---
title: "What the sources say about the Signal Crayfish | AnimalTracks.wiki"
description: "47 claims from the Signal Crayfish profile, each beside the words of the source that backs it."
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# What the sources say about the Signal Crayfish (*Pacifastacus leniusculus*)

> 47 claims from the Signal Crayfish profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Signal Crayfish](https://animaltracks.wiki/animals/signal-crayfish/)

## Signal Crayfish (Pacifastacus leniusculus) Ecological Risk Screening Summary. U.S. Fish and Wildlife Service.

https://www.fws.gov/sites/default/files/documents/2026-01/ecological-risk-screening-summary-signal-crayfish-dec-2025.pdf

| The page says | The source says |
| :--- | :--- |
| A plague-resistant crayfish brought to Europe to supplement stocks the plague decimated | imported to Sweden and introduced throughout Europe in an attempt to establish a plague resistant species that would supplement stocks decimated by the crayfish plague. (note: tagline, first half. Quoted in the FWS summary from Procopio (2021). Carrier half has its own claim.) |
| a carrier of the disease itself | Signal Crayfish serve as carriers of the crayfish plague, which is caused by a fungus-like organism ( Aphanomyces astaci ) (note: tagline, second half. Quoted in the FWS summary from Procopio (2021).) |
| Highly resistant to the crayfish plague | While P. leniusculus are highly resistant to the illness (note: stats.superpower. Quoted in the FWS summary from Procopio (2021).) |
| Small streams, large rivers and natural lakes | P. leniusculus can be found in a variety of habitats, from small streams to large rivers and natural lakes. (note: stats.habitat. Quoted in the FWS summary from Houghton and Allen (2014).) |
| native to the Columbia River Basin and Oregon's coast | the native range spans northwest up the mainstem to tributaries that reach into Washington, Oregon, Idaho, and British Columbia. The native range extends south from the Columbia River along Oregon’s coast where the Klamath River and its drainages form its southern boundary (note: stats.habitat. Procopio (2021), quoted in the FWS summary; replaces Houghton and Allen's (2014) British Columbia to central California range, which the same document's more recent sources show includes introduced populations (California, Nevada, Utah, Montana).) |
| many European countries | In the 1960s , P. leniusculus was introduced into Europe and now occurs in many countries from the UK and France in the west, to Russia in the east. (note: stats.habitat. Quoted in the FWS summary from Houghton and Allen (2014).) |
| Beginning in the 1960s, signal crayfish were imported to Sweden and introduced across Europe to build a plague-resistant stock that would supplement the stocks the plague had decimated. | Beginning in the 1960’s, Pacifastacus leniusculus were imported to Sweden and introduced throughout Europe in an attempt to establish a plague resistant species that would supplement stocks decimated by the crayfish plague. (note: Quoted in the FWS summary from Procopio (2021).) |
| a disease caused by a fungus-like organism called Aphanomyces astaci | the crayfish plague, which is caused by a fungus-like organism ( Aphanomyces astaci ) (note: Quoted in the FWS summary from Procopio (2021).) |
| Its spread across Europe has helped the plague spread too, decimating native crayfish populations. | The spread of P. leniusculus throughout Europe has enabled Aphanomyces astaci , the crayfish plague, to spread as well, decimating native crayfish populations (note: Quoted in the FWS summary from Houghton and Allen (2014), who cite Holdich et al. (2009).) |
| The signal crayfish is highly resistant to the plague. Asiatic, Australian and European crayfish are very susceptible to its ill effects. | While P. leniusculus are highly resistant to the illness, Asiatic, Australian, and European crayfish are very susceptible to the plague’s ill effects (note: Quoted in the FWS summary from Procopio (2021), who cites Unestam (1969).) |
| The average adult has a carapace, the hard shell over its head and chest, 50 to 70 mm long. | The average Signal Crayfish attains a carapace length (CL) of 50-70 mm (Capurro et al. 2007). (note: Quoted in the FWS summary from Procopio (2021). The gloss of carapace is a definition, not a source claim.) |
| In the wild a signal crayfish may survive up to 9 years or more | the Signal Crayfish may survive up to 9 years or more when living in the wild (Goldman and Rundquist 1977). (note: Quoted in the FWS summary from Procopio (2021), citing Goldman and Rundquist (1977).) |
| The back is typically brownish-tan. | The dorsal surface of Signal Crayfish is typically brownish-tan in coloration. (note: Quoted in the FWS summary from Procopio (2021); dorsal surface glossed as back.) |
| The claws are bright red underneath, and a white or turquoise patch sits at the base of each claw joint. | A bright red coloration on the underside of claws, and a white or turquoise colored patch present at the base of each claw joint is distinctive to the Signal Crayfish (note: Quoted in the FWS summary from Procopio (2021).) |
| it may eat more animal than plant material when it can | although more animal than plant material may be consumed if available (note: Quoted in the FWS summary from GISD (2023).) |
| In crowded populations, competition and cannibalism can greatly affect survival. | Competition and cannibalism can greatly affect survival in dense populations. (note: Quoted in the FWS summary from GISD (2023); the quote follows survivorship to age 2.) |
| Females carry their eggs through the winter | females carry the eggs throughout the winter (note: Procopio (2021), quoted in the FWS summary) |
