EUTROPHICATION AND ITS CONTROL BY BIOMANIPULATION - AN ENCLOSURE EXPERIMENT

Biomanipulation experiments were carried out in small enclosures in a small, shallow eutrophic lake in eastern England. The effects of fish removal on water quality and planktonic communities were examined in r elation to nutrients and macrophytes. Exclusion of fish resulted in en hanced densities of the large-bodied Daphnia hyalina which, in turn, l ed to improvements in water quality. The provision of refuges from fis h predation also enhanced Daphnia populations enough to suggest this s trategy as feasible for the restoration of this lake. The development of a mysid population in enclosures without fish indicated that some i ndirect effects might occur if fish are completely removed.