The dwarf galaxias (Galaxiella pusilla) is a threatened freshwater native fish from southeastern Australia. Along Dandenong Creek and its floodplain, as in many parts of its range, dwarf galaxias habitats have been degraded and fragmented as agricultural and urban areas have expanded. Their habitats (e.g. wetlands, swamps, billabongs and small streams) have been impacted by the creation of drainage channels, direct filling, piping, channel incision, concrete-lining, levees, vegetation clearing and changes in hydrology. The spread of invasive fish, especially eastern gambusia (Gambusia holbrooki), has placed further pressure on dwarf galaxias populations from predation and competition.
In 2013, Melbourne Water initiated a large-scale conservation project that aims to re-establish a sustainable dwarf galaxias metapopulation along an approximately 18 kilometre reach of Dandenong Creek in the south eastern suburbs of Melbourne. This project involves the creation or improvement of 20 inter-connected floodplain habitats, as well as fish breeding and translocation. Here we describe the habitat designs, particularly the importance of natural wetting and drying regimes, and the need for intermittent connectivity between habitats during floods for dispersal and colonisation. We balance the risk of invasion by exotic fish during floods with the need for dwarf galaxias dispersal by providing habitats with varying degrees of hydrologic connectivity. We also outline our approach for establishing a genetically diverse breeding stock and subsequent translocations, as well ongoing monitoring to assess the success of the project, and plans to reintroduce nationally threatened Yarra pygmy perch (Nannoperca obscura) into some of the habitats.