The ECA project finds out how different environmental factors influence on the fish production along the Baltic Sea coastal waters, to develop ecosystem network modeling to estimate the contribution of nutrient loading (bottom-up control of the food-web) as well as fish and fisheries (top-down control) on the ecosystem function and fish production in the Archipelago Sea (NE Baltic Sea). The project contributes to the modeling of the economics of the targeted fishing as a livelihood and as a method for ecosystem management and restoration. We value of the ecosystem services provided by aquatic environments and foodwebs for the society from improving or conserving water quality. We analyze the monetary use and non-use values people place on the ecosystem services provided by the aquatic ecosystem, such as water-based recreation, biodiversity, habitat for fish reproduction and nursing, and fishing. To determine where the largest benefits to the society can be accrued by improving or conserving the services we investigate how valuations are affected by socio-demographic and spatial issues. Furthermore, we create tools and guidelines to generalize the results of case specific valuation studies to new decision situations. To date, the fundamental trade-off between environmental damage from phosphorus accumulating in water ecosystems and profits from agricultural production has not been analyzed in a comprehensive way. ECA will fill the gap by 1) producing an ecological-economic model that accounts for phosphorus accumulation in agricultural land, its impact on the release of phosphorus into surrounding water ecosystems, the accumulation of phosphorus in the water ecosystem, and the environmental damage caused by water ecosystem degradation and by (2) analyzing efficient policies to control agricultural phosphorus loading in this setting. The choice and setting of an instrument to implement the optimal strategy of biomanipulation, have to our knowledge not been considered in previous literature. The economic literature on fishery regulation focuses on preventing the overexploitation of fish stocks. Here the question instead is one of how to provide incentives for fishers to produce a public good through harvesting species that have no commercial value. In the absence of regulation fishers will not target such species. We examine how to provide incentives for fishers to provide this public good, and how fishers’ strategic behaviour affects the incentive mechanisms and the total cost of biomanipulation. Further, there are two alternative ways to incentivize the fishing activity needed for stock abatement: to steer local professional fishers to target fishing efforts to desired non-commercial species or – in the absence of local professionals – to contract fishers specialized in targeted fisheries currently operating elsewhere.