A MODEL OF SURVIVAL AND GROWTH OF STRIPED BASS LARVAE MORONE-SAXATILIS IN THE POTOMAC RIVER, 1987

A Stella(TM) model based on laboratory-derived growth data was developed to simulate abundances, cohort survival and growth rates of striped bass eggs and larvae. The goal was to compare the simulations to 1987 field survey results from the Potomac River (Cheasapeake Bay, USA). Key factors in the model were striped bass egg production, water temperature, surface light and penetration, turbidity and zooplankton concentration. Growth and survival were simulated from the predicted effects of turbidity, light at depth, and zooplankton concentration. Predation terms simulated survival under different predation pressures. The model estimated daily instantaneous growth rates ranging from -0.07 to 0.19 d-1. The model predicted poor survival and growth of cohorts produced early in the spawning season when water temperatures and zooplankton concentration were low. Mortality of eggs was predicted to be 54 % by simulation with most of the mortality attributable to low temperatures early in the spawning season. Simulated growth rates ranged widely and were highest in the down river sections of the Potomac. Predicted growth was in close agreement with field estimates during the second half of the spawning season. Early in the season, field growth rates were higher than those modeled, possibly because survival was more growth-rate dependent at that time than later when temperature, light and food levels were nearer to optimum. Trends in simulated larval abundances resembled Potomac River estimates but there were differences in simulated peak abundances. Mortality was partitioned and attributed to causes other than that caused by low temperature anomalies and growth-dependent factors. The difference between modeled and field observed larval abundances estimated a rate of mortality for 'other' causes at 13.7 % d-1, a rate that can readily be attributed to predation.