Combining efforts to make maximum sustainable yields and good environmental status match in a food-web model of the southern North Sea

The southern North Sea is the stage of conflicting objectives of beam trawlers targeting flatfish; of shrimp trawlers fishing for brown shrimp with bycatch of juvenile flatfish; and of demersal trawlers, the main fishery on cod, a key predator of shrimp and other groups. To expose trade-offs between the fleets’ objectives and to explore what a possible variant of a multi species maximum sustainable yield (MSY)could look like, we parameterized an ecosystem model and subjected it to a range of different fishing effort levels of the three fleets. Long-term projections highlighted multiple fishing regimes that lead to catches of at least 30% of all focal stocks’ single species MSYs at the same time. Trade-offs between the yields of shrimp fishers and demersal trawlers made higher simultaneous yields impossible. Besides optimizing multi species catches, we identified effort regimes that satisfied a set of descriptors of good environmental status (GES). We found that GES can only be obtained through low efforts of beam and demersal trawlers,which cannot be aligned with our multi species MSY variant without accepting trade-offs in fishing yields and/or conservation goals.