The effect of denil fishway length on passage of some nonsalmonid fishes

This paper documents the success of passage of some non-salmonid fishes through Denil-type steep-pass fishways of varying length and slope. Length ranged from 7.9 m (26 feet) to 20.1 m (66 feet), and slope ranged between 23.3 and 28.7 percent. American shad, Alosa sapidissima ; common carp, Cyprinus carpio ; chiselmouth, Acrocheilus alutaceus ; northern squawfish, Ptychocheilus oregonensis ; Pacific lamprey, Lampetra tridentata ; and suckers, Catostomus sp., were observed at Bonneville and McNary dams on the Columbia River and Little Goose Dam on the Snake River from 1971 to 1979. Observations indicate that Denil ladders of selected length could be used, if desired, to pass salmonid fishes over small barriers while denying upstream access to certain unwanted nonsalmonids.