Ambiguous influences of omnivorous fish on trophic cascade and alternative states: Implications for biomanipulation from an ecological model

Abstract

An ecological model was developed to systematically analyze the comprehensive influence of omnivory level and predation intensity of fish on the dynamic state and strength of trophic cascade of a lake ecosystem. Results showed that a higher fish omnivory level reduced the strength of trophic cascade and increased the occurrence of alternative states, while an increase in predation intensity resulted in opposite effects. With the combination of these two factors, the occurrence of alternative states was dependent on the relative increase in the predation intensity. The model was further applied to a subtropical shallow lake in China. Modeling results revealed that the heavy stock of omnivorous fish in the lake increased the occurrence of alternative states and decreased the strength of trophic cascade. Results indicated that the long-term effect of biomanipulation would be significant and therefore high rates of fish removal would be required. The information from this study indicated the importance of understanding the dynamic state and strength of trophic cascade when predicting the long-term effects of biomanipulation.