Traders fear their brands, and the entire state, will suffer a costly hit if aquaculture and other human threats drive the Maugean skate to extinction.

Authorities estimate there are just 40 to 120 adults left in Macquarie Harbour – the only place on earth where the species exists.

The federal government is spending millions on a captive breeding program as the salmon industry resists calls to destock the harbour.

The industry is trialling efforts to artificially oxygenate the harbour to offset what farmed fish take out and boost the prospects of a species that dates back 60 million years.

Federal Environment Minister Tanya Plibersek has promised to save the skate, but the newly formed Business Alliance for the Maugean Skate says she should be doing more to protect the species and Tasmania’s reputation.

More than a year has passed since the federal government’s own conservation advice called for urgent action to eliminate or significantly reduce fish farming impacts on the harbour’s oxygen levels.

In an open letter to the minister, the group warns the “lack of action could have severe consequences for the Tasmania brand”.

The letter cites research by the Tasmanian government’s place branding authority about the value Australians and international visitors place on the state’s unique natural environment, pristine beauty, and the protection of its unusual assets.

“A growing number of Tasmanian businesses are concerned about the future of the endangered Maugean Skate, and what the potential extinction of this ‘Thylacine of the sea’ could mean to the Tasmanian brand.”

The group has 28 members, including tourism businesses and food and beverage producers.

Individual members include Vince Trim, the executive chef at MONA, the Museum of Old and New Art in Hobart, and Australian actress and singer Essie Davis.

The group is an initiative of Environment Tasmania and concerned business owners.

It’s hoped membership will swell beyond 100 in coming weeks, with other businesses urged to endorse the open letter.

The minister is reviewing permits granted for salmon farming in Macquarie Harbour.

“I will make a decision in accordance with the law and the science, as I’m required to do,” Plibersek said.

The University of Tasmania’s Institute for Marine and Antarctic Studies has been monitoring environmental conditions in Macquarie Harbour for more than a decade.

It says the harbour has naturally low levels of dissolved oxygen in its mid-bottom waters, where the skate lives.

Research has shown oxygen levels declined from 2009 to 2013, with salmon farming, natural and controlled river flows, and climate change influencing those levels.

The government’s conservation advice says the most important anthropogenic contributor to the oxygen problems in the harbour is salmon farming.

The university is observing outcomes of the artificial oxygenation trial and this month said there were early, promising signs.

“The loads and scale of delivery and effect are now quite significant, especially in the context of potentially improving bottom-water dissolved oxygen levels in target areas that are important Maugean skate habitat, and for offsetting the estimated demands of salmon aquaculture,” Associate Professor Jeff Ross said.

– AAP