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 3: Janech through O'Sullivan

(MGJ) Medical University of South Carolina Marine Biomedicine and Environmental Sciences,221 Fort Johnson Rd. Charleston, South Carolina 29412, USA; (RC, RVP, DWP, WRF) Musc, Dept. of Medicine, Nephrology 96 Jonathan Lucas Street, P.O. Box 250623 Charleston, Sc 29425, USA; (DHM) Musc, Dept. of Pharmacology 173 Ashley Ave, P.O. Box 250505 Charleston, SC 29425, USA

A putative renal urea transporter cloned from the euryhaline stingray, Dasyatis sabina

In elasmobranch fishes changes in urinary urea excretion are due in part to changes in fractional urea excretion. In mammals, changes in fractional urea excretion are mediated through facilitated urea transporters (UT) which regulate tubular urea permeability. Regulation of urea permeability in the elasmobranch nephron may also be controlled by UTs as a UT has been cloned from the kidney of a stenohaline shark Squalus acanthias. We hypothesized that a UT would be also present in the kidney of the euryhaline Atlantic stingray Dasyatis sabina. Degenerate primers were used to identify a 220bp UT fragment by RT-PCR using total kidney RNA from D. sabina. Subsequently, a 2.6kb cDNA encoding a putative UT protein (431 amino acids in length) was cloned using 5'/3' RACE. The first 381 and 397 deduced amino acids are 81% and 58% homologous to the shark UT and rat UT-A2 protein sequences, respectively. Northern analysis detected 2.6 and 4kb transcripts from kidney poly(A+) RNA, suggesting multiple UT isoforms are present in the kidney of D. sabina. The high degree of homology with other UTs suggests that the cloned cDNA from the stingray may encode a functional UT that contributes to the regulation of tubular urea permeability.

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


Dept. of Ecology & Evolutionary Biology, University of Connecticut, Storrs, Connecticut, 06269-3043, USA

Tapeworms of elasmobranchs from the Gulf of California

Forty-three species of sharks and rays were examined for tapeworms during the summers of 1993 and 1996.Specifically, 21 species in the superorder Galea belonging to 12 genera and 22 species in the superorder Squalea belonging to 13 genera were necropsied, their spiral intestines removed and examined for tapeworms. Of those 43 species, only 1 species (Urobatis halleri) had previously been examined for parasites in the Gulf of California. Twenty-one species had been examined for tapeworms elsewhere in the world. The remaining 21 species had never been examined for tapeworms. All elasmobranch species examined were parasitized by at least 1 species of tapeworm. A total of over 200 different species of tapeworms were identified, almost 50% of which are new to science, including 7 new genera. The number of different tapeworm species per species of elasmobranch ranged from 1 (Carcharhinus porosus, C. limbatus and Galeocerdo cuvier) to 16 (Urobatis maculatus and U. halleri). On average, members of the Galea were parasitized by 4 different species of tapeworms, while members of the Squalea were parasitized by 7 different species of tapeworms. Whether this tapeworm fauna is unique to the Gulf of California remains to be investigated.

16/06/2000 - 11:30:00 AM - Salon Madre Perla


Academia Sinica, Nankang , Taipei, Taiwan,115 R. O. C.

Systematics of Dasyatidae based on mitochondrial 12S Ribosomal DNA sequences

The current systematics of stingrays based on morphological characters are still under debate, which need a thorough revision, especially for that in the subfamily Dasyatinae. We analyzed the DNA sequences of the complete mitochondrial 12S rRNA gene to see if the molecular data is consistent with the current morphological classification from the eleven species in family Dasyatidae, including 9 species of subfamily Dasyatinae and 2 species of subfamily Potamotrygoninae. The phylogenetic tree from the 12S rRNA nucleotide sequences are constructed by employing maximum likelihood, maximum parsimony and neighbor-joining methods. The results suggest that the dichotomous classification of Dasyatinae and Potamotrygoninae both included in family Dasyatidae is reasonable. However, some other genera such as Dasyatis, Himantura, Taeniura and Urogymnus belonging to subfamily Dasyatinae can be reassigned and merged into one genus Dasyatis.

18/06/2000 - 05:00:00 PM - Salon Madre Perla


University of Hawaii, P.O. Box 1346, Kaneohe, HI, 96744, USA

Head morphology and electroreceptor distribution of Carcharhinid and Sphyrnid sharks

Selection to increase electroreceptive sensitivity may have driven evolution of the sphyrnid head morphology. Although gross head morphology clearly differs between carcharhinid and sphyrnid sharks, a quantitative examination is lacking. Head morphology was compared between a carcharhinid, Carcharhinus plumbeus, and two sphyrnid sharks, Sphyrna tiburo and S. lewini. The raked head morphology of neonatal S. lewini pups is hypothesized to be an adaptation to facilitate parturition in this species where the head is oriented orthogonal to the body axis. The anterior head angle decreases in post-parturition S. lewini pups while this change is much less dramatic for the other two species. Electroreceptor pore distribution and pore counts were also compared across species. The general pattern of pore distribution on the head is conserved across species despite the differences in gross head morphology. S. lewini has a mean of 3070 pores, S. tiburo has a mean of 2030 pores and C. plumbeus has a mean of 2300 pores and the number of pores remains constant with age. Sphyrnids have a greater number of pores on the ventral surface of the head while C.plumbeus has an even distribution on dorsal and ventral surfaces. The comparatively small head volume combined with the greater number of pores gives S. lewini the highest density of electroreceptors per unit volume.

