Is Ichthyoplankton Predation an Important Source of Copepod Mortality in Subtropical Coastal Waters?

Abstract

The significance of ichthyoplankton-induced mortality to copepods was examined at three localities in the northern Gulf of Mexico: in the winter at a site of an exceptionally high concentration of larval spot, Leiostomus xanthurus; in the winter at a highly productive region near the Mississippi River delta; and in the summer in a highly eutrophic estuary dominated by larval bay anchovy, Anchoa mitchilli. In each region, ichthyoplankton ingestion of copepod eggs, nauplii and copepodids was compared with production rates and stocks of the dominant copepod species in the same waters. In all cases, predation from the dominant larval species and from the total ichthyoplankton assemblage was much less than prey production. It is concluded that ichthyoplankton predation in these regions rarely has any significant effect on copepod population dynamics, and therefore larval competition for food is unlikely to contribute to density-dependent mortality.