EFFECT OF SEX RATIOS ON REPRODUCTIVE PERFORMANCE OF NILE TILAPIA (OREOCHROMIS NILOTICUS) AND BLUE TILAPIA (OREOCHROMIS AUREUS)

This study was carried out in circular earthen ponds belonging to Central Laboratory for Aquaculture Research (CLAR), at Abbassa, Shark­ia Governorate. The study aimed the investigation of the effect of differ­ent sex ratios on fry production intra species and between two species of Oreochromis niloticus and Oreochromis aureus. The results indicated that there were no significant differences among different sex ratios for number of fry / female and number fry / gm of female body weight of Oreochromis niloticus. There were significant differences between the different sex ratios 1:1 and (1:2, 1:3) in number fry / female, while there were no significant differences between different sex ratios 1:1, 1:2 and 1:3 in number fry / gm of female body weight of 0. aureus. The results indicated that there were no significant differences between mass spawning of Oreochromis niloticus and Oreochromis aureus at sex ratio 1:1, while, there were significant differences between Oreochromis niloticus and Oreochromis aureus at sex ratios 1:2 and 1:3 in number of fry / female. The relative fecundity (number fry / gm of female body weight) showed that there were no significant differences between mass spawning of Oreochromis niloticus and Oreochromis aureus at different sex ratios 1:1, 1:2 and 1:3. This study showed that there were no signifi­cant differences between mass spawning of Oreochromis niloticus and Oreochromis aureus at the different sex ratios 1:1, 1:2 and 1:3 in num­ber fry / gm of female body weight. However, the sex ratio of 1 male to 3 females is more economical for fry production.