2019 Supplemental Data Collection for WFIP Effectiveness Monitoring

In the Willamette River and associated side channels, alcoves, and wetlands - the expansion and widespread occurrence of Ludwigia has potential to fundamentally change habitat conditions in affected waterbodies. Treatment to remove Ludwigia is a key strategy of the Willamette FIP program with anticipated ecological outcomes of reduced cover of aquatic invasive species, improved water quality, and improved habitat for native fishes, though these relationships are not well understood. Using ArcGIS and aerial photographs we mapped off-channel habitat and emergent aquatic vegetation cover from the confluence of Coast Fork and Middle Fork Willamette Rivers (Lane County) to Newberg Pool (Yamhill County) and develop preliminary relationships between plant cover, hydrogeomorphology, water quality, fish communities, and Ludwigia control efforts. Because complete eradication of Ludwigia from the system will be nearly impossible, Ludwigia management will remain a common activity in the future.

Monitoring will benefit salmon, steelhead, native fish, and other aquatic and riparian-dependent species in the mainstem Willamette by 1) helping to ascertain how Ludwigia affect the presence and distribution of listed and resident native fishes, 2) providing information to adaptively improve Ludwigia treatment protocols and WFIP Strategic Actions to address Ludwigia invasions, and 3) characterizing the impacts of Ludwigia on the Willamette River system. Altogether this information will better prioritize and inform restoration actions that best support salmon and steelhead habitat.