South Atlantic blue shark stock: Just Another Bayesian Biomass Assessment

Bayesian State-Space Surplus Production Models were fitted to South Atlantic blue shark tuna catch and CPUE data using the ‘JABBA’ R package. The thirty-six distinct scenarios were based on a life history parameters, steepness and model weighting. All scenarios were based on a PellaTomlinson production function from an Age-Structured Equilibrium Model (ASEM). All scenarios showed similar trends for the trajectories of B/BMSY and F/FMSY over time. In general, B/BMSY showed a decreasing pattern in the first half of the time series followed by a slight increase after 1998. The F/FMSY showed a general pattern with a sharp increasing trend during 1990s, followed by stable trend. Kobe stock status plots had shown median quantities estimated for the last data year in the green quadrant. However, the scenarios based on a more conservative values of steepness (0.5) were more pessimistic than others.