Recent flooding has resulted in hypoxic blackwater events, which is having a devastating effect on fish along the Murray River in New South Wales. OzFish have been working alongside authorities to deploy our Fish Emergency Recovery Team to save as many affected fish as possible.

Fish Emergency Recovery Teams have been rescuing distressed native fish and crayfish across states and borders, relocating them to safer waters. Indicators of stress in native fish include discolouration, gasping for air and appearing at the water’s surface.

Recovery and relocation activities should only be done by authorised parties. It’s illegal to relocate fish and aquatic life without approval – picking them up or moving them may cause them more distress.

OzFish have been given the authority to rescue and relocate fish and crayfish by the relevant government agencies in each state. You can get involved directly in the emergency response by joining one of our Fish Emergency Recovery Teams.

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What is a blackwater event?

Blackwater events occur naturally when floods wash leaves, grass and other organic materials off riverbanks and floodplains into waterways. In small amounts, this is an excellent food source for fish and other aquatic organisms. However, when floods of a significant magnitude occur, the volume of organic matter being swept into waterways increases and becomes a problem.

When the organic material begins to decompose, the bacteria on it uses up the oxygen in the water and fish have less dissolved oxygen available to them. This can happen across the floodplain and then move into the river, or within the river itself. 

 

It is this deoxygenated water that has led to the heartbreaking scenes of large Murray cod and Golden perch floating lifeless, and Murray crayfish walking from the water in an effort to survive.

Once out of the water, taking sanctuary on riverbanks, trees, or logs, crayfish are extremely vulnerable to land-based predators and illegal harvesting.

What is the long-term impact?

We expect this event will have an ongoing negative impact on crayfish and native fish populations in the affected stretches of river.

The timing of this event is likely to worsen its impact too – with this being when crayfish eggs begin to hatch. Mature female crayfish carry their eggs and juveniles under their tails which means these are also at high risk when the female is forced to exit the river.

What can be done to help the recovery?

Our Fish Emergency Recovery Team will seek to save and relocate as many native fish and crayfish as possible, with these being re-introduced to the river when it is safe.

In addition to saving them from the event, OzFish will be working hard to ensure healthy habitat is restored to the hardest hit areas.

Equally important is playing a role in the monitoring of your local waterway. By gaining a greater understanding of how rivers respond to floods, it helps to inform the review and adaptation of river management in the future. We want you to watch out for any fish kills in your local area and report it to the relevant local authority, NSW (1800 043 536) or the Victorian Government (1300 372 842). Alternatively, contact us here at OzFish and we’ll do it for you.

Latest News

4 NOV 2022 | Helping with fish rescues in the Murray River

The blackwater events resulting from the recent floods are unfortunately continuing to have a terrible impact on native fish living along the Murray River. Working together with an alliance of like-minded organisations, our Fish Emergency Recovery Teams are set to go into action to save as many affected fish as possible. We learned back in 2019/20 with the drought rescues that there is power in our collective response when it’s coordinated and collaborative.

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27 OCT 2022 | OzFish response to blackwater event in the Murray

It’s always a distressing moment when we have to deploy our Fish Emergency Recovery Teams. Doing so is always a last resort and indicates that native fish are in distress and under severe and imminent threat. Unfortunately, that’s the current situation in Echuca and Swan Hill along the Murray River in New South Wales. A hypoxic blackwater event has occurred and is having a devastating effect on fish in the waterway.

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The OzFish Fish Emergency Recovery Teams are working in conjunction with NSW DPI Fisheries, the Murray Darling Basin Authority, Mallee Catchment Management Authority, the Victorian Fisheries Authority, First Nations communities, aquaculture organisations and community members, with funding support from our major partner BCF – Boating Camping Fishing.