en Biology & physiology Biology & physiology پژوهشي Orginal research papers 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. Huso huso, Growth performance, Hypoxia, Hyperoxia, Oxygen consumption 533 549 http://jifro.ir/browse.php?a_code=A-10-600-21&slc_lang=en&sid=1 F. Bagherzadeh Lakani 10031947532846007685 10031947532846007685 No M. Sattari msattari@guilan.ac.ir 10031947532846007686 10031947532846007686 Yes B. Falahatkar 10031947532846007687 10031947532846007687 No