18/06/2000 - 11:30:00 AM - Salon Madre Perla


University of Massachusetts, Boston BUMP, MBL, Woods Hole, MA 02543

Organochlorine contaminants in pregnant grey reef sharks (Carcharhinus amblyrhynchos) from Johnston Atoll

Samples from the grey reef shark, Carcharhinus amblyrhyncos, were analyzed for polychlorinated biphenyls (PCBs), dioxins, and furans to examine the extent of bioaccumulation in this top predator at Johnston Atoll, Central Pacific Ocean. Four females were collected from an aggregation that occurs annually off of Sand Island (see talk by Lobel). All four sharks were pregnant, ranging in size from 154 to 173 cm TL. Liver samples were analyzed for the presence of 25 specific PCB congeners and 17 dioxin or furan congeners. Total PCBs in liver ranged from 131.0 to 946.0 ng/g. Toxic equivalents (TEQ) for 2, 3, 7, 8 tetrachlorodibenzo-p-dioxin in shark liver ranged from less than 0.001 to 77.910 pg/g. Contaminants were also measured in muscle tissue and embryos of two sharks that had developmental defects. One adult shark was missing a gill arch on one side while another shark contained an embryo with a deformed vertebral column. A third shark contained an embryo that had ceased developing at the four-cell stage. The extent to which these abnormalities normally occur is unknown.

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


(KJT) Museo de Historia Natural, Universidad Autónoma de Baja California Sur. Carretera al sur, km 5.5, La Paz, B.C.S., C.P. 23080, Mexico., (LAR) Baja Quest & Niparaja, A.C., La Paz, B.C.S

Observations on the seasonal occurrences of whale sharks (Rhincodon typus Smith, 1828) in the southern Gulf of California

Historical records of whale sharks in the Gulf of California are anecdotal and unreliable for the most part. In spite of recent reports of whale sharks associated with seasonal plankton blooms in the Bay of La Paz, formal studies on their distribution and abundance within the Bay and neighboring areas are almost non-existent. For this reason, a five year survey on whale shark occurrences started since 1995 in the Bay of La Paz and neighboring islands such as San Jose, Espiritu Santo and Cerralvo, plus offshore islets and seamounts. A spotter plane and different vessels were used in order to search these areas during the plankton bloom seasons (May-June and October-November). During each sighting information such as location, size, sex, markings and behaviour of each individual were recorded by swimming close to each animal both free-diving or by using SCUBA. Our observations indicate that younger animals occur more commonly feeding on plankton blooms closest to the coastline in the Bay of La Paz, whereas older animals tend to appear non-feeding in offshore areas such as El Bajo and east of Espiritu Santo island. The locations with the highest number of occurrences were the area between the phosphate mine in San Juan de la Costa and Punta Mogote, and El Bajo seamount. Overall, females were larger, especially those apparently pregnant seen in offshore areas, and more abundant than males in all locations. The continuity of studies such as these will help to build a solid background for future studies on population and migratory patterns of whale sharks in the area, that will ultimately support conservation and managememt efforts for this species in the Gulf of California.

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


University of Colorado at Boulder Dept. EPO Biology, Cb 334, Boulder CO 80309

A comparison of heat shock 70 gene diversity in cartilaginous fishes

Heat shock genes have been identified in all groups of organisms and are best known for their role in stress responses. Our interest in the heat shock 70 gene family centered on using this multigene family to test hypotheses of phylogenetic relationships among cartilaginous fishes. In order to base our analysis on homologous, not paralogous, gene copies, we need to recover as many copies of this multigene family as possible. We cloned PCR products that amplified portions of the heat shock 70 gene, and these clones were screened for gene diversity by dideoxy fingerprinting. Representatives of the unique fingerprint patterns were then sequenced. To date we have surveyed gene diversity in one freshwater ray (Pomomotrygon motoro) and six species of sharks (1 carcharhinoid and 5 lamniform). We detected two major clades of heat shock 70 genes, but the diversity of gene copies within the freshwater ray far exceeded the number of copies detected within the sharks. Sampling additional taxa may allow us to speculate as to whether this pattern is a result of phylogenetic history or is possibly indicative of the different selective pressures found between marine and freshwater environments.

18/06/2000 - 01:30:00 PM - Salon Madre Perla


(ERL) Marine Biomedicine and Environmental Sciences, (JC) Department of Cell Biology, (EEB; CS) Department of Biochemistry and Molecular Biology; Medical University of South Carolina,171 Ashley Avenue, Charleston, South Carolina,29425,USA.

