- Four more grey nurse aggregation sites found; only one previously known
- Federal Govt reviewing threatened grey nurse shark’s recovery plan
- WA Govt needs to implement monitoring program on commercial fishing boats
A new study into Western Australia’s threatened grey nurse shark population has uncovered four previously unknown sites where the sharks aggregate, but it highlights the need for more data on the threatened species, especially from the commercial fishing industry.
The Australian Marine Conservation Society (AMCS) and Humane Society International (HSI) encourage the WA Government to fully implement independent monitoring of fishing vessels to address data needs to reduce fishing impacts and support the identification of additional aggregation sites, particularly along the southern coast.
The paper, published in the Endangered Species Research journal, found four new sites where grey nurses aggregate, often over long periods, with one shark being sited at the Exmouth navy pier in 12 consecutive years. The study was based on 16 years of data (2006−2021) from divers’ observations (2347 sightings) and commercial fisheries’ bycatch records (574 sharks).
Only one aggregation site had previously been recorded, the Exmouth navy pier, but these four new sites are closer to Perth: Shark Cave at Rottnest Island; Opera House north of Rottnest; Direction Bank offshore of Two Rocks; and Key Biscayne offshore of Lancelin. The sites all occur in areas closed to commercial fishing. Evidence of fishing injuries was found on 17% of all grey nurses photo-tagged at Shark Cave.
AMCS shark scientist Dr Leonardo Guida said: “This new study gives us critically needed information about the threatened grey nurse shark on Australia’s west coast where we know relatively little compared to those on the east coast. It’s exciting and heartening that much of this information has come from passionate citizen scientists who have logged their observations of grey nurse sharks over the years.”
HSI Head of Campaigns Nicola Beynon said: “The grey nurse shark has been studied extensively on Australia’s east coast where it is protected as Critically Endangered and most of its critical aggregation sites placed in sanctuaries. This study is important so that our understanding and protection for the species on the west coast can catch up.”
The study highlights the need for more information on the ‘labradors of the sea’ as they are affectionately known, especially from commercial fisheries where we know many are caught, as these new aggregation sites identified occur in waters closed to the commercial shark fishery.
Dr Guida said: “The WA Government and the WA Fishing Industry Council are making positive steps trialling an independent observer program on commercial fishing vessels, but it’s critical this program is fully implemented by 2024 so we know where and to what extent grey nurse sharks are being caught.
“It’s pretty clear that accurate fishing data coupled with resourced citizen science programs can provide a better idea of where grey nurses, including pregnant females, aggregate in commercial fishing waters so that we can better protect these areas, not just in WA but on the east coast too.”
HSI nominated the grey nurse shark for its listing as a Vulnerable species in WA and, where we had more information, a Critically Endangered Species on the east coast.