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The American Elasmobranch Society


Abstracts of AES Scientific Papers
American Elasmobranch Society 1997 Annual Meeting
Seattle, Washington
ABSTRACTS - Part 2: Feldheim through Hueter
Feldheim, Kevin F., Ashley, Mary V., Gruber, Samuel H.

 Population structure and dynamics of the lemon shark, Negaprion brevirostris, on a local scale: microsatellite and mitochondrial DNA analysis.

Very little is known about the mating system of sharks. Using both microsatellite and mitochondrial DNA (mtDNA) analysis, we will determine the genetic mating system of a population of lemon sharks, Negaprion brevirosttis, in Bimini, Bahamas. A genomic library for lemon sharks has been screened, and ten primer pairs have been developed for polymerase chain reaction (PCR) amplification. Over 400 fin samples from both juvenile and adult lemon sharks have been collected over the past four years from Bimini lagoon. PCR-amplification of microsatellite loci and mtDNA haplotyping will be used to genotype every sample. We propose to address the following questions: 1) How many adult females use the Bimini lagoon as a nursery? 2) What is the reproductive cycle of those females returning to Bimini? 3) What is the mating system of this population? Do single males sire an entire litter or does multiple paternity occur? Is there skewed male mating success? Is there inbreeding in the population?

Ferreira, Allison, R., Kohler, Nancy E.

 An assessment of fisheries impacting juvenile sandbar sharks (Carcharhinus plumbeus) in Delaware Bay: Implications for managing shark nursery habitat.

Data obtained from 3 fisheries databases and one gill net survey were used to assess the sources of fishing mortality on juvenile sandbar sharks in Delaware Bay, a primary nursery ground for this commercially important shark species. Recent commercial landings data (1990-1994) were used to identify the commercial fisheries likely impacting the population of juvenile sandbar sharks in Delaware Bay. The landings associated with the gear types used by the commercial fisheries operating in the region, and the overlap of these fisheries with the sandbar shark's nursery season (May through October) were used as the basis for this assessment. Recreational sandbar shark catch estimates for Delaware Bay (1990-1995) were used to assess sources of recreational mortality on this species. Additionally, tag and recapture data provided information regarding where recreational anglers have caught sandbar sharks from this region in recent years, and the size ranges that these anglers are catching. Finally, information from the aforementioned data sets was used to evaluate two management measures based upon their ability to reduce sources of recreational and commercial fishing mortality on sandbar sharks in Delaware Bay.

Ferry-Graham, Lara A.

 Feeding kinematics of newborn swellsharks, Cephaloscyllium ventriosum (Scyliorhinidae): the importance of predator size vs. predatory experience.

Survival past the newborn life-history stage depends on energy acquisition. Energy acquisition is determined by an organism's morphology and its use of that morphology, or behavior. Unfortunately, previous studies of newborn feeding behavior have been unable to separate changes in behavior caused by additional feeding experience from changes caused by morphological transitions (i.e., the larvae-juvenile transition). Swellsharks, Cephaloscyllium ventriosum, lack such morphological transitions and were thus chosen to investigate the importance of predatory experience in determining feeding behaviors. First-feeding sharks were filmed using high-speed video, and the resulting kinematic variables (used to describe and quantify behavior) contrasted with predatorily experienced one-year olds. Newborn prey captures were high-velocity, ram-dominated attacks while one-year-old prey captures had a suction component. Significant kinematic differences, however, do not appear responsible for shifting prey-capture mode. Timing differences between ages were not detected. a scaling analysis confirmed that swellsharks grow isometrically, thus changes in feeding behavior could not be attributed to ontogenetic morphological changes. This is further supported by a flow model which indicated that isometric increases in buccal volume do not require changes in prey-capture timing to negate a potential size effect; flow rates through the buccal cavity of sharks of both sizes are similar.

Fournier, Robert W., Morrissey, John F.

 The metabolic rate of two species of benthic elasmobranchs, nurse sharks and southern stingrays.

