Carcharhiniformes

(Ground sharks)

Class Chondrichthyes

Order Carcharhiniformes

Number of families 8

Evolution and systematics

The fossil history of ground sharks (Carcharhiniformes) is known from a handful of preserved skeletons, but long intervening periods exist in which fossil skeletons of ground sharks have not been recovered. Ground sharks first appear in the late Jurassic (some 150 million years ago) Solnhofen limestones of Germany. These early fossils (e.g., Macrourogaleus) are not well preserved, but they bear some resemblance to modern catsharks (family Scyliorhinidae). After a long absence from the fossil record, fossil ground shark skeletons reappear in the late Cretaceous chalk deposits of Lebanon (ranging in age from 84 to 95 million years ago, or mya). These sharks (e.g., Pteroscyllium and Paratriakis) are thought to be related to catsharks and hound sharks (Triakidae), respectively, but on scant evidence. A few species of fossil catsharks from Lebanon are even placed in the living genus Scyliorhinus, which would give it a remarkable longevity of some 90 million years. These fossils have been studied only superficially, however, and they probably represent extinct genera of uncertain affinity. Partial skeletons are present in the Monte Bolca beds of northeastern Italy (Eogaleus and Galeorhinus) of Eocene age (some 52 mya), again after a hiatus of more than 30 million years.

Many extinct species of ground sharks are known from isolated teeth, which are widespread and provide a fairly robust stratigraphic record. Tertiary ground shark fossils are relatively modern in their level of diversity. Ground shark fossils are present on every continent, indicating that they have been distributed widely for the past 65 million years at least. Remarkably, the fossil record of ground sharks parallels their phylogenetic history, where the most "primitive" family (Scyliorhinidae) also is the oldest.

Ground sharks are related closely to bullhead (Heterodontiformes), carpet (Orectolobiformes), and mackerel (Lamniformes) sharks among living elasmobranchs (sharks and rays), forming the larger group known as the Galeomorphii. Galeomorph sharks are characterized by several evolutionary innovations, such as the unique placement of the hyomandibula (a cartilage supporting the jaws posteriorly) on the skull. Within the Galeomorphii, carcharhiniforms are related most closely to the mackerel sharks, as they share a tripodal rostrum (the anterior extension of the skull) supporting the snout internally. All carcharhiniforms have specialized secondary lower eyelids ("nictitating" eyelids, which are absent from all other sharks) as well as unique clasper skeletons. Similarly to lamnoids (a subgroup within mackerel sharks), there is also a group of "higher carcharhiniforms" characterized by plesodic pectoral fins (with internal supports reaching the fin margin).

There are approximately 216 species, 48 genera, and eight families in the Carcharhiniformes. This amounts to slightly more than half of all shark species and about half of all shark genera. The eight families are the Scyliorhinidae (catsharks, 15 genera and some 105 species—the largest shark family of any order), Proscylliidae (finback catsharks, three genera and five species), Pseudotriakidae (false catshark, monotypic), Leptochariidae (barbeled hound shark, monotypic), Triakidae (hound sharks, 10 genera and 39 species), Hemigaleidae (weasel sharks, four genera and seven species), Carcharhinidae (requiem sharks, 12 genera and 50 species), and Sphyrnidae (hammerhead sharks, two genera and eight species). New carcharhiniform species have been described in recent years, particularly of catsharks, and additional new species await formal description. Phylogenetic relationships among ground shark genera require further study, which may result in the merging of several currently monotypic genera and even of some of the families.

Physical characteristics

There are many different morphological and ecological trends within the Carcharhiniformes, which is to be expected from a large group that inhabits waters from the intertidal

zone to the lower reaches of the continental slope. However, the morphological differences among ground shark families are not as great compared with the other orders of sharks, even though some families are quite distinctive. One of these families is the hammerhead shark (Sphyrnidae), which is unique among all sharks in having a laterally expanded head (the hammerhead, or cephalofoil, with eyes on the lateral extremes). Hammerhead sharks are otherwise very similar to requiem (carcharhinid) sharks. Catsharks (Scyliorhinidae) also are recognized easily, as their first dorsal fins are situated either on the same level as or behind the pelvic fins. The false catshark (Pseudotriakidae) is unique among sharks in having a first dorsal fin that is much longer than the caudal fin. The differences among the remaining families are subtle, and one must look at their teeth, labial furrows, and even intestines to identify them.

Carcharhiniforms are small, medium, or large sharks; adults usually range from 18 in (45 cm) to 20 ft (6 m) in length. The proscylliid Eridacnis radcliffei reaches only about 9.4 in (24 cm) in length and is one of the smallest known species of sharks. Ground sharks have two spineless dorsal fins (one species, Pentanchus profundicolus, with only one), the first larger than the second. There is a large caudal fin with a greater upper lobe, a prominent anal fin about as large as the pelvic fins (or even larger in some catsharks, especially Apristurus species), and moderately developed pectoral fins. There are five gill openings. The snout can be conical or broadly rounded (elongated in Isogomphodon). The eyes are elliptical, but they are rounded in some genera (e.g., Rhizoprionodon). The spiracles vary from a small pore to an opening just smaller than the eyes. When present, labial furrows (grooves alongside the mouth corners) vary from long to short. There is either a spiral or a scroll intestinal valve. The teeth may vary considerably between adults and juveniles of the same species, upper and lower jaws, and males and females and between species, genera, and families. A single broad, slanted, or erect cusp may be present, or there may be as many as five cusps per tooth (Proscylliidae). Many species are identified by their dental morphological features and formulas. The body is covered with small dermal denticles that do not form larger spines.

Carcharhiniforms vary widely in coloration. Shallow-water catsharks can be spectacularly colored, with many spots, saddle-like markings, and blotches, whereas deeper-water catsharks usually are drab or dark brown or black. Many species (requiem and hammerhead sharks) are gray or brown dorsally and laterally, with creamy or white ventral surfaces. Many triakids also are spotted or have other conspicuous markings similar to those of scyliorhinids. Many ground shark species have unique coloration.

Distribution

They are found worldwide in tropical to temperate waters, including cool boreal seas, but they are most abundant in tropical and warm temperate regions. Carcharhiniform sharks inhabit all major oceans except the Antarctic seas. (Deepwater catsharks of the genus Apristurus may inhabit Arctic waters.) They also are present in tropical freshwaters (rivers and lakes) in South, Central, and North America; Africa; Asia; and Australia.

Habitat

Carcharhiniforms are most abundant in tropical continental shelf regions. Most inshore, littoral habitats, including coasts, estuaries, river mouths, open bays and lagoons, atolls, and coral reefs (both coastal and barrier reefs), are occupied by ground sharks. They also are abundant offshore, off oceanic and continental islands, and are present in deeper waters along the upper continental slopes (especially species of Apristurus and Pseudotriakis). Some species are epipelagic in deeper ocean basins.

