Taxonomic name: Procambarus clarkii (Girard, 1852)
Synonyms:
Common names: Louisiana crayfish (English), red swamp crayfish (English)
Organism type: crustacean Procambarus clarkii is a hardy warm water freshwater crayfish that is typically found in marshes, rivers, slow flowing water, reservoirs, irrigation systems, and rice fields. It may become a keystone species, affecting many components of the ecosystem inhabits and altering the nature of native plant and animal communities. It is an aggressive competitor with native crayfish, and its burrowing behaviour may cause significant agricultural problems. Management strategies include prohibiting the transport of live crayfish, restocking habitats with native crayfish, and improving public education about the risks alien crayfish pose to the environment. Encouraging farming of native species as well as research into managing, economically productive harvests of native crayfish has the potential to reduce the numbers of alien crayfish imported and farmed. Description
Usually coloured a dark red, Procambarus clarkii is capable of reaching sizes in excess of 50g in 3-5 months (NatureServe, 2003; Henttonen and Huner, 1999). Adults reach about 5.5 to 12cms (2.2 to 4.7 inches) in length. Its rostrum is cuminate with cervical spines present and its areola linear to obliterated. The palm of cheliped come with a row of tubercles along the mesial margin of palm. The chela is elongate. There are hooks on the ischia of male at the 3rd and 4th pereiopods. A male's first pleopod terminates in four elements, and the cephalic process is strongly lobate with a sharp angle on the caudodistal margin that is lacking subapical setae. The setae have a strong angular shoulder on cephalic margin that is quite proximal to terminal elements. The right pleopod is wrapped around the margin to appear reduced or absent (Washington Department of Fish and Wildlife, 2003). Similar Species
Procambarus zonangulus
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Occurs in:
agricultural areas, lakes, water courses, wetlands Habitat description
Procambarus clarkii is a native species of northeastern Mexico and the south central USA (Henttonen and Huner, 1999). Unlike the native crayfish species of Europe (which belong to the small family Astacidae) P. clarkii is able to tolerate dry periods of up to four months (Henttonen and Huner, 1999; Ackefors, 1999). Because of this, it is able to occupy a wide variety of habitats, including subterranean situations, wet meadows, seasonally flooded swamps and marshes, and permanent lakes and streams. It thrives in warm, shallow wetland ecosystems, such as are found in natural and agricultural areas throughout south central Europe, where it has been introduced (Henttonen and Huner, 1999). In the cooler regions of Europe it prefers small permanent ponds, unable to tolerate the predatory fishes found in large water bodies (Troschel and Dehus, 1993; Roqueplo et al., 1995; Demastro and Laurent, 1997, Huner, pers. obs., in Henttonen and Huner, 1999). In countries where it occurs it is commonly found in irrigation reservoirs and channels, and rice fields (Oliveira and Fabião, 1998). It can even be found in sluggish streams and lentic situations, being tolerant of low oxygen levels and high temperatures. It is one of few North American crayfishes with tolerance for saline waters (NatureServe, 2003). General impacts
When introduced into a suitable habitat Procambarus clarkii may quickly become established and eventually become a keystone species (a primary contributor to the ecosystem it inhabits). Its introduction may cause dramatic changes to occur in native plant and animal communities (Schleifstein, 2003). For example, P. clarkii has contributed to the decline of native European crayfish (in the family Astacidae) by introducing interspecific competition pressure and acting as a vector for the transmission of the crayfish fungus plague, Aphanomyces astaci. P. clarkii has also been associated with the crayfish virus vibriosis in crayfish farms, and is an intermediate host for numerous helminth parasites of vertebrates (Thune et al., 1991; Hobbs III et al., 1989, in Holdich, 1999). P. clarkii also reduces the value of the freshwater habitats in which it occurs by consuming invertebrates and macrophytes and degrading river banks by its burrowing activity (Holdich, 1999). A successful coloniser, P. clarkii employs an r-strategy, exhibiting a short life cylce and high fecundity. In comparison, native European species (such as Astacus astacus) employ a k-strategy, exhibiting a long life cycle and low fecundity. As a result, A. astacus, is more competitive in mature ecosystems, while P. clarkii is more competitive in disturbed habitats (including those areas modified by humans such as rice fields). If present in irrigation structures (such as reservoirs, channels or rice fields) P. clarkii may cause significant economic loss. This is both due to its burrowing activity, which alters soil hydrology and causes water leakage, and its feeding, which causes damage to rice plants (Correia, 1993; Ilhéu and Bernardo 1993a, b, in Oliveira and Fabião, 1998). Attempts to control populations of P. clarkii by rice farmers to prevent yield reduciton, may result in an increased use of toxins (Ganhão, Germano and Grilo, 1991, in Oliveira and Fabião, 1998). In Spain rice farmers have used organophosphorous pesticides to control populations of P. clarkii (MacKenzie, 1986, in Holdich, 1999). The reproductive success of P. clarkii, its ability to tolerate environmental changes and its ability to feed on almost anything contribute to its huge potential to colonise new locations and exploit natural resources (Momot, 1995; Gutierrez-Yurrita et al., 1998; Kreider and Watts, 199, in Gutierrez-Yurrita and Montes, 1999). Uses
Its ability to grow and mature rapidly and to adapt to seasonal waters enabled the establishment of P. clarkii as the most dominant freshwater crayfish in the world during the 20th century (Henttonen and Huner, 1999). In fact, it is considered to be the most ecologically plastic species of the entire Decapoda order. In Louisiana (USA) this has created a multi-million dollar industry, with more than 50 000 ha under cultivation (Guierrez-Yurrita et al., 1999). In Europe, the introductions especially benefited Spain, creating a flourishing crayfish industry and revitalising the local economy in certain districts (Ackefors, 1999). The commercial success of P. clarkii is partly due to its ability to colonise disturbed habitats and resist the crayfish fungus plague, Aphanomyces astaci (which native European crayfish are susceptible to) (Lindqvist and Huner, 1999). Geographical range
Native range: Northeastern Mexico and the south central USA (Henttonen and Huner, 1999).
