2009 AES Abstracts

Portland, Oregon

143 AES GRUBER AWARD I, Parlor ABC, Thursday 23 July 2009

Jeremy J. Vaudo, Michael R. Heithaus

Florida International University, Miami, FL, United States

Foraging Ecology of a Nearshore Australian Batoid Community Inferred from Stable Isotopic Analysis

Shark Bay, Australia, supports a diverse batoid fauna that show a high degree of spatial overlap. To explore whether these species are engaged in interspecific competition and how they might partition resources, we examined the foraging ecology of six batoids using stable isotope analysis. Delta 13C values indicate all species feed predominantly from a seagrass-based food web. Despite considerable overlap in delta 15N values obtained from all species, interspecific differences were detected. Himantura fai and Glaucostegus typus are slightly elevated in 15N compared to the other the species, suggesting that they feed at a higher trophic level, while Aetobatus narinari has lower delta 15N values compared to all other species. Examination of stomach contents suggests that similar delta 15N and 13C values are the result of similar diets. Over the size ranges examined, H. fai, Pastinachus sephen, and G. typus displayed relationships between size and both delta 15N and 13C values, suggesting ontogenetic shifts in diet. Glaucostegus typus tended to become less enriched in 13C and more enriched in 15N as length increased. Himantura fai and P. sephen displayed the opposite pattern with larger individuals more enriched in 13C and less enriched in 15N. With the exception of A. narinari, there is little evidence that Shark Bay's batoid species are partitioning food resources. Lack of resource partitioning could be the result of the high productivity of Shark Bay's seagrass beds (i.e., resources are not limiting) and population regulation occurring at life history stages not feeding on the flats we studied.

 

 

65 AES GRUBER AWARD I, Parlor ABC, Thursday 23 July 2009

Edward Brooks1, Katherine Sloman3, David Sims2, Andy Danylchuk1

1Cape Eleuthera Institute, Eleuthera, Bahamas, 2Marine Biological Association of the United Kingdom, Plymouth, Devon, United Kingdom, 3University of Plymouth, Plymouth, Devon, United Kingdom

Seasonal Abundance, Demographics and Habitat Use of the Caribbean Reef Shark (Carcharhinus perezi) in the North East Exuma Sound, The Bahamas

The Caribbean reef shark (Carcharhinus perezi) is a large, reef-associated apex predator common throughout the tropical western Atlantic and Caribbean. Despite the ecological and economic importance of C. perezi, relatively little is known about its basic ecology and life history throughout its range, including the Bahamian archipelago. To examine the abundance and habitat use of C. perezi in the northeast Exuma Sound, longline surveys were conducted across the four seasons and in three coastal zones differentiated by coarse habitat type and distance from pelagic waters. Soak time for longlines was 90 minutes and each shark landed was sexed, measured, and tagged. In addition, a subset of sharks were implanted with acoustic transmitters and tracked using a fixed receiver array spanning approximately 50 km2. To date, 142 sharks (male n=45 female n=93 unknown n=4) have been captured during 192 sets across three seasons of sampling. Results show distinct variation in relative abundance with a greater number of sharks occurring in the summer when compared with autumn and winter (mean CPUE Summer=1.656, Winter=0.818, Fall=0.352 sharks 100 hooks-1 hour-1; p<0.0001, F=13.0180). Significant differences also occurred between habitat zones with a greater abundance of sharks being caught in the deep reef area immediately adjacent to the Exuma Sound (p<0.0001, F=29.6639). During the summer months sharks exhibit highly developed philopatry as illustrated by 9.5% recapture rate and a mean linear dispersal between capture and recapture of 1.1 km. Strong philopatry was also evident from the acoustic telemetry data.

 

457 AES GRUBER AWARD I, Parlor ABC, Thursday 23 July 2009

Lucy Howey1, Bradley Wetherbee2, Anthony Wood2, Mahmood Shivji1

1Guy Harvey Research Institute, Nova Southeastern University, Dania Beach, FL, United States, 2University of Rhode Island, Kingston, RI, United States

Comparative Habitat Utilization of the Blue Shark (Prionace glauca) and Shortfin Mako (Isurus oxyrinchus)

Blue and shortfin mako sharks are both highly migratory, widely distributed, pelagic species common in western North Atlantic continental shelf waters during summer months. Both undergo seasonal migrations to warmer or southern locations. Mako sharks are regional endotherms that maintain elevated temperatures in specific body parts, whereas blue sharks are typical ectotherms. Despite striking physiological and morphological differences between these species, they utilize roughly the same habitat on the continental shelf. To compare fine-scale habitat use of these two species we used pop-up satellite tags which archive depth, temperature, and light to examine environmental utilization of blue (n=10) and shortfin mako (n=6) sharks during migrations away from the shelf. All blue shark and two shortfin mako displayed long- distance migrations. Both blue and mako sharks occupied water of similar depth and temperature on the shelf, despite different prey preferences. During migration, mean depth of blue sharks was 85m compared to 50m for mako sharks. Both blue and shortfin mako sharks utilized 16-22 °C waters for 75% and 60% of their time, respectively. Both species dove frequently during migration with maximum recorded depths of 855m for a blue shark and 866m for a mako. The greatest straight-line distance traveled by a blue shark was 2485km (Cape Cod to Puerto Rico) and 2100km for a mako (Cape Cod to the Bahamas). Differences between these species while on the continental shelf appear to reflect prey consumption rather than habitat utilization; whereas, during migration the two species exhibited more pronounced differences in habitat utilization.

 

250 AES GRUBER AWARD I, Parlor ABC, Thursday 23 July 2009

Aleksandra Maljkovic, Isabelle Côté

Simon Fraser University, Burnaby, BC, Canada

Hey, Where's My Dinner Gone? Fishing and the Trophic Consequences for Caribbean Reef Sharks

Across marine ecosystems, the selective removal of large quantities of high trophic level species has been termed ‘fishing down the food web’. While the direct consequences of these fisheries are receiving much attention, the indirect impacts on the structure and functional integrity of marine communities remain far from understood. In this study, we quantify the indirect effects of coral reef-based fisheries on the trophic ecology of Caribbean reef sharks (Carcharhinus perezi) over a gradient of fishing pressures in the Bahamas. Using a combination of prey availability surveys, stable isotope analysis and remote acoustic telemetry, we show that reef sharks inhabiting un-fished and lightly fished sites feed at significantly higher trophic levels, and over smaller ranges, than sharks at heavily fished sites. The results suggest direct competition between reef sharks and fishers for the same resources, with potential costs to the sharks in terms of maintaining minimum energy requirements and/or optimal foraging. Human-mediated depletion of preferred prey species is likely to have wider ecosystem consequences than previously thought.

 

326 AES GRUBER AWARD I, Parlor ABC, Thursday 23 July 2009

Katherine Jirik, Christopher Lowe

California State University Long Beach, Long Beach, CA, United States

Influence of Temperature on the Habitat Use and Movement Patterns of Round Stingrays in a Southern California Estuary

Sexual segregation among elasmobranchs often results in differential habitat use, with females of some species moving into shallow, inshore environments during certain seasons. Generalizing habitat preferences can be complicated further if thermal regimes differ between habitat types within an inshore environment (e.g. restored vs. natural estuarine areas). We compared the abundance and movement patterns of round stingrays (Urobatis halleri) in restored and natural habitats of the Anaheim Bay Estuary (California, USA) to determine whether rays prefer warmer water habitats and if females utilize restored areas during pregnancy. Rays were seasonally abundant with the highest densities occurring from June-August. Higher ray densities correlated with warmer seafloor water temperatures. Ray densities were also higher in the restored habitat than the natural habitat. All rays collected in restored areas during summer were female, but sex ratios in natural areas were only slightly female-biased. Pregnancy was confirmed for female rays collected in restored habitat using ultrasonography. Ultrasound image analysis revealed a difference in the developmental stages present between mid-summer and early fall. In addition, a study of ray short-term movements showed that the proportion of time female rays spent in restored habitat decreased as water temperatures decreased. Longer-term movements indicated that most rays that used restored areas emigrated from the estuary in late summer or early fall, just before water temperatures in restored habitat began to decrease. Water temperature influences ray habitat preference, and pregnant females that aggregate in restored areas may attain a thermally-derived reproductive benefit by selecting warmer habitats during gestation.

824 AES GRUBER AWARD I, Parlor ABC, Thursday 23 July 2009

Thomas Farrugia1, Mario Espinoza1, Dale Webber2, Frank Smith2, Chris Lowe1

1California State University, Long Beach, Long Beach, CA, United States, 2VEMCO Ltd., Halifax, Nova Scotia, Canada

Testing a New Long-term Fine-scale Positional System for Tracking Multiple Fish Simultaneously

Quantifying the fine-scale movement of coastal elasmobranchs is important in determining life history characteristics, resource utilization and the role of elasmobranchs in coastal communities. However, traditional active tracking requires a large amount of time and effort and yields very short-term data (days). We describe and test a novel acoustic telemetry technique using Vemco VR2W acoustic receivers that will provide long-term fine-scale positional data of elasmobranchs fitted with coded transmitters. The VR2W Positional System (VPS) uses stationary transmitters placed throughout a VR2W array to synchronize the internal clocks of the receivers. Differences in times of arrival from transmitters placed on elasmobranchs to three or more receivers are used to triangulate a position for the animal, potentially every time the transmitter pulses. The VPS was found to estimate the location of a stationary test transmitter with a mean accuracy of 3.18 m and a mean precision of 3.02 m. Ninety percent of the VPS estimates fell within 6.06 m of the actual transmitter location. A shovelnose guitarfish and a gray smooth-hound, were double-tagged and tracked simultaneously using active tracking and the VPS. Movement parameters (including distance and direction traveled) binned in one-hour intervals did not differ significantly between VPS and active tracking for either species. Our results suggest that the VPS provides fine-scale data comparable to active tracking over the entire life of a coded transmitter (years), providing significantly longer term, fine-scale data for numerous individuals simultaneously.

542 AES GRUBER AWARD I, Parlor ABC, Thursday 23 July 2009

Steven Kessel1, Samuel Gruber2, Rupert Perkins1, Todd Gedamke3, Bryan Franks2, Demian Chapman4

1Cardiff University, South Wales, United Kingdom, 2Bimini Biological Field Station, South Bimini, Bahamas, 3National Marine Fisheries Service, Miami, FL, United States, 4Stony Brook University, Stony Brook, NY, United States

Movements and Migrations of the Jupiter Lemon Sharks (Negaprion brevirostris)

The presence of large aggregations of adult lemon sharks (Negaprion brevirostris) in the coastal waters of Jupiter, FL, present the first opportunity to study the mature life stage of this otherwise well-studied species. During winter research seasons from 2006-2009, 138 sharks were obtained using drifted drop-line gear. Fifty four lemon sharks were implanted with Vemco V16H transmitters (27 males, 27 female; 165 - 225 cm PCL). Wildlife Computer MK10 tags were also attached to five adults and programmed to detach after 120 days. Localized movements were detected on a 17 station array, each with temperature profiler, stretching along 65 km of coastline. There were distinct seasonal patterns in the formation of lemon shark aggregations. Long range movements outside of the winter aggregation season were captured on more than 20 Vemco receivers contained in the FACT and ACT arrays stretching along ~2,400 km of coast on the U.S. Eastern seaboard. At the beginning of the 2009 winter season, 22 of 35 adult lemon sharks tagged during past seasons had returned to the aggregation. Adult males that were detected on receivers at the mouth of Altamaha River, GA, (N=3) and in at Winyah Bay, SC (N=1) during the summer, had returned to the Jupiter aggregation the following winter. New study sites were established at lemon shark aggregation sites in the Bahamas and Cape Canaveral to better assess population connectivity on a regional scale. We also implanted 8 bull sharks (Carcharhinus leacus) with V16H transmitters to compare movement patterns between species.

876 AES GRUBER AWARD I, Parlor ABC, Thursday 23 July 2009

Kristine Stump1, John McManus1, Samuel Gruber2

1University of Miami - RSMAS, Miami, FL, United States, 2Bimini Biological Field Station, Bimini, Bahamas

Applying Individual-Based Modeling Techniques to Address Potential Impacts of Essential Habitat Loss in a Lemon Shark Nursery

Individual-Based Modeling (IBM) is a powerful heuristic tool used to understand complex ecological processes. "Agents" representing individuals are assigned rules that dictate their behavior and influence interactions with other agents and the environment. After multiple iterations of the model, population- and ecosystem-level patterns may emerge from interactions of independently-acting agents. The goal is to develop a model such that emergent patterns reflect patterns of interest observed in the field. In the present study at Bimini, Bahamas, the mangrove-fringed lagoon comprises several important nurseries for lemon sharks (Negaprion brevirostris). The study site is a critical nursery, as it affords ample prey and protection from larger predators. A significant volume of research exists concerning the life history, physiology, diet, bioenergetics, growth and behavioral ecology of lemon sharks in Bimini. This study will utilize a twenty-year database combined with ongoing field observations to create an IBM that combines the behavior and bioenergetics of juvenile lemon sharks with that of their prey and predators as they interact within the nursery ecosystem. The field-validated model will be used to describe the functioning of the nursery ecosystem and address actual and potential ecological impacts of planned coastal development in the area, serving as a tool to assess management alternatives. The model will help elucidate the role of top predators in a mangrove-fringed lagoon ecosystem, as well as the potential consequences of a decline or loss of such predators.

407 AES GRUBER AWARD I, Parlor ABC, Thursday 23 July 2009

Derek Burkholder1, Michael Heithaus1, Jordan Thomson2, Aaron Wirsing3

1Florida International University, Miami, FL, United States, 2Simon Frasier University, Vancouver, British Columbia, Canada, 3University of Washington, Seattle, WA, United States

Does Tiger Shark (Galeocerdo cuvier) Predation Risk Influence Habitat Use of Green Sea Turtles (Chelonia mydas) at Multiple Spatial Scales?

Trade-offs between predation risk and food availability shape habitat use decisions of many species. However, these factors can vary significantly at differing spatial and temporal scales. Because foraging by large-bodied herbivores can alter the dynamics of plant communities it is important to understand the factors driving their habitat use. From 1999-2009, we assessed habitat (deep waters vs shallow seagrass banks) and microhabitat (bank edges and interior portions of banks) use of green sea turtles (Chelonia mydas) in relation to the availability of food and perceived risk from tiger sharks (Galeocerdo cuvier) in Shark Bay, Western Australia. Habitat use was assessed using belt transects and predation risk was determined using catch rates on drumlines (temporal variation) and acoustic tracking from previous studies (spatial variation). At the level of habitats, green turtles selected shallow banks where food availability was high and, surprisingly, did not show a significant shift into safer, deeper waters when tiger shark abundance increased. Similarly, we did not detect population-level shifts in microhabitat use; the distribution of turtles between more dangerous interiors and safer edges did not shift seasonally. This may be due to the year-round presence of sharks during years when we assessed microhabitat use (i.e. shark abundance changed but they never abandoned the bay) or the possibility that green turtles manage predation risk primarily at the microhabitat level and based on their individual body condition whereby low-condition animals are willing to take risks to forage in high-risk but high- gain interior habitats when sharks are abundant.

731 AES GRUBER AWARD I, Parlor ABC, Thursday 23 July 2009

Wade Smith1, J. Fernando Márquez-Farías2, Jessica Miller1, Selina Heppell1

1Oregon State University, Corvallis, OR, United States, 2Universidad Autonoma de Sinaloa and Instituto Nacional de la Pesca, Centro Regional de Investigación Pesquera de Mazatlán, Mazatlán, Sinaloa, Mexico

Distinguishing Natal Origins from Vertebral Chemical Composition: the Utility of Trace Elements as Natural Markers in Elasmobranch Populations

The identification of nursery areas and understanding of their importance provides insight into the structure and dynamics of populations. Knowledge of dispersal pathways and population connectivity provides valuable details for successful conservation. Elements are naturally assimilated into the tissues and calcified structures of many species as a byproduct of respiration and feeding. The resulting combinations and ratios of these elements may reflect the physiochemical environment in which an organism lives or has previously occupied. The segregation of juvenile and adult habitats among many elasmobranchs through the use of nursery areas creates the potential for distinctive elemental markers to be incorporated into vertebrae as a result of the differing physical and chemical characteristics encountered as young-of-the-year. Trace elemental analyses have proven to be powerful markers in ecological studies, however, these tools have not previously been applied to investigations of shark and ray populations. To determine if differences in elemental composition can be detected in cartilaginous vertebrate and are geographically consistent, we are conducting a field study of young-of-the-year scalloped hammerhead sharks (Sphyrna lewini) from various pupping locations. Samples were collected from artisanal fishery landings along the Pacific coast of Mexico over four consecutive months in both 2007 and 2008. Vertebrae were cleaned, thin-sectioned, and analyzed using Laser Ablation Inductively Coupled Plasma Mass Spectrometry. Multivariate analysis of variance was used to examine intra- annual differences in vertebral chemistry within sample locations. The ability to successfully classify individual specimens to their site of natal origin was assessed through quadratic discriminant function analysis.

Life History Aspects of Two Bering Sea Skate Species, Bathyraja lindbergiand B. maculata  MISSING!!

 

 

 

 

 

 

 

 

 

 

 

253 AES Behavior & Morphology, Galleria South, Thursday 23 July 2009

Michelle Heupel1, Colin Simpfendorfer1, Richard Fitzpatrick2

1James Cook University, Townsville, QLD, Australia, 2Australasian Natural History Unit, Townsville, QLD, Australia

Preliminary Analysis of Grey Reef Shark Movements on the Great Barrier Reef

Data on the presence and distribution of reef sharks on the Great Barrier Reef (GBR) are currently limited. In addition, recent research examining the abundance of reef sharks has produced contradictory results about the status of these populations. This results in a need for a better understanding of the movement and space utilization of these species to help interpret the limited data available for these populations. This pilot study examined the movements of grey reef sharks (Carcharhinus amblyrhynchos) on 6 reefs in the northern GBR to define whether individuals remained attached to a single reef platform and define the efficacy of Marine Park Zoning in sheltering these individuals from fishing pressure. Five different management zone areas were represented in the study site. A series of 31 VR2 acoustic receivers were deployed to passively track the movement of reef sharks from January to July 2008. Eight sharks ranging in size from 84 - 152 cm total length (TL) were monitored for periods of 13-167 days and detected on 1- 130 days during that period. Three patterns of movement were observed from the eight sharks fitted with transmitters: 1) long-term presence at a single reef, 2) movement away from the monitored area, and 3) movement between and among reef platforms. Implications of these movement patterns for research and management of these populations will be discussed.

 

 

272 AES Behavior & Morphology, Galleria South, Thursday 23 July 2009

James Franks1, Eric Hoffmayer1, William Driggers III2

1University of Southern Mississippi, Gulf Coast Research Laboratory, Ocean Springs, MS, United States, 2NOAA Fisheries, Southeast Fisheries Science Center, Mississippi Laboratories, Pascagoula, MS, United States

Diel Movements Of A Scalloped Hammerhead Shark (Sphyrna lewini) In The Northern Gulf of Mexico As Determined By High-Rate Pop-Up Satellite Archival Tagging

Diel behavior and essential habitat of scalloped hammerhead sharks (Sphyrna lewini) in the Gulf of Mexico are poorly understood. A high-rate pop-up satellite archival tag (PSAT; Microwave Telemetry, PTT-100 HR) affixed to a mature female caught at a deep water petroleum platform in the northern Gulf of Mexico in June 2008 recorded data on the shark's diel behavior and use of vertical habitat as related to temperature and depth for a period of 27 days. Data recovered from the tag were used to document fine-scale, diel vertical movements previously unreported for S. lewini in the Gulf region. The shark spent ~85% of daylight hours at depths and temperatures between 20-100m and 24-29oC, respectively, with no deep dives. The shark spent ~70% of night time hours between the surface and a depth of 50 meters, with the remainder of night time spent in repetitive vertical excursions >700m, the deepest being 964m at a temperature of 5.8oC. Deep dive rates of descent were significantly faster than ascent rates. It is presumed that throughout the entire 27-day period of PSAT attachment the shark remained at or near the petroleum platform during daytime hours and made repetitive, deep water forays into the adjacent Mississippi Canyon at night.

