Ensuring consistency in spatially-stratified stock assessment models: An analytical solution for equilibrium population structure with connectivity for age-and size-structured models Fisheries Research

Spatial stock assessment models are utilized for management advice, but movement complicates calculation of equilibrium population structure and stock status. Although a generalized analytical solution exists for determining equilibrium dynamics, it is not widely recognized and many models rely on approximations. We provide a derivation of the analytical solution in spatial age- and size-structured models, then perform deterministic comparisons of methods, and provide an application with Alaska sablefish (Anoplopoma fimbria). Despite equilibrium quantities not differing widely across most methods, the analytical solution retains consistency with model assumptions, coherence in deterministic and stochastic population projections with respect to reference points, avoids subjective decisions, and should be used in future spatial assessment models.