UTAS Professor Barry Brook says more work needs to be done for true picture of Maugean skate numbers

A team of scientists will review population projections for the endangered Maugean skate after questions were raised over key data. Latest.

The state government will put together a team of independent scientists to review population projections for the endangered Maugean skate after questions were raised over key data.

University of Tasmania conservation ecologist Barry Brook was commissioned by Salmon Tasmania to review current projections of the skate’s population decline over the coming decades.

Maugean Skate

He has written to Federal Environment Minister Tanya Plibersek saying more work was needed to get a clearer picture of the skate’s future as current estimates potentially overstated the decline in the skate population.

Conservation groups have called on Ms Plibersek to revisit a 2012 decision allowing an expansion of fish farming in the area.

Macquarie Harbour is the last place in the world the Maugean skate is known to exist.

Minister for Parks and Environment Nick Duigan announced the new review on Friday.

“Professor Brook’s analysis raises questions in relation to the modelling used to inform current population assumptions for the skate,” he said.

“The report by Professor Brook today is yet further evidence there are many differing views in relation to the skate and its population viability.

“It is critically important to understand the status and trajectory of the skate population to inform our conservation efforts.”

Australia Institute Tasmania director Eloise Carr said the salmon industry was playing for time.

“This is one scientist that has been paid by the industry that pollutes Tasmania’s coastal waters, makes massive profits and pays no tax, compared to Australia’s top scientists at the Threatened Species Scientific Committee who have provided the best available evidence which could not be clearer — salmon farming is the number one threat to the Maugean skate and should be eliminated or significantly reduced in Macquarie Harbour.

“It’s a move straight out of the fossil fuel industry playbook: cast doubt on the science, confuse the issue and the result is to delay stronger regulation of a harmful industry.”

Saturday is Threatened Species Day, the anniversary of the death of the last thylacine.

Predictions over Maugean skate numbers need work, says scientist

September 6, 5am

Predictions of the decline of the endangered Maugean skate in Macquarie Harbour were overblown and more work was urgently needed to better guide conservation efforts, a University of Tasmania scientist says.

Conservation ecologist Barry Brook was commissioned by Salmon Tasmania to review current projections of the skate’s population over the coming decades.

Macquarie Harbour is the last place in the world the species – dubbed the Tasmanian tiger of the seas – is known to exist.

Conservation groups have called on Federal Environment Minister Tanya Plibersek to revisit a 2012 federal government decision allowing an expansion of fish farming in the area as skate numbers fall under pressure from the impact of human activity including aquaculture, dams and climate change. Her decision is pending.

Professor Brook has written to Ms Plibersek saying more work was needed to get a clearer picture of the skate’s future.

Professor Barry Brook.

He said 2023 Population Viability Analysis of the Maugean Skate was hampered by methodology that potentially overstated the decline in the skate population.

“My analysis found that the reported outcomes from this modelling were essentially ‘baked in’ by the choices made when selecting the baseline parameters for the 2023 PVA,” he said.

“This meant it was not predictive, and did not allow for proper assessment of either the causes of decline or the likely impact of conservation-management interventions.

“In other words, the 2023 PVA’s results were effectively a preordained outcome and cannot be relied upon to draw firm conclusions about the future of the Maugean skate.

“In my view, to ensure the long-term success of any conservation plan for the Maugean skate, the whole exercise should be redone from the ground up.”

A baby Maugean skate has been hatched for the first time in captivity.

Professor Brook recommended the federal government fund two workshops to review and improve the forecasts and conservation advice.

The skate has been listed as endangered since 2004.

The 2012 federal decision to allow the expansion of salmon farming operations in Macquarie Harbour was made on the understanding it would not affect adversely impact the species.

Skate numbers fell by 47 per cent between 2014 and 2021 and a 2023 study predicted the species could decline by between 97.8 per cent and 99.7 per cent by 2041.

The most recent estimate put the number of skates to be about 1300.

Four skates were detected in Bathurst Harbour, but none for 30 years.

On Thursday, the University of Tasmania announced the Macquarie Harbour Oxygenation Project had been successful at delivering and retained oxygen at depth, which is expected to help the skate.

“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,” IMAS Associate Professor Jeff Ross said.

Originally published as UTAS Professor Barry Brook says more work needs to be done for true picture of Maugean skate numbers