Florida Museum of Natural History

Abstracts of AES Scientific Papers

American Elasmobranch Society 16th Annual Meeting
June 14-20,2000 La Paz, B.C.S., México, U.S.A.
ABSTRACTS - Part 1: Alava through Crozier

(AMNR; ACA) World Wildlife Fund - Philippines 23 Maalindog St., UP Village, Diliman, Quezon City 1101, Philippines; (MMML; GJPA; UABR) Marine Laboratory, Silliman University,Dumaguete City 6200, Philippines

Elasmobranch biodiversity and conservation project in the Philippines (Phase 1)

In October 1998, WWF-Philippines iniated a 3-year research and conservation project on elasmobranch biodiversity in the highly diverse Sulu Sea. The project endeavors to identify conservation and management needs of Philippine elasmobranchs through fisheries assessments in selected sites around the Sulu Sea, ultimately leading to a National Plan of Action ensuring sustainable elasmobranch utilization in the country. This initiative is supported by WWF-US and implemented in the Visayas and Mindanao by Silliman University Marine Laboratory. Between October 1998 and June 1999, Phase 1 project activities involved: 1) profiling of elasmobranch fishery sites based on primary and secondary data sources; 2) assessm,ents of fishery, trade and resource utilization of elasmobranch populations in selected sites; 3) voucher specimen collection from market and landing sites; and 4) education and information campaign. Secondary sources showed a collective list of 114 species under 24 chondrichthyan families caught in at least nine different fishing methods in about 44 provinces. Collections from market and landing sites revealed a preliminary checklist of 59 species under 20 families, 24 species of which were considered potentially new records to the Philippines and/or to science. Highlight of the education and information component, was the convention of the First Philippine Elasmobranch Biology and Taxonomy Training-Workshop in Silliman University, southern Philippines on 7th-13th May, 1999.

16/06/2000 - 03:15:00 PM - Salon Madre Perla


Universidad de Guadalajara. Centro Universitario de Ciencias Biológicas y Agropecuarias. Km. 15.5 Carretera a Nogales. Las Agujas, Nextipac, Zapopan, Jalisco.

Environmental Education as a tool in the study of the elasmobranchs

Many people still believe that sharks are the most dangerous specie worldwide but if we try to improve its image using strategies such the environmental education, we can reinforce a better reputation of this top-predator. With this material I offer to all of you and helping me with some games and educative material I wish I would like to make conscience, mainly to children, whom I made this poster in order to play and learn at the same time, and respect this species.

19/06/2000 - 08:00:00 AM - Salon Madre Perla


(AM; BK; AR) University of Colorado, USA; ( AP; CJ), University of Aberdeen, Scotland; (GC) Natal Sharks Board, South Africa; (JS; HM; BBD) CSIRO, Australia; (MF; CD) New Zealand; ( SA; PP), PT. Reyes Observatory, USA

Population genetics of the great white shark

White sharks were sampled from Australia, New Zealand, Japan, California, Brazil and South Africa. Phylogenetic analysis of complete control regions sequences revealed two major groups that differ at about 4% of the sites, and within each clade several distinct haplotypes were discovered. The two major clades were largely separated by Ocean Basins, with one clade in the Pacific and the other in the Atlantic and Indian Oceans. Only one individual was out of place. Overall, the mtDNA data show a high degree of geoographic differentiation. A notable exception is that the samples from Australia and New Zealand appears as if they conprise the same population.

18/06/2000 - 03:00:00 PM - Salon Madre Perla


Shark Research Insitute, P.O. Box 40, Princeton, New Jersey 08540,

Aggregations of whale sharks (Rhincodon typus) occur each year off South Africa (Indian Ocean) and in the waters surrounding Utila, Bay Islands Honduras (Caribbean Sea) where they form the basis of an ecotourism industry

In 1998 and 1999 the Shark Research Institute deployed satellite tags on 5 whale sharks in an effort to gather information on their long term and short term movements. Problems were encountered with the attachment of the tags to the sharks. Satellite tags were attached to the sharks by divers and various tag-anchors were utilized with varying degrees of success. Tethered tags were attached by divers and a variety of tag-anchors were utilized. Data received so far is encouraging, which will enable us to drawn a picture of the day to day life of a whale shark.

15/06/2000 - 02:45:00 PM - Salon Madre Perla


Instituto de Geología,U.N.A.M. Ciudad Universitaria, Delegación Coyoacán, D.F., C.P. 04510, México.

The Carcharocles, Carcharodon question

Recently investigators and amateur paleoichthyologists have stated that they had a case for placing Carcharodon megalodon in a separate genus "Carcharocles". The argument being that the living Carcharodon carcharias was derived from a fossil ancestor "Cosmopolitodus" which is a name used for Isurus xiphodon. This contradicts the phylogeny given by others. Jordan named "Carcharocles' for Carcharodon auriculatus an Eocene species, which has strong lateral denticles and erroneously said to have teeth narrower and more erect with their edges being finely serrated. The teeth of C. auriculatus are curved and strongly serrate. Therefore Jordan's suite of characters are not completely applicable to the "Carcharocles" question, on the contary It will be shown that C. carcharias and C. megalodon are very close but distanctly different from any species of Isurus living or fossil. The genus Isurus can be shown to be separated from Carcharodon in many characters other then teeth. We therefore still believe that C. megalodon has a close relationship with C. carcharias and together they should be placed in the same genus.

