EXPERTS say that record temperatures and low oxygen levels are to blame for dead fish being washed up on riverbanks and beaches across WA.

Dead fish, eels and crayfish have been found on shores - with the coastline of Green Head, some 290km north of Perth, covered in now-rotting carcasses.

Green Head resident Rod Wilson said: "It's very heartbreaking. I've been here for 28 years and I've never seen anything like it. To us it's a local ecological disaster."

Reports state that in a cleanup operation at Green Head, 20km north of Jurien Bay, more than 15,000 dead fish were collected.

"Our biggest concern is how long is this going to take to right itself," Mr Wilson added.

With fish carcasses washing up for more than a week, local residents are being urged to stay out of the water for fears of harmful bacteria.

Experts say WA's coastal waters have seen the highest rise in temperature in the world with up to 4C rise than normally seen this summer.

Dr Brian Jones from the Department of Fisheries said: "Anybody who as sat in Perth for the last few months without airconditioning knows what heat does.

"Fish are the same. They are cold blooded so they feel the heat."

It follows a similar case in the US where millions of dead anchovies were found floating in a Los Angeles marina.

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