NOVA Online | Island of the Sharks

Order

Family

Species

Carcharhiniformes
Ground sharks
This is the most dominant of shark groups, with nearly 200 described species. They are common in tropical and temperature waters, and certain species, such as the blue, silky, and oceanic whitetip sharks, are the most numerous of pelagic sharks. The order ranges from the primitive catsharks to the large hammerheads and requiem sharks.

Ground sharks feature an anal fin, two dorsal fins, an elongated snout, and a long mouth that reaches behind the eyes, with teeth ranging from small and cuspidate to large and bladelike. They have a third eyelid as well.

SCYLIORHINIDAE
Catsharks
Appearance: Small sharks with elongated, catlike eyes and large spiracles. The first dorsal fin is over or behind the pelvic fins, there are no precaudal pits, and the caudal fin has no strong ventral lobe. Many shelf species have colorful and variegated patterns of spots, blotches, saddles, stripes, and reticulations, but those found in deeper water often lack them, and range from uniform whitish or pinkish to jet black.

Galeus melastomus
Blackmouth catshark

Size: The largest catsharks reach a length of about five ft, but most are less than 32 in long, and some dwarf species do not exceed a foot in length.

Habitat: Most catshark species are deepwater slope sharks. None is oceanic, and most occur on or near the bottom, though some deepwater slope species range well above the substrate. Catsharks occur in coastal marine waters, from the intertidal to the outer shelf and down the slopes to depths of over 6,600 t. None occurs in fresh water.

Distribution: Catsharks have a vast geographic range in tropical to cold temperate and boreal waters, in all oceans except the Antarctic.

Diet: Invertebrates, especially crustaceans and cephalopods, small bony fishes and small sharks and rays. Many take bottom prey, but a number of species feed on midwater bony fishes such as lanternfishes and lightfishes.

Shark bite: The filetail catshark travels in gender-segregated schools of several thousand.

92 Species

PROSCYLLIIDAE
Finback Catsharks
Appearance: This family of small, plain or brightly patterned sharks is very similar to the true catsharks (Scyliorhinidae), but its members have their first dorsal fins positioned in front of the pelvic fins. They also have elongated, catlike eyes and comblike rear teeth.

Proscyllium habereri
Graceful catshark

Size: The largest of the group, the slender smoothhound, reaches about 3.3 ft; the pygmy ribbontail catshark matures at between 6 and 7.2 in.

Habitat: Outer shelves and upper slopes at depths reaching to 2,300 ft.

Distribution: A scattered distribution in the western north Atlantic and Indo-Pacific.

Diet: Small bony fishes, crustaceans, cephalopods, and bivalves.

Shark bite: It is possible that female pygmy ribbontail catsharks grow considerably when pregnant, as only the larger females have near- or full-term young, while small females have only embryos in earlier stages.

Six Species

PSEUDOTRIAKIDAE
False Catsharks
Appearance: A large shark with a long, low keel-like first dorsal fin on the back in front of the pelvic fins. It has elongated, catlike eyes, very large spiracles, a large mouth, and numerous small teeth.

Pseudotriakis microdon
False catshark

Size: Adults reach almost 12 ft in length.

Habitat: A singular inhabitant of continental and insular slopes at depths of between 660 and 5,000 ft. Sometimes occurs inshore.

Distribution: Ranges widely in the north Atlantic; also occurs in the western Indian Ocean and in the western and central Pacific.

Diet: Probably feeds on deepwater bottom fishes and invertebrates.

Shark bite: The large body cavity, soft fins, and soft skin and musculature of the false catshark suggest that it is relatively inactive and sluggish.

One Species

Family

Species

LEPTOCHARIIDAE
Barbeled Houndshark
Appearance: Closely resembles the true houndsharks and the finback catsharks, but differs from them in its longer labial furrows and in combining nearly circular eyes, minute spiracles, and nostrils with barbels.

Leptocharias smithii
Barbeled houndshark

Size: Maximum length 32.8 in.

Habitat: Common at depths from 33 ft to 247.5 ft, especially off river mouths. It favors muddy bottoms.

Distribution: The West African tropics, from Mauritania to Angola; may range north off Morocco and into the Mediterranean.

