Breaking down barriers to fish passage

Freshwater ecosystems are one of the habitats most threatened by human activity. The fish that inhabit these diverse freshwater ecosystems are a direct resource for humans, but their role in maintaining the health, functionality and ecosystem robustness is often ignored. In the Murray-Darling Basin, native fish are estimated to have declined to just 10% of pre-European levels. A major cause of fish population declines, and the cascading losses of freshwater biodiversity, is habitat fragmentation. This fragmentation is caused by artificial instream barriers such as dams, weirs and culverts (the pipes that carry water under roads, railways and embankments). There are over 5000 such physical barriers in New South Wales alone. These barriers prevent fish from migrating, accessing habitat and escaping predators. We have developed and tested a new culvert remediation design that significantly improves the performance of juvenile and small-bodied Australian fish species in high-velocity water flows.