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Tilapia - Oreochromis mossambicus (Mozambique mouthbrooder)

Tilapia mariae (Black mangrove cichlid)

Tilapia zilii (Redbelly tilapia)

Tilapia
Photos: Gunther Schmida

INTRODUCTION

These three tilapia species were introduced into Australia through the aquarium trade. They are extremely hardy fish with highly efficient breeding strategies (including mouthbrooding), simple food requirements and flexible habitat preferences.

There are no existing populations of tilapia in NSW. However, they have established successful breeding populations at several sites in Queensland, Victoria and Western Australia, and have impacted native fish populations through competition for food and space.

It is usually extremely difficult to eliminate pest fish once they have become established in the wild. It is therefore vital to prevent noxious pests such as tilapia from entering or spreading further in our waterways.

NATURAL DISTRIBUTION AND BIOLOGY

Tilapia belong to a large family of fish (Cichlidae) that are found naturally in the warm, fresh and brackish waters of Africa, South and Central America, southern India and Sri Lanka. Approximately 150 species have been imported into Australia as aquarium fish.

Mozambique mouthbrooder

Of all the tilapia species the Mozambique mouthbrooder has the most widely distributed feral populations in Australia.

Mozambique mouthbrooders can grow to more than 36 cm and live for up to 13 years. However, size varies according to environmental conditions, with poor conditions sometimes producing many small (but still mature) fish.

They become sexually mature in 3 years when around 15 cm, although stunted fish can breed at 9 cm. Breeding males become very dark (almost black) with red edging on their fins. They have a highly successful breeding strategy (up to 1200 eggs a year, in up to 4 broods) and low juvenile mortality. After spawning the female takes the eggs in her mouth, where they hatch. The fry remain in their mother's mouth for up to 14 days before they are released, and may remain near the mother and re-enter the mouth when threatened until about 3 weeks old, thus receiving protection from predators.

Mozambique mouthbrooders are hardy fish, tolerating a wide range of temperatures and surviving in high salinities and low dissolved oxygen. Consequently they have colonised a variety of habitats including reservoirs, lakes, ponds, rivers, creeks, drains, swamps and tidal creeks. They usually live in mud bottomed, well-vegetated areas, and are often seen in loose aggregations or small schools.

Black mangrove cichlid

Black mangrove cichlids grow to around 25 to 30 cm. They become sexually mature at about 10 to 15 cm. They prefer to spawn on hard substrates (such as logs) which they clean beforehand. They do not build nests and are not mouthbrooders, but the eggs and fry are carefully guarded by one or both parents. The parents continue to care for the young until they are about 2-3 cm.

Black mangrove cichlids are less tolerant of cooler temperatures than Mozambique mouthbrooders.

Their diet consists mainly of plants although it appears they will also eat animals when there is limited aquatic vegetation available.

Redbelly tilapia

This is another species considered to be a potential threat if introduced into NSW waterways. They are normally found in sheltered waters over rock, sand or mud, including shallow pools, lagoons and the margins of rivers.

WHERE ARE THEY IN AUSTRALIA?

Mozambique mouthbrooders have established several breeding populations in northern and southern Queensland, including around Brisbane, Townsville and Cairns. They have also become established north of Geraldton in Western Australia.

Black mangrove cichlids are found in northern Queensland waters around the Cairns region. They have also established a self-sustaining population in the heated waters of the Hazelwood power station pondage near Morwell in Victoria.

An outbreak of redbelly tilapia occurred near Perth in Western Australia in 1975, but was eradicated by the local fisheries department.

There are currently no records of established breeding populations of any of these tilapia species in NSW. However, anecdotal evidence suggests they have been present, on occasion, in NSW waters in the past. The present distribution and abundance of Mozambique mouthbrooders in southern Queensland suggests that other river systems, including the Murray-Darling, may be at risk from this fish. Because of their high reproductive rates, tilapia have the potential to establish large populations within a short period of time if not controlled.

