Interagency Quagga and Zebra Mussel Rapid and Extended Response Plan for the Snake River in Washington State (2025)

Quagga Dreissena rostriformis bugensis and zebra Dreissena polymorpha mussels are freshwater mollusks native to Ukraine and Russia that have a long history of invasion and successful establishment outside their native range. Once established, these mussels can cause catastrophic ecosystem impacts, outcompeting native mussels and other filter feeding invertebrates, altering habitat complexity, changing food web dynamics, and reducing water quality. They can also have direct economic and safety impacts, clogging water intake structures, fish screens, and boat engines; overtaking docks, buoys, boat hulls, anchors, and beaches; and contributing to disease outbreaks in species that consume them.

Quagga and zebra mussels were first discovered in the United States in the Great Lakes region in the 1980s and are thought to have been transported in ballast waters of trans-oceanic ships. Since the late 2000s, they have been spreading throughout the western United States (Nevada [2007], California [2008], and Montana¹ [2016]), with the most recent detection in the Snake River in Idaho in 2023. While a comprehensive eradication effort continues in the Snake River, the presence of dreissenid mussels in the Columbia River Basin presents an imminent threat and led to the development of this site-specific Interagency Quagga and Zebra Mussel Rapid Response Plan for the Snake River in Washington State (Plan).

¹ Quagga and zebra mussels did not ultimately establish in Montana despite having positive veliger detections.