California Department of Fish and Game, 245 W. Broadway, Suite 350, Long Beach, California 90802.
SEXUAL MATURITY AND FECUNDITY IN THE COMMON THRESHER SHARK (Alopias vulpinus) FROM SOUTHERN CALIFORNIA WATERS.
Common thresher sharks (Alopias vulpinis) 99 o, 108 +), including 18 pregnant females, were examined from southern California waters from October 1980 to November 1982. Through analysis of reproductive tissues, it was determined that males mature at a total length (TL) of 330 cm and females mature close to 390 cm TL. Pregnant females typically were found to carry four embryos. Gestation lasts approximately 9 months beginning around October. Pups are born between April and June. At birth pups are approximately 150 cm (TL). The presence of yolk-containing egg capsules in the uteri and the discovery of large quantities of yolk and fragments of the capsules in the stomachs of embryos supply the first direct evidence of oophagy in this species. Differences in size at maturity and the number of embryos carried between common thresher sharks caught off southern California and those reported in the literature from the equatorial central Pacific and Indian Oceans suggests separate stocks.
Department of Zoology, The University of British Columbia, Vancouver, B.C., V6T 2A9 Canada
SPATIAL DISTRIBUTION OF PARASITIC COPEPODS ON GILLS OF THE BLUE SHARK.
The spatial distribution of 1913 Kroyeria carchariaegluuci on gills of blue sharks was analyzed. The number of copepods per shark was positively related to gill surface area and host size. Copepod burdens ranged from 116 to 1250 individuals per shark. Copepods were evenly distributed among hemibranchs. Females typically attached within the middle 40 per-cent of each hemibranch. Males were relatively more evenly dispersed. Eighty percent of all copepods attached to secondary lamellae; the remainder were in the underlying excurrent water channels. Most copepods were located between 10 and 25 mm along the lengths of gill filaments. Overall, the distribution of copepods was quite specific in all study planes. Various aspects of copepod distribution can be explained in terms of selective pressures, however, it is possible that the distribution pattern is phylogenetically determined and may have little to do with contemporary selective constraints.
I.N.P. Centro Regional de lnvestigacion Pesquera de Yucalpeten, A.P. #73, Progreso, Yuc. 97320, Mexico.
THE SHARK FISHERY OF YUCATAN, MEXICO: AN INTRODUCTION AND PRELIMINARY RESULTS.
Almost nothing is known about the shark populations subjected to commercial fishing in Mexican waters. As an effort to determine the best criteria to optimize exploitation of the shark fishery of Yucatan, a study concerning shark populations and the associated commercial fishing activities began in August of 1984. An overview including objectives and methodologies used is given. The first part of the study was to determine which species are present in the commercial catches, their relative importance, meristics, and population structure. To January 1987, 2305 sharks representing 25 different species have been recorded. The Carcharhinidae is the most important family in terms of the number of species and individuals captured, although some members of Sphyrnidae and Triakidae are also important in the catches. Length frequencies of the most important species are given as well as the numerical relationships for different lengths and between weight and length.
P.0. Box 2193, College Station, TX 77841, USA.
EARLY LIFE HISTORY STRATEGIES OF CARCHARHINOID AND LAMNOID SHARKS IN THE GULF OF MEXICO: A REVIEW.
The size of most newborn sharks makes them susceptible to predation from their own kind and other large fishes. In the Gulf of Mexico, juvenile nursery grounds can be generally classified as to whether or not the young are exposed to such predation. Several related factors – number of young produced, breeding frequency, size at birth, early growth rate – are counterbalanced to offset early natural mortality. The counterbalancing of factors that occurs for each species results in several different early life history strategies. These range from the production of only 1 or 2 large young every 2-3 years, to the production of numerous small young each year. Combined with this, growth rates vary for each species; K values have been estimated to range from 0.05 to 0.50 for various sharks. These different strategies are discussed and compared.
Woods Hole Oceanographic Institution, Woods Hole , MA. 02543 USA.
TRACKING BLUE SHARKS IN COURSE AND DEPTH.
