What is the largest species of fish?

The largest species of fish is the whale shark. Despite its name, this gentle giant is a shark, not a whale, and it is the largest known living fish species.

Whale sharks can grow to extraordinary sizes, with reliable records exceeding 12 metres and reported maximum lengths approaching 18 metres. They are filter feeders, straining plankton, small fish and other tiny organisms from seawater rather than hunting large prey. Their enormous mouths can be more than a metre wide, but their diet is surprisingly small.

Whale sharks live in warm and tropical oceans worldwide and often gather seasonally where plankton blooms or fish spawn. Their distinctive pale spots and stripes are unique to each individual, allowing researchers to identify them photographically.

A common mix-up is the blue whale, which is much larger but is a mammal, not a fish. Among bony fish, the giant sunfish is a major contender, but it is still far smaller than a whale shark.