The metabolism of two benthic elasmobranchs was determined using a tunnel respirometer. At 20 C, the standard metabolic rate of the nurse shark, Ginglymostoma cirratum, was found to be 79.08 ± 16.7 mgO2/kg/hr and is the lowest value of oxygen consumption obtained for any shark to date. Its sedentary lifestyle continued even in the respirometer. The southern stingray, Dasyatis americana, was more active in the respirometer. Therefore, routine, rather than standard metabolism was determined to be 164.3 ± 8.9.0 mgO2/kg/hr at 20 C. This value is comparable to results from previous studies of batoids.

Gelsleichter, J., Grubbs, R. D., Musick. J. A.

 Morphology and histology of the reproductive tract of a hermaphroditic spiny dogfish, Squalus acanthias.

We report on the recent collection of a hermaphroditic spiny dogfish, Squalus acanthias. Externally, this individual appeared male and possessed well-developed siphon sacs and calcified claspers complete with accessory spurs. Internally, the animal possessed ovarian tissue containing pale ova of variable sizes. There was no evidence of nidamental glands, yet the anterior portions of the reproductive tract resembled oviducts in structure. These ducts led to enlarged, fluid-filled sacs which emptied into the urogenital papillae. Fluid obtained from both sacs was clear and did not appear to contain sperm. Additional observations on the histology of the reproductive organs are discussed. In addition, sexual differentiation and intersexuality in elasmobranchs are reviewed.

Gelsleicher, Jim, Musick, J. A.

 Hormonal regulation of proteoglycan synthesis in vertebral cartilage of the clearnose skate, Raja eganteria.

The role of insulin-like growth factor-I (IGF-I) in elasmobranch vertebral cartilage physiology was examined in vitro. Incorporation of 35S-sulfate into cultured vertebral cartilage from the clearnose skate, Raja eglanteria, was used to examine the hormonal regulation of vertebral proteoglycan synthesis. Addition of human recombinant IGF-I to the culture system significantly stimulated 35S-sulfate incorporation into vertebral cartilage, thus indicating enhanced synthesis of calcifiable proteoglycan growth and vertebral cartilage development which may be mediated through IGF-I. Furthermore, this study suggests a link between seasonal variations in somatic growth and vertebral calcification.

Gonzalez, Manoel M. B., Cunha, Carlo M. da

 Fish and cetacean mutilation by cookiecutter shark Isistius brasiliensis (Squaliformes: Squalidae) in São Paulo coast, southeastern Brazil.

Mutilation of fish and cetacean by cookiecutter shark, Isistius brasiliensis (Chondrichthyes, Squaliformes), was studied at the São Paulo coast, southeastern Brazil. Makaira nigricans andTetrapturus albidus (Istiophoridae), Thunnus thynnus (Scombridae), Epinephelus niveatus (Serranidae), Prionace glauca (Carcharhinidae), Megaptera novaeangliae (Balaenopteridae) were, in decreasing order, the fish mutilated with higher frequency. Shark attacks on fishes and cetaceans were directed mainly to the lateral region of prey 92's body. Although a secondary food item in the cookiecutter diet, fish and cetacean parts obtained by mutilation may be an important animal protein source to this shark. This sharks feeds crustaceans, gonostomatids, and other invertebrates. One of the possible consequences of the loss of body parts, were bacterial infection or invertebrate parasites.

Gottfried, Michael D., Fordyce, R. Ewan

 An associated specimen of Carcharodon angustidens (Chondrichthyes, Lamnidae) from the Oligocene of New Zealand.

Cenozoic sharks are represented in the fossil record by relatively abundant isolated teeth and occasional vertebral centra, but only very rarely by associated specimens. The giant lamnid sharks of the genus Carcharodon are no exception --- while a few associated tooth sets of fossil Carcharodon species have been collected, typically only single teeth are found. Recently an associated specimen of C. angustidens was recovered from the Late Oligocene of New Zealand's South Island. The specimen includes ca. 160 teeth associated with 34 anterior vertebral centra, all clearly from one individual. The full range of dental variation is preserved, including uppers and lowers and anterior through posterior tooth positions. These allow for an accurate reconstruction of the dentition in C. angustidens which is poorly known relative to the Mio-Pliocene species C. megalodon . Extrapolating from a regression relating tooth size to body length (TL) in living white sharks (C. carcharias, the specimen of C. angustidens had a TL of ca. 9m, significantly larger than living white sharks but well below the 16m maximum TL estimated for C. megalodon.

