Effects of dietary shifts on the stable isotope signature of Pacific white shrimp Litopenaeus vannamei and implications for traceability

Because the number of mislabelled seafood products in the globalised market is increasing, there is a need for additional effective technologies to trace the origin of these products. Several issues need to be clarified regarding the delta C-13 and delta N-15 analyses used to trace seafood products in order to increase their reliability. Herein, a laboratory experiment involving dietary shifts was conducted with shrimp culture to demonstrate that dietary changes elicit isotope changes. Feeding shrimp four different food sources with different isotope values revealed a significant relationship for delta C-13 and delta N-15 values between shrimp and food sources (P < 0.05). The shrimp fed different brands of commercial feed had significantly different delta N-15 values (P < 0.05), but not the delta C-13 values (P > 0.05) at the end of the study. However, the delta C-13 and delta N-15 values for shrimp that were fed live food were much higher than those for shrimp fed on commercial feed (P < 0.05), indicating that it is more reliable to distinguish seafood products using a method with distinctively different food sources. The shrimp rapidly achieve isotopic equilibrium with their diets after 3 weeks, and, for traceability, it is recommended to sample shrimp being consistently fed with one feed for more than 3 weeks.