
Thresher
Shark Alopias vulpinus
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.

Distinguishing
Characteristics
- Extremely large caudal fin that may be up
to 50 percent of the body length
- Relatively large eyes
- Relatively small teeth and
jaw
|