Pacifastacus leniusculus - NOBANIS

NOBANIS - Invasive Alien Species Fact Sheet 

Pacifastacus leniusculus 

Authors of this fact sheet: 

Stein I. Johnsen, Norwegian Institute for Nature Research (NINA), Fakkelgården, NO-2624 Lillehammer, Norway; +47 

73801628; stein.ivar.johnsen@nina.no 

Trond Taugbøl, Glommen’s and Laagen’s Water Management Association, P.O.Box 1209 Skurva, NO-2605 

Lillehammer, Norway; +47 93466712; tt@glb.no 

Bibliographical reference – how to cite this fact sheet: 

Johnsen, S.I. and Taugbøl, T. (2010): NOBANIS – Invasive Alien Species Fact Sheet – Pacifastacus leniusculus. – 

From: Online Database of the European Network on Invasive Alien Species – NOBANIS www.nobanis.org, Date of 

access x/x/201x. 

Species description 

Scientific names: Pacifastacus leniusculus (Dana, 1852), Astacidae. 

Synonyms: no common synonyms used. 

Common names: signal crayfish (GB), rak signální (CZ), signalkrebs (DK), Signalkrebs (DE), 

signaalvähk (EE), täplärapu (FI), žymėtasis vėžys (LT), signālvēzis (LV), Californische rivierkreeft 

(NL), signalkreps (NO), rak sygnałowy (PL), сигнальный рак (RU), signalkräfta (SE). 

Fig. 1. Pacifastacus leniusculus, note the white-turquoise patch on the upper side of the claw 

(chelae), photo by Eilif Byrnak.

Species identification 

The signal crayfish is similar to and can be confused with the noble crayfish (Astacus astacus) 

which is native to parts of the region. The signal crayfish is distinguished from the noble crayfish, 

both as juvenile and adult, by the more smooth nature of the chelae and the lack of a row of spines 

on the shoulders of carapace behind cervical groove. The white-turquoise patch on the upper side of 

the chelae is also unique to the adult signal crayfish (Fiskeriverket/Naturvårdsverket 2005, Lewis 

2002, Pöckl et al. 2006). 

Native range 

The native range of the signal crayfish is the northwestern USA and southwestern Canada where it 

occurs from British Columbia in the north, central California in the south, and Utah in the east 

(Lewis 2002). 

Alien distribution 

History of introduction and geographical spread 

In 1960, a small batch of signal crayfish was introduced to Sweden from California, USA, in an 

attempt to find a species which could replace the populations of the indigenous noble crayfish, 

which was severely depleted by the crayfish plague from 1907 onwards 

(Fiskeriverket/Naturvårdsverket 1998). The signal crayfish was considered to occupy the same 

ecological niche and presumed to be able to restore the recreational and commercial important 

crayfish fishery in the plague affected areas. The fact that it was also a carrier of crayfish plague 

was unknown at the time (Unestam 1972). Trials were successful and in 1967-69, a large number of 

signal crayfish were imported from USA and introduced into Swedish and Finnish waters (Lowery 

and Holdich 1988, Westman 1995). These were followed by further secondary introductions, 

including large numbers of domestic hatchery-reared juveniles. Further introductions, especially of 

juveniles from Sweden, were made to many European countries (Lowery and Holdich 1988). The 

signal crayfish is at present most established in Sweden where it occurs in approximately 4000 

localities (Edsman and Schröder 2009). An increasing number of signal crayfish introductions have 

taken place during the last 30 years in Denmark and this illegal practice still goes on. The crayfish 

has been released in many small lakes, wherefrom it has spread to a number of the larger river 

system on Zealand and in Jutland. In the summer 2010 it was found in coastal waters in the Danish 

part of the Baltic Sea as well (Eilif Byrnak, pers. comm.; Søren Berg, pers. comm..). In Austria, 

