Survival, development, and growth of Snake River fall Chinook salmon Embryos, Alevins, and Fry Exposed to Variable Thermal and Dissolved Oxygen Regimes
Fall Chinook salmon (Oncorhynchus tshawytscha) initiate spawning in the Hells Canyon reach of the Snake River, Idaho (rkm 240-397), at water temperatures above 16 C. This temperature exceeds the states of Idaho and Oregon water quality standards for salmonid spawning. These standards are consistent with results from studies of embryos exposed to a constant thermal regime, while salmon eggs in the natural environment are rarely exposed to a constant temperature regime. The objective of this study was to assess whether variable temperatures (i.e., declining after spawning) affected embryo survival, development, and growth of Snake River fall Chinook salmon alevins and fry. In 2003, fall Chinook salmon eggs were exposed to initial incubation temperatures ranging from 11-19 C in 2 C increments, and in 2004 eggs were exposed to initial temperatures of 13 C, 15 C, 16 C, 16.5 C, and 17 C. In both years, temperatures were adjusted downward approximately 0.2 C/day to mimic the thermal regime of the Snake River where these fish spawn. At 37-40 days post-fertilization, embryos were moved to a common exposure regime that followed the thermal profile of the Snake River through emergence. Mortality of fall Chinook salmon embryos increased markedly at initial incubation temperatures >17 C in both years. A logistic regression model estimated that a 50% reduction in survival from fertilization to emergence would occur at an initial incubation temperature of {approx}16 C. The laboratory results clearly showed a significant reduction in survival between 15 C and 17 C, which supported the model estimate. Results from 2004 showed a rapid decline in survival occurred between 16.5 C and 17 C, with no significant differences in survival at initial incubation temperatures <16.5 C. There were no significant differences across the range of initial temperature exposures for alevin and fry size at hatch and emergence. Differences in egg mass among females (notably 2003) most likely masked any size differences. Egg mass explained 86-98% of the variation of the size of alevins and fry at hatch and emergence. In 2003, maximum alevin wet weight increased as the initial temperatures increased, whereas the number of days it took to reach maximum wet weight decreased with increasing temperature. The number of days from fertilization to eyed egg, hatch, and emergence was highly related to temperature. Eggs exposed to initial temperatures of 13 C took 30-45 days longer to reach emergence than eggs initially exposed to 16.5 C. Overall, this study indicates that exposure to water temperatures up to 16.5 C will not have deleterious impacts on survival or growth from egg to emergence if temperatures decline at a rate of >0.2 C/day following spawning.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 896691
- Report Number(s):
- PNWD-SA-7223; TRN: US200703%%729
- Journal Information:
- Transactions of the American Fisheries Society, 135(6):1462-1477, Journal Name: Transactions of the American Fisheries Society, 135(6):1462-1477
- Country of Publication:
- United States
- Language:
- English
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