Editing Signal crayfish (section)

==Introduction into Europe==
[[File:Pacifastacus leniusculus 01 by-dpc.jpg|thumb|left|A signal crayfish in Spain]]
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=Stein I. Johnsen|author2=Trond Taugbøl|name-list-style=amp|year=2010|title=NOBANIS – Invasive Alien Species Fact Sheet – ''Pacifastacus leniusculus''|publisher=Online Database of the European Network on Invasive Alien Species – NOBANIS|url=https://www.nobanis.org/globalassets/speciesinfo/p/pacifastacus-leniusculus/pacifastacus_leniusculus1.pdf|access-date=10 October 2024}}</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 has been included in the list of Invasive Alien Species of Union concern (the Union list) since 2016.<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 identify effective mitigation strategies for the detrimental impact of the settlement — and subsequent overpopulation — of invasive signal crayfish in Europe. This includes studies regarding effective upstream barriers against signal crayfish that do not adversely affect fish migration,<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 |bibcode=2013BCons.159..521F |issn=0006-3207|url-access=subscription }}</ref><ref name=":0" /> as well as other, aggressive but more efficient approaches which may cause further harm to existing ecosystems, 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 |bibcode=2020FrEnS...809129K }}</ref>