The skate is recognised as one of the Gondwana-era natural values of Tasmania’s Wilderness World Heritage Area (TWWHA) . Its potential extinction carries global significance.[5]
Description
The Maugean skate is a medium-sized skate with a maximum total length of approximately 74 cm in males and 87 cm in females. It has a quadrangular disc-shaped body, a narrowly pointed, elongated snout and dark edged ventral pores. The dorsal surface of the skate is almost uniformly dark grey to brown with small and faint white spots. The tail is moderately broad at the base and tapers towards large dorsal fins. Males have three rows of thorns along the tail, whereas females have five.
The Maugean skate is distinguishable from its closely related Zearaja species by its smaller adult size, longer snout and smoother dorsal surface. The only other skate species known within its distribution is the thornback skate (Dentiraja lemprieri) which can be distinguished by its smaller size, brown to grey-black dorsal surface with fine spots and reticulations, short, rounded snout and long, narrow claspers.[3]
Distribution and habitat
The Maugean skate is restricted to brackish, estuarine waters in two isolated estuaries on the west coast of Tasmania; Macquarie Harbour and Bathurst Harbour. No individuals have been found in marine waters outside of these harbours. Its preferred habitat is benthic, shallow channels between 5 and 15 metres in depth with poor light penetration, high tannin loads and silty substrate.[3]
There have been only four confirmed observations of the species in Bathurst Harbour, the last in 1992. Multiple surveys between 1992 and 2022 have failed to verify the presence of the species, and recent eDNA samples collected in 2022 have detected minimal amounts of Maugean skate DNA. This suggests it may be either locally extinct, vagrant, or occurring in very small numbers.[1][3]
Diet
The Maugean skate holds a high trophic position (3.7) in the food web. Their diet consists of benthic prey species, with crustaceans as their dominant prey type.[6]
Research by The Australia Institute indicates that 58 percent of Australians are in favor of stopping farming of salmon in Macquarie Harbour, which could cause the extinction of the Maugean skate.[7] The National Environment Law requires that the federal Environment Minister, Tanya Plibersek, reconsider the decision[8]that permitted large-scale salmon farming in Macquarie Harbour "as soon as practicable."[7]
The Australia Institute has written an open letter to UNESCO and the IUCN take appropriate action to protect the Maugean skate and ensure the heritage value of the TWWHA is preserved.[9][10]
In previous submissions, the Australia Institute recommended a significant increase in fully protected areas, greater state government accountability, and full implementation of the proposed Macquarie Island Marine Park expansion[11]. More than 80 organizations worldwide have called for an end to greenwashing practices linked to farmed salmon certifications, citing the role of the industry in the potential extinction of the critically endangered Maugean skate.[12]
^Weltz, Kay; Lyle, Jeremy M.; Bell, Justin D.; Semmens, Jayson M. (2019). "Dietary analysis reveals the vulnerability of the endangered Maugean skate (Zearaja maugeana) to benthic changes in Macquarie Harbour". Marine and Freshwater Research. 70 (5): 745–753. doi:10.1071/MF18231.
