Application of the nursery-role hypothesis to an estuarine fish

In this paper, we address a recent article by Beck et al. (2001, Bioscience 51:633-641), in which it was proposed that the value of a juvenile fish habitat could be most efficiently measured as the production of adults from each juvenile habitat on a per area basis. Based upon retrospective microchemical analysis of otoliths, we calculated this metric (nursery value) for tidal freshwater and brackish littoral habitats of an estuarine fish, white perch Morone americana, in the Patuxent River estuary, Maryland (USA). In dominant year-classes of the population, brackish habitats had the highest nursery value, whereas in all other year-classes, freshwater habitats had the highest nursery value. This result highlights the importance of inter-annual variability in habitat use, and consequently presents a challenging trade-off for applying the nursery-role hypothesis to facilitate habitat conservation and management. Despite this limitation, the nursery-role hypothesis provides an enriched and much needed perspective on population connectivity.