Stable carbon and nitrogen isotopic fractionation between diet and tissues of captive seals: implica

Keith A. Hobson1, Don M. Schell2, Deane Renouf3, and Elizabeth Noseworthy3
1. Prairie and Northern Wildlife Research Centre, Canadian Wildlife Service, 115 Perimeter Rd, Saskatoon, SK, Canada, S7N 0W0
2. Institute of Marine Sciences, University of Alaska, Fairbanks, AK, U.S.A., 99775
3. Ocean Sciences Centre, Memorial University of Newfoundland, St. John's, NF, Canada, A1C 5S7
Canadian Journal of Fisheries and Aquatic Science. 53: 528 - 533. 1996
Abstract: We measured stable carbon (13C/12C) and nitrogen (15N/14N) isotope ratios in nail, whiskers, skin, hair, and blood of captive harp seals (Phoca groenlandica), harbour seals (Phoca vitulina), and ringed seals (Phoca hispida) held on a constant diet of herring (Clupea harengus) for at least 2 years. In addition, isotope ratios were measured in the muscle and liver of two harp seals, and in the lung, kidney, heart, and spleen of a single harp seal that had died in captivity. Isotopic fractionation values between dietary herring (13C: -20.3 +/- 0.7%; 15N: 13.0 +/-0.4%, n =33) and these tissues ranged for nitrogen from +1.7 to +3. I% for blood and liver, respectively, and for carbon from +40.6 to +3.2% for liver and whiskers, respectively. No differences in isotopic fractionation values among species or age groups were detected. These values will permit more accurate dietary reconstructions on the basis of isotopic analysis of the tissues of seals and other marine mammals. For two captive harp seals, carbon and nitrogen isotope values showed small variation along the length of six whiskers (range of standard deviations for 13C: 0.21 to 0.57%, for 15N: 0.27 to 0.45%) but showed some evidence of being inversely correlated.



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