More than 300 carp had to be temporarily re-homed in a local leisure park swimming pool following an incident at a lake at Little Ranch Leisure Caravan Park at Begdale, near Wisbech.
Environment Agency fisheries officers were called out following a report of about 200 dead fish on Friday evening. They took a water sample for chemical analysis to try to find out the cause.
Tests revealed the water had high salinity levels which has been known to lead to the presence of the alga, Prymnesium, which can produce a toxin lethal to fish.
Paul Wilkanowski, ecological appraisal officer, said: ‘Acting quickly was key to preventing the death of more fish in Begdale and we were able to identify the cause of this incident very quickly.’
The lake was dosed with hydrogen peroxide to kill the alga and prevent any further release of toxins. Further tests a few days later showed that the Prymnesium had in fact been killed by the chemical.
The carp have now been returned to the lake and discussions are taking place regarding the re-opening of the lake for fishing.
Paul added: ‘Anyone who sees dead fish, fish in distress, or pollution in our rivers and streams should call our emergency hotline number as soon as you can.
‘In this case, it was the swift action of our officers that saved the carp, but the story could very easily have been different.’
Environment Agency emergency hotline number 0800 80 70 60.
Some of the fish could not be saved