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Faxonius virilis
(virile crayfish)

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Datasheet

Faxonius virilis (virile crayfish)

Summary

  • Last modified
  • 02 January 2020
  • Datasheet Type(s)
  • Invasive Species
  • Threatened Species
  • Host Animal
  • Preferred Scientific Name
  • Faxonius virilis
  • Preferred Common Name
  • virile crayfish
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Arthropoda
  •       Subphylum: Crustacea
  •         Class: Malacostraca
  • Summary of Invasiveness
  • F. virilis is thought to be one of most widely invasive crayfish species in the USA (Larson and Olden, 2011), and...

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Pictures

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PictureTitleCaptionCopyright
Faxonius virilis (virile crayfish); large adult male FI, caught from River Lee, UK.
TitleMale
CaptionFaxonius virilis (virile crayfish); large adult male FI, caught from River Lee, UK.
Copyright©Environment Agency
Faxonius virilis (virile crayfish); large adult male FI, caught from River Lee, UK.
MaleFaxonius virilis (virile crayfish); large adult male FI, caught from River Lee, UK.©Environment Agency
Faxonius virilis (virile crayfish); adult female, with radio-tag attached for monitoring.
TitleFemale
CaptionFaxonius virilis (virile crayfish); adult female, with radio-tag attached for monitoring.
Copyright©Environment Agency
Faxonius virilis (virile crayfish); adult female, with radio-tag attached for monitoring.
FemaleFaxonius virilis (virile crayfish); adult female, with radio-tag attached for monitoring.©Environment Agency
Faxonius virilis (virile crayfish); juvenile.
TitleJuvenile
CaptionFaxonius virilis (virile crayfish); juvenile.
Copyright©Environment Agency
Faxonius virilis (virile crayfish); juvenile.
JuvenileFaxonius virilis (virile crayfish); juvenile.©Environment Agency
Faxonius virilis (virile crayfish); juvenile, ca.30 mm. Charlotte's Quest Nature Center, Manchester, Carroll County, Maryland, USA.  August 2016.
TitleJuvenile
CaptionFaxonius virilis (virile crayfish); juvenile, ca.30 mm. Charlotte's Quest Nature Center, Manchester, Carroll County, Maryland, USA. August 2016.
Copyright©Smithsonian Environmental Research Center/original image by Robert Aguilar/via flickr - CC BY 2.0
Faxonius virilis (virile crayfish); juvenile, ca.30 mm. Charlotte's Quest Nature Center, Manchester, Carroll County, Maryland, USA.  August 2016.
JuvenileFaxonius virilis (virile crayfish); juvenile, ca.30 mm. Charlotte's Quest Nature Center, Manchester, Carroll County, Maryland, USA. August 2016.©Smithsonian Environmental Research Center/original image by Robert Aguilar/via flickr - CC BY 2.0
Faxonius virilis (virile crayfish); adult. Michigan, USA. August 2017.
TitleAdult
CaptionFaxonius virilis (virile crayfish); adult. Michigan, USA. August 2017.
Copyright©USFWS Midwest Region/original image by Patricia Thompson-USFWS/via flickr - CC BY 2.0
Faxonius virilis (virile crayfish); adult. Michigan, USA. August 2017.
AdultFaxonius virilis (virile crayfish); adult. Michigan, USA. August 2017.©USFWS Midwest Region/original image by Patricia Thompson-USFWS/via flickr - CC BY 2.0
Faxonius virilis (virile crayfish); adult. West of Nogales, Santa Cruz County, Arizona, USA. July 2012.
TitleAdult
CaptionFaxonius virilis (virile crayfish); adult. West of Nogales, Santa Cruz County, Arizona, USA. July 2012.
CopyrightPublic Domain - Released by Alan Schmierer/via flickr - CC 1.0
Faxonius virilis (virile crayfish); adult. West of Nogales, Santa Cruz County, Arizona, USA. July 2012.
AdultFaxonius virilis (virile crayfish); adult. West of Nogales, Santa Cruz County, Arizona, USA. July 2012.Public Domain - Released by Alan Schmierer/via flickr - CC 1.0
Faxonius virilis (virile crayfish); natural enemy. A Goldeneye duck (Bucephala clangula) predates an adult crayfish. Seedskadee NWR, Sweetwater County, Wyoming, USA. January 2016.
TitleNatural enemy
CaptionFaxonius virilis (virile crayfish); natural enemy. A Goldeneye duck (Bucephala clangula) predates an adult crayfish. Seedskadee NWR, Sweetwater County, Wyoming, USA. January 2016.
Copyright©USFWS Mountain-Prairie/original image by Tom Koerner/USFWS/via flickr - CC BY 2.0
Faxonius virilis (virile crayfish); natural enemy. A Goldeneye duck (Bucephala clangula) predates an adult crayfish. Seedskadee NWR, Sweetwater County, Wyoming, USA. January 2016.
Natural enemyFaxonius virilis (virile crayfish); natural enemy. A Goldeneye duck (Bucephala clangula) predates an adult crayfish. Seedskadee NWR, Sweetwater County, Wyoming, USA. January 2016.©USFWS Mountain-Prairie/original image by Tom Koerner/USFWS/via flickr - CC BY 2.0

Identity

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Preferred Scientific Name

  • Faxonius virilis (Hagen, 1870)

Preferred Common Name

  • virile crayfish

Other Scientific Names

  • Orconectes virilis (Hagen, 1870)

Local Common Names

  • Netherlands: geknobbelde Amerikaanse rivierkreeft
  • USA: fantail crayfish; northern crayfish

Summary of Invasiveness

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F. virilis is thought to be one of most widely invasive crayfish species in the USA (Larson and Olden, 2011), and has been translocated to a large number of states outside of its natural range. Populations have also been found in Mexico and Europe (UK and the Netherlands). Many translocations within the USA and Canada have been attributed to anglers using the species as bait. The two populations in Europe are thought to be linked to aquarium escapees (Ahern et al., 2008). F. virilis is highly mobile, fecund and tolerant of a wide range of environmental variables making the species very successful invaders. They are however locally threatened within parts of their native range (Hamr, 2002).

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Arthropoda
  •             Subphylum: Crustacea
  •                 Class: Malacostraca
  •                     Subclass: Eumalacostraca
  •                         Order: Decapoda
  •                             Suborder: Reptantia
  •                                 Unknown: Astacoidea
  •                                     Family: Cambaridae
  •                                         Genus: Faxonius
  •                                             Species: Faxonius virilis

Notes on Taxonomy and Nomenclature

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Formerly part of the North American genus Orconectes, classified as Orconectes virilis by Hagen, 1870; according to Crandall and De Grave (2017), the accepted name of the species is now Faxonius virilis (Girard, 1852) (many other Orconectes species have also been moved to Faxonius). Other previous names include: Cambarus virilis, Cambarus debllis, Cambarus wisconsinensis and Cambarus couesi (Hobbs, 1974). The species received its name from the long white hair-like structures that can be found on the copulatory stylets of sexually active males. F. virilis are sometimes known as ‘Northern Crayfish’, as they are naturally found at higher latitudes than any other crayfish species.

Description

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Diagnostic Characteristics taken from ‘Identifying native and alien crayfish species in Europe’, a key produced as part of the European CRAYNET project (Pöckl et al., 2006):

Rostrum: Smooth, borders more or less parallel until shoulder region; acumen prominent, shoulders with prominent spine; median carina absent.

Body: Carapace smooth, one pair of post-orbital ridges; areola very narrow; row of tubercles on shoulders behind cervical groove, one with prominent spine; hepatic spines absent; areola narrow. Females with annulus ventralis located between bases of posterior walking legs, cornified in sexually mature individuals. Hooks on each side of the second abdominal segment absent. Colour typically chestnut or chocolate, posterior end of carapace with a bowl shaped or wine glass shaped light brown pattern, which is not usually as clear as in Faxonius immunis. Abdomen without longitudinal or transverse bands.

Appendages: Chelae broad, flattened, tuberculate: moveable finger with straight margin; prominent yellow tubercles typically arranged in two rows along the inferior margin of the propodus and dactylus; tips of the fingers yellow in colour, cutting edges with yellow teeth; upper surface same colour as body, under-side dirty white in colour. Prominent spur on inferior margin of cheliped carpus. Form I males have larger chelipeds than form II and have a distinct grasping hook on the ischium of the second pair of walking legs that are used during mating; form I gonopods become hardened.

Size: Within their introduced range in England, mean total length of F. virilis in established populations is 88mm (44mm carapace length), although in the build up phase of the population individuals were found up to 135mm total length (67mm carapace length (CL)). Within the northern part of their native range maximum carapace length (CL) is around 55mm (Weagle and Ozburn, 1972), however they have been reported up to 69mm CL in more southerly regions (Hazlett and Rittschof, 1985; Page, 1985).

Distribution

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In some areas within the USA where historic data is not present there appears to be differing opinions of the native/introduced status of virile crayfish. The native range of the species covers a large part of North America, east of the continental divide (Larson and Olden, 2011). In many areas F. virilis co-exists with other species; however it has been shown to be outcompeted by invasive F. rusticus (Hayes et al., 2009).

In Europe, F. virilis is only known to be present in the Netherlands and the UK. It is believed to have been introduced to the Netherlands via the aquarium trade and has only recently become established and widespread (Soes, 2007; Ahern et al., 2008). In the UK, a population of the species was detected in the River Lee system of North London in 2004. The extent of its impacts and establishment remain unknown (Ahern et al., 2008).  

