Updated SCAA/ASPM assessment of Gulf of Maine Cod

Abstract

The Alt-VPA methodology of Butterworth and Rademeyer (2008a) is applied to updated data for the Gulf of Maine cod population for the period 1982-2006 for which catch-at-age data are available. The fits of the models show a preference for domed over asymptotically flat selectivity. However, the narrow range of estimates of B sp values virtually precludes fits of different stock-recruitment curves from being able to distinguish between options as different as Ricker and Beverton-Holt (from which also very different estimates of Reference Points follow). Because of the clearly high variance that would accompany Reference Points inferred from this analysis, they are not advanced, with a preference for approaches that can accommodate a wider range of data and hence achieve reasonable precision being expressed.