Advertisement

Mutant goldfish sparks warnings for Aussies

Australian scientists are pleading again for unwanted pet goldfish not to be flushed down toilets after discovering mutant monsters as big as footballs in the country’s waterways.

Giant goldfish up to 40cm long and weighing more than 2kg have been discovered by boffins in rivers across Western Australia (WA).

Dr Stephen Beatty has been finding goldfish weighing more than 2kg in WA's rivers. Source: Caters/Dr Stephen Beatty/Murdoch University
Dr Stephen Beatty has been finding goldfish weighing more than 2kg in WA's rivers. Source: Caters/Dr Stephen Beatty/Murdoch University

The creatures – considered an "alien" species here in Oz – are believed to be getting into the water by being flushed down the toilet by owners who no longer want them as pets.

And experts have issued a renewed plea not to give goldfish the flush after revealing the invaders have now been found in estuaries, sparking fears they have adapted to tolerate saltwater and could use it to move between rivers.

"This research indicates goldfish could start using estuaries as a 'salt bridge' to invade and colonise new rivers. Clearly the fish are capable of tolerating saline conditions for several months," Dr James Tweedley, from the Centre for Fish and Fisheries Research at Murdoch University in Perth, said.

"This raises the concerning possibility goldfish might use estuaries to access and expand distribution into new waterways."

Enormous goldfish have started showing up in Australia's waterways. Source: Caters/Dr Stephen Beatty/Murdoch University
Enormous goldfish have started showing up in Australia's waterways. Source: Caters/Dr Stephen Beatty/Murdoch University

"They are a known vector for the introduction of parasites and diseases so this is bad news for native fish species and the overall health of our precious water systems.

"It is important unwanted goldfish are returned to reputable aquariums rather than released into rivers."

RELATED: Twitter reacts to sea lice eating teen's legs

Goldfish are native to eastern Asia but are now considered one of the world's worst invasive aquatic species because they eat vegetation, silt up waterways and release harmful nutrients.

They are defined as an alien species in Australia and once they become established in water bodies their eradication is extremely difficult.

Dr Tweedley's new findings – which he said had major implications for the management and control of goldfish in Australia – were made while conducting surveys of 526 of the creatures in the Vasse and Wonnerup estuaries near Busselton in WA.

Scientists first discovered huge football-sized goldfish were stalking the waterways last August – and have been catching smaller specimens in the Lower Vasse River since 2003.

The outsized fish look just like ordinary pet goldies, but many times bigger. Source: Caters/Dr Stephen Beatty/Murdoch University
The outsized fish look just like ordinary pet goldies, but many times bigger. Source: Caters/Dr Stephen Beatty/Murdoch University

The species, which travels hundreds of kilometres each year through WA's waterways, can impact water quality, introduce disease, disturb habitat and compete with native species.

Last year Dr Stephen Beatty, also from the Centre for Fish and Fisheries Research, said: "Once established, self-sustaining populations of alien freshwater fishes often thrive and can spread into new regions.

"This is having a fundamental ecological impact and are major drivers of the decline of aquatic fauna."

A paper on the new research has been published in the International Aquatic Research journal.

With additional reporting by Caters News.

Want more celebrity, entertainment and lifestyle news? Follow Be on Facebook, Twitter, Pinterest, Tumblr and Instagram