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UBC Theses and Dissertations

Thermal acclimation potential of Australian rainbow trout, Oncorhynchus mykiss Adams, Olivia


With impending global warming predictions, surviving animals will need to either escape increasing temperatures in their current biogeography, acclimate or adapt. As temperature increases above the optimal range of an animal, physiological performance is negatively affected, which results in decreased growth, feeding, reproduction and aerobic scope. My thesis studied a hatchery-raised strain of rainbow trout (Oncorhynchus mykiss, H-strain) previously selected for upper thermal tolerance at the Pemberton Freshwater Research Centre (PFRC) in Australia to understand their acclimation potential. This H-strain of rainbow trout was acclimated to six experimental temperatures (15, 17, 19, 21, 23, 25˚C) for over one month before performing a range of tests at each acclimation temperature that determined the optimal temperatures, or acclimation potential, for growth, digestibility (specific dynamic action; SDA), feed conversion (feed conversion ratio; FCR), aerobic performance and the response of maximum heart rate (fHmax) to acute warming. Intermittent-flow respirometry was used to determine respiratory oxygen uptake for analysis of SDA, standard metabolic rate (SMR), maximum oxygen uptake (ṀO₂max), excess-post exercise oxygen consumption (EPOC) and hypoxia tolerance (ILOS). Growth, feed efficiency, SDA duration and fHmax had acclimation potential up to 23˚C. ṀO₂max was also maintained up to 23˚C, while SMR followed a typical exponential increase; the calculated difference between ṀO₂max and SMR is absolute aerobic scope (AAS), which had an acclimation potential up to 21˚C. With acute warming, the critical thermal maximum (CTmax) plateaued at an acclimation temperature of 23˚C (reaching 31.2˚C), and the temperature of fHmax and arrhythmia had acclimation potential up to 23˚C. This integrative approach in assessing physiological performance illustrates that this warm-tolerant strain of rainbow trout has a broad thermal range for performance and a large-scale consideration of the thermal tolerance of other strains of rainbow trout is warranted given that rainbow trout are typically considered a cold-water species.

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