Investigating the diet of the white shark (Carcharodon carcharias) using DNA metabarcoding approaches

The white shark (Carcharodon carcharias) is a key apex predator essential to the functionality of temperate and sub-tropical marine ecosystems around the world. However, C. carcharias has suffered significant declines in recent decades, and effective conservation efforts are needed to protect C. carcharias populations and the ecosystems they support. Unfortunately, conservation management is complicated by increasingly frequent human-shark interactions and shark attacks globally, and a general lack of information on the species’ biology and ecology. In this study, DNA metabarcoding analyses of cloacal swabs from 167 eastern Australian subadult C. carcharias individuals was performed to address current knowledge gaps around shark diet and feeding behaviour. Findings indicate C. carcharias diets to consist of a large variety of prey items including elasmobranchs, marine mammals, birds, and predominantly teleost fish. Statistical analyses revealed no effect of shark sex, size or sampling time, on diet composition, however, significant spatial effects were evident. In corroboration with previous research, this study suggests C. carcharias is a generalist, opportunistic feeder, with potential for some targeted predatory behaviour toward particular fishes. The information gained from this study offers new insights into marine trophic interactions in eastern Australia, the resilience of C. carcharias to environmental change, and the key prey species that support C. carcharias populations and could act as bioindicators of C. carcharias nearshore visitations. Overall, this study provides a valuable framework for guiding future management towards conserving C. carcharias populations and reducing risks of shark attack in Australian waters.