Why do lanternfish glow on their bellies?

To hide their outline from below

What helps lanternfish eyes catch more light?

A mirror layer called the tapetum lucidum

Lanternfish

Hygophum

Lanternfishes (family Myctophidae) are small deep-sea fishes, most under 15 cm long, named for the rows of light organs called photophores along their bellies and sides. About 250 species live in all the world's oceans, and many swim up hundreds of metres at night to feed near the surface, then sink back into the dim twilight zone by day. The genus Hygophum, shown here, has nine species; their males and females carry their tail lights in different places.

Also known as Myctophid, Myctophids, Lanternfishes

Lanternfish abilities

300–800 m climbed at dusk (Hygophum hygomii)
At dusk many lanternfish swim up from the dark twilight zone to feed near the surface, then sink back down before sunrise.
- Hygophum hygomii spends the day 600–800 m down and the night between the surface and 300 m.
- This daily up-and-down trip, made by huge numbers of ocean animals, is described as the largest migration of animal life on Earth.
- Not every animal goes: in a round-the-world sonar survey, about half of the twilight-zone echo made the trip, from about 20% in the Indian Ocean to about 90% in the eastern Pacific.
- Scientists think travelling in the dark helps migrators avoid being seen while they feed, and resting in cool deep water may save energy.
Daytime depth of four Hygophum species
Hygophum hygomii600–800 m
Hygophum hanseni608–728 m
Hygophum benoitibelow 700 m
Hygophum reinhardtiibelow 1,000 m
Bars show midpoints or the upper limit. At night they are found from the surface to 300 m, at 57–110 m, above 600 m and in the top 200 m.
Sources [8, 11, 15, 16, 17, 18]
Downwards reflectors aim the glow
Light organs on the belly glow softly, so that from below the fish's dark outline blends into the faint light from the surface. This camouflage is called counter-illumination.
- Lanternfish use the photophores on their lower sides and belly for counter-illumination.
- A blue-green, mirror-like reflector of guanine crystals sits behind each light and points it downwards.
- Some counter-illuminating animals match the brightness of the light from above. How lanternfish check their own glow is still unknown: a 2023 study of nine species found no light organs shining into the eyes, unlike in some other deep-sea fishes.
Sources [5, 6, 19, 20]
♂ top · ♀ below tail light (Hygophum)Still debated
A bright light gland near the tail can flash on and off. In Hygophum it sits on top of the tail stalk in males and underneath in females.
- In Hygophum reinhardtii, males have one supracaudal gland (above the tail stalk) and females have three merged infracaudal patches (below it).
- Tail glands are wired with many nerves and linked light cells, which may explain their very fast flashes.
- Scientists think these lights help lanternfish signal, perhaps to find a mate. But the differences between the sexes are often small, and a courtship role has not been shown.
- The flash rhythm in this animation is for illustration only; it is not a measured pattern.
Flash code 3.1 s, repeats
flash 400 ms · dark 500 ms · flash 400 ms · dark 1.8 s
Sources [1, 7, 8, 9, 10]
≈252 species, each with its own light layout
The pattern of photophores is different in each species, a bit like a barcode made of lights. Scientists use it to tell species apart.
- There are about 252 lanternfish species in 34 genera.
- A 2014 study found that deep-sea fishes with species-specific light organs, such as lanternfishes and dragonfishes, form new species faster than deep-sea fishes that use light only for camouflage or hunting.
- That fits the idea that lanternfish recognise their own kind by their lights, although no one has yet watched them do it in the wild.
Sources [5, 7, 21]
6.2 mm eye on a 4.5 cm fish
Big eyes with a mirror layer at the back help lanternfish see in one of the dimmest places on Earth, where much of the light comes from other animals' glow.
- The twilight zone, about 200–1,000 m down, is one of the dimmest habitats in the world, lit by faint sunlight and flashes of bioluminescence.
- Lanternfish eyes have a tapetum lucidum (a reflective layer), an extra gap beside the lens that lets in more light, and a retina made only of rods.
- Their visual pigments are tuned to the light around them: faint sunlight from above and the glow of other animals.
Eye size vs body length (Hygophum benoiti) 45 mm body
eye 6.2 mm (≈14%)
One measured fish (standard length).
Sources [1, 2, 3, 22]
38 kHz echo sounders that map the layerStill debated
Gas in many lanternfish swim bladders bounces sonar back so well that a crowd of them looks like a solid band, the deep scattering layer. Early sonar users mistook it for the sea floor.
- When ships first used sonar to measure depth, the sea floor seemed to rise at night. The false bottom was echoes from huge numbers of small gas-filled fish, mostly lanternfish, migrating upwards.
- Scientists now map these layers with 38 kHz echo sounders. By day they averaged about 590 m deep in the southern Indian Ocean and about 350 m in the eastern Pacific.
- Turning echoes into fish numbers is tricky: siphonophores (jelly relatives, some with gas floats) also echo strongly, and some lanternfish have no gas at all. That is why fish totals are still debated.
Sources [5, 12, 18, 23]
≈16% of sinking carbon carried by fish (estimate)Still debated
Lanternfish eat near the surface at night and digest in the deep by day. Along the way they carry carbon downwards, which helps the ocean store it.
- Migrating lanternfish carry food from the surface down into the deep, where they breathe out carbon dioxide and release waste.
- Carbon in waste that sinks to the deep can stay out of the air for a very long time.
- A 2021 review estimated that fish of all kinds carry about 16% of the carbon leaving the sunlit layer, give or take 13%: a rough figure with big uncertainty.
- Because so much is unknown, researchers urge a careful approach before any large fishery for twilight-zone fish.
Sources [4, 13, 14, 15, 24]

