Trophic enrichment factors (TEFs) varied considerably among foods (Fig. 1), although values were within expected ranges from previous literature reviews (Post, 2002; Vander Zanden and Rasmussen, 2006). TEFs for chironomid larvae in tanks and live prey in ponds were about 1‰ in δ13C (Fig. 1C, E) and 4‰ in δ15N (Fig. 1D, F). By comparison, TEFs for feed were 2.4‰in δ13C (Fig. 1A) and 3.3‰in δ15N(Fig. 1B), suggesting that fish differentially assimilated individual components within the feed mixture. Thus, experimental evaluation of food-specific TEFs is critical for diet studies using stable isotopes, especially when using different feed mixtures in aquaculture studies.