Effects of dietary lipid source on spawning performance of Nile tilapia (Oreochromis niloticus) broodstock reared at different water salinities

The effects of dietary lipid source and water salinity on spawning performance of Nile tilapia broodstock and growth of their larvae were studied. Three isonitrogenous (40% crude protein), isocaloric (18.6 MJ GE/kg) diets containing three different oil sources, soybean oil (SBO), fish oil (FO) and soybean oil/ fish oil mixture (oil mix), were prepared. The diets were fed twice a day to satiation to duplicate groups of broodfish (19.2 g) at a female/male ratio of 3:1, reared at three salinities (0‰, 7‰ and 14‰), for 165 days. The size at first maturation was not significantly affected by dietary oil source and salinity. Spawning intervals of broodfish reared at 0‰ were not significantly affected by dietary oil source. At 7‰ and 14‰, fish fed FO or oil mix spawned more frequently, at shorter intervals, than those fed SBO. Dietary FO increased the absolute fecundity and number of eggs per spawn at each salinity. At 0‰, spawning performance and larval weight were not significantly affected by dietary oil source. At 7‰ and 14‰, fish fed SBO needed more time for egg hatching and yolk-sac absorption and resulted in poorer larval weight than those fed FO or oil mix. This result revealed that Nile tilapia broodfish reared in brackishwater require a source of dietary n−3 HUFA for optimum spawning performance, while plant oil (SBO) may meet the requirements of broodfish reared in freshwater.