1986 AES Annual Meeting Abstracts

Keynote Address – Shark Aggresssion Against Man: a position paper

Four decades of research, supported primarily by the United States Navy, have provided an enlightened beginning to the understanding of shark aggression against man. The incidence of reported serious attack is surprisingly low, and the resulting wounds are most often survived. Attackers represent the full size range of sharks in general, with a median length only slightly greater than the height of a moderately tall man. Attack can occur anywhere and at anytime that a man and a shark are likely to meet. Most reported attacks are single-event encounters; i.e., one strike by a solitary shark resulting in one wound or set of wounds. The shark’s arsenal for doing violence includes teeth for grasping and cutting, scaled hide for abrading, and momentum for forcing. Ferocities range from almost gentle inflictions of gash-type wounds to the extreme violence of a frenzied attack. Shark behavior and wound characteristics convincingly suggest a high percentage of reported attacks against man are not determined attempts by the sharks to devour their victims. Continuing efforts to develop antishark measures should thus give much greater consideration to overcoming motivating forces for aggression other than the feeding drive. Individual protection by use of chemica1 repellent packets appears inherently impractical.

ATP and GTP in red cells of Mustelus canis and Squalus acanthias

Red cells from many species of fishes have all showed high concentrations of ATP (1-6 mM), but variable GTP. Unlike any other vertebrate, certain fishes contain pools of GTP in their red cells as large or larger than ATP. GTP may play an important role in oxygen transport in these fishes by modifying the oxygen affinity of hemoglobin. Red cells of two dogfish sharks, Mustelus canis and Squalus acanthias were compared. Mustelus had a high content of red cell GTP, while that of Squalus in striking contrast was very low. There was little difference between the two fishes in the concentration of ATP in red cells of embryos, newborns and adults. In Mustelus, GTP was absent in red cells of embryos, at a low level in the newborn and at the adult level a few days after birth. Incubation of red cells of adult Mustelus for a few moments with P32-labeled inorganic phosphate gave equal concentrations of radioactivity in ATP and GTP showing that the pools of the two nucleotides were in rapid equilibrium.

Elasmobranch evolution inferred from phylogenetic analysis of parasites

The family Microbothriidae Price, 1936 consists of seven genera of monogenetic trematodes all parasitic on elasmobranchs. Phylogenetic analysis of the Microbothriidae resulted in a cladogram for these parasites which was congruent with the presumed phylogeny of their elasmobranch hosts. Specifically, the Microbothriidae appears to have long ago diverged along two major evolutionary lines, each seemingly having arisen on more primitive elasmobranchs and hence having coevolved with more derived taxa. This and similar studies with ectoparasitic copepods and endoparasitic tapeworms indicate that phylogenetic analyses of chondrichthyan parasites can assist in unravelling the somewhat problematic evolutionary history of these interesting fishes.

Age and growth estimates of the Bull Shark, Carcharhinus leucas, in the Northern Gulf of Mexico

Length-at-age and growth rates for 96 bull sharks, Carcharhinus leucas, collected from the northern Gulf of Mexico were estimated from the band patterns formed seasonally in the vertebral centra. The data were applied to a von Bertalanffy growth model producing parameter estimates of L° = 285 cm TL, K = .076, and to = -2.97 yr, and were compared to available literature records. Growth is apparently slow and individually varied. Growth rates for males and females are similar except that males do not attain as great a length or longevity as females. Growth rates are estimated to be 15-20 cm/yr for the first five years, 10 cm/yr for years VI-X, 5-7 cm/yr for years XI-XVI, and less than 4-5 cm/yr thereafter. Males mature at 210-220 cm TL or 13-16 yr of age; females mature at > 225 cm TL or 18+ yr of age. The largest male (245 cm TL) vas 21.3 yr old; the largest female (268 cm TL) was 24.2 yr old.

