'I looked into the river and saw all these dead fish'

When Helen Masters walked her usual route along the River Wye one morning in late June, she knew something was wrong before she reached the bank. The smell reached her first. Then she saw the fish — thousands of them, floating belly-up in the shallows, their silver bodies stretching as far as she could see.

"It was like a cemetery," she said. "I've walked this river for thirty years. I've never seen anything like it."

The Wye, one of Britain's most celebrated salmon rivers, has been in decline for years. Agricultural runoff, sewage discharges and the warming climate have combined to degrade water quality to the point where the river's ecosystem is under sustained pressure. But the fish kill that Masters witnessed was different in scale and suddenness, suggesting an acute pollution event rather than the slow decline that has characterised the river's recent history.

Environment Agency investigators are examining whether a combination of low water levels, high temperatures and a pulse of pollution — possibly from a combined sewer overflow or agricultural source — created a dissolved oxygen crash that suffocated the fish. The agency has taken water samples and is conducting an investigation, but has not yet identified a definitive cause.

The incident has galvanised local campaign groups who have been warning for years that the Wye was approaching a tipping point. The river, which forms part of the border between England and Wales, has become a symbol of the wider crisis in Britain's waterways. Campaigners argue that voluntary measures have failed and that only legally binding targets and meaningful enforcement will restore rivers like the Wye to health.

Masters has joined the campaign. "I don't want my grandchildren to ask me what a salmon looked like," she said. "I want them to see one."