2000 signal crayfish were imported in summer 1970 from California and released in several 

provinces. Today, the species is present in all provinces, widely distributed, particularly in the 

eastern provinces, and locally abundant. The crayfish was introduced to Czech Republic in 1980 

from Sweden for commercial production. Until 2006, the signal crayfish was recorded in 24 

European countries/regions (Souty-Grosset et al. 2006). Signal crayfish was recorded in Norway in 

2006 (Johnsen et al. 2007), but this population is now most likely eradicated with chemicals 

(Sandodden and Johnsen 2010). However, signal crayfish was recorded in a larger watercourse in 

south-eastern Norway in 2008 (Johnsen and Vrålstad 2009). Records of signal crayfish in Norway, 

Slovakia (Maguire et al. 2008) and Croatia (Petrusek and Petruskova 2007) extends the list from 

2006 (Souty-Grosset et al. 2006) to 27 European countries/regions (Holdich et al. 2009). This 

makes the signal crayfish the most widely spread alien freshwater crayfish species in Europe 

(Souty-Grosset et al. 2006, Holdich et al. 2009). In the Nordic-Baltic region it is found/established 

in all countries except Russia (nor in Iceland, Greenland and Faroe Islands where no freshwater 

crayfish species occur). In 2008 the first specimen was found in Estonia (Hurt and Kivistik 2009). 

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Fig. 2. Present distribution of signal crayfish (Pacifastacus leniusculus) in Europe. © Publications 

Scientifique MNHN, Paris, 2006. (After Souty-Grosset et al. 2006). The records of signal crayfish 

in Norway (Johnsen and Vrålstad 2009, Slovakia (Maguire et al. 2008) and Croatia (Petrusek and 

Petruskova 2007), Estonia (Hurt and Kivistik 2009) and Jutland, Denmark (E. Byrnak pers. comm.) 

are not represented in the map. 

Pathways of introduction 

The most common pathway of introduction into natural waters is stocking by humans. In the 1970- 

80s the stocking policy in the region was liberal, and the signal crayfish was introduced legally into 

a large number of natural waters. From the late 1980s onwards, the introduction of the signal 

crayfish into new areas was restricted by the environmental authorities due to the threat it posed to 

the indigenous, red-listed noble crayfish (Troschel and Dehus 1993, Skurdal et al. 1999, Edsman 

2004). However, the distribution of the signal crayfish is still rapidly increasing, including more and 

more watercourses. The crayfish can spread by natural migration only within a watercourse, 

between migration barriers. Most of the current spread is therefore due to illegal introductions by 

humans. 

Alien status in region 

The signal crayfish has been introduced to all countries in the region, except Russia and the North 

Atlantic Islands (see table 1). In Estonia, one specimen of signal crayfish was found in R. 

Mustjõgi (northern Estonia) in 2008. In 2009, a bigger survey was carried out, no alien crayfish was 

found, but no native crayfish was found where the alien crayfish had been found previously. Thus, 

the signal crayfish might have been the carrier of crayfish plague (Hurt and Kivistik 2009). It is 

very common in Sweden and Finland, common in Germany, Denmark and Austria and found in a 

more limited number of localities in Poland, Lithuania and Latvia (Souty-Grosset et al. 2006). In 

Norway, signal crayfish is now only confirmed to exist in one locality (Johnsen and Vrålstad 2009). 

3

Country Not Not Rare Local Common Very 

found established 

common 

Austria 

Belgium 

X 

Czech republic X 

Denmark X 

Estonia X 

European part of Russia X 

Finland X 

Faroe Islands X 

Germany X 

Greenland X 

Iceland X 

Ireland X 

Latvia X 

Lithuania X 

Netherlands X 

Norway X 

Poland 

Slovakia 

X 

Sweden X 

Not 

known 

Table 1. The frequency and establishment of Pacifastacus leniusculus, please refer also to the 

information provided for this species at www.nobanis.org/search.asp. Legend for this table: Not 

found –The species is not found in the country; Not established - The species has not formed selfreproducing 

populations (but is found as a casual or incidental species); Rare - Few sites where it is 

found in the country; Local - Locally abundant, many individuals in some areas of the country; 

Common - Many sites in the country; Very common - Many sites and many individuals; Not 

known – No information was available. 