Tap a pin on the model or a part below.

6.2 mm eye of a 4.5 cm Hygophum benoiti
- Lanternfish have big eyes for their size. In one 4.5 cm Hygophum benoiti, each eye measured 6.2 mm across.
- Behind the retina sits a mirror-like layer, the tapetum lucidum, which gives light a second chance to be caught.
- The retina has only rods, the cells that work in dim light, and they are long and tightly packed.
- Eye size varies a lot: scientists measured 61 species and think big eyes evolved more than once in the family.
Sources [1, 2, 3]
Copepods main prey
- Lanternfish are small predators of zooplankton. Copepods, tiny crustaceans, are the main prey of the species that migrate.
- Hygophum benoiti is a generalist: what it eats changes with the zooplankton living in each area.
- Most species feed in shallower water at night, after their climb from the deep.
Sources [4, 5]
Blue-green colour of the light
- Photophores are small light organs set in rows along the belly and sides. Lanternfish have an extra row along their sides.
- In the species studied in detail (Diaphus watasei), each body photophore has a curved, mirror-like reflector made of guanine crystals that sends the light downwards.
- The layout of photophores differs from species to species, so scientists use it to tell lanternfish apart.
Sources [5, 6, 7]
Top or bottom male or female (Hygophum)
- Near the tail sits a separate light gland. In Hygophum reinhardtii, males have one gland on top of the tail stalk, filling about half the space there; females have three merged patches underneath.
- Tail glands are packed with nerves, and their light cells are linked to each other, which may let the whole gland flash very fast and all at once.
- Because they differ between the sexes, scientists think tail lights are used for signalling, but this has not been proven.
Sources [7, 8, 9, 10]
8.1 cm largest Hygophum hygomii
- Hygophum species are small: Hygophum hygomii reaches about 8.1 cm and Hygophum reinhardtii about 6 cm.
- Across the whole family, lanternfish range from about 2 to 30 cm, but most are under 15 cm.
- Counting fin rays helps with identification: Hygophum reinhardtii has 13–15 rays in its dorsal fin and 21–25 in its anal fin.
Sources [5, 8, 11]
Gas or none depends on the species
- Many lanternfish have a small gas-filled swim bladder. Gas reflects sound strongly, so these fish show up on ships' echo sounders.
- Not all of them: some species keep gas all their lives, some never have any, and some lose it as adults.
- In the Southern Ocean, several of the most common species have no gas in their swim bladder, so sonar surveys can miss them.
Sources [5, 12]
≈10% of primary production, respired by twilight-zone fish (estimate)
- Lanternfish fill their guts near the surface at night, then digest, breathe and release waste back down in the deep.
- That carries carbon from the surface into deeper water. One study estimates twilight-zone fishes may respire about 10% of the ocean's primary production (the growth of tiny plant-like plankton) in deep water.
- For all fish together, a 2021 review estimated they carry about 16% of the carbon sinking out of the sunlit layer, give or take 13%.
Sources [4, 13, 14, 15]
600–800 m daytime depth, Hygophum hygomii
- The tail fin powers the daily commute. Hygophum hygomii spends the day 600–800 m down and rises to between the surface and 300 m at night.
- Hygophum reinhardtii goes even deeper by day, below 1,000 m, and comes up into the top 200 m at night.
- These daily trips are part of what is described as the largest migration of animal life on Earth.
Sources [8, 11, 15]

