A DESTRUCTIVE feral fish has been discovered in the Swan River, sparking a Department of Fisheries survey.

The Department of Fisheries has initiated surveys of the Swan River, near Eden Hill and Caversham, for feral pearl cichlids, after a member of the public found several of the unwanted species in the river last week.

Subsequent surveys by researchers have not yet located any further samples, but the find has raised concerns that pearl cichlids may have already established in the Swan River.

Director of Aquatic Management Greg Paust said the species was first located in Bennett Brook in 2006 and action was taken in a bid to control their spread.

“We fear that the freshwater aquarium species, which was probably dumped in a local waterway that  feeds into Bennett Brook, could end up impacting on the native fish species that currently inhabit the  upper reaches of the Swan River,” Mr Paust said.

“This common aquarium fish, which is a prolific breeder and can survive in saline waters, could impact on the local ecosystem, but the extent of its impact is unknown at this stage.”

Mr Paust said, when the cichlids were first discovered in March of 2006, steps were taken to limit their  spread through various control techniques in a range of water bodies – at Altone Park, the Altone Park Golf Course irrigation ponds, drainage systems and natural streams like Bennett Brook.

“The Department of Fisheries has spent approximately $300,000 over the last three years on the difficult  and challenging control program,” he said. “As recently as last year the fish poison rotenone was applied in Bennett Brook, to try and limit downstream movement of cichlids, but unfortunately, it appears that this may not have successfully contained the feral population.”

Mr Paust said the Department of Fisheries would continue to monitor the Swan River in the area where the cichlids were found to confirm whether the species has become established, but action to eradicate them was not considered a viable option.

“Likely impacts on the Swan River ecosystem are unknown because, while the cichlids could dominate native species in freshwater environments, their ability to reproduce, spread and compete in the more saline sections of the river is unknown,” he said.

“The Department of Fisheries is working closely with the Swan River Trust in respect to this recent
development and meeting key stakeholders again this week to discuss the issue. The Swan River Trust has also provided $12,500 funding for research on cichlids, since they were found in Bennett Brook.

“This incident highlights the major problems, costs and environmental impacts that can occur when people dispose of exotic species into our aquatic ecosystems.”

Mr Paust urged aquarium owners to never release exotic fish, algae or other aquatic life in our waterways as, in most cases, it was impossible to eradicate these unwanted species once they had been established.