Pest fish tilapia threatening our waterways
  |  First Published: July 2014

Fishing is one of Australia’s greatest recreational past times, with one in four of us enjoying casting a line. However, with the enjoyment of our rivers, dams and waterways comes responsibility for their sustainability and wellbeing.

The Murray-Darling Basin, Australia’s largest catchment, offers some outstanding angling opportunities including the mighty Murray cod, golden perch, silver perch and tandanus catfish.

If we want to continue to enjoy these fantastic fishing expeditions, we need to ensure we take care of our waterways by fishing responsibly and knowing what lives in our waterways.

Tilapia, one of the most invasive pest species in the world, is spreading rapidly throughout Queensland. Condamine Alliance is urging everyone to be vigilant in the fight to stop it spreading into the Murray-Darling Basin.

Tilapia are regarded as one of the greatest threats to Australia’s aquatic ecosystems. They are known as the cane toads of our waterways and once they have become established in a flowing river or creek, they are almost impossible to eradicate.

Mozambique tilapia are now distributed throughout many locations in southern Queensland and are well established in four neighbouring catchments of the Murray-Darling Basin and are 3km away from the basin in some areas.

The Murray-Darling Basin is one of the most important freshwater ecosystems in Australia. It is home to 46 native fish species, including Australia’s largest and most significant freshwater fishing species the Murray cod.

If tilapia become established in the Murray-Darling Basin, they have the potential to decimate recreational fishing opportunities and negatively impact the ecosystems, economies and communities of the basin.

Covering more than a million square kilometres of land, the Murray-Darling Basin is Australia’s largest river system and one of the biggest river systems in the world. The basin includes 23 major rivers and passes through five states and territories—Queensland, New South Wales, the Australian Capital Territory, Victoria and South Australia.

These pest fish cannot move overland so they rely on people to unwittingly or deliberately move them to new areas. Using tilapia as live or dead bait, releasing live aquarium fish and populating farm dams with tilapia present some of the greatest risks for them entering the Murray-Darling Basin. Tilapia are mouth brooders so keep live eggs and babies in their mouth. Even moving dead adult fish into the basin is high risk as live eggs or babies could be in their mouth.

Tilapia are the perfect invasive pest fish due to:

• Highly efficient reproduction: tilapia are prolific breeders with a high survival rate due to parental care of fry. During drought conditions tilapia stunt and continue breeding to dominate drought refuge waterholes.

• Adaptable: tilapia can adapt to a wide variety of aquatic habitats, food sources and water quality. They can successfully survive in fresh and brackish water and will consume both plant and animal matter. Tilapia actively prey on small and juvenile native fish and are highly aggressive.

• Evolved to deal with the extremes: tilapia thrive in stressed aquatic habitats. They have evolved unique adaptations to overcome drought, withstand high salinity and out-breed competitors. Tilapia dominate the fish biomass or stressed river systems.

Why are tilapia so bad?

Tilapia are a very adaptable and hardy fish. They can destroy aquatic habitats, outcompete native fish for food, and their feeding and nesting resources, and can degrade water quality. If tilapia become established in the Murray-Darling Basin the pest would quickly dominate the water body.

Potentially the largest impact of tilapia becoming established in the Murray Darling Basin will be on water quality. This would likely impact on potable water treatment costs and water availability (stock, domestic and irrigation) for agriculture and food production. In addition, further reductions could be devastating to native fish numbers.

In winter tilapia can die off and in significant events choke and pollute waterways. This would impact on native fish in a similar way to black water events currently do. Tilapia can quickly outnumber native fish and often runt when resources and habitat are under pressure. All of these impacts are potentially damaging to recreational fishing industries.

How can you help?
Know how to identify tilapia

Tilapia vary in colour from dark olive to silver-grey, depending on their age and their environment. They are generally deep-bodied fish with thin profiles, long snouts and pronounced lips/jaws. Their dorsal (upper) fin is continuous and ends in an extended point. Most native species have a dorsal fin with a dent/gap in the middle and a rounded end.

Their pelvic (belly) fins are long and almost touch the front of the anal (bottom) fin. This is unlike most native species, which have short pelvic fins.

Don’t spread tilapia

Tilapia infestations are usually caused by people moving the fish between waterways.

Don’t use tilapia as live or dead bait. It is illegal to use them as bait. Tilapia are mouth brooders and even dead adults may still be carrying viable eggs/larvae in their mouths.

Don’t return tilapia to the water. If you catch any tilapia, kill them humanely and either bury them or put them in a bin.

Don’t empty aquariums or stock dams or ponds with tilapia.

It is illegal to stock, possess or release tilapia. Heavy fines of up to $200,000 in Queensland and $11,000 in New South Wales apply.

Lastly, spread the word. Tell your friends and family about tilapia. Our community is our best defence against this potentially devastating infestation.

Report tilapia sightings

The state governments track pest fish infestations. If you catch or sight any tilapia, or if you suspect someone of stocking or moving tilapia, report it. You will need to provide information such as the date, location, description of the fish, a photograph (if possible) and a description of the waterway.

An easy way to report tilapia sightings is by downloading Condamine Alliance’s mobile phone app. The NRM Mobile Phone Plus App was designed to make it easy for the community to record sightings of tilapia.

The NRM Plus App helps to generate, store and share information about the environment, and is particularly useful when it comes to noting a potential invasion of a pest such as tilapia.

By sharing observations and findings with this app we can develop a greater understanding of the habits of tilapia, and track their movements in our waterways.

To report a tilapia sighting or for further information, contact Queensland Department of Agriculture, Fisheries and Forestry on 13 25 23 or visit www.daff.qld.gov.au/fisheries/pest-fish or the New South Wales Department of Primary Industries on (02) 4916 3877 or Victoria DEPI on 13 3474.

The Northern Basin Tilapia Exclusion Strategy is funded by the Murray Darling Basin Authority. – Condamine Alliance

How to help

• Don't bring tilapia into the Murray-Darling Basin alive or dead

• Spread the word - tell your friends and family about tilapia

• Don’t use tilapia as bait for fishing – dead or alive

• Don’t empty your aquarium into rivers, creeks or dams

• Don’t stock tilapia in dams or ponds – use native fish instead

• If you catch tilapia, kill it humanely and bin it or bury it

• Report any tilapia sightings or catches and if possible take a photo

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