At least 20,000 birds are killed annually by the Norwegian longlining fleet, the RSPB said, and the combined activities of the vessels from Norway, the Faeroes and Iceland probably accounted for between 50,000 and 100,000 casualties each year.
Most of the birds killed are fulmars - the stiff-winged gull-like petrels that glide over the waves, dip to the surface to scavenge bait and get hooked in the process.
A traditional and widespread way of fishing in Norway and other nations in northern Europe, longlining has been regarded as environmentally friendly as far as fish stocks are concerned. It is also believed to avoid the damage to the sea bed that trawling inflicts, and to be relatively specific in the species of fish caught. However, the "bycatch" of sea birds is becoming an increasing problem: it has already been highlighted in the southern oceans, where between 50 and 100 million longline hooks are thought to be set annually, and 250,000 birds, mostly albatrosses and petrels, are snared each year. Consequently some species are believed to be threatened with extinction.
The RSPB is attempting to bring attention to the problem in the north Atlantic by carrying out a study in co-operation with the Norwegian Ornithological Society and Britain's joint nature conservation committee, which involved placing observers on Norwegian longliners over two years.
The size of the operations is at the core of the problem: the Norwegian fleet, which fishes for ling, cod and other species living near the sea bed, comprises sixty big off-shore vessels and hundreds of in-shore longliners, the RSPB said, which set between 30,000 and 40,000 baited hooks every day on lines that can be as long as several kilometres.
Euan Dunn, the RSPB's marine policy officer, said: "This is the first time the scale of the problem has been estimated in the north-east Atlantic. Technological solutions already exist to reduce the toll of sea-birds killed. The Nordic countries should be compelling their longline fleets to adopt the necessary safeguards to reduce this needless bycatch.
"It also makes economic sense for the fishermen because every hook that loses its bait to a sea bird is one less hook to catch a fish."
Devices that vessels can use - some of them pioneered by the Norwegians themselves - to reduce the incidence of bird drownings include a tube that sets the line underwater, weighted lines that sink faster, and the deployment of a "streamer" line that scares birds away from danger.
The RSPB is calling on Norway and the other Nordic countries to adopt a national action plan to reduce the death toll of sea birds.Reuse content