A Model Analysis of Strategies for Enhancing Stocking Success of Landlocked Striped Bass Populations

Abstract

Poor first-year winter survival of stocked fingerling striped bass Morone saxatilis, resulting from slow summer growth and small body size in the fall, has limited the sport fishery of Smith Mountain Lake, Virginia. We used an individual-based model to examine different strategies for improving the success of the striped bass stocking program. For two spatially explicit compartments (littoral and pelagic zones) assigned for Smith Mountain Lake, the model simulates daily movement, consumption, growth, and mortality of juvenile striped bass from the time of stocking in early summer until 1 May of the next year. Model predictions of fish prey consumption, predator–prey size relationships, first-year survival, and fall versus spring length-frequency distributions were similar to observed data. Simulations were conducted to examine the effects of fingerling size, stocking density, and day of year at introduction on first-year growth, survival, and recruitment to age 1 and to determine the sensitivity and robustness of the proposed versus the existing stocking strategy to interannual variation in the population dynamics of alewife Alosa pseudoharengus and water temperature regimes. Results indicated that stocking striped bass at a median total length of 52 mm on 8 June (rather than 42 mm on 15 June as is presently done) and maintaining the current stocking density at 300,000 fingerlings would result in the largest percent increases in first-year growth, survival, and the number of age-1 recruits. Sensitivity-analysis results indicated that those factors influencing predator–prey size relationships (e.g., timing of alewife spawning, age-0 alewife growth rate, and water temperature) resulted in the largest percentage changes among model prediction variables for all stocking strategies. For these simulations, the proposed stocking strategy was always more robust to variations in alewife population dynamics and water temperature regimes than the existing stocking strategy.