Inferring Patagonian toothfish dispersal from circadian rhythm in swimming behavior

Analysis of depth time series data from six Patagonian toothfish (105-126 cm total length) tagged with popup satellite archival tags in the South Atlantic revealed bimodal distributions. These findings suggest that diel swimming behaviors can be used to estimate longitude from transmitted time series data. Our results demonstrate a strong correspondence between the estimated longitude and the overall trajectory of the tagged fish. From Davis Bank, some fish were estimated to have traveled eastward towards Shag Rocks, while others moved westward towards Burdwood Bank and the Patagonian Continental Shelf. Notably, four fish eventually returned to the vicinity of their release sites, providing the first evidence of return migrations in this species. The biological and ecological implications of diel behavior and circadian rhythm in Patagonian toothfish, a deep-sea species, remain largely unexplored and offer promising avenues for future research.