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Physiological basis of growth-performance trade-offs : insights from different strains of rainbow trout Allen, David William


Growth rate is a fundamental life history trait common to all taxa. Despite its importance, the underlying physiological mechanisms and constraints associated with growth remain poorly understood. The purpose of my research was to explore the physiological correlates and trade-offs associated with high growth. I examined a suite of physiological variables related to growth including metabolic rate, digestive capacity, and tissue energy content. Three strains of juvenile rainbow trout (Oncorhynchus mykiss) were chosen based on known differences in ecology and growth. Fish from each strain were assigned to one of three food ration treatments: (i) satiation over eight hours every day, (ii) fed 1% of body mass over eight hours every day, and (iii) complete deprivation of food. A wide range of growth rates were observed within and across all strains. I found that fast growing rainbow trout (hatchery strain) had higher standard metabolic rates and lower maximum metabolic rates and aerobic scopes, suggesting that high growth rate results in a reduced capacity to do metabolic work. I also found that trout with high growth rates, generally, had larger gastrointestinal tracts, higher maximum food consumption rate, and higher growth efficiency. Lipid content and water content had opposing correlations with growth rate; larger individuals with higher growth rates had a higher body lipid content, while water content was highest amongst smaller individuals. I show that there is a suite of physiological traits that correlate with growth rate, that these traits are affected by both genotype (strain) and environment (food ration), and that these traits appear to be consistently traded off against other correlates of performance.

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Attribution-NonCommercial-NoDerivs 2.5 Canada