Abstracts of AES Scientific Papers
American Elasmobranch Society 2001 Annual Meeting
ABSTRACTS - Part 1: Applegate through Francis
State College, Pennsylvania
APPLEGATE, SHELTON P.
Melchor Ocampo 461-8, University of Mexico, Mexico D,F, Mexico 11590 Mexico
The Origin of the Lamniform Sharks a Study in Morphology and Paleontology of Recent and fossil genera.
The oldest undoubted lamniform sharks are known from the Aptian of Texas. These consist of teeth that although small, show all of the charactistics and tooth positions of the genus Carcharias. Because of this,it is maintained that Carcharias is the most primitive lamniform genus,rather than Mitsukurina as currently thought.The orectolobid suite contention that precludes an ancestral relationship to the lamniform sharks is challenged. The taxonomic position of the Jurassic Palaeocarcharias is discussed, and it is suggested that this transitional genus warrents the ordinal rank of Palaeocarchariformes. Reasons for this placement are given. The dentitions,endocrania,fins and vertebrae of Orectobus,Palaeocarcharias,Carcharias, Scapanorhynchus and Mitsukurina are shown and there relationships considered. Some ideas are also given on ecological and behavioral changes. (Session 10, Saturday, July 7, Penn Stater, Room 207, 2:30)
*BLACKBURN, JASON K., NEER, JULIE A., THOMPSON, BRUCE A.
Wetland Resources Building, Louisiana State University, Baton Rouge, LA 70803
Using GIS and VHF radio telemetry to evaluate shark ecology and movements in Louisiana
Little data exist for sharks in Louisiana's coastal waters. The Coastal Fisheries Institute is conducting a three-year study to quantify the existence of shark nursery grounds in Louisiana. Experimental gillnets were used in Timbalier Bay and to date, eight species representing two families, have been observed. A Geographic Information System (GIS) was designed to investigate spatial relationships present within individual shark species and species assemblages. A shift in spatial distribution of blacktip, Carcharhinus limbatus, and Atlantic sharpnose, Rhizoprionodon terraenovae, sharks was observed. Bonnethead, Sphyrna tiburo, and scalloped hammerhead, Sphyrna lewini, sharks were only observed in the 2000 samples. A pilot study using VHF radio telemetry is currently being conducted to investigate bull shark, Carcharhinus leucas, movements in the Atchafalaya Basin. Six VHF radio transmitters were embedded in foam float tags and attached to juvenile sharks approximately one meter in length. Tagged individuals were relocated every five days and movements monitored for 24-48 hours. Telemetry data are being interpolated and analyzed in a GIS environment. GIS can be a powerful tool for examining spatial and temporal patterns in biological data, provided that the technology is utilized within the context of the biological system being examined. (Session 10, Saturday, July 7, Penn Stater, Room 207, 11:15)
Widdergasse 8, CH-8001 Zurich, University of Zurich, Winddergasse, Zurich CH-8057 Switzerland
Jumping sharks, with special emphasis on the blacktip shark, (Carcharhinus limbatus)
A lot of attention has lately been given on breaching white sharks, (Carcharodon carcharias), using decoys to trigger such reactions. The motivational reason for these animals seem clear, nevertheless detailed experiments have to be conducted to understand this behavior completely. Other sharks species jump as well but for different motivational reasons. One of the most spectacular jumpers in the Caribbean and Bahamian waters is the blacktip shark, (Carcharhinus limbatus). For the first time, some of these jumps and starts have been filmed underwater making it possible to investigate this behavior from a new point of view. This paper gives an overview of why sharks jump, with special emphasis on the blacktip shark and its motivational reason. (Session 7, Saturday, July 7, Penn Stater, Room 207, 8:15)
BURGESS, GEORGE H., *COYNE, KEVIN R., KNICKLE, CRAIG D.
