Oceanic whitetip and silky shark in longline fisheries between 20 N and 20 S and outside the area to evaluate CMM 2022-04 (Project 116)

The purpose of the working paper is to evaluate CMM 2022-04 (Conservation and Management Measure for Sharks). Paragraph 28 in CMM 2022-04 states “In 2024, and commencing periodically thereafter, the SC shall review the impact of fishing gear on sharks that are not retained, including oceanic whitetip shark and silky shark, inside and outside of the area between 20 N and 20 S, and provide advice on potential mitigation measures that would benefit such shark species.” Longline fishing data were analyzed from the WCPFC Regional Observer Program (ROP) from 2010 to 2023 for three spatial areas: 1) to the north of 20°N, 2) between 20°S and 20°N and 3) south of 20°S. Nominal CPUE was estimated by flag, deep and shallow longline sectors and annually. The area between 20°S to 20°N has higher nominal CPUE for both oceanic whitetip shark and silky shark which reflects the latitudinal habitat preferences of each species. In the deep-set sector, oceanic whitetip shark CPUE is 6.7 and 12.2 times higher in the spatial area 20°S to 20°N, than north of 20°N and south of 20°S; respectively. In the deep-set sector, silky shark CPUE is 68.8 and 37.1 times higher in the spatial area 20°N to 20°S, than north of 20°N and south of 20°S; respectively. The higher silky shark CPUE reflects a latitudinal preference for a tropical habitat compared to an oceanic whitetip shark which has additional habitat to the north of 20°N and south of 20°S.