Known introduced range: inter-state introductions into at least 15 other states in the USA (Holdich, 1999) and trans-continental introductions into Africa, Asia, Europe and South America (Hobbs III et al., 1989, in Holdich, 1999). In Europe only physical and, to some extent, climatic barriers limit the spread of P. clarkii, which is reported in reproductive populations in the cooler Netherlands, Germany, Italy and Switzerland and in large, expanding populations in the warmer regions of Portugal, Spain and France. Introduction pathways to new locations
Agriculture: Procambarus clarkii is a popular dining delicacy, accounting for the vast majority of crayfish commercially produced in the United States (Washington Department of Fish and Wildlife, 2003). It was the most dominant freshwater crayfish in the world during the 20th century and its commercial success led to intentional introductions throughout Spain, France and Italy during the 1970s and 1980s (Henttonen and Huner, 1999).
Biological control: In Kenya attempts have been made to use P. clarkii as a biological control agent to reduce the numbers of snails that act as intermediate hosts for the disease-causing organism that causes schistosomiasis (Bilharzia) (Hofkin et al., 1991, in Holdich, 1999). This may have encouraged the spread of P. clarkii within the Africa (Holdich, 1999).
Live food trade: Commerce in live crayfish from neighbouring Spain and more distant countries including the Far East, the USA and Kenya have been responsible for some of the introductions of P. clarkii into England, the Netherlands, France, Germany and Switzerland (Henttonen and Huner, 1999).
Natural dispersal: Natural dispersal from Spanish waters are thought to have facilitated the spread of P. clarkii into southern Portugal (Henttonen and Huner, 1999).
Other: Procambarus clarkii can spread to new areas by anglers using them as bait (Aquatic Non-native Species Update, 2000). Popular as a bait species for largemouth bass, this is believed to have been the most likely cause for their introduction into Washington (The Washington Department of Fish and Wildlife, 2003).
Pet/aquarium trade: The habit of selling Procambarus clarkii alive as an aquarium or garden pond pet may have accelerated the spread of the species through natural waterways in Europe (Henttonen and Huner, 1999).
Smuggling: The crayfish that now occur in African freshwaters are thought to have been introduced without the knowledge and permission of the relevant authorities (Mikkola, 1996, in Holdich, 1999).
Local dispersal methods
Natural dispersal (local): There are reports of migrations of males over several miles in comparatively dry areas, especially in the rainy season (Nature Serve, 2003).
Other (local): Procambarus clarkii can spread to new areas by anglers using them as bait (Aquatic Non-native Species Update, 2000). Management information
Possible management options include the elimination (or reduction) of alien crayfish via mechanical, physical, chemical or biological methods, the restocking of native crayfish populations (threatened by the crayfish plague fungus and interspecific competition with alien species), the development of plague-resistant strains of native crayfish and the use of legislation to prohibit the transport and release of alien crayfish. Preventative measures: Legislation designed to prevent the spread of crayfish has proven difficult to enforce due to the presence of conflicting social motivations (such as the desire to propagate the species for recreational or commercial purposes). Political barriers, particularly in Europe, may hinder conservation goals; for example the free trade policy backed by the European Union has hindered the attempts of European countries to prohibit the importation of live crayfish from other countries within the EU (Holdich et al., 1999). Physical: Reduction may be possible by physical methods, although eradication is unlikely unless the population is particularly resitricted in range and size. All physical methods have environment costs, which should be weighed up against the environmental benefits of employing them. Mechanical methods to control crayfish include the use of traps, fyke and seine nets and electro-fishing. Continued trapping is preferrable to short-term intensive trapping, which may provoke freedback responses in the population such as stimulating a younger maturation age and a greater egg production. Bait, such as roach, bream, bleak or white bream, may increase the number of crayfish caught in traps, although freshwater fish should be avoided to prevent spread of the crayfish plague fungus (which may be transmitted on their scales) (Westman, 1991; Alderman et al., in Holdich, Gydemo and Rogers, 1999). Physical methods of control include the drainage of ponds, the diversion of rivers and the construction of barriers (either physical or electrical). Chemical: Chemicals that can be used to control crayfish include biocides such as organophosphate, organochlorine, and pyrethroid insecticides; individual crayfish are differentially effected depending on their size, with smaller individuals being more susceptible. Since no biocides are crayfish-specific other invertebrates, such as arthropods, may be eliminated along with crayfish, and may subsequently have to be re-introduced. There is cause for