Insights from cloacal swab fecal DNA metabarcoding: a dietary assessment of juvenile white sharks (Carcharodon carcharias) off California

Context The white shark (Carcharodon carcharias) is a large-bodied, cosmopolitan predator. In Southern California, juvenile white sharks (JWS) can be found at both nearshore and offshore habitats across the Southern California Bight. Understanding their foraging behavior at this early life stage is essential for assessing their ecological roles and interactions with fisheries. Aim This study used cloacal swab DNA metabarcoding to identify prey items in JWS incidentally captured offshore to assess dietary composition and explore preliminary patterns across sex and size classes. Methods Cloacal swabs were collected from 12 JWS caught >5 km offshore in commercial gillnet fisheries between 2020 and 2022. DNA was extracted and sequenced using MiFish primers, with taxonomy assigned using a regional 12S reference library. Key results A total of 19 prey families were detected, including both pelagic and demersal fishes suggested that JWS are generalist feeders. Conclusion This study adds to the increasing body of evidence that DNA metabarcoding from cloacal swabs provides a less invasive tool to assess recently consumed prey in juvenile sharks. These preliminary findings suggest that JWS foraging offshore exhibit generalist diets, consistent with insights from prior dietary studies using traditional and molecular techniques. Implications This study supports previous studies done in the region and provides more information on the diet and resource use of the JWS in Southern California waters.