Marine heatwaves in Tasmanian waters are likely to become more commonplace in the coming decades, scientists warm.
Temperatures in waters off the state's east coast peaked at nearly three degrees above average in the summer of 2015/16.
The record spike in temperature was linked to the Tasmania's first Pacific Oyster Mortality Syndrome (POMS) outbreak, which killed millions of oysters and caused a reported industry loss of nearly $6 million.
A paper published in the international journal Nature Communications says the heatwave was "almost certainly" due to climate change.
Researchers found it was caused by an growing flow of warm water travelling south on the East Australian Current.
"It's the strongest we've seen and we can expected them to be more frequent and more intense," co-author and University of Tasmania associate professor Neil Holbrook said.
"The evidence shows that the frequency of extreme warming events in the ocean is increasing globally.
"In 2015 and 2016 around one quarter of the ocean surface area experienced a marine heatwave that was either the longest or most intense recorded since global satellite records began in 1982."
The heatwave in the Tasman Sea affected an area more than seven times the size of Tasmania for 251 days, the study found.
Near-surface waters are warming at nearly four-times the global average, making ocean off south-eastern Australia a global warming "hotspot".
The study, titled the unprecedented 2015/16 Tasman Sea marine heatwave, looked closely at temperature data from September 2015 to May 2016.
Abalone, lobster and salmon industries were also under stress during that period, the report noted.
"There were reports salmon were not as healthy or growing as much as normal," Prof Hollbrook said.
In a bid to combat POMS, scientists in May released selectively bred POMS-resistant oysters into a waterway near Hobart.
