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Hydroacoustic Evaluation of Juvenile Salmonid Behavior at Cougar Dam, 2010
Ida Royer
,
Ecology Group, Pacific Northwest National Laboratory, North Bonneville, WA
Fenton Khan
,
Ecology Group, Pacific Northwest National Laboratory, Richland, WA
Gary E. Johnson
,
Marine Sciences Laboratory, Pacific Northwest National Laboratory, Portland, OR
Gene R. Ploskey
,
Ecology Group, Pacific Northwest National Laboratory/Battelle, North Bonneville, WA
We evaluated juvenile salmonid behavior at Cougar Dam on the McKenzie River, Oregon during 2010. The study was conducted by the Pacific Northwest National Laboratory for the U.S. Army Corps of Engineers, Portland District (USACOE). The goal of this study was to provide information on fish behavior at the dam to support decisions on long-term measures and operations to enhance dam passage conditions. An understanding of juvenile salmonid behavior as they pass through the dams and the size distribution of fish that are passing will be important components for developing operations and structures that pass fish safely and efficiently. The study period was from February 1, 2010 to February 15, 2011. The objective was to examine fish behavior and movement patterns in the nearfield (<20 m) forebay of the Water Temperature Control Tower intakes of the dam. We used a Dual Frequency Identification Sonar (DIDSON) acoustic camera to obtain fish behavior data. The DIDSON was deployed on a barge at the tower and aimed across the tower intakes. Data were collected 24hr/d, 7d/wk for the course of the study period. The data was sub-sampled bi-weekly (24h/d) for analysis. To date we have analyzed data through December.
A total of 24 days of data were processed yielding 1,277 events (an event is when a fish or group of fish enter and exit the sample volume). Fish abundance peaked mid-May with 6,036 fish in one 24-hour period (~145 mm FL). Fish counts decreased to 15 fish (~200 mm) mid-July before a smaller, secondary peak in mid-October (356 fish; ~155 mm). Predator activity was correlated to fish abundance and accordingly peaked mid-May with 12 predator events. Milling was the most common fish behavior. Traversing in front of the tower was the second most common behavior. East-to-west and west-to-east movements were more common in spring and fall. From March through November, passage into the tower was low (≤20%, one outlier) and balanced by fish exiting the tower, suggesting low passage numbers for fish entering the tower from the surface. In December more fish (~15%) entered the tower than exited.
