General Impact
Procambarus clarkii is a successful colonizer which may quickly become established and eventually become a keystone species, a primary contributor to the ecosystem it inhabits. Its introduction may cause dramatic changes in native plant and animal communities (Schleifstein, 2003). P. clarkii may severely impact native crayfish through competition and transition of the crayfish plague, reduce macrophyte assemblages and diversity, alter water quality and sediment characteristics, accumulate heavy metals, interact with additional invasive species, damage agricultural irrigation systems, impact fishing industry, and reduce populations of invertebrates, mollusks, and amphibians through predation and competition.
P. clarkii has contributed to the dramatic decline of the European native crayfish in the Astacidae family through its transmission of the crayfish plague (Aphanomyces astaci) and direct competition. Specifically threatened species include the endangered white clawed crayfish Austropotamobius pallipes), the “vulnerable” noble crayfish (Astacus astacus), and the stone crayfish Austropotamobius torrentium (Garcia-Arberas et al, 2009; Dehus et al, 1999; Gherardi, 2006, Gil-Sanchez & Alba-Tercedor, 2006). P. clarkii is also known to compete with native crayfish in Japan (Kawai & Kobayashi, 2005).
Intense herbivory by P. clarkii often causes the reduction of macrophyte mass and biodiversity and has been recorded in the Lake Chozas, Spain (Rodriguez et al, 2003); Lake Naivasha, Kenya (Smart et al, 2002); Lake Massaciuccoli, Italy (Gherardi et al, 1999); Lake Doccia, Italy (Gherardi & Acquistapace, 2007); Mediterranean wetlands (Geiger et al, 2005); and the Iberian peninsula (Rodriguez et al, 2003 in Cruz & Rebelo, 2007). Affected species include Nymphoides peltata, Potamopeton crispus, Ultricularia australis, Potamogeton spp. (Gherardi & Acquistapace, 2007; Gherardi et al, 1999).
Another effect of the feeding, as well as burrowing, behavior of P. clarkii is altered water quality, increased bioturbation, and increased nutrient release from sediment (Angeler et al, 2001). These changes in water characteristics alter aquatic ecosystems and are believed to induce cyanobacterial blooms (Yamamoto, 2010). These effects have been recorded in Las Tablas de Daimiel National Park, Spain (Angeler et al, 2001); Alentejo, Portugal (Geiger et al, 2005); and Japan (Yamamoto, 2010).
P. clarkii is known to compete with, prey on, and reduce populations of a wide variety of aquatic species including amphibians, mollusks, macroinvertebrates, and fish. Competitive pressure and predation on native amphibians have been recorded from the Iberian Peninsula (Cruz & Rebelo, 2005), Sweden (Nystrom et al, 2002 in Ilheu et al, 2007), Europe (Gherardi, 2006). More specific reports include effects on Rana sp., Bufo bufo, and Triturus vulgaris in Italy (Gherardi et al, 2001; Renai & Gherardi, 2004 in Ilheu, 2007) and the Natterjack Toad (Bufo calamita in Donana Natural Park, Spain (Cruz et al, 2006b), and the California newt, Taricha torosa, in California (Gamradt & Kats, 1996 in Nystrom, 1999). Predation and competition pressure on mollusks include native snails in Doccia Lake, Italy (Gherardi & Acquistapace, 2007) and in the Iberian Peninsula (Cruz & Rebelo, 2007). P. clarkii preys on fish eggs and young as well and was found to consume lake trout (Salvelinus namaycush), gila chub (Gila intermedia), suckers (Catostomusspp.), and speckled dace (Rhinichthys osculus) in the laboratory (Mueller et al, 2006). It may also reduce macroinvertebrate populations and diversity (Correia et al, 2008).Effects on agriculture and fisheries have been recorded from many locations. The burrowing and behavior of P. clarkii is often problematic to levees, dykes, and irrigation systems which can result in water loss and damage to fields (Holdrich, 1999; Yue et al, 2010a). This has been reported from China (Yue et al, 2010a), Japan (Sako, 1987 in Kawai & Kobayashi, 2005), Egypt (Hartnoll pers. Comm., in Holdich, 1999), Kenya (Picard, 1991 in Arrignon et al, 1999), Italy (Gherardi et al, 2000), Spain (Holdrich, 1999), and the United States (Chang & Lange 1967 in Holdich, 1999). P. clarkii frequently becomes a dominant species in disturbed habitats such as rice fields. If present in irrigation structures including reservoirs, channels of rice fields, P. clarkii may cause significant economic loss due to its burrowing activity, which alters soil hydrology and causes water leakage, and its feeding, which damages to rice plants (Correia, 1993; Ilhéu and Bernardo 1993a, b, in Oliveira and Fabião, 1998). Additionally, this damage may lead farmers to use aggressive pesticides such as