GENETIC STOCK STRUCTURE OF WESTERN ALASKA CHUM SALMON AND A COMPARISON WITH RUSSIAN FAR-EAST STOCKS

Substantial genetic divergence was found among chum salmon (Oncorhynch us keta) populations collected from North America and Russia. Five maj or groups of populations can be identified by geographic region: (1) l ower Yukon River summer run; (2) upper Yukon River fall run; (3) Brist ol Bay area; (4) Alaska Peninsula; and (5) Russia. Mean heterozygositi es were 0.064, 0.062, 0.065, 0.064, and 0.063, respectively; and the p ercent polymorphic loci values at the 0.99 level were 33.7, 31.3, 32.6 , 30.6, and 30.9%, respectively. The hierarchical gene diversity analy sis showed that 95.42% of the diversity can be explained by heterogene ity within sites, 1.36% among sites, 0.49% between Yukon River run tim ing, 1.69% among areas, and 1.04% among countries. The Alaska Peninsul a populations are genetically more similar to populations from Russia than to those from western Alaska, and two populations from the upper Yukon River are distinct from other nearby populations. Possible reaso ns for these findings concern the complex glacial histories of the wat ersheds.