Dickinson Hall, Florida Museum of Natural History, Gainesville, FL 32611
Bycatch data for the southeastern United States commercial shark fishery
From 1994 to 2000, at-sea observers from the Florida Museum of Natural History Commercial Shark Fishery Observer Program (CSFOP) monitored and collected data on 785 longline sets, totaling 6.7 million hook hours observed. Utilizing at-sea data, we are able to quantify bycatch composition and bycatch disposition, and fishing effort. This information is unobtainable in dockside observer programs. Bycatch was allocated into six broad categories (marine mammal, sea turtle, fish, invertebrate, alga, human refuse). Fish and turtle catches were identified to species level, invertebrate catch to lowest taxonomic level. Total bycatch and catch per unit of fishing effort (CPUE) for all bycatch (2543 individuals, 3.78 individuals per 10,000 hook hrs) was significantly lower than that for targeted sharks (35554, 53.1 sharks per 10,000 hook hrs). The Florida Gulf Coast region had the highest total bycatch of all sample areas (60% of total bycatch) and highest CPUE (2.27 per 10,000 hook-hrs). There was no significant variation from year to year in total bycatch or bycatch composition. Fish dominated total bycatch composition (67.8% of total bycatch) and bycatch CPUE (2.57 per 10,000 hook-hrs) followed by invertebrates (28.4%, 1.08 per 10,000 hook-hrs). Perciform and batoid fishes comprised 87% of the total fish bycatch. The Florida Gulf coast region had the greatest diversity of fishes and invertebrates. Disposition of bycatch varied with type and commercial value. Commercially valuable fish bycatch was dominated by serranids (Epinephelus morio and Mycteroperca microlepis) encompassing 43% of the total fish bycatch, Rachycentron canadum (7%), and lutjanids (Lutjanus analis and Lutjanus buccanella, 6%). Of these commercially valuable fishes, greater than 40% were retained for sale. 57% of Sphyraena barracuda and anguilliform fishes (8% and 9% of total fish bycatch, respectively) caught were utilized as bait. Echinoids and asteroids dominated the invertebrate bycatch (44% of invertebrate bycatch). Greater than 90% of invertebrates caught as bycatch were discarded. Species of special conservation interest (sea turtles, dolphins, and seabirds) comprised less than 1% of the total bycatch (34 sea turtles, 1 dolphin, and 1 pelican). Of the 34 sea turtles caught (24 Caretta carreta, 3 Dermochelys coriacea, and 7 unidentified), 18 were released alive and 7 discarded dead. Nine turtles were released at the vessel without knowledge of condition. The single dolphin was released alive and the pelican, discarded dead. Total bycatch numbers are low when compared to the target species (sharks) catch, making this a relatively clean fishery. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)
BURGESS, GEORGE H., KNICKLE, CRAIG D., *COYNE, KEVIN R.
Dickinson Hall, University of Florida, Florida Museum of Natural History, Gainesville, FL 32611
Overview of the Commercial Shark Fishery Observer Program (CSFOP)
The Commercial Shark Fishery Observer Program (CSFOP) is a cooperative effort of the Florida Museum of Natural History and the fishers of the United States Atlantic commercial shark fishery. Historically supported by grants from U.S. Department of Commerce funding programs, the CSFOP places fishery observers on cooperating commercial shark fishing vessels to observe the composition and disposition of the catch and by-catch. Monitoring of the southeastern United States shark fishery began in January 1994 and funding is in place through the summer of 2001. Data gathered in this program is utilized in developing management strategies for the fishery. Since the shark catch is headed, gutted and finned at sea, port sampling is not a viable means of quantifying the catch because the marketed carcasses are difficult, if not impossible, to identify to species. In addition, by-catch in the fishery is discarded at sea or used as bait and thus cannot be quantified at the dock. The CSFOP's ground-truthing of the at-sea catch provides an invaluable source of information for both fishers and regulators alike. This accurate data, gathered by an unbiased team of academic observers, serves as a common starting point for management discussions during the regulatory process. Through the end of 2000, the CSFOP program monitored 6.7 million hook-hours of effort on 785 long-line sets, collecting biological data on 34 species and more than 35,000 individual sharks. The sandbar shark, (Carcharhinus plumbeus), a large coastal species, made up the majority of the overall catch (35.5 %), while a small coastal, the Atlantic sharpnose shark (Rhizoprionodon