The Inverurie castle is one of the few habitats in northern Scotland that support the rare Northern Damselfly and Azure Damselfly, the former being one of the charity’s priority species.
The work carried out includes the repair of a sinkhole and leaks at the castle’s Flight Pond, a popular attraction within the castle’s grounds and home to a variety of Odonata, the collective name for dragon and damselfly species. Alongside these repairs, the Trust also carried out surveys of the fish stock within the pond and identified a critically endangered eel estimated to be between 30 – 60 years old that was re-released back into the pond.
The project, supported by funds raised by players of People’s Postcode Lottery through its Postcode Earth Trust, follows the publication of the National Trust for Scotland’s new Plan for Nature, which sets out its ambitions to conserve the nature in its care. The Northern Damselfly has been identified as one of 26 priority species within the plan, which the Trust has special responsibility for. The plan outlines the focus for the charity to carry out further research to understand their conservation status and ecological requirements, as well as improve conditions for the species.
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The work carried out was required following the appearance of a sinkhole next to the pond’s boundary because of heavy rainfall and flooding at the end of 2023, causing the closure of the neighbouring Alton Brae Trail to visitors due to health and safety concerns.
Vivian Bisset, National Trust for Scotland Ranger in the North East who has been leading the project, said: “It is really satisfying to see the pond back in action after work to fix the sinkhole took place earlier in the year. We ended up using over 18.5 tonnes of clay to reinforce the side of the pond.
“A 17-metre stretch of path along the Alton Brae Trail was dug out in sections to form a trench that was filled with high density clay and a Terram membrane was installed by our contractor to hold it in place. During the work, additional underground leaks were identified that would have caused a similar issue on the opposite side of the pond over time, so we made the decision to address these during the work to help prevent future leakages from occurring.
“By doing this we have helped protect the integrity of the pond and improved its longevity while also protecting the habitat for our Odonata assemblages. We are pleased that we’ve been able to address a health and safety concern caused by the sinkhole while also making improvements at the same time.
“We’ve been able to widen a 20-metre stretch of the Alton Brae trail to two metres, and level it out and re-surface to improve accessibility. We’re enhancing the visitor experience further by installing new information boards and way markers around the Flight Pond to improve engagement that will be installed in early 2025.
The Trust is enhancing the visitor experience further by installing new information boards and way markers around the Flight Pond to improve engagement that will be installed in Spring. (Image: NTS)
“Alongside the repair of the pond, we also carried out a fish stock survey to assess the different types of fish present. We made an exciting discovery of a critically endangered European Eel (Anguilla anguilla), a protected species, which was re-released back into the pond. It was around 70cm in length and the team estimated it to be anywhere between 30-60 years old.
“Eel can travel upstream and across land, so it is very exciting that it has found its way from the Sargasso Sea to Castle Fraser as a part of its epic migration journey. Based on its advanced age, it is possible the eel may eventually leave to return to the Sargasso Sea to breed. We also removed some non-native fish from within the pond, thought to have been released by a member of the public without our knowledge.”
The National Trust for Scotland team at Castle Fraser has been developing ideas for how to improve the habitat further.
One idea being explored is the creation of a new wetland area, and topographic, soil, and peat surveys have been carried out to understand its potential and suitability as an additional home for the resident Odonata. Further survey work is required in Spring 2025 to confirm if the idea is feasible.
Vivian continued: “We’ve been collaborating closely with the British Dragonfly Society on the idea for the potential new wetlands to create a mosaic of habitats for the dragon and damselfly species to thrive in. We’re exploring the feasibility for the proposed wetlands, which are subject to the necessary surveys and planning permissions, that will help to bolster Odonata in the area and offer increased protection for nationally scarce species, such as the Northern Damselfly.
“It is thanks to the continued generosity of our members and supporters, including players of People’s Postcode Lottery, that we’re able to continue our vital work to care for and protect Scotland’s natural heritage at this special place for everyone to enjoy, now and into the future.”