A mapping tool that plots the impact of climate change on Scottish rivers has been developed by Scottish Government scientists and UK academics in an effort to help safeguard wild salmon.
Water temperature is an important factor in the health of fish populations, so global warming could have serious consequences.
Freshwater fisheries bring in more than £79 million a year to the Scottish economy, but fears have been raised that Scottish rivers could become less suitable for the fish in the future.
It is estimated that the number of adult fish returning to the Scottish coast to breed have declined by over 50 per cent, from around 1.25 million in the late 1960s to less than 600,000 by the end of 2016.
A number of factors are thought to be responsible, including climate change and the impacts of fish farming.
Optimum conditions for young fish occur at around 16C. Juveniles cannot survive if temperatures reach 32C.
Now a team from Marine Scotland and Birmingham University have created an interactive online resource that predicts maximum daily river temperatures and sensitivity to climate change of rivers all over the country.
It will allow fisheries and river managers to plan how and where to focus works aimed at counteracting warming, such as planting trees to create shade and controlling water demand.
Alan Wells, chief executive of Fisheries Management Scotland, said: “Increases in freshwater temperature, associated with climate change, will increasingly need to be managed.
“Our member district salmon fishery boards and fisheries trusts are engaged in projects to plant trees near rivers to provide dappled shade and reduce extremes of temperature in our rivers.
“This model will be a valuable tool in targeting these efforts.”
The Scotland River Temperature Monitoring Network was set up in 2013. It is a scientific collaboration between the government’s Marine Scotland Science Freshwater Fisheries Laboratory and the university, with support from fisheries trusts and boards.
Mark Bilsby, of the River Dee Trust, believes the new tool will allow resources to be targeted on the parts of a river in most need of shady trees.
“Planting trees to offset the local impacts of warming temperatures is well proven and this will put them where they’re most needed,” he said.
Cromarty Firth Fishery Board has also been involved in restoring native woodland for a number of years. The board’s Simon McKelvey added: “The ecological benefits of riverside woodland are well recognised in terms of nutrient input, sediment control, cover for wild fish and natural flood management. This work will allow us to plan planting to ensure that the maximum benefits from shading are also achieved.”
The team is predicting that the most climatically sensitive rivers are those without bankside trees in mountainous areas.
Scottish environment secretary Roseanna Cunningham said: “This research identifies areas where our famous salmon rivers are at risk due to climate change and will help fisheries managers to protect stocks and increase the resilience of our fresh waters.”