Salmon producers in Tasmania are scrambling to find a vaccine to combat viruses blamed for killing one million farmed fish over the last six months.
Tasmania’s Environment Protection Authority (EPA) has confirmed 1.35 million salmon have died in Macquarie Harbour since October last.
The main cause has been put down to an outbreak of pilchard orthomyxovirus (POMV), transferred from wild populations, according to an area management agreement classified report provided by Huon Aquaculture, Petuna, and Tassal, who hold leases in the west coast harbour.
“It is above what they would normally predict to have lost, significantly above. The companies are working on investing in a vaccine,” EPA director Wes Ford told ABC Hobart.
He said all three companies had lost fish, e 2017 fish class was hit harder than expected, with the harbour’s salmon population at greatest risk.
The breakdown of deaths between them was not known though the disease has been described as “a bit like the flu” with fish under stress at greater risk of infection.
Spreading out the population within the harbour has been put forward as one solution.
Added Ford: “One of the reasons why the fish got the disease in the first place was mixing young fish with old fish, so by providing that year class separation, there’s at least a kilometre separation between the young fish and the fish already in the harbour.
“POMV can be exacerbated by stress caused by heat, low oxygen, and I think this summer we’ve seen some elevated temperatures and clearly some concerns about oxygen.”
Environment groups claiming the harbour has been damaged — perhaps irrevocably — are demanding the Government step in.
“We have to have a moratorium on all fish farming. The salmon farming companies have to get out of Macquarie Harbour,” said Green party spokeswoman, Rosalie Woodruff.
“It’s clearly the case that the system there is damaged, possibly beyond repair,” she claimed.
Environment Tasmania said more than 2,000 Tasmanians had petitioned salmon companies to release a fish death toll, and accused the Government of concealing the figures in the lead up to the March state election.
Laura Kelly from Environment Tasmania said the government was still seeking answers.
The EPA said it would be reducing Macquarie Harbour’s biomass limit by 21 percent over the next two years, from 12,000 tonnes to 9,500 tonnes.
With a series of mass fish deaths and stock reductions over the past two years, the reduction would not come as a surprise to farmers, Ford said.
He added: “Clearly, I’ve had to step down the biomass over a number of years now because the harbour has not been performing as it should. I expect the harbour will actually improve because of the reduction, but of course there can be no guarantees.”
But environment groups claimed the EPA’s latest biomass limit would not be enough to restore healthy levels, and are demanding Macquarie Harbour should be emptied of fish and given a chance to recover.