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).
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.
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
Photo © Jeremy Stafford-Deitsch;
used with the gracious permission of the photographer, who asks that you support
the Shark Trust.