As many as a million fish are believed to have died along the banks of a major river system in drought-battered eastern Australia, and the authorities are warning of more deaths to come, AFP reports.
The banks of the Murray-Darling Rivers are thick with rotten fish, with officials putting the number of dead at hundreds of thousands and saying the toll is likely closer to one million.
Further high temperatures forecast for this week could make the situation worse, the New South Wales government has warned.
Low water conditions and the heat may also have encouraged an algae bloom that starves the fish of oxygen and produce toxins.
'The sheer visual image of this is just terribly upsetting'
The deaths have become a national issue, sparking angry allegations about the cause and who is responsible.
"It's a devastating ecological event," said Prime Minister Scott Morrison, pointing to apocalyptic scenes. "The sheer visual image of this is just terribly upsetting."
Morrison's government has blamed the fish deaths on drought and defended policies which some locals say has caused the systemic depletion and pollution of the river system.
But for years scientists have been warning of people extracting vast amounts of water without a check for irrigation or other uses, undercutting billions of dollars of investment.
"Dead fish and dying rivers are not because of the drought, it's because we are extracting too much water from our river," said John Williams, an expert in water economics at the Australian National University.