Basking shark

Basking shark Temporal range: Early Oligocene–Present PreЄ Є O S D C P T J K Pg N
Conservation status
Vulnerable (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Superorder:	Selachimorpha
Order:	Lamniformes
Family:	Cetorhinidae T. N. Gill, 1862
Genus:	Cetorhinus Blainville, 1816
Species:	C. maximus
Binomial name
Cetorhinus maximus (Gunnerus, 1765)
Range of the basking shark
Synonyms
click to expand Cetorhinus blainvillei Capello, 1869 Cetorhinus maximus infanuncula Deinse & Adriani, 1953 Cetorhinus normani Siccardi, 1961 Hanovera aurata van Beneden, 1871 Halsydrus pontoppidiani* Neill, 1809 Polyprosopus macer Couch, 1862 Scoliophis atlanticus* Anonymous, 1817 Selachus pennantii Cornish, 1885 Squalis gunneri* Blainville, 1816 Squalis shavianus* Blainville, 1816 Squalus cetaceus Gronow, 1854 Squalus elephas Lesueur, 1822 Squalus gunnerianus Blainville, 1810 Squalus homianus Blainville, 1810 Squalus isodus Macri, 1819 Squalus maximus Gunnerus, 1765 Squalus pelegrinus Blainville, 1810 Squalus rashleighanus Couch, 1838 Squalus rhinoceros* DeKay, 1842 Squalus rostratus Macri, 1819 Tetraoras angiova* Rafinesque, 1810 Tetroras angiova* Rafinesque, 1810 Tetroras maccoyi Barrett, 1933 ---- * ambiguous synonym

The basking shark (Cetorhinus maximus) is the second largest living fish, after the whale shark, and one of three plankton-eating sharks along with the whale shark and megamouth shark. Adults typically reach 6–8 m (20–26 ft) in length. They are usually greyish-brown, with mottled skin. The caudal fin has a strong lateral keel and a crescent shape.

The basking shark is a cosmopolitan migratory species, found in all the world's temperate oceans. A slow-moving filter feeder, its common name derives from its habit of feeding at the surface, appearing to be basking in the warmer water there. It has anatomical adaptations for filter feeding, such as a greatly enlarged mouth and highly developed gill rakers. Its snout is conical and the gill slits extend around the top and bottom of its head. The gill rakers, dark and bristle-like, are used to catch plankton as water filters through the mouth and over the gills. The teeth are very small and numerous, and often number one hundred per row. The teeth have a single conical cusp, are curved backwards, and are the same on both the upper and lower jaws. This species has the smallest weight-for-weight brain size of any shark, reflecting its relatively passive lifestyle.

Basking sharks are believed to overwinter in deep waters. They may be found in either small schools or alone. Small schools in the Bay of Fundy and the Hebrides have been seen swimming nose to tail in circles in what may be a form of mating behaviour. Despite their large size and threatening appearance, basking sharks are not aggressive and are harmless to humans.

It has long been a commercially important fish, as a source of food, shark fin, animal feed, and shark liver oil. Overexploitation has reduced its populations to the point where some have disappeared and others need protection.