Spatial and Age-Related Changes in the Food Spectrum of the Common Bream <i>Abramis brama</i> in the Middle and Lower Course of the Northern Dvina River (Russia)

Abstract

Data on spatial and age-related changes in the qualitative composition of food spectra (species and taxonomic diversity of invertebrates used as food objects) and quantitative characteristics (dominant types of food) of the common bream Abramis brama (L., 1758) are presented. Changes in nutrition and the ratio of prevailing taxonomic groups in different age groups are shown as the bream grows in the middle and lower reaches of the Severnaya Dvina River. Analysis of the results showed that the composition food’s lump included both representatives of the bottom fauna and planktonic organisms. Amphibiotic insect larvae, mollusks, and aquatic vegetation were the most numerous among the feeding objects. In addition, juvenile fish were present in the food lump of some age groups. Age variability in bream nutrition is reflected in the size-breadth of the food spectrum – in juveniles and older individuals, the components of nutrition are significantly less than in middle-aged fish.