Signal crayfish
Pacifastacus leniusculus (Dana, 1852)
LCLeast Concerncrabs and lobsters
The signal crayfish (Pacifastacus leniusculus) is a crustacean in the family Astacidae, listed in the animal subgroup crabs and lobsters. It belongs to the genus Pacifastacus, superfamily Astacoidea, suborder Pleocyemata, order Decapoda and class Malacostraca, within the phylum Arthropoda.
Quick facts about the signal crayfish
The species is assessed as Least Concern on the IUCN Red List in a global assessment, which is not an IUCN threatened category. Other English names for it are Klamath signal crayfish, American signal crayfish and Columbia river signal crayfish.
- Weight
- Not recorded
- Length
- Not recorded
- Lifespan
- Not recorded
- Main food
- Not recorded
- Habitat
- freshwatersrc for Habitat
- Young per litter or clutch
- Not recorded
- Conservation status
- Least Concern (IUCN)src for Conservation status
- Countries on record
- Not recorded
Photos of the signal crayfish
Only freely licensed photos are shown. Each carries its creator and licence.
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Where does the signal crayfish live?
Not recorded
What is the signal crayfish?
Pacifastacus leniusculus, commonly known as the signal crayfish, is a species of freshwater crayfish in the family Astacidae, native to western North America. They are thought to have originated from the Columbia River Basin.
Physically, they are characterized by a smooth carapace and a distinctive white to pale blue-green patch at the base of the claw joint. Reminiscent of the white flags that signalmen used for directing trains, this light patch is responsible for the species' common name. Due to its heightened aggression and opportunistic polytrophic diet,P. leniusculus has become an established invasive species found across North America, Europe, and Japan, displacing many of the regions’ native species.
During the twentieth century, P. leniusculus was intentionally introduced to many regions of Europe to replace declining populations of the native Astacus astacus, which had been affected by outbreaks of crayfish plague. At the time of introduction, it was not widely known that North American crayfish species, including P. leniusculus, commonly act as asymptomatic carriers. As a result, P. leniusculus facilitated the continued spread of crayfish plague across European freshwater ecosystems, continuing to decimate native crayfish.
From the Wikipedia article “Signal crayfish” (en.wikipedia.org/w/index.php?title=Signal_crayfish&oldid=1384666959), by Wikipedia contributors, licensed under CC BY-SA 4.0 (creativecommons.org/licenses/by-sa/4.0). This block is kept separate from our own text.
Is the signal crayfish endangered?
The signal crayfish is listed as Least Concern on the IUCN Red List: it is not currently at risk of extinction.
- LCLeast Concern
- NTNear Threatened
- VUVulnerable
- ENEndangered
- CRCritically Endangered
- EWExtinct in the Wild
- EXExtinct
Category via Wikidata (CC0). Find the full assessment on the IUCN Red List. See all Least Concern species.
How is the signal crayfish classified?
- kingdomAnimalia
- phylumArthropoda
- classMalacostraca
- orderDecapoda
- familyAstacidae
- genusPacifastacus
- SpeciesPacifastacus leniusculus (Dana, 1852)
Synonyms Astacus klamathensis, Astacus klaymathensis, Astacus leniusculus, Astacus oreganus, Astacus trowbridgii, Pacifastacus klamathensis, Pacifastacus leniusculus klamathensis, Pacifastacus leniusculus leniusculus, Pacifastacus leniusculus trowbridgii, Pacifastacus trowbridgi, Pacifatacus leniusculus
Other names and names in other languages (28)
- American signal crayfishEnglish
- Columbia river signal crayfishEnglish
- Columbia river signal crayfishEnglish
- Klamath signal crayfishEnglish
- Klamath signal crayfishEnglish
- cámbaru señalAsturian
- Cranc senyalCatalan
- rak signálníCzech
- SignalkrebsGerman
- Cangrejo señalSpanish
- signaalvähkEstonian
- täplärapuFinnish
- ecrevisse signalFrench
- écrevisse de CalifornieFrench
- Écrevisse du PacifiqueFrench
- Écrevisse signalFrench
- jelzőrákHungarian
- Gambero segnalatoreItalian
- ウチダザリガニJapanese
- Žymėtasis vėžysLithuanian
- signalkrepsNorwegian Bokmål
- Californische rivierkreeftDutch
- Rak sygnałowyPolish
- Lagostim-SinalPortuguese
- Американский сигнальный ракRussian
- rak signálnySlovak
- signalni rakSlovenian
- signalkräftaSwedish
Catalogue of LifeWikipediaiNaturalistTAXREFWikidataWoRMSWoRMSIUCN Red List
Relatives of the signal crayfish
Other species in the same genus Pacifastacus.
Sooty crayfish
Pacifastacus nigrescens
Placid crayfish
Pacifastacus fortis
Snake river pilose crayfish
Pacifastacus connectens
Pilose crayfish
Pacifastacus gambelii
Misfortunate crayfish
Pacifastacus malheurensis
CompareSignal crayfish vs Sooty crayfishSignal crayfish vs Placid crayfishSignal crayfish vs Snake river pilose crayfishSignal crayfish vs Pilose crayfish
Common questions
Each answer is written from the sourced facts on this page, and only where they hold the answer.
What kind of animal is the signal crayfish?
The signal crayfish is a crustacean in the family Astacidae and the order Decapoda, placed in the animal subgroup crabs and lobsters.
What is the scientific name of the signal crayfish?
Its scientific name is Pacifastacus leniusculus, in the genus Pacifastacus.
Is the signal crayfish endangered?
No. It is listed as Least Concern on the IUCN Red List in a global assessment, which is not an IUCN threatened category.
Is the signal crayfish extinct?
No. The Catalogue of Life lists the signal crayfish as a living species, not extinct.
What other names does the signal crayfish have?
It is also called the Klamath signal crayfish, American signal crayfish and Columbia river signal crayfish.
Sources and how to cite this page
Data as of 2026-11-11. How this page is put together.
- Catalogue of Life eXtended Release · CC BY 4.0 · 2026-10-16 XR
Catalogue of Life (2026). Catalogue of Life eXtended Release, version 2026-10-16 XR. Catalogue of Life Foundation, Amsterdam, Netherlands. https://doi.org/10.48580/dgzlf - Wikimedia Commons · per file (CC0 / public domain / CC BY green, CC BY-SA amber, anything else not displayed) · 2026-11-11
Wikimedia Commons contributors. Wikimedia Commons. https://commons.wikimedia.org (each file credited to its author under its own licence). - Wikidata · CC0 1.0 · 2026-11-11
Wikidata contributors. Wikidata. https://www.wikidata.org (data retrieved via the Wikidata Query Service). - Wikipedia (English) · CC BY-SA 4.0 · 2026-11-11
Wikipedia contributors. Wikipedia, The Free Encyclopedia. https://en.wikipedia.org (text under CC BY-SA 4.0; each block names its article and revision).
Embed a card for this animal on your own site
Copy this code. The card shows the photo with its credit, key facts and a link back to this page.
CreatureData. (2026). Signal crayfish (Pacifastacus leniusculus). Retrieved from https://creaturedata.com/animals/signal-crayfish
“Signal crayfish (Pacifastacus leniusculus).” CreatureData, 2026, https://creaturedata.com/animals/signal-crayfish.
@misc{signal_crayfish_2026,
title = {Signal crayfish (Pacifastacus leniusculus)},
author = {{CreatureData}},
year = {2026},
url = {https://creaturedata.com/animals/signal-crayfish},
note = {Data as of 2026-11-11}
}