2011 AES Abstracts

Minneapolis

0583 AES Behavior & Ecology, Minneapolis Ballroom G, Thursday 7 July 2011

George H. Burgess1, Galal Nasser1

1Florida Program for Shark Research, Florida Museum of Natural History, University of Florida, Gainesville, FL, USA, 2Environment Department, Chamber of Diving and Watersports, Egyptian Environment Affairs Agency, South Sinai, Egypt

Sequential and Serial Shark Attacks on Humans Over an Abbreviated Period of Time and Space in Sharm el-Sheikh, Egypt: 6 Days, 5 Attacks, 2 Species - 2 Sharks?

In 2010, the tourist community of Sharm El Sheik, Egypt was shaken by the unprecedented occurrence of five severe shark attacks (one a fatality) over a six day period. All incidents took place within a stone’s throw from shore and within a nine km stretch of coastline. A pair of attacks separated by 20 min and several hundred m occurred on 30 November and on the following day another pair occurred 6 km away and less than five minutes and 20-30 m apart. The testimony of abundant credible witnesses, fortuitous photographic evidence, and examination of wound characteristics allowed identification of the attacking species as shortfin mako (Isurus oxyrinchus) and oceanic whitetip (Carcharhinus longimanus) sharks, two pelagics not normally implicated in nearshore attacks. Evidence confirms that single individuals of each species were the attackers in two pairs of incidents. Although identification of the attacker in the fifth incident couldn’t be confirmed, the wounds produced indicate the perpetrator was a carcharhinid of the same size as the twice-implicated attacking whitetip. When considered within the temporal-locational sequence, this suggests that a single whitetip could have been a partner to three attacks and that two sharks were responsible for all five. Furthermore, underwater photographers documented the movements and aggressive behavior of the attacking whitetip in the days immediately following the final attack. Biotic and abiotic factors contributing to this unique event are discussed with particular reference to elevated water temperatures, dumping of refuse by ocean-going vessels, overfishing, and attraction of marine life by feeding.

 

5 AES Behavior & Ecology, Minneapolis Ballroom G, Thursday 7 July 2011

Randy Honebrink1, Robert Buch2, Peter Galpin3, George Burgess4

1Hawaii Division of Aquatic Resources, Honolulu, HI, USA, 2NOAA Fisheries Service, NERO, Gloucester, MA, USA, 3Maui Memorial Hospital, Wailuku, HI, USA, 4University of Florida, Gainesville, FL, USA

First Documented Attack by a Cookiecutter Shark on a Human

Anecdotal reports of bites by the cookiecutter shark (Squaliodea, Dalatiidae, Isistius sp.) on people in various waters have been made, but are rare and undocumented. The International Shark Attack File database includes two incidents involving Isistius bites which were judged to have occurred postmortem. In this case, an adult long-distance swimmer attempting to cross the Alenuihaha Channel between the Hawaiian islands of  Hawai‘i and Maui was twice bitten by a cookiecutter shark (I. brasiliensis Quoy and Gaimard 1824). One of these bites presented as an open, round, concave wound typically observed in cookiecutter shark bites inflicted by members of this genus on a broad spectrum of large biota such as marine mammals, elasmobranchs, and bony fishes. The open wound was debrided, subjected to negative pressure wound therapy, and a split thickness skin graft harvested from the left thigh. Post-operative recovery was complicated by delayed healing of the inferior portion of the graft, and cultures and biopsy were normal skin flora and normal tissue, respectively. At six months following the incident, the area appeared to be healing with a stable eshcar, and by nine months the wound was healed. Humans entering pelagic waters at twilight and nighttime hours in areas of Isistius sp. occurrence should do so knowing that cookiecutter sharks are a potential danger, particularly during periods of strong moonlight, in areas of man- made illumination, or in the presence of bioluminescent organisms.

 

0723 AES Behavior & Ecology, Minneapolis Ballroom G, Thursday 7 July 2011

John Tyminski1, Robert Hueter1, Rafael de la Parra2

1Mote Marine Laboratory, Sarasota, FL, USA, 2Proyecto Domino, CONANP, Cancun, Quintana Roo, Mexico

Patterns in Diving Behavior of Whale Sharks Identified through Pop-up Satellite Archival Tagging in the Gulf of Mexico

Pop-up satellite archival transmitting (PSAT) tags were attached to 33 whale sharks (Rhincodon typus) off Mexico’s northeast Yucatan Peninsula 2003-2010, to examine these sharks’ long-term movement patterns and gain insight into the underlying factors influencing their habitat selection. Archived data were received from 26 PSATs on immature and mature sharks of both sexes (9 males, 17 females) with total lengths of 5.5- 8.5 m. Seven of these tags were physically recovered facilitating their direct download and a detailed view into the sharks’ vertical movements (range of 2-180 days). Analyses using the fast Fourier transform revealed a distinct diel pattern in diving behavior that can be explained by regular and conspicuous depth-change events often coinciding with sunrise or sunset. Whale sharks feeding primarily on fish eggs off Isla Mujeres initiated an extended period of surface swimming at sunrise that abruptly changed to a pattern of regular vertical oscillations in the mid-afternoon. When in oceanic waters, R. typus often demonstrated a pattern of repetitive epipelagic dives that were punctuated by very deep dives followed by ascents initiated almost immediately after reaching maximum depth. Analysis of these extreme dives (those exceeding 500 m; max 1,888 m) revealed a mean descent rate (36.6 m/min) that was significantly faster than the mean ascent rate (25.7 m/min). An additional 7m male whale shark tagged off the southwest Florida Gulf coast in 2010 displayed the deepest dive we have yet recorded, to 1,928 m in the northern Gulf.

 

0538 AES Behavior & Ecology, Minneapolis Ballroom G, Thursday 7 July 2011

Amy E. Carlson, James A. Sulikowski

University of New England, Biddeford, ME, USA

Vertical and Horizontal Movement Patterns of Archival Satellite Tagged Spiny Dogfish in the Northwestern Atlantic

The spiny dogfish (Squalus acanthias) stock abundance in the Northwest Atlantic Ocean has been of concern due to conflicting population trends over the last several years. To obtain a better understanding of the movement dynamics of this species, Microwave Telemetry Pop-Up Archival X-Tags have been attached to 10 adult male and 13 adult female dogfish off the coast of Portland, Maine. Eighteen of the tags have released and transmitted data. Of these 18 tags, three have been physically recovered, and 11 have been filtered and modeled. Approximate geolocations and vertical movements within the water column were derived from archival light level, pressure, and temperature records and has been filtered and fitted with bathymetric and sea surface temperature data using derivations of kftrack and ukfsst modeling packages in R and Matlab. Reconstructed tracks ranging in lengths from 2 to 12 months are helping to elucidate the seasonal migration patterns, which appear to be more regional (between the Gulf of Maine and New Jersey) and local (between the Gulf of Maine and Cape Cod) in nature. In addition, vertical movements show distinct diel patterns with recorded depths ranging from 70 to over 600 meters. Based on this preliminary data, it appears that the movement patterns of dogfish may prevent this species from being effectively captured by NEFSC otter trawl surveys.

0509 AES Behavior & Ecology, Minneapolis Ballroom G, Thursday 7 July 2011

Shara Teter1, Bradley Wetherbee2, Dewayne Fox3, Chi Lam4, Dale Kiefer4, Paul Howey5, Mahmood Shivji1

1Guy Harvey Research Institute, Nova Southeastern University, Dania Beach, FL, USA, 2University of Rhode Island, Kingston, RI, USA, 3Delaware State University, Dover, DE, USA, 4University of Southern California, Los Angeles, CA, USA, 5Microwave Telemetry, Columbia, MD, USA

Migratory Patterns and Habitat Use of Sand Tiger Sharks (Carcharias taurus) in the Northwest Atlantic

Though there is concern over declines in sand tigers (Carcharias taurus) in the Northwest Atlantic Ocean, details of their habitat use and movement patterns in the open ocean are limited. We report on the vertical and horizontal movements of sand tigers off the US east coast using archival pop-up satellite transmitters. Transmitters were deployed on 13 sand tigers (168 - 232 cm TL) in Delaware Bay in late summer 2008. Duration of tracks ranged from 12-154 days (x ̄=105), allowing reconstruction of 12 horizontal tracks using light-level data and a Kalman filter state-space model. Seven of the males exhibited directed movements south along the US east coast to waters off North Carolina, whereas all three females initially moved eastward into deeper offshore waters and remained largely in waters off New Jersey to Virginia. While in Delaware Bay, sand tigers spent the majority of their time at depths of less than 10 m and at 19-22oC. During their migration south, males occupied deeper water, primarily 20-80 m (max depth 188 m), and upon arrival in North Carolina waters in late 2008 or early 2009, some males moved into shallower water. Female sharks generally inhabited shallower water during their migrations, remaining predominantly at depths < 50 m (maximum depth 92 m). Water temperatures occupied by sharks ranged from 13-26oC, with females averaging 21-23oC and males 19-24.5oC. These initial results suggest possible differences in the movement behavior of male and female sand tigers, but need confirmation by tracking more animals of each gender.

 

0672 AES Behavior & Ecology, Minneapolis Ballroom G, Thursday 7 July 2011

Bradley Wetherbee1, Guy Harvey2, Neil Burney3, Choy Aming3, Shara Teter2, Mahmood Shivji2

1University of Rhode Island, Kingston, RI, USA, 2Guy Harvey Research Institute Nova Southeastern University, Ft. Lauderdale, FL, USA, 3Bermuda Shark Project, Bermuda, Bermuda

Are Tiger Sharks Reef Sharks or Pelagic Sharks? Movements of Tiger Sharks in the Western North Atlantic

The tiger shark (Galeocerdo cuvier) is a large, far-ranging species that exhibits a variety of movement patterns depending on location and season. These sharks are managed by NMFS as part of the “large coastal” species complex under the Atlantic Highly Migratory Species Fishery Management Plan, but are occasionally observed far at sea and caught in pelagic fisheries. To investigate movements of tiger sharks, we tagged 26 individuals in Bermuda in late summer of 2009 and 2010 with fin-mounted “spot” satellite transmitters. Although a number of sharks made fairly rapid (~2 weeks) and straight-line moves from Bermuda to the Bahamas, other sharks followed meandering paths eventually reaching the Bahamas after several months. Several smaller individuals remained in Bermuda over the winter. Some sharks spent the winter months moving within relatively small, near shore areas within the Bahamas, and subsequently moved north into pelagic waters where they remained during summer months. Other sharks left the Bahamas a short time after arrival, moving into pelagic waters during winter months. Several individuals tracked over consecutive winters (>19 months) occupied similar wintering areas within the Bahamas. North-south seasonal movements for many sharks appeared to be related to water temperature, with the majority of time spent at 24-28oC. Most sharks demonstrated the ability to seamlessly shift between pelagic and insular habitats spending approximately equal time in both environments. Although movements vary substantially among individuals, tiger sharks demonstrate high mobility trophically connecting widespread and disparate marine ecosystems in the Western North Atlantic.

0725 AES Behavior & Ecology, Minneapolis Ballroom G, Thursday 7 July 2011

Marcus Drymon1, Matthew Ajemian2, Sean Powers2

1Dauphin Island Sea Lab, Dauphin Island, AL, USA, 2University of South Alabama, Dauphin Island, AL, USA

Monitoring Movements of Bull Sharks (Carcharhinus leucas) in Coastal Alabama Using Acoustic Telemetry

Many commercially and ecologically important species have complex life histories that involve ontogenetic and behavioral movements over large marine and estuarine landscapes. The highly mobile nature of many of these species has made it historically difficult to evaluate their habitat use and seasonal distribution in these large water bodies, and thus has potentially impeded effective management measures. We sought to address these concerns for the bull shark (Carcharhinus leucas) using acoustic telemetry implemented through the Coastal Alabama Acoustic Monitoring Program (CAAMP). During 2009 and 2010, 40 bull sharks were tagged with LOTEK MM-MR-16-50 transmitters, two of which were detected during both 2009 and 2010, indicating a small degree of fidelity or homing behavior between consecutive years. Bull shark detections ranged from the mouths of barrier islands to the entrances of multiple rivers that comprise the Mobile-Tensaw delta. In particular, bull sharks utilized the Tensaw, Blakely and Apalachee rivers within this area. In addition, bull sharks were detected through Dog and Fowl rivers, though were less commonly reported in these areas compared to Mobile-Tensaw rivers. Bull sharks were also found to utilize the main passes between Dauphin Island and Fort Morgan, as well as the Katrina cut entrance to Mississippi Sound. Gillnet, longline and acoustic monitoring data also suggest that the region of Mobile Bay north of Gaillard Island (including the associated rivers) represent prime nursery habitat for bull sharks. Future acoustic monitoring of these important predators will continue to identify important habitats and how these shift with ontogeny .

0669 AES Behavior & Ecology, Minneapolis Ballroom, G, Thursday 7 July 2011

Johanna Imhoff1, Jason Romine1, George Burgess1

1Florida Museum of Natural History, University of Florida, Gainesville, FL, USA, 2Columbia River Research Laboratory, USGS, Cook, WA, USA

Use Of Passive Acoustic Telemetry To Track Juvenile Bull Sharks In The Indian River Lagoon System, FL, USA: Culmination Of A Three-Year Study

The Indian River Lagoon system (IRL), consisting of the Indian River, Banana River and Mosquito Lagoon, is an estuary on the east coast of FL, USA, connected to the Atlantic Ocean only by five inlets, spaced greater than 20 km apart. The IRL is known to be a nursery area for juvenile bull sharks (Carcharhinus leucas), but little is known about movements, habitat use and residence time within this estuary. We used passive acoustic telemetry methods to monitor the movements of juvenile bull sharks within the IRL system. Since December 2008, 26 juvenile bull sharks (61-137 cm FL) have been tagged with Vemco V13 and V16T acoustic tags, and 21 of these tagged sharks have been detected within the acoustic array. All sharks were tagged inside the IRL, but eleven sharks were also detected in inlets, and five sharks were detected on offshore receivers in the Atlantic Ocean. Preliminary reports of this dataset discussed the use of the IRL as a winter refuge for juvenile bull sharks, movements of sharks between lagoons of the IRL, and emigrations from the IRL through inlets, including sudden emigrations during the severe cold snap of January 2010. Diel activity patterns, seasonal movements and migrations, and residence times will be further investigated. Abiotic factors influencing shark movements, such as temperature, salinity and tidal flow in inlet areas will also be examined.

 

0511 AES Behavior & Ecology, Minneapolis Ballroom G, Thursday 7 July 2011

Steven Kessel1, Samuel Gruber2, Katie Gledhill2, Mark Bond3, Rupert Perkins1

1Cardiff University, Cardiff, UK, 2Bimini Biological Field Station, South Bimini, Bahamas, 3Stony Brook University, Stony Brook, NY, USA

The Use of Aerial Survey to Estimate Population Abundance for a Carcharhinid Species

Aerial survey is a technique that has been widely used to assess species population abundance for both terrestrial and marine vertebrates. For marine species, the employment of aerial survey census techniques has been mainly limited to marine mammals and reptiles, and to date for sharks has been largely limited to whale sharks (Rhincodon typus) and basking sharks (Cetorhinus maximus). The Bimini lemon shark (Negaprion brevirostris) population, with high site-attachment to a shallow sandy lagoon, provided a very good opportunity to employ the aerial census technique to produce population abundance estimates. The aims of this study were to 1) obtain population abundance estimates; 2) define the distribution of individuals and the effects of tidal variations in water depth; 3) investigate seasonal variation in abundance, and 4) assess the effectiveness of the aerial survey technique for establishing population abundance estimates. Surveys were conducted from light aircraft with sharks counted by visual census. Results were corrected for ‘availability', ‘perception' and ‘survey intensity' to produce abundance estimates. Abundance was found to be greatest in the central area of the lagoon, with a low tide shift in abundance to the east and west. Mean abundance was estimated at 50 individuals and monthly abundance was significantly correlated with mean water temperature. The aerial survey technique proved effective for establishing population abundance estimates. The successful implementation of the aerial survey technique highlighted the potential of further employment for shark population assessments in similar habitats.