Behavior

Carcharhiniform sharks are present in many habitats, from the littoral to the oceanic; as a consequence they vary from sluggish, primarily bottom dwellers (such as many catsharks) to swift swimming, more active pelagic forms (e.g., blue shark and oceanic whitetip shark). The behavior of certain ground shark species has been studied in both captive and natural conditions (in particular, the lemon, gray reef, and bonnethead sharks). In general, pelagic species appear to cruise at low speeds, occasionally bursting into sudden activity, while bottom-dwelling species are more territorial and mostly nocturnal.

Some carcharhiniform species form aggregations, often by size or sex (except during mating season). Schooling is a very common social behavior in hammerhead sharks (e.g., the scalloped hammerhead, Sphyrna lewini, off the eastern Pacific coast of Mexico, where some 225 individuals may school together), but most carcharhiniforms spend much of their lives alone. Gray reef sharks (Carcharhinus amblyrhynchos) form schools in the Marshall Islands, as do lemon sharks (Negaprion brevirostris) in the Bimini Islands, Bahamas. Schools typically form during the day and break up for individuals to feed at night. Additionally, some species are now known to rest in caves for long periods; the whitetip reef shark, Triaenodon obesus, rests mostly during the day and sometimes in groups.

Sharks spend much of their lives as solitary predators and do not form family groups or cooperate with each other. Their types of behavior are less complex than those of marine mammals, but only a handful are known. In particular, aggressive display has been documented (e.g., for the gray reef shark), which may involve jerky head movements, arching of the back, and downward pointing of the pectoral fins. Social displays and social organization are particularly well known for the bonnethead, Sphyrna tiburo. Some of these displays are an outcome of size-dependent dominance hierarchies, such as swimming in a straight line. Bonnetheads do not show much aggressive behavior, a possible indication that more social species may be less aggressive.

Feeding ecology and diet

Ground sharks are voracious predators; none are filter feeders. Food items consist of numerous families of bony fishes, sharks and rays, marine mammals and marine mammal carrion, seabirds, marine reptiles (mostly turtles), and a wide range of invertebrates, including crustaceans, squid, octopi, cuttlefish, and shelled mollusks. Benthic ground sharks feed on items more readily available on or close to the bottom,

such as hard-shelled invertebrates and certain fishes, whereas open-ocean forms feed intensely on pelagic fishes, such as tunas and their allies (Scombridae). Larger sharks prey on ground sharks, and larger species of ground sharks may feed on smaller ones. The tiger shark has the least selective diet of all sharks. Most species are not highly specialized in their feeding habits, but hammerheads are known to have a particular predilection for stingrays.

Reproductive biology

Carcharhiniform sharks are either oviparous (egg layers) or viviparous (giving birth to live young). Oviparous species deposit egg cases that contain the developing embryo along with its yolk reserves (in the yolk sac). These species include the majority of the catsharks (Scyliorhinidae, except Cephalurus and possibly some Halaelurus species) and Proscyllium habereri (Proscylliidae). The egg cases are secreted by the nidamental gland in the upper oviduct and usually are amber to greenish in color, with tendrils at the extremities that serve to anchor them to the substrate. In species with retained oviparity, the egg cases remain for a longer period in the uterus, with most embryonic development taking place inside the mother. In other oviparous species, the eggs are laid shortly after they are formed (less than one month in some cases), and most development of the fetus, which may take up to one year, occurs inside the egg cases in the environment.

Slightly more than half of carcharhiniform species are viviparous. Viviparous species can be yolk sac viviparous (ovoviviparous or aplacentally viviparous—the young deriving nourishment solely from the yolk sac, such as in the tiger shark, Galeocerdo), but many viviparous species form maternal-fetal connections in the form of yolk sac placentae. In these cases, the yolk sacs are modified into highly vascularized, nutrient-supplying structures fused to the internal uterine walls. Placentae are formed in the Hemigaleidae, Carcharhinidae (except Galeocerdo), Sphyrnidae, and some triakid species.

Gestation periods vary considerably; oviparous species lay eggs after a short gestation of just a few weeks, but some viviparous species retain the embryos for more than a year.

Litters vary from one to 135 per gestation. In many species, females give birth in shallow nursery areas. Males bite females during courtship, and mating has been observed in the wild for a few species (such as the whitetip reef shark, Triaenodon obesus). There is no parental care after birth.

Conservation status

The following species are listed by the IUCN: Glyphis gangeticus (as Critically Endangered); Carcharhinus melanopterus, C. borneensis, and Glyphis glyphis (as Endangered); Galeorhinus galeus (as Vulnerable); Mustelus antarcticus (as Lower Risk/Conservation Dependent); C. amboinensis (southwestern Indian Ocean subpopulation only), C. amblyrhynchoides, C. amblyrhynchos, C. brevipinna, C. leucas, C. limbatus, C. longimanus, C. melanopterus, C. obscurus, C. plumbeus (northwestern Atlantic subpopulation only), Furgaleus macki, Galeocerdo cuvier, Negaprion brevirostris, Poroderma africanum, Prionace glauca, Scoliodon laticaudus, Triaenodon obesus, Triakis megalopterus, and T. semifasciata (as Lower Risk/Near Threatened); C. brevipinna (northwestern Atlantic subpopulation only), C. hemiodon, C. limbatus (northwestern Atlantic subpopulation only), C. obscurus (northwestern Atlantic and Gulf of Mexico subpopulation only), and Galeorhinus galeus (as Vulnerable); and C. amboinensis and Smyrna mokarran (as Data Deficient).

Significance to humans

Ground sharks are fished intensely, both for food and recreationally. Because they are abundant in shallow and oceanic waters, ground sharks frequently are fished by trawlers and longlines and are either targeted directly or captured as bycatch. Their flesh is marketed frozen, fresh, dried-salted, smoked, and even canned for human consumption. Their skin is used for leather products, their fins for the Chinese shark fin soup industry, their carcasses for fishmeal, and their liver oil for the extraction of vitamin A (in decline as vitamins are synthesized). Tourists often procure trophies, in the form of jaws and teeth. Recreational fisheries and angling tournaments capture large quantities of ground sharks, especially tiger sharks in shallow waters and blue sharks in oceanic settings. Internal fertilization, long gestation periods, production of few offspring, and relatively advanced ages at sexual maturity are all factors that constrain the exploitation of shark populations.

Ground sharks have been implicated in numerous shark attacks, especially the tiger and bull sharks, which account for more than 50% of shark attacks worldwide. This proportion is to be expected because of the high number of carcharhiniform species and their shallow-water predominance.

