Amitabh Chandra Dwivedi, Priyanka Mayank and Sheeba Imran
Fish is a rich source of protein, vitamins and minerals. New knowledge on the role of omega-3 fatty acids in human physiology and their high contents in fish has added a new dimension to their importance in�health and nutrition. Oreochromis niloticus (Nile tilapia) is one of the fish species of great economic importance in the globe. Reproductive biology of O. niloticus in the Yamuna was studied. Samples of O. niloticus were collected monthly during August 2011 to July 2012. The fishes breed in months of March to June and September to November. Sex ratio of male and female fishes was equal in 43.1-46.0 cm size group. Male proportion was higher in all size groups except 43.1-46.0 cm size group. In 10.1-13.0 cm, 25.1-28.0 cm and 28.1-31.0 cm size groups? female proportion was half as compared to male fishes. Observed difference was not significant in all size groups, except 19.1-22.0 cm size group. Chi-square values were recorded maximum in 19.1-22.0 cm size group with 4.56 and minimum in 31.1-34.0 cm size group with 0.02. Higher proportion of male was observed in the stock, sex ratio of male and female was 1:0.78 and Chi-square value was 7.94 and the difference was significant. The fecundity and breeding frequency of O. niloticus indicated that the climate condition of the Yamuna river most suitable for O. niloticus.