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

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 multi-species (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 ecological 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.