diurnal vertical migration

Diurnal vertical migration is a common behavior in marine ecosystems where organisms move up and down the water column daily. Many plankton, fish, and squid spend daylight hours in the darker, deeper waters below the photic zone to avoid visual predators. As dusk approaches, they ascend to shallower waters to feed, returning to the depths before dawn. This migration is primarily driven by light levels and can help organisms find food and avoid predation.1

Some aquatic animals also use vertical migration to take advantage of different currents at various depths, aiding in dispersal or reaching new habitats. For instance, larger invertebrates in coastal waters may move into the water column at night to find mates or disperse, as visual predators have reduced hunting capabilities in the dark. While most migrations are horizontal, vertical movements are also observed, such as certain fish moving between deep and surface waters seasonally.12