A NSW Government website

Soft shell clam

Soft shelled clams (Mya japonica) are a large marine bivalve native to the northern hemisphere. In 2018 they were detected in eastern Tasmania having not previously been detected in Australia or other parts of the southern hemisphere.

They are considered an invasive species of concern due to their potential to outcompete native species for habitat.

The Soft shelled clam is listed as notifiable matter under the NSW Biosecurity Regulation 2017 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 and any person suspecting the presence of Soft shelled clam is required to notify an Authorised officer.


If you think you have seen Soft shelled clam in NSW, please take several clear, high resolution photos of the clam. For identification, we need to see the:

  1. Shell hinge showing difference in two valves
  2. Shell colour and growth lines
  3. Gapes at both ends when closed
  4. Shell shape (thin and oval)

Please send photos to aquatic.biosecurity@dpi.nsw.gov.au, along with details of when and where the clam was seen.


Oval shaped shells of Mya Japonica, soft shelled clam, top is hinged two halves showing outside chalky white, rough shell with uneven growth lines, underneath is the inside of the two halves which is smooth and white. To the right is up close photos of the hinge which has a scooped out projection on one side and a pit on the other. Key features:

  • Chalky white, rough shell (may be discoloured in black or red mud)
  • Valves are different – one side has a large scooped out projection at the hinge, the other has a pit
  • Shell shape thin and oval
  • Gape at both ends when closed
  • Uneven growth lines
  • Grows up to 15cm

Known locations:

  • Eastern Tasmania


  • Buried in mud, sand, gravel.
  • Lower intertidal and subtidal areas, and in estuaries.


  • Spread via vessels ballast water (larvae) and people illegally releasing adults


  • Competes with native clams for space
  • Reduces food availability for oysters, mussels and scallops
  • Change sediment composition affecting bottom dwelling communities

Similar native species

These native species may be confused with the Soft shelled clam. These species do not need to be reported.

Two halves of a Gaper clam (Lutraria rhynchaena) shell showing the off white elongated shell, with a brown skin on the right edge of the right half.Gaper clam (Lutraria rhynchaena)

Key features

  • Off white shell, often covered with a brown skin
  • Solid elongated shell
  • Gapes when shut
  • Concentric (fine evenly spaced) ridges
  • Up to 12cm long

Known Locations

  • NSW, Vic, Tas, SA and southern WA


  • Mud, sand and sheltered shores

Venus cockle (Venerupis galactites)Open two halves of the Venus cockle (Venerupis galactites) which are solid white, identical and with very faint growth lines.

Key features

  • Solid white shell
  • Identical valves that close completely
  • No scooped-out projection
  • Up to 5cm long

Known Locations

  • NSW, Vic, Tas, SA and southern WA


  • Sandy shores
  • Bays, estuaries and sheltered coasts

Lantern/Gaper shell (Laternula recta/rostrata)One half of a Lantern clam (Laternula gracilis) shell sitting open and facing upwards, Picture shows the shell as white in colour with clear concentric circles inside. There is a brown edge to the shell.

Key features

  • White in colour
  • Elongated shell
  • Gapes at both ends when closed
  • Concentric (fine evenly spaced) ridges
  • Up to 6cm long

Known Locations

  • NSW, Vic, and SA


  • Mud
  • Sand