Shifting baselines and deciding on the desirable form of multispecies maximum sustainable yield

Abstract

Abstract Multispecies, multigear fisheries occur in most ecosystems in the world, but are typical in tropical ecosystems and especially in emerging economies. However, much of fishery science has been developed from a single-species perspective. Management schemes based on single-species reference points often ignore the trophic link among species and the technical interaction between gears, essentially disconnecting management objectives from the context of an ecosystem—or socioecological system—where fisheries operate. Using the Gulf of Thailand fishery as an example, we demonstrate how aggregate production models can be used to estimate system-level fishery reference points for multispecies fisheries. Our results show that the multispecies maximum sustainable yield changes with ecosystem state—the systemic productivity level due to species composition and ecological (trophic/habitat, etc.) structure—under various development levels of fishing and varies with management objectives such as biodiversity, system resilience, total catch, total value, and employment. Aggregate approaches are a tractable way of estimating sustainable ecosystem-scale extraction for multispecies fisheries, avoiding the dilemma of facing conflicting advice derived from single-species methods and providing a practical, operational step toward ecosystem-based management. However, these methods are sensitive to the ecosystem states over time and decision makers need to make informed decisions on which state they want to maintain (or recover) and thus which system-level reference points to use. Consequently, management of multispecies fisheries must be clear on their system-level fisheries policy objectives.