Crayfish are freshwater crustaceans resembling small lobsters. Over 350 of the world’s approximately 500 species live in the streams and lakes of the United States. The majority of crayfish species occur east of the Rocky Mountains and in the Southeastern states. About 65 of the 400 crayfish species in North America are endangered; nearly half of the native crayfish species have been estimated as needing protection.
Habitat loss is the leading cause of population declines or extinction for aquatic animals; the second leading cause is the introduction of nonnative organisms. While native crayfish are an important part of the ecosystem, nonnative crayfish are a major threat to aquatic biodiversity. They cause the decline of native crayfish by spreading crayfish diseases, and they prey upon eggs, young fish, amphibians and native crayfish, as well as eliminating native water plants and habitats.
Crayfish are spread by a variety of pathways. Introductions of discarded bait from anglers, and releases by aquarium owners have been responsible for spreading crayfish into new ecosystems. Some schools curriculums also involve use of crayfish, which, after use in the classroom, have been released into the wild by sympathetic students, causing havoc in new ecosystems. Sea Grant and other groups have been working to educate teachers, to shut this pathway.
Status in the Pacific Northwest: Two species of crayfish of particular concern to the Pacific Northwest include the rusty crayfish, (Oroconnectes rusticus), and the northern crayfish, (O. virilis). They are not yet known to be present in the Northwest, and we hope not to see them here.
What can you do? Learn to recognize the native crayfish, and if you see a crayfish that looks unusual to you, catch or photograph it if possible, and report any sightings to the appropriate state office:
In Washington: 1-360-902-2700 (WDFW)
In Oregon 1-866-INVADER (hotline)
In Idaho 1-208-332-8686 (ANS Coordinator)
In Alaska 1-877 INVASIVE (hotline)
The links provided may be outside the EPA.gov domain.
Crayfish Distribution maps
Red Swamp Crayfish (Procambarus clarkia) Fact sheet
Rusty Crayfish (Oroconectes rusticus) Fact sheets
Northern Crayfish (Oroconectes virilis) Fact sheet