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The challenge

Understanding shark populations

Our research is helping with the management of grey nurse sharks ©  David Harasti

Australia is home to more than a quarter of the world's Chondrichthyan fauna (sharks and rays).

Many species are vulnerable to mortality above natural levels, either through harvesting by commercial or recreational fishing, or through other sources such as habitat degradation or shark control activities.

We need to better understand shark populations, their ecology and habitats, so that the threats to sharks can be identified and managed.

Our response

Managing threats to sharks

In 2013, we were part of a global study that analysed the conservation status of more than a thousand shark and ray species, and found that a quarter of them were under threat of extinction.

The study called for species assessments with better population estimates that could be linked with effective management practices.

We're developing new techniques in areas including taxonomy and biogeography, tagging and tracking, population estimates and monitoring and management approaches.

Their application includes reef sharks, deep-water sharks in the Great Australian Bight, the sharks of Australia's northern rivers including the critically endangered speartooth shark, as well as commercial shark fisheries.

For white sharks, a recent breakthrough combining cutting edge genetic techniques with novel statistical methods has enabled our scientists to estimate adult white shark populations in Australian waters.

We are also playing a key role in grey nurse shark population estimates to assist ongoing management and recovery of the species, and to determine if protective measures are working.

A Port Jackson shark.

The results

New breakthroughs for sharks and rays

Naming new species of sharks and rays

Our Australian National Fish Collection is internationally recognised for its Indo-Pacific sharks and rays and acts as a focal point for national and international collaboration.

Using a tag pole to attach an acoustic tag to a white shark

Using a tag pole to attach an acoustic tag to monitor white shark journeys ©  Justin Gilligan

We're contributing to international processes including the Convention on International Trade in Endangered Species and the International Union for the Conservation of Nature Red List of Threatened species.

Our research also supports decisions about shark conservation required under the Australian Government's Environment Protection and Biodiversity Conservation Act1999, and to shark management by state and local government agencies.

Estimating white shark populations

We have developed a world-first genetic analysis technique to estimate adult white shark numbers for both the eastern Australasian and southern-western white shark populations, all without having to catch or even see any adult white sharks. Instead, they locate the tell-tale marks of the parents in the DNA collected from juveniles, a method known as close-kin mark recapture.

Close-kin mark-recapture first involves taking a tissue sample from a juvenile shark and obtaining a genetic profile of that animal; this is then compared to all of the other sharks to determine if the shark is related, and how. This highly detailed genetic data sampling is then combined with a breakthrough statistical method to estimate adult white shark numbers.

This innovative research is being shared with local, state and federal authorities, research agencies, and other Australian and international white shark tagging and research initiatives to provide scientific insight into white shark populations to better understand their movements, and is being used to evaluate the success of Australia's white shark National Recovery Plan.

This technique has also been applied to conservation efforts for grey nurse sharks. We estimate that there are less than 2,200 grey nurse sharks living on the east coast of Australia.

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