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Pressure-sensitive radio transmitters were used to determine swimming depths of adult chinook salmon (Oncorhynchus tshawytscha) in relation to season and gas-supersaturated water in the lower Snake River, southeastern Washington. Thirty radio-tagged fish, 15 with external and 15 with internal transmitters, were monitored in supersaturated water in spring 1976. Nine fish with internal and 30 with external transmitters were monitored in the absence of supersaturation in fall 1976 and spring 1977 respectively.

Spring chinook salmon spent about 89% of their time below the critical supersaturation zone in 1976. Swimming depths of fall 1976 and spring 1977 chinook, migrating in normally saturated water, were shallower and differed significantly from those of fish migrating in supersaturated water in spring 1976.