Salmon Mortality Event 2025

​Media Statement

Situation
A large and unprecedented salmon mortality event has unfolded since mid-February 2025 in the lower D'Entrecasteaux Channel. Huon Aquaculture Company (Huon) and Tassal operate salmon farms in this area.

Mortalities affect salmon farming worldwide and are typically elevated during summer months, including in Tasmania, when warmer waters and other factors affecting salmon health are more likely to occur.  Tasmania's Chief Veterinary Officer (CVO) has made a statement on the cause of the mortality event, available at Salmon mortalities | Department of Natural Resources and Environment Tasmania.

Controlled Waste Management
One consequence of the mortality event is that congealed oily material, confirmed to originate from fish, has been found on beaches in the lower D'Entrecasteaux Channel area, including Verona Sands, Randalls Bay and Roaring Bay, Drip Beach in the lower Port Cygnet area, and beaches on the western side of South Bruny Island. It is thought that oil released from deceased salmon has moved out of pens in the lower Channel, congealed into multiple small balls, and been deposited by wind and wave action onto beaches.  Previous summer salmon mortality events in Tasmania have not resulted in reports to the EPA of this material on beaches.

This material is considered a controlled waste under state environmental laws administered by the Environment Protection Authority (EPA). Controlled wastes are required to be managed in ways that avoid uncontrolled, unauthorised release to the environment to mitigate potential environmental nuisance or harm. The EPA issu​ed di​rections to both companies on 6 March 2025 requiring removal of deceased fish and waste derived from them at a rate and in a manner sufficient to prevent discharge of a controlled waste to the environment​.

The EPA considers that loss of containment of a controlled waste at salmon farms, leading to environmental contamination, has occurred in the lower D'Entrecasteaux Channel.

Investigation
As well as formally directing and working with the two salmon companies to prevent further loss of containment of this material, the EPA is conducting an investigation into the circumstances that have led to it being found in the environment, outside salmon farms, and whether breaches of environmental licence conditions, the Environmental Management and Pollution Control Act 1994 or associated regulations, have occurred.

The investigation is pursuing several lines of inquiry.  These are complex and scientific in nature and will take time to complete.  Various investigative actions are being used to determine the facts, including chemical analysis of deceased fish and oily material; inspections of fish farm activities and offshore and land-based facilities where deceased fish are handled; and assessment of salmon company mortality reports and information.

Sampling and testing
As part of the investigation, the EPA has been collecting samples of the oily material when it is reported by the public on beaches, and having those samples tested for lipids and antibiotics. Lipid testing was commissioned to help confirm the origin of the material (i.e. salmon farming). Antibiotic testing was also commissioned because Huon notified the CVO and the EPA, as it is required to do, and advised the public, that it was undertaking a single round of antibiotic dosing using oxytetracycline (OTC) in one of its leases in the lower Channel. The antibiotic is delivered by incorporating it into a specific batch of fish feed.

The OTC dosing by Huon occurred between 13-26 February 2025 to protect the salmon and help bring the mortality event under control. Use of antibiotics in salmon pens is regulated by both the EPA and the Department of Natural Resources and Environment Tasmania and is relatively rare.       

Release of Results, Preliminary Interpretation and Next Steps
Notwithstanding the ongoing investigation, the EPA has determined it is in the public interest to make available the test results for the oily material found in the environment outside pens - as they come to hand - along with expert advice on what the test results mean so far as can be determined at this time. A sample of fish feed treated with antibiotic, and a sample of oily material was voluntarily provided to the EPA by Huon early in the event and are included in the released results.

All samples and results for OTC and lipids received to date are summarised in the attached table which will be progressively updated as results become available. Final laboratory test certificates received to date are attached. Additional certificates will be published as they become available.

In summary, the test results for the oily material to date indicate the lipids in the material are consistent with fish oil. Test results for some samples indicate presence of OTC at low levels.

The results in particular raise further questions about the presence of OTC in the broader environment.  While levels of residual OTC in the environment after a dosing event will progressively decline, there are sound reasons for wanting as little contamination of our environments with antibiotics as possible, particularly to reduce the selection of antibiotic-resistant bacteria.

The EPA will endeavour to obtain a better understanding of the situation through additional environmental monitoring. It has required Huon Aquaculture Company to undertake expanded antibiotic residue testing which is in progress and includes beach sediments at four locations. The residue testing schedule​ is available to view. The EPA is also determining a program of independent environmental monitoring to commence as soon as possible, details of which will be publicly available when finalised.

In the meantime, and while structured environmental monitoring is being designed (EPA) or undertaken (Huon), the CVO and the Director of Public Health have reviewed the test results and provided comments on what they mean.

The CVO advises that from an animal health perspective neither the lipids nor the antibiotics at the low levels found in samples to date are cause for concern, whether for animals that may encounter the oily material in the sea or on beaches.

The Director of Public Health considers that the low quantities of OTC indicated in the samples do not raise human health concerns.

Any skin exposure to OTC from the OTC-containing material would involve very low quantities and concentrations of OTC, readily eliminated by washing with soap and water. In the (implausible) circumstance of a person consuming the oily material, they would have to eat many kilograms for this to pose a health concern. Similarly, while wild fish, including those caught and consumed, could ingest very small quantities of OTC from eating the oily material, they would need, again implausibly, to consume many kilograms of the material for this to contribute to a consumer's intake of OTC.

Therefore, the conclusions of the 2007 FSANZ Risk Assessment of Oxytetracycline in Tasmanian Salmon and Wild Fish still hold, that consumption of wild-caught fish that may have been exposed to OTC in the vicinity of fish farms does not raise health concerns, noting the importance of validating this by the wild-fish monitoring required by the EPA as part of company antibiotic residue testing.

Hence, the current public health advice remains the same. It is:

• The presence of fatty fish material on beaches, while unpleasant and smelly, will not harm health.
• Public Health advice is to not handle or consume the fish material, and to avoid activities that will bring you into contact with it.
• This same advice applies to other dead animal parts in the natural environment. Leaving such material alone eliminates any risk.
• If you do make contact with the material, wash it off with soap and water.
• The marine bacterium Piscirickettsia salmonis (P. salmonis) is a fish pathogen and does not cause human or companion animal disease.
  

ENDS.​

​Expanded Antibiotic Residue Monitoring Schedule 

The EPA requires companies to conduct detailed antibiotic residue monitoring of sediments and wild fish following application of antibiotics to fish farm pens. Further to the usual requirements, on 7 March the EPA issued expanded antibiotic residue monitoring requirements that include sampling of water, sediments and oil globules (where present) at four beaches around the southern D’Entrecasteaux Channel that are known to have been impacted by oil globules.

 Antibiotic Residue Monitoring Schedule MF141 and Signed Letter 7 March 2025 (PDF 514Kb)

​​Direction to Cease Discharge of Controlled Waste 6 March 2025

The EPA issued directions to Tassal and Huon Aquaculture on 6 March requiring removal of deceased fish and waste derived from them at a rate and in a manner sufficient to prevent discharge of a controlled waste to the environment.

​

​​Summary of Sampling and Testing Results

^Collected by members of the public.

‡Collected by Huon Aquaculture Company.

Unless indicated all other samples collected by the EPA.

​#DMB is dry matter basis.​​