Fishways in Australia – an adaptive approach to improving fish passage along a large river system
The Murray-Darling Basin is one of the world's great natural resources. Dominated by the 2,500km long Murray River. The basin supports over 40% of Australian agricultural production and is home to more than 2 million people. However, development within the basin has come at a price. Large-scale habitat degradation and water extraction have had a profound effect on the health of the river and its fish assemblages.
A significant amount of evidence, in the form of historical catch data, commercial fishing returns and data from long-term sampling programs have demonstrated significant declines in the range and abundance of many native fish species in the Murray River. As part of a broader strategy to rehabilitate native fish within the Murray-Darling Basin, the ‘Lake Hume to the sea project’, was recently established by the Murray-Darling Basin Commission (MDBC). The project aims to restore fish passage at 12 weirs along the length of the Murray River by constructing suitable fishways. To monitor the effectiveness of these new fishways, the MDBC established a tri-state research team composed of agencies from Victoria, New South Wales and South Australia.
Initially, fish were collected by boat electrofishing immediately downstream of weirs, to identify where fish are accumulating during upstream migrations. Interestingly, most fish were caught in areas of lowest flow over the weir crest. Subsequently, the monitoring team recommended the placement of fishway entrances in these areas accumulation. Fish were also trapped at the exit of each fishway to determine whether fish were successfully gaining passage. The first completed fishway passed a total of 13,238 fish, from 10 species, in its first 5 weeks of operation. All targeted species, ranging from 45-673mm, were successful in gaining passage and the fishway was dubbed successful.
The tri-state team will continue to sample at the remaining eleven weirs to ensure all other proposed fishways are equally effective and their entrance location is optimised. These data will be used to maximise the efficiency of future fishways so that fish passage improvements can be delivered to other sites in the Murray-Darling Basin.