PNNL Studies Inform Pacific Northwest Fisheries Management
Sediment Retention Structure and the North Fork Toutle River in southwestern Washington State (photo courtesy of http://www.pubs.usgs.gov).
The Federal Columbia River Power System's 14 hydropower dams on the main-stem Columbia River and several of its major tributaries provide about one-third of the electricity used in the Pacific Northwest. This system also enables flood control and irrigation, and affects 13 species of Columbia River Basin salmon and steelhead listed for protection under the Endangered Species Act (ESA). The U.S. Army Corps of Engineers (USACE), which manages 12 of the dams, is committed to improving conditions for fish passing through its hydroelectric projects and continues to implement mitigation strategies to increase salmonid survival in the Columbia and Willamette River Basins. The results of two recent studies for the USACE by researchers in PNNL's Ecology group are informing Pacific Northwest fisheries management decision-making related to listed fish populations in Oregon and Washington.
In Hydroacoustic Evaluation of Juvenile Salmonid Passage and Distribution at Foster Dam, 2013-2014, researchers evaluated juvenile and adult fish passage and distribution at Foster Dam on the South Santiam River in western Oregon. Its baseline data of ESA-listed fish support decision-making about long-term measures for enhancing downstream salmonid passage at Foster and other dams in the river system.
The other report, Fish Presence/Absence and Habitat in Areas Affected by Sediment from Mount Saint Helens, 2013-2014, documents PNNL's assessment of habitat quality, use by species at different life stages, and distribution of species in areas potentially influenced by sediment from the 1980 eruption of Mount Saint Helens. A Sediment Retention Structure, approximately 7 kilometers downstream of the North Fork Toutle River (NFTR) tributaries examined during this study was constructed in 1989 to help alleviate downstream accumulation of sediment. Its installation blocked access to up to 80.5 kilometers of upstream fisheries habitat. Now reaching its holding capacity, the structure is allowing the continued buildup of sediment behind the structure, thereby affecting upstream fisheries habitat.
This study verified the downstream presence of larval lamprey, and amount and quality of upstream habitat available to baby (fry), juvenile, and adult fish trapped and transported upstream to both Bear and Alder Creeks. Information about life-cycle impacts that the increase in deposited sediment is having on downstream species and all salmonid life stages upstream was needed for decision-makers to determine how to further manage the NFTR and the retention structure. The results will inform a related environmental impact statement and the National Marine Fisheries Service’s Biological Opinion being developed to protect and increase populations of Chinook salmon and steelhead in the NFTR above the retention structure.