To test the hypothesis that stable isotope ratios from marine organisms vary, the d15N and d13C values from fish and squid collected in Alaskan waters were measured across years (1997, 2000, and 2005), seasons, geographic locations, and different size/age classes, and between muscle tissue and whole animals. Temporal, geographic, and ontogenetic differences in stable isotope ratios ranged from 0.5–2.5‰ (d15N) to 0.5–2.0‰ (d13C). Twenty-one comparisons of stable isotope values between whole organisms and muscle tissue revealed only four small differences each for d15N and d13C, making costly and space prohibitive collection of whole animals unnecessary. The data from this study indicate that significant variations of stable isotope values from animals in marine systems necessitates collection of prey and predator tissues from the same time and place for best interpretation of stable isotope analysis in foraging ecology studies. |
