THEY are known as "cane toads of the waterways" and they have recently been found in the Fitzroy system.
Tilapia, also known as the Mozambique mouth- brooder, is an invasive pest fish species. Aggressive and territorial, they can drive native fish from their habitat, drastically impacting recreational fishing.
They are becoming more prevalent in waterways across Queensland and recent local sightings have authorities on alert. Once established in a flowing river or creek, tilapia are almost impossible to eradicate.
Fisheries Queensland district officer Gary Muhling said there had been three confirmed sightings in the Fitzroy in the past 18 months, the most recent about two months ago.
A recreational fisherman using a cast net in the catchment near Rockhampton caught six tilapia, the biggest about 18cm long. (Tilapia can grow as big as 40cm, but the average is 30cm to 35cm.)
"We need to halt this as quickly as we can," Mr Muhling said yesterday. "Within the Fitzroy they are only in a low-level population at the moment but we need to try to eradicate or control them."
Queensland Fisheries and the Fitzroy Basin Association want community members to learn how to identify tilapia and report any sightings.
That will allow authorities to determine where the fish are and in what numbers.
Mr Muhling said that surveys were being done to identify any infestations and research was continuing on water temperatures to understand reproduction rates.
Eradication methods are effective only for isolated populations, such as in dams, or when detected early and population numbers are low. Methods include netting, the use of a chemical compound or electro-fishing, in which an electric shock is sent into the water, stunning the fish.
FBA water and agriculture manager Tom Coughlin said tilapia could out-compete native fish for habitat and food.
"We are really concerned because they also have a high reproductive rate," he said. "They can reproduce pretty much all year round, depending on the temperature, and they can spread really, really quickly."
The most common cause of infestation was from people moving the fish between waterways.
Anyone who catches tilapia should kill the fish humanely. They should bury it 20m away from the waterway or wrap it in plastic and place in a bin.
It is illegal in Queensland to possess tilapia alive or dead for any purpose. Fines may apply. Report sightings or catches to Fisheries Queensland on 13 25 23 or at fisheries.qld.gov.au.
Tilapia are prolific breeders and can reproduce year round.
They are omnivores and feed on a wide variety of plant and animal matter.
Tilapia can adapt to a variety of aquatic habitats, including habitats that have high salinity.
STOP THE SPREAD
Don't use tilapia as bait (dead or alive). They are mouth-brooders and even dead adults may be carrying viable eggs/larvae in their mouths.
Don't empty aquariums into local waterways.
Don't stock dams or ponds with tilapia. Use local native fish instead.
Don't return tilapia to the water. If you catch any, kill them humanely and either bury them or put them in a bin.