They warn that tough restrictions are needed to save exotic species such as the orange roughy, the black scabbard fish and the Portuguese shark.

Fisheries ministers from across Europe are preparing for a meeting of the European Union fisheries council on Tuesday that will decide how heavily stocks can be exploited.

One of the documents they will consider comes from the International Council for the Exploration of the Sea, which co-ordinates marine and fisheries research for 19 countries bordering the north Atlantic. It will warn that catches should be reduced until they can be shown to be sustainable.

David Griffith, the council’s general secretary, said: “Deep-sea fish are long-lived, slow- reproducing fish that can withstand only low levels of fishing.” In Britain these fish are mainly used in processed food.

Griffith is particularly concerned about deep-sea sharks such as the Portuguese and the leafscale gulper, whose populations have fallen by more than 80%. He wants a ban on fishing them.

The crisis for deep-water species began 20 years ago with a rapid decline in the population of cod, hake, haddock and other shallower-water species. This prompted fishermen to seek stocks further offshore in water up to 3,000ft deep. Such species are popular with Spanish and Portuguese fishermen who use high-tech echo sounders to target them.

A few years of heavy fishing have sent populations plummeting. Conservationists say that the techniques used to catch such fish are also destructive and wasteful.

A WWF study has criticised the fisheries around Britain as among the worst, with Spanish boats sailing under the British flag making extensive use of gill nets — long strips of net that sit in the water killing everything that gets trapped in them.

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