Fear dynamically structures the ocean's pelagic zone

Fear of predation can have wide-ranging ecological effects.This is especially true in the ocean’s pelagic zone, the Earth’s largest habitat, where vertical gradients in light and primary productivity force numerous taxa to migrate vertically each night to feed at the surface while minimizing risk from visual predators. Despite its importance, and the fact that it is driven by spatial differences in perceived risk, diel vertical migration (DVM) is rarely considered within the “landscape of fear” framework. It is also far from the only such process in the pelagic zone. We used continuous, year-long records from an upward-looking echosounder and broadband hydrophone at a cabled observatory off Central California, USA, to observe avoidance reactions by several groups of pelagic animals to the presence of their predators. As expected, vertical migration was ubiquitous, but we also observed behaviors at shorter and longer time-scales which were best explained by fear of predation. The presenc...