Procambarus clarkii

Pre 2017

2017 - 2020


Conservation status

Least concern

Legal status

Third schedule listed species under regulations 49 & 50 in the European Communities (Birds and Natural Habitats) Regulations 2011 (Note: regulation 50 not yet enacted).

Listed as a Schedule 9 species under articles 15 & 15A of the Wildlife Order (Northern Ireland) 1985 (Note: article 15A not yet enacted).

Regulated invasive species of Union concern under the European Regulation on the prevention and management of the introduction and spread of invasive alien species [1143/2014].


Invasive species - risk of High Impact

Irish status


Introduction pathways - 1

Escape from Confinement

Introduction pathways subclass - 1

Pet/aquarium species, Live food and live bait

Introduction pathways - 2

Transport Contaminant

Introduction pathways subclass - 2

Transport of habitat material, Angling/fishing equipment

Invasive score


NAPRA Ireland risk assessed

Yes. This species underwent a Non-native species APplication based Risk Analysis in 2014.

Overall risk of this species to Ireland is categorised as: MAJOR with a VERY HIGH level of confidence.

Overall conclusion summary: This crayfish species has the potential to seriously threaten the conservation of the native White-clawed Crayfish populations and amphibians in Ireland. In addition, native biodiversity and ecosystem function are also likely to be threatened if abundant populations establish in the wild in Ireland. Furthermore, this non-native crayfish species could interfere with bank stability, block drainage and irrigation channels and reduce the value of commercial and recreational fisheries.

View the full risk assessment:

Species Biology


Dark red or maroon coloured body. Elongated claws are covered in bright red tubercles and spines. Reaches 8.5-9cm in length. Aggressive nature (Holdich & Sibley, 2009).


Aggressive opportunistic omnivore consuming detritus, fish, tadpoles, plants, macroinvertebrates (Aldridge, 2016), amphibians. As other crayfish species Procambarus clarkii are 'ecosystem engineers', particularly with their consumption of macrophytes, they can shorten nutrient and energy flows, altering the trophic structure of aquatic communities.

Their burrowing activities,which can extend down 2m (Aldridge, 2016), increase water turbidity, decreasing light penetration for plants (Aldridge, 2016) and degrade riverbanks, levees and dikes (reviewed in GISD, 2011). 

This species has high fecundity, early sexual maturity, and rapid growth allowing large populations to develop in short periods in favourable conditions (Holdich & Sibley, 2009, NNSS, 2011).

They are likely to impact our native crayfish the White-clawed crayfish (Austropotamobius pallipes) as a superior competitor for resources. Likely to also impact the common frog (Rana temporaria), common newt (Lisotriton vulgaris) and possibly the triangular club rush (Schoenoplectus triqueter) through predation and grazing (Millane & Caffrey, 2014). In Mediterranean countries they damage rice plants and seeds causing reduced yields ((NNSS, 2011).

Tolerant of salinity (up to 10ppt), drying out (up to 4 months), eutrophication, low oxygen levels and extreme temperatures (Gherardi & Panov, 2006). Accumulate heavy metals, radioactive elements and other pollutants in their tissues which can then be passed up the food chain, including to humans (Delsinne, 2013).

They are an intermediate host for the trematode Paragonimus, which can infect humans and pets if undercooked crayfish is eaten (Gherardi & Panov, 2006).

May be predated by coots (Fulica atra), herons (Ardea cinerea), perch (Perca fluviatilis), pike (Esox lucius), otter (Lutra lutra), mink (Mustela vison) and eels (Anguilla anguilla) as may Orconectes limosus (Holdich & Black, 2007).


Mating takes place in spring, with spawning in July/August. A female can produce up to 600 eggs. Hatching occurs from August to October. The hatchlings remain attached to the female for 2 moults when they become independent. They mature within 3-5 months and breed the following spring. Breeding is temperature dependant and ceases below 10°C but may occur twice a year in warmer areas (Aldridge, 2016). Males and females display cyclic dimorphism alternating between Form I (sexually active form) during the mating season and Form II (non-breeding form) once the mating season is over (Holdich & Sibley, 2009).

Pathway and vector description

Mainly introduced to Europe for aquaculture, they then escaped into the wild and this is the mostly likely pathway for introduction to Ireland (Millane & Caffrey, 2014). Once they are introduced they have a high capacity for spread (Millane & Caffrey, 2014). They can survive for extended periods out of water and can climb relatively well (Aldridge, 2016). They can disperse 3km in a night (Gherardi & Panov, 2006) or 17km over 4 nights (GISD, 2011). They are readily purchased online as an aquarium species and from there could reach suitable habitat through dumping of aquariums (Delsinne, 2013). There is also a small risk of introduction as a contaminant of imported fish stocks or angling gear (Millane & Caffrey, 2014).