Acoustic transmitters were attached to 20 blue sharks, Prionace glauca, which were followed for periods of one day or more. The sharks swim up and down between the surface and depths of 200-400 m in regular oscillations with a period of 1-4 hours. They readily pass through the thermocline and experience large changes in body temperature. This motion was typical of sharks in deep water but was not seen in 5 trials with sharks on the continental shelf. There may be a seasonal component to the activity as it occurred in all sharks during late summer, fall and winter but not in 4 trials during late spring and early summer. The average depth was usually shallower and the vertical movements smaller in amplitude at night than during the day. On the continental shelf the sharks moved about on an irregular course within a small area, but in deep water they maintained fairly constant headings and speed both day and night as they moved in a general offshore direction.
Dept. of Biology, Albion College, Albion, Ml. 49224 USA.
CONTRIBUTIONS TO THE BIOLOGY OF THE NURSE SHARK(Ginglymostoma cirratum BONNATERRE): GROWTH, MOVEMENT AND ECTOPARASITES.
Nurse sharks from a 2 mi2 shallow bay on Big Pine Key in the Florida Keys have been followed through a tagging study. In excess of 150 animals have been tagged, ranging in size from 10.7 cm (TL) to 180 cm (TL); 24.8% have been recaptured once with an average at-large time of 255 days; 6.0% have been recaptured two or more times with an average at-large time of 511 days. The greatest distance moved between tagging and recapture was 1 mile. Growth rates calculated from recapture measurements predict an annual growth of 9.93 +/- 4.54 cm/yr and 2.71 +/- 0.95 kg/yr. Tracking with ultrasonic telemetry suggests a correlation between tidal cycles and daily movements. Seasonal movement shows an additional correlation with water temperature. Most animals captured between May of 1986 and March of 1987, including lemon sharks (Negaprion brevirostris Poey) were infected with leeches (Stibarobdella macrothela Schmarda, 1861). Additionally, isopods(Rocinela aries Schioedte & Meinert) have been taken from two G. cirratum and one N. brevirostris.
NOAA/NMFS/NEFC, Narragansett Laboratory, Narragansett, RI 02882 USA.
FIRST RECORD OF THE GULPER SHARK, Centrophorus granulosus(BLOCH AND SCHNEIDER, 1801), OFF THE NORTHEASTERN UNITED STATES.
On March 5,1987, three gulper sharks (Centrophorus granulosus) were caught by theF/V Audrey Lynn near Norfolk Canyon (37° 06’N), 74° 40’W). The vessel was bottom longlining for tilefish (Lopholatilus chamaeleontieps) in depths of 300 to 600 meters (m). Two of the specimens, estimated to be 26 kg, were not retained. The third was a 145 cm (TL) immature female weighing 19 kg; its stomach was empty. Previous reports of C. granulosus from U.S. waters are limited to two trawl caught specimens; one taken off the coast of Louisiana at 380 m, the other taken off the coast of Georgia at 320 m. C. granulosus has also been reported from Cuba, the West Indies and Surinam. The C. granulosus specimens taken in Norfolk Canyon represent the first record of this species in northeastern U.S. waters and a northern extension of its range in the western Atlantic of approximately 400 miles. C. granulosus may prove to be much more common than current records indicate. An explanation for its apparent rarity is that it occupies depth zones that lie beyond traditional fishing grounds. The morphology and distribution of C. granulosus is discussed and compared to other members of the genus Centrophorus.
Department of Biological Sciences, Clemson University, Clemson, South Carolina 29631 USA
THE BIOLOGY OF THE SMALLEYE HAMMERHEAD (Sphyrna tudes) OFF TRINIDAD.
The smalleye hammerhead is a poorly known species that inhabits the northeastern coast of South America from Venezuela to Uruguay. It is found in coastal waters at depths of 5-20 fathoms over muddy bottoms. It is a small species; most adults are about 970 mm in total length and weigh 400 g, although exceptional females may reach 1200 mm TL and 9100 g. The most unusual characteristic of the species is its striking bright orange or yellow color. Immatures are bright orange while adults are yellow. Their coloration is apparently due to pigments present in the diet; immatures feed primarily on shrimp, while adults feed on fish and catfish eggs. Characterization of the pigments is being carried out. Males reach sexual maturity at about 800 mm TL; females mature at about 980 mm TL. Ovulation and mating occur in August. Gestation lasts eight or nine months. Parturition occurs in shallow waters from late March to late May. Litters consist of 8-10 pups that measure 300 mm TL at birth.