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Last updated: 10 Jan 2020
Continent/Country/Region Distribution Last Reported Origin First Reported Invasive Reference Notes

Europe

NetherlandsPresent, WidespreadIntroduced2004InvasiveSoes (2007)
United KingdomPresent, LocalizedIntroduced2004InvasiveAhern et al. (2008)Currently confined to the River Lee in South-East England

North America

CanadaPresentCABI (Undated)Present based on regional distribution.
-AlbertaPresentNativeAiken (1969); Williams et al. (2011)
-ManitobaPresentNativeSebastian and Reinhart (1989); Huner (1990)
-New BrunswickPresentIntroduced2005InvasiveMcAlpine et al. (2006)
-OntarioPresentNativeBerrill (1978)
-QuebecPresentHuner (1990)
-SaskatchewanPresentHuner (1990); Williams et al. (2011)
MexicoPresentIntroduced1982Campos-Gonzales (1985)A small number of crayfish found in Chihuahua State in 1982
United StatesPresentCABI (Undated)Present based on regional distribution.
-AlabamaPresentIntroducedInvasiveSchuster et al. (2008)
-ArizonaPresentIntroducedInvasiveHuner (1990); Davidson et al. (2010)Introduced in early 1970s, no native crayfish species present. Causing significant ecological damage
-ArkansasPresentNativeTaylor et al. (2007)
-CaliforniaPresentIntroducedInvasiveRiegel (1959)
-ColoradoPresentIntroducedInvasiveOlden et al. (2011); Martinez (2012)
-ConnecticutPresent, WidespreadIntroducedBellucci et al. (2011)
-IdahoPresentIntroducedInvasiveLarson and Olden (2011)
-IllinoisPresentNativeBrown et al. (1995)
-IndianaPresentNativeSiewert and Buck (1991)
-IowaPresentNativeCaldwell and Bovbjerg (1969)
-KansasPresentIntroducedTaylor et al. (2007)
-KentuckyPresentNativeBouchard (1974)
-MainePresentNativeMartin (1997)It is unclear whether this species in native or introduced within Maine
-MarylandPresentIntroduced1963InvasiveOdell and Grimm (1966)
-MassachusettsPresentIntroducedHobbs et al. (1989)
-MichiganPresentNativeDye and Jones (1974)
-MinnesotaPresentNativeHuner (1990)
-MissouriPresentNativeBovbjerg (1953)
-MontanaPresentIntroducedInvasiveLarson and Olden (2011)
-NebraskaPresentNativeHuner (1990)
-New HampshirePresentIntroducedAiken (1965)
-New MexicoPresentIntroducedHuner (1990)
-New YorkPresentNativeHobbs et al. (1989)Thought to be native
-North DakotaPresentNativeHuner (1990); Williams et al. (2011)Thought to be native
-OhioPresentNativeLoughman and Simon (2011); Huner (1990)
-OklahomaPresentNativePeck (1985); Varza and Covich (1995)
-PennsylvaniaPresentIntroducedTaylor et al. (2007)
-Rhode IslandPresentIntroducedTaylor et al. (2007)
-South DakotaPresentNativeHuner (1990)
-TennesseePresentIntroducedHuner (1990)
-TexasPresentNativeTaylor et al. (2007)
-UtahPresentInvasiveJohnson (1986); Larson and Olden (2011)Unclear from the literature whether the species is considered native or not
-VermontPresentIntroducedHobbs et al. (1989)
-VirginiaPresentIntroducedTaylor et al. (2007)
-WashingtonPresentIntroduced2006InvasiveLarson et al. (2010)Introduced to Columbia River Basin
-West VirginiaPresentIntroducedTaylor et al. (2007)
-WisconsinPresentNativeThreinen (1958); Olden et al. (2006)Under threat from introduced O.rusticus
-WyomingPresentIntroducedInvasiveHubert (1988); Larson and Olden (2011)Replaced native P.gambelii

History of Introduction and Spread

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The range extension of F. virilis across the USA and Canada appears to be largely linked to anglers using the species as fishing bait, and consequently moving crayfish between catchments and even states. Although it occurs naturally in many regions in the USA and Canada it has been introduced to some regions such as New Brunswick, Canada. It has also been introduced to Chihuahua in Mexico.

Within Europe it is thought introductions are linked to accidental or deliberately released aquarium specimens. It was deliberately introduced into France in 1897 and Sweden in 1960 but both attempts were unsuccessful. Currently in Europe, F. virilis is only known to be present in the Netherlands and the UK. It was introduced to both countries in 2004, and is likely to be as a result of the aquarium trade. In the Netherlands the species has only recently become widespread (Ahern et al., 2008).

Risk of Introduction

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The use of crayfish as live bait by anglers is attributed as a major factor in the spread of non-native crayfish species within the USA (Lodge et al., 2000; Distefano et al., 2009). The use of live baits is regulated within some states, with certain species prohibited. Risk of introductions can be limited by the use of live baits caught within the same water body, although this is open to abuse. Within Europe, England has banned the use of any species of crayfish as live bait allowing for more realistic regulation.

The two introduced F. virilis populations within Europe are thought to be linked to released aquarium specimens. The species is not commonly kept in aquariums, and in England the keeping of any crayfish species other than Cherax quadricarinatus is prohibited. As it is impossible to know what is kept in private aquariums, further releases of F. virilis within Europe may be inevitable.

In areas where crayfish are harvested either recreationally or commercially there is concern that the movement of live crayfish will result in either deliberate seeding of waterways or accidental introductions to new watercourses. Therefore, the moving of live crayfish should be kept to a minimum to reduce the risk of future introductions.

Habitat

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F. virilis is a generalist when it comes to habitat, and can be found in a range of flowing and still waters within its natural and introduced ranges. It can be found in streams, rivers, canals, ponds and lakes. In Iowa, it is suggested that F. virilis are more prominent in rock-bottomed rivers and streams than in ponds and lakes, where other species dominant (Caldwell and Bovbjerg, 1969). In England, the species appears to be doing equally well in small gravel substrate rivers, heavily modified canals and water filled gravel pits. Where present, the species will use excavations under rocks and cobbles for cover, and if suitable substrate is present some populations have been known to construct burrows.

Experimental studies have shown that acidification can affect the moulting process in F. virilis. Low pH values effected crayfish in post-moult stages and a slower progression of the moult process was observed at pH6 and below (Malley, 1980). Crayfish have been shown to survive for up to 10 days in pHs as low as 4, when not moulting. France (1984) suggested that an average annual pH below pH5.5 could result in eventual population extinction in lentic systems. Newly hatched crayfish and juveniles are more susceptible to low pH than adults, possibly because of the higher number of moults in juveniles (France, 1984). In a 10 week study 25% of F. virilis died at pH5, 70% at pH4 and 95% at pH3 (Siewert and Buck, 1991).

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Freshwater
 
Irrigation channels Principal habitat Natural
Lakes Principal habitat Natural
Reservoirs Principal habitat Natural
Rivers / streams Principal habitat Natural
Ponds Principal habitat Natural

Biology and Ecology

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Genetics

Work has been carried out to compare genetics of European introduced F. virilis to that of the species in its wide USA range. Both populations within Europe were genetically similar, but formed a separate clade from any found in North America. In addition a population sampled from Iowa (USA) also represented a new clade (Filipova et al., 2010). This work suggests that lineage variation within F. virilis is high.

Reproductive Biology

Female Form Alternation

Form alternation in female F. virilis, similar to that in conspecific males, has been suggested by Wetzel (2002). In this study a number of orconectid females were classed as form I when observed with either swollen white glair glands, dependant offspring (embryos to 3rd instar juveniles) or egg stalks with remnants of eggs attached to pleopods. Only form I females were observed mating with form I males, therefore it was proposed that form I in females denotes sexually active individuals. Morphological differences were tested, carapace length to pleonite 2 width ratio (CL/P). Form I females had a wider abdomen than similar size form II females. Form II females were most prevalent during summer growing seasons, form I females appeared in the autumn mating season and were the dominant form until the spring spawning season (Wetzel, 2002). For F. virilis in particular, form I females appeared only in September/October, which was deemed as the mating season. Initial results from work in the UK suggest that female F. virilis alternate between FI and FII although work is still ongoing.

Reproduction

F. virilis reproduce once a year, with mating tending to occur during autumn and the young hatching in the following spring. In Michigan lakes (Momot and Gowing, 1975) and in both lentic and lotic systems in Iowa (Caldwell and Bovbjerg, 1969) reproduction takes place at the end of the second growing season. Two year old females are thought to produce most of the eggs in a population (92.5%)(Momot, 1967).

In a Michigan lake, pairs of crayfish were observed copulating from mid-August to September. Females with eggs were first observed mid-May and on average 94 eggs were found attached to the abdomen. This study found that the number of ovarian eggs increased linearly with the size of the parent, although carapace length (CL) and number of eggs on the abdomen were not linear. Females continued to feed while carrying eggs (Momot, 1967).

Studies in Ontario have found the mean number of external eggs per female to be from 139 to 214 with a maximum egg count of 310 (Weagle and Ozburn, 1972; Corey, 1987). Weagle and Ozburn (1972) observed egg laying occurring from 28th May to 3rd June in the McIntyre River, which coincided with a 5°C rise in water temperature. There did not appear to be a linear relationship between the number of eggs on the carapace and the carapace length (CL).

