Endangered Maugean skate choking in big salmon toilet
Main photo: Adult Maugean skate. Photo Institute for Marine and Antarctic Studies
Tasmania’s Maugean skate has been around since the dinosaurs but it could become the world’s first ray or shark to become extinct in modern times as a direct result of human activity unless drastic action is taken, the Australian Marine Conservation Society (AMCS) and Humane Society International (HSI) Australia said on the eve of National Threatened Species Day.
A recent study showed the skate’s numbers have plummeted, and scientists fear it could become extinct within 10 years or wiped out in another extreme weather event. After intense coastal storms in 2019, the population was cut in half to about 1500 individuals.
The Maugean skate – part of the cartilaginous group of fishes that includes sharks and rays – lives solely in Macquarie Harbour on the remote west coast of Tasmania. The water quality in Macquarie Harbour, with its narrow, shallow entrance, is extremely poor, primarily because the water is depleted of oxygen from intensive salmon farming as well as manipulated river flows into the harbour that prioritise hydro electricity generation. The skates and any eggs they lay are deprived of the oxygen they need to live.
Urgent recovery measures are needed before the end of this year, including restoring the health of Macquarie Harbour, implementing a captive breeding program and ongoing monitoring of the population. In February this year, AMCS and HSI Australia nominated the Maugean skate for Critically Endangered status under Australia’s nature laws.
AMCS shark scientist Dr Leonardo Guida said: “The Maugean skate has been around since Tyrannosaurus rex roamed the Earth but is now literally being choked to death in its home that we have turned into a giant salmon toilet. If the Australian Government does not act now, it may disappear on our watch.
“The Maugean skate’s only home is Macquarie Harbour, where intensive salmon farming is depleting what little oxygen there is, and manipulated river flows to generate electricity are limiting oxygen-rich seawater from entering the harbour.
“Imagine snorkelling in a toilet while trying to breathe through a straw – that’s what life has been like for the skate for more than a decade, and it has gotten progressively worse. Tassie-grown produce is driving an extinction and nobody wants another Tasmanian Tiger.
“The skate is one extreme weather event away from extinction so increasing oxygen throughout the harbour is critical to provide resilience. An El Nino event is likely to occur this year, bringing warmer waters that hold less oxygen, which could push the skate and its eggs beyond what they can handle.
“Federal Environment Minister Tanya Plibersek must do everything in her power to save the skate, including stopping salmon aquaculture in Macquarie Harbour, managing river flows to allow seawater to sufficiently recharge the harbour with oxygen, and resourcing an effective captive breeding program.”
HSI marine biologist Lawrence Chlebeck said: “This is an extinction emergency. The Maugean skate should be listed as ‘Critically Endangered’, and it is having to fight for its existence with the salmon aquaculture industry.
“Federal Environment Minister Tanya Plibersek has no choice but to upgrade protection for the Maugean skate and ensure urgent recovery measures are put in place to halt its advance toward extinction. ‘No new extinctions’ was the ambition from this Government and that ambition is being put to the test here and now.”
Australian Marine Conservation Society