'Thylacine of the seas' risks extinction, warn experts

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Scientists warn an ancient fish species faces extinction, as the numbers of the "thylacine of the seas" plunge in its last remaining habitat in Tasmania.

The maugean skate is found only in Macquarie Harbour on Tasmania's west coast and marine researchers say environmental changes in the waterway have left the declining fish vulnerable to extreme weather.

The fish's numbers fell by almost half over a seven-year period, a drop environmental activists blame on reduced oxygen levels in the harbour brought about by climate change and the local salmon industry.

Environment Tasmania has called for the skate to be listed as critically endangered and says its demise would make a mockery of the federal government's "no new extinctions" pledge.

The skate's lineage goes back to the time of the dinosaurs and the bottom-dwelling fish has been dubbed the thylacine (or Tasmania tiger) of the sea.

The University of Tasmania's Institute for Marine and Antarctic Studies (IMAS) monitored skates since 2021 and found its population fell 47 per cent between 2014 and 2021.

"We recently found that Macquarie Harbour was the last remaining habitat for maugean skate and, like other endemic species, this limited range means their conservation is inextricably linked with the health of the system they live in," IMAS researcher David Moreno said.

The fall in the skate's numbers and its limited range and genetic diversity "is clear evidence that the population is at risk".

IMAS professor Jayson Semmens said the harbour's environmental changes had increased the skate's vulnerability to "sudden high-impact events, such as water column turn-over driven by westerly winds, which can happen at any moment and potentially decimate the population".

Environment Tasmania said it supported called for the maugean skate to be upgraded from endangered to critically endangered and called on federal Environment Minister Tanya Plibersek to intervene.

"Without drastic action, Tasmania will have the grim record of the second bony fish extinction in the world on its record, after the smooth handfish," marine campaigner Rebecca Howarth said.

"Not only would the extinction of the maugean skate be an absolute tragedy for Tasmania, but it would also be an embarrassment to federal Environment Minister Tanya Plibersek, who pledged zero extinctions on her watch."

Dr Moreno said activities such as recreational fishing in the harbour needed to be managed, along with those that affected the environment such as salmon aquaculture and river flow management for hydro production.