Figure 1.

Map of the Yakima River system. The three spring Chinook salmon populations spawn in the American River, the Naches River, and the upper Yakima River above Roza Dam. The upper Yakima population is the target of the Cle Elum Supplementation and Research Facility (CESRF). All adults returning to the upper Yakima River are sampled at Roza Dam and allowed to spawn naturally (natural-origin and integrated line fish) or are removed from the system (all segregated line fish). Spawning and rearing for the hatchery lines occurs at CESRF. Prior to outmigration in spring, juveniles are transferred to the Easton, Jack Creek, and Clark Flat acclimation sites, where they are held for approximately two months before volitional release.