Relations between the Food Spectrum of Fishes and the Composition of Zooplankton and Benthos in a Subarctic Lake

Abstract

The seasonal variations in the biomass of planktonic and bottom invertebrates and their contributions to the diet of perch Perca fluviatilis and vendace Coregonus albula (>10 cm in body length) in an oligotrophic subarctic lake (Lake Krivoe) are studied. The distinct relationship between the food spectrum of fish with the composition of zooplankton and zoobenthos is revealed. It is shown that fish prefer to feed on mass objects (mainly zoobenthos), but both the seasonal variability of their contribution to the diet and their relative importance in fish of different lengths are significant. Amphipods (Gammarus lacustris and Monoporeia affinis) accounted for >90% in summer and >40% in autumn in the total weight of perch stomach content. Vendace consumed amphipods in the summer (>50%) and mollusks (up to 50%) in the autumn. Cladocerans are important food items in the autumn diet of fish (18–25%). In the diet of larger (18–25 cm) perch, the contributions of sticklebacks and vendace increased, but amphipods still prevailed (>40%).