Evaluation of flocculated concentrates from intensive shrimp pond water as a substitute for microalgal concentrates in the nursery culture of juvenile oyster (<Emphasis Type="Italic">Crassostrea belcheri</Emphasis>)

Intensive shrimp pond water typically contains high densities of microalgae and may have a great potential as a substitute for microalgae in the nursery culture of juvenile oysters as this stage needs large amount of microalgae. Two experiments with different phytoplankton composition in flocculated concentrates from shrimp pond water were investigated to compare the effect on preservation and use of flocculated concentrates from intensive shrimp pond as a partial substitute for microalgae concentrates for the nursery culture of juvenile oysters (Crassostrea belcheri) was evaluated. The results show that total crude protein content in flocculated concentrates mostly contain unidentified nanocyanobacteria preserved in refrigerator at 4 °C gradually decreased from the first week in experiment 1, while a slight decrease in crude protein content appeared after the third week in flocculated concentrates dominated by the Bacillariophyceae and unidentified nanocyanobacteria groups in experiment 2. The pheophytin a:chlorophyll a ratio suddenly increased during the third week of storage and most of the fatty acid composition was absent after four weeks of storage in both experiments. Substituting 75 % of microalgal concentrates in feed with flocculated concentrates from shrimp pond water showed no significant differences in growth performance in experiment 1, but higher growth performance in experiment 2 in comparison with control treatment (100 % microalgal concentrates). Our findings indicate that a partial substitution of flocculated concentrates of up to 75 % from shrimp pond water for microalgal concentrates would lead to better growth in juvenile oysters.