Relationships between the Food Spectrum of Perch Fry (Perca fluviatilisL.) and the Structure of Zoobenthos in Experimental Mesocosms

In experimental ecosystems that accommodate perch fry (Perca fluviatilis), significant structural changes within the benthic communities occurred under the effect of fish feeding on oligochaetes and on the larvae of chidonomids and other insects. Perch fry began to consume benthic animals at early developmental stages (C₁–C₂). The transition to regular feeding under experimental condition occurred at the D₂–Estage (days 30–40), when the benthic community reached a developmental peak. The quantitative parameters characterizing the compositions of perch stomach contents and the main groups of zoobenthos closely correlated with each other. The dynamics of quantitative parameters of these animal groups (except for mollusks) proved to be determined both by the specific features of their life cycles and by the degree of consumption.