Morphology and biochemistry of the alkaline gland in the Atlantic stingray, Dasyatis sabina

The alkaline glands are present in male skates and stingrays but not sharks. Glands consist of paired, blind-ended sacs on the distal end of each kidney. A duct drains a highly alkaline fluid (pH 8-8.2) into the cloaca. This study examined the morphology and histochemistry of the gland, trans-epithelial transport of the mucosa, and fluid composition in the Atlantic stingray. A simple columnar epithelium lines the gland lumen and secretes a burgundy colored fluid into the sac lumen. Ultrastructure showed these cells with an extensive endoplasmic reticulum and large secondary lysosomes containing lipofuscin. Carbonic anhydrase activity was localized within intracellular spaces. In Vitro electrophysiology suggested the presence of apical epithelial bicarbonate exchangers that are sodium and chloride dependent, basal sodium and bicarbonate transport and a short circuit current that is not totally dependent on a sodiupotassium ATPase. Chromatography, electrophoresis, sequence analysis and mass spectrometry of the fluid revealed a molecule of 2 polypeptide chains of 4 and 9 kDa, with 27 and 54 amino acids in the A and B chain respectively and an N-linked asialo oligosaccharide. This molecule is the first member of the relaxin family of peptides identified in a non-homeotherm male and the first reported to be glycosylated.

18/06/2000 - 11:15:00 AM - Salon Madre Perla


CSIRO Marine Research, Marine Laboratories, Castray Esplanade, Hobart, 7001, Australia

Elasmobranchs of Australian rivers and estuaries - conservation issues

More than 100 shark and ray species venture into Australian rivers and estuaries. Several elasmobranchs breed opportunistically or occur seasonally in these habitats but only seven species are considered to be dependant on non-marine habitats. These include carcharhinids (3 species), dasyatids (2 species), pristids (1 species), and rajids (1 species). Much of the region remains inadequately surveyed so knowledge of the biology and distribution of the obligate freshwater/estuarine component remains poor despite a flurry of effort to describe the fauna in the last decade. Anecdotal evidence, however, suggests that this component has been detrimentally affected by human activities and that the level of impact varies across the continent. Deteriorating water quality and increasing fishing pressure are thought to be the main culprits. Misidentification of species, mainly through the confusion of freshwater species with their marine siblings, have reduced the value of some historical data. The status of two river sharks (Glyphis spp) is of particular concern as both are known from very limited ranges and very few specimens of either species have been identified. These issues are discussed in the light of recent knowledge and a baseline conservation strategy for the fauna is proposed.

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

Lobel, Phillip S.

Boston University Marine Program, Marine Biological Lab. Woods Hole, MA

Grey reef shark aggregation behavior at Johnston Atoll, Pacific Ocean

Female Carcharhinus amblyrhynchos exhibit an annual pattern of migration and aggregation at Johnston Atoll, Central Pacific Ocean. Beginning in Febuary and continuing into May, females migrate daily from outer reef slopes into the middle of the lagoon. They aggregate at one specific site in shallow water adjacent to an island. This pattern has been documented since 1992. Daily numbers of sharks range from a few to 107 and fluctuate cyclically. Only females have been seen aggregating. At the same time males and other females are seen on the outer reef. Four females collected from the aggregation were pregnant (see poster by Kerr). Acoustic tags were used and revealed that individuals return to the site repeatedly. In 1999, 2 year duration acoustic tags were attached to five females and a series of fixed station monitors were deployed around the atoll. Data will be downloaded after this abstract is due, so I hope it works. I will present results of the daily census surveys and the acoustic tracking study. {revised abstract}

17/06/2000 - 10:15:00 AM - Salon Madre Perla


University of Charleston Grice Marine Laboratory 205 Fort Johnson Charleston, SC 29412

Life History of the Atlantic sharpnose shark, Rhizoprionodon terraenovae, in the South Atlantic Bight

The life history of the Atlantic sharpnose shark (Rhizoprionodon terraenovae), is well documented in the Gulf of Mexico, yet there are no published age and growth data available on this species in the South Atlantic Bight. A

total of 1090 specimens were collected from Virginia to northern Florida from April 1997 to March 1999. Frontally sectioned vertebral centra were used to age each specimen, and the periodicity of circuli deposition was validated through marginal increment analysis. Atlantic sharpnose shark reached a maximum size of 810 mm precaudal length (PCL, or 1067 mm TL) at age 11+. Sexual maturity (100%) was reached at age three and size 601 mm PCL (801 mm TL) for females, and age three and size 617 mm PCL (827 mm TL) for males. Mean back-calculated lengths at age ranged from 448 mm PCL (602 mm TL) at age one to 731 mm PCL (965 mm TL) at age nine for males, and 445 mm PCL at age one (599 mm TL) and 785 mm PCL (1034 mm TL) for females. Observed length at age data yielded the following von Bertalanffy growth equations: Males Lt = 745 mm PCL (1 - e-0.50(t - (-0.90)), Females Lt = 749 mm PCL (1 - e-0.49(t - (-0.94)) The 95% confidence intervals for L¥, K and t0, respectively, were: 734-758, 0.46-0.56 and -1.01 t0 -0.806 for males and 740-760, 0.45-0.54 and -1.04 t0 -0.844 for females. The data presented are a final update from the preliminary results presented at the 1999 meeting.

