For years lobsters were thought to be the main predator for sea urchins, but University of Newcastle researchers have found sharks also have a taste for the marine pest.
The research, led by marine ecologist Jeremy Day, involved tethering sea urchins to the entrance to a lobster den near Wollongong over 25 nights in the spring of 2023.
It was anticipated that lobsters would be drawn to the urchins but they mostly walked past.
Instead sharks proved to be the main predator, eating 45 per cent of the urchins, while lobsters ate four per cent.
"We expected that would result in higher rates of predation by lobsters, but it's not what we found," University of Newcastle marine ecologist Jeremy Day said.
"Sharks came in and smashed them."
The research was recently published in the journal Frontiers in Marine Science.
Port Jackson sharks and crested hornsharks are common along the NSW coast but are fewer in number compared to lobsters.
Mr Day said like lobsters they are a migratory species which seasonally spend time in-shore - and it is during those periods when urchins are eaten.
He said the sharks' grinding tooth arrangement allows them to eat the urchins.
"They are docile predators which are capable of eating lots of spiky things," Mr Day said.
While they are native to NSW, long-spined urchins have extended their range into Victoria and Tasmania, where they pose a threat to local ecosystems and fisheries, as waters have warmed due to climate change.
"It is a massive ecological issue, particularly for the southern states - here in Tasmania, where we've lost 15% of our east coast reefs - with the same problem across eastern Victoria," Dr John Keane from the University of Tasmania said.
Mr Day had highlighted a complex puzzle of marine food webs on the east coast.
He said a pilot study that he conducted in 2020 also showed that Port Jackson sharks ate longspined sea urchins.
