Does spawning stock affect recruitment of New England groundfish?

Abstract

We evaluated the effects of spawning-stock size on the recruitment abundance of 11 groundfish stocks in waters off New England. Empirical patterns of association between spawning biomass and recruitment were investigated using nonparametric approaches. For most stocks, higher recruitment occurred at high stock sizes and lower recruitment at low stock sizes. Survival ratios, indexed by recruitment per unit of spawning biomass, were higher at low stock sizes and lower at high stock sizes-as expected under density dependence. To assess assumptions about recruitment dynamics, we analyzed constant-recruitment and compensatory and overcompensatory stock-recruitment models with uncorrelated and autocorrelated error structures, using Bayesian methods of statistical inference. Although no single model was adequate for all stocks, most groundfish had better than even odds of having density-dependent dynamics, and most had better than even odds of having dynamics with uncorrelated environmental variation. While some geographic and taxonomic differences in potential productivity were apparent, all stocks exhibited compensation in survival ratio at low stock sizes, albeit with substantial variation. These results indicate that conservation measures intended to increase the spawning biomass of New England groundfish will, on average, result in higher recruitment and, eventually, in increased and more stable fishery yields.