1989 AES Annual Meeting Abstracts

DISTRIBUTION AND HABITAT OF CHAIN DOGFISH, SCYLIORHINUS RETIFER, IN THE MID-ATLANTIC BIGHT

In the Mid-Atlantic Bight of the US.A the chain dogfish, Scyliorhinus retifer, is distributed at the edge of continental shelf based on the trawl capture of 381 individuals during the period from 1963-1988. Submersible observations in the vicinity of Hudson and Baltimore submarine canyons, indicate this species prefers structured habitats. Small pups to adults have been consistently observed resting in association with rocks, boulders and man made artifacts such as piles of trawl wire, cable etc. This type of association may explain, in part, their relative infrequency in trawl samples. On two occasions, field collections of relatively large numbers of egg cases and developing embryos help to confirm earlier. laboratory observations (Castro et al. 1988) of egg laying in vertically structured habitats. Similarly, the range in size of the embryos (19-83 mm) from one collection imply that egg laying occurs over a prolonged period.

BLOOD VALUES FROM TRANSPORTED SHARKS IN WHICH AN INFUSION OF A BALANCED SALT SOLUTION WAS UTILIZED

The purpose of this study was to determine if an Elasmobranch Balanced Salt Solution (EMBSS) administered as a drip would enhance the survivability of sandbar sharks,Carcharhinus plumbeus, during an extended transport (8 hrs.). Wild caught mature sandbar sharks that had an acclimation period of at least 24 hrs. after capture were used in the study. A simulated transport of 8 hrs. was conducted in a stationary transport vehicle. The sharks were anesthetized, placed in shark boxes, and monitored for 8 hrs. Two experimental sharks were used in which the EMBSS was introduced into the abdominal cavity. Two controls were also used and they received no fluid replacement. Blood was drawn at the start of the experiment, at the termination, and 24 hrs. later. The results of the major osmotic components of shark serum as well as the osmolilty of shark serum between the two groups demonstrated no difference.

THE COLLECTION AND TRANSPORT OF SHARKS AT THE NATIONAL AQUARIUM IN BALTIMORE

This video presentation will describe collection and transport techniques for sand tigersOdontaspis taurus, and sandbar sharks, Carcharhinus plumbeus, at the National Aquarium in Baltimore.

A THIRD SPECIMEN OF MEGAMOUTH SHARK, MEGACHASMA PELAGIOS, FROM WESTERN AUSTRALIA.

The third known specimen of M. pelagios washed ashore near the entrance of Mandurah Inlet (32°31’S and 115°43’E) about 50 km S of Perth, Western Australia on 18 August 1988. The male measured 5.15 meters total length, had a girth of 1.79 meters, and its frozen weight was 690 kg +/- 20 kg. A probable cookie-cutter shark wound was present above the gill slits. Details of the logistics of preserving an unexpected 5 meter shark are described.

GENE EXPRESSION AND VARIATION IN THE LACTATE DEHYDROGENASE ISOZYME SYSTEM OF SHARKS

Expression of lactate dehydrogenase (LDH) was examined via starch gel electrophoresis in 16 species of sharks. Relative to that of advanced teleost fishes, LDH expression in sharks is quite conservative in terms of number of loci, tissue specificity of expression, heterotetramer formation, and intraspecific variation. Sharks express only two LDH loci, Ldh-A and Ldh-B. In most species, these gene products are distributed in a generalized fashion among tissues, and form all expected heterotetrameric combinations. Limited intraspecific variation was revealed in Carcharhinus limbatus (Ldh-A and Ldh-B), andRhizoprionodon terranovae (Ldh-B). Interspecific variation among species from the Gulf of Mexico and the NW Atlantic was also limited. LDH may serve in a limited capacity as a population-level marker and in a greater capacity as a character to distinguish species and estimate intrafamilial relationships.

LIFE HIST0RY OF A TIGER SHARK (GALEOCERDO CUVIER) IN THE WORLD’S LARGEST AQUARIUM

The Living Seas at EPCOT Center, Walt Disney World was home to a tiger shark for over three years. This is believed to be the longest period of time that a tiger shark has been kept on display. The Living Seas is one of the few aquariums in which both fish and sharks are displayed toqether. An overview is presented an the husbandry involved in maintaining this animal. The shark’s behavior patterns, feeding habits and growth are discussed. The effects of chemical treatments in the aquarium on the shark should prove useful to other public aquariums that hold sharks.

DATABASE MANAGEMENT OF THE INTERNATIONAL SHARK ATTACK FILE USING ORACLETM

Information originally compiled and copyrighted by H. David Baldridge and presented by Baldridge in 1974 has been re-computerized using the relational database management program ORACLETM on a Digital VAX 11/750 computer running VMS. Originally encoded from punchcards, a new entry scheme using common English from on-screen prompting permits rapid data entry from standard shark attack report sheets. Data query using the SQL query language facilitates rapid examination of suspected shark attack patterns without the necessity of programming skills. The relational nature of the program easily provides for protection of sensitive case or victim information, and can readily be modified to allow access to particular information only through password authorization. Access and data query may eventually be accomplished via modem from microcomputers with appropriate authorization of the Shark Attack Committee.

A COMPARISON OF GROWTH BETWEEN CAPTIVE AND FREE NURSE SHARKS, Ginglymostoma cirratum

Growth rates determined from recapture studies of free-ranging nurse sharks (Ginglymostoma cirratum) averaged 13.1 +/- 9.5 cm/yr and 2.3 +/- 1.3 kg/yr. Growth measurements on three captively maintained nurse sharks, averaged over a three-year period, resulted in growth rates which were slightly faster (19.1 +/- 4.9 cm/yr and 4.0 +/- 1.7 kg/yr). The captive study, however, was able to reveal that growth rates decreased as the age of the animals increased (from approximateIy three to six years of age). Estimation of growth in the captive population at times when animals were of similar size as those tagged in the wild resulted in growth rates which were considerably closer (13.8+/- 2.3 cm/yr and 3.7 +/- 2.2 kg/yr). Percent changes in total length for free-ranging nurse sharks and captive nurse sharks of similar size were 11.4%/yr and 11.3%/yr, respectively, while percent changes in body mass averaged 32.7%/yr for recaptured animals compared with 31.6%/yr for comparably sized nurse sharks in captivity.

FISHES OF THE GENUS RAJA (RAJIFORMES: RAJIDAE) FROM TAIWAN

Previous workers described eight species of Raja from Taiwan: R. tengu, R. fusca, R. kenojei, R. hollandi, R.macrophthalma, R. olseni, R. acutispina, and R. porosa porosa.R. porosa porosa. R. porosa porosa. In this paper, fishes of this genera were studied in detail. From the result, R. fusca and R. porosa porosa were considered to be the samespecies of R. (Okamejei) kenojei. R. kenojei, R. hollandi, R. macrophthalma and R.olseni were considered to be the species of R. (Dipturus) kwangtungensis, R.(Okamejei) boesemani, R. (0.) meerdervoortii and R. (0.) hollandi respectively. In addition, a new recorded species of R. (Dipturus) macrocauda was obtained from the northeastern Taiwan waters. A key to the above mentioned species of Raja from Taiwan is presented.

