The fish Oreochromis niloticus (Nile Tilapia) and Cyprinus carpio (common carp) are the important exotic fish species on the Indian continent. Protein, vitamins and minerals are present in sufficient amount in fish. In Yamuna river at Prayagraj approximate annual catch was dominated by O. niloticus (149.51 kg day-1) followed by C. carpio (141.20 kg day-1) and other major contributions are of a diverse group of fishes (99.61 kg day-1) and there calculated annual percentage is 23.50%, 22.08% and 16.01%, respectively. The Indian major carps viz. L. rohita, C. catla and C. mrigala shared smaller proportions i.e. 3.34%, 2.10% and 6.03, respectively indicating a decline in their fishery. Significant detrimental effects of exotic fish species O. niloticus and C. carpio on the endemic fish diversity have been reported to cause a rapid decline in the catches of native fish species.