1992 AES Annual Meeting Abstracts

Anatomical observation and description of the ampullae of Lorenzini in the shortfin mako shark Isurus oxyrinchus

Aadland, Christopher R. and William G. Raschi
Department of Biology, Bucknell University, Lewisburg, PA 17837 

The electroreceptive system in eight specimens of Isurus oxyrinchus were observed by dissection and compared to see if ontogenetic changes were evident. The gross morphology and histology of the ampullary systan in I. oxyrinchus was then described. In addition ampullae from I. oxyrinchus were compared with ampullary data from several species of charcharinids to determine the level of complexity and development of I. oxyrinchus’sampullary system. This data showed that I. oxyrinchus had fewer and less well developed ampullae as compared to charcharinids in general. Isurus oxyrinchus is an open ocean pelagic predator inhabiting clear water indicating that vision is probably the most important sensory system used in prey acquisition. Raschi and Adams (1988) suggest that there is a definite correlation between the use of vision and electroreceptor complexity to depth inRaja radiata. Tricas and McCosker (1984) suggest that innbsp;Carcharodon carcharias the ampullary system is used primarily at the moment of attack when the eyes have rolled back into the head for protection and vision is no longer used to locate prey. This data supports the hypothesis that ampullae in I. oxyrinchus play a lesser role than other sensory systems in prey acquisition as compared to elasmobranch species inhabiting low light or murky water conditions. Saturday, 6 June, 3:00 P.M., Opera Rehearsal (session 13)

A scanning electron microscopy study of the dermal denticles of the bull shark,Carcharhinus leucas

Bargar, Tom W.1 and Thomas B. Thorson 2
1Department of Veterinary Science, University of Nebraka, Lincoln, NE 68583-0905 221233 SW Martinazzi, Tualatin, OR 97062 

Dermal denticles of Carcharhinus leucas were examined by scanning electron microscopy. Skin samples were taken from three fetal stages and an adult. Samples to be examined were collected from the same body locations on each of the fetal stages and the adult. Five distinct morphological conditions were noted: 1. denticles cusped and ridged, 2. denticles oval with both the ridges and cusps reduced or absent, 3. denticles cusped with the ridges absent or reduced, 4. denticles with cusps reduced or absent, but ridged, and 5. denticles absent. The use of dermal denticles for taxonomic purposes is discussed within the context of the varied morphologies. A hydrodynamic function is suggested by the morphologically different dermal denticles and the pattem of their location on the body of the shark. Three functional zones for the pattern of the dermal denticles are proposed. 1. A zone of smooth denticles which maintain minimal turbulent deflection of the boundary of water. 2. A zone of ridged or cusped denticles covering most of the body surface promoting low turbulence and minimal friction. 3. A zone of no denticles located at the posterior edges of the fins, allowing for flexibility during generation of vortices at the beginning of wake formation. Saturday, 6 June, I:00 P.M., Opera Rehearsal (session 12)

Molecular phylogeny of the prickly shark

Bernardi, Giacomo and Dennis A. Powers
Hopkins Marine Station, Stanford University, Department of Biological Sciences, Pacific Grove, CA 93950 

The classification of the genus Echinorhinus is still under debate. Echinorhinus is most commonly classified in the family Echinorhinidae (Squaliformes) or in the family Squalidae (Squaliformes). Some authors have suggested a closer relationship of Echinorhinus to the order Hexanchiformes.

DNA was extracted from a blood sample taken from a specimen of the rare prickly shark(Echinorhinus cookei ) which stranded alive at Moss Landing, Monterey Bay, Califoxnia Two genes widely used in molecular phylogeny studies, the cytochrome b, and the 18S rRNA genes, have been sequenced. In order to test the controversial phylogeny of the prickly shark, the same genes have been sequenced in the two potential relatives, the spiny dogfish Squalus acanthias (Squaliformes) and the sevengill shark Notorynchus cepedianus (Hexanchiformes).

The prickly shark, the dogfish, md the sevengill shark were found to be equally distant from one another in this analysis. These results suggest that the prickly shark is neither in the order Squaliformes, nor in the order Hexanchiformes. Friday, 5 June, 4:15 P.M., Opera Rehearsal (session 2)

Distribution and abundance of the cownose ray, Rhinoptera bonasus (Mitchell 1815), in lower Chesapeake Bay

Blaylock, Robert A.
Virginia Institute of Marine Sciences, College of William and Mary, Gloucester Point, VA 23062 and National Marine Fisheries Service, SEFSC Miami Laboratory, 75 Virginia Beach Drive, Miami, FL 33149. 

Aerial surveys were conducted in the lower Chesapeake Bay during 1986-1989 to estimate abundance and examine the distribution of the cownose ray, Rhinoptera bonasus,during its seasonal residence, May-October. Most of the survey effort was concentrated in the lower and mid-Bay regions. No clear pattern of east-west spatial distribution was detected; cownose rays appeared uniformly distributed across the Bay. North-south distribution varied and reflected the general seasonal migration pattern. Mean abundance increased stepwise monthly from June through September and declined dramatically in October with their emigration from the Bay. Abundance estimates from individual surveys varied. The greatest range of individual survey abundance estimates occurred in September (0 – 3.7 x 107 cownose rays) due to differences in school abundance between surveys and large school sizes. Monthly mean cownose ray abundance ranged from 0 in May and November to an estimated maximum of 8.6 x 106 individuals in September. Saturday, 6June, 10:00 A.M., Opera Rehearsal (session 6)

Parasitological evidence concerning the evolution of neotropical freshwater stingrays

Brooks, Daniel R.
Department of Zoology, University of Toronto, Toronto, Ontario M5S 1A1 Canada 

Members of the freshwater stingray family Potamotrygonidae occur throughout the major river systems of eastern South America that empty into the Atlantic Ocean. Ichthyologists have assumed that the ancestor of the potamotrygonids was an Atlantic marine ar euryhaline stingray that dispersed into freshwater, presumably during the marine ingression 3-5 millionyears ago. The helminth parasites that inhabit potamotrygonids suggest an alternative perspective on their origin. Phylogenetic and biogeographic analysis of the helminths inhabiting potamotrygonids suggest that the hosts are derived from an ancestral Pacific urolophid stingray that was trapped in freshwater by the uplifting of the Andes beginning perhaps as early as the early Cretaceous and ending by the mid-Miocene, changing the course of the Amazon River, which previously had flowed in to the Pacific Ocean.Saturday, 6 June, 11:30 A.M., Opera Rehearsal (session 6)

