Threser Shark

Photo modified from Sharks and Rays. TC Tricas, K Deacon, P Last, JE McCosker, TI Walker, L Taylor. 1997. Nature Company Guides, Time Life Book Series. Weldon Owen Pty Ltd., San Francisco.

The thresher shark is characterized by its large upper caudal fin. This tail fin may often be 50 percent of the total length of the shark. It has a short snout and large eyes placed forward on the head. The second dorsal fin is much smaller than the first. The thresher is a strong swimmer and can leap clear of the water. The jaws are small with small, curved sharp teeth without basal cusps or serrations. Colour varies from brown to black with metallic hues from above and irregular white markings on the underside. In Canadian waters sizes have ranged from 3.3 to 5.5 meters (10.8 to 18 feet) long. The maximum size recorded for this species is 6.1 meters (20 feet), however they generally are between 2 to 5 meters (10 to 16.5 feet) in length.

Diet

The thresher shark eats schooling fish, such as herring and mackerel and cephalopods such as squid. The large caudal fin is used to slap the surface of the water forcing fish to form tighter schools; the tail can then be used as a whip to stun or kill the prey.

Reproduction

This shark is ovoviviparous, with the eggs being hatched inside the female, and 2 to 6 live pups being delivered at a size of 1.5 meters (5 feet) long. During development the young may cannibalize their siblings within the uterine chamber.

Habitat

The thresher often swims at the surface of coastal waters. However it can also occur at depths of 350 meters (1,150 feet) or more. The young may be found inshore in shallow water.

Range

The thresher shark is a summer visitor to the Canadian Atlantic region. They have been captured from July to November, but most frequently during August and September. The thresher ranges through all warm and temperate areas of the worlds oceans. Its northernmost range in the western Atlantic is eastern Newfoundland and it ranges all the way down the Atlantic to the West Indies and northern South America.

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