Facts about Blue Shark

The blue shark (Prionace glauca) is an open ocean fish and is wide ranging as its habitat includes the Atlantic ocean, Indian ocean and the Pacific ocean. It lives in tropical and temperate waters, and prowls the waters around New Foundland, from Canada to Argentina and from Norway to South Africa, including the Mediterranean, in the Atlantic ocean. Its wide range includes South Africa to Indonesia and Japan to New Zealand in the Indian and western Pacific Oceans. The Gulf of Alaska to Chile is part of its territory in the eastern Pacific ocean.

Blue sharks swim below the surface of the ocean to 1,148 ft (350 meters) in depth. As they prefer cooler waters, they may swim deeper in tropical ocean regions. While blue sharks rarely swim near the shore, they may patronize inshore areas of oceanic islands and places where the continental shelf is narrow. They usually move at a lethargic leisurely pace, but are perfectly capable of rapid movement. There are records of blue sharks migrating long distances, such as from New England to South America. Blue sharks are also called 'wolves of the sea' due to the structure of their schools, which is sometimes based on sex and size.

The blue shark has a long sleek streamlined body that is dark blue on the top, light blue on the sides and almost completely white on the belly. This pattern of colors on its smooth skin is called counter shading, and provides it a perfect camouflage in its natural habitat. The shark has a conical pointed snout and large eyes. It has two very long pectoral fins, one moderately sized dorsal fin and triangular serrated teeth. The length of the blue shark usually lies between the range of 6 to 10 feet. Blue sharks can live for up to 20 years.

While the blue shark is perfectly capable of taking large prey, majority of its diet comprises small bony fish, such as herring and sardines, and invertebrates, such as squid, cuttlefish and pelagic octopi. If the opportunity presents itself, they will feed from nets or on carcasses. Blue sharks are naturally preyed upon by California sea lions and larger sharks. These sharks are usually host to a wide variety of parasites.

A distinctive fact about the blue shark is that it is viviparous and gives birth to live offspring that have hatched from eggs internally. Depending on the mothers size, it is capable of giving birth to over 100 pups at one time. It goes through a gestation period of between 9 and 12 months. Another interesting fact about the blue shark is that as the mating ritual includes biting, the females skin is three times as thick as the males.

The threat that they present to humans is greatly outweighed by the threat we present to them. They are considered dangerous to humans and may attack open-water divers. There are accounts of people stranded in the ocean as the outcome of an air disaster or a shipwreck, being attacked by blue sharks. The International Shark Attack File contains documentation of twelve unprovoked attacks and four boat attacks by blue sharks. On the other hand, they are compromised by human fishing nets in which they often get entangled. Thus, though they are not fished for much on a commercial level (as their meat ammoniates quickly), their numbers deplete as they become a by product of commercial fishing. While they are sometimes released, more often their fins are cut and sold.

The World Conservation Union (IUCN) lists the status of blue sharks as "Near Threatened". While they are not over fished, the preservation of the species is possible by finding ways to minimize the loss of blue sharks caught as bycatch.