Page 32 - World of Animals - Book of Sharks & Ocean Predators

Sharks & Ocean Predators
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Speartooth shark

Rarely seen by humans, the speartooth shark
unusually inhabits tropical rivers and estuaries
Few sharks are as elusive as the speartooth. Unlike most other species
of shark, it uses tidal currents to aid its movement in water; fl ooding
tides carry it upstream while ebbing tides return the speartooth back

downstream. They prey mainly on small, bony fish and crustaceans
at night, and are perfectly adapted to hunting in almost complete
darkness. This is thanks to their small eyes and abundant ampullae
(electroreceptors). Speartooths are threatened by mainly unregulated

fishing and habitat degradation. Speartooths are also facing drastic

habitat modification, as dredging and mining damage the ecosystem
in which they live. There are thought to be no more than 2,500 in the
wild, although this is only an estimate.

This rather comic looking shark is
capable of some incredible things in Porbeagle shark
order to survive
Often referred to as blue dogs or
mackerel sharks, the porbeagle can raise
its body temperature to 10oC (50oF)
above the surrounding water
This shark’s ability to change its body temperature is vital,
allowing it to adapt to the variable temperatures of the
North Atlantic Sea. This is achieved through a process
called thermoregulation, and helps the shark to swim
faster when hunting for prey. Although the porbeagle is
most commonly seen in the North Atlantic it can be found
all over the world, including South African and Australian
waters. The shark’s most distinctive feature is its jagged,
three-cusped teeth, but it can also be identified by a white

blotch on its first dorsal fin. Aggressive fishing in Norway

and other areas has caused porbeagle numbers to drop –
they are often caught by accident and then often die as a
result. Like the gulper shark, they have a low reproductive
rate, which has unfortunately led them to become an
endangered species.
“The shark’s distinctive
feature is its jagged,

three-cusped teeth”

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