Some Aspects of Reproductive Biology with Emphasis on the Effect of Pollution on the Histopathological Structure of Gonads in

Abstract: Fish samples of Oreochromis niloticus were collected from two main fishing sites on the Rosetta Nile Branch (Kafr El-Zayat and Desok areas), the first area is considered to be more polluted than the later one due to the highly industrial activities. The present work aimed to study some aspect of the reproductive biology of the dominant species (O. niloticus) with emphasis on histopathological changes in the gonads. Fish attain the first sexual maturity at length 13.8 cm. The monthly distribution of maturity stages was studied. The gonadosomatic index and the gonads histological examination indicated that, the fish has prolonged spawning activities with a peak value in June. Six stages of gonadal maturation for both sexes were identified. The histopathological changes in gonads due to exposure to different pollutants have been studied. It was concluded that fish exposed to higher concentrations of pollutants showed higher incidence of gonadal abnormalities in the form of deformed oocyte and spermatocyte with reduction in their numbers and lack of active oogensis and spermatogenesis