Hammerhead sharks and giant devil rays are threatened with extinction, according to the first worldwide conservation survey of the species.

A third of open-ocean sharks and rays face the same predicament. Growing appetites for shark meat and for the Asian delicacy shark-fin soup are proving too much for populations of the slow-growing animals, the shark specialist group of the International Union for Conservation of Nature said.

“Sharks will be the first to go,” says Sonja Fordham, policy director of the Shark Alliance and one of the authors of the report. “Despite mounting threats, they remain virtually unprotected on the high seas.”

Sharks are more vulnerable to overfishing than most marine species because of their late sexual development and small numbers of young. They used to be mainly accidental victims of hooks and nets set for tuna and swordfish but are increasingly being caught for their meat and fins. The fins offer huge profits, with market values of up to £6,000 per kilo in China. Although shark finning is banned in most international waters, weak legislation allows the practice to continue. Britain is one of only five EU nations that permits fins to be removed at sea.

Great and scalloped hammerhead sharks are now classified as globally endangered on the conservation union’s Red List, owing to a combination of the size and quality of their fins and their preference for living in coastal areas on continental shelves where they are more accessible. Scalloped hammerheads are made even more vulnerable by their tendency to congregate in large schools around seamounts.

The Mediterranean Sea was a haven for hammerheads but since the early 19th century more than 99 per cent have been lost. Their numbers are low in other seas: at least 120 vessels are illegally catching hammerheads in the Indian Ocean and there is illegal fishing in the waters surrounding the Galápagos Islands.

The fins of just two hammerhead species make up more than 4 per cent of the identifiable shark fins passing through the Hong Kong markets (which in turn accounts for 80 per cent of the world’s trade in fins), according to the report, equating to between 1.3 and 2.7 million individuals a year.

The giant devil ray, found in deep offshore waters of the Mediterranean, joins the hammerheads in the globally endangered category. A decade ago an international plan of action was agreed at the UN that would help to defend their numbers, but so far only Croatia and Malta have extended legal protection to them.

“The vulnerability and lengthy migrations of most open ocean sharks call for co-ordinated, international conservation plans,” Ms Fordham said. “There is a clear need for immediate action on a global scale.”

The Convention on the International Trade in Endangered Species currently protects only whale, basking and great white sharks, though other species are being considered, amongthem Porbeagle sharks – whose European populations are critically endangered. The Convention on Mirgratory Species is also working on a mechanism that will facilitate the international co-operation necessary.

Sharks are apex predators that dominate many oceanic food webs. Far from depleting fish stocks that could otherwise feed humans, their presence ensures the balance that keeps ecosystems productive.

“Top predators are important for keeping an ecosystem in balance,” Ms Fordham said.

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