A FISH species from the same family of the invasive and dangerous Tilapia was found in a Gladstone pond this week.
Up to ten Oscar fish were reported to be seen at the Gladstone duck pond on Glenlyon Rd on Tuesday.
Bill Sawynok, who has a fish monitoring webpage, was told by someone who had seen the fish.
They were initially thought to be Tilapia, but after some research, Mr Sawynok said it was an Oscar.
Mr Sawynok, the founder of fish stock monitoring site Crystal Bowl, said Oscar is an introduced pest species that should be treated just like Tilapia, killed and disposed of.
Oscar and Tilapia are from the cichlid family and are dangerous for native species because of their fast breeding and aggressive nature.
"Because the duck pond is a small area, it's generally isolated to the other waterways.
"There's a number of different ways to get them out of there and the Fitzroy Basin Association have been notified so they will look at the most appropriate ways," Mr Sawyknok said.
With Tilapia already prolific in Rockhampton waters, Mr Sawynok it was more a case of when, not if, Tilapia came to Gladstone.
"Our native fish are under enough pressure without having more from an introduced pest species," Mr Sawynok said.
He said he thought Mr Sawynok believed the Oscar were was introduced into the pond after being released from an aquarium.
Crystal Bowl is a fish monitoring organisation based in Rockhampton that also investigations Gladstone fish stocks.