History and Background

Quagga and zebra mussels arrived in the United States from Europe in the 1980s and spread to many eastern waterways, rivers, and lakes. Quagga mussels were discovered in Lake Mead, Lake Mojave, and Lake Havasu on the Colorado River in January 2007. Zebra mussels were confirmed to be present in San Justo Reservoir in California in January 2008.

These mussels spread in numerous ways, mainly by floating in the currents of the water body or by "hitching" a ride on a boat or other water vessels that are used in infested water and then transported to another water body. Knowledge and experience in the Eastern United States indicates that once introduced, the mussels are almost impossible to eradicate in water bodies and facilities comparable to Reclamation facilities. A key observation of quagga and zebra mussels in the Western States is not all contemporary measures can be applied to other facilities; one size does not fit all. The observations show that mussels react differently at different facilities because of water temperature, chemistry content differences, and a host of other unknown factors. Spread of these mussels will cause significant impacts and damage to operation and maintenance of water storage, water delivery, and hydropower structures and systems; recreational use; and aquatic ecosystems.

Reclamation is concentrating on proactive measures to help reduce the post-introduction spread and impacts of the mussels to Reclamation facilities and structures, thereby lessening the need for time-consuming and most costly measures of control.

Reclamation has an invasive mussel corporate task force that is focused on a four-part strategy; monitoring and prevention of infestation, outreach and education, research and control and mitigation. This strategy guides Reclamation in the effective and efficient use of staff and resources with a focus on those facilities where mussels have been confirmed and those facilities that will likely be impacted in the future. In developing a corporate strategy the integration, involvement, and communication within Reclamation and with other affiliated organizations outside of Reclamation remains consistent.

More Information

Fact Sheets

Related Websites

Zebra and Quagga Mussel Sightings Distribution Map

Last Updated: 1/4/18