‘The sores on the fish are nasty’: what’s behind the changes in the River Severn?

The River Severn and the Malvern Hills, near Kempsey, Worcestershire, England. Photograph: robertharding/Alamy

The sores were unlike anything veteran anglers had seen before. Black, swollen and blister-like, they started appearing on fish being caught in the River Severn in early summer.

For anglers who spend many hours on the banks of the Severn around Shrewsbury, the blistering skin was yet another warning that the river, and its wildlife and habitats, are suffering.