Media Release Climate Change

The price of a heatwave - how the Tasmanian salmon industry is undercooking its climate risk

October 14, 2026
  • Tassal’s climate report states 1°C of warming raises deaths from 15 to 18.5 per 100 fish, but does not disclose the financial impact of those deaths. UTS Institute of Sustainable Futures (ISF) estimates this loss at $23.7 million per year in dead salmon.
  • Tasmanian waters have been 2-3°C above average since at least August, with strong-to-severe heatwaves forecast into Christmas. 
  • ISF’s report finds salmon companies have not disclosed costs for climate adaptation. No company has clear plans to reduce inshore sea-cage farming despite “growing” and “considerable” climate-related risks to industry.

A single degree of ocean warming could cost Tasmania’s biggest salmon farmer, Tassal, around $23.7 million a year in dead salmon. While Tassal estimated a percentage reduction, no cost was disclosed, nor did it reference the 2025 mass mortality event in its mandated climate-related financial disclosure (CRFD), University of Technology Sydney’s Institute of Sustainable Futures (ISF) has found in its report, commissioned by the Australian Marine Conservation Society. 

South-eastern Tasmanian seas have been 2-3 degrees above average since at least July, and strong-to-severe marine heatwaves are forecast in the region through to Christmas. Tassal states that 1°C of warming would lift fish deaths from 15 to 18.5 fish in every 100. The ISF report notes that $23.7 million per year in mortalities “is a substantial cost, roughly 30 times the feed figure published ($800,000 for increased feed due to warmer waters) and arguably much more material” and that “costs would increase substantially at higher temperature.”

Mass mortality events are not rare incidents and have occurred in eight of the past ten years. In 2025, more than 4 million salmon (20,133 tonnes) died with more than half (2.7 million; 13,500 tonnes) occurring in January-March alone. The Tasmanian Government’s own review found the 2025 event was likely triggered by summer warming.

From February 2026, salmon companies are required to publicly disclose monthly mortality figures to the Environment Protection Authority (EPA) Tasmania. Prior to this change, mass mortality events and their scale only surfaced under intense public pressure. Mass mortality events are structural, clustering tightly around the warmer months on either side of, and during, summer.

Dr Leonardo Guida, marine biologist at the Australian Marine Conservation Society (AMCS) said, “For years, Tasmanians and the broader Australian community have been kept in the dark about if, when and how many fish were dying. Now they’re kept in the dark about what a warming ocean will cost.”

In simple terms, a CRFD report outlines a company’s key climate-related risks and opportunities including financial implications, and the strategy to address these, alongside supporting governance and metrics and targets. UTS ISF was not able to locate the CFRD report for Huon, and Petuna is not yet required to lodge a CRFD. In contrast to salmon companies farming in Australia, Norway’s Mowi, the world’s biggest salmon farmer, puts euro figures on specific climate risks. From January 2025, large companies meeting certain thresholds in Australia must lodge CRFD reports under the Corporations Act 2001.

Hollie Cheung, report co-author and researcher at ISF said, “Climate change is already having devastating impacts on salmon farmed in Tasmania. The full economic, environmental and social costs of warmer waters, marine heatwaves and numerous disease outbreaks are not disclosed by companies for impacts now or in the future. Clear disclosures and transition plans are an urgently needed start so that all stakeholders – the companies, their investors, the local communities – can build resilience into the future”

Tasmanian salmon production has fallen by about a sixth since 2020-21. Yet no company plans to cut inshore farming, or says what adapting will cost its workers. Mass mortality events, antibiotic use, fish growth, carcass disposal, and tighter biomass caps are all trending the wrong way in warming in Tasmanian waters.

Dr Guida said, “Transparent and detailed reporting lets workers, investors and communities judge a business before the bill lands on the environment and taxpayers. The cost of farming Atlantic salmon in Tasmania has been borne by the Maugean skate, by local fishing businesses who can’t export wild-caught seafood because of antibiotic residue, and by communities who question whether they can dip in the ocean without getting sick from salmon carcasses.

“Ironically, the industry already raises young salmon in land-based tanks to shorten their time in a warming sea. Transitioning fully onshore early and not after tightening regulations, lost product, and/or forced closures, is what protects jobs and regional communities.

“Workers, communities and investors don’t just deserve to know what tomorrow looks like; they need to.”

 

–ENDS-

Editors notes:

Swimming Against the Tide was commissioned by AMCS and written by UTS Institute for Sustainable Futures researchers. 

Further reading:

 

AMCS is Australia’s leading voice for ocean conservation. As an independent charity, we have been protecting our precious marine life and habitats since 1965.

We are a passionate community of scientists, educators and advocates dedicated to safeguarding Australia’s oceans. Our work has helped establish vital marine reserves, protect endangered species like the Australian sea lion, stop super trawlers and lead efforts to ban whaling.

From the Great Barrier Reef to Ningaloo, together with our community of ocean lovers, AMCS fights for healthy oceans and marine wildlife every day.