Author: (Hermann, 1783)
Field Marks:
Unique large sharks that combine a broad, low caudal fin about as long as the rest of the shark with nasoral grooves, barbels, a small transverse mouth in front of the lateral eyes, two spineless dorsal fins and an anal fin, the first dorsal much larger than the second and with its origin far foward on back, prominent ridges on the sides of the body, but no strong lateral keels on the caudal peduncle, and a banded or spotted colour pattern. Young sharks are dark brown above, yellowish below, with vertical yellow stripes and spots breaking the dorsal coloration into dark saddles; between 50 and 90 cm length the saddles break up into small brown spots on a yellow background, these becoming less linear and more uniformly distributed with further increase in size. There is considerable variation in the colour pattern between individuals of like size. An albino specimen was once collected.
Diagnostic Features:
Body cylindrical, with prominent ridges on sides. Head broad conical, and somewhat flattened, without lateral flaps of skin, snout very broadly rounded or truncated; eyes laterally situated on head, without subocular pockets; spiracles subequal in size to eyes but not below them; gill slits small, fifth overlapping fourth; internal gill slits without filter screens; nostrils with short pointed barbels but without circumnarial folds and grooves; mouth moderately large, subterminal on head, and transverse, without a symphyseal groove on chin; teeth not strongly differentiated in jaws, with a medial cusp, lateral cusplets and weak labial root lobes; 28 to 33/22 to 32. Caudal peduncle without lateral keels or precaudal pits. First dorsal larger than second, with brigin expanded well ahead of pelvic origins and insertion about over the pelvic bases; pectoral fins rather large, broad and rounded, much larger than pelvic fins, with fin radials partly into fin web but falling well short of its distal edge; pelvic fins smaller than first dorsal but larger than second dorsal and as large or larger than anal fin; anal fin larger than second dorsal, with its origin about opposite second dorsal midbase or insertion; anal fin with broad base and angular apex, separated by a space or narrow notch much less than base length from lower caudal origin; caudal fin with its upper lobe at a low angle above the body axis, about half as long as the entire shark, with a strong terminal lobe and subterminal notch but no ventral lobe. Supraorbital crests present on cranium, these laterally expanded. Valvular intestine of ring type. Colour pattern of dark saddles in young, changing to dark spots in adults.
Geographical Distribution:
Indo-West Pacific: From South Africa and Red Sea to Pakistan, India, Sri Lanka, Bangladesh, Indonesia, Thailand, Viet Nam, Kampuchea, the Philippines, China, Japan, Australia (Western and Northern Australia, New South Wales), New Caledonia, Palau.
Habitat and Biology:
This is a tropical inshore shark, of the continental and insular shelves of the Indo-West Pacific, that is very common on coral reefs. Its behaviour is little known, but it has been photographed resting on sandy areas within reefs, propped up on its pectoral fins and facing a current with open mouth. It apparently is rather sluggish, at least during the daytime, and may be more active at night like nurse sharks (Ginglymostomatidae). Because of its rather slender, flexible body and caudal fin it is able to squirm into narrow cracks, crevices and channel in reefs while searching for food. In captivity, it spends most of its time resting on the bottom (at least during the day), but becomes active when food is introduced into its tank.
Oviparous, laying eggs in large (17 cm long, 8 cm wide and about 5 cm thick), dark brown or purplish-black cases with fine lateral tufts of hairlike fibers, which serve to anchor the cases to the substrate. Probably lays more than one or two eggs at once, as four fully formed, encased eggs were found in one oviduct of an adult female.
Feeds primarily on molluscs (gastropods and bivalves) but also crustaceans (crabs and shrimps) and small bony fishes.
A hardy shark, readily kept in captivity. The zebra shark is unaggressive when approached underwater, and has not been involved in attacks on people. Although this shark is apparently not dangerous, and has very small teeth, its jaws are strong and could deliver a painful bite to an unwary human tormentor.
Size:
Maximum total length possibly 354 cm, males mature between 147 and 183 cm, females between 169 to 171 cm and reaching at least 233 cm; young hatching at a size between 20 and 36 cm.
Interest to Flsheries:
A common shark in the Indo-West Pacific, regularly taken in inshore fisheries in Pakistan, India, Thailand, Malaysia, Taiwan (Province of China), and elsewhere where it occurs. It is caught in bottom trawls, in floating and fixed bottom gillnets, and with longlines and other line gear. The meat is utilized fresh and dried salted for human consumption; livers processed for vitamins; fins dried and processed for the oriental sharkfin trade; and offal utilized for fishmeal.
Remarks:
The earliest name for the zebra shark is Squalus varius Seba, 1758, which has been used by various writers (such as Garman, 1913, Klausewitz, 1960, and Bass, d'Aubrey and Kistnasamy 1975b) as Stegostoma varium. However, an examination of Seba's (1758) descriptions of fishes showed that his nomenclature was haphazardly uninomial, binomial, and polynomial, although the name of the zebra shark could be construed as binomial: "Squalus varius; naribus ori proximis; foraminibus pare oculos; spiraculis utrinque quaternis; cauda longifilis." (Seba, 1758, p. 105).
In addition to the above name-diagnosis, Seba includes a long, accurate Latin description of the zebra shark, and a legend caption in French for a good illustration of a juvenile zebra shark (Seba, 1758, pl. 34, no. 1). I hesitate to use Stegostoma varium as a name for this shark because Seba's nomenclature was not consistently binomial, but note that the International Commission on Zoological Nomenclature may have to rule on its availability.
Type material:
Holotype: None. Type Locality: Uncertain, probably Indonesia.