It’s not there, but it could be: a renewed case for reintroduction of a keystone species into the Lower River Murray

ABSTRACT The extinction of species not only contributes to the loss of biodiversity but also the disruption of ecological interactions, processes and functioning. This is particularly true with the loss of keystone species where considerable ecological shifts are anticipated. Strongly justified and well-managed translocations are increasingly employed in an attempt to mitigate the loss of species. Once widespread, Murray Crayfish Euastacas armatus is an iconic and keystone species that has suffered a considerable decline in distribution and abundance, including in the Lower River Murray where it is assumed to be rare or locally extinct. In the present study, we conducted targeted sampling at 30 sites from Lower River Murray over 2013–2017 to confirm its local extinction and then propose a strategy to reestablish the species, which defines a meaningful objective and monitoring indicators to assess reintroduction success, identifies suitable receiving habitats and source populations, defines reintroduction scenarios (e.g. numbers and duration) required (based on population modelling) and discussion limitations. Although first proposed a quarter of a century ago, we are now in an informed position to achieve this reintroduction objective. Considerable ecological and social benefits are anticipated with the successful reestablishment of a keystone species into the Lower River Murray.