A broad range Organo-Phosphate pesticide, Chlorpyrifof-Ethyl, used to control caterpillars and other insects had been found in samples taken from the river Ouse, Lewes, East Sussex. The amount of chemical released is calculated to be small, only about half a pint. Analysis of river water shows concentration levels to be less than 0.001mg per litre, however this is sufficient to kill river bed invertebrates and cause harm to fish.
It is believed that the pesticide weakened the fish sufficiently that they succumbed to a bacterial infection which attacked their flesh. Fish were found in a very poor condition, some still alive with their spines protruding.
Environment Agency Sussex Area Fisheries Manager, Stuart Taylor said, “The fish were in a shocking state and we have been working hard over the last week to try to get to the bottom of the problem. We believe that the presence of the pesticide in the water was the initial cause of these fish deaths, although we will also be continuing to research the source of the bacterial infection.
“The pesticide will deactivate within between 10 and 20 days and the river will recover, but it will take time. Our investigations have found that all aquatic insects along a 20 kilometre stretch from the Sheffield Bridge area downstream, have been wiped out. This will leave a significant gap in the food chain. Although molluscs have also been hit, we have seen some that have survived and there are also fish that remain healthy in the Ouse.
“Fortunately the other tributaries are fine, which will enable the repopulation of the main river. We will be continuing to monitor the progress of the river very carefully over the next few months.
“We have traced the point at which the pesticide entered one of the feeder streams of the Ouse and legal action is being considered by the Agency’s Legal Team. The amount of pesticide involved in this incident is small but it has caused tremendous environmental damage. Individuals must take all the proper precautions when using any agricultural chemical and make sure that containers are washed out and disposed of properly.
“The low concentration of the pesticide in the water means that it does not pose a serious threat to river users, however we would still urge the Public to exercise caution and recommend that they do not touch the dead fish or eat any which have been affected.
“We have been very grateful for the help from the Public by way of our hotline, once again their vigilance has helped to save the environment from further damage.”
If anyone wishes to report any environmental incident relating to air, land or water they should ring the Environment Agency’s 24 hour Hotline on 0800 80 7060.
