Shark research continues on Norfolk Island

A team of scientists from Flinders University in South Australia are set to return to Norfolk Island in February 2022 to continue research on the local tiger, dusky and Galapagos sharks. With the help of Mark Scott and the Fitzpatricks, the team is working to understand what these sharks eat, where they go, and how healthy they are.

To understand what they eat, the team catches the sharks and secures them alongside the boat or on the pier, where the scientists draw blood and take a small piece of muscle. These samples are then taken back to the lab for biochemical analysis to reveal what these sharks eat and where they sit in the food chain. The 2020 and 2021 samples revealed that mutton bird might be an important part of tiger shark diet, but that this might be changing a little bit each year so the research team is looking forward to seeing what the 2022 samples show.

In 2020 and 2021, the research team tagged 20 tiger sharks with a satellite tag that sends a signal when the sharks swim on the surface, allowing them to be tracked in real time. This helps the team understand how much time the sharks spend around Norfolk Island, or if they go over to Australia, New Zealand, or New Caledonia. Of these 20 tagged sharks, most undertook large migrations up to New Caledonia, Vanuatu, and further. Shark “Headstone” travelled all the way to Papua New Guinea, down to the Queensland coast near Mackay, back to Norfolk Island, started swimming towards New Zealand, but then moved back to New Caledonia all within a year! To continue to build our understanding of shark movement, the team plan to tag 15 new sharks in 2022, and you can track them using the OCEARCH shark app, or by going to http://dev.ocearch.org/tracker to see where they check in.

The 2021 sharks all have unique names chosen by the Norfolk Island School and the local team working on the project. You can follow Meg, Geoff, Freidi, Nehsi, Isla Belle, Jap, Scotty 2, Nomad, Philip, and Nepean as they journey around the Pacific Ocean. Sharks Scotty 2 and Nepean are already on eastern side of New Caledonia, and the research team wants to watch where they go next.

To learn where the tiger, dusky, and Galapagos sharks go around Norfolk, the team also surgically implanted 40 acoustic tags which have a 10-year battery life, so they can track the sharks long-term. However, these tags cannot communicate with satellites or provide real-time locations. Instead, they emit a “ping” sound that is detected by the 16 underwater listening stations the team deployed around the island in February 2021 with the help of Mitch Graham. Hopefully they are all still in place in February 2022 when the team returns to collect them so they can learn where these 40 sharks have been hanging out.

To understand the shark’s health, the team took skin microbes to identify the natural bacteria that live on the surface of shark skin. Because the skin of sharks is covered in dermal denticles (teeth-like structures) it is very hard for the microbes to attach to this irregular surface. However, once they do attach they play an important role in keeping the sharks healthy. The microbes collected on the 2022 expedition will be compared with those from 2021 and 2020, which showed that each species has their own unique set of skin microbes. They will also be compared with microbes from the skin of whale sharks from around the world, thresher, leopard, horn, angel and swell sharks from California and Port Jackson sharks from Sydney to best understand how sharks around the world stay healthy.

In addition to researching the sharks, the team is also working to understand the yellowtail kingfish. To measure how quickly they grow in the productive waters around Norfolk Island, the team dissected yellowtail kingfish heads to remove the otoliths, which are the fish’s ear bones. These otoliths lay down annual growth rings, like a tree, so allow the researchers to assess how old the fish are. This project will compare the kingfish from Norfolk to those from Australia’s east coast, where researchers are currently collecting enough otoliths for the comparison.

The research team wants to thank Mark Scott and his family, Luke and Dean Fitzpatrick (thanks Fitzy’s Farm!), and Mitch Graham for their ongoing support with this research. Thank you also to those at the pier who provided fish frames and information about the wildlife around Norfolk Island.