Exploring the use of artificial baits to avoid shark capture in a Hawaii-based tuna fishery

Abstract

Despite recent bycatch mitigation efforts to reduce fishery effects on populations of pelagic shark species, commercial fisheries continue to affect this vulnerable group. The widespread deployment of natural baits coupled with sharp olfaction of elasmobranchs continues to drive longline bycatch, regardless of policies prohibiting retention. We explored the use of artificial baits for catching tuna species and minimizing shark bycatch in a shortline fishery off Hawaii. Assessments of catch performance were conducted around the Cross Seamount from February 2022 through April 2023 to test hypotheses that artificial baits can be used to 1) effectively catch tuna species and 2) reduce shark bycatch compared to that with natural baits. During experimental deployments, we alternated using baskets of illuminated artificial baits and those of natural sardine baits, following initial tests with different artificial bait sizes, colors, and illumination sources. Preliminary catch data from 29 sets deployed during Phase 1 trials and 45 sets conducted in Phase 2 trials indicate that artificial baits were highly selective, with catch of only marketable species and no elasmobranchs. Although initial tuna catch rates were lower with artificial baits than with natural baits, preliminary findings indicate that further refinement of artificial bait configurations and light sources may provide a practical option to avoid shark interactions during longline operations.