Fig. 3. Antioxidant enzyme activities and lipid-peroxidation levels in the plasma of sturgeon Acipenser naccarii during acclimation to seawater (35) and after a period of 20 days at this salinity. Values are means ± S.E.M. Data values with different letters are significantly different (one-way analysis of variance, P<0.05, N=5 fish at each salinity). Catalase (CAT) and glutathione peroxidase (GPX) activities, 1 unit (U) = 1 mmol min^-1; superoxide dismutase (SOD) activity, 1 U = 50% inhibition of cytochrome c reduction min^-1; lipid-peroxidation levels are expressed as malondialdehyde (MDA) concentration (nmol MDA ml^-1).