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White-Clawed Crayfish

White-clawed crayfish habitat, ecology, mitigation & the law

Ecology and Habitat
Current Status
  Legislation covering all crayfish Mitigation
What to do:
        Crayfish on your land
        Habitat is threatened
        Crayfish and development

The white-clawed crayfish (Austropotomobius pallipes) is also known as the Atlantic stream crayfish. It is widely distributed in England, mid-Wales and Ireland. However it is declining in numbers throughout its European range due to habitat modification, declining water quality and the introduction of non-native crayfish species. They are protected by UK and European law.

Identification of white-clawed crayfish

Although the white-clawed crayfish is the UK’s only native crayfish there are many other non-native species now established around the UK. The most widespread species is the Signal crayfish Pacifastacus leniusculus (also known as American crayfish). Other non-native species are very localised but can be very numerous where they do occur. This can cause problems in obtaining positive identifications in the field, especially young crayfish as these tend to look very similar. The case in Ireland is made easier as presently there is no evidence that any other species of crayfish other than white-clawed occurs there. Identification of crayfish in the water is too difficult to be practical so it is best to contact a qualified and licensed professional if a definite identification is needed.

Adult white-clawed crayfish may reach 12 cm in length from the tip of the rostrum (‘head’) to the end of the telson (‘tail’). This is much smaller than adult signal crayfish that can grow to 30 cm. There is a single pair of post-orbital (behind the eyes) ridges unlike the signal crayfish that has two pairs. The body of white-clawed crayfish is smooth, generally brown to olive in colour with a pitted appearance. Signal crayfish also have a smooth body but the colour is often more reddish-brown. Claws of signal crayfish are smooth and red on the underside with a white-turquoise patch on top of the junction of claw (which gives them their common name of ‘signal’) and are usually very large (if they have not been previously lost and re-grown). White-clawed crayfish have rough top sides of their claws with dirty-white to pink colour on the underneath (hence their common name).

Ecology and habitat of white-clawed crayfish

White-clawed crayfish live in small streams, brooks, rivers, lakes, reservoirs and water-filled quarries. They prefer clear, well-oxygenated water without too much fine sediment. Typical habitat features favoured by white-clawed crayfish include crevices in rocks, gaps between stones, submerged plants and tree roots, which all provide refuges for them to hide in. They are therefore very susceptible to pollution and intensive river works especially dredging and canalisation.

White-clawed crayfish feed on most organic matter. This typically includes fallen leaves, dead fish and other animals but also live organic matter is eaten, such as aquatic invertebrates and vegetation as well as cannibalising other crayfish. Recently moulted individuals are particularly vulnerable until their exoskeleton has had time to harden.

Young crayfish are eaten by fish (for example perch, trout, chub, pike and eels), birds and carnivorous invertebrate predators such as the larvae and nymphs of beetles and dragonflies. Larger predators such as herons, otters, mink and rats take the adults. Crayfish are mostly nocturnal helping reduce the risk of predation.

Crayfish activity varies through the year. The period of least activity is during the winter when they spend much of their time in a state of torpor, often in burrows in riverbanks. The peak of activity is between July to September. However, the actual timings of the life cycle differ depending on latitude and altitude.

Mating takes place in autumn and early winter (September to November) when the water temperature drops below 10 oC for an extended period. Females carry the developing eggs in a dense cluster attached to the underside of their tail, over the winter. The number of eggs in a cluster can vary from 20 to 160, but is usually no more than 100. When the eggs hatch the young remain attached to the female. Release of the young varies in timing according to geographic location and temperature but usually begins in June.

  Distribution of white-clawed crayfish

White-clawed crayfish is Britain’s only native freshwater crayfish. Although quite widespread in Ireland and most of England and Wales they are, however, absent from the extreme southwest of England, west Wales and also from Scotland. They are most common in chalk streams and limestone rivers but they are not confined to these as they are also found in streams on Midland clays, streams and rivers draining the Pennines and Lake District as well as some gravel pits.

The UK is the most northwesterly limit of the white-clawed crayfish species range. They are confined to Europe ranging from the UK, Portugal and Spain east to Italy and former Yugoslavia.
Current status of white-clawed crayfish

There has been a substantial reduction in the extent of their distribution in recent years due to reduced quality and pollution of watercourses, competition and disease transmitted by introduced species of crayfish and, habitat modifications along many rivers and streams to aid water management. As more and more catchments in England and Wales become populated by non-native species of crayfish many populations of white-clawed crayfish are becoming increasingly isolated or lost. Presently, our British populations represent the greatest concentration of the species in Europe.