Carcharhiniforms also are very important in the growing ecotourism market. Many species can be encountered in the wild through commercial operations that specialize in taking tourists to areas where specific carcharhiniform species are common. These operations are worldwide, and surveys indicate that shark watching is a highly profitable enterprise. Certain ground shark species are common in public aquaria as well, especially Triaenodon obesus, Carcharhinus plumbeus, and Triakis semifasciata.

Species accounts

List of Species

Gray reef shark

Carcharhinus amblyrhynchos

family

Carcharhinidae

taxonomy

Carcharias (Prionodon) amblyrhynchos Bleeker, 1856, Java Sea, near Salambo Islands, Indonesia.

other common names

French: Requin dagsit; Spanish: Tiburón de arrecifes.

physical characteristics

Somewhat elongated snout but with a rounded anterior profile, first dorsal fin much larger than the second, and rounded eyes. Upper teeth have posteriorly slanted cusps with faint serrations; lower teeth are slender and more erect. Coloration is grayish dorsally and laterally, but with a distinctive black caudal fin margin. Reaches some 8 ft (2.5 m) in length.

distribution

Occurs in mostly tropical waters of the Indian and Pacific Oceans.

habitat

An inshore shark but also occurs pelagically and sometimes frequents oceanic waters from the intertidal zone down to about 330 ft (100 m). A common species in coral reefs, atolls, and shallow lagoons. Usually found close to the bottom but also may be seen near the surface.

behavior

A curious shark that investigates "novel" circumstances while swimming. Approaches divers frequently but typically disappears shortly thereafter. Can be aggressive when in pursuit of prey. A particular threat display has been observed and documented, in which the gray reef shark arches its back, points its pectorals downward, lifts its head, moves its snout from side to side repeatedly, and even swims in a horizontal spiral. Considered to be a very social species.

feeding ecology and diet

Feeds on bony fishes (especially those that inhabit reefs and are shorter than 12 in, or 30 cm), octopi, squid, and a wide variety of crustaceans. Notable for being able to capture prey in tight crevices in reefs.

reproductive biology

Viviparous, with a yolk sac placenta and litters raging from one to six young. Gestation period is about one year. Individuals are sexually mature by seven to seven and a half years old. Males are mature at a length of 51–57 in (130–145 cm) and females when they reach 48–54 in (122–137 cm).

conservation status

Listed as Lower Risk/Near Threatened by the IUCN because of its relatively late age at maturity and increasing pressure from unmanaged fishing.

significance to humans

A very common reef shark, with great potential for dive tourism, as is readily seen by ecotourists in many locations (e.g., Australia, Mauritius, and the Philippines). Fishing and utilization mostly unrecorded.

Bull shark

Carcharhinus leucas

family

Carcharhinidae

taxonomy

Carcharias (Prionodon) leucas Valenciennes in Müller and Henle, 1839, Antilles.

other common names

French: Requin bouledogue; Spanish: Tiburón sarda; Portuguese: Cabeça-chata.

physical characteristics

Characteristically short and blunt snout, somewhat arched back, and relatively small eyes. Large first dorsal fin (much larger than the second dorsal fin). Triangular upper teeth with small cusplets. Upper teeth more broad than lower teeth, which are smooth laterally. Thirteen upper tooth rows and 12 lower rows. Gray to brownish dorsal and lateral coloration. Reaches 11.5 ft (3.5 m) in length.

distribution

Worldwide in tropical shallow waters but also ascending tropical rivers and freshwater lakes. Freshwater occurrences include the Amazon and Ucayali Rivers in South America, reaching upriver as far as 2610 mi (4,200 km) from shore); the Mississippi and Atchafalaya Rivers of the United States; Lake Nicaragua and San Juan River (Nicaragua); Lake Izabal and Dulce River (Guatemala); and the Patuca River (Honduras). Also in freshwaters in Belize and probably elsewhere in other neotropical systems. Other freshwater occurrences include many African rivers (Gambia, Ogooué, and Zambezi Rivers), Middle Eastern rivers (the Tigris), Indian waters (Hooghly Channel of the Ganges River), New Guinea waters (Lake Jamoer), and systems in Australia (Brisbane River). Present in some oceanic islands (Fiji).

habitat

In the sea the bull shark is widespread in inshore, shallow waters, frequenting bays, estuaries, river mouths, and waters off piers and docks, usually down to a depth of 98.4 ft (30 m) but reaching 492 ft (150 m). Its capacity to penetrate freshwaters extensively and remain in them, tolerating great ranges in salinity, has been the subject of much scientific research. Freshwater populations are not believed to be landlocked, however, and migrate frequently to the sea, such as in the Lake Nicaragua system.

behavior

Active both during the day and at night. May aggregate to migrate to cooler waters in the summer from equatorial latitudes, returning when water temperatures become too cool. Smaller, younger individuals may be more common close to shore, whereas larger individuals may inhabit slightly deeper waters. Appears somewhat sluggish but is capable of swift movements and sudden bursts of activity.

feeding ecology and diet

Feeds extensively on many different bony fishes as well as sharks and rays but is capable of consuming a wide range of

prey, including invertebrates and marine mammals, reptiles, and birds.

reproductive biology

Viviparous with a yolk sac placenta; litters range from one to 13 young. Gestation periods range from 10 to 11 months. Breeding in freshwaters may occur (e.g., in Lake Nicaragua), but most breeding takes place in the sea. Sexual maturity is attained at about 98.4 in (250 cm) in length, after some six years. Pups frequently are born in sheltered nursing areas. Lengths at birth range from roughly 19.7 to 31.5 in (50–80 cm).

conservation status

Listed as Lower Risk/Near Threatened by the IUCN, mainly because of its occurrence close to heavily populated areas and frequency of capture by local fisheries.

significance to humans

A hardy aquarium species; individuals have lived for 15 years. Captured as bycatch by fisheries in many places, leading to a concern that the bull shark may be threatened in some areas. Its meat is consumed fresh, dried/salted, and smoked, and its liver is particularly rich in oil. Also captured recreationally on hook and line in many regions. Considered a dangerous shark, with many attacks reported. It is believed that some attacks are caused by other species, such as the great white in temperate waters and the Ganges shark in the Ganges-Hooghly river system. Some attacks have occurred in freshwater (e.g., in Lake Nicaragua). The bull shark can be encountered in the wild in many places worldwide (e.g., the Bahamas, Cuba, and Belize).

