Cat Cooper, Project Officer, Scottish Invasive Species Initiative, published March 2025
When the Scottish Invasive Species Initiative began operations in 2018 we faced a situation where there was no carryover mink trapping network remaining from the Scottish Mink Initiative (SMI) which ended in 2015. This meant that we had to rebuild a trapping network from scratch and in combination with rolling out landscape scale plant control in the Tay system – mink are not our sole focus and so our resources are spread more widely. Our initial emphasis was placed on re-establishing a core trapping network on the main stem of the Tay and Tummel, with targeted deployment where possible to smaller rivers and tributaries and areas of environmental importance like the Tay Reedbeds and Loch of the Lowes. From 2018 to 2024 a robust network was built up and maintained in these areas, catching more mink than any other Scottish Invasive Species Initiative project area in that time. However, with additional seasonal project staff employed in 2024, there was an opportunity to grow the network to fill gaps and expand west, to bring rivers like the Earn into the project area. Cat Cooper (now Project Officer for the Esk catchments) played a leading role in delivering that expansion over her time working with us as a Seasonal Project Officer in 2024.
“Remoti – Unit Activation.”
These words via text have become a regular occurrence in the past couple of months, and with each comes the excitement of knowing that there may be another American mink waiting in a live trap within the Tay system…
I began my seasonal role in May 2024 with the Scottish Invasive Species Initiative, working alongside the Project Officer on the River Tay and its tributaries. As part of my role I was given the opportunity to work on the expansion of the mink trapping network into the River Earn and to fill in a gap within the current network on the River Ericht. American mink trapping was a new undertaking for me and I was keen to get started.
The Earn: Expanding the network
The Earn is roughly 74km long, beginning at Loch Earn on the edge of the Trossachs and joining the Tay at Abernethy. Whilst we knew there was a population of American mink on the Earn, this tributary in the south-west of the Tay catchment (a border region for the project) hadn’t yet been reached. However, contact had been made with the River Earn Improvement Association to establish interest, and a list of willing volunteers was waiting to get set up and change that situation.
Once I had my list, I reached out to each potential volunteer and arranged a site visit to determine a suitable location for a raft and live trap. Many of our new recruits are gamekeepers, ghillies and estate employees who have been working the land for years (in some cases over 40!!) and their knowledge of the area and past mink experiences was invaluable to identify the right locations.
At each site we looked for areas where mink had been spotted historically but also for locations that would provide excellent territory for them. Ponds, streams and ditches were all investigated as well as the main stem of rivers and their confluences (where two or more watercourses join).
Once we had agreed on a site the next phase would begin – deploying the equipment as quickly as possible. Our set up includes a floating raft and tunnel, a live capture trap, and a Remoti unit. The Remoti devices have proven to be invaluable to many of our new volunteers – particularly if they are busy with their day-to-day tasks or responsible for large areas of land or river beats. The Remoti unit is attached to a live capture trap and is triggered when the trap closes – this sends a text message to both the volunteer and the Project Officer to alert them. On our first new site success arrived much faster than even we had expected, with five mink caught and dispatched within the first week of operation. Many of these captures were on an estate pond but we also had success on the main stem of the river… we even had two mink in one day!
Sometimes we didn’t get the trap position quite right first time around and needed to make small changes to the location to maximise the chances of mink entering the trap – and minimise the likelihood of non-target species being captured. One volunteer had two red squirrels and even a hedgehog but these were safely released to continue their day and we subsequently moved the raft…and even camouflaged it!
By the end of 2024 we had 18 mink captures on the River Earn and 10 volunteers in place, with twelve traps deployed and a further ten awaiting placement next season, with coverage from Bridge of Earn all the way to Loch Earn. Mink activity slows down over winter and most volunteers will bring their equipment out of the water to avoid damage and lost equipment in storms and spates, but this end of year coverage puts us in an excellent position to hit the ground running in spring 2025.
The Ericht: A Gap in the Network
The Ericht originates in Highland Perthshire, where the Rivers Ardle and Blackwater meet near the Spittal of Glenshee, and flows down to Blairgowrie where it merges with the Isla. Historically the Ericht was a vital source of power, driving numerous mills and factories along its banks, particularly in Blairgowrie. Today the river is known for its salmon fishing, diverse habitats, and scenic walks. However, like many Scottish waterways, it faces ecological threats from invasive species like the American mink.
The Ericht has proved tricky for us to set up a consistent network so this was a key target area for me in May 2024. The only coverage up until this point had been through a gamekeeper who began trapping on the upper Ericht in mid-2023.
As with the River Earn, we had already received interest from one of the local estates. The keepers, ghillies, and their guests were regularly seeing mink travelling up the river systems so they were keen to lend their time and expertise to the project. One volunteer, Adam, had several sites in mind, including an adventurously out of the way hill loch where he had spotted mink in the past, and a confluence on the main river. One obstacle we faced here was the patchy mobile network. Remoti units operate using mobile phone masts and in Highland Perthshire this can be tricky, but Adam was happy to trial these and give it a go – knowing that he might have some additional journeys to make if the signal were to dip out.
Rafts were placed and traps were set. On this occasion we decided to maximise our chances by placing mink scent in the back of the traps and less than 24 hours later we had a juvenile female – followed the next day by a young male!
In total, the Ericht had 16 mink captures in 2024 and, like the Earn, we expect to catch more when activity heightens again in spring. We now have six volunteers together monitoring 11 traps in the Ericht catchment – thank you to everyone who has signed up!
The Earn and Ericht expansion have already seen 34 mink captures between them since we started to expand these networks in July 2024. We are also delighted to welcome Comrie Men’s Shed to the project, our newest construction recruits who have kindly agreed to make rafts and tunnels for us to be deployed in the new year. Volunteers are absolutely essential to the Scottish Invasive Species Initiative and without them there simply wouldn’t be the time and skills available to cover such an expansive area. Thank you to each and every person who has offered advice, cups of coffee and, most importantly, their time to get these new networks up and running.
In total the Scottish Invasive Species Initiative captured 74 American mink from across the Tay catchment in 2024, with the help of over 50 volunteers. Of these, 34 captures were from the Earn and Ericht systems – a great success following these local expansion efforts. American mink are an invasive non-native species which have severe detrimental impacts on native wildlife. By controlling their population we aim to reduce their impact on native species and protect local wildlife. Thank you to everyone who has been involved across the Tay catchment!
To find out more about the Scottish Invasive Species Initiative and how to get involved, you can visit our website, follow us on social media or contact us on sisi@nature.scot