Purification and Characterization of shark serum propteins which agglutinate bacteria of the family Vibrionaceae

Ongoing research in our laboratory has determined that Vibrio spp. are autoch- thonous flora of free-ranging healthy, neritic sharks. It was our intent to investigate shark immunity to specific marine bacteria, to determine the level and scope of immunity, and to purify and characterize those substances with agglutinating and binding activity. Microagglutination and whole cell ELISA assays showed that lemon, nurse, blacktip, and tiger shark sera possessed agglutinating activity against Vibrio cholerae, Vibrio parahaemolyticus, Vibrio carchariae, Vibrio damsela, and Aeromonas hydrophila. The titers varied considerably among shark species and individuals. Binding protein was purified by DEAE ion exchange and Sephadex G-200 gel filtration chromatography. The elution patterns suggested that the binding protein was similar to the IgM subclass of immunoglobulin. Therefore, sharks appear to develop an immunity to the marine bacterial flora in their environment.

Structure and Growth zone formation of vertebral centra from captive Okinawan whale sharks (Rhincodon typus)

Virtually nothing is known about age and growth of the whale shark, Rhincodon typus. Recently, however, 6 whales sharks have been kept in captivity at the Okinawa Expo Aquarium for as long as 630 days. Vertebrae from 2 such specimens were utilized for age determination. Since the 630 day specimen was fed krill and small fishes containing oxytetracycline (OTC) on a recorded schedule, it was possible to use the fluorescent marks where the OTC incorporated into the actively calcifying zones to verify that one pair of opaque and translucent marks was deposited annually in this specimen. Since details on the reproduction and development of this species are not available, we cannot evaluate early growth zone formation. Thus, we cannot yet interpret age from the 15, 16, and 18 total band pairs in the 4.4 m male and the 5.2 m and 8.0 m female whale shark vertebrae (respectively ) examined to date. We are now searching for vertebrae from additional wha1e shark specimens of different sizes to compile additional growth informati on.

Distribution of the Longfin Mako (Isurus paucus) in the Northwest Atlantic

In the Northwest Atlantic, sharks of the genus Isurus are represented by two species, the shortf1n mako (I. oxyrinchus) and the longfin mako (I. paucus). I. oxyrinchus is a common species along the coast of North America. I. paucus was first reported from U.S. waters in 1979. Since then longfin makos have been taken on pelagic longlines over a geographical range from the Gulf of Mexico to the Grand Banks. Observations on 50 I. paucus include data on season, size, sex, water temperature, associations with other species and a pregnant female. The pregnant female (330 cm TL) was caught in Mona Passage in January (1983) and contained 8 embryos (4 males, 4 females) in a size range from 109 to 125 cm in total length. Between North Carolina and the Grand Banks, longline catches of I. paucus were made from May through October. The distribution of I. paucus in the northern part of its range is limited to the Gulf Stream and outer edges of the continental shelf. Species taken on the same longlines included swordfish; bluefin, yellowfin and bigeye tunas; and blue, shortfin mako, hammerhead and sandbar sharks. Other aspects of the life history of I. paucus are discussed.

The reproductive biology of the Chain Dogfish, Scyliorhinus retifer

The chain dogfish, Scyliorhinus retifer is a small, comnon benthic shark of the continenta1 slopes. In spite of its abundance, its reproductive processes have not been described. Here we describe mating, egg laying, embryanic growth and development, and general biology of the species. Mating and egg layirg were observed in the laboratory. More than two hundred specimens were captured and dissected in order to study reproductive biology.

White shark attacks on divers from Santa Barbara County, California and Isla de Guadalupe, Baja

In their discussion of California and Oregon shark attacks, Miller and Collier (198l) recorded 21 of 28 unprovoked white shark attacks on divers from seven locations.

This report details four, white shark attacks on divers. Two from Santa Barbara County, California, noted but not described by Miller and Collier, and two from Isla de Guadalupe, Baja.

Commercial abalone diver, Gary Johnson, had a swim fin bitten at Pt. Conception, Santa Barbara County, California, 19 July 1975. Robert Rebstock, abalone scuba diver, was viciously attacked at the same 1ocation, 23 July 1975.

