Since their introduction to the Great Lakes region of North America in the 1980s, invasive dreissenid mussels (zebra mussels (Dreissena polymorpha) and quagga mussels (Dreissena rostriformis bugensis)) have expanded their distribution across North America. From 2012–2018, the states of Washington, Oregon, Idaho, and Montana intercepted a total of 394 dreissenid-fouled watercraft that originated from throughout North America. In 2016, invasive mussel larvae were discovered in Tiber and Canyon Ferry Reservoirs in Montana—this was the first documented detection of dreissenids near the perimeter of the Columbia River Basin (CRB). The westward expansion of dreissenids, primarily via watercraft vectors, precipitates the need for contingency plans and other planning efforts to prepare entities for an introduction of dreissenids by facilitating a rapid response. 

This toolkit provides resource managers with the tools and information to effectively implement a response to a dreissenid introduction. The toolkit includes information on Columbia River Basin geography; entities; dreissenid biology and distribution; environmental, economic, and cultural effects of dreissenids; use of the Incident Management System; response resources; and environmental compliance, including Endangered Species Act (ESA) consultation steps.

This toolkit has been prepared to facilitate a rapid response to an introduction of dreissenids. The anticipated consequences of taking no action would include long-lasting, significant, and detrimental economic, environmental, and social/cultural effects that would alter ecosystem function and processes throughout the CRB and affect quality of life for people who live in the basin. There are many factors influencing whether or not attempts to eradicate dreissenids in any CRB waterbody will be successful. And the potential effects of response actions to listed species and critical habitats are never fully known prior to control actions. Thus, at the time of an actual response, it is prudent to weigh the short-term and long-term economic and environmental costs of eradication attempts with the likely long-term costs of established populations of dreissenids.