal pumping is possibly advantageous for embryos to regulate oxygen intake by changing pumping frequency in an unstable oxygen environment.
Victoria Elena Vásquez1, David A. Ebert1, Douglas J. Long2
1Pacific Shark Research Center, Moss Landing Marine Laboratories, Moss Landing, CA, USA, 2Department of Biology, St. Mary’s College, Moraga, CA, USA
A New Lanternshark (Squaliformes: Etmopteridae: Etmopterus) from the Eastern Central Pacific Ocean
A new species of lanternshark shark, genus Etmopterus is described from specimens collected off the Pacific coast of Central America. The new species is placed in the ‘Etmopterus spinax’ clade by a lack of flank markings and small hook-like conical dermal denticles distributed throughout the body. This new species can be separated from its congeners based on: proportional body measurements, meristic measurements of spiral valve and vertebral counts, arrangement of dermal denticles, and dark fin margins that contrast with other species in the ‘E. spinax’ clade, which typically possess white fin margins. The dorsal fins in the new species are much similar in size compared with its congeners while the second dorsal spine is significantly larger than the first, as is typical for the genus. The dark coloration of this new species makes photophore markings difficult to identify. However, the dorsal portion of the head is unique from other Etmopterus in possessing parallel linear markings with a light brown patch in between. The head portion is also distinct from other members of the ‘E.spinax clade’ in having a dense concentration of dermal denticles closely surrounding the eyes, mouth, gills and spiracles. This is the only Etmopterus species presently known from the Pacific coast of Central America.
Rachel H L Walls, Nicholas K Dulvy
Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada
A Tale of Two Seas: The Contrasting Status of Europe’s Elasmobranchs
The International Union for Conservation of Nature’s (IUCN) Red List Assessments provide the motivation and foundation for global and regional conservation and fisheries management efforts. Some of the earliest assessments were done in Europe, which led to improved fisheries management measures specific to elasmobranch protection in the Northeast Atlantic. Conversely in the Mediterranean Sea, there has been little scientific or management progress. The IUCN Shark Specialist Group recently reassessed all elasmobranchs in European waters, which allows us to review status changes since 2005 for both the Northeast Atlantic and Mediterranean regions. Our comparison revealed striking differences in the overall status of elasmobranchs since the previous assessments and between regions. While the status of elasmobranchs in the Northeast Atlantic has improved, the Mediterranean status has actually worsened. Approximately 35% of Northeast Atlantic elasmobranchs are considered “safe” compared to only 10% of Mediterranean species. Similarly, 31% of Northeast Atlantic species are threatened with an elevated risk of extinction, compared to almost 50% in the Mediterranean: the highest proportion of threatened species in any region globally. It is likely that the lack of appropriate management measures implemented in the Mediterranean specific to elasmobranchs since the previous Red List assessment is the primary reason for these differences, and this will be explored in greater detail.
Kristin A. Walovich, David A. Ebert
Moss Landing Marine Laboratories, Pacific Shark Research Center, Moss Landing, CA, USA
A Revision of the Short-nose Chimaeras (Genus Hydrolagus) from Southern Africa: Conservation and Management Implications of an Enigmatic Fish Group
A lack of taxonomic clarity has negative implications for many facets of chondrichthyan research including proper identification, acquisition of basic life history information, and the implementation of fishery management and conservation efforts. The Order Chimaeriformes, also known as ghost sharks or chimaeras, is an enigmatic and understudied group of fishes particularly vulnerable to impacts of deep-sea fisheries. This vulnerability is compounded by taxonomic uncertainties and a paucity of life history information, especially for chimaeras of the genus Hydrolagus (Family Chimaeridae) from the southern African region. Given historical and current taxonomic ambiguity and its impacts on management and conservation, the main objective of this study is to provide a qualitative, quantitative and genetic assessment of the diversity of the genus in the Southern African region. Full elucidation of species composition will enable the development and dissemination of reliable identification material and range maps to improve fisheries statistics, initiate ecological research and facilitate appropriate conservation efforts.
