Bull Trout Population and Habitat Surveys in the Middle Fork Willamette and McKenzie Rivers, Annual Report 2002.

Abstract

Bull trout in the Willamette River Basin were historically distributed throughout major tributaries including the Middle Fork Willamette and McKenzie rivers. Habitat degradation, over-harvest, passage barriers, fish removal by rotenone, and hybridization and competition with non-native brook trout are all likely factors that have led to the decline of bull trout in the Willamette Basin (Ratliff and Howell 1992). The U.S. Fish and Wildlife Service listed the Columbia River bull trout population segment as Threatened under the federal Endangered Species Act in 1998. Four bull trout populations were isolated in the upper Willamette River following the construction of flood control dams on the South Fork McKenzie River, McKenzie River, and Middle Fork Willamette River that created Cougar, Trail Bridge, and Hills Creek reservoirs. Buchanan et al. (1997) described the population in the main stem McKenzie as 'of special concern', the South Fork McKenzie population as 'high risk of extinction', the population above Trail Bridge Reservoir as 'high risk of extinction', and bull trout in the Middle Fork Willamette as 'probably extinct'. Various management efforts such as strict angling regulations and passage improvement projects have been implemented to stabilize and rehabilitate bull trout habitat and populations in the McKenzie River over the past 10 years. Since 1997, bull trout fry from Anderson Creek on the upper McKenzie River have been transferred to the Middle Fork Willamette basin above Hills Creek Reservoir in an attempt to re-establish a reproducing bull trout population. This project was developed in response to concerns over the population status and management of bull trout in the McKenzie and Middle Fork Willamette Rivers by the Oregon Department of Fish and Wildlife during the early 1990s. The project was conducted under measure 9.3G(2) of the Columbia Basin Fish and Wildlife Program to monitor the status, life history, habitat needs, and limiting factors for bull trout within sub basins of the Columbia River. Also, this project provides information to develop native fish recovery plans such as the Oregon Plan for Salmon and Watersheds and the U.S. Fish and Wildlife Bull Trout Recovery Plan.