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Rainbow trout (Oncorhynchus mykiss)

Rainbow trout were introduced to Australia and are widely stocked as a recreational fishing species. They can seriously affect native freshwater animals, including threatened galaxias, other native fish, frogs and crayfish.

Key facts

Type: Pest animal, fish.

Native to: Western coastal drainages of North America.

Established in: NSW, ACT, VIC, TAS, SA, WA.

Other names: Steelhead.

Identification

  • A medium-sized, laterally compressed fish with a slightly forked tail.
  • Adults usually have a prominent pink stripe along the sides, fine black spots on the body and tail, and a greenish or steely-blue back above a white belly.
  • The adipose fin is opaque with a black border.
  • Some lake-dwelling fish are silvery and lack the pink stripe; juveniles may have dark side blotches called parr marks.
  • Look-alike: Brown trout are similar in shape, but usually have reddish-orange spots on the sides and no spots on the tail; rainbow trout usually have a pink side stripe and black spots on the tail.

Where it lives

In Australia, rainbow trout live mainly in cool upland streams and lakes, including montane catchments and small headwater streams.

Why it matters

  • Rainbow trout have seriously reduced the distribution and abundance of native galaxiids in south-eastern Australia, including threatened species such as Barred galaxias and Stocky galaxias.
  • They prey on native fish such as Two-spined blackfish and Southern pygmy perch, and are suspected of harming Trout cod and Macquarie perch.
  • They also prey on threatened frogs, including the Spotted tree frog, and on spiny crayfish in upland waters.

How it spreads

  • Rainbow trout were introduced to Australia as fertilised ova from New Zealand, with the first Australian introduction in 1894 to the upper Murrumbidgee River.
  • Fisheries agencies in Victoria and New South Wales release approximately 2.5 million rainbow trout each year, and private hatcheries also make releases.
  • They can reproduce in suitable waterways and occupy connected streams within the catchments where they occur.

Control methods

  • Plan any control with the relevant fisheries or state government agency; handling, capture and removal may require permits and trained operators.
  • Where approved and suitable for the site, use targeted methods such as electrofishing, netting or trapping, with care to avoid harm to native fish.
  • Do not move or release captured trout into other waters, and follow local rules for their disposal.
  • Coordinate follow-up surveys and any repeat removals with the agency, and report a new detection to the relevant state fisheries or biosecurity authority.

Site hygiene and welfare

  • Clean and dry boats, nets, waders and other equipment before moving between waterways.
  • Drain water from boats and gear, and never transfer live fish or water between waterbodies.
  • 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.

  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • Australian Capital Territory: Biosecurity Act 2023 (ACT), administered by ACT Biosecurity
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • Tasmania: Biosecurity Act 2019 (Tas), administered by Biosecurity Tasmania
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development

Sources