Predation of cyclopoid copepods on sunshine bass fry

Low and variable survival rates have been observed for the fry of sunshine bass (female white bass Morone chrysops x male striped bass M. saxatilis) i n rearing ponds despite adherence to the standard procedures used to stock fry of striped bass and palmetto bass (female striped bass x male white bas s). A mismatch between sunshine bass fry and forage of suitable size is reg arded as the primary cause of fry mortality. Mortality could also be due to direct predation on the fry by carnivorous copepods. To test the latter hy pothesis, recently hatched sunshine bass fry were exposed to a concentratio n gradient of cyclopoid copepods (0, 5, 50, and 500 copepods/L) during a 24 -h period. No significant differences in survival rates were found among th e first three treatments, but fry suffered high mortality in the 500-copepo d/L treatment. Adult copepods are observed at similarly high densities in c ulture ponds. Results were also used to test an empirical model that predic ts predation rates on fish larvae by a variety of predators, including cope pods. This study indicates that stocking sunshine bass fry in ponds contain ing only rotifers and copepod nauplii will reduce the risk of predation and ensure suitable forage.