In the Beaver-Amisk river system  in Alberta mature females have been observed to move to winter hibernacula by the 1st October, secluded in darkness at low temperatures (0-4°C) for approximately seven months (Aiken, 1969). Mesocosm experiments showed four and a half months of darkness at 4°C were required for optimum ovarian growth. With less than four months darkness the number of eggs layed after a ‘spring’ stimuli was greatly reduced. Egg laying was shown to be stimulated by a water temperature of 10-11°C, and not by photo period. However, ovarian maturation was stimulated by both temperature and photoperiod (Aiken, 1969). In Ontario, females have been found to carry eggs at temperatures of 8°C in the spring (Berill, 1978).

During breeding season, when offered a choice between female crayfish pheromones and food stimuli males showed a significant preference for the pheromones, even when starved of food (Pecor and Hazlett, 2008).

F. virilis in Iowa were found to copulate at any time when males were in FI form, females free of eggs and young, and temperatures high enough to permit activity, early July to mid-April in this case, with the exception of the winter months (Caldwell and Bovbjerg, 1969).

Egg Laying/Hatching

Egg laying generally tends to occur in spring from April to May, although the exact time varies geographically. For instance, surveys in Wisconsin have found berried females as early as the beginning of April up until the third week in June and in Ontario oviposition has been observed as late as the end of May (Threinen, 1958). It is thought that the process is closely timed between females within a population for example, one study found 26 of 27 females collected carried eggs of a similar developmental stage that were thought to have been laid from mid-April. The majority of females are free of eggs and start to moult by mid-June, however in Ontario and some lentic areas females have still been found carrying young at this time, with hatching occurring in mid-July (Weagle and Ozburn 1972; Caldwell and Bovbjerg, 1969).

In Michigan, in a cool low productivity lake, newly hatched young of year had a CL of 4.5mm, when they leave the female in the spring the young are 6mm long (Momot, 1967). Juveniles undertake five moultsmoult in the first summer, one while still attached to the mother (Weagle and Ozburn, 1972). By September males have an average CL of 15.2mm and females are 14.1mm in Michigan (Momot, 1967). In the UK, females are found with external eggs between April and the end of May, and by mid August juveniles reach a mean carapace length of 18mm.

Sexual Maturity/Growth

In Michigan F. virilis males become sexually active (FI) after the summer moult in July at age 1 (Momot, 1967). In Ontario, 40% of year 1 males reached maturity on their third moult and an additional 10% reached maturity on their fourth moult. In Ontario, the smallest mature (FI) male was found to be 24.9mm (CL) by Weagle and Ozburn (1972) and 26mm (CL) by Berill (1978). The smallest female found with mature ovaries in autumn was 23.9mm (CL) and the smallest female found bearing eggs in spring was 25.4mm (CL) (Weagle and Ozburn, 1972). In Michigan, berried females of less than 35mm were rarely found in the population (Hazlett and Rittschof, 1985), however this may be attributed to faster growth rates in this population. In Ontario, 64% of year 1 females reached a mature size, however examination of ovaries in spring suggested that few year 1 females had mates, this was attributed to dominance for larger females in attracting males (Weagle and Ozburn, 1972).

Yearling males in a lentic environment in Michigan have a mean CL of 31.2mm and age 2 males have a mean CL of 36.5mm. Yearling females are 29.5mm (CL) and age 2 females 36.4mm (CL). However, variation in growth rate during the first growing season can be significant. Yearling males collected in May ranged from 16-25mm, females from 14-24mm. By August, males ranged from 24-33mm, females from 20-30mm (Momot, 1967). Another study in Michigan, this time with a lotic population extrapolated known growth in larger crayfish to estimate size/year classes for the population as:  0 (6-20mm), 1 (20-40mm), 2 (40-62mm), 3 (62-69mm) (Hazlett and Rittschof, 1985). In a cool, low productivity Michigan lake males had faster growth rate than females and after their first year, mortality was greater in females than in males. Both sexes matured after a moult in July at age 1, mating followed and eggs were laid the following spring. Overwintering mortality of all ages and both sexes was severe, very few males but no females lived through the fourth winter (Momot, 1967).

In a Michigan stream F. virilis of 58-62mm (CL) were common, with the largest male 64mm and the largest female 69mm (Hazlett et al., 1974). It is suggested that these larger sizes are caused by increased growth rates rather than increased survivorship or longevity (Hazlett and Rittschof, 1985). In this population it is proposed that adult females moult twice in the summer and some males moult three times, however sexual form was not recorded. One study in Lake Winnipesaukee, New Hampshire found that most males completed their summer moult within a week (Aiken, 1965). The late summer moult (FII-FI) takes place during the last week in August, and the spring moult (FI-FII) takes place during the final week of June. In Aiken’s study (1965) over 90% of males passed through winter as FI and following spring moult 35-40% of males were FI, 7% of which moulted from FII to FI in the spring. The remainder were large males that didn’t moult to FII. 

Physiology and Phenology

F. virilis inhabit shallow river systems in their northern most range in Ontario, Canada. These rivers freeze in winter but F. virilis do not appear to have any physiological adaptation to allow them to survive freezing (Aiken, 1967). Nor are they thought to burrow to escape freezing temperatures but instead this species tends to hide in crevices under or between rocks, which may become silted over. Furthermore, both males and females move into deeper areas of the river as temperatures drop. Distribution of young of the year (YOY) and yearlings, however, appeared random, utilising both deep and shallow areas (Aiken, 1967).

Longevity

In most cases F. virilis was thought to live to 3 or 3.5 years (Momot and Gowing, 1975; Hazlett et al., 1979). Threinen (1958) however, found the life span of males to be from two growing seasons to two years, for females two years, with occasional specimens living to three years old. Due to the difficulty in ageing wild crayfish it can be difficult to get accurate estimates of population structures. In Europe, it is possible that F. virilis may live for 4 or 5 years.

Activity Patterns

Crayfish activity is linked to water temperature, and F. virilis activity decreases at very low temperatures. They have been shown to migrate between different water depths in relation to water temperature (Aiken, 1967; Momot and Gowing, 1972).

Population Size and Density

It is difficult to get quantifiable density data for wild crayfish populations, especially in larger water bodies. In an Oklahoma spring F. virilis density varied from 1-9/m2, with peaks in May, June and July (Varza and Covich, 1995). Within its introduced range the species has been found in densities of up to  9.2/m2 (Martinez, 2012).

Nutrition

Many crayfish species are poly-trophic omnivores, and will take advantage of whatever food source is locally abundant. F. virilis has been shown to actively graze on aquatic plants, with a preference for small, short bottom dwelling plants such as Chara and Lemna (Chambers et al., 1991; Dorn and Wojdak, 2004). It has been suggested that males may graze more heavily on some species of aquatic plants than females (Chambers et al., 1990b).

F. virilis was found to feed on Lake Trout eggs in Canada, the effect was more pronounced with larger substrate (Savino and Miller, 1991). A further study to see if crayfish could be used as a biological control for the invasive zebra mussel (Dreissena polymorpha) found that F. virilis would predate on zebra mussels, although trout eggs were preferred if available (Love and Savino, 1993). It was concluded that F. virilis preferred prey that provided the greater net benefit.

Macro-invertebrates can play a significant part in the diet of F. virilis, a study in Canada found abundance of snails was greatly reduced in the presence of F. virilis (Hanson et al., 1990), the same study found the crayfish would show preference for macro-invertebrate food even when plant material was present. Within the River Lee (UK) the diet of F. virilis was found to consist of Molluscs and Crustaceans (Pisidium sp. (14%) andGammarus Pulex (14%)) with detritus making up approximately 25% of their diet. Initial finding suggest F. virilis may have a lower degree of diet flexibility than the co-existing P. leniusculus (Jackson et al., Unpublished).

Natural Food Sources

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Food SourceFood Source DatasheetLife StageContribution to Total Food Intake (%)Details
Algae
Aquatic macrophytes All Stages
Detritus
Fish eggs All Stages
Macro-invertebrates All Stages

Climate

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ClimateStatusDescriptionRemark
C - Temperate/Mesothermal climate Preferred Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C
Cf - Warm temperate climate, wet all year Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year
Cs - Warm temperate climate with dry summer Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Cw - Warm temperate climate with dry winter Preferred Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)
D - Continental/Microthermal climate Preferred Continental/Microthermal climate (Average temp. of coldest month < 0°C, mean warmest month > 10°C)
Df - Continental climate, wet all year Preferred Continental climate, wet all year (Warm average temp. > 10°C, coldest month < 0°C, wet all year)
Ds - Continental climate with dry summer Preferred Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)
Dw - Continental climate with dry winter Preferred Continental climate with dry winter (Warm average temp. > 10°C, coldest month < 0°C, dry winters)

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
54 28

Air Temperature

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Parameter Lower limit Upper limit
Mean maximum temperature of hottest month (ºC) 26
Mean minimum temperature of coldest month (ºC) 0

Water Tolerances

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ParameterMinimum ValueMaximum ValueTypical ValueStatusLife StageNotes
Dissolved oxygen (mg/l) 5 9 Optimum (Weagle KV and GW Ozburn, 1972)
Hardness (mg/l of Calcium Carbonate) 2.7 70 Optimum (Lawrence SG, 1981)
Water pH (pH) 6.5 9 Optimum (Malley DF, 1980; France RL, 1984)
Water temperature (ºC temperature) 0 26 Optimum (Lawrence SG, 1981)

Notes on Natural Enemies

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Crayfish provide an important function within aquatic ecosystems; they are largely omnivorous and provide a food source for a wide variety of fish, birds and mammals. A study in Michigan showed that Brook Trout (Salvelinus fontinalis) significantly preyed on crayfish that were under a year old. However, increasing or decreasing trout numbers did not affect crayfish density due to compensatory mortality found with low predation (Gowing and Momot, 1978).