NOAA Fisheries, La Jolla, CA, USA
The Elasmobranch Gill: A Window into Evolution and Physiology
Due to its multiple functions in respiration, osmoregulation, pH balance, and nitrogenous waste excretion, many comparative physiologists consider the fish gill one of the most complex animal organs. Although the functional unit of the fish gill (the gill filament) has remained structurally and functionally intact throughout the course of fish evolution and diversification from lampreys to teleosts, the elasmobranch gill has a number of largely unique features. Perhaps most notably is the connection of the gill filaments to interbranchial septa, which affects not only the flow of water through the gills, but may provide specific advantages and disadvantages to elasmobranch respiration. Thus, in many ways, the elasmobranch gill provides unique insight into the evolutionary factors that sculpt gill morphology and function. Because many elasmobranchs (and other fish groups) are large, live in remote or inaccessible habitats, and or have high activity levels, direct physiological studies conducted in the laboratory or under controlled conditions may not be feasible. For such groups, examination of branchial morphology can provide significant insight into metabolic requirements and other important aspects of a species physiology.
Bradley Wetherbee1, Michael Byrne5, Jeremy Vaudo2, Guy Harvey3, Mahmood Shivji4
1University of Rhode Island, Kingston, RI, USA, 2Guy Harvey Research Institute, Ft Lauderdale, FL, USA, 3Guy Harvey Ocean Foundation, Ft Lauderdale, FL, USA, 4Save Our Seas Foundation Shark Center, Ft Lauderdale, FL, USA, 5Warnell School of Forestry and Natural Resources University of Georgia, Athens, GA, USA
Orientation of Mako Sharks (Isurus oxyrinchus) to Environmental Conditions in the Open Ocean
Mako sharks (Isurus oxyrinchus) are frequently captured in long line fisheries and are heavily targeted by recreational anglers in many parts of the world. Given the fishing pressure on mako shark populations there is a great deal of interest in management of their stocks. However, information about movements and migrations of mako sharks that would enable comprehensive understanding of interactions with fisheries and delineation of distribution patterns in waters under the jurisdiction of numerous countries is sparse. We tagged 45 mako sharks with satellite transmitters and tracked their movements over the span of several years. A state space model was used to construct continuous tracks for sharks and to categorize their locations into two behavioral states – searching and transiting. Remote sensing databases were used to determine environmental conditions of sea surface temperature, chlorophyll, productivity, upwelling and frontal index at each location and values in areas searched were compared with those for locations when sharks were transiting. Environmental conditions of specific water temperature and productivity were associated with the searching behavioral mode indicating that mako sharks orient towards a specific set of water conditions for presumably engaging in foraging behavior.
John Whalen1, Jim Gelsleichter1, Dean Grubbs2
1University of North Florida, Jacksonville, FL, USA, 2Florida State University Coastal and Marine Laboratory, St. Teresa, FL, USA
Using DNA Adducts to Examine Polycyclic Aromatic Hydrocarbon Exposure in Shark Populations Affected by the Deepwater Horizon Oil Spill
The Deepwater Horizon oil spill (DWH) released 5 million barrels of crude oil into the Gulf of Mexico (GOM) between April and July of 2010, posing significant health risks to deepwater shark species because of the high concentration of oil and its most toxic components, polycyclic aromatic hydrocarbons (PAHs). Exposure to PAHs results in increased expression of metabolic enzymes necessary for the biotransformation and excretion of these compounds. Occasionally, metabolites resulting from this process can bind to DNA, forming adducts and creating the potential for mutagenic effects. The objective of this study was to determine if increased PAH-DNA adduct formation occurred in two abundant and ecologically important Gulf of Mexico shark species: Squalus cf. mitsukurii and Centrophorus granulosus. Animals were collected using demersal long lines from the Northeast GOM at varying distances from the origin of the DWH in 2011 and 2014. The presence of DNA adducts was determined in peripheral blood cells using immunofluorescence. Adduct formation was examined in relation to relative levels of oil exposure. A total of 52.5% of individuals examined possessed DNA adducts, ranging from 0 to 19 per 500 cells. The proportion of C. granulosus with adducted cells increased from 0.273 to 0.875 while the proportion of S. mitsukurii remained constant at 0.571, suggesting possible oil-related effects in the former. This is the first study to examine and detect the presence of PAH-DNA adducts in sharks, suggesting that they may provide a useful tool for assessing PAH effects in these fishes.
