Tasmanian government and Tassal criticised for pre-election secrecy over antibiotic use at Bruny Island


Tasmania's largest salmon company used a controversial antibiotic to control a potentially deadly fish disease just weeks before Premier Jeremy Rockliff called the state election, but the company and government made no public announcement at the time, reports the Tasmanian Inquirer.

In response to a request by Inquirer, the Tasmanian EPA confirmed that Tassal used 180 kilograms of oxytetracycline from January 9 to control a disease outbreak at the Soldiers Point salmon lease near Bruny Island.

Gerard Castles, president of the Killora Community Association on Bruny Island, said it was alarming that Tassal's use of an antibiotic was kept secret until after the election. 

"This was a deliberate act to avoid raising issues that would have been exposed to public scrutiny," he said. "The community needs to know when public waterways are being exposed to antibiotics. It is not a closed system. It would not be tolerated on land if a neighbour was chemically treating an area of the property and allowing 'drift' outside their boundaries. It is the same in public waterways,"

Tim Walsh, a professor of medical microbiology at the University of Oxford and a global expert on the emergence of antimicrobial-resistant bacteria, told a recent University of Tasmania symposium that it was "unquestionably" better to rely on vaccines than use antibiotics at fish farms. Walsh said the problem with using a broad-spectrum antibiotic such as tetracycline to treat a specific disease was that it could lead to antimicrobial resistance beyond the target bacteria.

Tassal used the antibiotic to treat salmon with tenacibaculosis, or mouth rot. Symptoms include the erosion of the lower jaw, ulcers and the rotting of the tail.

The company and the government did not announce the disease outbreak or the use of the antibiotic. Tassal updates information about antibiotic use on its website in June and December, but says it displays "visible orange signage" on the affected fish cages during treatment to notify waterway users.

Castles said residents believed the government should notify the public. "The government should proactively communicate this information and notifications of antibiotic use, fish deaths and chemical treatment to stakeholders who have an interest in a particular site. This would ensure complete transparency," he said.

Tassal did not respond to a request for clarification on how many fish died in the outbreak, or whether there had been previous outbreaks at Soldiers Point or other leases.

Tassal said it would submit its antibiotic residue monitoring report to the EPA within the "regulated timeframe", but declined to clarify when this would occur. The authority's past practice has been to not issue any public notification when monitoring reports are published on its website.

Read the full report in the Tasmanian Inquirer