As was the case with HSP70, RBC Ub levels were comparatively lower than in liver (Fig. 7). RBC Ub changed over time and between temperature treatments (F4, 160 = 4.78, P = 0.001; F3, 160 = 15.03, P < 0.001; Table 2). Similar to liver Ub, all three thermal groups had significantly greater RBC Ub than the control at 16–21°C (P < 0.001), but did not differ significantly from one another (P = 0.47–0.99). RBC Ub significantly increased at t = 72 h, after the peak of the first heat cycle (P = 0.007). Unlike the case in liver where Ub levels were no longer significantly different from pre-thermal exposure at 120 h (P = 0.91), RBC Ub remained significantly higher than the pre-thermal exposure (t = 48 h) after the final thermal cycle (t = 120 h; P < 0.001). Figure 7:RBC Ub in juvenile salmon exposed to the following diel cycles: (A) 16–21°C only; or multi-day thermal stress (closed symbols; 60–120 h) of (B) 18–27°C; (C) 20–27°C; (D) 22–27°C. Points represent mean ± SEM (n = 4–9). Pre-thermal stress sampling (open symbols; t = 12 and 24 h) assessed the effect of ‘trial’ and was not included in the analysis. Asterisks indicate significant differences between treatments. Lettered shaded bars indicate significant differences between time points (P < 0.05).