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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 4: Remirez De Aguilar through Young
*RAMIREZ DE AGUILAR, A. M.;VILLAVICENCIO GARAYZAR, C. J.;GUTIÉRREZ SÁNCHEZ, F. J.

(RAAM, VGC) Universidad Autónoma de Baja California Sur, Departamento de Biología Marina, Área Interdisciplinaria de Ciencias del Mar, Laboratorio de Elasmobranquios; (GSF) Av. IPN s/n, Col. Playa Palo de Sta. Rita, 23090 La Paz B.C.S.

Ictiofauna of estero El Coyote, Baja California Sur, México

The results obtained in the study of the fishes in the Estuary El Coyote, Baja California Sur, during the months of February, April and June of 1997, captured mainly, with a hand pulled fine net and helped with otter trawl and a gallnut net. The total fish comunity was represented for 43 species of 34 genera, 24 families and 11 orders. With the fine net found a total of 2104 organisms, with a total weight of 74 610g, represented in 30 species of 22 genera and 17 families. The best represented for abundance using the BVI index being: Mugil cephalus, Sphoeroides annulatus, Atherinops affinis, Fundulus parvipinnis, Eucinostomus gracilis, Hypsopsetta guttulata, Urobatis halleri and Etropus crossotus, coinciding for biomass except for Etropus crossotus. It was found that the 37.2% of the species belongs to the Californian province, 27.9% at the Panamic, 13.9% of east Pacific, 9.3% of the Mexican province, 9.3% of the Cortés province, and 2.3% of circumtropical species. Demostrating that this is a zoogeographic transition zone. In an ecologycal view, the Estuary El coyote, is a zone of low diversity, by the Shanon -Weiner index, due to the few availability of microhabitats, variability and inestability of the ambient, which provides a high dominance; but it is an important zone for protection, feeding and nursing of fishes.

18/06/2000 - 08:00:00 AM - Salon Coromuel


*RECHISKY E. L;WETHERBEE, B. M.

(ELR) University of Rhode Island, Fisheries, Animal and Veterinary Science Kingston, RI 08221; (BMW) NOAA/NMFS/NEFSC 28 Tarzwell Dr. Narragansett, RI 02882

Effect of tidal currents on short-term movements of juvenile sandbar sharks, Carcharhinus plumbeus, on their nursery grounds in Delaware Bay

Acoustic telemetry was used to investigate short-term movements of neonate and juvenile sandbar sharks, Carcharhinus plumbeus, on their nursery grounds in Delaware Bay during the summers of 1998 and 1999. Twenty-five sharks were tracked continuously for between 2.5-75 hours. The majority of the sharks caught and tracked on the Delaware side of the bay remained in this area for the entire duration of the tracks. Sharks tracked on the New Jersey side of the bay appeared to roam farther afield into deeper water and farther from shore, and occupied a larger activity space. Several sharks made longer offshore movements into the deepest section of the bay (37 m), and two sharks completely crossed the bay from Lewes, DE to Cape May, NJ and vice versa. In most cases tidal flow appeared to strongly influence the fine-scale movements of these sharks, and in general, sharks exhibited northwest up-bay movements during a rising tide and southeast, down-bay movements as the tide receded. This pattern was observed for the majority of sharks tracked, both in neonate and juveniles and on both the Delaware side and New Jersey side of the bay. Delaware Bay is a shallow bay with strong tidal currents, therefore it is possible that newborn and young sharks take advantage of the tidal currents to conserve energy by moving (either actively or passively) with the tidal

17/06/2000 - 10:30:00 AM - Salon Madre Perla


REYES GONZÁLEZ, J. A.

CICESE, Carr. Tij.-Ens. km. 107. C.P 22830. Ensenada, B.C., México.

Shark fishery interspecific associations in Veracruz, Gulf of Mexico

Shark commercial catches from November 1993 to December 1994, at four fishing camps from Veracruz, Gulf of Mexico, were studied through cluster analysis (Euclidean distance and UPGMA). The fishing trip was the unit of effort grouped in two gillnets and longline gears to catch sharks. A total of 7,837 individuals of sharks comprising 12 species, were recorded from 1,860 fishing trips along the study period. Maximum distance link for each gear defined: interspecific group (20%), joint species (21 to 40%), and no affinity (more than 41%). Each fishing gear selected a different shark community. However, finetooth (Carcharhinus isodon), spinner (C. brevipinna), bull (C. leucas), scalloped (Sphyrna lewini), blacknose (C. acronotus), and sandbar (C. plumbeus) sharks characterize this fishery, probably due to similar feeding and migratory habits. The data show that the shark fishery is multispecific in the area, suggest that finetooth and spinner sharks form an interspecific association, and that the Atlantic sharpnose (Rhizoprionodon terraenovae) does not have affinities with the other sharks.

16/06/2000 - 02:15:00 PM - Salon Madre Perla


REYIER, E. A.

Florida Institute of Technology, Melbourne/ Dynamac Corporation, Kennedy Space Center, FL

Swimming and feeding of bahamian epibathyal sharks with comments on fin morphology

Between March 27 and April 1, 1997, 14 submersible dives were made off Bimini and South Cat Islands, Bahamas, ranging in depth from 330 to 670 meters, in an attempt to record the swimming and feeding behavior of Odantaspis ferox, at the location of its first W. Atlantic capture. The search area was contained between 25º 30.0' and 25º 50.0' N. and 79º 18.0' and 79º 23.0' W. Of over 14 hours of recorded bottom time, seven species of shark were attracted via baited traps and filmed. They included Hexanchus griseus, Hexanchus vitulus, Centrophorus uyato, Squalus cubensis, Carcharhinus signatus, Carcharhinus perezi, and Mustelus canis insularis. Using mounted lasers and other reference objects, it was possible to estimate the size of these animals as well as their swimming speed and turn angles. Unique feeding behaviors are also observed. There is considerable morphological variation between the species documented and results suggest that these species generally conform to the hydrodynamic limitations postulated by previous authors. Through the synthesis of these observations with recent behavioral and paleontological information, conclusions are drawn as to the ecological and evolutionary forces that have defined fin placement and morphology in these species.

