Looking to the Past to Ensure the Future of the World's Oldest Living Vertebrate: Multi-Decadal Trophic Ecology of the Australian Lungfish

The Australian lungfish, Neoceratodus forsteri, is one of only five surviving lungfish species in the world and is likely the oldest living vertebrate on the planet with fossil records dating back 380 million years. At one time there were at least seven species of lungfish whose distributions extended across Australia, but at present native populations of the Australian lungfish persist in only two river systems. Despite being a federally listed threatened species, globally recognized as a scientific icon and sacred to indigenous peoples, the long-term persistence of the Australian lungfish is in jeopardy. Here, we provide the first ever investigation of long-term trends in lungfish trophic ecology by conducting a retrospective analysis of the isotopic composition of annual growth rings associated with individual fish scales. Coupled with radiocarbon dating to back-calculate age, we inferred multi-decadal patterns in feeding behavior in response to agriculture land-use (Mary River) and flow alteration by dams (Burnett River), and for an introduced population (Brisbane River). Our results provide a unique glimpse into how resource utilization by lungfish (which can live for 80+ years) has responded to environmental change, and will help guide conservation actions to ensure the future of the world's oldest living vertebrate.