Drying method has no substantial effect on δ15N or δ13C values of muscle tissue from teleost fishes

RATIONALE Stable isotope analysis (SIA) is a powerful tool in many fields of research that enables quantitative comparisons among studies, if similar methods have been used. The goal of this study was to determine if three different drying methods commonly used to prepare samples for SIA yielded different δ¹⁵N and δ¹³C values. METHODS Muscle subsamples from 10 individuals each of three teleost species were dried using three methods: (i) oven, (ii) food dehydrator, and (iii) freeze-dryer. All subsamples were analysed for δ¹⁵N and δ¹³C values, and nitrogen and carbon content, using a continuous flow system consisting of a Delta V Plus mass spectrometer and a Flush 1112 elemental analyser via a Conflo IV universal interface. The δ¹³C values were normalized to constant lipid content using the equations proposed by McConnaughey and McRoy. RESULTS Although statistically significant, the differences in δ¹⁵N values between the drying methods were small (mean differences ≤0.21‰). The differences in δ¹³C values between the drying methods were not statistically significant, and normalising the δ¹³C values to constant lipid content reduced the mean differences for all treatments to ≤0.65‰. A statistically significant difference of ~2% in C content existed between tissues dried in a food dehydrator and those dried in a freeze-dryer for two fish species. There was no significant effect of fish size on the differences between methods. CONCLUSIONS No substantial effect of drying method was found on the δ¹⁵N or δ¹³C values of teleost muscle tissue.