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The purpose of this study was to determine the extent to which juvenile hatchery summer steelhead Oncorhynchus mykiss and wild winter steelhead overlap in space and time, to evaluate the extent of residualism among hatchery summer steelhead in the South Santiam River, and to evaluate the potential for negative ecological interactions among hatchery summer steelhead and wild winter steelhead. Wild winter steelhead populations have declined in the upper Willamette River Basin and are consequently listed as "threatened" under the Endangered Species Act. The U.S. Army Corps of Engineers funded the Pacific Northwest National Laboratory (PNNL) to determine whether releases of non-native hatchery summer steelhead juveniles into the South Santiam River (a tributary of the upper Willamette River) have the potential to negatively affect the river's wild winter steelhead population. The 2014 study objectives were to 1) estimate the proportion of hatchery summer steelhead that residualized in the South Santiam River in 2014, 2) determine the extent to which hatchery and naturally produced O. mykiss overlapped in space and time in the South Santiam River, and 3) characterize the behavioral interactions between hatchery-origin juvenile summer steelhead and naturally produced O. mykiss. We used a combination of radio telemetry and direct observations (i.e., snorkeling) to determine the potential for negative interactions between hatchery summer and wild winter steelhead juveniles in the South Santiam River. Both radio telemetry and direct observations were used to determine the spatial and temporal distribution of hatchery summer steelhead in areas containing naturally produced O. mykiss. In addition, radio telemetry was used to estimate the proportion of hatchery summer steelhead that residualized in the South Santiam River. Direct observations were used to assess ecological interaction rates and types among and between naturally produced and hatchery-origin O. mykiss and to evaluate the overlap in habitat use between the two groups. A total of 199 hatchery summer steelhead juveniles from the South Santiam Hatchery were implanted with radio transmitters on March 20 and 21, 2014. The radio-tagged fish were held in a raceway at the hatchery for 11 to 12 days until the gate was pulled that allowed fish to volitionally leave the raceway to enter the South Santiam River in the Foster Dam tailrace. Thirty-five radio-tagged steelhead (17.6%) did not leave the hatchery during the volitional release period and were euthanized. Radio-tagged fish that did leave the hatchery were detected by fixed receivers located on Foster Dam, at the mouths of the South Santiam and Santiam rivers, in the Willamette River, and during mobile tracking surveys conducted in the South Santiam River. Direct underwater observations were conducted at multiple locations in the South Santiam River between June 14 and July 31, 2014 to characterize the relative fish size, abundance, distribution, and behavioral interactions between residual hatchery summer steelhea...

Providing a means to quantitatively define flow-ecology relationships is integral in establishing flow regimes that are mutually beneficial to power production and ecological needs. This paper presents a geographic information system (GIS) framework for large river geomorphic classification that is flexible, accurate, and easily integrated with Ecological Limits of Hydrologic Alteration (ELOHA) initiatives. A case study was conducted integrating the base geomorphic aspect of this framework with the Modular Aquatic Simulation System two-dimensional (MASS2) hydraulic model and field collected data to establish optimal juvenile salmonid rearing habitat under varying flow regimes throughout an impounded portion of the lower Snake River, USA. Defining regions of optimal juvenile salmonid habitat at varying flows was used to distinguish areas that have a high potential for the creation of additional shallow water habitat. Findings indicated that the potential to create additional shallow water habitat does exist for juvenile salmonid rearing regardless of the flow scenario (discharge exceedence levels of 1, 25, 50, 75, and 99 percent) for the sample time frame (May -June 2011). The left-bank habitat of the lower Snake River was also found to be preferable for juvenile salmon rearing compared to right-bank habitat. The results from the case study suggest that the GIS framework is a capable tool when used to diagnose flow-ecology relationships. Additionally, an alternative hydrologic classification system is explored that couples well with the geographically independent nature of this GIS framework. Future applications of this framework are to utilize it in other large river systems throughout the contiguous United States. The framework also allows for the organization of large river data to be quickly accessed and used for multi-river comparison and analysis. Future development of a backend database within an interactive web platform would be highly beneficial to create a readily available and standardized mechanism to facilitate classification efforts conducted at the national scale.iv