Department of Zoology, University of Maryland, College Park, Maryland 20742 USA.
OBSERVATIONS ON SIXGILL SHARKS, Hexanchus griseus AND H. vitulus,FROM SUBMERSIBLES.
Deep water sharks were lured to fish baits placed in front of stationary, quiet and darkened submersibles used as blinds. Halogen and strobe lights were turned on only for quick scans and photography. Dim green thallium iodide and Cyalume chemical stick lights were used at other times. We used the PISCES VI submersible at 610 m off Bermuda and the PC-1802at 305 m off Grand Cayman. The largest sharks attracted were Hexanchus griseus, about 240 to 360 cm TL, and one mature male H. vitulus about 150 cm TL. Markings and color variations enabled identification of some individuals that returned repeatedly. Smaller sharks, Mustelus sp., Centrophorus uyato, morays, conger eels, gempylids, epigonids, and other teleosts and invertebrates also came in during 4 to 12-hour dives with the submersible settled on a ledge of the steep continental slope. Most of the fish left within half a minute after halogen lights were turned on.
RSMAS, Universify of Miami, Miami, Florida 33149 USA.
FOOD, FEEDING HABITS AND FIRST ESTIMATES OF DAILY RATION OF YOUNG LEMON SHARKS, Negaprion brevirostris (POEY).
Two analyses of the diet of the lemon shark were conducted. In the first, 78 stomachs of specimens caught in the Florida Keys and at Bimini, Bahamas, from 1981 to 1985 were examined; in the second, 86 stomachs of lemon sharks collected from the Florida Keys during the summer of 1986 were examined. In both, teleosts were the most important food followed by crustaceans and molluscs. In the second study 22.6% of the stomachs were empty. Weight of stomach contents of males and females did not differ significantly. Analysis of number of items per stomach, stage of digestion, weight of stomach contents and feeding periodicity indicated that feeding is asynchronous and intermittent, and that meals are generally consumed after an interval of 32 h or longer. No diel pattern in feeding activity was found. Six models were applied to estimate daily ration. One of these involved laboratory experiments in which a relation was established between daily ration and gross production efficiency (K1). First estimates place the daily ration for the young lemon shark close to 2% BW. An overall model of feeding for this shark is presented. Supported by NSF-OCE 8601146 to SHG.
Neurobiology Dept., N.E. Ohio U., College of Med., Rootstown, OH 44272 and Neurobiology Unit, Scripps Inst. of Oceanography and Neurosciences Dept. A-001, UCSD, La Jolla, CA 92093 USA.
ELASMOBRANCH SUPRASPINAL PATHWAYS: A COMPARISON BETWEEN A SHARK, Heterodontusfrancisci, AND A RAY, Platyrhinoidis triseriata.
Cruce and Newman (84 Amer. Zool. 24:733-753) hypothesized that the reticulospinal nuclei of non-mammals exhibit a level of complexity comparable to that of mammals. This hypothesis emerged from work in reptiles and should be tested in representatives of other vertebrate classes. Previous studies in elasmobranchs (e.g. a shark, Scyliorhinus, Smeets and Timerick, 81, J. Comp. Neurol. 202:473-491) only distinguished the three classical reticular subdivisions (superior, middle and inferior). Therefore, we investigated two distinctly different elasmobranchs, the horned shark and the thornback guitarfish, using the retrograde transport of horseradish peroxidase and fluorogold injected into the spinal cord, We recognized mammalian homologies in spinal projecting nuclei and indicated these homologies by adopting the mammalian names, particularly for reticular nuclei (using those of Newman, 85, J. Hirnfsch. 26:187-226, 385-418). The results in the two elasmobranchs are similar and comparable to the mammalian level of organization, including the presence of a rubrospinal pathway in a shark as well as a ray.
University of Miami, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Cswy., Miami, FL 33149 USA.
LIFE HISTORY STRATEGIES OF SHARKS: THEORY AND PRACTICE.
