Dams, weirs, barrages and a multitude of other regulating structures fragment riverine and estuarine ecosystems, and obstruct the movement of fish. Fishways are used worldwide to facilitate fish movement and partially mitigate the impact of barriers. Implementing effective fish passage is reliant on knowledge of migratory fish, including spatio-temporal patterns of movement, behaviour and physiology. The early history of fishway construction in Australia provides numerous examples of fishways that were designed in the absence of such scientific knowledge, and consequently, resulted in ineffective structures.
The Murray Barrages, at the terminus of the Murray-Darling Basin, are long (7.6 km collectively), low-level (~1 m) structures that separate the freshwater Lower Lakes from the Coorong Estuary and Southern Ocean, and represent significant barriers to fish movement. From 2003 to the present, the barrages have been the subject of substantial investment in fish passage, with a total of 11 fishways either completed or under construction. Throughout this period, monitoring and research have greatly improved knowledge of migratory fishes and fishway function at the site, leading to refinements in models of fish movement and fishway hydraulics. Ultimately, this has led to improved fishway design, as well as more environmentally sensitive operation of the barrages.
Whilst the collection of scientific data was fundamental in achieving this outcome, the dissemination of this information and collaboration between scientists, natural resource managers, engineers and river operators was equally important. We provide a summary of the science used to inform fish passage at the Murray Barrages with a focus on the importance of collaborative relationships and lessons learned throughout.