It stands to reason in a healthy environment that prey should always vastly outnumber the predators that eat them. But an international study has found that sometimes, even in the most untouched environments on the planet, the food pyramid can be turned upside down.

Led by Macquarie’s Dr Johann Mourier, a research team has discovered that a population of reef sharks in French Polynesia has tipped the local food pyramid on its head, thanks to prey delivering themselves straight onto the sharks’ dinner plates.

Under normal conditions, the sharks would actually have been starving, because food is scarce around their location. But for some reason spawning aggregations (breeding groups) of fish from other reefs were directly delivering themselves to the sharks.

“We noticed the massive number of sharks in this channel, especially gray reef sharks, and questioned how such a large number can be maintained and where they find their food,” Mourier says.

“We have to recognise that predator and prey interactions are very complicated mechanisms to understand and our next project will focus on doing the same type of study in different reefs with different levels of exploitation of fish aggregations.”

Johann – a French native – says he has been interested in sharks since he was young.

“The first time I saw a shark was in an aquarium and I have been intrigued by these animals leading me to learn more about them,” he says. “Their bad reputation also pushed me to better understand sharks and devote my life to  increasing our knowledge on their ecology and behaviour.”