  Conservation of white-clawed crayfish

In Britain one of the biggest threats to our only native freshwater crayfish is the presence of an introduced species, the signal crayfish (Pacifastacus leniusculus). Since it was introduced to the country for farming in the late 1970’s and early 1980’s, signal crayfish have escaped and naturalised in many of England’s watercourses, most notably in the South. Signal crayfish can not only competitively exclude our native crayfish, but also carries a fungal disease called aphanomycosis (Aphanomyces astaci) or crayfish plague, to which the native white-clawed crayfish has no defence. Thus present conservation efforts focus on preventing the introduction and spread of non-native crayfish in the wild. Legislation implemented in 1996 now helps to control the importation and farming of crayfish and a Code of Practice was introduced advising fish markets, hotels and restaurants on how to keep crayfish securely, and of their responsibilities under the Wildlife and Countryside Act.

Several watercourses have been designated Special Areas of Conservation for their populations of white-clawed crayfish, in accordance with the Habitats Directive. A main aim for SAC site selection for white-clawed crayfish is to provide a wide geographic representation of their populations. Most sites are in areas where the keeping of non-native crayfish is prohibited except under licence and the water is free of crayfish plague. A good variety of habitats have been selected including rivers, natural lakes and artificial lakes. However, a relatively low proportion of the total UK population is contained within the SACs, emphasising that many recorded populations are in areas vulnerable to crayfish plague. The SAC series makes a contribution to securing favourable conservation status for this species but wider measures are also necessary to support its conservation in the UK. These include actions supported through their Species Action Plan (SAP). The leading partner in the white-clawed crayfish SAP is the Environment Agency, supported by a huge number of local action plans covering most of the species’ range. Although white-clawed crayfish are not covered by legislation as comprehensively as other Schedule 5 species, there is growing pressure to enforce mitigation and compensation projects for developments that impact populations. For example, soft engineering solutions rather than concrete canalisation are promoted, moving works to areas unfavourable to crayfish, and control of sediment released during works are advised.
Legislation for the white-clawed crayfish

White-clawed crayfish are fully protected under UK and European legislation:

Bern Convention 1979: Appendix III
IUCN Red Data List
Wildlife & Countryside Act (as Amended) 1981: Schedule 5
EC Habitats Directive 1992: Annex II and V(a)
The Prohibition of Keeping of Live Fish (Crayfish) Order 1996 (implemented under the Import of Live Fish (England and Wales) Act 1980)
Countryside Rights of Way Act 2000 (CRoW 2000)

White-clawed crayfish are listed on Schedule 5 of the Wildlife & Countryside Act 1981, but only receive protection under Sections 9(1) and 9(5). Section 9(1) of the Act makes it an offence to take white-clawed crayfish. Under Section 9(5) it is
an offence to offer for sale, transport for sale, advertise for the purpose of trading any live, dead, part, or derivative of,
white-clawed crayfish. Section 9 applies to all stages in their life cycle.

Their inclusion on the Habitats Directive allows areas to be designated as Special Areas of Conservation (SAC) for the presence of white-clawed crayfish. Such a designation brings legal restrictions to the management and operations and development that can occur in such sites, to help conserve the white-clawed crayfish and the specific habitat it requires.

The maximum fine on conviction of offences is currently £5000. The CRoW Act amended the 1981 Act to allow for a custodial sentence of up to six months instead of, or in addition to, a fine. Fines may be imposed in relation to each offence committed, so operations involving many animals or repeated offences can potentially accrue large fines. In addition, items or equipment, which may constitute evidence of the commission of an offence, may be seized and detained. The CRoW Act also amends the Police and Criminal Evidence Act 1984 to render Section 9 offences ‘arrestable’, giving the police significant additional powers.

If in doubt over any legal issue relating to white-clawed crayfish contact the relevant Statutory Nature Conservation Organisation (SNCO) for advice (Links).

This is only a brief interpretation of the law concerning white-clawed crayfish – reference should always be made to the original texts of the legislation if more detailed interpretation is needed (UK & European Legislation).
Legislation regarding non-native species of crayfish

Legal controls on the keeping of non-native crayfish were implemented in 1996 under the Import of Live Fish (England and Wales) Act 1980, titled The Prohibition of Keeping of Live Fish (Crayfish) Order 1996, often shortened to the Crayfish Order. This legislation was introduced to help protect the now endangered native crayfish populations by preventing the spread of non-native species.

Under the Wildlife and Countryside Act 1981 it is an offence to release any crayfish species (other than white-clawed) to the wild except under licence. Therefore any person responsible for introducing crayfish to water bodies from which they are able to escape, such as ornamental ponds, or farm ponds without a licence is liable to prosecution. Under the Crayfish Order it is now also an offence to keep non-native crayfish without a licence.

