Lessons from seabird conservation in Alaskan longline fisheries

Also published as ACAP SBWG9 Doc 11.

We compared seabird bycatch per unit effort (BPUE) in Alaskan longline fisheries before and after the adoption of streamer lines (bird scaring lines) using 23 years of fishery observer data (> 0.25 million sets of > 1 billion hooks). Streamer lines were adopted voluntarily in 2002 and mandated in 2004 based on two years of highly collaborative research with the fishing industry, which found that streamer lines reduced BPUE of surface-foraging seabirds by 88–100% compared to no deterrent. In the 14 years following streamer line adoption, mean albatross and nonalbatross BPUE decreased by 89% and 78%, respectively, in all fisheries combined. Seabird BPUE, however, varied by target species and seabird grouping, and models showed an increasing trend in BPUE in two target fisheries following streamer line adoption. Night setting reduced albatross BPUE by > 90%, most nonalbatross BPUE by > 51%, while increasing target fish catch rates by > 7%. Northern fulmar was the exception: BPUE increased by 40% during night sets. Most vessels in recent years had no seabird bycatch (67% to 72%); however, fleet BPUE was driven by a small number of vessels with anomalously high seabird bycatch. Although area and season were significant predictors in nearly all models, a clear pattern suggesting a coherent time-area management strategy was not evident. Alaskan longline fisheries represent one of the few cases where sharp reductions in seabird BPUEs demonstrated in research translated into sharp reductions in seabird BPUEs when results were applied to an active commercial fishery. Seabird conservation in a large, complex fishery was achieved using a single technical measure–streamer lines–and available evidence from Alaskan fisheries does not support mandating additional measures such as night setting, line weighting or time-area management that are included in ACAP Best Practice Advice. This case history provides strong evidence that seabird bycatch reduction measures should be fishery and seabird assemblage specific.