Researchers from the University of Western Australia (UWA) say there are clear signs an ocean heatwave along the mid-west coast has seriously altered the marine environment.

A warm current of water swept along the WA coast last summer increasing temperatures near Jurien by as much as 10 per cent.

The area recorded its highest ever temperatures.

UWA's Thomas Wernberg says it appears the ocean environment appears to be undergoing a major change as a result.

He says there are signs of seaweed species completely dying off and warm-water fish previously unknown to the area moving in.

"A lot of the basic ecology of our coastal systems in the temperate zones depend on these large seaweeds and this is everything from the fishes we go and catch when we go out on a Sunday afternoon to important organism in a system," he said.

"We've definitely seen new fish recruit into the Jurien Bay area, fishes that are normally found further north in warmer water that we saw quite a lot of those immediately after the heatwave.

"We don't know how many of those will hang around and survive there in the long run and what they will do if they do stay in the Jurien Bay area."

A group of researchers will re-examine the health of the Jurien Bay environment in coming weeks.