Distribution of alien species of macrozoobenthos in tributeries of the Kuybyshev and Saratov reservoirs

Changes in the taxonomic composition, abundance, and distribution of macrozoobenthic alien species in mouths of the rivers Sok, Samara, Chapaevka, Bezenchuk, Chagra, Malyi Irgiz (tributaries of the Saratov Reservoir) and Sviyaga, Utka, Mayna, Usa, Bol’shoy Cheremshan (tributaries of the Kuybyshev Reservoir) according to our study over the period of 2009-2013 are presented. It is shown that mollusks Dreissena polymorpha as well as amphopods Pontogammarus robustoides and Dikerogammarus haemobaphes have the highest invasiveness in comparison with other species in tributaries of the reservoirs. For the first time there were found amphipods Dikerogammarus villosus that along with P. robustoides are considered ones of the most aggressive predators-invaders in the water bodies of the Europe. The life history traits of mass amphipod species that promote their spread in the reservoirs of Middle and Lower Volga and its tributaries are determined.