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 to 8 m in length. They are usually greyish-brown, with mottled skin.
The basking shark is found in all the world’s temperate oceans. A slow-moving filter feeder, its name comes from its habit of feeding at the surface, appearing to be basking in the warmer water there. It has adaptations for filter feeding, such as a greatly enlarged mouth and highly developed gill rakers. Its snout is cone shaped 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 100 per row. The teeth have a single cone-shaped cusp, are curved backward, 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 have been shown from satellite tracking to overwinter in both continental shelves and deeper waters. 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.