Changes in the distributions of freshwater mussels (Unionoida: Hyriidae) in coastal south‐eastern Australia and implications for their conservation status

Abstract

1. The conservation of freshwater mussels is neglected in Australia, and poor historical data may mask trends in species' range and abundance. A combined-evidence approach using published data, targeted surveys, historical records and a GIS-based, reach-scale measure of physical habitat quality was used to assess trends in the distributions of nine species in the south-eastern coastal region.2. Geomorphic impairment is widespread in upland and lowland streams, but not in rugged escarpment zones, with 16.8% of rivers in 'poor' geomorphic condition, 39.6% in 'moderate' condition and 43.6% of rivers in the region in 'good' condition.3. Reductions of 44.4, 12.5 and 39.7% in site occupancy over the past 200 years were estimated for Hyridella depressa, Hyridella drapeta and Hyridella australis from logistic regression models of occupancy versus river geomorphic condition. Nonetheless, all species remain widely distributed and qualify as 'least concern' according to IUCN Red List criteria.4. Hyridella narracanensis and Hyridella glenelgensis have fragmented or limited ranges and are vulnerable to threats, and both appear to meet IUCN Red List criteria for threatened species. The former species is listed as 'data deficient' but arguably should be 'vulnerable' as documented here. The latter species is not included on the IUCN Red List. Under the Australian EPBC Act (1999), H. narracanensis is not listed while H. glenelgensis is listed as 'critically endangered'. 5. The Tasmanian endemic, Velesunio moretonicus, shows some evidence of decline but its population status is equivocal owing to the lack of monitoring data. It would qualify as 'data deficient'. The three remaining species, Cucumerunio novaehollandiae, Alathyria profuga and Velesunio ambiguus are widely distributed and show no evidence of decline.6. Additional surveys are needed to determine the current status and spatial distribution of freshwater mussel species in the region, and to establish baselines for future monitoring.

Freshwater mollusc assemblages and habitat associations in the Danube River drainage, Hungary

“…Indeed, there is a general lack of data concerning basic ecological characteristics such as density, biomass and biotic and abiotic requirements for each species and the Hungarian Danube River Drainage is no exception. This kind of information is also lacking worldwide (Jones and Byrne, ; Lopes‐Lima et al ., ) although it should be the basis of effective conservation efforts.…”

Research priorities for freshwater mussel conservation assessment

“…Predicting suitable habitat and the potential distribution of freshwater mussel species is a high priority for conservation (Jones and Byrne, 2014). However, predicting freshwater mussel diversity hotspots differs from assessments for many other aquatic and terrestrial species because it is easier to locate a population than to predict its distribution, and is dependent on the characteristics of the whole catchment (Abell et al, 2006;Graf and Cummings, 2011).…”

Freshwater mussels in Mediterranean‐climate regions: Species richness, conservation status, threats, and Conservation Actions Needed

“…Four mussel species occur within SA ( Alathyria jacksoni , Hyridella glenelgensis , Hyridella narracanensis , and Velesunio ambiguus ), and it is the only southern hemisphere med‐region with multiple species. Alathyria jacksoni and V. ambiguus are wide ranging in the eastern states of Australia, with most of their distribution falling outside of the med‐region (Jones & Byrne, 2014; Walker, Jones & Klunzinger, 2014a). Both species have shown some evidence of decline within the med‐region, and V. ambiguus has been lost from parts of the lower Murray River in SA as a result of increasing salinity caused by evapoconcentration (Kingsford et al, 2011; Walker, 2017).…”

“…Hyridella narracanensis is rare and sparsely distributed in coastal south‐eastern Australia, and it is only known from one location within the med‐region, whereas H. glenelgensis is endemic to a single freshwater tributary of the Glenelg River in western Victoria (Playford & Walker, 2008; Jones & Byrne, 2014). Preliminary genetic evidence suggests that H. glenelgensis and H. narracanensis are morphological variants of one species (Playford & Walker, 2008).…”