On Grosvenor’s Reay Forest Estate in the north-west Highlands of Scotland, we’re working in partnership with conservation charity the Atlantic Salmon Trust (AST) to deliver a landscape scale, ecosystem-wide, conservation project with the goal of restoring wild Atlantic salmon and sea trout populations.
The River Laxford has been a stronghold of wild Atlantic salmon and sea trout for centuries - its name is Old Norse for salmon fiord - but in recent years their populations have seen a rapid decline, mirroring conditions throughout the north Atlantic.
Delivering this 10-year project, one of the largest catchment wide restoration projects in the UK, we hope to restore 118km2 of the landscape and plant up to a million trees, enhancing biodiversity and benefitting the whole ecosystem while enabling wild Atlantic salmon and sea trout to thrive.
In partnership with the AST and supported by Marine Directorate, the government body which manages Scotland’s seas and freshwater fisheries and the West Sutherland Fisheries Trust, a charity which works to protect and restore fish populations in the area, our collective aim is to improve understanding of the pressures limiting wild Atlantic salmon and sea trout production in the Laxford catchment.
The dwindling number of salmon and sea trout in the River Laxford is extremely worrying. The data we collect from the study will not only be vital for the salmon restoration project, but also the biodiversity of the entire Reay Forest, and surrounding areas in Scotland.
The Duke of Westminster
The first step in the process was to complete a catchment audit to better our understanding of the Laxford’s current condition, capacity to support salmon and trout and the key factors limiting production, informing where to prioritise restoration efforts for the greatest effect.
There are a number of barriers to fish migration across the Laxford catchment.
The most significant of these is a stepped concrete bridge apron where a local road crosses the Allt Ceann Locha (the Kinloch Burn, pictured below), presenting at least a partial barrier to the upstream migration of salmon and trout.
Photo credit: Google (2023) Achfary, Scotland. Available at: http://maps.google.co.uk (Accessed: 30/10/2023)
Wild Atlantic salmon and sea trout are susceptible to a wide range of diseases, whether viruses, bacteria, fungi or parasites, which occur naturally in the environment and that have the potential to be exacerbated by the aquaculture industry.
The incidence of wider disease in wild Atlantic salmon and sea trout populations is generally poorly understood.
Due to the prevalence and distribution of fish farming in the region, wild Atlantic salmon populations in the Laxford catchment are considered to be at risk from the negative impacts of breeding with escaped farmed fish.
This would have the potential to impact upon the genetic fitness of the local population.
There is evidence of a historical realignment at the mouth of Abhainn an Loin (the Lone Burn), in the Loch Stack management unit.
Subject to a detailed feasibility study, we believe that restoring the original river channel could increase the available spawning and nursery habitat in the lower river by approximately 30%.
The loss of native riparian (riverside) vegetation is arguably the key freshwater factor influencing the status of salmon and sea trout populations in the Laxford catchment. The leaves on trees provide shade during the summer months, help to cool the water and reduce thermal stresses on the fish.
Tree roots help to strengthen banks and provide shelter. Falling twigs, leaves and insects provide an important food source and larger woody debris, such as fallen logs and branches help to shape the river channel.
Anecdotal evidence suggests that harbour seals penetrate the lower reaches of the system (see video below) throughout the year to feed on salmon and sea trout.
Significant numbers of goosanders, mergansers and cormorants habitat the Laxford catchment predating on juvenile fish and impacting salmon and sea trout production.
Other pressures include the impact of invasive and non-native species including fish, American mink (pictured) and plants, development of offshore renewable energy sources, potential local expansion of fin fish aquaculture, pelagic fisheries, exploitation, historical stocking operations and sedimentation.
While the wild Atlantic salmon is the focus of this initiative, no single species can be managed in isolation. The health of our salmon populations is heavily influenced by processes taking place throughout the wider catchment.
By taking an ecosystem approach to wild Atlantic salmon and sea trout restoration, naturalising and balancing their environment, it will benefit not only the fish, but also enhance wider biodiversity across the catchment. This approach will require us to address the complex set of relationships and interdependencies in the riverside areas and throughout the wider landscape.
Informed by detailed habitat restorations plans, continually assessing the impact of any interventions and in keeping with environmental designations. Our restoration strategy is focussed on four key interventions.
Woodland regeneration is limited by deer grazing pressure. The deer eat and trample young trees and other vegetation, stopping them from growing and impacting the wider habitat.
Enhanced and evidence based deer management across the Laxford catchment area will allow us to establish sustainable deer densities.
The resulting reduction in grazing pressure will allow catchment wide biodiversity benefits to be realised.
The key to restoring the habitat within the Laxford catchment will be re-establishing native riparian woodland. We’re aiming to plant up to a million trees near to rivers, burns and streams. In the longer-term, natural regeneration will occur across a wide range of habitat types within new restoration enclosures.
Our riparian woodland and habitat restoration plans are centred on three large enclosures, areas which will be fenced off across the catchment, covering a total area of over 25km2 – approximately a quarter of the entire catchment.
Over a period of about 50 years, the woodland and wider habitats within these protected areas will naturally recover as deer grazing pressure is removed. This will enhance biodiversity across the catchment, benefiting a wide range of species and habitats including breeding birds, blanket bog, sub-alpine heaths and montane acid grasslands.
The strategic placement of large woody structures, such as fallen trees, roots and branches, which under natural conditions are delivered into the river system via erosion or windblown trees, provides a refuge for juvenile salmon.
Debris from trees helps to deposit essential nutrients into the water creating a habitat for algae and aquatic insects, boosting biodiversity and providing a vital food source for young fish. In the longer term, the restoration of native riparian woodland in priority areas will provide a source of natural woody debris.
We believe the Lone burn, a tributary to the Laxford, was realigned in 1888. We estimate that restoring the original river channel could increase the available spawning and nursery habitat in the lower river by approximately 250m providing a 30% increase on the existing 800m of accessible habitat.
The efficacy of our management actions will be assessed over time using robust science and the latest monitoring techniques.
Four Passive Integrated Transponder tag arrays have been installed at strategic locations within the catchment. This state-of-the-art fish tracking equipment is helping to build a detailed picture of the timing, speed and direction of smolts, invaluable information which will help us to better protect these iconic fish.
A PIT tag is a small, pill-shaped cylinder of glass (about the size of a grain of rice) that houses a radio transponder with a unique code, which is carefully inserted into a fish. They don’t require a battery and so stay with a fish for its entire life.
So far we’ve tagged, measured and weighed more than 1,400 salmon – which will help to determine whether shape, size, sex or origin of the fish within the catchment has a bearing on their survival. Going forwards we’re aiming to sample and tag up to 2,000 in September and October each year.
We’ve deployed an Adaptive Resolution Imaging Software (ARIS) fish counter, which uses high-definition sonar to record images of passing fish. This sophisticated technology will provide an accurate count of the total number and average sizes of adult salmon and sea trout, or ‘spawners’, returning to the river each year.
Analysis of environmental DNA (eDNA) has become a cost-effective way of identifying species present in a target location or habitat.
By analysing the eDNA present in water samples, we can determine the presence of fish, other vertebrates and invertebrate species at key sampling locations. In addition, a series of 14 automated temperature loggers will record the water temperature every 15 minutes at strategic locations across the catchment to monitor the impact of temperature on fish populations.
In addition, a series of 14 automated temperature loggers will record the water temperature every 15 minutes at strategic locations across the catchment to monitor the impact of temperature on fish populations.
View the film in full below
Project Laxford - full length feature from Grosvenor on Vimeo.