Individual study: Reintroduction of white-clawed crayfish Austropotamobius pallipes in September 2000 to the River Lathkill, Derbyshire, England
(2003) Reintroducing the white-clawed crayfish into the River Lathkill. Conserving Natura 2000 Rivers. Conservation Techniques Series No. 8. English Nature, Peterborough, UK (added by: Bird J.P. 2006).
In Britain, the native white-clawed crayfish Austropotamobius pallipes is becoming increasingly scarce since the introduction of the larger North American signal crayfish Pacifastacus leniusculus, which kill and eat or displace native crayfish. Furthermore they carry a fungal disease which has wiped out several populations of white-clawed crayfish in the UK.
In 1993, the River Lathkill in western England, lost its entire population of white-clawed crayfish in a mass mortality event (thought to be due to an outbreak of crayfish plague). The UK LIFE project “Safeguarding Natura 2000 rivers in the UK” aims to expand the range or increase populations of white-clawed crayfish where suitable habitat is available but not presently occupied due to past historical impacts that had resulted in their extirpation. As part of this project, a pilot crayfish reintroduction in 1999/2000 demonstrated that conditions in the River Lathkill were such that it could once again support white-clawed crayfish.
English Nature and David Rogers Associates conducted an experimental reintroduction and looked at methods of rearing large numbers of white-clawed crayfish from relatively small numbers of imported stock (of UK origin). This case study outlines this reintroduction of white-clawed crayfish to the River Lathkill.
Source population: By September 2000, 79 crayfish had been trapped from Bestwood Ponds, Nottinghamshire, and quarantined in facilities at David Rogers Associates (Castle Donington, Leicestershire). On 26 September 2000 these 79 crayfish were introduced directly from the quarantine facility into the River Lathkill.
The release site was selected based on the habitat requirements of the white-clawed crayfish (see Holdich & Rogers 2000) but also taking into consideration that a site with reasonable access for monitoring and not interfered with by the general public, was needed.
The site selected was downstream of a small waterfall with moderately fast flowing water and and a riverbed of stones and boulders, which provided ample cover and refugia for the released crayfish. It is within the Derbyshire Dales National Nature Reserve, a Site of Special Scientific Interest and a Special Area of Conservation under the European Habitats Directive.
Monitoring: In order to monitor the movement and population size of the crayfish introduced into the River Lathkill, each crayfish was marked individually using pleural and uropodal clipping (see Chien & Avault, 1979 for details). Searches were undertaken in May, July, August and October 2001.
Following the release, monitoring was undertaken as follows:
1) In May 2001 English Nature staff searched the vicinity of the crayfish introduction site for crayfish. No crayfish were found.
2) On 4 July 2001 English Nature staff again searched the area and found one crayfish 200 m downstream of the introduction site.
3) On 25 August 2001 David Rogers Associates searched a 300 m stretch of the River Lathkill downstream of the introduction site. No crayfish were found.
4) In October 2001 English Nature staff observed crayfish whilst undertaking remedial works 300 m downstream of the introduction site.
Sightings of crayfish in the vicinity of the release site indicate that some of the introduced crayfish did survive at least one year and it is possible that breeding may have occurred although no evidence could be found.
Conclusions: The reintroduction of white-clawed crayfish into the River Lathkill appears to have been at least been partially successful. A clearer understanding of how many individuals have survived since reintroduction, and whether breeding has occurred, is needed. If the reintroduced population is to become self-sustaining in the long-term, additional releases of crayfish may be required.
Detection of low-density crayfish populations is known to be difficult. As the habitat into which the crayfish were introduced consists of very large numbers of rocks and stones, even extended periods of searching may not expose areas that could be occupied by the introduced crayfish. Therefore, it may be worthwhile to attempt live-trapping for monitoring purposes in the future.
Chien Y.H. & Avault J.W.Jr. (1979). Double cropping rice, Oryza sativa, and red swamp crawfish, Procambarus clarkii. Freshwater Crayfish, 4, 263-271.
Holdich D.M. & Rogers W.D. (2000). Habitat requirements of the white-clawed crayfish, Austropotamobius pallipes. Proceedings of Crayfish Conference, Leeds, April 2000.
Note: If using or referring to this published study, please read and quote the original paper.