AN investigation is under way after dozens of fish were found dead in the River Foss in York.

The Environment Agency is investigating after large pike, weighing up to 7lbs, roach and perch were found floating on the top of the water by anglers in the Foss at Haxby and Huntington following heavy rainfall last weekend.

Angler Paul Sorbie, 43, of Buttermere Drive, Rawcliffe, said he was walking along the riverbank with his dog when he spotted the dead fish in Haxby, Huntington and New Earswick.

He said: “It was all mature fish that seem to have died and all that’s left were the tiddlers.

“It’s heart-breaking to see this because it takes so long for the river to recover and the fish that are there take so long to get to that size.”

An Environment Agency spokeswoman said the most likely cause was a drop in the overnight oxygen levels in the water after heavy rain.

She said: “We are investigating whether the storm drains were operating at the time.

“In times of very heavy rainfall, the water company is allowed to put storm water into the river under certain circumstances.

“The Foss is a slow running river with very good fish stocks and a lot of plant life. This means that the plants produce a lot of oxygen during the day, but take this out at night when they are not photosynthesising and the oxygen levels may have dropped below normal if there was a lot of organic matter washed into the river using up oxygen also.

“The Foss remains a very well-stocked river, even with the loss of 50 fish.

“And the fish that have died will be the ones that are old or diseased.”