A group of Port Jackson Sharks have been released into the wild after taking part in a research project seeking to unlock the secrets of shark society.

The sharks have called Taronga Zoo home for the past two months as part of a joint project between Taronga and the Behaviour Ecology and Evolution of Fishes lab at Macquarie University.

Five females and one male were used in a study to investigate shark movement. We made special harnesses for each of the sharks and put a small accelerometer device on the harnesses.

Accelerometers are now found everywhere. They tell your phone when to flip the screen horizontally or vertically, and in a Fitbit they help to tell you how many steps you've taken.

By leaving the accelerometers on the sharks for a week, we recorded the sharks' movements constantly and were able to see the activity patterns that occur naturally in the sharks.

We found out that Port Jackson Sharks are nocturnal, they rest most of the day and swim further and at faster speeds at night. We also saw that all of the sharks were at their most active from sunset to midnight and that all of the sharks started resting again before sunrise.

In the future, we want to use accelerometers to help us identify more shark behaviours like resting, swimming, foraging and mating.

We also observed and recorded very important social behaviours and interactions between the Port Jackson Sharks. Many shark species, like the Port Jackson Shark, have complex social hierarchies, and using the videos recorded at Taronga we are able to take a peek into the social dynamics and better understand how they interact in the wild.

On Friday we had the pleasure of releasing the sharks back into Sydney Harbour, where they spend their winter season. We plan to continue our research next year in the hope of finding out more details about the cryptic lives of sharks and share our work with the community.

- Shark Researchers, Julianna Kadar - Catarina Vila-Pouca and Brianne Lyall