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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|lastauthoramp=yes|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|accessdate=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> |
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|lastauthoramp=yes|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|accessdate=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> |
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[[File:Aphanomyces astaci (trés probable).jpg|thumb|[[mycelia]]l filaments from ''[[Aphanomyces astaci]]'' on membranes of ''Pacifastacus leniusculus'']] |
[[File:Aphanomyces astaci (trés probable).jpg|thumb|[[mycelia]]l filaments from ''[[Aphanomyces astaci]]'' on membranes of ''Pacifastacus leniusculus'']] |
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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 |
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 web | url=http://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2664.13758 | 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 12 October 2020 Journal of Applied Ecology DOI 10.1111/1365-2664.13758 | date=12 October 2020 }}</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"/> Ireland is the last European country having no alien crayfish. |
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In both Sweden and Finland (where crayfish are eaten), the catch of signal crayfish exceeds that of the [[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 both Sweden and Finland (where crayfish are eaten), the catch of signal crayfish exceeds that of the [[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> |
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'''Signal crayfish''' were introduced in [[England]] in the 1970s but have since become invasive there also. They have been [[trapping|trapped]] but this is not getting rid of them, while it is [[bycatch|accidentally catching]] some of the native endangered [[white-clawed crayfish]], and may in fact be spreading [[crayfish plague]] to the natives.<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 web | url=http://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2664.13758 | 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 12 October 2020 Journal of Applied Ecology DOI 10.1111/1365-2664.13758 | date=12 October 2020 }}</ref> |
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==References== |
==References== |
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P. leniusculus
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| Pacifastacus leniusculus | |
The signal crayfish (Pacifastacus leniusculus) is a North American 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 6–9 centimetres (2.4–3.5 in) long, although sizes up to 16–20.32 centimetres (6.30–8.00 in) are possible.[3] 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,[4] like the white flags that signalmen used for directing trains—hence the name.
The lifecycle of the signal crayfish is typical for the family Astacidae. Around 200–400 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.[3] The eggs hatch into juveniles, which pass through three stages (two moults) before leaving their mother. Sexual maturity is reached after two to three years, and the lifespan can be up to 20 years.[3]
The signal crayfish is an omnivore, with most of its dietary intake being detritus.[5]
The signal crayfish is native to North America west of the Rocky Mountains, including the Canadian provinceofBritish Columbia, and the U.S. statesofWashington, Oregon, and Idaho.[6] It was introduced to California in 1912 into the San Lorenzo River watershed and from there rapidly spread throughout the state.[7] The only native crayfish remaining in California is the Shasta crayfish, of Shasta County, California (Pacifastacus fortis), where efforts are being made to create a barrier to signal crayfish invasion.[8] Within North America, it has also been introduced to Nevada, and the populations in Utah may be the result of introductions.[6] 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.[1]
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.[3] At the time, the signal crayfish was not recognized as a carrier of the crayfish plague.[3] 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.[9]
The signal crayfish is now the most widespread alien crayfish in Europe, occurring in 25 countries, from FinlandtoGreat Britain and from SpaintoGreece.[3][10] It was first introduced to Great Britain in 1976[11][12] 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.[9] Ireland is the last European country having no alien crayfish.
In both Sweden and Finland (where crayfish are eaten), the catch of signal crayfish exceeds that of the noble crayfish. The former is sold at roughly half the price compared to the latter.[13]
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| Pacifastacus leniusculus |
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| Astacus leniusculus |
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