Northwest Fisheries Science Center

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Document Type: Contract Report
Center: NWFSC
Document ID: 7259
Title: Evaluation of the fingerling bypass system outfalls at McNary and John Day Dams
Author/Editor: Carl W. Sims, Richard C. Johnsen
Publication Year: 1978
Publisher: National Marine Fisheries Service
Contracting Agency: U.S. Army Corps of Engineers. Walla Walla, Washington
Contract Number: DACW57-77-F-0148
Date: 1978

The location of fingerling bypass system outfalls in the tailrace areas below dams has a significant effect on the survival of juvenile salmonids.  Discharging fingerlings into areas of predator concentrations could result in greater mortality than passing fingerlings through turbines.  If we are to optimize juvenile salmonid passage at the dams on the Snake and Columbia Rivers, an assessment of fingerling mortality associated with existing bypass system outfalls is essential.  Research directed at this problem was initiated in 1976:  0–age chinook salmon were used to define mortality associated with both the north and south bypass outfalls at McNary Dam.  Results of the 1976 tests indicated that survival of test fish released into the north outfall at McNary Dam was significantly higher than for fish released into the south outfall.  In addition, survival at the north outfall was greater during the day than at night.  Research was continued in 1977.  Releases of yearling chinook salmon and steelhead trout were used to define mortality associated with the north outfall at McNary Dam, and with the single outfall at John Day Dam.