Cetorhinus

Cetorhinus is a genus of cartilaginous fishes in the family Cetorhinidae, within the order Lamniformes. The genus is represented today by a single living species, Cetorhinus maximus, commonly known as the basking shark. The genus also appears in the fossil record, with several extinct species described from various geological periods.

The basking shark has a broad, flattened head, a long, slender body, and a very large mouth that opens widely to filter plankton. Its interior of the mouth contains small teeth and a basket-like array of gill rakers that trap plankton from seawater as the animal swims forward. Water exits through five large gill slits. The skin is rough and often gray or brown. Adults can reach substantial sizes, with reported lengths well over several meters, and they possess a relatively small dorsal fin and a strong, crescent-shaped tail.

Distribution and habitat span temperate and subpolar oceans worldwide. Basking sharks are most often observed near the surface or in the upper water column, frequently around areas of abundant plankton. They undertake seasonal movements, following plankton blooms and changing prey availability.

Ecology and behavior include slow, deliberate swimming as they filter-feed. Reproduction is ovoviviparous, with females giving birth to live young after a gestation period. The species plays a role in marine ecosystems as a large, selective filter feeder.

Conservation status: the basking shark is listed as Endangered by the IUCN. Historical overexploitation for oil, meat, and fins, along with bycatch and habitat changes, have contributed to population declines. Protective measures exist in many regions.