Editing Signal crayfish

{{Short description|Species of crustacean}}

{{Speciesbox

|genus = Pacifastacus

|species = leniusculus

|authority = ([[James Dwight Dana|Dana]], 1852)<ref>{{ITIS|taxon=''Pacifastacus leniusculus'' (Dana, 1852) |id=97326|access-date=December 18, 2019}}</ref>

The '''signal crayfish''' ('''''Pacifastacus leniusculus''''') is a [[North America]]n species of [[crayfish]]. It was introduced to Europe in the 1960s to supplement the North European ''[[Astacus astacus]]'' fisheries, which were being damaged by [[crayfish plague]], but the imports turned out to be a carrier of that disease. The signal crayfish is now considered an [[invasive species]] across Europe, Japan, and California, ousting native species there.

Members of this species are typically {{convert|6|-|9|cm|abbr=on}} long, although sizes up to {{convert|16|-|20|cm|abbr=on}} are possible.<ref name="Nobanis"/> They are bluish-brown to reddish-brown in colour, with robust, large, smooth claws. They have a white to pale blue-green patch near the claw hinge,<ref>{{cite journal|url=http://www.wbrc.org.uk/WorcRecd/Vol1Iss2/crayFish.htm|title=Crayfish in Worcestershire|journal=Worcestershire Record|volume=1|issue=2|year=1997|page=4|author=Mike Averill}}</ref> like the white flags that signalmen used for directing trains&mdash;hence the name.

The [[Biological life cycle|lifecycle]] of the signal crayfish is typical for the family [[Astacidae]]. Around 200–400 [[egg (biology)|eggs]] are laid after mating in the autumn, and are carried under the female's tail until they are ready to hatch the following spring.<ref name="Nobanis"/> The eggs hatch into [[juvenile (organism)|juveniles]], which pass through three stages (two [[ecdysis|moults]]) before leaving their mother. [[Sexual maturity]] is reached after 2–3 years, and the [[longevity|lifespan]] can be up to 20 years.<ref name="Nobanis"/>

The signal crayfish is native to [[North America]] west of the [[Rocky Mountains]], including the [[Provinces and territories of Canada|Canadian province]] of [[British Columbia]], and the [[U.S. state]]s of [[Washington (state)|Washington]], [[Oregon]], and [[Idaho]].<ref name="Fetzner">{{cite web|author=James W. Fetzner Jr.|date=January 14, 2008|title=''Pacifastacus (Pacifastacus) leniusculus leniusculus'' (Dana, 1852). Signal crayfish |work=Crayfish Taxon Browser|publisher=[[Carnegie Museum of Natural History]]|access-date=August 8, 2010|url=http://iz.carnegiemnh.org/crayfish/NewAstacidea/species.asp?g=Pacifastacus&s=leniusculus&ssp=leniusculus}}</ref> It was introduced to [[California]] in 1912 into the [[San Lorenzo River]] watershed and from there rapidly spread throughout the state.<ref>{{cite news|title=Fighting the Bay Area Invasion of Signal Crayfish|author=Joe Eaton|newspaper=Berkeley Daily Planet|date=May 17, 2005|url=http://www.berkeleydailyplanet.com/issue/2005-05-17/article/21428?headline=Fighting-the-Bay-Area-Invasion-of-Signal-Crayfish-By-JOE-EATON-Special-to-the-Planet|access-date=December 18, 2019}}</ref> The only native crayfish remaining in California (aside from ''Pacifastacus leniusculus klamathensis,'' a subspecies of signal crayfish believed to be native to the Klamath River in Northern California) is the [[Shasta crayfish]], of [[Shasta County, California]] (''Pacifastacus fortis''), where efforts are being made to create a barrier to signal crayfish invasion.<ref>{{cite web|title=PG&E Joins Forces to Save the Endangered Shasta Crayfish|publisher=PG&E|url=http://www.pge.com/about/environment/pge/stewardship/crayfish/|access-date=September 4, 2011|archive-url=https://web.archive.org/web/20111019103453/http://www.pge.com/about/environment/pge/stewardship/crayfish/|archive-date=October 19, 2011|url-status=dead}}</ref> Within North America, it has also been introduced to [[Nevada]], and the populations in [[Utah]] may be the result of introductions.<ref name="Fetzner"/> It has also been found in Alaska, specifically Kodiak Island, in the Buskin River and Buskin Lake. It is listed as a species of [[least concern]] on the [[IUCN Red List]].<ref name=IUCN>{{cite iucn|author1=G. A. Schuster|author2=C. A. Taylor|author3=J. Cordeiro|title=''Pacifastacus leniusculus''|page=e.T153648A4526314|year=2010|doi=10.2305/IUCN.UK.2010-3.RLTS.T153648A4526314.en|access-date=7 October 2023}}</ref>

From 1907, [[crayfish plague]], an infectious disease caused by the [[water mould]] ''Aphanomyces astaci'', damaged stocks of the native European crayfish ''[[Astacus astacus]]''. Since the signal crayfish occupied a similar [[ecological niche]] in its native range, it was imported in the 1960s to [[Sweden]] and [[Finland]] to allow recreational and commercial crayfish capture.<ref name="Nobanis">{{cite web|author1=Trond Taugbøl|author2=Stein I. Johnsen|name-list-style=amp|year=2006|title=Invasive Alien Species Fact Sheet – ''Pacifastacus leniusculus''|work=Online Database of the North European and Baltic Network on Invasive Alien Species|publisher=NOBANIS – European Network on Invasive Species|url=http://www.nobanis.org/files/factsheets/Pacifastacus_leniusculus.pdf|access-date=August 28, 2010}}</ref> At the time, the signal crayfish was not recognized as a [[Asymptomatic carrier|carrier]] of the crayfish plague.<ref name="Nobanis"/> All American species carry the infection, but it is only lethal to individuals that are already stressed; to European species, the infection is rapidly fatal.<ref name="Summer">{{cite book|editor=Norman Maclean|year=2010|title=Silent Summer: The State of Wildlife in Britain and Ireland|publisher=[[Cambridge University Press]]|chapter=Other invertebrates|pages=556–575|author1=[[Richard Chadd]]|author2=Brian Eversham|isbn=9781139788694}}</ref>

