In the 6000 ha Lake Volkerak-Zoom, a new freshwater system in the estu
arine southwest of The Netherlands, biomanipulation is used as a tool
in ecosystem development. The basic ecological concepts for ecosystem
development are described. Key factors in the integrated water managem
ent are fish stock management and water level management, geared towar
ds creating optimal conditions for northern pike, the dominant predato
r in mesotrophic waters. The main aspects of the water level managemen
t and the fish stock management are outlined.