Conservation Services Programme Project MIT2015-02: Mitigating seabird captures during hauling on smaller longline vessels
Seabird captures in longline fisheries may occur on the set, soak or haul. Bycatch reduction measures are best developed, tested and implemented for reducing seabird captures occurring during longline sets. Measures affecting the nature and extent of haul captures, and mitigation approaches to reduce those captures, are not well-known. Further, the difficulty of accurately identifying captures as occurring on the haul means that live seabird captures are typically used as a proxy for haul captures in bycatch datasets.
A global review shows four broad categories of mitigation used during longline hauling: physical barriers, measures that reduce the attractiveness of the haul area, deterrents, and operational approaches that are part of fishing. Of devices that operate as physical barriers to seabirds, bird exclusion devices, tori lines and towed buoys have been tested and proven effective in reducing seabird interactions with hauled longline gear. Discharging fish waste such that seabirds are not attracted to the hauling bay is another effective measure, and seabird abundance around vessels is reduced by retaining fish waste during hauling. While a number of deterrents and ad hoc or reactive approaches to reducing haul captures have been discussed in the literature (e.g. water sprays), these have generally not been empirically tested.
Information collected by government fisheries observers on 73 bottom longline and 60 surface longline trips that have occurred since 1 October 2012 on New Zealand vessels