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


*ROJAS, J. R.;CAMPOS, J.;RODRÍGUEZ, O.;SEGURA, A.

Instituto de Recursos Costeros y Marinos (INRECOSMAR). A.P. 108-2015, San José, Costa Rica

Preliminary observations of the reproductive biology and food habits of the smooth-hound shark, Mustelus dorsalis, in the Gulf of Nicoya, Costa Rica

Although the smooth-hound shark is an abundant and a commercially important species in the Pacific coast of Costa Rica, its reproductive biology and feeding habits are poorly known. A study on its biology was conducted in the Gulf of Nicoya between March 1999 and February 2000. A total of 190 sharks, caught with long line gear, were collected from commercial landings. Higher abundances were observed in March, May and October. During the study period, females were dominant (sex ratio was 2.5:1). From May to August, only non-rape organims were captured, but from January to March and from September to January , rape specimens were abundant. Observed maximum lenghts were 66 cm for males and 63 cm for females. Smooth-hound has a gestation period of about five months. Mating and ovulation takes place in April. Females carried from 4 to 8 embryos per litter. Embryos are found in differents stages of development and are born at approximatley 18 cm of total length. Sixty one percent of the stomachs were empty. The primary prey were stomatopods mostly (Squilla hancocki and S. parva), however we found bony fishes (Caranx caninus, Anchoa sp., Myrophis vafer) and molluscs (Loligo sp. and Octopus sp.).

18/06/2000 - 08:15:00 AM - Salon Madre Perla


*ROMERO, A.;SALAZAR, C. G.;AGUDO, A. I.

(AR; CGS): Department of Biology and Environmental Studies Program, Macalester College, 1600 Grand Ave., St. Paul, MN 55105 (AIA): Fundacetacea, P.O. Box 010; Florianopolis; Santa Catarina- SC; Brazil.

Whale shark records and conservation status in Venezuela

The number of records of whale sharks, Rhincodon typus, in Venezuelan waters reflect a geographical distribution that is congruent with areas and periods of high productivity. We provide evidence that this species is occasionally harpooned or accidentally netted in those waters, thus raising a concern for its conservation status. We propose long-term population and behavioral studies tracking individual animals to provide an accurate picture of the distribution and abundance of whale sharks not only in Venezuelan waters but worldwide. At the present time we advise that this species be classified as threatened based on the Precautionary Principle.

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


*ROSENBERGER, L. J.;WALKER, J. A.

Field Museum of Natural History, Div. of Fishes, 1400 S. Lake Shore Dr., Chicago, IL 60605

Batoid morphospace: A study in behavioral and ecological associations with disc shape

Batoids (skates, rays, and their relatives) are a diverse, monophyletic group of elasmobranch fishes, that have close to 500 species. They are unique among cartilaginous fishes because of their dorsoventrally flattened bodies and pectoral fins that have greatly expanded and fused to the head above the level of the eye, forming a disc that includes the head, trunk, and pectoral fins. Recent phylogenies of batoids are used to explore the evolution of disc shape among a phylogenetically, behaviorally, and geographically diverse range of species. We use Elliptic Fourier Analysis to represent the outlines of discs as a series of Fourier harmonics and Principal Components Analysis to obtain the major axes of disc shape variation. Shape axes are compared with aspect ratio and wing (fin) tip shape in order to assess the ability of these traditional variables to measure disc shape. We explore the association between disc shape and phylogeny, geography, preferred swimming habitat, and swimming behavior, with particular focus on two major radiations of batoids, the skates (rajids) and stingrays (myliobatids).

16/06/2000 - 04:15:00 PM - Salon Madre Perla


*RYBURN, J. A.;FEDRIGO, O.;LOPEZ ÁNDRES;NAYLOR, G. J. P.

Zoology and Genetics, Iowa State University, Ames, IA 50011, USA

Inference of Orectolobiform phylogentic relationships based on DNA sequences

The order Orectolobiformes includes 31 species of sharks, divided among 13 genera and 7 families. A noteworthy feature of the orectoloboids is the extraordinary morphological diversity across genera. While several detailed studies in morphology have been carried out in an effort to establish taxonomic relationships within the order, opinions differ as to the relationships among families and genera. This study uses a molecular approach to test hypotheses forwarded by morphological data. We obtained DNA sequence data from three mitochondrial genes, NADH-2, NADH-4, and Cyt b and one single-copy nuclear gene, Rag 1 for 11 of the 13 described genera, representing all 7 families within the Orectolobiformes and multiple outgroup taxa. A phylogenetic analysis of these sequence data is presented.

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


*SEPULVEDA, C. A.;BERNAL, D.;GRAHAM, J. B.;DICKSON K. A.

(CS; SKD) California State University, Fullerton; (BD; BJG) Scripps Institution of Oceanography

Similarities in alopiid and lamnid red muscle morphology and biochemistry

Conservation of metabolic heat and a warmer than ambient aerobic locomotor muscle (red muscle, RM) temperature (endothermy) has been documented in the shark family Lamnidae and in the tunas (family Scombridae, tribe Thunnini). Lamnids and tunas display a marked evolutionary convergence in specializations for endothermy. In both groups RM is distributed more anterior in the body and nearer to the backbone than in ectothermic fishes. Also, blood perfusing RM passes through vascular retia that function as counter current heat exchangers. Lamnids and tunas are also active pelagic predators and obligate swimmers with a high capacity for oxidative metabolism. Thresher sharks (Family Alopiidae) also have internalized RM and small lateral retia, however, the RM distribution of these fishes, the presence of RM endothermy, and RM enzyme activities have not been quantified. A study of these RM properties in the common thresher, Alopias vulpinus indicates it has an anterior RM distribution (peak in RM mass at ª45% fork length), that RM endothermy is present, and that RM enzyme activities are elevated and similar to those of lamnids. Current phylogenetichypotheses hold that lamnids and alopiids are paraphyletic, which indicate that their RM properties are convergent.

