Dozens of 'stressed' fish found dead in Sheffield park lake
A spokesman said: "This is not unusual for the time of year as it is spawning season and often low oxygen due to low water levels can cause fish to become stressed.
"We are monitoring the situation across the country and would urge members of the public to report these kind of incidents which show that fish are struggling to us."
Angler Gary Hinde said: "I find it very disgusting.
"A place I used to fish as a child has been so neglected. There are dead fish all over the pond.
"This is a family park with children walking about but there are swarms of flies everywhere due to the dead fish."
Another park visitor, Gary Dorchester said: "All the fish are dead because they have never maintained the water.
"There's a pond at Crookes Valley which is fine but the Graves one has dead fish floating on the surface. If it had been dead cows or sheep there would be uproar."
Anyone wanting to report concerns over dead fish in local parks, ponds, lakes, rivers and streams can contact the Environment Agency on 0800 80 70 60.