A risk-based framework for assessing the cumulative impact of multiple fisheries

Effective conservation of marine ecosystems requires the assessment and management of cumulative impacts of multiple activities occurring in the ecosystem. Productivity Susceptibility Analysis (PSA) is a widely used tool to assess the potential impacts of fishing activities on marine ecosystems, particularly in data-poor regions. Yet, PSA and other risk-based approaches often do not account for the cumulative effects of multiple fisheries operating in the same region. Here we amend PSA to incorporate multiple fisheries by proposing a new index for cumulative risk assessment, i.e. Aggregated Susceptibility (AS). We applied this extended PSA to 81 species caught in 5 small-scale fisheries along the coast of Baja California, Mexico, and compared the results to the original PSA. Using the original PSA approach, 18 species (22.2%) were scored as high risk, and twenty-five species (31%) are at low risk from all of the fisheries conducted in this region. When the cumulative risk posed by all fisheries is assessed using our proposed methodology, the proportion of species at high risk increases to 38.3%, whereas the proportion of species at low risk decreases to 21%. For 13 species, the high-risk assessment is made only when scores are aggregated. Among the 5 fisheries, the set gillnet fishery has the greatest impact, which accounted for half of the high risk species and should be the focus of further investigation on how to best manage this fishery. Our analysis demonstrates the importance of accounting for the potential cumulative impacts of multiple co-occurring fisheries for the conservation of coastal marine ecosystems, identifies relative risk imposed by multiple fisheries, and provides a tool for a preliminary evaluation of the possible outcomes of management alternatives.