The concept of Life History Theory is reviewed as background to the seminar on life history of the elasmobranchs. The elements of life history, i.e., the organism’s lifetime pattern of growth, differentiation storage, behavior and especially reproduction are listed and discussed. The significance of life history patterns in evolution ecology and fisheries science is given. Arguments are put forward showing that life history patterns are subject to evolutionary pressure just as are physiological mechanisms or anatomical structures; and that successful life history patterns increase overall fitness that in turn tends to produce optimal life histories within the constraints of the species. The theory of r and K selection is discussed and life history strategies are related to density-dependent selection. Finally, the relation between life history patterns and the abundance of fish stocks is discussed. The review concludes with a description of the life history of a carcharhinid shark. Experimental-techniques are shown and data given on growth, age validation, age at first reproduction, resource (food) partitioning, metabolic rates and other factors defining the life history strategy of the lemon shark, Negaprion brevirostris. Supported by NSF OCE 86-01146.
University of South Florida, Department of Marine Science, St. Petersburg, Florida 33701 USA.
REPRODUCTIVE BIOLOGY, AGE, AND GROWTH OF THE BLACKTIP SHARK, Carcharhinus limbatus NEAR TAMPA BAY, FLORIDA.
Reproduction, age, and growth of the blacktip shark was investigated in the Tampa Bay area during 1984-1986. Two hundred and twelve blacktips were captured, 129 females, and 83 males. Maturity of females occurs at 158-162 cm TL, and was determined by observations in ovarian egg diameter and uterine breadth. Rapid development and elongation of claspers and siphon sacs indicated males mature at 133-136 cm TL. Mating occurs during June and July, and gestation lasts l0-11 months. Catch per unit effort is closely correlated with water temperature. Length-frequency analysis reveals 3 distinct size classes for blacktips < 120 cm TL. Age of blacktips was estimated from 134 vertebral centra. Minimum and maximum number of rings was 0 and 11. Marginal increment analysis indicated ring deposition occurs during December-February. Growth rates for blacktips age 0 and 1 is 21 and 19 cm TL/year, respectively. Age at maturity is 6-7 years for females and 4-5 years for males. Von Bertalanffy growth parameters were estimated.
>University of Maryland, College Park, Maryland, USA.
UREA HYDROLYSIS BY BACTERIA IN THE LIVER OF CARCHARHINID SHARKS.
The blood and liver of two carcharhinid shark species, Galeocerdo cuvieri andNegaprion brevirostris, were examined for bacterial ureolytic activity using a 14C-urea tracer method. Fresh tissue homogenates were incubated with trace quantities of 14C-urea, and 14CO2 evolution was measured over 48 hours as an indicator of urea hydrolysis. There was no ureolytic activity in the blood of either species, while significant urea hydrolysis was consistently detected in liver homogenates. It was found that liver ureolytic activity could be eliminated by the addition of either of two antibiotics, ampicillin or the vibriostatic agent 0/129, indicating that bacteria alone are responsible for this activity. These findings, in conjunction with consistent isolation of ureolytic bacteria from shark tissues and observation of bacteria within liver macrophages, provide evidence of a regulatory role for bacteria in shark urea metabolism.
College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331 USA.
PRELIMINARY TESTING OF SEVERAL DRUG REGIMENS FOR TRANSPORT OF HAMMERHEAD SHARKS (Sphryna lewini).
A series of trials was run in which hammerhead sharks (Sphryna lewini) were subjected to varying treatments prior to simulated transport. All regimens were unsuccessful in prolonging viability during transport beyond 5 hours. This paper reports the effects of common veterinary drugs in hammerheads, and offers suggestions for further study and applications.
UC Santa Cruz, CA 95064 and Steinhart Aquarium, San Francisco, CA 94118 USA.
CRATER WOUNDS ON NORTHERN ELEPHANT SEALS: THE COOKIECUTTER SHARK STRIKES AGAIN.
While examining northern elephant seals, Mirounga angustirostris, on and near Isla del Guadalupe, we discovered wounds that appeared to be caused by cookiecutter sharks,Isistius sp. The range of I. brasiliensis, the likely culprit, is extended within the eastern Pacific, based on SIO specimens. Several hypotheses are presented to explain the seal/shark interactions. Extensive historical seal census data since 1971 indicate thatMirounga/lsistius interactions in northern California were first observed in 1986.
