Rusty Crayfish

Habitat

• Permanently clear and well-oxygenated rivers, streams, ponds and lakes with substrates that have plenty of debris for hiding
• Both fast flowing and slow-moving waterbodies, usually with a depth of less than 1m
• Water deeper than 20cm is inhabited by adults and less than 15cm is inhabited by juveniles

Description

• A highly invasive freshwater crayfish reaching densities of up to 113 crayfish/m²
• Brownish-green in colour with rusty red spots on the abdominal segments
• Average length of 10cm (not including claws) with males being larger than females
• Two pairs of antennae, two large claws which form an oval shaped gap when closed and a fan shaped tail
• There are two types of males; reproductive and non-reproductive. Reproductive males have larger claws
• Has a variety of food sources and is known for having an insatiable appetite
• It can successfully mate with Faxonius propinquus, another species of crayfish, to produce viable offspring
• Reproduction occurs 1-2 times per year

Origin and Worldwide Distribution

• F. rusticus is native to the river and lakes of the Ohio river basin in the USA
• Now established in 20 US states, present in all 5 great lakes of America and in 3 Canadian provinces
• Not yet present in the wild outside of North America but it is present in the ornamental trade in Europe

Potential or Known Impacts

• Its varied and insatiable diet reduces resource availability for native species
• Impacts food webs and ecosystem function, especially when present in high densities
• Decline in commercially important fish populations as a result of egg predation
• Reduces native biodiversity by outcompeting native crayfish, reducing aquatic plant cover and reducing both the abundance and diversity of macroinvertebrates

Is it found in Northern Ireland?

• It is not currently present in Northern Ireland

How could it get here?

• Its spread in North America is likely down to the introduction as a bait for anglers
• Once present, it can disperse naturally across interconnected waterways
• Spread in Europe would likely be a result of the illegal release (intentional and/or accidental) into the wild from the ornamental/aquarium trade

Management/Methods for Prevention:

• Prevention via enforcing the IAS (Enforcement and Permitting) Order (Northern Ireland) ensuring that F. rusticus is not introduced to Northern Ireland
• Reporting any sightings so that Rapid Response can be instigated
• If Rapid Response is not successful, management can include both physical, biological and chemical control methods or a combination

Current Legislative Position (Listed on 02 August 2022)

• 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.

Research

Species Related Files:

RA_Faxonius_rusticus_Rusty_crayfish