Ecosystem Considerations and the Limitations of Ecosystem Models in Fisheries Management:

Over the past 10 years there has been increasing criticism of management decisions that are based on single-species approaches and a call for the implementation of ecosystem approaches. The major criticism of single-species models is that they cannot predict changes in community struc-ture. Unfortunately, our experience in modeling the Bering Sea shows that these same criticisms can also be leveled against ecosystem models. We employed trophic mass-balance models (Ecopath and Ecosim) to examine some possible explanations for the changes that occurred in the Bering Sea between the 1950s and 1980s. We removed fish and mammals 610 Trites et al. — Ecosystem Models in Fisheries Management from the modeled system and tracked how other components of the eco-system responded. Our mass-balance models indicate that neither whal-ing nor commercial fisheries were sufficient to explain the 400 % increase in pollock biomass and other changes that may have occurred betwee