Hundreds of fish have been killed in the River Blackwater due to the recent heatwave.

The Environment Agency has confirmed it has been investigating a stretch of the river, near Straits Mill, Bocking, where residents found dead fish floating on the surface of the water.

Low oxygen levels have been blamed for the deaths of the wildlife, with thunderstorms followed by a prolonged period of high temperatures thought to be the cause.

A spokesman for the Environment Agency said: “Following reports of dead fish at Straits Mill on the River Blackwater at Bocking we found 250 which had died.

“We removed them from the river.

“Dissolved Oxygen concentrations were found to be lower than normal for this time of year but since then have recovered naturally and remain stable.

“No fish are in distress and no new fish deaths have been observed.”

According to the agency, the animals’ struggles are not uncommon, however with 30 degree temperatures having been the norm for more than two weeks, more are dying this year than before.

The spokesman continued: “At this time of year we regularly respond to reports of fish in distress due to natural processes reducing oxygen levels in the water.

“Hot, sunny weather can lead to low flows in rivers.

“In addition, when we experience a heavy storm after a long dry period, debris that has accumulated in the drainage systems is flushed into the rivers.

“As a result, the algae and micro-organisms in the rivers rapidly multiply which causes a significant drop in oxygen levels.

“This results in the fish being starved of oxygen.

“We have teams on standby and responding to such incidents across the region.

“If people see dead fish or fish gasping for breath, they should contact our incident hotline on 0800 80 70 60.”

Thousands of fish have also been discovered dead in the River Colne, in Colchester, Holland Brook, in Clacton and at Canvey Lake, in Canvey Island.