Northwest Fisheries Science Center

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Document Type: Contract Report
Center: NWFSC
Document ID: 6560
Title: Biological design criteria for fish passage facilities: high-velocity flume development and improved wet-separator efficiency, McNary Dam 1999
Author/Editor: R. Lynn McComas, Benjamin P. Sandford, C. D. Magie, John W. Ferguson
Publication Year: 2003
Publisher: National Marine Fisheries Service
Contracting Agency: U.S. Army Corps of Engineers. Walla Walla, Washington
Delivery Order: E86910060
Pages: 73
Date: 10/01/2003

We evaluated the influence of physical mechanisms for inducing volitional size–separation in salmonid smolts using a prototype high–velocity flume (HVF) wet separator at Ice Harbor Dam.  Prior to use, the prototype was evaluated for fish safety (using hatchery smolts as test fish), and structural parameters were established which would result in the hydraulic conditions for comparison treatments (i.e., valve settings, flume slopes, and false-floor elevations).  No test fish were injured during passage through the prototype HVF over four replicate releases.  However, several areas of concern were found with fish-handling portions of the flume.  These problems were corrected prior to the juvenile migration of spring 1999.  Three treatment factors were used in different combinations for a total of eight treatments.  The three treatment factors were separation-bar style (pedestal and non-pedestal), water velocity (1 and 2 m/s), and separation-bar depth (50 and 100 mm).  Effects of the eight treatments on separation efficiency, separator exit efficiency, and fish condition were evaluated using river-run juvenile salmonids over their migration period.  Fish were separated into small-fish (< 180 mm fork length) and large-fish (≥ 180 mm FL) groups by using a separation-bar spacing of 17 mm.

Twelve replicates were completed for each of the eight treatments, and results were analyzed using a block experimental design.  For the total catch (all salmonids combined), there was no significant interaction among conditions for separation efficiency.  Total catch separation efficiency was highest (78.3%) using pedestal separation bars, a water velocity of 2 m/s, and a depth of 50 mm.  Separator exit efficiency was over 90% for all treatments and size groups.  For the total catch, mean descaling values ranged from 2.7 to 4.1% for all combinations of separation-bar style and depth.  Descaling was higher with water velocity at 2 m/s (3.9%) than at 1 m/s (3.0%).