Basking Shark (Cetorhinus maximus)

SharkFilter FeederTemperate Seas

Overview

The basking shark (Cetorhinus maximus) is the second-largest living fish, after the whale shark, and one of only three sharks that live by filtering plankton. It gets its name from its habit of cruising slowly at the surface, apparently basking in the sun, with its enormous mouth held open.

Where the whale shark is a tropical animal, the basking shark is a creature of temperate seas. It has a conical snout, huge gill slits that nearly encircle the head, and a cavernous mouth lined with bristle-like gill rakers that strain food from the water.

Basking sharks are entirely harmless to people. Their teeth are tiny and non-functional for feeding, and they take nothing larger than plankton.

Habitat & Range

Basking sharks occur in temperate coastal and shelf waters of the Atlantic and Pacific, in both hemispheres. They are seen at the surface where plankton concentrates — along fronts, tide lines and headlands — and were long assumed to disappear in winter, but tracking has shown they move to deeper water and travel considerable distances rather than hibernating.

Diet

Basking sharks eat zooplankton, chiefly small copepods and other tiny crustaceans. Unlike the whale shark, which can actively suck water in, the basking shark filters passively: it swims forward with the mouth open, and water passes over gill rakers that trap the plankton before the water exits through the gill slits.

Behavior

Basking sharks are slow-moving and often seen alone, but they aggregate where food is dense, sometimes forming groups that swim nose-to-tail in circles — behaviour linked to courtship. They shed and regrow their gill rakers, and they undertake long migrations and deep dives that were unknown until satellite tagging revealed them.

Human Interaction & Conservation

Basking sharks were heavily fished historically for their large, oil-rich livers, and their slow growth and late maturity made populations very slow to recover. They are now legally protected in many countries. Present-day risks include entanglement in fishing gear, boat strikes — they are vulnerable because they feed at the surface — and disturbance. This profile gives no guidance on approaching or handling basking sharks; follow local regulations. Verify current status at the IUCN Red List.