terraenovae), comprised 30% of the total catch. Overall, 61% of all sharks caught were landed and marketed, 21% were used for bait and 14% were tagged and/or released. CPUE (catch per unit effort) for large coastal species in three major fishing areas (Florida Atlantic coast, Florida Gulf coast and North Carolina) has shown a gradual increase since the inception of the program. Variation in catch composition and disposition has been observed from region to region. Off the Florida East coast, R. terraenovae represented 57% of the total catch while C. plumbeus comprised 14.5%. By comparison, 33% of sharks caught off Florida's Gulf coast were C. plumbeus and 18.5% were blacktip sharks (Carcharhinus limbatus). Off North Carolina, C. plumbeus dominated the total catch at 64% with R. terraenovae at 11.5%. For each region, the percentage of the total catch marketed was 68%, 71% and 80%, respectfully. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)
*BURGESS, GEORGE H., MOREY, SEAN
Dickinson Hall, University of Florida, Florida Museum of Natural History, Gainesville, FL 32611
The shark in modern culture: beauty and the beast
Sharks have always elicited a mixture of emotions in humans, ranging from fear and loathing to respect and admiration. Modern culture has been greatly influenced by mass marketing, as print and video media have become routinely accessible throughout much of the world. Sharks commonly are used in advertising campaigns where they often are portrayed as strong, fierce, and dangerous, or humorously lampooned as inept and cowardly. They frequently appear as protagonists in films and television shows, video and print cartoons, video games, and comic strips. Political cartoonists frequently portray politicians, lawyers and other seedy professionals as shark caricatures. The public image of sharks in North America has changed perceptibly in recent years as the mass media have begun to air natural history programming that presents a more balanced view of sharks featuring the words of contributing biologists and conservationists. (Session 26, Monday, July 9, Penn Stater, Room 207, 2:30)
*CAILLIET, GREGOR M., BURTON, E. J., COPE, J. M., KERR, L. A., LEA, R. N.
(GMC, JMC, LAK) 8272 Moss Landing Road, Moss Landing Marine Laboratories, Moss Landing, CA 95039; (EJB) 299 Foam Street, Monterey Bay National Marine Sanctuary, Monterey, CA 93940; (RNL) 20 Lower Ragsdale Drive, California Department of Fish and Game, Monterey, CA 93940
A database of existing literature on the life histories of selected nearshore fishes of California
As part of the Marine Life Management and Protection Acts, the California Department of Fish and Game (CDFG) must produce stock assessments and fishery management plans for fishes inhabiting nearshore habitats of California. We compiled a list of 124 nearshore fish species currently taken as part of California=s nearshore and live-fish fisheries, and analyzed the existing knowledge of their life histories (age, growth, maturity, longevity, habitat utilization, reproduction, recruitment, trophic relationships, and population/stock health, structure, and genetics) relative to their management and vulnerability. We thoroughly surveyed the existing literature, directed by a life history parameter questionnaire, and constructed a life history data matrix of the nearshore fish species on the list. Many gaps in the existing knowledge were identified, and specific research projects initiated on such subjects as age and size at maturity, age validation, genetics, and mobility of fish stocks subject to the nearshore fisheries of California. It is hoped that this project will be useful to those involved with the management of nearshore fisheries, and will be complimented by additions from future literature on the life histories of these fishes. It is available from the CDFG web site (www.dfg.ca.gov/Marine Resources) or from Nancy Wright (email@example.com). (Session 4, Friday, July 6, Penn Stater, Room 206, 4:00)
*CARLSON, JOHN K., CORTES, ENRIC, BETHEA, DANA
(JKC, EC) 3500 Delwood Beach Rd, National Marine Fisheries Service, Panama City, FL 32408; (DB) 1100 University Parkway, University of West Florida, Pensacola, FL 32514
Population dynamics of the finetooth shark, Carcharhinus isodon, in the northeast Gulf of Mexico
The population dynamics of the finetooth shark, Carcharhinus isodon, in the northeastern Gulf of Mexico were studied by determining age, growth, size-at-maturity, natural mortality, productivity, and elasticity characteristics of the population.
Von Bertalanffy growth parameters were estimated as
Linf =1587 mm total length(TL),
K=0.23 yr - 1, and to 2.12 yr for females and 1352 mm TL,
K=0.38 yr - 1, and to =-1.48 yr for males.
