Conservation status of Westralunio carteri Iredale (Bivalvia: Hyriidae)
Klunzinger, M.W., Beatty, S., Morgan, D. and Lymbery, A. (2012) Conservation status of Westralunio carteri Iredale (Bivalvia: Hyriidae). In: Molluscs 2012: Meeting of the Malacological Society of Australasia, 3 - 6 December, Melbourne, Australia.
The freshwater mussel Westralunio carteri Iredale, 1934 (Bivalvia: Hyriidae) is the only hybrid species found in south-western Australia (SWA). Its disappearance from salinised waterways was first noted in the mid-1970s. The species was nominated to the IUCN Red List in 1996 as ‘Vulnerable’ and as a ‘Priority 4’ (P4) species by the Western Australian Department of Environment and Conservation (DEC) following a biodiversity survey of the agricultural zone of SWA. From 2009 to 2012, we compiled a database containing 1114 records of W. carteri from 199 museum records, six publications, five technical reports, 60 public surveys and 380 field surveys. From the database, we mapped historic (pre-1990) and current presence/absence and constructed ‘alpha-hulls’ to determine historic and current extents of occurrence (EO0), using IUCN guidelines. We estimate historic EOO to be 43,579.8 km2 and current EOO as 16,011.9 km2; a decline of 63.3% in the last 50-100 years. In salinised rivers within the region, only empty shells of W. carteri could be found. Analysis of the environmental determinants of current distribution identified variables affecting stream flow and likelihood of drying as explaining most of the variation in the current distribution data, while the difference In distribution between historical and current records was principally explained by stream salinity. Acute salinity tolerance experiments indicated that the mussel was extremely sensitive to Increasing salinity, with values of 1.3 to 3.0 g L-1 and LD values of 3.6 to 4.3 g L-1 for mussels sourced from spring-fed and mildly brackish localities, respectively. In January 2011, W. carteri was changed to ‘Least Concern’ on the IUCN Red List, but remains a P4 species by DEC. We use the results of our study to argue for a re-evaluation of the conservation status of W. carteri.
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