Tilapia (Oreochromis mossambicus or the Mozambique Mouth Brooder) is an introduced fish species found in Australia and many other parts of the world. The species is native to Africa and a member of the Cichlid family. It is particularly harmful to natural waterways in Australia, threatening native fish species and their habitats. World authorities consider this pest to be one of the top 100 invasive species.

A typical Tilapia or Mozambique mouth brooder (Oreochromis mossambicus) showing typical adult colouration.
Do not be fooled by apparent pretty colours. A different colour pattern for tilapia with a large protruding mouth.

Tilapia most likely arrived in Australia as an aquarium pet, but has since become established in a few natural waterways and continues to spread in a number of Queensland and NSW coastal river systems, and even a catchment in Western Australia. So far, Tilapia is yet to be introduced to the Murray-Darling Basin, with the help of a targeted exclusion program. 

While certain related and legal species of cichlids may have striking colour forms, it is important that unwanted aquarium fish are not released into the environment and enthusiast fish keepers confine their collections to legal species such as the African lake cichlids shown here.

The cost of invasive species in Australia

Invasive pests of all kinds have had huge and often devastating effects on Australia’s unique ecosystems, particularly throughout the Murray Darling Basin.

Australia has seen the devastating impacts, both economic and environmental, of rabbits, feral pigs, feral cats, blackberry, lantana and carp, just to name a few. Some reports indicate that over the last 60 years, invasive and pest species have cost Australians around $390 billion. However, these reports often ignore the huge economic and ecological impact pest fish also have had in Australia. 

So why aren’t pest fish mentioned as a problem that costs our society?

It is difficult to put a dollar value on environmental and social costs. In the case of pest fish, if the problem is out of sight, it doesn’t physically attack us and it doesn’t eat our livelihood, then as a community we don’t pay as much attention. 

Pest fish have been quoted in other studies to probably cost the community many millions. So, if Tilapia got into the Murray Darling Basin, it would amount to incalculable losses.

A tilapia spawning site, with an adult male guarding the left hand side.
Tilapia spawning sites are not a welcome sight.

Impacts of introducing Tilapia

The Tilapia has already been implicated in the rapid demise of native fish in many other parts of the world, such as the Pacific Islands and now in parts of Australia. There are real fears by fisheries authorities that if Tilapia becomes established within the Basin, the already stressed native fishes and aquatic communities will be further changed irreparably.

Nic Whysall holding a large tilapia removed from a Queensland coastal stream.

The Mozambique Mouth Brooder has a number of breeding and living strategies that allow it to reproduce under stressed environmental conditions. These provide a significant survival advantage over Australian native fish. 

  • As the name suggests it is a mouth brooder. The female provides a safe haven for its eggs and young within the mouth, leading to high survival of young. 
  • Tilapia are also able to breed rapidly in drought refuge waterholes when stressed, pushing out native fish and taking necessary resources. 
  • In large numbers they are capable of re-suspending nutrients creating blue green algae blooms which can become toxic to native fish and impact on people’s health. 
  • Tilapia also eat smaller native fish species, endangering their population numbers. 

Tilapia thrive in conditions that are often not suited to native fish. Dr Stuart Rowland in his book “The Codfather” suggests (in the chapter titled ‘Goodbye Darling’) that the Darling River ecosystem as a whole is already extinct. Given the existing degradation of the Darling River in particular and the present management systems in place, the system is more likely to experience periods of low to no flow – these are the conditions that Tilapia are most likely to thrive in.

A small impacted Queensland coastal stream with a large population of the Mozambique mouth brooder.

What is being done?

Despite the lockdowns and restrictions to travel brought about by Covid-19, 2021 marks a significant 10-year milestone for the Tilapia Exclusion Strategy. For 10 years this program has successfully aided in keeping Tilapia out of the Murray-Darling Basin. The Murray-Darling Basin Authority (MDBA) Demonstration Reach Program began the Tilapia Exclusion Strategy in 2011 and continues to fund an education program that aims to keep the Basin free of the pest fish, also commonly known as the Mozambique Mouth Brooder. So far, despite Tilapia infestations in catchments close by, the Basin has remained Tilapia free, which is a great achievement to protect native habitats and species in the Basin. 

