Hundreds of fish found in a waterway on the edge of Spalding died because of “low oxygen levels in the water”, according to environmental officers.
Dog walkers and passers-by discovered the fish lying dead in Vernatts Drain, near Johnson Community Hospital, on Friday and Monday.
Specialists from the Environment Agency used air pumps to raise oxygen levels in the water, repeating a similar exercise carried out nearly four years ago when hundreds more fish died in similar circumstances.
George Scott, chairman of Spalding and Peterborough Transport Forum, said: “I was walking my dog along Blue Gowt Drove and turned left towards the hospital when I saw what I thought were a lot of lilies out on Vernatts Drain.
“Then I looked again and saw hundreds of fish, including some big ones, dead in the water.
“I’d never seen anything like it before and someone told me that they may have been there since Friday.
“I remember when the fire service came out a couple of years ago to pump oxygen into the water, but I wasn’t sure whether it was a case of lack of oxygen this time.
“It’s good to report things like this rather than just walk past and ignore it because if it’s worth noticing then it’s worth reporting to somebody.”
During the summer, fish are in danger because of low rainfall and high temperatures which can lead to lower oxygen levels in the water.
Keith Morgan, team leader at the Environment Agency, said: “We have responded to a report of dead fish in Vernatts Drain, near Spalding, where our officers attended immediately and identified that this was due to low oxygen levels in the water.
“This is a fairly common occurrence at this time of year which can be caused by low water flows, water temperature or the weather.
“We have used aeration pumps to help increase the amount of oxygen in the water back to where it should be.”