Adelphi University, Garden City, NY 11530 USA.
INTERRELATIONSHIPS OF THE CHONDRICHTHYES
The relationships of the subclasses Holocephali and Elasmobranchii to each other and their cladistic relationships within the class are explored on the basis of several new taxa from the Bear Gulch Limestone Mississippian. Both subclasses are monophyletic sister groups constituting the Euchondrichthyes. The Paraselachii are a monophyletic assemblage containing the Orodontiformes and derivative Edestiformes, the Petalodontiformes and a new sister order; this is considered a sister taxon to the Holocephalimorpha. The Holocephalimorpha consist of the Helodontiformes, Psephodontidae, Cochliodontiformes and Chimaeriformes. Some undescribed taxa and the Iniopterygii are considered the primitive sister group of the Paraselachii, while Diademodus and the Cladodontida +Cladoselache are plesiomorphous to the Euchondrichthyes
Southeastern Massachusetts University, North Dartmouth, MA 02747 USA.
MORPHOLOGY OF THE ELECTRIC ORGAN IN THE LITTLE SKATE, Raja erinacea, AND WINTER SKATE, Raja ocellata.
Size and composition of the electric organs in two Western North Atlantic skates, Raja erinacea, and Raja ocellata were studied. Organ weight, length, and electroplaque composition were correlated with size, body weight, and sex on 25 skates of each species.
University of Miami, Miami, FL 33149 and California State University at Long Beach, Long Beach, CA 90840, USA.
PATTERNS OF ACTIVITY AND SPACE UTILIZATION OF THE LEMON SHARK (Negaprion brevirostris): A PROGRESS REPORT OF A NEW APPROACH.
An automated, bottom-mounted ultrasonic receiver system has been designed, constructed, and is being tested to examine the activity patterns of lemon sharks, Negaprion brevirostris. In a preliminary manual tracking study, nine sharks were tracked intermittently for periods ranging from 1 to 113 h. Two sharks had areal activity spaces of 18 km2 and 93 km2, and seven sharks exhibited a diel east/west shift of their activity space. The telemetered swimming speeds of two sharks was greatest at dawn and dusk. This work has been previously reported at ASIH. The new automated system will remove the observer from the data collection phase of this study and will eliminate several drawbacks inherent in manual tracking studies. Initial problems include leakage, short transmitter life, ‘aliasing’, and signal interference. One tiger shark, Galeocerdo cuvieri, and two lemon sharks have been monitored successfully with the DLM’s in the field for periods ranging from 1 to 27 h. This work was supported by NSF OCE 86-01146 to SHG.
Virginia Institute of Marine Science, School of Marine Science, The College of William and Mary, Gloucester Point, VA 23062 USA.
ENERGY LIMITATION AND THE BATHYMETRIC LIMITS OF SHARK DISTRIBUTION IN THE DEEP SEA – AN HYPOTHESIS.
Energy availability to demersal communities decreases exponentially with distance away from continental land masses and with depth. These patterns are a direct reflection of surface productivity. Because of entropy, the highest trophic levels in demersal communities reflect limitation by energy availability closer to the continental margins at more shallow depths than the lower trophic levels. Squaloid and hexanchoid sharks usually occupy the highest trophic position in bathyal fish communities. Probably because of energy limitations, viable populations of these groups cannot be supported much beyond the continental slopes (2000-2500 m) (other than occasional individual strays). As a corollary, shark populations may occur deeper where productivity is higher.
Graduate School of Oceanography, University of Rhode Island, Narrangansett, Rhode Island, 02881 and Moss Landing Marine Laboratories, PO. Box 450, Moss Landing, California 95039 USA.
VERTEBRAL GROWTH ZONE DEPOSITION IN ANGEL SHARKS: AN ENIGMA.
