Basking sharks are one of the largest sharks of the world's temperate
oceans. Only the mighty whale shark is bigger. Despite a superficial
similarity to the fearsome great white shark and a massive jaw one metre
wide, basking sharks are actually harmless filter feeders. They use
more than 5,000 gill rakers to strain plankton from around 1.5 million
litres of water per hour. Basking sharks are born travellers, covering
large distances in search of food, at the very leisurely pace of only
three miles per hour. There is only one species of basking shark.
The
basking shark (Cetorhinus maximus) is the second largest living fish,
after the whale shark, and the second of three plankton-eating sharks,
the other two being the whale shark and megamouth shark. It is a
cosmopolitan migratory species, found in all the world's temperate
oceans. It is a slow moving filter feeder and has anatomical adaptations
to filter feeding, such as a greatly enlarged mouth and highly
developed gill rakers. The shape of its snout is conical and the gill
slits extend around the top and bottom of its head. The gill rakers are
dark and bristle-like and are used to catch plankton as water filters
through the mouth and over the gills. The basking shark is usually
greyish-brown in color with mottled skin. The caudal (tail) fin has a
strong lateral keel and a crescent shape. The teeth of the basking shark
are very small and numerous and often number one hundred per row. The
teeth themselves have a single conical cusp, are curved backwards and
are the same on both the upper and lower jaws.
Basking sharks are
a migrating species and are believed to overwinter in deep waters. They
may occur in either small schools or alone. Small schools in the Bay of
Fundy and the Hebrides have been seen swimming nose to tail in circles
in what may be a form of mating behavior. Despite their large size and
threatening appearance, basking sharks are not aggressive and are
harmless to people. It has long been a commercially important
fish, as a source of food, shark fin, animal feed, and shark liver oil.
Overexploitation has reduced its populations to the point where some
have disappeared and others need protection.
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