Abstract:
The growth performance of Scatophagus argus (25.53±0.89g) reared in Songkhla Lake, a backish lagoon, were evaluated after feeding them diets containing hot water extract of the seaweed, Sargassum polycystum at levels of 0, 0.1, 0.3, 0.5 and 1 g/kg diet. The fish were reared in net cages (50x50x60 cm) at a density of 20 fish/cage. Isonitrogeneous and isocaloric diets were fed to triplicate groups of fish twice a day to apparent satiation for 8 weeks. The results showed that fish fed extract at 0.5 g/kg diet demonstrated the highest mean average weight, weight gain, specific growth rate, average daily weight gain, and protein efficiency ratio with the differences significant at P < 0.05, whereas no significant differences in the rate of feed intake, feed conversion ratio, feed conversion efficiency and survival rate were found among the groups (P > 0.05). Investigation of the nutritional value of the fish found that the protein and ash composition was significantly different (P < 0.05) while the moisture and lipid values were not (P > 0.05). Fish fed with the 0.5 g/kg and 1 g/kg diet exhibited the highest protein (49.08±0.01) and ash (14.93±0.01) content respectively. Therefore, the appropriate level of seaweed extract supplementation for spotted scat was found to be 0.5 g/kg diet.