TREATMENT OF BACTERIAL DISEASE IN JUVENILE SANDBAR SHARK,CARCHARHINUS PLUMBEUS (NARDO), IN CAPTIVITY

Nine newborn sandbar sharks, C. plumbeus, were dissected out from a female captured from Delaware Bay. After a month in captivity, a circular white fuzzy patchiness was developed on the dark surface of one shark. The patch subsequently appeared on all of the other pups and increased in size with time. Examination of skin scrapings showed no evidence of infestation of protozoa, fungi or helminthes. The affected sharks showed no abnormal swimming or feeding behavior. Neither lesion nor hemorrhage was observed in the dead ones. Necropsy showed heavy bacterial infections of internal organs and cloudy hemoglobinemic fluid in the abdomen. A gram negative beta-hemolytic rod bacteria was isolated from heart puncture. The bacteria is sensitive to chloramphenicol, neomycin, nitrofurantoin, tetracycline and potentiated sulfame-thoxazole. The remaining 4 pups were treated by feeding with tetracycline at 250 mg/shark for 4 days then changed to trimethoprim (80 mg) and sulfamethoxazole(400 mg)/shark/day for additional 10 days. The sharks were completely recovered with no further mortality. Subsequent blood samples from two healthy sharks showed no bacterial growth on marine or TCBS agars.

BREEDING MIGRATION OF THE SAND TIGER SHARK IN SOUTHERNCarcharias taurus AFRICAN WATERS

The sand tiger shark Carcharias taurus is common in the nearshore waters along the east coast of Southern Africa. In September adult females enter Natal waters from the south; mature males arrive soon thereafter and mating occurs between late October and the end of November. The females continue northward and spend much of the 9 month gestation period in the clear, tropical waters of northern Natal and southern Mocambique. During this period aggregations of up to 80 females may be encountered. These females are docile and very slow moving; over 150 individuals have been marked with tags inserted by snorkel divers using spearguns. Accumulation of hydroids on the teeth suggest that feeding is infrequent. Between June and August the females appear to move rapidly southward, carrying well developed embryos. The embryos are born to the south of Natal as this species requires a warm temperate nursery ground. Not all migrating females are sexually active and recaptures of tagged specimens indicate that females reproduce biennially. The whereabouts and movements of mature males outside the mating season are unknown.

REPRODUCTIVE BIOLOGY OF THE SANDBAR SHARK, CARCHARHINUS PLUMBEUS, IN THE CHESAPEAKE BIGHT

The shallow waters surrounding the Delmarva Peninsula are used extensively and exclusively as a nursery area by the sandbar shark, Carcharhinus plumbeus. Numerous longline collections made between 1974 and the present have resulted in the capture of 115 mature females in the Chesapeake Bight region, 85% of which were found to be carrying full-term embryos or exhibited immediate post-partum uterine conditions. Females with embryos were taken only in late May and early June, and contained an average of 8.5 embryos (range 4-12) of an average size of 59 cm TL (range 44-68 cm), the same size as free swimming neonates taken concurrently. Both liter size and embryo size were weakly positively correlated with maternal size. The largest female encountered (231 cm TL) was carrying 4 normally developed and 6 severely atrophied embryos, indicating the possibility of senescence. Mature females were not encountered in shallow waters after June.

Only eight mature males were taken, and were encountered only in outer shelf and shelf break waters later in the summer, indicating that no mating occurs in the Chesapeake Bight area. This is substantiated by the fact that no females with developing eggs or fresh mating scars were taken.

DISTRIBUTION OF DEEP-BENTHIC CHONDRICHTHYIANS ON THE WEST COAST OF SOUTHERN AFRICA

From 1986 onwards the benthic chondrichthyians collected on the biyearly hake demersal cruises of the Sea Fishery Research Institute’s RV Africana — off the west coast of southern Africa have been identified, routinely assayed for biological data, and preserved for systematic study. The bathymetric and geographic distribution of 47 bottom-dwelling species (27 sharks, 16 rays, and six chimaeras) collected at depths below 200 m and from the Agulhas Bank to Central Namibia is presented. The species fall in three successive bathymetric faunal groups with considerable overlap: a shelf extension fauna from 200 to 300 m, a hake zone fauna from 200 to 600 m, and a deep slope fauna below 600 m. Geographically there are differences between the hake zone and deep slope faunas off Namibia and the Western Cape, with some endemism in the latter area.

COMPARISON OF SERUM IRON AND SERUM COPPER LEVELS IN CAPTIVE AND WILD NURSE SHARKS (GINGLYMOSTOMA CIRRATUM)

Serum iron, serum copper and hematocrit values were determined for captive and wild nurse sharks (Ginglymostoma cirratum). The serum ranges, means and standard deviations of captive nurse sharks respectively were: iron 30-74 (ug/dl), 51.1 +/- 12.8; total iron binding capacity 274-343 (ug/dl), 317.1 +/- 23.0; percent saturation of iron binding sites 11-20, 15.7 +/- 3.1; copper 44-70 (ug/dl), 54.7 +/- 10.7. The serum ranges, means and standard deviations of wild nurse sharks respectively were: iron 17-45 (ug/dl), 31.1 +/- 10.0; total iron binding capacity 166-546 (ug/dl), 277.4 +/- 142.7; percent saturation of iron binding sites 07-24, 14.7 +/- 6.4; copper 39-57 (ug/dl), 47.8 +/- 6.5. The ranges, means and standard deviations of hematocrit in captive and wild nurse sharks respectively were: 23-27.5(%), 24.8 +/- 1.7; 16.5-21.7(%), 18.7 +/- 1.7. Significant differences (P<.01) were detected for iron and hematocrit. Based on this information dietary supplements of iron and copper appear unwarranted in captive nurse sharks fed a fish diet.

STUDIES ON THE NEURAL PATHWAY FOR CLASPER MOVEMENT IN STINGRAYS.

The innervation of the clasper has been studied in several batoids with most emphasis onUrolophus halleri. Several large nerve trunks run posteriorly from the lower spinal cord (area about 1 cm above the base of the tail in a 340 gm animal) to innervate the clasper muscles and skin. The nerves are heavily myelinated as indicated by osmium staining. Low level electical stimulation (less than 150 uA) of the individual bundles evokes specific clasper movements including: rotation, elevation, medial and lateral extension and opening. The responses are abolished by treatment of the nerves with xylocaine. Stimulation (85 uA) in the lower spinal cord also evokes clasper movements, including opening. Clasper control is discussed as a potential hormonally-dependent sensorimotor system which should be amenable to neurophysiological analysis.

REPRODUCTIVE BIOLOGY OF CAPTIVE ELASMOBRANCHES: NEEDS AND STRATEGIES

To date, few elasmobranchs have been bred in captivity and very few breeding colonies have been established. Such colonies can provide low cost animals for research and display and possibly lead to methods for captive breeding of endangered or threatened species. Considerable information in a number of areas of reproductive physiology and behavior will be necessary to develop additional breeding programs. To encourage such development, our presentation will focus on: 1.) a brief overview of elasmobranch reproductive biology; 2.) a description of current methods for: assessment of sex- hormones using non-injurious blood sampling; tissue banking for later histological preparation and hormone analysis; and documentation of reproductive behavior; 3.) the necessity for corelation of field and laboratory studies; 4.) suggestions for developing a formal organization to assimilate and disseminate information concerning elasmobranch reproduction.

