Research Documents the Influence of Water Temperature on Life Histories of Rainbow Trout and Steelheads
Water temperature influences a variety of behavioral and physiological processes in salmonids. For species like Oncorhynchus mykiss that can be either anadromous (steelhead) or a fresh water resident (rainbow trout), understanding the influence of temperature on life-history expression is critical for their management. Increases in temperature elevate the energy needed for survival and, thus, may reduce energy available for growth and maturation. Researchers found that for O. mykiss reared under contrasting temperature regimes, warmer water temperatures reduced rates of freshwater maturation and increased anadromy. Females were more likely than males to become anadromous, regardless of rearing temperature, a pattern that mirrors findings from populations throughout the west coast of North America. Individual variation in metabolism also influenced life histories: females with relatively fast metabolic rates had an increased probability of becoming anadromous. These results indicate that a combination of sex, metabolic rate, and water temperature are important determinants of salmonid life histories. These studies reveal a suite of processes influencing life-history expression in salmonids. The results will inform conservation and recovery programs for steelhead populations listed under the Endangered Species Act. The influence of temperature on O. mykiss life histories had not been documented previously and, thus, these results will be crucial for anticipating the effects of climate change.
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