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Muddying the Scenery – Tilapia pest fish

Invasive Tilapia threaten our rivers, fish, and our holiday experience.


© The State of Queensland, Department of Agriculture and Fisheries 2022


After two years of COVID lockdowns and devastating weather events, the open road awaits, and we can finally get back to exploring all our beautiful country has to offer. For many of us this includes visiting the unique Murray–Darling Basin to discover and enjoy its internationally significant wetlands and 18 imperilled native freshwater fish species including the iconic Murray cod [1]. One thing the Basin doesn’t yet have is the pest fish Tilapia, and we’d like to keep it that way.


© The State of Queensland, Department of Agriculture and Fisheries 2022


Tilapia are a noxious pest and rank in the top 100 most invasive species worldwide [2]. Tilapia have a wide range of environmental impacts in Australia and internationally. Tilapia directly impact most native fish like golden perch, silver perch, Murray cod, and freshwater catfish by eating their eggs and young, competing for food and space, impacting water quality, destroying aquatic vegetation, and increasing turbidity [2]. Tilapia also spread diseases & parasites, promote algal blooms by resuspending nutrients into the water column, and damage the banks and bottoms of rivers, making our waterways less suitable for our unique native species and less enjoyable for our own swimming, boating, and fishing– all important parts of an Aussie adventure [2].

Our travellers and holiday makers contribute large sums of money to our regional community economies, and they also continue to play an important role in protecting our beautiful Murray–Darling Basin and our way of life from these impacts by stopping the spread of Tilapia.


© The State of Queensland, Department of Agriculture and Fisheries 2022


  • Never spread or release Tilapia, dead or alive. Even releasing dead Tilapia can spread the pest further, because female Tilapia carry the eggs and babies in their mouths [3]. Instead, dispose of Tilapia as soon as possible.

  • Humanely dispose of Tilapia in a bin or bury above the high–water mark. Tilapia eggs can survive for a long time after the adult dies and burying Tilapia below the high tide mark could wash their eggs into the waterway, creating a new generation of Tilapia [3].

  • Know how to identify Tilapia and differentiate from native fish. While most Tilapia have instantly recognisable features that are different from our natives, with bright red fin tips or black spots, some Tilapia can be more difficult to identify because of how their colours can change based on their age and their environment [4]. It’s important to be able to recognise Tilapia not just on their distinct colours, but also from their body features.

These three are key:

o a continuous dorsal (upper) fin with an extended tip

o a rounded caudal (tail) fin

o a long pointed pelvic (belly/anal) fin [4].


  • Report any Tilapia you see or catch to the state authorities immediately, using the appropriate phone numbers, websites, or email addresses on the image below. If you’re in the Murray–Darling Basin, it’s important we see the Tilapia too, by either a photo of the fish and the location, or preferably freeze the fish with information on where and when you caught it.


The Stop the Spread Tilapia exclusion strategy has been a fantastic achievement with the community, by keeping Tilapia out of the Murray–Darling Basin by stopping the spread, with 2022 marking a decade of success of this Tilapia education and awareness raising project. By keeping Tilapia out of the Basin, you're helping to protect this unique environment – healthy native fish and rivers which support our people, plants, animals, and regional economies that have been hit hard with recent flooding. We all have a responsibility to help protect our waterways from further Tilapia introductions so we can celebrate another decade of Tilapia–free Murray–Darling Basin!


Sources

1. Murray-Darling Basin Authority (nd) The Murray–Darling Basin and why it’s important, https://www.mdba.gov.au/importance-murray-darling-basin

2. Hutchison M, Sarac Z, Norris A (2011) Mozambique Tilapia- The potential for Mozambique Tilapia Oreochromis mossambicus to invade the Murray–Darling Basin and the likely impacts: a review of existing information


Mariah Millington Freshwater fish biologist– Independent contractor E: fathomfreshwaterconsulting@gmail.com

Mariah receives joint programs funding from the Native Fish Demonstration Reaches project to raise awareness of the threat of Tilapia to the Murray–Darling Basin. The joint programs are coordinated by the Murray–Darling Basin Authority to promote effective planning, management and sharing of the water and other natural resources of the Murray–Darling Basin.

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