Vertebrate and body size measurements were taken from 334 angel sharks collected from commercial gill netters off Santa Barbara, California from September 1979 to November 1983. Radiographs of centra from 247 of these were studied to delineate calcified bands for age determination. Our smallest newborn sharks (260 mm TL) had 6 or 7 bands while the largest (1140 mm TL) had 42. Bands do not appear to be deposited annually. Rather we propose that band deposition is more closely related to somatic growth than to monthly or yearly time periods. This hypothesis is supported by the number of bands in embryos and newborn angel sharks, allometric growth patterns of girth and weight measurements and vertebral centrum dimensions, labortory grow-out studies including 3 angel sharks which deposited bands subsequent to tetracycline injection, field growth evidence from 6 tag-returns which had been marked with tetracycline, and radiometric age estimates using Lead -210 decay rates in centra of 2 adult angel sharks.
Department of Marine Science, University of South Florida at St. Petersburg, St. Petersburg, Florida 33701, USA.
ENERGY BUDGET OF THE BONNETHEAD SHARK, Sphyrna tiburo.
The general energy budget equation (C = P + M + E), where C = consumption, P = production, M = metabolism and E = excretory products, was used as the basis for examining the life history of the bonnethead shark, Sphyrna tiburo. Animals held in captivity at the Sea World Marine Science and Conservation Center and wild-caught animals from Tampa Bay and the Florida Keys were used for the study. Consumption (C) was measured for animals held in captivity and estimated for wild-caught animals. Examination of growth rates in captivity, the construction of growth curves based on validated vertebral ring ages and the determination of reproductive output provided the necessary estimates of production (P). The design and application of a new type of respirometer for use with large active fish species allowed an estimate of metabolism (M). Measurements of swimming velocities and daily activity patterns allowed an estimate of the energy consumed during routine activity. Geographic differences in life history characteristics between the Tampa Bay and Florida Keys populations were noted.
NOAA/NMFS/NEFC, Narragansett Laboratory, Narragansett, RI 02882 USA.
REPRODUCTION IN THE MALE WHITE SHARK (Carcharodon carcharias).
Thirty-eight white sharks landed at tournaments and on research cruises in the Mid-Atlantic Bight, (MOB), between June 1971 and August 1986 were dissected for reproductive information. Twenty-seven males ranging in size from 117 cm to 493 cm fork length (fl) (16 to 1,568 kg) contributed information toward understanding maturity, organ structure, function and fecundity. The reproductive anatomy is typical of lamnoids thus far examined. Paired radial testes deliver spermatozoa to highly coiled, glandular epididymides. The ductus deferens is a large relatively straight storage organ lined with septa and usually filled with spermatophores in the adult. Claspers are robust, each bearing a retractile straight spur. Sexual maturity occurs between 240 cm and 280 cm fl. Although the four large males dissected had ductus deferens turgid with spermatophores, no direct evidence of mating could be ascertained from ductus or clasper condition. Circumstantial evidence is presented that suggests that the MOB may be a mating area for the white shark.
Biology Department, Bucknell University, Lewisburg, PA 17837 USA.
DEPTH-RELATED MODIFICATIONS OF THE ELECTRORECEPTIVE SYSTEM OF THE EURYBATHIC SKATE, Raja radiata (CHONDRICHTHYES: RAJIDAE).
The peripheral component of the electroreceptive system (the ampullae of Lorenzini) in theeurybathic skate, Raja radiata, is similar in general arrangement to that previously described in other species. The majority of the pores are located on the ventrum, with the mouth situated at the geometric center. The ampullae are restricted to four bilaterally located connective tissue capsules, and each exhibits an ontogenetically constant number of alveoli. The gross structure of individual ampullae shows considerable variation, with the number of alveoli and the overall ampulla size increasing with depth, particularly in those anatomical areas most closely associated with the feeding strike. It is suggested that these differences represent intraspecific modifications for enhanced electroreceptive sensitivity that correlate with bathymetric variation in the prey-depauperate deep-sea.
National Aquarium in Baltimore, 502 East Pratt Street, Baltimore, MD 21202 USA.
HUSBANDRY TECHNIQUES WITH CAPTIVE ELASMOBRANCHS IN THE NATIONAL AQUARIUM IN BALTIMORE, 1986-87.
