Northern Crayfish (Orconectes virilis) and Red Swamp Crayfish (Procambarus clarkia)
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 United States. These crayfish usually are 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 and since has become widespread in the Sammamish River 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 River basin. The rusty crayfish is known to be present only in the John Day River in Oregon.
Why Should I Care?
The 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.
How Can We Stop Them?
Because crayfish are introduced by humans, responsible disposal of unused bait may 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 2-5 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, which is 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.
WISC=Washington Invasive Species Council