Tiger Shark (Galeocerdo cuvier), named for the dark
strips on its gray back, which is pronounced in juveniles
but become pale or disappear in large adults, has tiger-like
markings on a dark back with an off-white underbelly. Pups
have spotted markings that grow together to form stripes that
fade with maturity. It has a large, thick-body with a blunt
snout. The first dorsal fin is much longer than the second.
The caudal fin is long and pointed. There is a dermal ridge
along the back between the 2 dorsal fins.
Its wide mouth, broad nose, barrel chest, and the slenderness
at the base of its tail are distinctive. So, too, are its
heavily serrated, cockscomb-shaped teeth. These, combined
with its jaw strength, allow it to cut the bodies of large
sea turtles, as well as seals, sea lions, and cetaceans.
Tiger sharks have a special gill slit (a spiracle) behind
the eyes that provides oxygen flow directly to the eyes and
brain. It also has a very good sense of smell, electroreceptors
sensitive to electric currents in the water, and keen eyesight.
They are active at night, and enter shallow reefs and lagoons
after dusk to feed. In certain areas they migrate between
island groups to take advantage of colonies of young birds
learning to fly over water. Generally, tiger sharks are sluggish,
but they can move quickly when feeding, and should be treated
carefully on the rare occasions they are sighted. If you see
one while diving, calmly leave the water, keeping it in sight
at all times.
Adult tiger sharks spend their days beyond the reef edge
to depths of about 500' (150m), except at certain times of
the year, when they also come inshore during the day.
The tiger shark ranges world-wide in tropical waters, but
has been spotted in the Bay of Fundy at the mouth of Le Preau
tangled in fishing weir. It is found throughout the world's
temperate and tropical waters, with the exception of the Mediterranean
Sea. It is a wide-ranging species that is at home both in
the open ocean as well as shallow coastal waters. Reports
of individuals from as far north as Iceland and the United
Kingdom have been confirmed but are probably a result of roaming
sharks following the warmer Gulf Stream north across the Atlantic.
This shark has a notable tolerance for many different kinds
of marine habitat but generally prefers murky waters in coastal
areas. It is commonly found in river estuaries, harbors, and
other inlets where runoff from the land may attract a high
number of prey items. Shallow areas around large island chains
and oceanic islands including lagoons, are also part of the
tiger shark's natural environment. It is often seen at the
surface and has been reported to depths of 1085 ft (350 m).
Tiger sharks undergo seasonal migrations. It is well known
that they move into temperate waters from the tropics for
the warmer months and return during the winter. These sharks
also make long oceanic migrations between islands and are
capable of traveling long distances in a short amount of time.