0485 AES Behavior & Ecology, Minneapolis Ballroom G, Thursday 7 July 2011

Iva Peklova1, Aaron Fisk1, Nigel Hussey1, Kevin Hedges2

1Great Lake Institute of Environmental Research, University of Windsor, Windsor, ON, Canada, 2Fisheries and Oceans Canada, Winnipeg, MB, Canada

Depth and Temperature Preferences of Arctic Skate (Amblyraja hyperborea) and Greenland Halibut (Reinhardtius hippoglossoides) in a Deep Water Arctic Marine Ecosystem

Animal movement plays a key role in determining the spatial, demographic and genetic structure of populations, and ultimately underpins species management. Quantifying movements can reveal behavioral patterns that provide insight into habitat preferences and responses of animals to environmental or human-induced changes. Given concerns about climate changes and exploitation of arctic marine resources, it is critical to expand our knowledge of the movements of largely unstudied deep-water arctic fishes. To address this knowledge-gap, we employed satellite telemetry in two arctic marine species, Arctic Skate (Amblyraja hyperborea) and Greenland Halibut (Reinhardtius hippoglossoides) in Cumberland Sound, Nunavut, Canada. MiniPAT tags were attached to fish for 70, 100 and 300 days and recorded depth and temperature at 150, 300 and 600 second intervals, respectively. Data obtained between August and November 2010 (70 and 100 day deployments) showed the mean water temperature encountered was 2.1 ± 0.007 °C for skates and 2.4 ± 0.001 °C for halibut. In general, skates showed higher vertical activity levels and traversed a larger depth range (400-1400 m) than halibut (800- 1400 m). Skates moved repeatedly across the Sound between deep and shallow waters. Halibut remained in deep water pockets for the entire period and mean distance traveled between tagging and pop-off locations (11.5 ± 4.6 km) was shorter than in skate (30.1 km). Depth and temperature profiles provide evidence for overlapping habitats but also suggest differences in activity levels and behavioral patterns in these two species. These data will contribute to regional species-specific management plans.

 

0206 AES Behavior & Ecology, Minneapolis Ballroom G, Thursday 7 July 2011

Camrin Braun1, Gregory Skomal2, Michael Berumen3, Simon Thorrold2

1The College of Idaho, Caldwell, ID, USA, 2Woods Hole Oceanographic Institution, Woods Hole, MA, USA, 3King Abdullah University of Science and Technology, Thuwal, Saudi Arabia

Movements of Juvenile Whale Sharks (Rhincodon typus) in the Red Sea
The whale shark (Rhincodon typus) is widely distributed in tropical and warm temperate

waters worldwide. Although trade has been banned in many countries, unregulated 50 whale shark fisheries are still common in some areas. Potential fisheries mortality and the lack of population information led the IUCN to list them as "vulnerable." The biology of the whale shark is poorly understood; however, the species is known to form seasonal aggregations near reefs. We recently discovered a globally significant group of juvenile whale sharks on the northern end of the Farasan Banks in the eastern Red Sea. Our study describes short- and long-term movements of whale sharks from this site. In 2010, forty-seven juvenile sharks were fitted with combinations of satellite and acoustic transmitters for tracking shark location and depth. A hydrophone array was constructed near the tagging locations to monitor acoustic tag signals. Much of the shark traffic in this area was concentrated in a small portion of the reef. Large-scale movements were determined from 10 SPOT5 satellite tag deployments. One individual moved to the northern end of the Red Sea before returning to the coast north of the tagging site after travelling 2,000 km in 115 days. Five whale sharks showed similar southerly movements toward Bab el Mandeb Strait before tag detachment. A single whale shark was confirmed off the southern coast of Oman after traveling 3,000 km over a 104-day period. Our results suggest the southern Red Sea may serve as an important nursery for juvenile whale sharks.

 

0762 AES Behavior & Ecology, Minneapolis Ballroom G, Thursday 7 July 2011

Neil Hammerschlag1, Jiangang Luo2

1University of Miami, RJ Dunlap Marine Conservation Program, Miami, FL, USA, 2University of Miami, Rosenstiel School of Marine & Atmospheric Science, Miami, FL, USA

High-resolution Movements of Large Coastal Sharks Satellite-tagged in the Subtropical Atlantic

Wide spectrums of behavioral and ecological processes are innately related to movement, including migration, dispersal, predator avoidance, mating and foraging. Quantifying animal movement provides spatial and temporal information on how animals interact with-and respond to-changes in their surrounding environment. The oceans have strong spatial and regional differences in prey fields; however, an understanding of how marine predators, particularly sharks, navigate toward and respond to resources remains poorly understood. In the present study we used Smart Position and Temperature Transmitters (SPOT tags) and movement analysis to examine the habitat use patterns of large coastal sharks in the subtropical Atlantic. Sharks demonstrated a combination of direct, straight-line movements and or complex searching patterns, at varying spatial scales and resource patches. These findings are compared with general principles of foraging ecology and discussed in terms of identifying areas important to the life history of these threatened species.

 

0518 AES GRUBER AWARD, Session I, Minneapolis Ballroom G, Friday 8 July 2011

Anabela Maia1, Cheryl D. Wilga1, George V. Lauder2

1University of Rhode Island, Kingston, RI, USA, 2Harvard University, Cambridge, MA, USA

Shark Dorsal Fin Function: an Integrated Functional Morphological Approach

Dorsal fins have diverse morphologies among shark species. However, little is known about the ability of sharks to control fin movements. White-spotted bamboo sharks, Chiloscyllium plagiosum, and spiny dogfish, Squalus acanthias, are two unrelated species that occupy different niches and have distinct dorsal fin morphology. During steady swimming, the first dorsal fin of Squalus moves independently of the body with higher lateral amplitudes at lower speeds, indicating a stabilizing function. The dorsal fins in Chiloscyllium move in synchrony with the trunk with relatively higher lateral range of motion than dogfish at both speeds. Electromyography data show simultaneous muscle activity on both sides of the first dorsal fin in Squalus regardless of speed, indicating active stiffening. The second dorsal fin in Squalus and both dorsal fins in Chiloscyllium have left and right alternating muscle activity, indicating active beating. Flow acceleration and vortex shedding in the wake of the second dorsal fin of Squalus and both dorsal fins in Chiloscyllium was revealed by particle image velocimetry. The first dorsal fin in Squalus contributes to stability while the second dorsal fin, as well as both dorsal fins in Chiloscyllium, contribute to thrust production. During maneuvers, the dorsal fin muscles are active on both sides in both species. Squalus have longer burst duration on the contralateral side, consistent with opposing resistance to the medium. In Chiloscyllium, activation might be insufficient to counteract the water resistance. Function of dorsal fins is more flexible and diverse than first thought and might underlie the morphological diversity.

 

0469 AES GRUBER AWARD, Session I, Minneapolis Ballroom G, Friday 8 July 2011

Jason Ramsay, Cheryl Wilga

University of Rhode Island, Kingston, RI, USA

Function of The Jaw Depressors during Feeding in Little Skates, Leucoraja erinacea

The coracomandibularis (CM) and coracoarcualis (CA) muscles of little skates are arranged in-series, extending from the pectoral girdle to the lower jaw. Shortening of the CM and CA should result in lower jaw depression. However, the CM and CA can potentially contract isometrically or eccentrically; functioning to transfer force and motion from the coracohyomandibularis (CHYM) muscles to the lower jaw or to support the buccal cavity, respectively. Hyomandibulae, upper and lower jaw kinematics, motor activity in the CM, CA and CHYMs, and fascicle shortening in the CM and CA were recorded simultaneously with buccal pressure during prey capture and processing. During prey capture the CM and CA are active along with the left and right CHYM. However, the CM actively shortens while the CA actively lengthens as the hyomandibulae and lower jaw are being depressed. During prey processing only the CM and CA are active. The CM shortens while the CA stays the same length. Hyomandibulae depression is reduced, but lower jaw depression is similar to that of prey capture. The patterns of CM and CA activity and strain in little skate suggests that during prey capture the muscles have taken on a supportive role, stabilizing the floor of the buccal cavity similar to a skeletal hyoid. In contrast, during processing the CM actuates jaw depression, while the CA stabilizes the CM origin. Such functional plasticity of the feeding muscles may have played a key role in the increased functional versatility of the feeding apparatus of batoids compared to sharks.

0452 AES GRUBER AWARD, Session I, Minneapolis Ballroom G, Friday 8 July 2011

Jayne M. Gardiner1, Jelle Atema3, Robert E. Hueter2, Philip J. Motta1

1University of South Florida, Tamp, FL, USA, 2Mote Marine Laboratory, Sarasota, FL, USA, 3Boston University, Boston, MA, USA

Making Sense of Shark Senses: Multimodal Integration in Prey Tracking and Capture

Our understanding of elasmobranch sensory biology is largely due to studies of individual senses rather than multiple senses working together, leading to important advances in our comprehension of the sensory systems in isolation, but not their complementary and alternating roles in difficult behavioral tasks, such as feeding. We investigaed three species from different ecological niches: benthic, suction-feeding nurse sharks hunt nocturnally for fish; ram-suction feeding bonnetheads scoop crustaceans off the bottom of seagrass beds; ram-biting blacktip sharks rapidly chase down midwater piscivorous prey. We deprived animals of information from the senses (olfaction, vision, mechanoreception, and electroreception), alone and in combination, to elucidate their roles in precisely localizing, striking at, and capturing live prey (capture kinematics). Nurse sharks rely primarily on olfaction. They may orient to prey using other senses, but will not ingest food if olfaction is blocked. Bonnetheads use olfactory-based tracking until they are close to the prey, vision to line up a strike, and electroreception to time the jaw movements for capture. Blacktip sharks also use olfactory tracking, but demonstrate sensory switching at a greater distance from the prey, focusing on visual cues to strike. Both bonnethead and blacktip sharks strike visually in the absence of odor cues and can use non-visual cues to locate and capture prey, but either olfaction or vision is required for feeding. If both are blocked, feeding behaviors cease altogether, suggesting that vision or olfaction is needed to identify targets as prey, while vision, lateral line, and electroreception are used for locating them.

 

 

0394 AES GRUBER AWARD, Session I, Minneapolis Ballroom G, Friday 8 July 2011

Christopher Mull1, Kara Yopak2, Nicholas Dulvy1

1Simon Fraser University, Burnaby, BC, Canada, 2University of California San Diego, La Jolla, CA, USA

Does More Maternal Investment Lead to Larger Brains? Evolutionary Relationships Between Reproductive Mode and Brain Size in Chondrichthyans

Chondrichthyans have the most diverse array of reproductive strategies of any vertebrate group, ranging from egg-laying to live-bearing with placental matrotrophy. Matrotrophy is defined as additional maternal provisioning beyond the yolk to the developing neonate; in chondrichthyans, this occurs through a range of mechanisms including uterine milk, oophagy, uterine cannibalism, and placentotrophy. Chondrichthyans also exhibit a wide range of relative brain sizes and patterns of brain organization. Brains are energetically expensive to produce and maintain, and represent a major energetic constraint during early life in vertebrates. In mammals, more direct maternal-fetal placental connections have been associated with larger brains. We test for a relationship between reproductive mode and relative brain size across 85 species from 6 major orders of chondrichthyans using several phylogenetic comparative analyses. Maximum body size had a significant influence on relative brain size, with the largest- bodied species (body mass > 100 kg) having smaller relative brains, across all analyses. Ordinary least squares (OLS) and reduced major axis (RMA) regression of body mass versus brain mass suggest that increased maternal investment results in larger relative brain size. Our findings were supported by a regression method that incorporates the evolutionary relatedness of species. This study suggests there may be a link between reproductive investment and relative brain size in chondrichthyans, but a more definitive test requires a better resolved phylogeny and a more nuanced categorization of the level of maternal investment in chondrichthyans.

 

0273 AES GRUBER AWARD, Session I, Minneapolis Ballroom G, Friday 8 July 2011

Tricia Meredith, Stephen Kajiura

Florida Atlantic University, Boca Raton, FL, USA

Electrophysiological Evidence for Multiple Types of Amino Acid Olfactory Receptors in Elasmobranchs

Marine environments contain a vast number and variety of dissolved chemicals that may be detected by the olfactory systems of the resident organisms. In vertebrates, odorants are detected when they bind to molecular olfactory receptors (ORs) on olfactory sensory neurons (OSNs). Each OSN expresses primarily a single type of OR, each OR can detect multiple odorants, and each odorant can be detected by multiple ORs; therefore, the discrimination of odorants results from the activation of different combinations of ORs and OSNs. Cross-adaptation experiments with teleost fishes, which aim to determine whether two agonists interact with independent or overlapping OR populations, found 4-6 OR types that detect particular groups of amino acid odorants based on their side-chain structure. The olfactory system of elasmobranch fishes is highly stimulated by amino acids; however it is unknown whether they possess similar amino acid OR types as teleosts. We performed cross-adaptation experiments with two distantly related elasmobranch species, the bonnethead shark (S. tiburo) and Atlantic stingray (D. sabina) (n≥8 each), by testing their electro-olfactogram (EOG) responses to ten test amino acids delivered separately over five background regimes. Under all adapting regimes, the test EOG responses were reduced in varying degrees compared to the unadapted state. The major cross-reactivity between adapting and test stimuli occurred when they shared side-chain characteristics, whereas amino acids with distinct side-chains evoked less cross-reactivity. Our preliminary results suggest that elasmobranchs, like teleosts, possess different ORs for neutral, basic, and aromatic amino acids. Further testing may reveal additional amino acid OR types.

 

0108 AES GRUBER AWARD, Session I, Minneapolis Ballroom G, Friday 8 July 2011

Charles Bangley, Roger Rulifson

East Carolina University, Greenville, NC, USA

Variation in the Feeding Ecology of Spiny Dogfish (Squalus acanthias) Overwintering in North Carolina Waters Based on Size and Habitat

Spiny dogfish (Squalus acanthias) are highly abundant in North Carolina waters from November through March. There has been much interest in the trophic ecology of spiny dogfish due to suspected predatory and competitive interactions with species important to commercial and recreational fisheries. The stomach contents of 399 spiny dogfish were collected during trawl surveys conducted in North Carolina waters in February and March, as well as size and sex data for the sampled sharks. Data on depth, water temperature, and relative abundance of other species were also collected at each sampling station. Stomach contents were identified to the lowest possible taxa and prey species were assigned to broad prey groups by taxonomic classification. Teleost fishes made up 94% of the diet by weight in February and 61% in March. Mature sharks consumed mostly fishes while crustaceans and other invertebrate species were more important prey for smaller sharks. Immature and male sharks occupied significantly deeper and warmer habitats than adult females. The most important fish species consumed in February was Atlantic menhaden (Brevoortia tyrannus) while sharks sampled in March consumed a variety of species. Striped bass (Morone saxatilis) showed high spatial overlap with adult female dogfish and made up about 2.4% by weight of teleosts consumed in February, which may indicate competitive and predatory interactions between these two species. These results suggest that the tendency of spiny dogfish to segregate by size and sex may significantly influence their trophic interactions with other species in North Carolina waters.

