Monitoring the Use of the Mainstem Columbia River by Bull Trout from the Walla Walla Basin Annual Report 2005/2006

A full stream width passive integrated transponder (PIT) detection array was installed in the

lower Walla Walla River and used to monitor bull trout presence/passage and possible

movement into the Columbia River from April 2005 through September 2006. The U.S. Fish

and Wildlife Service captured and PIT-tagged eleven bull trout in the mainstem Walla Walla

River from June through July 2006. Additional bull trout tagged by other agencies in Mill Creek

(tributary to the Walla Walla River), the South Fork Walla Walla River and the mainstem Walla

Walla River were available for detection at the monitoring site in the lower Walla Walla River.

No PIT-tagged bull trout from the Walla Walla Basin were detected moving through the lower

Walla Walla River toward the Columbia River during the monitoring period, however the PIT

detection array was only partially functional during that time period.