17/06/2000 - 02:15:00 PM - Salon Madre Perla


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

Phylogenetic relationships of Triakid genera inferred from DNA sequences

Compagno (1988) places nine carcharhiniform shark genera, totaling approximately 39 species, in the family Triakidae. There is no morphological evidence to unambiguously support the monophyly of the Triakidae. Compagno divides the triakids into two subfamilies: the Triakinae and the Galeorhininae. Triakin genera are the more primitive Mustelus, Scylliogaleus, and Triakis. The Galeorhininae consists of the tribes Iagini, for ago, Furgaleus, Hemitriakis, and Gogolia, and Galeorhinini for Galeorhinus and Hypogaleus. Although Compagno's study of carcharhiniform morphology was thorough and extensive, he did not present clear evidence to support his hypothesis of triakid inter-relationships. We have analyzed DNA sequence data from three mitochondrial and one nuclear protein coding genes, totaling approximately 5,000 nucleotide sites, to test the hypotheses of triakid monophyly and triakid inter-relationships proposed by Compagno. Our analyses included sequences from representatives of all but two of the triakid genera and several representatives from four other carcharhiniform families. We discuss our results in the context of Compagno's morphology based inference of triakid relationships.

18/06/2000 - 03:15:00 PM - Salon Madre Perla


(CGL) Dept. of Biol. Sci., CSU-Long Beach, 1250 Bellflower Blvd., Long Beach, CA 90840; (BMW) NOAA/NMFS/NEFSC, 28 Tarzwell Dr., Narragansett, RI 02882; (KNH) Himb, Univ. of Hawaii, P.O: Box 1346, Kaneohe, HI 96744 USA

Movement patterns of tiger sharks in Hawaii: reef residents or ramblers?

During the summer months, seabirds, sea turtles and Hawaiian monk seals increase in abundance within the Northwestern Hawaiian Islands and represent large source of prey for sharks. Suspected increases of shark predation on endangered monk seals has prompted interest on the behavior of tiger sharks near seal haulout and pupping areas at French Frigate Shoals (FFS). Preliminary tracks of two tiger sharks fed transmitters showed that these sharks frequently visit small islands where seals, turtles, and fledging birds are common. Movements of these sharks were often closely associated with shallow reefs and the sharks repeatedly returned to the small island where tracking was initiated. Behaviors of tiger sharks observed at FFS differed markedly from those of tiger sharks captured on longlines and tracked near Oahu, Hawaii. Nearly all of the Oahu sharks made directed offshore movements, crossing water as deep as 600 m, and traveled considerable distances after their release. Several of these sharks were recaptured or detected off Oahu near the original site of capture, but were reacquired after a period of weeks or months. Differences in the observed movement patterns may be attributed to variations in habitat, prey availability, method of transmitter attachment and human population.

17/06/2000 - 11:45:00 AM - Salon Madre Perla


Baja Quest, Scuba Diving and Adventure Travel Service & NIPARAJA A.C. - Environmental Group, La Paz, B.C.S. C.P. 23060, México

A proposed management program for the whale sharks Rhincodon typus of La Paz Bay, B.C.S.

Recorded whale shark (Rhincodon typus Smith, 1828) sightings during the last 5 years show that aggregations occur in La Paz Bay at specific locations during seasonal plankton blooms. The sites are currently well known by the local dive operators and other outdoor service providers. The relatively predictable presence of the sharks in the proximity of the city has increased the number of tourists who come to La Paz to interact with the whale sharks. Even though whale sharks are not commercially fished in Mexico, the increased tourism may generate detrimental impacts to the whale sharks feeding or migration patterns. The presence of whale sharks represents economic revenue for La Paz tourism industry and an ideal location for research and monitoring of their biology and ecology. Very little is known about the abundance, distribution and reasons why they aggregate in La Paz Bay, consequently, tourism impacts are difficult to estimate. This paper suggests a precautionary approach to manage the area where whale sharks seasonally occur. The program's objectives are to provide guidelines for sustainable human-whale shark interactions and to implement a monitoring program that will generate scientific information. The proposed management program takes into consideration the Mexican authorities' environmental regulations and their criteria for protected areas.

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


(LMMA, GJP, RUAB) Silliman University Marine Laboratory, Dumaguete City, Philipines; (AMN; AC)World Wildlife Fund-Philippines, Quezon City, Philippines.

A preliminary report on the fishery, conservation and management of chondrichthyan fishes in selected areas of the Visayas and Mindanao, Philippines

A survey to determine chondrichthyan fishery and fishers´s attitudes towards chondrichthyans was conducted in selected areas of the Visayas and Mindanao, Philippines from January to April 1999. This survey was done in order to determine the status of the fishery, identify conservation and management needs and initiate conservation and management of chondrichthyan fishery in the Philippines. Information was collected through interviews conducted with fisherfolks using prepared data forms and questionnaires. Of 178 fishers interviewed, 66% were directly or indirectly involved in chondrichthyan fishery and 85% owned fishing boats. Seven types of fishing gears and methods used in catching possibly more than 104 species of chondrichthyans were: handline, longline, surface gillnet, bottom set gill net, fishtrap, trawl and speargun. The fishing gear with the highest catch per unit effort (CPUE) was trawling in Toboso, Negros Occidental (at 149 individuals/trip). Lowest CPUE estimates were reported for handline in Pagatban, Basay, Negros Oriental and Bug-ong, Mambajao, Camiguin (0.01 individual/trip). On the uses of chondrichthyans, about 7.32% of the fishers believed that they have supernatural powers and 85.71% utilized shark oil, dried skin, liver and heart as medicine for rheumatism and skin diseases. Only 5% believed sharks have ecological functions and 31.71% saw a need for chondrichthyans to be conserved. Based on preliminary findings, information and education campaigns are necessary if conservation and management efforts are to be implemented in the future.

