Effects of Stocking Density on Growth, Body Composition, Digestive Enzyme Levels and Blood Biochemical Parameters of Anguilla marmorata in a Recirculating Aquaculture System

We conducted a 71-day experiment to investigate the effects of stocking density in a recirculating aquaculture system (RAS) on the growth performance, body composition, digestive activity, and blood biochemical parameters of the marbled eel Anguilla marmorata. We stocked marbled eel in 1.0 m tanks at stocking densities of 12, 20, and 28 kg/m, which were designated the low-density (LD), medium-density (MD) and high-density (HD) groups. The fish weighed 169.72 ± 2.75 g at the baseline level. Results revealed that the fish in the LD and MD groups had a higher ash content than fish in the HD group. The crude lipid content was significantly lower in the MD and HD groups than in the LD group. The protease activities in the stomach and intestine did not differ among the three groups. The total protein and aspartate aminotransferase levels were higher in the LD group than in the MD group. The alanine aminotransferase level was significantly lower in the LD group. These results indicate that a greater increase resulted in stress and significantly affected the growth of the fish. The optimum stocking density of A. marmorata can be achieved at 20.0 kg/m in a RAS.