Permit seeks higher antibiotic dosage for diseased Tasmania salmon

A federal regulator is assessing an application to allow farmed salmon in Tasmania to be treated with a higher dose rate of antibiotic florfenicol.

The salmon industry's permit was revoked after drug residue was detected in wild fish several kilometres away.

The Greens are calling for the permit application to be rejected.

An animal health company has applied to "increase the dose rate" of the controversial antibiotic florfenicol in salmon farms in Tasmania, the federal regulator has confirmed.

Florfenicol was first used in the state's south-eastern waters in November last year after an emergency permit was approved by the Australian Pesticides and Veterinary Medicines Authority (APVMA).

It was in response to a bacterial disease that led to the deaths of 15,000 tonnes of salmon in early 2025, and resulted in fish parts washing up on beaches.

However in March this year, the emergency permit for florfenicol was revoked by the APVMA on the basis of "unacceptable risk of residue exposure to non-target species".

The revocation occurred after traces of the antibiotic were detected in wild fish species up to 10 kilometres from the nearest salmon pen in which the antibiotic had been used.

Florfenicol was later found in abalone up to 14km away.

At a Senate estimates hearing earlier this week, APVMA chief executive Scott Hansen outlined details of a renewed push by pharmaceutical company Abbey Animal Health, known as Abbey Labs, to use florfenicol in Tasmanian waters this summer.

"There's a second application, which is a minor use permit," Mr Hansen said in response to questioning from Greens senator Vanessa Bleyer.

"It's looking to move the location to not just the south-eastern biosecurity zone, but the eastern biosecurity zone as well.

"And to increase the dose rates and the treatment regime that's proposed.

"That obviously has a significant amount of work that is being done on that to look at environmental impacts, to look at any microbial resistance impact, as well as residues and depletion."

Mr Hansen said Salmon Tasmania had separately sought approval for another emergency use permit with the same dose rates and treatment frequency as its previously revoked permit.

The previous permit allowed for 10 to 20 milligrams per kilogram of fish per day for 10 consecutive days, with no re-treatment permitted.

No details were disclosed during the hearing about the degree to which Abbey Labs wants to increase its dose rate or treatment regime.

The APVMA said it could not comment on the new proposed dose rates because they were still under assessment.

The use of florfenicol last summer forced the closure of some rock lobster and abalone fisheries amid concerns any detections could trigger international export bans.

The Tasmanian Rock Lobster Council [TRLC], Abalone Council and Commercial Divers Association have previously warned of further fishery closures if florfenicol use resumes.

"Increasing dosage rates and treatment duration will increase both the likelihood and extent of environmental exposure," the groups said in the TRLC's newsletter in July.

In June, it emerged that a total of 5.4 tonnes of the antibiotic had been used last summer, during which about 9,000 tonnes of salmon died.

Tasmania's Health Department has said there were no reports of adverse human health effects from eating seafood with florfenicol residues.

However, as a precaution it has said people can avoid seafood caught within 3km of a treated salmon pen.

In a statement, Senator Bleyer called on the APVMA to reject the florfenicol applications from Abbey Labs and Salmon Tasmania.

"We saw last time around that the antibiotic ended up in other animals such as rock lobster and abalone in our wild fisheries, jeopardising exports and threatening human health by increasing antibiotic resistance.

"Despite being labelled by the Australian Pesticides and Veterinary Medicines Authority (APVMA) as a 'minor use' permit, the risks are anything but that."

Earlier this month, the Department of Natural Resources and Environment (NRE) released a plan designed to reduce the risk of antibiotics entering wild fisheries.

The plan involves setting up multiple zones, in which rock lobster and abalone fisheries would be closed for at least six weeks if an antibiotic is administered.

Mr Hansen told the Senate hearing that the NRE's plan would form part of the APVMA's assessment of Salmon Tasmania's emergency use permit application.

Salmon Tasmania chief executive John Whittington said florfenicol was one part of a "much broader fish health strategy".

"It provides veterinarians with an important treatment option when additional support is required to protect fish welfare," he said.

"Its use is tightly regulated, clinically justified, and managed within a framework designed to protect animal welfare, food safety, environmental management, commercial fisheries and market access."

If a new florfenicol permit is issued, Mr Whittington said the number of fish needing treatment, according to veterinary advice, would dictate how much florfenicol is used.

"Our aim is to reduce the need for medication as much as possible through a range of strategies, including selective breeding, vaccination and other management practices."

The ABC contacted Abbey Labs for comment, but did not receive a response.