 

0319 AES GRUBER AWARD, Session I, Minneapolis Ballroom G, Friday 8 July 2011

Angela Cicia1, Lela Schlenker2, James Sulikowski3, John Mandelman1

1University of New England, Biddeford, ME, USA, 2Dauphin Island Sea Lab, Dauphin Island, AL, USA, 3New England Aquarium, Boston, MA, USA

The Seasonal Blood Biochemical Status of the Little Skate, Leucoraja erinacea, Exposed to Graded Bouts of Aerial Exposure

Sustained bouts of air exposure occur during capture/handling processes, functionally inhibiting ventilation in obligate water-breathing fishes. However, few studies have investigated the direct physiological alterations it causes, particularly in elasmobranchs. In the laboratory, blood samples were obtain from little skates (Leucoraja erinacea) subjected to three air exposure durations (0, 15, 50 min) during two distinct temperature (winter and summer) regimes. Additional blood samples were collected 5 day after initial experiments to assess recovery. Results indicate acid-base status (pH, pCO2), whole-blood lactate, and K+ became progressively more disturbed the longer skates were exposed to air in both the winter and summer studies. In addition, glucose, Na+, Cl-, Ca2+ and Mg2+ were only affected by aerial exposure in the summer study. Lastly, disturbances in blood chemistry were resolved in all surviving skates after the five-day recovery periods in both temperature studies. However, mortality was also exaggerated during the summer study (winter: 18% and 37% for the 15 and 50 min group; summer: 87% and 100% for the 15 and 50 min group). Thus, a qualitative comparison revealed that the magnitude of physiological alterations and rates of mortality were more pronounced during the summer study. This infers acute thermal shock associate with rapid transfer from the seafloor to the vessel deck during commercial capture, may exacerbate the physiological impairment and mortality rate in the little skates subjected to aerial exposure.

 

0661 AES GRUBER AWARD, Session I, Minneapolis Ballroom G, Friday 8 July 2011

Jonathan Dale, Kim Holland

University of Hawaii at Manoa, Honolulu, HI, USA

Metabolic Rates and Bioenergetics of Juvenile Brown Stingrays, Dasyatis lata, in Kāne‘ohe Bay, Oahu, HI

Many species of elasmobranchs use coastal bays and estuaries as nursery habitats. Yet the ecological impacts of juveniles within these nursery habitats have received relatively little attention. Static respirometry was used to determine standard metabolic rates (MO2) for 20 juvenile brown stingrays ranging in size from 1.03 to 9.85 kg. Experiments were conducted on seasonally acclimatized rays at temperatures from 22.5 to 27.3 °C. Estimates of mass-specific MO2 ranged from 53.06 mg O2 kg-1 h-1 for a 9.85 kg individual at 23 °C to 115.99 mg O2 kg-1 h-1 for a 1.16 kg animal at 27 °C. A general linear model was used to test the effects of mass (M) and temperature on whole-animal MO2. Both mass and temperature had significant effects on MO2 (P < 0.001) and explained 98% of the variance in MO2 values. Standard metabolic rates increased with temperature at a Q10 (22-27 °C) of 1.82 and increased with mass following the allometric equation: MO2 (mg O2 h-1) = 107 x M0.78. A bioenergetics model was used to estimate daily ration for brown stingrays and to evaluate the impacts of brown stingrays on their primary prey items in Kāne‘ohe Bay.

0424 AES GRUBER AWARD, Session I, Minneapolis Ballroom G, Friday 8 July 2011

Aleksandra Maljkovic1, Sabine Wintner2, Geremy Cliff2, Isabelle Côté1

1Tropical Marine Ecology Lab, Biological Sciences, Simon Fraser University, Burnaby, BC, Canada, 2KwaZulu-Natal Sharks Board, Umhlanga, South Africa, 3Biomedical Resource Unit, University of KwaZulu-Natal, Durban, South Africa

Decadal-Scale Shifts in the Isotopic Signatures of Predatory Sharks in the Western Indian Ocean

Because the elemental signatures in the tissues of consumers predictably reflect those of their diets, stable isotope analysis has proven useful as an alternative to dietary analysis in elucidating food web architecture, as well as temporal, spatial and ontogenetic trends in species’ diets. Using a time series of vertebrae from sharks caught in the protective nets off KwaZulu-Natal, South Africa, we investigated trends in δ13C and δ15N signatures across ontogeny, and over a 20-year time period, for seven predatory shark species. While δ13C values were highly variable within species and showed only weak patterns over time, larger sized individuals of Carcharhinus limbatus, C. brevipinna, Carcharias taurus and Isurus oxyrinchus exhibited stepwise declines in δ15N, and an overall reduction in δ15N range across ontogeny, between 1985 and 2004. A single species, Sphyrna lewini, showed a stepwise increase and concomitant expansion of δ15N range over ontogeny, during the same period. No such patterns were observed in the isotope signatures of Carcharhinus leucas and Galeocerdo cuvier. Our results therefore suggest tropho-dynamic shifts in sharks that exploit a relatively narrow range of prey guilds. Food web restructuring, resulting from fisheries and/or climate change impacts, is the most likely driver of change in shark prey populations the western Indian Ocean. Our study provides a novel method by which broad-scale ecological change may be measured over time in marine ecosystems.

0043 AES GRUBER AWARD, Session I, Minneapolis Ballroom G, Friday 8 July 2011

Aaron Carlisle1, Daniel Madigan1, Kenneth Goldman2, Thomas Kline3, Barbara Block1

1Hopkins Marine Station of Stanford University, Pacific Grove, CA, USA, 2Alaska Department of Fish and Game, Division of Commercial Fisheries, Homer, AK, USA, 3Prince William Sound Science Center, Cordova, AK, USA

Reconstructing the Life of a Pelagic Shark: Investigating Ontogenetic Changes in Trophic Ecology and Habitat Use in Salmon Sharks (Lamna ditropis) Using Stable Isotope Analysis

Salmon sharks (Lamna ditropis) are wide-ranging apex predators in the North Pacific. As endothermic upper trophic level predators they likely play an important role in North Pacific marine ecosystems, yet virtually nothing is known about trophic ecology and habitat use of young salmon sharks or of possible ontogenetic shifts in diet and habitat use. We used stable isotope analysis (SIA) of salmon shark vertebrae to elucidate ontogenetic changes in habitat use and trophic ecology. The stable isotope composition of an organism is directly related to that of its prey, and isotope signatures of different food webs, which vary spatially due to differences in biogeochemical processes. Consequently, SIA data can be used to provide information on salmon shark diets and habitat use. The tissue in each annulus of a salmon shark's vertebrae provides an isotopic record that reflects movements and foraging integrated over a year of a shark's life. As a result, by serially sampling vertebral annuli for stable isotope ratios of carbon (13C/12C) and nitrogen (15N/14N) we were able to reconstruct the general dietary and migratory history of individual sharks. We used a basic isoscape of the major ecoregions of the eastern North Pacific to estimate use of different regions. Electronic tagging data was used to inform SIA results by characterizing annual patterns of ecoregion residence. Integrating electronic tag and stable isotope data provides a unique and powerful way to study the ecology and life history of these important and difficult to study predators.

 

0033 AES GRUBER AWARD, Session I, Minneapolis Ballroom G, Friday 8 July 2011

David Shiffman1, Bryan Frazier2, John Kucklick3, Tracey Sutton4, Kristene Parsons4, Gorka Sancho1

1College of Charleston, Charleston, SC, USA, 2South Carolina Department of Natural Resources, Charleston, SC, USA, 3National Institute of Standards and Technology, Charleston, SC, USA, 4Virginia Institute of Marine Sciences, Gloucester Point, VA, USA

Detection of an Ontogenetic Shift in the Diet of the Sandbar Shark (Carcharhinus plumbeus, Nardo 1827) Using Minimally Invasive d13C and d15N Stable Isotope Analysis.

The sandbar shark, Carcharhinus plumbeus, is a common and economically important species in the western North Atlantic. Additional diet and trophic level information would facilitate the creation of an ecosystem-based management plan. Diet analyses using stomach contents in other regions have revealed an ontogenetic shift in the diet of sandbar sharks in two different areas, but whether this shift takes place throughout their range is unknown. ∆13C and ∆15N stable isotope analysis is a minimally invasive and non-lethal method for determining diet and trophic level. Significant differences in ∆13C signatures were found between young-of-year and juveniles, suggesting that South Carolina sandbar sharks have a similar ontogenetic shift as sandbar sharks in other regions. Differences in total occupied niche area and ∆15N range indicated that young-of- year sharks have more diverse diets than juveniles. Data from suspected prey species is also described.

 

0167 AES GRUBER AWARD, Session I, Minneapolis Ballroom G, Friday 8 July 2011

Sora Kim1, Tim Tinker3, James Estes3, Paul Koch2

1University of Wyoming, Laramie, WY, USA, 2University of California, Santa Cruz, Santa Cruz, CA, USA, 3U.S. Geological Survey, Western Ecological Research Center, Long Marine Laboratory, Santa Cruz, CA, USA, 4Center for Ocean Health, Long Marine Laboratory, University of California, Santa Cruz, Santa Cruz, CA, USA

Dietary Specialization Among White Sharks in the Northeast Pacific

White sharks (Carcharodon carcharias) are top-level predators. Stomach contents, tooth morphology and coastal observations suggest that white sharks typically feed on pinnipeds off the California coast. However, the complete breadth of white shark diet is unknown. We focus on white shark diet using a stable isotope analysis. Stable isotope ratios of carbon (13C/12C) and nitrogen (15N/14N) elucidate feeding patterns in birds, mammals, teleosts, and are gaining use in shark ecology. First, we established vertebrae- to-diet trophic discrimination factors for leopard sharks during a controlled experiment. We then applied this information to interpret data from 15 white sharks caught off the California coast from 1936 to 2003. White shark vertebrae record diet in accreted growth bands. The δ13C and δ15N values of collagen extracted from these bands allow us to track a shark’s lifetime diet. Our results illustrate that the California white shark population has a generalized feeding structure with variable δ13C and δ15N values rather than an exclusive focus on pinnipeds. Furthermore, many individuals undergo an ontogenetic dietary shift, but the extent of this trophic switch varies among individuals. Additionally, isotopic patterns reveal individual specialists and generalists within the California white shark population. These dietary patterns persist even as pinniped populations increased after the passage of the Marine Mammal Protection Act in 1972.

 

0717 AES Physiology & Genetics, Minneapolis Ballroom G, Friday 8 July 2011

Cathy Walsh, Carl Luer, Stephanie Leggett, Theresa Cantu, Jodi Miedema, Jennifer Yordy

Mote Marine Laboratory, Sarasota, FL, USA

Shark Immune Cell-derived Factors Induce Apoptosis (Programmed Cell Death) in T-cell Leukemia Cells

Research in our laboratory has demonstrated that protein factors secreted into the surrounding medium by short-term cultures of shark epigonal cells (epigonal conditioned medium, ECM) will kill human tumor cells in vitro by inducing apoptosis (programmed cell death). Studies presented here were designed to contribute to our understanding of the molecular mechanism through which ECM destroys tumor cells. Using a T-cell leukemia cell line (Jurkat) as the target cells, key enzymes in the apoptotic pathway are activated in Jurkat cells treated with ECM for 24 h compared with untreated control Jurkat cells. Both an initiator caspase (caspase-9) and an effector caspase (caspase- 3) are converted from precursor forms to active enzyme forms as visualized using Western blots. These conversions are accompanied by several-fold increases in enzymatic activity for both caspase-9 and caspase-3. Enzymatic activity of another initiator caspase (caspase-8) is also increased in ECM treated Jurkat cells. In addition, Western blots confirmed that lysates of ECM treated Jurkat cells contain fragments of PARP (poly ADP-ribose polymerase), a nuclear enzyme responsible for DNA repair. Inactivation of PARP by caspase-3 cleavage in a specific domain of the enzyme allows DNA damage to go unrepaired and apoptosis to proceed. Molecular sizes of PARP fragments are consistent with caspase-3 cleavage and further support induction of apoptosis in Jurkat cells by ECM.

 

0371 AES Physiology & Genetics, Minneapolis Ballroom G, Friday 8 July 2011

Christina J. Walker1, James J. Gelsleichter1, J. Marcus Drymon2

1University of North Florida, Jacksonville, FL, USA, 2Dauphin Island Sea Lab, Dauphin Island, AL, USA

Assessing the Impacts of the Deepwater Horizon Oil Spill on Sharks Caught off the Coast of Alabama

The Deepwater Horizon oil spill (DHOS) is considered to be the largest offshore oil spill in U.S. history and the resulting contamination of the Gulf of Mexico (GOM) has posed health threats to many pelagic species that live in these waters. Studies on wildlife following past oil spills (i.e., Exxon Valdez oil spill) have provided evidence of population-level effects in some species following exposure to the toxic constituents, including polycyclic aromatic hydrocarbons (PAHs), of oil. However, these assessments are often difficult to perform based on the lack of baseline data on oil exposure in wildlife. Therefore, in response to the DHOS, this study will employ a biomarker approach in order to compare levels of PAH exposure in fifteen species of elasmobranchs caught both before and after the GOM oil spill from various locations off the coast of Alabama. Cytochrome P4501A1 (CYP1A1) activity, a reliable biomarker for PAH exposure, will be measured in the livers of these sharks (n≈700). It is expected that baseline levels of PAH exposure (CYP1A1 activity) in sharks collected prior to the oil spill, or prior to coming in contact with oil, will be lower than sharks collected near areas contaminated with oil from the spill.

 

0274 AES Physiology & Genetics, Minneapolis Ballroom G, Friday 8 July 2011

Jeff Kneebone1, John Chisholm2, Greg Skomal2, Diego Bernal1

1University of Massachusetts Dartmouth, School for Marine Science and Technology, Fairhaven, MA, USA, 2Massachusetts Division of Marine Fisheries, New Bedford, MA, USA

The Physiological Effects of Capture Stress, Recovery, and Post-release Survivorship of Juvenile Sand Tigers (Carcharias taurus) Caught on Rod and Reel

Current state and federal fishery regulations prohibit the retention of sand tigers in U.S. waters, effectively mandating that all sand tigers captured incidental to commercial and recreational fisheries be released immediately upon capture. Despite these protective regulations, it is unclear how these sharks are affected by the stress of capture and if they die as a result of angling stress. To quantify the physiological effects of capture stress on sand tigers, blood samples were drawn from 75 sharks immediately following capture on standard recreational rod and reel fishing gear. For each capture event, angling time, hook location, time out of water, and release condition were noted. Blood samples were analyzed to evaluate changes in blood acid base chemistry and plasma metabolites and electrolytes in response to the duration of the stress event. To examine post-release survivorship, 38 of the 75 sharks were tagged internally with acoustic tags and monitored using a fixed passive acoustic receiver array within the sampling area. In addition, baseline (i.e. unstressed) physiological conditions and post-release recovery were assessed by repeated blood sampling of captive sand tigers subjected to a simulated rod and reel capture event. Collectively, the results of our study suggest that though sand tiger blood biochemistry is markedly affected by the stress of rod and reel capture, sharks recover from angling stress within 24 hours and demonstrate high post- release survivorship.

