Comparative tolerance of four stocks of cuttthroat trout to extremes in temperature, salinity, and hypoxia

Authors

Eric J. Wagner, Fisheries Experiment Station, Utah Division of Wildlife Resources, Logan, Utah
Ronney E. Arndt, Fisheries Experiment Station, Utah Division of Wildlife Resources, Logan, Utah
Mark Brough, Fisheries Experiment Station, Utah Division of Wildlife Resources, Logan, Utah

Abstract

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 (CTM_eq) and onset of spasms (CTM_s). There were no significant differences in CTM_eq among test fish acclimated to 18.0 °C, but CTM_s 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 CTM_eq or CTM_s. 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.

Recommended Citation

Wagner, Eric J.; Arndt, Ronney E.; and Brough, Mark (2001) "Comparative tolerance of four stocks of cuttthroat trout to extremes in temperature, salinity, and hypoxia," Western North American Naturalist: Vol. 61: No. 4, Article 7.
Available at: https://scholarsarchive.byu.edu/wnan/vol61/iss4/7