Calico crayfish
Faxonius immunis
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Photo credit: USGS© Chris Lukhaup, courtesy the Missouri Department of Conservation
Faxonius immunis - Calico crayfish
Description :
Habitat:
Origin and Distribution:
Impacts:
Is it found in Northern Ireland?
How could it get here?
Prevent Spread
Current legislative position (Entered into Force: 07 August 2025): 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.
For further queries, you can contact the Invasive Non Native Species (INNS) Team in the Northern Ireland Environment Agency on 028 9056 9558 or Email: invasivespecies@daera-ni.gov.uk
Faxonius immunis - Calico crayfish
Description :
- A plain grey‑green crayfish with a distinctive pale band running along the middle of the carapace and abdomen
- Pincers typically have orange tips, while breeding males often show a pale purple tint
- Body size ranges from 4.3–8.9 inches
- Morphology and colouration in males may shift slightly during breeding season
- Previously known as Orconectes immunis before being reclassified to Faxonius in 2017
Habitat:
- Found in shallow ditches, sloughs, and edges of medium to large rivers, especially where plant debris is abundant
- Prefers mud‑bottomed, stagnant or slow-moving waters
- Tolerant of high turbidity and can thrive in disturbed or low‑visibility environments
- Uses aquatic plants and plant debris for shelter and protection
- A burrowing species, capable of moving between ponds or wetlands by overland or subsurface travel
Origin and Distribution:
- Native to North America particularly Great Lakes drainages including Lakes Erie, Ontario, Huron, and southern Lake Michigan
- Established in Europe, primarily along the Upper Rhine River system, with significant populations in Germany and France
Impacts:
- As a burrowing generalist species, it may pose future risks to native crayfish, macroinvertebrates, or aquatic vegetation
- Could potentially influence ecosystem sediment stability or water turbidity through burrowing behaviour
Is it found in Northern Ireland?
- It is not currently present in Northern Ireland
How could it get here?
- Via trade as it commonly sold as bait, with most introductions likely resulting from bait bucket releases
- Secondary spread may occur when anglers move live crayfish between fishing sites
- Its burrowing and tolerance of degraded habitats may aid in accidental expansion
Prevent Spread
- Prevention via enforcing the IAS (Enforcement and Permitting) Order (Northern Ireland) ensuring that Faxonius immunis is not introduced to Northern Ireland
- Reporting any sightings so that Rapid Response can be instigated
- Following Check Clean Dry
- You can help by reporting any sightings:@ the Centre for Environmental Data & Recording (CEDaR) - Or via the iRecord App.
Current legislative position (Entered into Force: 07 August 2025): 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.
For further queries, you can contact the Invasive Non Native Species (INNS) Team in the Northern Ireland Environment Agency on 028 9056 9558 or Email: invasivespecies@daera-ni.gov.uk