Stock Status and Dynamics of Rainbow Trout and Redband Trout in Lake Roosevelt, WA

Hatchery origin rainbow trout, Oncorhynchus mykiss spp., have supplemented resident rainbow and redband trout, Oncorhynchus mykiss gairdneri, stocks in Lake Roosevelt for decades through a multi-agency collaborative effort. The Washington State Department of Fish and Wildlife, Spokane Tribe of Indians, and the Colville Confederated Tribes, coordinate to adaptively manage the recreational and subsistence fisheries based on the best available research. Currently, a total hatchery plant of 750,000 triploid (98% ± 2%), adipose clipped, rainbow trout (six to the pound) are released into the lake every May. These fish successfully fulfill their portion of management goals by providing a quality fishery in combination with the wild resident trout as indicated by strong numbers in creel surveys. While this positive outcome is encouraging, the importance of maintaining native stocks has also been identified. Understanding how the hatchery and native stocks interact is vital to successfully manage and improve the fishery. Distinct redband trout populations occur in some tributaries and represent an important component of genetic diversity. Consequently, studies are underway to evaluate naturally reproducing populations of redband trout. We are currently PIT tagging juvenile wild rainbow trout collected in screw traps located in tributary streams and rivers in combination with collecting tissues from unmarked trout encountered during creel interviews to determine origin. Additional genetic analysis may be incorporated in the future to more precisely quantify tributary genetic stock structures. Long-term monitoring using proactive, adaptive, management tactics should clarify existing population dynamics and facilitate a more stable and self-sustaining fishery on Lake Roosevelt.