Recently introduced "environmentally friendly" longline fishing is proving to be not so friendly to seabirds whose encounters with these lines often results in their death.

Longline fishing entails setting mainlines up to 100km long with up to 15 000 baited hooks on short branch lines. It is often seen as an "environmentally friendly" alternative to drift-nets or trawling because relatively few non-target species are caught. However, if the hooks do not sink quickly, and other measures such as bird-scaring lines are not fitted, seabirds swallow the hooks, or get tangled in the lines, dragged underwater, and drown.

An investigation by the Percy FitzPatrick Institute of African Ornithology into South Africa's three longline fisheries has found that measures designed to reduce bird bycatches are not being enforced. This is resulting in the deaths of biologically significant numbers of seabirds, causing the global population to decrease.

The three longline fisheries that operate in South African waters at present include fisheries for hake, tuna and Patagonian toothfish.

Earlier this year members of the FitzPatrick Institute identified measures to limit bird bycatches in local longline fisheries. These include fishing at night when most birds are inactive, limiting the amount of light on boats, travelling slowly while setting lines and using sufficient weights to ensure the lines sink rapidly; avoiding gutting on board, and dumping the offal away from the area where hauling takes place.

However, scrutiny of South Africa's hake, tuna and Patagonian toothfish fisheries has revealed that these measures are not always adopted, and legislation is needed to make them mandatory. Even strict legislation will not solve the problem on its own, according to Dr Peter Ryan of the FitzPatrick Institute.

"Legislation alone is ineffective. We have to educate fishermen as to the need to implement legislation and place observers on board to ensure compliance," he said.

South Africa's experimental longline hake fishery commenced in 1994, when it killed an estimated 8 000 whitechinned petrels. Subsequently it has adopted some of the FitzPatrick Institute's recommendations which have resulted in a marked drop in the number of seabirds caught. At present the fishery is catching seabirds at roughly a tenth of its previous rate, but the total number of seabirds caught is still cause for concern according to Or Ryan.

Despite the relative success of this project, he is fearful that appropriate measures to limit bird mortality may not be adopted when the three-year experimental fishery terminates at the end of this year. During the first summer of operation South Africa's longline fishery for Patagonian toothfish killed unsustainably large numbers of seabirds. This was due to the fact that the fishery which operates near the Prince Edward Islands, home to 5% of four of the world's albatross species, enforced very few of the internationally recognised recommendations for longline fishing in the area. This resulted in unsustainable levels of mortality amongst local seabird populations.

"The problem is made worse by the low reproductive rates of these species, many raise at most one chick every two years, coupled with the killing of breeding adults, most of which are males. Fortunately the legal fishery has responded positively to the costly lesson from the first season's fishing, and is already changing its fishing practices to reduce seabird bycatch. However, the impact of the illegal fishery remains a significant problem, and urgent steps are needed to curb illegal fishing in the area," said Dr Ryan.

Little is known about the longline tuna fishery off South Africa and how many seabirds it kills, but Dr Ryan estimates that perhaps 60 to 70 million hooks are set each year by this fishery in the waters south of Africa.

Dr Ryan and researcher Mr Christian Boix gained some information from Taiwanese operators who comprise 75% of the tuna fishery, but were unable to gain any information at all from Japanese operators who make up the remainder of the fishery.

"A survey of Japanese tuna vessels was not possible because we received no assistance from the Japanese authorities in Cape Town. However, observers on Japanese vessels operating off southern Africa provide the only hard evidence of bird mortality. Extrapolating from these data suggests that some 20 000 albatrosses and 10 000 other seabirds are killed annually by tuna vessels in the area south of Africa," said Dr Ryan.

Despite these horrifying statistics there does appear to be a glimmer of light at the end of the tunnel. South African authorities are in the process of issuing 30 permits to local operators and the new permits will include control measures to reduce seabird bycatch and make provision for observers on vessels to help monitor the situation.

A drowned Wandering Albatross on a tuna longline, showing how the buoyant bird acts as a float, keeping adjacent hooks from reaching the correct fishing depth. (picture: Graham Robertson)