Connor White1, Yukun Lin2, Jerry Hsiung2, Christopher Clark2, Christopher Lowe1
1California State University Long Beach, Long Beach, CA, USA, 2Harvey Mudd College, Claremont, CA, USA
Habitat Selection of the Leopard Shark, Triakis semifasciata, Using Fine Spatio-Temporal Movement and Temperature Data
Environmental conditions are largely considered to be drivers of elasmobranch movements and behaviors. However, conditions are in constant flux and can be highly variable over small spatial extents. Thus to understand how individuals interact with surrounding environmental conditions, researchers must be able to measure the movements of individuals and environmental conditions at high spatio-temporal resolutions. We developed an autonomous underwater vehicle (AUV) designed to actively track an acoustically tagged elasmobranch, providing better spatial accuracy than a human (AUV: 6.1 ± 4.8 m, Researcher: 16.6 ± 9.7 m, F = 31.1, p = 0.005), while generating significantly more localizations (AUV: 45.2 ± 10.5 detection/min, Researcher: 12.2 ± 9.1 detections/min, t2.41= 3.96, p = 0.04). These positions were further refined by integrating magnetic heading of the animal provided by animal-borne inertial measurement units (IMU). Using this system 5 leopard sharks were tracked in Big Fisherman’s Cove (BFC), Catalina Island. Seafloor temperature was collected every 5 min from 20 locations in the cove to derive interpolated temperature maps. Comparing the fine-scale shark movements with the fine-scale temperatures availability in the cove, showed leopard sharks disproportionately utilized warmer areas of the cove (χ2 =432.3, p <0.001). By utilizing tools that provide fine-scale information on the movement and behaviors of animals, researchers will be able to begin to tease apart how elasmobranchs interact with their environment, and ultimately, how these interactions structure the distributions of species.
Lisa B. Whitenack1, Matthew Kolmann2
1Allegheny College, Meadville, PA, USA, 2University of Toronto, Toronto, Ontario, Canada
Integrative Chondrichthyan Paleobiology: The Present is the Key to the Past
The chondrichthyan fossil record is composed primarily of teeth, though occasionally other body parts are preserved. This often translates into using fossils for studying taxonomy, biostratigraphy, paleoecology, and evolutionary history. Studies that integrate across disciplines are few, and those that do tend to utilize extant taxa. We will discuss those studies that have used integrative techniques, focusing on the use of fossil teeth to understand chondrichthyan evolution in a broad sense. We then will examine trends in tooth morphology coincident with trends in prey availability across geological time. Finally, we will identify holes in our knowledge of chondrichthyan evolution and look forward to how integrative techniques can help us explore this topic.
South-East Zoo Alliance for Reproduction and Conservation, Yulee, FL, USA
The Changing Face of AES
There has been a steady demographic shift occurring in life sciences over the last 30 years, so maybe it’s not so unexpected to see it in the field of elasmobranch science as well. While all fields of science have historically been largely male-dominated, there are now far more women training in biological fields than men; however, the proportion of women entering and remaining within professional careers is still proportionally behind that of males. This trend is particularly true for women and underrepresented groups in AES. Not unlike other fields in the life sciences, pioneers like Eugenie Clark, one of the first women to establish herself as force among elasmobranch scientists in the 1960s, led the way for the next generation of female scientists. Despite increasing numbers of female student members, the number of women remaining in the society as professional members has not increased proportionally. Male AES members have served as president for 26 out of the 30 year history of the society and only two women have been elected as President of AES, the first being Merry Camhi in 2002. There has been a growing number of women serving important leadership roles in AES, particularly over the last 10 years, which is needed to support the needs of our changing society. However, there is also a need to further enrich our ranks with greater diversity.