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Across the Pacific Northwest, there are many examples of artificial structures created to allow upstream-migrating salmon to pass over natural barriers such as waterfalls.

A team of USGS and BLM researchers studied the upstream passage of adult coho salmon across three structures installed in 1989 to allow salmon to pass over Lake Creek Falls, a series of three natural waterfalls in central Oregon. 87 salmon were radio tagged and tracked during migration and spawning between October 2019 and February 2020. Later than normal precipitation delayed migration, and most fish arrived late in the season. Fish that were tagged earlier in the season were more likely to successfully cross all three structures and pass over the waterfalls. Although it was clear that large numbers of fish are capable of crossing the waterfalls during certain conditions, longer-term studies involving more fish are necessary to draw firm conclusions about the influences of the passage structures on fish populations. 

Fisher, R.B., Dunham, J.B., Scheidt, N., Hansen, A.C., and Heaston, E.D., 2022, Passage of adult coho salmon (Oncorhynchus kisutch) over Lake Creek Falls, Oregon, 2019: U.S. Geological Survey Open-File Report 2022–1083, 19 p.,


a fish ladder with a waterfall in the background
Middle falls at Lake Creek Falls, consisting of bedrock sheet flow and a vertical drop. Entry to the Denil-style fish ladder is visible in foreground.
a waterfall with a rectangular stone fish ladder structure in the background
Vertical drop of upper falls at Lake Creek Falls, Oregon, with entry to Denil-style fish ladder visible in background.

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