Four species of fish were tested for tolerance to dissolved atmospheric gas supersaturation in 10-day bioassays. Based on median times to death at four levels of gas saturation, the fish displayed the following increasing order of tolerance: mountain whitefish (Prosopium williamsoni) < cutthroat trout (Salmo clarki) < largescale sucker (Catostomus machrocheilus) < torrent sculpin (Cottus rhotheus). Increasing hydrostatic pressure due to water depth reduced the levels of saturation of dissolved gases and increased survival. Torrent sculpins typically developed large bubbles of gas which caused them to float and would contribute indirectly to death.