|Document Type:||Contract Report|
|Title:||Studies to evaluate the effectiveness of extended-length screens at John Day Dam, 1996|
|Author/Editor:||Dean A. Brege, R. F. Absolon, Benjamin P. Sandford, Douglas B. Dey|
|Publisher:||National Marine Fisheries Service|
|Contracting Agency:||U.S. Army Corps of Engineers. Portland, Oregon|
During the juvenile salmon migrations of spring and summer 1996, we conducted fish guidance efficiency tests using fyke nets, descaling evaluations, and orifice passage efficiency tests using a mark and release method at John Day Dam. Fish guidance efficiency, descaling, and orifice passage efficiency tests were conducted in the B slot of Turbine Unit 7, which was equipped with an extended-length submersible bar screen (ESBS) and inlet flow vane. Descaling and orifice passage efficiency tests were also conducted in the B slot of Turbine Unit 6, which was equipped with a standard-length submersible traveling screen (STS). In addition, dip-basket efficiency and gatewell-mortality tests were conducted.
For spring tests, fish guidance efficiencies were 84.0% (95% CI ±1.6%) for yearling Chinook salmon, 94.1% (±1.8%) for steelhead, 94.8% (± 2.6%) for coho salmon, and 78.9% (±3.8%) for sockeye salmon.
Descaling was quite low throughout the spring season. Yearling Chinook salmon descaling was 0.4% for the ESBS and 0.8% for the STS. Mean orifice passage efficiencies for yearling Chinook salmon were 98.7 and 80.5% with the ESBS and STS, respectively. The difference in orifice passage efficiency between the ESBS and STS slots was statistically significant, at 18.2% (±5.0%; P <0.05).
In summer tests, mean fish guidance efficiency for subyearling Chinook salmon was 60.2% (95% CI ± 6.3). Other salmonid species were not present in large enough numbers during the summer tests for statistical analysis.
Descaling was also quite low throughout the summer season. Subyearling Chinook salmon descaling was 0.4 and 1.2% for the ESBS and STS, respectively. Mean orifice passage efficiency for subyearling Chinook salmon was 97.1 and 97.5% with the ESBS and STS, respectively. The difference in orifice passage efficiency between the ESBS slot and the STS slot was -0.4% (±2.6) and was not statistically significant.
A recapture efficiency and mortality test on 1 June in Slot 6B with yearling Chinook salmon resulted in a recapture efficiency of 100%. Another recapture efficiency/mortality test on 3 July in Slot 7B with subyearling Chinook salmon resulted in a recapture efficiency of 99%. Marked fish were recovered in nearly the same condition as when they were released. Descaling and mortality due to handling were minimal.