Eradication of Invasive Crayfish in Ballachulish Quarry

5th June 2012

The Highland Council has confirmed proposals for the eradication of North American signal crayfish in Ballachulish Quarry this summer. The site is currently owned by the Council and managed by the Planning and Development Service for public recreation. The crayfish, a small lobster like species that can have a devastating effect on native wildlife, were first discovered in the Ballachulish Quarry pond by one of the Council's own Countryside Rangers in August 2011.

This is the first time that signal crayfish, have been found in Lochaber and it is the most northerly recorded occurrence of this species on the west coast of Scotland. Where they occur, signal crayfish can compete with fish for food and shelter, and they can be a significant predator of a range of freshwater animals. This means that their presence is of concern to conservationists and anglers alike.

Since making the discovery The Highland Council has been in liaison with a number of stakeholders and agencies, including Lochaber Fisheries Trust, Scottish Environment Protection Agency (SEPA) and Scottish Natural Heritage (SNH). Detailed proposals for eradication have been prepared by the Lochaber Fisheries Trust and an appropriate course of action has now been agreed.

The eradication attempt will involve the controlled application of a chemical called Pyblast to the two ponds in the quarry and this work is planned to commence on June 11th 2012, subject to suitable weather conditions, and is expected to complete within a four week period. Pyblast is toxic to fish, crustacea and insects but has very low toxicity to mammals and birds, so the risk to humans or any otter, mallard, heron and domestic dogs that use the site will be low. There are no wildlife species of conservation concern within the ponds.

The crayfish in the ponds will be killed within the first three days after treatment, after which the toxicity of the pond will begin to fall. Recovery of the pond will then be enhanced by actively pumping the water within the ponds to accelerate breakdown. Pumps will also be used to disturb and suspend the layer of sediment present on the bed of the ponds as this will also speed up the recovery process. The toxicity of the ponds will be monitored throughout and the site is expected to have returned to normal within 21 days.

The ponds have no surface connection to any other waterbody. The nearest natural freshwater waterbody to the treatment pond is the River Laroch, 400m away. There is no history of either pond flooding. The proposal to use Pyblast has been subject to formal authorisation through SEPA and approval through the Health and Safety Executive Chemicals Regulation Directorate.

Access to the ponds will be restricted during treatment and until monitoring indicates the chemical has broken down. Temporary fences will be erected around the ponds, but access to the wider site for recreational purposes, will not be restricted. Signs will be erected to make the public aware of sensible precautions and the public are reminded that it is illegal to catch or remove crayfish in Scotland without a licence. Members of the public who think they have seen signal crayfish anywhere else in the area should report this to the Lochaber Fisheries Trust.

The cost of the eradication attempt is approximately £76000, nearly half of which is the cost of the Pyblast chemical. Specialist supervision will be undertaken by the Lochaber Fisheries Trust and SPB Environmental, with manpower being supplied by Highland Council and the Fisheries Trusts. Funding has been provided by the Highland Council, SEPA and SNH and the operation will provide a valuable training opportunity for a range of Highland organisations to increase their knowledge, skills and awareness in relation to this unwelcome invasive species.

Signal crayfish were first introduced to waters in England and Wales from fish farms in the 1980s. In Scotland, they were first recorded in the catchment of the Kirkcudbrightshire Dee in 1995. Since then, specimens have been found in ponds, rivers and lochs in 13 Scottish river catchments. They are now found as far north as the Inverness area.

This species is a voracious predator which feeds on insects, frogs and young fish and their eggs. Signal crayfish also have an impact on the banks of rivers and lochs by burrowing into them. This can lead to increased erosion and damage to the spawning grounds of a variety of fish. In some situations it may cause some banks to become unstable.

Sightings of the crayfish outwith Ballachulish Quarry should be reported to the Lochaber Fisheries Trust: Tel. 01397 703728; Email Lochaberfisheriestrust[AT]gmail.com.