Feral Koi Carp - scourge of the wetlands. A cautionary environmental tale from Perth.

Koi (or Amur) Carp (Cyprinus rubrofuscus) are native to Asia but are unfortunately widespread in lakes on the Swan Coastal Plain, including in Herdsman Lake. They have been released into our lakes by irresponsible people who no longer want them as pets. Koi Carp disrupt the ecology of our lakes by stirring up sediments as they feed, making the water turbid, releasing methane (a potent greenhouse gas) and releasing nutrients that may drive blooms of algae and cyanobacteria (or blue-green algae). One way of reducing Koi numbers is by electrofishing, where a current is passed through the water between two electrodes (a cathode and an anode), stunning the fish and making them easy to catch. Electrofishing for Koi was done by the Harry Butler Institute of Murdoch University in May 2023, and funded by the Western Australian Department of Biodiversity, Conservation and Attractions (DBCA). Over 300 kilograms of Koi were removed from the lake in two days of electrofishing.