Fishing for MSY: using “pretty good yield” ranges without impairing recruitment

Pretty good yield (PGY) is a sustainable fish yield corresponding to obtaining no less than a specified large percentage of the maximum sustainable yield (MSY). We investigated 19 European fish stocks to test the hypothesis that the 95% PGY yield range is inherently precautionary with respect to impairing recruitment. An F-MSY range was calculated for each stock as the range of fishing mortalities (F) that lead to an average catch of at least 95% of MSY in long-term simulations. Further, a precautionary reference point for each stock (F-P.05) was defined as the F resulting in a 5% probability of the spawning-stock biomass falling below an agreed biomass limit below which recruitment is impaired (B-lim) in long-term simulations. For the majority of the stocks analysed, the upper bound of the F-MSY range exceeded the estimated F-P.05. However, larger fish species had higher precautionary limits to fishing mortality, and species with larger asymptotic length were less likely to have F-MSY ranges impairing recruitment. Our study shows that fishing at F-MSY generally is precautionary with respect to impairing recruitment for highly exploited teleost species in northern European waters, whereas the upper part of the range providing 95% of MSY is not necessarily precautionary for small-and medium-sized teleosts.