Abstract
Water resources of the Chu and Talas river basins are mainly used for artificial irrigation of fields. Therefore, in most reservoirs, the hydrological regime is unfavorable for indigenous fish species. Such alien species as stone moroco Pseudorasbora parva , Amur false gudgeon Abbottina rivularis , common sawbelly Hemiculter leucisculus , and Amur goby Rhinogobius sp. have spread widely in lakes, ponds, and tributaries of the main rivers. In some bodies of water, alien species are dominant in fish communities. They have been found even in absolutely isolated lakes in the desert. As compared to the data of past years, the ranges of such alien fishes like Balkhash perch Perca schrenkii and tench Tinca tinca have been reduced significantly. In the Talas River watershed, such species widespread for the Ily and Syrdarya river basins as bitterling Rhodeus sericeus , medaka Oryzias latipes , and beautiful sleeper Micropercops (Hypseleotris) cintus have not been recorded.