At least 4 million salmon died prematurely at Tasmanian fish farms in 2025, with new data from the state’s Environmental Protection Authority (EPA) suggesting about 500,000 fish died in November and December as ocean temperatures warmed.

Scientific studies indicate Atlantic salmon are adversely affected when ocean temperatures approach 18C. At higher temperatures, salmon encounter less oxygenated water, suffer from liver and kidney damage, have less appetite and become more vulnerable to disease.

More than 2,500 tonnes of salmon died in the last three months of 2025, bringing the death toll for the year to 20,133 tonnes lost before being processed for public consumption, according to EPA data published on Friday afternoon.

More than 40 tonnes of salmon prematurely died per day in December, almost triple the monthly average for July to October.

Stewart Frusher, a retired professor from the Institute for Marine and Antarctic Studies at the University of Tasmania, said the increase in salmon deaths in December was an ominous sign for the months ahead. “We are essentially at the stage where the waters in south-eastern Tasmania aren’t fit for purpose for salmon,” he said.

Call to fine companies

Tasmanian companies produced nearly 68,000 tonnes of gutted salmon for public consumption in 2024-25.

Tasmania’s Animal Welfare Act states that owners “must not use a method of management of the animal or group which is reasonably likely to result in unreasonable and unjustifiable pain or suffering to the animal or an animal in the group”.

Frusher said while the RSPCA has made it quite clear that salmon feel pain, there had been no apparent regulatory action over the mass salmon deaths.

“There is currently a public debate interstate about possible penalties for leaving dogs in cars on hot days, and Premier Rockliff has committed to phasing out greyhound racing because of animal welfare concerns. But when it comes to mass salmon deaths, there’s just silence,” he said.

In Norway, mass fish deaths at salmon farms can attract significant fines. In November 2025, the Norwegian Food Safety Authority fined the aquaculture company Salaks 1.86m kroner (A$286,000) for breaching fish welfare standards that resulted in the deaths of about 106,000 salmon. Later that month, the authority fined another company, Tombre, for the deaths of 132,000 salmon.

Coughlan said the lack of fines did little to spur the salmon industry to prevent mass deaths. “Penalties must apply, as they do in Norway, as a disincentive to allowing current mortality rates to become the new normal, and bring animal welfare back into focus for an industry that is clearly beyond control,” she said.

Salmon Tasmania, which represents Tasmania’s three marine salmon producers, was approached for its response to calls for companies to face substantial fines for mass fish deaths. It did not respond.