Nine new species of sharks, including the scalloped hammerhead, are to be added to the official list of animals at global risk of extinction, scientists have revealed. The World Conservation Union (IUCN) will add them to its "red list" of vulnerable species later this year after recent analyses showed over- fishing has reduced some populations by as much as 99 per cent.

Experts are particularly concerned at the rapid decline of the scalloped hammerhead, which the IUCN will list as "endangered" - its second highest of five levels of concern. Sharks' fins are highly prized as a delicacy in Chinese cooking, and prices can reach as much as £150 per kg.

An estimated 100 million sharks are killed every year, with many fishermen simply slicing off their fins before throwing them back into the water where they usually drown or bleed to death. Dr Julia Baum, a member of the IUCN's Shark Specialist Group, revealed the plans to add the species to the endangered list at the American Association for the Advancement of Science (AAAS) conference in Boston.

Dr Baum, a marine ecologist at Scripps Institution of Oceanography in San Diego, said: "Our oceans are being emptied of sharks and the scale of the problem is global. "If we carry on without doing anything about it we are looking at a high risk that some of these could be extinct within our lifetime.

"On the high seas and in international waters there are no regulations or catch limits. It's a free for all. "Over the last decade conservation concerns have been mounting. Now we need to convert that into action to introduce effective measures that are strictly enforced." There are 126 sharks listed as at risk of extinction - defined by the IUCN as critically endangered, endangered or vulnerable.

Research by Dr Baum and colleagues found numbers of tiger, bull, dusky, smooth and scalloped hammerhead shark have collapsed by between 95 and 99 per cent off the US east coast since 1970. Last year the Shark Specialist Group of the IUCN met to assess the risks to oceanic shark species - those that are highly mobile and live primarily in the open ocean, away from coastal areas.

Apart from classifying the scalloped hammerhead as endangered, the smooth hammerhead, the shortfin mako, the bigeye thresher and the common thresher will be listed as vulnerable. Tiger, dusky and bull sharks will either be classed as vulnerable or "near threatened" - a category defined as close to the threshold for risk of extinction. The silky shark will also be classed as near threatened.

Scalloped hammerheads congregate in large numbers around seamounts and islands, making them easy targets for fishermen. It takes 16 years for them to reach maturity, meaning that populations take a long time to recover. There are no catch limits in international waters and existing bans on "finning" are ineffective. Spanish fishing fleets in particular have been targeting sharks.

Millions of sharks are also taken by recreational fishermen and as bycatch by fleets fishing for tuna and swordfish. In December the United Nations passed a resolution calling for catch limits and true shark-finning bans, and the European Union is currently drawing up a plan of action.

Sonja Fordham, of the Shark Alliance conservation alliance, said: "People think these wide-ranging, fast sharks are resilient to fishing; however, this is not the case. "Concerned citizens can really help by making their fisheries ministers aware that they support conservation measures such as catch limits."

(By Nic Fleming, Telegraph, 19/02/2008)