Charru mussel

Charru mussels (Mytella strigata) can be present at very high densities, reaching close to 100% cover, smothering benthic organisms, and have been observed competing with important aquaculture species for resources. They also attach to vessels, affecting performance and increasing fuel costs.

What to look for

Features:

Symmetrical shelled mussel, with an average size of 2.2-5cm
Individual mussels have a diversity of external colour schemes from black, brown, grey, orange and (rarely) green
M. strigata can be differentiated from similar species by its blueish to purplish opalescent interior and more angled shell valve
The species external shell pattern can include zig zags, spots or concentric bands
Two, small, obscure teeth present internally of the beak which is generally short and rounded
Yellowish flesh covering internal cavity of both shells.
Has a pitted resilial ridge along the dorsal margin internally (see Fig. 1)
The sculpture on the outside of the shell valves consists of weak concentric striations with fine radial ribs ventrally.

Fig. 1. 2g for location of resilial ridge (lig), 2h – example of pitted resilial ridge (prr). 2i – anterior margin of shell showing two small teeth (at). (Adapted image from Jayachandran et al.)

Where to look

Look in or around:

bedrock
rocky reef
artificial structures
soft sediment
on top of other sessile organisms

Likely habitats include:

intertidal and shallow waters of estuaries. This mussel can be found in a wide range of temperatures and salinity, generally favouring warmer waters.

Similar native species

These native species look similar to Charru mussel. They do not need to be reported.

Australian Blue Mussel (Mytilus galloprovincialis planulatus)

Features:

grows larger (typically 5-8cm, but can reach up to 15cm)
purplish black shell that is thicker and smoother
no pitted resilial ridge along the dorsal margin internally (Fig. 1. highlights a pitted example)

Habitat:

found in temperate zones usually in shallow water

Horse Mussels (Modiolus spp.)

Features:

brownish
have no teeth anteriorly
no pitted resilial ridge along the dorsal margin internally (Fig. 1. highlights a pitted example)
commonly have bristles on the outside of the shell

Flea Mussels (Xenostrobus spp.)

Features:

Typically small (to 0.5 cm)
blackish
have no teeth anteriorly
no pitted resilial ridge along the dorsal margin internally (Fig. 1. highlights a pitted example)
tends to be found higher up on the intertidal range, further out of the water than most other mussels

Scorched Mussels (Brachidontes spp.)

Features:

have forking radial ridges on the exterior of the shell
have no teeth anteriorly
no pitted resilial ridge along the dorsal margin internally (Fig. 1. highlights a pitted example)

Report it

See something unusual? Report it. Even if you’re not sure.

If you see something you think is a pest:

note the exact location (screenshot your map app or enable photo geotagging on your phone)
take a photo (use something for size reference, for example a coin)
contact your state or territory authority.

Report