2000 AES Annual Meeting Abstracts

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

In October 1998, WWF-Philippines iniated a 3-year research and conservation project on elasmobranch biodiversity in the highly diverse Sulu Sea. The project endeavors to identify conservation and management needs of Philippine elasmobranchs through fisheries assessments in selected sites around the Sulu Sea, ultimately leading to a National Plan of Action ensuring sustainable elasmobranch utilization in the country. This initiative is supported by WWF-US and implemented in the Visayas and Mindanao by Silliman University Marine Laboratory. Between October 1998 and June 1999, Phase 1 project activities involved: 1) profiling of elasmobranch fishery sites based on primary and secondary data sources; 2) assessm,ents of fishery, trade and resource utilization of elasmobranch populations in selected sites; 3) voucher specimen collection from market and landing sites; and 4) education and information campaign. Secondary sources showed a collective list of 114 species under 24 chondrichthyan families caught in at least nine different fishing methods in about 44 provinces. Collections from market and landing sites revealed a preliminary checklist of 59 species under 20 families, 24 species of which were considered potentially new records to the Philippines and/or to science. Highlight of the education and information component, was the convention of the First Philippine Elasmobranch Biology and Taxonomy Training-Workshop in Silliman University, southern Philippines on 7th-13th May, 1999.
16/06/2000 – 03:15:00 PM – Salon Madre Perla

Environmental Education as a tool in the study of the elasmobranchs

Many people still believe that sharks are the most dangerous specie worldwide but if we try to improve its image using strategies such the environmental education, we can reinforce a better reputation of this top-predator. With this material I offer to all of you and helping me with some games and educative material I wish I would like to make conscience, mainly to children, whom I made this poster in order to play and learn at the same time, and respect this species.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

Population genetics of the great white shark

White sharks were sampled from Australia, New Zealand, Japan, California, Brazil and South Africa. Phylogenetic analysis of complete control regions sequences revealed two major groups that differ at about 4% of the sites, and within each clade several distinct haplotypes were discovered. The two major clades were largely separated by Ocean Basins, with one clade in the Pacific and the other in the Atlantic and Indian Oceans. Only one individual was out of place. Overall, the mtDNA data show a high degree of geoographic differentiation. A notable exception is that the samples from Australia and New Zealand appears as if they conprise the same population.
18/06/2000 – 03:00:00 PM – Salon Madre Perla

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

In 1998 and 1999 the Shark Research Institute deployed satellite tags on 5 whale sharks in an effort to gather information on their long term and short term movements. Problems were encountered with the attachment of the tags to the sharks. Satellite tags were attached to the sharks by divers and various tag-anchors were utilized with varying degrees of success. Tethered tags were attached by divers and a variety of tag-anchors were utilized. Data received so far is encouraging, which will enable us to drawn a picture of the day to day life of a whale shark.
15/06/2000 – 02:45:00 PM – Salon Madre Perla

The Carcharocles, Carcharodon question

Recently investigators and amateur paleoichthyologists have stated that they had a case for placing Carcharodon megalodon in a separate genus “Carcharocles“. The argument being that the living Carcharodon carcharias was derived from a fossil ancestor “Cosmopolitodus” which is a name used for Isurus xiphodon. This contradicts the phylogeny given by others. Jordan named “Carcharocles‘ for Carcharodon auriculatusan Eocene species, which has strong lateral denticles and erroneously said to have teeth narrower and more erect with their edges being finely serrated. The teeth of C. auriculatusare curved and strongly serrate. Therefore Jordan’s suite of characters are not completely applicable to the “Carcharocles” question, on the contary It will be shown that C. carcharias and C. megalodon are very close but distanctly different from any species ofIsurus living or fossil. The genus Isurus can be shown to be separated from Carcharodonin many characters other then teeth. We therefore still believe that C. megalodon has a close relationship with C. carcharias and together they should be placed in the same genus.
18/06/2000 – 02:45:00 PM – Salon Madre Perla

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

 In Patagonian waters, Argentina. Squatina guggenheim (Marini, 1936) commonly known as angel shark, “escuadro” or “angelote”, is a cartilaginous fish found in Argentinean sea waters. In the San Matías gulf (San Antonio Oeste, Pcia. de Río Negro), they are caught as by-catch of the hake, Merluccius hubssi, fishery. It is a matter of concern that the raise of the fisheries commercial activity may have a negative impact on those species that are caught as by-catch and specially on those with low fecundity and slow growth as most shark species. But data on the reproductive biology of this species are lacking. In this context, the purpose of this study was to investigate the reproductive biology and testicular dynamic of angel sharks collected from commercial bottom drawl fishery. Standard morphometric parameters were measured and the gonads were removed . Testis were processed for classical histological procedures, analyzed and photographed in a microscope. The onset of sexual maturity was obtained for females and males from morphometric data. Based on our results it is suggested that this is not a breeding area for this species. Testicular structure is polyspermatocystict and with a diametric maturation type. The germinal and interstitial compartments are described and the spermatogenetic cycle was divided in seven stages.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

Temperature effects on mako shark locomotor muscle enzyme kinetics

The mako, Isurus oxyrinchus, is a high performance shark having locomotory specializations similar to tunas including endothermy. Quantification of mako high performance requires determination of the extent that metabolic potential is increased relative to other sharks and approaches that of tunas. We studied the effect of temperature on the aerobic (citrate synthase, CS) and anaerobic (lactate dehydrogenase, LDH) enzyme activities of mako red (RM) and white muscle (WM). The hypotheses were: that RM and WM enzyme activities are higher than in other sharks at comparable temperatures, and that activities at in vivo locomotor muscle temperatures significantly enhance muscle performance. CS and LDH activities in mako RM at 20ºC are not significantly different from other ectothermic sharks (e.g., Prionace glauca, Sphyrna leweni). However, using Q10 values for mako RM enzyme activities (1.51 – 1.78) and correcting for in vivo temperature elevates RM performance capacity. Mako WM enzyme activities at 20ºC are significantly higher than in other sharks and WM metabolic capacity also increases with temperature. Thus, mako WM parallels tuna WM in having a greater aerobic capacity compared to ectothermic species and increasing the capacity for rapid gluconeogenesis, suggesting a role for WM in both sustained and burst swimming and recovery from oxygen debt.
16/06/2000 – 05:15:00 PM – Salon Madre Perla

Site description for the Gulf of California

The Gulf of California is a 1,070 km long, narrow marine inlet located between Baja California and the west coast of mainland Mexico. The Gulf was formed about 5 million years ago when the convergence of the Pacific, Farallon, and North American Plates resulted in a strike-slip fault and the disassociation of a land mass from the North American plate. A spreading center was created east of present-day Isla Angel de la Guardia, moving Baja California northwestward (presently at 5.5 cm/yr). The upper Gulf is shallow (< 200 m) and flat and is dominated by terrestrial sediments. South of the Midriff Islands, the sea floor expands in depth (up to 3,700 m) and complexity. Mean surface temperatures are more continental than maritime and range between extremes of 8º and 33ºC. Surface current flow is highly correlated with wind patterns and flows southeasterly in winter and spring, and northwesterly in summer and fall. Species migrations, including those of pelagic sharks, are associated with these dominant current regimes. The combination of upwelling and large tidal flux stirs nutrients into the euphotic zone, providing a rich food base for the diverse assemblage of temperate, subtropical, and tropical marine organisms inhabiting this region.
16/06/2000 – 08:00:00 AM – Salon Madre Perla

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

The locations and activities of all artisanal fishing camps on the Gulf of California coast of Baja California Norte (BCN) were determined during 1998 and 1999. Seventeen camps were identified, of which 15 targeted elasmobranchs. Elasmobranch landings and effort were highest at camps located in southern BCN. Thirty-two elasmobranch species (16 sharks and 16 rays) and 4,492 specimens were observed in landings of 160 boats.Rhinobatos productus (26.45%) and Mustelus spp. (21.48%) numerically dominated overall landings. Interannual differences were noted in species composition of elasmobranch catches and effort. A drift net fishery for large sharks operated during the summer and early fall around the Midriff Islands and targeted primarily: Alopias pelagicus, Carcharhinus falciformis, Carcharhinus limbatus and Sphyrna spp. Batoids and small sharks were the main constituents of the elasmobranch fishery. While these groups appear to be targeted throughout the year, CPUE was highest for batoids in the summer months (26.1/boat) and for small sharks in spring (31.4/boat). Females seasonally dominated catch composition and gravid females (esp. Rhinobatos productus, Carcharhinus faliciformis and Alopias pelagicus) were noted primarily during the summer months. Juvenile elasmobranchs were captured year-round. Although elasmobranchs are important components of the BCN fishery, most artisanal effort targets either shrimp or teleosts.
16/06/2000 – 08:30:00 AM – Salon Madre Perla

Gross brain morphology in the yellow stingray, Urolophus jamaicensis.

