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Ace Press News From Cutting Room Floor: Published: May.30: 2023:
#AceNewsDesk - How did the latest mass fish kill happen? How does it differ from previous events and how can we stop it happening again?
The scenes come just four years after the area witnessed a series of mass fish kills with millions of native fish perishing, prompting an independent inquiry.
Fish kill Blue Green allege
So what's behind this current event? How and why did it happen, and could anything be done to stop it happening again?
What happened?
On Friday, locals in Menindee reported seeing millions of dead fish in the river. State government authorities confirmed an unfolding fish-kill event.
Most of the fish affected are bony bream, but other native species caught up in the carnage include Murray cod, golden perch, silver perch and the invasive European carp.
Authorities and locals have said the current event has seen more fish die than in the previous mass fish kills in the summer of 2018-19.
The investigation by authorities includes toxicology and pesticide tests, but there is broad agreement the deaths were probably related to a drop in oxygen levels in the water.
Experts have said it's likely a series of events has caused the fish deaths.
The region experienced major flooding in January, after three relatively wet years.
Soil and vegetation would have been washed into the river, causing bacteria and micro-organisms to grow – this uses up oxygen.
In recent days, heatwave conditions have swept across the area with temperatures above 40C. Warmer water holds less oxygen, worsening conditions.
Where did all the fish come from?
Fish kill Blue Green allege
Murry River
For there to be a mass fish death, there needs to be masses of fish.
The wet conditions over the past three years have given native fish a chance to reproduce. The flooding in January meant more water in the river and even more chance to breed.
"There's a good few years of fish and they will have been hanging out for quite some time in the channels and lakes. The biomass has been building for a couple of years," Prof Fran Sheldon, of Griffith University's Australian Rivers Institute, says.
"Bony bream are the kind of fish that you think will die just when you look at them. They're not particularly tolerant to low oxygen. But they breed really rapidly and they'll have grown in massive numbers."
The bream are known for their "boom and bust" cycles that respond to the conditions in the river.
Sheldon says even without the heatwave, it is likely some of the bream would have perished because there would not have been enough food in the river to sustain that many fish.
But critically, Sheldon says the bream tend not to move large distances so – unlike other native species like the cod and perch – they will not have been able to swim away to better parts of the river as oxygen levels dropped.
Once the fish start to die, the decomposition further pulls oxygen from the water, exacerbating the problem.
What is being done?
Fish kill Blue Green allege
Murry River
Late on Saturday, the NSW police set up an emergency operations centre in the town to coordinate work by state government departments, WaterNSW and the Central Darling shire council.
Assistant commissioner Brett Greentree, overseeing the centre, said on Monday they were speaking to contractors to physically remove "as many of the dead fish as possible". Some of these contractors were also used to remove fish in 2018 and 2019.
Nets would be used to remove the fish, which would be trucked to a landfill site for burial.
The river is a key water supply for the town and Greentree said water from a treatment plant was still of "high quality".
But he said water would be trucked in for those people who usually drew water direct from the river.
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Contractors were still en route to the area. But Sheldon said in a matter of days the dead fish would probably sink, where they would continue to decompose.
A spokesperson for the NSW Department of Planning and Environment said water had been released from Lake Pamamaroo after tests showed oxygen levels downstream of Menindee were approaching critical levels. Some large-bodied fish – such as golden perch – were dead or dying.
The spokesperson said: "Our early readings indicate the [dissolved oxygen] levels have significantly improved and we believe many fish have been saved as a result.
"We are very aware of the importance of balancing water releases to improve environmental outcomes while also maximising water storage ahead of any future drought."
What else could be done to help the fish?
Sheldon said: "The dead fish will just decompose or be eaten. The big question is the fish that remain."
The Darling-Bakka River is part of the sprawling Murray-Darling Basinthat covers 14% of Australia.
The basin includes two major rivers – the Murray and Darling – as well as 20 smaller but significant other rivers. The whole system is heavily modified.
Since the sheep farming boom of the 1800s, the catchments have been cleared of vegetation.
As other farmers moved in – including cotton, rice and almonds – more locks and weirs were built to store and use water.
