Stable nitrogen and carbon isotope ratios in multiple tissues of the northern fur seal Callorhinus ursinus: implications for dietary and migratory reconstructions

摘要

We investigated changes in trophic level and feeding location over time in juvenile male northern fur seals Callorhinus ursinus from the Pribilof Islands, Alaska, using stable nitrogen(δ~15N) and carbon(δ~13C)isotope analyses of their fur, muscle, blubber, brain, liver, and kidney tissues. Meanδ~15N values were non-uniform between tissues and ranged from 14.9/1000(fur)to 17.1/1000(lipid Extracted blubber). Meanδ~13C values also varied with tissue type and ranged from-24.7/1000(non-lipid Extracted blubber)to-17.5/1000(fur). Mean isotope values of tissues clustered into groups coincident With their estimated protein and isotope turnovel times, with fur representing the most remote incor- Poration of isotopic data, followed by muscle(δ~15N = 15.1 to 15.6/1000,δ~13C≈-18.1/1000), brain(δ~15N≈ 17.0/1000;δ~13C = -18.4 to -18.1/1000), blubber(δ~15N = 17.1/1000;δ~13C = -19.7/1000 to -18.1/1000), kidney(δ~15N≈ 16.4/1000;δ~13C = -18.5 to -18.2/1000), and liver(δ~15N = 16.0/1000 to 16.2/1000;δ~13C = -18.4/1000 to -18.2/1000).