Investigating the movement, habitat selection and foraging ecology of broad whitefish (Coregonus nasus) in Colville Watershed, Alaska
Subsistence fisheries on the North Slope
provide an important ecosystem service in the form of a food resource for the majority of Arctic communities. Despite the historical importance of the summer broad whitefish subsistence fishery to Nuiqsut there has not been a comprehensive study conducted within the Colville Watershed to describe the basic ecology of broad whitefish. Here we are proposing to conduct research focused on the ecology of broad
whitefish in the Colville River Watershed to address three main questions: (1) What are the seasonal migration patterns and life history variations present for populations? (2) Where are critical freshwater habitats located and what local and landscape attributes are associated with each habitat type? (3) Does foraging ecology change across life stages and are marine food-resources important? We are targeting migratory populations in summer and winter riverine habitat, sampling diet, muscle tissue, and otoliths, and will use radio tags to determine seasonal movements among habitat types. Climate change and petroleum development are expected to alter freshwater habitats, and understanding how fish seasonally utilize habitat and the attributes associated with important habitat types is critical to better understand associated impacts to the subsistence resources in the Colville Watershed, on the Arctic Coastal Plain.
Landscape controls on winter dissolved oxygen concentrations in Arctic lakes
Winter habitat is a limiting factor for fish in the Arctic coastal plain. Most ponds and lakes freeze up to 2m thick during the extended winter which creates a gridlock for aquatic species and greatly limits where fish can overwinter. In order to adapt to harsh conditions many fish make large seasonal migrations to adequate overwintering locations after feeding in productive summer locations. While numerous other variables are important for the quality of overwintering habitat, adequate dissolved oxygen (DO) concentrations is the most important water quality parameter and if concentrations are reduced it can negatively impact fish. DO concentrations are influenced by a variety of complex physical, biologic and chemical processes, but little is know about how geomorphic lake attributes influence concentrations. I am currently collaborating with researchers at UAF and the BLM to explore the geomorphic landscape controls on winter dissolved oxygen concentrations for lakes in the Arctic coastal plain, Alaska.
Limited information is known about winter dissolved oxygen concentrations in lakes across the NPR-A due to the difficulty of conducting research during the winter. Chironomids (midges) are well suited as an indicator for dissolved oxygen due to their wide distribution and unique limnological condition requirements that reflect lake conditions over the midge life cycle. Further, when midges complete their life cycle, typically 1 year or more, their head capsules are preserved in lake sediments providing a detailed environmental record of lake conditions. Using midge assemblages and subfossils as an indicator for winter DO conditions offers a potential solution to understand where low winter DO conditions exist in fish overwintering habitat without physically sampling under lake ice. Midge-based inference models have been used to reconstruct duration of hypoxia in lakes estimate average hypolimnetic oxygen concentration and predict volume weighted average hypolimnetic oxygen concentration. I am currently collaborating with scientists at the University of Alaska Anchorage to explore the feasibility of using lake midge assemblages within a quantitative transfer function model to understand the distribution of hypoxic (low oxygen) overwintering fish habitat in the Arctic coastal plain.
Linking climate change projections for an Alaskan watershed to future coho salmon production
Climate change is predicted to dramatically change hydrologic processes across Alaska, but estimates of how these impacts will influence specific watersheds and aquatic species are lacking. We linked climate, hydrology, and habitat models within a coho salmon (Oncorhynchus kisutch) population model to assess how projected climate change could affect survival at each freshwater life stage and, in turn, production of coho salmon smolts in three subwatersheds of the Chuitna (Chuit) River watershed, Alaska. Based on future climate scenarios and projections from a 3-dimensional hydrology model, we simulated coho smolt production over a 20-year span at the end of the century (2080-2100). The direction (i.e., positive vs. negative) and magnitude of changes in smolt production varied substantially by climate scenario and subwatershed. Projected smolt production decreased in all three subwatersheds under the minimum air temperature and maximum precipitation scenario due to elevated peak flows and a resulting 98% reduction in egg-to-fry survival. In contrast, the maximum air temperature and minimum precipitation scenario led to an increase in smolt production in all three subwatersheds through an increase in fry survival. Other climate change scenarios led to mixed responses, with projected smolt production increasing and decreasing in different subwatersheds. Our analysis highlights the complexity inherent in predicting climate-change-related impacts to salmon populations and demonstrates that population effects may depend on interactions between the relative magnitude of hydrologic and thermal changes and their interactions with features of the local habitat.