Rites of Passage: the role of riverine connectivity in habitat restoration
Non Technical Summary
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.
Historically, fishways were constructed on steep slopes and targeted stronger-swimming recreational species, as these were thought to be the only fish that migrate. However, recent research suggests that small-bodied species with poorer swimming abilities also have an upstream migratory phase. Therefore, biologists and engineers adopted an 'entire community' approach to fish passage rehabilitation and developed a new range of fishway specifications to cater for fish as small as 45mm.
The first completed fishway passed a total of 3,818 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. NSW Fisheries, in conjunction with staff from Victoria and South Australia, will continue sampling at the remaining eleven weirs to ensure all other fishways are equally effective.