SHARK SWIMMING PERFORMANCE

The large, portable swimming tunnel at Scripps Institution of Oceanography has made studies of shark swimming performance a reality. Using this instrument we have measured variables such as critical swimming speed (Ucrit), V02, tail beat frequency (TBF) and gill ventilation (GV) in three different shark species. The Ucrit of Triakis semifasciata ranges from 0.49 to1.86 L/sec, is inversely related to body size, and is only slightly lower than that of comparably sized Oncorhynchus nerka (0. nerka, mean = 57 cm, Ucrit = 2.3; Triakis, 57 cm, Ucrit = 1.5). Metabolic data for Triakis, Negaprion brevirostris, and Isurus oxyrinchus show that active sharks have a higher V02 and greater aerobic scope.than suggested in earlier literature. The increase in TBF with swimming speed (U) is linear in both Triakis and Negaprion but becomes asymptotic near maximal U. Maximum TBF is also inversely related to size in Triakis, and this fish has a higher TBF than does Negaprionof the same size. GV analyses in larger Triakis indicate that a transition to ram ventilation occurs with increased U.

FEEDING ECOLOGY OF SKATES (FAMILY RAJIDAE) OFF THE WEST COAST OF SOUTH AFRICA

The diets of eleven species of skates (Order Rajiformes, Family Rajidae) were studied along the southwest African coastline during a series of cruises conducted by Sea Fisheries Research Institute reseach vessel RV Africana. Summer and winter surveys were made between 1986 and 1989. Skates in the area fall into two distinct fauna1 zones; the biscuit skate zone between the intertidal and down to about 350 m depth and the gray skate zone from about 400 m down to at least 1016 m depth. The important prey items for each species were identified and ranked according to their importance. Food habits were compared between species, over depth, and with seasonality, and the results are presented.

FEEDING BIOLOGY OF GREY NURSE SHARKS (EUGOMPHODUS TAURUS) IN CAPTIVITY.

An analysis of feeding behaviour and preliminary nutritional data collected from three captive Grey Nurse sharks (Eugomphodus taurus) over a period of three years at Australia’s Underwater World Oceanarium. Our hypothesis that seasonal food drive responses are triggered by water temperature changes will be discussed. Observed feeding behaviours and preferences are also analyzed in relation to the logistics of keepingEugomphodus taurus specimens. These behaviours are briefly related to our aquarium design and husbandry techniques.

SIMILAR IN VITRO REACTIVITY OF HUMAN AND ELASMOBRANCH CELLS TO CONDITIONED MEDIA

The immunology of cartilaginous vertebrates is poorly understood, and yet, research in this area may provide information pertinent to understanding the ontogenesis and phylogeny of immunity. Conditioned media generated in vitro using shark and stingray peripheral blood immunocytes are shown to be stimulatory to elasmobranch and human peripheral blood leukocytes. Reactivity suggests elasmobranchs may be used to study the evolutionary and developmental potentials of the vertebrate immune system.

THE APPLICATION OF TISSUE CULTURE TECHNOLOGY TO CAPTIVE FISH BIOLOGY

The significance of in vitro leukocyte studies to the biology of captive elasmobranchs is addressed in this communication. Cell viability, rate of proliferation, reactivity, and state of differentiation are assessed through temperature, stimulation and cell separation experiments. Long and short term maintenance of shark and sting ray cells suggests that elasmobranch peripheral blood cells tolerate stresses typically lethal to other vertebrate cells. Observations from histological and tissue culture analyses are discussed in relation to conditions of captivity and treatment of immunologically compromised animals.

REPRODUCTION OF CHONDRICHTHYANS IN CAPTIVITY AT SHIMODA FLOATING AQUARIUM

Twenty-seven species of sharks, 12 species of rays and one species of ratfishes have been kept in captivity at Shimoda Floating Aquarium, Izu Peninsula, central Japan. Reproduction of the following 14 species was observed: Heterodontus japonicus, Cephaloscyllium umbratile, Scyliorhinus torazame, S. sp. 1, S. sp. 2, Mustelus manazo, Triakis scyllia,Orectolobus japonicus, Narke janonica, Rhinobatos schlegelii, Platyrhina sinensis,Urolophus aurantiacus, Dasyatis sp., Chimaera phantasma. Fertilization occurred in captivity in the species of H. japonicus, C. umbratile, S. torazame, S. sp. 1, S. sp. 2 andT. scyllia. Mating behavior was observed in the species of H. japonicus, S. torazame, 0. japonicus, U. aurantiacus and D. sp. Chimaera phantasma spawned two egg capsules. One of them is under keeping in the tank. The reproduction of these chondrichthyans with various data on the new born youngs are presented.

SHARK MORTALITIES AT THE NATIONAL AQUARIUM IN BALTIMORE , 1981-1988

We evaluated data on 103 shark mortalities (10 different species) at the National Aquarium in Baltimore from 1981 to 1988. Of the 87 animals for which we had entry and exit dates, 69% died within one year, which was attributed to their inability to acclimate. After one year in captivity, the mortality rate declined, with a seasonal peak occuring during the months of June, July, August and September, the months when we usually introduce new specimens. Of the 73 animals for which we had a definite cause of death, 51% were related to infection, 31% involved trauma and 18% were due to iatrogenic/euthanasia procedures. Increasing the number of water changes (3 in 1985, 6 in 1988) and installing an ozone chamber in 1986, appears to have had no effect on the rate of mortalities.

1987 TEXAS SHARK ATTACKS–ARE CLUMPED ATTACKS RANDOM?

Three shark attacks in 1987 (2 in one day) at Port Aransas occurred after a similarly rare red tide in late 1986 killed a large number of beach fishes. In 1984 a similar incident occurred on South Padre Island after a severe freeze killed many fishes in 1983. Other shark attacks in the Gulf of Mexico in the Shark Attack File are clumped and four attacks on the west coast of Florida followed a severe red tide. While other factors may have been involved in the Texas and other attacks it may be worthwhile to study the relationships of attacks to red tides and other perturbations to the environment. There is good evidence that one Port Aransas attack was by a Carcharhinus, probably, C. limbatus.

INTESTINAL BITING: A NEWLY DOCUMENTED CAUSE OF MORTALITY IN CAPTIVE CARCHARHINID SHARKS

During 1986-1988, eleven cases of mortality in captive blacktip reef sharks (Carcharhinus melanopterus) and reef whitetip sharks (Triaenodon obesus) were the result of intestinal lacerations. These case studies represented both acute and chronic, progressive death syndromes. Necropsy examinations on acute specimens revealed large intestinal lacerations or missing sections of the intestine. Chronic specimens had small puncture wounds of the intestine and associated peritonitis/septicemia. The intestinal lacerations are the result of bite wounds incurred during periods of intestinal eversion. During this apparent natural flushing action, part or all of the intestine is exposed and vulnerable to biting by other sharks. This paper adds intestinal biting as a cause of mortality in captive sharks with a scroll intestine.

