Acid treatment of Atlantic salmon (Salmo salar) scales prior to analysis has negligible effects on δ(13)C and δ(15)N isotope ratios

There is debate in the literature as to whether scales of fishes require acidification to remove inorganic carbonates prior to stable isotope analysis. Acid‐treated and untreated scales from 208 Atlantic salmon from nine locations on both sides of the Atlantic were analysed for δ(13)C and δ(15)N. Linear mixed‐effect models determined the effect of acid treatment to be statistically significant. However, the mean difference was small (δ(13)C 0.1 ± 0.2‰, δ(15)N −0.1 ± 0.2‰) and not of biological relevance. This study concludes that Atlantic salmon scales do not need to be acidified prior to stable isotope analysis.