The restoration of shallow eutrophic lakes,and the role of northern pike,aquatic vegetation and nutrient concentration

The feasibility of biomanipulation is related particularly to reducing the production and recruitment of planktivorous fish stocks. For assessing the level of predation needed to suppress planktivorous fish stocks, the relation between fish P and B, on one hand, and nutrient concentration on the other were analyzed. The carrying capacity of shallow lakes in terms of biomass is related to the total phosphorus concentration and nature of the lake bottom substrate. The production of planktivorous fish was 60–80% of the maximum carrying capacity. It is argued that aquatic vegetation and northern pike are effective tools to maintain water quality, but these are limited by the maximum nutrient concentration aquatic vegetation can sustain.