Production and ecological characteristics of zooplankton in water bodies of lower reaches and delta parts of river Volga

The article considers the figures of zooplankton communities’ abundance and productivity the most important data in assessment of the overall production potential of water bodies. The aim of the research was to examine the qualitative and quantitative compositions of zooplankters and to determine the food capacity of water bodies (the Volga river, its tributaries the Akhtuba, the Bakhtemir, the Buzan, the Kizan and the ecosite of Zaburunka). To achieve this aim, there were applied standard methods of hydrobiological and hydrochemical research. During the whole vegetation period the quality of water in all reservoirs met the fishery requirements. It has been found out that cladocerans (Cladocera) dominated in the Akhtuba river, and copepods (Copepoda) dominated in the Buzan river. In the Volga river, as well as in the Bakhtemir, the Kizan and the Zaburunka ecosite rotifers (Rotifera) dominating in spring were replaced by copepods (Copepoda) that remained dominant zooplankters until the end of the vegetation period. Taken all together, copepods are the dominant and subdominant species in all the examined water bodies throughout the whole vegetation period. For the most part, copepods are represented by predators, i. e. food competitors of fish. The dynamics of zooplankton population and biomass was seasonal: the figures increased mainly from spring to summer, gained their maximum in summer, and then decreased to the minimum in autumn. The Buzan river was an exception: the maximum indices were recorded there in spring, whilst in summer they decreased quite dramatically (population by 76%, biomass by 75%) and in autumn stabilized slightly. The maximum indices of food capacity (above average) were registered in summer in all the examined water bodies, except the Kizanriver where the food capacity remained minimal throughout the whole season.