18/06/2000 - 02:45:00 PM - Salon Madre Perla


(ACA)Pringles 837, 4th floor, Apt. 10 (1183) Cap. Fed., Buenos Aires, Argentina. (LAL) Lab. de Embriología Animal, Fac. Cs. Exactas y Nats., U.B.A. (1428) Bs. As., Argentina. (GS) Instituto de Investigaciones Biomédicas, Fundación Pablo Cassará, (1440) Bs. As., Argentina. (DGE) Inst. de Biología Marina y Pesquera "Alte. Storni" CC 104, 8520 San Antonio Oeste, Río Negro, Argentina.

Reproductive biology and basic aspects of spermatogenesis in the angel shark, Squatina guggenheim, Marini, (Elasmobranchii, Squatinidae)

 In Patagonian waters, Argentina. Squatina guggenheim (Marini, 1936) commonly known as angel shark, "escuadro" or "angelote", is a cartilaginous fish found in Argentinean sea waters. In the San Matías gulf (San Antonio Oeste, Pcia. de Río Negro), they are caught as by-catch of the hake, Merluccius hubssi, fishery. It is a matter of concern that the raise of the fisheries commercial activity may have a negative impact on those species that are caught as by-catch and specially on those with low fecundity and slow growth as most shark species. But data on the reproductive biology of this species are lacking. In this context, the purpose of this study was to investigate the reproductive biology and testicular dynamic of angel sharks collected from commercial bottom drawl fishery. Standard morphometric parameters were measured and the gonads were removed . Testis were processed for classical histological procedures, analyzed and photographed in a microscope. The onset of sexual maturity was obtained for females and males from morphometric data. Based on our results it is suggested that this is not a breeding area for this species. Testicular structure is polyspermatocystict and with a diametric maturation type. The germinal and interstitial compartments are described and the spermatogenetic cycle was divided in seven stages.

19/06/2000 - 08:00:00 AM - Salon Madre Perla


(DB; JBG)Scripps Institution of Oceanography Scholander Hall #313 & #315, La Jolla, CA 92093-0204. (KAD) Department of Biological Science California State University, Fullerton Fullerton, CA 92834-6850

Temperature effects on mako shark locomotor muscle enzyme kinetics

The mako, Isurus oxyrinchus, is a high performance shark having locomotory specializations similar to tunas including endothermy. Quantification of mako high performance requires determination of the extent that metabolic potential is increased relative to other sharks and approaches that of tunas. We studied the effect of temperature on the aerobic (citrate synthase, CS) and anaerobic (lactate dehydrogenase, LDH) enzyme activities of mako red (RM) and white muscle (WM). The hypotheses were: that RM and WM enzyme activities are higher than in other sharks at comparable temperatures, and that activities at in vivo locomotor muscle temperatures significantly enhance muscle performance. CS and LDH activities in mako RM at 20ºC are not significantly different from other ectothermic sharks (e.g., Prionace glauca, Sphyrna leweni). However, using Q10 values for mako RM enzyme activities (1.51 - 1.78) and correcting for in vivo temperature elevates RM performance capacity. Mako WM enzyme activities at 20ºC are significantly higher than in other sharks and WM metabolic capacity also increases with temperature. Thus, mako WM parallels tuna WM in having a greater aerobic capacity compared to ectothermic species and increasing the capacity for rapid gluconeogenesis, suggesting a role for WM in both sustained and burst swimming and recovery from oxygen debt.

16/06/2000 - 05:15:00 PM - Salon Madre Perla


(JJB) Moss Landing Marine Laboratories; 8272 Moss Landing Rd.; Moss Landing, CA 95039; (JBO): Monterey Bay Aquarium; 886 Cannery Row; Monterey, CA 93940

Site description for the Gulf of California

The Gulf of California is a 1,070 km long, narrow marine inlet located between Baja California and the west coast of mainland Mexico. The Gulf was formed about 5 million years ago when the convergence of the Pacific, Farallon, and North American Plates resulted in a strike-slip fault and the disassociation of a land mass from the North American plate. A spreading center was created east of present-day Isla Angel de la Guardia, moving Baja California northwestward (presently at 5.5 cm/yr). The upper Gulf is shallow (< 200 m) and flat and is dominated by terrestrial sediments. South of the Midriff Islands, the sea floor expands in depth (up to 3,700 m) and complexity. Mean surface temperatures are more continental than maritime and range between extremes of 8º and 33ºC. Surface current flow is highly correlated with wind patterns and flows southeasterly in winter and spring, and northwesterly in summer and fall. Species migrations, including those of pelagic sharks, are associated with these dominant current regimes. The combination of upwelling and large tidal flux stirs nutrients into the euphotic zone, providing a rich food base for the diverse assemblage of temperate, subtropical, and tropical marine organisms inhabiting this region.

