The whale shark is not a whale, but a large plankton-eating shark found in all tropical seas of the world. Adults can grow over 40 feet in length, making them the largest fish in the world. They can weigh up to 47,000 lbs, and there are unconfirmed reports of sharks weighing even more. The mouth can reach up to 4.9 feet and contains ten filter pads and between 300 and 350 teeth. The whale shark has two small eyes and five large pairs of gills. They are mostly gray in color with a white belly, and three prominent ridges run along their side. The skin is usually 3.9 inches thick and marked with a checkerboard pattern of pale yellow spots and stripes. The spots are unique to each individual and are used by biologists to monitor their populations. The whale shark has a pair of dorsal fins and pectoral fins.
Whale sharks and are found in all tropical and warm-temperate seas. Although these sharks are massive, they are generally docile and inoffensive to humans. They even sometimes allow human swimmers to hitch a ride. (This practice is discouraged by shark biologists and conservationists.) They prefer warm waters and are known to migrate every spring to the continental shelf of the central west coast of Australia. Coral spawning of the area's Ningaloo Reef provide these sharks with a mass supply of plankton. Whale sharks are filter feeders and one of the only three known filter feeding shark species. It feeds mostly on macro-algae, krill, plankton, crab larvae, squids and vertebrates. Whale sharks can also feed on other small fish, eggs, and sperm during mass spawning of fish shoals. Little is known about the whale shark's mating habits, as mating has never been observed. One female whale shark that was captured was pregnant with 300 pups. It is believed that the eggs remain in the body and the females give birth to live young that are 16 to 24 inches long. The young reach sexual maturity at around 30 years. Whale sharks can live up to 100 years.
The whale shark is listed as "vulnerable" with the IUCN. This species is often targeted and hunted by commercial fisheries in several areas of its range. In some areas, whale sharks are susceptible to propeller strikes and collisions with boat hulls. The population is unknown and in some areas, the fishing, selling, importing and exporting of whale sharks has been banned.