USGS Science to Support the Elwha River Restoration Project
At least 16 fish species reside in the Elwha River, including steelhead, resident trout, charr, and 5 species of Pacific salmon. Salmon are limited to the lower 8 kilometers of the river downstream of the Elwha Dam, where degraded spawning habitat has contributed to population declines. Resident rainbow trout and bull trout, listed as threatened under the Endangered Species Act, occur throughout the watershed and dominate the fish assemblage between and upstream of the dams. Introduced species, such as brook trout, currently are limited to parts of the river between the dams.
USGS researchers—working in collaboration with other federal, state and tribal partners—have been conducting studies to describe the distribution and abundance patterns of fish communities throughout the Elwha River; identify patterns of age, growth, and residence of juvenile salmon and trout; and document baseline conditions of fish habitat throughout the watershed. Additionally, studies of marine-derived nutrients from adult salmon returning to the Elwha River and the status of aquatic macroinvertebrate communities (which are reliable water-quality indicators and a food source for fish) have been conducted in anticipation of the dam removals. Future studies during and following dam removal are planned to monitor changes in the ecosystem, including the rebuilding of Elwha River salmon populations.This research has resulted in numerous publications that document the patterns and trends of salmon within the Elwha River system. For more information about these results, see these publications.
More than 100 species of wildlife are known to eat salmon during one or more stages of the salmon’s life cycle. Additionally, nutrients delivered upriver by migrating salmon permeate wildlife food webs near salmon-bearing rivers. Despite a general appreciation that salmon are key to sustaining many species of wildlife in the riverine environment, few studies have described the effects of salmon on wildlife diversity, abundance, or distribution patterns largely because there have been so few opportunities for large scale experimentation and long-term studies.
The removal of the dams on the Elwha River offers an opportunity to investigate this aspect of salmon-wildlife interactions. The USGS, National Park Service, and Lower Elwha Klallam Tribe have conducted many baseline studies of wildlife distribution and species diversity patterns to set the stage for assessing wildlife community changes associated with dam removal and salmon restoration. Scientists have used Global Positioning System radio-telemetry, molecular genetics, remotely triggered cameras, ‘sign’ and visual surveys, and small mammal trapping to determine pre-dam removal distribution patterns of black bears, small carnivores, amphibians, and small mammals. These studies are providing characterization of current wildlife communities and species distributions prior to dam removal, and the comparative baseline needed to evaluate long-term effects of watershed restoration on wildlife resources in the Elwha River ecosystem.
For more information regarding these wildlife studies, contact Kurt Jenkins.