Lipid Correction for Carbon Stable Isotope Analysis of Yellowfin Tuna

Abstract

Carbon stable isotopes (δ13C) are widely used in ecological studies to understand diet, food web dynamics, and movements of marine fishes. Still, δ13C is influenced by lipid content and often requires chemical extraction or mathematical correction. Here, we developed a species-specific mathematical lipid correction for white muscle tissue of yellowfin tuna (Thunnus albacares), a highly migratory finfish of considerable economic and ecological value. Lipid extraction was conducted on yellowfin tuna white muscle tissue (C:N range: 2.96–6.49), and both linear and non-linear lipid correction models for δ13C were fitted and assessed. Lipid extraction increased δ13C, and to a lesser extent, δ15N values in yellowfin tuna white muscle tissue, but had no effect on δ34S. Both non-linear models provided better fits to the data than the linear model, suggesting an asymptotic relationship between C:N and ∆δ13C. Results support the growing body of evidence that C:N ratios can be used to predict lipid corrected δ13C and highlight the value of mathematical correction approaches. We provide species-specific parameter estimates that can be used for lipid correction of white muscle tissue for δ13C analysis in yellowfin tuna and similar species for which species-specific models have yet to be developed.