VISUAL SENSITIVITY IN JUVENILE VS. ADULT LEMON SHARKS: A MISMATCH RESOLVED

The visual pigment of the rod photoreceptors in the lemon shark (Negaprion brevirostris) was reported by Bridges (1965) to be a homogeneous rhodopsin with an absorption spectrum peaking in the blue-green end of the visual spectrum, at a wavelength (lambdamax) of 501 nm. This maximum absorbance should match with the peak in dark-adapted spectral sensitivity measured in either the isolated eye or in the whole animal. But psychophysical studies by Gruber (1967) and electrophysiological studies by Cohen (1977, 1985) on lemon sharks did not show a match with the 501 nm peak, instead revealing a lambdamax of about 520 nm, in the yellow-green end of the spectrum. However, Bridges’ study was conducted on an adult while those of Gruber and Cohen were on juveniles. We therefore explored this mismatch by repeating Bridges’ experiment on one adult and extracting the rod pigment from several juveniles. Bridges’ finding was confirmed, but the juveniles were found to possess an entirely different rod pigment: a porphyropsin, with a lambdamax of 520 nm. These data suggest that a biochemical changeover occurs in the lemon shark’s visual sensitivity as the animal matures. Such a shift is consistent with the spectral nature of the differing habitats occupied by juvenile vs. adult lemon sharks.

MORPHOLOGICAL COMPARISON OF THE EGG-CAPSULES OF SKATES AROUND THE WORLD

Egg-capsules of about 60 species of skates (suborder Rajoidei) were examined, which belong to 17 out of 26 supraspecific taxa of skates. They are 15 species of the genusBathyraja, three species of the genus Rhinoraja, one species of the genus Notoraja, one species of the genus Psammobatis, one species of the genus Sympteryqia, one species of the genus Cruriraja, three species of the subgenus Pavoraja (subgenus A), three species of the subgenus Gurgesiella (Fenestraja), three species of the subgenus Raja(Amblyraja), one species of the subgenus R. (Atlantoraja), 10 species of the subgenus R.(Dipturus), five species of the subgenus R. (Leucoraja), two species of the subgenus R. (Malacoraja), five species of the subgenus R. (Raja), two species of the subgenus R. (Rajella), one species of the subgenus R. (Rostroraja) and five species of the subgenus R. (Okamejei).

VARIATION IN THE ELECTRIC ORGANS OF SKATES (ELASMOBRANCHII, RAJOIDEI)

Weak electric organs along the lateral aspect of the tail are considered a unique derived character of skates although they have been described for a relatively small number of skate species. Specimens from 15 of the 29 supraspecific taxa (genera and subgenera) were examined macroscopically and histologically to estimate the extent of variation in electric organ development and structure. Variation was estimated both within and among supraspecific taxa. Variation in electric organs was compared with a working phylogenetic hypothesis of skates to both test and possibly further refine the working hypothesis.

A DESCRIPTION OF PREDATORY ATTACKS BY WHITE SHARKS ON PINNIPEDS

Behavioral types, states, and their temporal relationships during predatory attacks of white sharks on northern elephant seals and California sea lions will be described diagrammatically and videographically from 81 attacks at Southeast Farallon Island. Most predatory attacks, positioned by compass or theodolite bearings, occurred in a high risk zone within 400 m from shore. Objects of sizes similar to those of attack interactants and small flocks of gulls, which alerted observers to attacks, were detected at greater distances than me attacks, indicating the outer boundary to this zone was not due to a decrease in visual acuity of observers with distance from shore. Seals pass through this zone before moving on shore to molt and reproduce and sea lions between foraging trips. The outer boundary of the zone is along the 12 m depth contour surrounding the island

FAT PEROXIDATION IN CAPTIVE ELASMOBRANCHS.

Sharks kept in the display tanks of Kelly Tarlton’s Underwater World for periods of up to four and a half years with a mean duration of 3.7 years show a gradual deterioration in condition. The symptoms include poor wound healing, anorexia, and at post mortem, severe hepatic lipidosis of the liver. Ten aquarium specimens of Galeorhinus australiswere compared with nine wild caught sharks of the same species and blood and liver tissue analysed for evidence of lipid peroxidation and antioxidant deficiency. Vitamin E levels were measured fluormetrically and molondialdehyde (MDA) by the thiobarbituric acid reaction in blood and liver biopsies taken immediately after capture. Blood and liver vitamin E levels were depressed in the.captive sharks. (Blood vit. E 39.2 +/- 4 micro mol/l vs 45 +/- 2.7 micro mol/l p=O.O5)* (Liver vit. E 101 +/- 26 micro mol/kg vs 168 +/- 27 micro mol/kg p=O.Ol)* MDA levels in blood and liver were significantly elevated in the captive sharks compared to the wild. (Blood MDA 48.6 +/- 8 micro mol/l vs 30.7 +/- 8.1 micro mol/l p=O.O5)* (Liver MDA 233 +/- 31 n moles/kg vs 105 +/- 13 n moles/kg p=O.Ol)* These indicate significant lipid peroxidation and the possibility of liver damage.
*unpaired t-test

ORGANIZATION OF THE CAUDAL SPINAL NERVES OF SKATES (RAJA EGLANTERIA AND RAJA ERINACEA)

Dissections of specimens stained with Sudan black B or macerated with nitric acid reveal an unusual branching pattern of those spinal nerve roots at tail levels of skates. Unlike the typical pattern of dorsal and ventral roots combining to form segmental spinal nerves, in skates dorsal and ventral roots each divide into two rami. Each of the two ventral root rami unites with the corresponding ramus of the dorsal root to form two mixed spinal nerves per segment. An explanation of this branching and subsequent recombination is that the two spinal nerves thus formed course caudally to join two longitudinal nerve trunks. One nerve trunk is situated dorsal and the other nerve trunk is situated ventral to the horizontal septum that divides the tail musculature into epaxial and hypaxial groups. The electric organ, a specialized structure that arises developmentally from the lateral hypaxial muscle bundle, is innervated by nerves that branch from the ventral root rami destined to join the hypaxial nerve trunk.

DEPOSITION OF CALCIUM AND MAGNESIUM IN RAJA ERINACEA EGG CAPSULE DURING FORMATION AND TANNING IN UTERO

Formation of skate egg capsule begins in the shell gland with secretion and assembly of capsular precursors which lack color and strength. In Raja erinacea post-secretory tanning and sclerotization of the capsule in utero is coincident with introduction of catechols and their oxidation to quinones. Measurement of calcium and magnesium in capsules at various stages of tanning showed that calcium and, to a lesser extent, magnesium are deposited in the capsule during formation but that binding of these minerals is directly related to catechol/quinone content. Capsules from the urogenital sinus where they are carried for several hours and are first exposed to sea water contained somewhat more calcium and five-fold more magnesium than capsules in utero.
These measurements show that calcium and magnesium are integral components of skate egg capsule and that these minerals are deposited in the capsule during formation and tanning in utero. The bulk of the calcium derives from maternal sources while most of the magnesium is obtained from sea water. These observations establish that oviparous elasmobranchs like many terrestrial oviparous vertebrates deposit minerals in their egg shells.

