Tasmania's big salmon producers say destocking their pens in Macquarie Harbour is not a realistic solution to save an ancient fish.
The federal government's new conservation advice for the maugean skate lists urgent actions needed before summer to ensure it does not become extinct.
It says salmon farming impacts on oxygen levels in the harbour must be eliminated or significantly reduced.
"The fastest and simplest way to achieve this is by significantly reducing fish biomass and feeding rates," the advice said, with mechanical solutions a possible "and/or" remedy.
Fewer than 1000 skates are estimated to remain and they are confined to Macquarie Harbour, a narrow-necked estuary conservationists have long argued is not suitable for commercial fish farming.
The conservation advice makes it clear salmon farming is the primary human activity contributing to the skate's number one threat: poor water quality.
But an industry body representing the three big salmon brands - Tassal, Petuna and Huon Aquaculture - say the skate's salvation lies in efforts to establish a captive population.
"The short term solution to secure the skate is to establish an ex situ population. Destocking the pens is not a realistic short term solution and there is no science to say it would have any immediate effect," Salmon Tasmania CEO Luke Martin told AAP.
Mr Martin said the industry had already more than halved production in the harbour - something the new advice notes was a response to water quality declines, including substantial mortality of farmed salmon in the past.
Mr Martin said the industry was committed to supporting "agreed" priorities from the conservation plan, having funded much of the research on the skate so far.
"This includes prioritising potential engineering solutions to further oxygenate the harbour," he said.
"The reality is there are factors well beyond our control influencing the oxygen levels in the harbour, including the release from the hydro system, storm flows, and warming waters. But we’re determined to do what we can."
The conservation advice did say the oxygen problems might "possibly" have been compounded by hydro-electricity generation changing river flows into the harbour, and the impacts of climate change.
But it also said altered river flows were not considered a primary cause of the low oxygen conditions.
"... the most important anthropogenic contributor to the oxygen debt in Macquarie Harbour is ongoing salmonid aquaculture," it said.
Mr Martin said Tasmania's Environment Protection Authority independently sets operating conditions for the industry including the level of production permitted.
AAP has asked the EPA for comment.
Federal Environment Minister Tanya Plibersek has promised $2.1 million to help the skate, including a captive breeding program to create an insurance population.
"... we urge the salmon industry and Tasmanian government to take the action needed to clean up Macquarie Harbour so the maugean skate can survive for another 100 million years," she said on Wednesday.
Greens senator Peter Whish-Wilson has spent years questioning the federal government about what it's doing to ward off the loss of the skate and says it's obvious salmon farms have been a major contributor to its decline.
He said the harbour must be destocked and it's now up to Ms Plibersek to compel actions that will save a species protected under federal law.