Mechanism of impact

Competition, Predation, Disease transmission, Grazing/Herbivory/Browsing

Management approach

There are no effective methods for control or eradication of crayfish at present (NNSS, 2011). It can be difficult to detect in the early stages of invasion (Delsinne, 2013).


Legislation and education are both necessary in preventing invasion in Ireland. There is an EU wide ban on the release or restocking of this species (European Commission, 2017). Education should focus on identifying non-native species and on the environmental damage that its presence could cause (Gherardi & Panov, 2006).


In the early stages of invasion barriers could be built around suitable benthic habitats to prevent further spread (Delsinne, 2013).


Currently trapping is most used but juveniles don't often enter the traps and the adults are very wary making them difficult to trap (Holdich & Black, 2006).


Biocides can be used but they are expensive and cannot be used in flowing water (NNSS, 2011). May have adverse effects on human health and the environment.


Increasing the numbers of native predatory fish for example pike (Esox lucius) or perch (Perca fluviatilis) or eels (Anguilla anguilla) combined with trapping may help to control numbers.

The efficacy of the sterile male release technique (SMRT) is under investigation (Gherardi & Panov, 2006).

Broad environment


Habitat description

Ponds, ditches, canals, rivers, reedbeds, coastal and inland marshes, wetlands, drainage channels, rice paddies.

Species group


Native region

North America

Similar species

White-clawed crayfish (Austropotamobius pallipes). A. pallipes is normally brown to olive coloured (can be blueish) and the claws, which are whitish underneath, lack the tubercles of Procambarus clarkii (National Biodiversity Data Centre, undated).


World distribution(GBIF)

This species is now present on all continents with the exception of Australia and Antarctica (Aldridge, 2016). Introduced in 10 EU member states (Austria, Belgium, Cyprus, France, Germany, Italy, the Netherlands, Portugal, Spain, the UK (European Commission, 2017).

Native distribution

South central USA and Northeast Mexico (Gherardi & Panov, 2006).

Temporal change

Records submitted to Data Centre in 2024

The following map is interactive. If you would prefer to view it full screen then click here.

How can you help

Report any sightings to the National Biodiversity Data Centre.

Further information

Delivering Alien Invasive Species In Europe (DAISIE) project list this as one of the 100 Worst Invaders in Europe.



Aldridge, D (2016) Red swamp crayfish, Procambarus clarkii. Factsheet. Non-native Species Secretariat (NNSS). Site accessed 12 October 2017.

Delsinne, T., Lafontaine, R.-M., Beudels, R.C., Robert, H. (2013). Risk analysis of the Louisiana Crayfish Procambarus clarkii (Girard, 1852). - Risk analysis report of non-native organisms in Belgium from the Royal Belgian Institute of Natural Sciences for the Federal Public Service Health, Food chain safety and Environment. 63 p. Site accessed 12 October 2017.

European Commission. (2017). Invasive Alien Species of Union Concern. European Union, Luxembourg.

Gherardi, F. and V. Panov. 2006. Data sheet Procambarus clarkii. DAISIE (Delivering Alien Invasive Species inventories for Europe). Available Accessed 12 October 2017.

Global Invasive Species Database (GISD) (2011) Species profile: Procambarus clarkii . Site accessed 12 October 2017.

Holdich, D & Black, J (2006) The spiny-cheek crayfish, Orconectes limosus (Rafinesque, 1817) [Crustacea: Decapoda: Cambaridae], digs into the UK. Aquatic Invasions 2 (1) pp. 1-15, Site accessed 6 October 2017.

Holdich D.M. & Sibley P.J. (2009) ICS and NICS in Britain in the 2000s; Brickland J, Holdich DM and Imhoff EM (eds) (2009). Crayfish conservation in the British Isles. Proceedings of a conference held on 25th March 2009 in Leeds, UK. Site accessed 9 October 2017.

Millane, M. & Caffrey, J. (2014) Risk Assessment of Procambarus clarkii (Girard 1852) – Red Swamp Crayfish. Prepared for Inland Fisheries Ireland and the National Biodiversity Data Centre Site accessed 12 October 2017.

Non-native Species Secretariat (NNSS) (2011) Rick assessment for Procambarus clarkii – Red swamp Crayfish. Risk assessment carried out for Great Britain. Site accessed 12 October 2017.

Animal Diversity Web

CABI Datasheet