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We used radiotelemetry to evaluate population composition, run timing, and reservoir harvest patterns for adult Columbia River fall-run Chinook salmon Oncorhynchus tshawytscha. Chinook salmon (n= 5.886) were collected at Bonneville Dam during August--October over 7 years. We selected for upriver bright (URB) populations en route to interior basin spawning sites because these groups are priority populations for both fisheries and conservation efforts. Run composition varied within and among years, but in all years a relatively large percentage of the earliest migrants returned to upper Columbia River sites and the majority of late-run fish returned to the Columbia River Hanford Reach. Deschutes, Yakima, and Snake River populations typically constituted small (≤ 17%) but relatively constant proportions of the run throughout each migration season. Population-specific migration timing distributions indicated modest but persistent timing differences among populations, particularly for Hanford Reach and upper Columbia River populations. Annual reported reservoir harvest estimates ranged from 12% to 26%. Harvest rates varied seasonally within years, from relatively low mean rates (≤11%) for fish tagged early and late in migrations to peak rates of over 25% for those tagged in late August and early September. These patterns suggest that it may be possible to increase harvest of abundant populations and reduce harvest of some vulnerable populations by adjusting the timing of fisheries. In addition, there was evidence that larger fish were harvested at higher riles and that mean fish size differed among populations. The combined results improve our understanding of the Columbia River URB fall Chinook salmon run and should help in refining harvest and escapement management plans. [ABSTRACT FROM AUTHOR]

Several evolutionarily significant units (ESUs) of Columbia River asin Chinook SalmonOncorhynchus tshawytschaand Coho SalmonO. kisutchare listed as threatened or endangered under the U.S. Endangered Species Act. Yet little is known about the spatial and temporal distributions of these ESUs immediately following ocean entry, when year-class success may be determined. We documented differences in dispersal patterns during the early ocean period among groups defined by ESU, adult run timing, and smolt age. Between 1995 and 2006, 1,896 coded-wire-tagged juvenile fish from the Columbia River basin were recovered during 6,142 research trawl events along the West Coast of North America. Three distinct ocean dispersal patterns were observed: (1) age-1 (yearling) mid and upper Columbia River spring-run and Snake River spring–summer-run Chinook Salmon migrated rapidly northward and by late summer were not found south of Vancouver Island; (2) age-0 (subyearling) lower Columbia River fall, upper Columbia River summer, upper Columbia River fall, and Snake River fall Chinook Salmon dispersed slowly, remaining mainly south of Vancouver Island through autumn; and (3) age-1 lower Columbia River spring, upper Columbia River summer, and upper Willamette River spring Chinook Salmon and Coho Salmon were widespread along the coast from summer through fall, indicating a diversity of dispersal rates. Generally, the ocean dispersal of age-1 fish was faster and more extensive than that of age-0 fish, with some age-1 fish migrating as fast as 10–40 km/d (0.5–3.0 body lengths/s). Within groups, interannual variation in dispersal was moderate. Identification of the distinct temporal and spatial ocean distribution patterns of juvenile salmon from Columbia River basin ESUs is important in order to evaluate the potential influence of changing ocean conditions on the survival and long term sustainability of these fish populations. Received March 25, 2013; accepted September 6, 2013 [ABSTRACT FROM AUTHOR]

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Abstract Recent declines in anadromous Pacific salmonids (Oncorhynchus spp.) have been attributed, in part, to degradation of freshwater habitat. Because riparian areas directly affect instream habitat, assessing riparian characteristics is essential for predicting salmon habitat quality and for prioritizing restoration projects. We quantified land use modification of anadromous fish-bearing streams in the interior Columbia River basin at multiple resolutions. We identified riparian areas in several land use and land cover classes using remotely sensed data. We then interpreted aerial photographs at random locations within each class to quantify riparian modifications at a local (stream reach) scale. Riparian areas in agricultural and urban areas were significantly narrower (∼30 m, median) than those in forested or shrub/grass areas (∼70 m). The largest proportion of modified riparian areas occurred in low-gradient streams with floodplains in semi-arid ecoregions. Riparian vegetation in these areas is unlikely to provide adequate in-stream functions, making these areas a natural starting point for restoration prioritization. We investigated how existing riparian restoration projects were spatially related to riparian land use and found that restoration effort varied among subwatersheds. Effective strategies for restoring high quality salmon habitat will be watershed-specific and must restore natural watershed processes. By using a hierarchical analysis to identify regional strategies, restoration or conservation activity can be focused in specific basins and thereby increase the likelihood that efforts will significantly improve habitat conditions for listed salmonids. [ABSTRACT FROM AUTHOR]

Passage of adult Pacific salmon Oncorhynchus spp. and steelhead O. mykiss at dams in the Columbia River basin has historically been determined by visual fish counts and radiotelemetry. Increasingly, however, passive integrated transponder (PIT) tags are being used for adult salmonid research and monitoring. Although both radiotelemetry and PIT tag technology provide accurate and cost-effective data under certain circumstances, neither alone meets all needs, and managers need to understand the strengths, weaknesses, and biases of each method. To evaluate the two tagging methods, we tagged over 3,200 adult Chinook salmon O. tshawytscha and steelhead during 2002 and 2003 with both a radio transmitter and a PIT tag as the fish migrated upstream past Bonneville Dam. We compared their performance in measuring upstream passage and fallback (i.e., downstream passage) behavior at each of four main-stem hydropower dams. Counts of fish passage at dams based on data from double-tagged fish were similar between methods (largest difference was 5.1%), but the two methods produced less consistent results for fallback behavior. Visual count escapement estimates based on PIT tags were 1% higher on average than those based on radio tags, suggesting there would be little impact on the management of salmonid populations with a switch from radiotelemetry to PIT tag systems as the primary data source. We also analyzed a broader group of PIT-tagged (but not radio-tagged) fish to simulate the analysis one could expect from PIT tag data without radiotelemetry validation. When compared with PIT tag data from double-tagged fish, data from the PIT tag-only fish showed slight differences in the timing of peak passage. These differences were due, at least in part, to the fact that the fish in each group comprised differing proportions of fish from multiple populations, highlighting the importance of having representative stocks of fish PIT-tagged as juveniles. [ABSTRACT FROM AUTHOR]