The biosecurity threat posed by a pest fish in a far north Queensland river has been likened to that of the march of the cane toad into the Northern Territory.

Spotted tilapia have been found in the Walsh River, which is in the Mitchell River catchment, connecting to the Gulf of Carpentaria.

Biosecurity authorities are now rushing to figure out whether the fish can be stopped from spreading to lucrative multi-million dollar barramundi and prawn industries before the looming wet season.

Researcher Brendan Ebner, from James Cook University, said the potential repercussions were massive.

"I would probably argue that it's analogous to the cane toad moving across from the eastern seaboard through northern Australia towards the Kimberleys," he said.

"That might sound alarmist, but when you think about the fact that the Gulf rivers are connected up during major flooding during the wet season, once this animal moves through one of those catchments, it's almost inevitable that it's likely to lead to a major explosion in the distribution of this tilapia species."

Lucrative fisheries under threat

Tilapia could threaten lucrative barramundi and prawn industries if they spread into the Gulf of Carpentaria. ( Supplied: Amanda Dimmock )

Dr Ebner said the potential impacts on the region's fisheries were difficult to measure.

"Undoubtedly it would have some sort of impact on how the native species are working, but for the barramundi fishery, the recreational fishery with species like the sooty grunter, I'm not sure how this will play out because it's just a complex space," he said.

"They would certainly be able to feed on the early instars and the juvenile phases of some of our prawns in the lower parts of our flood plains and freshwater systems, so the banana prawns in particular might be negatively affected by this species."

Control plan up in the air

Whether or not the tilapia can be eradicated before the wet season depends on how far they have already travelled within the river system, which is not yet known.

Biosecurity Queensland general manager for invasive plants and animals, John Robertson, said authorities were using surveillance helicopters to quickly establish the extent of the infestation.

"If the infestation is too large, it's probably not feasible to eradicate because we don't have many control options when you're dealing with an open water system," he said.

"The only one is the use of Rotenone which kills them, but it also can kill other things as well, so other fish and reptiles, so there's other impacts that might be too significant to do it."

Human link to origin of infestation

Nobody knows for certain how the fish came to be in the Walsh River in the first place, but it is suspected humans are to blame.

Concerning officials is a theory that the tilapia may have travelled down the Mareeba-Dimbulah irrigation channel from Tinaroo Dam on the Atherton Tablelands.

About tilapia: Tilapia were first introduced into Australia in the 1970s as an ornamental fish

Tilapia were first introduced into Australia in the 1970s as an ornamental fish Two species are established in Queensland — the Mozambique tilapia and the spotted tilapia

Two species are established in Queensland — the Mozambique tilapia and the spotted tilapia Tilapia are restricted noxious fish under the Biosecurity Act

Tilapia are restricted noxious fish under the Biosecurity Act Tilapia have the potential to rapidly outnumber native fish and dominate aquatic communities

"They may have well come down that catchment in flood events, where they might have got around the screens that are there to stop them coming down, but we just don't know and we'll never know I presume," Mr Robertson said.

In a statement, dam operator Sunwater said it inspected its tilapia screens daily, and every two years conducted a survey of fish species downstream from the screen.

A spokesman said the most recent survey in 2015 did not find any signs of tilapia.

It is not the first time the species has been discovered in the Mitchell catchment.

In 2008, an infestation was successfully eradicated after being found in Eureka Creek, a tributary of the Walsh River.

Mr Robertson said it was possible but unlikely the two cases were linked.

"With the monitoring after that we didn't find anything so we assumed we'd done a good job, but you never quite know what might have got away," he said.