Scientists have seen a recent upward trend in the relative abundance of Maugean skate in Macquarie Harbour and it's a potential sign that the wild population of this iconic endangered species has improved, with research catch rates returning to levels last seen in 2014.
Scientists at the University of Tasmania's Institute for Marine and Antarctic Studies (IMAS) have been conducting dedicated monitoring of the Maugean skate in Macquarie Harbour using research netting since 2021, building on previous monitoring programs from 2012 to 2019.
The new study released today has assessed the entire monitoring data set and confirmed that, while the number of skate caught per unit of netting effort (CPUE)* showed a substantial decline in relative abundance between 2014 and 2022, recent surveys indicate a significant increase from 2022.
"We are pleased to report that these current estimates are similar to 2014, with the timing of this trend aligning with improved environmental conditions in the harbour, particularly an increase in dissolved oxygen levels," said IMAS researcher and lead author, Dr David Moreno.
"We found that the progression of juveniles to the adult population has shown a trend of year-on-year improvements up to at least 2019. Meanwhile, the capture of young individuals in 2022 and 2023 suggests there was some hatching success until at least 2020/21.
"But these levels have not yet returned to the pre-2009 rate of juveniles contributing to the population," he said.
IMAS Maugean Skate Research Program leader and co-author, Professor Jayson Semmens said the recent upward trend in the relative abundance and capture of young individuals following a prolonged period of decline is a positive sign for the Maugean skate population.
"While we are cautiously optimistic, there is still a long way to go. Only continued monitoring of the Maugean skate population in Macquarie Harbour will allow us to know the long-term trajectory of recovery of this endangered species," he said.
IMAS Fisheries and Aquaculture Centre Head and co-author, Professor Sean Tracey said IMAS acknowledges the valuable support from the Tasmanian Government to date for research on the Maugean skate in the Harbour, which underpins the recovery strategy for the species, and also welcomes the significant financial contribution announced by the Federal Government in late 2024.
"Robust science is the cornerstone of building evidence-based conservation action plans that will help to put the Maugean skate on a sustained pathway to recovery," Professor Tracey said.
"Together with ongoing support from the Tasmanian Government, this funding will boost the Maugean Skate recovery program and make increasing our research and knowledge of the wild population in the Harbour possible.
"The funding support from both the Tasmanian and Federal governments will advance research into the important next phase – securing the ongoing success of the captive breeding program, building a deeper understanding of how skate use the harbour and react to environmental variability, and developing more robust population estimates.
"This work is critical to rebuilding the wild population of this endangered species," he said.
The 2021–2024 study was supported with funding from the Department of Natural Resources and Environment Tasmania (NRE Tas) and from the University of Tasmania, including through the Sustainable Marine Research Collaboration Agreement (SMRCA). The 2012–2018 study was funded by the Australian Government's Fisheries Research and Development Corporation (FRDC) and NRE Tas through the SMRCA. Monitoring funding from 2021has been provided by NRE Tas.
* Catch per unit of effort (CPUE) is a measure of relative abundance, which is a standard proxy for total abundance.
Cover image: Maugean skate in Macquarie Harbour. Credit: Jane Ruckert IMAS
