Biosecurity efforts are ramping up in the Gulf of Carpentaria as the invasive pest tilapia weaves its way through Queensland’s northern waterways, dodging eradication and putting the aquaculture industry on edge.
After Cyclone Jasper barrelled through Far North Queensland in late 2023, subsequent flooding caused the invasive species to spread further into northern rivers.
Tilapia threatens native endangered species in Queensland waterways. (ABC News: Christopher Gillette)
After a sighting in 2024, a Griffith University study published in January this year discovered two species of tilapia — the Mozambique and spotted — in the upper Mitchell River catchment, which flows directly into the Gulf.
“It does really seem like [we’re] fighting a losing battle … it’s not great news,” Griffith University researcher Kaitlyn O’Mara said.
“Eventually they could even make their way over to Kakadu, which is a serious concern.”
Dr Kaitlyn O’Mara says the discovery of tilapia closer to the Gulf is concerning. (Supplied: Dr Kaitlyn O’Mara)
As the pest creeps closer to the Gulf, experts worry its trajectory could have devastating consequences for northern wetlands and the commercial barramundi industry.
Chris O’Keefe, a barramundi farmer of 40 years and manager of the Les Wilson Barramundi Discovery Centre in Karumba, said a tilapia outbreak in the Gulf would devastate the species.
Chris O’Keefe says a Gulf tilapia outbreak would threaten barramundi stock. (ABC Rural: Abbey Halter)
He said while barramundi was a saltwater fish, juveniles tended to stay in freshwater areas where tilapia was the dominant species.
Mr O’Keefe said breeding estuaries for native fish were also in the firing line.
Tilapia can hold more than 1,000 eggs in their mouths. (Supplied: Qld DAFF)
“It’s hard to tell the timeframe, but it’s kind of like comparing it to the cane toad … they’re going to get there, it’s only a matter of when,” he said.
“They’re going to eat [anything that] breeds … [native fish] are going to be consumed by the tilapia.”
High risk of spread
Dr O’Mara said the highly invasive species aggressively defended its nests against natives, damaged substrate and vegetation, and could ingest the eggs of native fish.
She said spotted tilapia could tolerate salt water, so the risk of spreading to waterways in the Gulf of Carpentaria during a flood was high.
Griffith University researchers have studied the Mitchell River tilapia outbreak. (Supplied: Dr Kaitlyn O’Mara)
Dr O’Mara said while the pest was currently restricted to the upper catchment, it was early days.
“The bad news is once they are established in several locations, it is difficult to eradicate them,” she said.
“The main thing we can do is just to try to prevent them from reaching vulnerable habitats and try to prevent them from establishing in other river systems in the Gulf.”
Tilapia is mostly found on Queensland’s east coast after being introduced to the country in the 1970s as an ornamental fish.
Spotted tilapia is one of the two tilapia species found in the Mitchell River. (Supplied: Dr Kaitlyn O’Mara)
Now considered a restricted and noxious pest, there is little hope it can be eradicated from Australia.
Dr O’Mara said tilapia was first found in northern Queensland waterways in 2008 but was eradicated through retinal poisoning.
In 2017, it was discovered downstream in the Walsh River and rose to established populations in 2019 and 2021.
Taking action
Mitchell River Watershed Management Group member and Kowanyama Aboriginal Shire Council special projects officer, John Brisbin, is not hopeful the pest can be eradicated.
He said the Indigenous community of Kowanyama and those living along the Mitchell River were concerned about tilapia and wanted to see the impact managed.
John Brisbin says he is not hopeful the pest can be eradicated. (Supplied: John Brisbin)
“It’s going to be devastating to their waterholes and the cultural access to country, and the bush tucker,” Mr Brisbin said.
He said more environmental funding would help improve the health of the country’s ecosystems.
“If money was spent on people being able to go out and be on country and act as stewards and custodians of country, that would be absolutely fantastic,” he said.
The Mitchell River in northern Queensland leads into the Gulf of Carpentaria. (Supplied: Dr Kaitlyn O’Mara)
Dr O’Mara said Biosecurity Queensland was conducting additional surveys in the Upper Mitchell catchment in response to the study’s recommendations.
A Biosecurity Queensland spokesperson said maintaining tilapia-free catchments was a priority.
“Current programs focus on innovative remote monitoring methods, such as eDNA water sampling, alongside traditional survey techniques,” the spokesperson said.
“These initiatives are supported through partnerships with First Nations groups, research institutions, the private sector, and state and local governments across Queensland.”
The Mitchell River flows into the Gulf of Carpentaria in Far North Queensland. (Supplied: Dr Kaitlyn O’Mara)
Local Indigenous rangers on the flood plains are training under the National Environment Science Program to identify tilapia in the Mitchell River catchment.
“These things put together will hopefully help to control their numbers, and that will reduce the risk of them going further downstream,” Dr O’Mara said.
