The early development of Ecosim as a predictive multi-species fisheries management tool

Ecosim is a recent addition to the family of surplus production fisheries models, and its multi-species nature raises the prospect of Large Marine Ecosystem (LME) management on the basis of predator/prey relationships. In particular, Ecosim appears to offer the promise of improved prediction of predator manipulations and their effects on exploited stocks, including the effects of removing a top predator from an ecosystem. The development of Ecosim represents a considerable addition of the theory of predator/prey relationships in LME ecology; however, at present, it is an untested model in the management arena. In particular, the sensitivity of Ecosim to assumptions about energy dissipation, respiration, and top-down vs. bottom-up control may lead to models which predict the unrealistic sustainability of dangerously high fishing levels. This is not a problem with the model theory but its application: at present, little substantive work has been done to bring the statistical calibration of Ecosim parameters to the level of other fisheries models. As an example, a preliminary examination of Ecosim’s sensitivities to assumptions about animal energetics is presented here. Currently, Ecosim’s primary role in ecosystem management is in exploratory analysis and developing the precautionary principle of ecosystem manipulations, and as such it shall continue to play a valuable role in increasing the understanding of ecosystem interrelations. However, in its current state of development, its results should not be used as a predictor for establishing large scale predator/prey manipulations as fisheries policy.