Marine heatwaves threaten Tasmania's aquaculture industry

HOT SUMMER: Human-induced climate change was almost certainly responsible for the heat waves experienced in the Tasman Sea. Source : UTas
HOT SUMMER: Human-induced climate change was almost certainly responsible for the heat waves experienced in the Tasman Sea. Source : UTas

Marine heatwaves pose a significant threat to one of the state’s major industries.

Tasmania’s aquaculture industry, which is susceptible to marine heatwaves, is worth more than $730 million, according to Brand Tasmania.

A UTas study released on Monday found marine heatwaves experienced off Tasmania’s east coast in 2015/16 were almost certainly because of human-induced climate change.

Lead author Dr Eric Oliver said, “Significant impacts were felt across marine ecosystems, including an outbreak of Pacific Oyster Mortality Syndrome, enhanced mortality of blacklip abalone, poor performance of salmon aquaculture, and intrusions by fish normally seen in warmer, more northerly waters”.

There was an increasing probability of extreme events in the future, he said.

Huon Aquaculture deputy chief executive officer Philip Wiese said the marine heatwaves meant there were “hard business decisions” made, including bringing forward salmon harvest to avoid negative effects on fish health and growth.

“This adversely impacted Huon's profitability for the 2016 financial year, but was necessary in order to provide a solid platform for the future,” Mr Wiese said.

Fortress Pen at Storm Bay. Picture: Huon Aquaculture Group

Fortress Pen at Storm Bay. Picture: Huon Aquaculture Group

However, selective breeding and fish nutrition programs were underway to mitigate the effects of marine heatwaves, he said.

Tassal Group corporate engagement senior manager Barbara McGregor said Tassal worked with an annual fluctuation in temperature of more than 10 degrees.

“[It] is well positioned through mitigation strategies and contingencies to cope with temperature fluctuation and variation between farming zones, as well as vertical temperature stratification within the water column,” Ms McGregor said.

HOT SUMMER: The marine heatwave off reached peak intensity of 2.9 degrees Celsius, which a University of Tasmania study found was human-induced. Picture: Supplied

HOT SUMMER: The marine heatwave off reached peak intensity of 2.9 degrees Celsius, which a University of Tasmania study found was human-induced. Picture: Supplied

The business undertook a long term approach to climate change with research assessing broodstock, enabling the identification of naturally resilient fish best able to adapt to temperature conditions, she said.

UTas study co-author associate professor Neil Holbrook said the ocean off south-eastern Australia was a global warming, with surface waters warming at nearly four times the global average rate.

The state government was contacted for comment.