Contribution of Nursery Areas to the Adult Population of Atlantic Menhaden

Abstract

Much is known about the life history of the Atlantic Menhaden Brevoortia tyrannus, and yet the impact of multiple nursery grounds on population structure remains a central challenge in understanding this species. Historic estimates hypothesized that the Chesapeake Bay is the predominant contributor of new recruits (age 1) to the adult stock, but no research has been done on which nursery grounds support the adult stock. In this study, we used previously established chemical signatures from juvenile otoliths to evaluate the natal origin of adult Atlantic Menhaden (ages 2-4) that correspond to the 2008-2010 year-classes. We found that, on average across ages, the northeastern, Chesapeake Bay, and southeastern nursery grounds each contribute about 30% of the recruits that persist into older age-classes and that over the 3 years of the study the proportion of nursery contributions from each nursery was relatively stable. This has repercussions for the fishery, as most fish ages 2-3 are fully mature and thus comprise the majority of the spawning biomass as well as the commercial landings in recent years. In addition to identifying regions that are essential for the persistence of this species, these results suggest that productive nurseries are related to ageand size-dependent migration as well as physical conditions in the ocean.