Delineation and estimation of the Maugean Skate population in Macquarie Harbour, Tasmania

The Maugean Skate is listed as Endangered under the Australian Environment Protection and Biodiversity Conservation Act (1999) (EPBC Act) and the Tasmanian Threatened Species Protection Act (1995) based on its small population size and restricted distribution. It is one of 100 priority species identified under the national Threatened Species Strategy.

The only known population of Maugean Skate exists at Macquarie Harbour on Tasmania’s west coast, where its numbers are thought to be declining in response to a long history of environmental degradation. An understanding of the population size and structure is urgently needed to support conservation actions for the species. Due to the cryptic nature of the Maugean Skate, however, and the challenging environmental conditions in the harbour, existing population estimates remain highly uncertain, with no current way to provide robust assessments of the relative changes to the population over time.

This project will use next generation genetic sequencing and novel imaging survey tools to delineate and estimate the size of the Macquarie Harbour Maugean Skate population. In addition, the research will examine the evolutionary potential of the Maugean Skate to adapt to the changing environmental conditions.

Approach

Population estimation methods for the Maugean Skate cannot be based on capture. Netting would no longer reliably catch a skate, and presents a potential risk to the health of a captured individual. Traditional video-based survey techniques are unsuited due to poor visibility in the shallow, turbid sediments. Two alternative methods being advanced in this project are acoustic imaging and next generation genetic sequencing.

Adaptive resolution imaging sonar (ARIS) and light detection and ranging (LiDAR) offer significant advantages over traditional visual methods for underwater survey in Macquarie Harbour. They are being trialled by the University of Tasmania Institute for Marine and Antarctic Studies as potential monitoring/abundance estimation alternatives for Maugean Skate and are showing significant promise. Development challenges include integrating these tools with an adequate deployment platform and additional sensors, optimising survey protocols, and managing the data stream.

Previous research based on DNA ‘barcoding’ found the Maugean Skate population to have very low genetic diversity. This project will use more advanced genetic technologies to detect finer-scale genetic structure, using 250 tissue samples previously collected from the Macquarie Harbour population. This will identify different genetic lineages, including those with adaptive potential.

Expected outcomes

Survey tools will be available to routinely estimate and monitor the population size of Maugean Skate in Macquarie Harbour. Managers at a Commonwealth, state and local level will have an improved knowledge base to guide conservation actions and potential adaptive management strategies such as captive breeding, and translocations of lineages from one geographical region to another.

Project location