Our site is currently being updated and pages are changing regularly. We thank you for your patience during this transition and hope that you find our new site easy to use.


Spotted Tilapia update

Spotted tilapia were recently found in Far North Queensland in the Walsh River (north of Chillagoe) and near Bruce Weir (near Dimbulah, west of Mareeba).

If you see or catch a spotted tilapia in the area, take a photo and report it online or call Biosecurity Qld on 13 25 23.

  • Image of 5 spotted tilapia
    Image of five sub-adult spotted tilapia with scale ruler. Sub-adults still have bands on body.
  • Spotted Tilapia: restricted noxious fish
    Spotted Tilapia: restricted noxious fish
  • image of a juvenile spotted tilapia
    Juvenile spotted tilapia (Tilapia mariae) captured from the Walsh River in October 2017
  • Tilapia Mozambique mouthbrooder: restricted noxious fish
    Tilapia Mozambique mouthbrooder: restricted noxious fish

Download a PDF copy of the catchment map (PDF, 409.5KB)

General information

Tilapia were first introduced into Australia in the 1970s as ornamental fish and are now regarded as one of the greatest threats to Australia's native biodiversity. Females carry juveniles and eggs in their mouths, and these can survive for a considerable time after the adult dies. Therefore, new incursions  can  occur  when  live  or dead fish are released into a waterway.

Tilapia is a restricted noxious fish under the Biosecurity Act 2014.

Scientific name

Oreochromis mossambicus and Tilapia mariae.

  • part of the Cichlidae family.
  • two species have established in Queensland - the Mozambique tilapia (Oreochromis mossambicus) and the spotted tilapia (Tilapia mariae)
  • O. mossambicus can grow to more than 36 cm and can live up to 13 years. They are usually dark grey or almost black but can be silver with 2-5 dark blotches/spots on the side. Breeding males can have red tips on their fins
  • T. mariae range from dark olive-green to light yellow and they have 8 or 9 dark bars or blotches on the sides (more evident in younger fish). They can grow to 30 cm
  • both species are deep-bodied with a thin profile and have long pointed fins.
  • omnivorous
  • O. mossambicus feed mainly on plankton, insects and weed but will take a wide variety of other foods
  • T. mariae mainly eats plants.
Life cycle
  • sexually mature at 3 years or less in favourable conditions
  • O. mossambicus are able to reach sexual maturity at small sizes in poor conditions or when they are overcrowded. This is known as 'stunting' and results in large populations of mature fish with small body sizes
  • O. mossambicus are mouth brooders - females protect eggs and larvae from predators by holding them in their mouths. Males build large circular breeding nests in soft silt or muddy substrate
  • T. mariae lay their eggs on hard substrate.
  • O. mossambicus are hardy fish and can survive temperatures between 8 and 42oC, although they require temperatures of about 16oC to remain active and feed. They can also withstand high salinites and low dissolved oxygen
  • T. mariae is less tolerant of cooler temperatures and therefore has a lower latitudinal range.


  • have successfully invaded and dominated many aquatic habitats due to their highly efficient reproductive strategy, simple food requirements and their ability to live in a variety of conditions
  • have the potential to rapidly outnumber native fish and dominate aquatic communities
  • can survive a range of environmental conditions which native fish find difficult to cope with.
  • unlike many native freshwater fishes, tilapia are able to retreat downstream into highly saline waters during drought and move back upstream when conditions improve
  • affect native species when competing for habitat and food, behaving aggressively and disturbing plant beds when building nests


  • loss of favourite fishing locations due to invasion and destruction caused by tilapia.
  • Biosecurity Queensland advocates the ethical euthanasia protocols recommended by the 2001 ANZCCART publication: Euthanasia of animals used for scientific purposes. The most appropriate method may involve stunning the fish via a sharp blow to the back of the head just above the eyes. When applied correctly, this causes brain            destruction—the fish's gill covers should stop moving and its eyes should remain still.
  • intensive fishing may have the potential to reduce pest fish numbers in small enclosed waterbodies, but it is very unlikely that fishing alone is an effective long-term control measure.


  • poisons have been used to eradicate pest fish in ponds and small dams, but are not practical for rivers and streams as these poisons also kill native fish
Legal requirements
  • Tilapia is a restricted noxious fish under the Biosecurity Act 2014.
  • it must not be kept, fed, given away, sold, or released into the environment without a permit.
  • if caught these species must be immediately humanely killed and disposed of responsibly away from the water body.
  • by law, everyone has a general biosecurity obligation (GBO) to take reasonable and practical steps to minimise the risks associated with restricted noxious fish under their control.

Further information