Carter's freshwater mussel - Westralunio carteri

This page was created in partnership with the Freshwater Fish Group and Fish Health Unit at Murdoch University

Identification

Carters freshwater mussel Westralunio carteri

The only large bivalve inhabiting freshwaters of the south-west region, growing to over 100 mm, however usually seen between 40 and 80 mm.

Colour generally from black to dark brown through to reddish-brown, and often covered in a thin layer of periphytic growth (e.g. algae) which also binds silt.

Commonly has a worn down section at the thickest part of its shell, near the hinge, where the pearly, calcium-carbonate material that forms the shell can be seen.

Distribution

Coastal freshwater rivers and lakes between Moore River in the north and the Waychinicup River in the south.

Museum records indicate that the species may once have ranged as far north as the Gascoyne River and east to Esperance. A detailed study of the contemporary locations of the species can be found in Klunzinger et al. (2015). http://www.publish.csiro.au/zo/ZO15002

The study demonstrated that its range has declined by 49% in less than 50 years, principally because of secondary salinisation and reduced water flow from a drying climate.

View map

Habitat

Occurs in greatest abundance in slower flowing waters where sediments are stable and soft enough to allow the species to burrow (<10 cm depth) but are usually visible from the surface; allowing the species to position themselves to best facilitate filter feeding. However, it also occupies lentic systems including large water supply dams and even on-stream farm dams.

Biology

A complex life cycle involving a parasitic larval stage. The larvae, or glochidia, attach to a fish host for several weeks to months (appears as small cyst typically on the fin or gills of fish), during which time they metamorphose into the juvenile form (resembling small adults). These drop off the fish host and the juvenile mussel then begins its life on the sediment.

The period of attachment to a fish host functions as an effective dispersal mechanism for this otherwise sessile animal. This highlights the importance of a robust ecological system for the survival of this species.

Low salinity tolerance (above 3 mg/L being lethal)

Conservation status

Threatened species: listed as Vulnerable (EPBC Act 1999 (Commonwealth) and Biodiversity Conservation Act 2016 (State, Western Australia)), based on a decline in the distribution of the species in the last few decades. Vulnerable (IUCN 1994).

Further information

Contact the Departments River Science team, or the Murdoch Freshwater Fish Group via email: fish@murdoch.edu.au, or go to their website: www.freshwaterfishgroup.com

Freshwater Fish Group Murdoch University    Harry Butler Institute