Fish exposed to 16–21°C lost equilibrium at 32.5 ± 0.09°C, a temperature significantly higher than those maintained at a stable acclimation temperature of 16°C (31.4 ± 0.09°C; F2, 48 = 43.0, P < 0.001). Overall, CTMax increased in all thermally cycled groups compared to the 16–21°C-control group (F3, 64 = 31.92, P < 0.001). Significant increases in CTMax were observed in all temperature treatments after one day of cycling (t = 72 h; P < 0.001), with no significant differences observed between groups (Fig. 2B–D; P = 0.11–0.77). No significant differences were observed between t = 72 h and t = 120 h of heat cycling within or between temperature treatments (pooled mean of all heat exposed fish = 33.1 ± 0.08°C; P = 0.96–0.99; Table 2; Fig. 2). Figure 2:CTMax of wild juvenile salmon exposed to diel cycles: (A) 16–21°C (control group); 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 = 5–10). Open symbols (t = 24 h) represent pre-thermal stress sampling time points and were secondarily used to assess the effect of ‘trial’. Asterisks indicate significant differences among treatments (P < 0.05).Table 2:Two-way ANOVA performed on physiological variables of juvenile Atlantic salmon exposed to multi-day thermal stressEndpointTimeTreatmentInteractiondfF-statisticP-valuedfF-statisticP-valuedfF-statisticP-valueCTMax11.140.290331.93<0.001*30.160.920L glycogen46.93<0.001*36.73<0.001*122.630.003*WB glucose41.720.14932.550.057121.440.155WB lactate45.65<0.001*32.330.077121.740.062L HSP704100.61<0.001*3177.05<0.001*129.68<0.001*L Ub44.290.002*32.540.058121.380.179RBC HSP70473.18<0.001*3207.50<0.001*1222.25<0.001*RBC Ub44.780.001*315.03<0.001*121.070.388Asterisks indicate significance of two-way ANOVA with α = 0.05 and P <0.05.