Threats of the West

The invasion of western waters by non-native species

The waters of the western United States are being invaded by plants, fish, and other animals from around the world. These plants and animals—also called aquatic nuisance species—arrive by various means. Some are transported in ship ballast water or by recreational boats moving from one water body to another. Others are planted along—and escape from—streams and ponds or are dumped into waterways from unwanted aquariums. While they may be harmless in their native waters, once introduced to a new area without their native predators, they can transform entire ecosystems.

Aquatic nuisance species not only threaten the natural environment, but they also cause serious economic damage. Each year, the United States alone spends billions of dollars attempting to control or slow the spread of these plants and animals. Recreational activities are impacted when invasive plants clog boating and swimming areas, and human health can also be impacted, as some aquatic nuisance species carry parasites and diseases.

The Western Regional Panel on Aquatic Nuisance Species (WRP) was created in 1996 to help prevent the spread of aquatic nuisance species. The WRP has produced a brochure and display describing some of the aquatic nuisance species that have already arrived in the West and suggesting ways to prevent their further spread. The WRP web site——provides a detailed listing of invasive species in the West, along with contacts for each western state or province. See also,, or contact Tina Proctor, Aquatic Nuisance Species Coordinator: To report sightings of invasive species, call toll-free: (877) STOP-ANS or (877) 786-7267.