Hook shielding devices to mitigate seabird bycatch: review of effectiveness
Bycatch of seabird species in pelagic longline fisheries is recognised as one of the most important and prevalent sources of their mortality, contributing to an increased risk of extinction. In 2016 the Agreement on the Conservation of Albatrosses and Petrels (ACAP) recognised hook-shielding devices as a best practice seabird mitigation option, providing a stand-alone alternative to their established advice which recommends the simultaneous use of branchline weighting, night setting and bird-scaring lines.
In this paper we describe the function of the Hookpod, one of the novel hook-shielding devices, which has been in development since 2007. It aims to provide a ‘one stop’ solution to seabird bycatch in pelagic longline fisheries. We summarise the results from numerous trials of Hookpods, highlighting evidence for their effectiveness at reducing seabird bycatch rates as well as any effect on catch rates of target fish species and other bycatch. We also discuss findings related to their influence on hook sink rates, their durability and cost, and their applicability in different fisheries.
Experimental trials clearly indicate Hookpods are extremely effective at reducing seabird bycatch to rates equal to or better than those achieved using existing mitigation methods, such as line weighting, birdscaring lines and night setting. No negative effect on target fish catch rates have been found, and trials have been conducted across pelagic longline fisheries in the Pacific, South Atlantic and Indian Oceans, indicating their wide applicability.
Hook-shielding devices represent an important advancement in the range of options to reduce seabird bycatch in pelagic longline fisheries. While some fishing operators may continue to prefer using existing methods, others seeking a stand-alone option will prefer hook-shielding devices, which may be particularly suited to fisheries where there have been challenges implementing other mitigation measures, such as line weighting or bird-scaring lines, or where seabird bycatch risk is particularly high. For example, the high diversity of vulnerable seabirds in New Zealand, the “seabird capital of the world”, provides challenges to mitigating bycatch. Having a greater range of proven and effective mitigation options to choose from will help fishing operators overcome these challenges. We make recommendations that hook-shielding devices should be added to the current list of mitigation measures as a stand-alone option in the Commission’s Conservation and Management Measure to mitigate the impact of fishing for highly migratory fish stocks on seabirds.