Hydropower and high productivity in the Hanford Reach: A synthesis of how flow management may benefit fall Chinook Salmon in the Columbia River, USA

Abstract

The fall Chinook Salmon (Oncorhynchus tshawytscha) population that spawns in the Hanford Reach of the Columbia River, USA is paradoxical because it is located above 4 and below 10 main stem Columbia River dams and yet is one of the largest and most productive C. salmon populations in the Pacific Northwest. A synthesis of information collected in the Hanford Reach reveals that the hydrosystem above the Hanford Reach and the management of river flows may have contributed to the recent size and productivity of this salmon population. Mechanisms for high survival and capacity at each freshwater life stage have been identified. Plausible mechanisms for contributing to high spawning capacity include: (a) more spawning habitat available during the spawning period. Plausible mechanisms for high egg‐to‐presmolt survival include: (a) reduced desiccation of redds, (b) reduced scour of redds, (c) reduced sedimentation in redds, (d) improved flow exchange within redds, and (e) increased food availability. Smolt survival may also be enhanced through the large size they attain in the Hanford Reach. This synthesis of information provides an uncommon assessment of some the positive effects of flow management from hydropower dams on a valued native fish that has occurred over the last three decades. WIREs Water 2018, 5:e1275. doi: 10.1002/wat2.1275 This article is categorized under: Water and Life > Stresses and Pressures on Ecosystems Water and Life > Conservation, Management, and Awareness

Stray Rates of Natural‐Origin Chinook Salmon and Steelhead in the Upper Columbia River Watershed

“…; Langshaw et al. ; Pearsons et al., in press). Summer Chinook Salmon spawn primarily in the main stems of four subbasins of the upper Columbia River (i.e., Wenatchee, Entiat, Methow, and Okanogan rivers) and support considerable fisheries in the Pacific Ocean and Columbia River.…”

Stray compositions of hatchery‐origin Chinook Salmon and steelhead in natural spawning populations of the upper Columbia watershed

“…Fall Chinook Salmon spawn in the Hanford Reach, the only free‐flowing reach of the Columbia River between Grand Coulee and Bonneville dams. These spawners comprise one of the largest Chinook Salmon populations in the United States and contribute large numbers of fish to harvest in the Pacific Ocean and Columbia River, making this population economically very important (Harnish et al 2014; Langshaw et al 2017; Pearsons et al 2020). Summer Chinook Salmon spawn primarily in the main stems of four subbasins of the upper Columbia River (e.g., Wenatchee, Entiat, Methow, and Okanogan) and support considerable fisheries in the Pacific Ocean and Columbia River.…”

Comparisons of donor stray percentages between hatchery‐ and natural‐origin Chinook Salmon and steelhead in the upper Columbia watershed

“…Fall Chinook Salmon spawn in the Hanford Reach, one of the few free-flowing reaches of the Columbia River downstream of Priest Rapids Dam, comprising one of the most abundant Chinook Salmon populations in the United States and contributing large numbers of fish to harvest in the Pacific Ocean and Columbia River, making this population economically very important (Harnish et al 2014;Langshaw et al 2017;. Summer Chinook Salmon spawn primarily in the main stems of four subbasins of the upper Columbia River (e.g., Wenatchee, Entiat, Methow, and Okanogan) and support considerable fisheries in the Pacific Ocean and Columbia River.…”