Fish are dying in "unprecedented" numbers after oxygen levels plummeted in rivers and canals, a charity has said.
The Canal and River Trust says it is carrying out emergency action across the country to address the situation.
Water oxygen levels naturally reduce during warmer weather without threatening fish stocks.
But the Canal and River Trust said recent heavy storms and large amounts of silt running into the water had exacerbated the issue.
The charity's angling manager John Ellis said canals were a "vital" habitat for wildlife.
"Whilst any instances of fish in distress is upsetting, seeing so many separate cases at the same time is unprecedented," he said. "We are doing all we can to support the regulators in England and Wales."
The trust said people should contact the Environment Agency if they see fish in distress.
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