0344 AES Physiology & Genetics, Minneapolis Ballroom G, Friday 8 July 2011

Lara Ferry1, Peter Reiser2

1Arizona State University, Glendale, AZ, USA, 2Ohio State University, Columbus, OH, USA

Masticatory Myosin Expression in Jaw Adductor Muscles of the Chimaeroids

Holocephalans were probably the dominant hard prey specialists of the late Paleozoic, and are uniquely derived in this aspect. The upper jaw is fused to the neurocranium. Further, all chimaeriform holocephalans possess(ed) tooth plates thought to have evolved specifically in response to the durophagous habit. However, bite force estimates from computational models of Callorhynchus callorhinchus and Hydrolagus collei cast doubt on the force producing abilities of these species. This prompted the study of the myosin isoforms in Callorhynchus and Hydrolagus jaw adductor muscle, along with other elasmobranchs and teleosts for comparison. SDS-PAGE and immunoblotting with an anti-masticatory myosin heavy chain (MHC) antibody (anti-MHC-M) were used to probe homogenates of jaw adductor muscles, as well as epaxial muscle and pectoral fin muscle as controls. Jaw adductors of Callorhynchus and Hydrolagus have an abundant MHC isoform (masticatory myosin) that is not present in the epaxial muscle or pectoral fin muscle, plus two other much less abundant MHC isoforms. Anti-MHC-M reacted strongly with jaw-adductor samples but did not react with epaxial or pectoral fin muscles. Consistent with other vertebrate species that express MHC-M, the myosin light chain isoforms (MLC) in the jaw adductor muscles also appear to differ from those in epaxial and pectoral fin muscles in the chimaeras. We conclude that jaw-closing muscles of Callorhynchus and Hydrolagus express masticatory myosin, which, in other vertebrate species, is associated with high force generation. Interestingly, these isoforms were present in the elasmobranch species included here, but were completely absent from any of the teleosts studied.

 

0096 AES Physiology & Genetics, Minneapolis Ballroom G, Friday 8 July 2011

Mikki McComb-Kobza1, Tamara Frank1, Robert Hueter3, Stephen Kajiura2

1Harbor Branch Oceanographic Institute at Florida Atlantic University, Fort Pierce, FL, USA, 2Florida Atlantic University, Boca Raton, FL, USA, 3Mote Marine Laboratory, Sarasota, FL, USA

Temporal Resolution and Spectral Sensitivity of the Visual System of Three Coastal Shark Species From Different Light Environments

Elasmobranchs have radiated into nearly every aquatic habitat on earth including the deep benthos, brightly lit coral reefs and even the murky freshwaters of the Amazon. As such, they experience tremendous variability in ambient lighting conditions which have resulted in remarkable adaptations within the visual system. Therefore, elasmobranchs represent an excellent group with which to compare and contrast visual function. Elasmobranch eyes rival higher vertebrates in function and complexity and aspects of the visual system are correlated with environmental factors. In this study, the visual temporal resolution (eye speed) and scotopic spectral sensitivity of three coastal shark species (bonnethead Sphyrna tiburo, scalloped Sphyrna lewini, and blacknose shark Carcharhinus acronotus) were investigated by electroretinogram. Temporal resolution was quantified under photopic and scotopic conditions using response waveform dynamics and maximum critical flicker-fusion frequency (CFF). Photopic CFFmax was significantly higher than scotopic CFFmax in all species. The bonnethead had the shortest photoreceptor response latency time (23.5 ms) and the highest CFFmax (31 Hz), suggesting that its eyes are adapted for a bright photic environment. In contrast, the blacknose had the longest response latency time (34.8 ms) and lowest CFFmax (16 Hz), indicating its eyes are adapted for a dimmer environment or nocturnal lifestyle.

Scotopic spectral sensitivity revealed maximum peaks (480 nm) in the bonnethead and blacknose sharks that correlated with environmental spectra measured during twilight, which is a biologically relevant period of heightened predation.

 

0491 AES Physiology & Genetics, Minneapolis Ballroom G, Friday 8 July 2011

Jim Gelsleichter, Jessie Livingston, Vito D'Angelo

University of North Florida, Jacksonville, FL, USA

Relaxin While Reproducin' II: Characterization of Relaxin Receptor-like Activity in Male Elasmobranchs

Relaxin is a 6-kd polypeptide hormone that is responsible for regulating several reproductive processes in female vertebrates, but its role in male reproduction remains unclear. Prior research on male bonnethead sharks Sphyrna tiburo has demonstrated that serum relaxin concentrations increase in this species during late spermatogenesis and the mating period, suggesting a role for relaxin in regulating processes such as spermiation, sperm transit through the male reproductive tract, and/or copulation. In this study, immunocytochemistry was used to detect relaxin receptor-like immunoreactivity in the reproductive tract of the male S. tiburo and a variety of other species including the Atlantic stingray Dasyatis sabina and the blacknose shark Carcharhinus acronotus. The results of the study suggest that relaxin receptor-like activity is primarily localized in late stage and evacuated spermatocysts in the testis of male elasmobranchs, strongly supporting a role for this hormone in regulating some aspect of spermiation and perhaps testicular remodeling. Possible relationships between relaxin and cellular actions that would mediate sperm release and spermatocyst turnover, such as increased production of extracellular matrix-degrading enzymes, will be discussed. In addition, evidence of relaxin receptor-like immunoreactivity in other components of the testis, the gonaducts, and in the stingray epigonal organ is presented.

 

 

 

0466 AES Physiology & Genetics, Minneapolis Ballroom G, Friday 8 July 2011

Marianne Porter1, Candido Diaz1, Adam Summers2, John Long1

1Vassar College, Poughkeepsie, NY, USA, 2Friday Harbor Labs, University of Washington, Friday Harbor, WA, USA

Squalus acanthias Swims Using its Vertebral Column as a Spring

In bony fishes, dynamically bending vertebral columns operate as springs, storing and returning elastic energy, which is hypothesized to be stored mainly in the pressurized intervertebral joints. Also, we assume joints undergo more strain than the stiffer, mineralized vertebrae. The underlying assumption that vertebrae are stiffer than joints has been challenged in cartilaginous fishes. We demonstrated that both joints and centra strain during bending in ex vivo segments of Squalus acanthias vertebral column. To determine if significant centra strain occurs in life, we measured in vivo vertebral column strains in five S. acanthias during a variety of behaviors. As predicted, both centra and joints strained during volitional and manual dynamic bending, with the greatest strains (6% strain in the centrum and 10% strain in the segment) occurring during turning. Centrum strain was similar during volitional swimming and manual undulation (3% strain), but strain was greater in the vertebral segment during manual undulation (5% strain). Thus, it appears that the entire vertebral column of sharks, both joints and centra, is mechanically engaged as a dynamic spring during locomotion. NSF IOS-0922605 supported this work.

            0478 AES Physiology & Genetics, Minneapolis Ballroom G, Friday 8 July 2011

Jeffrey Gersch1, Harold Pratt2, Theo Pratt2, Jeffrey Carrier3, Edward Heist1

1 Southern Illinois University Carbondale, Carbondale, IL, USA, 2Mote Marine Laboratory, Summerland Key, FL, USA, 3Albion College, Albion, MI, USA

Microsatellite and Mitochondrial DNA Analyses of Genetic Structure in the Nurse Shark, Ginglymostoma cirratum, from the Western Atlantic Ocean

The nurse shark, Ginglymostoma cirratum, is a large but relatively sedentary shark found in the littoral tropical and subtropical Atlantic and Pacific coast of the Americas. This species has a small home range compared to other shark species of only a few hundred square kilometers making it possible for genetic structure to be developed across relatively small geographic distances. We tested for genetic structure using genotypes from 10 DNA microsatellite loci in populations from the Bahamas (n=32), Belize (n=30), and the Florida Keys (n=91) and found a small and non-significant amount of genetic structuring among populations (FST = 0.0017, p = 0. 068). We sequenced the entire 1048 base pair mitochondrial DNA (mtDNA) control region in 44 nurse sharks and found a 1048 base pair segment with only three variable sites and four haplotypes, three of them rare (nucleotide diversity = 0.000087). Thus the nurse shark has one of the lowest, if not the lowest, mtDNA diversity in any shark species reported to date. The low levels of mtDNA variation were insufficient for a powerful test of genetic structure. Based on these data we are unable to confidently reject the hypothesis that there is sufficient gene flow throughout the sampled region to homogenize genetic polymorphisms.

 

0643 AES Physiology & Genetics, Minneapolis Ballroom G, Friday 8 July 2011

Marloes Poortvliet1, Jeanine Olsen1, Donald Croll1, Giacomo Bernardi1

1University of Groningen, Groningen, The Netherlands, 2University of California Santa Cruz, Santa Cruz, CA, USA

Population Genetics of the Spinetail Devil Ray (Mobula japanica) in the Pacific Ocean

Rays of in the genus Mobula (Mobulidae), like other elasmobranchs of the open ocean, are subject to high mortality from bycatch and targeted fisheries. In light of the extremely low fecundity and type of life history of these species, it is clear that continued high levels of (by)catch will be detrimental. However, development of a realistic management program is difficult given the paucity of data on mobulids. Population genetic data can provide important information for their conservation by helping to define conservation units on the basis of genetic populations. Here we focus on Mobula japanica, a circum-tropical pelagic species, which is one of the more common rays in the Pacific Ocean. Using twelve variable microsatellite loci and two mitochondrial genes (CO1 and ND5) we surveyed genetic structure across the Pacific Ocean. Samples were collected from six locations spanning the Pacific Ocean basin. Conventional FST analyses revealed no significant population structure for either mitochondrial or microsatellite data. The apparent absence of population structure in Mobula japanica provides a compelling argument for development of broad international approaches for management and conservation of this charismatic species.

0427 AES GRUBER AWARD, Session II, Minneapolis Ballroom G, Saturday 9 July 2011

David Kacev1, Rebecca Lewison1, Andrew Bohonak1, Daniel Cartamil3, Russ Vetter2, John Hyde2

1San Diego State University, San Diego, CA, USA, 2Southwest Fisheries Science Center, La Jolla, CA, USA, 3Scripps Institution of Oceanography, La Jolla, CA, USA

Characterizing Genetic Diversity of Two Species of Pelagic Shark

Both shortfin mako (Isurus oxyrinchus) and common thresher (Alopias vulpinus) are abundant worldwide and are highly exploited in temperate coastal seas of the north and south Pacific Ocean. These shark species experience high fishing pressure throughout the Pacific Ocean from commercial and recreational fisheries. Despite their economic and ecological importance, very little is known about their regional population structure. Satellite telemetry and conventional tagging studies indicate some regional partitioning of populations, which would make regional management prudent. The generally low level of genetic variation in elasmobranchs and mako and thresher species in particular has hampered a full understanding of the genetic structure underlying observed movement patterns. In this study, we present initial results for 15 new microsatellite markers per species for both mako and thresher. We describe genetic diversity for both species in terms of allelic diversity and heterozygosity across these loci. We then compare our findings to previous studies that used mtDNA to look at diversity in these two species from the same region. In addition, we look at the population structure of makos from various locations in the Pacific Ocean using these new microsatellite markers and compare to the results found in previous mtDNA analyses. We test to see if tropical seas serve as a barrier to gene flow for this species as suggested by previous mtDNA studies. Similarly, we look at whether these new markers support population structure between the eastern and western portion of the South Pacific, which was previously suggested by mitochondrial studies.

 

0670 AES GRUBER AWARD, Session II, Minneapolis Ballroom G, Saturday 9 July 2011

Jimiane Ashe1, Kevin Feldheim3, Samuel Gruber2, Demian Chapman1

1Stony Brook University, Stony Brook, NY, USA, 2University of Miami, Bimini Biological Field Station, Miami, FL, USA, 3Field Museum of Chicago, Chicago, IL, USA, 4Bimini Biological Field Station, Bimini, Bahamas

Testing Predictions of the "Natal Homing Hypothesis" for Sharks, Using Lemon Sharks (Negaprion brevirostris) in the Western Atlantic as a Model Species

Some animals return to their birthplace to breed even though individuals from different breeding populations are mixed at most other times ("natal homing"). It has been hypothesized that natal homing by females is common in coastal sharks, which may explain why localized shark fisheries often collapse. This hypothesis predicts that juvenile sharks in their natal nursery area should be genetically distinct from other such groups, while older life-stages collected over the same range are mixed. We tested these predictions in lemon sharks (Negaprion brevirostris) of the Western Atlantic. The natal homing hypothesis predicts that (a) continuously distributed populations of lemon sharks are genetically structured and (b) newborn/small juveniles sampled in their natal nurseries should be more structured than subadult/adult individuals sampled from proximate locations. We sequenced 1,648 bp of the mitochondrial genome and analyzed 8 microsatellite loci in 480 specimens from 12 locations from central Florida to Brazil. Although microsatellite markers were not structured, possibly due to male-mediated dispersal, mitochondrial sequences were highly structured into at least four distinct geographic groups (global ΦST=0.35, p<0.000001). In Florida and the western Bahamas we found that nursery collections separated by as little as 300 km were genetically distinct (ΦST=0.165, p<0.0000001), whereas subadult/adult collections were more homogeneous across a similar range (ΦST=0.001, not significant). These data support the predictions of the natal homing hypothesis for lemon sharks and have implications for coastal shark conservation and fisheries management.

 

0271 AES GRUBER AWARD, Session II, Minneapolis Ballroom G, Saturday 9 July 2011

Chris L. Chabot

The University of California, Los Angeles, Los Angeles, CA, USA

The Resurrection of Galeorhinus zyopterus in the Northeastern Pacific and its Global Congenerics Based on Genetic, Life-history, and Morphological Evidence

The soupfin shark, Galeorhinus galeus, is a commercially important member of the Triakidae that has suffered a long history of global exploitation resulting in historic population collapses. In order to effectively manage and conserve populations of G. galeus, it is important to determine the levels of connectivity among globally distributed populations and assess the taxonomic status of the species. Thirteen polymorphic microsatellite loci were used to determine the population connectivity of geographically isolated populations of G. galeus from Africa, Australia, North America, South America, and the United Kingdom. Genetic analyses revealed significant structure among all populations indicating a lack of gene flow and evidence of a genetic bottleneck in the northeastern Pacific. These findings indicate that globally distributed populations of G. galeus are isolated and should be managed as distinct, independent stocks. Furthermore, the observation of private microsatellite alleles, unique region-specific mitochondrial haplotypes, and regional differences in morphology and life-history suggest that a resurrection of Galeorhinus zyopterus in the northeastern Pacific as well as the resurrection of its global congenerics may be warranted.

 

0087 AES GRUBER AWARD, Session II, Minneapolis Ballroom G, Saturday 9 July 2011

James Knuckey1, David Ebert1, George Burgess2

1Moss Landing Marine Laboratories, Moss Landing, CA, USA, 2University of Florida, Gainesville, FL, USA

Etmopterus sp. nov., a New Species of Lanternshark (Squaliformes: Etmopteridae) From Taiwan

A new species of lanternshark, Etmopterus sp. nov., is described from the deep waters off north eastern Taiwan. The new species is similar to other species of the "Etmopterus pusillus group" in having concave, flattened dermal denticles that are scattered irregularly across the body, a lateral line that ends in an open groove, no posterior branches on the flank photo-markings and a relatively cylindrical body, but can be separated from its congeners based on the following characteristics: gill slit height, tooth morphology, fin size and shape, interdorsal space and flank photo-markings. The new species has a shorter preoral length and the gill slit height does not vary much compared to other members of the "Etmopterus pusillus group." The teeth in the lower jaw of Etmopterus sp. nov are slender, with relatively oblique cusps compared to those of its congeners. The pectoral fins of Etmopterus sp. nov are more squared posteriorly and the caudal fin is shorter than the other members of the "Etmopterus pusillus group." The pectoral axil to first dorsal fin origin measurement of Etmopterus sp. nov fits into the interdorsal space about three times. The new species possesses flank photo-markings which are distinctive when compared to its congeners.

