A million fish, including bone herring, Murray's cod, golden perch, silver ramp and carp, have died in a river basin near Menindee, New South Wales, Australia, according to media reports.
Presumably, the cause of the death was the abnormal heat that set in on Australia's east coast in early March. This weather caused oxygen levels in the river water to drop significantly.
"These fish deaths are related to low oxygen levels in the water (hypoxia) as flood waters recede," the government said in a statement.
The authorities of New South Wales believe that the huge amount of dead fish in the river poses a great risk to the health of people and animals living on the shore. Local residents have received notices asking them to stay out of the water.
The fishing division of the state's Department of Primary Industries has dispatched officers to the area of the incident. They are currently determining the cause of the fish deaths and assessing the extent of the problem.