An invasive tapeworm never previously recorded in Western Australia has been discovered in two feral fish species caught from a popular Perth lake by Murdoch University scientists.

The researchers say the discovery of the Asian fish tapeworm indicates a serious potential danger to the unique freshwater fish fauna of South-West Australia, and are urging that measures are taken to control their spread.

A writhing mass of the tapeworms was discovered by Murdoch PhD researcher Cindy Palermo when she dissected a number of the goldfish and carp pulled from a lake in the City of Joondalup earlier this year by fish biologists Associate Professor David Morgan and Dr Stephen Beatty.

Ms Palermo discovered the intestines of some of the fish were completely blocked.

Associate Professor Alan Lymbery, Director of the Centre for Sustainable Aquatic Ecosystems in Murdoch University’s Harry Butler Institute, said the tapeworm could potentially spread to native fish species.

“The Asian fish tapeworm is a very serious pathogen of cultured fish like carp and goldfish and it could be even worse for native fish,” he said.

“Infection is usually fatal in young fish and those of a small size. Also, this tapeworm does not appear to have a preferred host.

“The pathogenic effects of introduced parasites are frequently more pronounced in native wildlife which have not had prior exposure.”

The Asian fish tapeworm has spread to more than 200 fish species throughout the world via aquarium or pond releases.

Professor Lymbery leads a group at Murdoch that is discovering more and more serious pests co-invading with introduced fish.

He said the discovery underlined the importance of not releasing unwanted pet fish like goldfish or carp into ponds of rivers.

“These alien species can impact water quality, disturb habitat and compete with native species, as well as introducing disease and parasites,” Professor Lymbery said.

“Healthy wildlife means healthier environments for all of us, so it is important we interact with our native species in the correct way to protect their health and wellbeing, as well as our own.”

If you find an aquatic pest, report it to FishWatch - 1800 815 507.