A Reference Case application of ASPM to the Georges Bank yellowtail flounder, together with three sensitivies, is presented. Strong residual patterns in the fits to survey indices of abundance, particularly to that for the Canadian DFO Spring survey, raise concerns about the compatibility of the population model and these indices. The model fits strongly favour domed over asymptotically flat selectivity. Selectivity assumptions are key to estimates of stock status, with fits to a fully flexible selectivity parameterization indicating the resource to be effectively at its MSY level sp BMSY , whereas imposing asymptotically flat selectivity sees the stock estimated to be below the “overfishing” threshold of 0.5 sp BMSY .