Single‐Nucleotide Polymorphic Genotypes Reveal Patterns of Early Juvenile Migration of Sockeye Salmon in the Eastern Bering Sea

We estimate patterns of nearshore migration in the eastern Bering Sea for out‐migrating Bristol Bay sockeye salmon Oncorhynchus nerka in their first year at sea. Over 3,000 juveniles were collected during the late summer of 2005–2007 as part of the Bering–Aleutian Salmon International Survey and tested with a regional genetic baseline of 45 single‐nucleotide polymorphisms. Population‐specific and westward migrations from natal rivers were evident. Populations from Wood River and northwestward predominated in the northern latitudes of Bristol Bay and the eastern Bering Sea and populations from the Egegik River and southwestward in the southern latitudes, while the populations spawning at the head of Bristol Bay had the highest proportions in the middle latitudes. These patterns were stable across years, apparently unaffected by marine productivity and temperature. This continuum of marine migratory patterns most likely reflects stable and population‐specific adaptations to buffer the distribution of dynamically shifting marine resources. As monitoring continues, these juvenile surveys will accumulate information to refine predictions of the magnitude of adult returns to their respective rivers of origin and thereby assist in the management of this valuable resource.