18/06/2000 - 02:15:00 PM - Salon Madre Perla


*SILLIMAN, B. R.;GRUBER, S. H.

(BS) 141 Pickwick PL Millersville, PA 17551 Bimini Biological Field Station, Bimini, Bahamas.

Telemetry tracking of the tpotted Eagle Ray (Aetobatus narinari) in Bimini, Bahamas

Spotted eagle rays, Aetobatus narinari, have attracted wide attention throughout the years, yet have received surprising little scientific study. From the Fall of 1998 through the Summer of 1999 ultrasonic telemetry was used to determine the movements and ehaviors of 17 free-swimming spotted eagle rays in Bimini, Bahamas. Ultrasonic transmitters were externally darted to rays with a modified harpoon and tracked continuously for periods up to 98 consecutive hours. The transmitters remained attached to these rays for periods up to 93 days post tagging. The spotted eagle rays of Bimini exhibited a tidally mediated diel behavior, showing high site fidelity to a core area during one portion of the tidal cycle and more transient movements during the remaining portion of the tidal cycle. These rays proved to be seasonal residents of Bimini as they moved off-shore during the early summer months only to return by the late summer months. These spotted eagle rays exhibited rather tight social interactions and behaviors during aggregations, regardless of their given gender, size or number in the given aggregation. Further analysis cataloged about a dozen apparently stereo-typed action patterns and social interactions from such aggregations.

17/06/2000 - 08:15:00 AM - Salon Madre Perla


SIMPFENDORFER, C. A.

Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, FL, 34236, USA

Impacts of pollution and habitat degradation on shark populations

Shark populations worldwide are impacted by a variety of environmental factors, including pollution and habitat degradation. However, little published information exists on the effects of these factors on sharks at the tissue, individual or populations level. Demographic models were used to assess the impact of a variety of environmental factors at the population level. The use of demographic models allowed for age-specific mortality effects to be assessed, as well as sub-lethal reproductive effects. The models also incorporated fishing mortality to investigate the combined impact of fishing and environmental degradation. The results of the models, and their implications for fisheries management and conservation are discussed.

16/06/2000 - 03:45:00 PM - Salon Madre Perla


*SOSA NISHIZAKI, O.;CASTILLO GÉNIZ, J. L.;VILLAVICENCIO GARAYZAR, C. J.

(SNO) CICESE, A.P. 2732, Ensenada, B. C., 22800, México; (LGC) Instituto Nacional de la Pesca, Pitagoras #1320, 4 Piso, Col. Santa Cruz Atoyac, 03310 D. F., México; (CVG) Depto. de Biología Marina, UABCS, Carr. al sur km. 5.5, La Paz, B.C.S. 23080, México.

What does Mexican fish products statistics can tell us about shark catches from the Gulf of California?

Shark catches from the Gulf of California contributed a mean average of 33% to the national shark landings in Mexico, during the period of 1987 to 1997. This production makes the Gulf to be the most important shark-fishing region in the country. Even so, very few information exist about the catch species compositions and the effort applied to make those landings. In this paper, an historical analysis of the landing trends, and their relationship with habitat variables and landing values of potential prey species will be presented. Moreover, trends of shark fins values in a national and regional level will be discussed. In addition, the needs and types of information required from the region will be suggested.

16/06/2000 - 09:45:00 AM - Salon Madre Perla


*STARR, R. M.;FELTON, J. M.;O'SULLIVAN, J. B.;DEWAR, H.;CAILLIET, G. M.;MAYER, N.;HEINE, J.

(SRM; JMF) UC Sea Grant Extension Program., (JMF; GMC; JH) Moss Landing Marine Laboratories.; (JOS) Monterey Bay Aquarium.; (HD) Pfleger Institute of Environmental Research.;(NM) Monterey Bay Aquarium Research Institute.

Movements of the prickly shark (Echinorhinus cookei) associated with the head of the Monterey submarine canyon

Named for their sharp, thorny dermal denticles, the prickly shark (Echinorhinus cookei) is a rare deepwater shark that inhabits both tropical and temperate waters of the pacific. It is one of two species of sharks known as bramble sharks in the family Echinorhinidae. Few facts have been published about the basic biology of prickly sharks, as the majority of reports are based on descriptions of a small number of dead animals incidentally caught in fisheries. During the late summer and fall of 1999, we caught and placed sonic transmitters on eight prickly sharks to learn more about the basic aspects of their biology. These sharks were caught at the head of the Monterey Submarine Canyon using a set-line attached to a surface buoy. Once on the surface and secured to the side of the boat, an acoustic tag, which transmitted depth information, was attached to the dorsal musculature of the shark using medical grade plastic darts. The sharks were then tracked for a total of 78 days using both a directional hydrophone off of a small whaler and a moored, subsurface, omnidirectional hydrophone/receiver. During that time, sharks moved frequently during the study and ranged in depth from as little as 5 m of water near the canyon head to as deep as 375 m a distance of 10 km off shore. Preliminary data analyses indicated four patterns of daily activity associated with prickly sharks: (1) present at the canyon headat night but in deepwater during the day, (2) in deepwater at night and at the canyon head during the day, (3) at the canyon head the entire day, and (4) completely absent from the canyon head.

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


*STOBUTZKI, I. M.;MILLER, M.;HEALES, D.