One impact of the Crayfish Order policy was that the keeping of ornamental aquarium crayfish was effectively prohibited. Therefore an exception was made for the keeping of one named tropical species of crayfish (redclaw crayfish Cherax quadricarinatus). All other non-native crayfish are considered to be temperate animals and as such they cannot be kept for ornamental purposes in England and Wales. The redclaw species is not considered to be a threat should it escape as it requires heated water and could not therefore survive in the UK’s natural environment.
A licence is required to import this tropical species (a DOF 8T licence) and also a general licence (issued under the Crayfish Order) to keep it in an aquarium. Licences are granted by DEFRA. To find out more and download application forms follow these links:

Government legislation web page

The Aquatic animal health and movements website offers excellent advice on the legislation of keeping and moving all things fishy

If in doubt over any legal issue relating to crayfish contact DEFRA for advice.

This is only a brief interpretation of the law so reference should always be made to the original texts of the legislation, especially if more detailed interpretation or citations are needed (UK & European Legislation and the above links).

  What to do if you have white-clawed crayfish on your land
Advice for landowners – how you can help

If you are lucky enough to have white-clawed crayfish on your land you should contact your local Biological Records Centre and Wildlife Trust . This will add valuable detail to the known distribution of white-clawed crayfish, helping to focus conservation efforts.

It is possible to help the conservation of white-clawed crayfish by acting locally and ensuring the habitat conditions on your land are suitable to maintain its population.

It is critical that the water remains clear and free of pollution from industrial, agricultural and livestock chemicals. The Environment Agency should be notified of any spillages in or near a water course and also notified of any works that you might have planned which may alter the banks, streambeds or water flow. Limiting the access of livestock to watercourses reduces poaching of the banks, disturbance of the streambed and effluent. Trampling of the streambed disturbs the cobbles and rocks that crayfish use for shelter and suspends excess silt in the water.
What to do if a white-clawed crayfish site is threatened by a development

Ideally, it is best if white-clawed crayfish and their habitat are protected before planning permission has been given for development of a site. If a known or suspected white-clawed crayfish site is threatened by a development, the local planning authority and the local office of the SNCO should be informed as far in advance as possible. These organisations will ensure that appropriate surveys are licensed to establish the status of crayfish on the site and that alternatives to the proposed development are considered as part of the planning process.
For activities that do not require planning permission it is best to contact the landowner before any work is due to start. The local SNCO or Wildlife Trust might be able to assist and provide advice to the landowner regarding conservation of their population of white-clawed crayfish.

If there is evidence that the law has been broken or is about to be, the police should be informed, the best contact being a Police Wildlife Liaison Officer. For offences or potential offences such as excessive works or modifications to riverbanks and riverbeds, fish and especially non-native crayfish stocking it is worth also contacting the local office of the Environment Agency.

  What to do if white-clawed crayfish are discovered during a development

If white-clawed crayfish have only been discovered after development of a site has commenced you can contact us for advice. All works should be halted until white-clawed crayfish surveys have been undertaken and appropriate measures taken to protect the crayfish on site. Remember that if white-clawed crayfish are present, it would be an offence to proceed works without an appropriate license.

For the development to proceed, special protection and compensation must be provided for the crayfish and their environment. This is termed mitigation, and specialist licensed ecological consultants such as JPR Environmental provide its strategies. Mitigation normally takes the form of isolating the population of crayfish during the development and enhancing the habitat to increase the future population. See below for more details.
  Mitigation for white-clawed crayfish

Experienced ecological consultants must provide mitigation strategies, as specific requirements need to be met if Local Planning Authorities are to grant permission for a development. Mitigation projects for white-clawed crayfish normally require licences from DEFRA or EN and these are normally arranged by ecological consultants. JPR Environmental offer a complete service for design, implementation and management of white-clawed crayfish mitigation projects.

Typical mitigation measures for white-clawed crayfish include removal of individuals from site areas during works, their reinstatement afterwards and creation or enhancement of the habitat affected if necessary.

In cases of permitted development or where planning permission has been granted to sites that contain white-clawed crayfish, they may have to be excluded from the target areas. During de-watering of the stretch of watercourse, crayfish can be collected as they emerge from crevices as the water level lowers. Depending on the length to be dewatered, it is often possible to place the crayfish in the water either side of the dams from where they can then re-colonise the developed area.

Creation or enhancement of white-clawed crayfish habitat typically involves the installation of rough stone walls as a way of supporting river banks and providing crevices for crayfish.
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