Characterizing the Juvenile Fish Community in Turbid Alaskan Rivers to Assess Potential Interactions with Hydrokinetic Devices

Installation of hydrokinetic power-generating devices is currently being considered for the Yukon and Tanana rivers, two large and glacially turbid rivers in Alaska. We sampled downstream-migrating fish along the margins of both rivers, a middle island in the Yukon River, and mid-channel in the Tanana River in order to assess the temporal and spatial patterns of movement by resident and anadromous fishes and hence the potential for fish interactions with hydrokinetic devices. Results suggest that (1) river margins in the Yukon and Tanana rivers are primarily utilized by resident freshwater species, (2) the mid-channel is utilized by Pacific salmon Oncorhynchus spp. smolts, and (3) only Chum Salmon O. keta smolts utilize both river margin and mid-channel areas. Some species exhibited distinct peaks and trends in downstream migration timing, including Longnose Suckers Catostomus catostomus, whitefishes (Coregoninae), Arctic Grayling Thymallus arcticus, Lake Chub Couesius plumbeus, Chinook Salmon O. tshawytscha, Coho Salmon O. kisutch, and Chum Salmon. Due to their downstream migration behavior, Pacific salmon smolts out-migrating in May–July will have the greatest potential for interactions with hydrokinetic devices installed in mid-channel surface waters of the Yukon and Tanana rivers. Feasibility and development projects for hydrokinetic devices, which utilize kinetic energy from water to turn a turbine that generates electricity, are being conducted for some rural communities in Alaska to reduce some of the energy demand on diesel generators (Seitz et al. 2011). One of these projects was located on the Yukon River at Eagle, Alaska (Figure 1), where a 25-kW, surface-mounted hydrokinetic device was installed in summer 2010. The turbine was suspended from a pontoon barge in the mid-channel, had a cross section of 2.4-m depth £ 4.9-m width, was positioned approximately 0.3 m below the river’s surface, and spun at a maximum rate of 22 revolutions/min. Another proprietary project to install a surface-mounted hydrokinetic device in the mid-channel of the Tanana River near Nenana, Alaska (Figure 1), is actively being developed (Seitz et al. 2011). Impacts of hydrokinetic devices on fishes are poorly understood, especially in large, turbid systems like the Yukon and Tanana rivers, both of which are glacially influenced (Seitz et al. 2011). In a natural environment, in order for any impacts on fish to occur, there must first be an interaction between the hydrokinetic device and the fish. To assess the potential for such an interaction in river systems like the Yukon and Tanana rivers, it is necessary to understand the species composition and relative abundance of the fish community as well as the spatial and temporal patterns of fish distribution in the river channel. Spatial and temporal patterns of downstream migration by juvenile fish are often species specific and variable among river systems (Achord et al. 2007). For example, juveniles of some species have higher relative abundances near the bottom *Corresponding author: [email protected] Present address: Alaska Department of Fish and Game, 1300 College Road, Fairbanks, Alaska 99701, USA. Received July 18, 2013; accepted June 9, 2015 1058 Transactions of the American Fisheries Society 144:1058–1069, 2015 American Fisheries Society 2015 ISSN: 0002-8487 print / 1548-8659 online DOI: 10.1080/00028487.2015.1064474 D ow nl oa de d by [ U ni ve rs ity o f A la sk a Fa ir ba nk s] a t 1 2: 16 1 7 A ug us t 2 01 5