The bigger picture

River regulation and instream barriers can affect natural river processes and the movement of fish. The conditions produced often benefit some of the most invasive species on the planet, such as the common carp. The natural migratory and breeding cycles of native fish can also be interrupted.

The Murray Darling Basin has over 3,600 instream barriers, such as dams, weirs and flow regulators. In 2001, the Murray Darling Basin Authority began working to mitigate the impacts of major instream barriers on fish movement.

An ambitious fishway construction program has now helped re-establish longitudinal connectivity to around 2,235km of the Murray River.

Catchment management authorities, water authorities and local councils are now working toward a similar goal. The North East Catchment Management Authority is improving fish passage at a number of instream barriers by constructing fishways and fish-friendly structures along the Ovens and Mitta Mitta rivers.

Both of these rivers are known for their recreational fish species, such as brown trout, Murray cod and golden perch. These fish require movement throughout the river to complete their life cycle. The Ovens and Mitta Mitta rivers are also important habitats for threatened species, such as trout cod and Macquarie perch. Blackfish and various Galaxias species are also present.