Blue Shark Facts: Size, Habitat, Reproduction

The upper or dorsal surface of the blue shark is blue in color.
The upper or dorsal surface of the blue shark is blue in color. Joost van Uffelen / Getty Images

The blue shark (Prionace glauca) is a type of requiem shark. It's related to the blacktip shark, blacknose shark, and spinner shark. Like other species in the requiem family, the blue shark is migratory and ectothermic, and it gives birth to live young.

Fast Facts: Blue Shark

  • Common Name: Blue shark
  • Scientific Name: Prionace glauca
  • Distinguishing Features: Slender shark with a long snout, blue coloring on top, and white underside
  • Average Size: 2 to 3 meters
  • Diet: Carnivorous
  • Lifespan: 20 years
  • Habitat: Worldwide in deep water of tropic and temperate oceans
  • Conservation Status: Near Threatened
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Chondrichthyes
  • Order: Carcharhiniformes
  • Family: Carcharhinidae
  • Fun Fact: Blue shark females bear bite scars because the mating ritual involves the male biting the female.

Physical Appearance

The blue shark takes its common name from its coloring. Its upper body is blue, with lighter shading along its sides and a white underside. The coloration helps camouflage the shark in the open ocean.

It is a slender shark with long pectoral fins, a long conical snout, and large eyes. Mature females are larger than males. Females average from 2.2 to 3.3 m (7.2 to 10.8 ft) in length, weighing 93 to 182 kg (205 to 401 lb). Males run from 1.8 to 2.8 m (6.0 to 9.3 ft) in length, with a weight of 27 to 55 kg (60 to 121 lb). However, a few unusually large specimens have been documented. One female weighed 391 kg (862 lb).

The upper teeth in the blue shark's mouth are distinctive. They are triangular in shape, serrated, and recurved. The teeth overlap each other in the jaw. The shark's dermal denticles (scales) are small and overlap, making the animal's skin smooth to the touch.

Habitat

Blue sharks inhabit cool ocean waters around the globe, as far south as Chile and as far north as Norway. They migrate in a clockwise direction, following ocean currents to seek water ranging in temperature from 7 to 25 °C (45 to 77 °F). In temperate regions, they may be found offshore, but in tropical waters they have to swim deeper to seek a comfortable temperature.

Blue shark range
Blue shark range.  maplab

Diet and Predators

Blue sharks are carnivorous predators that feed mainly on squid, other cephalopods, and fish. They have been known to eat other sharks, cetaceans (whales and porpoises), and seabirds.

The sharks will feed anytime within a 24-hour period, but are most active in the early evening and at night. Sometimes blue sharks hunt as a "pack" and herd their prey. Normally, the sharks swim slowly, but they can jet forward quickly to catch prey and secure it with their recurved teeth.

Predators of blue sharks include killer whales (Orcinus orca) and larger sharks, such as the white shark (Carcharadon carcharias) and shortfin mako shark (Isurus oxyrinchus). The shark is also subject to parasites that can damage its eyesight and gill function. It is the definitive host of the tetraphyllidean tapeworm, which it likely acquires by eating the worm's intermediate hosts.

Reproduction

Male sharks mature by four or five years of age, while females mature at five to six years of age. The courtship ritual includes the male biting the female, so one way to sex a blue shark is to look for the bite scars always found on mature females. Female sharks have adapted to the behavior by having skin that is three times thicker than that of male sharks. Blue sharks give birth to large litters, ranging from as few as four pups to as many as 135. The pups are an important food source for other predators, but sharks that survive to maturity may live 20 years.

Conservation Status

Although the blue shark inhabits a wide range, grows quickly, and readily reproduces, this species is listed as Near Threatened by the IUCN. The shark isn't usually targeted for fishing, but is a major bycatch of fishing operations.

Blue Sharks and Humans

While blue sharks are often caught by fishermen, they aren't considered particularly tasty. Also, shark flesh tends to be contaminated by the heavy metals lead and mercury. Some shark meat is dried, smoked, or made into fish meal. The fins are used to make shark-fin soup, while the liver yields oil. Sometimes blue shark skin is used to make leather. Because of their attractive coloration and shape, sport fishermen may catch and mount blue sharks to display them.

Blue sharks swim into glass and other smooth surfaces, injuring themselves.
Blue sharks swim into glass and other smooth surfaces, injuring themselves. imagedepotpro / Getty Images

Like other requiem sharks, blue sharks do not do well in captivity. While they'll readily accept food, they tend to injure themselves by running into the walls of their tank. Replacing glass or other smooth surfaces with rock helps prevent accidents. Also, blue sharks are eaten by other species of sharks if they are housed together.

Blue sharks rarely bite humans and almost never cause death. In the past 400 years, only 13 biting incidents have been verified, of which four resulted in fatalities.

Sources

  • Bigelow, H.B. and Schroeder, W.C. (1948). Fishes of the Western North Atlantic, Part I: Lancelets, Cyclostomes, Sharks. Memoirs of the Sears Foundation for Marine Research, 1 (1): 59-576.
  • Compagno, Leonard J. V. (1984). Sharks of the World: An annotated and illustrated catalogue of shark species known to date. Food and Agriculture Organization of the United Nations.
  • Compagno, L.; M. Dando & S. Fowler (2004). Sharks of the World. HarperCollins. pp. 316–317. ISBN 0-00-713610-2.
  • Stevens, J. (2009) Prionace glauca. The IUCN Red List of Threatened Species doi:10.2305/IUCN.UK.2009-2.RLTS.T39381A10222811.en