 

0748 AES GRUBER AWARD, Session II, Minneapolis Ballroom G, Saturday 9 July 2011

Austin Gallagher1, Neil Hammerschlag1

1University of Miami, Abess Center for Ecosystem Science and Policy, Miami, FL, USA, 2University of Miami, Rosenstiel School of Marine and Atmospheric Science, Miami, FL, USA

Stressed-out: Species-Specific Responses to Angling Pressure Among Various Coastal Sharks

The sustainability of catch-and-release fishing relies upon the major assumption that all caught individuals will survive and recover when released. While there have been a wide range of studies covering this issue in various game fishes, similar studies on elasmobranchs-particularly threatened species of shark-are lacking. We employed two quantitative methods to provide insights into the physiological and metabolic stress responses of various shark species subjected to fishing pressure in the Florida Keys and Bahamas. Results from both blood-acid base analyses and nictitating membrane reflex impairment provided a relative species-specific framework of sensitivities and tolerances to angling pressure. Great hammerhead (Sphyrna mokarran) and blacktip (Carcharhinus limbatus) sharks represented the most physiological sensitive species across fight regimes and season. Accordingly, we discuss potential recommendations for the recreational angling community, and discuss the need to focus specific conservation approaches on species may be at a higher risk of post-release mortality.

 

0260 AES GRUBER AWARD, Session II, Minneapolis Ballroom G, Saturday 9 July 2011

Megan Winton1, Enric Cortés2, David Ebert1, Gregor Cailliet1

1Moss Landing Marine Laboratories, Moss Landing, CA, USA, 2NOAA Southeast Fisheries Science Center, Panama City, FL, USA

Comparative Demography of Two Populations of the Roughtail Skate, Bathyraja trachura (Gilbert, 1892), in the Eastern North Pacific

The roughtail skate, Bathyraja trachura, is among the longest-lived, latest maturing, and slowest growing skate species reported to date. Results of life history studies may indicate a latitudinal pattern in size and growth of the species, with individuals from the eastern Bering Sea (EBS) growing more slowly and reaching higher maximum ages than previously reported for the species off the United States west coast from the California Current ecosystem (CC). Age-structured demographic models were constructed based on empirical estimates of longevity and maturity from both ecosystems to investigate how observed differences in life history parameters affect population growth rates, to identify portions of the population most important from a management perspective, and to estimate the species’ relative vulnerability to exploitation. Monte Carlo simulations were used to incorporate uncertainty in vital rates and generate mean estimates of demographic parameters and elasticities for each scenario. Mean annual population growth rates were higher for B. trachura from the CC (λ = 1.184 yr-1) than from the EBS (λ = 1.003 - 1.072 yr-1), with corresponding population doubling times ranging from 7.3 to 38.9 years. Elasticity analyses indicated that population growth rates of B. trachura are more influenced by juvenile and adult survival than either egg case survival or fecundity. The results of this study suggest that B. trachura is relatively unproductive with a limited harvest potential compared to other elasmobranchs.

 

0627 AES GRUBER AWARD, Session II, Minneapolis Ballroom G, Saturday 9 July 2011

Jennifer McKinney, Eric Hoffmayer, Wei Wu, Richard Fulford

University of Southern Mississippi, Ocean Springs, MS, USA

Predicting Suitable Habitat for Whale Shark, Rhincodon typus, Aggregations in the Northern Gulf of Mexico

Whale shark, Rhincodon typus, aggregations have been documented in large numbers in the northern Gulf of Mexico since 2003 through the Gulf Coast Research Laboratory Whale Shark Sighting Survey. Species distribution modeling provides a unique approach to analyzing this presence data. Due to their protected status, understanding critical habitat for whale sharks is essential on a regional basis for proper management. The goal of this study was to describe the probable distribution of whale shark aggregations in the northern Gulf of Mexico using Maximum Entropy (MaxEnt) and Ecological-Niche-Factor-Analysis (ENFA), two algorithms designed for predicting species distribution. Models were developed using sightings locations with feeding animals (>2 individuals) for the temporal period of June through September of 2008 and 2009 with the following predictor variables: bathymetric slope, distance from physical features and remotely sensed sea surface temperature, chlorophyll concentrations and sea surface height anomalies. Cohen's kappa and the area under the receiver operating characteristic curve (AUC) were used to evaluate model performance with an external testing dataset. Kappa values ranged from 0.28 - 0.69 and AUC values ranged from 0.73 - 0.80, indicating that the predicted distribution had a fair to substantial agreement with the testing data. Distance to continental shelf edge, petroleum platforms and chlorophyll were the predominant contributors to model output, likely due to an associations with high food availability. The spatial distribution of suitable habitat is dynamic; therefore, a long-term study is recommended to delineate trends in distribution and consistent areas of high suitability.

 

0588 AES GRUBER AWARD, Session II, Minneapolis Ballroom G, Saturday 9 July 2011

Karen Dove

Duke University, Beaufort, NC, USA

The Presence of Great White Sharks: Associations with Environmental Factors

The great white shark (Carcharodon carcharias) can be regarded as one of the greatest ambush predators on Earth. White sharks have learned the best techniques, places, and times to hunt to maximize their success. This paper looks at the frequency of white shark sightings compared to wind speeds in Mossel Bay, South Africa. The hypothesis is that more sharks will be on the prowl during high wind speeds because this affects water visibility and swell height. Ambush predators like the white shark benefit from poor water visibility and large swells which put their prey at a visual disadvantage. Stronger winds also blow seal excreta farther out to sea which attracts young roving sharks in the area. Sharks in Mossel Bay must rely on water visibility more than water depth to conceal their presence because it is relatively shallow thus making wind speed especially important here.

 

0724 AES GRUBER AWARD, Session II, Minneapolis Ballroom G, Saturday 9 July 2011

Andrea Kroetz, Sean Powers

University of South Alabama, Dauphin Island Sea Lab, Dauphin Island, AL, USA

Ecology of Bonnetheads (Sphyrna tiburo) in the Northern Gulf of Mexico

Several marine fish species have life histories that include ontogenetic movements across estuarine habitats. For species that occupy dynamic coastal environments, such as bonnetheads (Sphyrna tiburo), a wide range of habitats may be encountered and occupied over a relatively small scale. Proper management of these species must be preceded with specific knowledge of habitat usage throughout their ontogeny. We used a combination of gillnet surveys, acoustic telemetry and gut content analysis to better understand the ecology of bonnetheads in the northern Gulf of Mexico. Our data show that bonnetheads demonstrate seasonality in their distribution only being present in the months of May-November in the coastal waters of Alabama. Bonnetheads demonstrate some degree of site fidelity to the saline waters around barrier islands, particularly to a small area around the West end of Dauphin Island, AL where the capture success rate is the highest for this species. Our data show that blue crabs (Callinectes sapidus) and other crustaceans make up the majority of the diet. Stomach content analyses were used to correlate bonnethead distribution to prey availability. Our data show that blue crabs frequently occur around the West end of Dauphin Island in the months of July- September which coincides with the highest detection rate of tagged sharks in that area. Understanding aspects of this species' ecology is important for the implementation of proper management, not only for this small coastal shark, but also for commercially important blue crabs.

                                                     

0536 AES GRUBER AWARD, Session II, Minneapolis Ballroom G, Saturday 9 July 2011

Corey Eddy1, Diego Bernal1, Greg Skomal2, Lisa Natanson3, Nancy Kohler3

1University of Massachusetts, Dartmouth, MA, USA, 2Massachusetts Division of Marine Fisheries, New Bedford, MA, USA, 3National Marine Fisheries Service, Narragansett, RI, USA

The Life History and Feeding Ecology of the Galapagos shark (Carcharhinus galapagensis) in the Waters off Bermuda.

The Galapagos shark (Carcharhinus galapagensis) is distributed worldwide in warm, temperate waters and is known to prefer oceanic islands. As such, it is the most common species in Bermuda, where commercial fishermen land approximately 200 sharks each year, primarily for their liver oil or as bait in lobster traps. The International Union for the Conservation of Nature has classified this species as "Near Threatened" because intense fishing pressure, a limited rebound potential, and evidence of local extinctions have cast doubt upon the survival of this species. Despite its ubiquitous presence, Bermuda's Department of Environmental Protection has only limited regulations in place to manage this species and the risk of local extinction due to severe overfishing is a real possibility. To help develop a management plan, this study was begun to investigate the life history and ecological role of these sharks. Size-at-maturity was investigated by examining the reproductive system of sharks collected from landings of commercial fishermen. Size-at-age and age-at-maturity estimates were derived from band pairs in the vertebral centra of these sharks. Elements of feeding ecology, such as trophic position and diet shifts, were investigated via stable isotope analysis of muscle, liver, and vertebrae. Stomach contents were analyzed to reinforce these results. Preliminary results suggest the largest shark sampled was only four years old, a few years short of reaching maturity, which is thought to occur at approximately seven years of age, at 200 to 250 cm fork length. This finding reinforces the need to effectively manage this fishery.

 

0035 AES GRUBER AWARD, Session II, Minneapolis Ballroom G, Saturday 9 July 2011

Kelsey James, David Ebert, Gregor Cailliet

Pacific Shark Research Center, Moss Landing Marine Laboratories, Moss Landing, CA, USA

Life History Characteristics of the Starry Skate, Raja stellulata, from the Eastern North Pacific.

Coastal skate species worldwide are subject to targeted and incidental fishing pressures. This has raised concerns since available data on elasombranchs are generally limited. Research of life history characteristics is essential for estimating population size, age structure, and fecundity, which in turn can be applied toward effective fisheries and conservation management plans. This is the first study to examine the distribution and life history characteristics of the Starry Skate, Raja stellulata. Specimens were collected from 2002 to 2010 during trawl and longline surveys conducted by the National Marine Fisheries Service (NMFS) in the eastern North Pacific. Collection of R. stellulata occurred most often over hard substrate (68%), followed by soft sediment (22%) and mixed substrate (10%). Likelihood ratio tests indicated that there was no difference between female and male growth (p = 0.688) so sexes were pooled. The three parameter von Bertalanffy growth function best explained the growth of R. stellulata where L∞ = 861 mm, k = 0.174 and t0 = -1.477. Maximum age estimates for females and males were 9 and 8 years respectively. Age and size at 50% maturity were determined for females as 6.2 years and 632 mm TL and for males as 5.4 years and 603 mm TL. Raja stellulata exhibited no reproductive seasonality and therefore, is assumed to reproduce year-round. The life history characteristics presented in this study provide valuable insight into the species- specific variability of eastern North Pacific skates.

 

0103 AES GRUBER AWARD, Session II, Minneapolis Ballroom G, Saturday 9 July 2011

Andrew Nosal, Daniel Cartamil, Nicholas Wegner, Jeffrey Graham

Scripps Institution of Oceanography, University of California - San Diego, La Jolla, CA, USA

Aggregation Behavior of the Leopard Shark (Triakis semifasciata) Associated with the Head of La Jolla Submarine Canyon, San Diego County, California

We investigated the demographics and movement patterns of leopard sharks (Triakis semifasciata), which aggregate by the hundreds near the head of La Jolla Submarine Canyon (LJSC) from spring to autumn. The function of this behavior remains unclear. Sampling to date (n=124) indicates these sharks are mature (111-159 cm TL) and mostly female (96.7%). To quantify the fine-scale movement patterns and long-term presence- absence of leopard sharks at LJSC, sharks were manually tracked (n=8) for uninterrupted periods of 24-48 h or surgically implanted with coded transmitters (n=12) and passively monitored by an acoustic receiver array (July 2009-present). Detection patterns varied among individuals, however some displayed marked synchrony. For example, 2 sharks returned to LJSC within 1.5 h of each other after absences of 218 and 306 days, respectively. Sharks also exhibited strong site fidelity, with some individuals detected at LJSC for >70 consecutive days. Manually tracked sharks occupied significantly greater depths at night (mean ± SD night: 4.52 ± 8.45 m, day: 1.71 ± 1.62 m), occasionally exceeding 50 m during roundtrip offshore excursions. Detection data also reflect these nocturnal departures. Leopard sharks may be attracted to the canyon head due to locally calm waters caused by bathymetric wave refraction and proximity to an abundant supply of market squid (Loligo opalescens), which spawn in the canyon and are the primary dietary component of these sharks.

 

0278 AES Ecology, Minneapolis Ballroom F, Saturday 9 July 2011

Gregory Skomal, John Chisholm, Steven Correia

MA Marine Fisheries, New Bedford, MA, USA

Implications of Increasing Pinniped Populations on the Diet and Abundance of White Sharks off the Coast of Massachuestts

Although the occurrence of the white shark, Carcharodon carcharias, is well documented in the North Atlantic, the species is relatively rare and much of what is known about its distribution and movements is based on historical sightings data. The advent of new tagging technology coupled with the existence of white shark "hotspots" near pinniped colonies have allowed researchers to investigate the ecology of this species in the Pacific and Indian Oceans, but its elusive nature in the Atlantic has hampered such studies in this region. However, the numbers of white shark sightings and white shark-pinniped predation events have been rising off the coast of Massachusetts in recent years and, in particular, near Monomoy Island on Cape Cod, which hosts a large growing population of gray seals (Halichoerus grypus). While the perceived increase in shark predation on gray seals can be attributed to several factors, it is feasible that white sharks, which were thought to primarily scavenge cetaceans in the Atlantic, are expanding their diet in response to regional changes in seal abundance. Based on documented changes in white shark populations exhibited in other parts of the world, we anticipate that the number of white shark sightings and seal interactions will continue to rise off the coast of Massachusetts.

 

0720 AES Ecology, Minneapolis Ballroom F, Saturday 9 July 2011

Alexander Tilley, Marie Smedley, John Turner

Bangor University, Wales, UK

Functional Ecology of the Southern Stingray (Dasyatis americana) in a Tropical Shallow Reef System

The Southern Stingray (Dasyatis americana) is one of the most common elasmobranch species in the Caribbean, found in shallow sand and seagrass habitats, yet its functional ecology within these systems is poorly understood. This study aimed to understand aspects of mesopredator ecology, and provide insight into the dynamics of top down control by working in an isolated reef, where the shark population is quantified. Movement patterns of Dasyatis americana were investigated at Glovers Reef Marine Reserve, Belize, using manual acoustic tracking & in-water follows, between June 2009 and August 2010. 15 rays (27-86cm DW) were tagged and manually tracked for 13-32 hours. Additionally, 45 hours of in-water follows for 86 rays for 1hr periods were analyzed for fine-scale foraging behaviour. Analyses show that as with other elasmobranch species, southern stingrays exhibit ontogenic expansion of activity space, and that foraging patterns increased in organisation with age. Stingray movements and habitat use showed diel periodicity, with rate and linearity of movement of tagged animals correlating with night and day. Tagged animals remained in a very precise depth (0.5-7m) and habitat band (accumulated algae fields at the base of a sand slope), foraging only occasionally in shallower sandflat habitat, and avoiding deeper lagoon areas entirely. Understanding of the ecological role of this mesopredator is important in enhancing MPA and fisheries management systems in Belize and the wider Caribbean.

 

0015 AES Ecology, Minneapolis Ballroom F, Saturday 9 July 2011

Mauro Belleggia2, Daniel Enrique Figueroa3, Claudia Bremec2, Felisa Sánchez1, Anabela Zavatteri1

1INIDEP (Instituto Nacional de Investigacion y Desarrollo Pesquero), Mar del Plata, Argentina, 2CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas), Buenos Aires, Argentina, 3UNMdP (Universidad Nacional de Mar del Plata), Mar del Plata, Argentina

Long Term Changes in the Spiny Dogfish (Squalus acanthias) Trophic Role in the Southwestern Atlantic

This study describes the diet of the spiny dogfish Squalus acanthias in the Southwestern Atlantic Ocean (35 °S - 55 °S) by examining stomach contents data collected between 1984 and 2010. Of the 3638 individuals examined, 2217 (60.77%) had prey, at different stages of digestion, in their stomachs. Generalized Linear Models were used to evaluate the support in our data for five independent variables (Sex, Predator’s Total Length, Season, Region and Decade) that may explain the consumption of given prey. Our results reveal changes in the trophic level and the diet composition over the time series. The frequency of Fish, M. hubbsi and Benthos in the stomachs decreased over the time series, whereas the squid Illex argentinus and Jellyfishes exhibited positive trends. We propose that the changes in the trophic relationships, which have been affected during the last 30 years, are probably a consequence of the increasing fishing effort. The trophic level of S. acanthias fell from 4.68 in 1980’s to 4.1 and 4.2 in 1990’s and 2000’s respectively, showing evidence of substantial “fishing down the food webs” phenomenon. The consumption of argentine anchovy (Engraulis anchoita) was best explained by Region and Season as independent variables; this underexploited species was the unique prey not explained by GLMs including Decade. In agreement with the distribution and abundance of E. anchoita, the spiny dogfish preyed more in Northern than in Southern Region, and the consumption was also greater in Warm than in Cold Season.

