1. Removal of zooplanktivorous fish (mainly bream) in 1987 from a shallow eutrophic lake in the Netherlands, Lake Zwemlust, resulted in a quick switch from a turbid state with cyanobacteria blooms to a clear state dominated by macrophytes. 2. The clear state was not stable in the long term, however, because of high nutrient loadings. 3. In 1999, another removal of zooplanktivorous fish (mainly rudd) had similar effects as in 1987, although macrophytes returned more slowly. 4. In the years directly following both interventions there was a 'transition period' of very clear water with high densities of zooplanktonic grazers in the absence of macrophytes; low oxygen concentrations indicate that during those years primary production was low relative to heterotrophic activity. 5. The transition period appears to provide the light climate necessary for the return of macrophytes. 6. Reduction of nutrient loading is necessary to improve water quality in Lake Zwemlust in the long term. In the short term, repeated fish stock reduction is a reasonable management strategy to keep Lake Zwemlust clear.
Original languageEnglish
JournalFreshwater Biology
Journal publication date2002

ID: 237009