Removing barriers to fish migration: Why it matters for Scotland’s rivers
Across Scotland, more than 300 man made barriers, such as weirs, dams and culverts, are currently preventing fish from reaching vital breeding, feeding and juvenile rearing habitats. These barriers fragment our rivers and prevent fish from completing their natural life cycle.
To address this, a major programme of work is taking place in rivers across Scotland to remove or modify existing man-made barriers to restore fish passage. Barrier owners have a key role to play in this programme of works, and SEPA is engaging directly with them to explain the objectives and their legislative responsibilities under the River Basin Management Plan to ensure obstacles to fish migration are being removed or passage over them, eased.
This work also supports the objectives of the Scottish Wild Salmon Strategy and helps critically endangered species regain access to free flowing rivers.
But improving fish migration isn’t just about fish. Removing obstacles brings wide-ranging environmental, social and economic benefits, from healthier rivers and stronger wildlife populations to reduced flood risk and improved recreational opportunities.
Why should we remove or modify fish barriers?
- A cost effective, reliable and quick way to improve access to habitat
Removing or modifying a barrier is often one of the most efficient ways to improve access to river habitat. Changes to barriers can open stretches of river, giving fish access to high quality habitat and may prevent the need for ongoing maintenance or repeated investment.
Once a barrier is removed or re-designed to incorporate fish passage, fish can move through the river. The benefits are often seen almost immediately, with migratory fish returning to newly accessible areas within weeks or months. Importantly, this approach makes use of existing riverine habitat, rather than trying to create new habitat elsewhere, and benefits multiple fish species at the same time. - Improves biodiversity and water quality
Healthy rivers depend on movement. Free flowing rivers allow natural processes to occur, including sediment continuity and species movement. This leads to:
• better water quality,
• healthier ecosystems, and
• rivers that are more resilient to pollution and climate change pressures. - Increases fish and invertebrate populations
Fish need access to different parts of the river at different stages of their lives. Removing or modifying man-made barriers allows them to reach spawning, feeding and shelter areas, helping populations recover and grow.
Invertebrates, such as aquatic insects and crustaceans also benefit from connected rivers. As their populations increase, they provide more food for fish, birds and other wildlife, strengthening the entire food web and supporting stable, self-sustaining river ecosystems. - Naturalises river channels and helps mitigate impacts of climate change and flooding
Obstacles often force rivers into unnatural shapes and flows. If full removal of a barrier is an option, this can allow rivers to return to a more natural form, slowing water down and reducing the risk of local flooding downstream.
Reconnected rivers overspill onto floodplains during heavy rainfall, storing water where it causes less harm. Natural river corridors also support vegetation that captures carbon, helping rivers play their part in climate change mitigation. Overall, natural river systems are better equipped to cope with extreme weather events. - Boosts tourism and amenity value
Healthy rivers aren’t just good for wildlife, they’re good for people. Free flowing rivers with strong fish populations attract anglers, kayakers, and create safer, more enjoyable places to spend time.
Restored rivers encourage visitors, support local businesses, and enhance the quality of life for local communities by making rivers more attractive and accessible. - Restores river continuity
River continuity means a river is connected from its source all the way to the sea. Barriers break this connection, disrupting the natural movement of fish, sediment and nutrients.
By restoring continuity, rivers can function as complete systems again. Fish and wildlife can move freely to feed, breed and shelter, while natural processes that maintain river health are re-established. - Reduces the risk of local flooding
Obstacles within river systems can cause water to back up during periods of high flow, increasing the risk of flooding upstream. Removal or modification of obstacles allows water to move through the river more naturally.
Natural channels slow and spread flood water, reducing pressure on vulnerable areas and helping protect nearby homes, roads and farmland from damage. - Keeps rivers cooler in a changing climate
Flowing water stays cooler, holds more oxygen and provides better conditions for fish and other aquatic life, especially during warm dry weather.
By removing or modifying barriers, rivers are able to cope with rising temperatures linked to climate change, helping protect wildlife now and in the future.
Download our infographic on improving fish migration to see all eight benefits in one clear, visual summary.
A Shared Opportunity
Removing or modifying barriers to fish migration is one of the most effective ways to restore the health of Scotland’s rivers. It supports endangered species, strengthens ecosystems, reduces flood risk, and delivers real benefits for communities and the wider economy.
Now is the time to work together to reconnect our rivers for fish, for people, and for a resilient future.
Further information