News & Events
Feral Fish Removed from Emu Lake
WRM field scientists have just completed a very successful round of exotic pest fish species removal from Emu Lake, located in the suburb of Ballajura in Perth’s northern suburbs. Using their brand new electrofisher boat, as well as tried-and-tested methods such as fyke and gill netting, the team was able to capture and remove a large number of invasive koi-carp (Cyprinus carpio), goldfish (Carassius auratus) and yabbies (Cherax destructor), as well as jewel cichlids (Hemichromis bimaculatus), a highly aggressive ornamental aquarium species originally from West Africa.
The survey was conducted as part of the City of Swan’s local area plan for Ballajura, which outlines several restoration measures for the iconic Emu Lake over the next five years. These include the removal of koi-carp and goldfish from the lake, followed by ongoing re-stocking with native freshwater fish, such as western pygmy perch (Nannoperca vittata). As well as removing exotics, WRM are assessing the overall ecological health of Emu Lake, and advising City of Swan on suitability of available habitat for native fish introductions.
Feral species such as koi-carp, goldfish, yabbies and ornamental cichlids, often released into the environment by ill-informed pet owners, can have a devastating impact on wetland habitats, by stirring up lake sediments and uprooting aquatic vegetation, leading to increased nutrient concentrations and potentially toxic algal blooms. These introduced species are usually more aggressive and breed more frequently than our native fish species, easily out-competing them for food and habitat. They also have the potential to bring exotic diseases to our native fish populations.
We hope that our studies will one day contribute to the re-introduction of native fish species to beautiful wetlands such as Emu Lake, but we face an uphill battle if populations of invasive species in urban environments are to ever be controlled. Prevention of new pest fish introductions is just as important as eradication, and requires effective public relations and education, such as the Western Australian Department of Fisheries’ “Don’t dump that fish” campaign.
If you spot a suspected feral fish species anywhere across WA, you can report it to the Department of Fisheries biosecurity team via the WA PestWatch portal
WRM’s electrofisher boat in action.
Large numbers of koi-carp (Cyprinus carpio) and goldfish (Carassius auratus) were captured and humanely euthanised.
Environmental Consultant Simon Ward holding a large koi-carp (Cyprinus carpio). Note the “whiskers” and extremely large mouth and lips, used by koi-carp to stir up sediments and uproot aquatic vegetation in search of food. It’s easy to see why these fish can have such a devastating impact on our beautiful aquatic environments.