Review and evaluation of three mitigation measures - bird-scaring line, underwater setting and line shooter - to reduce seabird bycatch in the Norwegian longline fishery

Abstract

Seabirds scavenge baits from the hooks of commercial longlines, resulting in incidental seabird mortality and bait loss. As interactions between seabirds and longline fishing may cause decline in seabird populations and reduced gear efficiency, the potential for solving this problem by means of various mitigation measures has been tested. Four fishing experiments were conducted in commercial longlining in the north Atlantic to investigate the effectiveness of a bird-scaring line, underwater setting and a line shooter in reducing seabird bycatch during longline setting. These results are reviewed and the performance of the mitigation measures is evaluated. Accidental catches of birds were reduced by all three methods, most clearly by the bird-scaring line that had an efficiency of 98-100%. The experiments also produced a reduction in bait loss and raised the catch rates of target species, which are important incentives for fishermen to employ mitigation measures.