(a) Changes in ethoxyresorufin-O-deethylase (EROD) activity at 3, 7, 14, 28 and 50 days in liver microsomes of juvenile rainbow trout fed either 3 μg BaP/g fish/day, 3 μg BeP/g fish/day or control diet for 50 days. Measurements (n=3) indicated with asterisk (*) are significantly different than control (ANOVA, p<0.05). (b) Staining intensity (mean ±SE of CYP1A in liver of juvenile rainbow trout at 3, 7, 14 and 28 days fed either 3 μg BaP/g/fish, 3 μg BeP/g/fish or control diet. Measurements (n=3–5) indicated with asterisk (*) are significantly different than control (ANOVA, p<0.05).