A NEGATIVE REPORT: SEVERAL DRUG REGIMENS FOR TRANSPORT OF YOUNG HAMMERHEAD SHARKS (SPHRYNA LEWINI)

Hammerheads often die within minutes of capture or handling. A series of trials were run in which these animals were subject to treatment regimens designed to prevent capture myopathy and circulatory collapse. No approach succeeded in prolonging viability beyond 5h in simulated transport. Further studies are recommended.

PHOTORECEPTOR MORPHOLOGY AND CHARACTERISTICS IN THE STINGRAY, Dasyatis sabina (MYLIOBATIFORMES: DASYATIDAE)

In a study of photoreceptor morphometry in rays of the order Myliobatiformes, the retina of the stingray Dasyatis sabina was examined by light microscopy. Peliminary data show the presence of two photoreceptor types which, based on morphology and the characteristics of the typicai vertebrate retina, can be classified as rods and cones. Their relative occurrence varies by the retinal region examined.

FIELD STUDIES ON THE BEHAVIOR OF THE PACIFIC ELECTRIC RAY,Torpedo californica: A PRELIMINARY REPORT

The predatory, defensive, and space-related behaviors of Pacific electric rays are being investigated at Abalone Cove, Palos Verdes Peninsula, California. These rays appear to be the most abundant large predator in the cove. However, length of residency remains uncertain; of over 25 rays tagged at the site, none have yet been reobserved on subsequent days. During the day rays are inactive, buried in the soft sand bottom, while at night they become active and swim in the water column. Predatory and defensive behaviors are induced by presenting rays with prey items (which they shock and engulf) or by rigorously prodding them with an electrode probe. Electric discharges are recorded in situ using a housed storage oscilloscope. Recordings show differences in wave-form and pulse rates between predatory and defensive electric discharges, with some exceeding 45 volts. Acoustic telemetry, using transmitters ingested in bait, is being used to monitor diel and seasonal movement patterns.

MINERALIZATION OF THE TOOTH TISSUES PLEROMIN PETRODENTINE

Many mineralized tooth tissues have been named among the gnathostome fishes but nomenclatorial debates have overshadowed analyses of these tissues and their significance for developmental and evolutionary studies. The dental hypermineralized tissues pleromin and petrodentine, for instance, have repeatedly been treated as synonym of each other: Quantitative electron microprobe studies were done on tooth plates of Hydrolagus collei,H. affinis, Callorhynchus callorhynchus (Chimaeriformes), and Protopterus annectensand Lepidosiren paradoxa (Dipnoi), The data show significantly different compositions for the tissues pleromin and petrodentine. The tooth plates of the Chimaeriformes consist ofosteodentine and pleromin. Pleromin is uniquely high in P, Mg, and Na, is characterized predominantly by Mg-whitlockite, and is found only in the tritors of the Chimaeriformes. Petrodentine and pleromin are therefore distinctly different dental tissues. Petrodentine is high in Ca relative to all dentines, is close to the composition of mineral apatite, and forms the tritoral tissue of the dipnoan tooth plates.

COMMERCIAL OCEANARIUM DESIGN; COMBINING GOOD DISPLAY VISIBILITY WITH ADEQUATE HABITAT REPRODUCTION FOR CAPTIVE SHARK SPECIMENS

Underwater World Oceanarium is used as a case study to discuss the design and logistical problems associated with commercial aquarium construction. In depth analysis of preferred captive habitat design is given in relation to our aquarium. The relative merits of various design features that affect sharks are assessed based on the behaviours of our specimens.

INNOVATIONS IN SHARK FISHING

The factor influencing the survival caught sharks is its sensitivity to lack of oxygen. Pelagic species must be in continuous motion to flush their gills, tired sharks will drown. No matter which gear is used, the caught shark must be transported to the aquaria within one hour. The first device I developed minimizes the release of the tangled shark down to 10 minutes. A transmitter, placed on the float of the line, is activated by the weight of the caught shark and delivers either a signal, a siren, or dials a phone number. As well as the fact that the shark is still in very good shape, it also allows the collector to select the size of the wanted live animal by graduating the transmitter. The second device allows the transportation of the captive shark.from the fishing ground to the aquaria, which may take a few days. This device consists of a chamber built up around a stretcher on which the captive sharks lie down. A strong water flow is pumped through the shark’s mouth toward:the.gills. The out-flow from the gill slits is collected in a closed system, oxygenated and flushed again to the mouth. Sharks treated wfth.these devices attained survival of more than 85% in the Coral World Observatory.

STABLE ISOTOPE VARIATION IN LEMON SHARK (NEGAPRION BREVIROSTRIS) VERTEBRAE AS A POSSIBLE INDICATOR OF LIFE HISTORY PATTERNS

Stable isotopes of oxygen and carbon were analyzed in CO2 extracted from vertebral centra of the lemon shark, Negaprion brevirostris. The CO2 is evolved from carbonate-apatite laid down during growth. By sampling along the centrum radius, isotope values were plotted as a function of growth, and preliminary interpretations were made concerning feeding histories and environmental waters in which the sharks inhabited. Long-term trends of isotopic enrichment and depletion occur in both 13C and 18O, with the total range of values between -4 /oo to -1 /oo for 13C, and -2 /oo to +l /oo for 18O (relative to PDB). We propose that isotopic excursions in 18O are indicative of the shark’s movement between regions of isotopicly enriched waters on Great Bahama Bank to depleted waters in the Florida Straits. We further propose that isotopic excursions in 13C are indicative of changes in the diet as the shark matures.

THE MATING BEHAVIOR AND MATING SYSTEM OF THE ROUND STINGRAY (UROLOPHUS HALLERI) IN THE GULF 0F CALIFORNIA.

Round stingrays were studied in a shallow bay in the Gulf of California where they form a large breeding assemblage. Observations were carried out during different phases of the reproductive cycle in March 1988 & 1989. Twelve distinct response patterns involved in mating were observed. Copulation was observed on 122 occasions; details on these mating bouts will be presented. All reproductive activity was limited to the morning; at this time nonreceptive females were buried, while receptive females formed large groups on the sand. Males actively searched for females in the morning and employ several different techniques to acquire mates. In the afternoon males were buried and females emerged from the substrate to forage in the adjacent grass beds.

NOTES ON THE CAPTURE, CARE AND SUITABILITY OF THE CARIBBEAN REEF SHARK AS AN EXHIBIT ANIMAL

The Caribbean Reef Shark, Carcharhinus perezii, is one of the most common sharks found on Bahamian reefs. It is an aggressive feeder and has been responsible for a number of attacks on spearfishermen in the Bahamas. In spite of its aggressiveness, the Caribbean Reef Shark has proven to be an excellent . display animal at Coral World Bahamas for more than two years.

