title: Use of chemical tracers in assessing the diet and foraging regions of eastern North Pacific killer whales.
abstract: Top predators in the marine environment integrate chemical signals acquired from their prey that reflect both the species consumed and the regions from which the prey were taken. These chemical tracers-stable isotope ratios of carbon and nitrogen; persistent organic pollutant (POP) concentrations, patterns and ratios; and fatty acid profiles-were measured in blubber biopsy samples from North Pacific killer whales (Orcinus orca) (n=84) and were used to provide further insight into their diet, particularly for the offshore group, about which little dietary information is available. The offshore killer whales were shown to consume prey species that were distinctly different from those of sympatric resident and transient killer whales. In addition, it was confirmed that the offshores forage as far south as California. Thus, these results provide evidence that the offshores belong to a third killer whale ecotype. Resident killer whale populations showed a gradient in stable isotope profiles from west (central Aleutians) to east (Gulf of Alaska) that, in part, can be attributed to a shift from off-shelf to continental shelf-based prey. Finally, stable isotope ratio results, supported by field observations, showed that the diet in spring and summer of eastern Aleutian Island transient killer whales is apparently not composed exclusively of Steller sea lions.
authors.affiliation: NOAA Fisheries, Northwest Fisheries Science Center, 2725 Montlake Boulevard East, Seattle, WA 98112, USA. peggy.krahn@noaa.gov
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Krahn
authors.forename: David P
authors.initials: DP
authors.lastname: Herman
authors.forename: Craig O
authors.initials: CO
authors.lastname: Matkin
authors.forename: John W
authors.initials: JW
authors.lastname: Durban
authors.forename: Lance
authors.initials: L
authors.lastname: Barrett-Lennard
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Burrows
authors.forename: Marilyn E
authors.initials: ME
authors.lastname: Dahlheim
authors.forename: Nancy
authors.initials: N
authors.lastname: Black
authors.forename: Richard G
authors.initials: RG
authors.lastname: LeDuc
authors.forename: Paul R
authors.initials: PR
authors.lastname: Wade
mesh_terms: D000273:Adipose Tissue / Q000737:chemistry*; D000818:Animals; D002247:Carbon Isotopes / Q000032:analysis; D004032:Diet; D004784:Environmental Monitoring; D005227:Fatty Acids / Q000032:analysis; D005247:Feeding Behavior; D005260:Female; D020387:Food Chain; D008297:Male; D009587:Nitrogen Isotopes / Q000032:analysis; D010140:Pacific Ocean; D011075:Polybrominated Biphenyls / Q000032:analysis; D011078:Polychlorinated Biphenyls / Q000032:analysis; D011235:Predatory Behavior; D014907:Whales / Q000502:physiology*
chemical_list: D002247:Carbon Isotopes; D005227:Fatty Acids; D009587:Nitrogen Isotopes; D011075:Polybrominated Biphenyls; D011078:Polychlorinated Biphenyls