Differences in regional oceanography and prey biomass influence the presence of foraging odontocetes at two Atlantic seamounts

The importance of seamounts as foraging hotspots for cetaceans depends on interactions between ocean flow and topographical features that concentrate prey. However, the oceanographic processes driving these aggregations are still unclear. Here, we analyzed two months of passive acoustic recordings from two remote seamounts in the Northeast Atlantic, Atlantis and Irving, in relation to regional oceanography and estimates of prey biomass. Delphinids and sperm whales were detected in both seamounts with higher foraging activity at night, indicating feeding on diel migrating prey. There were more detections of delphinids and sperm whales at Atlantis than at Irving. These two seamounts lie in different oceanographic settings created by the Azores Current that separates colder and less saline water masses in the north (Atlantis seamount) from warmer and more saline waters in the south (Irving seamount). Irving seamount is only affected by transient features like eddies that enhance productivity for short time periods. These conditions translate into more productive waters at Atlantis seamount than at Irving, as shown by predicted prey biomasses that ultimately attract top predators. Comparative studies such as this one can help to explain the main drivers of presence of top predators at seamounts.