Ontogeny in marine tagging and tracking science: technologies and data gaps

The field of marine tagging and tracking has grown rapidly in recent years as tag sizes have decreased and the diversity of sensors has increased. Tag data provide a unique view on individual movement patterns, at different scales than shipboard surveys, and have been used to discover new habitat areas, characterize oceanographic features, and delineate stock structures, among other purposes. Due to the necessity for small tag-to-body size ratio, tags have largely been deployed on adult animals, resulting in a relative paucity of data on earlier life history stages. In this study, we reviewed tagging efforts on multiple life history stages for seabirds, marine mammals, marine turtles, and fish and enumerated studies focusing on each guild that targeted larvae, juveniles or hatchlings. We found that turtles and fish had higher proportion of studies focusing on juveniles (> 20%) than seabirds and marine mammals (<10%). On both juveniles and adults, tags were used in a targeted manner with passive and transmitting tags as the main tools for population demography and connectivity studies, while GPS and archival tags were used more frequently for habitat analyses and foraging ecology. These findings identify the need to focus on novel approaches in tagging multiple life history stages both to study marine predator ecology and to effectively manage marine populations.