UPDATE: Environment Agency officials have taken action after around 1,500 fish in the River Lark in the Abbey Gardens died following the recent soaring temperatures.
An area of river which runs through the gardens near the Abbots Bridge in Bury St Edmunds has a number of dead fish on the surface today.
Elsewhere in Suffolk the agency has been aerating the River Gipping at Needham Market because of a similar problem.
Agency staff yesterday pumped hydrogen peroxide into the water in the Lark to increase oxygen levels and today, having monitored the situation, say levels have increased. The number of fish affected includes small fry as well as larger fish.
Hot weather causes oxygen levels in the water to drop and this can be fatal to fish.
An Environment Agency spokeswoman said: “We went back out today and oxygen levels have gone up so we are not planning to redose the water with hydrogen peroxide at present.”
Aeration is another method of increasing oxygen in the water. Hot weather can also cause a lack of movement in the water which adds to the problem.