Aquatic resources - notably many fish species - are central to Inuit health, culture, and economic development. Understanding the environmental drivers of fish availability and quality in the context of a rapidly changing Arctic is essential to ensure their continued sustainability and availability. Our long-term (>15 years) research program in Cambridge Bay has documented spatial, temporal, and physiological aspects of habitat use and migrations of Arctic Char. We’ve used cutting-edge approaches, incorporating acoustic telemetry, genomics, ecological physiology, contaminant monitoring, and oceanography. Here, including field seasons in May and August, we aim to build upon these ongoing research efforts but also significantly extend the reach of our program by expanding acoustic tracking, physiological, and ecotoxicological investigations into several ecologically and culturally important fish species such as lake trout, cod (ogac) and sculpins (kanayok). Acoustic tracking will be used to monitor the movement, behaviour, and habitat use, and to identify critical habitats such as those used for spawning and overwintering in several species of importance. This method involves the implantation of small acoustic tags into the body cavity of the fish that can then be “heard” by acoustic receivers that will be deployed thought the marine and freshwater environments. Physiological measurements will be used to characterize the influence of temperature and oxygen changes (both seasonal and rapid changes) on the health and function of fishes. This work will involve measuring several parameters related to fish health such as heart function, metabolism, and energy balance. Acoustic tracking data will also provide information on temperatures experienced by fishes in the area which can be integrated with information regarding their physiology. Ecotoxicological work will be used to investigate the types and abundance of emerging contaminants, including plastics, ship- / oil-based pollution, and PFAS, in key habitats in the region in addition to the sources, fates, and transport of these contaminants. Aquatic passive samplers will be used to track sources and transport of these contaminants in the environment and biological sampling to track the fate and transport of contaminants through the ecosystem. These aquatic passive samplers compliment decades long aquatic passive sampler deployments in Nunavut through the AQUA-GAPS network and Environment and Climate Change Canada. Sampling of surface water, aquatic and thawed surface sediments, and Arctic char tissues will also be used to answer questions and concerns from the EHTO and community partners on the release of contaminants via permafrost thaw into critical fish and their habitats. Water samples will be obtained by filling 1L stainless steel, glass, and/or polyethylene water bottles (40L/year). Sediment samples will be taken by scooping sediment into 100-500ml whirl-pak bags and/or stainless steel/glass jars (20L/yr). By taking paired water and sediment samples, we will begin to understand the of contaminants that are entering critical fish habitats, and through contaminant pattern assessments begin to pin-point potential sources (e.g., permafrost thaw, wastewater effluent, shipping); thus, informing priority contaminants to monitor as the Arctic experiences rapid warming. Further, new collaborations will be built to explore the biological drivers of fish habitat quality in both freshwater and in the oceans. In lakes, we will explore how juvenile fish habitat use is linked to seasonal and diel patterns of plankton vertical migrations and abundance. Using our acoustic array in the marine environment, we will assess if kelp forests in the Cambridge Bay area are important marine summer feeding habitats for Arctic Char and other fish species. Finally, we will use environmental DNA (eDNA) methods to help characterize seasonal and spatial variation in the distribution and abundance of these fish species. Most work will be based out of the community of Cambridge Bay with personnel residing on site at the Canadian High Arctic Research Station (CHARS) except for two 5-10 day camps on the land per year. Camps will consist of 4 people with a total of 80-person camp days per year. The team has been working in close collaboration with the Ekaluktutiak Hunters & Trappers Organization (EHTO) for > 16 years and the board has provided support and will be a key partner on the project, assisting with sampling logistics (including the hiring of local experts) and in the organization of annual community outreach events. Overall, the proposed project will contribute significantly to our understanding of climate change impacts on fish and the fisheries they support. It will do so through extended long-term monitoring of contaminant trends, fish behavior and performance in relations with physicochemical habitats characteristics. Furthermore, by bridging data on lower food web and aquatic habitats, this project will also lay the foundations for an ecosystem-based management approach of culturally and economically important Arctic fish species.