Washington, Jan 18 : Biologists have indicated that the migratory whale sharks, which are the world’s largest shark species are facing the threat of extinction, mainly due to overfishing.

According to a report in National Geographic News, out of all the species of sharks, the migratory sharks have been found to be the most at risk.

The three species of migratory sharks that have been signaled out as being in urgent need of protection are whale sharks, basking sharks, and great white sharks.

But among the three, the whale sharks are most at risk, known to travel more than 8,000 miles (12,875 kilometers) across the Pacific Ocean, from Mexico to the Tonga Islands.

"Every time a migratory shark moves from one spot to another, there's a greater chance that it might be targeted by fishermen or subject to habitat destruction," said Zeb Hogan, a fisheries biologist with the University of Reno in Nevada.

For studying the whale sharks, Hogan visited La Paz, on the Gulf of California, in particular, because they face many of the same threats that large fish living in lakes and rivers around the world encounter.

"Large freshwater fish like the Mekong giant catfish share some of the same life-history traits with these large migratory sharks," said Hogan.

"They live a long time, don't reproduce until a late age, and often need vast areas to survive. "This makes them more vulnerable to threats like overfishing and habitat destruction," he added.

According to Hogan, whale sharks may be protected in some national waters; once they move 200 miles (320 kilometers) off the coast they are in the high seas, where fisheries remain almost completely unregulated.

The conservation of migratory sharks like these is quite important because of the fact that 45 percent of the migratory sharks and rays are threatened with extinction. (ANI)