16/06/2000 - 08:00:00 AM - Salon Madre Perla


Moss Landing Marine Laboratories; 8272, CA.

The artisanal elasmobranch fishery of Baja California Norte (Gulf of California, Mexico)

The locations and activities of all artisanal fishing camps on the Gulf of California coast of Baja California Norte (BCN) were determined during 1998 and 1999. Seventeen camps were identified, of which 15 targeted elasmobranchs. Elasmobranch landings and effort were highest at camps located in southern BCN. Thirty-two elasmobranch species (16 sharks and 16 rays) and 4,492 specimens were observed in landings of 160 boats. Rhinobatos productus (26.45%) and Mustelus spp. (21.48%) numerically dominated overall landings. Interannual differences were noted in species composition of elasmobranch catches and effort. A drift net fishery for large sharks operated during the summer and early fall around the Midriff Islands and targeted primarily: Alopias pelagicus, Carcharhinus falciformis, Carcharhinus limbatus and Sphyrna spp. Batoids and small sharks were the main constituents of the elasmobranch fishery. While these groups appear to be targeted throughout the year, CPUE was highest for batoids in the summer months (26.1/boat) and for small sharks in spring (31.4/boat). Females seasonally dominated catch composition and gravid females (esp. Rhinobatos productus, Carcharhinus faliciformis and Alopias pelagicus) were noted primarily during the summer months. Juvenile elasmobranchs were captured year-round. Although elasmobranchs are important components of the BCN fishery, most artisanal effort targets either shrimp or teleosts.

16/06/2000 - 08:30:00 AM - Salon Madre Perla

BRIAN, K. W.;FAHY, D. P., and *SHERMAN, R. L.

Nova Southeastern University Oceanographic Center (USUOC) 8000 N. Ocean Drive, Dania Beach, FL 33004

Gross brain morphology in the yellow stingray, Urolophus jamaicensis.

The yellow stingray, Urolophus jamaicensis, a short-lived, relatively small elasmobranch species (35-40 cm total length), is a common inhabitant of hard bottom and coral reef communities in southeastern Florida and many parts of the Caribbean. Its small size and abundance make this animal an ideal candidate for many ecological and physiological studies. We decided to use this species as an experimental subject for examining the elasmobranch histaminergic system. However, there are relatively few published studies dealing with the yellow stingray in general, and apparently none on the gross morphology of its nervous system. In this preliminary study we compared gross brain structure of the yellow stingray with published studies on other batoid elasmobranchs. Male and female rays were killed with a lethal dose of anesthesia (MS222) and dissected. In general, the external brain structure of Urolophus jamaicensis is similar to that reported for other Dasyatoidea, including presence of an asymmetric cerebellum. Comparatively, stingrays possess a brain three to ten times the size of their sister groups, the electric rays, guitarfish, and skates (Northcutt, 1989). The yellow stingray is no exception. Its bilaterally symmetric brain is well developed and quite large in proportion to body size (approx. 1%bw). Labeled illustrations of dorsal, ventral and sagittal views are available from the first author.

16/06/2000 - 08:00:00 AM - PingPong Area


CSIRO Marine Research, GPO Box 1538 Hobart Tasmania, Australia. 7001.

Movement patterns of white sharks tracked with archival and satellite tags in Southern Australia

Two archival tags and a single satellite transmitter were deployed on separate white sharks in southern Australia to collect detailed data on long-term movement patterns. One of the archival tagged sharks was captured 74 days later some 600km from the Neptune Islands where it was tagged. Swimming depth and ambient water temperature were recorded every 4 minutes and an approximate position was calculated daily during the period at liberty. The shark spent about 8% of its time at the surface and cycled extensively through the water column to a maximum depth of 94 m. The number and timing of dives varied considerably on a daily basis. Position data was more problematic, however, the shark probably stayed in the vicinity of the Neptune Islands until early September before moving north into the shallower waters of Spencer Gulf. The shark then moved rapidly westwards in mid-October reaching the Great Australian Bight by about 25 October, where it stayed until it was caught on 2 November. In a second exercise, a 2 m female white shark was captured off Ninety Mile Beach, Victoria and fitted with a satellite tag. The shark was tracked for 3 h via an acoustic tag after release to ensure its initial survival. Since release, the satellite tag has successfully transmitted the shark's position approximately every day. By mid March, two weeks after release, the shark had moved steadily in a south west direction over a distance of 80 km tracking the coast at approximately 5-13 km from shore with one excursion into the coast in the vicinity of a large coastal inlet.

