Living with an Alien Invasion
|Signal Crayfish populations in local area.|
Dramatic, but not as dramatic as the Foot and Mouth crisis of 2001 when 750 000 cattle from 1500 farms in Galloway and Dumfries were slaughtered and burnt. The Army had to be called in to help.
I have written a timeline for the alien invasion. It has been going for 20 years.
Signal Crayfish in Dumfries and Galloway
Since 1996, when first discovered, an initially small population of American Signal Crayfish has increased to become a major problem. Proposals for eradication were made in 2004 but not acted upon. By 2009, the numbers in Loch Ken, the epicentre of the problem, had grown to the extent that the removal of 700 000 signal crayfish over three months made little impact.
A three year programme of trapping on Loch Ken was suggested in 2009, but not acted upon. By 2014 signal crayfish had spread to two reservoirs, one 15 km and the other 25 km from Loch Ken. The smaller of the reervoirs will be drained later this month in an attempt to eliminate the crayfish. There are no plans to eliminate crayfish from the other one.
Loch Ken is a popular visitor destination for coarse fishing, sailing, water skiing, canoeing and windsurfing. To prevent the spread of signal crayfish from the loch a ‘Check, Clean, Dry’ biosecurity campaign is in place. However, any attempt to strictly enforce bio- security would risk deterring visitors and conflict with the promotion of the natural heritage value of the area.
There is therefore a major conflict of interest developing between the need to halt the spread of signal crayfish beyond Loch Ken and the impossibility of eradicating or even controlling the millions of signal crayfish in the loch.
1.The North American Signal Crayfish was introduced to the UK in 1976 . It was farmed to produce crayfish for restaurants. It was first recorded in Dumfries and Galloway in 1996 in tributaries of the Ken/Dee river system. By 1999 it had reached Loch Ken.
2. 1 In 2004 Scottish Natural Heritage commissioned a report ‘Strategy for the containment and possible eradication of American signal
crayfish (Pacifastacus leniusculus) in the River Dee catchment and Skyre Burn’. (The Skyreburn flows into the Fleet estuary near Gatehouse of Fleet.)
2.2 In 2004 SNP MSP Richard Lockhead asked a question (S2W-11046) in the Scottish Parliament about signal crayfish. Lewis MacDonald replied 27 October 2004-
“Scottish Natural Heritage has taken steps to deal with the signal crayfish issue in Scotland. As well as helping to fund eradication programmes, it has also commissioned a research report entitled, Preparation and Implementation of a Strategy for the Containment of American Signal Crayfish in the River Dee Catchment, Kirkcudbrightshire. SNH is also involved in the development of publicity materials for this species, which are designed to educate the public about the dangers of translocating signal crayfish to other waters.”
4. In 2009, as part of her PhD research, Zara Gladman monitored the impact of trapping approximately 650 000 signal crayfish in Loch Ken. [Note: Dr Gladman has explained she carried out a before and after study, not the main trapping exercise] http://theses.gla.ac.uk/3977/
Following this research a further three year trapping programme was recommended, but this did not happen.
“It was recommended that the trapping programme continue on Loch Ken for a further three years with part justification that the initial research had suggested that a heavy trapping programme may have a significant impact on the crayfish population. However, no further action has been taken on this recommendation.”
5. 1 In 2014 SNP MSP Joan McAlpine asked a question (S4W-20621) about signal crayfish in Lochrutton and the Lochfoor Burn near Dumfries.
