Tasmania is home to a globally unique species that emerged 60 million years ago – the Maugean Skate. But the millennia-old Maugean skate is fighting for its existence against the polluting foreign-owned salmon farming industry in its only remaining habitat, Macquarie Harbour.
Tucked away in the tannin-rich waters of Macquarie Harbour on Tasmania’s west coast is the world’s rarest skate species and the only skate known to inhabit brackish water – the Maugean Skate (Zearaja Maugeana). First discovered by scientists in 1988 and only formally described in 2007, the Maugean skate is a relic of an ancient era in Earth’s history.
Macquarie Harbour is the last remaining home of the IUCN red-listed endangered Maugean Skate. One third of the harbour is located within the boundaries of the Tasmanian World Heritage Wilderness Area. The skate is listed as a World Heritage value. With less than 1,000 individuals left, the Maugean skate is projected to be uplisted to critically endangered by the Australian Government over the next year.
The science is clear – salmon farming is the primary threat to the skate
Salmon farming started in Macquarie Harbour in 1987 as a small boutique Tasmanian owned industry. Today, the entirely foreign owned salmon industry’s pursuit of ever increased production and profits has led to salmon farming being the leading cause of pollution in Macquarie Harbour. This has resulted in dangerously low oxygen levels within the Maugean skate’s habitat with catastrophic consequences for the future of the species.
The science:
Macquarie Harbour is a stratified body of water that relies on ocean water to penetrate through the narrow and shallow mouth of the harbour allowing oxygenated water to reach the deeper areas and recharge them. The Maugean skate lives and lays its eggs in these deeper areas of the harbour. The Skate has adapted to the complex and challenging environment it inhabits, however aquaculture has thrown the unique ecosystem of Macquarie Harbour out of balance - threatening the Maugean skate with extinction.
In May 2023, Institute for Marine and Antarctic Studies (IMAS) scientists took the unprecedented step of releasing an interim report and calling for urgent conservation action in response to findings that between 2014 -2021 the Maugean skates population crashed declining by 47% in relative abundance and the species was only one extreme weather event away from extinction. The scientists stated that dramatically low oxygen levels caused by human activities, namely nutrient pollution from salmon farming, were suffocating the Maugean skate and its eggs. The skate’s highly specialised habitat had become a liability.
Conservation Advice provided to the government by the Threatened Species Scientific Committee identified salmon farming operations as a “very high risk” threat that is “almost certain to impact the Maugean Skate throughout the entire harbour” with “catastrophic” consequences. The advice explicitly called for an immediate destock of salmon farms by Summer 2023/24. To date, the industry continues to retain a chokehold on the harbour, with no actions taken by the Australian or Tasmanian governments on the Conservation Advice’s destock call.