 

 

 483 AES Behavior & Morphology, Galleria South, Thursday 23 July 2009

Nicholas Whitney1, Wes Pratt2, Theo Pratt2, Jeffrey Carrier3

1Center for Shark Research, Mote Marine Laboratory, Sarasota, FL, United States, 2Center for Shark Research, Mote Marine Laboratory Center for Tropical Research, Summerland Key, FL, United States, 3Department of Biology, Albion College, Albion, MI, United States

Biologging Love: Identifying Shark Mating Behavior Using a Three- dimensional Acceleration Data Logger

In the few shark species for which it has been observed, mating behavior has involved various postures and movements that appear to be very different from those involved in typical daily activities such as swimming, feeding, and resting. A data logger that records these postures and movements may therefore allow us to identify mating behavior in species for which direct observations are impossible. We applied Vemco, three-dimensional acceleration data loggers, sampling at a rate of 5 Hz, to four adult nurse sharks during their mating season in the Florida Keys. Loggers were carried for periods ranging from 24 to 106 hrs, and were recovered through animal recapture or logger shedding and recovery after corrosion of a galvanic link. Logger-equipped sharks were directly observed carrying out several behaviors (e.g., resting, slow swimming, avoidance, fast swimming, courtship/mating) providing visual corroboration of acceleration data. This allowed us to distinguish the movements associated with mating from those associated with other behaviors, and thereby differentiate the time and duration of mating-related events. We also used acceleration data to construct ethograms for each animal over the experimental period, and we discuss these results and the potential for these devices in future studies of shark reproductive behavior.

 

878 AES Behavior & Morphology, Galleria South, Thursday 23 July 2009

Jayne Gardiner1, Jelle Atema2, Robert Hueter3, Philip Motta1

1University of South Florida, Tampa, FL, United States, 2Boston University/Marine Biological Laboratory, Woods Hole, MA, United States, 3Mote Marine Laboratory, Sarasota, FL, United States

Odor Orientation Behavior in Sharks

Sharks are hypothesized to orient to odors by performing bilateral comparisons between the nares, turning towards the side receiving the highest concentration. Results from previous experiments have left unclear the question of whether animals respond to differences in concentration or in the timing of odor arrival at the nares. We fitted smooth dogfish, Mustelus canis, with headsets made of tubing to deliver odor to the two inflow nares, connected to computer-controlled programmable syringe pumps to precisely control the timing of odor delivery. First, the nares were presented with squid rinse of identical concentration with the timing varied such that one naris received the pulse ahead of the other with 0.1, 0.2, 0.5, and 1s delays. Secondly, both nares were simultaneously stimulated, one with full strength squid rinse, the other with a 100 fold dilution. Finally, the nares were stimulated with these concentration differences but with a 0.5s delay such that the weather odor was received before the stronger odor. For delays of less than 1s, animals displayed turns towards the side receiving the first odor pulse, regardless of concentration differences. Simultaneous pulses of different concentrations and pulses of equal concentration with a 1s delay resulted in turns towards either side with equal frequency. These results suggest that the temporal pattern of odor patches presents the most salient information for orientation in this species and the decision to turn is made within 0.5 seconds, regardless of subsequent, stronger odor pulses.

 

898 AES Behavior & Morphology, Galleria South, Thursday 23 July 2009

Alex Hearn3, James Ketchum1, Pete Klimley1, Eduardo Espinoza1

1UC Davis, Davis, CA, United States, 2Galapagos National Park, Galapagos, Ecuador, 3Charles Darwin Foundation, Galapagos, Ecuador

Hotspots Within hotspots? Aggregations of Pelagic Fishes at Southeastern Corner of Wolf Island, Galapagos

Are pelagic species such as sharks and tuna distributed homogenously in the oceans? Large assemblages of these species have been observed at seamounts and offshore islands in the Eastern Tropical Pacific, which are considered hotspots of pelagic biodiversity. Is the species distribution uniform at these hotspots or do species aggregate at a finer spatial scale? We employ three techniques to demonstrate that the aggregations of scalloped hammerhead sharks, Sphyrna lewini, and other pelagic species are confined to the southeastern corner of Wolf Island (Galapagos Marine Reserve). Coded ultrasonic beacons were placed on individuals and they were detected by monitors moored at the southeastern corner of Wolf Island and not by monitors deployed at other sites surrounding the island. Hammerhead and Galapagos sharks were tracked for two-day periods and shown to reside a disproportionately large fraction of their time at the southeastern corner. Visual censuses were carried out seasonally at the eight monitor sites at Wolf Island, recording the abundance of tunas, jacks, and many other species. The highest diversity and abundance of these species occurred in the southeastern corner of the island. Future oceanographic studies will be carried out to determine whether some aggregating species provide "a wall of mouths" to consume plankton caught in an entrainment zone up-current of the island and other species use this volcanic site with lava flows leading from it, each with a unique magnetic signature, to guide them as they migrate nightly to their offshore feeding grounds in the open ocean.

 

522 AES Behavior & Morphology, Galleria South, Thursday 23 July 2009

Carl Meyer1, Kim Holland1, Laurent Dagorn2, Yannis Papastamatiou1

1Hawaii Institute of Marine Biology, Kaneohe, HI, United States, 2Institut de Recherche pour le Développement, Victoria, Seychelles, France

First Use of Mobile Peer-to-Peer Network (MP2P) Technology on a Marine Animal

Mobile peer-to-peer (MP2P) technologies offer new opportunities for characterizing interactions between animals and retrieving data about these events. The key attribute distinguishing the MP2P approach from traditional biotelemetry is the exchange of information between individuals (peers) rather than exclusively and directly from individuals to a base station such as a tracking receiver. We equipped 4 Galapagos sharks (Carcharhinus galapagensis) with prototype MP2P technology (VemcoTM ‘Business Card Tags' - BCTs) which used ultrasonic encoding to exchange unique identification codes between host animals during spatial encounters. During the experiment, the island of Oahu was surrounded by an array of 24 stationary receivers (Vemco VR2Ws) capable of detecting both BCTs and conventional coded transmitters.  Before the BCTs were deployed, 32 sharks (Galapagos, sandbar and tiger) were captured at the study site and equipped with conventional coded acoustic transmitters (Vemco V16). Thus the experimental design allowed BCT-equipped sharks to: (1) detect one another, (2) detect other sharks equipped with conventional transmitters, and (3) be detected by fixed receivers stationed around the island of Oahu. Two BCTs were recovered after 20 and 132 days at liberty respectively. Recovered BCTs had recorded 4,506 and 4,875 detections of 28 and 30 transmitter-equipped sharks each, and had detected all 3 other BCT-equipped sharks on multiple occasions. Integration of both mobile (V16 and BCT-equipped sharks) and fixed peers (VR2 receivers) provided greater insight into shark behavior than would have been derived independently from either method. This study represents the first use of MP2P technology on a marine animal.

555 AES Behavior & Morphology, Galleria South, Thursday 23 July 2009

Eric Hoffmayer1, James Franks1, William Driggers III2, Mark Grace2

1Gulf Coast Research Laboratory, The University of Southern Mississippi, Ocean Springs, MS, United States, 2National Marine Fisheries Service, Southeast Fisheries Science Center, Pascagoula, MS, United States

Habitat Preferences and Movement Patterns of Dusky (Carcharhinus obscurus) and Silky (Carcharhinus falciformis) Sharks in the Northern Gulf of Mexico: Preliminary Results

Dusky (Carcharhinus obscurus) and silky (C. falciformis) sharks were once common in the western north Atlantic Ocean; however, due to commercial exploitation their populations are thought to be in decline. Few data exist describing the essential habitats of these two species. This information is imperative to understanding the behavior of these sharks so proper management practices can be implemented to aid in population recovery. The goal of this study was to describe movement patterns and habitat preferences of dusky and silky sharks in the northern Gulf of Mexico. During summer of 2008, thirteen sharks were tagged in the northern Gulf using pop-up satellite archival tags: seven silky (1.3-1.8 m, TL) and six dusky (2.7-3.1 m, TL). All tags popped off and reported data, with deployment durations ranging from 14 to 124 days. The majority of the dusky sharks traveled relatively long distances (>200 km), while all silky sharks remained within 150 km of the initial tagging location. Dusky sharks spent the majority of their time between 21 and 100 meters, with occasional dives below 100 meters, whereas silky sharks spent 99% of their time in the top 50 meters of the water column.

Water temperature ranges were relatively similar with dusky sharks preferring slightly cooler temperatures between 23 and 26 ̊C and silky sharks preferring warmer temperatures between 26 and 29 ̊C. One dusky and one silky shark moved to the southern Gulf of Mexico, which demonstrates the need for shared stock management of these imperiled species.

974 AES Behavior & Morphology, Galleria South, Thursday 23 July 2009

Dewayne Fox1, Bradley Wetherbee2, Lori Brown1, Mahmood Shivji3, Kenneth Sulak4, Johnny Moore1

1Delaware State University, Dover, DE, United States, 2University of Rhode Island, Kingston, RI, United States, 3NOVA Southeastern University, Fort Lauderdale, FL, United States, 4US Geological Survey, Gainesville, FL, United States

Coastal Movements of Sand Tiger Sharks (Carcharias taurus) in the Northwest Atlantic as Determined by Acoustic and Satellite Telemetry

Prior to a recent harvest moratorium, sand tiger sharks (Carcharias taurus) were the focus of both directed and non-directed fisheries in the northwest Atlantic. Sand tigers occupy a high public profile due to their size and relative ease of public display. In contrast with many other large coastal sharks, limited information is available on the coastal movements of sand tigers including locations of overwintering areas. In 2008 we outfitted 13 sand tigers (1.4-3.3m FL) with acoustic (VEMCO Ltd. V-16-6H) and satellite (Microwave Telemetry Inc.) transmitters in Delaware Bay. Twelve of the thirteen acoustic transmitters were detected a total of 8,030 times prior to departing Delaware waters in September and October. Similarly, twelve of the satellite transmitters were detected within scheduled pop-off times (4-6 months post-deployment). Most sand tigers made relatively direct movements to overwintering areas in the Hatteras Bight Region, arriving within weeks of departing Delaware waters. An additional male sand tiger (1.09m FL) outfitted with an acoustic transmitter was detected off Cape Canaveral, FL in January-February, 2009 after departing Delaware Bay in September. Female sand tigers occupied significantly (p <.0001) warmer waters compared to males although occupied depths did not vary significantly (p=.1054). Although perceived as a relatively sluggish species, telemetered sand tigers were documented making rapid movements in the water column from surface waters to depths of 188m. Our results underscore the need for coast-wide approaches to recover sand tigers as this charismatic shark is particularly vulnerable to anthropogenic impacts.

432 AES Behavior & Morphology, Galleria South, Thursday 23 July 2009

Tristan Guttridge1, Samuel Gruber2, Jens Krause1

1University of Leeds, Leeds, United Kingdom, 2Bimini Biological Field Station, Bimini, Bahamas

Refuging and Social Behavior of Free-ranging Juvenile Lemon Sharks, Negaprion brevirostris in a Tropical Lagoon

Group behaviours are widespread in sharks however comparatively little is known about the interactions between individuals and how these might shape the structure and organisation of groups. In this study 40 juvenile lemon sharks Negaprion brevirostris were monitored for a period of 24 months in two shallow water sites at Bimini, Bahamas. Sharks were externally marked with colour coded tags that enabled accurate visual identification of individuals in both solitary and social encounters, such as following, paralleling and circling. Scan sampling on 84 observation days was completed resulting in a data base of 8000 records. Group size ranged from 2-11 individuals with some individuals interacting regularly throughout the 24 month period. Group behaviours were related to environmental variables and assessed through the use of social network theory. This network approach provided a quantitative framework enabling the characterisation of social structure at both the individual and population level. Associative patterns were investigated for a number of shark attributes such as body length, sex and relatedness. This study offers an assessment of and insight into the social life of a predatory shark providing quantitative information on group behaviours of free-ranging sharks. Further, the application of the latest analysis techniques will enable these results to be interpreted and evaluated alongside studies of other animal groups.

 

958 AES Behavior & Morphology, Galleria South, Thursday 23 July 2009

Mateus Soares, Marcelo Carvalho

Universidade de Sao Paulo, Sao Paulo, SP, Brazil

Morphological and Evolutionary Patterns of the Spiracularis Muscle in Batoids (Chondrichthyes)

The present study was conducted to reveal evolutionary implications of the different patterns of the spiracularis muscle in batoids. The spiracularis originates on the neurocranial otic region and generally inserts on the distal aspect of hyomandibula. In Torpedo, Rhinobatos and Pristis the muscle is simple, composed of a single bundle. In other genera it is subdivided into two portions, one lateral, which usually does not vary significantly, and one medial, which varies considerably. In Narcine, the medial spiracularis extends over the lateral portion and inserts on Meckel's cartilage. In Zapteryx, the insertion occurs between the hyomandibula and the palatoquadrate. Within rajiforms, the medial spiracularis extends directly to the palatoquadrate either in a simple manner as in Leucoraja, or overlying the lateral spiracularis as in Rajella and Gurgesiella, or it may present a tendinous connection with the hyomandibula as in Atlantoraja and Rioraja. In pelagic myliobatiforms the spiracularis components are more indistinguishable, and insert onto the palatoquadrate. In dasyatids the muscle remains closely associated with the mandibular joint, slightly projecting towards Meckel's cartilage, whereas in urolophids the insertion is entirely on Meckel's cartilage. In Taeniura, the muscle projects ventromedially to insert on its antimere, which also occurs in Potamotrygon and Plesiotrygon, but not in Paratrygon, in which there is only a slight ventromedial projection. Additionally, in Potamotrygon and Plesiotrygon, the spiracularis merges ventrally with the depressor hyomandibulae. The spiracularis is employed for branquial ventilation in batoids, but the different patterns found may support its use for more varied functions.

 

357 AES Behavior & Morphology, Galleria South, Thursday 23 July 2009

Daniel Figueroa1, Paula Rivera1, Belleggia Mauro3, Delpiani Gabriela2, Shimabukuro Valeria1, Scenna Lorena2, Barbini Santiago4, Bovcon Nelson5

1Lab. Ictiología, Depto. Ciencias Marinas, Universidad Nacional de Mar del Plata, Buenos Aires, Argentina, 2Lab. Ictiología, Depto. Ciencias Marinas, Universidad Nacional de Mar del Plata. CONICET, Buenos Aires, Argentina, 3Lab. Ictiología, Depto. Ciencias Marinas, Universidad Nacional de Mar del Plata. CONICET. INIDEP., Buenos Aires, Argentina, 4Lab. Ictiología, Depto. Ciencias Marinas, Universidad Nacional de Mar del Plata. CIC., Buenos Aires, Argentina, 5Universidad Nacional de la Patagonia San Juan Bosco, Chubut, Argentina

Teeth of Skates in the Southwest Atlantic

Dentition in skates are used not only for feeding but also for reproduction, both are influential factors on tooth morphology. Despite teeth of elasmobranchs are very abundant skeleton elements in fossil records, the study of dentition of skates has not reached the development achieved in sharks. Southwest Atlantic appears to be a great radiation center of skates, probably due to its large continental shelf, and its transitional waters. Fossil teeth of skates in this region were recorded since the Cretaceous. A total of 23 species of skates inhabit Argentinean continental shelf. Their feeding habits are very diverse. Adult individuals of some species have specialized diet in fishes and large sharp tooth cusps, showing no sexual dimorphism (e.g. Bathyraja brachyurops and Bathyraja magellanica). On the other hand, some species have a specialized diet in polychaetes (e.g. Bathyraja albomaculata and Bathyraja macloviana) and evidence a very clear sexual dimorphism, with males presenting larger and sharper tooth cusps than females. In both groups tooth rows of males are well spaced which allows their proper differentiation. An extreme case is Bathyraja multispinis, with teeth without cusps and a quincunx pattern, its diet is based on crabs. In Amblyraja doellojuradoi have appeared curious dental anomalies, such as bicuspid teeth and row duplication. Given the fact that the dentition of many species has not been studied yet and considerable variations in tooth morphology were shown between the species of skates studied, future research is necessary for intra and interspecific comparations.

856 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Jason Ramsay, Cheryl Wilga

University of Rhode Island, Kingston, United States

Hyoid Anatomy and Hypobranchial Muscle Function During Feeding in White-Spotted Bamboo Sharks

White-spotted bamboo sharks exhibit many characters associated with suction feeding such as labial cartilages to occlude the lateral portions of the gape and hypertrophied hypobranchial musculature to power hyoid depression against high negative pressures generated in the buccal cavity. The hyoidiomandibular ligament (LHMM) may assist in lower jaw depression by harnessing and amplifying force generated by the in-series coracohyoideus (CH) and coracoarcualis (CA) and transferring it to the lower jaw to assist the coracomandibularis (CM) in depressing the jaw. Hyoid, upper and lower jaw kinematics and fascicle shortening in the CM, CH and CA were quantified using sonomicrometry, while muscle activity and buccal pressure were recorded simultaneously. Active shortening of the CM occurs prior to the onset of jaw opening and buccal pressure decrease, while jaw depression to peak gape occurs during CM lengthening. The CH actively lengthens and the CA actively shortens by 13% prior to onset of jaw and hyoid depression. Peak active CM shortening, onset of active CH shortening, depression of the hyoid and buccal pressure decrease occur simultaneously. A catch mechanism involving the LHMM and CM that would allow the CH to be lengthened by the CA and released, resulting in high powered expansion during suction feeding is proposed. Consequently, the CM initiates lower jaw depression while the CH and CA drive the jaw and hyoid to peak depression. The LHMM in bamboo sharks appears to be a biomechanical link coupling lower jaw and hyoid depression that is convergent with the mandibulohyoid ligament in bony fishes.

216 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Cheryl Wilga1, Anabela Maia1, Sandra Nauwelaerts2, George Lauder3

1University of Rhode Island, Kingston, RI, United States, 2Michigan State University, East Lansing, MI, United States, 3Harvard University, Cambridge, MA, United States

Prey Capture Using Whole Body Fluid Dynamics in Batoids

Traditionally, suction feeding is described as rapid expansion of the buccal cavity. However, when feeding on the substrate, suction can be generated by lifting the body away from the substrate. This mechanism has been exploited by batoid species, in particular, due to the dorsoventrally flattened body form. Digital particle image velocimetry and high speed video was used to compare the hydrodynamics of feeding behavior in little skates, Leucoraja erinacea and round stingrays Urobatis halleri. We hypothesize that the difference in stiffness of the rostrum and extent of the pectoral fins onto the head between the species should result in behavioral differences; the more flexible rostrum and greater fin area of stingrays will allow more extensive use of body suction. When simulating attached or buried prey, stingrays approach the prey with raised rostral ends of the pectoral fins and then press the edges against the substrate to constrain prey. Stingrays make a tent by raising the rostrum and curling up the pectoral fin edges, then raising the head while rapidly projecting the fins forward and over the prey to generate suction. Skates show a similar behavior, although the smaller fin area does not allow lateral occlusion, thus resulting in weaker flow. Also, skates use a rostral strike behavior that pushes fluid towards the substrate potentially to stun or uncover prey. Thus skates and rays use the body to direct flow in different ways to accomplish similar tasks. This may be explained by the evolutionary divergence in rostral and pectoral fin morphology.

201 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Misty Paig-Tran, Adam Summers

University of California, Irvine, CA, United States

Morphology and Selective Particulate Filtration in Cartilaginous Fishes: Models, Mantas and Whale Sharks

There are 13 species of filter feeding elasmobranchs, which include: manta ray, devil rays, whale shark, basking shark, and mega mouth shark. Understanding the basic biology of these fishes including the movement patterns, mechanics of prey capture, and food preference is necessary for successfully predicting migratory patterns and for assessing and maintaining well-managed stocks. Our approach has been to consider the effect of swimming speed, morphology and water flow on capture efficiency and prey size selection. We found that with simple, cylindrical models of neonatal whale sharks, we could determine parameters that had a significant effect on filtration efficiency and prey selectivity (e.g. gill morphology, swimming speed, etc). We were able to induce passive prey size selectivity by adjusting morphological parameters and swimming speed. This implies that fish with differing physical morphologies could feed in the same plankton bloom, but passively filter different sizes and species of prey. We have catalogued the anatomical differences between the gill raker structures of elasmobranch suspension feeders using computed tomography, physical examinations and permeability measurements. Although there are four main gill raker morphologies, 1) bristle-like gill rakers 2) fur-like, short gill rakers 3) widely spaced, flattened gill rakers and 4) rigid, leaf-like, folded raker structures, the permeability measurements indicate that the resistance through the their raker structures is minimal. The differences in each species' ecology and physiology indicate that these elasmobranchs may filter their prey using a variety of mechanisms (e.g. cross-flow filtration, hydrocyclone filtration, and dead end sieving).

