High river temperatures this baking-hot spring are sparking fears for the future of the UK’s freshwater fish, an environmental charity has warned. West Cumbria Rivers Trust has found a number of waterways’ temperatures at or nearing 18C (64F) – the point where cold-water fish such as trout and salmon begin to experience stress, potentially impacting breeding and feeding habits.
The charity says the “unseasonably warm” weather of recent weeks has added to the long-term effects of climate change. Britain has suffered the driest start to spring for 69 years according to the Environment Agency, leaving some farmers with tinder-dry fields, and wildlife on moors and country parks struggling for water.
Now, West Cumbria Rivers Trust is calling for more tree planting near rivers to help provide shade and keep temperatures lower.
The trust found St John’s Beck, a tributary of the River Derwent flowing from Thirlmere Reservoir, to have a temperature of 18C, while the River Greta at Keswick was 17C (62F).
The Upper Derwent, at Seathwaite, meanwhile, was 16.1C (61F) with water levels very low – new images this week show some river beds almost bone dry.
The organisation’s assistant director, Luke Bryant, said data showed the rivers were reaching a “critical point” ahead of the summer.
He said: “Key species would be salmon and trout, but there are also eels and lots of other types of fish.
“We’re also seeing some rivers drying out, for example, the upper reaches of the Derwent that feed into Keswick, and that can affect food sources with wetland plants and insects potentially dying or their eggs being wasted.
“We are very anxious about it. It’s been quite an unusual April and May that we’ve had – unseasonably warm.”
He said while rain forecast for next week “would help”, if there were a dry June or July then that could potentially lead to “even higher temperatures”.
“Sometimes you might have to do drastic things like perform fish rescues. We go in and try and move the fish out of a section if we think the river is going to dry up, but that’s quite an undertaking and it’s not something we can do every day,” he said.
Mr Bryant said the local picture was also being seen nationally following decades of trees being cut down to straighten rivers and maximise space for sheep and cattle.
Now he stressed re-planting of trees by rivers is desperately needed to protect wildlife.
He added: “There are great tree-planting projects all over Cumbria and indeed the UK, but there’s more to do, and obviously, it takes years for trees to mature.
“All river systems need a variety of habitats. It’s about having a sort of dappled effect, with a bit of sunlight in places and shade in others, because different species like different conditions.”
