Population dynamics in fishes: recruitment processes, environmental variation, adaptation and harvest

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The abundance of fish populations is highly variable, whether comparing across water bodies or within a single water body over time. The goal of my research program is to understand the degree to which environmental characteristics and harvest control these variable populations. It appears as if the majority of this variability originates from variation in fish growth and survival during their first year of life. I am therefore studying how the behaviour and physiology of young fish impacts their early success in terms of growth, energy storage and survival. Young fish face many challenges in that they are very susceptible to predators and to starvation during their first winter if they have not stored sufficient energy to survive a period with little prey available. I study how young fish trade-off time spent foraging, which makes them susceptible to predators, with the energetic constraints of sufficient energy storage for winter survival. By contrasting how fish make this trade-off in different environments we are learning the importance of these processes to survival and of adaptation of fish to their home environments. In addition we are interested how resilient fish populations are to harvesting and how the production of young fish is curtailed as we overharvest fish populations. Our general approach to this work is to use a combination of field experiments, observations and models to assess the contribution of environmental variability and harvest to fish population viability. Experiments in lakes which vary in environmental conditions and within which we can manipulate prey and predator density and harvest rate provide the contrasts necessary to assess the contribution of these factors to fish population variability. This fundamental biological research has important implications to issues such as impacts of climate change and harvest on the long-term sustainability of fishes.