Zebra mussel

Zebra mussels (Dreissena polymorpha) are a highly invasive freshwater mollusc native to Eurasia. They are recognised globally for their ability to rapidly colonise hard surfaces, outcompete native species, and cause significant ecological and economic damage. In the United States, millions of dollars are spent annually to remove zebra mussels from the water intake systems of power stations and drinking water plants.

Additionally, growth of zebra mussels along shorelines has been known to present human health risks and could cause lacerations from the sharp shells.

Zebra mussels are not currently established in Australian waterways, but they pose a serious biosecurity risk. They can hitchhike on aquarium fish and aquatic plants, in particular in products such as “moss balls”, and spread through the release of water from aquaria into the environment.

Reporting

If you think you have seen a zebra mussel in NSW, please take several clear, high-resolution photos of the mussel. For identification, we need to see the:

1. Shell size – please include something for reference (e.g. a coin, ruler)
2. Shell colour and markings
3. If possible, an internal view of the shell showing the ‘beak’ (pointed end).

Please report via the 24 hour EAD Hotline and send photos to aquatic.biosecurity@dpird.nsw.gov.au, along with details of when and where the mussel was seen.

Identification

Key features

• Freshwater mussel densely colonised by zebra mussels.
• Typically the size of a fingernail, reaching a maximum size of 50 mm.
• D-shaped shells, with a flat underside.
• Usually striped with dark and light bands, resembling a zebra pattern.
• Shells are hard and may feel sharp to the touch.

Known locations

• Not in Australia

Habitat

• Can inhabit a wide range of substrates including rock, metal, wood, glass, vinyl, rubber, fibreglass, paper, and aquatic plants.
• Tolerates fresh to brackish water.
• Forms dense mats in muddy or sandy substrates.

Vectors

• Aquarium “moss balls” – freshwater algae used for ornamental displays.
• Movement of aquaculture stock, vessels, and recreational fishing equipment.
• Release of aquaria products or waste into waterways.

Impacts

• Outcompetes native species for food and space.
• Alters habitat structure and water chemistry.
• Fouls infrastructure such as water intake pipes, marinas, and vessels.
• Causes economic damage to utilities and aquaculture.
• Presents human health risks due to sharp shells along shorelines.
• Significant biosecurity risk to the aquarium industry.

More information

Zebra mussel alert