Fisheries-induced life history changes in herring (Clupea harengus)

Abstract

Fishing changes not only the population abundance of the target species, but also its population dynamics and life-history traits. A number of studies have shown that life history traits related to the timing of maturation can respond quickly to fishing mortality. Because changes in such life-history traits feed back into population dynamics and, consequently, may also affect the yield and thus profitability of a fishery, we need better understand the factors that hasten or hinder such changes. In this study we analyze how fisheries have affected the maturation process of an economically important herring (Clupea harengus) stock, the North Sea (NSH) herring. The harvest of North Sea herring targets both mature and immature individuals. Life-history theory predicts that under this kind of mortality re-gime fisheries can be expected to induce an adaptive decrease in the age at maturation. This kind of studies are a critical for testing theoretical predictions, and will facilitate our understanding under which conditions large life history changes can and cannot be ex-pected. Such understanding is needed for evolutionarily enlightened management of ma-rine biodiversity. The results will provide guidance for evolutionarily enlightened manage-ment strategies, particularly with respect to fisheries targeting mature and immature indi-viduals differently.