The whale shark is the world’s largest living fish, despite feeding mainly on plankton.
Individuals can reach at least 18 metres in reliable modern records, although exceptional claims are difficult to verify. The whale shark is a filter feeder: it swims with its enormous mouth open and strains plankton, small fish, and other tiny organisms from the water.
Despite its name and whale-like size, it is a shark rather than a whale. That distinction matters because whales are mammals, while whale sharks breathe through gills and are cartilaginous fish.
Whale sharks occur in warm tropical and subtropical oceans. They are generally slow-moving and are known for distinctive pale spots and stripes. These markings are unique to individuals, allowing researchers to identify them photographically.