Application of isozyme characters in elasmobranch systematics

Buth, Donald G.1, Ingo H. Gaida1, Blaise J. Eitner1 and Gregory S. Whitt2
1Department of Biology, University of California (UCLA), Los Angeles, CA 90024-1606 2Department of Ecology, Ethology & Evolution, University of Illlinois, Urbana, IL 61801 

The “isozyme characters” of (1) number of genes controlling multilocus enzyme systems, (2) tissue specificity of gene expression, and (3) heteropolymer assenbly of multimeric enzymes have held great potential in systematics but have yet to find widespread application in any major vertebrate group. ‘Ihe elasmobranchs may be an exception, especially in regard to diverse patterns of tissue-specific expression of selected enzymes. Our preliminary investigation of enzyme expression in 10 tissues in 16 species (9 families) has elucidated examples of all three isozyme characters, but with tissue-specific expression differences being the most numerous. Application of these characters in elasmobranch systematics will be discussed. Friday, 5 June, 1:30 P.M., Opera Rehearsal (session 2)

Growth and demography of the Pacific angel shark (Squatina californica), based upon tag returns off California

Cailliet, Gregor M.1, Henry Mollet2, Greg Pittinger3, Dennis Bedford4 and Lisa J. Natanson1,5
1Moss Landing Marine Laboratories, Moss Landing, CA 95039 2Monterey Bay Aquarium, Monterey, CA 93940 3Downey High School, 11040 Brookshire Avenue, Downey, CA 90241 4California Department of Fish and Game, Long Beach, CA 90802 5GIROQ, OPEN, Pavillon Vachon, Cité Universitaire, Québec, Canada G1K 7P4 

For most elasmobranchs, valid estimates of age, growth, age-specific mortality and natality, demography, and population growth are unavailable. All ageing techniques on the Pacific angel shark (Squatina californica) have failed. Recently, however, we have accumulated data on 69 tag recaptures, which we have used to model the Von Bertalanffy Growth Function (VBGF) to predict growth of this commercially exploited shark species. Our subsequent demographic analysis yielded a net reproductive rate (R0) of 2.26, a generation time (G) of 14.5 yrs, and an estimate of the instantaneous population growth coefficient (r) of O.06 yr-1, using a natural mortality (M) only of 0.2. When reasonable estimates of fishing mortality (F) are included in the survivorship function, R0 and r are reduced considerably. Considering that Pacific angel sharks now first enter the fishery at the same size and age at which they first reproduce, it would be prudent to set a size limit several cm TL past this size to protect the California stock. Sunday, 7 June, 9:45 A.M., Opera Rehearsal (session 18)

Deep-sea fish assemblages of the Farallones: a comparison of beam trawl and camera sled samples

Cailliet, Gregor M.1, Waldo Wakefield2, Guillermo Moreno1, Allen Andrews1 and Kevin Rhodes1
1Moss Landing Marine Laboratories, Moss Landing, CA 95039 2School of Fisheries and Ocean Sciences, University of Alaska, Fairbanks, AK 

Camera sled and beam trawl data characterized a fish assemblage dominated by the families Macrouridae, Zoarcidae, Moridae, and Rajidae. Fishes both trawled and photographed were the macrourids Coryphaenoides leptolepis, C. armatus, and C. filifer; the zoarcids Bothrocara spp., Pachycara lepinium and Lycenchelys spp.; the morid Antimora microlepis; the rajid Bathyraja trachura, and the liparidid Careproctus ovigerum. One unidentified liparidid (Paraliparis sp.) and two unidentified Lycenchelyswere trawled but could not be identified from photographs. Observed only in photographs were Corypaenoides acrolepis, the liparidids Paraliparis rosaceus and Careproctus melanurus, bythitid Spectrunculus grandis, synodontid Bathysaurus mollis, and notocanthid Notacanthus chemnitzii. Thus, both techniques are important to characterize deep benthic fish assemblages. Trawls provide specimens for taxonomic and life history studies, but avoidance, escapement, and poor estimates of area sampled bias results. Observations of dispersion, habitat utilization, and interactions are impossible. Camera sleds provide zonation, dispersion, habitat, and behavioral observations, but positive identification of some species is impossible without specimens. Monday, 8 June, I:45 PAf., Choral Rehearsal (session 36)

Internal parasites of the goblin shark (Mitsukurina owstoni)

Caira, Janine N.
Department of Ecology & Evolutionary Biology, University of Connecticut, Storrs, CT 06269-3043 

Internal parasites are reported from the Goblin shark (Mitsukurina owstoni) for the first time. The individual examined was a 190 kg male collected off of Ulladulla, Australia and deposited at the Australian Museum in Sydney. Three species representing three tapeworm orders were recovered from the spiral valve. These included: one trypanorhynch; 25 specimens of a new species of tetraphyllidean; and 20 specimens of a new species ofLitobothrium (order Litobothridea). Without further material the trypanorhynch is unidentifiable. The tetraphyllidean is unusual in its possession of bothridia with extremely elongated peduncles. Four detached specimens retained tips of mucosal villi within their bothridia; the peduncles allow this species to stretch its scolex for attachment to up to four villi simultaneously. The generic placement of this tapewonn is problematic: although clearly a tetraphyllidean, it is inconsistent with the descriptions of all current genera in the order. The Litobothridea currently consists of only 5 species: one parasitizes the smalltooth sand tiger (Odontaspis ferox), the remaining 4 parasitize the bigeye thresher (Alopias superciliosus). The discovery of a litobothridean parasitizing the Goblin shark is consistent with the systematic placement of the Mitsukurinidae within Lamniformes, and preliminarily indicates close affinities between the Alopiidae, Odontaspidae and the Mitsukurinidae.Sunday, 7 June, 10:15 A.M., Opera Eehearsal (session 18)

Geographic distribution and new data on the reproductive biology of the marbled stingray, Dasyatis marmorata (Steindachner, 1892) (Pisces, Dasyatidae) from the Mediterranean lagoon of Bibans (southern Tunisia)

Capapé, Christian1 and Jeanne Zaouali2
1Laboratoire d’lchthyologie, Université Montpellier II, Sciences et Techniques du Languedoc, place E. Bataillon, case 102, 34095 Montpellier cedex 05, France 2Départment halieutique, Institut national agronomique de Tunisie, 43 avenue Charles Nicolle, 1002 Tunis-Belvéidère, Tunisie. 