Free diver, Al Schneppershoff, was fatally injured while spearfishing at Caleta Melpornene Cove, Isla de Guadalupe, Baja, 9 Sept 1973. A second free diving spearfisherman, Harry Ingram, was attacked but not injured, at the same location, 11 Sept 1984.

Recent records of White Shark distribution and feeding behavior in cold waters of the North Pacific ocean and Bering Sea: 1976-1985

Until relatively recently it was believed that the white shark, Carcharodon carcharias, inhabited tropical and warm temperate seas in the Pacific Basin. However, data collected by direct observation or compelling physical evidence in seven instances since 1976 off the coasts of Oregon and Alaska has shown that white sharks are present and feeding actively in waters as cold as 8.3 °C. to 10.6 °C. Temperatures that were once thought to constitute an effective thermal barrier to the distribution of white sharks into northern waters have not impeded the movements of these animals. The possible adaptive role of the rete system in cold water movements of this species will be discussed.

Reports on some shark attacks and posthumous scavenging on humans from the Eastern coast of South Africa 1974 – 1985, and an update of treatment of shark attack victims in Natal.

Shark attacks at netted and unnetted beaches are reviewed. The increase in incidents involving surfers, spear-fishermen and SCUBA divers over swimmers is discussed. Cases of posthumous scavenging are recorded for forensic purposes. Valuable supportive data are available from shark captures at nearby netted beaches.

The general principles of treatment of victims in Natal are those of Davies & Campbell (1962) but the equipment used for primary care has been modified and updated. “Rheomacrodex” is replaced by human albumen solution (4 x 50 ml) for intravenous administration with Ringer lactate (2 x 1 l). Plastic cannulae replace the 18g needle on the I.V. fluid administration sets. Career and voluntary lifeguards now receive accredited paramedic training. Premature movement of a seriously injured victim with uncompensated hypovolaemia is one of the most important causes of death after a shark attack. Minimal stabilisation time 30 minutes before transportation to hospital. Constant reassurance of the victim is essential.

Gill-nets as anti-shark measures and small sharks as prey items of larger sharks netted in the Natal Sharks Board nets.

Gill-nets are practical, economic and to date, the mosi effeci:ive anti-shark measures applied along the Natal beaches; they are also excellent biological sampling and monitoring devices providing an extensive data base for detailed study of fourteen shark species commonly caught. The gross dietary preferences of 6,125 sharks caught between 1978 and 1984 have been recorded. Small sharks were found in only 6% of the stomachs of larger predators. A species breakdown of the latter and their small shark prey is presented. Results are discussed with reference to an increased abundance in catches of small sharks by shore-based competition anglers along the Natal coast. The hypothesis that the elimination of large predatory sharks by the shark nets is directly responsible for the proliferation of small sharks is not substantiated by these data.

Comments on the natural history of the epaulette shark, Hemiscyllium ocellatumi on the great barrier reef

Aspects of the natural history of the epaulette shark, Hemiscyllium ocellatum, were studied during in situ field work conducted off Lizard Island Research Station in September and October 1985. Comments will be made on breeding season, egg laying, breathing rates, feeding, and movement.

Taxonomy and distribution of the nurse shark Ginglymostoma cirratum.

Three isolated populations of the nurse shark, Ginglymostoma cirratum Bonnaterre, 1788), exist: in the eastern Atlantic ocean off West Africa; in the western Atlantic Ocean off the U.S.A. to Brazil; and in the eastern Pacific Ocean off California to Peru. These three populations were examined morphometrically and were found to differ from one another somewhat. Combined with plate tectonic information, conclusions are drawn on the biogeography of the nurse shark and speciation rates in sharks.

Some nechanical aspects of the teeth of several carcharhinid sharks.

A considerable variation in teeth form exists within the Carcharhinidae. It is expected that each type has its own mechanical implications. This preliminary assessment chooses some common types for examination from the standpoint of static function. It is noted that this approach is a necessary first step in the biomechanical analyses of tooth form; but that further information based upon a greater array of tooth types, and upon detailed data on the kinematics and dynamics of biting are needed before fully rounded, adaptive hypotheses can be posed.

Toxic soles (Pardachirus sp): are they sharkproof?

