Data collected between 2021 and September 2024 by the University of Tasmania's Institute for Marine and Antarctic Studies suggest the population, which is endemic to Macquarie Harbour, may be stabilising although numbers remain significantly lower than historical levels.
Current estimates of skate numbers range from as few as 40 to 120, following mass-mortality events in 2019 that wiped out thousands.
Current estimates of skate numbers range from as few as 40 to 120, following mass-mortality events. (HANDOUT/INSTITUE FOR MARINE AND ANTARCTIC STUDIES)
The small ray has been at centre of battle between conservationists and the salmon industry after oxygen levels declined from 2009 to 2013 as a result of salmon farming in the harbour on the Tasmanian west coast.
Federal conservationists suggested salmon farming is the main human contributor to poor water quality and the primary threat to the skate's existence, prompting federal Environment Minister Tanya Plibersek to invest over $2.1 million in a captive breeding program.
Earlier this month, the minister decided to review the permits granted for salmon farming in Macquarie Harbour, a move welcomed by a coalition of business advocates known as Business Alliance for the Maugean Skate.
Institute researcher David Moreno said additional data was needed to determine whether the observed presence of young skates would lead to a sustained recovery.
"Updated population models and action plans are needed to ensure the species' survival in Macquarie Harbour, its last remaining habitat," he said.
While the apparent stabilisation in the population was welcome, Australian Marine Conservation Society campaign manager Alexia Wellbelove said it wasn't "cause for celebration".
"Removing salmon farming is the fastest way to improve oxygen levels for the skate to survive and recover," she said.
The Maugean skate population may be stabilising, although it remains lower than historical levels. (HANDOUT/INSTITUE FOR MARINE AND ANTARCTIC STUDIES)
"Salmon farm stocking in Macquarie Harbour peaked in 2015 at about 20,000 tonnes; the salmon industry has not reduced biomass far enough since then."
She said the Albanese government had mad a commitment to "zero new extinctions" yet the the Maugean skate is on the "brink of extinction" in its only home.
But Tasmanian state Labor MP Janie Finlay said the improved skate numbers - alongside Environmental Protection Authority research showing oxygen levels in Macquarie Harbour had improved - was information Ms Plibersek couldn't "ignore".
"It shows that it is possible for the Maugean skate and salmon aquaculture to coexist in Macquarie Harbour," she said.
"It shows that continued investment can mean a strong aquaculture industry and a healthy harbour environment."
But University of Tasmania Associate Professor Jeff Ross says improvements across the entire harbour can be attributed to good, natural recharging conditions over three of the last four summers, and the salmon industry being ordered to cut production a few years back.
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