Feeding of whitefish Coregonus lavaretus pidschian (Coregonidae) in the lower reaches of the Northern Dvina River

Abstract

Analysis was performed of the feeding of whitefish in the basin of the Northern Dvina River, including the tributary of the first order—Emtsa River and the middle course of the river, its delta part, and sites of the near-mouth offshore. It was established that, according to the pattern of feeding, whitefish is a euryphage with sufficiently wide food spectrum, including over 40 groups of food organisms at the level of classes, orders, families, and genera. The bulk of its feeding is formed by aquatic larvae of insects (mainly chironomid larvae), secondary food consists of mollusks, crustaceans, worms, and sponges. Changes in the feeding of whitefish depending on habitats, food biotopes, and difference with respect to years and seasons of the year, as well as on the age of fish, were revealed. Sufficiently high feeding intensity, as well as small changes in the feeding of whitefish in different years and at different sections of the channel indicate stable feeding conditions in the middle part of the Dvina basin. Food possibilities of the delta and the near-mouth offshore also satisfy trophic demands of the feeding school of whitefish.