19/06/2000 - 08:00:00 AM - Salon Madre Perla


Laboratory for Vertebrate Paleontology; Department of Biological Sciences; University of Alberta; Edmonton, Alberta; T6G 2E9 Canada

Sexual dimorphism in number of first dorsal fin basals of Squalus acanthias Linnaeus, 1758

Analysis of 93 first dorsal fins of Squalus acanthias shows sexual dimorphism in the total number of basals supporting the first dorsal fin. 57 specimens examined are cleared and stained. 36 specimens examined are display skeletons prepared by biological supply houses for teaching comparative anatomy labs. Counts of the number of basals (1 supporting spine not counted) supporting the first dorsal fin for the 63 males examined found a range of 10 to 18, a mode of 13, and a mean of 12.810. Counts of basals for the 30 females examined found a range of 7 to 13, a mode of 12, and a mean of 11.767. This is the first report of sexual dimorphism in number of basals of the first dorsal fin for any shark. This observation might be of use in sexing some fossil sharks when the median fins are well preserved and the pelvics are not. {Revised abstract}.

18/06/2000 - 04:45:00 PM - Salon Madre Perla


(JB) University of Zurich Winterthurerstr. 190, 8057 Zurich, Switzerland; (EKR) Green Marine P.O. Box 33283, Miami, FL 33283, USA P.O. Box 832946, Miami, FL 33283, USA.

Removal of shark suckers as a possible origin of agonistic displays in sharks

Blacktip sharks (Carcharhinus limbatus) show clearly defined behavior patterns to remove shark suckers (Echeneis naucrates). Some of these patterns clearly resemble agonistic displays. Although the act of feeding has been attributed as the most likely origin of that behavior, removing shark suckers must also be discussed as a potential origin. In this study we describe and define different behavioral patterns, focusing on the positions and movements of the shark sucker along the shark's body. Preliminary results show that different areas of the shark's body trigger different reactions. Several scenarios will be discussed illustrating shark sucker irritation of shark sensory and hydrodynamic capacities as the basis for behavioral displays and its possible relation to the origin of agonistic display.

17/06/2000 - 05:15:00 PM - Salon Madre Perla


Hawaii Institute of Marine Biology Univ. of Hawaii, Zoology Dept.; Honolulu, HI 96822

Gastric evacuation and revised estimates of daily ration in juvenile scalloped hammerheads, Sphyrna lewini

The effect of temperature on the rate of gastric evacuation (GE) in juvenile scalloped hammerheads has been presented previously. However, there are several other factors that can affect GE. The effect of meal size was investigated for a teleost prey item, Herklotsichthys quadrimaculatus. Meals of 4.2% of the body weight and 0.5%BW were 80% evacuated in 15 hours and 6-7 hours, respectively. Gastric evacuation of another teleost prey, Hazeus nephodes (0.5%BW) was 80% complete in 5 hours while GE of a shrimp, Alpheus malabaracus, (0.5%BW) was 40% complete in 3 hours, at which time digestion seemed to stop. Faster rates of GE were measured for the most important prey items, (H. nephodes, and A. malabaracus), at meal sizes close to those observed in the field. The difference in GE rates of the two teleost prey items is probably due to the higher caloric value of H. quadrimaculatus. Different rates of GE affect estimates of daily ration. Daily ration estimates using the Diana method varied from (.32%) to (1.43%BW). The higher estimate of daily ration is based on predominate prey items and more a more realistic meal size. It is also closer to the maintenance ration predicted for Sphyrna lewini.

19/06/2000 - 08:00:00 AM - Salon Madre Perla


Univ. of Hawaii, Zoology Dept; Honolulu, HI 96822; Hawaii Institute of Marine Biology

Diet and diel feeding periodicity of juvenile scalloped hammerhead sharks, Sphyrna lewini, in Kaneohe Bay, Hawaii

Dietary data were collected from 779 sharks in Kaneohe Bay, Oahu, Hawaii from 1995-1998. Sharks were caught in gill nets and were between 32.7-79.0 cm (x=43) FL, and 340-5091g (x=739). Eighty percent of all sharks contained food in their stomach, but only 41% of sharks with an open umbilical scar had food in their stomachs, as opposed to 87.8% of sharks with healed umbilical scars. Sharks with unhealed umbilical scars were used in calculating IRI, but were not used in any other dietary analysis. Alphied shrimp (primarily one species) made up 38.7% of the diet (IRI), while various teleost accounted for 52.0%. This seems to reflect the availability of prey items on the bay floor, and differs from the diet reported by Clarke (1971). The differences in diet may be explained by changes in the bay's ecology as a result of anthropogenic impacts. A Kruskal-Wallis test of stomach fullness, (as %BW), indicates that there are significant variations in stomach fullness over a 24 hour period. Stomachs contained the most food from midnight to 0900, and the least from noon to 0600. The trend for the proportion of empty stomachs is similar, with more sharks having empty stomachs in the day (16.8%) than at night (4.1%).

19/06/2000 - 08:00:00 AM - Salon Madre Perla


(AB; KH; CM; SK) Hawaii Inst. of Marine Biol. and Department of Zoology, Univ. of Hawaii (CL) Dept. of Biological Sci., California State Univ. Long Beach (BW) National Marine Fisheries Service

A review of tagging and telemetry methods used to study the movements of tiger sharks off the south shore of Oahu, Hawaii.

