Integrated weight longlines with paired streamer lines - best practice to prevent seabird bycatch in demersal longline

Dietrich, K.S., Melvin, E.F., Conquest, L.
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Biological Conservation
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Integrated weight longlines (IW) were tested for their ability to reduce sea bird bycatch in demersal longline fisheries. The target fishery for testing was the Pacific cod fishery operating in the Bering Sea, Alaska, USA. Three experimental mitigation techniques were tested: 1) IW line alone, 2) IW paired with streamer lines (IWPS) and 3) unweighted longlines with paired streamer (UWPS) against a control (UW). Information on catch rates, seabird abundance and attack rate, and gear sink rate and performance were collected. Seabird bycatch was dramatically reduced with all three experimental longlines. Surface foraging seabirds had higher reduction in mortality rates (91-100%) compared to diving seabirds (80-97%). The IWPS mitigation technique performed best because it allowed the gear to sink within the protection of the streamer, completely eliminated surface foraging and reduced shearwater catch by 97%. UWPS and IW reduced surface foraging catches rates by 98% and 91%, respectively. Shearwater catch rates were reduced by 87% with UWPS and 80% with IW. Catch rates of Pacific cod did not vary across mitigation techniques and the control.