 

0322 AES Ecology, Minneapolis Ballroom F, Saturday 9 July 2011

Lisa Marie Leclerc2, Christian Lydersen1, Tore Haug3, Lutz Bachmann4, Aaron T. Fisk5, Kit M. Kovacs1

1Norwegian Polar Institute, Tromsø, Norway, 2University of Tromsø, Department of Arctic and Marine Biology, Tromsø, Norway, 3Institute of Marine Research, Tromsø, Norway, 4National Centre for Biosystematics, Natural History Museum, University of Oslo, Oslo, Norway, 5University of Windsor, Windsor, Ontario, Canada

Analyses of Gastro-intestinal Tracts of Greenland Sharks (Somniosus microcephalus) from Svalbard, Norway

Gastrointestinal tracts (GITs) from 45 Greenland Sharks (Somniosus microcephalus) collected in Svalbard, Norway, in 2008 and 2009, were analyzed to study the diet of this sleeper shark. The role of these sharks as potential seal predators was of particular interest in this study. The sharks ranged from 229-381 cm (fork length) and 136-700 kg (body mass), and all were sexually immature. Seal and whale tissue were found in 42.3% and 18.2% of the GITs that had contents (N = 33), respectively. The dominant seal prey species found in the sharks was ringed seal (Phoca hispida) while bearded seal (Erignathus barbatus) and hooded seal (Cystophora cristata) tissues were each found in a single GIT. Ringed seal tissues found in the sharks were derived from both pups and adult animals. All of the whale tissue was from minke whales (Balenoptera acutorostrata) that had been harvested in the commercial fishery near Svalbard. The sharks also ate various fish species, with Atlantic cod (Gadus morhua), Atlantic wolffish (Anarhichas lupus) and haddock (Melanogrammus aeglefinus) being the most important prey species. The largest fishes swallowed whole were an Atlantic wolffish (8.6 kg) and an Atlantic cod (4.2 kg). Strong circumstantial evidence suggests that the sharks actively preyed on the seals and fishes, in addition to eating carrion such as the whale tissue. Active predation on seals, in combination with the apparently high numbers of Greenland sharks in the Svalbard area, makes this predator a potentially significant source of mortality for seals that is generally neglected.

 

0305 AES Ecology, Minneapolis Ballroom F, Saturday 9 July 2011

Philip Matich, Michael Heithaus

Florida International University, North Miami, FL, USA

Ontogenetic Shift in the Habitat Use and Diet of Juvenile Bull Sharks in a Coastal Estuary

Ontogenetic niche shifts are experienced by a variety of species and numerous factors have been found to be important drivers. Yet, we lack a strong understanding of the ecological importance these shifts may have on both the species and ecosystem(s) they reside within, especially for large, aquatic predators. We investigated the potential drivers of shifts in the habitat use and diet of juvenile bull sharks during their growth within a nursery, and their potential ecological impacts. Acoustic tracking and quantitative longline fishing revealed that sharks expanded their use of the estuary as they grew until reaching a size of 135 cm total length or greater, at which time they inhabited coastal waters adjacent to the Gulf of Mexico. Stable isotope data suggested that bull shark diet also changed with size, and their role within the trophic systems of the estuary shifted from that of a freshwater predator to a marine predator. Environmental factors, such as salinity, may be important drivers of juvenile bull shark behavior, but these size-based shifts were most likely influenced by site-specific competition and predation risk. This ontogenetic niche shift helps shape the role of juvenile bull sharks within this coastal ecosystem, and provides a functional link between the freshwater and marine habitats through trophic interactions within our study area. As predator populations continue to decline and climate change alters ecosystems, it is important that we continue to investigate the drivers of ontogenetic niche shifts, especially in highly mobile predators, and their ecological importance.

 

0155 AES Ecology, Minneapolis Ballroom F, Saturday 9 July 2011

Brandi Neifert1, Alton Dooley1

1Roanoke College, Salem, VA, USA, 2Virginia Museum of Natural History, Martinsville, VA, USA

A Comparison of Tooth Breakage Rates in Miocene Carcharhinid Sharks from the Carmel Church Quarry, Caroline County, VA

Excavation of marine sediments of the middle Miocene Calvert Formation at the Carmel Church Quarry has resulted in the collection of thousands of shark and ray teeth. Genera of teeth commonly found include Hemipristis, Carcharhinus, and Galeocerdo, among others. Unlike most large collections of shark teeth, the Carmel Church specimens were all collected in situ from a single bed with a maximum thickness of less than 1 m. While the majority of teeth from Carmel Church represent clearly reworked specimens, a substantial portion show no evidence of reworking and provide a sample that may represent the local population of sharks over a relatively short period of time. Multiple shark taxa with similar tooth morphologies and body sizes may have coexisted through niche partitioning. This could have been achieved through behavioral variations such as temporal segregation (diurnal or nocturnal habits, or seasonal movements) or through variations in dietary preferences. In order to test for evidence of variation in dietary preferences, tooth breakage frequency and height-thickness ratios were examined in three shark genera that are broadly similar to each other in size and tooth morphology – Hemipristis, Galeocerdo and Carcharhinus. Preliminary results show Carcharhinus with a low frequency of breakage at the apex of the tooth. Further results pending.

0443 AES Ecology, Minneapolis Ballroom F, Saturday 9 July 2011

Nigel Hussey1, Aaron MacNeil2, Jill Olin1, Bailey McMeans1, Demian Chapman3, Michael Kinney4, Aaron Fisk1

1GLIER, University of Windsor, Windsor, Ontario, Canada, 2Australian Institute of Marine Science, PMB3, Townsville MC, Townsville, Queensland, Australia, 3Institute for Ocean Conservation Science and School of Marine and Atmospheric Science, Stony Brook University, Stony Brook, NY, USA, 4Fishing and Fisheries Research Centre, School of Earth and Environmental Sciences, James Cook University, Townsville, Queensland, Australia

Stable Isotope Dynamics in Elasmobranchs: Methods and Assumptions

Stable isotopes can function as powerful chemical tracers enabling the examination of diet, trophic position and movement as well as more complex questions concerning community dynamics and feeding strategies/behaviour of both terrestrial and aquatic organisms. The inherent difficulty of studying large, highly mobile marine predators such as sharks has led to the increased use of stable isotope analysis (SIA) in answering such questions. We provide a review of the current state of SIA in sharks, focusing on modes of application and methodological issues relating to effects of lipid extraction, tissue type, and diet-tissue discrimination factors. We discuss these in terms of assumptions made in SIA and the requirement that investigators standardise analytical approaches. Recommendations are made for future stable isotope experiments and fieldwork that would improve our understanding of isotope dynamics and advance their application in the study of these ecologically important species.

 

0345 AES Ecology, Minneapolis Ballroom F, Saturday 9 July 2011

Heather McCann1, Aaron Fisk1, Sabine Wintner2, Geremy Cliff2, Sheldon Duffy2, Mike Meyer3, Brian Fryer1, Nigel Hussey1

1Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON, Canada, 2KwaZulu-Natal Sharks Board, Umhlanga Rocks, KwaZulu-Natal, South Africa, 3Department of Environmental Affairs &Tourism, Marine & Coastal Management Branch, Cape Town, Western Cape, South Africa

Trophic Ecology and Movement Dynamics of South African White Shark (Carcharodon carcharias) Inferred from Stable Isotope Profiles in Vertebrae

The white shark (Carcharodon carcharias) is a large, highly mobile keystone predator that is known to prey on pinnipeds and spend associated periods of residency at seal haul outs interspersed with coastal and oceanic migrations. Understanding trophic dynamics of regional populations, both at the individual (i.e. over ontogeny) and population level is important for species-specific management plans. Elasmobranch vertebrae grow incrementally and record a seasonal ‘isotopic diary’ (δ15N and δ13C) throughout ontogeny, providing a measure to examine trophic ecology and coarse level movement patterns. White shark vertebrae from KwaZulu-Natal, South Africa (55), and Kenya (1) were serially sampled and analyzed for stable isotopes. Sharks ranged in size from 124cm to 487cm PCL. Stable isotope values varied across individuals and ontogeny, δ13C values ranged from -17.68 to -10.59‰ and δ15N values ranged from 10.96 to 18.67‰. For animals <200 cm PCL, δ13C values were more variable compared to sharks > 200 cm PCL. Additionally δ15N values increased at approximately 220-280 cm PCL (~4 years of age), indicating a shift to higher trophic level prey in agreement with stomach content data and previous stable isotope work on Pacific and North Atlantic populations. The δ13C values of a large near-term pregnant female (487 cm) declined in the year before capture and then increased in the year of capture which supports an offshore migration and a return to coastal waters while pregnant. These data demonstrate that trophic ecology and habitat use vary widely across ontogeny, which needs to be considered in regional management plans.

 

0347 AES Ecology, Minneapolis Ballroom F, Saturday 9 July 2011

Silvia Hinojosa- Alvarez1, Xavier Chiappa-Carrara1, Felipe Galvan-Magaña2

1UNAM,ICMyL, Distrito Federal, Mexico, 2CICIMAR, La Paz, Mexico

Trophic Ecology of Giant Manta (Manta birostris, Walbaum 1792) Using Stable Isotopes of δ15N and δ13C in the Northeast of the Yucatan Peninsula

Although mantas are available worldwide, there are surprisingly few data pertaining to their basic biology. Protective measures preclude analysis of gut contents, so a non invasive technique uses stable isotopes to quantify 13C and 15N . Supported by the isotopic values of δ13C the study verified that manta rays are feeding in the area to exploit the upwelling resulting from the Yucatan Current. When manta ray arrived its average 13C isotopic signal was -12‰ and when leaving -14.5‰, this value was similar to those of the prey and of the water in the area. The 13C values suggested that the zoeas of crustaceans contribute the largest proportion of manta ray diets; this was most evident in July when the zoeas 13C values switch from oceanic to coastal (-17‰ to - 14.5‰) and correspond to the values found in manta rays the following month. Using Iso Source TM to verify our isotopic data also supported the conclusion that zoeas were the main prey source with 91% and fish larvae with 0.08% in carbon composition. Previous elasmobranch studies have reported a switch in the values of δ15N due to dietary changes during a year round due to prey availability, but in this case the isotopic values did not exhibit this pattern.

 

0679 AES Ecology, Minneapolis Ballroom F, Saturday 9 July 2011

Wade D. Smith, Jessica A. Miller

Department of Fisheries and Wildlife, Coastal Oregon Marine Experiment Station, Hatfield Marine Science Center, Oregon State University, Newport, OR, USA

The Effects of Temperature, Growth, and Water Concentration on the Elemental Composition of Elasmobranch Vertebrae

Otolith elemental signatures have proven to be valuable natural markers, providing insight into migratory patterns, population structure, and natal origin of many species. Sharks and rays lack the calcium carbonate otoliths of teleosts but possess mineralized vertebral cartilage that is typically deposited in an annual banding pattern and continues to grow throughout an individual's life. If the incorporation of elements in vertebrae is related to environmental conditions, the geochemical composition of cartilaginous vertebrae may also serve as natural tags and records of environmental history in elasmobranch populations. To determine the relationship between water and vertebral elemental concentrations, we conducted two controlled laboratory studies using round stingrays, Urobatis halleri, as a model species. First, we determined the extent of partitioning and quantified the effects of temperature (16°C, 18°C, 24°C) and growth rate on vertebral elemental composition (Li:Ca, Mg:Ca, Mn:Ca, Zn:Ca, Sr:Ca, Ba:Ca). Second, we further evaluated the relationship between water and vertebral elemental composition by manipulating the dissolved concentrations of barium in each tank. In the first experiment, vertebral elemental concentrations were significantly influenced by temperature. Temperature negatively affected the incorporation of Mg:Ca, Sr:Ca, and Ba:Ca. In the second experiment, vertebral Ba:Ca was positively correlated with water Ba:Ca. Elemental incorporation was not found to be effected by variable growth rates. This study represents the first validation experiment on elemental incorporation in elasmobranch cartilage, provides support for the assumption that vertebral composition reflects environmental variation, and highlights the potential use of elemental signatures in the vertebrae of elasmobranchs as natural markers.

 

0301 AES Reproduction & Morphology, Minneapolis Ballroom G, Saturday 9 July 2011

Atsuko Yamaguchi, Keisuke Furumitsu, Takeshi Ito, Shigeki Fujiwara, Yuki Minei, Gen Kume

Nagasaki University, Nagasaki, Japan

Reproductive Biology of Shortspine Spurdog, Squalus mitsukurii, around Ishigaki Island, Okinawa, Japan

Size at sexual maturity, reproductive cycle, and fecundity of the shortspine spurdog, Squalus mitsukurii (Jordan and Snyder, 1903), were examined based on specimens collected around Ishigaki Island, Okinawa, Japan from November 2006 until October 2010. Size [total length (TL)] ranged from 435 mm to 702 mm for males and from 430 mm to 945 mm for females, respectively. Females reached sexual maturity at a larger size than males (TL at 50% sexual maturity: males, 560 mm; females, 727 mm). Monthly gonadosomatic indices of males decreased from February to September. Nearterm embryos were observed in females with preovulatory ova from February to August. Uterine eggs, which were recognized as recently fertilized, were observed around the same time. Accordingly, parturition period is lengthy, which occurred from February to August, immediately followed by mating, ovulation, and fertilization. Based on monthly variations of size frequencies of embryos and ovarian ova, the gestation period was estimated to be approximately 1 year although previous studies suggested that it would take two years. Fecundity increased with TL and ranged from 1 to 5 (mean, 3.1) embryos per litter.

 

0498 AES Reproduction & Morphology, Minneapolis Ballroom G, Saturday 9 July 2011

Eric Hoffmayer1, Jill Hendon2, Lisa Jones1, William Driggers1, Madison Walker2, Travis Holland2, James Sulikowski3

1National Marine Fisheries Service, Mississippi Laboratories, Pascagoula, MS, USA, 2University of Southern Mississippi, Gulf Coast Research Laboratory, Ocean Springs, MS, USA, 3University of New England, Biddeford, ME, USA

Reproductive Biology of the Atlantic Sharpnose Shark, Rhizoprionodon terraenovae, in the Northern Gulf of Mexico

Recently, significant variability in the reproductive biology of at least two species of sharks within the family Carcharhinidae has been observed in the western North Atlantic Ocean. While elasmobranchs, as a group, are typically characterized by having slow growth and late age at maturity, relative to other carcharhinids, the Atlantic sharpnose shark, Rhizoprionodon terraenovae, is an exception. As such, the Atlantic sharpnose shark is an ideal candidate for examining temporal fluctuations in reproductive parameters such as age and size at maturity, gametogenesis, gestation time, fecundity, size-at-birth and time-at-parturition in a coastal shark species. The objective of this study was to provide an updated synopsis of the reproductive biology of Atlantic sharpnose sharks in neritic waters off Mississippi, compare our findings with those of studies conducted in the past and provide contemporaneous baseline data that could be critical to examinations of potential reproductive effects of future perturbations.

