The Tasmanian endemic Maugean skate (Zearaja maugeana) is listed as endangered under both Tasmania’s
Threatened Species Protection Act 1995 and the
Environment Protection and Biodiversity Conservation Act 1999.
The species is also included in the top 110 priority threatened species under the Australian Government’s Threatened Species Strategy Action Plan 2022-2032.
Maugean skate. Copyright Jane Rucker/IMAS
The Maugean skate is a medium-sized species, with mature females reaching a maximum of 84cm in total length, and males reaching a maximum of 70cm. Male Maugean skate can be told apart from females by the presence of claspers at the beginning of the tail.
The Common Thornback Skate (Dentiraja lemprieri) also occurs in Tasmanian estuaries, and can be differentiated from the Maugean
skate by its smaller size, short, rounded snout and long and narrow claspers.
Why is the Maugean skate threatened?
Two of the key threats to the Maugean skate are habitat degradation and loss, particularly documented declines in dissolved oxygen levels and in sediment health, and unintended mortalities from entanglement in fishing nets set to catch other species.
Other identified threats or limiting factors include predation (for example from fur seals and parasitic sea lice); pollution, such as from historic mining runoff; habitat changes linked to altered river flows from hydroelectric production; increased nutrient loadings from aquaculture operations; low genetic diversity and inbreeding, as well as climate change impacts.
Need for conservation action
skate is known only from Macquarie Harbour and Bathurst Harbour, on Tasmania’s remote west coast. However, the status of the population in Bathurst Harbour has long been uncertain, with only four individuals ever found.
Recent research by the Institute of Marine and Antarctic Studies (IMAS) shows that the species now survives only in Macquarie Harbour. The reason for the skate’s disappearance in Bathurst Harbour is not known.
monitoring shows that the remaining skate population in Macquarie Harbour has also declined significantly in recent years, including a likelihood that a significant proportion of the population may have died during 2018 and 2019. There are also signs of decreased breeding success for the remaining population. An additional risk is genetic in-breeding due to small population size.
Together, these factors suggest that the species faces a high risk of extinction, that every skate is now important to the survival of the species, and that urgent conservation actions are required to stabilise and recover the skate’s population.
What is being done to help the Maugean skate?
The Tasmanian Government is implementing a range of coordinated conservation actions to reduce the likelihood of extinction for the species. These include:
Publication of a Listing Statement
Listing Statement provides a basis for detailed conservation planning. It summarises contemporary species and population data, identifies threats to the species and outlines research and conservation and management needs.
Changes to gill-netting rules in Macquarie Harbour
Recent research indicates that Maugean
skate sometimes rely on shallow areas of Macquarie Harbour to access highly oxygenated water. This behaviour increases the likelihood that skate may encounter gill-nets set to catch other species. Gill-nets set for long periods of time increase the chances of mortality for any skate entangled. Changes to where and when gill-nets can be used in Macquarie Harbour are therefore needed, as a precautionary measure to minimise the risk of interactions between skate and fishers.
Remediation of environmental conditions in Macquarie Harbour
In September 2022, the Environment Protection Authority issued a
Total Permissible Dissolved Nitrogen Output for Macquarie Harbour, to improve environmental indicators including levels of dissolved oxygen. The new determination will reduce dissolved nitrogen outputs by approximately 10% compared with 2021 levels.
The Tasmanian Government has also initiated a working group to inform options to remediate environmental conditions in Macquarie Harbour. The working group includes representatives from IMAS, CSIRO, state government, and Hydro Tasmania.
Other working groups are being planned to explore other potential threats to the species, along with appropriate management strategies.
Conservation Action Plan
Findings from the workshops will be incorporated into a Conservation Action Plan (CAP) for the species. The CAP will identify and prioritise areas of research and management strategies for both the short- and long- term recovery of the species, and will be overseen by a Maugean
skate recovery team.
Community education and awareness
Addressing threats to the Maugean
skate depends on community understanding of the species' status and engagement in its recovery. The Cradle Coast Authority's
Maugean Skate Awareness Project will use a variety of community-based activities to engage with diverse audiences on the topic of skate conservation.