16/06/2000 - 01:45:00 PM - Salon Madre Perla


(CAM) Center For Shark Research Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, FL 34236 USA (LELR)Oregon Graduate Institute, PO Box 91000, Portland, OR 97291 USA (EC) National Marine Fisheries Service, 3500 Delwood Beach Road, Panama City, FL 32408 USA

Infertility in bonnethead sharks, Sphyrna tiburo, in the eastern Gulf of Mexico may be caused by endocrine disrupting chemicals in the environment

Previous studies have demonstrated a high frequency of occurrence of infertile ova present in the uterus of pregnant female bonnethead sharks along the central Gulf coast of Florida. We hypothesized that this infertility was caused by disruption to the endocrine system and that this infertility could be correlated with the presence of environmental contaminants, especially organochlorines. To test these hypotheses, we collected samples from bonnethead sharks from three areas that represented three different levels of organochlorine contamination. These included Florida Bay in the Florida Keys (representing the least contaminated control area), Anclote Key near Tampa Bay ( a highly contaminated area), and Apalachicola Bay in the Florida Panhandle (an area of intermediate contamination). Samples were examined to determine differences in serum concentrations of reproductive steroid hormones, sites of hormone production, sperm counts and sperm viability, tissue concentrations of various organochlorines, food source (portunid crabs) concentrations of the same organochlorines, serum concentrations of stress hormones, growth and reproductive parameters, and resultant population intrinsic rates of increase. These data will allow for calculations of risk assessment for shark populations in the Gulf of Mexico. Although the study is not fully complete, preliminary results indicate significant differences among the three sites.

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


Programa Tiburón. Centro Regional de Investigación Pesquera. Instituto Nacional de La Pesca. SEMARNAP. Calle 20 Sur # 605. Col. Cantera. CP 85400, Guaymas, Sonora.

Gillnet selectivities for rays determined from surveys of the Gulf of California artisanal fishery: A preliminary analysis

The length-based highly selective nature of the gillnets suggests that caution must be taken for proper interpretation of catch data. The Gulf of California is home to the largest ray fishery in Mexico which is characterized by using bottom gillnets. Under fishery dependent conditions, the Kirkwood and Walker (1986) method was used for estimating the selectivity parameters for the main species in the Gulf of California artisanal fishery. The estimation of selectivity parameters for Rhinobatos productus were q1= 75.2 and q2= 23730.6 (mesh 3.5", 5", 6", 8", 8.5"), Dasyatis brevis q1= 44.9 and q2 = 29300.5 (mesh 6", 8", 8.5", 10", 12", 13"), Gymnura marmorata q1= 57.6 and q2 = 40432.2 (mesh 6", 8", 8.5", 13"), Myliobatis californica q1= 63.5 and q2 = 23431.9 (mesh 6", 8", 8.5", 13"), Rhinoptera steindachneri q1= 53.6 and q2 = 89033.1 (mesh 6", 8", 8.5", 10", 13") with mesh sizes from 6", 8" and 8.5" the most common. High variance (q2) is associated with the behavior of the species, oceanographic variables, and other technical properties of the net. The effect of the gillnet fishery operating in a multispecific complex elucidates differences in the exploitation pattern. The advantage in using a maximum-likelihood model will be discussed.

16/06/2000 - 10:15:00 AM - Salon Madre Perla


(JFMF; ALO) Programa Tiburón. Centro Regional de Investigación Pesquera. Instituto Nacional de La Pesca. Semarnap. Calle 20 Sur # 605. Col. Cantera. CP 85400, Guaymas, Sonora. (JFMF; JPT; REH; PMS) Center For Shark Research, Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, Florida 34236, USA.; (EGC; ZMA) Instituto Tecnológico del Mar. Km. 4 Carr. Al Varadero Nacional. C.P. 85480.

The artisanal elasmobranch fishery in Sonora

A collaborative two-year project was conducted during March 1998 to November 1999 which focused on the elasmobranch artisanal fishery in the Gulf of California (GoC). Sonora represents the state with the largest production of rays in the GoC. Different kinds of fishing camps, fishing grounds, and targeted species were documented. Participants of the fishery includes local and distant groups of fishers with an extreme socio-economical and seasonal dependence in this activity. Seasonal movements of fishers within the state were observed.A total of 44 species of elasmobranchs (23 sharks and 21 rays) were observed. Elasmobranchs represent important by-catch in other regional fisheries. Fundamental fishery characteristics, catch composition data, and pertinent biological information were obtained to understand the dynamics of the fishery and to co-participate in the multi-disciplinary process of delineating future conservation measurements.

