Preliminary stock synthesis (SS3) model runs conducted for North Atlantic blue shark (1971-2021)

Stock Synthesis model runs were conducted for the North Atlantic blue shark based on the available catch, CPUE, length composition, and life history data compiled by the Shark Species Group. A sex-specific model was implemented in order to allow for observed differences in growth between sexes. Beverton-Holt stock-recruitment was assumed. The steepness of the stock recruitment relationship and natural mortality at age were fixed at independently estimated values. A two-stage data weighting approach was implemented. Model sensitivity was evaluated to CPUE groupings, to the steepness of the stock recruitment relationship, and to natural mortality at age compiled by the Shark Species Group. A wide range of model results were obtained from these preliminary structural uncertainty analyses that could be useful to inform a structural uncertainty grid for the 2023 blue shark stock assessment. A preliminary reference case model was identified that may be useful as a starting point for continued model development during the 2023 blue shark stock assessment.