The yellow stingray, Urolophus jamaicensis, a short-lived, relatively small elasmobranch species (35-40 cm total length), is a common inhabitant of hard bottom and coral reef communities in southeastern Florida and many parts of the Caribbean. Its small size and abundance make this animal an ideal candidate for many ecological and physiological studies. We decided to use this species as an experimental subject for examining the elasmobranch histaminergic system. However, there are relatively few published studies dealing with the yellow stingray in general, and apparently none on the gross morphology of its nervous system. In this preliminary study we compared gross brain structure of the yellow stingray with published studies on other batoid elasmobranchs. Male and female rays were killed with a lethal dose of anesthesia (MS222) and dissected. In general, the external brain structure of Urolophus jamaicensis is similar to that reported for other Dasyatoidea, including presence of an asymmetric cerebellum. Comparatively, stingrays possess a brain three to ten times the size of their sister groups, the electric rays, guitarfish, and skates (Northcutt, 1989). The yellow stingray is no exception. Its bilaterally symmetric brain is well developed and quite large in proportion to body size (approx. 1%bw). Labeled illustrations of dorsal, ventral and sagittal views are available from the first author.
16/06/2000 – 08:00:00 AM – PingPong Area

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

Two archival tags and a single satellite transmitter were deployed on separate white sharks in southern Australia to collect detailed data on long-term movement patterns. One of the archival tagged sharks was captured 74 days later some 600km from the Neptune Islands where it was tagged. Swimming depth and ambient water temperature were recorded every 4 minutes and an approximate position was calculated daily during the period at liberty. The shark spent about 8% of its time at the surface and cycled extensively through the water column to a maximum depth of 94 m. The number and timing of dives varied considerably on a daily basis. Position data was more problematic, however, the shark probably stayed in the vicinity of the Neptune Islands until early September before moving north into the shallower waters of Spencer Gulf. The shark then moved rapidly westwards in mid-October reaching the Great Australian Bight by about 25 October, where it stayed until it was caught on 2 November. In a second exercise, a 2 m female white shark was captured off Ninety Mile Beach, Victoria and fitted with a satellite tag. The shark was tracked for 3 h via an acoustic tag after release to ensure its initial survival. Since release, the satellite tag has successfully transmitted the shark’s position approximately every day. By mid March, two weeks after release, the shark had moved steadily in a south west direction over a distance of 80 km tracking the coast at approximately 5-13 km from shore with one excursion into the coast in the vicinity of a large coastal inlet.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

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

Analysis of 93 first dorsal fins of Squalus acanthias shows sexual dimorphism in the total number of basals supporting the first dorsal fin. 57 specimens examined are cleared and stained. 36 specimens examined are display skeletons prepared by biological supply houses for teaching comparative anatomy labs. Counts of the number of basals (1 supporting spine not counted) supporting the first dorsal fin for the 63 males examined found a range of 10 to 18, a mode of 13, and a mean of 12.810. Counts of basals for the 30 females examined found a range of 7 to 13, a mode of 12, and a mean of 11.767. This is the first report of sexual dimorphism in number of basals of the first dorsal fin for any shark. This observation might be of use in sexing some fossil sharks when the median fins are well preserved and the pelvics are not. {Revised abstract}.
18/06/2000 – 04:45:00 PM – Salon Madre Perla

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

Blacktip sharks (Carcharhinus limbatus) show clearly defined behavior patterns to remove shark suckers (Echeneis naucrates). Some of these patterns clearly resemble agonistic displays. Although the act of feeding has been attributed as the most likely origin of that behavior, removing shark suckers must also be discussed as a potential origin. In this study we describe and define different behavioral patterns, focusing on the positions and movements of the shark sucker along the shark’s body. Preliminary results show that different areas of the shark’s body trigger different reactions. Several scenarios will be discussed illustrating shark sucker irritation of shark sensory and hydrodynamic capacities as the basis for behavioral displays and its possible relation to the origin of agonistic display.
17/06/2000 – 05:15:00 PM – Salon Madre Perla

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

The effect of temperature on the rate of gastric evacuation (GE) in juvenile scalloped hammerheads has been presented previously. However, there are several other factors that can affect GE. The effect of meal size was investigated for a teleost prey item,Herklotsichthys quadrimaculatus. Meals of 4.2% of the body weight and 0.5%BW were 80% evacuated in 15 hours and 6-7 hours, respectively. Gastric evacuation of another teleost prey, Hazeus nephodes (0.5%BW) was 80% complete in 5 hours while GE of a shrimp, Alpheus malabaracus, (0.5%BW) was 40% complete in 3 hours, at which time digestion seemed to stop. Faster rates of GE were measured for the most important prey items, (H. nephodes, and A. malabaracus), at meal sizes close to those observed in the field. The difference in GE rates of the two teleost prey items is probably due to the higher caloric value of H. quadrimaculatus. Different rates of GE affect estimates of daily ration. Daily ration estimates using the Diana method varied from (.32%) to (1.43%BW). The higher estimate of daily ration is based on predominate prey items and more a more realistic meal size. It is also closer to the maintenance ration predicted for Sphyrna lewini.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

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

Dietary data were collected from 779 sharks in Kaneohe Bay, Oahu, Hawaii from 1995-1998. Sharks were caught in gill nets and were between 32.7-79.0 cm (x=43) FL, and 340-5091g (x=739). Eighty percent of all sharks contained food in their stomach, but only 41% of sharks with an open umbilical scar had food in their stomachs, as opposed to 87.8% of sharks with healed umbilical scars. Sharks with unhealed umbilical scars were used in calculating IRI, but were not used in any other dietary analysis. Alphied shrimp (primarily one species) made up 38.7% of the diet (IRI), while various teleost accounted for 52.0%. This seems to reflect the availability of prey items on the bay floor, and differs from the diet reported by Clarke (1971). The differences in diet may be explained by changes in the bay’s ecology as a result of anthropogenic impacts. A Kruskal-Wallis test of stomach fullness, (as %BW), indicates that there are significant variations in stomach fullness over a 24 hour period. Stomachs contained the most food from midnight to 0900, and the least from noon to 0600. The trend for the proportion of empty stomachs is similar, with more sharks having empty stomachs in the day (16.8%) than at night (4.1%).
19/06/2000 – 08:00:00 AM – Salon Madre Perla

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

A research program was initiated in 1993 to study the movements and site fidelity of tiger sharks off the south shore of Oahu, Hawaii. This program is ongoing, and has used a variety of techniques from traditional tag and release to acoustic telemetry to an archival pop-up satellite tag. Recapture rates for sharks with standard identification tags ranged over time from 23% to 17% (141 sharks tagged). Sharks implanted with acoustic pingers were electronically “recaptured” by stationary data loggers at a rate of 50% (n=20). Differences in recapture rates suggest internal acoustic tags and remote data loggers are a more effective way to study site fidelity than traditional tag and recapture methods. Currently, sharks are being implanted with long life archival acoustic tags that record depth and temp and download their information when the shark swims within range of a data logger on the sea floor. The role of the various methods in elucidating the movements of tiger sharks in Hawaiian waters will be discussed, as well as their relative merit in studying movements of elasmobranchs in general.
17/06/2000 – 11:30:00 AM – Salon Madre Perla

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

A total of 104 stomachs contents were analized: 37 were stomachs of Carcharhinus falciformis, 17 were of Nasolamia velox and 50 were of Sphyrna lewini, that were captured in the Gulf of Tehuantepec, Chiapas, México. Carcharhinus falciformis is a selective feeder, who fed primarily on the crab Portunus xantusii affinis. The females and adults of Nasolamia veloxi> fed mainly on Portunus xantusii affinis meanwhile the males and medium sharks of this specie fed primarily on the decapod Squilla biformis. FinallySphyrna lewini has demostrated to be a generalist feeder that have ontogenetic dietary shifts., the smaller sharks fed primarily on the shrimp Trachypenaeus sp., the medium sharks fed mainly on the crab Portunus xantusii affinis and the larger sharks fed primarily on teleosts.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

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

During 1994-1998, 1,023 Carcharhinus falciformis were caught in four fishing camps in the central Gulf of California. Observations of sizes and reproductive biology were made, providing data on the monthly frequency, sex ratios, sizes a maturity, fecundity, embryo sizes, and ovarian development. Males ranged from 130-279 and females 125-271 cm TL. The overall sex ratio was 3.49 females per male. The sex ratio at birth was 1.34 males per females. Both sexes appear to mature at 180 TL. Fecundity ranged from 4-12 per female, increasing significantivally in larger females. The largest ovum diameter was 30 mm. This species has a biannual ovarian cycle, the females presumably rest one year between parturition events, and the gestation is probably 12 months.
16/06/2000 – 11:00:00 AM – Salon Madre Perla

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

From 1995 through 1998, we studied the fishing camps at 9 sites in Sonora. A total of 2,595 specimens representing 36 species was sampled, including 20 species of sharks and 16 rays, and were measured. The most important fishing camp by the number of species and organism was Baha de kino. Other important fishing camps were Yavaros, La Manga, El Cholludo and Puerto Penasco. The most abundant species were Dasyatis brevis (35.38%), Rhinoptera steindachneri (19.42%), Gymnura marmorata (7.17%), and Rhizoprionodon longurio (6.86%). The big sharks Alopias pelagicus, A. Vulpinus, Carcharhinus leucas, Prionace glauca, Carcharhodon carcharhias and Isurus oxyrinchus were rarely encountered. Gymnura marmorata, D. brevis, R. steindachneri and Rhizoprionodon longurio are species that used the Sonora coast as reproduction and nursery areas.
16/06/2000 – 09:00:00 AM – Salon Madre Perla

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

Two collecting expeditions to the Gulf of California were conducted from July to October, 1993 and from May to July, 1996. Six main sites were visited each trip: Puertecitos, Bahia de Los Angeles, Santa Rosalia, Loreto, Punta Arenas and San Jose del Cabo. Elasmobranchs were collected using a diversity of gear including hand spears, gill nets, long lines, etc., generally in conjunction with local fishermen. A total of 766 individuals, representing 13 families, 25 genera and approximately 45 species of elasmobranchs was examined. A number of taxa presented identification problems. Species of some, such as Mobula and Urotyrgon, were initially difficult to identify in the field, but their identities were essentially resolved following consultation with appropriate experts and/or literature. Specific identities of others, such as Gymnura, Rhinobatos and Urobatis, were established with some confidence only following sequencing and phylogenetic analysis of the mitochondrial gene NADH-2. The specific identities of some specimens of yet other taxa, such as Mustelus, remain unresolved. This survey also facilitated collection of data on some aspects of the biology of the elasmobranchs of this region. For example, embryos were seen in species of 17 genera, most commonly in Alopias, Diplobatis, Gymnura, Mustelus,Narcine, Urotrygon and Zapteryx.
16/06/2000 – 11:45:00 AM – Salon Madre Perla

