Overall, relative RBC HSP70 levels were lower than those observed with liver HSP70 (Fig. 6). Similar to liver HSP70, a significant interaction (F12, 160 = 22.25, P < 0.001; Table 2) between thermal cycle and time was observed. RBC HSP70 was induced at the peak of the first heat cycle (t = 60 h) in all three-temperature treatments. At t = 60 h, RBC HSP70 in 22–27°C group was significantly higher than the other treatments (P < 0.001; Fig. 6). However, at the next sampling point (t = 72 h), relative RBC HSP70 was greater in the 18–27°C group than in the other temperature treatments. At the end of the experiment (t = 120 h), RBC HSP70 remained elevated in all thermal groups, but was significantly lower in the 20–27°C group compared to the 18–27°C and 22–27°C groups. Figure 6:RBC HSP70 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 = 5–9). Pre-thermal stress sampling (open symbols; t = 12 and 24 h) assessed the effect of ‘trial’ and was not included in the analysis. Letters indicate significant differences among treatments (P < 0.05) within sampling time points.