organophosphorous to control P. clarkii (Ganhão, Germano and Grilo, 1991, in Oliveira and Fabião, 1998; MacKenzie, 1986, in Holdich, 1999). P. clarkii interferes with commercial fishing by damaging nets, preying on fish eggs, competing for food with tilapia, reducing the number of submerged macrophytes, and disturbing nesting grounds of Tilapia zilli (Holdich, 1999; Gieger et al, 2005). Additional impacts associated with P. clarkii include its accumulation of toxins and heavy metals, acting as an intermediary host for trematodes, and serving as a primary food source for other introduced species. It is known to accumulate heavy metals and toxins produced by cyanobacteria such as Microcystis aeruginosa and may transfer them up the food chain and to humans (Gherardi & Panov, 2006). P. clarkii also serves as an intermediary host to trematodes of the genus Paragonimus which are potential human pathogens if the crayfish are undercooked and consumed (Gherardi & Panov, 2006). P. clarkii has been found to promote other invasive species populations including largemouth black bass (Micropterus salmoides and pike by serving as a primary food source (Hickley et al, 1996 in Holdich, 1999; Elvira et al, 1996 in Holdich, 1999). Finally, direct impacts of P. clarkii may cause additional indirect impacts and cascading ecological changes. Dramatic reduction of aquatic vegetation results in many indirect effects as it serves habitat for invertebrates, amphibians, and fry; as a substrate for epiphytic algae; source of refuge for prey, and a primary food source for birds and other species (Nystrom, 1999; France, 1996 in Nystrom, 1999; Steinman, 1996 in Nystrom, 1999). For example, the introduction on P. clarkii to Lake Chozas, Spain caused a reduction of macrophyte plant coverage by 99% which in turn caused a 71% loss in macroinvertebrate genera, 83% reduction in amphibian species, a 75 loss in duck species, and a 52% reduction in waterfowl (Rodriguez et al, 2005).
Location Specific Impacts:Africa 
Ecosystem change: Correlative studies in ponds suggest that Procambarus clarkii may cause a shift in the composition of macroinvertebrates. In particular, numbers of swimming and/or burrowing taxa are thought to be favoured as they can avoid predation by P. clarkii and are not dependent on macrophytes for refuge. As there are no indigenous freshwater crayfish in Africa (Hobbs Jr 1988), the kinds of ecosystem changes incited by P. clarkii, and other alien crayfish, may be particularly important (Nystrom, 1999; Holdich, 1999). China
Agricultural: Procambarus clarkii has been problematic to irrigation canals in China because their burrowing damages them and causes loss of water and damage to fields (Yue et al, 2010a).
Ecosystem change: Procambarus clarkii threatens native crustaceans, fish, and macrophyte assemblages and alter freshwater ecosystems in China (Yue et al, 2010a). Egypt
Habitat alteration: In the Nile Procambarus clarkii burrows into irrigation damns (Hartnoll, pers. comm., in Holdich, 1999).
Predation: In the Nile Procambarus clarkii interfers with the tilapia fishery by eating fish eggs (Hartnoll, pers. comm., in Holdich, 1999). Europe
Competition: There are five native Euroepan crayfish species: Astacus astacus see IUCN Red List of Threatened Species, A. leptodactylus, A. pacypus, Austropotamobius pallipes see IUCN Red List of Threatened Species and Austropotamobius torrentium. Three are considered to be threatened species by the IUCN: Astacus astacus, Austropotamobius pallipes and Austropotamobius torrentium (Groombridge, 1993, in Holdich et al., 1999). In areas where the ranges of P. clarkii and native crayfish overlap, the alien crayfish has the potential to aggressivly native species (Arrignon et al., 1999).
Disease transmission: Procambarus clarkii is known to be a vector for the oomycete fungus Aphanomyces astaciwhich causes the crayfish plague. It is regarded as the most severe crayfish disease and is lethal to all native European species. The disease wiped out many crayfish populations in the late 19th century (Hofer, 1904, in Vogt, 1999).
Ecosystem change: The loss of vegetation caused by Procambarus clarkii has several indirect effects on biodiversity. Macrophytes are important sources of food for many invertebrates, function as a substrate for epiphytic algae and reduce predation of invertebrates, small fish and amphibians by providing safe refuges (France, 1996; Steinman, 1996, in Nystrom, 1999). The reduction of macrophyte biomass by P. clarkii results in a decrease of the value of a freshwater habitat for invertebrates, amphibians and trout fry. Bird species dependent on macrophytes or invertebrates for food may also be affected (Nystrom, 1999).