Means of Movement and Dispersal

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Natural Dispersal (Non-Biotic)

Crayfish are mobile and will extend their range when resources become scarce. It is therefore possible that a natural movement will facilitate new areas being colonised.

Vector Transmission (Biotic)

There is a possibility of crayfish being moved between water bodies by birds or mammals, however the potential for long range, inter-catchment movements are limited. Female F. virilis are able to store sperm after mating so a single female, even if not carrying eggs could be enough to start a new population.

Accidental Introduction

Within the USA and Canada a large number of translocated crayfish populations have been attributed to the fishing bait industry; a good review of this can be found in Distefano et al. (2009). As many as 49% of US and Canadian fisheries agencies reported aquatic resource problems linked to “bait bucked introductions”.

F. virilis is also widely used in schools and experimental facilities as a test animal, which heightens the risk of both accidental and intentional releases (Larson and Olden, 2008).

Intentional Introduction

It is thought that the two European F. virilis populations can be attributed to released aquarium specimens. Within England it is illegal to keep the species without a specific licence from the regulatory board, Natural England. There is also evidence that crayfish have been introduced to ponds to control weeds, and have consequently escaped (Larson and Olden, 2008).

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Biological controlThought to be introduced to ponds for weed control Yes Yes Larson and Olden, 2008
Hunting, angling, sport or racingCrayfish used as livebait and moved between catchments Yes Yes
Pet tradeThought to be introduced into Europe through aquarium trade Yes Yes Ahern et al., 2008
ResearchSpecimens used for education and research can escape and be released into the wild Yes Yes Larson and Olden, 2008

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
BaitJuveniles and adults used as fishing bait Yes Yes DiStefano et al., 2009; Lodge et al., 2000
Live seafoodWhen crayfish are harvested and moved live for re-sale there is a risk of further introductions Yes Yes
Pets and aquarium speciesCrayfish are distributed both legally and illegally through the aquarium trade Yes Yes Ahern et al., 2008

Impact Summary

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CategoryImpact
Environment (generally) Negative

Economic Impact

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While there have been direct economic impacts of other introduced crayfish species such as damage to river banks, and flood defences; there are no specific examples for F. virilis.

Environmental Impact

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Impact on Habitats

While many impacts of invasive crayfish may be relatively generic there are a number of studies that have been carried out specifically on F. virilis. In a small channel near Kamerik, Netherlands there has been a significant shift from clear, macrophyte dominant waters to turbid, macrophyte poor waters (Soes, 2007). This shift has coincided with an increase in the abundance of the invasive F. virilis. A similar effect has been found in Arizona where streams have shifted from clear to muddy waters (Davidson et al., 2010). The effect of this species on macrophytes has been considered experimentally, and crayfish were found to significantly affect the biomass and density of four macrophyte species (Chambers et al., 1990a).

Impact on Biodiversity

Invasive crayfish are likely to have wide ranging ecological impacts, only some of which are currently understood. As a result of their broad diets and high population densities it is likely that there will be simultaneous effects on multiple trophic levels (Dorn and Wojdak, 2004). Experimental studies have shown F. virilis to have negative effects on the White Sands pupfish Cyprinodon tularosa, a threatened species in New Mexico. Rogowski and Stockwell (2006) found that F. virilis affected the reproduction and survival of pupfish and that the magnitude of these effects were dependent on the density of crayfish present.

The effects of introduced F. virilis are likely to be greatest where no indigenous crayfish are present, or where indigenous species are less gregarious. One such introduction was in Arizona, USA where no native crayfish species exist. Here introduced F. virilis have had negative impacts on a range of native and threatened species including: Chiricahua leopard frog (Rana chiricahuensis), juvenile desert suckers (Catostomus clarkii), the Sonora sucker (Catostomus insignis), Little Colorado spinedase (Lepidomeda vittata), and the critically endangered Three Forks spring snail (Pyrgulopsis trivialis) (Davidson et al., 2010). There is no evidence of hybridisation between F. virilis and other closely related species (Perry et al., 2001), although this can’t be ruled out completely.

All crayfish species endemic to North America are thought to be potential carriers of Aphanomyces astaci, commonly known as crayfish plague. This is lethal to all indigenous European crayfish species, and has caused widespread loss of the native White clawed crayfish (Austropotamobius pallipes) in England. The population of F. virilis from the River Lee, England was tested for crayfish plague and was found to have one of the highest infestation rates of any population of crayfish found in the UK. Many other North American crayfish species have been introduced into Europe and are widespread, so the specific threat of F. virilis spreading crayfish plague further is limited.

Threatened Species

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Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Cyprinodon tularosaVU (IUCN red list: Vulnerable)New MexicoCompetition - monopolizing resources; Predation
Lepidomeda vittata (Little Colorado spinedace)EN (IUCN red list: Endangered); USA ESA listing as threatened speciesArizonaCompetition - monopolizing resources; PredationIUCN, 2012
Pyrgulopsis trivialis (three forks springsnail)CR (IUCN red list: Critically endangered); USA ESA listing as endangered speciesArizonaPredationIUCN, 2012
Rana chiricahuensis (Chiricahua leopard frog)VU (IUCN red list: Vulnerable)Mexico; Arizona; New MexicoCompetition - monopolizing resources; PredationIUCN, 2012

Social Impact

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There is concern in Europe that large numbers of invasive crayfish, which are more aggressive and reach higher densities than native crayfish, may affect recreational angling.

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Has a broad native range
  • Abundant in its native range
  • Highly adaptable to different environments
  • Capable of securing and ingesting a wide range of food
  • Highly mobile locally
  • Fast growing
  • Has high reproductive potential
  • Gregarious
  • Has high genetic variability
Impact outcomes
  • Altered trophic level
  • Changed gene pool/ selective loss of genotypes
  • Damaged ecosystem services
  • Ecosystem change/ habitat alteration
  • Modification of natural benthic communities
  • Reduced native biodiversity
  • Threat to/ loss of endangered species
  • Threat to/ loss of native species
Impact mechanisms
  • Competition - monopolizing resources
  • Herbivory/grazing/browsing
  • Hybridization
  • Predation
  • Rapid growth
Likelihood of entry/control
  • Highly likely to be transported internationally deliberately
  • Highly likely to be transported internationally illegally
  • Difficult to identify/detect as a commodity contaminant
  • Difficult to identify/detect in the field
  • Difficult/costly to control

Uses

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Economic Value

The species has been commercially harvested within its native range (Morgan and Momot, 1988), however it is not generally considered a crayfish of great economic importance.

Uses List

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Animal feed, fodder, forage

  • Bait/attractant

Environmental

  • Biological control

General

  • Laboratory use
  • Pet/aquarium trade
  • Sport (hunting, shooting, fishing, racing)

Human food and beverage

  • Meat/fat/offal/blood/bone (whole, cut, fresh, frozen, canned, cured, processed or smoked)

Similarities to Other Species/Conditions

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Faxonius virilis may be confused with a number of other Faxonius species, such as the papershell crayfish (F. immunis), but can usually be distinguished by its broader, flattened tuberculate chela with straight margin of dactyl, and male gonopod morphology. Compared to the rusty crayfish (F. rusticus), F. virilis is typically more blue in colour (without rust markings) with broader shorter chelae bearing distinct yellow tubercles, whereas the rusty crayfish has larger more elongated fingers of claws without tubercles (Hamr, 2013). Unlike the spothanded crayfish (F. punctimanus), F. virilis does not have a narrow crescent-shaped saddle mark at the back end of its carapace. Dark specks on its pincers may also distinguish these two species (USACE, 2013). When first found in England it was confused with F. limosus.

Prevention and Control

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Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

SPS Measures

F. virilis have already been spread widely throughout Canada and the USA, largely attributed to “bait bucket introductions”. In 2009 only 4% of USA states and Canadian provinces banned the use of live crayfish bait although a higher percentage has some form of regulation in place. Where possible the use of live crayfish as fishing bait should be stringently regulated.

Public Awareness

Public awareness of non-native invasive crayfish varies considerably between regions and countries. Where possible water users should be educated; particularly recreational anglers who play a role in both introductions and detection of populations.

Eradication

There is currently no known sanctioned method for eradication of crayfish populations, a number of methods have been tried including biocide (Peay et al., 2006) and trapping (Ibbotson et al., 1997). There has been considerable review of the subject, and while numbers of crayfish can be drastically reduced, no one method has led to long term eradication (Rogers and Holdich, 1998; Rogers and Loveridge, 2000; Smith and Wright, 2000; Wright and Williams, 2000; Peay, 2001; Hiley, 2002; Kozak and Policar, 2002; Stebbing et al., 2002; Hyatt, 2004; Hiley and Peay, 2006; Peay et al., 2006; Davidson et al., 2010).

Containment/Zoning

Where possible inter-catchment, and inter-regional movement should be reduced. Currently F. virilis is limited to North America, Mexico and Northern Europe but there is potential for more introductions around the globe. In the UK, fact sheets have been prepared by the Environment Agency for anyone applying to trap crayfish in areas where F. virilis are found. It is hoped this will reduce the risk of accidental releases into the wild.

