An Exploratory Simulation Model of Competition and Predation in a Demersal Fish Assemblage on Georges Bank

A multispecies model of a demersal fish assemblage on Georges Bank was constructed to investigate the causes of major changes in species composition and relative abundances that occurred during 1963–1978. In particular, we investigated whether simulations of competition, predation, and prey turnover rate could mimic historic population trends. Results suggest that competition and predation, especially acting in concert, could account for some of the variability in fish biomass and abundance in this assemblage. Because the model was developed with a priori hypotheses, the findings suggest that interspecific interactions may be important in determining fish population abundance in assemblages of marine demersal fishes. However, neither the sharp decreases in biomass that occurred in some demersal species in the early 1970s nor the magnitude of increase in others could be accounted for with these hypotheses. This model provides a good first step at organizing and investigating the complex processes that drive this type of marine demersal assemblage, but subsequent models that include different interspecific mechanisms and structures or environmental influences appear to be justified.