In the Mediterranean, the marbled stingray, Dasyatis marmorata (Steindachner, 1892), has only been mentioned in the Gulf of Gabes (southern Tunisia) and in the eastern Atlantic from Mauritania coasts southward. In the Gulf of Gabes, the species is caught in the lagoon of Bibans, where a plentiful supply of nutrients allow the fattening of the juveniles. Once they have grown to adults, they leave the lagoon and return into the Gulf for reproduction. Using specimens caught in Tunisian waters, several aspects of the reproductive biology ofD. rnarmorata have been studied. The sizes at first sexual maturity for males and females are respectively about 30 cm and 32 cm disk-width The largest male and the largest female are about 38 cm and 40 cm disk-width. The mean disk-width of fully developed fetuses is 11.6 cm. Pregnancy lasts about four months and there are probably two litters per year at the minimum, since vitellogenesis continued after the end of gestation. Ovarian fecundity, five oocytes at the maximum, and uterine fecundity, four encapsulated eggs or three embryos, are small. Sex ratio is almost 1 for adults and embryos. Saturday, 6 June, 11:45 A.M., Opera Rehearsal (session 6)

Current status of freshwater elasmobranchs in Lake Nicaragua

Casco, Sergio Martinez 


Saturday, 6 June,  1:45 Pilf., Opera Rehearsal (session 12)

Genome size, protein content and cell size of Batoidea

Chen, Che-Tsung and Hui-Yun Chang
Graduate School of Fisheries, National Taiwan Ocean University, Keelung 202, Taiwan R.O.C. 

The cellular DNA contents, protein contents and cell volumes of 23 Batoidea have been studied by flow cytometry. The DNA content ranged from 3.0 pg/cell (Dasyatis sp., freshwater) to 24.1 pg/cell (Crassinarke dornitor). The DNA content of Dasyatidae seems to decrease f’rom marine to freshwater. From our observation, the evolutionary tree of Batoidea inferred by the genome-size evolution model conforms to the tree proposed by Compagno (1977).

No significant correlation between DNA content and cell volume was found in this study. The linear correlation between protein content and cell volume is significant (r=0.76, n=25, p<<0.01), with Yij= 0.55 + 0.69 Xij; (Yij = protein content index, Xij = cell volume index, i = species, j = individual; erythrocyte of chicken acts as the standard.). Cell volume against protein/DNA ratio shows that it can differentiate them easily. Friday, 5 June, 2:45 P.M., Opera Rehearsal (session 2)

The exploitation and conservation of freshwater elasmobranchs – status of stocks and prospects for the future

Compagno, Leonard J. V.1 and Sid F. Cook2
1Shark Research Center, South African Museum, Box 61, Cape Town 8000, South Africa, 2Argus-Mariner Consulting Scientists, 6427 SE 94th Avenue, Portland, OR 97266-5255 USA 

A number of sharks, rays and sawfishes are represented in lacustrine and limnological environments of the world, most notably those of Central and South America, Africa, and the Indian subcontinent. While much has bem learned about distribution, biology and ecology of these species in recent years, little is known of the patterns of exploitation, use and health of stocks in these environments. As human populations grow out of control in areas contiguous to the aquatic habitats occupied by the f’reshwater representatives of the elasmobranchii, considerable concern is arising with regard to the future of these populations. In extreme cases, such as those of the Ganges river shark (Glyphis gangeticus), inferential indications are that populations may be very near to the point of physical extinction. This paper will review the distributions of freshwater elasmobranchs, examine human impacts from direct exploitation and development that degrades habitat, and set down recommendations for future research and management protocols that will be required if these populations are to be stabilized and rehabilitated. Saturday, 6 June, 2:00 P.M., Opera Rehearsal (session 12)

Relationships of South American potamotrygonid stingrays

Dingerkus, Guido Ichthyologie Générale et Appliquée
Muséum National d’Histoire Naturelle, 43, rue Cuvier, 75231 Paris cedex 05, (B.S. – Antenne ORSTOM), France 


Saturday, 6 June, 11:M A.M., Opera Rehearsal (session 6)

Molecular systematics of elasmobranchs

Dunn, Katherine A. and John F. Morrissey
Department of Biology, Hofstra University, Hempstead, NY 1l550 

Investigations of elasmobranch anatomy have led to the development of several controversial phylogenetic hypotheses. Our objective is to deduce the phylogeny of elasmobranchs using molecular data. We have extracted DNA from 15 species representing a majority of elasmobranch lineages. Then we PCR amplified and sequenced a portion of the 12S mitochondrial gene from each extract. The resulting sequences were aligned using a holocephalan as an outgroup and analyzed using PAUP. These analyses resulted in a single most parsimonious tree with relatively high consistency and retention indices. The topology of this tree supports the monophyly of elasmobranchs, making traditional views of squalomorphs and galeomorphs paraphyletic. This work was funded in part by NIH grant #GMS 42563 to DEP and CJP. Friday,5 June, 4:00 P.M., Opera Rehearsal (session 2)

Phylogenetic relationships within the genus Alopias determined by allozymes and mitochondrial DNA analyzed with restriction enzymes

Eitner, Blaise J.
Department of Biology, University of California, Los Angeles, CA 90024-1606 

The genus Alopias (thresher sharks) consists of three species whose phylogenetic relationships with each other are uncertain. Phylogenetic relationships within the genusAlopias were determined using two different databases: allozymes, and mitochondrial DNA analyzed with restriction enzymes. Phylogenetic analyses were performed using PAUP with shortfin mako sharks (Isurus oxyrinchus) serving as an outgroup. The abilities of these twodatabases to resolve phylogenetic relationships within the genus Alopias were compared and discussed. Friday, 5 June, 2:15 P.M., Opera Rehearsal (session 2)

Evolutionary aspects of gene expression in the Pacific angel shark, Squatina californica