Ecology 

Habitat description 

The native habitat of the signal crayfish ranges from small streams to large rivers, and lakes from 

the coastal to the sub-alpine regions. Signal crayfish can also survive in brackish water (Holdich et 

al. 1997). The distribution of the signal crayfish in Europe comprises the same range of habitats 

(Souty-Grosset et al. 2006). 

Reproduction and life cycle 

The signal crayfish has a typical life cycle of a member of the crayfish family Astacidae (Lewis 

2002). Mating and egglaying occurs during autumn, mainly in October. Egg numbers usually range 

from 200 to 400. After egg laying the female carry the eggs under the tail until hatching. Hatching 

time varies greatly depending on temperature, and in natural populations it may occur from late 

March to the end of July. The eggs hatch into miniature crayfish that stay with the mother for three 

stages (two moults). In the third stage the juvenile crayfish gradually become more and more 

independent of the mother, adopting a solitary life. Size at maturity is usually 6-9 cm total-length 

(from tip of head to edge of tail-fan) at an age of 2-3 years. Estimates of survivorship to age 2 vary 

from 10-52%, being dependent on both abiotic and biotic factors. Competition and cannibalism can 

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greatly affect survival in dense populations. Maximum age and size are reported to be approx. 20 

years and 16-18 cm, but such sizes are very seldom. 

Dispersal and spread 

Humans are the overall most important vector for dispersal and spread (see above) of the signal 

crayfish. Due to fisheries in natural waters in most regions where it occurs, signal crayfish are easily 

accessible as stocking material. Within the watercourse the signal crayfish can spread by own 

migration. Upstream migration rates of more than 1 km per year are reported from rivers in Finland 

and England. Downstream spread can be faster (Westman and Nylund 1979, Guan and Wiles 

1997a, Peay and Rogers 1999). There are also indications that the signal crayfish may pass dams 

and waterfalls by walking on dry land (Hiley 2003). Probably this behaviour is triggered by high 

density or other unfavourable conditions. Normally, the crayfish would not leave the water and 

expose itself to great predation risk on land, but at least this shows its potential for self dispersal. 

Impact 

Affected habitats and indigenous organisms 

The signal crayfish occupies the same ecological niche as the indigenous noble crayfish. It occurs 

mainly in localities previously inhabited by these species, and maintains in general the same effects 

on natural habitats. It is considered to be a non-burrowing species in North America, but in Europe 

it constructs burrows in river and lake banks (Holdich and Reeve 1991), similar to the noble 

crayfish. As an opportunistic polytrophic feeder it also consumes detritus and thereby plays an 

important role in the degradation and mineralization of dead organic matter. It may exert a 

significant grazing pressure on macrophytes, aquatic insects, snails, benthic fishes and amphibian 

larvae. Several studies indicate that signal crayfish have a stronger impact on the food web structure 

than the indigenous noble crayfish (Guan and Wiles 1997b, Nyström 1999, 2002 and references 

herein). 

The most severe effect of the signal crayfish is the extermination of the noble crayfish, caused by 

the transmission of the crayfish plague (another invasive species) (Alderman 1997). Indigenous 

European crayfish species have no resistance to against this disease and experience total mortality. 

American crayfish species on the other hand have co-evolved with the crayfish plague and 

developed defence systems making them a natural host for and carrier of this parasitic disease 

(Unestam 1972, Evans and Edgerton 2002). Most, if not all, signal crayfish are infected by the 

crayfish plague. Thus, if a signal crayfish population is established in a watercourse, the crayfish 

plague is also established, and there is no possibility for the noble crayfish to co-exist. For this 

reason, the spread of signal crayfish is the most serious threat to the indigenous noble crayfish. 

