Golovatyuk L. V. RussiaTogliattiInstitute of Ecology of the Volga River Basin, Russian Academy of Sciences, 10 Komzin Str., Togliatti 445003, Russiagollarisa@mail.ru Author's articles ESTIMATION OF THE ZONAL DISTRIBUTION OF SPECIES OF THE BOTTOM COMMUNITIES IN RIVERS OF THE MIDDLE AND LOWER VOLGA BASINS ESTIMATION OF THE ZONAL DISTRIBUTION OF SPECIES OF THE BOTTOM COMMUNITIES IN RIVERS OF THE MIDDLE AND LOWER VOLGA BASINS