This study focused on population structure, species diversity and abundance of the Chitgar Lake fishes in October 2014. Based on the lake location fish samples were collected at 34 stations in water body. In this study , 8 families belonging to 18 species comprised of Cyprinidae (11 species), Cichlidae (one species), Loricariidae (one species), Pangasiidae (one species), Serrasalmidae (one species), Poeciliidea (one species), Salmonidae (one species), and Scaridae (one species) were identified. Among the fishes just one native fish from Capoeta bohsei species observed during the study. The dominant lake fishes were invasive species Hemiculter leucisculus, Alburnus hohenackeri, Carassius auratus, Carassius gibelio and Pseudorasbora parva. The highest abundance of fishes were H. leucisculus 62 % and A. hohenackeri 35 % by Seine net. Furthermore, those were dominant abundance (69 and 12 % respectively) in Gill net method. Finally, in Cast net method A. hohenackeri 38 %, Pseudorasbora parva 21 % and H. leucisculus 17 % were dominated in the shore region. The lowest fishes abundance were P. hypophthalmus and Parrotfish. Overall more than 90 % of the fish population were invasive and alien species. Thus, the presence of invasive fishes and lack of predator fishes in the Chitgar Lake might be reason for increasing of trophic level.