The Great Fiji Shark Count

Counting Fiji's sharks, rays and turtles

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You are here: Home / Species / Shark Species / Blue shark

Blue shark

The blue shark (Prionace glauca) is a species of requiem shark, family Carcharhinidae, that inhabits deep waters in the world’s temperate and tropical oceans. Preferring cooler waters,[clarification needed] blue sharks migrate long distances, for example from New England toSouth America.

Although generally lethargic, they can move very quickly. Blue sharks areviviparous and are noted for large litters of 25 to over 100 pups. They feed primarily on small fishand squid, although they can take larger prey. Blue sharks often school segregated by sex and size, and this behavior has led to their nickname “wolves of the sea”.

Anatomy and appearance

Blue sharks are light-bodied with long pectoral fins. The top of the body is deep blue, lighter on the sides, and the underside is white. It grows to 3.8 meters (12.5 ft) long and can weigh up to 204 kilograms (450 lb). The highest reported weight was 391 kilograms (860 lb).[3]

Reproduction

Blue Shark by Robert Lupo DionThey are viviparous, with a yolk-sac placenta, delivering 4 to 135 pups per litter. The gestation period is between 9 and 12 months. Females mature at 5 to 6 years of age and males at 4 to 5. Courtship is believed to involve biting by the male, as mature specimens can be accurately sexed according to the presence or absence of bite scarring. Female blue sharks have adapted to the rigorous mating ritual by developing skin 3 times thicker than male skin.[4]

Ecology

Range and habitat

The blue shark is the most widely distributed animal in the world. It is an oceanic and epipelagicshark found worldwide in deep temperate and tropical waters from the surface to about 350 meters.[5] In temperate seas it may approach shore where it can be observed by divers, while in tropical waters it inhabits greater depths. It lives as far north as Norway and as far south as Chile. Blue sharks are found off the coasts of every continent, except Antarctica. Its greatest Pacificconcentrations occur between 20° and 50° North but with strong seasonal fluctuations. In the tropics it spreads evenly between 20° N and 20° S. It prefers waters with a temperature range of 7–16 °C (45–61 °F) but will tolerate temperatures of 21 °C (70 °F) or above. Records from the Atlantic show a regular clockwise migration within the prevailing currents.[4]

Feeding

Blue sharkSquid are important prey for blue sharks, but their diet includes other invertebrates such as cuttlefishand pelagic octopuses, as well as lobster, shrimp, crab, a large number of bony fishes, small sharks, mammalian carrion and occasional sea birds. Whale and porpoise blubber and meat have been retrieved from the stomachs of captured specimens and they are known to take cod from trawl nets.[4]Blue sharks rarely eat tuna.

Predators

Adult blue sharks do not suffer predation on a regular basis, except by humans. Young and smaller individuals may get eaten by any sufficiently larger sharks such as the Great White Shark and theTiger Shark . However, they are host to several species of parasites. For example, the blue shark is thedefinite host of the tetraphyllidean tapeworm, Pelichnibothrium speciosum (Prionacestus bipartitus). They become infected by eating intermediate hosts, probably Opah, (Lampris guttatus), and/orlongnose lancetfish, (Alepisaurus ferox).

http://en.wikipedia.org/wiki/Blue_shark

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Welcome to The Great Fiji Shark Count !

Throughout the months of April and November every year, you have the opportunity to help celebrate and record Fiji’s amazing coral reef biodiversity, show you care about our world’s delicate coral reef systems, and have fun, by taking part in the FIJI-WIDE SHARK COUNT!

Easy to do, this is suitable for visitors and locals alike, whether you like to fish, snorkel, or SCUBA dive. We hope that tourists, school children, scientists and all people with an interest in the marine environment will take to the reefs with us to search for the Sharks of Fiji!

The Great Fiji Shark Count will be held across Fiji every April and November every year.

You can do a single count, or take part as many times as you like during that month, so that you cover different reefs. All data will be gratefully accepted!

So, see your resort, watersports operator or travel agent, get your Shark identification materials and dive into the beautiful blue waters of Fiji, to be a part of history!

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