The oldest aged specimens were 8.1 and 8.2 yr, and theoretical longevity estimates were 15.3 and 9.1 yr, for females and males, respectively. Median length at maturity was 1187 and 1230 mm TL, equivalent to 4.1 and 4.5 yr, for males and females, respectively. Instantaneous rates of natural mortality ranged from 0.598 to 0.848 when expressed as annual rates of survivorship. Rebound potentials averaged 0.037 yr-1 when the population level that produces maximum sustainable yield is assumed to occur at an instantaneous total mortality rate equaling 1.5M, and 0.066 yr - 1 when Z=2M. Mean generation lengths averaged 7 yr. Stage elasticities averaged 12.5% for age-0 survival, 49.7% for juvenile survival, and 37.8% for adult survival. In all, the finetooth shark exhibits population characteristics intermediate to those sharks in the small coastal complex and those from some large coastal species. (Session 3, Friday, July 6, Penn Stater, Room 207, 2:45)
*CARTAMIL, DANIEL, VAUDO, JEREMY, LOWE, CHRISTOPHER, WETHERBEE, BRADLEY, HOLLAND, KIM
(DC, JV, CL) 1250 Bellflower Boulevard, California State University, Long Beach, Long Beach, CA 90840; (BW) NOAA/NMFS/NEFSC, NOAA/NMFS/NEFSC, Narragansett, RI 02882; (KH) Hawaii Institute of Marine Biology, Hawaii Institute of Marine Biology, Kaneohe, HI 96744
Diel movement patterns of the Hawaiian stingray, Dasyatis lata, in Kaneohe Bay, Hawaii.
The Hawaiian stingray, Dasyatis lata, is likely the most abundant benthic elasmobranch in nearshore Hawaiian waters. Acoustic telemetry was used to track the movements of seven rays in Kaneohe Bay, Oahu, Hawaii. Rays were tracked continuously over 50 hr periods. Geographical position was determined at 15-minute intervals during tracks, and was analyzed to determine space utilization and rate of movement. Rays were found to utilize significantly larger average activity spaces at night (0.83 - 0.70 km2) than during daylight hours (0.12 - 0.15 km2). Rates of movement were also significantly higher at night and crepuscular periods (p<0.001) than during the day. Mean total activity space for rays tracked was 1.32 km2, and maximum swimming speed was approximately 1.9 km/hr. D. lata and juvenile scalloped hammerhead (Sphyrna lewini) pups in Kaneohe Bay show overlap in habitat use and time of activity; this may indicate competition for food resources. (Session 10, Saturday, July 7, Penn Stater, Room 207, 10:45)
Central Park West at 79th Street, American Museum of Natural History, New York, NY 10024
Taxonomy of the Neotropical freshwater stingrays (Chondrichthyes: Potamotrygonidae).
The Neotropical stingrays of the family Potamotrygonidae are confined to South American river drainages that flow into the Caribbean Sea or Atlantic Ocean. Even though frequently imported by the aquarium trade, species of the family remain poorly known in relation to their systematics and general biology. Factors that further complicate species identification are the great amount of intraspecific variation in color pattern and generally conservative meristic and morphometric features. Furthermore, many nominal species have been inadequately described in the literature and have poorly preserved type specimens. A revision of the family was initiated ten years ago, and to date at least four new species have been found. Although there is variation within species, coloration does distinguish some of them, and combinations of characters are ususally employed to separate species. A conservative estimate indicates the existence of 18 previously described valid species (in addition to the new species). This total may increase as some widespread species may require further subdivision. New species exist in all three valid genera (Potamotrygon, Paratrygon and Plesiotrygon), but primarily in Potamotrygon. This summary of the family was prepared originally for the CLOFFSCA project. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)
*CASPER, BRANDON M., LOBEL, PHILLIP S., YAN, HONG Y.
(BMC, PSL) 7 MBL St., Boston University, Woods Hole, MA 02543; (HYY) Thomas Hunt School of Biological Sciences, University of Kentucky, Lexington, KY 40506
Comparative hearing sensitivity among free-swimming and bottom-dwelling elasmobranchs.
Corwin (1978) found a correlation between size and structure of auditory anatomy and feeding strategies among elasmobranchs. Based on this correlation, he hypothesized that free-swimming elasmobranchs have more sensitive hearing than bottom-dwelling elasmobranchs. Hearing sensitivity, however, has rarely been explored in free-swimming elasmobranchs (n=2 carcharinids) or bottom-dwelling elasmobranchs (n=1 heterodontid), and has never been examined in skates or rays. For this project an audiogram was obtained for the little skate, Raja erinacea (Rajidae), using two methods, behavioral conditioning and auditory brainstem response (ABR). This audiogram was compared to those of free-swimming and bottom-dwelling elasmobranchs to elucidate the relationship between hearing sensitivity, auditory anatomy and feeding strategy. Results suggest that R. erinacea has less sensitive hearing than free-swimming elasmobranchs. The most sensitive hearing frequency of R. erinacea (200 Hz) is more than 20 dB re 1 Pa lower than the most sensitive hearing frequency of either of the free-swimming carcharinids (320 Hz). This corroborates Corwin&'s (1978) hypothesis, which was based on anatomical data. Anatomical auditory data, including the size of the macula neglecta and number of hair cells, will be obtained from R. erinacea and compared with Corwin&'s (1978) data to further test this relationship. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)
CASTRO, JOSÉ I.
