The fish samples were collected from the Gomti river at Lucknow, India. Two non-native fish species, Cyprinus carpio and Oreochromis niloticus were selected for the present study. The size of fishes varied from 126-379 mm and 143-684 mm of O. niloticus and C. carpio, respectively. The size data indicated that the both species powerfully invaded from the Gomti river, India. The maximum fishes of O. niloticus was exploited in 211-240 mm size classes with 23.46% while in case of C. carpio 391-440 mm size classes fishes with 16.07%. The largest size of fishes constituted small proportion in the exploitation in both fishes. The stock of O. niloticus and C. carpio was dense by middle size classes from the Gomti river at Lucknow, India.