The whale shark (Rhincodon typus) is a graceful, slow-moving giant and the largest fish in the world. At 1.5 m wide, its mouth is large enough to fit a human inside, but it is a harmless filter feeder that eats only plankton and small fish. Accounts of these giants describe sightings of individuals up to 20 m in length.
To obtain the huge amount of food it needs, it sucks water into its mouth and pumps it out over its gills, where particles of food become trapped by bony projections called gill rakers and are later swallowed. This shark has the thickest skin of any animal, at up to 10 cm thick. Prominent ridges run the length of its body, and it has a large, sickle-shaped tail. The pattern of white spots on its back is unique to each fish, enabling scientists, through analysis of photographs, to identify individuals. While little is known of their ocean trabels, satellite tagging has shown that some whale sharks migrate across entire oceans. Whale shark eggs hatch inside the mother, and she gives birth to live young that reach up to 60 cm in length.
Every year, around April, whale sharks migrate to Ningaloo Reef off northwestern Australia for a plankton feast. The plankton explosion results from a simultaneous mass spawning of the reef’s corals, possibly triggered by the full moon.
Whale sharks are killed for their meat and fins (used in soup), although they are legally protected in some countries.
Photo © Ken Knezick & Erik Schlögl