| usually 200 to 400 | Egg numbers usually range from 200 to 400 (note: Quoted in the FWS summary from GISD (2023).) |
| At home it is native to the Columbia River Basin, whose tributaries reach into Washington, Oregon, Idaho and British Columbia, and south along Oregon's coast to the Klamath River. | the native range spans northwest up the mainstem to tributaries that reach into Washington, Oregon, Idaho, and British Columbia. The native range extends south from the Columbia River along Oregon’s coast where the Klamath River and its drainages form its southern boundary (note: Procopio (2021), quoted in the FWS summary.) |
| tolerates water temperatures up to 33°C | Its ability to tolerate water temperatures up to 33°C has allowed it to prosper in many environments. (note: Quoted in the FWS summary from Houghton and Allen (2014).) |
| In Europe it now occurs in many countries, from the UK and France in the west to Russia in the east, and from Norway, Sweden and Finland in the north to the Iberian Peninsula in the south. | now occurs in many countries from the UK and France in the west, to Russia in the east. ... the northern extent is Norway, Sweden and Finland, while the southern extent is the Iberian Peninsula. (note: Quoted in the FWS summary from Houghton and Allen (2014).) |
| It has also been introduced to Japan. | [Introduced to] Hokkaido, Fukushima, Shiga, Nagano, Tochigi and Chiba Prefs [Japan]. (note: Quoted in the FWS summary from NIES (2023).) |
| At sites with high crayfish density, benthic macroinvertebrate biomass, the weight of bottom-dwelling animals without backbones, was 99% lower than at low-density sites. | At high crayfish density sites, benthic macroinvertebrate biomass was 99% lower, and taxa richness was 50% lower than at low crayfish areas. (note: Scordo (2023), quoted in the FWS summary; Crater Lake is in Oregon per the FWS text (Crater Lake, OR.). The gloss is a definition.) |
| Wild signal crayfish may survive up to 9 years or more. | the Signal Crayfish may survive up to 9 years or more when living in the wild |
| other estimates say it may be as long as 20 years | other estimates state that it may be as long as 20 years (note: GISD (2023), quoted in the FWS summary) |
| Estimates using lipofuscin, a pigment that builds up with age, suggest some individuals can live 16 years | Based on the use of the lipofuschin technique it has been estimated that some individuals can live 16 years (note: GISD (2023), quoted in the FWS summary; source spells it lipofuschin. The pigment gloss is a definition.) |
| Usually 200 to 400, although some females of 66 mm carapace length have been reported with over 500. | Egg numbers usually range from 200 to 400, although some individuals of 66mm CL have been reported as having over 500 eggs. (note: GISD (2023), quoted in the FWS summary) |
| The eggs take 166 to 280 days to hatch. | Egg incubation time ranges from 166 to 280 days. (note: GISD (2023), quoted in the FWS summary) |
| They are known to occur in brackish water along the Pacific Coast at salinities as high as 20 ppt | It is also known to occur in brackish waters along the Pacific Coast in salinities as high as 20 ppt (Riegel, 1959). (note: Houghton and Allen (2014), quoted in the FWS summary) |
| a lab study found they can occupy water of about 26 ppt, 75% seawater, for several days | Wheatly & McMahon (1983) revealed via a laboratory study that Signal Crayfish can occupy waterways with salinity as high as ~26 ppt (75% seawater), for several days. (note: Procopio (2021), quoted in the FWS summary) |
| usually 200 to 400 of them | Egg numbers usually range from 200 to 400 (note: GISD (2023), quoted in the FWS summary) |
| carries the plague itself | Signal Crayfish serve as carriers of the crayfish plague (note: Procopio (2021), quoted in the FWS summary) |
| It lives in everything from small streams to large rivers and natural lakes | P. leniusculus can be found in a variety of habitats, from small streams to large rivers and natural lakes. (note: Houghton and Allen (2014), quoted in the FWS summary) |
| People have also established it in new waters in Oregon, Washington, California, Nevada, Utah | has been introduced to and is established in regions of Oregon, Washington, California, Nevada, [and] Utah (note: Procopio (2021), quoted in the FWS summary. "regions of" kept as "new waters": the native range covers parts of Oregon and Washington, and the 2025 summary notes the subspecies ranges are contested) |
| and Montana | USGS (2025) reports nonnative introductions of Pacifastacus leniusculus in Montana that resulted in an established population (note: body) |
| Japan | [Introduced to] Hokkaido, Fukushima, Shiga, Nagano, Tochigi and Chiba Prefs [Japan]. (note: stats.habitat; NIES (2023), quoted in the FWS summary) |
| Crater Lake in Oregon had no signal crayfish until they were stocked there in 1915 to feed game fish. | Signal Crayfish in Crater Lake, OR., were historically restricted from entering the waterbody, but later stocked there in 1915 to provide food for game fish previously introduced to the lake (note: Procopio (2021), quoted in the FWS summary) |
| introduced to new waters in the western US | has been introduced to and is established in regions of Oregon, Washington, California, Nevada, [and] Utah (note: stats.habitat; Procopio (2021), quoted in the FWS summary) |
| A white or turquoise patch marks the base of each claw joint of a signal crayfish, against claws that are bright red underneath. | A bright red coloration on the underside of claws, and a white or turquoise colored patch present at the base of each claw joint is distinctive to the Signal Crayfish (note: vibe.reason; Quoted in the FWS summary from Procopio (2021).) |

