| Summary: | This thesis applies food web modelling to increase our understanding of how the interaction of climate change and exploitation have historically altered, and continue to alter, marine polar ecosystems. Understanding stressors responsible for ecosystem level changes is important not only to the people and industries reliant on the resources, but for managers to make future decisions on resource uses. The first two chapters develop models of Hudson Bay (Arctic) and Antarctic Peninsula (Antarctic) marine ecosystems, focused on re-creating changes in the past 30 years. Both ecosystems have undergone changes due to environmental factors, which are incorporated into the models. While the Hudson Bay model exhibits a shift from benthic to pelagic species, the Antarctic Peninsula model is identified to have more uniform declines across all species, as the main trophic link in the ecosystem, Antarctic krill declines. Model simulations are continued in the next two chapters, whereby future environmental changes are tested in conjunction with multiple exploitation levels. For Hudson Bay, continued harvest of marine mammals at current conditions results in large-scale declines for some species (narwhal, eastern Hudson Bay beluga, polar bears, and walrus), indicating current harvest levels are too high to sustain long term. Further shifts from benthic to pelagic species in the lower trophic levels favor fish species such as capelin and sandlance. Future simulations of the Antarctic Peninsula identify large reductions in ecosystem biomass of all species due changes in environmental conditions and an overall reduction in krill, with minimal ecosystem impacts from harvest. In the last chapter, an economic model is constructed to assess the use value of hunting narwhal and beluga in the Hudson Bay region. The economic impact to northern residents is considered as future model simulations of Hudson Bay reveal that these species may be susceptible to population declines, and issues of food security are becoming increasingly important. Economic analysis reveals the motivation to hunt in Hudson Bay may not be economically-driven, there are substantial benefits derived by northern communities through narwhal and beluga hunts. Results for each ecosystem are discussed as they pertain to future research and management of each ecosystem. Science, Faculty of Resources, Environment and Sustainability (IRES), Institute for Graduate
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