Distribution of Westralunio carteri Iredale 1934 (Bivalvia: Unionoida: Hyriidae) on the south coast of southwestern Australia, including new records of the species

Westralunio carteri Iredale 1934 is the only hyriid in southwestern Australia. The species was listed as ‘Vulnerable’ by the IUCN, due to population decline from dryland salinity, although the listing was recently changed to ‘Least Concern’. The Department of Environment and Conservation lists the species as ‘Priority 4’, yet it lacks special protection under federal or state legislation. Accuracy in species accounts is an important driver in determining conservation status of threatened species. In this regard, discrepancies in locality names and vagary in museum records necessitated the eastern distributional bounds of W. carteri to be clarified. Here we present an updated account of the species’ distribution and describe two previously unknown populations of W. carteri in the Moates Lake catchment and Waychinicup River, resulting in an eastern range extension of 96–118 km from the Kent River, formerly the easternmost river where W. carteri was known. For mussel identification, samples (n = 31) were collected and transported live to the laboratory for examination and internal shell morphology confirmed that the species was W. carteri. Due to an acute salinity tolerance of 3.06 g/L (LD 50 ), the species is unlikely to exist in catchments east of the Waychinicup River where salinities are known to be as high as 45 g/L. The current study clarifies the eastern distribution of W. carteri and will allow monitoring of its range decline to be made in the future.