Are dead dolphins the price paid for catching sea bass?

The first cause for concern came several weeks ago when a scarred, decomposing dolphin carcass washed up on a beach in the Cornish fishing village of Coverack. It was the start of a gruesome period in which carcasses have been appearing with increasing regularity, on one occasion 11 in a single day, along a stretch of coastline from Falmouth to Whitsand Bay.

Post-mortem examinations have yet to be carried out on any of the 20 dead cetaceans which have washed up but the scars on some suggest they are the victims of pair trawling, a practice illegal in British waters but still practised by some foreign trawlers, in which a large net is strung up between two craft to improve a catch of fish.

Cornwall braces itself for the consequences every January when French trawlers lay nets and prepare to fish for lucrative sea bass. Several dolphins and porpoises were caught up in the nets and killed last year but the appearance of so many in this year's early "by-catch" (as the creatures caught accidentally are known) suggests that the season's toll may be worse than ever.

Maddi Precious, who staffs a 24-hour strandings hotline for the Cornwall Wildlife Trust (CWT), is aware of the damage this form of fishing has caused. "The phone has not stopped ringing," she said. "Distressed members of the public keep calling us to tell us of yet more bodies."

Under the 1981 Wildlife and Countryside Act, all cetaceans (porpoises, dolphins and whales) are protected species and anyone convicted of ill-treating them faces a six-month prison sentence or a £5,000 fine. The Government also declared with a flourish, 16 months ago, that trawlers were to be banned from fishing within 12 miles of the shore.

But the strategy has not worked. The dolphins washed up on Cornish beaches may have been further out to sea when shoals of small fish enticed them into nets laid to catch sea bass. Alternatively, they may have been caught up in the inshore nets laid by the local gillnet fishery. "Either way, it is apparent that the... 12-mile limit is not working," said Joanna Doyle, marine conservation officer with CWT.

These are not the only creatures falling victim to trawling. Greenpeace staged a rooftop demonstration at Asda's headquarters in Leeds yesterday in protest at their policy of selling fish caught by "bottom trawling" - a practice in which a net is dragged along the seabed. The method scrapes the seabed bare of smaller and younger fish, as well as starfish, anenomes and cold-water corals. A third of the catch is discarded as worthless, Greenpeace says. Asda responded by announcing that it had "delisted" skate wings, dover sole, ling and dogfish in response to Greenpeace's concerns.

But the future for dolphins in Cornish waters looks bleak because the French government has refused to ban pair trawling. "We need international co-operation or Cornwall risks losing part of its wildlife heritage and we'll be the poorer for it," said Ms Doyle.