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Whale Shark

(Rhincodon typus)

Short Description

The Whale Shark is a slow moving shark that uses a filter-feeding mechanism to filter out its food as it moves through the ocean. It is the largest of the fish specias and belongs to the shark family. The shark is distinctive by having an enormous mouth and a mottled colouration. Despite the large mouth, they feed mainly on microscopic plankton, but have been known to eat larger prey and even small fish. Found in tropical and temperate oceans around the world, it lives in open waters and has a lifespan of about 70 years.

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Long Description

Size
The largest confirmed individual had a length of 12.65 metres (41.50 ft) and a weight of more than 21.5 tonnes (47,000 lb), but unconfirmed claims report considerably larger whale sharks. Its large mouth can be up to 1.5 metres wide and contain over 300 rows of tiny teeth. The skin is very thick (up to 10 cms)

Identification
The body is mainly grey with a white belly or underside, and three prominent ridges run along each side of the animal, the skin being a checkerboard of pale yellowish spots and stripes (this pattern is unique to each individual and used for population counting). It has 5 large pairs of gills and two small eyes located towards the front of the wide flat head. A pair of dorsal and pectoral fins, the tail becomes quite crescent-shaped in adulthood.

Diet
The Whale Shark is a filter feeder, feeding on macro-algae, plankton, krill, crab larvae, and small fish such as squid. It is one of three known filter-feeders, the others being the Basking Shark and the Megamouth. The many rows of teeth play no role in feeding, but instead the shark sucks in a mouthful of water, closes its mouth and expels the water through its gills. During the slight delay between closing the mouth and opening the gill flaps, plankton is trapped against the dermal denticles which line its gill plates and throat. This fine sieve-like apparatus, prevents the passage of anything but fluid out through the gills, trapping anything above 2 to 3 millimetres (0.079 to 0.12 in) in diameter. Material caught in the filter between the gill bars is swallowed.

Social Groups and Activity
The whale shark is not an efficient swimmer since it uses its entire body to propel itself, (unusual for a fish) and maintains an average speed of only around 5-kilometre-per-hour. Despite being a shark, they are gentle creatures 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

Reproduction
The capture of a female in July 1996 which was pregnant with 300 pups indicates that whale sharks are ovoviviparous. The eggs remain in the body and the females give birth to live young which are 40 to 60 centimetres (16 to 24 in) long. It is believed that they reach sexual maturity at around 30 years and the life span is an estimated 70 to 100 years.

Distribution

The whale shark inhabits all tropic and warm-temperate seas. Primarily pelagic, seasonal feeding aggregations occur at several coastal sites such as Gladden Spit in Belize; Ningaloo Reef in Western Australia; Útila in Honduras; Donsol, Pasacao and Batangas in the Philippines; off Isla Mujeres and Isla Holbox in Yucatan Mexico; Ujung Kulon National Park in Indonesia; Nosy Be in Madagascar Off Tofo Reef near Inhambane in Mozambique, and the Tanzanian islands of Mafia, Pemba and Zanzibar. Although typically seen offshore, it has been found closer to land, entering lagoons or coral atolls, and near the mouths of estuaries and rivers. Its range is generally restricted to about ±30° latitude. It is capable of diving to depths of 700 metres (2,300 ft), and is migratory.

The whale shark is targeted by commercial fisheries in several areas where they seasonally aggregate. The population is unknown and the species is considered vulnerable by the IUCN. In 1998, the Philippines banned all fishing, selling, importing and exporting of whale sharks for commercial purposes, followed by India in May 2001, and Taiwan in May 2007.

Distribution Map

Whale Shark  Distribution Map

Various

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