Development of fish communities in lakes after biomanipulation
Published source details
Meijer M.-L., Lammens E.H.R.R., Raat A.J.P., Klein Breteler J.G.P. & Grimm M.P. (1995) Development of fish communities in lakes after biomanipulation. Aquatic Ecology, 29, 91-101
Published source details Meijer M.-L., Lammens E.H.R.R., Raat A.J.P., Klein Breteler J.G.P. & Grimm M.P. (1995) Development of fish communities in lakes after biomanipulation. Aquatic Ecology, 29, 91-101
In order to restore lakes affected by eutrophication in the Netherlands, as a follow-up to reducing nutrient loading (primarily due to agricultural run-off), major fish stock reduction and introduction of young pike Esox lucius (pike having declined or extirpated due to poor water conditions) has sometimes been undertaken. In three small shallow lakes (Noorddiep, Bleiswijkse Zoom and Zwemlust) nutrient reduction measures resulted in a clear water and re-establishment of submerged macrophytes. Here, development of fish communities at Zwemlust after initial restoration, are presented.
Study site: Zwemlust (surface area 1.5 ha; average depth 2 m), prior to nutrient loading reduction, had high nutrient concentrations; Secchi disc transparency of the water was low (0.2-0.3 m) and algal biomass high.
Fish stock manipulation:In 1987, the total fish stock (1,000 kg/ha) was removed from the lake (mostly bream, >90%). In 1987, 140 adult rudd Scardinius erythrophtalmus and 1,600 O+ (yearling) pike were added. In 1988, a further 1,500 O+ pike were added, and in 1989, 169 adult roach Rutilius rutilus.
Monitoring: Fish biomass and fish composition were monitored to 1992. The density of fish was estimated by mark-and-recapture, and density was converted to biomass. Young-of-the-year cyprinids could not be marked, thus their estimated biomass was based on seine-net catches.
Macrophytes: Macrophyte cover was determined by a survey in the summer.
In the first year after fish removal the water became clear; macrophyte cover increased from 5% in 1987 to 80% thereafter (Nuttall's pondweed Elodea nutallii dominated initially, replaced by rigid hornwort Ceratophyllum demersum in later years).
The pike biomass increased to 16 kg/ha in the first year to approximately 30/kg ha thereafter i.e. approaching the 38 kg/ha prior to removal. Before manipulation, the pike population was dominated by older individuals; in the first two years after manipulation, the pike were of small size. Biomass of O+ pike decreased dramatically and the average length of the pike increased to 1992. The rudd population increased from 7 kg/ha in 1987 to 300-400 kg/ha in 1992.
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