Lanternfish in scientific drawings

Living lanternfish are rarely photographed, so these are historical scientific illustrations from Wikimedia Commons.

Myctophum nitidulum, from The deep-sea fishes of the Hawaiian Islands (Gilbert, 1905)Photo: Unknown illustrator, in Gilbert (1905), Public domain
Myctophum punctatum, from the Prince of Monaco's scientific expeditionsPhoto: Emma Kissling, Public domain
Myctophum lutkeni, type illustration from Gilbert (1905)Photo: Charles Henry Gilbert (1905), Public domain
Myctophum evermanni, type illustration from Gilbert (1905)Photo: Charles Henry Gilbert (1905), Public domain
A lanternfish from Francis Day's The Fishes of India (1878)Photo: C. L. Griesbach, Public domain

Lanternfish by the numbers

Measured by scientists and fish databases. Big estimates come with big ranges.

Lanternfish species: ≈252; in 34 genera; other counts say 245+⁠[7, 5]
Hygophum species: 9; the genus shown on this card⁠[26]
Length: 2–30 cm; whole family; most are under 15 cm⁠[5]
Hygophum size: up to 8.1 cm; Hygophum hygomii, total length; mature from about 5.8 cm⁠[11]
Daytime depth: 600–800 m; Hygophum hygomii⁠[11]
Night-time depth: 0–300 m; Hygophum hygomii, from the surface down to 300 m⁠[11]
Twilight-zone fish, worldwide: 1.8–16 Gt; middle half of one model's estimates (1 Gt = 1 billion tonnes); lanternfish are a major part; Upper estimates are about 100 times the yearly catch of all the world's fisheries⁠[23, 27, 13]
Southern Ocean: 274–570 Mt; twilight-zone fish biomass estimate (2022)⁠[28]
Share that migrates: ≈50%; of twilight-zone sonar echo; from ≈20% to ≈90% by region⁠[18]
Carbon carried by fish: ≈16%; of carbon sinking out of the sunlit layer, all fish, give or take 13%⁠[14]

Lanternfish myths and facts

Tap Myth or Fact for each claim, then check the answer.

0 of 8 answered

“Lanternfish are the most numerous fish on Earth.”
“The sea floor rises at night.”
“Lanternfish glow on their bellies to hide.”
“Every lanternfish has a gas-filled swim bladder.”
“Male and female lanternfish look exactly the same.”
“Scientists know how much lanternfish there is in the ocean.”
“Every lanternfish swims to the surface every night.”
“Lanternfish use their lights to lure prey.”

Lanternfish records

Superlatives, each checked against its source.