References

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Abrahamsson S, 1973. Methods for restoration of crayfish waters in Europe-the development of an industry for production of young of Pacifastacus leniusculus. Freshwater Crayfish, 1:204-210

Adams JA, Pecor KW, Moore PA, 2009. Dissolved organic matter from elevated C02 detritus and its impact on the orientation of crayfish (Orconectes virilis) to a fish food source. Journal of the North American Benthological Society, 28:638-648

Ahern D, England J, Ellis A, 2008. The virile crayfish, Orconectes virilis (Hagen, 1870) (Crustacea: Decapoda: Cambaridae), identified in the UK. Aquatic Invasions ["Invasive species in inland waters of Europe and North America: distribution and impacts" 30th Congress of the International Association of Theoretical and Applied Limnology, Montreal, Quebec, Canada, August 2007.], 3(1):102-104. http://www.aquaticinvasions.ru/2008/AI_2008_3_1_Ahern_etal.pdf

Aiken DE, 1965. Distribution and ecology of three species of crayfish from New Hampshire. The American Midland Naturalist, 73:240-244

Aiken DE, 1967. Subdivisions of stage e (ecdysis) in the crayfish Orconectes virilis. Canadian Journal of Zoology, 46:153-155

Aiken DE, 1967. The crayfish Orconectes virilis: Survival in a region with severe winter conditions. Journal of Zoology, 46:207-211

Aiken DE, 1969. Ovarian maturation and egg laying in the crayfish Orconectes virilis: Influence of temperature and photoperiod. Canadian Journal of Zoology, 47:931-934

Aiken DE, Waddy SL, 1992. The growth process in crayfish. Reviews in Aquatic Sciences, 6:335-381

Beauchene M, 2011. Work summary document. Crayfish distribution project. Connecticut, USA: Connecticut Department of Energy and Environmental Protection Bureau of Water Protection and Land Reuse

Bergman DA, Moore PA, 2003. Field observations of the intraspecific agonistic behaviour of two crayfish species, Orconectes rusticus and Orconectes virilis, in different habitats. Biological Bulletin, 205:26-35

Berrill M, 1978. Distribution and ecology of crayfish in the Kawartha lakes region of southern Ontario. Canadian Journal of Zoology, 56:166-177

Bondar CA, Bottriell K, Zeron K, Richardson JS, 2005. Does trophic position of the omnivorous signal crayfish (Pacifastacus leniusculus) in a stream food web vary with life history stage or density? Canadian Journal of Fish and Aquaculture Science, 62:2632-2639

Bondar CA, Richardson JS, 2009. Effects of ontogenetic stage and density on the ecological role of the signal crayfish (Pacafastacus leniusculus) in a coastal pacific stream. Journal of the North American Benthological Society, 28:294-304

Bondar CA, Zhang Y, Richardson JS, Duane J, 2005. The conservation status of the freshwater crayfish, Pacifastacus leniusculus, in British Columbia. British Columbia, USA: Ministry of Water, Land and Air Protection, Province of British Columbia

Bouchard RW, 1975. Geography and ecology of crayfishes of the Cumberland Plateau and Cumberland Mountains, Kentucky, Virginia, Tennessee, Georgia and Alabama: Part i. The genera Procambarus and Orconectes. Freshwater Crayfish, 2:563-584

Bouchard RW, 1977. Distribution, systematic status and ecological notes on five poorly known species of crayfishes in western North America (Decapoda: Astacidae and Cambaridae). Freshwater Crayfish, 3:409-423

Bouchard RW, 1978. Taxonomy, distribution, and general ecology of the genera of North American crayfishes. Fisheries, 6:11-19

Bovbjerg RV, 1953. Dominance order in the crayfish Orconectes virilis (Hagen). Physiological Zoology, 26:173-178

Bovbjerg RV, 1970. Ecological isolation and competitive exclusion in two crayfish (Orconectes virilis and Orconectes immunis). Ecology, 51:225-236

Bovbjerg RV, Stephen SL, 1975. Behavioural changes with increased density in the crayfish Orconectes virilis. Freshwater Crayfish, 2:429-441

Brown PB, Tazik P, Hooe ML, Blythe WG, 1990. Consumption and apparent dry matter digestability of aquatic macrophytes by male and female crayfish (Orconectes virilis). Aquaculture, 89:55-64

Brown PB, Wilson KA, Wetzel JE, Hoene B, 1995. Increased densities result in reduced weight gain of crayfish Orconectes virilis. Journal of the World Aquaculture Society, 26:165-171

Caldwell MJ, Bovbjerg RV, 1969. Natural history of the two crayfish of northwestern Iowa, Orconectes virilis and Orconectes immunis. Iowa Academy of Science Proceedings, 76. 463-472

Campos-Gonzales E, 1985. First record of Orconectes virilis (Hagen) (Decapoda, Cambaridae) from Mexico. Crustaceana, 49:218-219

Capelli GM, 1982. Displacement of northern Wisconsin crayfish by Orconectes rusticus (Girard). Limnology and Oceanography, 27:741-745

Capelli GM, Munjal BL, 1982. Aggressive interactions and resource competition in relation to species displacement among crayfish of the genus Orconectes. Journal of Crustacean Biology, 2:486-492

Carpenter J, 2005. Competition for food between an introduced crayfish and two fishes endemic to the Colorado river basin. Environmental Biology of Fishes, 72:335-342

Celada JD, Carral JM, Gaudioso VR, González J, Lopez-Baissón C, Fernández R, 1993. Survival and growth of juvenile freshwater crayfish Pacifastacus leniusculus Dana fed two raw diets and two commercial formulated feeds. Journal of the World Aquaculture Society, 24(1):108-111

Chambers PA, Hanson JM, Burke JM, 1990. The impact of the crayfish Orconectes virilis on aquatic macrophytes. Freshwater Biology, 24:81-91

Chambers PA, Hanson JM, Burke JM, Prepas EE, 1990. The impact of the crayfish Orconectes virilis on aquatic macrophytes. Freshwater Biology, 24:81-91

Chambers PA, Hanson JM, Prepas EE, 1991. The effect of aquatic plant chemistry and morphology on feeding selectivity by the crayfish, Orconectes virilis. Freshwater Biology, 25:339-348

Corey S, 1987. Comparitive fecundity of four species of crayfish in southwestern Ontario, Canada (Decapoda, Astacidea). Crustaceana, 52:276-286

Crandall KA, De Grave S, 2017. An updated classification of the freshwater crayfishes (Decapoda: Astacidea) of the world, with a complete species list. Journal of Crustacean Biology, 37(5), 615-653. https://doi.org/10.1093/jcbiol/rux070

Creed RPJ, 1994. Direct and indirect effects of crayfish grazing in a stream community. Ecology, 75:2091-2103

Davidson EW, Snyder J, Lightner D, Ruthig G, Lucas J, Gilley J, 2010. Exploration of potential microbial control agents for the invasive crayfish, Orconectes virilis. Biocontrol Science and Technology, 20(3/4):297-310

Dieter C, 1991. Crayfish in sand lake national wildlife refuge. Prairie Naturalist, 23(4):205-208

DiStefano RJ, Litvan ME, Horner PT, 2009. The bait industry as a potential vector for alien crayfish introductions: problem recognition by fisheries agencies and a Missouri evaluation. Fisheries (Bethesda), 34(12):586-597. http://www.tandfonline.com/doi/pdf/10.1577/1548-8446-34.12.586

Dorn NJ, Mittelbach GG, 2004. Effects of a native crayfish (Orconectes virilis) on the reproductive success and nesting behavior of sunfish (Lepomis spp.). Canadian Journal of Fisheries and Aquatic Sciences, 61(11):2135-2143

Dorn NJ, Wojdak JM, 2004. The role of omnivorous crayfish in littoral communities. Oecologia, 140:150-159

Dye L, Jones PD, 1974. The influence of density and invertebrate predation on the survival of young-of-the-year Orconectes virilis. Freshwater Crayfish, 2:529-538

Ellis A, England J, 2009. Crayfish in hertfordshire. Transactions of the Hertfordshire Natural History Society, 41:192-197

Fetzner JW Jr, Sheehan RJ, Seeb LW, 1997. Genetic implications of broodstock selection for crayfish aquaculture in the midwestern United States. Aquaculture, 154(1):39-55

Filipova L, Grandjean F, Chucholl C, Soes DM, Petrusek A, 2011. Identification of exotic North American crayfish in europe by DNA barcoding. Knowledge and Management of Aquatic Ecosystems, 401:11

Filipová L, Holdich DM, Lesobre J, Grandjean F, Petrusek A, 2010. Cryptic diversity within the invasive virile crayfish Orconectes virilis (Hagen, 1870) species complex: new lineages recorded in both native and introduced ranges. Biological Invasions, 12(5):983-989. http://www.springerlink.com/content/7v84562052u1113k/?p=37f800824c4a427ea5a986ef99cf25a5&pi=1

Foster HR, Keller TA, 2011. Flow in culverts as a potential mechanism of stream fragmentation for native and nonindigenous crayfish species. Journal of the North American Benthological Society, 30(4):1129-1137. http://www.bioone.org/doi/abs/10.1899/10-096.1

France RL, 1984. Comparitive tolerance to low pH of three life stages of the crayfish Orconectes virilis. Canadian Journal of Zoology, 62:2360-2363

