Range decline and conservation status of Westralunio carteri Iredale, 1934 (Bivalvia:Hyriidae) from south-western Australia

Abstract

Abstract.Westralunio carteri is the only species of freshwater mussel found in south-western Australia and, owing to a lack of comprehensive information on its ecology, its conservation status has been speculative. To more accurately predict the true conservation status of this species, the historical and contemporary distributional records were modelled with environmental data that identified salinity, perenniality and total nitrogen as variables responsible for limiting the species' current extent of occurrence, inferring threatening processes. The species was found to have undergone a 49% reduction in extent of occurrence in less than three generations, due primarily to secondary salinisation. Current distribution is bounded by Gingin Brook in the north to the Kent, Goodga and Waychinicup Rivers in the South, within 50-100 km of coastal south-western Australia. Field observations indicated that W. carteri was almost never found at sites where mean salinity was >1.6 g L -1 . This was corroborated by laboratory tolerance trials that showed that W. carteri has an acute salinity tolerance (LD 50 ) of 1.6-3.0 g L -1 . Application of IUCN Red List criteria indicates that W. carteri qualifies for listing as vulnerable. Conservation management measures should focus on maintaining existing populations.

Upstream recolonization by freshwater mussels (Unionoida: Hyriidae) following installation of a fishway

“…While freshwater systems in some parts of the world contain multispecies mussel assemblages, the SWCDD has only one species, the endemic Carter's freshwater mussel (Westralunio carteri, Iredale 1934) (Walker et al, 2014). Research on this species was almost entirely neglected until recent work on its ecology, life history and conservation status (Klunzinger, 2012). It is a host generalist, and glochidiosis has been observed on seven of the region's 11 native fish, as well as four exotic species, but successful metamorphosis of glochidia has not been confirmed for most species, and host infestation rates vary among rivers and habitat types (Klunzinger, Beatty, Morgan, Thomson, & Lymbery, 2012b).…”

“…It is a host generalist, and glochidiosis has been observed on seven of the region's 11 native fish, as well as four exotic species, but successful metamorphosis of glochidia has not been confirmed for most species, and host infestation rates vary among rivers and habitat types (Klunzinger, Beatty, Morgan, Thomson, & Lymbery, 2012b). Although W. carteri is widespread and sometimes found in densely populated beds, it is experiencing a decline in distribution and abundance caused by stressors such as secondary salinity, dewatering, and instream barriers (Klunzinger, Beatty, Morgan, Pinder, & Lymbery, 2015). The extent of occurrence has decreased by 49% in less than three generations leading to the species being listed as Vulnerable (VU A2c) by the International Union for Conservation of Nature (IUCN, 2014;www.redlist.org;Klunzinger et al, 2015).…”

“…Although W. carteri is widespread and sometimes found in densely populated beds, it is experiencing a decline in distribution and abundance caused by stressors such as secondary salinity, dewatering, and instream barriers (Klunzinger, Beatty, Morgan, Pinder, & Lymbery, 2015). The extent of occurrence has decreased by 49% in less than three generations leading to the species being listed as Vulnerable (VU A2c) by the International Union for Conservation of Nature (IUCN, 2014;www.redlist.org;Klunzinger et al, 2015). Given that mussels are known to be integral ecological components in freshwater systems globally (Aldridge, Fayle, & Jackson, 2007;Atkinson & Vaughn, 2015;Vaughn & Hakenkamp, 2001), the importance of conserving W. carteri in this region is high.…”

Aquatic fauna refuges in Margaret River and the Cape to Cape region of Australia’s Mediterranean-climatic Southwestern Province

“…fishes, decapod crustaceans, and bivalve molluscs) being endemic to this region (Morgan et al, 2011(Morgan et al, , 2014a. Some of these endemic species have suffered dramatic range declines during the past century, mainly due to impacts associated with deforestation and agricultural development, whilst others are naturally restricted to narrow ranges (Morgan et al, 1998(Morgan et al, , 2011Unmack, 2001;Allen et al, 2002;Klunzinger et al, 2015). While land clearing is now less prevalent, the entire regional aquatic fauna is becoming increasingly jeopardised by a number of anthropogenic stressors and environmental threats, not the least of which is human-induced global climate change (Suppiah et al, 2007;Morrongiello et al, 2011;Beatty et al, 2014;IPCC, 2014;Morgan et al, 2014a).…”

“…The obligate freshwater macrofauna of the CCR comprises 13 native species (Morgan et al, 2011), four of which are listed as threatened under the Wildlife Conservation Act 1950 and/or Environment Protection and Biodiversity Conservation (EPBC) Act 1999. Two additional species are listed as 'priority taxa' by the Department of Parks and Wildlife, Government of Western Australia (Morgan et al, 2011(Morgan et al, , 2014a (Morgan et al, 2014b, Klunzinger et al, 2015. Notwithstanding the threat posed by climate change, these Threatened fauna of Australia's Cape to Cape region DOI: 10.29094/FiSHMED.2017.002 rare species also face a number of further specific threats (see Burnham et al, 2012;Duffy et al, 2014;Klunzinger et al, 2015).…”