AFSC/NMML: North Pacific Killer whale genetic dataset, 1990-2010

The difficulties associated with detecting population boundaries have long constrained the conservation and management of highly mobile marine species, especially for wide-ranging cetaceans such as killer whales (Orcinus orca). In this study, we use molecular genetic data to test a priori hypotheses about population subdivisions generated from a decade of killer whale surveys across the northern North Pacific. A total of 462 skin biopsies were collected from free-swimming killer whales from 1990 to 2010 between the northern Gulf of Alaska in the east and the Sea of Okhotsk in the west, representing both the piscivorous resident and the mammal-eating Biggs (or transient) killer whales. Geographic patterns of genetic differentiation were supported by significant regions of genetic discontinuity providing evidence of population structuring within both lineages, and corroborating direct observations of restricted movements of individual whales. In the Aleutian Islands (Alaska), population strata were largely delimited by major oceanographic boundaries for resident killer whales. In contrast, subdivisions among Biggs killer whales indicated multiple genetic clusters in the Eastern Aleutians and Bering Sea. The presence of sympatric genetic clusters within Biggs whales suggests the presence of isolating mechanisms other than geographic distance within this highly mobile top predator.