Changes in the aquatic vegetation of two gravel pit lakes after reducing the fish population density

  • Published source details Wright R.M. & Phillips V.E. (1992) Changes in the aquatic vegetation of two gravel pit lakes after reducing the fish population density. Aquatic Botany, 43, 43-49.


Action: Control populations of wild vertebrates

A replicated, before-and-after study in 1982–1989 of two lakes in Buckinghamshire, UK (Wright & Phillips 1992) found that after removing planktivorous fish, the abundance of submerged macrophytes increased. Before fish removal, submerged macrophyte stands covered 1–48% of each lake bed. In these stands, the average summer biomass was <1–48 g/m2 (peak: 3–95 g/m2). Within two summers after fish removal, submerged macrophyte coverage had increased to 93–95%. Average summer biomass had increased to 60–133 g/m2 (peak: 161–482 g/m2). Methods: In November 1987 and 1988, all adult fish were removed (with seine nets) from two gravel pit lakes (2–17 ha, average depth 1.0–1.5 m). The water level was lowered to facilitate fish removal. Submerged macrophytes were surveyed between March and October. Coverage was estimated by a snorkeller in 1982 and 1989. Biomass was collected in 1986–1989 (10–40 cylinders/lake/survey, each cylinder 0.05 m2) then dried and weighed.

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