During the period 1990 to 2000 the wild populations exhibited no trend in body size of age 4 fish. Because the wild control population in the Naches experienced the same rate of decline as the upper Yakima natural and hatchery origin groups between 2001 and 2006, we concluded that the supplementation program was not the cause, and reduced size over time is more likely related to large scale phenomenon such as oceanic and/or main stem Columbia River environments shared by all the populations.