16/06/2000 - 08:45:00 AM - Salon Madre Perla


(CTM) University of Rhode Island; (NEM;PAT;HLP) Apex Predators Program, USDOC, NOAA, NMFS, NEFSC University of Rhode Island Building #50, East Farm Campus, Kingston, RI 02881

Distribution and movements of juvenile sandbar sharks, Carcharhinus plumbeus, in the western North Atlantic

The sandbar shark, Carcharhinus plumbeus, represents a significant portion of the commercial catch and landings of large coastal sharks on the U.S. East Coast and Gulf of Mexico. Data obtained with directed commercial longline operations indicate that the sandbar shark may represent 90%+ of the catch in various areas (Branstetter 1996). Traditionally, the sandbar shark has been an important recreational species, particularly in the mid-Atlantic and northeast regions of the U.S. The Apex Predators Program (APP) of the National Marine Fisheries Service has been gathering data on the age, growth, distribution, and migratory patterns of Atlantic pelagic and coastal shark species for over 30 years through a Cooperative Shark Tagging Program (CSTP). The sandbar shark is a major component of this program as commercial and recreational fishermen, biologist and fisheries observers routinely tag and release this species. Since 1998, The Cooperative Atlantic States Shark Pupping and Nursery (COASTSPAN) Survey has conducted a standardized investigation of the U.S. east coast shark nursery grounds. Data from these two programs have been analyzed to describe the distribution and movements of neonate and juvenile sandbar sharks in the western North Atlantic. Preliminary temporal and spatial analyses of this data will be presented.

18/06/2000 - 10:30:00 AM - Salon Madre Perla


(RCM)Universidad Nacional de La Plata Facultad de Ciencias Naturales y Museo, Paseo del Bosque s/n, 1900 La Plata, Argentina (MFWS)Institut Für Seefischerei, Bundesforschungsanstalt Für Fischerei, Palmaille 9, D-22767 Hamburg, Federal Republic of Germany.

Distribution, environment and biology of batoid fishes off Argentina and Brazil. A review

Information on distribution, environment and biology of batoid fishes off Brazil and Argentina is reviewed for sixty species. The Magellanic fauna is a well-defined biological unit. The northern fauna changes gradually from the temperate Bonaerensean District off northern Argentina, Uruguay and southern Brazil, to a subtropical and tropical fauna along most of the Brazilian coast. Within the area studied, rajids are the dominant batoid family in the southern part and replaced to the north by rhinobatids and myliobatoids. A cluster analysis of distribution results in nine groups agreeing with other information: Group I of Magellanic species, Group II of three southern species extending into the Bonaerensean District, a small Group III of species with uncommon distributions, Group IV of Bonaerensean species, Group V of relatively rare deep water species, Group VI of northern migrants into the Bonaerensean District, Group VII of Brazilian species occurring in both the South Brazilian and Brazilian districts, a small group VIII formed by the deep water skate Bathyraja schroederi and D. cf. pastinaca and a completely different Group IX of Northern Brazilian species with their southern limit usually at Rio de Janeiro.

17/06/2000 - 03:00:00 PM - Salon Madre Perla


(FJM) National Oceanic and Atmospheric Administration, Woods Hole (FGM, MJT) Chesapeake Biological Laboratory, University of Maryland P.O. Box 38, Solomons, Md 20688, USA.

Estimation and analysis of biological parameters in elasmobranch fishes: A comparative life history study

Life history parameters for many elasmobranch fishes have not been determined. Elasmobranch fishes lack ossified vertebrae, making it difficult to use traditional techniques to determine age. Published life history parameters for sharks, skates, and rays over a wide geographic range were used to develop predictive models to estimate parameters that are difficult to measure or have not yet been estimated. We determined empirical relationships between body size (total length) and length at maturity (Lm) and age at maturity (Tm). These and the von Bertalanffy parameters, natural mortality (M), and maximum age (Tmax) were used to describe the life history strategies of elasmobranch fishes. We found that the M/k ratio in elasmobranchs is significantly different from other animal groups and that the value of products of k·Tmax in some elasmobranchs, notably the family Carcharhinidae, are high. We linked elasmobranchs life history strategy to potential population decline under exploitation and found that larger species of elasmobranchs are most susceptible to overfishing. A life history method for prioritizing species for management concerns is given with recommendations for their conservation. Keywords: Elasmobranchs, Age at maturity (Tm), Length at maturity (Lm ), Life history invariance, Maturation, Growth, Mortality, Longevity, Exploitation.

17/06/2000 - 04:15:00 PM - Salon Madre Perla


Monterey Bay Aquarium 866 Cannery Row Monterey CA 93940 USA.

Methodology for estimating length-at-maturity with application

It is difficult to determine the exact length-at-maturity of elasmobranch specimens. The corresponding length-frequency distribution is expected to follow a normal distribution function (ZDF) with parameters mean length-at-maturity and standard deviation sigma. Available maturity data of specimens of length L are binomial (immature = 0, mature = 1). The normal cumulative function Y = ZCF (a + bL) is the most appropriate model function for fitting such data. Two meaningful, not correlated parameters, namely mean TL-at-maturity (MTL = - a/b) and slope at MTL (S = b/sqr(2 pi) = b/2.51 = 1/sigma) can be expressed in terms of a and b as given. The logistical function Y = 1/(1 + exp-(a + bL)) is similar and the two meaningful, not correlated parameters are MTL = - a/b and S = b/4. Parameter estimates are easily obtained with the help of non-linear statistical packages, which eliminates the need of cumbersome probit or logit transformations/calculations. MTL and slope at MTL of selected sharks are calculated from available maturity data. The advantages of these methods over conventional reporting are outlined.