concern about toxin bioaccumulation and biomagnification in the food chain (although this is less of a problem with pyrethroids). Another chemical solution lies in the potential to use crayfish-specific, or even species-specific, pheromones to trap animals. This has been used to control insect populations, but has not been researched with respect to crayfish, although crustaceans do use similar pheromones. Biological: Possible biological control methods include the use of fish predators, disease-causing organisms (that infect crayfish) and use of microbes that produce toxins, for example, the bacterium Bacillus thuringiensis var. israeliensis (Pedigo, 1989, in Holdich et al., 1999). Only the use of predaceous fish has been used successfully; eels, burbot, perch and pike are predators are all partial to crayfish (Westman, 1991, in Holdich et al., 1999). The amount of cover, type of fish predator used and location are all important variables in determining the success of such an approach, and in general reduced coverage is correlated with increased predation rates. Nutrition
Ilhéu and Bernardo (1993) studied the food preferences of P. clarkii in Portugal and found that detrital plant matter constituted the largest proportion of their diet. In laboratory conditions P. clarkii prefered macroinvertebrates to plant matter, preying largely on species with slow escape reactions (such as Odonata, Ephemeroptera and snails) and less on species with fast escape reactions, such as live mosquito fish (Gambusia affinis). Crayfish may be cannabalistic or prey on individuals of other crayfish species. P. clarkii prefers high-protein food (such as freshwater macroinvertebrates) because it stimulates a high growth rate but is an opportunistic feeder and will consume plant matter and detritus when it is prey is lacking or it is unable to catch prey (Ilhéu and Bernardo, 1993, in Nystrom, 1999). Reproduction
Procambarus clarkii matures when it reaches a size of between 6 and 12.5 centimetres. A 10cm female may produce up to 500 eggs, while smaller females may produce around a 100 eggs. The eggs are 0.4mm, notably smaller than those produced by members of the family Astacidae. Newly hatched crayfish remain with their mother in the burrow for up to eight weeks and undergo two moults before they can fend for themselves (Ackefors, 1999). Unlike the European native Astacus and Austropotamobius species, populations of P. clarkii contain individuals that are incubating eggs or carrying young throughout the year (Huner and Barr, 1994, in Lindqvist and Huner, 1999). The allows P. clarkii to reproduce at the first available opportunity, which contributes to its colonisation success (Huner, 1992, 1995, in Gutierrez-Yurrita and Montes, 1999). In places with a long flooding period (greater than 6 months), there may be at least two reproductive periods (in autumn and spring). The spring period is longer and more prolific and persists until the drying of the marsh. For large females to reproduce it is necessary to have hormonal induction (produced by the photoperiod), a hydroperiod longer than four months, a temperature above 18 °C, and a pH between 7 and 8 (Gutierrez-Yurrita, 1997). If females have only a short period to prepare themselves for reproduction they must prematurely their burrow to feed; in such circumstances many females will die of dehydration, bringing about a depression in the population (Huner, 1995; Gutierrez- Yurrita, 1997, in Gutierrez-Yurrita and Montes, 1999). Lifecycle stages
Procambarus clarkii exhibits a cyclic dimorphism of sexually active and inactive periods alternating during the lifecycle. After the young hatch, metamorphosis takes place, followed by two to three weeks of voracious eating. After this they moult and again assume their immature appearance (Hunter and Barr, 1994, in Ackefors, 1999). Egg production can be completed within six weeks, incubation and maternal attachment within three weeks and maturation within eight weeks. Optimal temperatures are 21-27 degrees and growth inhibition occurs at temperatures below 12 degrees celcius (Ackefors, 1999). P. clarkii shows two patterns of activity, a wandering phase, without any daily periodicity, characterized by short peaks of high speed of locomotion, and a longer stationary phase, during which crayfish hide in the burrows by day, emerging only at dusk to forage. Other behaviours, such as fighting or mating, take place at nighttime. During the wandering phase, breeding males move up to 17 km in four days and cover a wide area. This intensive activity helps dispersion in this species (Gherardi and Barbaresi, 2000). Reviewed by: Dr. Francesca Gherardi, Dipartimento di Biologia Animale e Genetica. Universita' di Firenze. Italy. Principal sources: Holdich, D.M., Gydemo, R. and Rogers, W.D. 1999. A review of possible methods for controlling nuisance populations of alien crayfish. In Gherardi, F. and Holdich, D.M. (eds.) Crustacean Issues 11: Crayfish in Europe as Alien Species (How to make the best of a bad situation?) A.A. Balkema, Rotterdam, Netherlands: 245-270.
Gutierrez-Yurrita and Montes, 1999.
Oliveira & Fabião, 1998.
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
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Last Modified: Friday, 31 March 2006
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