Regional trade-offs from multi-species maximum sustainable yield (MMSY) management options

Abstract

The maximum sustainable yield (MSY) is, theoretically, the largest yield that can be taken from a single species' stock over an indefinite period. Formulation of strategic MSY management goals is, however, complicated by the need to move beyond biological single-species considerations. Interactions among species necessitate multispecies (MMSY) definitions, incorporating ecological, economic and social considerations. We developed an ecological-economic model of the Baltic Sea, simulating stock dynamics of interacting populations of cod Gadus morhua, herring Clupea harengus and sprat Sprattus sprattus. We investigated a set of different strategic management options. These likely, yet non-formalized experiments evaluate and illuminate alternative regional trade-offs. We computed multi-species maximum economic yield (MMEY) under certain eco-logical constraints, with profits as a performance indicator. An unconstrained profit-maximizing management strategy would lead to a highly profitable cod fishery in a cod-dominated ecosystem. Concurrent sprat stock size (and profits) would be low, falling below ecological precautionary reference points. Consideration of ecological constraints on minimum stock sizes leaves a range of strategies, including the change from a cod-dominated to a more clupeid-dominated system. The regional distribution of profits depends on the management. Therefore, adjustment payments or other forms of compensation might be needed to achieve a concordant agreement on strategic multi-species management goals.