The impact of catastrophic channel change on freshwater mussels in the Hunter River system, Australia: a conservation assessment

Abstract

Abstract Australia has a distinct suite of endemic freshwater mussel species, several of which are restricted to south‐eastern Australia, an intensively modified region supporting much of the nation's population and where pressures on freshwater ecosystems are increasing. Surveys were made of 78 sites in the Hunter River system to determine the distribution and abundance of the six mussel species occurring in the region, to identify threatening processes and to locate populations of high conservation value. Mussel populations were mainly distributed in the hydrologically stable southern Barrington rivers, where those in the Williams River have the highest conservation value. Strongholds for Hyridella drapeta were found in Wollombi Brook. Mussels were not detected at 40% of the sites, some of which supported mussels in the past. These were mainly reaches that have undergone river metamorphosis. Where found, most mussel populations had low densities and were highly fragmented. Major threats to these remnant populations are degradation of riparian and instream condition from agricultural activities, extreme climatic events (flood and drought) and the introduced macrophyte, Salvinia molesta. While threat mitigation can be achieved by habitat protection and strategies to reconnect mussel populations, managers are largely unaware of this invertebrate group. Formal recognition of regionally threatened mussel populations would do much to focus efforts on conservation. The proposed construction of a large dam on the Williams River is a potential threat to the most important mussel populations in the Hunter River system. Copyright © 2009 John Wiley & Sons, Ltd.