As was the case with HSP70, liver Ub was significantly increased over time (F4, 160 = 4.29, P = 0.002; Fig. 5), but we did not observe statistically significant differences among thermal groups (F3, 160 = 2.54, P = 0.058; Table 2). Although in several cases, differences between sampling time points approached significance (t = 48 h and t = 72 h, P = 0.06; t = 60 h and t = 108 h, P = 0.07; t = 108 and t = 120 h, P = 0.066), the only significant difference in liver Ub was observed at t = 108 h, where Ub was significantly higher than pre-thermal exposure values, t = 48 h (P = 0.003). Figure 5:Liver Ub in juvenile salmon exposed to 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. Data are presented as mean ± SEM (n = 6–9). Pre-thermal stress sampling (open symbols; t = 12 and 24 h) assessed the effect of ‘trial’ and was not included in the analysis. Lettered shaded bars indicate significant differences between time points (P < 0.05).