Spread of the non-native redclaw crayfish Cherax quadricarinatus (von Martens, 1868) into natural waters of the Pilbara region of Western Australia, with observations on potential adverse ecological effects

The redclaw crayfish, Cherax quadricarinatus (von Martens, 1868), inhabits freshwater creeks and water bodies, and is native to the tropics of Queensland and the Northern Territory in Australia, as well as south-eastern Papua New Guinea. It has been translocated to other parts of Australia and around the world, often becoming established in the wild and potentially having negative impacts in invaded ecosystems. In north-western Australia, which lacks native crayfish, this species is known from the Ord River system in the Kimberley Region and from a water supply reservoir, Harding Dam, in the Pilbara region. Following a report of their presence in another area of the Pilbara region, Karijini National Park, a rapid assessment of crayfish occurrence was undertaken in and around Karijini and Millstream-Chichester National Parks. Redclaw crayfish were found at the known site within Karijini National Park and at a river pool west of the park. They were also detected in George River within Millstream-Chichester National Park. A separate baseline aquatic fauna survey, undertaken later as part of a mining environmental impact assessment, also recorded populations of the species in a tributary of the Fortescue River, located between these parks. The survey suggests that redclaw presence is associated with significant reorganisation of faunal and floral assemblages of river pools. With the new records presented here, the redclaw crayfish is now known from four catchments in the Pilbara Region, spread across three of the region's five drainage basins. Management options for this alien species are limited in this remote area, but would require further surveys to better understand their current distribution and dispersion capability, setting up public education campaigns and targeted control measures to minimise their spread to new catchments and their impact on high conservation value aquatic ecosystems.