FACTORS AFFECTING SPACE UTILIZATION OF LEMON SHARKS,NEGAPRION BREVIROSTRIS.

A full understanding of the ecology of any animal entails knowing the animal’s patterns of movement. Most vertebrates confine their activity to specific areas. Properties of these activity spaces (e.g., size, location) should have adaptive significance. Only since the advent of ultrasonic telemetry techniques has continuous observations of movements of individuals become possible. During the summer of 1988 and the winter of 1989 nine juvenile lemon sharks were manually tracked in Bimini, Bahamas. During the summer these young sharks maintain a very restricted activity space, close to the mangrove-fringed shoreline, which averages 400 m in length and 50 m in width and which is overlapped largely by the activity spaces of neighboring sharks. Hence, these juvenile lemon sharks are highly social and home ranging. Preliminary evidence suggests that as these sharks age (i.e., increase in body size) their activity space is moved out of the sound into deeper water and greatly increases in size. Preliminary evidence also suggests that the activity space of juvenile lemon sharks is more than four-fold larger during winter months.

WHOLE BLOOD ELEMENT ANAYLSIS OF CAPTIVE AND WILD LEMON SHARKS (Negaprion brevirostris) BY INDUCTIVELY COUPLED PLASMA EMISSION SPECTROSCOPY

Whole blood samples from wild populations of Lemon sharks and individual Lemon sharks (Negaprion brevirostris) maintained at Sea World of Florida were analyzed for twenty-four elements utilizing inductively coupled plasma emission spectroscopy (ICP). Of the twenty-four elements, eight were below detectable limits in both populations utilizing the ICP technique. In all cases here elements were within detectable limits (sixteen elements), the levels in the wild populations were consistently higher than the captive individuals. The number of captive males was not large enough to compare statistically with wild males however wild females and males showed no statistical differences.

DEEP SEA CHONDRICHHYANS FROM THE EASTERN NORTH ATLANTIC: MID-ATLANTIC RIDGE,GRAND CANARY AND TENERIFE

Thirty-three sets, 3655 hooks, were fished in three primary locations at depths from 380-3750 meters. Chondrichthyans accounted for 66% or 215 of the 326 fish caught with at least 18 species represented. Tenerife (640-123O m) accounted for 19% of the total effort and 6.7% of the total catch, Grand Canary (380-3750 m), 50% of the effort and 69.9% of the catch and the Mid-Atlantic Ridge (2050-319O m), 31% of the effort and 23.4% of the return. Chondrichthyans represented 83.3% of the Tenerife catch and consisted ofCentroscymnus coelolepis (25%); Deania calcea (25%), C. cryptacanthus (16.7%),Centrophorus acus (12.5%) and Hexanchus griseus (4.2%). Grand Ganary, 86.9% Chondrichthyans, included at least 14 species with C. coelolepis (40.6%) and Etmopterus princeps (21.6%) being the commonest. The Mid-Atlantic Ridge consisted of four species of Chondrichthyans; Hydrolagus affinis (4.8%), Raja sp. (3.6%), Somniosus microphalus (2.4%) and C. coelolepis (1.2%) for 11.9% of the catch.

TAXONOMY OF DEEPWATER CATSHARK APRISTURUS FROM THE PACIFIC OFF NORTH AND SOUTH AMERICA

Apristurus is a genus of deepwater catsharks, with 36 species mostly from depths of Northern Hemisphere. The genus is one of the most taxonomically confusing taxa in elasmobranchs, and some gradual or local revisions are necessary. Five species are reported from the Pacific off North and South America, but their taxonomic relations have never been discussed.

After checking existing type specimens and other available specimens of world species, the author sub-divided all the known species into several distinct species groups. A. brunneusfrom U.S. waters belongs to one group, together with Chilean nasutus. A. brunneus is a good species, but relation of nasutus to brunneus can not be determined, mainly because of loss of its type specimen. The other three species, i.e., spongiceps, kampae andstenseni, belong to an another group. A. kampae is distinct from spongiceps. Examination of type specimens of stenseni suggests its closer relation to kampae, but very poor condition of the types and wide size gap between available specimens of kampae andstenseni make the solution difficult. In addition, the type series of stenseni apparently consist of two species, which belong to two different species groups.

FLUCTUATIONS IN SERUM CALCIUM LEVELS OF CAPTIVE JUVENILE LEMON SHARKS, NEGAPRION BREVIROSTRIS

Age estimation in elasmobranchs is accomplished by counting calcified rings in vertebral centra without the knowledge and understanding of the importance of serum calcium. Blood from twelve juvenile lemon sharks, Negaprion brevirostris was collected caudally via venipuncture once weekly for a period of 19 weeks. Calcium levels ranged from 12.1 mg/dl to 19.0 mg/dl. Highest calcium levels during the study period occurred during August and were followed by lowest levels in September. Since we believe that calcium needed for calcification of vertebral rings is obtained from the serum, we propose that this zenith and nadir in serum calcium levels is the time of annual ring deposition in lemon sharks. Time series analysis demonstrated a periodicity in serum calcium levels of 30 to 40 days and autocorrelation showed no relationships of serum calcium to other blood parameters. Presently, these fluctuations in serum calcium levels are being correlated with calcified rings in vertebral centra to determine the relationship between calcium levels and deposition of circuli (sub-annual rings) in lemon sharks.

PRELIMINARY BASELINE BLOOD PARAMETERS FOR CAPTIVE JUVENILE LEMON SHARKS, NEGAPRION BREVIROSTRIS

Twelve juvenile lemon sharks, Negaprion brevirostris, maintained under controlled conditions of temperature (25 +/- 1° C), salinity (28 to 31 % ) and light (12L:12D) and fed at 15% body weight per week, were sampled once per week during a five month period. Two hundred fifty-four blood samples were taken caudally via venipuncture and a total of 21 standard blood parameters were analyzed. Mean values and ranges of blood parameters investigated varied from those found in wild lemon sharks. These differences may be attributed to the small sample sizes of wild sharks, the differences of maturity levels (ages) of individual sharks or stress induced by capture of wild sharks. Significant differences in blood parameters included urea (bun) which was twice as high as wild levels and triglycerides which were four times as high as wild levels. Many of the values of blood parameters were found to be lower in captive sharks in comparison to wild sharks.

STANDARDIZATION OF THE MEASUREMENT OF SHARK DENTITION

A measuring instrument is described to more stringently quantify the dimensions of the shark buccal cavity. The Kinetic Dentometer provides measures of the gape width, gape angle, palatoquadrate length, Meckel’s cartilage length, and distance to individual teeth from a reference point mid-way between the jaw symphyses. Tooth height, width, displacement from the midline and degree of tooth erection are also provided. A system of tooth enumeration is also described which denotes the position of individual teeth with reference to the functional row and position on the jaw relative to the midline.