Genetic effects 

No hybrids with other crayfish species have been reported. Signal crayfish can mate with noble 

crayfish, but the eggs are not fertile. 

Human health effects 

No human health effects have been reported, although allergies towards shellfish may occur. 

Economic and societal effects (positive/negative) 

In many countries in the region, especially Sweden and Finland, the signal crayfish populations 

support a large, commercially and recreationally important, fishery (Ackefors 1999). In Europe as a 

whole, a total of 355 tonnes of signal crayfish was estimated from capture fisheries in 1994 

5

(Ackefors 1998). This level has increased considerably, and in 2001 the Swedish catch was 

estimated to 1200 tonnes. In recent years, however, levels have dropped for unknown reasons. 

Viruses in combination with a chronic plague infection have been suspected as a possible reason 

(Söderhäll 2004). The amount of cultured amount of signal crayfish in Sweden was estimated to 42 

tonnes in 1996 (Ackefors 1998). 

The most serious negative effect of the signal crayfish is the extermination of the indigenous noble 

crayfish, due to the uncontrolled spread of the signal crayfish to more and more watercourses. The 

noble crayfish has great sociocultural/-economic traditions in the region (Swahn 2004) and is more 

valuable than the signal crayfish, also from the pure economic point of view. First and foremost 

because of the uncontrolled spread of signal crayfish, the noble crayfish is recognized as a 

threatened species included in the international Red List, the Bern Convention and EU’s Habitat 

Directive. 

Management approaches 

Prevention methods 

Preventing the further introduction of signal crayfish to new water bodies by humans is the greatest 

management challenge (for efforts, see below). In most countries in the region the introduction of 

live non-indigenous crayfish species, like the signal crayfish, is not permitted (Skurdal et al. 1999). 

In Latvia the import of live crayfish is allowed, only a veterinary certificate is needed (Arens and 

Taugbøl 2005). In all countries stocking of live crayfish in natural waters requires permission from 

the authorities. The lack of effective control and enforcement is, however, a problem. 

Eradication, control and monitoring efforts 

When the signal crayfish is established in a water body there is no practical way of eradication, 

except perhaps in very small, enclosed waterbodies where insecticides or other chemicals might be 

applied (Sandodden and Johnsen 2010). Extensive trapping may reduce population density and slow 

down the speed at which it spreads naturally, but it is not an effective control method. There is 

important research into pheromone trapping of male signal crayfish (Stebbing et al. 2004, Stebbing 

et al. 2005), this method could become in the future be used as a control and eradication method. 

Monitoring of the distribution and identifying new populations by test-fishing provide important 

information necessary in a management strategy. Monitoring of crayfish distribution and occurrence 

takes place in several countries in the region and reveals that illegal signal crayfish introductions 

occur to a large extent and is the major reason for further spread. 

Information and awareness 

The key factor to prevent further spread of the signal crayfish is information about the negative 

effects. It is imperative to convince landowners/fishermen that the indigenous noble crayfish is the 

best alternative for crayfish harvest. With live signal crayfish easily accessible from natural waters 

not far away, it is impossible to prevent (illegal) stocking if local people want to do so. Information 

campaigns, including folders/brochures, media contact and education in schools are important. 

Likewise concrete projects aimed at conservation and sustainable use of noble crayfish and the 

prevention of further spread of signal crayfish, through information and involvement of relevant 

interest groups. The so-called “Astacus”-project, an inter-regional collaboration project between 

Norway and Sweden, is an example of such a project (www.astacus.org). 

6

Knowledge and research 

Several research topics have been carried out on the signal crayfish in the region, especially in 

Sweden and Finland. Prevalent topics are on its ecology, immunology, behaviour, population 

biology and environmental impact (see Nyström 1999, 2002, Söderhäll and Söderhäll 2002 and 

references herein). There has also been some research into improving methods for its culture. 

