Causes and consequences of the trade-off between compensatory growth and swim performance in teleost fish

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For many animal species, bigger is better. Larger body size reduces the risk of being consumed by predators, and can also lead to an increase in the number of offspring that an animal is able to produce. Despite these apparent benefits of increased body size, mounting evidence suggests that most organisms do not grow at the maximum rates that are physiologically possible, and that there may actually be significant costs associated with rapid growth. Compensatory growth (the rapid growth which occurs in many organisms after a period of food deprivation) provides a useful means to study these potential costs, and in fish, individuals that have undergone a period of growth compensation tend to display reduced swimming performance later in life. While such a cost could have an important influence on both survival and reproductive success, the underlying mechanism responsible for this trade-off between compensatory growth and impaired swimming ability is not understood. There is also nothing known about individual variation in the compensatory growth response in fishes, and the extent to which the costs may differ between individuals. Overall, our lack of knowledge makes it impossible to accurately predict the consequences of compensatory growth for the survival and reproductive success of individual fish, and its effects on the dynamics of wild fish populations. Such information would be valuable, especially considering the increased likelihood of fluctuations in food availability due to factors such as climate change. The proposed research will examine muscle fibre structure, biochemistry, metabolism, and swim performance in individual fish to gain insights into the mechanisms responsible for the trade-off between growth rate and swim performance. Additional laboratory studies will be performed to examine the influence of predator presence on individual variation in the growth response, and also to study the consequences of compensatory growth for individual risk-taking behaviour and reproductive success. Finally, theoretical studies utilizing individual-based mathematical models will compliment these laboratory experiments by incorporating empirically-derived estimates of variability to investigate the implications of variation in growth rate for individual fitness. Overall, this interdisciplinary study will allow us to better understand the mechanistic underpinnings of the costs of rapid growth in fish, and also the consequences of this trade-off for behavioural and evolutionary ecology.