Port Jackson sharks gather in Bass Strait, possibly to feast on scallops before embarking on a long journey north to spawn.
Port Jackson sharks snuggle together on the ocean floor. (Video: NESP-IMAS)
A remotely operated vehicle (ROV) captured footage of thousands of Port Jackson sharks (Heterodontus portusjacksoni) sleeping together on the ocean floor in Beagle Marine Park at Bass Strait, Australia, as reported by IFL Science on August 15. They were first discovered six years ago, and the research team returned to investigate how conditions in the area have changed.
The ROV was operated from the MRV Ngerin research vessel of the South Australian Research and Development Institute (SARDI). “It was exciting to pass over a section of exposed reef and see the sharks sleeping at a depth of 65 meters below the vessel, almost exactly where they were six years ago,” said Dr. Jacquomo Monk, the lead explorer from the Institute for Marine and Antarctic Studies at the University of Tasmania (IMAS).
“The stunning scene was streamed to us via a remotely operated device equipped with seven cameras developed by Boxfish Robotics in collaboration with IMAS. Thousands of sharks lay intertwined like a carpet spread across the ocean floor,” Monk added.
Thousands of sharks lay intertwined like a carpet spread across the ocean floor.
Port Jackson sharks are characterized by their blunt heads and saddle-like markings on their bodies. They typically inhabit rocky environments near the ocean floor in southern Australia. They feed on soft-bodied animals, crustaceans, sea urchins, and small fish, often foraging at night, according to the Australian Museum.
The research team noted that all the Port Jackson sharks sleeping together on the ocean floor were female. Scientists are unsure of the exact reason, but Port Jackson sharks are known to gather primarily during mating, with males and females usually living separately for most of the year.
“We are not exactly sure why the females are here. Perhaps they are enjoying the local delicacy – doughboy scallops – before embarking on a long journey north to spawn,” Monk explained. This journey can extend 600 to 800 kilometers, connecting mating grounds with spawning sites.
The presence of Port Jackson sharks in the area six years after the initial study indicates that this habitat is important to them. Beagle Marine Park has protected various diverse underwater habitats, such as coral reefs and sponge gardens, playing a significant role for sharks as well as many other terrestrial and aquatic species.
