Acoustic devices can scare the porpoises off

"It won't happen tomorrow, or in the next 20 or 30 years probably, though nobody can be certain what other human influences are affecting the animals.

"But we believe the number dying in gillnets each year is something like 4.3% of the population.

"Several international groups, including Ascobans (the Agreement on the Conservation of Small Cetaceans of the Baltic and North Seas), say 1.7% is a critical precautionary level. What's happening is more than twice that.

"If nothing changes, then there'll be a very high risk of eventual extinction."

Harbour porpoises are small animals with a blunt short-beaked head and a low wide-based triangular dorsal fin. Adults are usually less than six feet (1.8m) long and weigh from 90 to 140 pounds (45 to 70 kg).

Warning devices

They get caught in the thin gillnets set on the sea bed for cod, turbot, plaice and other species. Most are then injured, or else drown.

Mortality rates are thought to be unsustainable

The UK and Denmark have been working on electronic "pingers", acoustic devices which are fixed to the nets and emit a high frequency signal to scare the porpoises away.

Problems with the pingers' reliability have now been resolved. Work is also going ahead on applying a reflective coating to the nets, to make them more visible.

The UK fisheries minister, Elliot Morley, has written to the European fisheries commissioner, Franz Fischler, asking for the problem of small cetacean bycatches to be included in the revision of the CFP.

Scientific concern

The International Council for the Exploration of the Sea (Ices), the world's oldest intergovernmental marine science organization, is to finalise a report on small cetaceans in the North Sea by the end of August.

The report will then go to the European Commission. An Ices spokesman told BBC News Online he could give no details of what it would say. But he said concern over the harbour porpoises was high in the scientific community.

Images copyright and courtesy of WWF Germany