Metabolic trait variation in Brown Trout
Metabolic rate defines the cost of living and is expected to be a trait of critical ecological relevance. However, despite its assumed importance, intraspecific variation in metabolic rate is widespread. The causes and consequences of this variation is not yet fully understood. I became particularly interested in metabolic variation during my PhD, when I started exploring the underlying/mechanistic drivers of life-history tactics in salmonids.
Using fish from different population backgrounds that were reared under experimental food reductions, I tested the role of instrinsic factors (population background, sex) and environmental factors (food availability) on metabolic traits of brown trout. I found that that fish experiencing low food enviroments tended to have lower standard metabolic rates (i.e., a lower baseline cost of living), suggesting a plastic response that reduced energy costs in inclement environments. I also detected population-level differences in metabolic traits that pointed towards some of the evolutionary drivers of metabolic variation. Read more about this study here.
To improve our understanding of species' responses to climate change, I also explored how metabolism is linked to performance in different warming scenarios. We used a long-term tank-rearing experiment with brown trout to explore how warming might affect the relationship between individuals' metabolism and growth rates. For fish in a natural thermal regime, baseline metabolism had positive effects on growth, but for those in a warm regime (simulating climate warming), we found the opposite relationship - relatively low metabolic rates were advantageous for growth. Overall, this research provided new evidence suggesting capacity to lower metabolism may allow energy-savings that can benefit growth in warmer environments. This study was the final chapter of my PhD, which has now been published here.