摘要：Killer whales (
Orcinus orca) are distributed widely in all oceans, although they are most common in coastal waters of temperate and high-latitude regions. The species’ distribution has not been fully described in the northwest Atlantic (NWA), where killer whales move into seasonally ice-free waters of the eastern Canadian Arctic (ECA) and occur year-round off the coast of Newfoundland and Labrador farther south. We measured stable oxygen and carbon isotope ratios in dentine phosphate (δ
18O
P) and structural carbonate (δ
18O
SC, δ
13C
SC) of whole teeth and annual growth layers from killer whales that stranded in the ECA (n = 11) and NWA (n = 7). Source δ
18O of marine water (δ
18O
marine) at location of origin was estimated from dentine δ
18O
P values, and then compared with predicted isoscape values to assign individual distributions. Dentine δ
18O
P values were also assessed against those of other known-origin North Atlantic odontocetes for spatial reference. Most ECA and NWA killer whales had mean δ
18O
P and estimated δ
18O
marine values consistent with
18O-depleted, high-latitude waters north of the Gulf Stream, above which a marked decrease in baseline δ
18O values occurs. Several individuals, however, had relatively high values that reflected origins in
18O-enriched, low-latitude waters below this boundary. Within-tooth δ
18O
SC ranges on the order of 1–2‰ indicated interannual variation in distribution. Different distributions inferred from oxygen isotopes suggest there is not a single killer whale population distributed across the northwest Atlantic, and corroborate dietary and morphological differences of purported ecotypes in the region.