France RL, 1985. Relationship of crayfish (Orconectes virilis) growth to population abundance and system productivity in small oligotrophic lakes in the experimental lakes area, northwestern Ontario. Canadian Journal of Fisheries and Aquaculture Science, 42:1096-1102

France RL, 1987. Reproductive impairment of the crayfish Orconectes virilis in response to acidification of lake 223. Canadian Journal of Fish and Aquaculture Science, 44:97-106

Gale KSP, Proctor HC, 2011. Diets of two congeneric species of crayfish worm (Annelida: Clitellata: Branchiobdellidae) from western Canada. Canadian Journal of Zoology, 89(4):289-296. http://www.nrcresearchpress.com/doi/abs/10.1139/z11-003

Gowing H, Momot WT, 1978. Impact of brook trout (Salvelinus fontinalis) predation on the crayfish Orconectes virilis in three Michegan lakes. Journal of Fisheries Research Board Canada, 36:1191-1196

Graham I, France R, 1986. Attempts to transmit experimentally the microsporidian Thelohania contejeani in freshwater crayfish (Orconectes virilis). Crustaceana, 51(2):208-211

Hamr P, 2002. Orconectes. In: Biology of freshwater crayfish [ed. by Holdich, D. M.]. Oxford, UK: Blackwell Science, 585-608

Hamr P, 2013. Crayfish Ontario: Ontario Crayfish Identification Guide. Ontario, Canada: Pinicola. http://pinicola.ca/crayfishontario/index.htm

Hanson JM, Chambers PA, Prepas EE, 1990. Selective foraging by the crayfish Orconectes virilis and its impact on macroinvertebrates. Freshwater Biology, 24:69-80

Hayes NM, Butkas KJ, Olden JD, Vander JM, 2009. Behavioural and growth differences between experiances and naive populations of a native crayfish in the presence of invasive rusty crayfish. Freshwater Biology, 54:1876-1887

Hazlett B, 1985. Chemical detection of sex and condition in the crayfish Orconectes virilis. Journal of Chemical Ecology, 11:181-198

Hazlett B, Rittschof D, 1985. Variation in rate of growth in the crayfish Orconectes virilis. Journal of Crustacean Biology, 5:341-346

Hazlett B, Rittschof D, Ameyaw-Akumfi C, 1979. Factors affecting the daily movements of the crayfish Orconectes virilis (Hagen, 1970) (Decapoda, Cambaridae). Crustaceana, 5:121-130

Hazlett B, Rittschof D, Rubenstein D, 1974. Behavioral biology of the crayfish Orconectes virilis l Home range. The American Midland Naturalist, 92:301-319

Hazlett B, Rubenstein D, Rittschof D, 1975. Starvation, energy reserves, and aggression in the crayfish Orconectes virilis (Hagen, 1870) (Decapoda, Cambaridae). Crustaceana, 28:11-16

Heckenlively DB, 1970. Intensity of agression in the crayfish, Orconectes virilis (Hagen). Nature, 225:180-181

Hein CL, Zanden MJvander, Magnuson JJ, 2007. Intensive trapping and increased fish predation cause massive population decline of an invasive crayfish. Freshwater Biology, 52(6):1134-1146. http://www.blackwell-synergy.com/loi/fwb

Henttonen P, Huner JV, Lindqvist OV, 1994. Occurrence of Psorospermium sp. in several North American crayfish species, with comparative notes on Psorospermium haeckeli in the European crayfish, Astacus astacus. Aquaculture, 120(3/4):209-218

Hiley PD, 2002. Management and Conservation of Crayfish [ed. by Sibley and Holdich, P. D.]. Bristol, UK: Environment Agency

Hiley PD, Peay S, 2006. Signal crayfish eradication - preliminary biocides trial. Freshwater Crayfish, 15:261-170

Hill AM, Lodge DM, 1994. Diel changes in resource demand: competition and predation in species replacement among crayfishes. Ecology, 75(7):2118-2126

Hill AM, Lodge DM, 1999. Replacement of resident crayfishes by an exotic crayfish: the roles of competition and predation. Ecological Applications, 9:678-6

Hill AM, Sinars DM, Lodge DM, 1993. Invasion of an occupied niche by the crayfish Orconectes rusticus: potential importance of growth and mortality. Oecologia, 94(3):303-306

Hobbs H, 1974. A checklist of the north and middle American crayfishes (Decapoda: Asticidae and Cambaridae). Smithsonian Contributions to Zoology, 166:1-161

Hobbs H, Pass JP, Huner JV, 1989. A review of global crayfish introductions with particular emphasis on two North American species (Decapoda, Cambaridae). Crustaceana, 56:299-316

Holdich D, 2009. Identifying crayfish in British waters. In: Crayfish Conservation in the British Isles [ed. by Brickland, J. \Holdich and Imhoff, D. E. (.]

Holthuis LB, 1962. The occurence of the crayfish Orconectes virilis (Hagen, 1870) in Montana, USA (Aecapoda macrura, Astacidae). Crustaceana, 3:246-247

Horns WH, Magnuson JJ, 1981. Crayfish predation on lake trout eggs in trout lake, Wisconsin. (Crayfish predation on lake trout eggs in trout lake, Wisconsin.) Rapports et proces-verbaux des reunions/Conseil permanent international pour l'exploration de la mer, 178:299-303

Hubert WA, 1988. Survey of Wyoming crayfishes. Great Basin Naturalist, 48:370-372

Huner JV, 1990. Biology, fisheries, and cultivation of freshwater crawfishes in the US. United States Review of Aquatic Science, 2:229-254

Hyatt MW, 2004. Investigation of crayfish control technology, 448-20181-02-J850. Phoenix, USA: Arizona Game and Fish Department, 89

Ibbotson AT, Tapia MT, Furse JM, Winder JM, Blackburn J, Scarlett P, Smith J, 1997. Impact of signal crayfish on the aquatic macroinvertebrate fauna, macrophytes and fish in the UK and the impact of trapping on crayfish population dynamics - operational investigation report. Thames Region, London, UK: Environment Agency

IUCN, 2012. IUCN Red List of Threatened Species. Version 2012.2. www.iucnredlist.org/

Jackson MC, Ellis A, England J, Grey J, 2012. Incorporating resource heterogeneity and individual specialisation into measures of isotopic niche width: Application to invasion ecology. Unpublished

Johnson JE, 1986. Inventory of utah crayfish with notes on current distribution. Great Basin Naturalist, 46:625-631

Jones PD, Momot WT, 1981. The bioenergetics of Orconectes virilis in two pothole lakes. Freshwater Crayfish, 5:192-209

Kozak P, Policar T, 2002. Management and Conservation of Crayfish [ed. by Sibley and Holdich, P. D.]. Bristol, UK: Environment Agency

Larson ER, Busac CA, Anderson JD, Olden JD, 2010. Widespread distribution of the non-native northern crayfish (Orconectes virilis) in the Columbia River basin. Northwest Science, 84:108-111

Larson ER, Olden JD, 2008. Do schools and golf courses represent emerging pathways for crayfish invasions? Aquatic Invasions, 3(4):465-468. http://www.aquaticinvasions.ru/2008/AI_2008_3_4_Larson_Olden.pdf

Larson ER, Olden JD, 2011. The state of crayfish in the pacific northwest. Fisheries, 36:60-73

Lawrence SG, 1981. Manual for the culture of selected freshwater invertebrates. Canadian Special Publication of Fisheries and Aquatic Sciences, 54:169

Light T, Erman DC, Myrick C, Clarke J, 1995. Decline of the Shasta crayfish (Pacifastacus fortis faxon) of Northeastern California. Conservation Biology, 9:1567-1577

Lodge D, M, Taylor CA, Holdich D, M, Skurdal J, 2000. Nonindigenous crayfish threaton North American freshwater biodiversity. Fisheries, 25:7-19

Lodge DM, Beckel AL, Magnuson JJ, 1985. Lake-bottom tyrant - aggressive and prolific, the rusty crayfish has clawed its way to the top of the food chain in Northern Wisconsin lakes. Natural History, 94:33-37

Lodge DM, Hill AM, 1994. Factors governing species composition, population size, and productivity of cool-water crayfishess. Nordic Journal of Freshwater Research, 69:111-136

Lodge DM, Kratz TK, Capelli GM, 1986. Long-term dynamics of three crayfish species in trout lake, Wisconsin. Canadian Journal of Fisheries and Aquaculture Science, 43:993-998

Loughman ZJ, Simon TP, 2011. Zoogeography, taxonomy, and conservation of West Virginia's Ohio River floodplain crayfishes (Decapoda, Cambaridae). ZooKeys, 73:1-78

Love J, Savino JF, 1993. Crayfish (Orconectes virilis) predation on zebra mussels (Dreissena polymorpha). Journal of Freshwater Ecology, 8:253-258

Malley DF, 1980. Decreased survival and calcium uptake by the crayfish Orconectes virilis in low pH. Canadian Journal of Fisheries and Aquatic Sciences, 37(3):364-372

Martin SM, 1997. Crayfishes (crustacea: Decapoda) of Maine. Northeastern Naturalist, 4:165-188

Martinez PJ, 2012. Invasive crayfish in a high desert river: implications of concurrent invaders and climate change. Aquatic Invasions, 7(2):219-234. http://www.aquaticinvasions.net/2012/AI_2012_2_Martinez.pdf

McAlpine DF, Fletcher TJ, Osepchook MA, Savoie J-C, 1999. A range extension for Orconectes virilis (Decapoda, cambaridae) and a third crayfish species for New Brunswick, Canada. Crustaceana, 72:356-358

