Fishy business in Townsville waterways
The mix of native and non-native fish species living in a waterway is a useful indicator of ecosystem condition.
Fish can tell us a lot about the health of our rivers and creeks. Healthy waterways tend to support a diverse range of native species, while waterways under pressure are often dominated by a smaller number of non-native species.
In the annual Townsville Dry Tropics Waterways Report Card, the balance between indigenous (native) and non-indigenous (introduced or invasive) fish species is used to measure ecosystem fish health in freshwater waterways.
Executive Officer for the Healthy Waters Partnership, Kara-Mae Coulter-Atkins, said fish are more than just a familiar sight in rivers and creeks.
“Fish play important roles in aquatic food webs, recycle nutrients back into the water through their waste and support one of the main reasons residents visit our local waterways, to wet a line,” she said.
Native fish face increasing pressure when waterways experience poor water quality, low flow, higher temperatures, habitat degradation and barriers that prevent them moving along the system. These conditions can create opportunities for invasive species to thrive.
So, what is the current state of fish health across the Townsville Dry Tropics? The latest Waterways Report Card paints a mixed picture, as data was examined at a finer scale for the first time.
A mixed catch for local waterways
In the 2026 Waterways Report Card basin-wide fish health remained unchanged, as grades were based on monitoring undertaken in 2022-23, which found ecosystem fish health to be ‘moderate’ in both the Ross and Black freshwater basins.
This year, however, the data was examined at a finer, sub-basin scale where three or more sites were sampled, providing a clearer picture of local conditions.
At this level, ecosystem fish health is mixed across the region.
In the Ross Basin, fish health was rated 'good' in the Lower Ross River and Alligator Creek sub-basins, but 'poor' in the Bohle River, which is consistent to the previous sampling period in 2019-2020.
In the Black Basin, Crystal Creek maintained a 'very good' grade, while the Black River declined from ‘poor’ to 'very poor.'
An encouraging finding was the widespread presence of the eastern rainbowfish, which was recorded at all sampling sites and remains the region's most recorded native fish species.
However, monitoring also revealed the presence of tilapia, an invasive species that was recorded at over half the sampling sites.
Meet the "cane toad" of our waterways
Tilapia can be described as the cane toad of freshwater waterways, and for good reason. Highly adaptable to different environmental conditions and able to breed rapidly, tilapia can quickly establish large populations.
“Invasive fish compete with native species for food and shelter, prey on eggs and juvenile fish, and can further degrade habitats already under stress” Ms Coulter-Atkins said.
“As invasive species become more dominant, biodiversity declines and the natural balance of aquatic ecosystems is disrupted.”
The widespread presence of tilapia highlights an ongoing threat to native fish in our freshwater ecosystems.
Reeling in trouble
One of the biggest challenges in managing tilapia is stopping them from spreading into new waterways. Unfortunately, these invasive fish sometimes get a helping hand.
The species first arrived in Australia through the aquarium trade in the 1970s. Over time, unwanted fish have been released into creeks and rivers, or sent down the drain, where they established wild populations.
In Townsville, stories persist of small tilapia being caught in the Palmetum and used as bait in the Ross River. While it may seem harmless, giving the pest a free ride into another waterway can have serious consequences.
Even disposing of a dead tilapia the wrong way can create problems. Female tilapia are mouth brooders, meaning they carry eggs in their mouths. Those eggs can survive for some time after the adult fish dies, which is why responsible disposal is so important.
Don’t keep it. Don’t feed it. Don’t give it away. Don’t sell it. And don’t release it into the environment. As a restricted noxious fish under the Biosecurity Act 2014, penalties may apply if you do any of these.
When it comes to tilapia, prevention is far easier than trying to remove an established population.
What should you do?
If you catch tilapia, humanely kill them. The most appropriate way may be to stun the fish with a sharp blow to the back of the head, just above the eyes. Bury the dead fish well away from the water edge or above the high tide mark or dispose of them in a general rubbish bin.
You can also report sightings to Biosecurity Queensland. When reporting tilapia, only report sightings if you suspect a new outbreak. It is already known they are well-established in the Black and Ross Rivers.
Community reporting plays an important role in detecting new outbreaks early, helping biosecurity agencies respond before invasive populations become established.
Help reel in the invasive pest at the Tilapia Takedown
Want to help tackle the region's most problematic invasive fish species while learning more about local waterways?
The Tilapia Takedown is a free, family-friendly, targeted fishing competition to raise awareness about invasive species and help remove tilapia from local waterways. The event will be held at Anderson Gardens on Wednesday 23 September 2026 from 8:30am to 12:30pm. Bookings are essential.
Participants can fish for tilapia between 8:30am and 11:00am, meet local experts, explore educational displays, and compete for prizes. Every tilapia removed during the event contributes to local management efforts, with fish recycled through Townsville City Council's Healthy Soils program.
The event is delivered by the Healthy Waters Partnership for the Dry Tropics, Townsville City Council and OzFish Unlimited, and operates under a special permit provided by the Department of Primary Industries.
(Please note, fishing is not allowed in Anderson Gardens at any other time.)
Be a waterway hero
Healthy waterways rely on healthy fish communities. By protecting native species and preventing the spread of invasive pests like tilapia, we can help maintain biodiversity, improve ecosystem resilience and support healthier rivers and creeks across the Dry Tropics.
