Evidence Based Management

At Fisheries Management Scotland, we champion an evidence-based approach to managing and conserving wild Atlantic salmon populations. This means decisions are informed by the best available science and real-world data — ensuring actions are targeted, effective, and transparent. We apply this approach through a clear, strategic model that operates in three key steps:

1. Identify Pressures

Effective salmon conservation starts with understanding the pressures they face. Working through the Scottish Fisheries Coordination Centre, we developed a national, web-based mapping tool to help fisheries managers identify and communicate the key threats to wild Atlantic salmon in their districts.

This Mapping Pressures on Wild Atlantic Salmon Project represents the first coordinated national assessment of pressures — ranging from habitat degradation and water quality issues to barriers to migration and the effects of climate change.

Explore the Pressures

2. Develop Fisheries Management Plans

Building on the evidence gathered, we supported the creation of 44 Fisheries Management Plans — developed by District Salmon Fishery Boards, the River Tweed Commission, and Rivers and Fisheries Trusts, and coordinated nationally by Fisheries Management Scotland.

Each plan sets out local pressures on wild salmon and sea trout, and the evidence-based actions needed to address them. These range from targeted fisheries management to catchment restoration and climate adaptation. Alongside this, a national dashboard brings together all actions into one place — highlighting shared themes, local and national challenges, and crucially, the costs and funding gaps associated with delivery.

This dashboard also helps identify projects that align with nature finance opportunities — creating a ready-made platform for investment in Scotland’s rivers.

Explore our Fisheries Management Plans

3. Enable Delivery Through Funding Mechanisms

Identifying actions and planning for change are only the beginning. To bridge the gap between planning and implementation, we’ve worked with partners through the FIRNS programme to design and test funding solutions. This includes the development of the Scottish Rivers Fund — a mechanism to unlock investment and support the delivery of on-the-ground conservation projects.

Learn More about Nature Finance

Monitoring

To support this model of evidence-based management, Fisheries Managers use a suite of monitoring techniques to gather the data needed to assess fish populations, track environmental change, and evaluate the effectiveness of interventions.

Electrofishing

Electrofishing is a technique used by scientists to study fish populations in rivers and lakes. It involves using highly specialised equipment to send a small electric current through the water, which temporarily stuns the fish without harming them. This makes it easier for biologists to catch the fish, measure them, and then release them back into the water. The process is safe for both the fish and the people conducting the study, and we provide training on this method of capture through the Scottish Fisheries Coordination Centre. Electrofishing helps scientists gather important data about fish species, their numbers, and their health, which is crucial for managing and conserving aquatic ecosystems. This technique can be dangerous for those without any training, and is an activity undertaken with a license from the Marine Directorate, or a District Salmon Fishery Board where Salmon or sea trout are the only species likely to be caught.

Additionally, electrofishing can be used in circumstances where construction will impact on a small area of water (such as a culvert), and it can be used to “rescue” fish which are in a temporarily impacted area.

Our members undertake monitoring for local priorities, but also feed into national projects such as the National Electrofishing Programme for Scotland (NEPS). This project, run by the Marine Directorate, uses a powerful statistical design to assess the health of juvenile salmon at a site and district scale.

Interested in learning how to carry out this type of monitoring? Visit our Training Page to find out how you can get involved and access professional courses delivered through the Scottish Fisheries Coordination Centre.

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Environmental DNA

Environmental DNA (eDNA) sampling is a modern technique used to monitor fish populations by analysing DNA fragments found in water. Fish release DNA into their environment through skin cells, mucus, scales, and waste. By collecting water samples and testing them for these DNA traces, scientists can identify which fish species are present in a particular area without needing to catch or see the fish directly. This method is non-invasive, cost-effective, and can provide detailed information about fish diversity and distribution. We are currently using this technique with our members and the Pink Salmon Task Group to track the invasion of Pink Salmon in Scottish rivers.