McAlpine DF, McApline AHE, Madden A, 2006. Occurrence of the potentially invasive crayfish, Orconectes virilis (Decapoda, Cambaridae) in eastern New Brunswick, Canada. Crustaceana, 80:509-511

Miller JE, Savino JF, 1992. Competition for food between crayfish (Orconectes virilis) and the slimy sculpin (Cottus cognatus). Journal of Freshwater Ecology, 7:127-136

Mirenda RJ, 1986. Acute toxicity and accumulation of zinc in the crayfish, Orconectes virilis (Hagen). Bulletin of Environmental Contamination and Toxicology, 37:387-394

Momot WT, 1966. Upstream movement of crayfish in an intermittent Oklahoma stream. The American Midland Naturalist, 75:150-159

Momot WT, 1967. Population dynamics and productivity of the crayfish, Orconectes virilis, in a Marl lake. The American Midland Naturalist, 78:55-80

Momot WT, 1977. Response of the crayfish Orconectes virilis to exploitation. Journal of the Fisheries Research Board, 34:1212-1219

Momot WT, 1978. The dynamics of crayfish and their role in ecosystems. The American Midland Naturalist, 99:10-35

Momot WT, 1986. Production and expoitation of the crayfish, Orconectes virilis, in northern climates. North Pacific Workshop on Stock assessment and management of invertebrates, Canadian Special Publication of Fisheries and Aquatic Sciences, 92:154-167

Momot WT, Gowing H, 1972. Differential seasonal migration of the crayfish Orconectes virilis (Hagen), in marl lakes. Ecology, 53:479-483

Momot WT, Gowing H, 1975. The cohort production and life cycle turnover ratio of the crayfish, Orconectes virilis, in three Michigan lakes. Freshwater Crayfish, 2:489-511

Momot WT, Gowing H, 1983. Some factors regulating cohort production of the crayfish, Orconectes virilis. Freshwater Biology, 13:1-12

Momot WT, Hauta PL, 1995. Effects of growth and mortality phenology on the cohort P/B of the crayfish, Orconectes virilis. Freshwater Crayfish, 8:265-275

Momot WT, Jones PD, 1977. The relationship between biomass, growth rate and annual production in the crayfish, Orconectes virilis. Freshwater Crayfish, 3:3-31

Morgan GE, Momot WT, 1988. Exploitation of Orconectes virilis in northern climates: Complimentarity of management options with self-regulatory life history strategies. Freshwater Crayfish, 7:69-80

Mueller KW, 2001. First record of the red swamp crayfish, Procambarus clarkii (Girard, 1852)(Decapoda, Cambaridae), from Washington State, USA. Crustaceana, 74:1003-1007

Odell MJ, Grimm WF, 1966. Orconectes virilis in Maryland. Journal of the Mitchell Society, 82:102

Olden JD, McCarthy JM, Maxted JT, Fetzer WW, Zanden MJvander, 2006. The rapid spread of rusty crayfish (Orconectes rusticus) with observations on native crayfish declines in Wisconsin (U.S.A.) over the past 130 years. Biological Invasions, 8(8):1621-1628. http://www.springerlink.com/content/g01284n33k810g33/?p=22e7683f90c2463bb26dc296739b51f1&pi=2

Olden JD, Zanden MJvander, Johnson PTJ, 2011. Assessing ecosystem vulnerability to invasive rusty crayfish (Orconectes rusticus). Ecological Applications, 21(7):2587-2599. http://www.esajournals.org/doi/full/10.1890/10-2051.1

Page LM, 1985. The crayfishes and shrimps (Decapoda) of Illinois. Illinois Natural History Survey Bulletin, 33:335-448

Payne JF, 1978. Aspects of the life histories of selected species of North American crayfishes. Fisheries, 3:5-8

Peay S, 2001. Eradication of alien crayfish populations - R and D technical report. Bristol, UK: Environment Agency

Peay S, Hiley PD, Collen P, Martin I, 2006. Biocide treatment of ponds in scotland to eradicate signal crayfish. (Biocide treatment of ponds in scotland to eradicate signal crayfish.) Bulletin Francais de la Peche et de la Pisciculture, 380-381:1263-1379

Peay S, Holdich DM, Brickland J, 2010. Risk Assessments of Non-Indigenous Crayfish in Great Britain. Freshwater Crayfish, 17:109-122

Peck SK, 1985. Effects of aggressive interaction on temperature selection by the crayfish, Orconectes virilis. The American Midland Naturalist, 114:159-167

Pecor KW, 2006. The mate pursuit-predation avoidance tradeoff in the virile crayfish (Orconectes virilis). Marine and Freshwater Behaviour and Physiology, 39:229-233

Pecor KW, Hazlett B, 2008. The tradeoff between reproductive and food resources in the crayfish Orconectes virilis. Marine and Freshwater Behaviour and Physiology, 41:273-280

Pecor KW, Hazlett BA, 2006. The influence of flowing water on the resource pursuit-risk avoidance tradeoff in the crayfish Orconectes virilis. Ethology, 112(4):332-338

Perry WL, Feder JL, Lodge DM, 2001. Implications of hybridization between introduced and resident Orconectes crayfishes. Conservation Biology, 15(6):1656-1666

Pockl M, Holdich D, Pennerstorder J, 2006. Identifying native and alien crayfish species in Europe. Melk, Austria: European Project CRAYNET, Guglar Cross Media, 47

Riegel JA, 1959. The systematics and distribution of crayfishes in California. California Fish and Game, 45:29-50

Rogers D, Holdich D, 1998. Eradication of alien crayfish populations R and D technical report, W169. Bristol, UK: Environment Agency

Rogers D, Loveridge S, 2000. Crayfish Conference, Leeds [ed. by Rogers, D and Brickland, J.]. Leeds, UK: Environment Agency

Rogowski DL, Stockwell CA, 2006. Assessment of potential impacts of exotic species on populations of a threatened species, white sands pupfish, Cyprinodon tularosa. Biological Invasions, 8(1):79-87. http://www.springerlink.com/(qilrqcrwdnown455f3xbal2a)/app/home/contribution.asp?referrer=parent&backto=issue,7,11;journal,2,31;linkingpublicationresults,1:103794,1

Rubenstein D, Hazlett B, 1974. Examination of the agonistic behaviour of the crayfish Orconectes virilis by character analysis. Behaviour, 50:193-216

Savino JF, Miller JE, 1991. Crayfish (Orconectes virilis) feeding on young lake trout (Salvelinus namaycush): effect of rock size. Journal of Freshwater Ecology, 6(2):161-170

Schuster GA, Taylor CA, Johansen J, 2008. An annotated checklist and preliminary designation of drainage distributions of the crayfishes of Alabama. Southeastern Naturalist, 7(3):493-504

Sebastian RJ, Reinhart BA, 1989. Impact of methoxychlor on selected nontarget organisms in a riffle of the Souris River, Manitoba. Canadian Journal of Aquaculture Science, 46:1047-1061

Siewert HF, Buck JP, 1991. Effects of low pH on survival of crayfish (Orconectes virilis). Journal of Freshwater Ecology, 6:87-91

Smith PA, Wright R, 2000. Crayfish Conference, Leeds [ed. by Rogers, D. \Brickland, J.]

Soes M, 2007. 15th International Conference on Aquatic Invasive Species. Nijegen, Netherlands: ICAIS

Somers KM, Green RH, 1993. Seasonal patterns in trap catches of the crayfish Cambarus bartoni and Orconectes virilis in six south-central Ontario lakes. Canadian Journal of Zoology, 71:1136-1145

Stebbing PD, Watson GJ, Bentley MG, Fraser D, Jennings R, Rushton SP, Sibley P, 2002. Management and Conservation of Crayfish, Nottingham [ed. by Sibley, P. \Holdich, D.]

Tablado Z, Tella JL, Sanchez-zapata JA, Hiraldo F, 2009. The paradox of the long-term positive effects of a North American crayfish on a European community of predators. Conservation Biology, 24:1230-1238

Taylor CA, Schuster GA, Cooper JE, DiStefano RJ, Eversole AG, Hamr P, Hobbs IIIHH, Robison HW, Skelton CE, Thoma RF, 2007. A reassessment of the conservation status of crayfishes of the United States and Canada after 10+ years of increased awareness. Fisheries, 32(8):373-389

Taylor CA, Warren ML, Fitzpatrick JF, Hobbs HH, Jezerinac RF, Pfieger WL, Robison HW, 1996. Conservation status of the crayfish of the United States and Canada. Fisheries, 21(4):25-38

Threinen CW, 1958. A summary of observations on the commercial harvest of crayfish in northwestern Wisconsin, with notes on the life history of Orconectes virilis. Fish Management Division of the Wisconsin Conservation Department Miscellaneous Report, 21. 1-14

USACE, 2013. Environmental laboratory: Orconectes virilis - Northern Crayfish. Mississippi, USA: US Army Corps of Engineers. http://el.erdc.usace.army.mil/ansrp/ANSIS/html/orconectes_virilis_northern_crayfish

Varza D, Covich AP, 1995. Population fluctuations within a spring community. Journal of the Kansas Entomological Society [Biodiversity of aquatic insects and other invertebrates in springs.], 68(2, Supplement):42-49

Weagle KV, Ozburn GW, 1970. Sexual dimorphism in the chela of Orconectes virilis (Hagen). Canadian Journal of Zoology, 48:1041-1043

