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UBC Theses and Dissertations

Variation in metabolic rate between individuals and species : cryptic physiological tradeoffs underlying habitat partitioning and life history strategies of juvenile salmonids Van Leeuwen, Travis Edward


Physiological traits such as standard metabolic rate have been shown to vary up to half an order of magnitude between individuals and species and influence key life history tradeoffs in juvenile salmonids (e.g. smolt timing). The purpose of my thesis research was to examine the relationship between food consumption, dominance and disproportionate feeding on physiological traits and adaptive strategies of juvenile salmonids. Results show that SMR is positively correlated with food consumption and growth in juvenile coho salmon which showed a reduction in SMR under low food and an elevation in SMR under high food (Chapter 2). Comparisons between hatchery and wild juvenile steelhead and coho salmon revealed no difference in Stnadard metabolic rate between wild coho and wild steelhead but a significant difference in the hatchery fish, with hatchery steelhead being higher. In both wild and hatchery populations I found a marked difference in maximal metabolic rate between steelhead and coho, leading to a greater aerobic scope and swim performance in wild steelhead but no difference in the hatchery fish. This result is consistent with a steelhead energy maximizing strategy, habitat partitioning and trade-offs between elevated SMR at higher growth and decreased swim performance. Interestingly, wild steelhead with higher maximum growth, swim performance, and maximum food consumption do not appear to tradeoff increased growth against lower swim performance, as commonly observed for high growth strains. Instead steelhead appear to be trading off higher growth for lower food consumption efficiency; highlighting potential differences in food consumption and digestion strategies as cryptic adaptations that have received little attention. In experiments conducted in semi-natural stream channels, I found that dominant coho salmon were able to achieve higher absolute growth rates compared to smaller subordinates, at high food ration but suffered significantly lower absolute growth at low food ration as larger dominant fish approached the capacity of their habitat (Chapter 4). Overall I demonstrated that the relationship between physiological traits, life history strategy and dominance rank depended on per capita food consumption rates, habitat characteristics (pools vs riffles) and the absolute size of individuals in a dominance hierarchy.

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