Vulnerability assessment of sharks caught in eastern Pacific Ocean pelagic fisheries using the EASI-fish approach

Griffiths S, Fuller L, Potts J, Nicol S (2022) Vulnerability assessment of sharks caught in eastern Pacific Ocean pelagic fisheries using the EASI-fish approach. In: IATTC - 13th Meeting of the Scientific Advisory Committee. IATTC SAC-13-11, Online

Sharks are a common catch, either as a target or incidental bycatch, in industrial and small-scale coastal (i.e., ‘artisanal’) pelagic fisheries in the eastern Pacific Ocean (EPO). In general, sharks are long-lived, slow growing, and have low reproductive output, resulting in conservation concerns for many species impacted by fishing. In recognition of these concerns for sharks, the IATTC has implemented a range of conservation and management measures (CMMs) since at least 2005 to limit or prohibit the capture of sharks, or to promote handling practices to maximize their post-release survival. Due to the common paucity of catch and biological data available for the majority of shark bycatch species caught in EPO pelagic fisheries an ecological risk assessment (ERA) approach, Ecological Assessment for the Sustainable Impacts of Fisheries (EASI -Fish), was used to quantif y the vulnerability of bycatch species to the cumulative impacts of multiple fisheries in the EPO. This approach can be used to guide fishery managers in prioritizing species that may require immediate management action to reduce the fishing mortality, or to highlight deficiencies in key information that are require d to be addressed before reassessment. A total of 49 shark species have been recorded to interact with industrial (purse-seine and longline) and artisanal (longline and gillnet) pelagic fisheries in the EPO, of which 32 species were formally assessed using EASI -Fish for the reference year 2019. Estimates of a proxy for fishing mortality (𝐹𝐹 2019) and the spawning stock biomass per recruit (SBR2019) in 2019 exceeded biological reference poi nts (F40% and SBR40%) for 20 species, classifying them as “most vulnerable” , including hammerhead sharks (4 species), requiem sharks (10 species), threshers (Alopias superciliosus and A. pelagicus), mesopelagic sharks (3 species) and the commercially important blue shark (Prionace glauca) and shortfin mako (Isurus oxyrinchus ). The remaining 12 species were classified as “least vulnerable” (9 species) or ‘increasingly vulnerable” (3 species) , data reliability scores for 7 of these species were low, indicating high uncertainty in the model parameter values used. Key knowledge gaps identified were the location of fishing effort and the shark catch in artisanal fisheries and basic biological information for several species. The EASI-Fish assessment provided a first comprehensive assessment for prioritizing research and management on shark bycatch s pecies. The flexibility and spatially-explicit framework of EASI-Fish can be used in future to rapidly and cost-effectively explore a range of potential hypothetical CMMs that may be implemented - in isolation or in combinationwithin the EPO to reduce fishery impacts on particularly vulnerable shark species identified, including silky, thresher and hammerhead sharks.