Various techniques that are employed in the husbandry of 20 sharks (4 species), 2 sawfish, and 3 rays, in The National Aquarium in Baltimore, have been recorded on videotape for educational purposes.
Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
MINIMUM AND SUSTAINED SWIMMING SPEEDS OF BLUE SHARKS(Prionace glauca): HYDRODYNAMIC CONSIDERATIONS.
Acoustic transmitters were used to obtain values for both minimum and sustained swimming speeds of blue sharks (Prionace glauca). Speed was recorded from three sharks, ranging in size from 220-270 cm FL, for periods of 2-3 days. The sharks exhibited fairly constant sustained speeds of 50-60 cm/s (approximately 0.22 body lengths/s). This value is lower than the theoretical optimum swimming speed predicted for fish of this size. The minimum observed swimming speed required to maintain hydrostatic equilibrium was 35-40 cm/s. This value, coupled with estimates of body weight, density, and fin area, yields a calculated lift coefficient of approximately 1.5 for the pectoral fins. Large fins and reduced density result in relatively lower fin loading and lower minimum speeds than found in some other negatively buoyant fish. It appears that, for the blue shark, hydrodynamic lift production is not the dominant factor determining cruising speed.
Department of Biological Sciences, Univ. Central Florida, Orlando, FL 32816 USA
AGE AND GROWTH IN THE ATLANTIC STINGRAY, Dasyatis sabina, IN A FLORIDA COASTAL LAGOON SYSTEM.
Size-at-age and growth rates are being studied in the Atlantic stingray, Dasyatis sabina,from the Indian River lagoon system in east central Florida. Age determination using vertebral centrum size and edge characteristics, growth zones in the centrum, and tetracycline marking are currently underway. Growth rates were estimated from lab housed pups and adults, and will be estimated for tag and recapture animals. Centrum diameter shows a positive linear relationship with disc width, r-square = .98. Preliminary results indicate pups grow from 2 to 8 mm disc width per month. Adults held captive for 6 and 12 months did not increase appreciably in disc width. Rapid growth in the first year followed by very slow adult growth would explain the observed size-frequency distribution.
NOAA/NMFS/NEFC, Narragansett Laboratory, Rhode Island 02882-l 199 USA.
GROWTH VERIFICATION FOR THE BLUE SHARK (Prionace glauca) FROM THE OBJECTIVE INTERPRETATION OF LENGTH-FREQUENCY DATA .
Since age and growth validation is difficult and often lacking for large migratory elasmobranchs, many studies rely on length-frequency analyses to define and/or verify growth estimates. Traditionally, such analyses involve the visual inspection of length-frequency modes resulting in subjective interpretations of the data. To overcome such bias, the more objective length-frequency analyses of Brey and Pauly (1986) and Shepherd (1986) were applied to blue shark (Prionace glauca) size data to derive von Bertalanffy growth parameters. The data set consisted of 3,357 male blue shark observations obtained in the western North Atlantic, pooled by month of capture and grouped into 10 cm intervals. Estimates of L , K, and to from the Brey and Pauly and Shepherd methods are 367 cm, Fl, 0.13, -0.89 and 313 cm Fl, 0.16, -0.85, respectively. The latter are realistic and comparable to previously reported growth estimates, whereas intrinsic problems associated with the Brey and Pauly method result in the biased overestimate of L.
Dept. Biological Sciences, U. Central Florida, Orlando, FL 32816, USA.
LIFE HISTORY OF THE STINGRAY Dasyatis sayi IN FLORIDA COASTAL LAGOONS
Dasyutis sayi is one of three stingray species inhabiting the brackish Indian River Lagoon system on the central east coast of Florida. It is the most common elasmobranch in the lagoons and is a year-round resident. We handled over 2400 specimens from the Cape Canaveral area between July 1975 and January 1978. Catch-per-unit-effort (CPUE) generally peaked in the spring and fall and was depressed in winter. CPUE was usually significantly higher at night, indicating greater activity during darkness. The species was consistently most abundant in Mosquito Lagoon, the most saline section of the study area. Females reached a size of 73 cm DW and 21 kg; males reached 52 cm and 7 kg. Females matured between 50-54 cm DW and males between 30-35 cm. The reproductive cycle was significantly different from that of the sympatric D. sabina. Ovarian egg size and male GSI both peaked in May, indicating that mating occurred in spring. Uterine eggs were present from June through the following March but no embryonic development was evident. Fetal development began in early April and parturition occurred in middle to late May, coincident with ovulation. There were l-6 young in a brood and neonates were 15-17 cm DW at birth.
