The effects of semi-chronic thermal stress on physiological indicators in steelhead Oncorhynchus mykiss Public Deposited

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  • The Effects of Semichronic Thermal Stress on Physiological Indicators in Steelhead
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  • The physiological response of juvenile steelhead (Oncorhynchus mykiss) to prolonged heat stress was examined by exposing replicated groups of fish to 25 consecutive days at 15°C, 23°C, and 25°C followed by a 55 day recovery period at 15°C. We found that at temperatures ≥25°C, steelhead consumed significantly less food per day and had elevated feed conversion rates but experienced slower growth, reduced body size, lower body fat, and elevated heat shock protein 70 (hsp 70) levels relative to fish 2°C and 10°C cooler. Growth decreased 24.4% and 27.1% for length and mass, respectively, between 15°C and 23°C, and an additional 60% and 56.5% between 23°C and 25°C during exposures. While growth increments and lipid levels recovered to control levels after water temperature was reduced, body size of the 25°C exposed fish lagged throughout the experiment. Our results indicate a temperature threshold after which steelhead exposed to semi-chronic thermal stress incur a physiological debt. Heat shock protein 70 levels were detectable up to 25 days post-stress in fin and liver tissues, providing evidence that this is a useful metric for thermal stress that can be assessed non-lethally, an important technique relevant for monitoring thermal-habitat restoration efforts for threatened and endangered salmonids.
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  • Kammerer, B. D., & Heppell, S. A. (2013). The effects of semichronic thermal stress on physiological indicators in steelhead. Transactions of the American Fisheries Society, 142(5), 1299-1307. doi:10.1080/00028487.2013.806349
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