Blue shark
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The blue shark (Prionace glauca) is a carcharhinid shark. They occur in the deep waters of the world's temperate and tropical oceans. They prefer cooler waters and are not found, for example, in the Gulf of Mexico, the Adriatic or Red Sea. Blue sharks are known to migrate long distances — from New England to South America for example. Although generally lethargic, they are capable of moving very quickly if the need arises. Blue sharks are viviparous and are noted for their large litters of 25 to over 100 pups. They feed primarily on small fish and squid although they are perfectly capable of taking larger prey should the opportunity present itself. They are often found in schools segregated by sex and size.
Distribution and habitat
The blue shark is found world wide in deep temperate and tropical waters, it is a pelagic shark. It is found from as far north as Norway down to South Africa. In temperate seas it is often found deeper than in more colder sea. In cold waters it may come closer to shore where divers sometimes can see it.
Anatomy and appearance
Blue sharks are light bodied with long pectoral fins. The top of the body is deep blue lightening on the sides. The underside of the shark is white. The animals grows to lengths of 3.8 meters or more, but the usual size is 1.8 to 2.4 meters. Typical weight is 60 to 80 kg, the largest recorded specimen being 205 kg. Blue sharks in the Pacific are generally smaller and does not exceed 2 meters (6 feet). Blue sharks are not easily confused with any other species.
Diet
Squid are an important prey item for blue sharks but their diet also comprises a large number of bony fishes as well as invertebrates, small sharks, mammalian carrion and occasional sea birds.Leonard J. V. Compagno, Sharks of the World: An annotated and illustrated catalogue of shark species known to date Vol 4. Part 2, Food and Agriculture Organization of the United Nations, 1984
Reproduction
They are vivaporous with 4 — 135 per litter. The gestation period is 9 — 12 months;
Importance to humans
They are occasionally sought as game fish. The flesh is edible, but not widely sought after. Blue sharks are frequent accidental catches by commercial fisherman seeking swordfish or tuna. Most interaction between blue sharks and humans takes place in deep water as they rarely venture close to shore. There are several documented attacks by blue sharks on people and boats.See also
References
- Stevens (2000). [Prionace glauca]. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Database entry includes justification for why this species is near threatened
- "[Prionace glauca]." FishBase. Ed. Ranier Froese and Daniel Pauly. 09 2005 version. N.p.: FishBase, 2005.
- [Prionace glauca (TSN 160424)]. Integrated Taxonomic Information System. Accessed on 15 November 2005.
- [Blue shark, Prionace glauca] [MarineBio]"
External Link
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