Gaida, Ingo H.
Department of Biology, UCLA, Los Angeles, CA 90024-1606 

This study employed horizontal starch gel electrophoresis to examine gene expression in the Pacific angel shark, Squatina californica. Forty enzyme systems encoded by 72 presumptive gene loci were scored for tissue expression in each of 12 tissues. The patterns of expression found were then compared to what is known about other vertebrate species in order to clarify aspects of enzyme evolution among the vertebrates. This study is important because many studies of the evolution of particular enzyme systems have not bothered to include elasmobranchs, and those that have have often been limited in scope by too few tissues or buffers. Examples of new findings described by this study regarding the evolution of enzyme systems in the vertebrates include, 1) the presence of a third CK locus, presumably Ck-B, in sharks, 2) the discovery of a new FBP locus, designated Fbp-C, and 3) the presence of only one sMDH, sMdh- A, as opposed to two sMDHs in other fishes. Studies such as this one which examine a large number of tissues for patterns of enzyme expression may also prove useful for uncovering isozyme characters for use in phylogenetic analyses. Friday, 5 June, 1:15 P.M., Opera Rehearsal (session 2)

Absence of a countercurrent system in the freshwater elasmobranch(Potamotrygon humerosa)

Grabowski, Gregory M.1, Enrico Reale2 and Eric R. Lacy1
Department of Anatomy and Cell Biology, Medical University of South Carolina, Charleston, SC 29425-2204 Laboratory of Cell Biology and Electron Microscopy, Hannover Medical School, W-2000, Hannover, Germany 

The near isotonicity of marine elasmobranch body fluids with surrounding seawater is attributed to the reabsorption of filtered urea, facilitated by a renal countercurrent system. Stenohaline freshwater stingrays (e.g., Potamotrygon humerosa) do not use urea as an osmolyte, however, the kidney structure is virtually unknown. The present study showed that, during the evolution of freshwater stingrays the basic marine tubule segmental sequencewas conserved, but its configuration has changed. The complex zone of the freshwater kidney consists of all the tubule segments of the countercurrent system in the marine kidney, however they are no longer segregated by a peritubular sheath. The simple zone in the freshwater kidney appears to be a modification of the sinus zone in the marine kidney, where one loop became incorporated into the complex zone and the remaining loop consists solely of the third segment of the proximal tubule. A juxtaglomerular apparatus similar to that in mammals and marine elasmobranchs was also noted, suggesting a mechanism to regulate glomerular-tubular balance and vascular pressure. The lack of a countercurrent system in freshwater stingrays supports the necessity of a countercurrent system for urea reabsorption in marine elasmobranchs. Saturday, 6 June, 10:45 AM., Opera Rehearsal (session 6)

Paraselachii (Lund, 1977), white marrow, and the question of holocephalan – selachian relationships

Grogan, Eileen D.1 and Richard Lund2
1Virginia Institute of Marine Sciences, Gloucester Point, VA 23062 2Biology Department, Adelphi University, Garden City, NY 11530 

The extant Holocephali and Elasmobranchii are currently considered to be sister groups, principally united by autapomorphous prismatic calcified cartilage endoskeletal mineralization. Two schools of thought have been advanced as to the relatedness of the subclasses: polyphyletic, with the Holocephali having arisen &om ptyctodont arthrodires; or monophyletically derived &om a basal gnathostome group, and subsequently divergent. Our search for the basal complex of the class, and its character states, takes a new perspective to examine previous fossil data as well as significant new material. Extant Chondrichthyes exhibit distinctly different plans of cranial anatomy, certain features of which appear correlated with the development of “white marrow” in chimaeroids but not in selachians. Fossil Chondrichthyes from the Bear Gulch Limestone (Upper Mississippian) were examined for these features and the soft anatomical evidence accompanying them. Paraselachii were found to display features of both holocephalans and selachians. A hypothesis is proposed for the development of chondrichthyan white maxrow. Factors of cranial anatomy and vascularization are included in a phylogenetic scheme explaining the derivation of selachian and chimaeroid plans from a paraselachian condition. Sunday, 7 June, 11:00 A.M., Opera Rehearsal (session 18)

The ecomorphology of vision in sharks

Gruber, Samuel H.1 and Robert E. Hueter2
1Bimini Biological Field Station, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL33149 2Center for Shark Research, Mote Marine Laboratoxy, Sarasota, FL 34236 

The visual capabilities of sharks have received limited attention in past reviews of sensory ecomorphology, perhaps due to our limited understanding of species-specific ecology and behavior, combined with the erroneous generalization of sharks as being all-rod vertebrates. As more has been learned about morphological and physiological features of the visual systems of these fishes, certain adaptations appear to be more related to species habitat, lifestyle, and behavior than to phylogenetic constraints. Structural aspects of the optical systems, retinas, and visual pathways in the CNS of sharks, when examined against the background of ecological demands on the whole organism, demonstrate that “quality” of vision in sharks is often an expression of functional design correlated with the environment – the essence of ecomorphology. By taking this approach in exploring a shark’s sensory niche, which is the total perceived environment of the animal in its natural habitat (Hueter, 1991), quality of vision in this group of vertebrates is being redefined. Particularly useful information in this regard is available for the lemon shark (Negaprion brevirostris), a species that has become a test case for studies on the ecomorphology of shark vision.Sunday, 7 June, 9:00 A.M., Burrill 124 (session 22)

Population genetics of the sandbar shark in U.S. coastal waters

Heist, Edward J.
Virginia Institute of Marine Science, Gloucester Point, VA 23062

The sandbar shark (Carcharhinus plumbeus) is the most common species of large coastal shark along the Mid-Atlantic coast of the United States, and is probably the most important species in the U.S. shark longline fishery. The major nursery area for the species is the Mid-Atlantic Bight, however it has been suggested that an additional nursery area occurs in the Gulf of Mexico. Mitochondrial DNA (mtDNA) restriction fragment length polymorphism analysis and allozyme electrophoresis were used to test the hypothesis of no genetic structure between juvenile sandbar sharks from the Mid-Atlantic Bight and adults found in the Gulf of Mexico. Allozyme analysis revealed a low degree of polymorphism and heterozygosity consistent with data previously reported for other species of sharks, including congeners. Mitochondrial DNA analysis, which typically exhibits higher heterogeneity revealed an extremely low nucleotide diversity. The low genetic diversity indicates that large sample sizes, either in the number of polymorphic allozyme loci surveyed or in the portion of the mtDNA molecule surveyed, are necessary to test hypotheses of stock structure in this species. Comparisons are made between the nucleotide diversity of the sandbar shark and that of several other species. Friday, 5 June, 2:00 P.M., Opera Rehearsal (session 2)

