One barrier at a time for our Atlantic Salmon

Atlantic Salmon are under threat in Wales with numbers declining at unprecedented rates. There are risks that they may even disappear completely from some Welsh rivers within the next few decades.

In this blog on behalf of the Natural Resources Wales (NRW) Four Rivers for LIFE Project, Stuart Rees from the South West Environment Team talks about the importance of Atlantic Salmon and how working in collaboration can help support the species.

Worryingly over the last 10 years the rod catch of wild Atlantic Salmon returning from the sea has fallen by as much as 70% in Wales. Today all 23 of our Principal salmon rivers in Wales are now categorised as being “At Risk”.  

This trend is not unique to Wales. Last year, Atlantic Salmon were reclassified by the International Union for Conservation of Nature (IUCN) from ‘Least Concern’ to ‘Endangered’ in Great Britain, as a result of a 30-50% decline in British populations since 2006. 

The importance of Atlantic Salmon to the natural environment

Atlantic Salmon play a crucial role in our freshwater ecosystems. As a ‘keystone’ species, they contribute to the overall structure and functioning of our river systems.

They are also an invaluable ‘indicator’ of the health of our rivers. Their need for healthy habitats and cold, clean water both in freshwater and at sea mean they are a very real barometer of the health and condition of the environment that they live in.

The dramatic decline in their numbers is signalling that there are significant problems in these habitats and ecosystems.

Protection of the species

Atlantic Salmon (Salmo salar L.) are afforded the highest protection both in the UK and on an international level by numerous pieces of legislation.

In Wales the status of the salmon population is monitored annually by Natural Resources Wales (NRW).

In 2024 monitoring data showed almost all river populations were performing poorly. More information about this can be found here.

Their decline is due to several factors linked to climate change; changing ocean conditions and poor marine survival affects all populations.

In addition higher river temperatures in winter and summer affects spawning, and more frequent and more extreme flooding events are washing out eggs and newly hatched salmon, triggering a  knock-on effect on juvenile survival in many Welsh rivers.

Local impacts such as water and habitat quality also have an adverse effect on fish numbers. Access to migration routes can also create challenges, with weirs and man-made barriers blocking access to spawning grounds further upstream.

To understand their complex needs and how we can help them we must first understand their migration journey.

Epic migration journey

Salmon spend the first and second years of their lives in rivers before migrating to sea as smolts (young salmon). They spend around four years in the sea, feeding and growing stronger in readiness for the difficult journey to come.

See salmon life-cycle image below

After four years at sea and as autumn approaches they instinctively wait at the river mouths for the first autumn rains. These rains raise river levels, and prompt the salmon to swim upstream in their river of origin to spawn as adults.

Some salmon can travel thousands of miles, swimming tirelessly against the current. Their main aim is to return to the very spot where they were born to spawn by using their sense of smell (olfaction), a process known as ‘homing.’

Smell plays an important role throughout the life of salmon, with adults identifying their home river through imprinting to the smell of the river during their migration to sea at the smolt stage.

When the adult salmon reach their spawning ground, the females dig shallow nests, called ‘redds’, in the gravel beds of the river by using their tails. They then lay thousands of eggs, which the males fertilize.

Images below: Salmon redds (nests) shown by lighter gravel against the surrounding darker gravel – credit Mark Thomas NRW.

 

The female then carefully covers the eggs, and the adult salmon leave, some die after spawning.

Spawning usually takes place from November to December although may occur earlier or later depending on varying factors. Watch the LIFE Dee River video of spawning behaviour.

Along their migration journeys they can face many natural and man-made challenges.

Natural predators take the form of otters, herons, and larger fish but man-made barriers present some of the greatest challenges.

Weirs, for example, can block salmon from reaching their spawning grounds. These structures force salmon to use up valuable energy attempting to leap over them.

Free and unimpeded access is therefore vital for them to successfully complete their journey.

How are we helping them?

A number of fish easements and passes have been delivered this year by NRW as part of various programmes.

Since 2022 the Welsh Government Water Capital funded ‘Salmon for Tomorrow’ programme has delivered 10 projects and opened up 159 kms (99 miles) of good quality river habitat.

This summer the Four Rivers for LIFE Project has also delivered several schemes to improve access for fish migration.

One such project was to install a Larinier fish pass at Jerusalem Weir on the Afon Clydach, a tributary of the River Tywi SAC. This will improve access for important and protected fish such as salmon and lamprey.

Initially Jerusalem Weir was highlighted as a barrier to fish migration by NRW Fisheries Specialists due to its deteriorated state and disrepair.

As the River Tywi SAC was within the catchment of the Four Rivers for LIFE Project it made sense to work together to use the knowledge and expertise of both teams.

The Larinier fish pass reduces flow velocities and, as a result, improves passage for salmon and trout, as well as a range of weaker swimming species like lamprey and eel.

Although it was delivered and funded by the LIFE project the fish pass will be maintained and monitored by NRW Fisheries in the future.

An important part of the maintenance work is to keep fish passes free of leaf build up and obstructions at this time of year, to ensure open and unimpeded access for important fish like salmon.

If you are concerned about any obstruction on a fish pass please report it to NRW by calling 0300 065 3000.

The salmon in the below image was seen on the Afon Sawdde mid-October and will now hopefully utilize the new fish pass at Jerusalem Weir on its migration journey.

Image below: Salmon on the Afon Sawdde, credit Stuart Rees, NRW

Hope for salmon in the future

The NRW ‘Salmon for Tomorrow’ programme has a pipeline of projects across all of Wales, some of which are extremely challenging and will take several years to deliver but will bring great benefits.

Next year more work is being done to improve fish migration on the River Usk SAC in Brecon as part of the Four Rivers for LIFE project.

Working together the NRW Fisheries Team, Four Rivers for LIFE, Bannau Brycheiniog, Canal and River Trust and Powys County Council will install a new smolt pass on Brecon Weir.

This work will help with downstream smolt (young salmon) migration on this important river.

Projects like this show how important it is to work in collaboration, we all want to see healthier rivers and improved water and habitat quality.

We cannot protect our rivers and wildlife alone, we must come together to share ideas and responsibilities to deliver long term solutions for our natural environment.

To read more about NRW’s river restoration work please go to the News Pages here.