Oceanic whitetip shark

Carcharhinus longimanus

family

Carcharhinidae

taxonomy

Squalus longimanus Poey, 1861, Cuba.

other common names

French: Requin océanique; Spanish: Tiburón oceánico.

physical characteristics

Short and blunt snout. First dorsal fin is characteristically large, with a unique, broadly rounded apex; pectoral fins are long and also unique, with broadly rounded apex. Small second dorsal fin and large caudal fin. Broad upper teeth that are triangular with lateral serrations; lower teeth have straight, slender cusp. Gray dorsal and lateral color, with uniquely white extremities of pectoral and first dorsal fins, sometimes with darker blotches. Second dorsal, pelvic, anal, and caudal fins have dark tips; caudal extremities sometimes also white. Reaches 13 ft (4 m) in length.

distribution

Worldwide in tropical and temperate inshore and oceanic waters.

habitat

Typically occurs close to the surface, in offshore oceanic waters but may venture close to shore occasionally in waters as shallow as 121 ft (37 m). More abundant in the tropics.

behavior

May segregate by sex and size, but little is known of its population structure. Slow moving but capable of quick bursts of energy. Oceanic whitetips appear to cruise with their pectoral fins widely spread out. Inquisitive, the oceanic whitetip will investigate potential prey items by circling them repeatedly.

feeding ecology and diet

Feeds on oceanic bony fishes of numerous families as well as on sharks and pelagic stingrays and invertebrates, such as oceanic cephalopods. Has been noted to feed voraciously on schools of fish. Also may feed on marine mammal carrion, seabirds, and turtles.

reproductive biology

Viviparous, with a yolk sac placenta and litters ranging from one to 15 young. Gestation periods of about one year have been reported, but little is known about the reproductive biology. Reproductive seasons may not strictly exist, at least in the central Pacific, where gravid females have been found year-round. Lengths at sexual maturity are between 71 and 78.7 in (180–200 cm) for females and 69 and 78 in (175 to 198 cm) for males; lengths at birth vary from 23.6 to 25.6 in (60–65 cm).

conservation status

Listed as Lower Risk/Near Threatened by the IUCN, because it is captured frequently as by-catch in pelagic tuna fisheries and owing to its presumably low reproductive capacity.

significance to humans

A few verified attacks on people have occurred, and the oceanic whitetip has been regarded as somewhat aggressive when approaching divers or boats. Regularly captured by pelagic longlines. The flesh is consumed fresh, dried/salted, and smoked, and the fins are coveted by the shark fin soup industry. Can be seen in the waters off Hawaii, the Red Sea, and Australia.

Tiger shark

Galeocerdo cuvier

family

Carcharhinidae

taxonomy

Squalus cuvier Peron and LeSuer, 1822, Australia.

other common names

French: Requin tigre commun; Spanish: Tintorera.

physical characteristics

Characteristically short and rounded snout. A large first dorsal fin (well anterior to the pelvic fin origin), well-developed caudal fin, and long upper labial furrows. Unique teeth, with posteriorly curved and serrated cusps. Coloration of dark vertical stripes (more apparent in juveniles) over a gray background. Large females reach 19.7 ft (6 m) in length, with unconfirmed records of up to 29.5 ft (9 m).

distribution

Worldwide in tropical to warm temperate, mostly continental waters but may occur pelagically in the western Pacific Ocean.

habitat

The tiger shark is mainly an inshore, warm-water species, occurring in continental waters as well as in remote oceanic islands from the intertidal zone down to about 459 ft (140 m). Very common in turbid waters, off river estuaries, near piers, and in coral reefs. May be found pelagically offshore but is not a truly oceanic shark like the blue shark.

behavior

A mostly nocturnal, active, and strong-swimming species, capable of frequenting very shallow lagoons. Usually solitary. Appears sluggish because it cruises at slow speeds near the surface. Can approach and display aggressive behavior toward divers, but in many instances tiger sharks have been turned away by strong retaliation.

feeding ecology and diet

Feeds on a wide variety of vertebrates and invertebrates, and is considered among the least specialized of sharks in relation to diet, scavenging opportunistically as well as being a top marine predator. Tiger sharks also have been known to ingest inedible objects (license plates, plastics, cans, and an amazing variety of trash). Prey items vary from large fishes (many sharks and rays as well as larger bony fishes, such as tarpon), marine reptiles, mammals, and birds to mollusks (octopi, squid, and cuttlefish) and crustaceans. Actively attacks birds resting on the surface, lifting its massive head out of the water to bite down on them as they attempt to escape.

reproductive biology

Aplacentally viviparous. (The only member of its family in which maternal-fetal connections do not form.) Gestation is slightly longer than one year. Gives birth to 10–82 rather large young (20.1–29.9 in [51–76 cm]). Inshore nursing grounds are common. Matures sexually between four and six years old.

conservation status

Considered to be Lower Risk/Near Threatened by the IUCN, as there is some evidence that several populations have declined where they are heavily fished.

significance to humans

Considered in many places to be a dangerous shark—many attacks on people and boats have been attributed to this species in tropical seas. Commonly hooked by fishermen and captured by longlines. The meat is utilized fresh, dried/salted, or frozen; the skin for leather; the fins for soup; and the oily liver processed for vitamin oil. Fished recreationally as well. Remains alive in aquaria for only short periods, not surpassing a few months. The tiger shark may be seen in the wild in Hawaii, Australia, and the Rangiroa Atoll (French Polynesia).

Ganges shark

Glyphis gangeticus

family

Carcharhinidae

taxonomy

Carcharias (Prionodon) gangeticus Müller and Henle, 1839, Ganges River.

other common names

French: Requin du Ganges; Spanish: Tiburón del Ganges.

physical characteristics

Snout rounded anteriorly, with very small eyes, large first dorsal fin well anterior to pelvic fin origin, large pectoral and caudal fins, small upper labial furrow, upper jaw teeth broadly triangular with minute serrations, lower jaw teeth very acute and slender with smooth edges. Gray coloration dorsally and laterally and white ventrally. Reaches more than 6.6 ft (2 m) in length.

distribution

Hooghly Channel of the Ganges River (India).

habitat

A freshwater species, the notorious Ganges shark is known from only two surviving specimens collected in the Ganges River. Its small eyes may indicate that this species lives exclusively in the murky Ganges. Needs confirmation by means of additional specimens from the Ganges and surrounding areas; unknown whether it is capable of tolerating marine waters.

behavior

Nothing is known.

feeding ecology and diet

Presumably fishes, but presently unknown.

reproductive biology

Unknown, but presumably reproduces in freshwater, as indicated by a newly born male specimen, 25.6 in (65 cm) long, collected from the Hooghly Channel of the Ganges River.

conservation status

Listed as Critically Endangered by the IUCN because of the paucity of specimens and information and considered at extreme risk of extinction.

significance to humans

The Ganges shark has an unproven, folkloric reputation as a "man-eater" in the Ganges River. As the bull shark (Carcharhinus leucas) also occurs there, many of the attacks attributed to the Ganges shark may be a result of misidentification. The Ganges shark is one of the least known and most mysterious shark species. It is known originally from three museum specimens, collected from freshwaters of the lower reaches of the Ganges-Hooghly river system in the nineteenth century, but of which only one is extant. An additional specimen was found subsequently in India (the newly born male mentioned previously), but no further confirmed specimens are known.