HUSBANDRY TECHNIQUES WITH CAPTIVE ELASMOBRANCHS AT THE NATIONAL AQUARIUM IN BALTIMORE, 1988-1989

A 14 minute videotape is used to illustrate various techniques used in the husbandry of captive elasmobranchs at the National Aquarium in Baltimore

METABOLIC RATE, HEART RATE, AND TAILBEAT FREQUENCY DURING SUSTAINED SWIMMING IN THE LEOPARD SHARK TRIAKIS SEMIFASCIATA

Heart rate, metabolic rate, and tailbeat frequency were simultaneously recorded from seven Ieopard sharks during steady swimming at controlled speeds to evaluate heart rate as a measure of field metabolic rate. Heart rate was monitored by acoustic telemetry using a frequency modulated ECG transmitter. Metabolic rate was measured as oxygen consumption in a swimming tunnel respirometer. For instrumented sharks, mean resting oxygen consumption rate and heart rate were 105.3 +/- 35.6 (SE) mg02.kg-1.hr-1l and 36.6 +/- 1.8(SE) beats.min-1. These rates increased to 229.3 +/- 13.2 mg02.kg-1.hr-1and 46.9 +/- 0.9 beats-1.min-1 in sharks swimming at the maximum sustained speed (0.84 +/- 0.03 lengths.s-1) f o r 30-60 min. Although a significant regression was obtained between metabolic rate and heart rate, the low overall r2 value may have resulted from varying individual regressions and confounding changes in stroke volume and/or arterio-venous oxygen difference. Heart rate was almost as closely correlated with oxygen consumption rate as swimming speed was. A significant linear relationship was obtained between tailbeat frequency and swimming speed for speeds to 0.75 lengths.s-1.

FEEDING HABITS AND GROWTH RATES OF BULL (CARCHARHINUS LEUCAS), SANDBAR (CARCHARHINUS PLUMBEUS), SANDTIGER (EUGOMOPHODUS TAURUS) AND NURSE (GINGLYMOSTOMA CIRRATUM) SHARKS MAINTAINED IN CAPTIVITY

Successful maintenance of captive elasmobranchs requires a fundamental understanding of their feeding patterns and growth dynamics. In an effort to increase our understanding of these requirements, we are investigating growth and feeding habits of 34 sharks of four species housed in a 2.5 million liter aquarium. Measurements on select animals were made sporadically since 1981. Systematic measuring of all sharks began in May of 1988. Preliminary results from data collected since 1981 indicate that captive sandtiger sharks grow 0.6 to 2.9 cm total length per month, or 7 to 35 cm TL per year. Growth rates for six neonatal bull sharks captured in 1985 averaged 2.3 cm TL per month, or about 28 cm per year. By individually feeding sharks a known quantity of food, we determined that mature sandtiger sharks consume approximately 2% of their body weight (BW) in food per week (N=9), mature nurse sharks consume about 2.3% BW per week (N=6). Mature sandbar and bull sharks consume more food proportionately than sandtiger and nurse sharks, about 3.5% of their BW per week (N=5). Length/weight of captive sharks compared with those of wild caught conspecifics indicate that some of our sharks are considerably heavier than wild animals.

THE TRACKING OF SHARK SWIMMING HABITS AT THE LIVING SEAS PAVILION.

The 5.7 million gallon re-created Carribean coral reef in The Living Seas Pavilion at EPCOT Center houses a variety of fish, rays, sharks and dolphins. At the onset of the study, the requiem shark population consisted of an 11 ft. female tiger shark (Galeocerdo cuvieri), a 7.5 ft. male bull shark (Carcharinus leucas), and a 6 ft. female brown shark (Carcharinus plumbeus). Various stimuli are present in the tank throughout the day such as divers, dolphin and feedings, yielding seven unique conditions. The three sharks were observed under the various conditions for approximately five months to establish a baseline showing where the sharks spent their time. A new female brown shark (6.5 ft.) was then added to the environment. After one month adjustment period the four sharks were observed in the same manner as “before”. The data from “before” was then compared to the data from “after” to determine the effect the new shark had on each of the existing sharks.

A MONOPHYLETIC GROUP COMPRISING BATOMORPHS, PRISTIOPHORIDS, AND SQUATINIDS: A WORKING HYPOTHESIS.

Batomorphs, pristiophorids, and squatinids are hypothesized to form a monophyletic group on the basis of critical review of recent thoughts on the higher elasmobranch phylogeny. Although the close affinities between batoids and angel sharks, and/or saw sharks have often been suggested, most workers have regarded skates and rays as a single group which did not contain any shark members. Monophyly of this hypothetical taxon is supported by the following synapomorphies: 1) cervical vertebrae expanding laterally, 2) absence of occipital half centrum, 3) a separate condyle for pectoral metapterygium, 4) presence of neural processes, and 5) caudal inclinator muscle connecting with ventral longitu-dinal bundle. Some notable characters, such as “suborbital shelf” in Squatina and an occipital half centrum, are commented in detail. This taxon may be in sister relation with the Squaloidei.

THE BIOLOGY AND RESOURCE USE OF TWO SYMPATRIC SHARKS,MUSTELUS MUSTELUS (LINNAEUS, 1758) AND MUSTELUS PALUMBESSMITH, 1957 (PISCES: TRIAKIDAE) OFF SOUTHERN AFRICA

Aspects of the life histories of two coastal shark species are described and compared to reveal that the size at sexual maturity, diet and habitat use differ between two sympatric species of Mustelus off southern Africa. M. mustelus is the larger of the two species and inhabits shallower water than its congener, although there is some overlap in the depth range. M. palumbes matures at a smaller size and lives in deeper water, M. palumbes is ovoviviparous, without a yolksac placenta, with litters of up to 18 but generally not exceeding 11 young. Unlike M. mustelus there is no clear reproductive seasonality. M. mustelus is viviparous, with a yolk sac placenta and has up to 23 viable young per season. Differences in uterine nutrition are discussed in relation to litter size and length at birth.

Cleaning Symbiosis in the stingray Dasyatis americana

Symbiotic cleaning has been widely reported in teleost fishes but accounts of elasmobranchs serving as hosts for cleaners either have been anecdotal or based on captive animals. We report a cleaning relationship between a ray and a wrasse in nature. The colony of southern stingrays, Dasyatis americana, occurs near a wreck east of Bimini, Bahamas, in about 6 m of water. The cleaners, Thalassoma bifasciatum, occupied cleaning stations over discarded conch shells. Rays were cleaned in one of two manners: (1) as they swam slowly over the cleaning station in tight circles or (2) when they settled on the bottom and assumed a sterotyped solicitation posture. Cleaning bouts lasted from several seconds to 26 minutes. Over five days of observation in May, 1988, at least six different rays were cleaned, two repeatedly. Wrasses, usually in pairs, cleaned primarily the dorsal surface and tail of the rays, and spent little time on the ventral surface. No branchial or oral cleaning was observed.

IN VIV0 MAGNETIC RESONANCE IMAGING AND SPECTROSCOPIC STUDIES OF ELASMOBRANCH HEPATIC LIPID RESPONSE TO PRESSURE.

