North American Signal Crayfish (Pacifastacus leniusulus)

Species	Distribution
North American Signal Crayfish (Pacifastacus leniusculus) Photo courtesy of GB Non Native Species Secretariat	To view NBN location data click here
Impacts	Pathways
Documented harmful impacts include eradication of indigenous population of white-clawed crayfish Austropotamobius pallipes through direct competition and transmission of lethal crayfish plague Aphanomyces astaci. Excludes salmonids from preferred habitat Impacts on other species and habitats also occur including benthic fish, aquatic invertebrates, macrophytes, and invertebrates.	Deliberate introduction (for wild harvest, fish food or weed control Accidental introduction with stocked fish. Inter-catchment spread via canals Natural colonisation of tributaries from main rivers Accidental or deliberate release of live crayfish intended for food in restaurants Occasional movement by predators
Management
Prevention Do not introduce into, or take crayfish from, the wild. It is illegal to be in possession of live crayfish or trap them without a licence. Licensing enquiries should be directed to: Salmon and Freshwater Fisheries, Pentland House, 47 Robb's Loan, Edinburgh EH14 1TY Tel: 0131 244 5244 If you see a crayfish in the wild, either live specimens or the remains of a dead crayfish please report it through this website (click here to make a report) and contact either: Fisheries Research Services Freshwater Laboratory, Faskally, Pitlochry, Perthshire PH16 5 LB Tel: 01796 472060. Email enquiries@marlab.ac.uk Scottish Natural Heritage, Caspian House, Mariner Court, Clydebank Business Park, Clydebank G81 2NR Tel: 0141 9514488 Email: enquiries@snh.gov.uk Scottish Environment Protection Agency, Erskine Court, Castle Business Park, Stirling FK9 4TR Tel: 01786 457700 Email: info@sepa.org.uk Physical control Once establishes physical removal of crayfish from a site has been shown to be ineffective. Moreover as large individuals are cannabalistic, it is also thought that their removal increases populations of smaller crayfish. Physical alteration of habitat by draining ponds or sections of streams has also been shown to bew ineffective as crayfish can shelter in their burrows and under stones for time periods up to several weeks depending on conditions. Click here for more information on Non Native Crayfish Control from the SNH funded "Prospects for the Control of Non Native Crayfish in Scotland" report. Chemical control Current chemical control measures are harmful to other species and have to date been ineffectual. However there are reports of some success using natural pyrethroids in small enclosed waterbodies. More information on this will be posted here when available. Biological control North American Signal Crayfish are susceptible to a number of disease causing agents but their impact in the wild is unknown. A major factor to be assessed in any form of biological control is the the impact it may have on the endangered White Clawed Crayfish (native to England and Wales and introduced to Scotland). The introduction of sterile males may be another possibility for future investigation.
Links
Non Native Species Secretariat identification guide Non Native Species Secretariat Fact Sheet SNH Species Action Framework