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

The National Marine Fisheries Service-Panama City Laboratory has conducted longline surveys in the northeast Gulf of Mexico since 1994. Surveys targeted small and large coastal species of sharks within coastal nursery areas from April to October. Generalized linear modeling was used to standardize catch rates to improve estimates of relative abundance. Trends in catch rates were examined using weighed least-squares linear regression. Depending on the species, significant effects in the model generally included year, area, and month. Results suggest that despite attempts to control for factors that may influence a fishery-independent assessment, certain effects unrelated to abundance can contribute significantly to the variability in catch rates.
16/06/2000 – 02:45:00 PM – Salon Madre Perla

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

A long-term study of mating behaviors of nurse sharks has shown that males and females move little during the period of mating and may therefore be tracked using ultrasonic telemetry from kayaks to minimize intrusion and modification of natural behaviors. Periodic position determinations made with the use of GPS and plotted on digitized nautical charts using recently developed computer software brings improved accuracy to tracking and provides insight into reproductive behaviors. Previously undiscovered mating sites have been identified and behaviors of males have been clarified using such combinations.{revised abstract}
17/06/2000 – 08:00:00 AM – Salon Madre Perla

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

Historically Sinaloa has been an important fishing state of sharks in the Mexican Pacific coast region. As part of the join US-Mexico project titled “The status of shark and ray resources in the Gulf of California: Applied research to improve management and conservation”, the DGIEMRP of the National Fisheries Institute of Mexico (INP) in collaboration with the CRIP of Mazatlán carried out during the period 1998-1999 the characterization of the main artisanal fishing camps dedicated to the exploitation of sharks, cazones and rays. In this period we surveyed 28 fishing camps in Sinaloa, of which in 17 of them captures and landings of elasmobranchs were observed. We documented the capture of 2,758 elasmobranchs landed from 112 fishing trips with small boats, belonging to 25 species of sharks and rays. The dominant species were Sphyrna lewini (36.0%),Rhinobatos glaucostigma (20.0%), Rhizoprionodon longurio (14.0%), Rhinoptera steindachneri (9.0%) and Dasyatis brevis (8.6%). Except for R. Longurio most of the landed individuals were immature of early stages: neonates and juveniles. We observed in Sinaloa two main fishery seasons for elasmobranchs, one targeting small shark species denominated cazones in the period January-March, and a second targeting rays and neonates and mature sharks of larger size in May-July. Both seasons periods related intimately with migratory movements of those species. An important proportion of gravid females were observed in June of the second year, which suggests the presence of shark nurseries areas along the coast of Sinaloa.
16/06/2000 – 09:15:00 AM – Salon Madre Perla

On the length of the reproductive cycles of sharks

The available data indicates that sharks generally have annual or biennial reproductive cycles. Longer cycles have been suggested, but there is little supporting evidence for them. The reproductive cycle of sharks includes two separate processes: the ovarian cycle and the gestation period. The ovarian cycle includes follicle development and vitellogenesis, and culminates in the ovulation of the ripe follicle. The gestation period starts with fertilization and ends with birth. The length of the reproductive cycle of sharks is determined by whether the ovarian cycle and gestation occur concurrently or consecutively. In annually reproducing species, such as Rhizoprionodon terraenovae, Mustelus canis and Sphyrna lewini, the ovarian cycle and gestation run concurrently and both last about a year. Parturition in these animals is quickly followed by mating, ovulation, and gestation. Thus they reproduce annually. Many other species show biennial cycles. In biennial species, gestation and the ovarian cycle can occur concurrently or consecutively. In Squalus acanthias and other squaloid sharks, gestation and vitellogenesis occur concurrently. They both last almost two years and the species reproduces biennially. In many species ofCarcharhinus, the ovarian cycle and gestation occur consecutively and not concurrently. A female giving birth in early summer will enter the ovarian cycle sometime after parturition and its oocytes will be ready to be ovulated one year after parturition. After ovulation and fertilization, gestation lasts for about another year. Thus the length of the reproductive cycle is two years.
18/06/2000 – 08:00:00 AM – Salon Madre Perla

Whale shark: What do we really know about it?

The maximum size of the whale shark is not known with certainty because actual measurements of large specimens are few. The largest measured specimens that we know of are a 12.1m female that stranded off Mangalore, India, and a male 12.18m from Bombay, India. Photographic evidence suggests that the whale shark may grow to a larger size. There are few reliable weights for adult specimens, given the lack of scales suitable for weighing such large animals. The weights of the 1912 Knights Key specimen often given in the literature have little or no scientific basis. Joung et al. (1996) gave the weight of a ~10.6m TL as 16,000 kg, as weighed by a construction crane. These authors also gave weights of 15,220 kg and 36,000 kg for sharks landed in Taiwan on 30 March 1994 but without adducing any other data or evidence. Whale sharks at birth range from 55 to 64 cm. The nurseries of the whale shark are poorly defined because very few small whale sharks have been captured. If the dates of capture of juveniles given in the literature are correct, newborn whale sharks can be found in summer as well as in winter, suggesting year round reproduction. The reasons for the paucity of small specimens in collection are probably the widespread nature of the nurseries in tropical waters and the unusually rapid growth of whale sharks. Remoras and cobias often accompany the whale shark. The remoras often enter the mouth, the spiracle and the anus, and sometimes they can be seen peering out of the anus.
15/06/2000 – 01:30:00 PM – Salon Madre Perla

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

Although application of microsatellite markers to shark biology is in its infancy, these markers are already proving useful for elucidating relationships at population and individual levels. Herein, we provide a preliminary evaluation of microsatellite loci to investigate life history traits and population structure of the bonnethead shark, Sphyrna tiburo. Mature female bonnetheads are known to store sperm in their oviducal gland for a period of about five months after insemination. Although there are no published observations of bonnethead sharks mating, recent studies on other sharks suggest that multiple males often participate in mating events involving a single female. If the bonnethead shark has evolved this type of multiple-male (polyandrous) mating system coupled with protracted sperm storage, it is possible that females are fertilized by multiple males in a single reproductive cycle. Using 8 microsatellite markers, we have assayed several litters of this species for multiple paternity. Three of the 8 microsatellite loci were isolated from the genome of S. tiburo. The remaining five were previously isolated from the blue shark, Prionace glauca, and were also found to be informative for S. tiburo. We also report on a preliminary assessment of micro-geographic population structure in this species from the SE United States.
18/06/2000 – 04:30:00 PM – Salon Madre Perla

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

The continental shelf of the northwestern Gulf of Mexico includes an array of submerged hard-banks, reefs and offshore oil and gas platforms that often support diverse reef communities. These features extend upward from the plane of the seafloor and provide significant vertical and structural relief in an otherwise level landscape, and are defined as topographic highs. Various species of elasmobranchs have been reported at these features, but most records are anecdotal by nature. Surveys conducted at five topographic highs in the northwestern Gulf of Mexico reveal seasonal assemblages of sharks and rays inhabiting these features. Aspects of elasmobranch diversity, social organization, and seasonal habitat use are characterized for mid-shelf and outer shelf topographic highs.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

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

The whale shark (Rhincodon typus) frequents the northern Gulf of Mexico, however, little is known regarding its seasonal distribution, abundance, and behavior in the region. This paper present the occurrences of whale sharks in the northern Gulf of Mexico, gathered using three different survey methods (aerial, underwater, and offshore platform). Data presented using geographic information system technology illustrates the seasonal distribution of whale sharks in the region, including strong evidence of seasonal habitat use of neritic waters in the northern Gulf during warmer months. The occurrence of whale sharks associated with topographic high communities and mass spawning events in the northern Gulf are also examined.
15/06/2000 – 03:45:00 PM – Salon Madre Perla
Chris, Huff – See Huff, Chris

Population structure of Manta birostris based on mtDNA sequence

The hypothesis that genetic population structure exists in the manta ray (Manta birostris) was tested using mitochondrial DNA sequence variation.
16/06/2000 – 08:00:00 AM – PingPong Area

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

The Northwest Atlantic population of dusky smoothhounds ranges from South Carolina up to Cape, Cod, Massachusetts. Recently a gillnet fishery for these sharks started on the eastern shore of Virginia and North Carolina. Dusky smoothhounds may be more capable of sustaining a fishery, with appropriate management, than many other shark species due to a proposed higher growth rate and fecundity. However, no demographic modeling has been done to predict how increased fishing pressures will affect this population. Although this is a seasonally abundant and well-known animal very little has been published about its growth and reproduction. We aged 800 dusky smoothhounds, created Von Bertalanffy growth curves for males and females, studied the reproductive cycle, fecundity, and lengths and ages of males and females at maturity of this population. A life table was created using this information. This life table was then used to examine the effects of various levels of fishing pressure on the population, and to explore the necessary compensatory responses for the population to remain stable.
17/06/2000 – 02:00:00 PM – Salon Madre Perla

