Stable isotope analysis
Immediately following the behavioral experiment all fish were euthanized with an overdose of phenoxyethanol. Fin and muscle samples were rinsed with deionized water and cleaned by carefully removing any skin or bone from the muscle samples. Samples were then dried at 55°C until fully dry. Elemental analysis-isotope ratio mass spectrometry was used for the carbon and nitrogen isotope analysis by the company Iso-Analytical (https://www.iso-analytical.co.uk/) using their standard quality control methods. The reference material used for both δ15N and δ13C was soy protein (IA-R068). The analysis was completed in batches, with the reference sample tested between each batch. Stable isotope analysis was repeated for every sixth sample. Repeat values all fell within a 0.20‰ range and the standard deviations of repeated analyses of the reference materials was less than 0.10‰. All values were within 0.10‰ of their certified values for δ15N and δ13C indicating both good precision and accuracy. The quality control samples used were soy (IA-R068), L-alanine (IA-R038) and tuna protein (IA-R046). All control samples were calibrated against international comparison standards distributed by the International Atomic Energy Agency.