Effect of stocking density on growth, biochemical composition and blood parameters in the Pacific shortfin eel Anguilla bicolor pacifica elvers

This study examined the effect of stocking density on growth, biochemical composition, and blood parameters of the Pacific shortfin eel <i>Anguilla bicolor</i> pacifica. Elvers (1.95 ± 0.14 g body weight) were randomly stocked in indoor tanks and reared over 186 d at three stocking densities (0.3, 0.6, and 0.9 kg m^-3) set up in triplicates. Except for survival and biometric indices, elvers maintained at 0.3 and 0.6 kg m^-3 densities exhibited higher growth and feed utilization than those held at 0.9 kg m^-3. Yield increased with stocking density, which were significantly higher at 0.6 and 0.9 kg m^-3. RNA/DNA ratio did not reflect growth rate, but trends in survival and RNA/DNA ratio with stocking density were positively related. In contrast to body proximate composition, increasing stocking density resulted in significantly higher erucic acid (22:1n-9) and total saturated fatty acid levels at 0.6 and 0.9 kg m^-3 densities, respectively. Serum glutamic pyruvic transaminase activity was significantly elevated at 0.6 kg m^-3, while total protein, glucose, and triglycerides slightly decreased with increasing stocking density. Results suggest that Pacific shortfin eel elvers can be reared in indoor tanks at a stocking density of 0.3 – 0.6 kg m^-3 to achieve acceptable growth, feed performance, and health condition.