Insights on shark conservation from stochastic demographic modeling

Most demographic models of sharks conducted so far have used deterministic life table analyses to project population growth rates and generation times. There is a clear need to incorporate uncertainty in estimates of vital rates and naturally occurring random variation in those rates into the modeling process. This paper uses Monte Carlo simulation to calculate both stochastic population growth rates and generation times to evaluate the potential for exploitation or recovery and stochastic matrix elasticities to identify the most vulnerable life stages for a suite of shark species. This approach eliminates potential problems associated with deterministic methods, such as ranking of elasticities based on projection of one specific set of vital rates. The ratios of adult to age-0 and juvenile to age-0 survival elasticities obtained from the simulations are also examined to predict the level of density-dependent compensation required to offset the effect of exploitation given the life-history constraints for each species.
17/06/2000 – 02:45:00 PM – Salon Madre Perla

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

In response to declining coastal commercial fisheries, a deep-water fishery developed in the early 1990’s in the North East Atlantic. Although this fishery mainly targets grenadiersCoryphaenoides rupestris and argentines Argentina silus, several species of deep-water elasmobranchs are taken as either directed landings or by-catch. Two species of deep-water sharks: the Portuguese Dogfish Centroscymnus coelolepis and the Leafscale Gulper Shark Centrophorus squamosus in particular, are landed on a regular basis. It is important to establish levels of these landings at the earliest possible stage in the development of the fishery in order to monitor status and formulate suitable management plans to prevent over-exploitation of the resource. It is hoped that by studying landing statistics, stock assessments and life biology using molecular techniques, correct manangement of elasmobranch populations will be facilitated.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

Gymnura marmorata (Cooper, 1863) and Gymnura crebripunctata (Peters, 1869), two species or sexual dimorphism?

The distribution of the butterfly ray Gymnura marmorata (Cooper, 1863), is from Punta Concepcion California to north of Perú and Gulf of California. Peters (1869) described  Gymnura crebripunctata as a new specie with a distribution from southwestern coast of Baja California to Ecuador and Gulf of California. Breder (1928), was the first in consider as an only specie. Castro Aguirre and Espinosa-Pérez (1996) considered G. crebripunctata as a valid specie. Observations in the fishery camp of Puerto Viejo in Bahía Almejas, western coast of Baja California Sur, México, reported since 1992, the presence of females of G. marmorarata and males of G. crebripunctata. We made morphometric measures to compare the growth, the form and the body structures including the rostrum length that McEachran and Notabartolo (1995) used for the species identification. The results indicated that the growth is similar for males and females (except rostrum length that has an alometric growth) and the males acquired their body form near reproductive size. We might say that G. marmorata enter to Bahía Almejas in spring-summer principally with reproductive intentions.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

Seasonal variation on diet of the narrownose smooth hound, Mustelus schmitti, Springer, 1939 (Chondrichthyes: Triakidae) from Puerto Quequen, Argentina

The narrownose smooth hound is an important economic resource for the coastal fleet at Quequén harbor (38° 37´S, 58° 50´ W). The aim of this study is to analyze the seasonal variation on diet for this species in the Puerto Quequén area. We studied 84 stomachs obtained from specimens captured by the trawl coastal fleet, between October 1998 and November 1999. We compared the diet among seasons and between sexes by Spearman correlation index, taking into account the frequency of each prey item. Winter season was not correlated with summer (rsc 0.38; p > 0.2), autumn (rsc 0.015 ; p > 0.5) and spring (rsc 0.33; p > 0.2). Diet was not correlated between sexes neither in spring (rsc 0.62; p > 0.05) nor in winter (rsc 0.85 p > 0.1). The most common prey item were crabs (Fo = 78.57 %), polychaetes (Fo = 96.43 %), and during spring season, bony fishes (Fo = 76.92 %). Our results showed that, as in other areas of the species distribution, Mustelus schmitti (the narrownose smooth hound) has a fundamental benthonic and carcinophagous diet, particularly during autumn and winter. During spring their diet includes Clupeids (v.g. anchovy, Engraulis anchoita) which are pelagic and neritic species. These results might be showing an opportunistic predator behavior in this species.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

Home range and diel movement patterns of the sub-adult lemon shark, Negaprion brevirostris, in Bimini, Bahamas

Knowledge of movement patterns is important for complete understanding of the natural history and ecology of a species. The lemon shark, Negaprion brevirostris, is a common shark of the shallow waters of Bimini Lagoon, Bahamas. Ultrasonic transmitters were surgically implanted in 29 sub-adult lemon sharks (144-198 cm in total length) to study spatial and temporal movements. During November 1992 to October 1995, 11817 position fixes were recorded. Sharks were tracked continuously for periods of 24 hours whenever possible and intermittently for up to 13 months. Using a modified minimum convex polygon method, mean home range estimates of sub-adults lemon sharks were an order of magnitude larger than those of juveniles (> 20 km+2). Juveniles and sub-adults used only a fraction of the available habitat. Home range overlapped and aggregations of up to 25 individuals occurred, suggesting that lemon sharks are not territorial. Sub-adult lemon sharks had distinct night and day centers of activity. Lemon sharks initially captured on the western side of the lagoon at night moved eastward at dawn and westward at dusk, whereas individuals captured in the eastern side of the lagoon appeared to have different diel patterns. These patterns may be related to feeding or refuging.
17/06/2000 – 04:45:00 PM – Salon Madre Perla

“El Niño”/Southern Oscillation effects on the shovelnose guitarfish, Rinobatos productus, and Pacific electric ray, Narcine entemedor, in Bahía Almejas, B.C.S., México

“El Niño” refers to a periodic warming of the sea surface along the coast of South America. “El Niño” also affected Baja California’s species near the coast. Rhinobatos productus andNarcine entemedor are two viviparous species that conclude the reproductive cycle in Bahía Almejas. The shovelnose guitarfish and Pacific electric ray, have an annual reproductive cycle, with ovulation and fertilization occurring in late summer (July-August), followed by offshore movements and embryonic diapause. During 1998, the reproductive cycle was affected, the embryos development in part of the females started in late March or the first days of April, when normally they start the last days of April. The ova had the same reaction, the mature ova were ready in the same period. The uterus also were found with eggs with out embryos development, and all melted. Finally we could find only a few females in July and no one in August.
18/06/2000 – 10:15:00 AM – Salon Madre Perla

Age and growth of the shovelnose guitarfish, Rhinobatos productus, in the western coast of Baja California Sur, México

The shovelnose guitarfish, Rhinobatos productus, has an annual reproductive cycle, with ovulation and fertilization occurring in early August followed by offshore movements and embryos diapause. Embryonic development started in May and completed by July or August (3 months). Males and females over 80 and 99 cm TL were mature. We describe the age and growth of the shovelnose guitarfish, on the western coast of Baja California Sur, Mexico. Samples were collected from artisanal fisheries in Bahía Almejas and Laguna San Ignacio from 1992 to 1998. The age was estimated from bands in the vertebral centra of 98 males and 321 females; the number of bands in females goes from one to 16 and in males from one to 11. The validation was attempted by using the marginal increment analysis; assuming an annual band formation. The length-weight relationship indicated an isometric growth for both sex (males = 2.92, females = 3.17). The Von Bertalanffy growth function parameters from the vertebral analysis were: L¥ = 100.5, K=0.24, to =-0.83 for males; L¥ = 136.69, K=0.16, to = -0.83 for females. The largest male and female were 106 and 142 cm TL.
17/06/2000 – 03:45:00 PM – Salon Madre Perla

Age and growth of juvenile tope shark, Galeorhinus galeus (Linnaeus, 1758), in the Azores

The age and growth of tope shark, Galeorhinus galeus, juvenile population segment in the Azores is presented. Vertebral centra were sampled between 1995-1997, during groundfish survey cruises aboard R/V “Arquipélago” within the Azorean EEZ. A modification of the cobalt nitrate technique provided highest reproducibility of age estimates and was therefore used in vertebral staining. Age estimates were based on calcified band counts. No significant differences in mean length-at-age data were found between males and females, hence von Bertalanffy juvenile growth parameters were estimated for sexes combined(L¥=207.34 cm, K=0.067, t0=-2.56). Empirical growth curve indicated that tope shark grows steadily at an average rate of 10 cm/year, in its first six years of life in the Azores. Periodicity of band deposition was assumed annual, according to previous research on the species. This assumption was not confirmed fully by independent length-frequency analysis (Bhattacharya method), however non-linear back-calculation (Monastirsky potencial equation) allowed verification of age readings. Comparison between these estimates and available published literature revealed significant differences on tope shark juvenile growth between the Azores and elsewhere. The possible causes and implications of the results are discussed, under the assumption of a single tope shark stock in the North-Eastern Atlantic.
17/06/2000 – 01:45:00 PM – Salon Madre Perla

Movements of thornback rays Raja clavata in the Irish Sea: A comparison of conventional and archival tagging methods

Conventional tagging methods are a cheap and widely used method for estimating patterns and rates of movement. However, the behaviour and distribution of fishers determine the quality and quantity of information. To independently evaluate the utility of conventional tagging we marked 1810 individuals with Petersen discs at six sites in 1995. In 1996 we tagged 96 adults with electronic data storage tags (DSTs) which logged depth (pressure) every 10-min. and temperature every 24hrs. For comparison we tagged 120 adults with Petersen discs. Most of the Petersen tagged individuals (79%) were recaptured within 60-km of the release site. There was no evidence for directional or seasonal migration. Five of the 17 recaptured DSTs recorded data for >50 days. The tidal components of the pressure data allowed geolocation with a resolution of 12-km. The spatial patterns of movement were small-scale similar to that detected by Petersen tags, an average of 62.4-km on an N-S axis and 64.8-km on an E-W axis. The DSTs indicated marked heterogeneity in vertical movement patterns anging from extended periods on the bottom to extended excursions into mid-water, occasionally for days. Both tagging methods indicate that that this species does not undertake extensive movements or seasonal migrations.
17/06/2000 – 09:15:00 AM – Salon Madre Perla

Are the whale sharks (Rhincodon typus) of Southeast Asia resident or migratory?

