The study, produced for the Ministry of Agriculture, Fisheries and Food, was carried out over the summer by scientists on board tuna fishing boats sailing from Cornwall.
As well as thousands of dolphins, the drift nets also caught leatherback turtles, sharks, storm petrels, shearwaters and gannets. The drift nets, dubbed "walls of death" by some environmentalists, are long stretches of net, up to 2.5 km in length and 15 m deep, that are left to drift in the water to catch fish, but also ensnare other animals that swim into them.
The scientists who did the research accompanied the crews of four boats on nine different trips to estimate the total number of dolphins killed by the whole British and European drift netting fleets working off the West coast of Europe.
They estimated that 165 dolphins were caught by the British fleet, representing about one kill per 200 tuna caught. When the results are scaled up to include all the European boats then about 1,500 dolphins are likely to have been killed.
A French study in 1993 estimated that about 1,600 dolphins were killed by their fleet each year. If these figures are scaled up using the newly estimated dolphin kill rate then about 3,000 cetaceans may die in the Atlantic tuna fishery each year.
Helen McLachlan, a dolphin expert from the RSPCA, described the figures as "shocking".
"This is an unacceptable number of kills because Europe is committed to protecting dolphins and reducing the number of bycatches [unintended kills].
"These animals die a horrible death. They obviously struggle a great deal and they frequently have broken flippers and teeth. It's just ghastly - they basically just suffocate to death."
The European Union is negotiating under the United Nation's Bonn Convention, designed to protect migratory species, to safeguard small cetaceans in all Continental waters. Dolphins are protected only in the Baltic and North Seas.
The United Nations banned large scale drift netting on the high seas in 1992. The nets sanctioned by the European Union can be up to 2.5 km in length and so evade the "large scale" definition of the nets.
Mike Townsend, spokesman for the Cornish Fish Producers' Organisation, said they had incorporated "dolphin gaps" in their nets to allow cetaceans to escape. But the dolphin doors made the nets longer than 2.5km and consequently they were cut by angry Spanish fishermen during the "tuna war" of 1994.
This year, when the research was conducted, he says the fishermen were forced to return to continuous lengths of net. "You can blame that on the Spanish fishermen who have ruined a dolphin friendly fishing system," Mr Townsend said.
The RSPCA, Greenpeace and the Whale and Dolphin Conservation Society are currently pressing the European Union to outlaw drift nets of all lengths. Both the European Commission and Parliament have also voted for their abolition. The proposed ban is likely to face stiff opposition from the Italians who have 600 drift netters operating in the Mediterranean. The total number of British, Irish and French drift netters operating off Western Europe is less than 100.Reuse content