North American signal crayfish
Pacifastacus leniusculus
Print Page
Send Via EmailOverview
Photo credit: ©GBNNSS
Other Potentially Invasive Crayfish Species:
Habitat:
Origin and Distribution:
Impacts:
How might it get here?
Is it found in Northern Ireland?
Prevent Spread:
You can help by reporting any sightings: @ the Centre for Environmental Data & Recording (CEDaR) - Or via the iRecord
Current Legislative Position (Listed on 03 August 2016)
Other Potentially Invasive Crayfish Species:
- Marble Crayfish (Procambarus sp),
- Louisiana Crayfish (Procambarus clarkii),
- Spiny cheeked crayfish (Orconectes limosus),
- Noble Crayfish (Astacus astacus).
Habitat:
- It inhabits wide range of habitats from small streams to large rivers.
Description:
- Its claws are robust and smooth on both surfaces, the underside is red in colour; with a single tubercle on the inner side of the fixed finger; and a white-turquoise patch on top of the junction of fixed and moveable fingers.
- Adult males are massive either lengthways or in width. Males are up to 16cm in length, females up to 12cm; much larger individuals have been recorded, i.e. 95mm carapace length. The weight is typically 60 and 110g at 50 and 70mm carapace length.
- Its colour bluish-brown to reddish-brown, occasionally light- to dark-brown.
Origin and Distribution:
- Signal crayfish are now widespread across many parts of Europe, but are not present in Ireland.
- The nearest neighbour populations to Ireland are present in England, Wales and parts of southern Scotland.
- Due to trade and travel links, Britain is considered the most likely source of non-native crayfish, but they are present across Europe, so there are a number of pathways that would bring non-native crayfish into Ireland.
Impacts:
- Invasive non native crayfish are known to have a detrimental effect on populations of white clawed crayfish. American crayfish species can be carriers of the so-called 'crayfish plague' - a disease caused by a fungus (Aphanomyces astaci). The 'plague' does the American crayfish little apparent harm but is lethal to European species such as the white-clawed crayfish (http://www.lbap.org.uk/bap/species/crayfish.htm). Crayfish plague carried by signal crayfish is one of the main reasons for the collapse and extinction of native white-clawed crayfish across Europe, including in Britain.
- Some species of invasive crayfish can cause additional damage to river systems by constructing burrows in the banks leaving them prone to collapse. This presents a hazard to human health and safety by weakening walkways and of the river side and impacts on the flood defence of the areas affected.
How might it get here?
- Intentional introduction or escape from aquaria is considered the most likely route into Ireland for each of these species.
Is it found in Northern Ireland?
- Not present in Northern Ireland.
Prevent Spread:
- To maximise the effectiveness of any control measures, and thereby protect the endangered white-clawed crayfish and other aquatic organisms, early detection of any introduced populations is crucial. Everyone is encouraged to report all potential sightings of the species of crayfish.
- If you see some of these animals on sale in your local areas, or suspect some have escaped into a river system near you, please report your sighting and include a photograph if you can.
- Remember the native white-clawed crayfish is an endangered species so please try not to disturb this species.
You can help by reporting any sightings: @ the Centre for Environmental Data & Recording (CEDaR) - Or via the iRecord
Current Legislative Position (Listed on 03 August 2016)
- This species must not intentionally be brought into the Union; kept; bred; transported to, from or within the United Kingdom, unless for the transportation to facilities in the context of eradication; placed on the market; used or exchanged; permitted to reproduce, grown or cultivated; or released into the environment.
NIEA Invasive Species Alert Poster - North American Signal Crayfish: Download
NIEA-ID-Guide-Signal-Crayfish