Dept. of Biology, California State University, Long Beach, CA 90840 USA.
BEHAVIORAL ECOLOGY OF THE HORN SHARK, Heterodontus francisci,WITH EMPHASIS ON SPACE UTILIZATION PATTERNS: A PRELIMINARY REPORT.
Twelve horn sharks were telemetered via surgically implanted transmitters at Santa Catalina Island, California. Thirty all-night trackings as well as bidaily position fixes were obtained during July and August, 1986. Unique to this study were the capabilities (1) to obtain diel positional data from a sample shark population on a very regular basis and (2) to follow the sharks by rowing, thus reducing artifacts in the movements due to engine noise. At dusk adults generally moved onto the main reef from deeper day-time refuges and, with the approach of dawn, descended steadily to the previous refuge area. Juveniles refuged at shallower depths on the reef or near the island. Night-time activity spaces were significantly larger than those for day-time. Based on the telemetry and over 250 conventional taggings, I will also review results to date on feeding, reproduction and habitat preferences as well as the impact on implantation surgery.
Biology Dept., Bucknell University, Lewisburg, PA 17837 USA.
COMMENTS ON THE FUNCTIONAL MORPHOLOGY OF PLACOID SCALES FROM BENTHIC AND/OR SEDENTARY SHARKS.
The gross structure of placoid scales from 42 species (19 genera) of benthic and/or sedentary sharks were examined in an attempt to define the parameters associated with scales primarily functioning in a protective capacity. In contrast with the scales from fast swimming pelagic sharks, scales from sedentary benthic species are generally larger and heavier while covering a smaller percentage of the integument. Taking natural histories into account, a relationship appears to exist beween scale weights, surface areas, crown morphologies and swimming activity. As swimming activity increases, there is a transition from relatively large, heavy scales with no crown ridging and low densities to small, light weight scales with crown ridging and present on the integument at higher densities. This relationship probably represents a functional transition from primarily protective scales to scales whose function is a balance between protection and drag reduction.
Monterey Bay Aquarium, 886 Cannery Row, Monterey, CA 93940 USA.
FEEDING AND GROWTH. OF CAPTIVE ADULT AND JUVENILE SEVEN-GILL SHARKS, Notorhynchus cepedianus.
Three adult and three juvenile seven-gill sharks held in a semi-open marine aquarium system consume approximately 5% and 20% of their body weight in food per month respectively. Food consumption may vary due to size of a previous meal and/or water temperature. Captive growth rates are compared to available information on natural growth rates. Over the past 20 months, juveniles have increased 40% to 50% in weight and 12% to 20% in total length. In addition, feeding and growth rate is reported for a recently captured six-gill shark, Hexanchus griseum
Moss Landing Marine Laboratories, PO. Box 450, Moss Landing, California 95039 USA.
AGE AND GROWTH OF THE GRAY SMOOTHHOUND, Mustelus californicusAND THE BROWN SMOOTHHOUND, M. henlei FROM CENTRAL CALIFORNIA.
Growth bands from x-radiographs of vertebral centra of 58 gray and 71 brown smoothhound sharks from central California between 1978 and 1985 were used to determine age composition, age at first reproduction, and growth rates. Total lengths and centrum widths were significant and linear. M. californicus ranged between 235 mm and 1250 mm TL, and were aged from 0 and 9. M. henlei ranged between 257 mm and 1000 mm TL (50 mm over the record) and were aged from 0 and 13. Age at first reproduction for both species was between 2-3 years. Von Bertalanffy and back-calculated growth curves were similar and asymptotic lengths of females of both species were greater than males. Edge analysis of the centrum clearly demonstrated annual periodicity of growth bands for M. californicus but M. henlei proved more difficult. These 2 California species of Mustelus have growth characteristics similar to those of other species of Mustelusreported.