CSIRO Marine Research, P.O Box 120, Cleveland, QLD, 4163, Australia

Assessing the sustainability of elasmobranch bycatch in a tropical prawn trawl fishery

Elasmobranchs are a common part of the bycatch in most tropical prawn trawl fisheries. In Australia's Northern Prawn Fishery (NPF), 56 elasmobranch species are caught in the bycatch, on average at least one individual per trawl. The sustainability of these elasmobranchs is an important issue for this fishery, but there is little biological or historical information available to assess their sustainability in a traditional stock assessment manner. Hence, we have developed an approach to examine the impact of trawling on these species and have applied this to the NPF. Two overriding characteristics determine the sustainability of bycatch species: their susceptibility to capture and mortality in a prawn trawl (susceptibility) and their capacity to recover once depleted (recovery). Species were ranked on each characteristic and the ranking reflects their ability to resist fishing pressure and therefore, their priority for management, monitoring and research. Twenty-seven species were high priority, they are the least sustainable, including stingrays (Dasyatidae), sawfishes (Pristidae), angel sharks (Squatinidae), zebra sharks (Stegastomatidae), shovelnose rays (Rhinobatidae) and nurse sharks (Ginglymostomatidae). They are all bottom dwellers which increases their susceptibility to capture. This process is valuable for identifying species of concern in a highly diverse bycatch where few data are available.

16/06/2000 - 01:30:00 PM - Salon Madre Perla


*SULIKOWSKI, J. A.;MORIN, M. D.;SUK, S. H.;HOWELL, W. H.

Department of Zoology, University of New Hampshire, Durham, NH 03824.

A preliminary study of the age and growth of the winter skate, Raja ocellata, in the Gulf of Maine

Preliminary age and growth estimates for the winter skate, Raja ocellata, have been collected from 155 fish ranging from 20 to 920 mm total length (TL). These early results suggest that males grow larger (average TL=850mm) and perhaps live longer (14 years), than do females (average TL=725mm; 12 years). The estimated age at first maturity is five years for females (TL= 575mm) and seven years for males (TL=775mm). It would appear from these initial results that the winter skate exhibits those characteristics that have made other large elasmobranchs highly susceptible to exploitation by commercial fisheries.

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


*SUMMERS, A. P.;FERRY GRAHAM, L. A.

(APS) Integrative Biology, Museum of Vertebrate Zoology, University of Califonia, Berkeley; (FGLA) Evolution and Ecology University of California, Davis.

Respiratory mecahnics of the little skate, Leucoraja erinacea, determined by sonomicrometry

A simple two-pump model, developed from the pioneering work of Hughes (J. exp. Biol. 37, 11-27, 1960), has served to describe how fish move water into the mouth and subsequently out the external gill openings during respiration. A key feature of this model is that water is pumped over the gills continuously and unidirectionally despite the episodic nature of water entering the mouth and exiting the gills. We suggest that in the little skate there are periods of pressure reversal indicative of flow reversal and that adduction of the gill bars may serve to attenuate the reversed flow. We used sonomicrometry to determine the movements of pertinant skeletal elements during respiration. In reconstructing kinematics from the sonmicrometry data several unexpected sources of error are apparent. While these do not undermine our conclusions they will be of interest to others interested in using this technique for measuring kinematics in aquatic environments.

18/06/2000 - 11:45:00 AM - Salon Madre Perla


*TAWNYA, P.;RUPP, J.

(TP) University of Washington; (JR) Point Defiance Public Aquarium, University of Washington 12000 Sandpoint Way N.E. Apt#1 Seattle, WA 98125

Social organization of a captive population of Ginglymostoma cirratum

The goal of this project was to determine if there was social structure within the captive population of Ginglymostoma cirratum at Point Defiance Aquarium. Their behaviors were separated into four categories: dominance, aggression, affiliation, and space utilization. The males were determined to have a non-linear dominance hierarchy. The two smallest males were the highest in rank. The males were observed to interact in sub-groups predominantly with specific individuals. The alpha male was the most successful at gaining acceptance to his affiliative displays. Affiliation was most often exhibited and successful within members of the same subgroup. The aggression hierarchy closely supported the established rank of the individuals, with a higher incidence of aggression between subgroups. The males did congregate in specific territories. The alpha and beta males territories did not overlap, but each had territories that overlapped with lower ranking males. There does appear to be definite patterns of social structure in all four of the categories tested. The findings warrant further investigation into the structure of other captive populations and wild populations.

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


*TONI, F.;RYBURN, J. A.;HUBBELL, G.;NAYLOR, G. J.P.

(TF; RJA; NG) 339 Science II, Ames IA, 50011, USA; (HG)150 Buttonwood Drive, Key Biskayne, FL 33149, USA;

Testing the species status of aberrant sharks

It has been suggested that undescribed species of sharks may exist within the order Lamniformes. This theory is based on two sets of observations: First, a controversial allozyme survey by Eitner (1995) uncovered evidence for four (rather than the currently accepted three) species of thresher shark present off the Southern coast of California. Second, occasional mako specimens that appear intermediate between Isurus paucus and Isurus oxyrinchus have been collected off the coast of Southern Florida.In an effort to discern the identity of these specimens, tissue samples were obtained for sharks of known identity and compared to those taken from representative ambiguous specimens. Both mitochondrial and nuclear DNA sequences were used in an effort to evaluate their species affinities. Results collected to date suggest that both sets of anomalous animals (threshers and makos) are not genetically distinguishable from their more typical looking counterparts. It would seem that in both cases the variants are simply aberrant individuals of their respective species.

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


*TORRES HUERTA A.;VILLAVICENCIO GARAYZAR, C. J.

(CVG)Universidad Autónoma de Baja California Sur, Laboratorio de Elasmobranquios, La Paz, B.C.S., México (ATH) Universidad del Mar Puerto Angel Oaxaca.

Reproductive biology of the scalloped hammerhead shark, Sphyrna lewini (Griffith and Smith, 1834)(Pisces: Sphyrnidae) in the Gulf of California, México

From 1990 to 1996 we visited eight commercial shark fishing camps in the Gulf of California. A total of 1,740 Sphyrna lewini were examined and total length (TL), weight, sex and state of maturity were noted. Female total lengths ranged between 41-363 cm and males 43-290 cm TL. The sex ratio in embryos, newborn and juveniles was 1:1, but in preadults and adults the sex ratio depended on reproductive condition. Male scalloped hammerheads reached maturity at 173 cm, while the size of maturity in females was 232 cm TL. The gestation period lasts 11 months and the highest fecundity was 32 embryos. Birth occurs in May and June, at a size between 47-49 cm TL. The juveniles were found in the Gulf of California all year long, with highest abundance during fall-winter in the southeast and in the southwest during spring-summer. On the other hand, adults migrate in spring toward the north region and southeast coast of the Gulf of California, presumably searching for a reproductive zone.