A research program was initiated in 1993 to study the movements and site fidelity of tiger sharks off the south shore of Oahu, Hawaii. This program is ongoing, and has used a variety of techniques from traditional tag and release to acoustic telemetry to an archival pop-up satellite tag. Recapture rates for sharks with standard identification tags ranged over time from 23% to 17% (141 sharks tagged). Sharks implanted with acoustic pingers were electronically "recaptured" by stationary data loggers at a rate of 50% (n=20). Differences in recapture rates suggest internal acoustic tags and remote data loggers are a more effective way to study site fidelity than traditional tag and recapture methods. Currently, sharks are being implanted with long life archival acoustic tags that record depth and temp and download their information when the shark swims within range of a data logger on the sea floor. The role of the various methods in elucidating the movements of tiger sharks in Hawaiian waters will be discussed, as well as their relative merit in studying movements of elasmobranchs in general.

17/06/2000 - 11:30:00 AM - Salon Madre Perla


Instituto Nacional de la Pesca. Pitágoras #130, 4º Piso. Col. Santa Cruz Atoyac. México, D.F. UNAM Canal de Miramontes 2960-35. Los Girasoles, Coyoacán. CP.04920 México, D.F.

Feeding habits of Carcharhinus falciformis, Nasolamia velox and Sphyrna lewini in the Gulf of Tehuantepec, México

A total of 104 stomachs contents were analized: 37 were stomachs of Carcharhinus falciformis, 17 were of Nasolamia velox and 50 were of Sphyrna lewini, that were captured in the Gulf of Tehuantepec, Chiapas, México. Carcharhinus falciformis is a selective feeder, who fed primarily on the crab Portunus xantusii affinis. The females and adults of Nasolamia velox fed mainly on Portunus xantusii affinis meanwhile the males and medium sharks of this specie fed primarily on the decapod Squilla biformis. Finally Sphyrna lewini has demostrated to be a generalist feeder that have ontogenetic dietary shifts., the smaller sharks fed primarily on the shrimp Trachypenaeus sp., the medium sharks fed mainly on the crab Portunus xantusii affinis and the larger sharks fed primarily on teleosts.

19/06/2000 - 08:00:00 AM - Salon Madre Perla


Universidad Autonoma de Baja California Sur. Laboratorio de Elasmobranquios Carretera al sur km. 5.5 La Paz, B.C.S. México.

Reproductive biology of the silky shark, Carcharhinus falciformis, in the central Gulf of California.

During 1994-1998, 1,023 Carcharhinus falciformis were caught in four fishing camps in the central Gulf of California. Observations of sizes and reproductive biology were made, providing data on the monthly frequency, sex ratios, sizes a maturity, fecundity, embryo sizes, and ovarian development. Males ranged from 130-279 and females 125-271 cm TL. The overall sex ratio was 3.49 females per male. The sex ratio at birth was 1.34 males per females. Both sexes appear to mature at 180 TL. Fecundity ranged from 4-12 per female, increasing significantivally in larger females. The largest ovum diameter was 30 mm. This species has a biannual ovarian cycle, the females presumably rest one year between parturition events, and the gestation is probably 12 months.

16/06/2000 - 11:00:00 AM - Salon Madre Perla


Universidad Autonoma de Baja California Sur. Laboratorio de Elasmobranquios Carretera al sur km. 5.5 La Paz, B.C.S. México

An overview of elasmobranch fisheries in the northeastern Gulf of California.

From 1995 through 1998, we studied the fishing camps at 9 sites in Sonora. A total of 2,595 specimens representing 36 species was sampled, including 20 species of sharks and 16 rays, and were measured. The most important fishing camp by the number of species and organism was Baha de kino. Other important fishing camps were Yavaros, La Manga, El Cholludo and Puerto Penasco. The most abundant species were Dasyatis brevis (35.38%), Rhinoptera steindachneri (19.42%), Gymnura marmorata (7.17%), and Rhizoprionodon longurio (6.86%). The big sharks Alopias pelagicus, A. Vulpinus, Carcharhinus leucas, Prionace glauca, Carcharhodon carcharhias and Isurus oxyrinchus were rarely encountered. Gymnura marmorata, D. brevis, R. steindachneri and Rhizoprionodon longurio are species that used the Sonora coast as reproduction and nursery areas.

16/06/2000 - 09:00:00 AM - Salon Madre Perla


(JNC;KJ) Department of Ecology & Evolutionary Biology, University of Connecticut, Storrs; (GJPN; JAR) Connecticut Department of Zoology & Genetics Iowa State University, Ames, Iowa

Some information on the elasmobranchs of the Gulf of California resulting from a parasite survey

Two collecting expeditions to the Gulf of California were conducted from July to October, 1993 and from May to July, 1996. Six main sites were visited each trip: Puertecitos, Bahia de Los Angeles, Santa Rosalia, Loreto, Punta Arenas and San Jose del Cabo. Elasmobranchs were collected using a diversity of gear including hand spears, gill nets, long lines, etc., generally in conjunction with local fishermen. A total of 766 individuals, representing 13 families, 25 genera and approximately 45 species of elasmobranchs was examined. A number of taxa presented identification problems. Species of some, such as Mobula and Urotyrgon, were initially difficult to identify in the field, but their identities were essentially resolved following consultation with appropriate experts and/or literature. Specific identities of others, such as Gymnura, Rhinobatos and Urobatis, were established with some confidence only following sequencing and phylogenetic analysis of the mitochondrial gene NADH-2. The specific identities of some specimens of yet other taxa, such as Mustelus, remain unresolved. This survey also facilitated collection of data on some aspects of the biology of the elasmobranchs of this region. For example, embryos were seen in species of 17 genera, most commonly in Alopias, Diplobatis, Gymnura, Mustelus, Narcine, Urotrygon and Zapteryx.