Lemon shark

Negaprion brevirostris

family

Carcharhinidae

taxonomy

Hypoprion brevirostris Poey, 1868, Cuba.

other common names

French: Requin citron; Spanish: Tiburón galano.

physical characteristics

Somewhat rounded and blunt snout, no labial furrows, first dorsal fin well anterior to pelvic fin origin, relatively large second dorsal and anal fins, and moderately large caudal fin. Teeth have slender, smooth, and triangular cusps. Coloration is gray to yellowish-brown dorsally and laterally, creamy white ventrally. Reaches about 11.5 ft (3.5 m) in length.

distribution

Tropical and warm temperate waters. Present in the eastern Pacific off the coasts of Mexico south to Peru; in the western Atlantic from New England to southern Brazil, Gulf of Mexico, and Caribbean; and in the eastern Atlantic off Senegal and probably elsewhere in Africa.

habitat

An inshore, coastal species common in coral reefs, mangroves, and bays; around piers and docks; and at river mouths, occurring from the surface down to about 328 ft (100 m). May penetrate freshwater but not only for short distances.

behavior

Lemon sharks are active both during the day and at night, with peaks of activity at dawn or dusk. They prefer shallow areas, and individuals may display site preferences, especially younger sharks. Their home range expands with growth, as young sharks may remain within a region encompassing 3.7–5 mi² (6–8 km²), which may expand to 186 mi² (300 km²) when they reach adulthood. Lemon sharks may remain active in low-oxygen environments because of their high respiratory efficiency. They typically are found resting on the bottom. Adults may undertake long seasonal migrations.

feeding ecology and diet

Feeds mostly on fishes (including many different rays), crustaceans, and mollusks. Also may consume seabirds occasionally. Young lemon sharks, 27.6 in (70 cm) in length, have been able to eat 3% of their body weight in captivity, with unlimited food available.

reproductive biology

A viviparous species with a yolk sac placenta. Litters commonly have between four and 17 young, and gestation periods last from 10 to 12 months. Young are born in shallow nursery areas and remain there for a short period. Sexual maturity is reached after about six and a half years. Both courtship and mating have occurred in captivity.

conservation status

Listed as Lower Risk by the IUCN, because young specimens inhabit coastal nursery regions that may be subject to development and habitat degradation.

significance to humans

A hardy species in captive conditions. Caught frequently on longlines and fished by anglers. The flesh may be consumed fresh or in other ways. There is evidence of population declines in the eastern Pacific and western Atlantic. Attacks on people have been recorded, largely owing to the lemon shark's preference for shallow water in areas that are heavily populated. The lemon shark, however, is not considered an aggressive species. May be seen in the wild in the Bahamas, Turks and Caicos, Florida, Belize, and many other Caribbean locations.

Blue shark

Prionace glauca

family

Carcharhinidae

taxonomy

Squalus glauca Linnaeus, 1758, "Oceano Europaeo."

other common names

French: Peau bleu; Spanish: Tiburón azul.

physical characteristics

The blue shark has characteristically long pectoral fins, a slender body with a large caudal fin, an elongated snout, widely separated dorsal fins, and first dorsal fin much larger than the second. Teeth have small lateral serrations and are slightly different in the upper and lower jaws. Deep blue dorsal coloration, with lighter blue sides and white ventrally. Reaches some 13 ft (4 m) in length.

distribution

Worldwide in tropical and temperate waters. It is perhaps the widest-ranging chondrichthyan.

habitat

The blue shark is an oceanic, epipelagic shark that enters littoral regions with frequency. Usually found close to the surface but has been captured at depths slightly more than 722 ft (220 m) in warmer latitudes.

behavior

May occur in loosely organized aggregations, cruising at slow speeds close to the surface, but capable of swift bursts of speed; may even jump out of the water. Known to circle potential prey items before attacking. May migrate seasonally, and tagged individuals have been recaptured at very distant locations (e.g., across the Atlantic). May bite objects or potential prey out of curiosity or in an attempt to "taste" them before committing to a feeding. Blue sharks are capable of making sharp, quick turns, an indication of their extreme versatility.

feeding ecology and diet

Consumes mostly pelagic bony fishes, and especially squid, that occur close to the surface but also may feed on other sharks (such as the piked dogfish, Squalus acanthias, and, in one case, the goblin shark, Mitsukurina owstoni), invertebrates, mammalian carrion, and even seabirds. Feeds massively on squid during breeding aggregations and on flying-fish eggs during spawning in the Adriatic.

reproductive biology

Viviparous with a yolk sac placenta; litters range from four to 135 young (the greatest range of any live-bearing shark). Gestation is from nine to 12 months. Sexual maturity is reached after some five years (slightly younger for males). Females are sexually mature at about 86.6 in (220 cm) in length, males at slightly smaller sizes. Females store sperm in the shell glands of their oviducts after copulation (which usually takes place from late spring to early winter in temperate regions and all year in tropical seas), utilizing it only when their ovaries ripen to produce and release eggs into the oviduct. Sperm may be stored in this manner for a period of one year. Courtship rituals involve biting, and the sexes can be distinguished readily according to the presence of scars on the body. Females may have skin three times as thick as males. Individuals may segregate by sex.

conservation status

Listed as Lower Risk/Near Threatened by the IUCN, mostly owing to the lack of data concerning the effects of presently being the most fished shark species in the world and an important keystone predator in the oceanic realm.

significance to humans

Heavily fished in much of its range, usually by means of pelagic longlines. Consumed fresh, frozen, and dried/salted. The skin may be used for leather and the fins for shark fin soup. Also fished recreationally. Attacks on people have been attributed to this species, but there also have been many harmless encounters. Nevertheless, the blue shark should be approached with caution. There are many places where tourists may take day trips to see blue sharks in the wild (e.g., California, Portugal, and New Zealand).

False catshark

Pseudotriakis microdon

family

Pseudotriakidae

taxonomy

Pseudotriakis microdon Capello, 1868, Setubal, Portugal.

other common names

French: Requin à longue dorsale; Spanish: Musolón de aleta larga.

physical characteristics

A unique shark, with an extremely elongated, low first dorsal fin; a tall, triangular second dorsal fin; a large anal fin, elongated, slitlike eyes; and a wide mouth with 200–300 rows of numerous minute teeth in each jaw. Covered in prickly denticles and with brownish-black coloration. Reaches 9.8 ft (3 m) in length.

distribution

Worldwide in tropical and temperate latitudes.

habitat

A deepwater, demersal species, occurring predominantly from 656 to 4,920 ft (200–1,500 m) along the continental slopes. May venture rarely into more shallow waters of the continental shelf.

behavior

Nothing is known.

feeding ecology and diet

Largely unknown but presumably consumes demersal fishes and invertebrates. The huge mouth of the false catshark probably allows it to ingest prey of considerable size.

reproductive biology

Aplacentally viviparous (ovoviviparous), with small litters (reportedly two to four young) but producing copious numbers of eggs (estimated at 20,000 in one ovary of a female 110 in, or 280 cm, in length).

conservation status

Not threatened.

significance to humans

Not consumed in significant quantities but occasionally captured with bottom longlines. Not considered dangerous.

