Inferring Natal Origins and Movements of Sharks and Rays: Novel Applications of Intrinsic Markers from Vertebral Chemistry

Sharks, skates, and rays (elasmobranchs) exhibit complex patterns of movement and habitat use which often vary by sex, season and ontogenetic stage. As a result, there remain large gaps in our understanding of the life history of most species, particularly among more mobile and pelagic species. Migratory pathways, environmental history, and source populations have been successfully reconstructed from chemical markers in the otoliths of teleost fishes, but this approach has only recently been applied to studies of elasmobranchs. Electronic tagging has demonstrated that elasmobranchs often exhibit a high degree of site fidelity to feeding, breeding or nursery areas. Differences in environmental conditions among these areas can be reflected in the chemical composition of elasmobranch vertebrae, providing valuable markers of individual, age- and sex-specific differences in geographic origins and habitat use. Here, we discuss the utility of intrinsic chemical markers deposited in elasmobranch vertebrae and apply vertebral elemental and isotopic composition to infer habitat use and discern geographic origins during the early life history of two highly mobile species; white (Carcharodon carcharias) and scalloped hammerhead (Sphyrna lewini) sharks. Analyses of vertebral chemistry offer a promising new tool for the study and conservation of highly mobile shark and ray populations.