Four species of ichthyocrinotoxic soles, distributed through the Indopacific ocean, possess dermal glands capable of secreting a presumed defensive substance consisting of two toxins: an amphipathic peptide (pardaxin) and a steroidic glycoside (pavoninin, mosesin). These compounds are strongly bioactive, haemo- lytic, ichthyotoxic and repel large predators including sharks. This paper reviews the behavior, biology, biochemistry, pharmacology and physiology of toxic soles and their defensive secretion and wil1 relate the role of pardaxin to the development of a chemical shark repellent.

Age and growth of the lemon shark, Negaprion brevirostris (Poey), as determined by mark/recapture data and examination tethacycline labelled vertebrae

A multiple-mark tagging program involving two lemon shark populations was conducted from 1979 to Dec. 1985. In the Florida Keys, 1935 sharks were marked with a variety of tags, injected with tetracycline, and released, as were 280 sharks in Bimini, Bahamas. There were 124 Keys recaptures and 104 in Bimini. Time at large as well as lengths at release and recapture were used from 123 recaptured sharks in a least squares method for estimating von Bertalanfly growth curve parameters of. L° = 274.9 cm, K = 0.058 and t o= -3.15, predicting maturity near age 16 and 95% L° after’ 48 years. Vertebral centra were removed from 56 recaptues and ground along a frontal plane. Annual bands and circulus for.mation occurring every 28 days were validated using the tetracycline marker. Estimated ages from circulus counts describe a growth curve with L° = 310.6 cm, K = 0.06 and t o= -2.28, predicting, maturity near age 13 and 95% L° after 50 years. Results show that this shark is slow growing and long-lived.

New sedation techniques for sharks: saffan administered by an underwater dart gun

Saffan, a mixture of the anesthetic steroids alphaxalone and alphadolone acetate commonly used in veterinary anesthesia, has been tested as a tranquillizing agent in elasmobranchs. The anesthetic was given intramuscularly using a newly developed laser-aimeri dart gun that allows the operator to fire an underwater projectile syringe into the animal while remaining outside the tank. Saffan has been applied by this route to dogfish shark Squalus acanthias held in display tanks at the Vancouver Aquarium, and permits easy netting of the animal within five minutes of injection. The drug has also been used successgully, during field collections, to sedate line-caught dogfish shark for transport.

Shark damage to acoustic sensors

Sharks, other fish and squid do damage to mooring lines and other equipment. During the past several years dozens of Navy acoustic sensors as well as sensors used by seismic exploration companies have been damaged by sharks. The characteristics of this damage wil1 be discussed along with potentia1 causes for the attacks, and possible preventive measures.

Swimming and feeding behavior of basking sharks off central California

In August-September 1976 a large number (30 plus) of basking sharks, Cetorhinus maximus, appeared in Carmel Bay, California. A 12-minute film showing the swimming and feeding behavior of this shark will be presented. There will be little narration — the photography itself tells the story. Although basking sharks are observed each year off central California the numbers since 1976 have been much fewer.

New Mississippian Holocephali (chondrichthyes) and the evolution of the Holocephali

The jaw plates of several new Mississippian species of Echinochimaera are described. The morphology and mode of growth are compareQ with the tooth plates of the recent chimaeroids Hydrolagus, Rhinochimaera, and Callorhynchus, and several ontogenetic stages of cochliodonts. The jaw plates of Echinochimaera are derived relative to the jaw plates of either chimaeroids or cochliodonts, while the plates of recent chimaeroids may most reasonable be derived from juvenile stages of cochliodont tooth plates by paedomorphosis. On the basis of the available evidence, Echinochimaeroidei are the sister group of the Chimaeroidei, and Chimaeriformes are the derived sister group of the Cochliodontiformes.

Attacks by white sharks: a review

Attacks upon humans by white sharks (Carcharodon carcharias) are reviewed on a worldwide basis, with partioular emphasis upon the Pacific northwest. Attacks upon humans are best explained as attempted feeding rather than territorial encounters, based on their similarity to attacks upon normal prey items. White shark behavior as observed in the field and in the Steinhart Aquarium will be presented. Feeding habits, ontogenetic dietary and morphological shifts, and other life history information will be reviewed. Advice to those frequenting white shark waters will be freely dispensed.