Movements of individual whale sharks (Rhincodon typus), are almost unknown. Recent studies from the Sea of Cortez, indicates that whale sharks are highly mobile and may range for thousands of kilometers. However, most information on distribution is related to seasonal occurrences based on anecdotal reports of occasional sightings. This lack of information on basic biology, especially movement and migration patterns is a problem for resource managers, as the species is increasingly utilized for ecotourism and commercial harvest. The latter use had become particularly intense in the Philippines, where an unregulated harvest burgeoned in response to a dramatic increase in the market for whale shark meat and fins in Taiwan. Catches had fallen steeply despite increasing fishing effort and rising prices. In January 1998 we initiated an international cooperative research program with the Borneo Marine Research Unit of the Univ. of Malaysia, Sabah, the Marine Laboratory of Silliman University, Dumaguete, Philippines; and the World Wildlife Fund-Philippines to determine if the whale sharks observed in the greater Sulu Sea region are resident or migratory. Using satellite telemetry we monitored the movements of whale sharks from the greater Sulu Sea region for up to 4 months. Results of this study will be presented.
15/06/2000 – 02:00:00 PM – Salon Madre Perla

Ultrasonic tracking of the yellow stingray, Urolophus jamaicensis

In order to initiate a study on the diel and seasonal movements of yellow stingrays in South Florida, we completed preliminary tracking utilizing ultrasonic telemetry. A 75-kHz tag (Sonotronics, Tucson, AZ) was sutured to the medial epaxial musculature of a 35-cm female stingray immediately after capture and anesthesia (MS-222). The stingray was returned to the capture site within 11 min of capture and tracked from a 9-m boat with a handheld directional hydrophone. The animal was tracked continuously for 28 h and locations were recorded at 30 – 45 min intervals. There was an increase in activity after sunset with peak activity between 0100 and 0700 hours. During photophase, the stingray apparently remained in a fixed location (at least within the 5-m circular error of our methodology as determined by previous accuracy tests). Direct observations during photophase showed the stingray to be buried in the sediment with only the transmitter uncovered. Laboratory testing for effects of transmitter placement on captive behavior demonstrated no apparent influence on swimming or feeding. Our study indicates that ultrasonic telemetry is a suitable methodology for studying the movements of yellow stingrays.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

Genetic variability of Western Atlantic lemon sharks, Negaprion brevirostris, based on microsatellite DNA analysis

The application of microsatellite DNA analysis in elasmobranch biology is becoming a powerful tool in determining genetic relationships within and between populations. We have developed several microsatellite markers for lemon sharks Negaprion brevirostris to assess within population variability and large-scale stock structure of this species. Screening approximately 15,000 colonies yielded 95 positive clones, of which 45 have been sequenced. Four loci, LS11, LS15, LS22 and LS 30, have been used to genotype several hundred individuals from four populations: Gullivan Bay, Florida (N=24), Marquesas Key, Florida (N=100), Bimini, Bahamas (N=400), and Atol das Rocas, Brazil (N=30). High levels of heterozygosity (.69-.90) and numerous alleles (18-41) were observed at all four loci. Analyses of the data suggest very little structure in Western Atlantic populations. Although Rho values between populations and Weir and Cockerham’s F were significant, all values were small (rho ranged from -.008 to .045; F=.019). Significance is likely attributable to our large sample size and high resolution of the markers and may not reflect biological differences. These low levels of differentiation and few observed private alleles suggest that the Western Atlantic populations may comprise one breeding stock.
18/06/2000 – 04:00:00 PM – Salon Madre Perla

Trophic role of sharks in the ecosystem and its response to exploitation

Characteristics like low reproductive potentials, slow growth rates, delayed sexual maturation, as well as newborn recruitment to artisanal fisheries, they point out sharks as highly vulnerable. The objective of this study is to obtain interpretations on the role of sharks in the ecosystem, and to evaluate its answer to the exploitation, using the dynamic simulation model ECOSIM. Starting from representative solutions of 11 ECOPATH ecosystem models, ECOSIM was used to simulate increments in exploitation rate of the sharks group, evaluating the answers through changes in biomass and stability properties of the ecosystem. The groups of sharks subjected habitually to fishing, showed a higher capacity to resist increments in the exploitation rate, their responses were bigger as the fishing effort increases and finally their recovery time was low. On the other hand, strong and fast responses were presented in sharks groups originally with smaller fish rate levels, the responses didn’t change significantly with the increment of the exploitation rate and their recovery was slow. Contrary to the rest, in reef ecosystems the impact is important and its recovery critical, although there were not bigger changes in the ecosystem.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

Chondrichthyans using evans blue dye techniques

Evans blue dye techniques were employed to estimate the plasma and blood volumes of two species of chondrichthyans: the gray smoothhound, Mustelus californicus (n = 10) and the leopard shark, Triakis semifasciata (n = 20). The dye was administered intravenously (0.5-0.6 mg/kg) and blood samples were collected at 10, 20, and 30 minutes after injection. Optical density of plasma samples was measured at 620nm using a spectrometer and compared against standard curves to find the concentration of the dye in the plasma. The concentration of dye in the blood at the time of injection was mathematically extrapolated and then used to calculate plasma and blood volumes. Mean plasma volumes were estimated to be 30.82 +/- 2.45ml/kg and 39.15 +/- 4.48ml/kg, for M. californicus and T. semifasciata, respectively. Likewise, after correction with simultaneously measured hematocrit values, mean blood volumes found were 45.49 +/- 2.99ml/kg and 54.16 +/- 5.96ml/kg. These values appear to fit into both the evolutionary trend previously proposed for fishes and the notion that within a phylogenetic group, blood volume increases with activity level (Thorson 1961; Smith 1982).
16/06/2000 – 08:00:00 AM – PingPong Area

A comparative assessment of biochemical measures of nutritional condition in two Antarctic fishes

Electrona antarctica and Bathylagus antarcticus, dominant components of the Southern Ocean pelagic ecosystem with disparate life histories, were utilized for a comparative study of 21 indices of nutritional condition. Indices were compared by observing spatial and temporal changes associated with the marginal ice zone bloom in the Northwestern Weddell Sea. Variability between indices and species were observed. Nutritional condition ofElectrona increased in 11 of 21 indices in response to the bloom. In contrast, only 3 indices changed in Bathylagus. Earlier work, which suggested that deeper living, non-migrating species would not be affected by the bloom until after shallower living, migratory species, was supported. Of the assays tested, RNA:DNA appeared to be the most sensitive; lipid analysis was also effective. The combined assessment of many measures, including biochemical, compositional, dietary, and age estimates from single specimens is possible if the samples are treated with sufficient care. The reliance upon a single measure to help interpret the ecology of a species, especially in nekton sized species, is not as effective as techniques used in combination.
16/06/2000 – 08:00:00 AM – PingPong Area

Preliminary investigations on the effects of exposure to the endocrine-disrupting compound 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) on clearnose skateRaja eglanteria development

Studies conducted on teleosts, amphibians, reptiles, birds, and mammals have established that exposure to endocrine-disrupting compounds during the critical period of embryogenesis can drastically impair normal developmental processes. However, little or no information is available on the effects of xenobiotic chemicals on development in elasmobranchs, animals that possess limited reproductive capacities and often tend to bioaccumulate environmental contaminants. In response to this need, the goal of this preliminary study was to investigate the effects of the putative endocrine disruptor 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) on sexual differentiation and immunological development of captive bred clearnose skate Raja eglanteria embryos. Skate embryos were exposed to one of two environmentally-relevant levels of DDT or vehicle via immersion during weeks 3-7 of the 12-week developmental period. Following chemical exposures, animals were sacrificed and patterns of sexual differentiation were investigated through histologic and immunocytochemical observations on primary and secondary sex characters. Development of the immune system was examined through peripheral white blood cell counts. Impairment of ovarian but not testicular development was observed in some skate embryos at both levels of chemical exposure. Disturbances in the development of secondary sex characters (gonaducts, claspers) were not observed in either sex. Significant reductions in peripheral white blood cell counts were associated with both levels of chemical exposure and may be associated with endocrine-related processes. Though preliminary, this study represents one of few investigations on the effects of endocrine disruption in this phylogenetically ancient and ecologically important vertebrate group. In addition, it introduces a sophisticated animal model for assessing chemically-mediated disturbances in embryonic development.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

Life and death in the oviducal gland: apoptosis during sperm storage in female bonnethead sharks, Sphyrna tiburo

Sperm storage is a complex mechanism that permits successful reproduction to occur despite temporal separation between between mating and ovulation. Although sperm storage has evolved independently in every vertebrate class except Agnatha, certain elasmobranchs are the only placental vertebrates other than some bat species that are known to store sperm for long periods of time (>2 weeks). Observations on sperm storage in elasmobranchs have largely been confined to reports on its presence or absence in selected species and little information is available on the actual maintenance of sperm viability in the oviducal gland, the organ responsible for sperm storage in female elasmobranchs. The present study examined apoptosis (programmed cell death) of spermatozoa in the oviducal gland of preovulatory female bonnethead sharks, Sphyrna tiburo, as part of a larger investigation on environmentally-mediated differences in reproductive success. Sperm apoptosis was detected in the oviducal gland through enzymatic in situ labeling of apoptosis-induced DNA strand breaks using the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) technique. Apoptotic sperm were detected in all oviducal preparations examined at varying levels of cellular density. However, no apparent differences in sperm viability were observed between females collected from two study sites. Thus, differences observed in the reproductive success of these groups cannot be attributed to differences in cell survival during oviducal sperm storage. Despite these observations, the present study describes a useful method for defining the physiological mechanisms that regulate sperm storage in elasmobranchs.
18/06/2000 – 08:45:00 AM – Salon Madre Perla

