Ecological risk assessment of shark bycatch in longline fisheries in Eastern Pacific Ocean

The Eastern Pacific Ocean (EPO) is the main operating area for global tuna fisheries, and the impact of tuna fishing in EPO on bycatch shark populations has always been highly concerned by the international community. Based on the Productivity Vulnerability Analysis (PSA), we conducted an ecological risk assessment on eight shark species caught in the East Pacific longline fishing industry, and performed a sensitivity analysis on the attributes used in PSA. The results show that the productivity index ranged from 1.40 to 2.20, with the highest being blacktip shark (Carcharhinus limbatus). The susceptibility index ranged from 2.17 to 2.83, the highest being shortfin mako shark (Isurus oxyrinchus). The vulnerability score ranged from 1.55 to 2.31, and the highest being bigeye thresher shark (Alopias superciliosus). Ecological risk assessments indicate that oceanic whitetip shark (C. longimanus), shortfin mako shark and bigeye thresher shark were at a high risk, while blacktip shark, silky shark (C. falciformis), blue shark (Prionace glauca), longfin mako (I. paucus) and scalloped hammerhead (Sphyrna lewini) were at a medium risk. The results of sensitivity analysis indicate that reproductive strategy, areal overlap and aggregation behavior had the greatest influences on the species vulnerability scores, with Root Mean Squared Error (RMSE) values being 0.210 1, 0.128 8 and 0.090 1, respectively. To sum up, C. longimanus, I. oxyrinchus and A. superciliosus are the priority species in the EPO for further data collection, assessment and management, so as to reduce the impact of fishing activities on their population.