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Ecology

Habitat Quality of Snake River Fall Chinook Salmon Spawning Areas

Initiated in 1998, we were contracted by Idaho Power Company to assess the importance of ground water inputs to fall chinook salmon spawning locations at various sites in the Hells Canyon Reach of the Snake River. Idaho Power Company manages the Hells Canyon Complex and wanted to know how operations of these projects impacted the availability of fall chinook salmon spawning habitat, specifically as it related to substrate quality and ground water – surface water interactions. During the first year of the study, we evaluated riverbed temperatures at four spawning sites, and concluded that water temperature of the bed was slightly warmer than the river and was affected by operations of Hells Canyon Dam. We reasoned this might have implications on when juvenile salmon emerged from the gravel in the spring of the year as embryo development is tightly coupled to incubation temperatures. The second year of the study evaluated sediment characteristics at two historic fall chinook salmon spawning sites in the upper Snake River. The primary objective of this evaluation was to measure sediment permeability within these areas to determine the potential quality of the habitat should anadromous salmonids be reintroduced to the upper Snake River. The substrate characteristics indicated the availability of good spawning substrate, as well as the potential for moderate to high survival from egg to emergence. The third year of the study returned to the Hells Canyon Reach in order to provide a context for the information gathered upstream of the anadromous block. Based on the results of this study, we concluded that substrate quality at three of the four sites in the Hells Canyon Reach was as good or better than substrate quality in the Hanford Reach and the upper Snake River. In addition, substrate quality at historic fall chinook salmon spawning areas above Hells Canyon Dam appears to be conducive to fall chinook salmon redd construction, incubation, and emergence success. This information will be important in assisting management agencies, including Idaho Power Company, in evaluating whether populations of Snake River fall chinook salmon are depressed from limited spawning habitat or from factors not related to habitat availability.

Products:

  • Hanrahan, T. P., D. R. Geist, and E. V. Arntzen. 2005. Habitat quality of historic Snake River fall Chinook salmon spawning locations and implications for incubation survival. Part 1: Substrate quality. River Research and Applications 21 (5): 455-467.
  • Arntzen, E. V., D. R. Geist, and T. P. Hanrahan. 2001. Sediment quality of fall chinook salmon spawning habitat: Hells Canyon Reach, Snake River, Idaho. Final Report to the Idaho Power Co. PNWD-3114.
  • Hanrahan, T. P., D. R. Geist, E. V. Arntzen, and G. A. McMichael, 2000. Sediment permeability of historic fall chinook salmon spawning habitat: Upper Snake River, Idaho. Final Report to the Idaho Power Co. PNWD-3072.
  • Geist, D. R., T. P. Hanrahan, E. V. Arntzen, Z. K. Bevens. 1999. Assessment of hyporheic discharge within fall chinook salmon spawning habitat in the Hells Canyon Reach of the Snake River. Final report to the Idaho Power Co. 55 pp

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