Crisis for Irish White-clawed Crayfish

The White-clawed Crayfish Austropotamobius pallipes is an endangered species. Ireland is the stronghold of this species due to the absence of non-native crayfish species and diseases. However, this status is now being threatened, with a major outbreak of Crayfish Plague on the Lower River Suir Special Area of Conservation (SAC) downstream of Clonmel, Co Tipperary. White-Clawed Crayfish are a key conservation interest of this Natura 2000 river, which is one of the largest remaining habitats for this species in Europe.

Crayfish Plague Aphanomyces astaci is a non-native water mold from North America that infects and kills White-Clawed Crayfish. Crayfish plague first arrived in Europe in Italy in the mid-1800s and thereafter spread quickly through Europe decimating native crayfish populations. In the late 1950’s to compensate for dwindling stocks of native crayfish, the North-American Signal Crayfish Pacifasticus leniusculus was introduced to Sweden. The Signal Crayfish was known to be resistant to crayfish plague. Unfortunately it was not known at that time that it was also a carrier of this disease. While the Signal Crayfish has thrived and spread across Europe, native European crayfish populations – which have no resistance to crayfish plague – have been decimated.

The White-Clawed Crayfish is an endangered species listed on Annex II and Annex V of the Habitats Directive and protected in Ireland under the Wildlife Acts.

Crayfish Plague was first reported in Ireland in the 1980’s but has never become established here – probably due to the absence of non-native Crayfish Plague carriers. However, It has long been known that Irish crayfish are at high risk from this disease. The risk has been there that someone may accidentally or even deliberately introduce non-native diseases-carrying crayfish species. It is not necessary for the American crayfish to be present – the plague fungus produces spores which can be transferred on canoes and boats, wet angling gear etc.

Other non-native crayfish species also carry plague, including the Red swamp crayfish Procambarus clarkii and the Spiny-cheeked crayfish Orconectes limosus. Each American crayfish species carries a different strain of the plague. The White-clawed crayfish are highly susceptible to crayfish plague and once introduced it quickly kills off this species in a short time. The ‘Pacifastacus’ strain appears completely lethal and eradicates all native crayfish.

By allowing a major canoeing course and Blueway to be developed in the Lower River Suir SAC without Appropriate Assessment, Ireland has failed to meet its international obligations to protect this endangered species

It is not known how crayfish plague ended up in the Lower River Suir. However, last year a major slalom canoeing course was built in Clonmel, and major canoeing competitions have taken place there since then. No Appropriate Assessment was completed for this development nor the associated Suir Blueway. Appropriate Assessment is required where a project or plan may give rise to significant effects upon a Natura 2000 site. The development of the Clonmel canoeing course involved extensive instream construction works and also significantly increased the biosecurity risk to this Natura 2000 river by attracting large numbers of canoeists – both significant impacts. The failure to comply with the provisions of the Habitats Directive here is of serious concern, and the survival of this annex II species in this Natura 2000 river is now uncertain.

Major instream works in the Lower River Suir SAC with no Appropriate Assessment completed.
A project like this requiring significant instream construction works within a Natura 2000 river – and ongoing disturbance and biosecurity risk from the operational slalom course – should never have been screened out from the requirement of Appropriate Assessment.

It is not known if this development was responsible for this outbreak of Crayfish Plague – however the disease has only so far affected the crayfish population downstream of the canoe course so the location and timing of the outbreak means that this may well be more than coincidental. What is certain is that the development of this course and associated Blueway increased the biosecurity risk – a potential significant impact which required Appropriate Assessment.

Ireland remains the only part of the EU with no introduced species of crayfish, and has up until now been relatively free of Crayfish Plague. This species is at risk of extinction in all other EU member states. By allowing a major canoeing course and Blueway to be developed in the Lower River Suir SAC without Appropriate Assessment, Ireland has failed to meet its international obligations to protect this endangered species. It is now impossible to not acknowledge that there was potential for significant adverse effects on the Lower River Suir SAC from the construction and operation of this major recreational development. Questions now have to asked regarding why this development was allowed to proceed in clear breach of the requirements of the Article 6(4) of the Habitats Directive.

Read the press release from the ‘Department of Arts, Heritage, Regional, Rural and Gaeltacht Affairs’ here:

For further information also see these links:

The appearance of Crayfish Plague in the Lower River Suir SAC has not been associated with the introduction of a non-native crayfish species (or at least there is no evidence of this yet). In the UK the spread of plague is usually associated with the non-native Signal Crayfish, which is immune to the disease – and carries it. The Signal Crayfish are larger than our native (?) species and out-compete, and in some cases, eat them. There are currently no records of non-native crayfish species in Ireland which gives some hope to containing the disease and protecting our remaining White-clawed Crayfish. The weirs in Clonmel  – for which the eel, lamprey and crayfish passage problems were never addressed at during either the construction of the Clonmel flood protection scheme and Clonmel slalom canoeing course – may now also provide a barrier to protect crayfish populations upstream. However these can be flooded out, and the disease may have already been transferred to upstream of here. It is very important that all water users practice biosecurity measures, and there will also need to be limitations placed on events planned for the Lower River Suir SAC (e.g. the Suir Descent).

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