Recommendations or comments from experts and local communities 

Signal crayfish should be managed as a valuable resource for recreational and commercial fishery in 

areas where it is established (Ackefors 1999, Taugbøl and Skurdal 1999). In other areas where the 

noble crayfish still has a chance to survive, the great values of this species should be emphasized, 

and it should be made clear to all stakeholders that the spread of signal crayfish to these areas is a 

tragedy to nature and to the socioeconomic/-cultural values the noble crayfish represents. In 

addition it is an environmental crime. 

Furthermore, in the light of decreasing catches and numerous collapses of signal crayfish 

populations in recent years, there is no guarantee that stocking of signal crayfish will give a 

harvestable population in the long run. 

References and other resources 

Contact persons 

Lennart Edsman (SE) Swedish Board of Fisheries, Freshwater Laboratory, Stångholmsvägen 2, SE- 

178 93 Drottningholm, Sweden; Phone: + 46 8-699 06 00, Fax: +46 8-699 06 50; E-mail: 

Lennart.Edsman@fiskeriverket.se 

Stein I. Johnsen (NO) Norwegian Institute for Nature Research, Fakkelgaarden, NO-2624 

Lillehammer, Norway; Phone: +47 73801628; E-mail: stein.ivar.johnsen@nina.no 

Stefan Nehring (DE) Federal Agency for Nature Conservation, Konstantinstrasse 110, D-53179 

Bonn; Phone: +49-228-84911444; E-mail: stefan.nehring@bfn.de 

Eilif Byrnak (DK) Natur and Miljø, Vestsjællands Amt, Alleen 15, DK-4180 Sorø; Denmark 

Phone: +45 57872829; E-mail: eby@vestamt.dk 

Gudni Gudbergsson (IS) Institute of Freshwater Fisheries, Vagnhofdi 7, IS-110 Reykjavik, Iceland; 

Phone: +354 5676400; E-mail: gudni.gudbergsson@veidimal.is 

Augusts Arens (LV) Latvian Crayfish and Fish Farmers' Association, 7-6 Alberta St., Riga LV- 

1010, Latvia; Phone/fax: +371-7-336-005; E-mail: earens@latnet.lv 

Przemyslaw Smietana (PL) University of Szczecin, Department of Ecology, ul. Waska 13, PL-71-412 

Szczecin, Poland; E-mail: leptosp@univ.szczecin.pl 

Margo Hurt (EE) Department of Fishery, Estonian University of Life Sciences, Krutzwaldi 48, EE- 

51006 Tartu, Estonia; Phone: + 372 731 3481; E-mail: margo.hurt@emu.ee 

Ari Mannonen(FI) Crayfish Innovation Center, Päijänne-Institute, Koulutuskeskus Salpaus, 

Laurellintie 55, FI-17320 Asikkala, Finland; Phone: +358 40 7082524; E-mail: 

raputietokeskus@jippii.fi 

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Links 

The International Association of Astacology (IAA) 

Global Invasive Species Data Base - Pacifastacus leniusculus (ISSG - Invasive Species Specialist 

Group) 

References 

Ackefors, H. 1998. The culture and capture crayfish fisheries in Europe. World Aquaculture 29: 12-24, 64-67. 

Ackefors, H. 1999. The positive effects of established crayfish introductions in Europe, in: Gherardi, F. and Holdich, D. 

M. (Eds), Crayfish in Europe as alien species. How to make the best of a bad situation. A. A. Balkema, Rotterdam: 

49-61. 

Alderman, D.J. 1997. History of the spread of crayfish plague in Europe, in: Crustaceans: Bacterial and fungal 

diseasaes. QIE Scientific and Technical Review 15: 15-23. 

Arens, A. and Taugbøl, T. 2005. Status of freshwater crayfish in Latvia. Bulletin Français de la Pêche et de la 

Pisciculture (376-377): 519-528. 

Edsman, L. 2004. – The Swedish story about import of live crayfish. Bulletin Français de la Pêche et de la Pisciculture 

(372-373): 281-288. 

