Depth zone200–1,000 m

Twilight Zone

Mesopelagic zone

Below the sunlight zone, only faint blue light filters down and photosynthesis is no longer possible. Many animals rise toward the surface at night to feed.

Conditions in this zone

Depth: about 200–1,000 metres
Light: dim and blue, fading to darkness; no photosynthesis
Cold water and steadily increasing pressure
Home to the daily vertical migration of countless animals

Life of the twilight zone

Many squid and jellyfish range into the twilight zone, and some sharks descend here on deep dives. Bioluminescence — light made by living things — becomes common.

FaunaHub profiles several twilight-zone specialists, including lanternfishes and marine hatchetfishes that migrate up to feed at night, and the tubular-eyed barreleye fish.

Animal profiles in this zone

Marine animals FaunaHub profiles that are documented in this zone. Many also occur in other layers.

Anglerfish
Deep-sea anglerfishes are documented in the dark midwater, commonly from the twilight into the midnight zone.
Broad / widespread
Source: WoRMS, Animal Diversity Web, IUCN Red List of Threatened Species
Hatchetfish
Marine hatchetfishes are documented in the twilight zone, ranging into the upper midnight; many migrate vertically.
Broad / widespread
Source: NOAA Ocean Exploration, Smithsonian Ocean, WoRMS
Jellyfish
Jellyfish drift through surface waters, and some occur down in the twilight zone.
Broad / widespread
Source: Animal Diversity Web, NOAA Fisheries, Encyclopaedia Britannica
Lanternfish
Classic twilight-zone fishes; many rise toward the surface to feed at night and sink by day.
Broad / widespread
Source: NOAA Fisheries, Britannica, IUCN Red List of Threatened Species
Shark
Many sharks hunt in sunlit surface waters; some descend into the twilight zone on deep dives.
Broad / widespread
Source: Animal Diversity Web, Britannica, IUCN Red List of Threatened Species
Squid
Squid range from surface waters down into the twilight zone.
Broad / widespread
Source: Animal Diversity Web, NOAA Fisheries, Encyclopaedia Britannica
Barreleye Fish
Barreleyes are documented in the deep twilight zone, ranging into darker layers; known mainly from a few live observations.
Representative
Source: Monterey Bay Aquarium Research Institute (MBARI), NOAA Ocean Exploration, WoRMS
Black Dragonfish
Documented in the deep twilight and midnight zones; females are reported to migrate upward at night to hunt.
Representative
Source: Monterey Bay Aquarium Research Institute (MBARI), NOAA Ocean Exploration, WoRMS
Vampire Squid
Lives in cold, low-oxygen midwater — commonly the twilight into the upper midnight zone (the oxygen-minimum zone).
Representative
Source: Monterey Bay Aquarium Research Institute (MBARI), Smithsonian Ocean, WoRMS

Source & methodology

Zone science here is summarised from authoritative ocean-science sources. Animal placements reuse each species' verified source and show a confidence label; a depth zone is not treated as a complete range, since many animals move between layers.

Frequently Asked Questions

How deep is the twilight zone?

The twilight zone (mesopelagic zone) spans roughly 200–1,000 m.

Do these animals live only in the twilight zone?

Not necessarily. Many marine animals move between depth zones, some migrating vertically each day. We show the zone(s) each animal is documented to occur in, with a confidence label.

Last updated: 2026-06-27