A Remote Sensing / GIS-Based Approach to Identify, Characterize, and Model Spawning Habitat for Fall Chum Salmon in a Sub-Arctic, Glacially-Fed River

At northern extremes, fish habitat requirements are often linked to thermal preferences and the presence of overwintering habitat. The goal of this study was to identify spawning habitat for fall chum salmon Oncorhynchus keta and model habitat selection from spatial distributions of tagged individuals in the mainstem Tanana River, Alaska. We hypothesized that the presence of groundwater, which provides thermal refugia for overwinter incubation, would be most important for fall chum salmon. Models included braiding, sinuosity, open water surface area (indicating significant groundwater influence), and open water persistence (consistent presence of open water for a 12 year period according to satellite imagery). Candidate models containing open water persistence were selected as most likely. Persistent open water areas were further examined using forward-looking infrared (FLIR) imagery; marked differences between sites were observed in the extent of thermal influence by groundwater. Persistent open water sites with strong groundwater influence appear to serve as core areas for spawning salmon; the importance of stability through time suggests the legacy of successful reproductive effort in these areas for this homing species. This study indicates that not only the presence of groundwater is important for spawning chum, but its persistence and extent of groundwater influence.