The present experiment aimed to study the effect of spawning month (January and February for broodstock and February, March, April and May for fry production) and protection method (uncovered without heater tanks, cover without heater and cover with heater tanks) on reproductive performance of Nile tilapia, Oreochromis niloticus broodstock. The obtained results indicated that, average body weight and length of the spawning females did not significantly differ for the two groups uncovered without heater and covered without heater while the differences between each of these two groups and the third group (cover with heater) were significant. The average ovary weight for spawning females significantly affected by spawning month. Covered and uncovered tanks without water heating did not significantly affect ovary weight of spawning females O. niloticus while ovary weight of the third female group (cover with heater) significantly increased the ovary weight of spawning females.
Gonado Somatic Index (GSI) significantly varied from 0.85 (January) to 0.93 (February) and 1.41 (March). Uncovered tanks showed the lowest value (0.69) of GSI while covering of spawning tanks and supplying tanks with electrical heaters increased the GSI. Spawning month and protection method had a significant effect on GSI. Covering of spawning tanks increased absolute fecundity and supplying the covered spawning tanks by electrical heaters significantly increased absolute fecundity. Neither spawning month nor protection method had significant effect on relative fecundity.
During the second spawning month (March) there were no fry in the uncovered tanks while fry production/tank found to be 4475 in covered tanks and supplying covered tanks with electrical heaters increased fry production to 13215/tank and the same trend was also observed during the other spawning months (April and May).
Average fry weight found to be 0.0087, 0.0087, 0.0140 and 0.0150 g for the spawning months studied, February, March, April and May, respectively and the average fry weight found to be 0.0078, 0.0108 and 0.0165 g for the uncovered, covered and covered with heater groups, respectively and the differences in individual fry weight due to the effect of protection method were significant.
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