Swellshark

Cephaloscyllium ventriosum

family

Scyliorhinidae

taxonomy

Scyllium ventriosum Garman, 1880, Valparaíso, Chile.

other common names

Spanish: Pejegato hinchado.

physical characteristics

Posterior margins of nasal flaps reaching the mouth, broadly rounded snout. The first dorsal fin behind the origin of the pelvic fins and larger than the second dorsal fin; relatively large anal fin and large eyes. Teeth have small lateral cusplets. Large brown blotches and saddles dorsally and laterally and small darker and lighter spots ventrally and laterally on a yellowish-brown background. Reaches about 3.3 ft (1 m) in length.

distribution

Occurs in the eastern Pacific Ocean from Monterey Bay, California, south to central Chile; not yet recorded from the south of Mexico to southern Peru.

habitat

Usually present in shallow waters, from 16.4 to 121.4 ft (5–37m) but occasionally caught deeper on the upper continental slope, to 1,500 ft (457 m). Found on rocky bottoms but also on substrates covered by algae.

behavior

A sluggish shark that remains mostly motionless, sheltered in caves or crevices during the day and becoming more active at night. Individuals may aggregate while resting. As their common name implies, swellsharks are capable of inflating their stomachs with water or air to escape predation (similarly to pufferfishes). They even may wedge themselves in crevices in this manner.

feeding ecology and diet

Feeds mostly on bony fishes but also may eat hard-shelled invertebrates.

reproductive biology

Oviparous (egg laying), depositing amber to greenish egg cases with smooth surfaces and elongated tendrils. Young hatch after a period of seven and a half to 10 months, at about 5.1–5.9 in (13–15 cm) in length. Young have a row of enlarged denticles along the back that may aid them when leaving the egg cases. Males sexually mature between 32.3 and 33.5 in (82–85 cm) in length.

conservation status

Not threatened.

significance to humans

Swellsharks do well in captivity and are featured in many aquaria. Females even lay egg cases in aquaria. These sharks are not consumed and probably are discarded if captured in trawls. Not considered dangerous to people but may become aggressive if harassed.

Pajama catshark

Poroderma africanum

family

Scyliorhinidae

taxonomy

Squalus africanus Gmelin, 1789, "Mari Africanum," probably off South Africa.

other common names

English: Striped catshark; French: Roussette rubanée; Afrikaans: Streep-kathaai.

physical characteristics

An unmistakable shark, with longitudinal, broad stripes from head to tail on the dorsal and lateral sides. Elongated eyes, first dorsal fin posterior to pelvic fin origin and larger than the second dorsal, and relatively short narial barbels. Reaches about 3.3 ft (1 m) in length.

distribution

Found primarily off South Africa but also in the eastern Atlantic near the mouth of the Congo River. Records needing confirmation exist from Madagascar and Mauritius.

habitat

A shallow-water, inshore species, occurring in waters down to 328 ft (100 m) deep. Common in caves and over rocky substrates.

behavior

A common, mostly nocturnal and somewhat sluggish shark, but behavior is poorly known.

feeding ecology and diet

Feeds on crustaceans, cephalopods, polychaetes, and many different bony fishes.

reproductive biology

An oviparous species, laying a single egg case per oviduct. One egg laid in an aquarium hatched after five and a half months. Males are sexually mature between 22.8 and 29.9 in (58–76 cm) in length and females between 25.6 and 28.3 in (65–72 cm).

conservation status

Listed as Lower Risk/Near Threatened by the IUCN, because of its restricted occurrence mostly in regions with high levels of human activity and fishing.

significance to humans

Readily kept in aquaria but not consumed or captured significantly. Occasionally captured as by-catch by bottom trawlers but usually discarded; fished recreationally. Not dangerous to people.

Chain catshark

Scyliorhinus retifer

family

Scyliorhinidae

taxonomy

Scyllium retiferum Garman, 1881, off Virginia, United States.

other common names

Spanish: Alitán mallero.

physical characteristics

Coloration unique, composed of numerous brown saddles with a conspicuous internal network pattern that also is present over the pectoral and caudal fins. First dorsal fin behind origin of pelvic fins and larger than the second dorsal fin, back somewhat arched. Elongated, slitlike eyes. Reaches about 19.7 in (50 cm) in length.

distribution

Present in the western North Atlantic from southern New England to Florida; found in the Gulf of Mexico from Florida south to Nicaragua.

habitat

A mostly deepwater species, demersal on the outer continental shelf to the upper slope region, from 29 to 1,800 ft (73–550 m) in depth.

behavior

Unknown.

feeding ecology and diet

Presumably feeds on fishes and invertebrates, as it lives mostly in close association with the bottom, but full stomach contents have yet to be examined. Cephalopod beaks were found in one specimen.

reproductive biology

Oviparous (egg laying), but most details concerning its reproduction are unknown. Males mature sexually at about 14.6–16.1 in (37–41 cm) in length, females from 13.8 to 18.5 in (35–47 cm). Length at birth is about 3.9 in (10 cm).

conservation status

Not threatened.

significance to humans

Captured occasionally as by-catch in bottom trawls but is not consumed and is discarded. Not dangerous, owing to its size and habitat.

Great hammerhead shark

Sphyrna mokarran

family

Sphyrnidae

taxonomy

Zygaena mokarran Rüppel, 1837, Red Sea.

other common names

French: Grand requin-marteau; Spanish: Cornuda gigante.

physical characteristics

Cephalofoil (hammerhead) with somewhat straight anterior margin with a slight median indentation. Hammerhead not very broad proportionally. Very tall first dorsal fin entirely anterior to pelvic fin origins, pelvic and anal fins with strongly concave posterior margins, and well-developed caudal fin. Serrated teeth. Uniform gray coloration. The largest of the hammerhead sharks, reaching some 20 ft (6 m) in length.

distribution

Worldwide in coastal tropical to warm temperate waters.

habitat

Common in inshore tropical waters but also present offshore, occurring close to the water'surface to depths of 263 ft (80 m).

behavior

A nomadic, migratory species, the great hammerhead shark can occur in great numbers, with individuals moving their heads from side to side as they cruise at midwater depth.