Allocation of the name Sphyrna tudes (Valenciennes, 1822) and the status of the nominal species Sphryna couardi Cadenat, 1951.

The name Sphyrna tudes (Valenciennes, 1822) has had a very confusing history, partially because the specimens examined by Valenciennes represent two or more species and all are late-term embryos. Gilbert (1967) selected a lectotype from the three available syntypes. However, Cadenat and Blache (1981) considered Gilbert’s lectotype a specimen of S. couardi. Examination of the three syntypes convinced us that two of them, Gilbert’s lectotype and a specimen from French Guiana are S. tudes. The other syntype from Algeria is S. zygaena. We also discovered that the available specimens of S. couardi cannot be distinguished from S. lewini and we recommend that S. couardi be synonymized with S. lewini.

Aspects of the reproduction of the bat ray, Myliobatis californica Gill, in Central California

Reproduction in bat rays collected from Elkhorn Slough in Central California appears to follow a well-defined annual cycle in which mature individuals enter the Slough in May to give birth and mate, and depart by late September. Data indicate that the bat. ray’s gestation period is between 9 and 12 months 1ong, similar to the few other species of rays studied. Disc width at birth ranges between 274 and 315 rm. In male bat rays, three indicators of sexual maturity (presence of mature spermatozoa, clasper-disc width relationship, and internal morphology) showed that onset of sexual maturity occurs at 2 to 3 years of age at a disc width of about 622 mm. In females, presence of mature ova indicate that 50% maturity occurs at approximately 5 years of age at a disc width of about 881 mm.

Age and growth determination of the bat ray, Myliobatis californica Gill, in central California

Two methods of enhancing grovth bands on vertebral centra – oil clearing and x-radiography – were found to successfully eluaidate the circuli in the centra of bat rays, Myliobatis californica Gill, from central California. The annual nature of band deposition was verified by comparison of modal disc widths (DN) from size frecpxency analysis of the first three age classes to mean back-calculated disc widths and changes in centrum edge mineralization patterns and tetracyline uptake. Significant differences in mean DW determined by each ageing technique occurred in only one age class for each sex. Comparison of calculated DW to published observed maximum disc widths indicated that, for males, the x-radiography technique produced the most realistic growth curve, while for females the oil clearing technique was best. The von Bertalanffy growth curves derived from these techniques indicate that female bat rays reach a greater asymptotic size (DW = 1587 mm) and have a lower growth rate (K = 0.0995) than males (DW = 1004 Inm, K = 0.229).

Shark repellent testing: comparison of different classes of repellent stimuli

Recent studies have shown that certain inexpensive chemicals, e.g., the surfactant sodium lauryl sulfate (SLS), in moderate concentrations, can be used to repell sharks by the squirt application method. In order to place the practicality of these findings in perspective, a study is underway to compare the chemical method to several other repellent methodologies useable – or suggested to be useable – by divers underwater or persons awaiting rescue at the surface. Tests are conducted on blue sharks, Prionace glauca, bait attracted to the boat off southern California. Arriving sharks are first marked with color-coded dart tags, then given one or more repellent or control “treatments” in randomized order. Treatments include the dart-tagging itself (which sometimes causes departure), seawater squirt (control), chemical squirt (SLS), air blast (sound, bubbles), physical prod (shark billy), electric prod, and the dipole electric “Shark Shield”. Data recorded include (1) level of repellency, and (2) stay-away time. The ease of using the method is also assessed. Early results indicate that the chemical squirt method yields relatively high repellency level and long stay-away time, but is not the easiest to use.

