FISHERIES RESEARCH INSTITUTE,MOA,TAIWAN

This study was carried out in three stages under various stocking density of cobia, Rachycentron canadum, in a recirculating system for over-wintering. In the first stage, 12,000 fish averaged 4.1 g were evenly stocked in 6 FRP tanks. Stocking density was 571 fish/m3. After 15 days, rearing average body weight of cobia was 18±1 g and survival rate was 92.24%. In the second stage, the stocking densities were 365, 480 and 594 fish/m3 and the trial was conducted with duplicates for each density. A diet of and commercial formulated eel floating pellets fed three times daily. After 45 days, rearing average body weights were 49±2, 47±2 and 46±3 g, growth rates were 0.69±0.05, 0.65±0.01 and 0.62±0.07 g/d, survival rates were 98.59±0.64, 98.69±0.25 and 98.94±0.15%, and productivities were 17.62, 22.19 and 26.78 kg/m3 respectively. In the third stage the stocking densities were 143, 214 and 286 fish/m3. After 30 days, rearing average body weights were 114±2, 111±5 and 107±2 g, growth rates were 2.18±0.18, 2.13±0.17 and 2.04±0.03 g/d, survival rates were all 100%, and productivities were 16.33, 23.70 and 30.46 kg/m3, respectively. The results showed that higher stocking density increased the productivity, but reduced the growth rate. Also, the higher the water temperature was, the higher the growth rate would be. When water temperature was 20℃, cobia grew very slow. When water temperature was raised to 23℃, the fish grew fast.
Key word: Cobia, High-density recirculating system, Over-wintering, Stocking density, Growth rate.