If the Covid-19 pandemic has taught us anything, it’s definitely that prevention is a far more desirable outcome than infection. The same applies to the pest fish Tilapia.

The Tilapia Exclusion Strategy has three key parts to prevent its introduction to the Basin:

  1. Raising awareness through education of the species impacts. 
  2. Preventing by educating the community about how to avoid translocating Tilapia. 
  3. Monitoring by training the community to identify and report Tilapia should an incursion occur.

Pre-Covid, Tilapia experts made regional visits to high-risk areas. High-risk areas are usually those with populations of tilapia already in the regional waterways, and geographically close to the northern reaches of the Murray Darling Basin, typically in Queensland.

A group of students from Kingaroy State High School after a tilapia education session. Kingaroy is located within the Burnett River catchment in Queensland, and lies adjacent to parts of the northern MDB in this state and is therefore a potential possible tilapia infestation source.

The experts would visit and present at regional shows, schools, fishing clubs and Landcare groups within the Northern Murray Darling Basin itself, where the risk of Tilapia being introduced is high. 

The Covid-19 Pandemic has severely reduced face-to-face educational opportunities. So the project has been trying a more media focused approach with more articles and online education, which has allowed the project to reach a broader and more remote audience more effectively. Although hopefully the face-to-face aspects of the program will return over the next few years. 

How can I help?

Learn to identify Tilapia:

Source: NSW DPI.
Source: NSW DPI.
  • Tilapia vary in colour from dark olive to silver-grey, depending on their age and environment.
  • They are generally deep-bodied fish with thin profiles, long snouts and pronounced lips/jaws.
  • Their dorsal (upper) fin (1) 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 (2) are long and almost touch the front of the anal (bottom) fin (3). This is unlike most native species, which have short pelvic fins.

Remain vigilant and alert:

  • Watch out for potential infestations.
  • Check on any dead fish you observe in rivers or other waterways, and know what tilapia look like.
  • Report suspected infestations and if possible keep a frozen or somehow preserved specimen for authorities to formally identify.
  • Above all, let us keep tilapia out of the Murray Darling Basin!
Use your visits to your favourite parts of the Murray Darling system to keep an eye out for unusual or different pests. Report any suspected infestations of tilapia to the relevant state Fisheries authorities.

Given that our local communities value our unique natural systems, it’s important to make sure that politicians know this is important and act in our shared interests. As a community we can’t afford to become complacent about our dwindling natural resources, let alone replace them with pests from elsewhere around the globe.

So as we begin to move around the country again, we must keep the unique and valuable resource that is the Murray Darling Basin as pest-free as we can. Keeping the Murray-Darling Basin Tilapia free for the last 10 years is an incredible achievement, and this effort needs to continue in the future to protect our native fish.

Who to contact for pest fish sightings:

If there is anyone who would like further information on tilapia or pest fish identification material, you can contact Rod Cheetham on 0427514704.

Further information

Author: Rod Cheetham
Consultant, Fisheries Aquaculture & Wildlife Developments
rch37222@gmail.com   |   0427 514 704

Rod has been working with Fisheries Departments in Victoria and Queensland for over 35 years. Other jobs have included working for Local Government for 3 years in Natural Resources as well as occasional work in the tackle industry. The Murray Darling Basin Authority is funding an educational project to educate the community on preventing the spread of tilapia from high risk areas. If anyone or organisation is interested in extension material relating to pest fish, particularly tilapia, feel free to contact him.

Featured image: The Murray Darling system is currently tilapia free. Let’s keep it that way.
Photo credits: Pest Fishing Adventures and Rod Cheetham (unless otherwise attributed)

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