Basking Shark Facts (Cetorhinus maximus)

The gentle giant with prickly skin

The basking shark is a filter feeder.
The basking shark is a filter feeder. Corbis/VCG / Getty Images

The basking shark (Cetorhinus maximus) is an enormous plankton-eating shark. After the whale shark, it is the second-largest living shark. The shark takes its common name from its habit of feeding near the sea surface, making it appear to bask in the sun. Although its large size may seem threatening, the basking shark is not aggressive toward humans.

Fast Facts: Basking Shark

  • Scientific Name: Cetorhinus maximus
  • Other Names: Bone shark, elephant shark
  • Distinguishing Features: Large gray-brown shark with highly enlarged mouth and crescent-shaped caudal fin
  • Average Size: 6 to 8 m (20 to 26 ft)
  • Diet: Filter feeder with a diet of zooplankton, tiny fish, and small invertebrates
  • Lifespan: 50 years (estimated)
  • Habitat: Temperate oceans worldwide
  • Conservation Status: Vulnerable
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Chondrichthyes
  • Order: Lamniformers
  • Family: Cetorhinidae
  • Fun Fact: Despite its enormous size, the basking shark can breach (jump out of the water).

Description

Thanks to their cavernous mouths and well-developed gill rakers, basking sharks are easily recognized when near the surface. The shark has a conical snout, gill slits extending around its head, and a crescent-shaped caudal fin. Its color is usually a shade of gray or brown.

Adult basking sharks typically reach 6 to 8 m (20 to 26 ft) in length, although specimens over 12 meters in length have been reported. Notably, the basking shark has the smallest brain for its size of any shark. Basking shark corpses have been misidentified as belonging to plesiosaurs.

Distribution

As a migratory species found in temperate water, the basking shark enjoys a large range. It occurs along continental shelves, sometimes venturing into brackish bays and crossing equatorial waters. Migration follows plankton concentrations, which vary according to the season. Basking sharks frequent surface waters, but can be found at depths of 910 m (2990 ft).

Basking shark range
Basking shark range. maplab

Diet and Predators

A basking shark feeds on zooplankton, tiny fish, and small invertebrates by swimming forward with an open mouth. The shark's gill rakers collect prey as water rushes past. While the whale shark and megamouth shark can suck water through their gills, the basking shark can only feed by swimming forward.

Killer whales and white sharks are the basking shark's only predators.

Reproduction and Life Cycle

Many of the details of basking shark reproduction are unknown. Researchers believe mating occurs in early summer, when the sharks form sex-segregated schools and swim nose-to-tail in circles (which may be a courtship behavior).

Gestation lasts somewhere between one and three years, after which a small number of fully developed young are born. Female basking sharks are ovoviviparous. Only the right ovary of the female basking shark functions, although researchers have not yet discovered why.

Basking shark teeth are small and useless in adults sharks. However, they may allow young to feed on the mother's unfertilized ova prior to birth.

Basking sharks are thought to reach maturity between the ages of six and thirteen. Their life expectancy is predicted to be about 50 years.

Basking Sharks and Humans

In the past, the basking shark held commercial importance. It was widely fished for its flesh for food, liver for squalene-rich oil, and hide for leather. Presently, the species is protected in many regions. However, it is still fished in Norway, China, Canada, and Japan for its fins for shark fin soup and its cartilage for an aphrodisiac as well as traditional medicine. Within protected areas, some specimens die as bycatch.

Basking sharks are not aggressive and cannot eat people.
Basking sharks are not aggressive and cannot eat people. JohnGollop / Getty Images

The basking shark tolerates boats and divers, so it is important for ecotourism. The species is not aggressive, but injuries have been reported when divers brushed against the shark's highly abrasive skin.

Conservation Status

While the basking shark does not face habitat loss or degradation, it has not recovered from past persecution and over-fishing. Its numbers continue to decline. The basking shark is categorized as "vulnerable" on the IUCN Red List.

Sources

  • Compagno, L.J.V. (1984). Sharks of the World. An annotated and illustrated catalogue of shark species to date. Part I (Hexanchiformes to Lamniformes). FAO Fisheries Synopsis, FAO, Rome.
  • Fowler, S.L. (2009). Cetorhinus maximusThe IUCN Red List of Threatened Species. e.T4292A10763893. doi:10.2305/IUCN.UK.2005.RLTS.T4292A10763893.en
  • Kuban, Glen (May 1997). "Sea-monster or Shark?: An Analysis of a Supposed Plesiosaur Carcass Netted in 1977". Reports of the National Center for Science Education. 17 (3): 16–28.
  • Sims, D.W.; Southall, E.J.; Richardson, A.J.; Reid, P.C.; Metcalfe, J.D. (2003). "Seasonal movements and behaviour of basking sharks from archival tagging: no evidence of winter hibernation" (PDF). Marine Ecology Progress Series. 248: 187–196. doi:10.3354/meps248187
  • Sims, D.W. (2008). "Sieving a living: A review of the biology, ecology and conservation status of the plankton-feeding basking shark Cetorhinus maximus". Advances in Marine Biology. 54: 171–220.