 

316 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Philip Motta1, Michael Maslanka2, Robert Hueter3, Ray Davis4, Rafael de la Parra5, Samantha Mulvany5, Maria Laura Habegger5, James Strother5, Kyle Mara5, Jayne Gardiner5, John Tyminski5, Leslie Zeigler5

1University of South Florida, Tampa, FL, United States, 2Georgia Aquarium, Atlanta, GA, United States, 3Mote Marine Laboratory, Sarasota, FL, United States, 4Comision Nacional de Areas Naturales Protegidas, Cancún, Quintana Roo, Mexico, 5University of California, Irvine, CA, United States

Filter Feeding in the World’s Largest Fish: Form, Function and Diet

Filter feeding is employed by the largest elasmobranchs. Among these the whale shark Rhincodon typus, utilizes ram and suction filter feeding. Archived satellite tag data and aerial observations indicate sharks ram filter feed near the surface approximately 7.5 hours per day in dense aggregations (4.5 g/m3) of plankton off Quintana Roo, Mexico from May through September. With swimming speeds averaging 1.1 m/s, computational fluid dynamics indicates the effective flow rate into the partially submerged mouth is 0.99 m/s. Calculated filter rates, based on mouth morphometrics and swimming speeds, combined with plankton tows and energetic analysis of the plankton, estimate consumed biomass of 11 kg/day for a 476 cm TL shark, and 20 kg/day for a 631 cm shark, equating to an approximate intake of 3,565 and 6,464 kcal/day, respectively. These estimates are compared to dietary intake of captive whale sharks and the filter-feeding basking shark. The novel filtering apparatus of the whale shark consists of a series of twenty filtering pads that lie dorsally and ventrally on either side of the pharynx. These pads, which overlay and completely occlude the branchial arches, have a mesh with holes averaging 1.2 mm in diameter, considerably smaller than the majority of their prey. A mechanism of crossflow filtration whereby particles are entrained and passively transported posterior to the pads is proposed. After passing through the pads an elaborate system of channels directs water through what appear to be collimator vents, and over the gill lamellae before exiting the pharyngeal slits.

295 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Daniel Huber1, Lisa Whitenack2, Stephen Wroe3

1University of Tampa, Tampa, FL, United States, 2University of South Florida, Tampa, FL, United States, 3University of New South Wales, Sydney, NSW, Australia

Structural Mechanics of Primitive and Derived Shark Teeth and Jaws

Finite Element Analysis (FEA) has emerged as a powerful tool for investigating form- function relationships in both extant and extinct taxa. In FEA, biologically relevant loading patterns on skeletal elements can be simulated via computational modeling, thereby revealing the structural performance of complex morphologies. In a comparative context, structural performance can be used to assess selective pressures on the evolution of skeletal morphology. Some of the most dramatic morphological changes in the evolutionary history of cartilaginous fishes have occurred in the feeding mechanism, particularly regarding the teeth and jaws. Through FEA of the teeth and jaws of primitive (sevengill shark Heptranchias perlo) and derived (white shark Carcharodon carcharias) extant sharks, we will identify the endpoints of a gamut of structural evolution in chondrichthyan feeding mechanisms. Preliminary analyses suggest that expansion of the bodies of the upper and lower jaws have substantially increased the strength of these structures, while changes in tooth morphology from multicusped to single-cusped do not affect structural strength of the tooth. Additionally, simulated comparisons of cartilaginous vs. bony jaws indicate that the structural performance and force-transmitting ability of prismatically calcified cartilage are surprisingly high. These data will assist in the development of a conceptual framework for future phylogenetically-informed studies on the structural evolution of chondrichthyan feeding mechanisms. As chondrichthyans are the most basal extant gnathostomes, these analyses will also shed light on both the evolution of jaws and the evolution of cartilage as a skeletal material.

 149 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Toni Ferrara1, Stephen Wroe1, Daniel Huber2, Colin McHenry3, Philip Clausen3, Victor Peddemors4, Mason Dean5, Michael Lowry4

1University of New South Wales, Sydney, NSW, Australia, 2University of Tampa, Tampa, FL, United States, 3University of Newcastle, Newcastle, NSW, Australia, 4NSW Department of Primary Industries, Cronulla, NSW, Australia, 5University of California, Irvine, CA, United States

Three Dimensional Computer Analysis of Jaw Mechanics in Great White and Sandtiger Sharks

The relationship between form and function of the elasmobranch feeding apparatus is central to our understanding of their evolution and ecology. Bite force has been utilized as a predictor of this relationship in many vertebrate taxa, and when combined with morphological studies, can provide valuable insight into cranial evolution, dietary limitations, niche segregation, and sexual dimorphism. However, bite force in sharks is poorly understood and accurate estimates are difficult to obtain. Finite Element Analysis (FEA) is a powerful tool used by engineers, and increasingly by biologists, to examine the mechanical behaviour of structures. In FEA, a 3 Dimensional (3D) computer model of a structure is generated and subjected to various loading conditions to evaluate mechanical performance. FEA provides not only a method to quantitatively assess bite force, but also provides a much broader analysis of form and function by demonstrating how a structure responds to the various forces which may be imposed upon it, such as when biting prey. The present study assembled sophisticated 3D Finite Element models based on computerized tomography (CT) scans and dissected specimens of the jaws of two species of shark, Carcharodon carcharias (great white) and Carcharias taurus (sandtiger). Comparisons of bite force, gape angle and mechanical behaviour in these two species is presented. Of key interest is how jaws constructed of flexible cartilage have evolved into an efficient feeding apparatus. Although the application of FEA to elasmobranch research is still in its infancy, this technique has potential benefit to many aspects of shark research.

 

549 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Mason Dean1, Adam Summers1

1University of California, Irvine, CA, United States, and Friday Harbor Laboratories, Friday Harbor, WA, United States

From Molecules to Jaws: Structural Hierarchy and Functional Morphology of the Tessellated Skeleton of Cartilaginous Fishes

The complex, multi-tiered design of biomaterials lends them unequalled emergent material properties; however, to understand the basis for these properties many structural levels must be taken into account. This is increasingly possible for biologists due to the growing accessibility of micro/nanoscale imaging and materials testing tools: we use a variety of high-resolution techniques to investigate the microstructure and material properties of cartilaginous fish skeletons, in an effort to understand material-, skeletal- and organismal-level performance. Endoskeletal elements of sharks and rays are comprised of an uncalcified, hyaline cartilage-like core overlain by a thin layer of mineralized hexagonal tiles (tesserae), often joined by intertesseral fibers. The macroscopic spatial relationships of the tissue phases (unmineralized cartilage, mineralized cartilage, fibrous tissue) are well-known — endoskeletal tessellation is a long-recognized synapomorphy of elasmobranch fishes— but the functional advantages of a tessellated and purely cartilaginous skeleton have been unclear. The tesserae are a necessary feature of a 'shelled' skeletal element that will grow and we have found several places where “typical” morphologies are modified, such as high-stress or curved regions of the skeleton. We also find that the micrometer-scale subunits of the skeleton —the tesserae and uncalcified cartilage — have material properties comparable to mammalian analogs, but when layered together, the resultant tissue is both stiff and good at damping mechanical energy. Furthermore, our structure level mechanical models suggest that the tessellated design helps to distribute bending stresses to the “safest” regions of the skeleton: tesserae on the compressive side of the element.

 

810 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009; AES GRUBER AWARD

Barbara E. Wueringer1, Lyle Squire Jr.2, Stephen M. Kajiura3, Nathan S. Hart1, Shaun P. Collin1

1The University of Queensland, School of Biomedical Sciences, Brisbane, Australia, 2Cairns Marine, Stratford, Cairns, Australia, 3Florida Atlantic University, Biological Sciences, Boca Raton, FL, United States

Functional Adaptations of the Elongated Rostrum of Pristid Sawfish

Within batoids, the two families of sawfish (extinct sclerorynchids and extant pristids), which are both derived from rhinobatid shovelnose rays, have evolved an elongated rostrum. Comparison of the internal structure of the rostrum in the three taxa indicates that in pristids the anterior portion of the rostrum lengthened, which results in a slimmer construction than that of the sclerorhynchid rostrum. Moreover, pristid rostral teeth grow continuously from the base, whereas sclerorhynchids possess functional rostral teeth and dormant replacement teeth. Both characteristics present in pristids are interpreted as adaptations to reduce weight and therefore allow fast lateral swipes of the rostrum during food manipulation, as observed in freshwater sawfish, Pristis microdon. Comparison of the two dimensional sensory array of the electroreceptive ampullae of Lorenzini in rhinobatids and pristids reveals how the elongation of the rostrum may have expanded the food spectrum of pristids: the total number of ampullary pores distributed ventrally on the head and rostrum of the pristid Anoxypristis cuspidata (490.3±68.7) equals that of the rhinobatids Glaucostegus typus (452.0±162.8) and Aptychotrema rostrata (461.5±17.7). However, A. cuspidata possesses more than seven times the number of pores on the dorsal surface of the rostrum (297.1±56.6 pores) than the rhinobatids (A. rostrata 40.7±2.3 pores, G. typus 24.9±5.1 pores), indicating that pristids can potentially sense the electric field of prey in the water column. Behavioural experiments demonstrate that, in P. microdon, the ability to detect weak electric fields in the water column might come with a decreased sensitivity for electric fields simulating benthic prey.

 

440 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009; AES GRUBER AWARD

Kyle R. Mara, Philip J. Motta

University of South Florida, Tampa, FL, United States

Evolution and Function of the Hammerhead Cephalofoil I: The Evolution of Cranial Form

The head must contain structures associated with feeding, respiration, neural integration, sensory reception, and musculoskeletal support. Functional and morphological trade-offs are particularly important within spatially limited structures such as the head. The sphyrnid head presents an excellent model for investigating these potential trade-offs. Carcharhinus acronotus, Eusphyra blochii, Sphyrna lewini, S. mokarran and S. tiburo were chosen to represent differences in head form through phylogeny. A combination of surface based geometric morphometrics and computed tomography volumetric analysis was utilized to investigate implications of change in head form. The more basal E. blochii has small anteriorly positioned eyes. Through phylogeny the relative size and position of the eyes changes, such that derived species have larger more medially positioned eyes. The position of the external nares is highly variable, showing no phylogenetic trend. Mouth size and position are conserved, remaining largely unchanged, however upper and lower jaw volume is variable. Relative to carcharhinid outgroups, the feeding muscles, nasal capsule, olfactory tract, braincase, and chondrocranium all increase in relative volume in the hammerhead sharks, potentially indicating a release in spatial constraint. However, within sphyrnid sharks jaw cartilages and jaw closing muscles show variable yet parallel changes in volume, and the volumes of the upper jaw protruding muscles increase while the volumes of the braincase, nasal capsule, and eye remain constant through phylogeny. These data indicate that much of the head is morphologically conserved, however the jaw cartilages and their associated muscles vary and account for much of the internal morphological diversity within the clade.

 

312 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Stephen Kajiura, Michelle McComb

Florida Atlantic University, Boca Raton, FL, United States

Evolution and Function of the Hammerhead Shark Cephalofoil 2: Functional Implications of Sensory Receptor Distribution

The unique head morphology of sphyrnid sharks provides a dorsal ventrally compressed and laterally expanded platform upon which sensory structures are distributed. The spatial distribution of sensory organs dictates how the sharks perceive their environment. This study examined the consequences of broadly separating the eyes at the distal tips of the cephalofoil. In sphyrnid sharks the eyes are canted slightly forward which provides them with greater binocular overlap (30 ̊) than their carcharhinid sister taxa (10 ̊). However, the widely spaced eyes create a larger blind area immediately anterior to the snout in sphyrnids which would seem to be a detriment especially for an apex predator. At close ranges (10s of cm) the electrosensory system informs the sharks about the location of prey near the head. Both carcharhinid and sphyrnid sharks orient to prey-simulating electric stimuli from a mean distance of 25cm, and maximally from a distance of 40cm. This electrosensory range completely overlaps the anterior blind area of the scalloped hammerhead shark, Sphyrna lewini, and overlaps approximately half the anterior blind area of a representative carcharhinid species, the blacknose shark, Carcharhinus acronotus. By integrating visual and electrosensory information, the sphyrnids are able to continuously track prey right up to the mouth with no loss of spatial information. Therefore, the sphyrnid head morphology confers several advantages and any potential disadvantages are mitigated by sensory integration.

 

593 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Laura Jordan

California Institute of Technology, Pasadena, CA, United States

Functional Morphology of Elasmobranch Mechanosensory Lateral Line and Electrosensory Systems

The elaborate network of canals associated with the mechanosensory lateral line and electrosensory systems of elasmobranchs have been described and illustrated since the 1600s. Both systems show high degrees of interspecific diversity. Recent studies provide quantitative analyses from system level anatomy down to the functional units or sensory cells. These morphological studies lay the groundwork to understand the functional roles of various structural components of these systems in extant elasmobranchs. Mechanosensory systems differ in distribution, complexity, and mechanoreceptor types. More derived species tend to have increased lateral line branching dichotomy, which is thought to increase receptive field and sensitivity to flow generated by prey, predators, conspecifics and the animals own flow field. Nonpored lateral line canals are unique to elasmobranchs and may facilitate tactile location of prey in benthic species with high proportions of these canals on the ventral body surface. Electrosensory systems vary in pore number and density as well as canal length and orientation. Interspecific differences are related to feeding habitat where benthic feeders tend to have a high number of electrosensory pores concentrated ventrally. While sensitivity to weak electric fields is similar among species tested, higher pore density around the mouth may enhance accuracy in locating the signal source.

912 AES Conservation & Management I/AES Age & Growth, Parlor ABC, Friday 24 July 2009

Mahmood Shivji1, Veljko Dragojlovic2

1Save Our Seas Shark Center, Nova Southeastern University, Dania Beach, FL, United States, 2Harriet L. Wilkes Honors College, Florida Atlantic University, Jupiter, FL, United States

Heavy Metals in Market-Destined, Dried Shark Fins

Exploitation of sharks to supply the market demand for shark fins is arguably the largest driver of shark mortality worldwide. Combating shark overexploitation and achieving sustained conservation outcomes may best be accomplished not only by effective fishery management practices but also by also reducing market demand for fins. As with all commercial products, influencing market demand is fundamentally based on altering consumer awareness and purchase behavior. As apex predators, sharks are known to bioaccumulate heavy metals of concern to human health (e.g., mercury) in their flesh, leading to widely issued government warnings about limiting consumption of shark meat. Given that shark fins have a large consumer market and do not typically contain shark meat, we have investigated the prevalence of heavy metals known to be toxic to humans in low concentrations (total Mercury, Lead, Arsenic, Cadmium) in dried fins confiscated by NOAA's Office for Law Enforcement. An initial assessment of these metals in 75 market-destined fins showed that ~ 20% of the fins contained Lead levels exceeding US Food and Drug Administration (US FDA) limits for safe consumption. Approximately 7% of the fins contained total Mercury close to or above US FDA levels. We report on these and ongoing analyses of heavy metals in more market fins in the context of various international government food safety guidelines.

 

251 AES Conservation & Management I/AES Age & Growth, Parlor ABC, Friday 24 July 2009

Colin Simpfendorfer1, Andrew Tobin1, David Welch2

1Fishing and Fisheries Research Centre, James Cook University, Townsville, Queensland, Australia, 2Queensland Department of Pdustries and Primary Industries and Fisheries, Townsville, Queensland, Australia

Shark Catches in the Inshore Waters of the Great Barrier Reef World Heritage Area

The take of sharks in fisheries in the Great Barrier Reef World Heritage Area have become increasingly controversial in recent times. To provide scientific information to inform the consideration of this issue, fishery-dependent surveys have been conducted throughout the area to document species and size composition of various sectors that take sharks. These data show that commercial net fishers catch over 25 species of sharks and ray, with the main species being Australian blacktip, spottail, scalloped hammerhead, milk, whitecheek and spinner sharks. Species composition, importance and size varies between different sectors of the commercial fishery. Discarding practices were also examined and varied by operator and sector, with some species (e.g. milk sharks) more likely to be discarded than others. Post-release survival of discards is unknown, but may be an important consideration in relation to the impact of the fishery. The majority of sharks taken were less than 150 cm in length. Data from recreational fishers was not able to provide detailed species composition data, but did demonstrate release rates >90%. The use of these data in an ecological risk assessment will be discussed.

 

650 AES Conservation & Management I/AES Age & Growth, Parlor ABC, Friday 24 July 2009

Fabio Hazin1, Paulo Oliveira1, Felipe Carvalho2, Mariana Rego1, Rui Coelho2, Andrew Piercy2, George Burgess2

1Universidade Federal Rural de Pernambuco, Recife,PE/NE, Brazil, 2University of Florida, Gainesville, FL, United States

By-catch of Crocodile Shark, Pseudocarcharias kamoharai, in the Tuna Pelagic Longline Fishery in the Southwestern Atlantic Ocean: Abundance, Distribution, Mortality and Reproductive Parameters

The crocodile shark Pseudocarcharias kamoharai is commonly taken as by-catch by the swordfish and tuna longline fishery in Brazilian waters of the tropical western Atlantic Ocean. In this paper, fisheries data recorded by observers on board since 2007 (in a total of 2,869 longline sets) and reproductive parameters estimated from 490 specimens (313 females, 177 males) caught between February 2005 and September 2007, were presented. Even though the crocodile shark accounts for less than 1% of the total catch (in number) of this fishery, it was recorded in 8.1% of the longline sets made and represented 4.2% of the total shark catch. The crocodile shark does not have a commercial interest to this fishery, so caught specimens are usually discarded. At-vessel fishing mortality was high (78.5% of the specimens), with the remainder 21.5% discarded alive. The size at birth was estimated at 41.5 cm total length (TL) and sampled specimens ranged from 65.5 to 109.0 cm TL for males and from 75.0 to 122.0 cm TL for females. Size at first maturity (L50) was estimated at 80.0 cm TL for males and 91.6 cm TL for females, and a high proportion of the specimens sampled were mature (68% of the females and 80% of the males). Pseudocarcharias kamoharai was recorded over and extensive geographical region throughout the study area, from latitudes 5oN to 25oS, but it was particularly abundant in the equatorial region, from 5o N to 5o S.

 

1001 AES Conservation & Management I/AES Age & Growth, Parlor ABC, Friday 24 July 2009

Christine Ward-Paige, Joanna Mills Flemming, Heike K. Lotze

Dalhousie University, Halifax, NS, Canada

Monitoring Sharks: Evaluating and Correcting for Bias in Underwater Visual Surveys

In visual sampling, animal density is commonly calculated as the number of animals observed standardized by area sampled. This calculation is suitable for stationary or slow moving organisms that are unlikely to leave or enter the area during the survey. In these cases, surveys produce reliable density estimates because they are essentially instantaneous counts and the same result would be obtained if conducted instantaneously or for a longer duration of time, assuming equal detectability in both scenarios. However, for mobile animals like sharks, counts depend upon the survey-time, the visibility, and the animal's speed. When densities of mobile animals are calculated using number per area calculations, overestimates of density result which considerably misrepresents their contribution to the total biomass. For example, an overestimate of 0.01 individuals·m-2 of an animal weighing 1000g and one weighing 10,000g would result in an overestimate of 10g·m-2 and 100g·m-2, respectively - a 10-fold difference. This apparent inconsistency raises fundamental questions about the significance of studies relying on visual censuses to estimate community abundance and/or biomass. We developed a model to simulate densities obtained by divers. Results were used to examine bias between observed and true density. Bias increased with fish speed and was a function of survey-time, visibility and diver speed. Generalized additive models were fit to develop corrections for better estimates of true density. Corrected estimates should allow for direct comparisons between species with differing mobility. Using the scientific literature, we demonstrate the impact these calculations have on density and biomass estimates.

 

1036 AES Conservation & Management I/AES Age & Growth, Parlor ABC, Friday 24 July 2009

Shawn Larson, Jeff Christiansen, Joel Hollander, Denise Griffing

Seattle Aquarium, Seattle, WA, United States

Seattle Aquarium's Sixgill Shark (Hexanchus griseus) Conservation Ecology Project

The Aquarium's Sixgill Shark (Hexanchus griseus) Population Ecology project is a long- term conservation research program to address gaps in the body of scientific knowledge on these relatively unknown animals. Living mainly at abyssal depths (2000-5000 feet) but also in shallow waters of Puget Sound, Washington, sixgills are thought to be long- lived and slow-growing, and appear to have established movement corridors and territories that remain relatively fixed over time. No information exists on how many sixgills are in Puget Sound, whether they are year-round or seasonal, local or migratory, or whether they use local water primarily for feeding or for recruitment. The Aquarium's sixgill population ecology research involves four interwoven techniques to determine aspects of basic sixgill biology using (1) genetics research, (2) visual marker tagging, (3) acoustic tracking and (4) video analysis. The aquarium began tagging and tracking these animals in 2003 and in 2008 began collecting data from our archived video taken since 2003. Here we present statistics on absolute numbers of sharks seen, number of sharks tagged, number of returned sharks, sex and size distribution from video analysis of sharks and tag return data. Population genetics parameters from analysis using 14 polymorphic microsatellite markers and summary statistics for sixgills within Puget Sound will also be presented. This research should substantially improve scientific understanding of abundance, relatedness and movement patterns in Puget Sound.

