Quagga mussel

Quaga mussels (Dreissena bugensis) are a highly invasive freshwater bivalve native to the Southern Bug and Dnieper Rivers of Ukraine. They are closely related to zebra mussels but can tolerate a wider range of environmental conditions, including deeper and colder waters. Quagga mussels are prolific breeders and can rapidly colonise hard and soft substrates, causing significant ecological and economic damage.

Quagga mussels are not currently established in Australian waterways but pose a serious biosecurity risk. The invasive species has been introduced to North America, the UK, and outside its native range in Europe including west to the Netherlands and Germany. They can hitchhike on boats, fishing gear, aquaculture equipment, and aquarium products, and spread through ballast water or the release of contaminated water from aquaria.

Reporting

If you think you have seen a quaga 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

• Triangular shell with rounded or fan-shaped mouth.
• Typically 20-40mm, but can grow up to 50mm.
• Shell pale to dark brown with concentric rings.
• Underside rounded allowing them to sit upright.

Known locations

• Not in Australia

Habitat

• Freshwater lakes, rivers, reservoirs and canals.
• Tolerates a wide range of temperatures (0-30°C) and depths (<130m).
• Can colonise both hard and soft substrates.
• Often found on water intake structures, boats, docks and natural substrates.

Vectors

• Ballast water from ships.
• Contaminated boats, trailers and fishing gear.
• Aquarium plants and equipment.
• Movement of aquaculture stock.

Impacts

• Outcompetes native species for food and space.
• Alters nutrient cycling and water clarity.
• Fouls infrastructure such as water intake pipes, marinas, and vessels.
• Increases maintenance costs for utilities and industry.
• Sharp shells can pose risks to swimmers and shoreline users.
• Significant biosecurity risk to the aquarium and aquacultures industries.