Murray-Darling Basin's Top Predator Returns

By Gavin McGrath

Topic: Fish

Murray cod is the top predator in the Murray-Darling Basin river system.

Murray cod can grow up to 1.8 meters long and weigh over 50 kilograms.

An adult Murray cod swims in rivers and creeks from Victoria to Queensland.

Even European carp stay away when a big cod is nearby.

Murray cod eat young carp.

But in the 1970s, they almost disappeared from their homes.

Now the big fish is coming back.

The decline

Murray cod and similar species used to be in charge of the rivers.

Overfishing, dams, and habitat damage made their numbers go down.

Commercial fishing hurt Murray cod numbers.

Many fishermen said Murray cod were hard to find in the 1970s and 1980s.

Murray cod are still vulnerable, but things are getting better.

Taylor Hunt with a Murray cod.

The recovery

A survey in the Ovens River found many Murray cod.

The Lindsay River and Mullaroo Creek cod have recovered.

Craig Eury and his daughter with a big Murray cod.

Dr. Hunt said the VFA's research and fishermen's feedback are positive.

There has been a big increase in Murray cod numbers.

People say they see cod everywhere.

Over 3,500 people responded to the VFA survey.

Most people support Murray cod conservation.

There are rules to protect Murray cod.

Angler Kate Norman with a big cod.

Murray cod numbers have increased in many Victorian rivers.

The Goulburn River, Ovens, and others have more Murray cod.

Dr. Hunt said the increases are due to fish production, habitat restoration, and fishing rules.

There is good news in New South Wales too.

Not all good news

The Darling River is in bad shape.

The Darling River has been neglected.

Where cod are gone, carp take over.

Dr. Rowland says native fish are hurt by river mismanagement.

The Darling River ecosystem is damaged.

Carp have changed the aquatic flora and fauna.

Stunning surveys

Electrofishing is a way to count fish.

It uses electricity to stun fish, then they are counted and released.

Electrofishing helps researchers count fish without harming them.

Surveys in Victoria show a positive picture for Murray cod.

But carp populations are a threat to other native fish.

European carp are a big problem.

When cod disappear, carp take over.

Murray cod can grow bigger than carp.

Carp are still a threat to other native fish.

Dr. Hunt wants more control over carp.

State of play

Murray cod numbers vary across states.

Lake Eildon has a healthy Murray cod population.

The Campaspe River has many Murray cod.

The Goulburn River has a flourishing population.

The Loddon River has more Murray cod.

The Lindsay River and Mullaroo Creek have recovered.

The Ovens River is healthy for Murray cod.

Voluntary catch-and-release helps Murray cod.

The Murrumbidgee River has a healthy population.

The Darling River has a big decline in Murray cod.

The Lower Murray River has limited breeding.

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