Wild Shark social networks

Sharks are apex predators and have played a key role in keeping our oceans healthy for millions of years. Our work on wild Port Jackson (PJ) sharks in Jervis Bay since 2012 using novel acoustic monitoring and genetic analyses has revealed important knowledge of their ecology and life history. For example, we now know that many PJ sharks migrate an incredible 2000km/year to complete their trek from breeding sites in Jervis Bay all the way to Bass Strait. In 2015 and 2016 a cohort of wild PJ sharks from Sydney harbour were temporally transferred to Taronga to allow our scientists to validate novel methods for monitoring the species’ feeding ecology in the wild. This work continued in 2017 during August to October with a new cohort of sharks. The sharks were in breeding mode during their stay at Taronga, and investigations into the impacts of changing oceanic conditions on shark biology and development were included.

Sharks were found to be nocturnal, with increasing activity by males late in the season corresponding to the timing of the southerly migration of PJs. Novel accelerometry data clearly differentiated four important behaviours that are associated with feeding and migration. The techniques developed here will be integrated with genetic analyses to classify and understand social behaviour and movements in free-ranging sharks that are unable to be observed directly. This science is crucial to advising policy on shark protection and management.