Apex predators shape marine ecosystems by regulating prey populations through predation and influencing energy flow across habitats. Understanding apex predator diet is critical to elucidating trophic linkages among species and across ecosystems.
Shark Bay, Western Australia, is a unique and climate-vulnerable ecosystem, hosting the world’s largest and most diverse seagrass meadows that sustain megafauna such as green turtles and dugongs, as well as tiger sharks (Galeocerdo cuvier), a key predator. In 2011, a severe marine heatwave caused extensive seagrass loss, leading to declines in green turtle and dugong sightings. However, tiger shark catch rates remained stable. As generalist predators that likely include turtles and dugongs in their diet, tiger sharks can exploit multiple habitats and food webs, potentially adapting their foraging strategies in response to changes in prey availability.
This study characterises tiger shark diet using stable isotope analysis of tissue samples from tiger sharks and potential prey, including dugongs, turtles, fish, sea snakes, dolphins, and invertebrates. We hypothesise that tiger sharks in Shark Bay exhibit opportunistic feeding, deriving energy from both seagrass-associated prey (e.g., turtles and dugongs) and pelagic prey (e.g., fish and other mobile species). These findings advance understanding of trophic connectivity and ecosystem responses to environmental change.