16/06/2000 - 11:15:00 AM - Salon Madre Perla


*TORRES HUERTA A.;VILLAVICENCIO GARAYZAR, C. J.

(CVG) Universidad Autónoma de Baja California Sur, Laboratorio de Elasmobranquios Carretera al Sur km. 5.5, La Paz, B.C.S., C.P. 23080, México (ATH) Universidad del Mar Puerto Angel Oaxaca.

Elasmobranch fisheries and nursery areas in the southeastern Gulf of California, México

From December 1997 through June 1998, we sampled the artisanal elasmobranch fishing camps called La Reforma, La Risión, Playa Sur and Teacapán, on the Sinaloa coast. A total of 17 species supports the fishery. The most abundant species were Sphyrna lewini, Rhinoptera steindachneri,  Rhizopronodon longurio, Carcharhinus falciformis and  Sphyrna zigaena. Capture areas and depths varied seasonally from 10 to 100 m. Information on juvenile occurreces suggest that the coast of Sinaloa is an important nursery area for Sphyrna lewini, P. glauca, C. falciformis, C. limbatus,  Nasolamnia velox, R. longurio, C, leucas and C. obscurus. Commercial captures were also taken from coastal lagoons, which also act as nursery areas for R. steindachneri, Dasyatis longus and Negaprion brevirostris.

16/06/2000 - 10:45:00 AM - Salon Madre Perla


TORRES, D. S.; LIM, I. A.; REYES, C. T.; NARIDA, E.

(STD; ALI) Dos Palmas Research Center, Arrecife Island, Barangay Manalo, Puerto Princesa City. (TRC; NE) Palawan Geographic Society, Lacao St., Puerto Princesa City.

Notes on the characteristics of whale sharks (Rhincodon typus) in Honda Bay (Palawan, Philippines)

Whalesharks were observed in Honda Bay from September 1999 to January 2000 through more than 60 research interactions using six types of observation platforms. No evidence of tags or tag scars were observed suggesting this whaleshark grouping has not been previously studied. Claspers were detected only on one whaleshark suggesting conformity with sex-segregation observed for other elasmobranchs. Modal class length was 4.4 - 5.6 meters (15-19 feet) suggesting conformity with size-segregation reported for other shark species. A maximum of nine whale sharks occurred simultaneously in two sightings (Sept. 21, 1999 and October 10, 2000). Sightings aggregated at a 40 km2 region adjacent to the 20-fathom isobath. Vertical feeding using active suction mechanism was a common foraging strategy. Whalesharks formed foraging assemblages with up to hundreds of birds and thousands of fishes indicating intense ecological processes in regions where whalesharks were encountered. Photo- and video-record analysis can identify at least twelve individuals, thus providing evidence for temporal segregation and shifts in individual composition through time. Six negative human-whaleshark interactions were recorded, two of which were fatal. These are: (1) deep cut across the left dorsal, anterior; (2) right pectoral amputated by straight, sharp object; (3) fishing gear fragments entangled on caudal peduncle; (4) scarring; (5) fatal entanglement in drift gill net; and (6) directed take. Government inspectors intercepted 829 kg of whaleshark meat in Puerto Princesa City Airport and are filing appropriate charges. Information generated enabled interested individuals and institutions in adjacent communities to initiate, coordinate and prepare conservation action plans addressing whaleshark related issues.

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


*TOVAR ÁVILA, J.;MÁRQUEZ FARÍAS, J. F.;ARENAS FUENTES, V.

(JTA)instituto Nacional de la Pesca Pitágoras 1320, Col. Santa Cruz Atoyac, C.P.03310 México D.F., México.; (FMF) CRIP Guaymas Calle 20 No. 605 C.P.85400 Guaymas, Son., México. (VAF) Instituo de Ciencias del Mar y Limnología, UNAM Ciudad Universitaria, C.P. 04510 México, D.F.

Age and growth of the blacktip shark, Carcharhinus limbatus, in the southern Gulf of Mexico

From july 1994 to december 1998 a total of 102 vertebral centra were collected and used to estimate the age and growth, Blacktip shark, Carcharhinus limbatus, caught in coastal waters off southern Gulf of Mexico. Marginal Increment Analysis was used to describe the temporal formation of growth rings. The Average Percent Error (APE) was used as a measure of agreement of lectures. For females, von Bertalanffy growth parameters were K= 0.19 1/y, 1799 mm of Total Lenght (TL) and to= -3.1 y. For males, K= 0.14 1/y, 1878 mm TL and to= -4.5 y. The results for females were similar to those obtained for individuals of Central Gulf of Mexico and Florida, but differents for males. Consistency of the parameters estimation and biological information with previous studies from northern Gulf of Mexico and tag-recapture results suggest a shared stock in Mexican and US waters.

17/06/2000 - 01:30:00 PM - Salon Madre Perla


*TYMINSKI, J. P.;JONES, E. M.;NEER, J. A.

(JPT) Center for Shark Research, Mote Marine Laboratory; ( EMJ) Moss Landing Marine Laboratories; (JAN) Coastal Fisheries Institute, Louisiana State University & Moss Landing Marine Laboratories

Nursery areas, revised sizes at maturity, and range extensions: findings from the Gulf of California artisanal elasmobranch fishery

As part of two-year collaborative study of the Gulf of California (GoC) artisanal elasmobranch fishery, biological data were routinely collected from catch samples to gain a more detailed understanding of the dynamics of this fishery. Neonates and young-of-the-year specimens of several species were a pervasive component within the catch, suggesting that some of the fishing grounds function as elasmobranch pupping and nursery areas. Knowledge of the location and range of these species' nursery areas is essential to understanding recruitment relationships and may prove critical for the long-term sustainability of the elasmobranch resources within the GoC. Pregnant females of 27 different species of sharks and rays also were documented in the catch records. In the case of several species, female specimens were pregnant at a size smaller than the reported size at maturity. Additionally, several shark and ray species were observed beyond their known geographic range. This paper will present some of these zoogeographical trends that have been revealed through a review of the catch and biological data collected from this project.

