The Effect of Denil Fishway Length on Passage of Some Nonsalmonid Fishes

Publication Date



Alosa sapidissima, American shad, barriers, behavior, carp, Columbia River, denil, fish passage, lamprey, Little Goose Dam, McNary Dam, non-resident fish, northern squawfish, Pacific lamprey, salmonids, shad, slope, Snake River, squawfish, steeppass, sucker, upstream

Journal or Book Title

Marine Fisheries Review


This paper documents the success of passage of some non-salmonid fishes through Denil-type steeppass 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. These fish were successful in ascending the 7.9 m (26 foot) fishway, and all but the common carp ascended the 15.2 m (50 foot) fishway. When the length was extended to 20.1 m (66 feet), no American shad or resident freshwater fish were observed ascending and passing through the Denil. Salmonids and Pacific lamprey, however, were able to successfully pass through all lengths of Denil fishways tested. These 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.







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