The hypothesis that elasmobranchs react to changes in depth by altering the lipid composition of their liver is examined. Arabian Carpetsharks (Chiloscyllium arabicum) were studied at surface pressures and at 240 PSI (depth equivalent of 0.1 mile) in a specially constructed life support apparatus designed to be compatible with the requirements of MRI. Images to locate the liver of the subjects were obtained on a G.E. Signa 1.5 Tesla medical imaging magnet. Hepatic lipid content was established relative to water using stimulated echo acquisition mode (STEAM) spectroscopy to isolate spectra from localized regions of liver. A relative increase in hepatic lipid content was observed after 22 hours under pressure. No alteration occurred in a matched surface pressure control.

THE REPRODUCTIVE BIOLOGY OF THE FRILLED SHARK,CHLAMYDOSELACHUS ANGUINEUS, FROM SURUGA BAY, JAPAN

The frilled shark Chlamydoselachus anguineus is one of the most primitive species in living sharks. This species is very rare in the world oceans except for Japanese waters. Therefore, the life history of the frilled shark remains poorly understood. We collected 139 males and 125 females from Suruga Bay untill December, 1988 and examined the reproductive organs in detail for making the reproductive activity, size at maturity and fecundity clear. Females had no defined breeding season. Males had active testes through a whole year. Females reached sexual maturity between 1400-1500 mm total length (TL) and a maximum size of 1852 mm TL. Males matured below 1100 mm TL and reached a maximum size of 1548 mm TL. Follicle was ovulated through a ovulating pore on the epithelium of ovary when it reached between 230-250 g. Litter size ranged between 2-10. Egg capsule came off when embryo reached between 60-80 mm TL. Total length at birth ranged between 550-600 mm TL.

ON THE KEEPING OF MOBULIDAE RAYS IN OKINAWA EXPO AQUARIUM

We have kept 19 Mobulidae rays of 4 species in captivity in Okinawa Expo Aquarium, Japan from 1975 to 1988. They consist of 4 Mobula japanica, 11 Mobula diabolus, 1Mobula tarapakana and 3 Manta birostris. All were kept in Kuroshio Tank (Capacity 1,100 ton, 27x12xD3.5m) with sea water of 24.6°C in average, ranging from 19.8° to 29.6°C. Their average survival times are 1.7 days in M. japanica, 3 days in M. diabolus, 2 days in M. tarapakana and 35.7 days in M. birostris. Judging from behaviors in captivity in addition to the average survival times, we conclude the difference by species in the adaptability to captive environments as follows: M. birostris > M. japanica > M. diabolus, > M. tarapakana. At present under the conditions of our aquarium, only M. birostris is thought to have good adaptability to captivity and possibility for display in Mobulidae. On a female M. birostris being kept as of January, 1989, the captu:e, transportation and husbandry are reported.

ELASMOBRANCH FISHES KEPT IN JAPANESE AQUARIA AND THEIR ADAPTABILITY TO CAPTIVE SETTINGS

At 44 aquaria and 4 zoological gardens in Japan 80 species of 14 families of sharks and 44 species of 12 families of rays were kept in captivity from 1978 to 1987. These 129 species, of elasmobranchs; their numbers kept, average survival times (days) and the longest survival times (days,) by species are reported. The average survival time is adopted as the index of adaptability to captive settings, We set up 3 grades of adaptability, that is, grade A means elasmobranch fishes with average survival times of 180 days and over; grade B, 30 up to 179 days and grade C, less than 30 days, In sharks, 23 of total 80 species kept in captivity belong to A grade (29% of total) and in rays, 9 of total 44 species do to A grade (20% of total). Among the above 14 families of sharks the families with relatively many component species and high rate of A grade species accounting for total species of the families are Triakidae (4 A grade species: 57% of 7 total species). Carcharhinidae (8 A grade species: 44% of 18 total species) and Orectolobidae (6 A grade species: 55% of 11 total species). Among the 12 families of rays, the family with the same is only Dasyatididae (7 A grade species: 50% of 14 total species).

MEDICAL MANAGEMENT OF A SHARK COLLECTION

Long term management of a sizeable elasmobranch collection can benefit from the incorporation of veterinary care principles similar to other species. This program requires the development of a wide basis of applicable information including disease detection, diagnosis, treatment, recovery and, when possible, prevention. Medical techniques currently utilized include complete blood counts, serum chemistries, bacterial culture, antibiotic investigation and use, nutritional supplementation, radiology, sonography, and endoscopy. The limiting factors influencing the development and success of a medical program are 1) facilities, 2) proper restraint which will not result in injury, and 3) interest and co-operation between the curatorial and veterinary staff.

OBSERVATIONS ON THE DEVELOPMENT AND GROWTH OF THE EPAULETTE SHARK (HEMISCYLLIUM OCELLATUM) IN CAPTIVITY.

The breeding biology of the Epaulette Shark (Hemiscyllium ocellatum) was studied over a 429 day period. Observations were recorded on the mating behavior and egg laying behaviour of the breeding groups. Grwoth rate (weight and length) were systematically recorded for the first 6 months of the juvenile sharks life in captivity.

REPRODUCTION AND USE OF COMMUNAL SPAWNING SITES BY DEEP WATER CATSHARKS

Large (l-l.5 x 0.25 m) columnar masses of catshark eggcases were observed attached to a rocky outcrop on the lip of the Monterey Submarine Canyon at or depth of 300 m. They were laid either by the whiteedged catshark, Apristurus sp. or the long-nose catshark, A. kampe. Developing eggs only occur at the periphery of the mass while hatched egg cases in various stages of degradation occur in the interior. Egg cases differ somewhat in size (55-60 mm. long x 22-25 wide) and morphological detail. Several females used the same spawning site over a period of years. This reproductive pattern enhances survival of individual eggs since the risk of death from limited predation is a function of the total number of egg cases. Also, if the spawning site is placed with the boundaries of a territorial fish species, the latter’s defense of territory will protect the catshark egg mass. Embryological development, estimated at 9-12 months, resembles that of the shallow-water catshark Scyliorhinus. Ambient temperature is 7-8 C. Embryos succumb to heat shock at incubation temperatures in excess of l2 C. Term embryos are black and possess two classes of denticles. Flank denticles are needle-like. The hypertrophied, recurved, eclosion denticles, an adaptation for hatching, lie in two parallel rows on either side of the middorsal line with their free margins pointing. They form a rachet that prevents retrogressive slippage during eclosion. (Supported by NOAA Office of Undersea Research.)

COMMENTS ON THE REPRODUCTIVE MODE OF THE FALSE CAT SHARKPSEUDOTRIAKIS MICRODON

Twelve specimens of the false cat shark were collected at water depths between 530 m arid 890 m around the Okinawa Islands, Japan. Three pregnant females carried two embryos respectively. The ratio of males to females in embryos was 1:1. The ovary contained numerous ova. Ovum yolk material was observed in uteri and weighed 730 g to 1010 g. Two embryos had ovum yolk materials and egg capsules in their stomachs as in oophagous species. The embryos seem to transfer the ovum yolk materials to both internal and maternal yolk sacs, and then store up yolk materials in the yolk sacs. The reproductive mode of the false cat shark seems to be different from the already classified modes, and it is a style midway between dependent solely on yolk reserves and oophagy.