South Shetland Island archipelago krill-predator survey 2025: region-wide census of imperiled fur seals and HPAI testing results

Antarctic fur seals (Arctocephalus gazella, AFS) are an important component of Antarctic marine ecosystems and a key indicator species for the CCAMLR Ecosystem Monitoring Program. Recent studies have clarified that AFS consists of at least four genetically-distinct subpopulations. The species as a whole, and three of those four subpopulations are in decline, including the subpopulation in the South Shetland Islands (SSI) archipelago region. Studies based on the two largest colonies indicate that South Shetland Antarctic fur seals (SSAFS) are in catastrophic decline, however a synoptic census across their entire range has not been completed since 2008, leaving uncertainty about the extent of the decline. Additionally, a high pathogenicity avian influenza strain (HPAI) has recently invaded seabird and marine mammal communities in the Antarctic Peninsula region raising calls for increased monitoring. Therefore, in January 2025 the United States Antarctic Marine Living Resources Program (U.S. AMLR), along with collaborators from the Chilean Antarctic Institute (INACH) and the University of Chile, surveyed the entire SSI to census SSAFS and monitor for HPAI. We found no evidence for wide-spread HPAI infection in seabird or pinniped colonies. Further, we estimate that the SSAFS subpopulation has decreased by over 88% since 2008 surpassing the IUCN criteria for a critically endangered subpopulation.