PARIS - A THIRD of the world's open water sharks - including the great white and hammerhead - face extinction, according to a major conservation survey released on Thursday.

The main culprit is overfishing. Sharks are prized for their meat, and in Asia especially for their fins, a prestige food thought to convey health benefits.

The survey of 64 species of open water, or pelagic, sharks - the most comprehensive ever done - comes days before an international meeting on high-seas tuna fisheries that could potentially play a role in shark conservation.

For decades, significant numbers of sharks - including blue and mako - have perished as 'by-catch' in commercial tuna and swordfish operations.

More recently, the soaring value of shark meat has prompted some of these fisheries to target sharks as a lucrative sideline, said Sonja Forham, Policy Director for the Shark Alliance, and co-author of the study.

The Spanish fleet of so-called surface longline fishing boats ostensibly targets swordfish, but 70 per cent of its catch, by weight, from 2000 to 2004 were pelagic sharks.

'There are currently no restrictions on the number of sharks that these fisheries can harvest,' Ms Fordham told AFP by phone. 'Despite mounting threats, sharks remain virtually unprotected on the high seas.' Sharks are especially vulnerable to overfishing because most species take many years to mature and have relatively few young.

Some 100 million sharks are caught in commercial and sports fishing every year, and several species have declined by more than 80 per cent in the past decade alone, according the International Fund for Animal Welfare (IFAW).

The IUCN issues the Red List of Threatened Species, the most comprehensive and authoritative conservation inventory of the world's plants and animals species. -- AFP