Appropriate Limit Reference Points for WCPO Elasmobranchs
Three closely related projects on pelagic elasmobranchs in the Western and Central Pacific Ocean (WCPO) have been conducted in recent years. The first was a thorough review of appropriate limit reference points (LRPs) which was completed in 2014 (Clarke and Hoyle, 2014). This study recommended a tiered framework, similar to that adopted for target species, for defining LRPs for elasmobranch bycatch. Since most elasmobranchs are data-poor stocks, the study strongly suggested that quantitative ecological risk assessments (ERA), also called risk-based approaches, be used for defining LRPs. As ERAs require many life history parameters (LHPs), the study also identified the collation of information on LHPs as a priority issue, which led to a second project that compiled a comprehensive LHP dataset and produced a report (Clarke et al., 2015). Using this dataset and some additional data from literature, a third project derived risk-based reference points for 15 elasmobranch stocks (Zhou et al. 2019). SC15 recommended that the key conclusions from Zhou et al. (2019) be summarized together with any other relevant information.
Several recommendations are provided in this report. The most significant one is to adopt Blim = 0.25B0 and
corresponding Flim = 1.5Fmsy as interim LRPs for WCPO elasmobranchs. We do not support the use of a constant percentage of SPR such as F60%SPR as a reference point for all stocks. Finally, it is important to continue research to provide and improve estimates of life-history parameters and gear selectivity. The estimated reference points should be reviewed and updated when new methods or additional data become available.