Grace, Mark A., Henwood, Terry

 Preliminary results of pilot studies to assess the distribution and abundance of coastal sharks in the U.S. gold of Mexico and western North Atlantic (1995 and 1996).

During 1995 and 1996, the National Marine Fisheries Service, Mississippi Laboratories, Southeast Fisheries Science Center, conducted pilot studies to develop survey methodology and a sampling strategy for assessment of coastal shark populations in the Gulf of Mexico and western North Atlantic. Longline gear similar to that used in the commercial shark fishery was deployed at randomly selected stations within 3 depth strata per 60 nautical mile grid from Browsnville, TX to Cape Ann, MA. The survey methodology and gear design used in these surveys proved effective for capturing many of the small and large coastal sharks regulated under the auspices of the 1993 Fisheries Management Plan for Sharks of the atlantic Ocean (NOAA 1993). Shark catch rates, species composition, and relative abundance documented in these pilot surveys were similar to those reported from observer programs monitoring commercial shark longlining activities (Branstetter 1996). During 78 survey days, 278 longline sets were completed with 879 sharks captured. Based upon the preliminary analyses, an index of relative abundance for shark management species can be obtained through fishery independent longline surveys.

Grogan, Eileen D.

 Description of the Chimaerid Jaw.

The definition of a chimaerid palatoquadrate has been extensively debated as it relateds to evolutionary analyses of jaw suspensoria and the interrelationships of Selachi, Holocephiali and particular Paleozoic fossil fishes. Embryological and adult analyses of the chimaerid cranium and jaw structure have been combined with comparative morphological studies of modern shark and select euchondrocephalan (autodiastylic paraselachian) crania. The dimensions of the palatoquadrate in modern chimaerids and related Paleozoic fishes are described. The caranial basitrabecular cartilage is described as a critical element in the plesiomorphous autodiastylic suspensorium and a structure which persists in chimerids today. Analyses of the extant and fossil data permit us to conclude that the primordial chondrichthyan palatoquadrate did not extend posteriorly to include an otic process. Rather, the posteriormost extent of this element is primitively found within or at the limits of the orbit; a region consistent with the basal connection and anterior limit of the common vertebrate basitrabecular element.

Grubbs, R. Dean, Musick, John A.

 Abundance and Age Composition of Juvenile Carcharhinus plumbeus in Chesapeake Bay and the Effects of a Directed Fishery.

Chesapeake Bay is a major western Atlantic nursery for Carcharhinus plumbeus, sandbar sharks. The primary nursery is located in the higher salinity, lower eastern portion of the bay. Recruitment of pregnant females and returning juveniles occurs in mid-May through June and the young remain in the bay until mid-September or early October. Virginia Institute of Marine Science (VIMS) longline data indicated that the abundance of juveniles in Chesapeake Bay increased substantially from 1990-1992 while the abundance of large coastal sharks in Virginia waters was the lowest since the survey began in 1974. Increased survivorship of younger age classes may explain the increased nursery abundance and is supported by a juvenescence trend in this population. Abundance in the nursery decreased in 1993 and 1994 but leveled off in 1995 concomitant with the reversal in juvenescence. In 1995 and 1996, a directed commercial gillnet fishery developed in Chesapeake Bay. More than 43,000 pounds of juvenile C. plumbeus were landed in 1996 in the primary nursery. The VIMS abundance index was the lowest ever and extreme juvenescence was observed. A large proportion of the nursery population likely was caught in 1996 stressing the need for protection of vital nursery areas for proper management of large coastal sharks.

Haenni, Eric G., Wourms, John P.

 Comparative morphology of the appendiculae, umbilical stalks, and placentae of sphyrnid sharks: Functional correlates.