 

962 AES Conservation & Management I/AES Age & Growth, Parlor ABC, Friday 24 July 2009

Kevin Weng1, John O'Sullivan2, Manuel Ezcurra2, Joe Welsh2, Scott Reid2, Mike Murray2, Chris Lowe3, Chuck Winkler4, Oscar Sosa Nishizaki5, Barbara Block6, Salvador Jorgensen6, Chris Perle1, Andre Boustany7

1University of Hawaii at Manoa, Honolulu, HI, United States, 2Monterey Bay Aquarium, Monterey, CA, United States, 3California State University at Long Beach, Long Beach, CA, United States, 4Southern California Marine Institute, Los Angeles, CA, United States, 5Centro de Investigación Científica y de Educación Superior de Ensenada, Ensenada, BC, Mexico, 6Stanford University, Stanford, CA, United States, 7Duke University, Durham, NC, United States

Juvenile White Shark Research at the Monterey Bay Aquarium

The Monterey Bay Aquarium initiated a research program into the biology and husbandry of juvenile white sharks in 2002. The program's goals are to learn about the biology of the most vulnerable life stages, determine the key conservation issues for the species, bring white sharks into the aquarium for exhibit, and educate the public about the species. Four white sharks have been brought into the Outer Bay Waters exhibit for public display, resulting in a major public education and awareness program, both through direct visitation as well as high profile media coverage. Satellite telemetry results for sharks in the wild indicate that zero to three-year-olds remain primarily in neritic waters, and undertake movements between US and Mexican waters. The home range of this age class of white sharks includes the California Current system off California and Baja California, as well as the Gulf of California. In contrast, adults and subadults do not appear to move between US and Mexican waters, instead making offshore movements from their respective nearshore aggregation sites into pelagic waters towards Hawaii. The neritic habitat of juveniles, combined with their smaller size, makes them more vulnerable to fishery interactions than adults. The primary management issue for white sharks in the Eastern Pacific is capture in gillnets in the US and Mexico. Adults are not reported in commercial or recreational fisheries with any regularity.

 

408 AES Conservation & Management I/AES Age & Growth, Parlor ABC, Friday 24 July 2009

Atsuko Yamaguchi, Keisuke Furumitsu, Gen Kume

Nagasaki University, Nagasaki, Japan

Elasmobranch Fauna in Ariake Bay, Japan

The study area-Ariake Bay-is recognized as an estuary, which has the largest tidal flat in Japan. This study aims to elucidate the species composition, abundance, and habitat of elasmobranchs in Ariake Bay. Samples were collected using small bottom trawlers, set nets, gill nets, and bottom long-lines from almost all areas of Ariake Bay. A total of 255 fish species including 21 elasmobranchs (9 sharks and 12 skates and rays) were identified, of which at least 59 species (5 elasmobranch species) were recorded for the first time in the study area. The most abundant elasmobranch genus was Dasyatis, which comprised at least 6 species (D. akajei, D. laevigata, D. zugei, D. izuensis, D. acutirostra, and Dasyatis sp.). From the central region of the bay, we could collect samples quantitatively: we found that elasmobranchs (especially rays) were more abundant than the teleostean species. The most abundant species was the fanray, Platyrhina sinensis. Some species such as P. sinensis and guitarfish Rhinobatos hynnicephalus were not found in the inner part of the bay. On the other hand, Myliobatiforme such as stingrays (Dasyatidae) and eagle rays (Myliobatidae) were distributed widely throughout the bay. At least 11 elasmobranch species, including Myliobatiforme and scalloped hammerhead shark Sphyrna lewini, use the rivers, which flow into the innermost area of the bay, and the tidal flat areas in the inner part of the bay as their nursery ground.

 

Life History Characteristics of the Fanray Platyrhina sinensisin Japan MISSING!!!

 

559 AES Conservation & Management I/AES Age & Growth, Parlor ABC, Friday 24 July 2009

Ivy Baremore, Kate Andrews

National Marine Fisheries Service, Panama City, FL, United States

Propagating Measurement Error through the Calculations of Parameter Estimates

Fishery biologists often take several morphometric measurements of fishes to assess growth and other life history characteristics of a stock or population. Published age and growth studies, however, generally restrict the results of a growth model to one measurement, such as total length, with conversion equations included to calculate one length from another. Measurement error can be higher for some measurement techniques, and this error can affect the outcome of growth models, such as the von Bertalanffy growth equation. Furthermore, when life history parameters from these models are then used as input for stock assessment, the error can be propagated. Length-at-age data from six species of sharks were used to determine if different length measurements (precaudal, fork, natural total, and stretched total) produced differing parameter estimates, specifically the k value, for the von Bertalanffy growth equation. Differences in the k values were detected among lengths for all six species, though the degree of difference varied by length measurement and species. Residual standard error of parameter estimates increased with increasing length measurement. The effect parameter estimate differences on the outcome of stock assessment were determined for two species of sharks: Rhizoprionodon terraenovae and Carcharhinus acronotus.

 

192 AES Conservation & Management I/AES Age & Growth, Parlor ABC, Friday 24 July 2009

Nicholas Dulvy

Simon Fraser University, Burnaby, BC, Canada

I have Aged some Sharks and Fitted a Growth Curve – Now what do I do?

Many budding elasmobranch scientists cut their teeth by painstakingly learning how to estimate the age and growth of sharks, skates and rays. Thankfully a large number can't kick the habit! Wouldn't it be nice if we could use these age and growth data to estimate fisheries sustainability and extinction risk in elasmobranchs? Here I outline a simple method for estimating relative risk of overexploitation and risk of extinction using only von Bertalanffy growth parameters and the size or age at first capture. The model calculates the capacity of a population or species to withstand dangerous levels of fishing mortality (F ) that will reduce the number of spawners produced per recruit (SSB/R) to below some arbitrary ‘jeopardy' level. I illustrate how this model can be used to rank elasmobranch species according to their relative intrinsic vulnerability to overexploitation and extinction risk.

977 AES Conservation & Management II, Parlor ABC, Saturday 25 July 2009

Johnny Moore1, Dewayne Fox1, Bradley Wetherbee3, Camilla McCandless4

1Delaware State University, Dover, DE, United States, 3University of Rhode Island, Kingston, RI, United States, 4NOAA/National Marine Fisheries Service, Narragansett, RI, United States

Critical Habitat for Sand Tiger Sharks During their Summer Residency in Delaware Bay

The population of sand tiger sharks (Carcharias taurus) along the US East coast has declined over the past several decades and recovery of stocks is limited by low reproductive rates coupled with continued take as bycatch in various fisheries. Identification of essential habitat is critical for enhanced recovery of sand tiger stocks. Delaware Bay is one of the most important areas used by this species on the US East coast. We have been using acoustic transmitters and an array of receivers in Delaware Bay to identify critical habitat of sand tigers during their Delaware Bay summer residency. We monitored the movements and habitat use of 69 sand tigers in the summers of 2006 - 2008. Males and females were segregated, with males more commonly found in the lower salinity middle portion of the bay and in shallower waters, whereas females were more common in deeper, higher salinity waters near the mouth of the bay. Habitat use varied between years with significantly shallower depths used in 2007 than in 2008. The importance of Delaware Bay as summer habitat for sand tigers is demonstrated by relatively high interannual site fidelity with 50% of sharks tagged in 2006 returning in 2007, and 60% tagged in 2007 detected in the bay the following summer of 2008. This study has been very successful in identifying habitat of high use within Delaware Bay and providing information for protection of discrete portions of the bay that are vital to the recovery of this imperiled species.

 

107 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Kara Yopak, Lawrence Frank

University of California San Diego, San Diego, CA, United States

Defying Evolutionary Expectations: Analysis of the Brain of the Whale Shark, Rhincodon typus, using Magnetic Resonance Imaging

Very little is known about the brain organization of the suction filter feeder, Rhincodon typus, and how it compares to other orectolobiforms, despite its specialized lifestyle. Brain size and overall brain organization was assessed in R. typus in relation to both phylogeny and ecology, using magnetic resonance imaging (MRI). In comparison to 60+ chondrichthyan species, R. typus demonstrates a relatively small brain for its body size, similar to lamniforms Carcharodon carcharias and Cetorhinus maximus. R. typus possesses a relatively small telencephalon, with some development of the dorsal pallium (suggestive of moderate social behavior), a relatively enlarged diencephalon, and a relatively reduced mesencephalon. The most notable characteristic of the brain of Rhincodon is a large, highly foliated cerebellum, one of the largest within the chondrichthyan clade. Enlargement and increased complexity of the cerebellum has been previously seen in active, pelagic species such as Alopias vulpinus and Sphyrna lewini; potential adaptive pressures for this neural characteristic will be discussed. Early development of the brain was qualitatively assessed from in situ MRI images of the brain and chondrocranium of a neonate specimen of R. typus. There was evidence that folding of the corpus appears in early development, although depth and number of folds may vary ontogenetically. Hierarchical cluster analysis shows evidence of convergent evolution with the large- bodied, filter feeding shark, C. maximus, supporting the claim that organization of the brain is more similar in species with analogous but independently evolved lifestyles than those that share taxonomic classification.

 

686 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Laura Macesic1, Adam Summers2, Stephen Kajiura1

1Florida Atlantic University, Boca Raton, FL, United States, 2University of California, Irvine, Irvine, CA, United States

Functional Morphology of Pelvic Fin Locomotion in Batoids

"Punting” is a form of benthic locomotion wherein a batoid (skate or ray) digs its pelvic fins into the substrate and thrusts itself forward. It was thought to be restricted to skates, but we have shown that it is widespread in Batoidea. By examining kinematic and pelvic fin musculature we previously revealed a continuum of punting ability with a corresponding continuum of pelvic fin musculature. True punters, such as Narcine brasiliensis and Raja eglanteria, use only their pelvic fins and possess more specialized and more robust muscles. Augmented punters, such as Urobatis jamaicensis and Dasyatis sabina, punt with assistance from their pectoral fins, and possess fewer and less substantial muscles. We also used three-point bending tests of the main skeletal element involved in punting, the propterygium, to test if flexural stiffness correlates with punting style. We found that propterygia of the true punters have approximately 80% greater flexural stiffness than the augmented punters (p<0.05). Moreover, propterygia of the augmented punters have almost twice the flexural stiffness of the non-punting pelagic stingray (Pteroplatytrygon violacea) (p<0.05). The concordance of musculature and skeletal stiffness with punting ability provides us with predictive power regarding the punting kinematics of other elasmobranchs based gross muscular examinations and skeletal material properties. By pairing our results with phylogenetic information, we can also gain a better understanding of the evolution and radiation of batoids.

 

228 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Marianne E. Porter, John H. Long Jr.

Vassar College, Poughkeepsie, NY, United States

Non-linear Viscoelasticity of Cartilaginous Vertebral Columns during Bending

The number and shape of vertebrae are important predictors of body curvature in sharks during routine turns. However, morphological correlates such as these predict only about 50% of body curvature among five species. We are interested in determining what other non-morphological and non-muscular features may be correlated with body curvature during swimming. Specifically, we predict that dynamic mechanical properties of the vertebral column in bending will be important determinates of whole- body curvature. As a first step in testing this prediction, we sought to determine the dynamic mechanical properties of cartilaginous vertebral columns and their response to varying frequencies, amplitudes, and length of the moment arm to reflect the loading of a shark swimming at varying speeds. We designed a rig that allowed us to measure the mechanical properties using a MTS Tytron 250 one-axis testing machine. In these tests, we used ten–centra-long segments of vertebral columns from three Squalus acanthias. Stiffness, a structure’s ability to resist loading, measured by the elastic modulus (E, in MPa), increases with frequency and is almost 2X greater at bending frequencies of 2.0 Hz than at 0.5 Hz. Additionally, stiffness increases with testing amplitude by more than an order of magnitude, and stiffness is greatest at the shortest moment arms. These data contribute to the growing understanding of how cartilaginous skeletons respond to loads, and how those responses are correlated with morphology and swimming performance. This work was supported by NSF DBI-0442269.

884 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Diego Bernal1, Scott Aalbers2, Chugey Sepulveda2

1University of Massachusetts Darmouth, Dartmouth, MA, United States, 2Pfleger Institute of Environmental Research, Oceanside, CA, United States

The Role of the Caudal Fin in the Common Thresher Shark, It's Not Just for Swimming

Threshers are a monophyletic group of pelagic sharks most commonly recognized by an elongate upper lobe of the caudal fin, which reaches a length equal to that of the trunk of the body. It has been hypothesized that threshers utilize the elongate fin to stun small- schooling prey while feeding. The bi-functional role of the caudal fin for both thrust production and predation represents a unique adaptation among elasmobranchs. Despite the commercial and recreational importance of the threshers, there are no published accounts on how the caudal fin is used during feeding. The objectives of this study were to 1) acquire video footage of feeding threshers, 2) examine the caudal fin morphology, and 3) to investigate the ocular morphology and potential range of eye movement. Of the 140 specimens captured and released, only 3% were hooked in the mouth and the remainder in the caudal fin. Video of free-swimming threshers yielded footage from 20 sharks showing the use of the tail during the feeding event. Morphological examination of the caudal fin revealed that the upper lobe is predominantly comprised of tendinous and cartilaginous support tissues and has both aerobic and anaerobic muscle fibers throughout its entire length. In general, the structural architecture of the thresher caudal fin is similar to that of lamnid sharks, but with much larger dorso-ventral cartilaginous support elements. Preliminary findings show that the eye has the capacity to rotate along the longitudinal within the orbit which may enhance vision in the posterior field.

 

874 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Diego Bernal1, Douglas Syme2, Jeanine Donley3, Scott Aalbers4, Chugey Sepulveda4

1University of Massachusetts Dartmouth, Dartmouth, MA, United States, 2University of Calgary, Calgary, Alberta, Canada, 3Miracosta College, Oceanside, CA, United States, 4Pfleger Institute of Environmental Research, Oceanside, CA, United States

Adaptations for Continuous Swimming: Functional Morphology of the Locomotor Muscles in Thresher Sharks

Threshers are a group of large, pelagic sharks easily recognized by their elongate upper caudal lobe and are the only genus with species having either a subcutaneous (lateral) or medial (internal) position of the red aerobic locomotor muscle (RM). This provides an ideal system in which to test the hypothesis that the medial RM position in the common thresher (Alopias vulpinus) provides the basis for a propulsion mechanism similar to that found in the lamnid sharks and different from that of sharks with a more lateral position of the RM such as the other two threshers (A. superciliosus and A. pelagicus). This study quantified the in-vivo muscle dynamics during sustained swimming in the RM and white muscle (WM) of 12 common threshers swimming in the wild. At a tailbeat frequency of 0.5Hz, RM strain (at first dorsal fin) was consistently greater than that of the WM and decreased significantly during simulated swimming movements (RM not activate; passive swimming). By contrast WM strain did not differ between active and passive swimming. A comparison of RM and WM shortening phase during swimming showed instances in which RM shortening both led and trailed that of the surrounding WM, with no phase difference observed during the passive swimming experiments. This finding suggests that, similar to lamnid sharks, the common thresher RM sheers relative to the WM. Therefore, these results suggest that the common thresher may exhibit a similar uncoupling of RM shortening and local body bending as seen in the thunniform lamnids.

 

777 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Nicholas C. Wegner1, Chugey A. Sepulveda2, Jeffrey B. Graham1

1Scripps Institution of Oceanography, La Jolla, CA, United States, 2Pfleger Institute of Environmental Research, Oceanside, CA, United States

Adaptations for Fast, Continuous Swimming: Functional Morphology of the Gills in the Shortfin Mako, Isurus oxyrinchus

The gills of the shortfin mako are highly specialized for increasing gas exchange required by high aerobic demands and for enhancing gill rigidity to maintain gill orientation in face of the high-pressure branchial flow induced by ram ventilation. The mako has larger gill surface areas and shorter diffusion distances in comparison to other elasmobranchs studied to date. Mako gill lamellae have a diagonal blood-flow pattern similar to that described for many high-energy demand teleosts (e.g. scombrids and billfishes) which likely increases functional gill area and decreases vascular resistance through the gills. Although the mako lacks the filament and lamellar fusions that are found in many ram-ventilating teleosts, the basic elasmobranch gill design stiffens the gill filaments, and the lamellae appear to be stabilized by previously undescribed vascular “sacs.” These sacs, which are located near the water-entry edge of the lamellae, may be subject to pressure-based or vasoactive control which may allow for some manipulation of size under varying physiological conditions. Despite a high degree of specialization for increased gas exchange and ram ventilation in comparison to other sharks, the basic elasmobranch gill design appears to limit the convergence of mako gill structure with that of tunas. Specifically, mako gill surface area is much smaller, and this may ultimately prevent the scope of sustainable aerobic performance achieved by tunas.

 

72 AES Functional Morphology Symposium, Grand Ballroom II, Friday 24 July 2009

Lara Ferry-Graham1, Adam Summers2

1Moss Landing Marine Laboratories, Moss Landing, CA, United States, 2University of California, Irvine, CA, United States

Ventilation in Chondrichthyans: A Decade of Research Reveals New Models of Aquatic Vertebrate Respiration

Over the last decade, investigations of the ventilatory mechanics of chondrichthyans have revealed a number of unique findings that seem to defy paradigms commonly invoked to describe aquatic vertebrate respiration. Aquatic vertebrate ventilation is typically represented by a model whereby two alternating pumps operate to generate water flow through the head and over the gills. These two pumps, the suction and pressure pumps respectively, are hypothesized to operate such that they are able to maintain both continuous and unidirectional flow at the level of the gill lamellae. Studies of sharks, skates, and chimaeras, however, reveal that the two pumps operate to varying degrees during routine respiration. Flow visualization techniques have revealed concomitant flow reversals, whereby water flows from posterior to anterior, both at the gross anatomical level (i.e., exterior to the head at the mouth and spiracles), and at the level of the respiratory structures (i.e., gill lamellae). Such flow reversals vary both within and among species, and may be negatively correlated with oxygen demand. The most extreme deviation from the paradigmatic norms are found in the chimaeras, in which a single pump dominates the ventilatory cycle. We postulate that during ventilation, water is drawn into the orobranchial cavity using primarily a very low- pressure suction pump, on the order of 100-1000 Pa. We suggest that chimaeras are utilizing an entirely novel mechanisms of generating flow into the head., whereby a slight amount of expansion of the orobranchial region is sufficient to pull water into the mouth.

 

 

419 AES GRUBER AWARD II, Parlor ABC, Friday 24 July 2009

Walter Bubley1, James Sulikowski2, Paul Tsang1, David Koester2

1University of New Hampshire, Durham, NH, United States, 2University of New England, Biddeford, ME, United States

Histological Staining of Vertebral Centra Increases Precision of Age Estimates Compared to Dorsal Fin Spines in Spiny Dogfish, Squalus acanthias

Spiny dogfish (Squalus acanthias) are considered to be the most abundant shark species in the Western North Atlantic, but recent concerns regarding a decline in their numbers argue for an update of previous life history parameters. However, wear and breakage of the spine, as well as variablility in interpretation of growth increments has resulted in conflicting age estimates in the literature. The uncertainty in estimating age in turn affects other parameters that are dependent on it, such as growth rate and age at maturity. Our hypothesis was that the growth increments of vertebral centra provided more consistent and reliable estimates of age than the dorsal fin spine method for spiny dogfish in the Western North Atlantic. Vertebrae and second dorsal fin spines were collected monthly from spiny dogfish from July 2006 - December 2008. The spines were examined whole while the vertebrae were sectioned and prepared using histological techniques to enhance the visualization of the growth increments. Using these two structures, two readers provided age estimates that were compared with coefficient of variation and average percent error. The vertebral centra produced more precise age estimates between and within readers compared to the dorsal spine method. Ultimately, the vertebral centrum provided a structure that produced a more reliable correlation between age and total length, a parameter critical to improving population models and successful management of spiny dogfish in the Western North Atlantic.

