AN ASSESSMENT STUDY OF GROWTH PERFORMANCE AND GONADS DEVELOPMENT OF MONO SEX NILE TILAPIA IN DIFFERENT AGE STAGES DURING THE PRODUCTION PERIOD

The objective of this study was to follow up the growth performance and gonads development of sex reversed male Nile tilapia. Fish fed commercial diet contained 30% crude protein at a rate of 3% of the biomass and 10 fish were randomly taken biweekly during the experimental period (16 weeks). Growth performance, feed utilization and survival rate were calculated. Histological examination of the gonads was done every two weeks to follow the growth and development of the gonads. Results showed positive interactions between growth parameters and reproductive development during different periods of fish productive cycle. Histological examination illustrated that during early ages, testicular sections of mono sex male’s tilapia had abnormal architecture with deterioration of germinative tissue. Despite abnormal testis texture, fish started spermatogenesis, a step toward puberty when their body weight reached 29.16g. As fish reached 4-5 months, male start to recover their testes normal structures and at age of 5.5-6 months, testicular sections appeared normally as pointed out by firmed testicular lobules, existence of all germ cell types and the intensively stored spermatozoa in testicular lumen and testicular ducts, confirming the full maturity of males. Based on the obtained results, it can clearly conclude that there is a relationship between age, body weight and development of sexual glands. It has also been shown that the hormonal treatment of tilapia seeds in the early stages for production of mono sex (all males) leads to a marked deterioration in the testes structure, continues near the fish enters the sexual maturity. At a later age, males can overcome this deterioration, restore the histological  structure of the testes and achieve full sexual maturity at the age around from 5.5 to 6 months.