Light and scanning electron microscopy of the placentae and yolk stalks of Sphyrna mokarran, Sphyrna lewini, and Sphyrna tiburo embryos reveals species-specific variations in structure. S. mokarran has an umbilical stalk devoid of appendiculae. Gestation appears to last 11-12 months. Term embryos measure 50-70 cm. Litters contain 13-42 pups. S. lewini has an umbilical stalk with many short branched, spatulate appendiculae. Gestation is postulated at 10-12 months. Term embryos measure 42-55cm. Litters contain 15-31 pups. S. tiburo has an umbilical stalk with many, elongate appendiculae. Gestation lasts 6-8 months. Term embryos measure 35-40 cm. Litters contain 4-16 pups. Several factors affect litter and embryo size, and length of gestation. There appears to be an inverse relationship between the size of term embryos and complexity of the umbilical stalk. There are also species-specific differences in placental size and morphology. Size of term embryos appears related to maternal size and length of gestation. Litter size within a species is usually a function of maternal size, whereas differences in litter size between species may reflect different reproductive strategies and allocation of resources. Length of gestation appears directly related to appendicular number and complexity, as well as other factors

Harkins, Heather K., Lowe, Christopher G., Holland, Kim N., Bush, Aaron

 Growth rates of juvenile scalloped hammerhead sharks Sphyrna lewini.

A tag and recapture study was conducted on juvenile scalloped hammerhead sharks in Kaneohe Bay, Hawaii. 503 sharks were caught using hook and line. All sharks were weighed, measured, sexed and tagged with nylon dart tags over a ten week period from 18 July to 21 August 1996 to determine neonatal growth rates. 63 sharks were recaptured during that period and subsequent months. CPUE over the tagging period was 0.05 sharks hook-1 hr-1. Time at liberty ranged from a few minutes to 145 days. Average growth was -0.03 cmd-1 and -2.50 gd-1. A measurement error test was conducted to determine measurement variability. Simultaneously, 10 shark pups were kept in a seawater pond. One group was fed once a day, while another group was fed once every 7 d. Pups fed every day grew faster over a 15-day period than those fed once every 7 d and those at liberty in the field over the same time period. Tagging seemed to have minimal effect on growth in the captive population. These results suggest that hammerhead shark pups in Kaneohe Bay grow slower than hammerhead shark populations in other locations.

Hazon, Neil, Tierney, Mary, Takei, Yoshio

 The role of the renin angiotensin system in elasmobranch fish.

Until the first elasmobranch angiotensin was isolated (Takei et al, 1993, J. Endocr., 138, 284-285) it was generally believed that the renin angiotensin system (RAS) evolved in primitive bony fish. Angiotensins (AI and AII) are highly conserved throughout vertebrates with amino acid substitutions in AII occurring at position 1 and 5. Elasmobranch angiotensins possess asparagine at position !, isoleucine at position 5 but usually have a proline residue at position 3 (Takei et al, 1993). To date most studies regarding the physiological role of RAS have been carried out in mammals where it plays a role in cardiovascular, renal and adrenocortical function as well as salt and water balance. Radioligand binding techniques have demonstrated specific receptor sits in gill cells, interrenal tissue and the unique elasmobranch salt secreting gland, the rectal gland. Using a blood pressure bioassay both dogfish AI and AII (0.001 -0.3nmol/kg) caused a dose dependent pressor response and captopril blocked the response to AI but not AII. Dogfish AII also stimulated corticosteroid release from the isolated dogfish interrenal gland and decreased secretion in an isolated perfused rectal gland preparation. These studies indicate a physiological role for dogfish AII in cardiovascular responses and fluid and electrolyte balance in elasmobranchs.

Hennigsen, Alan D.

 Observations of the reproductive biology of captive southern stingrays, Dasyatis americana.

Data were collected from 33 litters of captive born southern stingrays, Dasyatis americana, from five females between March, 1993 and January, 1997 at the National Aquarium in Baltimore (NAIB). Information from 124 pups (55 males, 69 females) was analyzed to yield results on sex ratios and size and weight at birth. Results will also be given on the gestation time in the captive population of southern stingrays at the NAB as well as the relation of maternal size versus litter size. In addition, qualitative observations were made on mating behavior following parturition.

Heupel, Michelle R., Bennett, Michael B., Simpfendorfer, Colin A.

 Analysis of tissue responses to dart and roto tagging in four shark species.

