Abstract
Very little is known about the vertical distribution of downstream-migrating juvenile Pacific salmon Oncorhynchus spp. in large rivers. This knowledge is important for understanding the potential interactions of fishes with in-river hydrokinetic devices, which harness a river's energy by spinning a turbine to produce electrical current without damming or impounding water. Currently, development projects for hydrokinetic devices are being considered in several rural Alaskan communities, including the Tanana River, near Nenana, AK. Therefore, the goal of this study was to determine the vertical distribution of juvenile Chinook salmon Oncorhynchus tshawytscha, coho salmon Oncorhynchus kisutch, and chum salmon Oncorhynchus keta, in the Tanana River, at a site (bottom depth ~8, channel width ~150 m) where future hydrokinetic turbines may be deployed. Using a suspended wing-less fyke net system during diurnal periods (0800-1800), juveniles of all three species were found at all depths of the water column and no significant differences in catch-per-unit-effort among four depth categories (surface, mid-water, deep water, bottom water) were found. The occurrence of juvenile salmon throughout the water column indicates that they may interact with hydrokinetic devices, regardless of the depth at which they are deployed. Future research should more comprehensively characterize fish distribution patterns and describe the outcomes of fish/turbine interactions to inform practices aimed at reducing potentially deleterious impacts of hydrokinetic devices on juvenile Pacific salmon.