Abstract
Coastal managers struggle globally both with declining stocks of large predatory fish, as well as decreases in *foundation species*; the submerged vegetation that forms the basis for many coastal ecosystems. Our research in the Baltic Sea indicates these issues may be intrinsically linked; availability of vegetated recruitment habitats appears to limit large predatory fish, whereas predatory fish indirectly control nuisance algae that otherwise smother vegetation. In the project PLANT-FISH we will explore the hypothesis that vegetation and predatory fish facilitate each other via a positive feedback loop, which enhances ecosystem health. To test this hypothesis, we will first assess the effect of vegetation on coastal fish stocks using statistical modeling based on 10.000 young fish surveys from the last decade. We will then assess if predation from adult fish benefits vegetation, and whether this feeds back positively on juvenile fish, using cage experiments and a detailed community survey along the central Baltic Sea coast. Finally, we will experimentally test if vegetation and predatory fish together strengthen ecosystem resilience to eutrophication. These results will inform managers about i) threshold levels of vegetation and predatory fish needed to uphold multiple ecosystem services, ii) the impacts of dredging, fishing, and eutrophication on these services, and iii) how integrated management of habitats, vegetation and fish could increase the health of the Baltic Sea.
Sweden