Australian Wildlife: Whale Shark





Whale Shark (Rhincodon typus)

The whale shark is a slow-moving filter feeding shark, the largest living fish species. Despite its size, the whale shark does not pose significant danger to humans. Although massive, whale sharks are docile fish and sometimes allow swimmers to hitch a ride. Whale sharks are actually quite gentle and can play with divers. Divers and snorkelers can swim with this giant fish without risk, apart from unintentional blows from the shark s large tail fin.

The whale shark is found in tropical and warm oceans, lives in the open sea with a lifespan of about 70 years.

In The Wild

Whale sharks can seen at close range by divers in many places in tropical waters around the world. In Australia, the only place where a diver can swim with whale sharks in Ningaloo Reef near Coral Bay, on the north west coast of Western Australia. Every year, between late March and early July, these gentle giants congregate in the Ningaloo Marine Park following the mass spawning of coral.

The opportunity to swim with whale sharks in the Ningaloo Reef region attracts visitors from far and wide to Exmouth and Coral Bay. It s one of very few regions in the world where they congregate regularly in coastal waters and are easily accessible for whale shark watching tours.



Description

The largest confirmed individual whale shark was 12.65 metres in length. The heaviest weighed more than 36 tonnes, but unconfirmed claims report considerably larger whale sharks. This distinctively-marked fish is the only member of its genus Rhincodon and its family, Rhincodontidae (called Rhinodontes before 1984), which belongs to the subclass Elasmobranchii in the class Chondrichthyes. The species originated about 60 million years ago. Although whale sharks have very large mouths, they feed mainly, though not exclusively, on plankton, microscopic plants and animals, although the BBC program Planet Earth filmed a whale shark feeding on a school of small fish.

Habitat

The whale shark inhabits all tropical and warm-temperate seas.They are known to migrate every spring to the continental shelf of the central west coast of Australia. The coral spawning of the area's Ningaloo Reef provides the whale shark with an abundant supply of plankton. Although typically seen offshore, it has been found closer to land, entering lagoons or coral atolls, and near the mouths of estuaries and rivers. It is capable of diving to depths of 700 metres , and is migratory.

Behaviour

The whale shark is not an efficient swimmer since it uses its entire body, unusual for fish, to attain an average speed of around 5-kilometre-per-hour.

With its streamlined shape and strong flippers, the Australian Fur Seal is an agile swimmer and can dive to depths of 200 m to catch fishes and squids. Despite its cumbersome appearance, it is also quite mobile on land, even over rocky terrain. Fur seals differ from other seals (true seals) because they have external ears and the ability to use all four limbs to move across land. Also, fur seals have two layers of fur while other seals have only one layer.

Food Habits

The whale shark is a filter feeder  one of only three known filter feeding shark species (along with the basking shark and the megamouth shark). It feeds on macro-algae, plankton, krill, crab larvae, and small nektonic life such as small squid or vertebrates. The many rows of teeth play no role in feeding; in fact, they are reduced in size in the whale shark. Instead, the shark sucks in a mouthful of water, closes its mouth and expels the water through its gills. Whale sharks migrate to feed and possibly to breed.

The whale shark is an active feeder, targeting concentrations of plankton or fish. It is able to ram filter feed or can gulp in a stationary position. This is in contrast to the passive feeding basking shark, which does not pump water. Instead, it swims to force water across its gills.

Conservation Status

The Whale Shark is listed as vulnerable and migratory under the Environment Protection and Biodiversity Conservation Act 1999.

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