Habitat alteration: The number of small ponds in Europe has declined due to human disturbances. These habitats are characterised by having a high invertebrate biomass, abundant submerged macrophytes and rare bird and amphibian species. Although native crayfish can not survive in these temporary habitats Procambarus clarkii is able to withstand dry periods by burrowing (Nystrom, 1999). As a consequence P. clarkii fills a relatively unoccupied freshwater crustacean niche and may threaten the survival of species that depend on this type of ecosystem for habitation or breeding (Lindqvist and Huner, 1999; Nystrom, 1999).
Herbivory: Procambarus clarkii. feeds on submerged macrophytes and seedling stages of emergent macrophytes, reducing macrophyte biomass and diversity. Compared to native European crayfish, introduced species such as P. clarkii have higher consumption rates and population growth rates, which results in a greater impact on macropyte biomass and diversity (Nystrom, 1999).
Predation: Procambarus clarkii is known to consume amphibian eggs and larvae. The spread of P. clarkii into ephemeral habitats (where no native European crayfish can survive) poses a considerable risk for breeding amphibians. Bufonid amphibians, while unpalatable to other crayfish, may be eaten by P. clarkii. Thin-shelled snails and less mobile invertebrates are considered to be the most vulnerable to crayfish predation.There are approximately 62 amphibian species in Europe. Most amphibians are limited in their ability to migrate long distances and are especially vulnerable to habitat loss. Mortality during the aquatic life cycle stages regulates the population size, making amphibians particularly sensitive to introduced aquatic predators (Nystrom, 1999; Gasc et al., 1997, in Nystrom, 1999). France
Agricultural: As an effect of burrowing, Procambarus clarkii has caused considerable damage to damns, dykes, and irrigation networks. Near the Adour River the density of the burrows was found to be two per m2 and the mean depth of each burrow 1.21m (Picard, 1991, in Arrignon et al., 1999).
Competition: All three of France's native crayfish species are listed as vulnerable and are threatened by competition from Procambarus clarkii (Ferey, 2003). Reno River Drainage Area (Italy)
Competition: In Bologna the danger of displacement of the native European crayfish Austropotamobius pallipes see IUCN Red List of Threatened Species by Procambarus clarkii. is particularly high because the ranges of the two species overlap. In laboratory experiments P. clarkii. has been shown to be dominant in agonistic interactions with similar sized A. pallipes (Dardi et al., 1996, in Gherardi, et al., 1999). Italy
Agricultural: In the suburbs of Florence Procambarus clarkii has caused deterioration to structures such as river banks and agricultural fields due to its intensive burrowing activity (Gherardi et al, 2000).
Competition: There are numerous threats posed by Procambarus clarkii to the European native crayfish species, Astacus astacus see IUCN Red List of Threatened Species, Austropotamobius torrentium see IUCN Red List of Threatened Species and Austropotamobius pallipes see IUCN Red List of Threatened Species, the latter of which is particularly widely distributed (Gherardi, 2006).
Ecosystem change: A study showed that Procambarus clarkiidrastically reduced hydrophyte abundance and diversity and consumed native snails, even at low densities, in Lago della Doccia, a study lake in the Province of Pistoia, Italy (Gherardi & Acquistapace, 2007).
Predation: Procambarus clarkii preys on embryos and tadpoles of the indiginous Rana sp., Bufo bufo, and Triturus vulgaris in Italy (Gherardi et a, 2001; Renai & Gherardi, 2004 in Ilheu, 2007). Lake Massaciuccoli (Italy)
Herbivory: In Lake Massaciuccoli Procambarus clarkii is destroying submersed macrophytes and negatively affecting the whole aquatic community. The deterioration of the community of Nymphaetum sp. and Utricularia australis are thought to be due to the voracious feeding of P. clarkii (Gherardi et al, 1999). Japan
Agricultural: The burrowing of Procambarus clarkii can cause damage to dykes, levees, and water control structures of the irrigated agricultural system (Sako, 1987 in Kawai & Kobayashi, 2005).
Competition: Procambarus clarkii competes with native crayfish in Japan (Kawai & Kobayashi, 2005). Kenya
Agricultural: Procambarus clarkii has interfered with the existing gill net fisheries for bass and cichlids by damaging nets and fish, competing with tilapia for food, and reducing the number of submerged macrophytes (Lowery and Mendes, 1977; Brummett and Alon, 1994; Harper et al., 1990, in Holdich, 1999).
