What are they?
Crayfish are freshwater crustaceans related to lobsters. In the Pacific Northwest, three species of invasive crayfish are present: northern, red swamp, and rusty. The northern crayfish is native to Montana, Wyoming, the upper Mississippi River, the Great Lakes, and the Hudson River. The red swamp and rusty are native to the southeastern U.S. These crayfish are usually found in brooks and streams where there is running water and shelter against predators.
Are they here yet?
Yes. The red swamp crayfish was first found in Pine Lake in King County. It since has become widespread in the Sammamish Basin. The northern crayfish is present throughout the Columbia River from Grand Coulee dam to the Chief Joseph dam and in several lakes in the Columbia Basin. The rusty crayfish is only known to be present in the John Day River in Oregon.
Why should I care?
These rapidly-reproducing non-native crayfish displace native crayfish populations by out-competing them for food and habitat. They also may impact fish populations through competition, predation, or habitat modification.
What should I do if I find one?
How can we stop them?
Because crayfish are introduced by humans, responsible disposal of unused bait can prevent their spread. Anglers should make sure their bait suppliers don’t sell non-native crayfish and should avoid using non-native crayfish as bait. Non-native crayfish may not be legally purchased or transported in Washington but they may be harvested as part of the legal limit. If caught, they must be kept separate containers from native crayfish.
What are their characteristics?
- The claws of all of the non-native species are stronger than those of native species, and usually have bumps or spines.
- Northern crayfish adults reach a maximum length of 5 inches. Rusty crayfish adults reach 4 inches in length.
- Red swamp crayfish are dark red with raised, bright red spots covering the body and claws, and a black wedge-shaped stripe on the top of the abdomen.
- They vary in length between 2 to 5 inches.
- Occasionally, a genetic mutation may turn the body and/or claws blue; however all other features including the red, raised spots remain the same.
How do I distinguish them from native species?
- There is only one native crayfish species in Washington; the signal crayfish, Pacifasticus leniusculus, whichis fairly easy to identify. All its surfaces, even its claws, are uniformly brownish and smooth compared to other species.
- Use this guide to distinguish the native signal crayfish from several other species invasive or potentially invasive in Oregon and Washington.