Pohnpei Island, Kingdom of rays

Homma, Kimiya1, Yosihiro Takeda2 and Hajime Ishihara2
1Kyowa Concrete Industry Co. Ltd., Yuraku Bldg., 1 Minami-ichijo-Nishi, Sapporo, 060, Japan, 2Suido-sha Co. Ltd., 1-54-302 Yurigaoka, Aso-ku, Kawasaki 215, Japan

Pohnpei Island, Federated States of Micronesia, is located in the tropical Pacific, 6° 55’N; 158°15’E. Only little has been known concerning the ray fauna of the island. The survey for rays has been conducted four times through May, 1991 to March, 1992 aad rays belonging to two families, four genera five species were collected, i.e., pairs of Dasyatis sephen, Himantura granulata, H. fai and Urogymnus africanus and a female Aetobatis narinari. Also Manta birostris was observed in the water outide of the coral reefs.

Rays are most abundant in number of species and individuals in the water near the Joy island. A female of U. africanas was pregnant in September and that of D. sephen in March. No other big fishes were present in the lagoon of the island. Therefore, the island seems to be a kingdom of rays. Sunday, 7 June, 11:30 A.M., Opera Rehearsal (session 18)

Temperature and salinity effects on the relative abundance of elasmobranchs in Tomales Bay, California

Hopkins, Todd E.
Wildlife and Fisheries Biology, University of California Davis, CA 95616I have been studying the effects of temperature and salinity on the relative abundance of elasmobranchs in Tomales Bay, CA, since August 1990. Monthly longline sets have shown that the abundance of bat rays, Myliobatis californica, leopard sharks, Triakis sonifasciata, and brown smoothhounds, Mustelus henlei, is highly seasonaL All species out- migrated during 1990 and 1991 in late November as the bay temperature neared 1PC and returned by March 1991 after temperatures rose above 1PC. No elasmobranchs have been captured in the bay between late-November and mid- February. Five rays with implanted sonic transmitters were tracked for one year but were never detected in the bay during winter months. In nearby San Francisco Bay, aad Elkhorn Slough elasmobranchs are captured year round although temperatures rarely drap below 1PC. Bat rays dominate the Tomales Bay elasmobranch fauna by biomass and numbers. About 500 bat rays have been tagged, with only two returns, after 4 and 20 months, both in Tomales Bay. Saturday, 6June, 4:00 P.M.., Opera Rehearsal (session 13)

Tagging small sharks in the estuarine nursery grounds of Tampa Bay and Charlotte Harbor, Florida

Hueter, Robert E., Sandy J. Zeiner and Randall S. DesRochers
Center for Shark Research, Mote Marine Laboratory, Sarasota, FL 34236

The shallow, inshore bays and estuaries of the Gulf coast of Florida are generally thought to serve as nursery grounds for various species of coastal sharks. These reputed nurseries are typically areas of high productivity where juvenile sharks find abundant prey and where they are less exposed to predation by larger sharks. Because these inshore areas support large commercial and recreational fisheries, fishing mortality of juvenile sharks in the nursery grounds may be significant, primarily as incidental bycatch. This project addresses the importance of two Florida Gulf estuaries, Tampa Bay and Charlotte Harbor, as nursery grounds for sharks, using both fishery-dependent and fishery-independent data. Captured juvenile sharks in good condition are tagged with a nylon-head, multi-recapture dart tag (Hallprint) using a specially designed tagging gun (Fielding Laurel) and are injected with oxytetracycline before release. Using catch and tag-return data, we are attempting to assess bycatch mortality of the juveniles, residence time in the nursery grounds, migratory behavior into and out of the estuaries, and age and growth of these young sharks. Sunday, 7 June, 11:15 A.M., Opera Rehearsal (session 18)

A strange potamotrygonid ray from the Amazon river system

Ishihara, Hajime1 and Toru Taniuchi2

1Suido-sha Co. Ltd., 1-5-4-302 Yurigaoka, Aso-ku, Kawasaki 215, Japan, 2Department of Fisheries, Faculty of Agriculture, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113 Japan

A strange ray was collected from the Amazon river system. Since the ray has an anteriorly directed prepelvic process on the pelvic fin, it should be placed in the family Potamotrygonidae. But, the ray does differ from the extant genera of the family(Paratrygon, Plesiotrygon and Potamotrygon) in the combination of the following characters: Disc nearly oval with roundish anterior margin; distance from mouth to anterior margin of disc long, about 2.8 times in disc width; tail uniformly slender without caudal sting, whose length about the same length with disc width; no finfold nor no rows of spines on tail; lateral areas of disc smooth without prickes; eyes small; spiracles without knob-shaped process; pelvic fins nearly opposed to posterior margin of disc. Saturday, 6 June, 11:15 A.M., Opera Rehearsal (session 6)

The reproductive life history of the Atlantic stingray in the St. Johns River, Florida

Johnson, Michael R.,
Department of Biology, University of Central Florida, Orlando, FL 32816

The Atlantic stingray (Dasyatis sabina) is broadly euryhaline and occurs in marine, brackish and freshwater habitats. A resident population exists in the freshwater portion of the St. Johns River in Florida, and perhaps has been isolated there since the separation of the River basin from the Atlantic coast during late Pleistocene. In order to determine any divergence of life history traits during this prolonged period of freshwater evolution, several life history components of the St. Johns population were examined and compared with marine populations. This report concerns only female reproductive characteristics. Between November 1990 and January 1992, 116 mature females were collected &om Lake Monroe at Sanford, Florida. Vitellogenesis began in the winter months and eggs were ovulated in mid-Aprilbbsp;at approximately 13 mm diameter. During gestation, a second clutch of enlarged ova were observed in the ovaries of all mature females from mid-June to mid-July. There was no evidence of ovulation or encapsulation of these ova, which apparently were reabsorbed as corpora lutea atresia. Partuition occurred late July – early August. Estimated neonate size was 100 mm mean disk width and mean hood size was 2.3. These and other results indicate only minor differences in reproductive life history between freshwater and marine populations of D. sabina in Florida Saturday, 6 June, 10:15 A.M., Opera Rehearsal (session 6)