183 AES GRUBER AWARD II, Parlor ABC, Friday 24 July 2009

Shaara Ainsley1, David Ebert2, Gregor Cailliet1

1Moss Landing Marine Laboratories, Moss Landing, CA, United States, 2Pacific Shark Research Center, Moss Landing, CA, United States

Age, Growth and Maturity of the Whitebrow Skate, Bathyraja minispinosa (Ishiyama & Ishihara, 1977), from the Eastern Bering Sea

Bathyraja minispinosa (Chondrichthyes: Arhynchobatidae) is an endemic skate species confine mostly to the Aleutian Islands and Bering Sea of which little is known about its life history. The species is taken mostly as by-catch in groundfish fisheries and as such may be especially susceptible to over-exploitation. To fill critical life history gaps a total of 226 vertebrae and caudal thorn samples was collected by during NMFS Alaska Fisheries Science Center (AFSC) trawl surveys along the Eastern Bering continental slope. AFSC observers and fisheries biologists collected additional samples. Observed total lengths for males ranged from 14.7-83.7cm and females from 13.6-89.5cm. Preliminary age estimates established a minimum longevity of 37 years. B. minispinosa reached first maturity at 65.7cm TL for males and 66.8cm TL for females. The largest immature male was 79.5cm TL, while the largest immature female was 73.3cmTL. Male B. minispinosa reach median size at maturity (TL50) at 70.1cm and females at 67.4cm (Males: r2 = 0.9597, p < 0.0001, n = 27; Females: r2 = 0.9958, p < 0.0001, n = 28).

 

968 AES GRUBER AWARD II, Parlor ABC, Friday 24 July 2009

Charles Cotton1, Dean Grubbs2, Toby Daly-Engel3, John Musick1

1Virginia Institute of Marine Science, Gloucester Point, VA, United States, 2Florida State University Coastal and Marine Laboratory, St. Teresa, FL, United States, 33University of Hawaii at Manoa, Honolulu, HI, United States

Age, Growth and Reproduction of Squalus mitsukurii from Hawaiian Waters

The shortspine spurdog, Squalus mitsukurii, is a medium-sized dogfish with a cosmopolitan, but patchy distribution throughout warm waters. This dogfish inhabits continental and insular shelves and upper slopes, as well as seamounts and ridges, usually in depths of 100-500 meters. This species is quite abundant around the Hawaiian Islands, where fishing pressure is likely minimal. Specimens were collected by demersal longlines, with sizes ranging from 39-cm to 101-cm for females and from 41- cm to 71-cm for males. Ages were assigned by counting bands on the enamel caps of both fin spines from 126 females and 30 males. Readability was similar between fin spines for both sexes. Likewise, age estimates obtained from each fin spine were similar for both sexes. However, sexual dimorphism of fin spines was noted, with male spines being somewhat more difficult to interpret, due to a constriction of the enamel cap on the anterior surface of each spine. Age estimates ranged from 3 to 25 years for females and 2 to 15 years for males. Growth parameters were estimated using several growth models. Spine morphometrics are also presented with growth model estimates. Age validation was not performed, though it is inferred though other age validation studies on a congener, S. acanthias. Observed fecundity, as well as maturity and maternity ogives are also presented. Our results are compared with other studies of S. mitsukurii from Pacific waters.

 

649 AES GRUBER AWARD II, Parlor ABC, Friday 24 July 2009

Felipe Carvalho1, Debra Murie1, Fabio Hazin2, Humberto Hazin2, George Burgess1

1University of Florida, Gainesville, Florida, FL, United States, 2Universidade Federal Rural de Pernambuco, Recife, Brazil

Blue Shark (Prionace glauca) Spatial Distribution and Catch Probabilities in the Southwest Atlantic Ocean

Generalized Regression Analysis and Spatial Prediction (GRASP) was applied to the catch per unit of effort (CPUE) data of blue shark from the Brazilian tuna longline fleet between 1997 - 2007 (44,633 longline sets), and size class data (11,932 individuals) from the Brazilian observer program between 2006 and 2008, in order to better understand the relationship between catch distribution and environmental factors (sea surface temperature, depth of mixed layer, chlorophyll concentration, and distance from coast). Results indicated that spatial catch probabilities for blue sharks were closely related to sea surface temperature. CPUE spatial prediction map indicated higher catch probabilities of blue sharks between 300 - 450S of latitude and 480 - 230W of longitude. Size class spatial prediction maps indicating higher probabilities of juveniles concentrating in latitudes below 41°S, adults and sub-adults in middle latitudes between 16o - 30oS, and large-adults in latitudes between 5N°-10°S. These results suggest that the spatial distribution in length class of blue sharks included the entire Southwest Atlantic, between 5°N and 45°S, and might be influenced by oceanographic events in the area.

 

485 AES GRUBER AWARD II, Parlor ABC, Friday 24 July 2009

Taylor Chapple1, Salvador Jorgensen2, Scot Anderson3, A. Peter Klimley1, Louis Botsford1, Barbara Block2

1University of California, Davis, Davis, CA, United States, 2Hopkins Marine Station, Stanford University, Pacific Grove, CA, United States, 3Inverness, CA, United States

A Mark-Recapture Population Estimate of Great White Sharks, Carcharodon carcharias, off California

Great white sharks, Carcharodon carcharias, occur circumglobally and are currently protected internationally under the Convention on International Trade in Endangered Species and the World Conservation Union (IUCN, Category VU A1cd+2cd). Recently, three large genetically distinct populations have been described (Australia/New Zealand, South Africa, north eastern Pacific [NEP]). To date, there is no estimate of abundance in the NEP. Within the NEP, sub-adult and adult white sharks show consistent yearly site fidelity at known aggregation sites off California or Guadalupe Island in Mexico, which supports use of mark-recapture frameworks to quantify their population. We used photo identification of dorsal fins to individually “mark” white sharks at aggregation sites off California over a three-year period. We collected 321 photo IDs representing 133 unique individuals over 1,141 hours of effort. Yearly recapture rates ranged from 23-27%. We analyzed these data in a sequential Bayesian algorithm incorporating informative priors. Results show the adult white shark population in central California is 261 ([200,365] lower and upper quantile, respectively) individuals. This estimate can function as a baseline for future studies concerning the health of the white shark population and support efforts to quantify their status, population trends and protection requirements. We also discuss the pitfalls and assumptions of this framework and how it can be expanded to include the white shark aggregation site in Mexico, approximating an abundance estimate for the entire NEP.

 

863 AES GRUBER AWARD II, Parlor ABC, Friday 24 July 2009

Angela Cicia1, William Driggers2, Jill Hendon3, Eric Hoffmayer3, John Mandelman4, James Sulikowski1

1University of New England, Biddeford, ME, United States, 2National Marine Fisheries Service, Pascagoula, MS, United States, 3Gulf Coast Research Laboratory, Ocean Springs, MS, United States, 4New England Aquarium, Boston, MA, United States

Investigating the Physiological Effects of Environmental Salinity on the Distribution of Adult Female Atlantic Sharpnose Sharks, Rhizopriondon terraenovae, in the Northern Gulf of Mexico

Understanding the habitat preferences exhibited by distinct life stages, particularly in nursery areas, can be instrumental for effective conservation and management of coastal shark populations. However, little is known about how abiotic factors such as salinity, temperature, and dissolved oxygen, influence the distribution of shark populations. Euryhaline waters of the Gulf of Mexico and South Carolina are both reported to be nursery areas for the ubiquitous Atlantic sharpnose shark, Rhizopriondon terraenovae. Interestingly, two studies have observed virtually the complete spatial segregation among R. terraenovae, with adult females rarely occurring in areas influenced by freshwater outputs. Nearly 10 years of sampling within the Mississippi sound have yielded less than 20 adult females, all of which were captured in salinities exceeding 30 ppt. Similar findings were reported off South Carolina, resulting in the capture of only 26 adult females over a six year study. The relative absence of adult females from low salinity areas suggests a physiological limitation could play a role in restricting inshore habitat utilizations. Thus, the objective of the current study is to provide insight into this anomaly by investigating compensatory changes in intracellular and extracellular solutes and hematological properties among sharks caught at differing salinities in the northern Gulf of Mexico.

 

399 AES GRUBER AWARD II, Parlor ABC, Friday 24 July 2009

Anabela Maia

University of Rhode Island, Kingston, RI, United States

Escape Responses in Young of the Year Spiny Dogfish

Most species encounter greater predatory pressure early in life, before maturation. To evade predators, the most common behavior an animal will use is an escape response. In this study, escape behavior is investigated in young of the year spiny dogfish, Squalus acanthias. Escape responses were elicited by gentle nudging of the tail region to represent a possible predatory event in seven individuals. The results were compared with published data on adult spiny dogfish escape responses. Similar to adult spiny dogfish, the young of the year exhibited C-type escape responses, characterized by a bend into a C shape in stage 1, followed by a return to a natural position in stage 2. Duration, center of mass speed, snout speed, turning rate, and turning angle were quantified for stages 1 and 2. Unlike spiny dogfish adults, young of the year spiny dogfish do not show a bimodal distribution in response type. Size corrected maximum velocity of the escape response is faster in the young of the year dogfish, with absolute values close to the values reported at the lower end of the spectrum of adult dogfish. Mean angular velocities in young of the year dogfish are similar to the faster values reported for adults, and maximum angular velocity was faster than in adults. This is consistent with previous reports on greater maneuverability in smaller sized fish. Overall, young of the year spiny dogfish are competent in fast starts although modulation of response type is absent.

35 AES GRUBER AWARD II, Parlor ABC, Friday 24 July 2009

Valentina Di Santo, Wayne Bennett

University of West Florida, Pensacola, FL, United States

Effects of Thermotaxis on Digestion Efficiency in Two Elasmobranchs

Recent telemetry and laboratory studies have shown that some rays and sharks feed in warmer water, but rest in cooler waters. Thermoregulatory behavior has been suggested as a means for elasmobranch fishes to improve the efficiency of metabolic processes such as digestion. For shuttling to be effective, however, temperature mediated movements must affect absorption and evacuation rates differently - a result that, to date, has never been empirically demonstrated. In this study, the post-feeding thermotaxis hypothesis was tested in the laboratory using two elasmobranch species, the Atlantic stingray (Dasyatis sabina) which inhabits thermally variable environments, and the whitespotted bamboo shark (Chiloscyllium plagiosum), a stenothermic fish living on thermally stable Indo-Pacific reefs. Experiments at temperatures similar to those experienced in nature reveled that temperature change had no significant effect on bamboo shark absorption (p=0.560) or evacuation rates (p=0.982), suggesting that sharks inhabiting thermally stable environments may lack the ability to exploit temperature differences as a means to improve digestion efficiency. On the other hand, Atlantic stingrays showed significantly lower evacuation (p<0.001) and absorption (p=0.035) rates at lower temperatures. The relative decrease was greatest for evacuation, however, resulting in a significant increase in total absorption (p<0.001), i.e., although absorption per minute decreased, slower evacuation allowed the food to remain in contact with the ileum longer, resulting in an overall increase in absorption. These data suggest that Atlantic stingray may benefit from using shuttling behavior to exploit thermal variability in their environment thereby maximizing energetic uptake.

 

481 AES GRUBER AWARD II, Parlor ABC, Friday 24 July 2009

Toby Daly-Engel1, Dean Grubbs2, Kevin Feldheim3, Brian Bowen1, Robert Toonen1

1Hawaii Institute of Marine Biology, Kaneohe, HI, United States, 2Florida State University Coastal and Marine Laboratory, St. Teresa, FL, United States, 3Field Museum's Pritzker Laboratory, Chicago, IL, United States

Beneficial or Unavoidable? Sexual Conflict Drives Low Multiple Paternity and Genetic Diversity in the Shortspine Spurdog Shark (Squalus mitsukurii)

Causes of multiple paternity derive from ultimate evolutionary mechanisms driving a proximate life-history strategy that promotes a polyandrous or polygynandrous mating system. The most frequently proposed benefit of multiple paternity is its potential for maintaining population genetic diversity. Here we examine mechanisms responsible for the evolution of a polyandrous mating system in sharks, in particular its role in the reproductive strategy of the shortspine spurdog shark, Squalus mitsukurii. S. mitsukurii has one of the longest reproductive intervals of any vertebrate, making it especially vulnerable to overfishing. To estimate rate of multiple paternity and characterize population structure of S. mitsukurii in Hawaii, we genotyped 27 litters using eight microsatellite loci and sequenced 670 bp of the mitochondrial control region in 112 unrelated individuals collected throughout the Hawaiian Archipelago. Parsimony analysis showed that S. mitsukurii in Hawaii are likely a single breeding population (K = 1), despite deep-water stratification between islands that exceeds the known depth range of this species. Direct allele count and Bayesian approximation methods returned concordant estimates of 11% multiple paternity in this population. Proximate causes such as sexual conflict-driven mating avoidance and an asynchronous reproductive cycle are likely responsible for the low rate of multiple paternity, the lowest observed in any shark species. S. mitsukurii also has the lowest observed nucleotide diversity (π = 0.0010 ± 0.0008). A correlation meta-analysis of published multiple paternity estimates for sharks revealed that 40% of genetic diversity is explained by variation in rate of multiple paternity.

 

144 AES GRUBER AWARD II, Parlor ABC, Friday 24 July 2009

Neil C. Aschliman, Gavin J.P. Naylor

Florida State University, Tallahassee, FL, United States

Diversity and Constraint in the Evolution of Skates and Rays (Chondrichthyes: Batoidea)

Skates, rays and their allies (Batoidea) are a prominent but under-studied clade of stem vertebrates that exhibit the majority of chondrichthyan morphological- and species diversity. Understanding the forces affecting the diversification of this group requires a reliable phylogeny. The most taxon-rich batoid phylogenies are morphological and suggest suites of characters that appear constrained and/or convergent. However, discordance with the fossil record and a lack of confidence in any one topology impede the resolution of critical questions posed by morphological trees. Three examples concern: (1) forces shaping the tremendous disparity in number between the derived skates [~300] and the relatively basal sawfishes [only seven]; (2) the number of convergent derivations of the flattened disc body plan; and (3) the pattern of changes in mode of parition, with skate oviparity a potential reversal from yolk sac viviparity. Most molecular phylogenies have included very few taxa and limited sequence data. We previously described novel but preliminary evidence for a rapid radiation among the extant groups of batoids. We attempted to resolve this basal polytomy using large DNA sequence datasets including the nuclear marker RAG-1 (~100 taxa) and the complete protein-coding complement of the mitochondrial genome (~40 taxa), sampling densely and evenly across Batoidea. Phylogenies were recovered using Maximum Likelihood and Bayesian approaches. We accommodated systematic biases in the data, statistically compared topologies, estimated divergence times and evaluated the prevailing signal against morphology and the fossil record. A number of well- supported clades were recovered. Some are novel, while others are anticipated by morphology .

928 AES Conservation & Management II, Parlor ABC, Saturday 25 July 2009

Daniel Ha1, Dean Grubbs2, Charles Cotton1, John Musick1

1Virginia Institute of Marine Science, Gloucester Point, VA, United States, 2Florida State University Coastal and Marine Laboratory, St. Teresa, FL, United States

Shark CPUE Trends from Virginia's Atlantic Waters: Trends 1972-2008

In this study we use the Virginia Institute of Marine Science's shark long line survey data set to examine trends in catch per unit effort (cpue) of common species in the Virginia portion of the Mid-Atlantic Bight. This survey started in 1972, and continues to the present day, using the same bottom long line gear throughout. Data from 1972 to 2008 were analyzed with a Generalized Additive Model after being arc-sine root transformed. The results show that most large shark species in the survey (Carcharhinus plumbeus, Carcharhinus obscurus, Carcharhinus limbatus, Galeocerdo cuvier, and Carcharias taurus) have declined significantly in CPUE since the beginning of the survey. One species, Carcharhinus brevipinna has increased in abundance over the course of the study, and one species (C. limbatus) has shown clear signs of a recovery. The trends for management groups as defined by the National Oceanic and Atmospheric Administration also are significant, showing drastic declines early in the study. Only for a small species of shark, Rhizprionodon terraenovae, is the trend in CPUE equivocal over the course of this study. The most likely cause of the declines shown in this study is fishing mortality, although other factors are discussed.

 

123 AES Conservation & Management II, Parlor ABC, Saturday 25 July 2009

Alexia Morgan1, Mike Allen1, Enric Cortes2, Colin Simpfendorfer3, George Burgess1, Jack Musick4

1University of Florida, Gainesville, FL, United States, 2NOAA/NMFS, Panama City, FL, United States, 3James Cook University, Townsville, Queensland, Australia, 4Virginia Institute of Marine Science, Gloucester Point, VA, United States

Population Assessment of the Dusky Shark in the Northwestern Atlantic Ocean Using an Age Structured Model

The objectives of this study were to build an age-structured model to assess the effects of fishing on population trends for dusky shark. This model included sensitivity analyses to assess the effects of time/area closures, reduced mortality as a result of reduced soak times for the bottom longline fishery, full selectivity of age-zero animals, combined CPUE series for all catch rates and changes to other model parameters on overall population sizes. Results showed that the impacts of fishing already imposed on the dusky shark will be difficult to overcome even with the implementation of time/area closures, gear modifications and/or catch and discards being reduced for another 20 years. Results of the base case, all scenarios and sensitivity analyses indicated that the population of dusky sharks in the northwestern Atlantic Ocean is at 9 to 50% of virgin biomass. Recent publications have shown that the Maximum Sustainable Yield (MSY) for dusky sharks may be well above 50% of the carrying capacity. Fisheries managers must determine whether the high depletion rates reported in these models suggest this species is overfished, and would therefore require long-term targets for population recovery to sustainable levels.

 

977 AES Conservation & Management II, Parlor ABC, Saturday 25 July 2009

Johnny Moore1, Dewayne Fox1, Bradley Wetherbee3, Camilla McCandless4

1Delaware State University, Dover, DE, United States, 3University of Rhode Island, Kingston, RI, United States, 4NOAA/National Marine Fisheries Service, Narragansett, RI, United States

Critical Habitat for Sand Tiger Sharks During their Summer Residency in Delaware Bay

The population of sand tiger sharks (Carcharias taurus) along the US East coast has declined over the past several decades and recovery of stocks is limited by low reproductive rates coupled with continued take as bycatch in various fisheries. Identification of essential habitat is critical for enhanced recovery of sand tiger stocks. Delaware Bay is one of the most important areas used by this species on the US East coast. We have been using acoustic transmitters and an array of receivers in Delaware Bay to identify critical habitat of sand tigers during their Delaware Bay summer residency. We monitored the movements and habitat use of 69 sand tigers in the summers of 2006 - 2008. Males and females were segregated, with males more commonly found in the lower salinity middle portion of the bay and in shallower waters, whereas females were more common in deeper, higher salinity waters near the mouth of the bay. Habitat use varied between years with significantly shallower depths used in 2007 than in 2008. The importance of Delaware Bay as summer habitat for sand tigers is demonstrated by relatively high interannual site fidelity with 50% of sharks tagged in 2006 returning in 2007, and 60% tagged in 2007 detected in the bay the following summer of 2008. This study has been very successful in identifying habitat of high use within Delaware Bay and providing information for protection of discrete portions of the bay that are vital to the recovery of this imperiled species.

An update on the status of the sand tiger shark, Carcharias taurusfor the U.S. Atlantic Ocean  MISSING!!!

 

394 AES Conservation & Management II, Parlor ABC, Saturday 25 July 2009

Michelle M. Evans, Daniel C. Abel, Sharon L. Gilman, Robert F. Young

Coastal Carolina University, Conway, SC, United States

Demographics and Habitat Partitioning of Elasmobranchs in Port Royal Sound, South Carolina

A longline and rod-and-reel survey for elasmobranchs was conducted in Port Royal Sound, a south-eastern South Carolina deep water embayment, from June - August 2007, and April - November 2008. The project's main objectives were: (1) to enumerate the elasmobranchs in Port Royal Sound; (2) to delineate nursery and breeding grounds, where present; and (3) to compare diversity and abundance of elasmobranchs at four locations at different distances from the mouth of the sound. Seventy-eight "adult" lines (16/0 hooks) and seventy-six "pup" lines (12/0 hooks), baited with Boston mackerel, were bottom-set during slack tides. Elasmobranch catch was identified, measured, tagged (only sharks) and released. We caught 540 elasmobranchs (n = 248 on longlines, 292 on rod-and-reel) comprising fourteen species: Rhizoprionodon terranovae (n = 368, adult M:F = 1:0), Carcarhinus limbatus (68, 0.3:1 ), Dasyatis sabina (24, 0.14:1), C. acronotus (19, 4.3:1), Sphyrna tiburo (13, 0.4:1), D. americana (12, 0.12:1), C. plumbeus (11), S. lewini (5, 1:1), Galeocerdo cuvier (4), C. isodon (2), Ginglymostoma cirratum (2), C. brevipinna (1), Negaprion brevirostris (1), and Raja eglanteria (1). Port Royal Sound may represent primary or secondary nurseries for C. limbatus, C. plumbeus and S. lewini. The location furthest (19.3 - 22.5 km) from the mouth had a significantly lower CPUE (#sharks.100 hooks.-1 h-1) than the three other locations. Port Royal Sound, whose watershed is rapidly developing and whose wetlands are highly susceptible to sea level rise, may represent Essential Fish Habitat for a number of species of sharks and rays.

