Dynamics and current state of cyclostomes and fish fauna of Saratov region is analyzed, on the basis of modern field research, collectible information and literature data. As a result of regulation of large and small rivers of the region, a significant restructuring of their ichthyocenoses took place. The overall index of changes in the species composition of the ichthyofauna was 49%, the final list (at the end of the observations) was 42%, and the index of intrapopulation changes was 51%.
