Tilapia

Alert

If you see or catch carp outside of their known distribution, take a photo and report it online or call Biosecurity Queensland on 13 25 23

Tilapia were introduced into Australia in the 1970s as ornamental fish and are now a major threat to Australia's native biodiversity. Females carry their eggs and small fry in their mouths, and these can survive for a long time after the adult dies. Therefore, releasing living or dead fish into waterways can cause new infestations. Tilapia is a restricted noxious fish under the Biosecurity Act 2014.

Scientific name

Oreochromis mossambicus (Mozambique tilapia)
Tilapia mariae (Spotted tilapia)

Other names

  • Part of the Cichlidae family: Mozambique tilapia
  • spotted tilapia

Description

O. mossambicus

  • Grows to more than 36cm.
  • Lives up to 13 years.
  • 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.
  • Deep-bodied with a thin profile and long pointed fins.

T. mariae

  • Ranges from dark olive-green to light yellow.
  • 8 or 9 dark bars or blotches on the sides (obvious in younger fish).
  • Grows to 30cm.
  • Deep-bodied with a thin profile and long pointed fins.

Habitat

O. mossambicus

  • Hardy fish, can survive temperatures between 8 and 42°C.
  • Requires temperatures of about 16°C to remain active and feed.
  • Can withstand high-saline waters and low-dissolved oxygen.

T. mariae

  • Less tolerant of cooler temperatures and therefore found at lower latitudes.

Life cycle

Breeding

  • Sexually mature at 3 years or less in favourable conditions.
  • O. mossambicus can become sexually mature at small sizes in poor conditions, or during times of overcrowding. Known as 'stunting', this results in large populations of mature fish with small bodies.
  • O. mossambicus are mouthbrooders. Females protect eggs and small fry from predators by holding them in their mouths. Males build large circular breeding nests in soft silt or muddy layers.
  • T. mariae lay their eggs on hard surfaces.

Diet

  • Diet is omnivorous.
  • O. mossambicus feed mainly on plankton, insects and weed but will take a wide variety of other foods.
  • T. mariae mainly eat plants.

Impacts

Environmental

  • Successfully invades and dominates many water habitats due to their high ability to reproduce and survive in very different conditions, and simple food needs.
  • Can rapidly outnumber native fish and dominate aquatic communities.
  • Can survive environments where native fish find coping difficult.
  • Unlike many native freshwater fish, tilapia can retreat downstream into highly saline waters during drought and move back upstream when conditions improve.
  • Affects native species as they compete for habitat and food, behave aggressively and disturb plant beds when building nests.

Social

  • Loss of favourite fishing locations due to tilapia invading and destroying native fish populations. Tilapia can create large, monospecific (single species) fisheries.

Control

How they are spread

  • Most new infestations are caused by human-assisted translocation (movement of live fish). This includes private dam stocking and moving tilapia between catchments to use as bait, or to create new 'fisheries'.
  • Biosecurity Queensland maintains a strict 'no-take' approach to manage tilapia and reduce the spread of this noxious fish.

Monitoring and action

  • If you catch tilapia in the wild, humanely kill them and do not return them to the water. If you see or catch carp outside of their known distribution, take a photo and report it online or call Biosecurity Queensland on 13 25 23.
  • Follow the ethical euthanasia code in Euthanasia of animals used for scientific purposes (PDF, 1.8MB), the 2001 Australian & New Zealand Council for the Care of Animals in Research and Teaching publication. The most appropriate way may be to stun the fish with a sharp blow to the back of the head, just above the eyes. When done correctly, this causes brain destruction—the fish's gill covers should stop moving and eyes should remain still.
  • Intensive fishing may reduce pest fish numbers in small enclosed waterbodies, but this practice alone is not an effective long-term control strategy.

Poisoning

  • Poisons can completely remove 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.
  • You must not keep, feed, give away, sell, or release tilapia into the environment without a permit.
  • If you catch these species, you must immediately humanely kill and dispose of them by burying them above the high-water mark or disposing of them in a nearby bin.
  • By law, you have a general biosecurity obligation (GBO) to take reasonable and practical steps to minimise the risks associated with restricted noxious fish under your control.

Further information

Contact

General enquiries 13 25 23