Bradford R W, Harasti D, Louden B, Westlake EL, Stephenson S, Kilpatrick C, Dwyer R, Cameron J, Wanganeen H, Sherman S, Ierodiaconou D, Travers M, Braccini M, Williams J, Newman SJ (2025). Project 4.15: Grey nurse shark aggregations. Report to the National Environmental Science Program. CSIRO Environment, Hobart, Tasmania.
Overview
This report provides a revised definition for what constitutes an aggregation of grey nurse shark (Carcharias taurus), provides a review of existing and potential aggregation sites in Western Australia, and details field efforts to further investigate GNS movements. It is intended for policy makers and sate management authorities.
The primary aim of this project was to synthesise existing data on grey nurse shark (GNS) distribution and known aggregation sites to inform a revised definition for a GNS aggregation to be used for future conservation efforts. Concurrently, the project expanded research into several potential (but currently unrecognised) aggregation sites in Commonwealth waters off Queensland and New South Wales. Further, this project supported training opportunities for Indigenous Rangers in Victoria from the Gunikurnai Lands and Water Aboriginal Corporation, Eastern Maar Aboriginal Corporation, and the Bunurong Land Council Aboriginal Corporation.
A GNS aggregation has been defined as a site where five or more grey nurse sharks can be observed. Although this definition served well during the initial stages of conservation actions in the early 2000s, a review of the definition is required to support future conservation efforts.
This project has proposed that a GNS aggregation be redefined as a discrete area where multiple GNS (two or more) can be observed on a predictable basis (e.g., annually, seasonally) and includes one or more behavioural driver consistent with the Biologically Important Areas (BIAs) and Important Shark and Ray Areas (ISRA) frameworks.
Field activities have been carried out in Queensland, New South Wales, and Victoria aimed at increasing our understanding of GNS presence and behaviour to better inform the derivation of a definition for a GNS aggregation.
In Queensland, additional acoustic receiver coverage has been installed at Barwon Banks within Commonwealth waters. In New South Wales, presence of GNS at the Outer Gibber Reef in the Commonwealth Hunter Marine Park has been further documented to provide baseline data on the importance of the site to GNS.
In Victoria, surveys of potential GNS habitat in western Gippsland were undertaken using baited remote underwater video systems (BRUVS), remote operated vehicles (ROV), and environmental DNA (eDNA). No GNS were detected. Activities in Victoria included members from the Gunaikurnai Lands and Water Aboriginal Corporation, Eastern Maar Aboriginal Corporation, and the Bunurong Land Council Aboriginal Corporation. The primary aim of the study in Victoria was to transfer skills in the use of these survey tools to the Rangers.
This study recommended that potential GNS aggregation sites be assessed with the BIA and ISRA frameworks in mind. Determining the temporal pattern of use and driver(s) behind aggregating behaviour are likely to require multiple site surveys over at least one year. To assist with documenting site use, Appendix F provides a standard suite of data aligned to the BIA and ISRA frameworks to collect for each site survey.