1600 Ken Thompson Parkway, NOAA/NMFS and Mote Marine Laboratory, Sarasota, FL 34236
On the origin of the English word shark and the Spanish tiburn
Sharks are conspicuously absent from the medieval bestiaries that described the known faunas and some imagianry animals as well. The reason for this omission is that large sharks were basically unknown until the voyages of discovery at the end of the 15th century. Medieval man fished rivers and the seashore and did not usually encounter large sharks. Both the Spanish and the English were familiar with the small sharks that inhabit their shores and had names for the small sharks, cazon and nuss respectively. When the Spanish encoutered large sharks in the Americas, they borrowed theCarib word tiburn to name them. The English later used the same word tiburn and used it through the 17th century. Later, in the late 1560&'s, the English borrowed the Mayan word xoc which means shark and tiburn disappeared from the English languaje. (Session 26, Monday, July 9, Penn Stater, Room 207, 9:30)
CASTRO, JOSÉ I.
1600 Ken Thompson Parkway, NOAA/NMFS and Mote Marine Laboratory, Sarasota, FL 34236
Reproduction in the smalltooth thresher shark, Alopias pelagicus off Baja California.
The smalltooth thresher is an aplacental species that nourishes its embryos through oophagy (egg eating). The first two egg capsules produced by ovulating females contain a single egg, and one goes into each uterus. Egg capsules produced subsequently contain multiple eggs. Embryos star feeding on eggs very early in development. Embryos do not acquire the distended yolk stomachs that other lamnoid embryos have. There are at least two types of feeding egg capsules. Egg capsules produced late in gestation are about 20 times larger than those produced early in gestation. Embryos reach about 140-150 cm at birth. Embryos of all sizes can be found at any time, indicating that the species reproduces throughout the year. Only two young are produced per brood. (Session 10, Saturday, July 7, Penn Stater, Room 207, 2:00)
*CHARVET-ALMEIDA, PATRICIA, ROSA, RICARDO S.
(PC) Rua dos Mundurucus, 2445 ap. 1202, Museu Paraense Emilio Goeldi, Belm, Par 66040-270 Brazil; (RSR) Departamento de Sistemtica e Ecologia, Universidade Federal da Paraba, Joo Pessoa, Paraba 58059-900 Brazil
A New Genus and Species of Freshwater Stingray (Potamotrygonidae) from the Lower Amazon Drainage
The family Potamotrygonidae Garman, 1877 includes freshwater stingrays found in most river systems of South America. There are three known genera for this family: Paratrygon, Plesiotrygon, both monotypic, and Potamotrygon, including aproximately 21 valid species. Two specimens of an unidentified genus and species recently were captured (August 2000 and January 2001) in the State of Par, northern Brazil. One of the rays is a juvenile individual while the other, considering clasper calcification, possibly is a sub-adult. Both cannot be assigned to any of the known species or genera. The main dignostic charcteristics of this new genus and species are: relatively long filiform tail, lacking dorsal and ventral finfolds; absence of caudal sting; disc nearly circular with an anteromedian prominence; lack of a knob-shaped process on the external margin of spiracle and non-pedunculate very small eyes. This ray is locally known as maramass or aramass ray. It is considered by local fishermen less agressive than other, more abundant, potamotrygonid rays and probably is rare in this region. No dissection of these specimens was performed yet and data concerning internal aspects are being obtained by means of radiological techniques. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)
Panama City Laboratory, National Marine Fisheries Service, Panama City, FL 32408
Demographic modeling under uncertainty: application to shark conservation
Incorporating the effect of uncertainty and random variation in vital rates into demographic analyses is a useful approach that is increasingly being applied in conservation biology, but rarely used for marine taxa and not explored for sharks. This paper uses Monte Carlo simulation to calculate population growth rates (), generation times, and matrix elasticities for a suite of shark populations. The potential for population exploitation or recovery is also evaluated and the most vulnerable life stages identified using this probabilistic approach. Elasticity patterns for shark populations are linked to life-history characteristics to categorize those populations according to their likely response to perturbation of the various life stages. The 41 populations examined fall along a fast-slow continuum of life-history characteristics linked to stage elasticity patterns. Sharks with early age at maturity, low longevity, and large litter size have high values and short generation times, whereas sharks that mature late, have high longevity, and small litter size have low values and long generation times. Sharks at the fast end of the spectrum tend to have comparable adult and juvenile survival elasticities, whereas sharks at the slow end of the continuum have very high juvenile survival and fertility elasticities. (Session 3, Friday, July 6, Penn Stater, Room 207, 2:15)
*DRIGGERS, WILLIAM B. I., ANDERSON, CHRISTOPHER J., DEAN, JOHN M., QUATTRO, JOSEPH M.
