Summer-Fall Distribution of Stocks of Immature Sockeye Salmon in the Bering Sea as Revealed by Single-Nucleotide Polymorphisms

We report stock composition estimates for immature (ocean-age .1 and .2) sockeye salmon Oncorhynchus nerka distributed across the Bering Sea in late summer and fall. We establish a baseline data set composed of single-nucleotide polymorphism markers that can achieve very high accuracies in identifying sockeye salmon stocks from throughout their range in Asia and North America. We demonstrate the capabilities of this data set to address high-seas salmon issues by analyzing samples collected by researchers from Russia, Japan, and the United States during late summer and fall 2002-2004 as part of the Bering Aleutian Salmon International Survey. According to our findings, (1) Gulf of Alaska (GOA) stocks formed a significant portion of the immature sockeye salmon migrating in the eastern and central Bering Sea in summer and fall, and western GOA stocks had a broader distribution in the Bering Sea than eastern GOA stocks; (2) Asian stocks migrated as far east as the western Aleutian Islands and the Donut Hole area (international waters in the center of the Bering Sea); and (3) Bristol Bay stocks were the most widely distributed, accounting for more than one-half of the mixtures in all areas except the central and southern areas of the Russian Exclusive Economic Zone (REEZ) in the western Bering Sea and north of the western Aleutian Islands. These results provide a significant increase in our knowledge of the distribution of sockeye salmon, firmly establishing that the REEZ is a summer-fall feeding area for immature North American sockeye salmon, particularly stocks of southeastern Bristol Bay origin. Bristol Bay sockeye salmon appear to enter and exit the REEZ primarily along a migration route that extends across the Aleutian Basin.