The Arctic is rapidly changing. Warming temperatures are both facilitating new opportunities and threatening biodiversity. Despite a global effort to conserve biodiversity, and the recent acceleration of related conservation initiatives in Canada, species are already responding to a changing Arctic. However, our abilities to assess these changes, including shifting distributions and their impacts, are limited. Therefore, innovative approaches are necessary to focus the vastness of the Arctic to key habitats, the breadth of species diversity to key indicators of change, and to integrate knowledge in order to predict and manage a future Arctic. In this thesis, I establish Pacific salmon Oncorhynchus spp. as indicators of ecosystem-level change in the Canadian Arctic. More broadly, however, I have developed tools and strategies to help assess the impending biodiversity crisis in the Arctic. I developed a novel model to successfully apply citizen science to monitor rapidly shifting biodiversity in the Canadian Arctic and I extend the breadth of community-based monitoring across species and their habitats to encompass broad-scale areas and fine-scale assessments. By aligning thermal tolerances with thermal regimes at critical groundwater spring oases, I developed a novel model that predicts watersheds vulnerable to colonizations by salmon, and identifies the associated risk of competition with native char. I also use genetic tools to establish that chum salmon O. keta colonized the upper Mackenzie River at deglaciation, and that vagrants are currently accessing the Mackenzie River via coastal pathways. Together, I advance science regarding: 1) the application of citizen science to monitor biodiversity shifts in the Arctic; 2) predictions of distributional shifts to extreme environments; and 3) assessing the viability of the Arctic freshwater and marine environments as fish habitat over the past several thousand years. By integrating the subsistence way-of-life with scientific approaches, we can better manage the development opportunities and predict the conservation impacts in a future Arctic.