Mass Die-Off Blocks Waterway with Millions of Dead Fish —Australia

This week, a mass die-off of fish in Australia's Darling River resulted in millions of dead fish clogging the river.

State fisheries officers were dispatched to evaluate the situation on Saturday.

Millions of Dead Fish

Low oxygen levels in Australia's second-largest river were cited as the cause of the mass kill by environmental authorities in the state of New South Wales.

Cameron Lay, the fisheries spokesman for the New South Wales government, said It's quite a confronting scene to see that there are tens of kilometers where there is fish.

RTE News shared a video of a boat trying to navigate through millions of dead fish on the surface of Australia's second-longest river on Twitter.

Mass Die-Off

The most populous state in Australia claimed that "millions" of fish had perished close to the small town of Menindee. The town is about 620 miles west of Sydney, the state capital. Since 2018, there have been three large die-offs in the region.

In the Darling River, recent floods had caused populations of bony herring and carp to explode, and now fish are disappearing as a result.

The government of New South Wales claims that these fish deaths are caused by hypoxia, or low oxygen levels in the water, as flood waters recede.

The water division of the NSW Department of Planning and Environment noted that there are numerous fish deaths in the Darling River between Menindee township and Lake Wetherell, most of which are Bony Herring.

The agency issued a warning that rising temperatures over the weekend could cause river oxygen levels to drop. Next week, cooler temperatures are expected to return.

According to DW, previous fish kills reported at Menindee had been attributed to a protracted drought and a toxic algal bloom.

Mass Die-Offs in Australia

According to researchers, in 2018 excessive water use resulted in river flows that were too low to properly flush nutrients from agricultural runoff through the system, causing large algal blooms. The blooms were then killed by a cold snap, and bacteria that fed on the dead algae drained the water of oxygen, killing between 100,000 and 1 million fish, Science reports.

Millions of dead fish were discovered during the state's devastating drought in 2019, which put the management of the Murray-Darling Basin under scrutiny.

Chris Minns, the leader of the opposition, said it was tragic for a community that had endured so much. Minns said that Over ten years of National Party rule resulted in poor management of the river system in far western NSW.

On Friday, an NSW representative said the state had increased monitoring of the Menindee Lakes region recently to track the effects of the area's protracted flooding.

One hour's drive separates Broken Hill from Menindee, a town of 500 residents. It has seen several large-scale fish kills recently, with a 40-kilometer algal bloom in 2019 being blamed for the deaths of one million fish.

The 2019 occurrence fell during a time of extreme heat in the southernmost region of the state and a drought in the river system. Thousands of fish were discovered dead at Menindee lakes once again last year, ABC News reports.