Tasmanian Greens Senator Peter Whish-Wilson has called for an "immediate" end to fish farming in Macquarie Habour, following a scientific report that claimed a nearly 50 percent drop in the number of prehistoric Maugean skate in the region over the last decade.
The report by the Institute of Marine and Antarctic Studies found that numbers of the endangered species dropped by 47 per cent between 2012 and 2021, and that a single extreme weather event could be enough to push the species to extinction.
The IMAS report suggested the species might be pushed to extinction by extreme hot weather, and Senator Whish-Wilson noted that Australia is entering an El Nino phase, where hotter weather is more likely.
He blamed input of nitrogen nutrients by fish farming in Macquarie Habour as one of the main reasons for the decline in skate numbers.
"This is a dire situation, they are very worried about a possible extinction of this this species," Senator Whish-Wilson said.
"The only thing we can do is to remove fish farms from Macquarie Harbour immediately, especially before this summer commences, and we start seeing more problems with dissolved oxygen, more problems with warming oceans, and more fish mortalities," he said.
He said an industry shutdown on the Harbour was "critical" and that there was a "narrow window" to act.
"Before this summer commences, before we start seeing more problems with dissolved oxygen in Macquarie Harbour, before more problems with warming oceans, and more fish mortalities."
But a spokesperson for industry advocacy group Salmon Tasmania labelled Senator Whish-Wilson's proposal as "just another attack on hard-working Tasmanians".
The industry is responsible for about 17 per cent of all jobs on Tasmania's West Coast, according to Salmon Tasmania, and employs 75 Tasmanians directly and hundreds more indirectly, according to West Coast Council Mayor Shane Pitt.
He said the shutdown proposal would have a "substantial impact" on the West Coast community, especially Strahan.
"It would be a fairly substantial impact on the West Coast community given the number employed director in aquaculture, but it would be all over the state, because we have a lot of drive-in, drive-out workers," Cr Pitt said.
He estimated that roughly 70 per cent of the industry's workers drove in from other parts of the state, and shutting the industry down on Macquarie Harbour would have impacts on Strahan's accommodation sector, as well as on hundreds of contractors and other suppliers to the farms.
He also cast doubt on Senator Whish-Wilson's claims that the fish farms were solely responsible for the decline of skate numbers in the Habour.
"There are many other factors in play," he said, saying activity by Hydro Tasmania and drainage was affecting dissolved oxygen levels.
"All of those things have been investigated by IMAS as well and their report does say it's a combination," Cr Pitt said.
He also said another factor was the growing number of seals in the Harbour taking skate as food.
In comments to parliament last week, Environment Minister Roger Jaensch said the situation of the Maugean skate was being monitored, and that a number of factors could be behind their decline in numbers.
"It is wrong for anyone to misrepresent these reports and indicate that aquaculture is the sole determinative of the future of this species, and to land that at the feet of government policy," he told parliament.
"Others include recreational gill netting, commercial fishing, hydro inflows and a range of other matters - there are multiple factors affecting the survivability of the species," he said.
The state government was already talking to the Australian government about accessing federal funding to help protect this species through a federal Threatened Species Action Plan, he said.
Mr Jaensch also pointed out that the Tasmanian Environmental Protection Authority has issued new limits relating to total permissible dissolved nitrogen outputs for fish farming in Macquarie Harbour area in response in part to IMAS' work.
Our journalists work hard to provide local, up-to-date news to the community. This is how you can continue to access our trusted content:
Sign up for our newsletter to stay up to date.