Stock synthesis model sensitivity to data weighting: an example from preliminary model runs previously conducted for north Atlantic blue shark

Stock Synthesis model sensitivity was evaluated to data weighting with a case study provided from preliminary Stock Synthesis model runs conducted for North Atlantic blue sharks. A two stage data weighting approach was investigated to iteratively tune (re-weight) variance adjustment factors for fleet-specific size data distributions (length composition) and fleetspecific relative abundance indices (CPUE) within a Stock Synthesis model. An example implementation of the approach is provided from preliminary model runs previously completed for North Atlantic blue sharks with Stock Synthesis. The two stage data weighting approach outlined here provides an example of a possible data weighting approach within an integrated stock assessment model that may be useful to explore in the upcoming shortfin mako assessment.