We already know that climate change is affecting most species and environments throughout the world. In Scotland, fisheries scientists have recently found that rivers in the Highlands and Uplands are already too warm in summer for wild Atlantic salmon populations. The fish use these rivers to spawn, rendering them important grounds for the survival of the species.
On the River Dee, for example, salmon catches have fallen by 80% since 1957. And the scientists blame climate change as one of the main reasons behind it. They measured that the water temperatures in 70% of rivers that usually see salmon were too warm for at least one day in the summer of 2018. Temperatures measured were above 23C. As the Atlantic salmon is a coldwater species, it prefers temperatures above 10C but below 33C. As scientists found out, 23C already tends to induce stress and changes in behaviour in salmon populations.
Lorraine Hawkins, the river director for the Dee District Salmon Fishery Board, said: “These rivers and burns are the nursery grounds for young fish and it’s the young fish which will be affected by summer temperatures – their feeding and growth rates are affected. If it gets hotter, we will see fish dying.”
As only 35% of Scottish rivers have adequate tree cover, the plan is now to plant millions of trees to protect wild salmon from the worst effects of climate change through providing shade to lower water temperatures. On the River Dee in Aberdeenshire, 250,000 saplings have already been planted by fisheries, with one million trees around the Dee planned by 2035.
Fishery boards across Scotland will follow suit with similar programmes. “We’ve seen situations where the temperatures in our rivers are approaching critical levels for our salmon, temperatures that they can’t tolerate. This will get worse. We need to grow trees now to create that cooling shade,” said Alan Wells, the director of Fisheries Management Scotland.
If you want to find out more about Atlantic salmon populations and how organisations are trying to protect the species, read this feature about the Missing Salmon Alliance.
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Photography courtesy of Unsplash.