Shark attack in Florida and adjacent waters: an overview, 1981-1986

Numerous incidents of shark attack have been recorded in Florida and adjacent waters of the Gu1f, Bahamas and Caribbean during the last five years (76 attacks with 20% attack-related deaths). Present information suggests that such attacks are on the increase. Unfortunately, data for analyses of the apparent causes for shark-human confrontations are extremely difficult to obtain. Daspite this, confrontations appear clearly correlated with surfing activities. Several factora associsaed with human demographics may wel1 be critical, however, to the increaae noted above, e.g., 1) differential growth and movement of the human population along Florida’s 8400 miles of coast1ine and 2) spec1fic water masses acting as attractants, e.g., sewage outfall. The relatfon existing betveen toxic microorgan1sms, e.g., toxic Vibrio and shark attack (including medical treatment thereof) also needs clarification. Funding is vital not only for continuing efforte to maintain an up-to-date record of shark-human confrontation, but to acquire a database adequate for examining the above-mentioned points, each of which appears to carry importance, at least in the state of Florida.

Stress effect on lactatei ph, and hematocrit levels in the hornshark, Heterodontus francisci 

In this study 10 adult horn sharks of 1.3 – 2.0 Kg., 55 – 71 cm TL, were stressed when removed from water and their caudal vein inserted with an intramedic PE- 50 catheter. The catheter, back-filled with heparinized elasmobranch Ringer’s, was secured to the caudal peduncle and its free, sealed end, extended 3 meters to a float at the surface of a 1000 gallon pool. Blood samples (0.3- 0.4 ml) were taken at 15 min. intervals during the first hour after stress and at less frequent intervals thereafter. Samples were analyzed for lactate, hematocrit, and pH levels. Experiment #9 is representative. After stress, lactate rose from 0.44 to peak at 1.76 m moles/1. in first 19 min., returning to 0.70 m moles/l. at end of 3 hrs. Hematocrit rose from 15.6 to peak at 19.0 % in first 90 sec., returning to 16.2 % at end of 3 hrs and pH dropped from 7.58 to 7.26 in 45 min., returning to 7.44 in 3 hrs. With minor variations horn sharks in 11 other experiments experienced similar rapid rises in lactate and hematocrit and lowering of pH immediately after stress.

Elasmobranch gonadal structure

Two distinctly different types of gonads have arisen among elasmobranchs. Investigations reveal that three species of Laminidae and two of the Alopiidae have testes comprised of 1obes. The germinal zone is in the center of each lobe and spermatozoa development proceeds radia11y from the germinal zone. Females of these two families have ovaries in which the ova are encapsulated in the epigonal organ and its epithelium. Ova exit via a pocket in the combined gland. All species of the fam1ly Carcharhinidae (10) and Sphyrnidae (1) examined have a more uniform testis in which the germinal zone is in a band along the entire distal-latera1 surface. Spermatozoa development proceeds diametrically, that is, along the cross-sectional width of the testis toward the proximally 1ocated efferent ducts. Ovaries of these families are borne on the distal surface of the epigonal organ. An investigation of other families may lead to findings of taxonomic significance.

Refutation of lengths of 9 and 11.3 m attributed to the great white shark (Carcharodon carcharias)

Randall (1973) showed that the 36.5-foot (11.1 m) length attributed to an Australian specimen of the great white shark (Carcharodon carcharias) by Günther (1870) is an error. The length determined from the jaws and teeth of this shark in the British Museum (Natural History) is about 17 feet (5.2 m). The largest specimen of this species reliably measured and reported in the literature was 21 feet (6.4 m) long. Wood (1982) presented a photograph of a white shark taken in the Azores which he claims vas 29.5 feet (8.99 m) in length. He also attempted to lend authenticity to a report of a 37-foot (11.3 m) white shark from New Brunswick, Canada reported by Vladykov and McKensie (1935). Evidence is presented to refute both of these lengths.

Recent advainces in mammalian semiochenical communication: applicabilities to elasmobranch studies.

