A serious health warning has been issued for Rockingham beach-goers after more than a thousand dead fish were washed ashore.
An investigation is now underway into what killed the huge shoal of scaly mackerel.
Early risers spotted more than one thousand dead scaly mackerel on Rockingham’s Palm Beach on Wednesday.
Witness Johann Maree said the photos do not fully represent the scale of the situation.
There were reports of dead fish on Tuesday, but inspectors from the Department of Primary Industries and Regional Development found none.
On Wednesday there were hundreds.
“It was strange – but what was strange also was it was one type of fish only – there were others still swimming around which looked fairly normal,” Mr Maree said.
Some locals claim brine discharged from the Perth Seawater Desalination Plant could be to blame.
But the Water Corporation says: “Comprehensive monitoring is conducted to ensure there are no adverse environmental impacts on the marine environment from our operations.”
Authorities have taken fish and water samples from the area for testing, but results could take a couple of days.
The beach remains open, but locals and tourists are being warned not to touch or eat the fish, use them as bait, or swim near them.
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