Temperature and diet affect carbon and nitrogen isotopes of fish muscle: can amino acid nitrogen isotopes explain effects?

► Temperature and diet affected δ13C and δ15N turnover and discrimination. ► Evidence for growth being the main contributor to isotope turnover. ► No significant treatment effects on δ15N of amino acids were detected. ► Three amino acids responded to treatments similarly to bulk δ15N. ► Precision of δ15N-amino acids restricted our ability to detect significant change.