Sea Lice

Sea lice are small parasites found in the marine environment, which attach to the skin of salmon and trout and feed on their mucus, blood, and skin. They occur naturally, although in aquaculture areas they can occur in unnaturally high numbers, due to many farmed fish in a small area providing an abundance of hosts. Sea lice larvae can drift in the ocean, and attach to adult fish as they migrate into rivers, or juvenile fish as they migrate out of rivers. Juvenile fish are at a higher risk of negative impacts from high sea lice densities, as they can not cope with the same numbers that adult fish can.

Fishery Trusts in the aquaculture zone (along the West coast of Scotland, the Western Isles and Northern Isles) undertake an annual programme of monitoring juvenile sea trout in order to assess the infestation pressure of sea lice. Fish are collected for sampling, and the lice present on each fish are counted. The data is then analysed to determine whether sea lice prevalence is at acceptable levels.

A strategic programme of sweep netting has been delivered in Scotland for many years. Sweep netting is a widely used and well practised technique that enables assessment of the condition of fish caught at a defined location. The specific process of sweep netting is dependent on the characteristics of the site being fished, but involves drawing a net out from the shore using a boat or wading out. Once the net is deployed the team returns toward the shore, drawing in both ends so that any fish encircled by the net can be sampled.

Another technique involves Coastal Fyke Nets. These are fixed nets, which have the potential advantage of capturing a more representative sample of the local population of fish, including juvenile salmon. Wild fish swim freely in the net until they are released, following sampling for sea lice by researchers.

Fish Counters

A key component of managing any population is knowing how many individuals there are. This information is often incredibly difficult and effort intensive to obtain in regards to fish. Instead of trying to count all of the fish in a river, fish counters are a useful tool for migratory species as they allow managers to know how many fish are entering a river or section of river.

Historically, many fish counters are installed at fish passes in dams or weirs, and provide evidence of the effectiveness of a fish pass. The technology has evolved over time, from electrical resistivity counters, to counters which use photographs and videos, and now some are using AI to process video footage. The downside of these is that they require a small channel to operate effectively, like a fish pass in a dam.

More recently, sonar technology is being used to count fish entering and leaving rivers. In Scotland, these types of counters are currently in place on the Rver Deveron and the River Laxford. These sonar cameras are capable of covering the whole width of a smaller river, and do not need to be built onto an obstruction to operate effectively. However they still require an operator to review a large amount of footage, so Fisheries Management Scotland has led a project with the Atlantic Salmon Trust and Deveron, Bogie and Isla Rivers Charitable Trust to develop an AI tool to speed up the process of reviewing footage. This work was funded by the Marine Fund Scotland.

Habitat

Assessing fish habitat is a key component of fisheries management. Managers assess characteristics of a stream such as the river bed substrate, depth and velocity of water and other physical features to determine whether that area of river or burn is suitable for certain fish species. Habitat surveys help to assess the quality of existing rivers and inform whether habitat improvements should be undertaken to benefit fish populations.

Invertebrates

Rivers and burns support more life than just fish, invertebrates are a key component of the freshwater food web, and are food for fish. There is a wide range of species in our rivers, and some species are specialised to live in different conditions. By looking at the species present, managers can glean information about the water quality in a certain area. Some species are more resistant to pollution than others, and their presence in a river may indicate a pollution event has occurred. Similarly some species are unable to withstand sediment inputs into rivers, and their absence may hint at a pollution event, or a problem with construction works where material has been washed into the river.

Scale Reading

Scale reading can provide a method for quantifying the age and growth rates of fish. This is a great way to age fish as the sampling process is harmless and quick. As fish grow, their scales get larger and when looked at under a microscope you can see growth rings – not too dissimilar from rings in a tree trunk. However, biologists look at the spacing between the rings (called circuli) to determine periods of fast summer growth (when circuli are far apart) and slow winter growth (when circuli are relatively close together). From this, the age of the fish can be determined. This information is key for assessing the health of stock components, and knowing how many grilse or salmon are returning to our rivers. The National Adult Salmon Sampling Programme (NASSP) has been looking at scales from fish collected from strategic rivers across Scotland over the past few years.