University of South Carolina, Columbia, SC 29208
Population structure of the blacknose shark (Carcharhinus acronotus) in the southeastern United States, based on mtDNA analysis
We describe the results of genetic assays of blacknose sharks (Carcharhinus acronotus) sampled from the western North Atlantic and Gulf of Mexico. Mitochondrial DNA (d-loop control region) sequence variation was assayed in 160 individuals. This genetic variation was partitioned into within and among basin components. These components are used to address the null hypothesis that the two basins sampled do not harbor genetically distinct populations of blacknose sharks. Recommendations for conservation management are discussed. (Session 3, Friday, July 6, Penn Stater, Room 207, 4:30)
*DUARTE, PEDRO N., MENEZES, GUI M., SILVA, ALEXANDRE A. D.
Cais Sta. Cruz, Universidade dos A´cores, Horta, A´cores 9901-862 Horta
Portugal Distribution and abundance of Velvet Belly, Etmopterus spinax, and Smooth Lanternshark, Etmopterus pusillus, in the deepwaters of the Azores
Sharks apparently play an ecological role of great relevance in the demersal community of the Azorean deepwaters. Two species are particularly significant, given their abundance and top predatory status in bottom waters deeper than 600m: Etmopterus spinax and E. pusillus. CPUE and size structure data collected from research cruise surveys on an annual basis are available for the Azorean main fishing grounds. However, no particular attention has yet been given to either species, since they hold no commercial relevance in the Azorean demersal fisheries. Trends on distribution, both geographical and bathymetrical, and abundance of Etmopterus spinax and E. pusillus are presented and discussed, in an attempt to shed some light on the ecological importance of both species in the Azorean deepwater domain. (Session 3, Friday, July 6, Penn Stater, Room 207, 1:45)
St. John&'s, Newfoundland, Memorial University of Newfoundland, St. John&'s, Newfoundland A1B 3X9 Canada
Behavioral and population studies of sixgill sharks (Hexanchus griseus) at a shallow water site using video and still imagery.
The bluntnose sixgill shark (Hexanchus griseus) is one of the largest of fishes, perhaps the most widely distributed vertebrate, and a top predator throughout its wide range. However, virtually nothing is known of its basic population biology or behavior. In British Columbia, this normally deep water shark is known to regularly frequent one shallow (20 m) reef (Flora Islets) in the Strait of Georgia where sixgill behaviour can be recorded using still and video imagery. A fully submersible time lapse video system was used to obtain quantitative data on the relative activity of sixgills at Flora as a function of time of year, time of day, tidal cycle, lunar cycle, water temperature, and illumination. A 3 camera stereo video system was used to obtain population size-frequency data by sex as well as measures of absolute swimming speed. Close-up 35 mm photographs were used to identify individual sharks based on distinctive scarring patterns. Resightings of these known individuals were used to study the time course of use of the reef by individuals and to provide a rough estimate of the size of the population of sixgill sharks that visit Flora in a particular year. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)
*FANGUE, NANN A., BENNETT, WAYNE A.
