Applying rapid risk assessment methods to bycatch in the WCPO

Considerations for SC17:
• Note that SPC in collaboration with the IATTC is evaluating the performance of EASI-Fish as a tool for assessing fishery impacts on data poor and bycatch species.
• Note the benefits of re-establishing a specific project for assessing the vulnerability of bycatch and species of special interest to fishing activities in the WCPFC jurisdiction. This would facilitate broader collaboration on the topic among WCPFC members and other organisations to routinely evaluate the impacts of fishing on bycatch.

Background
WCPFC is increasingly utilising or proposing the use of rapid risk assessment methods to evaluate the vulnerability of data-poor stocks and species of special interest to fishing activities occurring within its jurisdictional boundaries (Tremblay-Boyer & Berkenbusch 2020; Neubauer et al. 2019; Peatman et al. 2019; Neubauer et al. 2018; Fu et al. 2017; Hoyle et al. 2017). These tools can be sensitive to the equations and variables used to summarise the population dynamics (Hordyk & Curruthers 2018) and the extent of fishing mortality (Murua et al. 2021). These sensitivities often mean that there is no one method that fits all purposes, and choice of method is therefore based on what assumptions are considered acceptable given the question posed.

The most recent of these tools is EASI-Fish (Griffiths et al. 2019), developed at the IATTC. EASI-Fish estimates fishing mortality based on the ‘volumetric overlap’ of each fishery with the distribution of each species. Fishing mortality is then used in a length-structured per-recruit model to assess population vulnerability status using conventional biological reference points (Griffiths et al. 2019). EASI-Fish also applies Monte-Carlo simulation methods to capture uncertainty in estimated vulnerabilities (Griffiths et al. 2019). These two features are advantageous as they allow presentation of vulnerabilities using metrics consistent with those regularly used in stock assessment of tuna species in the WCPFC...