This record provides an overview of the NESP Marine and Coastal Hub Research Plan 2024 Emerging Priorities project "Modelling adult abundance and habitat distribution of Maugean skate". For specific data outputs from this project, please see child records associated with this metadata.
The Maugean skate (Zearaja maugeana) is listed as Endangered under Tasmania’s Threatened Species Protection Act and the Commonwealth Environmental Protection and Biodiversity Conservation Act 1999. Its known population is small (~3,000 individuals, Macquarie Harbour, 2016) and highly restricted, having only been recorded in two isolated estuaries: Bathurst Harbour and Macquarie Harbour in south-western/western Tasmania. This constitutes one of the most limited distributions of any known extant elasmobranch.
A Roadmap of Agreed Actions has been published by the Maugean skate recovery team. In this document, the recovery team agreed that Close Kin Mark Recapture (CKMR) be investigated as a priority action for determining historical abundance of the species in the harbour, and potentially as a complimentary monitoring tool going forward. The Commonwealth’s 2023 Conservation Advice for the Maugean skate has also identified this as a priority action.
The CKMR method has been developed and operationalised for various finfish and elasmobranch species. The method uses next-generation sequencing methods to inform on the prevalence of closely related individuals (parent-offspring/half-siblings) within a set of sampled animals. This data is fed into statistical models of the population in order to obtain estimates of abundance of the breeding adults, adult survival rate, and given sufficiently informative data, population trend. CKMR will provide crucial independent estimates of the size of the Maugean skate spawning population in the Macquarie Harbour. This will be of significance for conservation decision processes which are ongoing and in determining monitoring options in the future.
A secondary component of this project is to model the critical habitat distributions of the species. Maugean skate are thought to be impacted by low dissolved oxygen (DO2) in Macquarie Harbour. This is influenced by combinations of exogenous factors (industrial usage, manipulation of flow regimes from riverine inputs) and climatic / weather forcing events. Remediation trials involving the addition of DO2 are underway to determine if low DO2 conditions may be ameliorated using anthropogenic supplementation. However, a crucial missing element required to guide this process, is the linking of biophysical models of the harbour to observations of the conditions observed to be selected by the skate.
This component of the project will combine synoptic biophysical predictions of the harbour with telemetry data from tagged Maugean skates which details the skates' selected temperature, depth and O2 conditions. These two information sources will be combined via habitat selection models - previously used to model habitat preferences of other species (e.g. Southern bluefin tuna) - to predict whether remediation, climate or other factors are likely to impact on the availability of selected skate habitat.
Initial potential habitat maps will be generated for a hindcast period (2017-18), and for a forecast period based on models currently under development that simulate recent and evolving water quality in near-real time. This will enable recent and evolving maps of suitable skate habitats. Simulated habitat maps will be assessed against the known collective knowledge of skate habitat to identify critical habitat areas within Macquarie Harbour and inform future spatial and temporal sampling strategies.
Outputs
• High-quality DNA sequences of Maugean skate [sequencing data]
• Hindcast maps (2017-18) of potential Maugean skate occupation [spatial data]
• Recent and forecast (evolving) maps of potential Maugean skate occupation under different management scenarios [spatial data]
• Estimates of spawning stock abundance of the Maugean skate from CKMR analysis [data contained in written report]
• Final project report [written]
