Warner Sucker and Redband Trout Passage and Screening on Twentymile Creek in the Warner Basin of Southeastern Oregon

Warner sucker (Catostomus warnerensis) and Warner Lakes redband trout (Oncorhynchus mykiss ssp.) are endemic to the Warner basin, in southeastern Oregon. USFWS listed the Warner sucker as threatened in 1985 because of habitat fragmentation and the threats from introduced non-native fish. Recent recovery efforts have focused on providing passage and screening at irrigation diversions on tributaries within the basin. Twentymile Creek is one of three primary tributaries supporting the target species. Two diversion structures on Twentymile Creek are barriers to sucker passage and likewise affect redband trout. RDG working with LCUWC, USBLM, and a private landowner, developed an adjustable orifice and weir fish ladder to provide varied hydraulic conditions and pathways to pass benthic-oriented sucker and more surface-oriented redband trout. Sucker swimming behavior data provided by ODFW were incorporated during ladder design. A Farmers Screen, a horizontal flat-plate screen, was installed in the diversion channel to exclude fish from the irrigation network. The project was completed in January 2015. ODFW PIT tagged a total of 147 suckers that will be monitored in 2015 to assess passage success at the site. The presentation will cover ladder and screen design, project implementation, and preliminary monitoring results.