Four stocks of cutthroat trout (Oncorhynchus clarki) were exposed to high temperature, high salinity, and low dissolved oxygen to determine inherent differences. The fish tested included 2 stocks of Bonneville cutthroat trout (O. c. utah), a lacustrine stock derived from Bear Lake and a fluvial-origin stock from southern Utah (Manning Meadow Reservoir). The other 2 stocks tested were from Electric Lake (largely Yellowstone cutthroat trout, O. c. bouvieri) and Jackson Hole, Wyoming (fine-spotted Snake River cutthroat trout, O. c. subsp.). Temperature tests were either critical thermal maximum (CTM) or 96-hour trials using juveniles acclimated between 12.5 °C and 18.0 °C. Two CTM end points were temperature at first loss of equilibrium (CTMeq) and onset of spasms (CTMs). There were no significant differences in CTMeq among test fish acclimated to 18.0 °C, but CTMs was significantly higher for Bear Lake Bonneville (30.0 °C) than for Snake River (29.6 °C) or southern Bonneville (29.7 °C) stocks. With fish acclimated at 13.0 °C, there were no significant differences among the stocks in CTMeq or CTMs. Differences among stocks varied significantly among nine 96-hour tests. Overall, it appeared that the southern Bonneville stock had slightly better survival at warmer temperatures than other stocks. In 24-hour survival tests at high salinities, the Snake River stock had the lowest tolerance, with significant mortality occuring at 18% (29.5 mS · cm−1 conductivity). The southern Bonneville stock had the highest tolerance, with no mortality until 22% (38 mS · cm−1). Bear Lake Bonneville and Electric Lake stocks had 60% and 30% mortality, respectively, at 21% (36 mS · cm−1). Hypoxia tolerance measured by resistance time, 24-hour mortality, or probit analysis (LEC50) did not differ among stocks. The 24-hour LEC50 was 2.34 mg O2 · L−1 for all stocks combined.
Wagner, Eric J.; Arndt, Ronney E.; and Brough, Mark
"Comparative tolerance of four stocks of cuttthroat trout to extremes in temperature, salinity, and hypoxia,"
Western North American Naturalist: Vol. 61
, Article 7.
Available at: http://scholarsarchive.byu.edu/wnan/vol61/iss4/7