16/06/2000 - 10:30:00 AM - Salon Madre Perla


*UCHIDA, S.;TODA, M;KAMEI, Y.;TERUYA, H.

Okinawa Expo Aquarium, Okinawa, 905-0206 Japan

The husbandry of 16 whale sharks Rhincodon typus, from 1980 to 1998 at the Okinawa expo aquarium

From 1980 to 1998 16 whale sharks, Rhincodon typus, were kept in captivity at Okinawa Expo Aquarium, Okinawa, Japan. They were captured around Okinawa Is. by set-nets the center of which is located at 26°23´N, 127°41´E from March to September. The sea water temperature of the time captured were 21.1 to 29.0°C at the depth of 20 m. Only two of 16 sharks were females and 14 were males, The mean value and range in total length and body mass were 4.8 m and 3.1 to 6.3 m, and 814 kg and 290 to 1750 kg respectively. They were kept in the Kurosio tank which is 27 m long, 12 m wide and 3.5 m deep 1,100 m3 in volume. Water parameters of the tank in mean and range were as follows : Water temperature(°C) was 24.6 and 19.8 to 29.6, ph 8.2 and 7.9 to 8.35, and salinity (o/oo) 35.79 and 33.04 to 37.36. Mean and range of survival time in the tank were 502 days and 3 to 2056 days (ca. 5y 8m). The Whale sharks were fed on Euphausia pacifica, E. superba, Sergia lucens, Loligo japonica and Spratelloides gracilis once a day 6 days week. Mean feeding rates (food quantity / body mass / week x 100) of a 3.65 m female were 11.0 % in the first year of keeping, 8.5 % in the second year and 8.0 % in the third year. Mean growth per year of this shark was 29.5 cm in total length ( survival time : 2056 days) , 4.5 m male shark 21.6 cm (1040 days) and 4.85 m male 25.5 cm (458 days) respectively. Feeding and other behaviors in tank are reported.

15/06/2000 - 01:45:00 PM - Salon Madre Perla


*VÉLEZ MARÍN, R.;MÁQUEZ FARÍAS, J. F.;MENDIZABAL ORIZA, D.

MVR, OMD) Centro Regional de Investigación Pesquera de Manzanillo. Instituto Nacional de La Pesca. SEMARNAP. Playa Ventanas s/n. A.P. 591. C.P. 28200. Manzanillo, Colima, México (FMF) Centro Regional de Investigación Pesquera. Instituto Nacional de La Pesca. SEMARNAP. Calle 20 Sur # 605. Col. Cantera. CP 85400, Guaymas, Sonora, México

The oceanic sharks with low frequency catch in the longline fishery in the Ocean Pacific of México (1986-1999)

In this study results of 40 trips of the longline fleet operating in the EEZ of México is presented. A total of 908 sets, 1244530 hooks and 94315 large pelagics in a 13 years period (1986-1999) were summarized. Catch composition was represented by 50.78% sharks, 40.76% billfishes, 4.59% dorado, 3.54% yelow fin tunna. The low frequency sharks in catches were Isurus oxyrinchus 518 (0.55%), Nasolamia velox 284 (0.30%), Carcharhinus longimanus 276 (0.29%), Alopias superciliosus 115 (0.12%), Galeocerdo cuvieri 84 (0.09%), Sphyrna zygaena 29 (0.03%), Carcharhinus leucas 17 (0.02%), Echinorhinus cookei 1 (0.001%). This woks reports information on catch zones, relative abundance (catch per 100 hooks), and information regarding to length, weight, and sex.

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


VILLAVICENCIO GARAYZAR, C. J.;*CADENA CÁRDENAS, L.;BALART, E. F.

(CJGV; LCC) UABCS, Laboratorio de Elasmobranquios Carretera al Sur km. 5.5, La Paz, B.C.S., C.P. 23080, México; (EFB) Centro de Investigaciones Biológicas del Noroeste, S.C., Laboratorio de Ictiología

Morphological and osteological development of Carcharhinus falciformis (Chondrichthyes: Carcharhiniformes: Carcharhinidae) embryos

Morphological and osteological development of the silky shark Carcharhinus falciformis is described from a series of 45 embryos 11-670 mm TL collected from artisanal fisheries in the Gulf of California. The change of body proportions with growth was assessed with the use of thirty-two morphometric measurements. Observation on the osteological development were done through cleared and stained specimens. Development was first concentrated on the head and pectoral areas. Fin supports form in the following sequence: pectorals, pelvics, first dorsal, second dorsal, and anal fin. Body proportions followed an almost isometric pattern but head measurements. Both left and right spiracles are present early in development but from 100 mm only the latter is still open. Tooth buds were observed from 113 mm and two tooth rows in both upper and lower jaws were already present by 175 mm.

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


*VILLAVICENCIO GARAYZAR, C. J.;CADENA CÁRDENAS, L.;TORRES HUERTA, A.;MARIANO MELENDEZ, E.;GUERRERO MALDONADO, L. A.

