Interaction between prey availability and feeding behaviour of age-1 and age-2 perch ( Perca fluviatilis L.) in a biomanipulated lake (Bautzen Reservoir, Germany)

Abstract

In this study, we have analysed the interaction between prey availability and feeding behaviour of age-1 and 2 perch in the top-down manipulated Bautzen Reservoir from 1986 to 1997. We focused on predation on daphnids and age-0 fish. Age-1 and 2 perch in Bautzen Reservoir were sampled with multi mesh size gill nets (10 to 32 mm bar mesh size). Stomach contents of age-1 and age-2 perch were analysed. To determine the year-class strength of age-0 fish, gill-nets with 6, 7 and 10 mm bar mesh size were used. Sampling of zooplankton was done using nets with mesh sizes of 500 and 750 μm and a 2-L Ruttner-sampler. Feeding behaviour of age-1 perch was strongly determined by the abundance of daphnids. There was a clear functional relationship between diet composition of age-1 perch and availability of D. galeata, but age-1 perch could not be described as important predators of daphnids due to their low abundance. This age group was at least partly piscivorous in all years analysed. Age-2 perch fed on D. galeata only at a low level. They were mainly piscivorous. Our study indicates that probably the good growth of perch in response to the high proportion of piscivores in the lake contributes to the strong overall piscivory of the perch population and therefore enhances the efficacy of a long-term biomanipulation experiment.