Herbivory: Procambarus clarkii was found to have a greater consumption rate of macrophytes than the predominant native consumer Cybister tripunctatus (Rosenthal et al, 2005). Lake Naivasha (Kenya)
Agricultural: Procambarus clarkii has interfered with the existing gill net fisherys for bass and cichlids by damaging nets and fish, competing with tilapia for food and reducing the number of submerged macrophytes (Lowery and Mendes, 1977; Brummett and Alon, 1994; Harper et al., 1990, in Holdich, 1999).
Herbivory: Herbivory by Procambarus clarkii on floating and submerged plants in Lake Naivasha is believed the cause of their dramatic decline and even dissapperance in 1982 and 1996 (Smart et al, 2002).
Interaction with other invasive species: In Lake Naivasha Procambarus clarkii has become the principle food source for the largemouth black bass (Micropterus salmoides , another invasive species (Hickley at al., 1996, in Holdich at al., 1999).
Other: Procambarus clarkii reportedly disturbs nesting grounds of Tilipia zili with its digging (Lowery & Mendes, 1977 in Geiger et al, 2005). Portugal
Agricultural: Procambarus clarkii has caused the most problems within the rice growing areas of Spain and Portugal, where its burrowing has resulted in considerable damage of irrigation structures and rice fields (Anastacio and Marques, 1997, Dieguez-Uribeondo et al. 1997, Fonseca et al., 1997, in Holdich, 1999).
Competition: Procambarus clarkii negatively impacts native amphibians through competition for resources and larval and embryonic predation in the Iberian peninsula (Cruz & Rebelo, 2005).
Disease transmission: A proven vector of the crayfish fungus plague, Procambarus clarkii has severly reduced the range of the European native crayfish Austropotamobius pallipes see IUCN Red List of Threatened Species in Spain and Portugal (Holdich, 1999).
Ecosystem change: Procambarus clarkii reportedly increases nutrient release from the Degebe stream, Alentejo, Portugal (Geiger et al, 2005).
Habitat alteration: The intensive burrowing and rapid colonization of a habitat by Procambarus clarkii may cause considerable environmental damage to earthen dykes, levees, and water control structures in irrigated agricultural systems (Holdich, 1999).
Other: Proliferation of Procambarus clarkii may lead to widespread use of very toxic pesticides, such as organophosphorous insecticides, by farmers, which has undesirable environmental consequences (Ganhão, Germano and Grilo, 1991, in Oliveira and Fabião, 1998). Guadiana River Basin (Portugal)
Agricultural: Because of the burrowing and feeding habits of Procambarus clarkii, its presence in irrigation reservoirs and channels, and in rice fields, poses a severe threat to rice culture. The galleries excavated by P. clarkii alter soil hydrology, causing water loss from reservoirs and rice ponds. P. clarkii feeds on rice plants, causing direct damage to the crop. Rice yields may be significantly reduced by these activities (Correia 1993; Ilhéu and Bernardo 1993a, b, in Oliveira and Fabião, 1998). South Africa
Ecosystem change: Introduced crayfish species are considered to be a potential threat to the fragile aquatic ecosystems that have so far only been home to freshwater crabs (Mikkola, 1996, in Holdich, 1999). Donana National Park (Spain)
Competition: The reproductive success of Procambarus clarkii, its ability to tolerate environmental extremes, and its opportunistic diet make it a great coloniser of new habitats and exploiter of natural resources (Momot, 1995; Gutierrez-Yurrita et al., 1998; Kreider and Watts, 1998). P. clarkii adapts surprisingly easily and rapidly to the hydrological conditions and temperatures of a new environement. Its physiological, feeding, defensive and reproductive behaviours may all be modified to fit into the prevailing environmental conditions allowing it to compete with native species (Gaude, 1983; Gutierrez-Yurrita et al.; 1996; Ilheu and Bernardo, 1996; Gutierrez-Yurrita and Montes, 1999).
Competition: Procambarus clarkii reduced suvivorship of the Natterjack Toad (Bufo calamita in Donana Natural Park (Cruz et al, 2006b).
Ecosystem change: In the Donana National Park, Spain, Procambarus clarkii acts as an ecological engineer species, substantially reducing submerged macrophyte biomass and reducing the availability of macrophytes, invertebrates and safe refuges for other species (Gutierrez-Yurrita and Montes, 1998b, in Gutierrez-Yurrita and Montes, 1999).
