The Environment Agency was able to quickly respond after reports of distressed fish in the Rags Brook, Cheshunt, were phoned in last week. When officers arrived at Rags Brook they found five roach and several crayfish already dead and saw other fish such as chub, roach, perch, eel, pike and minnow in distress.
The incident appeared to have been caused by a combination of low flow, high temperatures and the large amount of fish being trapped in a very small area of approximately four metres of the stream. This led to a critical drop in dissolved oxygen levels, leading to some of the fish struggling to breathe. Meter readings taken at the time showed the dissolved oxygen levels being as low as five per cent. Ideal levels of dissolved oxygen would be 50 per cent or greater for that type of watercourse.
The attending officers worked rigorously to clear debris allowing fish to move further downstream. After 40 minutes of clearing debris and flushing extra water over the weir to improve the dissolved oxygen levels, the fish and the water conditions returned to a normal state.
Environment Agency officer James Burton who helped attend the site said:
“We want to thank the local residents, staffmbers from Hertfordshire County Council Highways department and other business owners who saw the fish in distress and reported the incident to us. With their quick reporting, we were able to attend the site before the situation became worse, significantly reducing the number of fish affected.
The Environment Agency has a free 24 hour Incident Hotline on 0800 80 70 60 and we encourage people to call if they see anything to report. With the help of the public, who are so often our eyes and ears on the ground, we can continue to react and help protect local wildlife and their environments.”
The Environment Agency revisited the site the following day and found the water course was flowing and remained in a stable condition. The dissolved oxygen was high at 95 per cent and there were no visible signs of any further fish in distress. The officers cleared further debris to maintain improvements and reduce risks in the future.
