FAO Species Identification Guide for Fishery Purposes Western

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1208 Sharks
HEXANCHIDAE
Cowsharks, sixgill, and sevengill sharks
by L.J.V. Compagno and V.H. Niem
Diagnostic characters: Small to large sharks with slender to stout bodies. Head with 6 or 7 pairs of
long gill slits, the last pair in front of pectoral-fin origins, the first pair not connected across throat;
short dermal gill rakers present on inner gill slits; spiracles present, small; nostrils without barbels or nasoral
grooves; no nictitating lower eyelids; snout short, acutely to bluntly pointed; mouth very long and extending
far behind eyes; teeth of upper and lower jaws unlike at sides of mouth, uppers small, narrow, with a
main cusp and often smaller cusplets, lowers very large, broad, compressed, and saw-like, with a series
of cusps or large cusplets. A single dorsal fin, posterior to pelvic fins; anal fin present; caudal fin much less
than 1/2 the total length, strongly asymmetrical, with a pronounced subterminal notch but lower lobe very
short. Caudal peduncle not depressed, without keels; no precaudal pits. Intestinal valve of spiral type.
Colour: grey, blackish, or brown above, lighter below.
6-7 gill
slits
a single dorsal fin
no precaudal pits
Habitat, biology, and fisheries: These are moderately abundant, inshore to deep-water sharks, found in
shallow bays down to the continental slopes and submarine canyons, near the bottom or well above it. They
feed on a wide variety of bony fishes, other sharks, batoid fishes, marine mammals, cephalopods, and
crustaceans. Cow sharks are comparatively unimportant but regular components of shark fisheries and
bycatches of other fisheries and are incidentally caught in trawls. They may bite aggressively during capture
but only the larger species are potentially dangerous, particularly when provoked.
Similar families occurring in the area
None. No other sharks in the area have a single dorsal fin and 6 or 7 gill slits.
subterminal
notch
teeth of left side (Hexanchus griseus) intestinal valve of spiral type
Key to the species of Hexanchidae occurring in the area
1a. Seven gill slits (Fig. 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heptranchias perlo
1b. Six gill slits (Figs 2 and 3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . → 2
7 gill
slits
Fig. 1 Heptranchias perlo