Family Triakidae:
Smoothhounds and
Houndsharks — 63 species
Intermediate between the scyliorhinids and carcharhinids in form and size are the smoothhounds and houndsharks (family Triakidae). The triakids include the beautifully marked Leopard Shark (Triakis semifasciata), which is often displayed in aquaria, and the commercially important Tope Shark — also known as the School or Soupfin Shark — (Galeorhinus galeus).
The handsomely-marked Leopard Shark (Triakis semifasciata) is endemic to the west coast of North America, ranging from Oregon to central Mexico. This species is usually found swimming close over the substrate in coastal habitats from the intertidal down to a depth of at least 300 feet (90 metres). It frequents rocky reefs (often in the vicinity of kelp beds) and bays with muddy or sandy bottoms. After a 12-month gestation period, 4 to 29 pups are born during the spring in shallow coastal bays, which serve as nursery areas. Born at a length of about 8 inches (20 centimetres), the Leopard Shark grows to a maximum length of 6 feet (1.8 metres). Diet of this pavement-toothed triakid includes crabs, shrimp, clams, innkeeper worms, octopuses, bony fishes (anchovies, herring, surf perches, gobies, rockfishes, sculpins, flatfishes), fish eggs, and other elasmobranchs (smoothhounds, guitarfishes, bat rays). Off California, adults of this species regularly feed on Innkeeper Worms (Urechis caupo), actually sucking them from their U-shaped burrows in the mud and swallowing them whole. Leopard Sharks sometimes mutilate their prey, consuming only part of them - such as seizing the siphons of buried clams and ripping them off with violent lateral head-shaking; it is not uncommon to find dozens of fleshy bivalve siphons (no shells, just the siphons) in the stomach of these sharks. Although generally regarded as harmless to humans, there is a report of a Leopard Shark charging a diver with a nosebleed.
Recent research has found that the Leopard Shark (Triakis semifasciata) has smaller and more numerous erythrocytes (red blood cells) than either of the other triakids that often share its estuarine habitat, the Brown Smothhound (Mustelus henlei) and the Grey Smoothhound (M. californicus). These blood characteristics give the Leopard Shark enhanced ability to absorb oxygen from turbid estuarine waters and thus a competitive advantage over both its relatives.
Photo © Jeremy Stafford-Deitsch; used with the gracious permission of the photographer, who asks that you support the Shark Trust.