Spatio-temporal patterns of white shark (Carcharodon carcharias) predation at the South Farallon Islands, CaliforniaKlimley, A. Peter1,2, Scot D. Anderson1, Peter Pyle1 and R. Philip Henderson1

1Point Reyes Bird Observatory, 4990 Shoreline Hwy., Stinson Beach, CA 94970, 2Bodega Marine Laboratory, University of California-Davis, P.O. Box 247, Bodega Bay, CA 94923

Spatial and temporal records of 146 predatory attacks by white sharks (Carcharodon carcharias) on four species of pinnipeds, one bird, and one human at the South Farallon Islands, Central California, from late August to early December during 1986-1989 will be presented. During each 3.5-month period, attacks were: 1) unevenly distributed in bouts separated by hiatuses in predation, 2) paired temporally within the same day, 3) at similar times and locations on consecutive days, and 4) during all daylight hours. Predation was observed most often within 450 m of shore with a decrease in atiack frequency with increasing depth. Within this high-risk zone, predation was concentrated near coastal departure and entry points of pinnipeds, and the predatory attack positions formed linear patterns leading away from the island. Consecutive predatory attacks were often near each other, yet at times alternated between localities on either side of the island. Sunday, 7 June, 11:45 A.M., Opera Rehearsal fsession 18)


Movements and distribution of hammerhead shark pups on their natal grounds

Lowe, Christopher G.1, Kim N. Holland2, Bradley M. Wetherbee1 and John D. Peterson1

1Department of Zoology, University of Hawaii at Manoa, Honolulu, HI 96822, 2Hawaii Institute of Marine Biology, University at Manoa, Kaneohe, HI 96744

Ultrasonic telemetry was used to detennine the movements and distribution of juvenile hammerhead sharks (Sphyrna lewini) on their natal grounds in Kaneohe Bay, Oahu, Hawaii. Transmitters were force-fed to six pups which were tracked for periods of up to 12 days. All animals showed a high fidelity to a shared daytime core area to which they repeatedly returned after exhibiting wider ranging nocturnal movements. During daytime, the shark pups formed a loose school which moved about within the core area, hovering about 1.5 m off the bay floor. TIhis daytime refuging behavior may serve an anti-predator function. Nighttime movements covered the bay floor and bases of patch and fringing reefs and probably represented foraging excursions. Occasional forays away from the core area also occurred during daytime. The small size of the total activity spaces may indicate a healthy forage base for the sharks. Nocturnal swimming speeds were greater than diurnal swimming speeds. Saturday, 6 June, 3:30 P.M., Opera Rehearsal (session 13)

Autodiastylic suspensoriums in Paleozoic Chondrichthyes

Lund, Richard1 and Eileen D. Grogan2

1Biology Department, Adelphi University, Garden City, NY 11530, 2Virginia Institute of Marine Sciences, Gloucester Point, VA 23062

The modern members of the chondrichthyan subclasses Elasmobranchii and Holocephali differ fundamentally in type of jaw suspensorium and neurocranial structure. The elasmobranchs have either hyostylic or amphistyhc suspensoriums, while the Chimaeriformes have holostyly, characterized by complete fusion of palatoquadrate to neurocranium. Hyostyly is considered the plesiomorphous condition for the gnathostomes, including the basal taxa of the Chondrichthyes. Autodiastyly, in which the palatoquadrate is suspended from the neurocranium without hyomandibular involvement, was coined by De Beer and Moy-Thomas for the intermediate condition between the two subclasses, but not demonstrated at that time. Autodiastyly can now be demonstrated in several Carboniferous Paraselachii, along with other critical cranial and postcranial characters differentiating them from the Elasmobranchii. The Paraselachii can be considered to be the sister-group of the Holocephali, and the Paraselachii plus Holocephali (Holocephalimorpha) the sister group of the Elasmobranchii. Sunday, 7 June, 10:45 A.M., Opera Rehearsal (session 18)

Inferring evolutionary history of sharks using mitochondrial DNA sequences

Martin, Andrew P.1 and Stephen R. Palumbi2

1Smithsonian Tropical Research Institute, NAOS Marine Laboratory, Unit 0948, APO AA3402-0948, 2Kewalo Marine Lab, Pacific Biomedical Research Center, Department of Zoology, University of Hawaii, 41 Ahui Street, Honolulu, HI 96813

Using PCR, mitochondrial DNA sequences were detennined for 31 species of sharks from two orders: the Lamniformes and Carcharhiniformes. The topology of relationships based on various methods of phylogenetic analysis of the DNA data for 7 species of lamniform sharks representing 3 distinct families (Alopiidae, Lamnidae, Odontaspidae) conflicts withphylogenetic hypotheses based on morphological characters. In the morphological tree published by Compagno, Alopiidae is the sister group to the Lamnidae. By contrast, the DNA data suggest that alopiids cluster more closely with odontaspids. Interestingly, both lamnid and alopiid sharks have adaptations for endothermy; thus the DNA data support the hypothesis that endothermy evolved twice in the lamniform sharks.

Phylogenetic analysis of 24 species of carcharhiniform sharks showed a completely different pattern of diversification than inferred for the lamnoid sharks. Instead of a bifurcating topology, the DNA data indicate that most of the extant lineages of carcharhiniform sharks originated in a brief period of time, probably associated with events of the late Eocene-early Oligocene. Our inability to find structure in topologies for carcharhiniform sharks does not allow us to support or refute previous phylogenetic hypotheses. The data suggest that much of the morphological evolution in this group occurred in a very brief period of time and stasis has reigned in the wake of diversification. Friday, 5 June, 3:00 P.M., Opera Rehearsal (session 2)

Phylogenetic assessment of batoid fishes (Chondrichthyes, Batoidea)

McEachran, John D.
Department of Wildlife Fisheries Sciences, Texas AA,M University, College Station, TX 77843

