Abstract
Filtration and ingestion rates of spat of Japanese pearl oyster, Pinctada fucata martensii (average hinge length: 2.61mm), fed the same concentration of micro-algae (Pavlova lutheri: 3.6×104cells/ml) at different water temperatures (20, 26, 32°C) for 14 days were determined. Growth rates of spat hinge length (20°C, 81μm/day; 26°C, 166μm/day; 32°C, 198μm/day) and whole weight (20°C, 123μg/day; 26°C, 288μg/day; 32°C, 424μg/day) increased with water temperature. Filtration rates of pearl oyster spat also increased with water temperature (20°C, 0.98ml/h/spat; 26°C, 2.22ml/h/spat; 32°C, 6.02ml/h/spat on day 4), as did ingestion rates (20°C, 4.75×104cells/h/spat; 26°C, 8.56×104cells/h/spat; 32°C, 17.4×104cells/h/spat on day 4). However, there was little difference in filtration and ingestion rates at 26°C and 32°C on days 7 and 14, respectively. Growth rate of the spat increased with ingestion rate. In sum, filtration and ingestion rates of the spat were affected by water temperature, and then the growth rate of the spat was affected by filtration and ingestion rates. There was a positive correlation between spat size and filtration rate and also between spat size and ingestion rate. The maximum ingestion rate of the spat was estimated to be 20×104cells/h/spat, and the maximum growth rate of spat hinge length was estimated to be 200μm/day.