17/06/2000 - 04:00:00 PM - Salon Madre Perla


Monterey Bay Aquarium, 866 Cannery Row, Monterey CA 93940 USA.

Captive biology of the pelagic stingray, Pteroplatytrygon (Dasyatis) violacea Bonaparte (1832) with comments on the distribution in the eastern Pacific

Pelagic stingrays, Pteroplatytrygon (Dasyatis) violacea, were collected as by-catch on NOAA/NMFS pelagic shark abundance indexing cruises in the Southern California Bight in summer/fall (1994-1997). The smallest males and females at capture had 40-45 cm disc width, weighed circa 2 kg, and were estimated to belong to the 2nd year class. Captive growth and feeding experiments were carried out from March - October 1995 (15 females), January 1996 - April 1999 (4 females, 2 males), and October 1997 - April 1999 (5 females). The largest male reached 68 cm disc width and 12 kg at estimated age of 5-6 years. The largest female reached 96 cm disk width and 46 kg at estimated age of 7-8 years. Additional captive data for a few litters from three aquaria in Japan and California were included in the analysis of the growth data. The Gompertz growth function predicted more reasonable parameters (i.e. size at birth or first year growth rates, maximum size, and longevity) than the von Bertalanffy growth function. Food intake was 6-7% squid of BM per day for juveniles ca. 2 years old and decreased to a mean 1.25% BM per day for adults. Food intake for both adult males and females was seasonal with 2 cycles per year which probably is related to reproduction.

17/06/2000 - 03:15:00 PM - Salon Madre Perla


Va Inst Mar Sci, Gloucester Pt. VA 23062,USA

Atlantic shark stocks:Has recovery begun?

The Va. Inst of Mar. Sci. has monitored the abundance of shark stocks in the Chesapeake Bight of the US Atlantic coast since 1974. These long-line surveys revealed fisheries related declines of 70-90% in many species from the 1970s to the early 1990s with lowest values recorded in 1992. A shark management plan was implemented in 1993, and subsequently revised to provide more precautionary management. Recent survey data suggest that sandbar sharks (Carcharhinus plumbeus) have begun to recover,with higher abundances of juvenile sharks recorded. It remains to be seen whether the current fishing mortality rate is sufficiently low to allow these juveniles to survive several more years untill they reach maturity. Recovery of other species with rebound potentials lower than those of sandbar sharks,appears to be much slower or equivocal at best.

16/06/2000 - 02:30:00 PM - Salon Madre Perla


Coastal Fisheries Institute, Louisiana State Univ.wetland Resources Bldg., Baton Rouge, LA 70803-7503

Shining light into a black hole: Shark research in Louisiana

Information on sharks in Louisiana's nearshore coastal waters is fragmented and mostly anecdotal. We present information on the use of various estuarine and nearshore habitats by six species of sharks: blacktip, spinner, bull, Atlantic sharpnose, finetooth, and lemon. We have tagged four of these species; have taken neonates of four species; have captured pregnant finetooth and Atlantic sharpnose; and are presently processing vertebrae for ageing of five species. Coastal erosion is a serious problem facing Louisiana and many present and future restoration projects may have a major impact on pupping and nursery habitat.

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


(DJN) University of San Diego, Department of Marine and Environmental Sciences, 5998 Alcala Park, San Diego, California, 92129 USA; (ASC) Hubbs-Sea World Research Institute, 2595 Ingraham St.; San Diego, California, 92110 USA University of San Diego, Department of Marine and Environmental Sciences 5998 Alcala Park, San Diego, California, 92129 USA

Local habitat distribution and utilization of whale shark (Rhincodon typus) within Bahia de Los Angeles, B.C.N., Mexico

Although the whale shark (Rhincodon typus) is the world's largest fish, the species has been the subject of very limited scientific study and much of this elusive creature's natural history is unknown. This project seeks to understand how the whale shark utilizes coastal ecosystems. Field research was conducted in Bahia de Los Angeles, B.C.N., Mexico, from July 28, 1999 through October 26, 1999. Research focused on movements and locations of observed whale sharks and feeding within the bay. Over 170 whale shark sightings were recorded, from which 19 individuals were identified. Several individuals (6) were tracked using VHF radio telemetry for periods of up to two weeks. Data collected included size, sex, distinguishing marks, behavior of the animal, as well as weather and water conditions. Sixteen plankton stations within the bay were sampled regularly throughout the field season. Samples were also taken during observed feeding events. Over 200 plankton samples were analyzed. The composition and densities of plankton samples taken during active feeding events were compared to the composition and densities of plankton samples taken from stations throughout the bay. Analysis of shark movements as they relate to plankton abundance/composition will be presented.