Weagle KV, Ozburn GW, 1972. Observations on aspects of the life history of the crayfish, Orconectes virilis (Hagen), in Northwestern Ontario. Canadian Journal of Zoology, 50:366-370

Wetzel JE, 2002. Form alternation of adult female crayfishes of the genus Orconectes (Decapoda: Cambaridae). American Midland Naturalist, 147:326-337

Wigginton AJ, Cooper RL, Fryman-Gripshover EM, Birge WJ, 2010. Effects of cadmium and body mass on two anti-predator behaviors of five species of crayfish. International Journal of Zoological Research, 6(2):92-104. http://scialert.net/qredirect.php?doi=ijzr.2010.92.104&linkid=pdf

Williams BW, Williams KL, Gelder SR, Proctor HC, 2011. Distribution of entocytheridae (Crustacea: Ostracoda) in the northern prairies of North America and reports of opportunistic clitellate annelids on crayfish hosts. Western North American Naturalist, 71(2):276-282. https://ojs.lib.byu.edu/ojs/index.php/wnan/article/view/3746

Wright R, Williams M, 2000. Crayfish Conference Leeds [ed. by Rogers and Brickland, D. J.]. Leeds, UK: Environment Agency, 81-88

Distribution References

Ahern D, England J, Ellis A, 2008. The virile crayfish, Orconectes virilis (Hagen, 1870) (Crustacea: Decapoda: Cambaridae), identified in the UK. Aquatic Invasions. 3 (1), 102-104. http://www.aquaticinvasions.ru/2008/AI_2008_3_1_Ahern_etal.pdf DOI:10.3391/ai.2008.3.1.18

Aiken DE, 1965. Distribution and ecology of three species of crayfish from New Hampshire. In: The American Midland Naturalist, 73 240-244.

Aiken DE, 1969. Ovarian maturation and egg laying in the crayfish Orconectes virilis: Influence of temperature and photoperiod. In: Canadian Journal of Zoology, 47 931-934.

Bellucci C J, Becker M, Beauchene M, 2011. Characteristics of macroinvertebrate and fish communities from 30 least disturbed small streams in Connecticut. Northeastern Naturalist. 18 (4), 411-444. http://www.eaglehill.us/nena DOI:10.1656/045.018.0402

Berrill M, 1978. Distribution and ecology of crayfish in the Kawartha lakes region of southern Ontario. In: Canadian Journal of Zoology, 56 166-177.

Bouchard R W, 1974. Geography and ecology of crayfishes of the Cumberland Plateau and Cumberland Mountains, Kentucky, Virginia, Tennessee, Georgia and Alabama. Part I. The genera Procambarus and Orconectes. In: Freshwater Crayfish, Vol. 2. 563-584.

Bovbjerg RV, 1953. Dominance order in the crayfish Orconectes virilis (Hagen). In: Physiological Zoology, 26 173-178.

Brown PB, Wilson KA, Wetzel JE, Hoene B, 1995. Increased densities result in reduced weight gain of crayfish Orconectes virilis. In: Journal of the World Aquaculture Society, 26 165-171.

CABI, Undated. CABI Compendium: Status inferred from regional distribution. Wallingford, UK: CABI

CABI, Undated a. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI

Caldwell MJ, Bovbjerg RV, 1969. Natural history of the two crayfish of northwestern Iowa, Orconectes virilis and Orconectes immunis. [Iowa Academy of Science Proceedings], 76 463-472.

Campos-Gonzales E, 1985. First record of Orconectes virilis (Hagen) (Decapoda, Cambaridae) from Mexico. In: Crustaceana, 49 218-219.

Davidson E W, Snyder J, Lightner D, Ruthig G, Lucas J, Gilley J, 2010. Exploration of potential microbial control agents for the invasive crayfish, Orconectes virilis. Biocontrol Science and Technology. 20 (3/4), 297-310. DOI:10.1080/09583150903514023

Dye L, Jones PD, 1974. The influence of density and invertebrate predation on the survival of young-of-the-year Orconectes virilis. In: Freshwater Crayfish, 2 529-538.

Hobbs H, Pass JP, Huner JV, 1989. A review of global crayfish introductions with particular emphasis on two North American species (Decapoda, Cambaridae). In: Crustaceana, 56 299-316.

Hubert WA, 1988. Survey of Wyoming crayfishes. In: Great Basin Naturalist, 48 370-372.

Huner JV, 1990. Biology, fisheries, and cultivation of freshwater crawfishes in the US. In: United States Review of Aquatic Science, 2 229-254.

Johnson JE, 1986. Inventory of utah crayfish with notes on current distribution. In: Great Basin Naturalist, 46 625-631.

Larson ER, Busac CA, Anderson JD, Olden JD, 2010. Widespread distribution of the non-native northern crayfish (Orconectes virilis) in the Columbia River basin. In: Northwest Science, 84 108-111.

Larson ER, Olden JD, 2011. The state of crayfish in the Pacific Northwest., 36 60-73.

Loughman Z, Simon T, 2011. Zoogeography, taxonomy, and conservation of West Virginia's Ohio River floodplain crayfishes (Decapoda, Cambaridae). Zookeys. 1-78.

Martin S, 1997. Crayfishes (Crustacea: Decapoda) of Maine. Northeastern Naturalist. 165-188.

Martinez P J, 2012. Invasive crayfish in a high desert river: implications of concurrent invaders and climate change. Aquatic Invasions. 7 (2), 219-234. http://www.aquaticinvasions.net/2012/AI_2012_2_Martinez.pdf DOI:10.3391/ai.2012.7.2.008

McAlpine DF, McApline AHE, Madden A, 2006. Occurrence of the potentially invasive crayfish, Orconectes virilis (Decapoda, Cambaridae) in eastern New Brunswick, Canada. In: Crustaceana, 80 509-511.

Odell MJ, Grimm WF, 1966. Orconectes virilis in Maryland. In: Journal of the Mitchell Society, 82 102.

Olden J D, McCarthy J M, Maxted J T, Fetzer W W, Zanden M J vander, 2006. The rapid spread of rusty crayfish (Orconectes rusticus) with observations on native crayfish declines in Wisconsin (U.S.A.) over the past 130 years. Biological Invasions. 8 (8), 1621-1628. http://www.springerlink.com/content/g01284n33k810g33/?p=22e7683f90c2463bb26dc296739b51f1&pi=2 DOI:10.1007/s10530-005-7854-2

Olden J D, Zanden M J vander, Johnson P T J, 2011. Assessing ecosystem vulnerability to invasive rusty crayfish (Orconectes rusticus). Ecological Applications. 21 (7), 2587-2599. http://www.esajournals.org/doi/full/10.1890/10-2051.1 DOI:10.1890/10-2051.1

Peck SK, 1985. Effects of aggressive interaction on temperature selection by the crayfish, Orconectes virilis. In: The American Midland Naturalist, 114 159-167.

Riegel J A, 1959. The systematics and distribution of crayfishes in California. California Fish and Game. 29-50.

Schuster G A, Taylor C A, Johansen J, 2008. An annotated checklist and preliminary designation of drainage distributions of the crayfishes of Alabama. Southeastern Naturalist. 7 (3), 493-504.

Sebastian RJ, Reinhart BA, 1989. Impact of methoxychlor on selected nontarget organisms in a riffle of the Souris River, Manitoba. In: Canadian Journal of Aquaculture Science, 46 1047-1061.

Siewert HF, Buck JP, 1991. Effects of low pH on survival of crayfish (Orconectes virilis). In: Journal of Freshwater Ecology, 6 87-91.

Soes M, 2007. 15th International Conference on Aquatic Invasive Species., Nijegen, Netherlands: ICAIS.

Taylor C A, Schuster G A, Cooper J E, DiStefano R J, Eversole A G, Hamr P, Hobbs H H III, Robison H W, Skelton C E, Thoma R F, 2007. A reassessment of the conservation status of crayfishes of the United States and Canada after 10+ years of increased awareness. Fisheries. 32 (8), 373-389.

Threinen CW, 1958. A summary of observations on the commercial harvest of crayfish in northwestern Wisconsin, with notes on the life history of Orconectes virilis. In: Fish Management Division of the Wisconsin Conservation Department Miscellaneous Report, 21 1-14.

Varza D, Covich A P, 1995. Population fluctuations within a spring community. Journal of the Kansas Entomological Society. 68 (2, Supplement), 42-49.

Williams B W, Williams K L, Gelder S R, Proctor H C, 2011. Distribution of entocytheridae (Crustacea: Ostracoda) in the northern prairies of North America and reports of opportunistic clitellate annelids on crayfish hosts. Western North American Naturalist. 71 (2), 276-282. https://ojs.lib.byu.edu/ojs/index.php/wnan/article/view/3746 DOI:10.3398/064.071.0215

Links to Websites

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WebsiteURLComment
Environment Agency (UK)http://www.environment-agency.gov.uk
GISD/IASPMR: Invasive Alien Species Pathway Management Resource and DAISIE European Invasive Alien Species Gatewayhttps://doi.org/10.5061/dryad.m93f6Data source for updated system data added to species habitat list.
Global register of Introduced and Invasive species (GRIIS)http://griis.org/Data source for updated system data added to species habitat list.

Contributors

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30/08/12 Original text by:

Adam Ellis, Ahern Ecology, 49 North Street, Wilton, Wiltshire, SP2 0HE, UK

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