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Deepseawaters
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Sea SharksCommon Thresher Shark
Common Thresher Shark
Common Name: Common Thresher Shark
Scientific Name: Alopias vulpinus
Description
The body of the common
thresher shark is moderately elongate. The snout
is rather short, and the mouth crescent shaped. The first
dorsal fin is large, and located midway between the pectoral
and ventral fins. The second dorsal and anal fins are very
small. The tail is distinctive since it is very long, almost
as long as the rest of the body. The coloration may vary from
brownish gray, bluish or blackish above to silvery, bluish
or golden below. The dorsal, pectoral and ventral fins are
blackish and sometimes the pectoral and ventral fins have
a white dot in the lip. The bigeye thresher also occurs off
the California coast. It can be distinguished by its large
eye; however, if you can count the teeth in the upper jaw,
the common thresher has 21 - 22 on each side while the bigeye
thresher has 10 - 11 on each side.
Range
The common thresher shark
occurs worldwide in warmer seas. In the eastern North Pacific,
it is found from central Baja California, to the Strait of
Juan de Fuca, British Columbia. The common thresher is an
inhabitant of the upper layers of deep offshore waters and
is most abundant in areas of steep bottom contour along the
edges of the continental shelf. During the spring and summer
months smaller threshers may occur near shore where they are
often seen leaping completely out of the water.
Natural
History
The food habits of the thresher
are not well known, but on the California coast they feed
mostly upon small fish such as sardines, anchovies, mackerel,
and squid. They are said to use their long tail as a flail
to frighten or stun their prey. The common thresher shark
bears live young and appears to become sexually mature in
6 or 7 years. Four pups are produced annually. A 18 foot female
contained four young that weighed 13.5 pounds each and were
4 to 4.5 feet long.
Fishing
Information
Most thresher sharks caught
off California have been taken on live sardines, anchovies,
or mackerel. Best localities have been the San Francisco Bay
area, the inshore coastal water between Point Conception and
Port Hueneme, and Santa Monica Bay, especially around Malibu
and Paradise Cove. They are most abundant during the summer
months. Considered a fine game species on light or medium
tackle, they often put on an aerial demonstration. At other
times the battle is entirely beneath the surface and consists
of brute strength and shift-towing tactics. An angler would
do well to bait a live mackerel on a 9/0 hook attached to
10 or so feet of heavy wire leader.
Other Common
Names
thresher, blue thresher, green
thresher, longtail shark, swiveltail, fox shark, sea fox
Largest
Recorded
20 feet; 1,000 pounds. Largest
taken off California by a recreational angler: 527 pounds.
Habitat
Pelagic
Environment.
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