Impact of Climate Deviation on Reproductive Profile of Nile Tilapia, Oreochromis niloticus (Linnaeus, 1758) from the Tons River, India

Nile tilapia, Oreochromis niloticus is among the leading farmed species around the world as well as a powerful invader in many countries globally. Studies were undertaken during the period from February 2019 to January 2020 from the lower stretch of the Tons River at Prayagraj, Uttar Pradesh, India. During the sampling period, 683 fish specimens of Nile Tilapia, Oreochromis niloticus (336 males and 347 females) were collected and studied for evaluation of sex ratio and sex structure. The sex ratios of male and female fishes were very close and reported 1.0:1.03 in the stock. The male ratio was higher in the small size group of fish with 81 to 200 mm size groups and 411 to 470 mm size group. The sex structure of males and females was observed at 49.19% and 50.81%, respectively in the case of stock. The female proportion was recorded as a minimum with 37.50% in the 441-470 cm size group and highest with 54.84% in the 381-410 mm size group. However, the male proportion was reported lowest at 45.16% in the 381-410 mm size group and highest at 62.50% in the 441-470 mm size group. In the present findings, O. niloticus was found to reach maturity starting below 138 mm of total length, taking individual fish. The fishes breed in the months of March to June and September to November of the year. The number of eggs per individual ranged from 393 to 4338 in the size of fish varied from 138-452 mm. The reported fecundity and sex ratio of O. niloticus indicated that the climatic condition or environmental condition of the Tons River was most suitable. The environmental condition (especially temperature) of the Tons River at Prayagraj is slightly warm compared to the Ganga River which is very favourable for O. niloticus. The water current velocity of the Tons River is very poor. Both parameters are very helpful for the stability of O. niloticus in the Tons River at Prayagraj. The high fecundity of O. niloticus in the Tons River at Prayagraj could probably be a result of a combination of different causes such as climatic conditions, habitat structure, food abundance, water quality, and quality of food. Therefore, the present study aimed to update the information on the sex ratio, sex structure, and fecundity of O. niloticus with respect to climate from the Tons River, India.