Development of an analytical method to exclude the effect of decomposition on carbon and nitrogen stable isotope ratios using muscle samples collected from stranded narrow-ridged finless porpoise (Neophocaena asiaeorientalis).

Prediction by the GAM showed changes in δ13 C and δ15 N values with a change in carbon and nitrogen content. The effect of decomposition can be excluded in statistical analysis of stranded samples by using samples with carbon and nitrogen content and C:N ratio equivalent to those of fresh samples or by using the carbon and nitrogen content and C:N ratio as an explanatory variable in the GAM.