The analysis of population genetic structure in Alaskan harbor seals as a framework for the identification of management stocks

Harbor seals (Phoca vitulina) occupy a near-continuous distribution in the coastal and continental shelf waters of Alaska from Dixon Entrance in the southeast, west throughout the Gulf of Alaska and the Aleutian Archipelago to Kuskokwim Bay in the Bering Sea (Figure ES1). This important marine predator occupies a diverse range of habitats, hauls out at thousands of discrete coastal sites and represents a significant marine resource to a range of users. Harbor seals have declined dramatically in some parts of their Alaska range over the past few decades while in other parts their numbers have increased or remained stable over similar time periods. These declines and differences in trend suggest areas with independent population dynamics, and therefore, highlight the need for the definition of biologically meaningful management units, also known as stocks. The spatial scale of these stocks is important for interpreting direct and indirect human-caused mortality in relation to abundance, population trend and other aspects of harbor seal biology.