As the stench of tens of thousands of rotting fish wafts over the town of Menindee in outback NSW, it triggers painful memories for local resident and Barkandji woman Michelle Kelly.
"When the river is healthy, our people are healthy, but right now the whole town smells like stinking fish" she said.
"Can you imagine your house smelling like carp fertiliser?"
It's a familiar sensation.
In the summer of 2018-19, over December and January, during the height of the drought.
This week, the Department of Primary Industries (DPI) has confirmed thousands of fish deaths along a 65 kilometre stretch of the Darling-Baaka River.
Some of the dead fish on the Darling-Bakaa River. Source: Supplied / Geoff Looney
"DPI understands that fish death events are distressing to the local community."
The latest environmental crisis comes weeks after floodwaters, which peaked just under 10.5 metres, inundated the town.
As the director of the Menindee Local Aboriginal Land Council, Ms Kelly wants authorities' focus to remain on water policy.
"I think these fish kills are being underplayed," she said.
"In 2019, we had politicians come out here to visit, the government commissioned a report.
"The premier visited now with the floods, but there has been absolutely nothing since. We haven't had any visits. We haven't had any information. It's not on any of the news."
Why are the fish dying?
In short, the fish are dying due to low dissolved oxygen levels in the water — which was the same cause of the mass fish kills in 2019.
Unlike then, the oxygen is being taken up by an increase in biomass (organic material) after flooding, rather than algal blooms that suffocated fish living in disjointed pools of water during the drought.
Freshwater ecologist Fran Sheldon was one of six scientists who panelled an(known as the Vertessy report), and said fish deaths after flood events aren’t uncommon.
"During the massive floods, the Menindee Lakes were inundated and so fish were breeding and generally doing really well," Professor Sheldon said.
"But as the water levels in the lakes fall, those fish are coming back into the river channel.
"With all that biomass of fish in there trying to breathe, the level of oxygen just gets really, really low and the fish start to die."
The fish died because of a lack of oxygen. Source: Supplied / Geoff Looney
While the DPI asserted the majority of fish dying were carp — a river pest — Professor Sheldon said more native fish such as the iconic Murray cod could yet be impacted.
"It could be that quite a few died in 2019, so it could be they just have not re-established to the numbers that they were at," she said.
"It's also probable that quite a few are moving upstream and getting out of the really nasty water–this time they can do that, because the river is connected."
The DPI said it would undertake samples of the fish populations in the Darling River near Menindee once flooding receded.
Calls for better water quality monitoring
Wildlife photographer Geoff Looney has lived in Menindee for 48 years and said he had "never seen a flood end this badly".
"There needs to be more transparency about the quality of water coming down the river. If the water quality is down, we should know about it," he said.
The DPI said it has been working with Water NSW, "who are implementing strategies to improve the quality of water released" downstream.
Menindee resident Graeme McCrabb — who was instrumental in the town’s recovery from the 2019 fish kills, said critical lessons still have not been learned.
"We don't have good enough data collection still, we need a proper monitoring regime, looking at oxygen levels, temperature gauges, and regular fish population sampling," he said.
Menindee resident Graeme McCrabb holding a dead fish during the 2019 fish kill episode. Source: SBS News / Sara Tomevska
As the Bureau of Meteorology predicts a shift back into hot, dry, , Professor Sheldon said ensuring regular flows through the river system was critical.
"What's going to be really important moving forward is maintaining the small and medium floods…. they're the ones that are impacted most by river regulation, irrigation industries and water obstructions," she said.
"So, rules around being able keep the small and medium pulses going through the system… are going to be really important to maintain those fish populations in the long run, and let them really recover from the last big drought."
Water NSW said it has increased monitoring at Menindee lakes in recent months to track water quality impacts resulting from prolonged flooding in the region.
