Use of stable isotopes to distinguish farmed from wild Atlantic salmon, Salmo salar

Abstract –  Stable isotopes of carbon and nitrogen ( δ ¹³C and δ ¹⁵N) were examined in wild and aquaculture origin Atlantic salmon, Salmo salar , to evaluate their utility to identify escaped farmed fish. Samples of muscle tissue obtained from wild Conne River, Newfoundland, salmon were significantly more enriched in nitrogen ( δ ¹⁵N: mean = 12.75; SD ± 0.38‰) but depleted in lipid corrected carbon ( δ ¹³C': mean = ?20.51; SD ± 0.23‰) by comparison with aquaculture specimens obtained from Bay d'Espoir, Newfoundland ( δ ¹⁵N = 10.96 ± 0.19‰;  δ ¹³C' = ?19.25 ± 0.17‰) resulting in a complete separation of the two groups. Aquaculture specimens differed in δ ¹³C' from analyses of commercial salmon diet by 0.24‰, within the enrichment range associated with trophic transfers, while the δ ¹⁵N values in salmon muscle were enriched by 5.01‰. Although differences occurred in direct comparisons of white muscle and adipose tissue ( N  = 49), the average δ ¹³C' and δ ¹⁵N signatures varied in absolute amounts by only 0.5‰, supporting the use of adipose tissue as a nonlethal means to determine isotopic signatures of Atlantic salmon.