Paul Wheelhouse replied
“I am advised by Scottish Natural Heritage that they have not yet identified an effective method for the eradication of North American signal crayfish in water bodies such as Lochrutton and the Lochfoot Burn, albeit this is an objective the Scottish Government is keen to pursue if at all possible. The Fisheries Trusts and Scottish Environment Protection Agency (SEPA) are working together to raise awareness of appropriate biosecurity measures that water users can take to avoid spreading the species, and other freshwater invasive species, to other parts of the catchment or to other parts of Scotland. This includes launching a number of biosecurity campaigns across Dumfries and Galloway this spring and summer to raise awareness of invasive non-native species, including the Check Clean Dry and Be Plant Wise initiatives across the region. All campaigns are being co-ordinated by SEPA with support from a variety of partner organisations such as Police Scotland, the Galloway Fisheries Trust, the Nith Catchment Fishery Trust, the River Annan Trust, Dumfries and Galloway Council Ranger Service, Solway Firth Partnership and Scottish Natural Heritage. These campaigns will be supported by the distribution of thousands of leaflets, identification guides, posters and signs across the region.”
5. 2 In 2015 there was a Petition, PE 1558, to the Scottish Parliament which called on the Parliament ‘to urge the Scottish Government to amend the existing licencing regime to allow for the commercial trapping of American Signal Crayfish in Scotland.’ This call was rejected. However, in May 2015 Scottish Natural Heritage and the Scottish Environmental Protection Agency produced a lengthy response to the Petition.
This included an action plan for the signal crayfish problem in Buittle (Dalbeattie) Reservoir which is part of the Urr catchment.
6. On 4 August 2016, the Galloway News revealed that Buittle Reservoir will be drained later in the month in an attempt to eliminate signal crayfish.
7. Between 2017and 2021, as part of the Galloway Glens Landscape Heritage project, a Loch Ken Fisheries Survey will be carried out. The survey will include identifying the extent of the loch’s signal crayfish population. This survey was proposed in the 2015 SNH/SEPA response to Petition 1558.
The EU Water Framework Directive of 2000 (2000/60/EC) required river systems to be brought up to ‘good ecological and chemical quality’ by 2015. However, ‘heavily modified water bodies’ were only required to achieve ‘good ecological potential’ by 2015. A 2002 case study identified the Dee/Ken river system as a heavily modified water body.
The main reason for this designation was the effects of the 1929 Galloway Water Power Company Act. This led to the construction of a hydro-electric scheme, completed 1935, which affected the Doon (Ayrshire), Ken and Dee (Galloway) river systems and their catchments.
The 80 year old hydro-electric scheme restricts the migration of salmon upstream. Modifications could be carried out to improve the system for salmon, but they would be expensive. The Water Framework Directive allows the benefits - in this case renewable energy- of heavily modified water bodies to be taken into account.
‘Appendices to the 2015 update to the river basin management plan for the Solway Tweed river basin district’ - Appendix 8.1, p. 51, explains the current situation.
Where restoring the water bodies to good ecological status would significantly compromise the benefits Scotland obtains from their modifications, we have designated them as heavily modified water bodies. Instead of good ecological status, our goal for these water bodies is to achieve good ecological potential. Good ecological potential is the ecological quality that can be achieved without a significant adverse impact on the benefits served by the modifications, including benefits to environmental interests, such as wildlife conservation.
In other words, even if it was possible to eradicate signal crayfish from the Ken/Dee river system, it would still only achieve ‘good ecological potential’ because it would remain a heavily modified water body. Likewise, an extensive programme of trapping, as proposed in 2009, might reduce the numbers of signal crayfish in Loch Ken, but the costs would be excessive for a heavily modified water body.
On the other hand, Loch Ken is a highly popular visitor destination for coarse fishing, sailing, wind-surfing, water-skiing and canoeing. All of these activities have the potential to allow the spread of signal crayfish to other locations. Loch Ken has been targeted by notices and information about the UK wide ‘Check, Clean, Dry’ campaign which is designed to limit the spread of invasive non- native species. http://www.nonnativespecies.org/checkcleandry/
However, while the Loch Ken Management Committee agree that biosecurity is important, they do not want create a message that the loch is ‘closed for business’ which would discourage visitors. During the 2001 Foot and Mouth crisis, access to the countryside in Dumfries and Galloway was effectively banned which had a major negative impact on tourism.