Effects of stocking density on mortality, growth and physiology of juvenile Amur sturgeon (Acipenser schrenckii)

To evaluate effects of stocking density on welfare of Amur sturgeon (Acipenser schrenckii), an experiment was designed using three initial stocking densities in flow-through tanks (LSD = 3.7 kg m(-3), MSD = 6.9 kg m(-3), and HSD = 9.3 kg m(-3), respectively) for 60 days. Growth, body composition, and haematological and biochemical parameters were monitored. The mortality and feed conversion rate (FCR) were not affected by stocking density. However, the specific growth rate (SGR), final weight and weight gain in the HSD group were significantly lower than in the LSD and MSD groups. The hepatosomatic (HSI) and viscerosomatic indices (VSI) varied inversely with regard to stocking density. Stocking density did not affect crude protein levels in fish. In contrast, the total lipid level was significantly higher in the LSD group compared to the MSD and HSD groups. The levels of erythrocytes and haemoglobin were positively correlated with stocking density. Serum total bilirubin and urea in HSD group were significantly higher than in the LSD group while serum triglycerides showed opposite tendencies. Differences between treatments were not registered for glucose, total protein and albumin. In conclusion, higher stocking density resulted in increased immunosuppression and enhanced energy mobilization. The latter was necessary to enable Amur sturgeon to cope with crowding.