The induction of heat shock protein 70 (HSP70) may be considered an ecologically relevant indicator of thermal stress for Atlantic salmon (Lund et al. 2002; Chadwick et al., 2015; Tunnah et al., 2017). Soluble protein in liver and RBC were extracted as in Tunnah et al. (2017) and LeBlanc et al. (2011), respectively, and assayed using the Lowry-based DC protein assay kit (Bio-Rad, Mississauga, ON, Canada). Standards (bovine serum albumin; Bio-Rad) and samples were diluted in protein extraction buffer or salmon saline, respectively, and absorbance read at 750 nm using a SpectraMax M5 plate reader and SoftMax Pro software. Samples were prepared using 15 µg soluble protein and western blots performed as in Kolhatkar et al. (2014). We used a rabbit anti-salmonid HSP70 primary antibody (AgriSera, AS05061; 1:50 000 dilution in blocking buffer) and a goat anti-rabbit secondary (Enzo Life Sciences; SAB-300 1:50 000) for immunodetection. This antibody is specific for the inducible form of HSP70 and does not cross-react with the constitutive isoform in salmonids (Rendell et al., 2006; Fowler et al., 2009; Tunnah et al., 2017). Protein bands were visualized using an ECL Advance Chemiluminescent Western Blotting Detection kit (Amersham Pharmacia Biotech) imaged using a Versadoc Imaging System and Quantity One software (Bio-Rad). Relative band density was quantified using Image Lab software (Bio-Rad) and calculated from the standard curve on each blot.