16/06/2000 - 11:45:00 AM - Salon Madre Perla


Fisheries Service; Southeast Fisheries Science Center; 3500 Delwood Beach Road; Panama City, FL; 32408.

Application of generalized linear modeling to catch-per-unit-effort data from a fishery-independent assessment of shark populations

The National Marine Fisheries Service-Panama City Laboratory has conducted longline surveys in the northeast Gulf of Mexico since 1994. Surveys targeted small and large coastal species of sharks within coastal nursery areas from April to October. Generalized linear modeling was used to standardize catch rates to improve estimates of relative abundance. Trends in catch rates were examined using weighed least-squares linear regression. Depending on the species, significant effects in the model generally included year, area, and month. Results suggest that despite attempts to control for factors that may influence a fishery-independent assessment, certain effects unrelated to abundance can contribute significantly to the variability in catch rates.

16/06/2000 - 02:45:00 PM - Salon Madre Perla


(JCC; NW; JB) Albion College Dept. of Biology, Albion, College, Albion, MI 49224 USA; ( HLP) National Marine Fisheries Service, Noaa/Nmfs, Narragansett Lab, 28 Tarzwell, Naragansett, RI 02882 USA.

GPS-supplemented tracking and plotting of the movement of reproductively active male nurse sharks Ginglymostoma cirratum

A long-term study of mating behaviors of nurse sharks has shown that males and females move little during the period of mating and may therefore be tracked using ultrasonic telemetry from kayaks to minimize intrusion and modification of natural behaviors. Periodic position determinations made with the use of GPS and plotted on digitized nautical charts using recently developed computer software brings improved accuracy to tracking and provides insight into reproductive behaviors. Previously undiscovered mating sites have been identified and behaviors of males have been clarified using such combinations. {revised abstract}

17/06/2000 - 08:00:00 AM - Salon Madre Perla


(CGL) Instituto Nacional de la Pesca/SEMARNAP Pitágoras # 1320, 4º Piso, Col. Santa Cruz Atoyac, México, D.F. C.P. 03310;(OTA; PG) Laboratorio de Ecología Pesquera, CICESE Km. 107 Carretera Tijuana- Ensenada, Ensenada, B.C. C.P. 22800, México; (CED) Centro Regional de Investigación Pesquera de Mazatlán, Instituto Nacional de la Pesca. Calzada Sábalo-Cerritos S/N. Ap 1177, Mazatlán, Sinaloa;

Characterization of the artisanal shark and ray fisheries off Sinaloa, southern Gulf of California

Historically Sinaloa has been an important fishing state of sharks in the Mexican Pacific coast region. As part of the join US-Mexico project titled "The status of shark and ray resources in the Gulf of California: Applied research to improve management and conservation", the DGIEMRP of the National Fisheries Institute of Mexico (INP) in collaboration with the CRIP of Mazatlán carried out during the period 1998-1999 the characterization of the main artisanal fishing camps dedicated to the exploitation of sharks, cazones and rays. In this period we surveyed 28 fishing camps in Sinaloa, of which in 17 of them captures and landings of elasmobranchs were observed. We documented the capture of 2,758 elasmobranchs landed from 112 fishing trips with small boats, belonging to 25 species of sharks and rays. The dominant species were Sphyrna lewini (36.0%), Rhinobatos glaucostigma (20.0%), Rhizoprionodon longurio (14.0%), Rhinoptera steindachneri (9.0%) and Dasyatis brevis (8.6%). Except for R. Longurio most of the landed individuals were immature of early stages: neonates and juveniles. We observed in Sinaloa two main fishery seasons for elasmobranchs, one targeting small shark species denominated cazones in the period January-March, and a second targeting rays and neonates and mature sharks of larger size in May-July. Both seasons periods related intimately with migratory movements of those species. An important proportion of gravid females were observed in June of the second year, which suggests the presence of shark nurseries areas along the coast of Sinaloa.