Relaxin n’ reproducin’ in the male bonnethead shark Sphyrna tiburo

Relaxin is a 6-kDa polypeptide that is best known for its role in regulating the extensibility of the reproductive tract of female mammals during pregnancy and parturition. Relaxin is also roduced in certain male vertebrates (i.e., elasmobranchs, birds, mammals) by the testes or accessory sex organs and appears to play some, albeit unclear, role in regulating sperm kinematics. The present study investigated changes in serum relaxin concentrations of immature and mature bonnethead sharks Sphyrna tiburo, in an effort to clarify its role in this gender. Serum relaxin concentrations in two groups of mature S. tiburo and one group of immature S. tiburo were measured by radioimmunoassay. In mature male S. tiburo,serum relaxin concentrations followed a pattern associated with the reproductive cycle in which peak levels occurred during late spermatogenesis and mating. No temporal pattern in serum relaxin concentrations was observed for immature male S. tiburo, also supporting the hypothesis that relaxin functions in sperm transport. Preliminary observations on the immunohistochemical localization of relaxin in the male reproductive tract will be presented to better define its specific role during reproductive events.
18/06/2000 – 09:30:00 AM – Salon Madre Perla

Distribution, segregation, and the potential for variable growth rates in salmon shark, Lamna ditropis, in the western and eastern North Pacific

The salmon shark, Lamna ditropis, is widespread in the boreal North Pacific, ranging between 35oN-65oN in the western Pacific and 30oN-65oN in the eastern Pacific. They are the largest apex fish predator in the upper pelagic zone there. Maximum size has been reported at 305cm TL, but average size range seems to be between 200-250cm TL. Like many other elasmobranchs they appear to exhibit a life history strategy characterized by slow growth, late maturity, low fecundity and, therefore, extremely low intrinsic rates of population increase. Their seasonal distribution is difficult to assess at this point, however there appears to be some north-south movement during the year in both the eastern and western Pacific. Additionally, there appears to be movement across the Pacific basin which may create mating aggregations in the Gulf of Alaska and Prince William Sound during late summer. Current research is focusing on age, growth, demographics and thermal biology of salmon sharks in Gulf of Alaska and Bering Sea waters, with the goal of fostering responsible long-term management. The potential variability existing between growth rates of salmon sharks in the western and eastern North Pacific, strong sexual and size segregation, and unknown amounts of bycatch all complicate management issues for this species.
17/06/2000 – 05:30:00 PM – Salon Madre Perla

Cenozoic Chondrichthyans assemblages from Baja California Peninsula

This study is part of my Master´s Thesis. Until now, it is the most complete record of sharks, batoids and chimaeroids in the Baja California Peninsula. At least nine time periods with records of these fossils are recognized. The first record is the Sepultura Formation (east-southeast of El Rosario, Baja California) with a small fossil fauna of sharks and rays corresponding to a Danian age (in correlation to the Tethys age reference) or Early Paleocene. It is dominated mainly by small specimens from Odontaspididae and Myliobatoidea. The second record is from the Tepetate Formation (arroyo El Conejo, west of La Paz). The fauna contains an increased number of 13 species of Thanetian age (Late Paleocene), including Paleocarcharodon orientalis (Sinzow 1899). This is probably the only seventh global record for this specie, including Russia, Congo, Marroco, Germany, Maryland and South Carolina. The third record is found in the Tepetate Formation (from the arroyo El Aguajito to the rancho La Fortuna, northwest of La Paz) and in the Bateque Formation (Mesas San Ramón and Todos Santos, east of the San Ignacio Lagoon, and Arroyo El Mezquital west-northwest of La Purísima) with a record of at least 30 species of sharks and batoids corresponding to a Lutetian – Bartonian age (Middle Eocene). The faunas are mainly dominated by Isurus praecursor (Leriche 1904), Carcharocles sokolowi (Jaekel 1895), Rhinobatus sp. and Coupatezia sp. The fourth record belongs to the basal bed of the San Gregorio Formation (rancho San Ramón, arroyo San Gregorio and rancho El Malbar, arroyo El Mezquital) and El Cien Formation.
18/06/2000 – 01:45:00 PM – Salon Madre Perla

Phylogenetic relationships among hammerhead sharks

Hammerhead sharks are considered to be closely related to the carcharhinid sharks based on the large number of shared morphological and molecular characteres. However, studes of the phylogenetic relationships within the family Carcharhinidae have yielded conflicting results. The family Carcharhinidae is not monophyletic unless the hammerheads are included within that family. Then, despite its many unique features, the Sphyrnidae is not a valid family? The resent family Sphyrnidae is currently divided into two genera: Eusphyra andSphyrna. This study attempts to understand the interspecificic relationships among the hammerhead sharks based on chondrocranium morphology, tooth arregement and external morphology data. Morphological features were contrasted for eight species of Sphyrnids, and two species of Carcharhinids sharks as outgroups for character polarization and for rooting. Maximum parsimony analyses were employed using quantitative and qualitative characters in the program PAUP 3.1.1.
18/06/2000 – 04:15:00 PM – Salon Madre Perla

Allometry and skull design in sphyrnids sharks

The hammerhead sharks, as all vertebrates, increases in size during development. This study shows the consequences of the changes of size for morphological shape and function of the skull in the sharks of the Family Sphyrnidae. Additionally, it represents an effort to elucidate evolutionary aspects about ontogeny, embriology and morphology of the group. Multivariate comparisons of head shape among species indicate that mensural attributes are highly correlated with head size, thus displaying strong evolutionary allometry. The ratio head length/total length considered diagnostic to Sphyrna blochii is as strongly dependent on body size as untransformed measurements and not reflect multivariate pattern of shape variation and, thus not can be useful in descriptive taxonomic studies. Size-independendent variation in form seems to be continuous among species with no apparent morphological gaps with which to distinguish natural species groups. Changes in morphology in these fishes are highly corservative and result from subtle, allometric and heterochronic changes in relative growth rates among skull structures.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

Population size estimates of whale sharks, Rhincodon typus, off the Belize Barrier Reef

At least 6 sites where whale sharks aggregate predictably are recorded for the Indo-Pacific and Pacific Oceans, whereas the literature reports none, save occasional sightings, for the Atlantic Ocean. Following an investigation of local fishermen’s reports, we document here a new aggregation site and possible centre of distribution of whale sharks Rhincodon typus in the Caribbean, on the Belize Barrier Reef. Gladden Spit, a promontory on the barrier reef harbours a dense and predictable aggregation of whale sharks that feed on the freshly released gametes of large spawning aggregations of 2 Lutjanid species during the full moon periods from April to June. A preliminary survey of the population in 1998 based on individual markings and scars yielded an estimated population of 25 individuals. A tagging programme undertaken in 1999 identified 15 sharks. Combined with a mark release recapture study undertaken in 1999, that also accounted for sighted but untagged sharks, the population is estimated at a minimum of 23 individuals. Mean tail length (TL) of tagged whale sharks was 5.05 m. Although the sex ratio could not be determined with confidence, only one shark possessed the TL to qualify it as sexually mature. Tagged individuals from the May full moon were re-sighted feeding during the June full moon indicating tag retention and site fidelity at Gladden Spit during the snapper spawning-season. Following this period, tagged whale sharks were re-sighted north, south, and east of the aggregation site outside the barrier reef in deep water, associated with schools of bonito, blackfin, bigeye, and skipjack.
15/06/2000 – 03:00:00 PM – Salon Madre Perla

Movements of juvenile Carcharhinus plumbeus in Chesapeake Bay, Virginia USA using sonic telemetry and mark-recapture methods

Ultrasonic telemetry was used to investigate short-tem movements of juvenileCarcharhinus plumbeus (sandbar sharks) in Chesapeake Bay. During the summers of 1997, 1998, and 1999 a total of ten juvenile (44-62 cm PCL) C. plumbeus were fitted with transmitters containing depth sensors and tracked continuously for 10-50 hours. CTD casts were made from surface to bottom hourly. Minimum convex polygon activity space estimates (N=7; tracks>24hrs) ranged from 39.5 to 249.5 km2. Bottom depth was one to forty meters and mean swimming depth ranged from 6.6 to 15.5 meters. Twenty to fifty percent of depth fixes were within two meters of the bottom and subjects frequently made rapid ascents to surface waters, even when bottom depth was >35 meters. Swimming depth was significantly deeper during daylight hours for three tracks. Movement patterns were analyzed with environmental data and tidal current models and compared with nursery delineation models using GIS. From 1995 to 1999, 1603 juvenile (<100cm PCL) C. plumbeus were tagged in Chesapeake Bay and Virginia coastal waters. Data from 39 recaptures (mean=230 days; range 4-918) were used to investigate longer-term movements within the summer nursery and during migrations to wintering areas and to investigate summer nursery fidelity in subsequent years.
17/06/2000 – 10:45:00 AM – Salon Madre Perla

Temporal and spatial nursery delineation for Carcharhinus plumbeus in the lower Chesapeake Bay, Virginia USA