Edsman L. and Schröder S. 2009. Åtgärdsprogram för Flodkräfta 2008–2013 (Astacus astacus), 

Fiskerivertet och Naturvårdsverket, Rap. 5955, 67 p. 

Evans L. H. and Edgerton B. F. 2002. – Pathogens, parasites and commensals, in Holdich D. M. (Ed.), Biology of 

freshwater crayfish. Blackwell Science, Oxford: 377-438. 

Fiskeriverket/Naturvårdsverket 1998. Åtgärdsprogram för bevarande av flodkräfta. 

Fiskeriverket/Naturvårdsverket 2005. Information folder. Web-version 

Guan, R-Z. and Wiles, P.R. 1997a. The home range of signal crayfish in a British lowland river. Freshwater Forum 8: 

45-54. 

Guan, R.-Z. and Wiles, P.R. 1997b. Ecological impact of introduced crayfish on benthic fishes in a British lowland 

river. Conservation Biology 11: 641-647. 

Hiley, P.D. 2003. The slow quiet invasion of signal crayfish (Pacifastacus leniusculus) in England – prospects for the 

white-clawed crayfish (Austropotamobius pallipes). Pp. 127-138 in: Holdich, D.M. and Sibley, P.J. (eds.) 

Management and Conservation of Crayfish. Proceedings of a conference held on 7 th November, 2002. Environment 

Agency, Bristol, 217 pp. 

Holdich, D. M, Harlioglu, M. M. and Firkins, I. 1997. Salinity adaptations of crayfish in Brittish Waters with particular 

reference to Austropotamobius pallipes, Astacus leptodactylus and Pasifastacus leniusculus. Estuarine, Coastal and 

Shelf Science 44: 147-154. 

Holdich, D. M., and Reeve, I. D. 1991. Alien crayfish in the British Isles. Report for the National Environment Research 

Council, Swindon. 

Holdich, D.M., Reynolds, J.D., C. Souty-Grosset, C. and Sibley, P.J. 2009. A review of the ever increasing threat to 

European crayfish from non-indigenous crayfish species. Knowledge and Management of Aquatic Ecosystems 394- 

395, 11. 

Hurt, M. and Kivistik, M. 2009 Signaalvähi ja jõevähi levik ja arvukus Jägala jõestikus. Report for the Ministry of the 

Environment. 

Johnsen, S.I., Taugbøl, T., Andersen, O., Museth, J. and Vrålstad, T. 2007. The first record of the non-indigenous signal 

crayfish Pasifastacus leniusculus in Norway. Biological Invasions 9: 939-941. 

Johnsen, S.I. and Vrålstad T., 2009. Signal crayfish and crayfish plague in the Halden watercourse – 

proposition for a measurement plan, NINA Report 474, 29 p. 

Lewis, S.D. 2002. Pacifastacus, in Holdich D. M. (Ed.), Biology of freshwater crayfish. Blackwell Science, Oxford: 

511-540. 

Lowery R. S. and Holdich D. M. 1988. Pacifastacus leniusculus in North America and Europe, with details of the 

distribution of introduced and native crayfish species in Europe, in Holdich D. M. and Lowery R. S. (Eds), 

Freshwater crayfish: biology, management and exploitation. Croom Helm, London: 283-308. 

Maguire I., Klobucar, G., Marcic, Z. and Zanella D., 2008. The first record of Pacifastacus leniusculus in 

Croatia. Crayfish News: IAA Newsletter, 30, 4, 4. 

Nyström P. 1999. Ecological impact of introduced and native crayfish on freshwater communities: European 

perspectives, in Gherardi, F. and Holdich, D. M. (Eds), Crayfish in Europe as alien species. How to make the best of 

a bad situation. A. A. Balkema, Rotterdam: 63-85. 

Nyström P. 2002. Ecology, in: Holdich, D. M. (Ed.), Biology of freshwater crayfish. Blackwell Science, Oxford: 192- 

235. 

