Northwest Fisheries Science Center

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Document Type: Chapter or Section
Center: NWFSC
Document ID: 7756
Type of Book: Technical
Section or Chapter Title: Some effects of excess dissolved gas on squawfish, Ptychocheilus oregonensis (Richardson)
Book Title: Gas bubble disease:  proceedings of a workshop, 8-9 October 1974. Richland, Washington
Author: Wallace W. Bentley, Earl M. Dawley, Timothy W. Newcomb
Editor: Duane H. Fickeisen, Mark Joseph Schneider (Eds.)
Publication Year: 1976
Publisher: Energy Research and Development Administration, Technical Information Center. Oak Ridge, Tennessee
Pages: 41-46

In the spring of 1974, large numbers of squawfish were encountered in the Snake River between Lower Monumental and Little Goose Dams.  Squawfish exhibited gas bubble disease symptoms within 1 week after the onset of 125 to 135% saturation.  A 12-d bioassay in shallow tanks to determine tolerance levels and resistance times at various gas concentrations was conducted.  We found squawfish to be similar to juvenile salmon and steelhead trout in their resistance to supersaturated concentrations of dissolved gas.  Feeding response changed after stress to high concentrations of dissolved gas.  Average daily food consumption of test groups decreased with increased supersaturation.  Squawfish captured in the field during periods of high supersaturation were less abundant, and only a small portion of them had been feeding compared with survey results taken during lower supersaturation.  Nitrogen supersaturation could be an important factor in assessing the effects of predation on juvenile salmonid migrants in the Columbia River system.