Basking shark

What it is

The basking shark is the second-largest living fish, trailing only the whale shark. It typically reaches lengths of seven to eight metres, though historical records note individuals exceeding twelve metres. Its body displays dark brown to black dorsal colouring that fades to white underneath. The head features a conical snout and cavernous jaws capable of opening wide enough for filter feeding. Distinctive traits include highly developed gill rakers resembling bristles, small eyes, and a strongly keeled tail fin. Despite its imposing size, the animal possesses the smallest brain-to-body ratio among sharks, reflecting a passive lifestyle.

Where it lives

This species inhabits temperate oceans globally, ranging from polar to warm-temperate zones. It frequents coastal areas and continental shelves but can dive deeper than nine hundred metres. The shark follows plankton concentrations, often surfacing where food is dense. Satellite tracking confirms extensive migrations, with some individuals crossing the equator to reach southern waters like Brazil during winter months. They avoid cold polar extremes and warm tropical central oceans, preferring temperatures between eight and fourteen degrees Celsius.

How it lives

Basking sharks are slow-moving ram feeders, swimming forward with mouths agape to strain zooplankton through their gill rakers. They target specific patches of copepods rather than feeding indiscriminately. Although generally solitary, they aggregate in large groups during summer months when plankton densities peak. These gatherings may involve courtship behaviours or social interactions. They face few natural predators, though killer whales and great white sharks have been observed scavenging or attacking them. Parasites like lampreys attach to their skin but rarely cause fatal harm.

Breeding and life cycle

Reproduction is ovoviviparous, meaning embryos develop inside eggs retained within the mother until hatching. Young sharks feed on unfertilized eggs produced by the mother, a behaviour known as oophagy. Gestation likely lasts two to three years, resulting in fully developed pups measuring one and a half to two metres long. Mating occurs in early summer, with births following in late summer. Females mature at lengths between four and six metres, with breeding cycles estimated at two to four years apart.

Fish and people

Historically, these sharks were heavily exploited for their oil, leather, and flesh due to their slow speed and placid nature. Modern fishing primarily targets their fins for soup, while other parts are used for feed or research. Conservation efforts have intensified as populations declined significantly from overexploitation. Several regions now classify the species as threatened or endangered, implementing management plans to protect remaining stocks. Research initiatives utilise satellite tagging and museum donations to better understand their biology and migration patterns.

Status and threats

The International Union for Conservation of Nature lists the basking shark as endangered. Populations have suffered severe reductions due to historical commercial hunting and modern bycatch in trawl nets. New Zealand classifies the species as nationally vulnerable following mass bycatch events in the late twentieth century. The eastern North Pacific population is considered a species of concern by US authorities. Protection measures vary by region, with some areas banning capture entirely while others monitor stock levels closely to prevent further decline.

Relatives and look-alikes

The basking shark belongs to the family Cetorhinidae, which contains no other living members. It shares filter-feeding habits with the whale shark and megamouth shark, though it lacks their ability to pump water actively. It is often confused with great white sharks due to similar body shapes, but differs in jaw structure, tooth size, and feeding method. Fossil evidence links the lineage to extinct genera like Keasius from the Eocene epoch, with modern forms appearing in the Miocene.

Questions people ask about Basking shark

Good reading and sources

• Basking shark on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos
• Wikidata recordOpen data