 

0600 AES Reproduction & Morphology, Minneapolis Ballroom G, Saturday 9 July 2011

Lyndell Bade, Susan McRae

East Carolina University, Greenville, NC, USA

Asymmetric Development of the Female Reproductive Tract in Elasmobranchs: A Comparative Analysis of Modes of Reproduction and Life History Traits.

Elasmobranchs (sharks, skates, and rays) exhibit diverse reproductive modes, including internal fertilization, and either oviparity with external development or internal development via viviparity or ovoviviparity. For example, in many batoid species, the eggs are held internally, develop in the egg sac, and then the fetuses are fed through the excretion of a uterine fluid. Asymmetric reproductive tract development in the female is exhibited across many taxa, predominantly with left-sided functionality and vestigiality of the right side of the uterine tract. This is remarkably similar to birds, where it is viewed as a flight adaptation. It is conceivable that this is an anatomical adaptation in elasmobranch species that is specific to aspects of migratory behaviors or habitat usage. A literature review will be used to identify reproductive modes and life history traits across elasmobranch diversity. Comparative analysis will be used to relate asymmetric development of the reproductive tract with reproductive mode and ecomorphology, as well as ecological traits such as migratory habit, migration distance, natal dispersal pattern, and habitat type. The study of elasmobranchs is a growing field and new species are continually being discovered, yet life histories and reproductive traits of these species are poorly understood due to difficulties with observation and capture.

This study will add to our knowledge of reproductive adaptation of these fascinating but imperiled animals.

 

0350 AES Reproduction & Morphology, Minneapolis Ballroom G, Saturday 9 July 2011

L. Jay Williams2, James Sulikowski1

1University of New England, Biddeford, ME, USA, 2Auburn University, Fairhope, AL, USA

An Assessment of Seasonal and Individual Variation in Reproductive Hormones from a Captive Population of Female Little Skates

In order to successfully manage an elasmobranch species it is essential to understand the reproductive biology. Previous studies suggest that the little skate, Leucoraja erinacea, exhibits a continuous reproductive cycle however, discrepancies exist surrounding the timing and quantity of reproductive peak(s). An effective non-lethal technique which has been used to describe the reproductive cycle in elasmobranch species is the analysis of circulating steroid hormones. Although an accurate technique, the ability to clearly interpret correlations between steroid hormones and the reproductive cycle has been limited in some continuously reproducing species due to high variability amongst individuals. Thus, the goal of this study was to address problematic aspects of previous studies by using circulating steroid hormones to define both the reproductive cycle and degree of individual variability in the little skate. Weekly blood samples were collected from 2008-2009 in a captive breeding population of little skates and analyzed for circulating levels of E2 and P4, by radioimmunoassay. Circulating levels of E2 and P4 ranged between 93.85 to 8,857.85 pg/ml and 12.5 to 12,817.96 pg/ml and varied greatly within individual skates, E2 (i.e. 3196.85 ± 2073.89 SD) and P4 (i.e. 689.59 ± 1864.51 SD). Similarly, variability in hormone levels between skates within each sampling week (i.e. E2 304 vs. 5,986 pg/ml) and month (i.e. E2 157 vs. 8,858 pg/ml) remained high suggesting an asynchrony in ovulation amongst females. The results from this study suggest that the little skate continuously reproduces throughout the year and lacks a reproductive peak in hormone concentrations.

 

0320 AES Reproduction & Morphology, Minneapolis Ballroom G, Saturday 9 July 2011

Bianca K. Prohaska1, Paul C.W. Tsang2, James A. Sulikowski1

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

Utilization of Steroid Hormones Extracted from the Skeletal Muscle Tissue of the Little Skate (Raja erinacea) and the Spiny Dogfish (Squalus acanthias) to Determine Reproductive Status

Currently, circulating levels of plasma steroid hormones have been used as a non-lethal method to determine reproductive maturity and reproductive cycles in elasmobranchs. However, this method can prove problematic to perform on large and/or endangered species, due to difficulties involved with specimen handling. These constraints make it imperative for new techniques to be developed. Previous work conducted on other vertebrates has shown that hormones can be successfully extracted from muscle tissue. The process of collecting muscle samples is quick, minimally invasive, and may be conducted without removing the animal from the water, facilitating its use on larger, and/or endangered species of elasmobranchs. The focus of this presentation will be the development of a valid method for extracting steroid hormones from the skeletal muscle tissue of the oviparous little skate (Raja erinacea) and the aplacental viviparous spiny dogfish (Squalus acanthias). For each species 80 females are currently being collected from the Gulf of Maine and will consist of 20 immature individuals, to act as control replicates, 20 maturing individuals, 20 mid-gestation individuals, and 20 near parturition individuals. Sample collections of spiny dogfish and little skates began in October 2010, and the remaining samples will be collected this spring. To verify the use of this tissue for reproductive analysis, steroid hormone levels extracted from skeletal muscle will be compared to the concentrations and patterns of those same steroid hormones extracted from plasma, via radioimmunoassay.

 

0268 AES Reproduction & Morphology, Minneapolis Ballroom G, Saturday 9 July 2011

Ashley Stoehr1, Cheryl Wilga2, Rebecca Allen3

1University of Massachusetts Dartmouth, Dartmouth, MA, USA, 2University of Rhode Island, Kingston, RI, USA, 3Ross University, Roseau, Dominica

Hyoid and Pharyngeal Arch Mechanics during Prey Processing in Elasmobranchs

The position of the hyomandibulae is related to prey capture in elasmobranchs; yet it is little understood how hyoid and pharyngeal arch morphology relate to prey processing mechanics. The kinematics of the jaws, hyoid, and 2nd pharyngeal arches were quantified by sonomicrometry and pressure transducers during prey processing in bamboo sharks, Chiloscyllium plagiosum, spiny dogfish, Squalus acanthias, and little skates, Leucoraja erinacea. These species possess different cranial morphologies with short lateral, longer lateral, and anterior hyomandibular orientations, respectively. Similar to prey capture, in all species oropharyngeal expansions generated subambient pressures during suction processing, while compressions created superambient pressures during bite processing. Bamboo sharks generated the strongest subambient and superambient pressures during prey processing. The mechanism of cavity expansion and compression differed between species and behaviors, with hyoid and pharyngeal widths increasing or decreasing. In dogfish the hyoid distance expanded vertically and horizontally during suction and decreased during bite, differing from prey capture. Contrastly, in bamboo sharks and little skates the hyoid distance increased vertically and decreased horizontally during suction, which was similar to prey capture. Bamboo sharks continued to decrease hyoid width during bite, but hyoid width movement either increased or decreased in skates. Pharyngeal width movements were more variable in the three species. Bamboo sharks are mechanistic specialists and more stereotyped in behavior compared to dogfish and skates, which are generalist predators. It appears differences during prey processing may reflect different degrees of morphological constraint among the elasmobranchs.

 

0283 AES Reproduction & Morphology, Minneapolis Ballroom G, Saturday 9 July 2011

Cyrena Riley1, Richard Cloutier1, Eileen Grogan2

1Université du Québec à Rimouski, Rimouski, Québec, Canada, 2St-Joseph’s University, Philadelphia, PA, USA

Ontogenetic Pattern of Mineralization in the Thorny Skate (Amblyraja radiata)

Skeletal development of organisms provides essential data for phylogenetic, evolutionary and biomechanical studies. Compared to osteichthyans in which chondrification and ossification sequence have been described for numerous species, the exact ontogenetic progression of prismatic mineralization (tesserae) in chondrichthyans is not well known. Two different types of tesserae arrangements have already been recognized in skates: (1) catenated, corresponding to long chains of single tessera and (2) crustal, corresponding to a continuous layer of tesserae. Patterns of direction of mineralization (e.g., proximo-distal, bidirectional) and patterns of distribution of mineralization (e.g., dorso-ventral, lateral), were analyzed using a cleared and double- stained growth series of 20 specimens (embryos and juveniles) of the thorny skate (Amblyraja radiata). Different distribution patterns occur simultaneously in different anatomical components within an individual. Pectoral fins exhibit catenated mineralization on the dorso-ventral surfaces of radials. Pelvic fins show two distinctly different patterns; on the crus, crustal mineralization is more important on the anterior portion of the radials, while the non-crus part of the fin has crustal and catenated mineralization on the dorso-ventral surfaces of radials. The direction of radial mineralization follows a proximo-distal pattern while basal elements of pectoral fins follow a bidirectional mineralization pattern. The posterior portion of the vertebral column mineralizes first. Although a phylogenetic component is not discarded, the ontogenetic progression of mineralization in skates suggests that mechanical stress may influence the formation of mineralization. Skate developmental patterns will be compared to those present in immature and mature specimens of different elasmobranch species and in osteichthyans as well.

 

0118 AES Reproduction & Morphology, Minneapolis Ballroom G, Saturday 9 July 2011

Philip Motta1, Maria Laura Habegger2, Amy Lang3, Robert Hueter4

1University of South Florida, Tampa, FL, USA, 2University of South Florida, Tampa, FL, USA, 3University of Alabama, Tuscaloosa, AL, USA, 4Mote Marine Laboratory, Sarasota, FL, USA

Placoid Scale Morphology, Erection and Function in the Shortfin Mako Isurus oxyrinchus

The shortfin mako Isurus oxyrinchus is perhaps the fastest swimming shark and exhibits a suite of physiological and morphological adaptations for sustained and rapid swimming. We investigated the functional morphology of the placoid scales from 16 regions on the body to investigate putative scale erection leading to drag reduction and compared this to the scales of a slower swimming blacktip shark Carcharhinus limbatus.

Scanning electron microscopy, histological staining, and manipulation of scales overlying pressurized skin revealed regions on the flank with extremely small (0.18 mm crown length) and flexible scales that can be manually erected to 50 degrees in mako sharks. The lateral flank scales had significantly greater erection angles (mean = 44o ± 1.44 SE) than both the dorsal (mean = 25.8o ± 0.78 SE) and ventral regions (mean = 25.1o ± 1.9 SE). Highly flexible scales were also found at the trailing edge of the pectoral fins. The scales on the trailing edge of the pectoral had the highest erection angles compared to the leading edge and the central region of the fin. Conversely, blacktip scales were larger (0.32 mm) and less flexible. Scale flexibility appears to be related to the length of the scale crown and base, the shape of the base, and anchoring to the dermis. These flexible scales on the flank and pectoral fin occur in regions most prone to flow separation and reversal, and scale erection most likely occurs passively at these regions of flow reversal resulting in a reduction of form drag.

 

0680 AES Reproduction & Morphology, Minneapolis Ballroom G, Saturday 9 July 2011

Jill Hendon1, Eric Hoffmayer1, Christian Jones2, Gregg Poulakis3, Joseph Quattro4, Justin Lewandowski4, William Driggers2, Matthew Ajemian5

1University of Southern Mississippi, Ocean Springs, MS, USA, 2NOAA Fisheries, Pascagoula, MS, USA, 3Florida Fish and Wildlife Conservation Commission, Tallahassee, FL, USA, 4University of South Carolina, Columbia, SC, USA, 5University of South Alabama, Dauphin Island, AL, USA

Evidence of a Second Rhinoptera Species Inhabiting the Northern Gulf of Mexico

In 2007, three rays were collected during a Mississippi fishing rodeo that were tentatively identified as the Brazilian cownose ray, Rhinoptera brasiliensis; a species not known to inhabit the northern Gulf of Mexico. Phylogenetic analyses of the mitochondrial COI locus revealed the specimens putatively identified as R. brasiliensis were genetically distinct from the Atlantic cownose ray, R. bonasus, which is the only member of the genus reported to be indigenous to the region. We have been unable to obtain tissue samples from vouchered R. brasiliensis specimens for comparison with our molecular data set, therefore, the identity of the rays is still unresolved. To investigate the broad scale distribution/occurrence patterns of the R. cf. brasiliensis in the northern Gulf of Mexico, cownose rays were collected with gillnet and trawls off Texas, Louisiana, Mississippi, and Florida. Thirty-five R. cf. brasiliensis have been collected to date with individuals occurring off the coasts of all four states. The ratio of R. cf. brasiliensis to R. bonasus in collections increased from east to west in the northern Gulf of Mexico, with the percentage of occurrence being lowest off Florida (2%), intermediate off Mississippi (20%) and highest in waters off Louisiana and Texas (69%).

 

0708 Conservation & Management, Minneapolis Ballroom G, Sunday 10 July 2011

David Marancik1, Donald Champagne1, Alistair Dove2, Alvin Camus1

1University of Georgia, College of Veterinary Medicine, Athens, GA, USA, 2Georgia Aquarium, Atlanta, GA, USA

Elasmobranch Infestations by the Marine Leech Branchellion torpedinis in Aquarium Settings

The marine leech Branchellion torpedinis is a parasite exclusive to elasmobranchs. When inadvertently introduced into aquaria, infestations have proven to be difficult to manage due to the leech’s direct life cycle, high reproductive capability, and a lack of proven chemotherapeutants. Infestations on the skin, gill slits, oropharynx, and cloaca can be severe, resulting in ulceration, lethargy, anorexia, anemia, and death. Secretory proteins of the B. torpedinis salivary gland are thought to be directly involved in the feeding mechanism of the leech and a main contributor to lesion development in elasmobranch tissue. Genetic sequencing of bioactive salivary gland compounds reveals proteins potentially involved in lesion development including proteases, anticoagulants, and thrombocyte inhibiting proteins. This data correlates with gross and microscopic lesions observed in elasmobranchs at leech attachment sites. The objective of this study is to investigate the pathologic potential of B. torpedinis with the goal that it will lead to better prevention and treatment techniques in aquarium, aquaculture, and natural environments.

 

0590 Conservation & Management, Minneapolis Ballroom G, Sunday 10 July 2011

Laura Jordan1, John Mandelman2, Stephen Kajiura1

1Florida Atlantic University, Boca Raton, FL, USA, 2New England Aquarium, Boston, MA, USA

Behavioral Responses to Weak Electric Fields and a Lanthanide Metal in Two Shark Species

The unintentional catch of sharks on hooks intended for other fish is an economic, environmental and safety concern. Recent research has sought to capitalize on the electrosensory system in elasmobranchs to repel sharks from lines without affecting target teleost catch through experiments with various lanthanide metals and alloys. We present a standardized approach to testing sharks responses to an ideal lanthanide metal with a strong electric field and relatively slow dissolution in seawater. Sharks responses to prey-simulating weak electrical signals were quantified to establish the sensitivity of the electrosensory system in Squalus acanthias and Mustelus canis. Both species demonstrated sensitivity to electrical signals below 1nV/cm, and responded similarly to other elasmobranchs. Sharks were then presented with food affixed to 2.5mm2 treatments of acrylic, stainless steel or Neodymium (Nd) metal pieces. S. acanthias only fed in groups and fed from Nd significantly less frequently than either control. M. canis were tested both individually and in groups and when alone fed less from Nd, however, in groups they ate food significantly more often from Nd. These results confirm variability in response to a lanthanide metal both across species and within a species in the presence of competition. Since observed differences are not due to differences in sensitivity, additional factors appear to influence behavioral responses and may compromise the effectiveness of lanthanide metals for the reduction of shark bycatch.

