Northwest Fisheries Science Center

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Document Type: Contract Report
Center: NWFSC
Document ID: 5469
Title: Evaluation of the effects of dissolved gas supersaturation on fish and invertebrates in Priest Rapids Reservoir, and downstream from Bonneville and Ice Harbor Dams, 1995
Author/Editor: Boyd P. Shrank, Earl M. Dawley, Brad A. Ryan
Publication Year: 1997
Publisher: National Marine Fisheries Service
Contracting Agency: U.S. Army Corps of Engineers. Portland, Oregon
Contract Number: E96940029
Pages: 45
Date: 1997

The long-term goal of this study is to develop a multiparameter model relating dissolved gas supersaturation levels (related to water flow and spill volumes) to signs of gas bubble disease (GBD) and mortality in juvenile salmonids and other shallow-water organisms.  Using regression analysis, we will compare duration and concentration of exposure to ambient dissolved gas levels with signs of GBD and mortality in organisms sampled from the river and held in net-pens at the three river sections.  Overall, we observed low prevalence of GBD signs in fish sampled during this study.  However, because we did observe high prevalence of GBD signs in fish below Ice Harbor Dam when saturation levels exceeded 120%, we recommend GBD monitoring whenever DGS exceeds 120%.  The disparity between GBD signs in the river reach and the net-pen negated the use of mortality data from the net-pen as a direct index of mortality in the river, even in locations where DGS was highest.  Therefore, we recommend that alternate locations for holding experiments be explored.