Largest migration on Earth
Every day
Twilight-zone animals, including lanternfish
The daily trip up at night and down by day is described as the largest migration of animal life on Earth.⁠[15]
Most diverse deep-sea fish family
≈252 species
Lanternfishes (Myctophidae)
Called the most diverse family of fish in the deep ocean.⁠[5, 7]
Most abundant vertebrates
1.8–16 Gt
Twilight-zone fishes, with lanternfish a major group
Together, mesopelagic fishes are thought to be the most abundant vertebrates on Earth.⁠[12, 23]
Top fish of the North Atlantic twilight zone
Most abundant
Glacier lanternfish (Benthosema glaciale)
The most abundant and widely spread mesopelagic species in the North Atlantic.⁠[31]
Deepest daytime layer in a round-the-world survey
≈590 m
Southern Indian Ocean scattering layers
Average daytime depth of the sonar echo; the shallowest was about 350 m in the low-oxygen eastern Pacific.⁠[18]
Biggest lanternfishes
≈30 cm
The largest species in the family
Most lanternfish are under 15 cm; the family tops out at about 30 cm.⁠[5]

A day in the life of a lanternfish

Follow Hygophum hygomii, the Bermuda lantern fish, through 24 hours.

Dawn
Sinking back down
As the sky brightens, it swims down into the dark, where it is harder for predators to see.⁠[15, 11]
Daytime
Resting at 600–800 m
It spends the day 600–800 m down, where only a trace of sunlight reaches. Big eyes with a mirror layer help it see.⁠[11, 22, 2]
Afternoon
Hidden in the layer
Ships' echo sounders show it and its neighbours as a deep scattering layer, hundreds of metres down.⁠[5, 18]
Dusk
The big climb
As the light fades, it rises hundreds of metres, part of the largest migration of animal life on Earth.⁠[15, 11]
Night
Plankton feast
Between the surface and 300 m it snaps up zooplankton, especially copepods. Its belly lights keep its outline hidden.⁠[11, 4, 6]
Midnight
Tail lights
Its tail light may flash. Males and females carry it in different places, and scientists think it helps them signal.⁠[8, 7]
Before dawn
Carbon delivery
It heads down with a full gut. Digesting and breathing in the deep helps move carbon away from the surface.⁠[4, 14]

Lanternfish vs anglerfish vs hatchetfish

Three glowing fishes of the deep, with three very different ways of using light.

Lanternfish vs deep-sea anglerfish vs hatchetfish
	Lanternfish	Anglerfish (bulbous dreamer)	Hatchetfish
Group⁠[7, 30, 32]	Family Myctophidae, ≈252 species	Oneirodes eschrichtii, one of many anglerfishes	Family Sternoptychidae, 74 species
Size⁠[5, 30, 32]	2–30 cm, most under 15 cm	Females up to 29 cm, males 2.8 cm	2.8–12 cm
Light organs⁠[5, 7, 30, 32]	Rows of photophores on belly and sides, plus tail (and in some, head) lights	One glowing lure on the female's forehead, lit by bacteria	Light organs over the body, pointing down
Main use of light⁠[6, 7, 30, 32]	Camouflage, and probably signalling	Luring prey	Camouflage (counter-illumination)
Food⁠[4, 30, 32]	Zooplankton, mostly copepods	Mainly smaller fish	Ostracods, copepods, small crustaceans, fish larvae
How it feeds⁠[5, 30, 32]	Most migrate to surface waters at night to feed	Flashing lure, large mouth, large teeth	Some species migrate up at night to feed

Anglerfish facts are for one species; anglerfishes vary a lot.

Are lanternfish endangered?

Not as far as we know. But the twilight zone is attracting fishing interest and is changing with the climate, and scientists say we need to understand it first.