The lower Chesapeake Bay represents a primary nursery for Carcharhinus plumbeus, sandbar sharks. The VIMS Longline Survey was expanded from 1993 to 1999 to include ancillary stations throughout the Virginia Chesapeake Bay to spatially delineate the nursery. Catch and environmental data from 120 stations were used to characterize nursery habitat using categorical analysis regression tree (CART) modeling and Spearman’s rank correlation. Distance from Bay mouth and salinity were the most influential parameters in these models. These data were used to construct GIS maps delineating areas of Chesapeake Bay meeting the environmental criteria thereby identifying essential nursery habitat for this species in Chesapeake Bay. The VIMS survey has included standard stations the lower Chesapeake Bay since 1980. CPUE and environmental data from two stations sampled consistently in summer months from 1990 to 1999 were used to temporally delineate utilization of this nursery. Immigration was highly correlated with surface temperature while emigration was highly correlated with length of day. From 1995-1999, 1603 juvenile C. plumbeus were tagged in Chesapeake Bay and Virginia coastal waters. Data from 39 reported recaptures support the temporal nursery dynamics described from the CPUE data as well as elucidate migration atterns and winter nursery areas.
18/06/2000 – 10:45:00 AM – Salon Madre Perla

Short-term survival and movements of small carcharhinid sharks after catch-and-release angling in the northeast Gulf of Mexico

Ultrasonic telemetry was used to assess short-term survival and movements of small hooked sharks (Carcharhinidae) after release in a coastal nursery area in the northeast Gulf of Mexico. Sharks were caught with standardized rod and reel gear during June-October 1999. Ten Atlantic sharpnose Rhizoprionodon terraenovae, three finetoothCarcharhinus isodon, two spinner C. brevipinna, and two blacktip sharks C. limbatuswere measured (<108 cm TL) and continuously tracked for a mean duration of 2.5 ±1.8 SD h (0.5-5.9 h). Activity and movement suggested short-term survival was at least 94%. The estimated rate of movement averaged 1.4 ±1.1 SD km/h, (0.5-5.2 km/h). The mean rate of movement of C. limbatus (3.6 km/h) was significantly faster than the other species (F=36.58, p<0.05). Differences in movements did not differ among hooking locations or fishing sites. Rate of movement was significantly correlated with playing time (r=0.671, p<0.05). The mean direction of net movement was 208° ±77 SD or south-southwest. These findings suggest that anglers should be encouraged to reduce handling time of recreational bycatch in shark nursery grounds. High short-term survival of small hooked sharks suggests catch and release may reduce bycatch mortality and may be used in management of recreational shark fisheries.
17/06/2000 – 09:30:00 AM – Salon Madre Perla

Reproductive biology of the scalloped hammerhead shark, Sphyrna lewini, in the southwestern equatorial Atlantic Ocean

The scalloped hammerhead shark, Sphyrna lewini, is globally distributed throughout tropical and temperate oceans. While aspects of their reproductive biology have been quantified in fishery-dependant studies at various locations, there is a paucity of relevant data from adult females and particularly gravid individuals throughout their distributions. Further, there is an absence of information describing life history in the southwestern equatorial Atlantic. In an attempt to address these issues, we examined ninety two specimens ranging in size from 121 to 321 cm total length (TL), collected from surface gillnetters operating off northeastern Brazil between January and December 1996. A common regression for TL and eviscerated weight (EW) was calculated as, logEW = -11.786+ 2.889 logTL. Females and males were categorised into reproductive stages (4 and 2, respectively) according to morphological changes in their gonads. Size at sexual maturity for females was estimated to be 240 cm TL, while males appeared to mature at between 180 and 200 cm TL. Gravid females had between 2 and 21 pups, varying in TL from 3 to 38 cm. Copulation and parturition occur outside the sampled area and possibly closer to the coast. Vitellogenisis and gestation each appear to take about 10 months with ovulation and parturition occurring during autumn and summer, respectively. With the exception of slightly lower uterine and ovarian fecundities, the results support the few existing data on the reproductive cycle of S. lewni in other areas.
18/06/2000 – 09:15:00 AM – Salon Madre Perla

Reproductive cycle of the blacknose shark, Carcharhinus acronotus, off northeastern Brazil

The blacknose shark, Carcharhinus acronotus, is a relatively small carcharhinid, typically occurring across continental shelf areas in the Atlantic Ocean, from North Carolina in the USA to southeastern Brazil. Its abundance and accessibility in nearshore areas off northeastern Brazil means that it often comprises a large proportion of elasmobranch catches from artisanal fishing operations. Despite its commercial importance, very little information is available with respect to life history traits and particularly reproductive biology off Brazil. To address this issue, we examined 129 specimens (81 females and 48 males), ranging in size from 49 to 131 cm total length (TL), caught by artisanal fishers using gillnets and research vessels using bottom longlines off the coast of Pernambuco, Brazil. Size at sexual maturity for males was estimated at between 93 and 104 cm TL, while females matured at between 101 and 106 cm TL. All gravid females (22 examined) contained 4 pups, varying in TL from 25.5 to 48.5 cm TL. Gestation appears to take between 8 and 9 months, with copulation and parturition occurring within the sampled area and mainly during April and December, respectively. The results provide evidence to suggest an annual reproductive cycle.
18/06/2000 – 08:30:00 AM – Salon Madre Perla

DNA microsatellites in blacktip shark (Carcharhinus limbatus): variation, population structure, and cross-species amplification

The blacktip shark (Carcharhinus limbatus) occurs in coastal waters of warm-temperate and subtropical oceans. To test the hypothesis that blacktip sharks in the US Atlantic and Gulfof Mexico comprise a single genetic stock a suite of polymorphic DNA microsatellite loci were developed and scored in blacktip sharks collected from Virginia, USA to Tamaulipas, Mexico. The power of individual loci to discern population structure was examined by scoring additional blacktip sharks from Baja California, Mexico. Cross-species amplification and the utility of microsatellite loci in carcharhinid sharks was evaluated by amplifying blacktip sharks DNA with primers developed in other species, and by amplifying DNAs from other species with primers developed in blacktip shark. The relationship between heterozygosity and the number of repeat units per microsatellite motif, and the relationship between number of alleles and statistical power for detecting stock structure will be discussed. Conclusions of genetic studies are compared to tagging data.
18/06/2000 – 03:45:00 PM – Salon Madre Perla

Tiger shark (Galeocerdo cuvier) habitat use and behavior in Shark Bay, Western Australia

Understanding the spatial distribution of animals, and the factors influencing these distributions, is one of the primary goals of ecologists. We used both acoustic telemetry and animal-borne video cameras (“Crittercams”) to study tiger shark (Galeocerdo cuvier) predatory behavior and determine the influence of prey availability on shark habitat use. Crittercams provided depth and video data, which allowed us to collect behavioral data and accurate estimates of shark habitat use. Tiger sharks were found to move regularly between surface waters and the bottom. This diving behavior may be energetically more efficient than constant-depth swimming and may aid in prey detection and capture. Despite multiple encounters with potential prey, sharks rarely engaged in high-speed chases, and did not attack potential prey items that were vigilant. The abundance of tiger sharks’ potential prey was significantly higher over shallow, seagrass habitats. Tiger sharks preferred these habitats, which is consistent with the hypothesis that shark distribution is at least partially determined by prey availability. Comparison of data collected simultaneously with Crittercams and acoustic telemetry showed no significant difference in average habitat use by tiger sharks, although, estimated habitat use of some individuals differed greatly between these methods.
17/06/2000 – 11:15:00 AM – Salon Madre Perla

The short term in vitro response of stingray trophonemata to exogenous agents

Myliobatoid rays reproduce via aplacental viviparity. Following absorption of the yolk, embryos consume organically rich uterine fluid (histotroph) produced by the uterine villi (trophonemata) for the remainder of gestation. Previous studues have suggested that endocrine changes during the reproductive cycle in female rays trigger the synthesis and release of histotroph. To examine the effects of several hormonal factors, a series of short term in vitro experiments (24 and 48 h duration) were conducted on trophonemata from adult female Atlantic stingrays, Dasyatis sabina, from the pre-ovulatory to post-ovulatory stage. A variety of peptide and steroidal hormones and activators of signal transduction pathways were evaluated for their ability to directly induce histotroph secretion in vitro. The preliminary results using estradiol, progesterone, ovine prolactin, bovine insulin, bovine growth hormone, forskolin, and a phorbol ester with trophonemata of non-gravid females failed to show a change in the rate of protein accumulation in the culture media.
18/06/2000 – 05:15:00 PM – Salon Madre Perla

Assessing post-release mortality of coastal sharks using a logistic model of relative survival

Assessing the survival of fish released from fishing operations (either sport or commercial) is an important but difficult step in managing a fishery to have acceptable mortality. We developed a logistic model of relative survival of live releases and applied it to data on two species of coastal sharks, the blacktip (Carcharhinus limbatus) and the bonnethead (Sphyrna tiburo). Sharks caught in a gillnet were tagged, released, and assigned to one of four condition categories based on their behavior on release. Condition 1 was assigned to sharks that swam away vigorously with no signs of stress; at the other extreme, sharks exhibiting signs of severe stress were assigned to category 4. If sharks in two condition categories have the same survival rate the ratio of catches, and presumably tag recaptures, of the two groups should remain constant over time. The relative survival rate of the two groups can be estimated from the way that the ratio changes over time. If it is assumed that all animals in category 1 survived the initial capture, then the absolute survival rate of animals in categories 2, 3, and 4 can be determined and, hence, the total number of released sharks that died can be determined. This method can be applied to estimates of discard mortality in fisheries as well as post-release mortality in tagging operations.
16/06/2000 – 05:00:00 PM – Salon Madre Perla

Patterns of movement by neonate blacktip sharks, Carcharhinus limbatus, within a coastal nursery area

