CCAMLR

By-catch was observed during two successive cruises of longliners fishing for Patagonian toothfish Dissostichus eleginoides in approximately 500m depth along the shelf slope in the west of Kerguelen. By-catch consisted mainly of Rajidae Bathyraja spp. (85 %). The proportion of species taken in the by-catch was low (less than 0.75%) and does not represent a problem at the present level of fishing. The results indicate that longlining therefore is a highly target-specific method of fishing in the patagonian toothfish fishery.

Incidental captures of seabirds were observed during 93/94 to 95/96 longlining fishing campaigns around Kerguelen islands (division 58.5.1). Mean by-catch rate is 0.81 birds / 1.000 hooks. The species mainly affected is the White-chinned Petrel Procellaria aequinoctialis (86 %), because of its diving faculty. The different ways to minimize seabird by-catch proposed by CCAMLR are tested and their effectiveness discussed.

Studies carried out over the past three decades at Crozet and Kerguelen Islands in the Indian Ocean indicate that wandering albatross Diomedea exulans populations declined markedly, but since 1986 have shown slow recovery. The population of the endangered Amsterdam albatross Diomedea amsterdamensis appears to have similarly recovered since 1985, but remains close to extinction. A demographic study of the Crozet population indicates that the earlier decline was mainly the result of increased adult mortality, and secondarily of low recruitment. Satellite tracking studies of breeding birds and band recoveries of non breeding birds indicate that during and outside the breeding season these populations are in contact with long-line fisheries, mainly the pelagic Japanese southern blue-Jin tuna fishery and to a lesser extent the Patagonian tooth-fish fishery operating on the Kerguelen shelf: Decreased fishing effort and a concentration outside the central Indian Ocean by the Japanese fishery during recent years has probably resulted in the slow recovery of these albatross populations as a result of improved adult survival and recruitment. Long-line fisheries still represent a major threat to great albatross populations, most which are still declining in the Southern Ocean. Possible conservation measures to reduce mortality in the fishery and to reduce contacts between fishing units and foraging albatrosses are examined.

Sea-birds taking baits during longline setting occationally become caught and are killed, while the associated bait loss may have serious impact on longlining efficiency and profitability. Two different setting methods were tested as a solution to this problem; lines were set either through a setting funnel that guided the baited line beneath the sea surface or when using a sea-bird scaring device. Bait loss and the catches of target species and sea birds were compared with those of lines set without using such devices. Accidental catches of birds were reduced by both methods, most effectively by the sea-bird scarer. Losses of mackerel bait were also significantly reduced by using the scarer, but not by using the setting funnel. No increase in the catches of target species was demonstrated by using either of the setting methods. However, bait loss caused by sea birds was regarded as a minor problem in this fishing experiment. Suggestions on how to improve the efficiency of the two methods tested were discussed.