16/06/2000 - 09:15:00 AM - Salon Madre Perla


National Marine Fisheries/NOAA, Mote Marine Laboratory 1600 Ken Thompson Parkway; Sarasota; Florida

On the length of the reproductive cycles of sharks

The available data indicates that sharks generally have annual or biennial reproductive cycles. Longer cycles have been suggested, but there is little supporting evidence for them. The reproductive cycle of sharks includes two separate processes: the ovarian cycle and the gestation period. The ovarian cycle includes follicle development and vitellogenesis, and culminates in the ovulation of the ripe follicle. The gestation period starts with fertilization and ends with birth. The length of the reproductive cycle of sharks is determined by whether the ovarian cycle and gestation occur concurrently or consecutively. In annually reproducing species, such as Rhizoprionodon terraenovae, Mustelus canis and Sphyrna lewini, the ovarian cycle and gestation run concurrently and both last about a year. Parturition in these animals is quickly followed by mating, ovulation, and gestation. Thus they reproduce annually. Many other species show biennial cycles. In biennial species, gestation and the ovarian cycle can occur concurrently or consecutively. In Squalus acanthias and other squaloid sharks, gestation and vitellogenesis occur concurrently. They both last almost two years and the species reproduces biennially. In many species of Carcharhinus, the ovarian cycle and gestation occur consecutively and not concurrently. A female giving birth in early summer will enter the ovarian cycle sometime after parturition and its oocytes will be ready to be ovulated one year after parturition. After ovulation and fertilization, gestation lasts for about another year. Thus the length of the reproductive cycle is two years.

18/06/2000 - 08:00:00 AM - Salon Madre Perla

*CASTRO, J. I., and CLARK, E.

(JIC) National Marine Fisheries/Noaa/Mote Marine Laboratory (EC) University of Maryland/Mote Marine Laboratory 1600 Ken Thompson Parkway; Sarasota, FL 34236

Whale shark: What do we really know about it?

The maximum size of the whale shark is not known with certainty because actual measurements of large specimens are few. The largest measured specimens that we know of are a 12.1m female that stranded off Mangalore, India, and a male 12.18m from Bombay, India. Photographic evidence suggests that the whale shark may grow to a larger size. There are few reliable weights for adult specimens, given the lack of scales suitable for weighing such large animals. The weights of the 1912 Knights Key specimen often given in the literature have little or no scientific basis. Joung et al. (1996) gave the weight of a ~10.6m TL as 16,000 kg, as weighed by a construction crane. These authors also gave weights of 15,220 kg and 36,000 kg for sharks landed in Taiwan on 30 March 1994 but without adducing any other data or evidence. Whale sharks at birth range from 55 to 64 cm. The nurseries of the whale shark are poorly defined because very few small whale sharks have been captured. If the dates of capture of juveniles given in the literature are correct, newborn whale sharks can be found in summer as well as in winter, suggesting year round reproduction. The reasons for the paucity of small specimens in collection are probably the widespread nature of the nurseries in tropical waters and the unusually rapid growth of whale sharks. Remoras and cobias often accompany the whale shark. The remoras often enter the mouth, the spiracle and the anus, and sometimes they can be seen peering out of the anus.

15/06/2000 - 01:30:00 PM - Salon Madre Perla


(DDC; MSS) Oceanographic Center, Nova Southeastern University 8000 North Ocean Drive, Dania Beach, Florida, USA 33004 (PP) The Queen's University, Belfast, N. Ireland, UK; (CM) Mote Marine Laboratory, Sarasota, Florida, USA.

Microsatellite DNA profiling in the bonnethead shark, Sphyrna tiburo: application to mating system and population structure studies.

Although application of microsatellite markers to shark biology is in its infancy, these markers are already proving useful for elucidating relationships at population and individual levels. Herein, we provide a preliminary evaluation of microsatellite loci to investigate life history traits and population structure of the bonnethead shark, Sphyrna tiburo. Mature female bonnetheads are known to store sperm in their oviducal gland for a period of about five months after insemination. Although there are no published observations of bonnethead sharks mating, recent studies on other sharks suggest that multiple males often participate in mating events involving a single female. If the bonnethead shark has evolved this type of multiple-male (polyandrous) mating system coupled with protracted sperm storage, it is possible that females are fertilized by multiple males in a single reproductive cycle. Using 8 microsatellite markers, we have assayed several litters of this species for multiple paternity. Three of the 8 microsatellite loci were isolated from the genome of S. tiburo. The remaining five were previously isolated from the blue shark, Prionace glauca, and were also found to be informative for S. tiburo. We also report on a preliminary assessment of micro-geographic population structure in this species from the SE United States.

18/06/2000 - 04:30:00 PM - Salon Madre Perla


Department of Wildlife and Fisheries Sciences, Texas A&M University Center for Coastal Studies; Texas A&M University-Corpus, Christi; 6300 Ocean Drive Nrc 3200; Corpus Christi, TX, USA; 78412

The social organization of elasmobranchs and their habitat use of topographic highs in the northern Gulf of Mexico

The continental shelf of the northwestern Gulf of Mexico includes an array of submerged hard-banks, reefs and offshore oil and gas platforms that often support diverse reef communities. These features extend upward from the plane of the seafloor and provide significant vertical and structural relief in an otherwise level landscape, and are defined as topographic highs. Various species of elasmobranchs have been reported at these features, but most records are anecdotal by nature. Surveys conducted at five topographic highs in the northwestern Gulf of Mexico reveal seasonal assemblages of sharks and rays inhabiting these features. Aspects of elasmobranch diversity, social organization, and seasonal habitat use are characterized for mid-shelf and outer shelf topographic highs.

