Unfathomable Death of Millions of Fish Clogging Up an Australian River Linked to Low Oxygen Levels in the Water

As a blazing heat wave sweeps over a rural town in Australia's outback, millions of dead and decaying fish have choked a wide length of the river.

According to Science Alert, social media photos and videos showed vessels smashing through a covering of dead fish coating the sea, with just the surface visible underneath. Most of the fish clogging up the river are bony bream, Murray cod, golden perch, silver perch, and carp.

Millions of Fish Died in the Australian River

On Friday, March 17, the New South Wales government confirmed that millions of fish have been killed in the Darling River near Menindee. It has been the third major death in the area since 2018.

Menindee resident Graeme McCrabb said in an interview that the horrible event has caused the fish death event in the area where the river is blanketed with dead fish. He added that it looks like it is worse than the prior ones and the environmental damage it caused is unfathomable.

The local government said that populations of fish such as bony herring and carp had exploded in the river during previous floods, but they were now dying off in large numbers as floodwaters retreated. They noted that these fish deaths are being attributed to low oxygen levels in the water, also known as hypoxia, which happens when flood waters recede.

The region's current hot weather is further increasing hypoxia because warmer water stores less oxygen than cold water, and fish require more oxygen at warmer temperatures.

Earlier fish fatalities in Menindee were attributed to a shortage of water in the river caused by a lengthy drought, as well as a poisonous algal bloom that spread for 40 kilometers (24 miles). The New South Wales government said in 2019 that this will not be the last.

Cameron Lay, a spokeswoman for the state government's fisheries department, told ABC that the sight of the river being clogged by dead fish was "confronting." Menindee has a population of about 500 people and has recently been destroyed by both drought and floods.

What Is Hypoxia?

According to the National Oceanic and Atmospheric Administration (NOAA), the term "hypoxia" when used in ocean and freshwater environments means low or depleted oxygen.

It is usually linked to the overgrowth of certain species of algae that depletes oxygen when they die and decompose. Unfortunately, it caused dead zones that lead to mass die-offs of fish, shellfish, corals, and aquatic plants

Hypoxia usually happens as a result of human-induced factors, especially nutrient pollution that is caused by agricultural runoff, fossil-fuel burning, and wastewater treatment effluent.

NOAA said that changes in global and regional climates could potentially make coastal and marine ecosystems more vulnerable to hypoxic conditions. In the US, federal agencies carry out interdisciplinary research to further understand the relationship between ecosystem function and climate change. Their findings could help in decision-making that addresses the challenges of protecting ecosystems.

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