What is the Murray-Darling Basin (MDB)?

The Murray-Darling Basin (MDB) covers more than a million square kilometres, equivalent to 14 per cent of Australia’s total area. It is the 20th largest river catchment in the world (about the size of France and Spain joined together) and one of the driest.‍

Quick Facts:‍

The MDB contains 77,000 kilometres of rivers, with the river system flowing some 3,750 kilometres (from its headwaters to the sea).
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The three major rivers of the Basin are the Murray (2,530 km length), the Darling-Baaka/Barwon (2,740 km length) and the Murrumbidgee (1,690 km length); the longest rivers in Australia, and there are a further 21 major rivers in the Basin.
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It is home to 23 major river valleys catchments and more than 30,000 wetlands contained within the Basin.
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More than 2.6 million people live in the Basin and >3.6 million people (including the entire population of Adelaide which is not in the Basin) rely on water from the Basin rivers for many uses, including drinking, washing, recreation, tourism, farming and irrigation.
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Around 40 per cent of Australia’s agricultural produce comes from the Basin, with the value of its agricultural produce exceeding $24 billion each year (as at 2021).

A juvenile golden perch near Menindee Lake.

Fish in the MDB

The Murray-Darling Basin is home to 63 fish species, 51 of which are native, including the iconic Murray cod, along with smaller species such as galaxias, gudgeons, hardyheads and perch, plus many more!

The Basin also has a high proportion of alien species—13 of the 63 fish species are alien or translocated, and make up about 70 per cent of the numbers and 80–90 per cent of the biomass of fish in many of the Basin’s rivers.

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Why have fish populations declined in the Basin?

Various factors have contributed to the decline in native fish numbers over the period of European settlement, and the impacts of climate change are posing an additional significant risk to several species currently and into the future. The nine major threats (historic and current) to native fish include:

Climate change and extreme events

Changes to rainfall, flow & temperature patterns & the increased occurrence of extreme events (fire, flood, drought) that will alter freshwater & riparian habitats.

Flow regulation

Loss of water to other uses (agriculture, water supply); loss of critical low flows; loss of flow variation, flow seasonality and low to medium floods; permanent flooding & high water (e.g. weir pools); increased periods of no flow; loss of sediment-flushing flows.

Habitat degradation

Damage to riparian zones (tree clearing, willow & weed invasion); removal of in-stream habitats (e.g. fallen timber); sedimentation smothering instream habitats & filling pools.

Lowered water quality

Increased nutrients, turbidity, sedimentation & salinity; artificial changes in water temperature; pesticides & other contaminants.

Barriers to movement

Impediments to fish passage from the construction & operation of dams, weirs, levees, culverts, etc.; non-physical barriers such as increased velocities, reduced habitat extent & quality, water quality & thermal pollution (changes in water temperature).

Alien Species

Competition and/or predation by Carp, Eastern gambusia, Oriental weatherloach, Tilapia, Redfin perch & trout and translocated native species such as Climbing galaxias.

Diseases and parasites

Outbreak and spread of Epizootic Haematopoietic Necrosis Virus (EHNV), anchor worm & other viruses, diseases & parasites.

Exploitation

Recreational & historical commercial fishing pressure on depleted stocks; illegal fishing.

Translocation and stocking

Loss of genetic integrity & fitness caused by inappropriate translocation & stocking of native species; competition & predation by stocked species outside their natural range.

Genetics

Many threatened species are slowly losing genetic diversity, reducing their capacity to adapt to future threats (e.g. climate change).

Learn More About Threats To Our Native Fish

What's being done to recover our native fish?

The Native Fish Recovery Strategy is a joint Australian Government initiative developed in partnership with Basin state governments, Aboriginal Nations and the wider community. It sets out a program of actions involving government, communities and industries across the Basin to ‘recover native fish for future generations’.

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Discover related content on the Finterest website, your home for stories about our Australian Freshwater Native Fish.

Since 2013, Finterest has been sharing great stories and information about the work being undertaken across Australia to bring back our native fish, particularly across the Murray-Darling Basin. It's a great source of inspiration and knowledge for anyone interested in Australian freshwater fish and native fish, and is updated with new stories regularly.

We Acknowledge and Respect the Aboriginal and Torres Strait Islander Peoples as the Traditional and Continuing Custodians of these lands, seas and skies.

We recognise and honour the traditional and continuing custodians of the Country on which we work, learn and live. We respect and learn from Elders past, present and emerging, valuing their knowledge, insights and connections to the waterways we love and care for.

Fishes of the
Murray-Darling Basin

The Murray-Darling Basin

The beating heart of Australia's waterways.

What is the Murray-Darling Basin (MDB)?

Fish in the MDB