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Improving Passage Efficiency of Adult American Shad at Low-Elevation Dams with Navigation Locks

Abstract
Use of navigation locks represents a low-cost alternative to the construction of fishways or lifts at low-elevation (<5 m) dams. We used sonic tracking to assess the passage efficiency of adult American shad Alosa sapidissima in 1996-1998 through the navigation locks at Lock and Dam 1 on the Cape Fear River, North Carolina. We also tested the passage efficiency at a steeppass fishway installed in 1997. Eighty-six tagged American shad were released below the dam over the 3-year study; passage efficiency ranged from 18% in 1997 (a year of high discharge during the tracking period) to 61% in 1998. During low flows, we were able to improve passage efficiency by (1) operating the lock to pass fish through until mid-June, (2) increasing attraction flows emanating from the lock entrance, (3) conducting as many lockages (i.e. use of locks to pass fish upstream) as possible in a day, and (4) closing one of the lower lock gates to better retain fish in the lock chamber after they had entered. The steeppass fishway was not as effective as the navigation locks for passage of American shad. Only three tagged fish (8%) used the fishway in 1998, probably because of design deficiencies and the lack of attraction flow at the fishway entrance.
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2000-01-01
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