A DNA test that identifies the kind of shark ending up in shark fin soup is being hailed as a conservation breakthrough.

It allows regulators to find out whether protected species are being hunted illegally for their meat.

This new identification method has big implications for shark fisheries and trade monitoring

Dr Ellen Pikitch, Wildlife Conservation Society

Shark fins are regarded as a delicacy in parts of Asia.

Conservationists estimate that about 100 million sharks are caught each year, many of them purely for use in shark fin soup.

They fear that some protected species, such as the basking shark, are targeted along with more common species.

Until now it has been difficult to tell, partly because of the common practice of cutting off a shark's fins, then throwing the mortally wounded shark back into the sea.

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The DNA test was developed by researchers from the New York-based Wildlife Conservation Society (WCS) and Nova Southeastern University in Florida.

The soup can cost up to $100 a bowl

It can identify up to 10 species of shark caught in the North Atlantic from fresh or dried fins.

In tests on fins on sale in a Hong Kong market, the researchers found that about 20% were labelled as coming from one kind of shark, when in fact they came from another.

The results are published in the journal Conservation Biology.

"This new identification method has big implications for shark fisheries and trade monitoring," says Dr Ellen Pikitch, director of the WCS's marine programme.

"Conservationists will finally be able to get a glimpse into the impact that high seas fisheries are having on wild shark populations."