Samples of dermal and epidermal tissues of sharks were examined histologically to assess damage caused by tagging. Tissues from dart tag and roto tag sites were removed at intervals of between 100 min-284 days and 5-553 days post-tagging respectively. Samples showed acute and chronic responses to tagging. Acute responses in dart tag sites consisted of localised tissue breakdown and haemorrhaging which occurred soon after tagging. The intermediate response was apparent 10 hours post-tagging and was characterised by further haemorrhage and white blood cell movement into the area. Chronic responses observed in 10-284 day dart tagged samples showed fibrous tissue formation around the tag. This provided a continuous barrier between the internal and external milieu. Similar responses were observed in fin tagged specimens, but proceeded more slowly with an acute tissue response present at 5 days and intermediate response present at 20 days post-tagging. Chronic tissue response began at 301 days and was complete at 553 days post-tagging. No secondary infections of tag sites were observed. Tagging generally produced minor localised tissue disruption, but 2.0% of dart tagged specimens showed a more severe external response and fin tag reactions ranged from scale loss and sores to tissue overgrowth of the tag.

Hiruda Hisoka, Mori Tohru, Miyake Motohiro

 A study on collection, transportation and breeding of a Scalloped hammerhead Sphyrna lewini.

Marine World Umino-nakamichi celebrated our grand opening in April, 1995. Since then Marine World has been maintaining collection activities of various species of sharks and rays. Those species of hammerhead have peculiar flat-shaped heads, which are extended horizontally, are very attractive to spectators. In the sea off Japan, three species of hammerhead are seen. They are Scalloped hammerhead, Great hammerhead and Smooth hammerhead. Marine World ever performed two series of collection work in Kasasa Town, Kagoshima. Prefecture in April through June, 1995 and July through October, 1996 respectively. Scalloped hammerhead are generally strong in swimming and very sensitive to lack of oxygen. Their eyeballs, which are located at the both edges of hammer-shaped head, are easily damaged by various external factors. Marine World, therefore, has been keeping our full attention to those conditions. The display of Scalloped hammerheads to the public commenced with our large water tank (1400 ton) in November, 1996 and its condition has been well maintained as of now. We will report this time on the transportation and breeding of Scalloped hammerhead in Kasasa Town, Kagoshima, southern-most prefecture in Japan in July through October, 1996.

Holland, Kim N., Kajiura, Stephen M., Bush, Aaron, Wetherbee, Brad M., Lowe, Christopher G., Meyer, Carl

 Movement patterns of tiger sharks in Hawaiian waters.

Acoustic telemetry and traditional tag-and-capture methods were used to elucidate both the short and long-term movement patterns of tiger sharks (Galeocerdo cuvier) around the southern shoreline of Oahu, Hawaii. Acoustic telemetry consisted of both active tracking and the use of anchored data loggers to record the return of telemetered animals to the location where they were initially caught, tagged and released. Transmitters were either attached to the dorsal musculature with a small arrowhead barb or placed intraperitoneally. Eighty tiger sharks have been tagged at a recapture rate of 23%. Eight of the 15 sharks carrying long life transmitters have been electronically detected by stationary data loggers. Three sharks have been electronically detected in excess of one year from transmitter implantation. Tag-and-recapture and data logger information suggests that tiger sharks along the south shore of Oahu show long term site fidelity. In addition, active tracking indicates tiger sharks are capable of long distance movements over short time periods and that home ranges appear to be very large.

Hueter, Robert E.

 Philopatry, natal homing and localized stock depletion in sharks: strictly a hypothesis

Although philopatry, defined by Ernst Mayr (1963) as an animal's drive or tendency to return to its home area, birthplace or another adopted locality, is common among many groups of vertebrates and even invertebrates, it is not widely recognized in marine fishes, especially actively swimming species including sharks. Philopatry of sharks for their natal pupping areas wouId lead successive generations of a population to reproduce at the same geographic location, as opposed to selecting a set of environmental conditions that are not always in the same place, the latter strategy tending towards dispersal (Cury, 1994). Without complete life-cycle tagging data, sharks have been assumed to primarily follow the second strategy. For philopatry for natal areas to exist in sharks, a natal homing mechanism(s) must be at work, which is plausible given sharks' elaborate sensory systems. Natal homing or philopatry for other range components, such as juvenile habitats, seasonal feeding areas or mating areas, would make sharks vulnerable to localized stock depletion either through local overexploitation or habitat destruction. Historical examples of such localized stock depletions, tag-recapture data and population genetic data are all needed to test this hypothesis. Evidence from the first two data categories is accumulating; the slow mutation rate of elasmobranchs has been problematic in the search for genetic evidence.