Structures for Passing Juvenile Coho Salmon Into Off-Channel Habitat
Fish Passage Policy and Technology: Proceedings of a Symposium
American Fisheries Society
In recent years fisheries scientists have documented the benefit of the upstream movement of coho salmon fry and fingerlings from the river mainstems into sheltered off-channel ponds. This habitat is typically found on or above abandoned flood plains near the base of the next higher river terrace and has been termed 'wall base habitat.' Since 1980, the Washington State Department of Fisheries (WDF) has developed about 30 off-channel habitat sites. An important component of many of these projects has been the design of water control structures or channels which provide a dual purpose of 1) creating a greater pool depth, and/or 2) providing fish passage into the pond. Several designs have been tested, and modified as necessary to provide optimum fish passage. Through the project development stage calculations and assumptions were made regarding the leaping and swimming capabilities of juvenile coho salmon. Passage success was determined empirically from observations of hydraulic conditions and trapping data. Design considerations, types of water control/passage structures, juvenile fish passage criteria and construction costs are presented.