Effect of different oxygen levels on growth performance, stress response and oxygen consumption in two weight groups of great sturgeon Huso huso

In the present study, different oxygen levels were examined in two weight groups of great sturgeon Huso huso including small size (with initial weight 280.9 ± 49.2 g) and large size (with initial weight 1217.9 ± 138.1 g). The fish were kept in hypoxia (2-3 mg/l), normoxia (5-6 mg/l) and hyperoxia (9-10 mg/l) conditions for 8 weeks and then were individually placed in the tanks with oxygen level of 6 mg/l to levels causing sedate fish and subsequently dissolved oxygen level in water was measured every 30 minutes. No significant effects on blood cortisol and glucose levels were observed after 8 weeks (P > 0.05), but there were significant differences in cortisol concentrations between treatments (P < 0.05) after stress. Significant differences were found in cortisol and glucose levels in pre and post stress conditions in small size, but no significant differences were observed (P > 0.05) in large size. There were no significant differences in oxygen consumption among treatments (P > 0.05). Results revealed that dissolved oxygen had a significant effect on growth of H. huso and also a low level of oxygen accompanied by reduction in feed intake resulted in lower growth and changes in stress response.