Asian date mussel or bag mussel

Asian date or bag mussel (Musculista senhousia) is a relatively small species of saltwater mussel that grows quickly and can smother seabed life. It can affect the productivity of commercial fisheries and aquaculture.

The Asian date/bag mussel is listed as prohibited matter under the NSW Biosecurity Act 2015 and is considered a major threat to native fauna and the environment. It may not be brought into NSW or released or allowed to escape into any waters in NSW.

Reporting

If you think you have seen an Asian date/bag mussel in NSW, please take several clear, high resolution photos of the mussel. For identification, we need to see the:

  1. Shell colour and markings
  2. Mussel size – please include something for reference (e.g. a coin)

Please send photos to aquatic.biosecurity@dpi.nsw.gov.au, along with details of when and where the mussel was seen. Please note if the mussel was found as a clump of individuals.

Identification

Key features
  • Smooth fragile shell (crushes easily)
  • Olive green/brown in colour
  • Shell has zigzag markings and iridescent radiating bands
  • Up to 3cm long
  • Often in clumps of many individuals
Known locations
  • Found in Vic, SA, Tas and WA
  • Not known to occur in NSW
Habitat
  • Soft sediment or hard surfaces
  • Occurs just below the low tide level in aggregated clumps
Impacts
  • Fouls man-made structures
  • Forms dense mats competing with natives for food and space
4 different sized Asian date or bag mussels opened at the hinge and laid out showing the iridescent zig zagging bands of dark brown on a lighter tan colour.

Asian date mussel on the substrate. Darker colour than other but can still clearly see the zig zagging bands

Similar native species

Blue mussel (Mytilus galloprovincialis planulatus)

Key features:
  • Large fan shaped shell up to 12cm
  • Blue/black colour
  • Usually found in clumps
Habitat:
  • Sheltered and moderately exposed reefs, pylons and pontoons
  • Up to 15m depth
Asian-Green-Mussel-3

Brachidontes rostratus

Key features:
  • Long flat shell up to 4cm
  • Purple colour, regular rounded ribs
  • Usually found in dense clumps
Habitat:
  • Exposed rock platforms
Asian-Date-Muss-5

Hairy mussel (Trichomya hirsuta)

Key features:
  • Numerous hairs on lower half of shell
  • Up to 6cm
Habitat:
  • Exposed reef up to 15m depth
  • Common intertidally and subtidally
Asian-Date-Muss-4

Little black horse mussel (Xenostrobus pulex)

Key features:
  • Small shiny inflated shell up to 2.5cm in length
  • Black colour
  • Forms dense clumps
Habitat:
  • Exposed rocky shores
  • Mid intertidal
Asian-Date-Muss-6