The effects of MS-222 and clove oil on blood biochemical parameters of juvenile Siberian sturgeon (Acipenser baerii) were studied. MS-222 caused higher glucose (GLU) concentrations in anaesthetic test groups than for the control group. Triglyceride (TGL) concentrations of fish in the 140 and 160mgL-1 groups were also significantly higher than those of other groups. Alanine aminotransferase (ALT) activity in the 140mgL-1 group was significantly higher than the level in 80, 100 and 120mgL-1 groups. Aspartate aminotransferase (AST) activity in the 140mgL-1 group was significantly higher than those in the 100 and 120mgL-1 groups. Levels of total protein (TP), cholesterol (CHOL) and alkaline phosphatase (ALP) in anaesthetic test groups were not significantly influenced by MS-222. Clove oil did not have significant effects on levels of GLU, TP, CHOL, ALT and ALP. TGL concentration of fish exposed to 180mgL-1 clove oil was significantly higher than those of the rest anaesthetic groups. AST activities of fish exposed to 120, 150 and 180mgL-1 were significantly higher than those of 60 and 90mgL-1. Overall, TGL and AST could be potentially used as indicators of anaesthetic stress for juvenile Siberian sturgeon. Based on blood biochemical parameters, the appropriate anaesthetic concentrations of MS-222 and clove oil were 80-120mgL-1 and 60-90mgL-1, respectively. Clove oil was a promising alternative to MS-222. ?? 2011 Blackwell Verlag, Berlin.