A marine heatwave off WA that flattened several fisheries and has been linked to a spate of shark attacks is likely to become more frequent, according to Australia's top science agency.

At a symposium in Perth today, the CSIRO will claim a sharp increase in ocean temperatures two years ago was caused by extreme climatic conditions in the Indian and Pacific oceans. The findings were released in a report published in a scientific journal on Friday.

Stocks including crabs, abalone and scallops were devastated off the Mid West and Gascoyne coast during the summer of 2010-11 when water temperatures soared up to 5C above normal.

Until recently scientists had been unsure of the causes behind the episode, which has also been blamed for widespread coral bleaching at Ningaloo and a significant increase in shark activity.

The CSIRO believes the event was driven by abnormally warm sea surface temperatures in the Pacific and Indian oceans leading to one of the strongest Leeuwin currents on record.

Lead author of the report Ming Feng dubbed the heatwave the "Ningaloo Nino" and said governments needed to "prepare for a future in which similar events may occur more frequently under global warming".

"Understanding the factors that influence the formation of events like the 2011 Ningaloo Nino is a vital first step in preparing for impacts from extreme warming events in the future," Dr Feng said.

Michael McPhaden, a US-based co-author of the report, said the events of 2010-11 highlighted how changes in the world's climate could have unforeseeable consequences.

"Nature always finds a way to surprise us and the Ningaloo Nino is just the latest episode in this continuing saga," Dr McPhaden said.

The remarks by the CSIRO come after the WA Fisheries Department said in December that the effects of the marine heatwave had been more serious than first expected and were still being felt.

Fisheries Minister Norman Moore said there was "no doubt" environmental factors had affected WA's fisheries in recent years.

However, he was hopeful the "heat pulse" two years ago was an aberration.

The West Australian

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