SPREADING ISSUE: Ipswich City Council has commissioned an extensive survey of the Bremer catchment, which identified pest fish tilapia at two locations.
SPREADING ISSUE: Ipswich City Council has commissioned an extensive survey of the Bremer catchment, which identified pest fish tilapia at two locations. Contributed

Pest fish invades Bremer

AUTHORITIES appear to be winning the battle to contain pest fish species tilapia with an extensive fish survey of the Bremer River identifying a small population of the declared noxious fish.

The first detailed fish species survey of the Bremer River catchment, commissioned by Ipswich City Council, identified 34 tilapia caught in two locations of the Bremer River from a sample of 1158 fish caught.

Commonly referred to as the rabbit of Queensland's waterways, the spread of tilapia in Australia has been alarming for authorities as the populations spread quickly and eat out the food source of native fish and even eat native fish eggs.

The invasive species has become a major problem in northern Queensland. In a four year period since 2004, tilapia had spread throughout 3000km of the Burdekin River system.

Council's survey identified 11 species caught through the Bremer. Eighty-eight per cent of fish caught were native species with the introduced species mosquitofish the majority of the remaining catch with 107 found.

The two month survey took in 12 sites, also covering a broader sample of the catchment at Western Creek, Warrill Creek, and Purga Creek.

Environment and Conservation Committee Chairwoman Heather Morrow said the survey also found native species fish that were not previously present in the Bremer and the small population of tilapia showed conditions in the river were supporting native habitat.

"At the moment the numbers (of tilapia) are not of heightened concern for the health of the river," she said.

"Council has asked local fishing enthusiasts that if found or caught, tilapia should be euthanized humanly and disposed of properly and reported to the Department of Agriculture Fisheries and Forestry."

Tilapia originate from the warm, fresh and salty waters of Africa, South and Central America, southern India and Sri Lanka.

The 11 species identified in the Bremer River portion of the survey were:

  • carp gudgeon - 598
  • glassfish - 127
  • flathead gudgeon - 101
  • crimson spotted
  • rainbowfish - 93
  • fly-specked hardyhead - 54
  • Australian smelt - 25
  • freshwater catfish - 11
  • long-finned eel - 8
  • spangled perch - 1
  • Exotic fish species recorded:
  • mosquitofish - 107
  • tilapia - 34

"The survey shows the habitat is still supporting a good mix of fish species in the river. Both tilapia and mosquito fish will occur in small numbers where the habitat is healthy and fit for native species so the programs we are doing to improve the river and introduce good habitat for native species will hopefully control the pest species," Cr Morrow said.

Revegetation projects along the riverbanks were an important step in improving water quality and habitat.

"By getting trees in, getting the waterways shaded, improving the water quality is the best way to keep the numbers of pest species down."

Cr Morrow said monitoring would continue as would efforts to improve the habitat in favour of native fish as part of Council's overall efforts to improve waterways across Ipswich.

A Fisheries Queensland spokeswoman said tilapia was first reported in the Bremer River in 2008 at Brassall, though numbers of fish were not recorded. The species was first reported in Wivenhoe Dam at Coominya and Somerset Dam in 1991. The first record of tilapia in the Brisbane River was at Cannon Hill in 2006.

"Once tilapia enter flowing water bodies such as a river, they are almost impossible to eradicate," she said.

"Over 90% of all pest fish incursions, including tilapia, are the result of human assisted movement, such as being used as live bait."

In Queensland, it is illegal to have a noxious fish such as tilapia in your possession. This includes eating them. Penalties of up to $220,000 apply. If you capture a noxious fish, you are required to humanely kill it and place it in a bin or bury it on site.

Sightings of suspected pest fish should be reported to Fisheries Queensland on 13 25 23 or online via fisheries.qld.gov.au A strategy to address the spread of tilapia can be found at daff.qld.gov.au/fisheries/pest- fish/operational-control-strategy.

Stop the spread

  • Don't move pest fish between waterways.
  • Don't use pest fish species - dead or alive - as bait.
  • Don't empty aquariums, dams or ponds into waterways or outlets that flow into waterways.
  • Don't stock dams or ornamental ponds with pest fish.
  • Don't return catches of pest fish to the water - kill the fish humanely.

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