They did find four big goldfish in a Cowaramup dam, but hope the difficulty of their search means they have nearly eradicated the pests.

The doctors from the Centre for Fish and Fisheries Research conducted their search with electrofishing to momentarily stun the fish and check them.

Drew McKenzie of the Cape to Cape Catchment Group said the result was not definitive, but the community fishdown last year, coupled with people keeping an eye out for them afterwards, had been a great help.

Dr Morgan said the goldfish competed with native fish for food and space, introduced parasites, and as bottom feeders deprived the water of nutrients and caused blue-green algae.

“They’ll eat anything,” he said, including native fish and fish eggs.

Small crustaceans directly attributed to goldfish have been found near Pinjarra and in the Canning River.

The doctors will continue to monitor the region for goldfish, including Wilyabrup, Vasse and the Warren River.

“It’s a great sign that the community has obviously done a fantastic job,” Dr Morgan said.

“(The goldfish) were everywhere last year and it’s very unlikely we missed them (this time).”

“If people have any reports, I’d be very interested to know,” Mr McKenzie said.

People can contact the CCCG on 9757 2202 or the centre at Murdoch University.

Unwanted goldfish can be returned to pet shops or humanely euthanased by putting them in the freezer.