## Pacifastacus leniusculus biological summary. Alaska Center for Conservation Science.

https://accs.uaa.alaska.edu/wp-content/uploads/Pacifastacus_leniusculus_BIO.pdf

| The page says | The source says |
| :--- | :--- |
| Males can reach 16 cm long, while females reach a maximum of 12 cm. | Male crayfish can reach a length of 16 cm, while females can only achieve a maximum size of 12 cm. (note: Also in the FWS summary, from Houghton and Allen (2014)) |
| Age at maturity varies from 1 to 3 years. | Age at maturity varies from 1 to 3 years |
| a life expectancy of up to 20 years is possible | a life expectancy of up to 20 years is possible |

## Pacifastacus leniusculus species summary. Smithsonian Environmental Research Center, NEMESIS.

https://invasions.si.edu/nemesis/species_summary/97326

| The page says | The source says |
| :--- | :--- |
| Omnivore: aquatic plants, freshwater invertebrates and carrion | aquatic plants, freshwater invertebrates, carrion (note: stats.diet; Trophic Status: Omnivore on the same page) |
| aquatic plants, freshwater invertebrates and carrion | aquatic plants, freshwater invertebrates, carrion |

## Sbragaglia & Breithaupt (2021). Daily activity rhythms, chronotypes, and risk-taking behavior in the signal crayfish. Current Zoology.

https://doi.org/10.1093/cz/zoab023

| The page says | The source says |
| :--- | :--- |
| It is a nocturnal species | previous studies showed that the signal crayfish is a nocturnal species |

## Schuster, Taylor & Cordeiro (2010). Pacifastacus leniusculus. The IUCN Red List of Threatened Species 2010: e.T153648A4526314.

https://doi.org/10.2305/iucn.uk.2010-3.rlts.t153648a4526314.en

| The page says | The source says |
| :--- | :--- |
| Least Concern | IUCN Red List category: Least Concern (LC). (note: stats.conservationStatus; assessed 2010, category read through GBIF's copy of the Red List) |
| The IUCN rates the species Least Concern. | IUCN Red List category: Least Concern (LC). (note: category read through GBIF's copy of the Red List; assessment year not stated in the body) |