Development of a flexible Ecological Risk Assessment (ERA) approach for quantifying the cumulative impacts of fisheries on bycatch species in the eastern Pacific Ocean
Ecological Risk Assessment (ERA) methods have been an increasingly popular alternative to traditional stock assessments for rapidly and cost-effectively assessing the relative vulnerability of non-target species in resource- and data-limited fisheries. The widely-used Productivity-Susceptibility Analysis (PSA) requires detailed fishery susceptibility and biological information for a large number of parameters, and cannot definitely determine species vulnerability or quantify cumulative impacts from multiple fisheries. This paper introduces a flexible quantitative approach that uses less input parameters than PSA to quantify the cumulative impacts of multiple fisheries on data-poor bycatch species. The method first produces a proxy of the instantaneous fishing mortality rate (F) of each species based on the ‘volumetric overlap’ of each fishery with the stock’s distribution. F is then used in length-structured per-recruit models to assess the vulnerability of each species using conventional biological reference points (e.g. FMSY, F0.1 and SSB40%). The method is illustrated with data from the eastern Pacific Ocean (EPO) tuna longline and purse-seine fisheries. Application of the method to 14 pelagic and mesopelagic teleost and elasmobranch non-target species, and classification of the vulnerability status of each species using a phase plot, is demonstrated. This approach may allow fisheries managers to more confidently identify the most vulnerable species to which resources can be directed to either implement mitigation measures, apply more detailed analysis, or collect further data to facilitate a formal stock assessment in the future.