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The scalloped hammerhead shark, one of the ocean’s most distinctive and iconic species, is to be declared endangered because of the impact of over-fishing to feed a burgeoning market for shark fins in China.

Populations of the shark, which was once considered among the most common top predators in coastal waters, have collapsed over the past 40 years to such an extent that it will be included on this year’s Red List of threatened species for the first time.

Another eight shark species will also be added to the International Union for the Conservation of Nature (IUCN) assessment of extinction risk when the newest version is published in October. The short-fin mako shark, the smooth hammerhead, the big-eye thresher and the common thresher will be declared vulnerable, the silky shark will be declared near-threatened, and the tiger, bull and dusky sharks will have either vulnerable or endangered status. All these species were not considered at risk when their conservation status was last assessed but new research led by Julia Baum, of the Scripps Institution of Oceanography in La Jolla, California, has revealed a rapid decline in numbers in recent years.

Dr Baum’s study of the US Atlantic coast found that the number of scalloped hammerheads fell by 98 per cent between 1970 and 2005. Great white, tiger and smooth hammerhead sharks have declined at a similar rate. Sharks have been “functionally eliminated” from the region, she said.

“Right now the oceans are being emptied of sharks, and the scale of the problem is global,” Dr Baum told the American Association for the Advancement of Science conference in Boston yesterday. “If we continue in the way we are going, we are looking at a really high risk of extinction for some of these species within the next few decades.” Shark fishing in the open ocean is unrestricted and the practice of “finning” — in which prized dorsal fins are cut off and the mortally wounded shark is thrown back into the water — makes the problem still worse. Limits on the number of fins that can be landed without carcasses are routinely avoided, Dr Baum said.

Some sharks are killed as bycatch by tuna fisheries, but more and more are being deliberately hunted for their fins, which are considered a delicacy in China. The country’s economic boom has increased demand for fins, which are often served at weddings and important business dinners. Fins sell for as much as £150 a kilogram.

Between 26 million and 73 million shark fins are sold in the main Hong Kong market every year, more than three times the total declared to the UN Food and Agriculture Organisation, Dr Baum said.

The threat to sharks is particularly remarkable as all the species to be added to the Red List have global ranges, which should make them less vulnerable to extinction. “The perception used to be that really wideranging species like this couldn’t become endangered, as while they might be threatened in one area they surely wouldn’t be threatened in every area,” Dr Baum said. “We’re now learning that that’s not the case.”

The scalloped hammerhead was once among the most abundant sharks. The species is particularly vulnerable because it takes 16 years for adults to reach maturity. This slow growth rate means that it cannot recover from overfishing. Scalloped hammerheads also often swim in schools, which makes them easier to catch .

The United Nations recently agreed a resolution calling for limits on shark fishing in international waters, though controls have yet to be implemented. Dr Baum said that quotas should be imposed immediately, and also called for an effective ban on shark finning.

Scalloped hammerhead

Latin name Sphyrna lewini
Length up to 3.1 metres. Pups measure 50cm at birth
Range found in all the world’s temperate and tropical oceans, mostly in coastal regions
Appearance olive, bronze or light brown colour, with a white belly. Bumps shaped like scallop shells on front edge of head
Diet near-top predator, feeding mainly on smaller sharks, skates and rays
Breeding habits Typical litter size is 14 to 26, and the sharks take 16 years to reach maturity
Longevity They are believed to live for about 25 years

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