Foote, Andrew David5; Vester, Heike2; Vikingsson, Gisli A.3; Newton, Jason4
1 Natural History Museum of Denmark, Faculty of Science, Københavns Universitet2 Ocean Sounds, Hjellskaeret, 8312 Henningsvaer, Norway3 Marine Research Institute, Program for Whale Research, PO Box 1390, 121 Reykjavík, Iceland4 NERC Life Sciences Mass Spectrometry Facility, SUERC, East Kilbride, G75 0QF, United Kingdom5 Natural History Museum of Denmark, Faculty of Science, Københavns Universitet
Epidermal skin samples from eastern North Atlantic killer whales, Orcinus orca, were analyzed for carbon and nitrogen stable isotope ratios. From those, compar- isons within a data set of 17 samples collected from Tysfjord, Norway, in November suggested that diet is relatively specialized during this time period at this loca- tion. There were significant differences between a small set of samples from Iceland and those collected from Norway, which had all been assigned to the same pop- ulation by a previous population genetics study. The results would be consistent with matrilines feeding on either the Norwegian or Icelandic stocks of Atlantic herring (Clupea harengus). There was no significant difference within Icelandic sam- ples between those assigned to the population known to feed upon herring and those assigned to a population hypothesized to follow Atlantic mackerel (Scomber scombrus). The greatest differences were between the epidermal samples analyzed in this study and tooth and bone collagen samples from the North Sea that were an- alyzed previously, which also showed significantly more variation in isotopic ratios than found for skin samples. These differences could reflect differences in turnover rate, differences in diet-tissue fractionation and discrimination due to the amino acid composition of the different tissues, and/or greater competition promoting dietary variation between groups in the North Sea.