Acquisition of environmental O₂ and its delivery throughout the body is essential for vertebrates and dictates habitat, life style, variation in anatomical form and function and even survival. Triploid (3N) rainbow trout (Oncorhynchus mykiss), which are important to the $0.5 billion British Columbia sport fishing industry, provide an informative model organism to study corporeal O₂ supply limitations and associated effects on survival in the wild. Triploid O₂ supply limitations likely stem from enlarged cells and contribute to poor 3N tolerance of sub-optimal conditions, which, in turn, may lead to high 3N population-level mortality rates in nature.
Therefore, in order to test the hypotheses that corporeal O₂ supply limits aerobic performance of 3N rainbow trout and that aerobic performance, in turn, limits survival in the wild, I compared the cardiorespiratory physiology of diploid (2N) and 3N Blackwater River rainbow trout facing a high temperature challenge in the lab and survival in the wild. I then investigated the potential of a 3N cardiac O₂ supply deficiency, using a modified Krogh diffusion model, and discussed its significance to temperature tolerance, endurance swimming and survival in the wild.
Both of my hypotheses were supported. A slower increase in 3N heart rate with warming suggested reduced O₂ convection through the body of 3N fish at high temperatures. Relating these results and endurance swimming rank with survival and habitat utilization in lakes revealed thermal tolerance and aerobic capacity as important variables influencing lake survival. The Krogh model showed 3N relative to 2N cardiac O₂ supply limitations that were primarily driven by reduced 3N arterial O₂ content, which I showed not to be caused by reduced 3N haemoglobin - O₂ affinity. In supporting the 2 main hypotheses of my thesis, this theoretically predicted 3N cardiac O₂ supply deficiency may explain reduced 3N aerobic swimming capacity and heart rate response to warming.
Thus, my findings are consistent with corporeal O₂ supply limitations to high temperature tolerance and aerobic swimming capacity of 3N rainbow trout, both of which can limit survival in the wild, depending on the biotic and abiotic conditions and physiological state of the organism.Science, Faculty ofZoology, Department ofGraduat
