Tasmania’s Environmental Protection Authority has concluded that florfenicol use at nine salmon farms in southern Tasmania between November 2025 and March 2026 posed a low risk of unacceptable environmental harm.
The EPA assessed antibiotic use deployed to combat salmonid rickettsial septicaemia (SRS), caused by the bacteria Piscirickettsia salmonis. The assessment drew on 4,240 water and sediment samples — the largest dataset of its kind collected for marine aquaculture globally, the authority said.
Fewer than 12% of the 4,240 samples contained any measurable florfenicol or its breakdown product, florfenicol amine. The highest single reading — 5.2 µg/L (parts per billion), collected inside a pen during active treatment — sat approximately 10 times below the EPA’s interim Default Guideline Value of 7 µg/L for pristine Tasmanian marine ecosystems. The average detected level was 0.4 µg/L, roughly 125 times below the limit.
Sediment presence was highly localised. Only 29 of 1,680 sediment samples tested positive, 24 of those from within farm lease boundaries. Florfenicol did not persist in sediment beyond 14 days post-treatment.
Salmon Tasmania, representing growers Huon Aquaculture, Tassal, and Petuna, said the findings align with available science and reinforce confidence in the sector’s regulatory framework.
EPA director Catherine Murdoch said the assessment confirms that the majority of administered antibiotic was taken up by the salmon themselves, leaving environmental concentrations consistently low.
The EPA has set a separate interim guideline of 50 µg/L for modified ecosystems such as the D’Entrecasteaux Channel, where several treated farms operate. Further monitoring will determine whether interim guideline values are formalised.