The batoids (electric rays, sawfishes, guitarfishes, skates and stingrays) are the largest putative monophyletic group of the chondrichthyans. Between 477 and 486 of the 859 to 868 estimated species of chondrichthyans are batoids. The five subgroups of batoids are clearly distinct from one another and each is generally considered to be monophyletic, although no synapomorphies are known for the guitarfishes. Lack of consensus as to the phylogenetic relationships among the five subgroups is due less to the paucity of anatomical information on the taxa than to the great distinctiveness of each of the subgroups. The subgroups share common batoid synapomorphies but share little in the way of obvious derived character states with other subgroups. Lack of synapomorphies among subsets of the five subgroups hinders an outgroup approach to elucidation of the phylogenetic interrelationships. Five character complexes (rostral cartilages, neurocrania, ventral gill arch skeletons, shoulder girdles and pelvic girdles) are investigated to elucidate the interrelationships among the five subgroups of batoids. Saturday, 6 June, 9:15 A.M., Opera Rehearsal (session 6)

Rostral oral tooth development in sawfish (Pristis perotteti)

Miller, William A.
School of Dental Medicine, State University of New York at Buffalo, Buffalo, NY 14214

The growth of the rostrum and rostral teeth of sawfish (Pristis perotteti, Muller and Henle, 1841) was studied (1) to describe the embryology of the initiation of the rostrum and its associated teeth, (2) determine if there is an order and sequence of rostral tooth development and (3) establish whether the rostral teeth are like dermal teeth (denticles) or oral teeth (tooth plates).

Sixteen embryos (265-165 mm body length) and 10 embryo rostra (285-785 mm estimated body length), fixed in Bouin or formalin, have been examined radiographically and histologically. The rostrum developed as an undifferentiated mesenchymal bud by 35mm bl and the central cartilage bars appeared by 74 mm bl. Lateral, paracentral canals developed by 133 mm bl. A central canal had started to develop by resorption by 80 mm rostral length (300+ mm estimated body length) and was well developed by 140 mm rostral length. Rostral teeth appeared initially as shallow epithelial invaginaions on the lateral aspect of the rostrum around 110 mm. Definite cap stages were visible at 160 mm. At this stage dermal denticles on the rostrum were still not visible. The oral teeth developed from a dental lamina which was clearly visible by 110 mm bl, initially as flat plates of dentin, situated buccally below the oral ectoderm by 160 mm bl. A transverse fiber system was seen in some regions of the rostra. Saturday, 6 June, 1:15 P.M., Opera Rehearsal (session 12)

Sperm storage in male elasmobranchs: a description and survey

Pratt, Harold L., Jr.1 and S. Tanaka2

1NOAA-NMFS, 28 Tarzwell Dr., Narragansett, RI 02882 USA, 2Tokai University, 3-20-1 Orido, Shimizu, Shizuoka, 424 Japan

Sperm packets are stored between the septa and in the lumen of the terminal ampulla of the epididymis and are the final product of the mature male elasmobranch reproductive tract. Their presence is a more reliable indicator of sexual maturity than clasper condition. The two basic types of spermatozoa packets, spermatophores and spermozeugmata, that are commonly found in different species of large squaliform sharks were investigated using lightand scanning electron microscopy. Spermatophores; packets (1000 pm diameter and larger) of randomly accreted clumps of sperm embedded in and surrounded by an eosinophilic matrix, were found in: Alopias superciliosus, Carcharias taurus,Carcharodon carcharias, Isurus oxyrinchus, and Lamna nasus. Spermozeugmata, 250 – 500 pm diameter packets of highly organized sperm clumps without an envelopingcapsule, were characteristically found in: Carcharhinus falciformis, C. limbatus, C.obscurus, C. plumbeus, C. porosus, Prionace glauca, Rhizoprionodon terraenovae,and Sphyrna lewini. Two types of spermozeugmata are here described, single layer spheres and larger multi-layer, compound structures. Sunday, 7 June, 9:15 A.M., Opera Rehearsal (session 18)

Dissection of a gravid shortfin mako, Isurus oxyrinchus from the North Atlantic

Pratt, Harold L., Jr., J. G. Casey, N. E. Kohler and C. E. Stillwell
NOAA-NMFS, 28 Tarzwell I3r., Narragansett, RI 02882

On January 15, 1992, a commercial swordfish longliner caught a pregnant shortfin mako,Isurus oxyrinchus in the Westexn North Atlantic which he shipped to us whole at our request. The robust female was 318 cm in total length, and weighed 313 kg. Only four pregnant makos have been reported from the Atlantic and this is the first one to be closely examined. Fourteen embryos were observed with one lost during transport for a total of fifteen. Six oophagus embryos with huge yolk stomachs occupied the left uterus; all male but one. The right uterus contained eight embryos, including four males. Mean embryo total length was 52 cm with a standard deviation of 1.31. There were no uterine compartments and no egg capsules remaining in the uterus. The ovary had ceased ova production and resembled the ovary of a non-gravid mature female. Embryos had calcified needle-like teeth directed inward on the distal surface of each jaw. Sunday, 7 June, 9:30 A.M., Opera Rehearsal (session 18)

Diet and gastric evacuation of gray smoothhound sharks, Mustelus californicus,from Elkhorn Slough National Estuarine Research Reserve, Monterey Bay, California

SanFilippo, Richard
P.O. Box 166, Moss Landing, CA 95039

Stomach contents of 68 live gray smoothhound sharks were collected from the Elkhorn Slough National Estuarine Research Reserve using a stomach eversion technique. The contributions of the various prey items were assessed by numerical importance, frequency of occurrence, volumetric and gravimetric importance and a combined index of relative importance. Crabs were the dominant prey group with the yellow shore crab,Hemigrapsus oregonensis, being the dominant species. Gastric evacuation was studied on four gray smoothhounds in a 4000 L tank maintained outdoors at a temperature of 15 ° C. Results were obtained by stomach eversions at prescribed times following a meal of shore crabs. Gastric evacuation proceeds in a slow but exponential manner and the gut is emptied in about 95 hours. The instantaneous rate of gastric evacuation was -0.04. Caloric content of the whole prey, the prey at various stages of digestion, and the fecal material were quantified using bomb calorimetry techniques. The change in the caloric value (expressed as calories per gram) of the meal with time suggests that lower energy components (i.e. exoskeleton) are digested first, within the stomach cavity, leaving the higher energy components (i.e muscle) to be passed on to the intestine where complete assimilation takes place. The fecal material contained no measurable caloric value. This suggests that gray smoothhound digestion is an orderly and efficient process resulting in maximum utilization of the prey it consumes. Saturday, 6 June, 3:45 P.M., Opera Rehearsal (session 13)