UABCS, Laboratorio de Elasmobranquios Carretera al Sur km. 5.5, La Paz, B.C.S., C.P. 23080, México

Elasmobranch fisheries on the east coast of Baja California Sur, Gulf of California

During 1998 and 1999 over one hundred fishing camps were visited in Baja California Sur (BCS). The catch was composed of 39 species, including 19 shark and 20 ray species. The port of Mulege was the most important fishing camp for small sharks and the southwestern coast was most important for pelagic sharks. The main species caught were Rhizoprionodon longurio (15.39%), Prionace glauca (15.07%), Carcharhinus falciformis (10.70%), Nasolamia velox (9.24%), Mobula munkiana (7.62%) and Isurus oxyrinchus (7.13%). The elasmobranch fisheries along the BCS coast during 1998 and 1999 were less important than previous years because the main fisheries targeted red snapper, yellowtail and giant squid. This shoreline is an important reproductive area for Squatina californica, R. longurio, P. glauca and C. falciformis.

16/06/2000 - 09:30:00 AM - Salon Madre Perla


WALSH, C. J.;BODINE, A. B.;NOYES, D. R.;*LUER, C. A.

(CJW; DRN; CAL) Mote Marine Laboratory, 1600 Ken Thompson Pkwy, Sarasota, FL, USA 34236; (ABB) Department of Animal and Veterinary Sciences, Clemson University, Clemson, SC, USA 29634

Preliminary evaluation of tumor cell growth inhibition by conditioned media from in vitro cultures of nurse shark (Ginglymostoma cirratum) and clearnose skate (Raja eglanteria) immune cells

The potential for immune regulatory factors to be secreted by shark and skate immune cells into the media bathing cultured cells (conditioned media, CM) was examined. Using CM from cultures of peripheral blood leukocytes (PBL) and immune cells from epigonal organ, Leydig organ, and spleen, preliminary experiments to assess effects on growth of interleukin-1 (IL-1) sensitive human malignant melanoma tumor cells (American Type Culture Collection, ATCC cell line A375.S2) were initiated. Inhibition of tumor cell growth was measured after 4 days of culture in the presence of various dilutions of CM, and was assessed colorimetrically comparing the conversion of MTT dye from yellow to blue by live cells in experimental and control cultures. Growth inhibition was visualized by comparing relative amounts of adherent versus unattached tumor cells. Mean inhibition for CM from 3-5 day cultures ranged from 10-30% for unstimulated shark and skate epigonal cells, from 23-47% for unstimulated skate Leydig organ cells, and from 46-62% for unstimulated skate spleen cells. CM from PBL stimulated with the mitogen, lipopolysaccharide, resulted in a 68% inhibition of tumor cell growth. Efforts to isolate and characterize an IL-1-like immune regulatory factor are currently underway.

18/06/2000 - 11:00:00 AM - Salon Madre Perla


WEST, G. J., and *STEVENS, J. D.

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

Position estimates and depth behaviour from archival-tagged school sharks (Galeorhinus galeus) in southern Australia

Thirty school sharks were released in October-November 1997 with externally attached archival tags, and another 16 in November 1998 with internal tags. To date nine external (30%) and five internal (31%) tags have been returned. Periods at liberty varied from 8 days to 18 months. Data from returned tags showed a relatively regular diel pattern of vertical movements with the sharks usually rising towards the surface at night and descending close to the bottom during the day. About 20 % of their time was spent in deep-water off the continental shelf when the diel vertical movements were up to 550 m in extent. Light data from the tags was used to estimate longitude when the sharks were at depths down to 150 m. Latitude was mostly estimated from bathymetry information in conjunction with the maximum daily depth recorded by the tag, assuming the fish were on the bottom. Latitude estimates based on light data and from the diving behaviour of the fish are also discussed. Only one of the recaptured sharks showed extensive movements outside of the general area bounded by the release and recapture positions. {revised abstract}

17/06/2000 - 09:00:00 AM - Salon Madre Perla


*WETHERBEE, B. M.;GRUBER, S. H.;ROSA, R. S.;GARLA, R. C

(WB), NOAA/NMFS/NEFSC 28 Tarzwell Dr.,Narragansett, RI 02882(GSH), Bimini Biological Field Station, 9300 SW 99th St., Miami, FL 33176(RRS), Departmentode Systematica e Ecologia,Universidade Federal da Paraiba, 58059-900 Joao Pessoa, PB, Brazil, (GRC) UNESP/Rio Claro, Sao Paulo, Brazil

Tidally based activity patterns of neonate lemon sharks (Negaprion brevirostris) at Atol das Rocas, Brazil

Atol das Rocas, located 3º 52' S latitude and 259 km east of Natal, Brazil, is a marine reserve containing a unique oceanic nursery for a population of approximately 65 juvenile lemon sharks. The study on this population was conducted to define temporal and spatial patterns of movement of young lemon sharks at the atoll and to compare their behavior with that of sharks from more typical nurseries. Seven data-logging receivers were placed on the sea floor in strategic locations in the northwestern portion of the atoll, where young lemon sharks had previously been observed.Then, seven neonate lemon sharks were fitted with 69 kHz ultrasonic transmitters, released, and monitored for 15 days. Data acquired by the receivers showed that the sharks shuttled between two habitats depending on the tidal cycle. During low tides, they were located in one of several 2,500 m2 pools on the NW perimeter of the atoll. At the higher portion of the tidal cycle, they entered a 350 x 30 m tidal creek, where they remained until the water level fell below mid-tide. Thus, movements in and out of the creek and tidal pools were closely timed with tidal flow. This general pattern was repeated daily. The movement patterns observed at Atol das Rocas differ from those of young lemon sharks in nurseries elsewhere and may be driven by predator avoidance. This study was supported by NOAA/NMFS/NEFSC, NSF/INT, CNPQ, and IBAMA.

17/06/2000 - 08:45:00 AM - Salon Madre Perla


*WYFFELS, J. T.;MORRIS, J. A.;WOURMS, J. P.;BODINE, A. B.;SNELSON, F. F.

