Incidental catch of seabirds in longline fisheries

Problem identification and mitigation measures

Issue

Although longline fishing often is regarded as an environmentally friendly fishing method, with no destructive impact on bottom habitats, good selectivity and low fuel consumption, a disadvantage is that incidental catches and thus killing of seabirds might occur, particularly during setting of the line. The impact of this incidental catch of seabirds has recently given raise to some international concerns and actions have been initiated regionally and globally to reduce the problem.

All longline gear is based on baited hooks attached to a mainline with snoods. A longline fishing vessel can operate from a few hundreds up to 30-40 000 hooks per day. The gear may be set at the seabed (demersal longlining), float off the bottom at variable depth (semipelagic longlining) or suspended from line drifting freely at the surface (pelagic longlining). These variations in gear configuration and operation affect seabird catch rate and type of mitigation measures that may prove to be most effective in reducing the incidental catch of seabirds.

Pelagic longlining, which mainly targets tunas, swordfish and billfishes, is operated widely from temperate to tropical waters in all oceans. Main target species are bluefin, bigeye, yellowfin and albacore tunas and swordfish. The majority of the global tuna catches are landed by about 2 500 vessels from Japan, the Republic of Korea and Taiwan Province of China, but many other countries also have vessels operating in this fishery.

The most important demersal longline fisheries are found in the north Atlantic and the north Pacific. Demersal fishing in the northeast Atlantic is conducted mainly by the Norwegian and the Icelandic fleets targeting species like cod, haddock, ling and tusk. In the northwest Atlantic, the Canadian longline fleet target groundfish, mainly cod. The longline fleet of the northeast Pacific consists of vessels of the United States and Canada, and the most important fishing grounds are found in Alaskan waters. Small vessels operating in coastal areas dominate the longline fishery around Japan. A longline fishery in the Southern Ocean for Patagonian toothfish has been developed over the last few years; vessels from several countries participate.

Certain longline fisheries result in large numbers of seabirds being hooked on setting lines. The major "problem" fisheries are the demersal fisheries of the Northeast Pacific, North Atlantic, Southern Ocean and the Atlantic coast of South America, and the tuna pelagic fisheries of cool temperate seas in the North Pacific and in the Southern Ocean. However, data on the incidental catch of seabirds are lacking for a number of longline fisheries, including on the Pacific coast of South America, the Mediterranean Sea and in tropical waters of all oceans. Of 61 seabirds species affected, 23 (38%) are considered threatened by the World Conservation Union. Species most commonly taken are the albatrosses, petrel, shearwaters, gulls and skuas. Other groups (penguins, cormorants, gannets, and boobies) of seabirds have rarely been recorded as incidental catch from longlining.

Possible solutions

A comprehensive number of mitigation measures for reducing incidental catch of seabirds in longline fisheries has been developed during the past 5-10 years. Some of them have been adopted by national and regional fisheries authorities, and regulations for their implementation are developed. In some longline fisheries are fishers using various technical measures when they want to reduce the loss of baits to birds foraging on them during setting of the line.

What is a mitigation measure? The best description is a modification of fishing practices and/or equipment that reduces the likelihood of incidental catch of seabirds. This description includes all strategies that can be employed for the purpose of reducing seabird mortality, ranging from fishing area or season closures to subtle adjustments in fishing equipment. Modifications, new fishing practices and equipment are more acceptable to fishers than are fishing area or season closures and therefore here lies the greatest potential for solutions.