Non-Native Trout Suppression and Eradication and Native Salmonid Recovery in Tributaries to Boundary Reservoir, WA

Native salmonid populations in tributaries to Boundary Reservoir in northeastern Washington State have been impacted or replaced by non-native trout.  A non-native trout suppression and eradication program is proposed in support of native salmonid recovery efforts for Seattle City Light’s Boundary Hydroelectric Project.  Twenty-seven tributaries enter Boundary Reservoir, but only nine of them are known to support trout populations.  The two largest tributaries are Sullivan Creek (378 square kilometers) and Slate Creek (84 square kilometers).  Salmonids present in tributary streams consist of cutthroat trout (Oncorhynchus clarki), eastern brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), rainbow trout (O. mykiss), and mountain whitefish (Prosopium williamsoni).  The objective is to recover self-sustaining populations of native westslope cutthroat trout.  Although bull trout populations are not present in any of the tributaries, Sullivan and Slate creeks have been targeted for developing self-sustaining bull trout populations.  Land surrounding the reservoir is primarily forest under management by the U.S. Forest Service.  As part of the February 2010 Settlement Agreement for relicensing the project, Seattle City Light has agreed to conduct non-native trout suppression on 45.8 kilometers of stream and eradication on 18.4 kilometers of stream and a 0.07 square kilometer lake (Lake Lucerne).  Ongoing suppression and removal of non-native trout will be part of a long-term commitment combining habitat manipulation, habitat protection, and potentially seeding treated reaches with native stocks.  Some of the factors considered during development of the plan include the distribution and genetic purity of existing cutthroat trout populations, choice of eradication/suppression technique(s), access to treatment reaches, public involvement, monitoring, and adaptive management during implementation of the program.