Food consumption and growth of sub-adult and adult lemon sharks, Negaprion brevirostris, maintained in a controlled environment

Schmid, Thomas H. and Frank L. Murru
Aquarium Department, Sea World of Florida, Orlando, FL 32821

We investigated aspects of the bioenergetics of three lemon sharks, two adults and one juvenile, maintained in a 2.5 million liter aquarium. Water temperature remained at a constant 24 ° C during the four year study period. The adult male shark consumed the most food, 8.4% body weight (BW) per week. The juvenile female consumed more food proportionately than the adult female, 6.9% versus 4.5% (BW) per week. Fork length increases for both adults averaged 0.8 cm per month (9 cm/year). The juvenile female grew at a rate of 1.3 cm per month (16 cm/year). Weight increases ranged from 2.1 to 3.1 kg per month (25 to 37 kg/year) for the adults, and 1.1 kg per month for the juvenile (13.4 kg/year). These results are compared with findings fxom our previous studies using similar sized sandbar sharks, Carcharhinus plumbeus, to elucidate differences between energy utilization of tropical water versus temperate water carcharhinid sharks. Sunday, 7 June, 10:00 A.M., Opera Rehearsal (session 18)

Elasmobranchs frequenting fresh and low saline waters of North Carolina 1971-1991

Schwartz, Frank J.
Institute of Marine Sciences, University of North Carolina, Morehead City, NC 28557

Twenty-two species and 232 occurrences of elasmobranchs have been verified from 1790 salinity documented collections in low saline or freshwaters of North Carolina 1971-1991. Nine (10.5%) of the total 86 species elasmobranch fauna have actually been recorded from freshwater. This frequency is lower than that for the elasmobranch faunas of Chesapeake and Tampa Bays. A number of reasons are given to account for the low occurrence of North Carolina’s sharks, skates, and rays in North Carolina’s freshwater or low saline coastal sounds and river systems. Saturday, 6 June, 9:45 A.M., Opera Rehearsal (session 6)

A molecular sequence investigation of the higher level diversity of elasmobranchs

Stock, David W. and Gregory S. Whitt
Department of Ecology, Ethology and Evolution, University of Illinois, Urbana, IL 61801

The 18S ribosomal RNA sequences of twelve species representing most of the major lineages of elasmobranchs were determined by a combination of direct RNA sequencing and sequencing of PCR-amplified DNA. These species include hexanchiforms(Chlamydoselachus and Heptranchias), a squatiniform (Squatina), a heterodontiform(Heterodontus), an orectolobiform (Chiloscyllium), a lamniform (Odontaspis),carcharhiniforms (Negaprion and Sphyrna), a torpedinifonn (Narcine), a rajoid (Raja), a rhinobatoid (Rhinobatos), and a myliobatiform (Dasyatis). Phylogenetic comparisons of the scquences (as well as those of the squaliforms Squalus and Echinorhinus – Bernardi, Sordino and Powers, in press) were performed using the sequence of the chimaeraHydrolagus as an outgroup. The most surprising finding was a difference in rates of evolution of two orders of magnitude between the rapidly evolving carcharhiniforms and the slowly evolving hexanchiforms. Although such rate differences make phylogenetic interpretations difficult, the data provide tentative support for a sister group relationship of batoids to all other elasmobranchs and for a grouping of Squatina with hexanchiforms and squaliforms. In addition, strong support exists for a sister group relationship of myliobatiforms to rhinobatoids (to the exclusion of rajoids). Galeomorph monophyly was not supported, but this result may be due to unequal rates of evolution among the included orders. Friday, 5 June, 3:30 P.M., Opera Rehearsal (session 2)

Body shape variability in the order Squaliformes

Tabit, Christopher
Virginia Institute Marine Sciences, Fisheries Department, Gloucester Point, VA 23062

The objective of this research was to gain insight into the hydrodynamic limitations and swimming capabilities associated with the variety of body shapes within Squaliformes. Nine species of squaloid sharks; Centrophorus granulosus, Centroscymnus coelolepis, Dalatias licha, Deania calcea, Echinorhinus cookei, Etmopterus princeps, Isistius brasiliensis, Oxynotus centrina and Squalus acanthias, were selected for this study as representing nine separate body shape morphologies. Morphometric variables, including standard length (SL), girth, surface area (SA), fineness ratio, fin placement and aspect ratio were measured for 95 specimens.

Preliminary regression analysis suggests that although the relationship between SA and SL is conservative within a species (high r2 values), the best intraspecific model for predicting SA includes the maximum girth; SA = 0.7 (girth * SL). Analysis of variance for fin aspect ratios yielded two separate groups on the bases of 95 percent confidence intervals of the means calculated from the pooled standard deviations. No interspecific differences based on sex were observed. Confidence intervals for the mean fineness ratio based on pooled standard deviations suggest that three morphologic categories can be defined. Theoretical hydrodynamic implications of the different morphologic shapes will be hypothesized.Saturday, 6 June, 3:15 P.M., Opera Rehearsal (session 13)

Observations on the embxyonic development and incubation period of the brown catshark, Apristurus brunneus

Van Dykhuizen, Gilbert
Monterey Bay Aquarium, 886 Cannery Row, Monterey, CA 93940

Egg cases were collected from the Monterey Submarine Canyon and transported to a deep sea holding facility at the Monterey Bay Aquarium. Yolk diameter, embryo length, gill and eye development were observed on a monthly or bimonthly schedule. Incubation perind is approximately 24 months and hatchlings survived 30-50 days with no feeding observed despite attempts to feed them. Sunday, 7 June, 9:00 A.M., Opera Rehearsal (session 18)

The biology of freshwater elasmobranchs: a historical perspective

Zorzi, George D.
Department of Ichthyology, California Academy of Sciences, Golden Gate Park, San Francisco, CA 94118

A review of the literature pertaining to freshwater elasmobranchs, from the earliest known records to the early 1960’s, reveals the shortcomings, if not outright errors, in our knowledge about the taxonomy, distribution and origins of most of these fishes. It sets the stage for the numerous and exciting advances made during the past thirty years. Saturday,6 June, 8:45 A.M., Opera Rehearsal (session 6)