Growth, mortality, and recruitment of larval Morone spp. in relation to food availability and temperature in the Hudson River

We measured age and growth of larval striped bass (Morone saxatilis) and wh ite perch (M. americana) and tested whether growth and survival were enhanc ed in relation to a seasonal pulse ("bloom") of high zooplankton abundance. Growth rates were lowest before the zooplankton bloom and highest afterwar ds for both fish species. An index of recruitment potential (instantaneous growth rate, G, divided by instantaneous mortality rate, Z) did not relate clearly to either water temperature or to zooplankton abundance in the case of striped bass but did relate to both factors for white perch. Retrospect ive analysis of hatch dates in recruited juvenile striped bass from the sam e year class indicated that later, faster growing cohorts were under-repres ented when compared to the larval cohort distribution, and that cohorts tha t co-occurred with high densities of the cladoceran zooplankton Bosmina fre yi were over-represented. Comparison of these results with similar analyses from other systems suggests that biotic controls on year-class strength ma y predominate in estuarine systems where physical factors are relatively da mped (Hudson) but may play relatively minor roles in those systems with hig h physical variability.