Acoustic-tagged juvenile Chinook salmon (Oncorhynchus tshawytscha) detections in Lookout Point Reservoir and downstream in the Middle Fork Willamette River, Oregon, 2024-25

Federally-threatened ago-0 spring Chinook salmon (Oncorhynchus tshawytscha) were acoustic tagged and released near Lookout Point Reservoir to estimate passage and survival during the second year of an experimental reservoir drawdown operation that was designed to facilitate downstream passage through two reservoirs and dams. The experimental operation consisted of lowering the water surface elevation of Lookout Point Reservoir on the Middle Fork Willamette River from 859 ft on August 1, 2024 to 750 ft by November 11 2024 and passing water through regulating outlets at Lookout Point Dam. This operation was intended to improve fish passage for juvenile Chinook salmon through Lookout Point Dam. During our study, acoustic-tagged juvenile Chinook salmon produced by Oregon State University's Wild Fish Surrogate Program were released in two groups, an initial early release the first week of August, and then weekly from late-September to mid-November to determine how fish responded to the drawdown. Detection sites were at the head of Lookout Point Reservoir, in Lookout Point Reservoir and Dexter Reservoir on the Middle Fork Willamette River; and near the city of Eugene, Oregon, and near Willamette Falls on the Willamette River. Some fish were additionally incidentally recaptured by gillnets in Lookout Point Reservoir and in smolt traps in the tailraces of Lookout Point and Dexter Dams. Estimates of fish survival through the study area were calculated from the release, detection and recapture records and combined with time-varying covariates of Lookout Dam operations and water temperature in Lookout Point Reservoir and the Middle Fork Willamette River.

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  "010:12"
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  "geospatial"
]