In the northern parts of the basin above Menindee, rainfall that would have flowed down the rivers is extracted under licence from WaterNSW and used for agriculture.
In the coming months, Sheldon said regulators will need to make sure enough of any further rainfall is allowed to flow down the river. The commonwealth could release water held in lakes – so called environmental water – to help fish downstream of Menindee.
Sheldon, a member of the independent panel that investigated the Menindee fish deaths in 2018-19, said: "Irrigators will want to grow cotton, but how do you manage the system that allows those fish to breathe a bit. The challenge is doing those two competing things."
The major uncertainty for those surviving fish is rainfall.
After three years of rain, the Bureau of Meteorology has said there is now a 50/50 chance of an El Ni̱o developing this summer Рa key driver of Australia's climate that means greater risks of extreme temperatures and drought.
Is this a re-run of 2019?
Not quite. The fish kills in the region in late 2018 and early 2019 came after several years of drought-like conditions.
There was less water in the river system and many long-lived native species like Murray cod became stuck in isolated areas and were unable to escape when temperatures rose, ultimately starving the fish of oxygen.
One slight note of optimism, says Sheldon, should be that the fish deaths this week illustrate – perhaps perversely – that native fish in the river system can still recover their numbers if they have enough water.
ABC reports on the Promise check: 450GL of water for South Australia under the Murray-Darling Basin Plan: Friday 19 May 2023 at 1:38am
Management of the rivers of the Murray-Darling Basin has been one of the most politically vexed environmental policies since federation.
In 2012, the federal, Queensland, NSW, Victorian, South Australian and ACT governments agreed to establish the Murray-Darling Basin Plan.
"At its heart, the Basin Plan sets the amount of water that can be taken from the Basin each year, while leaving enough for our rivers, lakes and wetlands and the plants and animals that depend on them," says the authority set up to manage the plan.
South Australia has been pushing for the full implementation of the plan, including "recovery of 450 gigalitres of water for the environment through projects that reduce water losses through irrigation, commercial use and public water supply infrastructure".
At a media conference in Adelaide during the election campaign, then opposition leader Anthony Albanese said Labor supported South Australia's position.
"An Albanese Labor government will make sure that the 450 gigalitres is delivered and we'll have policies in place to deliver on the full Murray-Darling Basin Plan," he said.
Professor of Economics at the University of South Australia and water policy expert Lin Crase told Fact Check the Basin Plan was devised to return water to the environment to offset the impacts of water diversions to dams, irrigation and other uses.
Under the plan, this would in part be achieved via "voluntary buy-back schemes where only those willing to sell would offer their water to the Commonwealth," he said.
In addition to water-buy backs, the plan called for a further 450 gigalitres of "environmental water" to be returned to the basin's river system through "water saving projects" funded by the Commonwealth and managed by the states and territories, Professor Crase added.
Under the Basin Plan, this target should be achieved by June 30 2024.
According to the Parliamentary Library, the additional environmental water flow was a compromise negotiated by the federal government to satisfy the South Australian government which argued for higher allocations of water in the system than their upstream NSW and Victorian counterparts.
During the press conference, Mr Albanese said South Australia had been "promised" the 450 gigalitres and the state's agreement to the plan was contingent on its delivery.
"If you don't have those environmental flows, the system will die. That is why it is so important for South Australia that we deliver on the 450 gigalitres, and that is precisely what federal Labor will do," he said.
The Department of Climate Change, Energy Environment and Water reports on the progress of targets set under the basin.
As of July 31 2022, just 2 gigalitres of the 450 gigalitre target of environmental water had been achieved.
In a March 2020 review of funding for the environmental water allocation required under the legislation, an independent panel said it was "not realistic" that the deadline would be met.
"The volume of water recovered through efficiency measures programs and transferred to the Commonwealth at 30 June 2024 will be well short of 450 gigalitres," the report reads.
Assessing the promise
This promise will be considered delivered if the 450 gigalitre target of environmental water under the Murray Darling Basin agreement is met by June 30, 2024.
THE AUSTRALIA GUARDIAN NEWS REPORT
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ABC NEWS REPORT
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Fish kill Blue Green allege
Murry River@acenewsservices
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