284 AES Conservation & Management II, Parlor ABC, Saturday 25 July 2009

Craig O'Connell1, Daniel Abel1, Eric Stroud1, Patrick Rice1

1Coastal Carolina University, Myrtle Beach, SC, United States, 2SharkDefense Technologies, LLC, Oak Ridge, NJ, United States, 3Florida Keys Community College, Key West, FL, United States

A Quantitative Analysis Examining the Effects of Permanent Magnets on Elasmobranchs in Recreational and Longlining Fisheries

Elasmobranch fishes (sharks and rays) detect magnetic fields through the process of indirect-based magnetoreception via electromagnetic induction using their ampullae of Lorenzini. We evaluated the feeding responses of elasmobranchs in the presence of permanent magnets in hook-and-line and longline fishing experiments. In the hook- and-line study, we used control, sham magnet, and neodymium magnet hook treatments. Longlines, 150 m in length and containing 24 hooks, were deployed with an alternating sham magnet hook - magnetic hook design. Atlantic sharpnose sharks (Rhizoprionodon terraenovae) were significantly repelled from the magnetic hook-and-line treatments (X2=11.967, d.f.=1, p=0.0005), while spiny dogfish (Squalus acanthias) were not (X2=0.532, d.f.=1, p=0.4658). On longlines, ceramic magnets significantly altered shark capture (X2=4.455, d.f.=1, p=0.035). Blacktip sharks (Carcharhinus limbatus; X2=4.455, d.f.=1, p=0.035) and southern stingrays (Dasyatis americana; X2=4.455, d.f.=1, p=0.035) significantly fed from the sham magnet hooks more than magnetic hooks, while sandbar sharks (Carcharhinus plumbeus; X2=1.286, d.f.=1, p=0.257) did not demonstrate a preference for hook type. Results suggest that magnetic-induced repellent behaviors may be a species-specific phenomenon. The effectiveness of these magnets may have large implications in elasmobranch population recovery in two areas where anthropogenic mortality is the leading contributor to elasmobranch declines, e.g. on commercial longlines.

 

60 AES Conservation & Management II, Parlor ABC, Saturday 25 July 2009

Marcus Drymon1, Sean Powers2, John Dindo3

1NOAA Fisheries, Southeast Fisheries Science Center, Mississippi Laboratories, Pascagoula,MS, United States, 2Department of Marine Science, University of South Alabama, Mobile, AL, United States, 3Dauphin Island Sea Lab, Dauphin Island, AL, United States

Comparing Distributions of Sharks Among Estuarine, Coastal and Oceanic Regions of the Gulf of Mexico

Increasing evidence of declines in shark populations has sparked researchers to investigate more prudent approaches for the conservation of these fish. As managers strive to improve data collection for stock assessment, fisheries surveys should expand to include data-deficient areas such as coastal regions. To that end, a nearshore longline survey was initiated in 2006; catch series from this survey was compared to a concurrent offshore survey with identical methodology to identify differences in habitat use by overlapping species as well as identify potential nursery areas within each survey. Five shark species occurred in both surveys: Atlantic sharpnose (Rhizoprionodon terraenovae), blacknose (Carcharhinus acronotus), blacktip (C. limbatus), spinner (C. brevipinna) and tiger shark (Galeocerdo cuvier). Of these, blacktip sharks were sampled in significantly higher abundance nearshore. Length frequency and sex ratio analyses suggest that sharpnose and blacknose sharks show sexual segregation and may be using offshore waters for parturition, whereas blacktip sharks are likely using coastal waters as nurseries. Cuban dogfish (Squalus cubensis), night shark (Carcharhinus porosus), shortspine spurdog (Squalus mitsukurii), slimy shark (Centrophorus granulosa) and smoothhound (Mustelus spp.) sharks occurred only offshore, whereas all sharks sampled nearshore were seen offshore during some time of the year. Comparisons such as these highlight the need for more spatially and temporally comprehensive time series, as well as the need for researchers to examine the distributional trends for species across the extent of their range.

 

568 AES Conservation & Management II, Parlor ABC, Saturday 25 July 2009

Kate Andrews1, William Gazey1, Scott Raborn1, Benny Gallaway1

1NOAA Fisheries Service, Panama City, FL, United States, 2LGL Ecological Research Associates, Inc., Bryan, TX, United States, 3W. J. Gazey Research, Victoria, BC, Canada

Calculating Shark Bycatch in the Gulf of Mexico Shrimp Trawl Fishery: a Collaborative Approach

The assessment of shark populations in the Gulf of Mexico (GOM) is conducted through the Southeast Data, Assessment, and Review (SEDAR) process. In 2007, the small coastal complex, blacknose (Carcharhinus acronotus), Atlantic sharpnose (Rhizoprionodon terraenovae), bonnethead (Sphyrna tiburo), and finetooth (Carcharhinus isodon), was assessed by scientists from the NOAA Fisheries Service. Using the catch data, indices, and life history parameters recommended by the members of the data workshop working groups, they determined blacknose to be an overfished population with continued overfishing. The largest component of the catches was the yearly estimate of bycatch in the shrimp trawl fishery. The estimation method used was of concern to the shrimp industry due to what they viewed as questionable assumptions and poor data, and their representatives approached NOAA scientists about collaborating to revise the method to use at the following SEDAR. The method had been used in other SEDARs previously, but this was the first application to the data poor shark fishery. Notable adjustments to the method include accounting for a Turtle Excluder Device (TED) effect and matching index data to the fishing behaviors of the commercial shrimpers. The consensus reached is evidence of the SEDAR process at work and illustrates a scientifically sound meeting of the minds, between managers and stakeholders.

 

581 AES Conservation & Management II, Parlor ABC, Saturday 25 July 2009

Joana Fernandez-Carvalho, George Burgess

Florida Program for Shark Research, Florida Museum of Natural History, University of Florida, Gainesville, FL, United States

The National Sawfish Encounter Database: Integration, Maintenance and Growth

The smalltooth sawfish (Pristis pectinata), the first marine fish to be listed under the U.S. Endangered Species Act (ESA), is currently listed as critically endangered by the IUCN, and is included in the Appendix I of CITES. During the species listing process, the National Sawfish Encounter Database (NSED) was created as a tracking database to gather information regarding smalltooth sawfish encounters and has been maintained ever since to assist recovery managers and researchers. In September 2008, the NSED was transferred from Mote Marine Laboratory to the Florida Program for Shark Research (FPSR), where it was merged with the FPSR database and four additional scientific and private databases. As a result, all information regarding U.S. sawfish is united for the first time in one place. Currently, the NSED has a total of 3368 records and includes data from 1782 to 2009. Preliminary analysis shows a depth-related size distribution, with the larger specimens occurring predominantly in deeper waters and smaller individuals inhabiting shallower waters. While juveniles have been observed throughout Florida waters, the highest frequency of occurrence occurs along the southwest (Gulf of Mexico) coast. Juveniles also are commonly encountered in the Florida Keys, where adults are observed most frequently. Adults also are often found along the east coast (Atlantic Ocean) of Florida, where juveniles are relatively scarce. The newly-augmented NSED provides enhanced information on the U.S. smalltooth sawfish population, assisting the Sawfish Implementation Team in the evaluation of the species abundance, range and habitat preferences.

 

737 AES Conservation & Management II, Parlor ABC, Saturday 25 July 2009

David McGowan

Florida Fish & Wildlife Conservation Commission, Tequesta, FL, United States

Evolution of the Recreational Shark Fishery of Florida, 1981-2008

Over the past 30 years, recreational anglers have accounted for a substantial proportion of the total shark harvest throughout the United States. Florida has been the epicenter for both recreational and commercial fisheries targeting large coastal sharks (LCS) and small coastal sharks (SCS) in the western Atlantic and Gulf of Mexico. After peaking in the early 1990s, commercial shark landings have steadily decreased due to more restrictive quotas and increased number of prohibited species. Recreational landings have decreased concomitantly; although this decline may be attributed less to regulatory changes, and more to social changes throughout the recreational fishing community. Catch disposition data collected by the Marine Recreational Fishing Statistics Survey (MRFSS) from 1981 to 2008 show a significant shift towards catch and release by recreational anglers. Throughout the 1980s, recreational anglers historically landed 54.1 and 58.5% of the total recreational LCS and SCS catches, respectively. The proportion of the total recreational shark catch that was harvested declined to 26.7 and 22.5% during the 1990s when management actions were first implemented, and further declined to 14.2 and 11.4% through the current decade. Despite these changes, segments of the recreational fishery continue to target sharks with sufficient regularity that their impact may not be adequately accounted for by the MRFSS. These directed recreational fisheries may result in significant mortality for some shark species, including blacktip, bull, scalloped hammerhead, great hammerhead, and bigeye thresher. Recommendations for improvements in monitoring efforts and public outreach are presented.

 

1004 AES Conservation & Management II, Parlor ABC, Saturday 25 July 2009

Manuel Mendoza-Carranza1, Edith Ramírez-Mosqueda1, José Alfredo Hernández-López1, Christian Carolina Hernández-Lazo1, Juan Carlos Pérez- Jiménez2

1El Colegio de la Frontera Sur, Villahermosa, Tabasco, Mexico, 2El Colegio de la Frontera Sur, Campeche, Campeche, Mexico

Does Southern Stingray Dasyatis americana Sustain the Artisanal Elasmobranch Fisheries in Western Campeche Bank?

The diminishment of shark volume captures has conducted to a crescent capture of less valuable commercial elasmobranch species like several rays species. This increases is reflected in official statistics. However, exist a scarce knowledge about fisheries, population dynamics and biology of this species, which precludes the generation of management programs. In western Campeche bank, specifically in the San Pedro’s port fleet, (composed by 150 fiberglass outboard motor vessels of 8m long) the stingray Dasyatis americana is the second in abundance among 18 teleost, 13 sharks and 3 ray species. Dasyatis americana CPUE (kg/100 hooks*hour) show no significant differences among depth range (5 to 50m). Seasonal D. americana CPUE variation was achieved, maximums was during February 2006 (3±1.3) and February 2007 (2.5±1.5). Adult Male:female proportion was 1:1.14. Males’ size was from 30 to 60cm of disk width (DW) and the females were from 60 to 120cm DW. The size at maturity of males and females, estimated with maturity ogive, was 52 and 84cm DW respectively. Gravid females were scarce (7% of total). Sex proportion of embryos was 1:1, average size for males and females were 12±9 and 16±12cm DW respectively. No correlation was achieved among embryos size and ovocite diameter this can indicate an asynchrony reproductive cycle. The high relative abundance and frequency of D. americana in the captures of artisanal fisheries in Western Campeche Bank indicates an important distribution area of this species, due to this more research about fisheries biology and ecology is necessary.

                          

98 AES Reproduction & Genetics, Galleria South, Saturday 25 July 2009

Rui Coelho1, Fábio Hazin2, Mariana Rego2, Mirna Tambourgi2, Paulo Oliveira2, Paulo Travassos2, Felipe Carvalho1, George Burgess1

1Florida Program for Shark Research, Florida Museum of Natural History, University of Florida, Gainesville, FL, United States, 2Universidade Federal Rural de Pernambuco, Recife, Pernambuco, Brazil

Abundance, Distribution and Reproductive Biology of the Oceanic Whitetip Shark Caught by the Tuna Pelagic Longline Fishery in the Southwest Atlantic Ocean

Oceanic whitetip sharks, Carcharhinus longimanus, are regularly caught as by-catch by northeastern Brazil-based longliners, targeting mainly tuna and swordfish. We analyzed fisheries data collected by fishery observers since 2004 and biological data gathered since August 2007, the latter to determine reproductive parameters. The oceanic whitetip represented 3.1% of the total shark catch by number and, even though it is not targeted directly by the fishery, captured specimens were usually retained for marketing. A high proportion of the catch was composed of juvenile specimens, and even though only a few mature specimens have been caught, preliminary analysis of the temporal variation in gonad morphology and weight suggests that size at maturity is occurring between 160 to 196 cm total length (TL) for males and 181 to 203 cm TL for females. Litter sizes in pregnant females varied from 1 to 14 embryos. In this region, mating seems to be occurring in March and parturition 10 to 12 months later. Carcharhinus longimanus occurred throughout the entire study area, from latitudes 5oN to 25oS. While juveniles dominated and were homogenously distributed throughout the region, it is interesting to note that the few pre-ovulatory females recorded occurred exclusively in the southern region (20oS to 25oS) while the few pregnant females recorded occurred exclusively in the equatorial region (around 5oS), suggesting spatial variations of this population in the southwest Atlantic Ocean.

 

551 AES Reproduction & Genetics, Galleria South, Saturday 25 July 2009

J. Fernando Marquez-Farias(1)4, Maya S. Rubio Lozano2, Luis Vicente Gonzalez- Ania3, Ricardo Rojas Peraza1

1Universidad Autonoma de Sinaloa. Facultad de Ciencias del Mar., Paseo Claussen S/N. Col. Los Pinos, CP 82000. Mazatlan, Sinaloa, Mexico, 2Universidad Nacional Autonoma de Mexico, Facultad de Ciencias, Universidad 3000 Circuito Exterior S/N, C.P. 04510 Ciudad Universitaria, Mexico, DF., Mexico, 3Instituto Nacional de Pesca. SAGARPA, Pitagoras 1320, Col. Santa Cruz Atoyac, CP 03310, Mexico, DF., Mexico, 4Instituto Nacional de Pesca, SAGARPA, Centro Regional de Investigacion Pesquera de Mazatlan, Calzada Sabalo-Cerritos S/N, CP 82010 Mazatlan, Sinaloa, Mexico

Observations on the Reproductive Biology of the Chilean Round Ray, Urotrygon chilensis From the Southern Gulf of California, Mexico

The Gulf of California (GOC) is a highly productive area with considerable ichthyofaunal diversity that forms the basis of several commercial fisheries. The largest batoid fishery in Mexico operates in the GOC, and bycatch in the regional shrimp trawl fishery is also substantial and may rival directed landings as a source of mortality. Close monitoring of this and other of non-commercially important batoid species is necessary to update or confirm their conservation status (i.e., IUCN Red List assessment). Despite the great diversity of elasmobranchs in the GOC, little life history information is available for most species. To address this lack of critical biological information, the reproductive biology of the Chilean round ray, Urotrygon chilensis, was investigated based on specimens obtained by fishery independent trawl surveys of the Instituto Nacional de Pesca. Maturity stages were assigned by visual inspection of the development of claspers and testes for males, and by measurements of the oviducal gland, largest ovum diameter, and uterus width for females. Fitting a logistic regression to binomial data (0=immature, 1= mature) yielded median size at fifty percent maturity values of 15.2 (15.1-15.7 cm) cm DW and 14.6 (14.1-15.3 cm) cm DW for males and females, respectively. Pups typically born during spring after a gestation period of approximately 5-6 months. Mean fecundity was estimated to be 1.8 (range 1-5, s.d. = 1.0) with a 1:1 sex ratio. Size at birth ranged from 6 to 9 cm DW. Gravid females were typically found in shallow subtidal waters (< 10 meters).

 

872 AES Reproduction & Genetics, Galleria South, Saturday 25 July 2009

James Sulikowski1, Angela Cicia1, William Driggers2, Jay Williams1, Jill Hendon3, Eric Hoffmayer1

1University of New England, Biddeford, ME, United States, 2National Marine Fisheries Service, Pascagoula, MS, United States, 3Gulf Coast Research Laboratory, Ocean Springs, MS, United States

Size and Age Estimates at Sexual Maturity for the Blacknose Shark, Carcharhinus acronotus, from the Northern Gulf of Mexico

The blacknose shark, Carcharhinus acronotus, is distributed throughout the western Atlantic Ocean from North Carolina to Brazil, including the Gulf of Mexico. Although the life history of the blacknose shark has been well described for specimens collected from the Atlantic Ocean, several key life history characteristics are lacking for specimens collected from the Gulf of Mexico. One particular parameter that is deficient, is a direct determination of age and size at sexual maturity based on reproductive tissues. This life history information forms the basis for the calculations of growth rate, and productivity, making it one of the most important variables for estimating a population’s status and assessing the risks associated with its exploitation. In order to gain insight into this life history parameter, age at size will be linked to maturity by using criteria from three endpoints; steroid hormone concentrations, gross morphological examination of reproductive tracts, and histological examination of spermatogenesis. This study is timely as stock assessments for this species suggest that it is currently overfished. In addition, this will be the first study to use the three aforementioned reproductive endpoints to asses reproductive maturity in a carcharhinid shark.

 

749 AES Reproduction & Genetics, Galleria South, Saturday 25 July 2009

Brittany Palm, Dave Koester, James Sulikowski

University of New England, Biddeford, ME, United States

Fecundity, Viability, and Gestational Rates of Little Skate, Leucoraja erinacea, Egg Cases in the Gulf of Maine

The direct determination of fecundity, viability, and gestation rates of little skate, Leucoraja erinacea, egg cases in the Gulf of Maine are unknown. Determining these reproductive parameters, are essential to the effective management of this and other skate species. Thus, the goals of this study were to determine these parameters for little skate specimens collected from the Gulf of Maine and housed under ambient conditions. Sexually mature little skates were maintained in tanks equipped with ambient, free flowing seawater to monitor the effects of seasonal variation over a full year. Fecundity was calculated at 49 eggs per year and egg deposition peaked in June but was consistently high during the summer months (June, July, August). Out of the 346 eggs laid by seven sexually mature females, 75.1% were viable at the termination of the study and viability was statistically lower in the spring when compared to summer, fall, and winter. Gestation lengths ranged from 22 weeks to 54 weeks and eggs that were laid in the fall displayed the longest gestational period (average=44.3 weeks, S.E. ± 0.13 weeks) while those laid in the spring displayed the shortest gestational period (24.8 weeks, ± 0.24 weeks). Skates developed slower and were statistically smaller in colder seasons than skates that developed faster and larger in warmer seasons. To further investigate the variability in gestation and total lengths, metabolic rates of embryonic skates are currently being measured over a full annual cycle under ambient conditions.

 

759 AES Reproduction & Genetics, Galleria South, Saturday 25 July 2009

L. Jay Williams, James Sulikowski

University of New England, Biddeford, ME, United States

The Use of Steroid Hormone Concentrations to Determine Individual Variability in the Reproductive Cyclicity of the Little Skate, Leucoraja erinacea, in the Western Gulf of Maine

The little skate, Leucoraja erinacea, inhabits a broad geographical range extending from Nova Scotia to Cape Hatteras, NC. In the Gulf of Maine (GOM), the little skate is considered to be the most common of the seven endemic inshore skate species. A recent study (2007), found the GOM population to be close to both the overfishing and minimum biomass thresholds. The analysis of circulating steroid hormones is a non- lethal technique proven to effectively assess reproductive parameters in elasmobranch species. However, describing reproductive cyclicity with this technique has been problematic due individual variability in the stage of ovulation amongst sampled mature females. The goals of this study are to investigate the appropriate temporal sampling periodicity in order to reduce the variability of hormone levels observed in previous studies. Circulating steroid hormones, estradiol (E2) and testosterone (T), will be used to establish individual variability and reproductive cyclicity in the little skate. Steroid hormones are currently being extracted from weekly blood samples collected from a laboratory population of mature little skates. Hormone levels will be determined by radioimmunoassay and variations in the concentrations of E2 and T between skates will be evaluated to assess the extent of individual hormone variability. In addition, trends of elevated hormone levels will be used to determine the annual reproductive cycle.

Phylogeography of Indo-West Pacific Sharks and Rays (≤10 spp), with Applications to Monitoring the International Shark Fin Trade MISSING!!!

431 AES Reproduction & Genetics, Galleria South, Saturday 25 July 2009

Ana Verissimo, Jan McDowell, John Graves

Virginia Institute of Marine Science, Gloucester Point, VA, United States

Worldwide Population Structure of the Spiny Dogfish Squalus acanthias

The spiny dogfish Squalus acanthias is a small, coastal squaloid shark that occurs in cold temperate waters of the Atlantic and Pacific oceans. It is also a heavily exploited resource in several regions along its range. The antitropical distribution of this species and its habitat preferences suggests that warm, tropical waters may act to isolate populations on the northern and southern hemispheres. However, long distance migrations along potentially suitable cold-temperate coastal areas, such as those reported between the east and west coasts of the North Atlantic and North Pacific, may connect populations at considerable geographic distances. To elucidate the worldwide population structure of the spiny dogfish, individuals collected from throughout the species' range (except South Africa) were genotyped at eight nuclear microsatellite loci and sequenced at the mitochondrial ND2 locus. Both types of molecular markers revealed strong divergence between North Pacific collections and those taken from the rest of the species' range. In addition, microsatellite loci detected small but significant differences between North Atlantic collections and those from all southern hemisphere locations. These data suggest that spiny dogfish comprise at least three genetic stocks: North Pacific, North Atlantic, and southern hemisphere. The magnitude of the genetic differences among regions suggests that North Pacific spiny dogfish have been isolated for a relatively long period of time, while gene flow between the North Atlantic and southern hemisphere fish seems to have been limited only recently.

