Basking shark

Basking shark Temporal range: Miocene–Present[1] PreꞒ Ꞓ O S D C P T J K Pg N
The size of basking sharks at various stages of growth and maturity with a human for scale
Conservation status
Endangered  (IUCN 3.1)[2]
CITES Appendix II (CITES)[3]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Subdivision:	Selachimorpha
Order:	Lamniformes
Family:	Cetorhinidae
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 shark and fish,^[4] after the whale shark. It is one of three plankton-eating shark species, along with the whale shark and megamouth shark. Typically, basking sharks reach 7.9 m (26 ft) in length. It is usually greyish-brown, with mottled skin, with the inside of the mouth being white in colour. The caudal fin has a strong lateral keel and a crescent shape. Other common names include bone shark, elephant shark, sailfish, and sunfish. In Orkney, it is called hoe-mother (contracted homer), meaning "the mother of the picked dogfish".^[5]

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 numerous and very small and often number 100 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.^[6]

Basking sharks have been shown from satellite tracking to overwinter in both continental shelf (less than 200 m or 660 ft) and deeper waters.^[7] They may be found in either small shoals or alone. Despite their large size and threatening appearance, basking sharks are not aggressive and are harmless to humans.

The basking shark 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.^[8]