Trade-offs in Ecosystem-scale Optimization of Fisheries Management Policies

Recent applications of ecosystem models have had some apparent success evaluating how fisheries and environmental changes have affected marine populations, and a stage has been reached where ecosystem models can be used to describe agents of mortality and trophic interdependencies in the marine environment with some credibility. This success has raised the stakes for modeling and caused its focus to evolve to include ecosystem-scale optimization policies aimed, modestly, at determining the mix of fishing fleets that will optimize a combination of objectives, subject to the assumptions inherent in the model—as is the case with all models. A resemblance between our model predictions and real-world conditions may indicate that trade-offs among economic, social, and ecosystem objectives resulting from optimization for fleet configurations are more pronounced than hitherto recognized. The present paper reports the consequences of such optimizations for a model meant to mimic aspects of the Gulf of Thailand ecosystem, intended to determine how the model reacts to different weightings for the objective functions individually and jointly to examine the trade-offs involved. The results indicate that optimizing for economic profit is consistent with including ecosystem considerations, whereas optimizing landed value is in conflict with profit as well as ecosystem optimization.