Wednesday, 28 December 2011

The Whale Shark (Rhincodon typus)

Photo By/ Patrick Torresan
 The whale shark is a the biggest shark and the biggest fish. It is NOT a whale. It has a huge mouth which can be up to 4 feet (1.4 m) wide. Its mouth is at the very front of its head (not on the underside of the head like in most sharks). It has a wide, flat head, a rounded snout, small eyes, 5 very large gill slits, 2 dorsal fins (on its back) and 2 pectoral fins (on its sides). The spiracle (a vestigial first gill slit used for breathing when the shark is resting on the sea floor) is located just behind the shark's eye. Its tail has a top fin much larger than the lower fin.The whale shark has distinctive light-yellow markings (random stripes and dots) on its very thick dark gray skin. Its skin is up to 4 inches (10 cm) thick. There are three prominent ridges running along each side of the shark's body.
This enormous shark is a filter feeder and sieves enormous amounts of plankton to eat through its gills as it swims.



The whale shark is a filter feeder that sieves small animals from the water. As it swims with its mouth open, it sucks masses of water filled with prey into its mouth and through spongy tissue between its 5 large gill arches. After closing its mouth, the shark uses gills rakers that filter the nourishment from the water. Anything that doesn't pass through the gills is eaten. Gill rakers are bristly structures (the thousands of bristles are about 4 inches or 10 cm long) in the shark's mouth that trap the small organisms which the shark then swallows. The water is expelled through the sharks 5 pairs of gill slits. The prey includes plankton. krill, small fish, and squid. The shark can process over 1500 gallons (6000 liters) of water each hour.

Whale sharks have about 3,000 very tiny teeth but they are of little use. Whale sharks are filter feeders who sieve their tiny food through their large gills. Photo by/ Michael Aw - National Geographic

The whale shark occurs in all of the world's tropical and warm-temperate oceans, usually between latitudes 30°N and 35°S, and is thought to prefer surface sea-water temperatures between 21 to 25°C.  Whale sharks are known to inhabit both deep and shallow coastal waters and the lagoons of coral atolls and reefs.  Red Sea  is one of the most reliable locations to find whale sharks in the world.

The Whale Shark  (Rhincodon typus) Distribution map
While little is known about the natural threats to whale sharks, humans are the biggest threat to whale shark populations.  Hunting is banned in most countries but illegal fishing still exists.  In Taiwan, whale sharks are known as ‘Tofu fish' because of the taste and texture of their flesh, and their fins can fetch up to US$15,000 on the black market for use in shark fin soup.  Whale sharks are also vulnerable to boat strikes as they often swim at the surface.

The whale shark is protected in Egyptian waters under State, Commonwealth and international legislation and it is illegal to disturb, harm or fish for whale sharks. The population of whale sharks is unknown and the species is listed as vulnerable to extinction in the IUCN Red List of Threatened Species.
To ensure that interacting with whale sharks is a safe and enjoyable experience and to prevent the animals themselves from being harmed or disturbed, the following Code of Conduct applies when interacting with whale sharks.


click image for larger image view
If you have been there then you know. If you haven't, then it is difficult to describe the feeling of sharing the water with this, the biggest fish in the sea. While some people are intimidated by its size, the whale shark is actually a gentle giant keen to avoid confrontations and generally trusting of humans. As for etiquette when diving with whale sharks, passive interaction is the best policy



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