What is a whale shark? The whale shark (Rhincodon typus) is the world's largest fish and is a harmless filter feeding shark. This species is closely related to the bottom-dwelling sharks, which include the wobbegong.
What does it look like? The whale shark has a mouth which can be up to 1.5 metres wide, a broad flat head and two small eyes located towards the front of the head. The body is mostly grey with a white belly. Three ridges run along the side of each animal and there are five large pairs of gills. The skin is marked with lots of spots and stripes. These spots are unique to each whale shark and because of this they can be used to identify each individual animal.
Vision courtesy of MIRG Australia (www.mirg.org.au)/Blue Office Productions
Where does it live? 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 - 25°C. Whale sharks are known to inhabit both deep and shallow coastal waters and the lagoons of coral atolls and reefs. Western Australia is one of the most reliable locations to find whale sharks in the world. From around mid-March to mid-May each year they are common in Ningaloo Marine Park. At times, in December and January, they have also been seen as far south as Shark Bay Marine Park and even Kalbarri. The sharks regularly appear at locations where seasonal food 'pulses' are known to occur, for instance, the mass spawning of coral triggers the arrival of whale sharks at Ningaloo Marine Park.
What they eat and how: The whale shark is one of only three filter-feeding sharks (the other two are the basking and megamouth sharks). It feeds on very small plankton including small crustaceans like krill, copepods and crab larvae as well other tiny invertebrates such as squid, small fish and jellyfish. Whale sharks have thousands of tiny teeth arranged in more than 300 rows but they neither bite nor chew their food. Instead, the shark sucks in a mouthful of water, closes its mouth and sieves prey as small as a millimetre through the fine mesh of the gill rakers. They are able to open their mouth wider than a metre, which optimises feeding. However, unlike the megamouth and basking sharks, the whale shark does not rely on forward motion but can hang vertically in the water and ‘suck' in food.
Threats: People are the biggest threat to the whale shark population. 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. Though little is known about natural threats to whale sharks, predatory sharks and killer whales have been known to attack whale sharks and there have been two reports of juvenile whale shark tissue in a blue marlin and blue shark.
Behaviour: The whale shark is largely solitary and is rarely seen in groups unless feeding at locations with abundant food. Males range over longer distances than females and they can dive to great depths of 1500 metres. Despite its enormous size, this species does not pose any significant danger to people. They are actually quite gentle and can be playful with divers. Divers and snorkellers can swim with this giant fish without any risk apart from unintentionally being hit by the shark's large tail fin.
Breeding and caring for young: Whale shark eggs hatch inside the mother's body and the females give birth to live young between 40 to 60 centimetres long. It is believed that they reach sexual maturity at around 30 years and their life span has been estimated to be between 70 and 180 years. One of the great whale shark mysteries is where they go to breed. Only one pregnant whale shark has ever been recorded and there have been very few juvenile whale sharks seen at any location throughout their range.
Conservation status: The whale shark is protected in Australian 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 .
How you can protect the whale shark: When snorkelling or diving with whale sharks you must follow a few simple rules: stay 3 metres away from the animal's head and 4 metres away from the tail, and do not touch the whale shark or use flash photography. If you are taking a picture try to photograph the whale's left side behind the gills, then send it to www.whaleshark.org so it can be added to a global database. Whale shark researchers will then try to match your image with other photos sent in by people around the world, to try to shed some light on where whale sharks go when they leave our waters, which means you'll be doing your bit to help protect and understand these amazing creatures .
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