11000 University Parkway, University of West Florida, Pensacola, FL 32514
Thermal Tolerance Dynamics of Laboratory Acclimated and Field Acclimatized Atlantic Stingray, Dasyatis sabina
Physiological thermal tolerance adaptations of elasmobranchs are entirely unknown, while responses of bony fishes to temperature extremes have been exhaustively studied for over 100 years. We used critical thermal methodology to investigate laboratory and field temperature tolerance responses of nearly 400 Atlantic stingrays, Dasyatis sabina, from St. Joseph&'s Bay, Florida. Stingrays acclimated in the laboratory at temperatures between 11.6 and 37.0¡C had critical thermal maxima (CTMax) and minima (CTMin) ranging from 35.6 to 43.2¡C and 0.8 to 10.8¡C, respectively. For every 1.0¡C increase in acclimation temperature, heat tolerance increased 0.31¡C and cold tolerance decreased 0.43¡C. Fish could not be acclimated above 37.0¡C regardless of the rate or pattern of change in acclimation temperature. An ecological thermal tolerance polygon of CTMax/CTMin on acclimation temperature yielded a total area of 1247¡C2 the second largest ever measured in a fish. Monthly CTMax and CTMin values of field acclimatized stingrays ranged from 37.6 to 41.8¡C and 2.6 to 6.6¡C, respectively. On average, CTMax values were 15.6¡C above, and CTMin values were 18.6¡C below, mean water temperatures. Our data demonstrate that Atlantic stingrays are remarkably eurythermic and well suited for inhabiting shallow inland bays and estuaries subject to dramatic diel and seasonal temperature changes. (Session 20, Sunday, July 8, Penn Stater, Room 207, 12:00)
*FERRY-GRAHAM, LARA A., SUMMERS, ADAM P., CAILLIET, GREGOR M.
(LAF) 1 Shields Ave, University of California Davis, Davis, CA 95616; (APS) 3060 Valley Life Sciences Building, University of California Berkeley, Berkeley, CA 94720; (GMC) 8272 Moss Landing Road, Moss Landing Marine Labs, Moss Landing, CA 95039
From Icons to Art: The Cultural Significance of Sharks and Man
Our goals in this symposium are two-fold: to trace the history of elasmobranchs&' influence on human cultures through the use of art, and to understand how they are now perceived given how much we now know scientifically. Art is a somewhat unusual subject for a meeting like AES/ASIH. However, historically speaking, science and art were different aspects of the same discipline. Many great thinkers, iconoclasts, and renaissance men realized that the study of objects for representation in art requires amazing attention to detail and a fine understanding of both biological function and the organism&'s role in a larger system. Science and art, in this sense, become complementary and interchangeable. A focus of our symposium is the shark as the object of art, how that art has influenced human cultures, and how it reveals cultural perceptions to us. The symbol of the shark has also changed over time, and we will explore how the interplay between recent scientific ventures and modern forms of expressive media (modern art, news &'media&', and public outreach and education) has affected the perception of sharks in our culture. (Session 26, Monday, July 9, Penn Stater, Room 207, 8:15)
*FISK, AARON T., SANDAU, COURTNEY D.
(ATF) National Water Research Institute, Environment Canada, Burlington, Ontario L7R 4A6 Canada; (CDS) Center for Disease Control, Center for Disease Control, Atlanta, GA 30341
Organochlorine contaminants and metabolites in elasmobranches: Have ecotoxicologists missed a susceptible animal?
Organochlorine contaminants (OCs) are industrial and agricultural chemicals (e.g., PCBs and DDT) that are an environmental concern because they are bioaccumulative, persistent and toxic. These chemicals have been shown to cause stress at the individual and population level in fish, birds, mammals and humans. Recently, metabolites of OCs, in particular halogenated phenolics compounds (HPCs), have been shown to be potent hormone mimics and potential endocrine disruptors. Although there is extensive data on OC levels and effects in wildlife there is almost no information on levels or effects of OCs and metabolites for elasmobranches. This is surprising because many elasmobranches occupy high trophic levels and may accumulate high levels of OCs through food web transfer and biomagnification. A recent measurement of OCs and HPCs in Greenland sharks (Somniosus microcephalus) showed this Arctic predator to be among the most contaminated organisms in the Canadian Arctic. High levels of HPCs suggest an active metabolic capacity in the sharks that requires further research. These results highlight the need to evaluate these chemicals in sharks, particularly those that feed in more contaminated regions of the world. (Session 16, Sunday, July 8, Penn Stater, Room 207, 8:15)
*FISK, AARON T., TITTLEMIER, SHERYL A., PRANSCHKE, JENNIFER L., NORSTROM, ROSS J.