Habitat alteration: At high densities Procambarus clarkii significantly reduces aquatic macrophyte biomass, modifying the routes of energy transfer and the availability of food resources and refuges for other species and significantly altering the structure and function of the marsh. Affected species include bladderworts (Utricularia australis and Utricularia exoleta) and water-milfoil (Myriophyllum alterniflorum and Ranunculus peltatus); as well as associated mollusc species such as Lymnaea peregra and Lymnaea stagnalis (Chambers et al.; 1990; Nystro and Strand; 1996; Gutierrez-Yurrita et al., 1998; Montes et al., 1993; Gutierrez-Yurrita, 1997, in Gutierrez-Yurrita and Montes, 1999). Guadalquivir Marshes (Spain)
Agricultural: The fishing mechanisms for catching Procambarus clarkii and other crayfish may affect native fauna. In the Guadalquivir marshes the netting of P. clarkii. inadventantly caused the death of large numbers of amphibians (Gutierrez-Yurrita et al., 1995, in Nystrom, 1999). Spain
Agricultural: Procambarus clarkii has caused problems within the rice growing areas of Spain and Portugal, where its burrowing has resulted in considerable damage of irrigation structures and rice fields (Anastacio and Marques, 1997, Dieguez-Uribeondo et al. 1997, Fonseca et al., 1997, in Holdich, 1999).
Competition: Procambarus clarkii negatively impacts native amphibians through competition for resources and larval and embryonic predation in the Iberian peninsula (Cruz & Rebelo, 2005).
Disease transmission: A proven vector of the crayfish fungus plague (caused by Aphanomyces astaci), Procambarus clarkii has severly reduced the range of the native European crayfish Austropotamobius pallipes see IUCN Red List of Threatened Species in both Spain and Portugal (Holdich, 1999).
Ecosystem change: Procambarus clarkii is believed to alter water quality and sediment characteristics in the floodplain wetland, Las Tablas de Daimiel National Park by increasing dissolved organic nutrients and suspended solids as a result of bioturbation from burrowing (Angeler et al, 2001).
Habitat alteration: The intensive burrowing and rapid colonisation of a habitat by P. clarkii may cause considerable environmental damage to earthen dykes, levees, and water control structures in irrigated agricultural systems (Holdich, 1999).
Herbivory: According to a correlative study undertaken in Spain Procambarus clarkii. was shown to significantly reduce macrophyte biomass (Gutierrez-Yurrita, 1997, in Nystrom, 1999). Its reduction of macrophytes has been recorded in Lake Chozas (Rodriguez et al, 2003).
Interaction with other invasive species: Procambarus clarkii has become the main prey item of pike, another introduced species (Elvira et al., 1996, in Holdich et al., 1999).
Other: As a consequence of the negative agricultural and economic impacts caused by Procambarus clarkii, Spanish rice farmers have increased the use of organophosphorous pesticides in an attempt to control crayfish populations. This may have disastrous effects on bird life (MacKenzie, 1986, in Holdich, 1999).
Threat to endangered species: Endangered species Austropotamobius pallipes suffered a severe population decline in Spain as the result of the introduction of Procambarus clarkii and its introduction of the crayfish plague caused by oomycete Aphanomyces
astaci and competition. P. clarkii continues to stifle re-introduction and conservation efforts by competing for resources (Gil-Sanchez & Alba-Tercedor, 2006; Gil-Sanchez et al, 2002; Garcia-Arberas et al, 2009). Sweden
Predation: Predation by Procambarus clarkii resulted in the decline of embryos and larvae of indiginous amphibians in Sweden (Nystrom et al, 2002 in Ilheu et al, 2007). England (United Kingdom (UK))
Competition: Because of its invasive capacities and high fecundity Procambrus clarkii may be a superior competitor with native crayfish Austropotamobius pallipes see IUCN Red List of Threatened Species especially since it is the only native crayfish in the British Isles, which are home to some of the largest remaining populations in Europe. (Reynolds, 1988, 1997b; Holdich and Reeve, 1991; Holdich et al 1995a; Holdich and Rogers, 1997a, in Holdich, Rogers and Reynolds, 1999).
Disease transmission: Procambarus clarkii is a vector of the crayfish plague fungus (Aphanomyces astaci). During the 1980s populations of the native species Austropotamobius pallipes see IUCN Red List of Threatened Species suffered due to outbreaks of the crayfish plague fungus (Vogt, 1999). United States (USA)
Modification of natural benthic communities: Procambarus clarkii has the potential to establish dense populations that cover stream bottoms, similar to impacts observed with the Zebra Mussel (Dreissena polymorpha) in the midwestern U.S. (National Park Service, undated). Washington (United States (USA))
Competition: There is concern that Procambarus clarkii will threaten signal crayfish Pacifastacus leniusculus and other native lake dwellers in Washington (Aquatic Non-native Species Update, 2000).
|
