Freshwater mussels are declining globally, and effective conservation requires prioritizing research and actions to identify and mitigate threats impacting mussel species. Conservation priorities vary widely, ranging from preventing imminent extinction to maintaining abundant populations. Here, we develop a portfolio of priority research topics for freshwater mussel conservation assessment. To address these topics, we group research priorities into two categories: intrinsic or extrinsic factors. Intrinsic factors are indicators of organismal or population status, while extrinsic factors encompass environmental variables and threats. An understanding of intrinsic factors is useful in monitoring, and of extrinsic factors are important to understand ongoing and potential impacts on conservation status. This dual approach can guide conservation status assessments prior to the establishment of priority species and implementation of conservation management actions.

The conservation biology of Australasian freshwater mussels is hindered by While the need for a taxonomic revision is paramount, progress in conservation may 33 depend also upon involving the wider community.

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.