Abstract
This study identified δ15N stable isotope ratios as a robust tracer for fishmeal inclusion in aquaculture feeds. δ15N and δ13C values from fish muscle samples derived from feeding trials with seven species (n = 3–5 fish per diet group) were evaluated (+/−0.1‰ for both δ15N and δ13C; ~1% relative to % N and % C) to verify whether the presence or absence of fishmeal (FM) in feeds could be detected. C and N isotopic data were also analyzed for feed in two of the trials. δ13C signatures did not differ consistently across diet groups for each species examined, with mean δ13C values for all species investigated being −20.2‰ ± 1.3. In contrast, a strong δ15N distinction was discerned between FM- and non-FM-fed fish for both muscle and feed samples, with FM-fed groups presenting higher values (p