8

Peay, S. and Rogers, D. 1999. The peristaltic spread of signal crayfish (Pacifastacus leniusculus) in the River Wharfe, 

Yorkshire, England. Freshwater Crayfish 12: 665-676. 

Petrusek A. and Petruskova T. 2007. Invasive American crayfish Pacifastacus leniusculus (Decapoda: 

Astacidae) in the Morava River (Slovakia). Biologie, Bratislava, 62(3): 356–359. 

Pöckl M, Holdich DM and Pennerstorfer J (2006) Identifying native and alien crayfish species in Europe. Craynet, p 47. 

Sandodden, R. and Johnsen, S. I. 2010. Eradication of introduced signal crayfish Pasifastacus leniusculus using the 

pharmaceutical BETAMAX VET.®. Aquatic Invasions 5(1): 75-81. 

Skurdal J., Taugbøl T., Burba A., Edsman L., Söderbäck B., Styrishave B., Tuusti J. and Westman K. 1999. Crayfish 

introductions in the Nordic and Baltic countries, in Gherardi, F. and Holdich, D. M. (Eds), Crayfish in Europe as 

alien species. How to make the best of a bad situation. A. A. Balkema, Rotterdam: 193-219. 

Souty-Grosset C., Holdich D.M., Noël P.Y., Reynolds J.D. and Haffner P. (eds.) 2006. Atlas of Crayfish in Europe. 

Muséum national d’Histoire naturelle, Paris, 187 p. (Patrimoines naturels, 64). 

Stebbing, P. D., Watson, G. J., Bentley, M. G., Fraser, D., Jennings, R. Rusthonm S. P. & Sibley, P. J. 2004. Evaluation 

of the capacity of pheromones for control of invasive non-native crayfish: part 1. English Nature Research Report 

No. 578. English Nature, Peterborough: 39 p. 

Stebbing, P. D., Watson, G. J., Bentley, M. G., Fraser, D., Jennings, R. & Sibley, P. J. 2005. Evaluation of the capacity 

of pheromones for control of invasive non-native crayfish: part 2. English Nature Research Report No. 633. English 

Nature, Peterborough, 46 p. 

Swahn, J.-Ö. 2004. The cultural history of crayfish. Bulletin Français de la Pêche et de la Pisciculture (372-373): 243- 

251. 

Söderhäll, I. and Söderhäll, K. 2002. Immune reactions,in: Holdich, D. M. (Ed.), Biology of freshwater crayfish. 

Blackwell Science, Oxford: 439-464. 

Söderhäll, K. 2004. Krasslig kräfta – tvivelaktig import. Miljöforskning 2004-08-10. 

Taugbøl T. and Skurdal J. 1999. The future of native crayfish in Europe: How to make the best of a bad situation?, in 

Gherardi F. and Holdich D. M. (Eds), Crayfish in Europe as alien species. How to make the best of a bad situation. 

A. A. Balkema, Rotterdam: 271-279. 

Troschel, H.J. and Dehus, P. 1993. Distribution of crayfish species in the Federal Republic of Germany, with special 

reference to Austropotamobius pallipes. Freshwater Crayfish 9: 390-398. 

Unestam, T. 1972. On the host range and origin of of the crayfish plague fungus. Rep. Inst. Freshw. Res. 

Drottningholm, 52: 192-198. 

Westman K. 1995. Introduction of alien crayfish in the development of crayfish fisheries: experiences with signal 

crayfish (Pacifastacus leniusculus (Dana) in Finland and the impact on the noble crayfish (Astacus astacus (L.)). 

Freshwater Crayfish 10: 1-17. 

Westman, K. and Nylund, V. 1979. Crayfish plague, Aphanomyces astaci, observed in the European crayfish, Astacus 

astacus, in Pihlajavesi waterway in Finland. A case study on the spread of the plague fungus. Freshwater Crayfish 4: 

419-426. 

Date of creation/modification of this species fact sheet: 08-11-2010 

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Pacifastacus leniusculus - NOBANIS

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