FISH choking for air were found “dead and distressed” in the River Delph after low dissolved oxygen levels were discovered in the water between Sutton Gault and Welches Dam.

Environment Agency staff are now aerating the water on the Ouse Washes and dosing it with hydrogen peroxide after making the find during routine monitoring of the area on Wednesday (August 15).

Tests revealed how flood water draining off the Ouse Washes into the Delph had caused the problem due to the fact July’s exceptionally high rainfall meant flood water was being held later in the year than usual.

Warm weather had also encouraged algal growth and sped up the deterioration of rotting vegetation in the standing water, affecting the levels of oxygen.

“It could take up to three weeks to finish pumping July’s rainfall off the Ouse Washes and out of the watercourse,” a spokesman for the Environment Agency says.

It now “expects water quality to continue to be affected” but says it “will monitor and treat the water until the oxygen levels are restored to acceptable levels”.

The Agency has now urged members of the public to be vigilant and call its hotline number, 0800 80 70 60, if they spot fish in distress.

Tell-tale signs include gasping at the surface of the water, swimming on their sides or swimming upside down.

“Different species of fish can tolerate different levels of dissolved oxygen,” the spokesman added.

“For example trout need a much higher water quality than pike but they all have limits and are harmed by rapid changes in the quality of the water.”

However he said: “Fish can often be saved if they are helped quickly.”