19/06/2000 - 08:00:00 AM - Salon Madre Perla


(JC) Center for Coastal Studies, Texas A&M University-Corpus Christi, 6300 Ocean Dr Nrc 3200, Corpus Christi, TX 78412; (CMB;KDM) Southeast Fisheries Science Center, NMFS/NOAA, Mississippi Laboratories, P.O. Drawer 1207, Pascagoula, MS 39568-1207; (JH) Aquarium of the Americas, #1 Canal Street, New Orleans, LA 70130;

The occurrence and distribution of the whale shark (Rhincodon typus) in the northern Gulf of Mexico

The whale shark (Rhincodon typus) frequents the northern Gulf of Mexico, however, little is known regarding its seasonal distribution, abundance, and behavior in the region. This paper present the occurrences of whale sharks in the northern Gulf of Mexico, gathered using three different survey methods (aerial, underwater, and offshore platform). Data presented using geographic information system technology illustrates the seasonal distribution of whale sharks in the region, including strong evidence of seasonal habitat use of neritic waters in the northern Gulf during warmer months. The occurrence of whale sharks associated with topographic high communities and mass spawning events in the northern Gulf are also examined.

15/06/2000 - 03:45:00 PM - Salon Madre Perla

Chris, Huff - See Huff, Chris



Texas A&M University, Department of Wildlife & Fisheries Science, Tamu 2258; College Station, TX 77843-2258; USA

Population structure of Manta birostris based on mtDNA sequence

The hypothesis that genetic population structure exists in the manta ray (Manta birostris) was tested using mitochondrial DNA sequence variation.

16/06/2000 - 08:00:00 AM - PingPong Area


Virginia Institute of Marine Science P.O. Box 1346, Gloucester Point, VA 23062

Age, growth, reproduction, and demography of the Northwest Atlantic, dusky smoothhound, Mustelus canis

The Northwest Atlantic population of dusky smoothhounds ranges from South Carolina up to Cape, Cod, Massachusetts. Recently a gillnet fishery for these sharks started on the eastern shore of Virginia and North Carolina. Dusky smoothhounds may be more capable of sustaining a fishery, with appropriate management, than many other shark species due to a proposed higher growth rate and fecundity. However, no demographic modeling has been done to predict how increased fishing pressures will affect this population. Although this is a seasonally abundant and well-known animal very little has been published about its growth and reproduction. We aged 800 dusky smoothhounds, created Von Bertalanffy growth curves for males and females, studied the reproductive cycle, fecundity, and lengths and ages of males and females at maturity of this population. A life table was created using this information. This life table was then used to examine the effects of various levels of fishing pressure on the population, and to explore the necessary compensatory responses for the population to remain stable.

17/06/2000 - 02:00:00 PM - Salon Madre Perla


National Marine Fisheries Service Southeast Fisheries; Science Center Panama City Laboratory 3500 Delwood Beach, Road Panama City, FL 32408, USA.

Insights on shark conservation from stochastic demographic modeling

Most demographic models of sharks conducted so far have used deterministic life table analyses to project population growth rates and generation times. There is a clear need to incorporate uncertainty in estimates of vital rates and naturally occurring random variation in those rates into the modeling process. This paper uses Monte Carlo simulation to calculate both stochastic population growth rates and generation times to evaluate the potential for exploitation or recovery and stochastic matrix elasticities to identify the most vulnerable life stages for a suite of shark species. This approach eliminates potential problems associated with deterministic methods, such as ranking of elasticities based on projection of one specific set of vital rates. The ratios of adult to age-0 and juvenile to age-0 survival elasticities obtained from the simulations are also examined to predict the level of density-dependent compensation required to offset the effect of exploitation given the life-history constraints for each species.

17/06/2000 - 02:45:00 PM - Salon Madre Perla


(PC; PV), University of Highlands and Islands, Dunstaffnage Marine Laboratory, P.O. Box 3, Oban; (JG), Dept. of Biology, Abbey College, Kennedy Street, Manchester, U.K.

The impact of the commercial fishery on deep-water populations of Elasmobranchs in the North East Atlantic

In response to declining coastal commercial fisheries, a deep-water fishery developed in the early 1990's in the North East Atlantic. Although this fishery mainly targets grenadiers Coryphaenoides rupestris and argentines Argentina silus, several species of deep-water elasmobranchs are taken as either directed landings or by-catch. Two species of deep-water sharks: the Portuguese Dogfish Centroscymnus coelolepis and the Leafscale Gulper Shark Centrophorus squamosus in particular, are landed on a regular basis. It is important to establish levels of these landings at the earliest possible stage in the development of the fishery in order to monitor status and formulate suitable management plans to prevent over-exploitation of the resource. It is hoped that by studying landing statistics, stock assessments and life biology using molecular techniques, correct manangement of elasmobranch populations will be facilitated.

19/06/2000 - 08:00:00 AM - Salon Madre Perla