|Document Type:||Contract Report|
|Title:||Adult fall Chinook salmon passage through fishways at lower Columbia River dams in 1998, 2000, and 2001|
|Author/Editor:||Brian J. Burke, Kinsey E. Frick, Mary L. Moser, T. J. Bohn, Ted C. Bjornn|
|Publisher:||National Marine Fisheries Service|
|Contracting Agency:||U.S. Army Corps of Engineers. Portland, Oregon|
|Project Number:||ADS-00-1, ADS-00-12|
As part of an ongoing study to examine fish behavior at hydropower dams, we gastrically implanted radiotelemetry tags in a total of 3,142 adult fall-run Chinook salmon Oncorhynchus tshawytscha and monitored their movements as they migrated upstream through the Columbia River Basin in 1998, 2000, and 2001. Radio receivers were placed along the Columbia River, at the mouths of most tributaries, and throughout the various fishways at four lower Columbia River dams (Bonneville, The Dalles, John Day, and McNary Dams). Passage efficiency at these dams ranged from 86.5 to 97.4% during the 3 years and varied little through time at three of the four dams (The Dalles Dam being the exception).
Similarly, differences in dam passage durations were greater between dams than between years (medians ranged from 10 to 30 h across all dams and years). McNary Dam produced the fastest passage times in each year, and passage duration in 2000 was most often the longest relative to other years within a dam. Although fish approached all entrances to the fishways, they tended to approach, enter, and exit from the main entrances the most, on both their first attempt and all subsequent attempts. Entrance usage patterns were dam-specific, but interannual variability in entrance use was low at all dams.
We determined the amount of time fish spent in various segments of the fishways. Although fall Chinook salmon spent the majority of their time in the tailrace and at the base of dams, they tended to do so both before and after attempting to pass the dam. Total time spent within the dam structure was consistently low, particularly in the collection channel and transition pool segments. However, these areas represented the most common places where fish turned around during failed attempts at dam passage. Turn-arounds were observed in all segments of the fishways at each dam examined. These trends were consistent among years but varied slightly among dams.
Rates of fallback at dams varied among dams, with rates at The Dalles Dam being the highest (7.0 to 10.5% of the fish that passed). At Bonneville and McNary Dams in particular, fallback rates depended on the fishway used to pass the dam; the Oregon shore produced proportionally higher fallback rates compared to the Washington shore fishways. Fallback rates varied among years by a few percent at each dam.