feeding ecology and diet

Eats a variety of bony fishes but seems particularly fond of stingrays, rays in general, groupers, and marine catfishes. Many fishes are commonly taken as prey (even smoothhound sharks). The venemous stings of stingrays and catfishes do not appear to harm the great hammerhead, as they frequently are found stuck in the mouth and pharynx. (One specimen apparently had more than 50 stings embedded in its mouth, throat, and tongue.) Also may feed on crabs and squid.

reproductive biology

Viviparous with a yolk sac placenta and litters ranging from 13 to 42 young. Equal numbers of males and females usually are born. Gestation may last seven months. Males are sexually mature at about 93–106 in (235–269 cm) in length and females from between 98 and 118 in (250–300 cm).

conservation status

Currently listed as Data Deficient by the IUCN, even though it is not targeted specifically by the fishing industry. Listed mainly because of its capture as by-catch (which may be significant) and high-value fins.

significance to humans

The flesh is consumed commonly in the tropics and sold frozen, dried/salted, and smoked. Because of its large size, the great hammerhead was once believed to be dangerous. Attacks by hammerheads have occurred, but identifying the particular species is difficult; this species should be treated with caution. Important in the growing shark tourism industry, as it is observed by divers in many locations (e.g., in the Bahamas, Turks and Caicos, and Australia).

Bonnethead shark

Sphyrna tiburo

family

Sphyrnidae

taxonomy

Squalus tiburo Linnaeus, 1758, "Habitat in America."

other common names

French: Requin-marteau tiburo; Spanish: Cornuda tiburo.

physical characteristics

Snout unique in being broadly rounded anteriorly (resembling a shovel) and without a median notch. Relatively tall first dorsal fin that is completely anterior to the pelvic fin origins; somewhat small second dorsal fin. Grayish-brown in color dorsally and on the sides and paler ventrally. Molariform posterior teeth. This is a small hammerhead species, reaching only about 5 ft (1.5 m) in length.

distribution

In the eastern Pacific from southern California south to Ecuador and in the western Atlantic, Caribbean, and Gulf of Mexico from North Carolina (exceptionally from New England) south to southern Brazil.

habitat

An inshore, coastal species, usually present in shallow waters down to depths of 82 ft (25 m) but occasionally down to 263 ft (80 m). Common in estuaries, sandy bottoms, coral reefs, shallow bays, and channels.

behavior

Forms large schools in many regions of its range and is a social species, occurring typically in numbers from three to 15 individuals. Migrates seasonally and is found as far north as New England during the summer months. Sexual segregation has been noted in this species, with females remaining near shallow nursery areas to give birth. The behavior of this shark has been studied more intensely than that of others, and some 18 separate postures and behavioral patterns have been reported. Behaviors include patrolling (relatively straight-line swimming), maneuvering (systematic rapid turns), explosive gliding (rapid swimming initiated by tail beats), rapid head shaking, head snapping (strong vertical movements of the head and trunk), jaw snapping (opening and closing of the mouth), chafing (sudden rolling of the body), gill puffing (rapid expansion of the gills), clasper flexing (strong single clasper movements), circling head to tail (two sharks swimming in a tight circle, head to tail), and following (individuals closely following each other), among others.

feeding ecology and diet

Feeds abundantly on many different crustaceans (such as shrimp, isopods, crabs, lobsters, and even barnacles) as well as octopi, bivalves, and small fishes.

reproductive biology

Viviparous with a yolk sac placenta and litters ranging from four to 16 young. Males are sexually mature at about 20.5–29.5 in (52–75 cm) in length and females by at least at 33 in (84 cm). Lengths at birth range from 13.4 to 15.7 in (34–40 cm).

conservation status

Not listed by the IUCN.

significance to humans

Taken frequently by small fishing operations, usually as by-catch in bottom trawls, and utilized fresh, frozen, dried/salted, and in other forms. Not considered dangerous, owing to its small size, but it occurs close to heavily populated areas and should be approached cautiously.

Leopard shark

Triakis semifasciata

family

Triakidae

taxonomy

Triakis semifasciata Girard, 1854, San Francisco Bay, California.

other common names

Spanish: Tollo leopardo.

physical characteristics

The coloration of the leopard shark is distinctive, with numerous dark gray saddle marks from nape to tail, dark blotches laterally, and a light gray background color. First dorsal fin anterior to the pelvic fin origins and large second dorsal fin ahead of the anal fin origin. Slitlike eyes and upper and lower labial furrows. Reaches about 71 in (180 cm) in length.

distribution

Restricted to the eastern Pacific from Oregon to central Mexico, including the Gulf of California.

habitat

Occurs in shallow waters, usually less than 33 ft (10 m) deep, but may be captured as deep as 328 ft (100 m). A bottom dweller, the leopard shark commonly is found over rocky, sandy, or muddy substrates. Also may enter bays and estuaries.

behavior

Leopard sharks are highly active, and the wide variety of prey items and their habitats indicate that they employ a wide range of feeding behaviors, from removing burrowing mollusks from their hard shells (clams) to feeding on schooling fishes. An abundant shark, with limited movements (as concluded by tagging studies), that is sometimes observed resting on the bottom.

feeding ecology and diet

Eats fishes and invertebrates; reported to prefer invertebrates, such as crabs, shrimp, polychaete worms, and octopi. Also reported to have fed on sharks (the brown smoothhound shark, Mustelus henlei), guitarfish (Rhinobatos productus), bat rays (Myliobatis californica), and fish eggs. Diet may vary according to size and season, at least locally off California. Feeds on many mud-burrowing prey items (clams, certain shrimps, and polychaetes), which suggests that feeding takes place close to the bottom. Feeding also has been observed closer to the surface, on schools of anchovies.

reproductive biology

Aplacentally viviparous, with four to 29 young per litter. Gestation lasts about 12 months. Reproductive maturity may take more than 10 years, as growth is very slow.

conservation status

Listed as Lower Risk/Near Threatened by the IUCN, because of the lack of regulation with respect to fishing.

significance to humans

Leopard sharks are kept easily in aquaria, where they can live for more than 20 years. Seldom captured by anglers but caught somewhat more frequently by small commercial operations, especially in Mexico. The flesh is sold fresh or frozen and is reported to be of good quality. Not considered dangerous.

Resources

Books

Bigelow, H. B., and W. C. Schroeder. "Sharks." In Fishes of the Western North Atlantic, edited by J. Tee-Van, C. M. Breder, S. F. Hildebrand, A. E. Parr, and W. C. Schroeder. New Haven, CT: Sears Foundation for Marine Research, Yale University, 1948.

Branstetter, S., ed. Conservation Biology of Elasmobranchs. NOAA Technical Report, NMFS 115. Seattle: U.S. Department of Commerce, 1993.

Cappetta, H. Chondrichthyes II: Mesozoic and Caenozoic Elasmobranchii. Handbook of Palaeoichthyology, vol. 3B. Stuttgart and New York: Gustav Fischer Verlag, 1987.