(JTW; ABB; JPW) Clemson University, Avs Deptartment, Clemson, SC 29634; (FFS;JAM) University of Central Florida, Department of Biology, Orlando, Florida 32816

Ultrastructure of the diapausing eggs and uterine mucosa of Dasyatis say

Dasyatis say is an aplacental viviparous ray common to the coast of the western Atlantic ocean. Diapausing, encapsulated eggs can be found in the uterus of females from May until the following March, when embryo development resumes. Partrution occurs prior to ovulation in May. Using epifluorescence microscopy, macrophotography, histology, and electron microscopy we examined the uterine mucosa and embryos of D. say throughout its diapause. The uterine mucosa has villiform projections termed trophonemata throughout the year. Trophonemata become increasingly vascular and develop glands that secrete nutritive histotroph. The trophonemata of diapausing rays consist of simple tubular glands and vascular connective tissue. The glands are composed of columnar cells with basal nuclei. Shallow pits formed by invaginating cells covered with microvilli mark gland openings on the surface of the trophonemata. The trophonemata of rays remain unchanged during diapause. Developmental arrest in diapausing embryos occurs at an early blastula stage. The blastoderm is demarcated from the remainder of the yolk mass by a wide zone of dense microvilli. A segmentation cavity lies beneath the blastoderm. The surface blastomeres vary in appearance from flat to bulging and are covered with varying amounts of microvilli. Blastoderms do not increase in total area throughout diapause.

18/06/2000 - 09:45:00 AM - Salon Madre Perla


*YANO, K.;TAKASHI, I. O;HIROFUMI, S.;TAKEHARU, K.

(KY; HS; TK) Seikai National Fisheries Research Institute, Ishigaki Tropical Station, 148-446 Fukai Ota, Ishigaki, Okinawa 907-0451 Japan; (TI) Marine Service Ito, 3400-1 Kohama, Taketomicho, Yaeyama-Gun, Okinawa 907-1221 Japan; Seikai National Fisheries Research Institute, Ishigaki Tropical Station 148-446 Fukai Ota, Ishigaki, Okinawa 907-0451 Japan

Telemetry studies on the movements of the manta ray, Manta birostris, at the Yaeyama Islands, Okinawa, Japan

The manta ray, Manta birostris (family Mobulidae), is the largest known ray and one of the largest living fishes, reaching a disc width of at least 6.7 m. The diurnal movements of manta rays were studied using ultrasonic telemetry at the Yaeyama Islands, Okinawa, Japan, from October 1997 to July 1999. Four male and two female manta rays (approximately 2.5-4 m DW) were equipped with ultrasonic, depth-sensing transmitters. The transmitters were attached to the edge of the pectoral fin of each manta ray by SCUBA diving at a cleaning site (Kabira Ishizaki of Ishigaki Island). Two types of horizontal movements were observed: 1) the manta rays swam around Kabira Ishizaki at a depth of 10-30 m during the day and swam in offshore areas (at depths of 100-200 m) during the night, and then returned to Kabira Ishizaki each morning; 2) the manta rays swam near Kabira Ishizaki for a short time before moving to the offshore reef slope (about 50-100 m in depth) during the afternoon and night, and they did not return to Kabira Ishizaki the next day. The swimming depth of the manta rays during the daytime was usually from the surface to about 50 m down. During the nighttime they swam very close to the sea floor, usually at depths from 50 m to about 200 m, with occasional trips upward to the surface.

17/06/2000 - 08:30:00 AM - Salon Madre Perla


YAPTINCHAY, A. A.;*ALAVA, MOONYEEN N. R.

World Wildlife Fund - Philippines,23 Maalindog St., UP Village, Diliman, Quezon City 1101

Philippines community-based whale shark conservation and ecotourism development

Report on a whale shark aggregate in Donsol, Sorsogon (southern Luzon) in January 1998 led to the discovery and promotion of the area as a potential whale shark ecotourism site. Media coverage of this discovery led to tourist influx to an ill-equipped community as well as hunters' encroachment to the site which otherwise had no history of hunting. The municipal waters of Donsol were protected by a local ordinance establishing the site as a whale shark sanctuary in early March 1998. Despite this ordinance, seven whale sharks were poached in the area. This raised a national alarm which ultimately led to the estbalishment of a Fishery Administrative Order (FAO) 193, also called as the Whale Shark and Manta Ray Ban, in late March 1998. WWF-Philippines was invited to help establish the whale shark exotourism activity and through a consultative effort with stakeholders, the Donsol Whale Shark (Butanding) Ecotourism Management Plan was developed, with financial support from UNDP. A tri-partite agreement was drawn up involving the local government of Donsol, a local NGO (Donsol Municiapl Torusim Council), and WWF-Philippines. The whale shark interaction tourism in Donsol has been operational for two seasons and tourism statistics is presented for 1998 and 1999. Tourism as an economic alternative to hunting has been proven to be successful. This strategy is able to support community development, conservation, and the tourism industry as well as provide a multitude of venues for increased appreciation of natural resources, protecting habitats and threatened species. However, politicial rivalries and administrative problems have blighted tourism management itself.

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


*YOUNG, F. A.; POWELL , D. C.; LERNER, R.

Monterey Bay Aquarium-retired 1019 Short Street Pacific Grove, CA 93950

Long distance transportation of the silky shark, Carcharhinus falciformis

Pelagic silky sharks (Carcharhinus falciformis) are challenging to collect and transport and make an impressive display candidate for large public aquariums. Not as delicate as the scalloped hammerhead, (Sphyrna lewini), they do require specialized handling techniques similar to those used with C. acronotus. They are significantly easier to transport than C. limbatus of the same length. The capture, transportation and husbandry of the silky shark has been undertaken by seaside aquariums however, no long distance transportation of this species has previously been attempted. The techniques used were developed for the transportation of S. lewini and other small free-swimming sharks (C. limbatus, C. acronotus and S. tiburo). The transport equipment was designed to facilitate ram ventilation, reduce obstruction of swimming patterns and minimize the depletion of energy reserves. Transport times of 24 to 36 hours resulted in minimal risk of specimen mortality. Transport times of up to 50 hours may be possible by modifying the size and shape of the transportation vessel and reducing of the size and number of specimens transported per shipping container.

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