The federal environment minister will write to her Tasmanian counterpart demanding “extreme intervention” to save an ancient fish from extinction.

Tanya Plibersek’s promise to ward off any new extinctions is only seven months old but it’s already in serious danger alongside the maugean skate.

An urgent report released last week warned the so-called “thylacine of the seas” – now found only in Macquarie Harbour – is on the brink of extinction and could be one extreme weather event away from vanishing forever.

Threatened Species Commissioner Fiona Fraser has told a budget estimates hearing the species has never had a recovery plan, despite being in hot water for some time.

Tasmanian Greens Senator Peter Whish-Wilson has been raising concerns about the fish for years.

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He fears it will become the first species to go extinct under Australia’s Environment Protection and Biodiversity Conservation Act, which has been in force for almost 23 years.

During Tuesday’s hearing the senator reminded the deputy secretary of the environment department about that, telling Dean Knudson:

“You may remember Mr Knudson I asked you many years ago whether there’d ever been an extinction under the Act.

“And you were pretty sure there hadn’t been. I asked ‘well are you confident this won’t happen’. I didn’t get a response to that. But it looks like we’re pretty close.”

Mr Knudson replied: “I think there’s no questions, senator, that we have relevant new information.

“We know there’s a sense of urgency with which we need to act and we are going to get onto that.”

Dr Fraser told the hearing Ms Plibersek was poised to write an urgent letter to Tasmania’s environment minister, after a new report found the skate population had plunged by almost half in just seven years.

“I’m told she intends to send a letter urging extreme intervention,” she said.

Environmental activists have blamed reduced oxygen levels in the harbour brought about by the local salmon farming industry, and climate change effects.

Dr Fraser agreed with that assessment but added other threats to the list including issues related to hydro electricity, water flows and gill netting.

“Those industry issues have really weakened the resilience of the skate which means they are very prone to pulse events or storms … or warming weather.

“They are, I guess, the urgent interventions which are within a human’s control, whereas the climate change and the skate’s special niche needs to survive are not.”

Senator Whish-Wilson noted that in 2012, the then federal government decided expanding salmon farming in Macquarie Harbour was not a controlled action under federal environment laws, as long as it happened in a particular way.

“The particular manner requirements relate to things like undertaking monitoring of water quality, implementing management responses if there are changes or adverse impacts on the water quality, on endangered species.

“Do you feel that the interim report that’s been released is evidence of adverse impacts?”

Departmental assistant director Cassandra Kennedy replied: “The minister is very keen to see action to ensure we can do as much as possible to try and put the maugean skate onto a better path. The minister understands that it’s urgent.”

-AAP