A trial evaluation of the effectiveness of the use of circle hooks to reduce mortality of shortfin mako shark in pelagic longline fisheries - Mortality of shortfin mako shark on circle hooks vs j-hooks

The recommendation by ICCAT on the conservation of North Atlantic stock of shortfin mako shark caught in association with ICCAT fisheries contemplated in ICCAT Rec. 17-08 includes that the SCRS shall take into its account the effectiveness of the use of circle hooks as a mitigation measure to reduce mortality in conducting review the effectiveness of the measures. In this study, the total mortality of shortfin mako shark was estimated and consists of at-vessel releases and post-release mortalities by hook types, i.e. circle hooks versus J-hooks, with 5 different combinations of at-vessel and post-release mortality rates of shortfin mako shark in pelagic long line fisheries based on the literatures. In conclusion, the estimated total mortality with circle hooks was more than 1.6 times higher than that with J-hooks in every combination. From this result, it was considered that the use of circle hooks may cause substantial increases of overall mortality of shortfin mako shark.