(ATF) NWRI, Environment Canada, Burlington, Ontario L7R 4A6 Canada; (SAT) NWRC, Carleton, Hull, Quebec K1A 0H3 Canada; (JLP) NWRC, Carleton University, Hull, Quebec K1A 0H3 Canada; (RJN) NWRC, Environment Canada, Hull, Quebec K1A 0H3 Canada
Organochlorine contaminants and stable isotopes of nitrogen and carbon in the Greenland shark (Somniosus microcephalus): Insights into the feeding ecology of the Arctic&'s only shark
Organochlorine contaminants (OCs), stable isotopes of N (15N) and C 15C) and stomach contents were measured in 17 Greenland sharks (Somniosus microcephalus) and 4 turbot (Reinhardtius hippoglossoides) collected in the Davis Strait region to provide insight on the feeding ecology of this little studied shark. Values of 15N increased with shark fork length suggesting a shift to larger prey with growth. Stable isotope values place the Greenland shark at the same trophic level as the turbot and ringed seal but with a more pelagic source of carbon. However, more study should be undertaken to determine whether high tissue urea levels found in sharks influence 15N values, as this may underestimate shark trophic position. Concentrations of OCs (lipid basis) in Greenland shark were 10-100 and 3-10 X higher than those observed in turbot and ringed seals, respectively, suggesting a higher trophic level for the shark than implied by 15N values. Concentrations of DDT in Greenland sharks are among the highest in Canadian Arctic biota, which may be related to low metabolism and a long life span. The presence of a ringed seal in the stomach of one shark, relatively high levels of oxychlordane in others, and high OCs concentrations suggest that seals may be a common prey item of Greenland sharks. (Session 7, Saturday, July 7, Penn Stater, Room 207, 8:30)
*FITZGERALD, TIMOTHY P., HOLLAND, KIM N.
PO Box 1346, University of Hawaii, Kaneohe, HI 96744
Electroreception in juvenile sandbar sharks, Carcharhinus plumbeus.
Sharks possess a sensory system, the ampullae of Lorenzini, which enables them to detect the bioelectric fields emanating from visually cryptic prey items. These electric fields are usually weak and either DC or of low frequency. This study quantifies the behavioral electrosensitivity of juvenile sandbar sharks, Carcharhinus plumbeus, to prey-simulating (2 cm dipole separation) and non-prey-simulating (>2 cm separation) fields. Electric field stimuli were varied in strength, size and sinusoidal frequency. Sharks responded to DC fields at field strengths between 10 and 150 nanovolts/cm (10 - 9 V/cm), as found for other species. Response rate (no. attacks/no. passes over a dipole) was proportional to field strength for both prey-simulating and non-prey-simulating stimuli. Sharks were exposed to dipoles of 2-20 cm separation, and showed no polarity preference at greater electrode separation. Sharks oriented to AC fields between 5 Hz and 10 kHz, although preliminary data show they are unable to detect frequency information above 50 Hz. The results indicate that juvenile sandbar sharks are capable of detecting a broad range of electric fields, including those of large dipole separation and high frequency, which may be important for behaviors other than foraging. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)
*FRANCIS, MALCOLM P., DUFFY, CLINTON A. J.
(MPF) P. O. Box 14901, National Institute of Water and Atmospheric Research, Wellington, Wellington New Zealand; (CAJD) P. O. Box 112, Department of Conservation, Hamilton, Waikato New Zealand
Hibernating, hiding or hanging out - what do basking sharks (Cetorhinus maximus) do in winter?
Basking sharks occur throughout New Zealand, and are seen inshore mainly in spring-summer. 208 sharks were recorded by scientific observers aboard trawlers over 10 years, with up to 14 sharks caught per tow. Most captures came from the hoki and barracouta fisheries off Banks Peninsula (EC), the hoki fishery off the west coast South Island (WC) and the squid fishery around the Snares and Auckland Islands (SA). The EC and SA fisheries catch sharks in spring-summer, whereas the WC fishery catches them in winter. Sharks were caught mainly in 100-300 m in SA, 100-600 m in EC and 500-800 m in WC. There is some evidence that sharks are taken mainly on or near the bottom. Most WC and SA sharks were males 7-8 m long. The EC fishery had a more even sex ratio, and a high proportion of immature sharks (4-6 m long). Few large females were recorded. Winter catches of sharks in WC at depths up to 800 m explain their absence from shallow coastal waters at this time. We suggest that basking sharks do not hibernate on the seabed in winter, but remain active on the upper continental slope. (Session 7, Saturday, July 7, Penn Stater, Room 207, 9:15)