Effect of lipid removal on carbon and nitrogen isotopes of Sthenoeuthis oualaniensis from South China Sea

The stable isotopes of carbon and nitrogen are important in evaluating feeding ecology and migration of organisms. Muscle tissues are commonly used as analytical samples, but lipids in muscles with low δ¹³C values can affect the stable isotopes analysis. To understand the effect of lipid removal on carbon and nitrogen stables isotopes in Sthenoeuthis oualaniensis muscle samples, we analyzed the stable isotopes of S.oualaniensis captured in the South China Sea in April, 2017. In addition, we compared different lipid removal models to get the best fitted model to revise δ¹³C values in S.oualaniensis muscles. The results show that after lipid removal, both δ¹³C and δ¹⁵N values changed significantly (P<0.01), increasing by 0.85‰ and 0.71‰, respectively. The lipid removal of δ¹³C values in S.oualaniensis muscles did not change with size and sex (P>0.05). Besides, Model 3 had the lowest Akaike information criterion value (AIC), indicating that it is the best fitted model for revising δ¹³C values. The results reveal that lipid removal is necessary in analyzing δ¹³C values in S.oualaniensis muscles, but δ¹⁵N values are affected when lipids are removed, so lipid removal is unnessary in δ¹⁵N values analysis.