Recent progress in mammalian chemocommunication includes innovative studies on intraspecies pheromonal interactions using a response-guided approach or a chemical-image method, and semiochemical investigations of repellent and/or attractant effects between species. A discussion is presented, i.n view of the authors’ background in elasmobranch research and current activities in the chemocommunicative field, examining these results for relevancies to elasmobranch chemosensory studies, especially elasmobranch deterrent investigations. Special emphasis is placed on the availability of trace study techniques of on-column capillary column gas chromatographic analysis and analytical combined with preparative high performance liquid chromatography, of special importance with regard to bioactive liquid-borne natural secretions,

Behavior of the free-swimming blue shark: depth and speed

Depth records obtained by acoustic telemetry from several blue sharks in NW Atlantic slope waters show a consistent pattern of vertical migration between the surface and depths as great as 500 meters, with the deepest dives occurring during the day and shallower dives at night. A propeller-type transmitter was used to record the swimming speed of a 220 cm fork length individual. Swimming speeds ranged from 35-50 cm/s (0.16-0.23 body lengths per second), with short bursts up to 180 cm/s (0.82 BL/s). Measurement of instantaneous swimming speed and rate of depth change during dives permits calculation of angles of ascent and descent. For seven dives deeper than 200 m, the descent angle averaged 14.6 ± 3.2 degrees (X ± SE) from the horizontal while the ascent angle was 10.2 ± 1.2 degrees. We have previously shown that blue sharks actively swim downward during most of the dive, with brief gliding periods. Since the observed behavior does not appear to be energetically optimum for migration, it may instead represent a strategy for encountering and capturing prey.

Life history of the stingray Dasyatis sabina in Florida coastal lagoons

The Atlantic stingray, Dasyatis sabina, is characteristic of coastal estuarine habitats from Chesapeake Bay to Nexico. It is one of four stingray species found in the Indian River lagoon system on the east coast of Florida. This ray was common to abundant in water less than 1 m deep in spring, summer, and fall. It moved into deeper water during cold winter weather but resumed activity on the shallow seagrass flats when temperatures rose above 17C. Males matured at about 20 cm DN and reached a maximum size of 32.6 cm and 1.6 kg. Males had active testes from November to March and copulation was observed in March. Females matured at about 24 cm DW and reached a maximum size of 37.1 cm and 2.2 kg. Females ovulated in Narch and carried yolked ova in the left uterus in April and May. Recogniz- able embryos first appeared in early June and young were born in late July through early August after an apparent gestation period of 2-2 1/2 months. Brood size ranged from 1-4 (mean=2.5) and neonates were 10-13 (mean=12.3) cm DW.

Periodic shedding and replacement of venomous spines of stingrays

Spine counts were made on 256 South American stingrays of 4 families; and 8 captive freshwater rays were observed 12 months for shedding and replacement of spines. The basic number of spines in most stingray species is 2, one from each of 2 adjacent loci, locus A (ant.) and locus P (post.) Each spine has its own developmental cycle consisting of early development (sti11 buried in the flesh), eruption, growth, and shedding. The cycles do not run concurrently, but are staggered, one lagging the other by about one-half the duration of the individual cycle. Both shedding and replacement alternate between loci A and P. The 8 captive Potamotrygon each shed twice a year, i.e., the spines of both loci completed a full cycle of one year each, staggered by 6 months. We are confident that the events of shedding and replacement are applicable to sting- rays in general but prefer not to generalize on the rate at which they occur (once or twice per year) until more evidence is available on a variety of species.

Anaerobic bacteria in shark tissue.

Mutilation of a human by shark hite is traumatic and often extensive. Added to the immediate trauma are complications in recovery due to bacterial infection. The present study was undertaken to isolate potential anaerobic pathogens from in and around shaxk mouths. It evolved into a study of anaerobic bacterial flora in healthy shark tissue. All tissue samples from tiger, nurse, blacktip, and bull sharks were placed into pre-reduced anaerobically sterilized chopped meat maintenance media. Screening for anaerobes was accomplished by plating ont anaerobic blood agar and by detection of volatile fatty acids with gas liquid chromatography. AI1 anaerobes isolated were purified, characterized and given tentative identification. The vast majority of these anaerobes were assigned to the genus Clostridium. It is hypothesized that concommitant high urea and salt concentrations in shark tissue inhibit growth of most anaerobes, except the sporulating clostridia.