HOW DID THEY GET HERE?

Tilapia, like many other cichlids, are very popular aquarium fish and were imported into Australia for this purpose. It is most likely that they have been introduced into natural waterways through accidental or deliberate releases of aquarium fish.

Tilapia can be spread to new areas through the release of live aquarium fish, the use of live or dead fish as bait, and via artificial pipelines and irrigation channels.

WHAT ARE THEIR IMPACTS?

Tilapia have characteristics that allow them to easily establish in new areas and become dominant at the expense of native fish populations. These characteristics include simple food requirements, flexible habitat preferences and highly efficient breeding strategies.

Tilapia can dominate local fish communities, displacing local species. They may also have an effect on native fish through aggressive behaviour and competition for food and space. They are also known to occasionally prey on the eggs and fry of other fish.

Tilapia are capable of colonising degraded habitats in which other animals cannot survive. They may also contribute to habitat degradation, with nest building by Mozambique mouthbrooder males having the potential to damage aquatic vegetation and lead to increased turbidity.

WHAT IS NSW FISHERIES DOING?

Tilapia (Oreochromis mossambicus, Tilapia mariae and Tilapia zilii) have been listed as Class 3 noxious fish in all NSW waters under the Fisheries Management Act 1994. It is now illegal to possess, buy or sell tilapia in NSW without a permit, and heavy penalties of up to $11,000 apply. In addition, NSW Fisheries has the power to seize and destroy the fish or require their destruction.

NSW Fisheries will seek compliance with the noxious species regulations for tilapia through inspections of aquarium shops and fish shipments, and through public education.

NSW Fisheries is also monitoring fish populations in coastal and inland rivers in NSW. If any populations of tilapia are discovered they will be monitored and, where possible, action taken to control or remove them.

HOW CAN YOU HELP?

Remember that it is illegal to possess, buy or sell any of these three fish species, and heavy penalties apply.

Be on the lookout for new species in your local waterways.

If you find any fish that you think might be tilapia or another species not native to the area, freeze the fish whole and contact your local NSW Fisheries office or the Threatened Species and Biodiversity Unit (see below).

Many other aquarium fish can also cause problems if they are released into the wild. Make sure you give any unwanted aquarium fish to friends or a petshop rather than letting them go in the wild (Note: it is illegal to release live fish into NSW waterways without a permit, and heavy penalties apply).

If you are involved in fish stockings, obtain a fish stocking permit from NSW Fisheries before buying fish for restocking, and buy fingerlings from local suppliers rather than outside the region or interstate, to minimise the chances of introducing other species not native to your area.

REFERENCES

Allen GR, Midgley SH, Allen M. (2002). Freshwater Fishes of Australia. Western Australian Museum, Perth.

McDowall R. (Ed) (1996). Freshwater Fishes of South-Eastern Australia. Reed Books, Australia.

Lever C. (1996). Naturalized Fishes of the World. Academic Press, San Diego.

Arthington AH, Bluhdorn DR. (1994). Distribution, genetics, ecology and status of the introduced cichlid, Oreochromis mossambicus, in Australia. Internationale Vereinigung fur theoretische und angewandte Limnologie/Communications 24: 53-62.

FOR FURTHER INFORMATION CONTACT:

Threatened Species and Biodiversity Unit
Port Stephens Fisheries Centre
Private Bag 1, Nelson Bay NSW 2315
Phone: 02 4982 1232
Email: tsadmin@fisheries.nsw.gov.au

For further information

Helping with protected and threatened species sightings

You can report a sighting by phone on 02 49163877, online, or by downloading the Protected, Threatened and Pest Species Sighting Form icon-pdf115KB and send to:

Port Stephens Fisheries Centre
Private Bag 1, Nelson Bay NSW 2315
Fax: 02 4916 3880
Email: tsadmin@fisheries.nsw.gov.au

Last Updated: July 11, 2005, 2:54 pm