 

0659 Conservation & Management, Minneapolis Ballroom G, Sunday 10 July 2011

Kevin Weng1, Chris Lowe1, Oscar Sosa-Nishizaki1, John O'Sullivan1

1University of Hawaii at Manoa, Honlulu, HI, USA, 2California State University - Long Beach, Long Beach, CA, USA, 3Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, Baja California, Mexico, 4Monterey Bay Aquarium, Monterey, CA, USA

Connectivity of US and Mexican White Shark Populations in the Eastern Pacific

In the eastern Pacific, aggregations of adult and subadult white sharks are known from the Farallones and Ano Nuevo in California, USA, and at Isla Guadalupe, Mexico. Interchange between these apparent population centers by adult sharks appears to be very low, with mixing occurring only in offshore waters. Genetic studies indicate a single population of white sharks in the eastern Pacific. One explanation of these apparently contradictory findings is that mating occurs in the offshore area, maintaining genetic panmixia. Another, related possibility is that both ‘US’ and ‘Mexican’ white sharks share a common, mixed nursery region. Parturition is thought to occur in the Southern California Bight and in Pacific waters of Baja California. Movement patterns of early juvenile life stages reveal consistent migrations from the Southern California Bight into Mexican waters of Baja California and the Gulf of California. Therefore, young-of- the-year and juvenile white sharks born in separate pupping grounds appear to share the same large nursery region. The recruitment into separate adult population centers may therefore be based not on ancestry, but instead on stochastic, environmentally mediated, density dependent, or facultative processes. Once an animal becomes associated with an aggregation, it shows fidelity through its lifetime, thereby maintaining two separate, but genetically homogenous groups.

 

0412 Conservation & Management, Minneapolis Ballroom G, Sunday 10 July 2011

Sebastian Pardo1, Andrew Cooper2, Nicholas Dulvy1

1Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada, 2School of Resource & Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada

Does it Fit? Choice of Growth Model can Bias Vulnerability Estimates in Sharks

Growth is an intrinsic ability of living organisms, and is of particular importance in marine systems where an individual's size can increase numerous orders of magnitude during their lifetime, and determines the niche they occupy in the ecosystem. Quantifying growth rates allows the calculation of parameters which are important in demographic modelling and for assessing the vulnerability of a species to extinction. In elasmobranchs, the von Bertalanffy growth function (VBGF) is commonly used as it provides biologically meaningful parameters, such as asymptotic size (Loo) and growth rate (k). A variant of the VBGF has been recommended for use in elasmobranchs; fixing the size at age-0 (L0) to an empirical estimate of size at birth. Using simulation modelling we demonstrate that this does not improve model fit but in fact biases growth parameters, resulting in the underestimation of vulnerability. Incorporating variability in L0 also biases results. The assumption that the L0 parameter from the VBGF is equal to actual size as birth is erroneous, with the former usually being ~15% lower than the latter; an analogous difference between asymptotic size and observed maximum length. The limitations of certain growth functions need to be taken into account as well as the difference between model parameters and life history traits in order to accurately predict demography and vulnerability of a species.

 

0635 Conservation & Management, Minneapolis Ballroom G, Sunday 10 July 2011

Rachel Scharer1, William F. Patterson III1, John K Carlson2, Gregg Poulakis3, Michael Cochran1

1University of West Florida, Pensacola, FL, USA, 2NOAA, National Marine Fisheries Service, Southeast Fisheries Science Center, Panama City, FL, USA, 3Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, Charlotte Harbor Field, FL, USA

Examination of Smalltooth Sawfish Life History in South Florida via Vertebral Aging and Laser Ablation ICPMS Analysis

Smalltooth sawfish, Pristis pectinata, is the first marine fish species listed as endangered, yet basic life history data critical for conservation are lacking for this species. To address this lack of information, we first estimated age of smalltooth sawfish by counting opaque zones in vertebrae of naturally deceased fish (n =12). Transverse sections were made through vertebral centra and read with transmitted light. Opaque and translucent zones were clearly defined in vertebral sections, and each section was read independently by two readers without any prior knowledge of fish size. Age ranged from zero to eight years for fish that ranged in size between 600 mm and 4,327 mm total length. A von Bertalanffy growth function fit to size at age data resulted in parameter estimates of 5.3 m for L∞ and 0.159 for K when t0 was fixed at -0.42 y, which corresponds to the estimated gestation period of the fish. Analysis of vertebral sections with laser ablation inductively coupled plasma mass spectrometry also was conducted to estimate freshwater, brackish, and saltwater residency of fish. Patterns observed in Sr:Ca ratios indicate gestation and birth (inferred from natal marks in vertebral sections) most likely occurred in estuarine waters (i.e., intermediate to high Sr:Ca values). However, neonates likely migrate to lower salinity waters where they remain through their first summer of life. Sr:Ca ratios generally increased for older fish, mostly likely indicating euryhaline to marine residency, but intra-annual patterns indicate some migration in and out of estuaries likely occurs.

 

0531 AES Conservation & Management, Minneapolis Ballroom G, Sunday 10 July 2011

Dana Bethea, Kelcee Smith, John Carlson

NOAA Fisheries, Panama City, FL, USA

Environmental Effects on the Recruitment of Smalltooth Sawfish, Prisits pectinata, in Southwest Florida, USA

The completion of the Smalltooth Sawfish Recovery Plan initiated a new phase of conservation objectives for the US population of smalltooth sawfish, Prisits pectinata. Research and monitoring priorities identified in the Recovery Plan include monitoring recruitment and juvenile abundance in designated critical habitat and identifying affecting factors. Over the last 3 years, major environmental differences existed during peak times of hypothesized recruitment of neonates. Early 2010 posted unusually cold air temperatures for southwest Florida, resulting in the mortality of over 200 Florida manatee and several species of teleosts fish. Average backwater temperature in February 2010 was 17 oC; whereas, temperatures in other years are generally above 23 oC. Additionally, southwest Florida experienced unusually high rainfall during the “dry season” (December – May) and usually low rainfall during the “wet season” (June – November) in 2010, causing average backwater salinity to drop below 10 at certain times. In 2010, we experienced a significant decline in juvenile smalltooth sawfish recruitment over previous years with annual catch-per-effort dropping from 0.12 animals per net hour to 0.06 animals per net hour. In addition, juvenile smalltooth sawfish were not captured in 2010 until June when they are historically first encountered in late-March. We believe the unusually colder temperatures and lower salinity levels are the cause of the lower catch rates in 2010 and may be indicative of a recruitment failure.

 

0728 AES Conservation & Management, Minneapolis Ballroom G, Sunday 10 July 2011

Nicholas Dulvy

Simon Fraser University, Burnaby, Canada

Global Shark Abundance Before Fishing

We are familiar with food chains and food webs as the typical way of viewing energy flow in ecosystems. However, size is often a more important biological attribute than species identity because most marine species grow throughout their lives. Consequently, many important properties, such as prey size and mean trophic level, change ontogenetically throughout a fish's life. These biological attributes lead to a regular size- based theory of ecosystem structure and dynamics, whereby the abundance, biomass and production varies in a predictable manner across a wide range of body mass classes. Indeed the depreciation of energy, abundance and biomass with increasing body size can be characterized using only two parameters: average predatory-prey mass ratio and transfer efficiency. If we assume only 12.5% transfer efficiency of energy from one trophic level to the next and that predators are on average 1000 times heavier than their prey and we combine these parameters with satellite-derived estimates of primary production we can calculate the theorectical abundance, biomass and production of fishes and sharks across the world's oceans. Here I summarise some recent work that suggests there could be as much 8.6 million tonnes of coastal and oceanic epipelagic sharks under current climate conditions in the absence of fishing.

0521 Conservation & Management, Minneapolis Ballroom G, Sunday 10 July 2011

John Froeschke1, Bridgette Froeschke2

1Gulf of Mexico Fishery Management Council, Tampa, FL, USA, 2Texas A&M University-Corpus Christi, Corpus Christi, TX, USA

Long-term Demographic Trends of Coastal Sharks in the Northern Gulf of Mexico: Evidence of Increasing Trends

Dramatic declines in elasmobranch populations have been reported worldwide. In addition to supporting fisheries, many shark species may affect a broad range of community interactions thus; demographic trends of sharks may provide evidence about both the fishery and ecosystem status of ecosystems they inhabit. To assess population status and trends of coastal sharks off the Texas, USA coast, fisheries independent gill net surveys were used to examine long-term patterns of abundance. Data were collected in a stratified random design (1977-2009) and trends were examined across nine bays systems along the Texas coast using generalized additive models. Results suggest that abundance varies substantially among bays due to differences in environmental conditions and there is evidence of increasing catch rates for some species in the central and northern bay systems of Texas. Additional research is necessary to determine if regional increases are related to changes in management or environmental conditions in the study area.

 

0255 AES Conservation & Management, Minneapolis Ballroom G, Sunday 10 July 2011

Aurélie Cosandey‐Godin1, John K. Carlson2, Valérie Burgener

Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada, 2National Marine Fisheries Service, Southeast Fisheries Science Center, Panama City Laboratory, Panama City, Florida, USA

Little effect of circle hooks on elasmobranch catch and atvessel mortality in pelagic longline fisheries

Fisheries bycatch is a main cause of population declines in several species of sharks and skates around the world. Circle hooks have gained attention as a cost‐effective bycatch mitigation tool in pelagic longline fisheries, particularly for marine turtles. Over the last few years, a growing number of studies have investigated the use of circle hooks and their effects on other species, including elasmobranchs. To elucidate the value of circle hook as a conservation tool for shark management in pelagic longline fisheries, we conducted a quantitative review of all studies to date, including recent data presented at the Circle Hook Symposium, Miami, Florida (May 2011). The effects of circle hooks on catchability and at vessel mortality rates were analyzed with random effects meta‐ analysis using an odds ratio test and analysis of covariance. Based on our review and meta‐analysis, the use of circle hooks (1) does not affect total catch of all shark species combined; (2) may slightly increase catch rates of mackerel sharks; (3) reduce catch rates of pelagic stingrays; and (4) does not significantly reduce at‐vessel mortality of shark species. In light of these largely trivial results we urged managers and scientists to explore other bycatch mitigation to reduce bycatch mortality of sharks.

 

0055 AES Conservation & Management, Minneapolis Ballroom G, Sunday 10 July 2011

Andrea Dell'Apa1, Simona Clò1

1ECU, Greenville, NC, USA, 2CTS, Rome, Italy

Comparative Analysis of Elasmobranch Vs Fish Landings in Italy Within the Frame of the Law 41/82: Consequences for Elasmobranch Fishery Management

Elasmobranchs are extremely vulnerable to overexploitation, owing to their specific biology and life history characteristics. European shark fisheries are virtually unregulated or unmanaged at both national and regional levels. We analyzed and compared national (ISTAT) historical data of elasmobranch and fish landings between 1959-2004, to investigate on changes in fishery exploitation toward elasmobranchs over time. Rays (Raja spp.) and smooth-hounds (Mustelus spp.) are the only elasmobranch categories present in the data, but other similar species could have been mistakenly annexed within these groups. Qualitative comparisons are useful since species description is often ambiguous and hard to be interpreted from landing data. Elasmobranch landings were steady until the beginning of the 1970’s, peaked in the 1990’s, then sharply declined. Mean annual landing for elasmobranchs in recent years (1997-2004) decreased 77% compared with previous years (1959-1982). This remarkable decrease may be attributed to elasmobranch overharvest occurred during the 1980’s and the 1990’s. That was likely an unreported effect of the 41/82 law issuing, known as “Plan for the rationalization and the development of commercial fishery”, and contributed to a serious decline in landings of sharks and rays. In order to foster elasmobranchs management and conservation, there is an urgent need to improve actual species stock assessment programs, to advance knowledge on catches, landings and production of sharks and rays species caught by Italian commercial fisheries. Also, elasmobranch management regulations should be tuned to their specific biology and life history characteristic, which significantly differ from those of teleost fishes.

 

0445 AES Conservation & Management, Minneapolis Ballroom G, Sunday 10 July 2011

Simon Gulak, John Carlson

National Marine Fisheries Service - Panama City Laboratory, Panama City Beach, FL, USA

Movements and Habitat Use of Dusky Shark, C. obscurus, in the Northwest Atlantic Ocean: a Preliminary Study Based on Archival Satellite Tags

In an attempt to improve the conservation status of dusky shark, the National Marine Fisheries Service established a time-area closure off North Carolina from January to July to reduce bycatch of neonate and juvenile dusky sharks. To better evaluate the closed area and determine critical habitat of dusky shark, we are deploying pop-off archival satellite tags (PAT). To date, seven tags have been deployed: two tags are pending pop- off, two tags transmitted unusable data, and three provided data that could be analyzed. Based on geolocation data, sharks generally traveled about 10 km day-1 with an average of 691 km in total. Overall, mean proportions of time at depth revealed dusky sharks spent the majority of their time in waters 20-40 m deep but did dive to depths of 400 m. Dusky sharks occupied temperatures of 24 °C over 50% of the time. Tagged sharks had varied movement patterns. One shark that was tagged off Key Largo, FL (USA) in January moved north along the US east coast to the North Carolina/Virginia border in June. A second shark also tagged off Key Largo, FL in March traveled south towards Cuba. The third shark, tagged off North Carolina in March, moved little from where it was initially tagged but problems with estimating the geolocation precluded fully determining its movement patterns in and around the closed area. Data from this study, along with future deployments, will be used to determine the efficacy of the time area closure for dusky sharks.

 

0091 Conservation & Management, Minneapolis Ballroom G, Sunday 10 July 2011

Romney McPhie1, Jackie King1, Sandy McFarlane1, Heather Brekke1

1Pacific Biological Station, Nanaimo, British Columbia, Canada, 2Fisheries and Oceans Canada, Vancouver, British Columbia, Canada

Have You Seen This Shark? Successes and Challenges in Monitoring the Endangered Basking Shark (Cetorhinus maximus) in British Columbia Waters through a Sightings Network

The Basking Shark (Cetorhinus maximus) is the second largest fish in the world, and one of the most imperilled. Historically, large groupings of this gentle, plankton-feeding giant were observed along the coast of British Columbia (B.C.), Canada, during the summer months; however, the entire northeast Pacific Ocean population ranging from Mexico to northern B.C. now numbers less than approximately 500 individuals. In February 2010, the Pacific population of Basking Shark was listed as endangered under Canada's Species at Risk Act. Broad strategies and approaches to recovery were identified by Fisheries and Oceans Canada, including Communication and Outreach, Monitoring and Inventory, and Stewardship. Integral to each of these strategies is the on-going implementation of a Basking Shark Sightings Network. Outreach materials are distributed yearly, and on-line, phone or e-mail reports of possible sightings are received from the public to determine how many Basking Sharks remain in B.C. waters and their potential for recovery. Since 2008, 58 reports have been made of both historical and current sightings, with 13 recent sightings (1996-2010) being confirmed. Future successes in connecting and cooperating with marine users in remote regions where Basking Sharks were historically abundant will ultimately determine the fate of this large - yet little-known - shark.

0510 Conservation & Management, Minneapolis Ballroom G, Sunday 10 July 2011

Michael McCallister, Ryan Ford, Christina Walker, Jim Gelsleichter

University of North Florida, Jacksonville, FL, USA

A Survey of the Shark Fauna in Northeast Florida Estuaries: Abundance, Distribution, and Identification of Potential Nursery Habitat

It is widely accepted that essential fish habitat (EFH) plays a crucial role in the life- history of many marine species. For many shark species, EFH includes nearshore and estuarine waters that serve as nursery habitat where sharks are born and/or juveniles spend the early part of their life. Examination of the literature shows the presence of shark nurseries in most major estuaries along the Atlantic and Gulf Coasts of the United States, however, there is a noticeable gap in data from the Northeast region of Florida. In May 2009 a long term bottom longline survey was initiated to assess the use of estuaries in Northeast Florida as shark nursery habitat. A total of 204 longlines were set in Nassau and Cumberland Sounds from June 2009 - October 2010 and 506 sharks, comprising 10 species, were caught. Atlantic sharpnose sharks (57.48% and 55.28%), blacktip sharks (15.35% and 19.88%), and bonnethead sharks (11.81% and 9.32%) were the most abundant species in both Cumberland and Nassau Sounds. Young of the year and juvenile individuals were caught for 9 of the 10 species. The data from this survey represents the first attempt to characterize the abundance and distribution of sharks in northeast Florida waters and to identify potential shark nursery habitat in this area.