Artisanal longline fisheries in Southern Chile: Lessons to be learned to avoid incidental seabird mortality

Industrial longline fisheries are considered worldwide as the main threat to albatross and petrel populations, particularly at open oceans. However, inside countries’ EEZ artisanal fleets account for a significant fishing effort and eventually, could represent a major threat to these species than industrial fishing. Here we provide the first assessment of incidental mortality in two artisanal fleets in southern Chile, targeting Austral hake and Patagonian toothfish, which accounts for 0.9 and 20 millions hooks/year, respectively. Fishing techniques of these fleets have many particularities that made their operation markedly different from the more known industrial longliners, therefore their characteristics and sink rates are thoroughly described. By-catch rates (BPUE) estimated were low: 0.030 and 0.047 birds per 1000 hooks in hake and toothfish fisheries, respectively, despite that no mitigation measured was in use. These low results may reflect the fast sink rate profile of the particular longline type used by these fisheries, although the low abundance of species present may influence too. Both fleets use a modified longline having secondary hook-lines placed vertical along the mother line, each having a weight that increases significantly its sink rate, reaching 0.33 and 0.69–0.22 m s−1 in the hake and toothfish longlines, respectively. Considering the big fishing effort deployed by the artisanal toothfish fleet, recommendations on mitigation measures are given for each fishery to further improve their fishing techniques.