| Procambarus clarkii | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Malacostraca |
| Order: | Decapoda |
| Suborder: | Pleocyemata |
| Family: | Cambaridae |
| Genus: | Procambarus |
| Species: | P. clarkii |
| Binomial name | |
| Procambarus clarkii | |
Procambarus clarkii, known variously as thered swamp crayfish,Louisiana crawfish ormudbug,[3] is aspecies ofcambaridcrayfish native to freshwater bodies ofnorthern Mexico, andsouthern andsoutheastern United States, but alsointroduced elsewhere (both inNorth America and other continents), where it is often aninvasive pest.[1]
P. clarkii is typically dark red, with long claws and head, small or no spines on the sides of itscarapace just below the head, and rows of bright red bumps on the front and side of the first leg.[4]
The native range ofP. clarkii is from northernMexico and far southeasternNew Mexico, through theGulf States to theFlorida Panhandle, as well as inland north through theMississippi Basin to southernIllinois.[1][4] It has also been introduced, sometimes deliberately, outside its natural range to countries inAsia,Africa,Europe and elsewhere in theAmericas.[1][4] Innorthern Europe, the populations are self-maintaining but not expanding, while insouthern Europe,P. clarkii is multiplying and actively colonizing new territories at the expense of the native crayfish,Astacus astacus andAustropotamobius spp. In some areas this species occurs in sympatry with another invasive crayfish,Pacifastacus leniusculus.[5] Individuals are reported to be able to cross many miles of relatively dry ground, especially in wet seasons, although theaquarium trade andanglers may have hastened the spread in some areas (anglers usingP. clarkii asfishing bait are thought to have introduced it to the state ofWashington). Attempts have also been made to useP. clarkii as abiological control organism, to reduce levels of thesnails involved in the life cycle ofschistosomiasis, leading to the dispersal ofP. clarkii in, for instance,Kenya.[citation needed]
In Europe,P. clarkii has been included since 2016 in thelist of Invasive Alien Species of Union concern (the Union list).[6] This implies that this species cannot be imported, bred, transported, commercialized, or intentionally released into the environment in the whole of the European Union.[7]
P. clarkii is most commonly found in warm freshwater bodies such as slow-flowingrivers,marshes,reservoirs,irrigation systems andrice paddies. It is considered to be the most ecologically plastic species in the orderDecapoda and is able to grow quickly even in only seasonally present water, being able to tolerate dry spells of up to four months.P. clarkii grows quickly, and is capable of reaching weights over 50 g (1.8 oz) and sizes of 5.5–12 cm (2.2–4.7 in) long.[8] It is also able to tolerate slightlysaline water, which is unusual for a crayfish. Additionally,P. clarkii are physiologically capable of tolerating relatively lowdissolved oxygen concentrations.[9] The average lifetime ofP. clarkii is five years, although some individuals are known to have reached ages (in nature) of over six years.[citation needed]
Theburrowing activities ofP. clarkii can damage existing water courses and to crops, particularlyrice, and its feeding can disrupt native ecosystems. It may outcompete the native crayfish species and is avector for thecrayfish plague fungusAphanomyces astaci, for crayfish virusvibriosis and for a number ofparasitic worms onvertebrates. Their burrowing activities may also be a threat to civil infrastructure such asstorm ponds andlevees.[10]
In 2007,troglomorphic specimens ofP. clarkii were found in centralPortugal in thekarst springs of theRio Anços in theSicó massif and of theAlviela River in theEstremenho massiff. In 2011, another cave-dwelling population was discovered in caves in theSan Giuliano Terme municipality in theProvince of Pisa inItaly. Both localities consist ofkarst landscapes with extensive cave formations. The Portuguese population is entirely depigmented, although pigmented specimens are present in nearby surface streams; the deepest recorded specimen was a male recovered at a depth of 240 metres (790 ft). 53% of Italian specimens displayed a blue-white coloration. The greater presence of pigmented individuals suggests either a more recent entrance, an external source of carotenoids, or movement between surface and underground waters. Collectively, these potations make up the first recorded instances of troglodytic crayfish in Europe. The invasive crayfish have the potential to pose an environmental threat to nativestygobitic fauna, due to the crayfish's recorded ability to prey on diverse sources of food and the highly restricted ranges of native cave fauna.[11]
Harvests ofP. clarkii forfood account for a large majority of the crayfish produced in theUnited States and elsewhere. Crayfish farming began inLouisiana in the 18th century, taking place in rice fields in a concurrent or alternate culture system. The concurrentpolyculture of rice and crayfish combination makes good use of land, resources, equipment and infrastructure already being used for rice production.
However, crayfish production has decreased in recent years due to an increase of imports fromChina, which is now the world's leading producer of farmed crayfish using arice-based system.[13] A number of species ofcrustaceans were introduced to China to create markets for aquaculture and because they are better adapted to growing in a rice field than native fish species. Rice-fish farming originated in China and is once again growing as the yields fromGreen Revolution practices used to grow rice are no longer increasing, and resources such as land and water are becoming more limited.[14] Crayfish are also cultivated asanimal feed forpoultry farms,fish farms andChinese edible frog farms, or used to add intoorganic fertilizers.[citation needed]
P. clarkii has also been introduced elsewhere for cultivation, such asSpain, where its success is attributable to its ability to colonize disturbed habitats that would be unsuitable for the native crayfish (Astacus astacus).P. clarkii is also marketed by biological supply companies for teaching and research.P. clarkii also exhibits differentcolour morphs, including white, blue and orange, which are commonly sold in pet stores.[citation needed]
The introduction ofP. clarkii has also resulted in economic losses in some regions. In theBaixo Mondego region ofPortugal, it caused a decrease in 6.3% of profits in rice fields.[15] However, this was on a wet-seeded field. All negative effects of crayfish can be avoided if adult crayfish are separated from the seed and seedlings.[16]
P. clarkii is eaten in China,Cambodia,Thailand, Europe, Africa, the United States,Canada,Australia,New Zealand and theCaribbean. In the United States, crayfish are particularly popular inLouisiana, where the standard culinary terms vary between "crawfish", "crayfish", "crawdaddy" or "mudbug", andcrawfish boils are popularsocial gatherings centered around eating the crustaceans.[17] Louisiana crawfish are usuallyboiled in a large pot with heavyseasoning (salt,cayenne pepper,lemon,garlic,bay leaf, etc.) and other items such aspotatoes andcorn on the cob. Many differing methods are used to season the dish, and there are an equal number of opinions on which one is correct.[18]
In 1990, Louisiana produced 90% of the crayfish in the world, and consumed 70% locally.[19] However, as early as 2003, Asianfish farms andfisheries produced more and continued to outpace production in any other part of the world. By 2018,P. clarkii crayfish production in the Americas represented just 4% of total globalP. clarkii supply.[20] Louisiana crayfish remain in demand for local production and consumption. In 2018, 93% of crayfish farms in the US were located in Louisiana.[21]
Procambarus clarkii normallyreproduces sexually, but research suggests it may also reproduce byparthenogenesis.[22]
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