The present study was carried out to evaluate the effects of Biofloc technology (BFT) on spawning performance of red tilapia broodstock and hatchability of their eggs under different water salinities. Three levels of salinity (18, 24 and 32‰) with or without BFT were examined. The fish with an average initial weight of 62.61±4.6 g for female and 98.99±3.1 g for male were stocked in triplicates in 3*1*1m3 concrete tanks at a density of 5 fish/m3, at a sex ratio of 3?:1?. Broodstock were fed on a commercial diet (25% crude protein) at a daily rate of 1-2% of their live body weight, twice a day, for 9 months. At high salinity level (32‰), time to first spawning was significantly longer than at 18 and 24‰, and significantly decreased with the application of BFT. However, time to first spawning of BFT-treated groups did not significantly vary at different water salinities. Inter-spawning intervals (ISI) showed irregular patterns in relation to salinity levels, however, at 18 and 24‰ salinity, the females tended to spawn at shorter intervals in BFT system. Spawning performances, including total number of spawnings per tank, number of spawnings per female, absolute fecundity and average number of eggs per spawn, were all significantly lower (P<0.05) in the non-BFT broodstock reared at 32‰ salinity than those reared in BFT system. Egg size was not significantly affected by salinity levels and presence of BFT. At all salinity levels, egg hatchability increased in BFT treatments compared to BFT-free groups. However, eggs produced from broodstock reared in BFT-free system exhibited significantly lower (P<0.05) hatchability, longer hatching time, less yolk-sac absorption time, and lower larval length than those reared in BFT system. These results suggest that BFT can significantly improve the spawning performance and larval productivity of red tilapia broodstock reared at high water salinity.
Keywords: boifloc technology, red tilapia, salinity, spawning performance, larval productivity.