The signal crayfish is now the most widespread alien crayfish in Europe, occurring in 25 countries, from [[Finland]] to [[Great Britain]] and from [[Spain]] to [[Greece]].<ref name="Nobanis"/><ref>{{cite journal|author=Silva, S.|author2=Outón, P.|author3=Nachón, D. J.|author4=Gómez-Sande, P.|author5=Sánchez-Hernández, J.|author6=Vieira-Lanero, R.|author7=Cobo, F.|year=2017|title=New data on the introduction of the invasive signal crayfish ''Pacifastacus leniusculus'' (Dana, 1852) (Crustacea, Decapoda) and ectosymbiont branchiobdellidans (Annelida, Clitellata) in NW Iberian Peninsula|journal=Nova Acta Científica Compostelana (Bioloxía)|volume=24|pages=63–68|issn=2340-0021|url=http://www.usc.es/revistas/index.php/nacc/article/view/3970/4199}}</ref> It was first introduced to Great Britain in 1976,<ref name="Brit-Eco-Soc">{{ cite web | url=http://www.britishecologicalsociety.org/crayfish-trapping-fails-to-control-invasive-species/ | title=Crayfish 'trapping' fails to control invasive species | date=13 October 2020 }}</ref><ref name="Daniel-Chadwick-et-al-2020">{{ Cite journal | title=A novel 'triple drawdown' method highlights deficiencies in invasive alien crayfish survey and control techniques Daniel D. A. Chadwick Eleri G. Pritchard Paul Bradley Carl D. Sayer Michael A. Chadwick Lawrence J. B. Eagle Jan C. Axmacher |journal=Journal of Applied Ecology | date=12 October 2020 | doi=10.1111/1365-2664.13758 | s2cid=225116874 | doi-access=free }}</ref> and is now widespread across the British mainland as far north as the [[Moray Firth]]. It has also been observed on the [[Isle of Man]], but not in [[Ireland]],<ref name="Summer"/> the last European country to have no alien crayfish.

In both Sweden and Finland (where crayfish are eaten), the catch of signal crayfish exceeds that of ''A. astacus'' (European/noble crayfish). The former is sold at roughly half the price compared to the latter.<ref>{{cite web|url=https://www.fws.gov/fisheries/ans/erss/highrisk/Pacifastacus-leniusculus-ERSS-revision-June2015.pdf|title=Signal Crayfish (Pacifastacus leniusculus) Ecological Risk Screening Summary|publisher=U.S. Fish and Wildlife Service|date=February 2011}}</ref>

In Europe, the signal crayfish is included since 2016 in the list of Invasive Alien Species of Union concern (the Union list).<ref>{{Cite web|title=List of Invasive Alien Species of Union concern - Environment - European Commission|url=https://ec.europa.eu/environment/nature/invasivealien/list/index_en.htm|access-date=2021-07-27|website=ec.europa.eu}}</ref> This implies that this species cannot be imported, bred, transported, commercialized, or intentionally released into the environment in the whole of the European Union.<ref>{{Cite web|title=REGULATION (EU) No 1143/2014 of the European parliament and of the council of 22 October 2014 on the prevention and management of the introduction and spread of invasive alien species|url=https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32014R1143&from=EN}}</ref> The signal crayfish is often considered a nuisance species amongst anglers in Europe.<ref>{{Cite web|date=2020-12-14|title=Avoiding Crayfish Carp Fishing - Beat the Crayfish!|url=https://carpsquad.com/avoiding-crayfish-carp-fishing/|access-date=2022-01-31|website=Carp Squad|language=en-US}}</ref>

Multiple studies have been published to find out how the damage caused by the settlement — and subsequent overpopulation — of invasive signal crayfish in Europe can be mitigated, including studies regarding effective upstream barriers against signal crayfish that don’t negatively impact the migration of fish,<ref>{{Cite journal |last1=Frings |first1=Roy M. |last2=Vaeßen |first2=Susanne C. K. |last3=Groß |first3=Harald |last4=Roger |first4=Sebastian |last5=Schüttrumpf |first5=Holger |last6=Hollert |first6=Henner |date=2013-03-01 |title=A fish-passable barrier to stop the invasion of non-indigenous crayfish |url=https://www.sciencedirect.com/science/article/pii/S0006320712005125 |journal=Biological Conservation |language=en |volume=159 |pages=521–529 |doi=10.1016/j.biocon.2012.12.014 |issn=0006-3207}}</ref><ref name=":0" /> as well as other, aggressive but more efficient approaches which may harm an existing ecosystem further, such as eradication (by means of drainage or destruction of waterways, and [[biocide]]s) and suppression (by means of extensive trapping, electrocution of waterways, and introduction of predatory fish), with eradication being most successful.<ref name=":0">{{Cite journal |last1=Raphael |first1=Krieg |last2=Alex |first2=King |last3=Armin |first3=Zenker |date=2020 |title=Measures to Control Invasive Crayfish Species in Switzerland: A Success Story? |journal=Frontiers in Environmental Science |volume=8 |language=English |doi=10.3389/fenvs.2020.609129 |issn=2296-665X|doi-access=free }}</ref>

==References==

{{Reflist}}

{{Commons category|Pacifastacus leniusculus|''Pacifastacus leniusculus''}}

{{Authority control}}