Diet: Crustaceans, octopuses, sponges, and small bony fishes.

Shark bite: Male barbeled houndsharks have much larger anterior teeth than females, which they may use to grip the female during courtship and copulation.

One species

TRIAKIDAE
Houndsharks
Appearance: Small to moderately large sharks with elongated to nearly circular eyes, large to minute spiracles, and nostrils with anterior flaps usually not formed as barbels.

Iago omanensis
Bigeye houndshark

Size: A few species reach a length of over six ft, but most do not exceed four ft; some reach maturity at less than a foot.

Habitat: Most occur on the continental and insular shelves. A few species are deepwater slope dwellers, and range to below 6,600 ft. None is oceanic. Houndsharks occur mostly on mud, sand, and rock bottoms, commonly in enclosed bays, but at least one species lives on coral reefs.

Distribution: Found in all tropical and temperate seas.

Diet: Most feed on bottom invertebrates, particularly crustaceans; some feed heavily on bony fishes and a few specialize on cephalopods.

Shark bite: Since houndsharks are small in size and fairly abundant in coastal waters, they are important to small commercial fisheries. They are utilized for their meat, liver oil, and for shark-fin soup base.

34 species

HEMIGALEIDAE
Weasel sharks
Appearance: Small to moderately large sharks that are very similar to the requiem sharks. They have nearly circular eyes, small spiracles, and nostrils without barbels.

Paragaleus pectoralis
Atlantic weasel shark

Size: Most do not exceed five ft in length, but one species, the snaggletooth shark, reaches almost eight ft.

Habitat: Inshore sharks, occurring in shelf waters at modest depths, from the intertidal to about 330 ft.

Distribution: Except for one species in the eastern Atlantic, weasel sharks are characteristic of the Indo-west Pacific, from South Africa and the Red Sea to Japan and Australia.

Diet: Bony fishes, small sharks and rays, crustaceans, cephalopods, and other invertebrates.

Shark bite: Two species of weasel shark feed on cephalopods and have shortened mouths that enhance suction feeding; the fish-eating weasel sharks have elongated mouths and sharper teeth.

Six Species

Family

Species

CARCHARHINIDAE
Requiem sharks
Appearance: Small to large sharks with circular or nearly circular eyes, usually without spiracles or barbels.

Triaenodon obesus
Whitetip reef shark

Size: Some of the small species do not exceed 28 in, but many species grow to more than nine ft long. The tiger shark reaches a length of over 18 ft and possibly as long as 25 ft.

Habitat: A very wide habitat range: from estuaries and the intertidal to the open ocean; from muddy bays and hypersaline estuaries to coral and rocky reefs; and in freshwater rivers and lakes (in the case of the bull shark). None is a specialist deepwater bottom dweller, but at least two species range down to 2,000 ft. and three species are oceanic.

Distribution: Extremely wide. Found in all tropical and temperate seas. This group dominates the tropical shark fauna in the diversity of species and often in numbers of individuals.

Diet: They are among the most important large marine predators and take a broad spectrum of prey: bony fishes, sharks and rays, cephalopods, sea-snails, crustaceans, carrion, even sea-turtles, sea-snakes, seabirds, and marine mammals.

Shark bite: The tiger shark is one of the few shark species that on occasion will consume human prey, and it is considered one of the most dangerous sharks in tropical waters.

48 Species

SPHYRNIDAE
Hammerhead sharks
Appearance: Hammerheads are unmistakable; when viewed from above or below their uniquely expanded and flattened heads have the shape of a hammer or mallet. They have circular, widely spaced eyes.

Sphyrna lewini
Scalloped hammerhead

Size: Five of the species are small and do not exceed five ft in length. The other four reach lengths of between 10 and 17 ft.

Habitat: Confined to coastal and offshore continental and insular waters, from the intertidal and surface down to at least 900 ft. None is benthic, deepwater, or oceanic.

Distribution: All warm temperate and tropical seas.

Diet: Bony fishes, other sharks, batoids, squid, octopuses, and cuttlefish, crabs, shrimps and other crustaceans and sea-snails.

Shark bite: Hammerheads swing their heads back and forth while they swim. This may be a way of increasing their chances of detecting food.

Nine Species