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Guppy (Poecilia reticulata)

Guppies have been introduced in Australia for mosquito control and have also escaped or been released from aquariums and ponds. Established populations can affect local fish populations, so preventing their spread and reporting new sightings are important.

Key facts

Type: Pest animal, fish.

Native to: Central and South America.

Established in: QLD, WA, NT.

Other names: Millionfish.

Best time to act: Look for and treat guppies when water levels are low and populations are confined to accessible pools, before wet-season flows can spread them.

Identification

  • A small, slender fish with an upturned mouth and a broad tail fin.
  • Males grow to about 35 mm and females to about 60 mm.
  • Males are generally smaller and more brightly coloured, while females are larger and less colourful.
  • Colour and fin shape vary widely, especially in aquarium-bred fish.
  • Guppies bear live young, and juveniles may be seen with adults in shallow water.
  • Look-alike: Eastern mosquitofish (Gambusia holbrooki) can look similar; guppies often have more colourful, larger tail fins, particularly the males.

Where it lives

In Australia, guppies live in freshwater ponds, drains, creeks and other waterways, and can also tolerate some brackish water.

Why it matters

  • Introduced guppy populations generally have a negative impact on local fish populations.
  • They can compete with native fish for food and habitat and consume small aquatic animals such as insect larvae and crustaceans.
  • They can become well established in waterways, including around Darwin, even where attempts have been made to remove them.

How it spreads

  • Guppies have been deliberately introduced for mosquito control and accidentally released from aquariums and ponds.
  • In the Top End of the Northern Territory, pond overflows during the wet season can carry guppies into drains and creeks.
  • Moving fish or water between waterbodies can spread them to new sites.

Control methods

  • Seek advice from the relevant state or territory fisheries or biosecurity agency before starting control, and use only methods approved for the site.
  • Where feasible and permitted, isolate or dewater the affected waterbody and remove fish using suitable fine-mesh nets or traps.
  • Dispose of captured fish securely and humanely; never release them into another waterway or pond.
  • Check treated sites repeatedly and remove any guppies found during follow-up surveys; report suspected new populations to the relevant agency.

Site hygiene and welfare

  • Drain water from boats, buckets, nets and other gear before leaving a site, and clean and dry equipment before using it in another waterbody.
  • Do not transfer live fish, aquarium contents or water between waterways.
  • Use methods set out in the national model codes of practice and standard operating procedures for the species.
  • Coordinate control with neighbours and the local government biosecurity plan, as isolated effort is quickly undone by reinvasion.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: General biosecurity duty. Not prohibited matter in NSW. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Not listed. Not found in the Western Australian Organism List. Check with DPIRD before moving or keeping it.
  • Tasmania: Not a declared pest. Not a declared pest or prohibited matter in Tasmania. Importing animals is still controlled by Biosecurity Tasmania.
  • Northern Territory: Not a declared pest. Not on an NT declared or prohibited list. Check with the NT Government before keeping, moving or releasing it.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • Queensland: Biosecurity Act 2014 (Qld), administered by Biosecurity Queensland (13 25 23)
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development
  • Northern Territory: Territory Parks and Wildlife Conservation Act 1976 (NT), administered by NT Department of Lands, Planning and Environment

Sources