 

677 AES Reproduction & Genetics, Galleria South, Saturday 25 July 2009

Katherine Allen1, Mark Roberts1, James Grady2, Joseph Quattro1

1University of South Carolina, Columbia, SC, United States, 2University of New Orleans, New Orleans, LA, United States

Two Genetically Distinct Lineages of the Shortfin Mako (Isurus oxyrinchus)

Despite expectations, highly vagile, cosmopolitan marine fishes often are genetically structured, even in the apparent absence of barriers to gene flow. The Shortfin Mako (Isurus oxyrinchus) is a pelagic, globally distributed species that is an important target of commercial and recreational fisheries, and fishing pressure on populations necessitates a thorough evaluation of population genetic structure. A previous RFLP analysis of genetic variation in I. oxyrinchus detected significant mtDNA haplotype heterogeneity that was regionally partitioned, but the data were insufficient to support genetically distinct stocks. Based on this suggestion of geographic structure, a finer scale genetic analysis was conducted by sequencing a 300 bp fragment of the mtDNA control region in 183 individuals from five regions (Northeast Pacific, North Atlantic, Southwest Atlantic, Southwest Pacific, and Africa). Sequencing recovered 30 haplotypes defined by 26 polymorphic nucleotide positions. Mean haplotype diversity (h=0.822) is consistent with RFLP results. Control region gene trees support two clades separated by 2.4% sequence divergence, and haplotype frequencies within and between clades exhibit significant regional partitioning. Evidence of lineage diversification and geographically partitioned genetic variation among mako shark populations should be incorporated in future management plans.

 

427 AES Reproduction & Genetics, Galleria South, Saturday 25 July 2009

Nicole Phillips1, Jennifer Chaplin1, David Morgan1, Stirling Peverell2

1Centre for Fish & Fisheries Research, Murdoch University, Murdoch, Western Australia, Australia, 2Queensland Department of Primary Industries & Fisheries, Sustainable Fisheries, Northern Fisheries Centre, Cairns, Queensland, Australia

Conservation Genetics of Pristis Species in Australian Waters

Information on the conservation genetics of the Critically Endangered (IUCN) sawfishes Pristis microdon, P. zijsron and P. clavata in northern Australia, which is believed to be their last stronghold, is vital to the development of management plans. Since these three species have different habitat requirements, such information also provides the opportunity to investigate whether their population structures vary with habitat usage. Nucleotide sequence variation in a portion of the control region of the mitochondrial DNA was used to investigate the extent to which the assemblages of each of these three species in the northwest and northeast of Australia are connected and also to compare the levels of genetic diversity in these assemblages. The results indicate that P. microdon, which utilizes freshwater rivers as juveniles and marine waters as adults, exhibits strong genetic subdivision between these two regions (FST=0.314; P = 0.000; N = 92). In contrast, P. zijsron and P. clavata, which spend their entire life in marine and/or estuarine waters, exhibited less genetic subdivision between the northeast and northwest. The overall level of genetic diversity for each species was moderate, however, the assemblages in the northeast appear to have lower genetic diversity than those in the northwest of Australia. The results suggest that populations of Pristis sawfishes tend to be spatially restricted and management plans should be developed accordingly.

 

472 AES Reproduction & Genetics, Galleria South, Saturday 25 July 2009

Christine Testerman1, Demian Chapman2, Mahmood Shivji3

1Guy Harvey Research Institute, Nova Southeastern University, Dania Beach, FL, United States, 2Stony Brook University, Stony Brook, NY, United States, 3Save Our Seas Shark Center, Guy Harvey Research Institute, Nova Southeastern University, Dania Beach, FL, United States

Population Genetic Structure of the Night Shark (Carcharhinus signatus) in the Western Atlantic Assessed Using Nuclear Microsatellite Markers and Mitochondrial Control Region Sequences

The night shark is a deepwater, coastal and semi-oceanic shark found in the Western Atlantic and along the west coast of Africa. It prefers tropical and warm temperate waters near outer continental shelves in depths of 300-400m during the day and around 200m at night. The night shark is of conservation concern because it is an important component of artisanal fisheries and is heavily fished off Cuba and Brazil. The night shark was assessed as Vulnerable by the IUCN Redlist in 2006, and is prohibited from landings in US waters. No information on stock structure for the night shark exists to assist in its stock assessments and guide its overall management. We report on the population structure of the night shark utilizing the complete mitochondrial control region sequence (1066 bp) and 11 microsatellite loci from 72 individuals sampled from part of its western Atlantic range. Analysis of the night shark mitochondrial sequence data set collected thus far reveals strong geographic subdivision with two genetically distinct populations (NW Atlantic and SW Atlantic), and overall high levels of genetic diversity. We are expanding these analyses with larger sample sizes and will also report on comparative inferences made from the nuclear markers.

 

115 AES Reproduction & Genetics, Galleria South, Saturday 25 July 2009

Adam Stow, Heidi Ahonen

Macquarie University, Sydney, Australia, Australia

Patterns of Dispersal and Genetic Variation in the Sand Tiger Shark (Carcharias taurus)

Population sizes of sand tiger sharks (Carcharias taurus) are considered to be in decline throughout their distribution. Anthropogenic impacts are believed to be the primary threats to the eastern Australian population of sandtiger sharks, which is listed as Critically Endangered, and the most threatened population globally. We have shown that sand tiger sharks sampled off eastern Australian are isolated and have relatively low levels of genetic diversity. However the degree of isolation between all extant populations is still uncertain. In this study mitochondrial DNA (mtDNA) and nuclear loci (AFLP's and microsatellites) are being used to estimate genetic partitioning among grey nurse shark populations throughout their global distribution. We have also increased our sampling density of the critically endangered east Australian sand tigers allowing us to comment on fine scale dispersal patterns within this population.

 

176 AES Reproduction & Genetics, Galleria South, Saturday 25 July 2009

Kevin Feldheim1, Samuel Gruber2, Joseph DiBattista3, Demian Chapman4, Andrew Hendry3, Elizabeth Babcock5, Ellen Pikitch4, Mary Ashley6

1Field Museum, Chicago, IL, United States, 2Bimini Biological Field Station, Bimini, Bahamas, 3McGill University, Montreal, Quebec, Canada, 4Stony Brook University, Stony Brook, NY, United States, 5University of Miami, Miami, FL, United States, 6University of Illinois at Chicago, Chicago, IL, United States

Long-term Philopatry and the First Case of Natal Homing in a Chondrichthyan Fish

Natal homing is an extreme form of philopatric behavior, in which females return to their birthplace to give birth. This phenomenon has been shown in some marine vertebrates including bony fish and reptiles, but not for the most basal jawed vertebrate lineage, the chondrichthyans, that includes sharks and their relatives. Using both physical and genetic tags coupled with pedigree reconstruction, we show long-term (up to 16 years) philopatric behavior by female lemon sharks (Negaprion brevirostris) to a tropical nursery lagoon. We also find evidence of males and females mating over several years, indicative of either long-term sperm storage or long-term associations between individuals. Finally, we provide the first evidence of natal homing in a shark. These results provide a potential explanation for why rapid, long-term population collapse is typical of local shark fisheries, which then has important implications for conserving these imperiled apex predators.

 

524 AES Reproduction & Genetics, Galleria South, Saturday 25 July 2009

Demian Chapman1, Kevin Feldheim2, Andrea Bernard3, Sabine Wintner4, Geremey Cliff4, Mahmood Shivji3

1Stony Brook University, Stony Brook, NY, United States, 2The Field Museum, Chicago, IL, United States, 3Nova Southeastern University, Fort Lauderdale, FL, United States, 4Natal Sharks Board, Durban, South Africa

Mating System and Paternity in an Intrauterine Cannibal: The Sand Tiger Shark

The sand tiger shark (Carcharias taurus) is the subject of heightened conservation concern worldwide because it is extremely vulnerable to even modest levels of fishing pressure. This vulnerability stems from the exceptionally low litter sizes (two) of this species, which occurs because the largest/eldest embryo in each uterus kills and consumes all of the other embryos ("intrauterine cannibalism" or "embryophagy"). This remarkable reproductive strategy suggests that competition between male sand tigers for paternity is likely to be especially intense when compared to species that produce larger litter sizes. In this context it is not surprising that male sand tigers have been observed guarding females, which may serve to prevent these females from mating with and being fertilized by additional males ("multiple paternity"). We therefore genetically- tested nine sand tiger litters (24 embryos) from Richards Bay, South Africa, to see if single paternity of litters was more typical in this species. This analysis revealed that the two surviving offspring in a sand tiger litter are more commonly half- rather than full- siblings, demonstrating multiple paternity. Competition for paternity therefore continues after copulation has taken place in this species (i.e. sperm competition). We also provide evidence that some males that successfully fertilize a female are still reproductively unsuccessful because their offspring are cannibalized prior to birth by embryos sired by a rival male. Competition between males for paternity therefore extends beyond fertilization in this species. We discuss these findings in the context of sand tiger mating system evolution and conservation.

 

158 AES Ecology I, Pavilion West, Saturday 25 July 2009

Gregory Skomal1, Stephen Zeeman2, John Chisholm3, Erin Summers4, Harvey Walsh5, Kelton McMahon5, Simon Thorrold5

1MA Marine Fisheries, Vineyard Haven, MA, United States, 2University of New England, Biddeford, ME, United States, 3MA Marine Fisheries, New Bedford, MA, United States, 4ME Dept. Marine Resources, Boothbay Harbor, ME, United States, 5Woods Hole Oceanographic Institution, Woods Hole, MA, United States

Mesopelagic Trans-equatorial Migrations by Basking Sharks in the Western Atlantic Ocean

The world's second largest fish, the basking shark (Cetorhinus maximus), is broadly distributed in boreal to warm temperate latitudes of the Atlantic and Pacific oceans from shallow coastal waters to the open ocean. Satellite archival tagging in the North Atlantic has shown that basking sharks move seasonally, are often associated with productive frontal zones, and may make occasional dives to mesopelagic depths. However, basking sharks are thought to be restricted to temperate latitudes and the extent to which they exploit deeper water habitat remains a mystery. Using satellite archival tags and a novel geolocation technique, we demonstrate that basking sharks are seasonal migrants to mesopelagic tropical waters. We deployed 25 pop-up satellite transmitting (PSAT) tags on basking sharks in the western North Atlantic off the coast of Cape Cod, MA during the summer and autumn months. In total, 18 (72%) tags transmitted data after deployment periods of 12-423 days (mean = 203 days). Tagged sharks moved from temperate feeding areas off the coast of southern New England to the Bahamas, the Caribbean Sea, and onward to the coast of South America and into the Southern Hemisphere. When in these areas, basking sharks descended to and, in some cases, remained at mesopelagic depths for weeks to months at a time. Our results demonstrate that tropical waters are not a barrier to migratory connectivity for basking shark populations and highlight the need for global conservation efforts throughout the species range.

 

293 AES Ecology I, Pavilion West, Saturday 25 July 2009

Hua Hsun Hsu1, Brad Norman, Elson Aca3, Shoou Jeng Joung1

1National Taiwan Ocean University, Keelung City 20224, Taiwan, 2Murdoch University, Murdoch, WA 6150, Australia, 3WWF-Philippines, Quezon City 1105, Philippines

North-South Migration of the Whale Shark (Rhincodon typus) in East Asian Waters and the Northwest Pacific

The migratory patterns and stocks distribution of the whale shark (Rhincodon typus) to date remain largely undefined. Pop-up archival transmitting (PAT) tags (Wildlife Computers Ltd.) were attached to a total of four whale sharks: two (4.02 m TL male and 3.80 m TL female, WS006 and WS007) released in Hualien (east of Taiwan) in July 2005; another 4.7 m TL male (WS200) released in Penghu (west of Taiwan) in September 2008; while another 7-8 m TL individual (sex unknown) (P-000) was tagged in Donsol (Philippines) in May 2007. The PAT tags attached to whale sharks were popped-off as follows: in the north of the East China Sea in September 2005 (WS006); east of Luzon (Philippines) in January 2006 (WS007); north of Luzon in February 2009 (WS200); and southwest of Taiwan in August 2008 (P-000), respectively. Light level signals converted to longitude-latitude data indicated that WS200 migrated south between the continental shelves of China and west of Philippines. P-000 migrated to an area south of Japan and then moved south towards southwest of Taiwan. This is the first study to prove that the range of whale sharks from South-east Asian waters and East China Sea overlap. These migration data, when combined with data on the discovery in February 2009 of a neonatal juvenile R. typus in Philippine waters and the capture of the only known pregnant female R. typus off Taiwan in 1995, suggest a breeding population that is likely to comprise one stock from the northwest Pacific.

 

101 AES Ecology I, Pavilion West, Saturday 25 July 2009

Yannis Papastamatiou1, Carl Meyer1, Katsufumi Sato2, Yuuki Watanabe3, Kim Holland1

1University of Hawaii at Manoa, Kaneohe, HI, United States, 2University of Tokyo, Otsuchi, Japan, 3National Institute of Polar Research, Tokyo, Japan

New “Ecological” Tags and their Use in the Study of Shark Behavior

While a variety of acoustic, satellite and archival tags are being used to quantify shark movements, very little is known about the factors regulating these movements. We have been deploying and testing “ecological” tags which measure a variety of parameters, in both captive and free-ranging sharks. These include gastric motility data loggers and acoustic pH transmitters to record foraging and digestion; a bio-acoustic probe which documents the external acoustic environment; and an acceleration/speed data logger to record swimming mechanics and detailed diving behavior. Although limitations exist with each type of tag, these new sensors will provide a more detailed insight into the underlying behaviors behind the movement patterns and habitat selection of free- ranging sharks.

 

471 AES Ecology I, Pavilion West, Saturday 25 July 2009

Bradley Wetherbee1, Mahmood Shivji2, Richard Nemeth3

1University of Rhode Island, Kingston, RI, United States, 2Guy Harvey Research Instittue, Oceanographic Center, Nova Southeastern University, Dania Beach, FL, United States, 3University of the Virgin Islands, St. Thomas, USVI, United States

Environmental Preferences of the Tiger Shark (Galeocerdo cuvier) Tracked with Pop-up Archival Satellite Transmitters in the US Virgin Islands

Tiger sharks are abundant apex predators worldwide, playing important roles in trophic dynamics of these ecosystems. However, in many ways tiger sharks are enigmatic and do not conform to typical patterns of feeding, reproduction, genetics, morphology, and migration into which many other species of sharks neatly fall. We investigated site fidelity, movement patterns fine-scale environmental preferences of depth, temperature and location by tracking seven tiger sharks (260-358 cm) tagged with pop-up archival satellite transmitters (Microwave Telemetry Inc.) in March and June 2008 at a grouper spawning site in the US Virgin Islands. Five sharks were tagged with transmitters that recorded light, temperature and depth at 3-min intervals for 30 days and two sharks were tagged with standard transmitters that record this data every 15-min over several months. Over 40,000 records of depth and temperature were obtained, which indicated that sharks spent over 80% of their time at less than 40 m depth and over 75% of their time in water 26-30oC. Although average depth and temperature occupied by sharks was fairly consistent, patterns of habitat utilization varied among individuals and there were no obvious consistent patterns or differences among size classes, sexes, or time of year. The majority of sharks moved less than 100 km in 30 days, but one shark moved nearly 1300 km from the tagging site in the USVI to coastal Venezuela. Overall, tiger sharks had surprisingly narrow environmental preferences and occupied a relatively restricted portion of the marine realm, but readily deviated from their preferred habitat.

 

411 AES Ecology I, Pavilion West, Saturday 25 July 2009

Jeff Whitty1, Stirling Peverell2, David Morgan1, Dean Thorburn1, Colin Simpfendorfer3

1Centre for Fish and Fisheries Research, Murdoch University, Murdoch, Western Australia, Australia, 2Queensland Primary Industries & Fisheries, Sustainable Fisheries, Northern Fisheries Centre, Cairns, Queensland, Australia, 3Fishing and Fisheries Centre, James Cook University, Townsville, Queensland, Australia

Movements and Habitat Use of Juvenile Freshwater Sawfish (Pristis microdon) in a Riverine Environment

Inhabiting rivers as juveniles, Critically Endangered (IUCN 2006) freshwater sawfish (Pristis microdon) are vulnerable to habitat degradation, although it is unclear to what extent as little is known about their habitat use. Between June 2007 and November 2008 passive acoustic tracking methods employing Vemco V13TP-1L and V16TP-5H tags, monitored by VR2W receivers, were used to investigate the movements and habitat use of P. microdon in a riverine environment. Tracking data revealed that individuals were selective of the depths they used at different ages, times of day and when exposed to different environmental parameters including depth and temperature. In general, new recruits (0+ age class) occupied shallow waters (<0.6 m) while ≥1+ age classes P. microdon inhabited deeper water (>0.6 m). A vertical movement pattern was observed primarily in ≥1+ P. microdon, moving to deeper water at sunrise and moving shallower in the afternoon. Body size, predator/prey interactions, temperature and light intensity are hypothesised to be reasons for depth selection as observed with other elasmobranchs. Data also revealed that tides influenced the direction of inter-pool movement for 0+ P. microdon, moving with tidal flow (98% of time), and provided ≥1+ P. microdon access through shallow runs normally only manoeuvrable by 0+ P. microdon. Due to varying behaviours of different age classes and habitat use changing with environmental conditions, investigating impacts of habitat degradation on P. microdon is a complicated process. However, it can be concluded from this study that decreased water levels will limit access to habitat and resources for P. microdon.

 

967 AES Ecology I, Pavilion West, Saturday 25 July 2009

Bryan Franks1, Eric Reyier2, Samuel Gruber3, Steven Kessel1, Demian Chapman4

1Bimini Biological Field Station, Miami, FL, United States, 2Dynamac Corporation, Kennedy Space Center, FL, United States, 3University of Miami, Miami, FL, United States, 4Stony Brook University, Stony Brook, NY, United States

Lemon Sharks (Negaprion brevirostris) on the Beach: An Update from a Winter, Surf-zone Nursery at Cape Canaveral, Florida

The lemon shark (Negaprion brevirostris) utilizes nursery areas mostly found around shallow, mangrove fringed coastlines from Florida to Brazil. Recently a large population (>500 individuals) of juvenile lemon sharks was found in the surf zone along Cape Canaveral, Florida. This presents a unique opportunity to study a population of juvenile sharks utilizing a nursery habitat that differs greatly from most of the known nurseries for this species. A majority of young individuals in this population suffer from an extremely heavy parasite load. To date, we have tagged 390 individuals with tag returns suggesting a northward migration in early spring. Some sharks moved at least 640 km from Cape Canaveral to Buzzard Bay, NC. In December 2008, we implanted Vemco transmitters in 4 male and 5 female lemon sharks (59 - 97 cm PCL) to obtain data on the seasonal movements around the Cape and to gauge the timing of their northward migration. We are monitoring local movements using Vemco monitors placed just off the beach. Large scale movements are being monitored through the FACT and ACT arrays along the eastern seaboard and through tag returns. Finally we are examining a possible connection between the Cape Canaveral juvenile sharks and a large, seasonal aggregation of mature sharks off Jupiter, Florida. Future directions for this project include assessing the population genetics of these juvenile sharks, expanding the tracking study to further evaluate local movements and migration patterns, and examining the health of the sharks with specific regard to their high parasite burden.

 

685 AES Ecology I, Pavilion West, Saturday 25 July 2009

Jason Romine1, Johanna Imhoff1, Christina Conrath2, George Burgess1

1Florida Program for Shark Research, Florida Museum of Natural History, University of Florida, Gainesville, FL, United States, 2RACE/AFSC/NOAA Fisheries, Kodiak, AK, United States

Movement Patterns of Two Species of Rays in Mosquito Lagoon, Florida, USA

Several species of batoids utilize coastal lagoonal habitats of eastern Florida, USA. In general, behavioral ecology of batoids within this region has been overlooked despite their significance to the ecosystem. We utilized passive acoustic tracking methods to elucidate movement patterns, habitat use and home range of two common ray species, Dasyatis say (Bluntnose Stingray) and Gymnura micrura (Smooth Butterfly Ray), within Mosquito Lagoon. Smooth butterfly rays exhibited larger mean home range than bluntnose stingrays within this region. Both species exhibited similar diel activity patterns, with greatest activity occurring during early morning hours and least activity during afternoon hours. Seasonal movement patterns were also similar with both rays utilizing larger areas and displaying greater activity during the summer months. Sites near grass-bed margins were most commonly frequented by both species. Ray emigration and immigration patterns suggest the Mosquito Lagoon may serve as a nursery area for these two species.

