Lake restoration and biomanipulation
Project cost: 200 000 Euro/year
Lake Vallentunasjön has had a problem with muddy water due to eutrophication. After extensive investigations initially, a project of depletion of fish has been carried out, in order to reduce the number of cyprinids and favour the fish of prey. In this way the amount of phyto plankton decreases, which cause the muddying, and favour grazing animal plankton. The fishing was carried out with trawling and stake nets, and the cyprinids have become bio-gas.
Parallel to the depletion of fish, follow up measures are carried out where the sediment in the lake and water coming into the lake is monitored.