15/06/2000 - 04:30:00 PM - Salon Madre Perla


(SN) Moss Landing Marine Laboratories, 8272 Moss Landing Rd., Moss Landing, CA 95039-9647; (JG, CAM) Center for Shark Research, Mote Marine Laboratory, 1600 Ken Thompson Pkwy, Sarasota, FL 34236

Preliminary observations on the role of calcitonin in reproduction in female bonnethead sharks, Sphyrna tiburo

Calcitonin is a phylogenetically ancient hormone that is produced by the parafollicular C-cells of the thyroid gland in mammals and the ultimobranchial gland of all jawed non-mammalian vertebrates. Calcitonin was historically believed to be a major factor involved in the fine regulation of plasma calcium homeostasis, yet recent evidence supports perhaps a more likely role in reproduction and/or development. The present study investigated the putative role of calcitonin in the reproductive cycle of female bonnethead sharks Sphyrna tiburo which, as elasmobranchs, represent the earliest living vertebrates to possess this hormonal system. Changes in serum calcitonin concentrations in mature female S. tiburo were determined using an enzyme-linked immunosorbent assay (ELISA) for salmon calcitonin and the presence of calcitonin in female reproductive tissues was investigated by immunohistochemistry. Serum calcitonin concentrations followed a pattern associated with the reproductive cycle in which peak levels occurred during late pregnancy, the period when the developing embryo is deriving nourishment through matrotrophy. Preliminary localization of immunoreactive calcitonin in uterine, placental and embryonic tissues is presented to better define the role of calcitonin during placentation.

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


City West Lotteries House 2 Delhi Street West Perth Western Australia 6005

Whale shark conservation via a collaborative approach

An ecotourism industry revolving around the whale sharks (Rhincodon typus) at Ningaloo Marine Park, Western Australia has been operating since 1993. A study aimed at determining how to minimise the impacts of ecotourist interactions on these sharks has been underway since 1995. This research was possible through the combined efforts of industry, government management agencies, Murdoch University and Australia's leading non-government marine conservation group - the Australian Marine Conservation Society (AMCS). Suggested amendments to some of the ecotourism management guidelines were tested during the 1999 'season', with excellent results. Through the development of a whale shark photo-identification library, it was possible to identify sharks that had returned to the same location on the northwest coast of Australia between 1995 and 1999. It is likely that sharks from Australian waters may migrate to areas where they active hunting is permitted. It is suggested that at the current level, fishing pressure on whale sharks is unsustainable. AMCS are currently coordinating a collaborative effort to encourage nations to ban the hunting of this species and work towards greater global conservation for the largest living shark.

15/06/2000 - 02:30:00 PM - Salon Madre Perla


(CICESE), Tijuana-Ensenada km. 107, C.P. 22830. Ensenada B.C. México

Biological and fisheries aspects of the bonnethaed shark, Sphyrna tiburo (Linnaeus, 1758) in the waters of Campeche, México

The species of sharks are part of the artistry fishery from State of Campeche.The fishery produccion has to considere the fisheries-ecological aspects.The Campeche was monitorel dury 14 months (Nov.1993-Dic.1994), registrering information Sphyrna tiburo about the catches,vessels and fishing gears. It was found that there is not any estationary fluctation in his abundance. From June. to October 1994, the catches were incresed, having their maximum in August. It was observed a size interval from 60-90 cm LT whit and average of 76.15 0.39 cm LT.The minimum size of sexual maturity for females is 91.2 cm LT and for males 65 cm LT. It was calculated the Catch Per Unit Effort (CPUE) as low as 1.64 kg./ vessel on May 1994 througt 18.0 kg./vessel on November 1993. Sphyrna tiburo has been over exploited because his biological characteristicts. The results of this study, the gestation period, fecundity, mating engravity was carry out in the Bank of Campeche were it was found all their stages. If we do not stop fishing juvenils, this fishery could be collapse in few years.

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


Gavin Naylor Lab, Department of Zoology and Genetics, 339 Science II Iowa State University Ames IA 50011 USA

Inferring extinction from molecular sequences the case for Lamniform sharks

Paleontological data suggest that Carchariniform and Lamniform sharks diverged 124-140 million years ago. Today Carcharhiniformes are represented by 199 extant species. By contrast, only 14 extant species are known for the Lamniformes. The fossil record for Lamniformes shows a peak of diversity in the middle Cretaceous followed by several extinction events. Molecular phylogenetic studies suggest that extant Lamniform sharks represent the surviving remnants an old explosive radiation, whereas extant Carcharhiniform shark diversity is the result of continuous and ongoing speciation. It is possible however, that the differing patterns of cladogenesis inferred from the molecular data are caused by differential patterns of extinction, rather than differing patterns of speciation. In order to test this hypothesis, we simulated extinction within the Carchariniformes by sub-sampling taxa that yielded divergences comparable to those seen for lamniformes. For 4 different genes (ND2,ND4, Cytb and Rag1),we subjected the sub-sampled data sets to phylogenetic analysis and compared inferred patterns of radiation to those of the Lamniformes.

18/06/2000 - 02:30:00 PM - Salon Madre Perla


Monterey Bay Aquarium 886 Cannery Row, Mtry. CA. Monterey Bay Aquarium 886 Cannery Row.

A fatal attack on a whale shark Rhincodon typus, by killer whales Orcinus orca off Bahia de Los Angeles, Baja California

In July of 1992 two killer whales Orcinus orca attacked, killed and fed on an 8-meter whale shark Rhincodon typus in the waters off Bahia de los Angeles. Throughout most of the year both of these species are common inhabitants in the Gulf of California, yet until this time there had been no observations on this behavior to date. Besides the activities of man, few predators have been speculated that have the ability to take the young, juveniles or adults of this species. A discussion on the need for regulations for the protection of this species from human activities in the waters of Mexico will be discussed.

15/06/2000 - 04:45:00 PM - Salon Madre Perla