Thursday, November 09, 2006

The Great White shark, an apex predator!

The Great White Shark is an efficient predator and because it is at the top of the food chain, its status is an indicator of the sea's health - if great white populations run into problems, it's likely that the marine world they inhabit is threatened, too.Adult females reach maturity between 14 and 16 years of age and can reach over seven metres in length.

Males generally mature around 10-12 years of age and can grow to more than five metres. They are skilled hunters, preying chiefly on seals, sea lions, fish, squid and even whales. Their colour is typically slate-grey or olive-brown, often with a bronzy sheen on the flanks; a strong, variable and blotchy line separates a dark upper and white lower surfaces.

Great whites are found throughout the temperate marine waters of the world, but they appear to prefer regions where there are or were substantial numbers of seals. Main populations of the great white are found in waters off southern Africa, Australia, New Zealand, Japan, the north-east and Californian coasts of America, southern Mexico, Chile and the Mediterranean. They can also be found in smaller numbers off the Brazilian coast, the Caribbean, the Azores, Hawaii, north-west Africa, the Philippines, Sri Lanka and the Seychelles.

No-one knows how many great whites there are: indeed, we cannot make even an educated guess. Within their known extensive range, white sharks seem to show up wherever and whenever it suits them - sometimes singly, other times in pairs or occasionally in larger numbers.Reproduction.

Great White Shark embryos hatch from eggs inside the mother, and are nourished until birth by the production of large numbers of extra unfertilised eggs. The gestation period (length of pregnancy) is uncertain but is thought to be more than a year. Pups are born in litters of between seven and nine, and they are between 120 and 150cm long. Current threats & problems. The Great White Shark has only one known natural enemy with which it competes - the killer whale or orca.

However, its only serious predators are humans, who kill it mainly for trophy sport, occasionally for food but also because we fear that it will otherwise kill us. What WWF is doing. WWF is funding work in the Mediterranean to protect the Great White Shark and other marine wildlife. The project will investigate its distribution and draw up a map of areas important to its survival. WWF will then assess the conservation status and management of these areas so we can lobby Mediterranean governments to provide vital protection for the Great White and other marine wildlife.

WWF also funds the Shark Trust, which we helped set up in 1996. The Shark Trust is the only non-profit making organisation working solely to protect sharks in British and European waters. This factsheet is based on information provided by the Trust.


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