Monitoring the Use of the Mainstem Columbia River by Bull Trout from the Walla Walla Basin. Annual Report 2007 (October 1, 2006 - September 30, 2007)

摘要

Bull trout distribution, abundance and habitat quality have declined range wide and several local extirpations have been documented. As a result, the Columbia River Distinct Population Segment of bull trout was listed as threatened under the Endangered Species Act in June 1998. Mainstem Snake and Columbia River dams have the potential to impact migratory bull trout. Use of the Columbia River by bull trout from the Walla Walla Basin is unknown and the need for further research is identified in the U.S. Fish and Wildlife Service Draft Recovery Plan. A full stream width passive integrated transponder (PIT) detection array was maintained in the lower Walla Walla River and used to monitor use of the Columbia River by bull trout from the Walla Walla Basin from October 2006 through September 2007. A second detection array with a different design was installed approximately 25 m upstream from the existing array in October 2006 and operated until May 2007. The U.S. Fish and Wildlife Service PIT tagged 12 bull trout in the mainstem Walla Walla River from May through September 2007.