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Fall Chinook Salmon Spawning in the Tailraces of Lower Snake River Hydroelectric Projects
Author(s) -
Dauble Dennis D.,
Johnson Robert L.,
Garcia Aaron P.
Publication year - 1999
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1999)128<0672:fcssit>2.0.co;2
Subject(s) - chinook wind , oncorhynchus , fishery , habitat , environmental science , hydroelectricity , endangered species , critical habitat , hydrology (agriculture) , geography , ecology , fish <actinopterygii> , geology , biology , geotechnical engineering
We conducted studies from 1993 to 1997 to identify and characterize potential spawning habitat of “endangered” fall chinook salmon Oncorhynchus tshawytscha in areas downstream of four Snake River dams. This information was needed to provide guidelines for future operation of the lower Snake River hydroelectric system, including assessment of reservoir drawdown, and for site‐specific construction planning. We used Geographic Information System mapping technology to direct our initial search efforts. Suitable spawning habitat was defined based on physical habitat characteristics of the tailrace areas. Redd surveys were conducted in primary search areas and planned construction sites from mid‐November through December with an underwater video system. The survey path and redd locations were mapped by using a Global Positioning System. During the 4‐year study, fall chinook salmon redds were found in the tailrace downstream of Lower Granite (LGR), Little Goose (LGO), and Ice Harbor (IH) dams. The redds were the first verified sightings of salmon spawning at their locations since these dams were constructed in 1970, 1975, and 1972, respectively. The total area used for spawning was about 2,560 m 2 for the LGR site and 580 m 2 for the LGO site. Only one redd was found downstream of the IH project. Redds were in water from 4.0 to 8.1 m deep and on cobble substrate. All redds were adjacent to the outfall flow from juvenile fish bypass systems and on the powerhouse side of the river. Although temporal use was variable among individual projects, within‐site fidelity was high. Tailrace spawning accounted for about 12% of the redds in the main stem of the Snake River during 1993 and 1994 but declined to less than 5% in 1996 and 1997.