An array of 14 remote acoustic hydrophone stations was used to monitor the movements of neonate blacktip sharks, Carcharhinus limbatus, within a coastal nursery area. The telemetry system provided continuous tracking data for 18 sharks over a seven-month period before the sharks left the nursery area. Sharks were tracked for periods of 3 – 159 days. Five sharks were present within the study site for greater than five months, six sharks were present for two to four months and seven sharks remained for one month or less. Five sharks that had left the study site returned intermittently throughout the study period. The acoustic array collected a vast amount of data that was sorted and condensed for analysis by the Remote Acoustic Telemetry Searcher program (RATS). Processed data was analyzed to examine diurnal or tidally influenced movements. The amount of time sharks spent in various portions of the nursery area was compared to environmental data to define possible reasons for site attachment. The direction of movement away from a station and associations between sharks fitted with transmitters were examined. These results are summarized to examine the overall use and habitat preferences of neonate C. Limbatuswithin this nursery area.
17/06/2000 – 09:45:00 AM – Salon Madre Perla

A random walk model for assessing the movements of neonate blacktip sharks

A Monte-Carlo simulation model of the movement of neonate blacktip sharks in a summer nursery area in Terra Ceia Bay, Florida, was developed and the results compared to data from remotely monitored individuals. The model contained 22 individual cells that replicated the shape of the bay. Fourteen cells corresponded to acoustic hydrophone stations that monitored the movements of tagged sharks. The model estimated the frequency of occurrence of individuals in each cell, and estimated the time it took to leave the study area. The model was used to test three hypotheses: (1) that sharks move randomly within the nursery area, (2) that sharks remain in the nursery area by directional movement to the north of the bay, and (3) that sharks remain in the nursery area by preferring to stay at the cell that they currently occupy rather than move to an adjacent cell. The results of the model indicated that early in the summer neonate blacktip sharks remain in the nursery area by being 3.5 times more likely to move north than other directions. Changes in the behavior of the blacktip sharks later in the summer failed to match any of those from the model.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

Whale sharks feed on gametes released from snapper spawning aggregations in Belize

Whale sharks (Rhincodon typus) are considered opportunistic planktivores, whose diet includes nektonic prey such as squid and small fry. They are commonly known to target dense patches of their prey. Here we report the first direct observations of whale sharks feeding on the freshly released gametes of reef fish in large spawning aggregations. This food source attracts the densest and most predictable aggregation of whale sharks ever reported with 25 individual whale sharks recorded in less than a 100m diameter area. Over 126 hours of underwater observations made during the April-June full moon periods in 1998 and 1999 indicate that whale sharks aggregate to feed at dusk on the spawn of two reef snappers, Lutjanus cyanopterus and L. jocu. Several additional species of finfish are also thought to spawn at Gladden Spit during this season, including mutton snappers (L. analis), and Carangids Caranx ruber and C. hippos. Scuba observations of these seasonally aggregating finfish in proximity to whale sharks, and gonadal analysis of captured fish, indicate that their spawn may also be targeted by feeding whale sharks. Whale shark feeding on spawning snapper has implications for traditional snapper fisheries, predictable whale shark visitations, and the burgeoning whale shark tourism at the site.
15/06/2000 – 03:15:00 PM – Salon Madre Perla

Survival of juvenile lemon sharks at Bimini, Bahamas, estimated by mark-depletion experiments

The survival rate of juvenile lemon sharks in North Sound, Bimini, Bahamas, was estimated by marking a cohort of small sharks (< 53 cm precaudal length) each spring from 1995 to 1999 and estimating the number of survivors one year later by using a depletion method on the marked population. Annual survival rate over the five seasons varied between 38 and 65% which was somewhat higher than the 39% steady-state survival predicted from a life cycle (Leslie matrix) model. This is the first direct estimate of survival rate of a juvenile elasmobranch and the results support modeling efforts that have been used in determining limits to sustainable exploitation of elasmobranchs. Estimates of survival rates in the present study were negatively correlated with estimated initial abundance and are consistent with strong density-dependent recruitment. Supported by the OCE/BO Division of the National Science Foundation.
17/06/2000 – 04:30:00 PM – Salon Madre Perla

A review of the principal shark nurseries of the Gulf of México and Caribbean Sea

Several Carcharhiniforms species use coastal areas, lagoons, bays and estuaries as nursery areas in the Gulf of México and the Caribbean Sea. The shallow, open coastal waters of Tamaulipas, Veracruz and the Campeche Bank are considered unprotected nursery areas for Rhizoprionodon terraenovae; Carcharhinus signatus, Carcharhinus falciformisand Sphyrna tiburo respectively. Protected shark nurseries in waters of the Gulf of México are mainly coastal lagoons. Madre Lagoon, Tamiahua Lagoon, Alvarado Lagoon, Términos Lagoon, Yalahau Lagoon, Asención Bay, Espíritu Santo Bay and Chetumal Bay, localized from the north to the southeast of the Gulf of México respectively, are of prime importance as shark nursery grounds for several species of sharks from the families Carcharhinidae and Sphyrnidae. Most of the tropical shark nursery areas identified in waters of the Gulf of México are also important fishing grounds for local communities. The protection of nursery areas is a key aspect of fishery management. The delineation of the number and kind of the shark nursery grounds, besides the species of sharks that use them in this area must be known if we are to have effective management of mexican shark resources.
19/06/2000 – 08:00:00 AM – Salon Madre Perla

Artisanal fisheries for elasmobranchs in the Gulf of California: a multi-institutional project

Mexican fisheries rely heavily on sharks and rays and more elasmobranch tonnage is landed in the Gulf of California than in any other Mexican region. To assess the status of sharks and rays in artisanal fisheries of the Gulf of California, two U.S. institutions (Mote Marine Laboratory and Moss Landing Marine Laboratories) and two Mexican institutions (Instituto Nacional de la Pesca and Universidad Autonoma de Baja California Sur) collaborated on a two-year project in 1998-99. Seasonal surveys of the four states bordering the Gulf were conducted to characterize target species, catch, fishing effort, and other parameters. A total of 171 fishing camps with over 5,300 active boats (pangas) were found, most of which targeted elasmobranchs to one degree or another. Over the two years, 394 sampling days resulted in direct observation of 165,513 elasmobranchs of 55 species in the artisanal catch, of which 14,142 specimens (9%) were measured by researchers. Total effort, catch and CPUE Gulf-wide by season is being estimated with survey data. Results will help identify elasmobranch populations at risk and be used to formulate management strategies for conservation of sharks and rays in the Gulf of California.
16/06/2000 – 08:15:00 AM – Salon Madre Perla

Tooth loss rate from one captive sandtiger shark (Carcharias taurus)

In 1942, C. M. Breder rejected F.G. Cawston’s (1940) argument against tooth succession in sharks. Breder believed shed sand tiger (Carcharias taurus Rafinesque, 1810) teeth on the bottom of an aquarium tank indicated continuous tooth replacement. His study resulted in an estimated C. taurus tooth replacement rate of one tooth approximately every two days. He suggested a more definitive answer regarding tooth replacement rates could be obtained by confining one animal in a clean tank and collecting all shed teeth over a given period of time (Breder 1942). A 1988 study by Neal Overstrom confirmed Breder’s findings, but Overstrom added the conditions of his study did not account for potential differences due to age and growth rates. In 1995, Joao P. Correia gathered C. taurus teeth from the bottom of a small tank in which water temperature varied during the course of the study, resulting in a potential correlation between increases in temperature, metabolic rates and tooth loss. The research progression of multiple sharks in a tank with a concrete bottom (Breder), to multiple sharks in a constant-temperature, substrate bottom tank (Overstrom), to multiple sharks in a variable-temperature, substrate bottom tank (Correia) has led to this project. The Texas State Aquarium maintains a single sand tiger in a large,constant-temperature, concrete bottom tank. This study will apply Breder’s original suggestion to C. taurus tooth replacement rates as well attempt to compare constant-temperature tooth loss rates with variable-temperature tooth loss rates in C. taurus. Preliminary findings will be presented. {revised abstract}

16/06/2000 – 04:00:00 PM – Salon Madre Perla

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

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

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 Urogymnusbelonging to subfamily Dasyatinae can be reassigned and merged into one genus Dasyatis.
18/06/2000 – 05:00:00 PM – Salon Madre Perla

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-parturitionS. 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

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

Observations on the seasonal occurrences of whale sharks (Rhincodon typusSmith, 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

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

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

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

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

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

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 primitiveMustelus, Scylliogaleus, and Triakis. The Galeorhininae consists of the tribes Iagini, for ago, Furgaleus, Hemitriakis, and Gogolia, and Galeorhinini for Galeorhinus andHypogaleus. 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

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

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

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

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

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

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

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

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

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

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

Captive biology of the pelagic stingray, Pteroplatytrygon (Dasyatis) violaceaBonaparte (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

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

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

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

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

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

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

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

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

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

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

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

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

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 (Loligosp. and Octopus sp.).
18/06/2000 – 08:15:00 AM – Salon Madre Perla

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

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

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

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 vulpinusindicates 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

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

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

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

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

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

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

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

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

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 andIsurus 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

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

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

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

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

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

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

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

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

Morphological and osteological development of the silky shark Carcharhinus falciformisis 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

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 wereRhizoprionodon longurio (15.39%), Prionace glauca (15.07%), Carcharhinus falciformis (10.70%), Nasolamia velox (9.24%), Mobula munkiana (7.62%) andIsurus 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 forSquatina californica, R. longurio, P. glauca and C. falciformis.
16/06/2000 – 09:30:00 AM – Salon Madre Perla

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

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

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

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

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

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

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