Invasive zebra and quagga mussels cause extensive economic damage in the United States, wreaking havoc on water intake and mechanical structures as well as upsetting the balance of aquatic ecosystems. Zebra and quagga mussels starve ecosystems by consuming important plankton at the base of aquatic food webs. As a result, not only do these invasive mussels interrupt the food chain by over-consuming plankton, but lack of plankton also promotes the growth of toxic harmful algae, which can kill numerous aquatic organisms directly or through the process of eutrophication. The mussels also rapidly reproduce and colonize iron and steel pipes and other mechanical equipment, fouling and plugging up systems and rapidly increasing the rate of corrosion. 

State, federal and Tribal agencies have worked for decades to prevent the spread of invasive mussels west of the 100th meridian, a longitudinal line that has long been considered an ecological divide between the relatively moist eastern states and the arid west. However, in September 2023, quagga mussels were detected for the first time in the Snake River in Idaho, a large tributary of the Columbia River. Efforts to eradicate the invasive mussels took place immediately; however, they were again detected a year later. Now there is growing concern that they could spread throughout the Columbia River Basin. 

The Columbia River Basin acts as an aquatic artery for much of the Northwest, home to salmon and other iconic species of critical economic and cultural importance. The river basin also contains important human infrastructure. This includes numerous hydroelectric dams, water diversions for agriculture and human consumption, locks for transportation, and hatcheries that produce salmon, steelhead, and other fish to support recreational and commercial fisheries and uphold Tribal treaty agreements.

Last fall, scientists from the U.S. Geological Survey’s Southwest Biological Science Center, Wetland and Aquatic Research Center, and the University of California - Davis began working with the Washington Department of Fish and Wildlife to develop a comprehensive model that assesses the risk of mussel invasion throughout the waters of the Columbia River Basin within Washington State. The effort builds upon an existing model for the Missouri River Basin produced by the same team along with USGS Western Fisheries Research Center’s late Tim Counihan.

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To assess potential risk of mussel invasion, the model receives input values for transport activity, relative availability of suitable habitat for invasive mussels, and the presence of at-risk hatchery and other infrastructure. With this information, the model can be used to isolate specific areas of the Columbia River Basin at greatest comparative risk to invasive mussel introduction and establishment. Relative risk assessments can be used to guide prioritization of financial resources for monitoring, management, and control of the invasive mussels. 

USGS Western Fisheries Research Center scientist Ramona Rapp is collaborating with Washington Department of Fish and Wildlife to develop a guidance document for management agencies related to mussel invasion. The document will evaluate risks to hatcheries and recommend potential improvements to hatchery infrastructure to prevent mussel intrusion or reduce their impact where risks are found to be highest.