Japanese mystery snail
Japanese mystery snail (Cipangopaludina japonica) is a large, invasive freshwater snail native to Japan, Korea, and Taiwan. It has been introduced to other regions through illegal release from the aquarium trade and food markets in addition to illegal stocking. This species gives birth to up to 120 young, allowing it to rapidly outcompete native molluscs for space and food resources, modifying environmental conditions. It is a known host for parasitic nematodes.
The Japanese mystery snail was introduced to North America and Canada in the 1940s and has since become prolific nuisance to fishermen.
Reporting
If you think you have seen a Japanese mystery snail in NSW, please take several clear, high-resolution photos of the shell. For identification, we need to see the:
- Shell size – please include something for reference (e.g. a coin, ruler)
- Shell shape and colour
- Close-up of the shell opening and operculum (lid-like structure).
Please send photos to aquatic.biosecurity@dpird.nsw.gov.au, along with details of when and where the snail was seen.
Identification
Key features
- The shell is smooth and somewhat spherical with 7-8 whorls
- Typically, 22-46mm wide and 30-65mm long with a large oval opening
- Colouration varies from light to dark brown as the snail ages
- Concentric markings on operculum (lid-like structure)
Known locations
- Not known to be established in Australia
Habitat
- Found in freshwater lakes or slow-moving rivers with medium to high nutrient levels
- Prefers mud, sand, or silt substrates
- Often on aquatic plants or buried in sediment in less than 4m of water
Vectors
- Illegal release from aquarium and aquatic plant trade
- Illegal release from live food trade
- Illegal stocking as a food source
Impacts
- Outcompetes native species for food and space.
- Disruption of net-based fishing methods
- Fouls infrastructure such as water intake pipes
- Increases maintenance costs for utilities and industry.
Similar native species
These native species may be confused with the Japanese mystery snail. These species do not need to be reported to biosecurity.
Billabong banded snail (Notopala kingi suprafasciata) (critically endangered)
Key features
- Outer shell is often polished and spherical, green to brown in colour
- Up to 32mm in size
- Lacks dark lines between the 5 whorls, but has bands diffused along shell circumference
Known locations
- Large ponds and billabongs throughout western New South Wales
Habitat
- Muddy sediment within waterbodies
Hanley’s river snail (Notopala hanleyi) (critically endangered)
Key features
- Outer shell is smooth and spherical, green to brown in colour
- Maximum width of 25mm
- Lacks dark lines between the 5 whorls
Known locations
- Murray River catchment, Lachlan and Murrumbidgee Rivers included
Habitat
- Attached to logs or rocks, or in sediment along riverbanks
- Artificial irrigation pipeline environments
Darling river snail (Notopala sublineata) (critically endangered)
Key features
- Outer shell is smooth and spherical, green to brown in colour
- Maximum width of 25mm
- Lacks dark lines between the 5 whorls
Known locations
- Formerly Darling River and associated tributaries, now restricted to irrigation pipes near Bourke, Brewarrina, and Walgett.
Habitat
- Attached to logs or rocks, or in sediment along riverbanks
- Artificial irrigation pipeline environments