The Environment Agency is going to poison the fish in a Cumbrian lake in an effort to wipe out an introduced species.
Ratherheath Tarn, near Kendal in Cumbria in the north of England, contains thousands of Clicker barbs, Pseudorasbora parva, which were illegally introduced some years ago.
The Environment Agency is planning to wipe out the non-native fish by removing the majority of the naturally-occurring British species and then applying a poison called rotenone to the lake to kill the remainder.
The barbs, which are also called Topmouth gudgeon, were introduced in the 1960s, and have bred so fast that their numbers have been difficult to control.
According to a report from the BBC, Environment Agency officials began netting some weeks ago and it is expected to take weeks for the piscicide (fish poison) to take effect through the whole lake.
The barbs were once an alternative coldwater fish, but are now illegal in the UK and have been on the controlled list for several years.