Publication Abstract

Sustainable recruitment: the bottom line

M.V. Bravington, T.K. Stokes and C.M. O'Brien

This paper develops a single-species perspective on the limits of sustainable fishing. Given uncertain data and assessments, the problem is to determine lower confidence limits for the minimum fishing mortality rate F_θ which, if maintained indefinitely, would drive the stock to extinction. For non-depensatory stocks, F_θ is determined by the slope of the stock-recruitment curve at the origin. The paper reviews three different approaches to making inferences about F_θ: recruit-per-biomass relationships (e.g. F_θ), parametric curves (e.g. Ricker), and constrained nonparametric curves (e.g. Cook's F_loss). Of these, constrained nonparametic curves are potentially the best, but at present suffer from practical difficulties in implementation and do not always give biologically sensible fits. These difficulties can be circumvented using two new nonparametric methods, CONCR (Concave Recruitment) and DIMPOS (Diminishing returns, Positive recruitment), which are described and applied to several ICES stocks. Finally, the paper explores issues surrounding the use of sustainable recruitment measures in assessment and management.

Reference:

M.V. Bravington, T.K. Stokes and C.M. O'Brien, 2000. Sustainable recruitment: the bottom line. Marine and Freshwater Research, 51(5): 465-475.