Carwardine, Mark, and Ken Watterson. The Shark Watcher's Handbook: A Guide to Sharks and Where to See Them. Princeton: Princeton University Press: 2002.

Compagno, L. J. V. Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. FAO Species Catalogue, vol. 4, part 1. Rome: Food and Agriculture Organization of the United Nations, 1984.

——. Sharks of the Order Carcharhiniformes. Princeton: Princeton University Press, 1988.

Compagno, L. J. V., and V. H. Niem. "Families Scyliorhinidae, Proscylliidae, Pseudotriakidae, Triakidae, Hemigaleidae, Carcharhinidae, Sphyrnidae." In Western Central Pacific Identification Sheets to Species, edited by K. E. Carpenter and V. H. Niem. Rome: Food and Agriculture Organization of the United Nations, 1999.

Compagno, L. J. V., C. Simpfendorfer, J. E. McCosker, K. Holland, C. Lowe, B. Wetherbee, A. Bush, and C. Meyer. Sharks. Pleasantville, New York: Reader's Digest Association, Inc., 1998.

Hamlett, W. C., ed. Sharks, Skates, and Rays: The Biology of Elasmobranch Fishes. Baltimore: Johns Hopkins University Press, 1999.

Hennemann, Raof M. Sharks and Rays: Elasmobranch Guide of the World. Frankfurt: Ikan, 2001.

Last, P. R., and J. D. Stevens. Sharks and Rays of Australia. Melbourne, Australia: CSIRO, 1994.

Myrberg, Arthur A., Jr., and Donald R. Nelson. "The Behavior of Sharks: What Have We Learned?" In Discovering Sharks, edited by S. H. Gruber. Highlands, NJ: American Littoral Society, 1990.

Perrine, D. Sharks and Rays of the World. Stillwater, MN: Voyager Press, 1999.

Pratt, H. L. Jr., S. H. Gruber, and T. Taniuchi, eds. Elasmobranchs as Living Resources: Advances in the Biology, Ecology, Systematics, and the Status of the Fisheries. Proceedings of the Second United States–Japan Workshop East-West Center, Honolulu, Hawaii, 9–14 December 1987. NOAA Technical Report NMFS 90. Seattle: U.S. Department of Commerce, 1990.

Randall, J. E. "Review of the Biology of the Tiger Shark (Galeocerdo cuvier)." In Sharks: Biology and Fisheries, edited by J. G. Pepperell. Melbourne, Australia: CSIRO, 1992.

Springer, S. "Social Organization in Shark Populations." In Sharks, Skates, and Rays, edited by P. W. Gilbert, R. F. Mathewson, and D. P. Rall. Baltimore: Johns Hopkins University Press, 1967.

Springer, Victor G., and Joy P. Gold. Sharks in Question: The Smithsonian Answer Book. Washington, DC: Smithsonian Institution Press, 1989.

Tricas, T. C., and S. H. Gruber. The Behavior and Sensory Biology of Elasmobranch Fishes: An Anthology in Memory of Donald Richard Nelson. Developments in Environmental Biology of Fishes, vol. 20. Dordrecht, Netherlands: Kluwer Academic Publishers, 2001.

Whitley, G. P. The Fishes of Australia. Part 1. The Sharks, Rays, Devil-fish, and Other Primitive Fishes of Australia and New Zealand. Sydney: Royal Zoological Society of New South Wales, 1940.

Wetherbee, B. M., S. H. Gruber, and E. Cortes. "Diet, Feeding Habits, Digestion, and Consumption in Sharks, with Special Reference to the Lemon Shark, Negaprion brevirostris." In Elasmobranchs as Living Resources: Advances in the Biology, Ecology, Systematics, and the Status of the Fisheries. Proceedings of the Second United States–Japan Workshop East-West Center, Honolulu, Hawaii, 9–14 December 1987, edited by H. L. Pratt, S. H. Gruber, and T. Taniuchi. NOAA Technical Report, NMFS 90. Seattle: U.S. Department of Commerce, 1990.

Wourms, J., and L. Demski. Reproduction and Development of Sharks, Skates, Rays and Ratfishes. Developments in Environmental Biology of Fishes, vol. 14. Dordrecht, Netherlands: Kluwer Academic Publishers, 1993.

Periodicals

Johnson, R. H., and D. R. Nelson. "Agonistic Display in the Gray Reef Shark, Carcharhinus menisorrah, and Its Relationship to Attacks on Man." Copeia 1973, no. 1 (1973): 45–55.

——. "Copulations and Possible Olfaction-Mediated Pair Formation in Two Species of Carcharhinid Sharks." Copeia 1978 (1978): 539–542.

Motta, Phillip J., Robert E. Hueter, and Timothy C. Tricas. "An Electromyographic Analysis of the Biting Mechanism of the Lemon Shark, Negaprion brevirostris: Functional and Evolutionary Implications." Journal of Morphology 210(1991): 55–69.

Myrberg, A. A., and S. H. Gruber. "The Behavior of the Bonnethead Shark, Sphyrna tiburo." Copeia 1974, no. 2(1974): 358–374.

Nelson, D. R. "Aggression in Sharks: Is the Grey Reef Shark Different?" Oceanus 24, no. 4 (1981): 45–55.

Nelson, D. R., and R. H. Johnson. "Behavior of Reef Sharks of Rangiroa, French Polynesia." National Geographic Society Research Reports 12 (1980): 479–499.

Strong, W. R. Jr., F. F. Snelson Jr., and S. H. Gruber. "Hammerhead Shark Predation on Stingrays: An Observation of Prey Handling by Sphyrna mokarran." Copeia 1990, no. 3 (1990): 836–840.

Tricas, T. C., Taylor, L., and G. Naftel. "Diel Behavior of the Tiger Shark, Galeocerdo cuvier, at French Frigate Shoals, Hawaiian Islands." Copeia 1981, no. 4 (1981): 904–908.

Wourms, J. P. "Reproduction and Development in Chondrichthyan Fishes." American Zoologist 17 (1977): 379–410.

Organizations

American Elasmobranch Society, Florida Museum of Natural History. Gainesville, FL 32611 USA. Web site: <http://www.flmnh.ufl.edu/fish/Organizations/aes/aes.htm>

Other

"2002 IUCN Red List of Threatened Species." (26 Dec. 2002). <http://www.redlist.org>

"Fish-Base." 16 Dec. 2002 (26 Dec. 2002). <http://www.fishbase.org>

"Catalog of Fishes On-line." 12 Nov. 2002 (26 Dec. 2002). <http://www.calacademy.org/research/ichthyology/catalog/fishcatsearch.html>

"Reef Quest Expeditions." (26 Dec. 2002). <http://www.reefquest.com>

Marcelo Carvalho, PhD