Stable isotope analysis has been used powerfully in tracing animal dietary sources.In the recent decades, many mixing models have been exploited to calculate source proportional contributions to a mixture based on stable isotope analyses.Here we present a case study by using Euclidean,Linear and Bayesian stable isotope mixing models to calculate proportion of Euphausia superba,Electrona antarctica and Gymnoscopelus nicholsi in Antarctic fur seal(Arctocephalus gazelle)diets over the 20 th century.The Euphausia superbaproportions in fur seal diets obtained from formula(1)and(2)of Euclidean method show a rising trend over the 20 th century,similar to those delta15 N of fur seal hairs.While the results given by formula(3)of Euclidean,Linear and Bayesian models show a declining trend,which are in accord with those recent changes in regional climate,sea ice extent and the observational Euphausia superba density.The results here can be used to study the biological response to climate change in a long time period.The calculated decline of krill proportion in seal diets over the past century indicates a decreasing trend of Euphausia superba population which is very likely due to the recent rapid regional warming and sea ice loss.Our results suggest that recent warming in the West Antarctic Peninsula has had an obvious impact on the regional marine food chains.