The effects of perch, Perca fluviatilis L., and bronze bream, Abramis brama (L.), on insect emergence and benthic invertebrate abundance in experimental ponds.

Abstract

The effects of perch and bronze bream predation on the production of insects emerging at the water surface and the autumn biomass of benthic macro-invertebrates were assessed in a series of experimental ponds. The study attempted to discover whether fish affect food availability for diving and dabbling ducks in freshwater habitats. Ten ponds (bisected by fine netting) were used for the study: one was left totally fish-free, whilst one half of each of three groups of three ponds was stocked with either perch, bream or perch plus bream. The relative abundance of emerging insects (mainly Choronomidae) was significantly reduced in two perch ponds, two perch + bream ponds and bream ponds. The autumn standing crops of invertebrate macroinvertebrates were significantly reduced in one perch pond, three bream ponds and one perch plus bream pond. These results support findings of a comtemporaneous large bio-manipulation experiment carried out in two adjacent lakes. During the biomanipulation studies, aquatic invertebrate stocks greatly increased after the removal of fish and decreased following restocking.