Effect of salinity, dietary lipid source and level on growth of milkfish (Chanos chanos) fry

Six semi-purified microparticulate diets containing coconut oil (CO), cod liver oil (CLO), and their 1:1 combination (CO + CLO) at 9% and 18% levels were fed to milkfish fry or late postlarvae in freshwater (0 parts per thousand), brackishwater (16 parts per thousand), and seawater (34 parts per thousand) for 30 days. A three-factor factorial design (3 x 2 x 3) with three replicates per treatment was followed. Sixty-five milkfish fry (5 mg, 6 mm) were stocked per 15-1 rectangular glass aquarium and fed with the experimental diets at 20% of biomass daily. Water temperature was 28 +/- 1 degrees C during the culture period. Survival was not affected by water salinity, and lipid source or level. Among the 18 treatments, freshwater-reared milkfish fry fed with 9% CO + CLO had the highest specific growth rate, but this was not significantly different from those of freshwater-reared fish fed with 9-18% CO and 9% CLO diets or brackishwater-reared fish fed with 9% CO diet (P > 0.05). As a main factor, salinity or dietary lipid level, but not lipid source, had significant effects on growth and feed conversion ratio of milkfish fry. Highest growth was observed in fish reared in freshwater and as salinity was increased, growth decreased (P < 0.05). Overall, the 9% lipid diets promoted better growth than the 18% lipid diets (P < 0.05). Except for the significant interaction between dietary lipid source and level indicating that milkfish fry fed with the 18% CLO was the shortest (P < 0.05), no other significant effects of the two- or three-factor interactions were found. (C) 1998 Elsevier Science B.V. All rights reserved.