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New Zealand mudsnail (Potamopyrgus antipodarum)

The New Zealand mudsnail was introduced to Australia, with records from Tasmania in 1872 and mainland Australia in 1895. It can become highly abundant and alter invaded aquatic ecosystems, so preventing its spread between waterways is important.

Key facts

Type: Pest animal, invertebrate.

Native to: New Zealand and adjacent islands.

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

Other names: Jenkins' spire shell, Hydrobia jenkinsi, Potamopyrgus jenkinsi.

Identification

  • Look for a small, solid, cone-shaped shell, usually up to 6–7 mm long in its non-native range.
  • The shell is light to dark brown and has 5–6 whorls that coil to the right.
  • Some individuals have spines in the middle of each whorl.
  • A solid operculum covers the shell opening; newborn snails are especially hard to detect because they are only about 0.4 mm long.
  • Look-alike: It can be confused with snails in the genera Plesiella, Belgrandia, Mercuria, Pseudamnicola, Colligyrus, Pyrgulopsis and Eremopyrgus, or with Fluminicola; reliable identification requires a specialist.

Where it lives

In Australia it has been reported in Tasmania and mainland Australia, and the species occurs in freshwater, brackish and salty waters, including streams, rivers, lakes, reservoirs, channels and estuaries.

Why it matters

  • At high densities, it can dominate secondary production and has been recorded at up to 500,000 snails per square metre in some US streams and 800,000 per square metre in a Swiss lake.
  • It can alter ecosystem nitrogen cycling by consuming green algae, which can increase nitrogen-fixing diatoms.
  • It can dominate mollusc communities and compete with native molluscs for space and food, reducing their growth; fish that eat many mudsnails may lose weight.

How it spreads

  • It can move upstream, drift downstream in currents or travel on floating aquatic plants.
  • Fish and birds can transport it; some snails survive passage through fish, and birds may carry them in their digestive tracts or on their legs and feathers.
  • Ballast water, boats, recreational vessels, aquatic plants, fish farms and anglers can spread it between waterways.

Control methods

  • Have suspected records confirmed by an expert, assess the feasibility of control, notify environmental agencies and establish monitoring.
  • Prevent transfers by treating ballast water, examining aquaculture products and quarantining live fish to reduce the risk of snails being carried in their digestive tracts.
  • Clean angling equipment and waders carefully, and use only legally approved control methods; chemical, temperature, desiccation and hydrocyclonic methods have been cited.
  • Eradication may be possible in isolated ponds or lakes and in fish-farm ponds, but is generally not feasible in rivers, streams or large lakes without unacceptable ecosystem damage.

Site hygiene and welfare

  • Carefully clean fishing equipment and waders before moving between waterways, and check boats and recreational gear for snails.
  • Do not rely on air exposure alone: the species can tolerate desiccation for several days.
  • 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
  • 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