Species · GBIF taxon 2226990
Signal Crayfish
Pacifastacus leniusculusAlso known as Klamath Crayfish, American Signal Crayfish
Signal crayfish are robust, bluish-brown to reddish-brown freshwater crustaceans distinguished by a bright white or light blue patch on the hinge of their large, smooth claws. They are highly adaptable omnivores that actively burrow into riverbanks, sometimes causing significant erosion and structural damage. In their introduced European range, they pose a severe ecological threat by outcompeting native crayfish and spreading the deadly crayfish plague water mold.
FreshwaterBurrowingCrustacean
—observations
—countries
—peak records
Least ConcernConservation statusIUCN Red List categoriesLCNTVUENCREWEXLeast ConcernRed List categories, explained →
Diet & prey
- Aquatic Plants
- Macroinvertebrates
- Detritus
Predators
- River Otters
- Herons
- Predatory Fish
ThreatsHabitat degradation in native range; widely managed as an invasive pest elsewhere
HabitatsStreams, rivers, lakes, and estuaries with rocky or muddy substrates
Life spanUp to 6 to 9 years
Size / weightNot available
Classification
- FamilyAstacidae
- SpeciesPacifastacus leniusculus
Range data is not available yet.
Interaction riskLow
- Low
- Moderate
- High
- Very high
- Why interaction risk is low
- Large claws can deliver a painful pinch; handle with care behind the carapace.
- Why it is dangerous
- Possesses powerful claws capable of delivering a painful pinch that can break the skin.
- How to recognize a risky encounter
- Identified by smooth, heavy claws with a prominent white or light blue spot at the joint.
- What to do
- Pick up from behind the thorax to keep fingers out of reach of the claws.
Responsible observation
- Identification: Look for the characteristic white or blue-green signal patch at the claw hinge.
- Handling: Grasp firmly but gently from the back of the carapace, just behind the claws, to avoid pinches.
- Biosecurity: Clean, drain, and dry all footwear and gear after visiting infested waters to prevent spreading disease.
Competitor 
Competitor David Gerke / CC BY-SA 3.0 · cc-by-sa
Competitor No machine-readable author provided. MikeMurphy assumed (based on copyright claims). / Public domain · cc0
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