Seabirds are among the most threatened groups of vertebrates worldwide with up to 70% of species currently in decline. Warming oceans, changing prey abundance, conflict with fisheries, and disease outbreaks are major concerns. However, our understanding of declining seabirds in the subantarctic region is often limited. Many of the penguin species in the subantarctic region have been in decline for decades, particularly the endemic species of New Zealand. However, the most dramatic declines have been seen in the Eastern Rockhopper Penguin (Eudyptes filholi), which occupies both the southern Pacific and Indian Oceans. Eastern Rockhoppers once outnumbered all other penguins in the New Zealand subantarctic, but they have declined by more than 90% since the 1940s. There has been limited work on Eastern Rockhoppers in the past decade and no assessments across their entire New Zealand range to identify conservation needs in the region. We aim to fill this gap by 1) assessing current population status and genetic diversity, 2) characterizing diet and foraging behavior, and 3) identifying key threats contributing to their decline. We will use a highly collaborative, transdisciplinary approach that combines genome sequencing, diet and foraging behavior, and disease screening to create a robust dataset from which to assess this species. We will work with collaborators to carry out simultaneous fieldwork on three subantarctic islands in the South Pacific. This will provide a crucial direct comparison between islands to evaluate the species at the island and regional scale as well as the marine ecosystem on which they depend. Finally, we will work with the New Zealand Department of Conservation to make policy recommendations for Rockhopper management and conservation, with particular attention to fisheries regulations and marine protected areas. Without a comprehensive, range-wide assessment and an effective management response we risk losing the Eastern Rockhopper in the South Pacific.