 

182 AES Physiology, Galleria South, Sunday 26 July 2009

Laura Enzor, Rachel Wilborn, Wayne Bennett

University of West Florida, Pensacola, FL, United States

The Spine of Atlantic Stingray, Dasyatis sabina: Venom Toxicity and Role in Life History

The stingray venomous spine is thought to be primarily a defensive adaptation, but has also been shown to play key roles in conspecific social interactions such as reproduction. My study quantifies metabolic costs associated with the venom delivery system, venom toxicity (LC50), and routine resting metabolism for the Atlantic stingray, Dasyatis sabina. Respirometry trials estimated an average routine resting metabolism for fish of 0.484 kcal·g-1·h-1; whereas the average metabolic rate of the venomous delivery system was 0.000162 kcal·g-1·h-1, or 0.04% of the fishes' resting rate. Ballistic bomb calorimetry revealed an average spine caloric density of 0.238 kcal per gram of spine. Acute toxicity tests using sheepshead minnow, Cyprinodon variegatus, as a surrogate, determined a venom LC50 value of 0.018 mg protein·g of fish-1. The low metabolic cost of the stingray envenomation system likely reflects its structural simplicity and low toxicity. While, low venom toxicity is likely necessary for a system that is used on conspecifics, it has the disadvantage of being less effective on large predators.

 

406 AES Physiology, Galleria South, Sunday 26 July 2009

James Gelsleichter1, Nancy Szabo2, Chris Fulcher1

1University of North Florida, Jacksonville, FL, United States, 2University of Florida, Gainesville, FL, United States

Toxicity of Polychlorinated Biphenyls in Atlantic and Gulf Populations of Juvenile Sharks

Polychlorinated biphenyls (PCBs) are persistent organic compounds used as coolants in various products including electrical transformers, but have been banned since the 1970s due to toxic effects. PCBs tend to persist in marine environments, and recent studies have demonstrated elevated concentrations of total PCBs in juvenile sandbar and blacktip sharks from the U.S. Atlantic coast. Since some PCBs are far more toxic than others, the purpose of this study was to compare the toxicity of PCB congeners in sharks from these locations and less contaminated sites on the U.S. Gulf coast. Emphasis was placed on six of the most toxic PCB congeners, for which health effects have been well characterized. Liver concentrations of these compounds were used to calculate the Toxic Equivalence Quotient, a standard measure of pollutant toxicity. TEQ values indicated that Atlantic sharks are exposed to higher amounts of toxic pollutants, but the levels observed are low compared to earlier studies.

475 AES Physiology, Galleria South, Sunday 26 July 2009

Sora Kim, Dave Casper, Paul Koch

University of California, Santa Cruz, Santa Cruz, CA, United States

Assessing Fractionation Factors and Tissue Turnover Rates for Sharks

Superorder Selachimorpha (sharks) is globally distributed, with species ranging tropical to artic oceans. Traditional methods (gut analysis, tagging) offer snapshots into individuals’ lives, but data integrated over spatial and temporal scales is difficult. Stable isotope analysis (SIA) offers data on diet, migration, and habitat preferences on a range of spatial and temporal scales. A crucial step in the application of SIA is calibration on animals in experimental or controlled settings. Commonly accepted fractionation factors (FF) and tissue turnover (TTR) rates are calculated from mammals, birds, and teleosts. Sharks are distantly related to these taxa, and they have a unique physiology that includes osmoregulation using urea. Thus the assumption that FF and TTR measured on teleosts, mammals, or birds apply to sharks may not be valid. We will calculate diet-to- tissue FF and TTR through an experiment on leopard sharks (Triakis semifasciata). We switched the diets of sharks between two isotopically-distinct foods to assess turnover for plasma, red blood cells, and muscle. Results suggest that leopard sharks have FF similar to mammalian carnivores and TTR an order of magnitude less than homoeothermic animals. This experiment monitored these parameters for 9 individuals over the course of 3 years, allowing for comparisons within and between individuals. These results are the first robust diet-to-tissue FF and TTR calculated for elasmobranches in a natural abundance experiment. Our results will be important for the growing number of studies applying SIA to shark tissues to elucidate aspects of life history that are difficult to study using traditional methods.

750 AES Physiology, Galleria South, Sunday 26 July 2009

James Patterson1, Diego Bernal1, Chugey Sepulveda1

1University of Massachusetts Dartmouth, North Dartmouth, MA, United States, 2Pflegler Institute of Environmental Research, Oceanside, CA, United States

A Comparative Study of the Capacity for Aerobic and Anaerobic Metabolism in the Muscle Tissues of the Three Species of Thresher Shark (Family Alopiidae)

A recent study of the three species of thresher shark (Family Alopiidae) has revealed some striking interspecific differences in locomotor muscle morphology. The common thresher (Alopias vulpinus) differs significantly in the position of the red myotomal muscle (RM) when compared to the bigeye (A. superciliosis) and the pelagic thresher (A. pelagicus), and is the only thresher known to have regional muscle endothermy. The objectives of this study were to 1) determine if the pelagic and bigeye threshers have warm RM and 2) to quantify the activity of citrate synthase (CS; an index of aerobic capacity) and lactate dehydrogenase (LDH; an index of anaerobic capacity) in the RM in order to determine if the metabolic biochemical capacities are species-specific. Temperature readings were taken in six longitudinal positions along the body of the sharks and show that the RM temperatures of common thresher were above that of the ambient temperature at depth caught, while the pelagic and bigeye thresher RM temperatures were closer to ambient temperature at depth caught. The CS and LDH activity at 20 ̊C in the RM of the common thresher was higher when compared to the other two species. In addition, thermal effects were determined over a wide temperature range (10-30 ̊C) and showed that the mean Q10 for CS and LDH did not differ significantly. These results indicate that although the thermal effect on enzyme activity is similar, the overall activity of these enzymes in the RM is higher for the common thresher shark.

 

599 AES Physiology, Galleria South, Sunday 26 July 2009

Jerome Mallefet, Marie Renwart, Julien Claes

Catholic University of Louvain, Lab MarineBbiology, 1348 Louvain-la-Neuve, Belgium

Study Of The Velvet Belly Lantern Shark, Etmopterus spinax, Luminous System

Bioluminescence is the ability of living organism to produce visible light thanks to a chemiluminescent reaction. Widely distributed among marine organisms, this property is observed from bacteria to fish, the only luminous vertebrates. In fish, luminous osteichthyes and chondrichthyes representatives are known. Production of light in chondrichthyes is still poorly understood in terms of physiology, ethology and biochemistry mainly because of the difficulties to obtain living specimens. One species, the velvet belly lantern shark, Etmopterus spinax has recently attracted a lot of interest at ecological and populational levels. A new research program developed in our lab focused on various aspects (physiology, ethology and biochemistry) of bioluminescence of this shark. First biochemical results reveal that light production is based on a luciferin called coelenterazine. Repartition of the luminous compounds, luciferine and luciferase, in different organs of sharks of differents sizes and sex were analysed. Test were carried out on free-swimming specimens as well as on embryos. Further characterisation of luminous compounds are required in order to confirm the hypothesis that (i) luminescence capabilities might be acquired by food chain; (ii) maternal transfert of luminescence to the embryo.

 

600 AES Physiology, Galleria South, Sunday 26 July 2009

Julien M. Claes, Jérôme Mallefet

Catholic University of Louvain, Louvain-la-Neuve, Belgium

Luminescent Camouflage in a Deepwater Shark

Pelagic organisms are particularly vulnerable as they live in an habitat which offers no places to hide and were predation is the only way to feed below 100 m. In response to this, many of them developped adaptations to render their body less conspicuous to their predators and/or their preys: organismal transparency, side silvering, counter- shading and counter-illumination. Counter-illuminating animals are animals which emit a ventrally-directed luminescence to replace the downwelling light absorbed by their body. The efficiency of this camouflage depends on the physical characteristics (intensity, wavelenght, and angular distribution) of the luminescence which have to be as close as possible as those of the surrounding environment. In this work we used different techniques including luminometry, spectrophotometry, pharmacology and light microscopy to analyse the bioluminescence characteristics of a luminous deep-sea shark, the velvet belly lantern shark Etmopterus spinax. Experiments show that the light emitted by this shark appears to be particularly well-designed for camouflage by counter-illumination. This result is discussed with the ecology of the animal.

 

125 AES Ecology II, Galleria South, Sunday 26 July 2009

Joseph J. Bizzarro1, Leonard J.V. Compagno2, Robin Leslie3, David A. Ebert1

1Pacific Shark Research Center, Moss Landing, CA, United States, 2Save our Seas Foundation, Capetown, South Africa, 3Marine and Coastal Management, Capetown, South Africa

Biology and Distribution of the Sixgill Sawshark, Pliotrema warreni Regan 1906, off Southern Africa

The sixgill sawshark, Pliotrema warreni, is one of six described sawshark species (Pristiophoridae) and the only member of its genus. Endemic to waters off southern Africa, this species has been reported from Cape Agulhas to Durban, South Africa, and from Madagascar, at depths of 26-455 m. Seventy-four individuals (42 females, 32 males) were collected primarily from fishery independent trawl surveys conducted between 1985 and 2007, facilitating a general biological assessment of this poorly known species. The occurrence of P. warreni was extremely localized and its captured was infrequent in survey trawls. Size at birth was estimated at > 35 cm total length (TL). The largest immature female was 118.5 cm TL, whereas the largest immature male measured 82.0 cm TL. Size at first maturity ranged from 109.1 cm TL for females to 91.1 cm TL for males Median size at maturity was 113.2 cm TL for females. Maximum size of females and males was 136.4 cm TL and 112.0 cm TL, respectively. Pliotrema warreni was a third- level consumer (trophic level = 4.13), with a diet comprised primarily of small, demersal fishes and, to a lesser extent, shrimps. This species is probably extremely vulnerable to fishing pressure, because it is endemic to the waters of southern africa, rare within its distribution, and easy to capture because of its toothed rostrum. Further study and monitoring should be conducted to determine the population status of the species.

 

343 AES Ecology II, Galleria South, Sunday 26 July 2009

Mario Espinoza, Thomas Farrugia, Christopher Lowe

California State University, Long Beach, CA, United States

Spatial and Temporal Patterns of Elasmobranchs in a Newly Restored Accessible Habitat

Approximately 90% of southern California coastal wetlands have been lost as a result of filling or dredging activities. In August 2006, a new ocean inlet was created in the Bolsa Chica wetland, allowing benthic coastal predators to enter and use the full tidal basin (FTB). Since elasmobranchs have not had access to the basin in over 100 years, it provides an ideal opportunity to study how coastal benthic predators may use this newly restored accessible habitat for different activities. Monthly abundance surveys (beach seines and long-lines) were used to quantify spatial and temporal patterns of elasmobranchs inside the FTB. Eight species of sharks and rays have been identified using the FTB (2008-2009). Round stingrays (n=521), gray smooth-hounds (n=239) and bat rays (n=234) were the most abundant elasmobranchs. The highest CPUE was found in the middle FTB between June and September 2008. CPUE and relative abundance for all elasmobranchs increased with water temperature (p<0.05). However, only gray smooth-hounds and round stingrays showed a clear seasonal pattern of occupancy during warmer months. Other species like shovelnose guitarfish and bat rays were found in relatively high numbers during the winter. Habitat restoration has become a popular mitigation approach in southern California; however, studies of the effectiveness of estuarine restoration as a viable ecological approach to increase habitat for coastal elasmobranchs have been very limited. This study provides valuable ecological information about how top benthic predators use the FTB of Bolsa Chica, a newly restored accessible habitat.

 

546 AES Ecology II, Galleria South, Sunday 26 July 2009

Matthew Ajemian, Sean Powers

University of South Alabama & Dauphin Island Sea Lab, Dauphin Island, AL, United States

An Integrative Approach to Evaluating the Ecological Role of Spotted Eagle Rays (Aetobatus narinari) in Bermuda

Reported increases in the abundance of Myliobatid rays may pose problems for fisheries management because many of their prey items include exploitable shellfish species. The spotted eagle ray (Aetobatus narinari) is the most abundant inshore elasmobranch in subtropical Bermuda, but its predatory role remains unexamined in this region. We utilized a combination of acoustic monitoring, benthic sampling and gut contents analysis (via gastric lavage) to assess the impact of spotted eagle rays to Bermudian shellfish resources. Movement behaviors of adult spotted eagle rays were documented over two summers with ten autonomous wireless hydrophones (Lotek WHS 3050) distributed throughout Harrington Sound and at the mouth of Flatts Inlet. Presence/absence data of rays within Harrington Sound reveal disproportional use of subregions, and significant diel behavior. Individuals fitted with pressure sensors showed a trend of occupying deeper regions of the sound during the middle of the day, a potential thermoregulatory behavior. In particular, spotted eagle rays appear to exhibit high site-fidelity in a region of southwest Harrington Sound characterized by sandy flats and a wide variety of potential prey organisms. Gut contents from animals experiencing gastric lavage reveal the major prey of adults is the Venerid calico clam (Macrocallista maculata), while smaller individuals may prefer thinner-shelled Lucinid clams. Finally, data from two "gate-keeping" hydrophones indicated residency periods beyond several tidal cycles and up to 29 days. High site fidelity and long-term residency combined with the energetic requirements of these large rays imply that these predators may largely impact local prey dynamics.

 

575 AES Ecology II, Galleria South, Sunday 26 July 2009

Johanna Imhoff, Jason Romine, George Burgess

Florida Program for Shark Research, Florida Museum of Natural History, University of Florida, Gainesville, FL, United States

Evidence of a Winter Refuge for Juvenile Bull Sharks (Carcharhinus leucas) in the Northern Banana River, Florida, USA

The Indian River Lagoon System (IRL), Florida, USA, consisting of the Indian River, Banana River and Mosquito Lagoon, is known to be a nursery area for juvenile bull sharks (Carcharhinus leucas), but little is known about movements and habitat use within this estuary. We used passive acoustic telemetry methods to monitor the movements of juvenile bull sharks within the IRL system. Four juvenile bull sharks (98-122 cm TL) were captured in the northern Banana River within the Kennedy Space Center Restricted Area between December 2008 and March 2009. Preliminary acoustic data indicated that these animals remained within the restricted area during winter months and exhibited similar movement patterns and equal home range sizes (2.35 km2). One animal was recaptured after 84 days suggesting strong site attachment and allowing for examination of the acoustic tag insertion site. Two sharks were captured during December and all four sharks were captured at temperatures below 20 °C. Previous studies have documented that during the winter months, juvenile bull sharks were typically captured at temperatures above 20 °C and used southern IRL areas such as the Sebastian Inlet. To our knowledge, this is only the second record of the presence of healthy juvenile bull sharks within the northern IRL in December and indicates that juvenile bull sharks overwinter within this area despite potentially deadly episodic cold kill events.

 

913 AES Ecology II, Galleria South, Sunday 26 July 2009

John Froeschke

Harte Research Institute Texas A&M University-Corpus Christi, Corpus Christi, TX, United States

Habitat Selection Patterns of Sharks in Northwestern Gulf of Mexico

Dramatic declines in shark populations worldwide have occurred from overfishing and habitat loss, and designation of Essential Fish Habitat has been congressionally mandated to sustain shark populations. However, this requires detailed knowledge of habitat selection and use that is currently unknown for coastal sharks in northwestern Gulf of Mexico. This study examined habitat selection patterns of five coastal shark species using fisheries-independent gill-net monitoring data from Texas Parks and Wildlife Department (1975-2006). The goals of this study were: 1) describe shark distribution patterns in Texas Bays and 2) relate patterns to environmental and spatial ecosystem attributes. Fifteen species of sharks were collected although only 5 species: Bull, blacktip, bonnethead, Atlantic sharpnose, and finetooth sharks were common enough for analyses. The relative influence of environmental and spatial variables was examined using Boosted Regression Trees, a novel and flexible approach for characterizing fish habitat. The relative influence of environmental attributes varied among species and spatial scales. Large-scale (coast wide) patterns were linked most closely with salinity while small scale (within-bay) patterns were associated with temperature. This study provides an example of a flexible method for identifying essential habitat that can be used for inference or prediction of habitat value for rare species.

 

418 AES Ecology II, Galleria South, Sunday 26 July 2009

John Szczepanski

University of Rhode Island, Kingston, RI, United States

Feeding Habits of Skates and Rays in Delaware Bay: an Analysis of Resource Usage and Comparison to Batoids of Narragansett Bay

Feeding habits of many batoid elasmobranchs (skates and rays) have been recorded but diets, prey selection, and resource partitioning within specific populations is not fully understood. Few studies compare diets of sympatric species that potentially overlap in resource usage (most are single species assessments), diets over time, or food preferences between different regions that vary in abiotic characteristics and trophic structure. Through gut content analysis, my dissertation examines the feeding habits of these fish to understand the impact they have on each other and their prey sources. Also, understanding the resource partitioning of these organisms becomes important as external pressures increase; specifically as they become targeted more for certain fisheries (since many are declining) and global climate changes continue to alter their habitat. Specimens are collected from Delaware (approx. 8-10 species) and Narragansett Bays (2-3 spp.) to give insight into how resources are partitioned based on the level of those resources and elucidate how competition plays a part in resource usage. Finally, I intend to examine the effect that collection method has on available data to evaluate the accuracy of my study as well as other similar ones. Various diet metrics, importance indices, and multivariate analyses will be used to incorporate the data from each species and relate it to the habits of the others as well as compare the interaction with those in a distinctly different estuary. This multispecies study will examine complex feeding dynamics and contribute to data that may be used in ecosystem-based modeling and management efforts.

 

339 AES Ecology II, Galleria South, Sunday 26 July 2009

Yannis Papastamatiou1, Britanny Graham2, Dana Bethea3, John Carlson3, Enric Cortes3

1Hawaii Institute of Marine Biology, University of Hawaii at Manoa, Kaneohe, HI, United States, 2Stable Isotopes in Nature Laboratory (SINLAB), Canadian Rivers Institute, University of New Brunswick, Fredericton, NB, Canada, 3NOAA Fisheries, Panama City Laboratory, Panama City, FL, United States

Can Bonnethead Sharks Digest and Assimilate Seagrass?

The increasing volume of shark diet studies show that sharks are carnivores, although plant material has been identified in the stomachs. Presently, it is assumed that plant material is accidentally consumed while sharks forage on benthic prey and that sharks with plant material found in their stomachs are unable to digest or assimilate this material. However, the digestive capabilities of sharks and their ability to assimilate plant material may have been previously underestimated. Sharks are capable of secreting even more acidic gastric fluids than herbivorous fish and may therefore be able to lyse plant cell walls in their digestive tracts. Diet studies conducted on bonnethead sharks (Sphyrna tiburo) in three areas of the eastern US Gulf of Mexico revealed that blue crabs are the most important dietary item, but that significant amounts of seagrasses are also found in their stomachs. The contribution of seagrass varies with life stage and geographic location (between 8-60%). Although we cannot conclusively state that bonnetheads digest plant material, it appears likely based on their isotope signatures. Omnivory could have significant implcations for trophic foodwebs in which these sharks are included.

 

1020 AES Ecology II, Galleria South, Sunday 26 July 2009

Michael Heithaus1, Craig Layman1, Phillip Matich1, Bryan Delius1, Aaron Wirsing2, Meagan Dunphy-Daly1

1Florida International University, North Miami, FL, United States, 2University of Washington, Seattle, WA, United States

Stable Isotopic Analysis Reveals Individual Variation in Feeding Behavior of Juvenile Bull Sharks

Increasingly, it is being recognized that individual variation in foraging ecology is an important component of ecological dynamics. However, because of the logistical difficulties of repeated sampling of individuals and the limitations of stomach contents analysis investigations into the potential for sympatric individuals to vary in their foraging behavior or trophic position have been limited in elasmobranchs. Stable isotopes, which integrate the signature of prey species consumed over relatively long time scales are perfectly suited to such investigations. We used stable isotope ratios in juvenile bull shark (Carcharhinus leucas) tissues to investigate variation in individual trophic interactions. There was no significant variation in mean trophic niches of sharks with sex, size, season, or position within their estuarine nursery. Mean δ13C suggested that sharks are opportunistic and forage from marine and freshwater/estuarine food webs. Mean values, however, masked substantial and ecologically important individual-level variation in feeding history. A number of individuals foraged primarily from marine food webs, others specialized in freshwater/estuarine food webs, and a third group had intermediate signatures. All three foraging tactics were found throughout the estuary, suggesting that 1) juvenile bull sharks might play important roles in community and ecosystem dynamics from marine to freshwater environments, and 2) focusing on mean trophic positions of mobile predators and ignoring individual- level variation in trophic niches may underestimate ecological impacts of declines in their populations.