A RESEARCH project aimed at identifying and eradicating feral fish incursions in WA’s waterways is struggling to gain financial backing despite growing evidence of the harmful and long-term impacts the fish are having on the State’s aquatic environments.

Murdoch University research fellows Dr David Morgan and Dr Stephen Beatty, from the Centre for Fish and Fisheries, have joined forces to investigate the impact of ecological imbalances brought about by aquarium fish illegally dumped into at least 12 of the State’s river and wetland systems.

Some of the feral fish infesting WA waterways are over 2kg in weight / Image: Courtesy Murdoch University

Their research shows a sharp reduction in native fish numbers and an associated increase in aquatic system diseases and imbalances when foreign species such as goldfish, guppies and swordtails are introduced.

Adding weight to their findings was the discovery earlier this year of more than 500 giant goldfish, in the Warren River, near Pemberton. The fish weighed an average of 2kg each and they are believed to have been in the waters for up to three years.

Similar infestations have occurred in the Serpentine, Canning, Swan, Murray, Harvey, Margaret and Blackwood Rivers.

Despite attracting significant government and industry attention for their research findings, Dr Morgan says the project had so far failed to secure the all-important dollars to move forward.

“Many people have shown an interest in what we are doing and there is no doubt in our minds as to the importance of what we are trying to achieve, but unfortunately we have not been able to get the backing we need.

“This is not a new phenomenon – people have been taking part in illegal fish dumping for many years but there has not been much research into the impacts of those actions.

“Stephen and I have done a lot of ecological research in the course of our work – we have targeted studies such as feral fish growth rates, size at maturity, dietary changes with growth, reproduction patterns, competition with native fish and their longevity in the wild.

“It is not a rosy situation, and we believe a co-ordinated approach is necessary firstly to prioritise the feral species in our waterways and then to effectively capture and eradicate them.”

Dr Morgan says the innate qualities of aquarium fish, such as their omnivorous appetite and their tendency to be tolerant of most environments, have enabled them to easily adapt to river ecologies.

“Most aquarium fish are good survivors and they will eat almost anything from vegetation and other fish to detritus.

“Much of what we find in their gut is mud-based so we know they are basically just bottom-feeders or scavengers.

“WA has the fastest-growing goldfish in the world and they thrive in our nutrient-rich waterways.

“The numbers are increasing despite our eradication efforts but without some level of funding, we cannot hope to get on top of the problem.”

Dr Morgan says aquarium owners can do their bit to help reduce the feral fish problem by returning unwanted fish to a pet shop rather than releasing them into the wild.

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