Impression of Various Water Reserves on Reproductive Performance of the Nile Tilapia “Oreochromis niloticus”

This work involved the investigation of the reproductive biology concerning the seasonal variations of the Nile tilapia (Oreochromis niloticus) broodstock. A total of 320 apparently healthy fish individuals were collected from four locations (El Manzala and El Abbassa fish hatcheries, Bahr Hadous drain and Ismailia Canal) during the period from 2020- 2021. Water parameters were seasonally evaluated. Besides, all fish samples were subjected to visual and histopathological examinations. The effect of water pollution with various heavy metals on the fish reproductive performance was studied with reference to corresponding bioaccumulation in fish reproductive organs. Water examination recorded a significantly low DO value in El Manzala (P< 0.05); whereas, a substantial rise was detected in water salinity, EC, BOD, COD and total ammonia. Water pollution was distinguished with a variety of heavy metals (iron, copper, zinc, cadmium, mercury, lead and arsenic), which exceeded their permissible limits and were significantly high in El Manzala (P< 0.05). The results revealed a distinctive surge of gonadosomatic index (GSI) and absolute fecundity of El Abbassa either farmed or wild fish rather than the perceptible retarded performance of both farmed and wild fish of El Manzala (P< 0.05), with evident alterations in their reproductive organs. Consistent bioaccumulation of these heavy metals was apparent in the liver and reproductive organs that exceeded their safe limits. Consequential devastating effects on the reproduction function were recorded as the female GSI was mostly affected by elevated water Fe, Pb and Cd and bioaccumulated Fe and Cd in their ovaries. While, their fecundity was influenced by high water Cu, Cd and Hg as well as the bioaccumulated Pb in their ovaries. On the other hand, the male GSI was mostly affected by high water Cu and Pb as well as bio-accumulated Zn and Hg in their testes.