A mass fish kill in the Murray River near North Yunderup was likely caused by low oxygen levels after recent rains, according to the Department of Water.
The Department took water-quality, fish and phytoplankton samples at a number of sites last week after around 30,000 fish, of a variety of species, died between Pinjarra Road Bridge and the river mouth.
“The cause of the event is likely to be poor water quality – specifically low dissolved oxygen levels,” said Dr Tim Storer, principal scientist from the Department of Water’s water science branch.
“Recent rains washed organic matter into the river and disturbed sediment that contains very little oxygen. These two factors resulted in dissolved oxygen falling below levels fish could tolerate.”
The Department of Water will continue to monitor the situation through its fortnightly water quality sampling along the Murray River.
The Department of Health advises against eating or handling fish found in these circumstances, or recreating in waterways during a fish kill or algal bloom event.
The departments encourages people to continue reporting any fish deaths to the Department of Fisheries FishWatch on 1800 815 507.
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