IUCN Red List

Least Concern (LC)

Trend unknown

Eight of the nine Hygophum species are listed as Least Concern; we found no listing for Hygophum atratum. There is no single assessment for all lanternfishes.⁠[11, 17, 33, 34]

IUCN Red List, 2012 (H. hygomii, H. benoiti)

Threats

Future fishing
There is growing interest in catching twilight-zone fish for fishmeal, feed for fish farms and supplements. The glacier lanternfish has been suggested as a target.⁠[27, 24, 31]
Shrinking habitat≈39%
In the California Current, one model projects the livable twilight zone could shrink by about 40 m (39%) by 2100 under high emissions, mainly because low-oxygen water rises.⁠[35]
Big unknowns
Estimates of how many twilight-zone fish there are differ several-fold, which makes it hard to set safe catch limits.⁠[23, 27]

What’s helping

Better counting
Researchers combine nets, sonar and swim-bladder scans to turn echoes into better fish numbers.⁠[28, 12]
Genetics for management
DNA shows glacier lanternfish form three separate groups across the North Atlantic and Mediterranean, information needed before any fishery starts.⁠[31]
A careful approach
Modellers recommend a precautionary approach to twilight-zone fishing, because it could affect how much carbon the ocean stores.⁠[24]

Hygophum species on the IUCN Red List

Hygophum hygomii (Bermuda lantern fish)Least Concern
Least Concern, assessed 2012.⁠[11, 34]
Hygophum benoiti (Benoit's lanternfish)Least Concern
Least Concern, assessed 2012.⁠[17]
Six more Hygophum speciesLeast Concern
H. bruuni, H. hanseni, H. macrochir, H. proximum, H. reinhardtii and H. taaningi are also listed as Least Concern.⁠[33]
Hygophum atratumNot Evaluated
We found no Red List category for this species; it may not have been assessed.⁠[33]

Lanternfish quiz

12 questions. Every answer is somewhere on this page.

Question 1 of 12Score 0

What are a lanternfish's light organs called?

Lanternfish field notes

Diet, food web, safety and badges from the Snappit field guide.

Diet & Feeding

Lanternfish are tiny predators that eat small plankton and crustaceans floating in the ocean.

Primary Foods

Copepods
Krill
Amphipods
Small larvae
Foraging Method: Foraging

Ecological connections

Whales and dolphinsEaten by
Many whales and dolphins eat lanternfish.
TunaEaten by
Tunas are among the many fish that eat lanternfish.
Humboldt SquidEaten by
Humboldt squid are among the many animals that eat lanternfish.
CopepodHunts
Lanternfish actively hunt and consume these small crustaceans.
Antarctic KrillHunts
Some lanternfish eat krill, but copepods are the main prey of the species that migrate.

Safety

Danger 1/5 · Very low

Lanternfish are not dangerous to humans but should be admired from a distance to protect their habitat.

Traits

Collections

Fish

Classification

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Myctophiformes
Family: Myctophidae
Genus: Hygophum

Also known as

Myctophid · Myctophids · Lanternfishes · Lantern Fish

Sources for these lanternfish facts

35 studies and references · checked Oct 16, 2026

Frequently Asked Questions

How to identify Lanternfish?

Look at body shape, where the fins sit and their outline, mouth position, stripes and spots. Young fish and breeding adults can wear different patterns, and aquarium color varieties can look nothing like wild fish. Fish Identifier: upload a photo and compare the visible details.

How long is Lanternfish?

2-30 cm

How much does Lanternfish weigh?

0.001-0.05 kg

How long does Lanternfish live?

1-5 years

What does Lanternfish eat?

Lanternfish are tiny predators that eat small plankton and crustaceans floating in the ocean.

Where is Lanternfish usually found?

Deep Sea

How does Lanternfish hunt?

Foraging

How deep can Lanternfish go?

1000 m

What is a lanternfish?

A small deep-sea fish of the family Myctophidae, named for its rows of light organs (photophores). There are about 252 species in all oceans, and most are under 15 cm long.

Why do lanternfish glow?

Mainly for camouflage: belly lights hide their outline from predators below (counter-illumination). Species-specific light patterns and tail lights probably also help them recognise and signal to each other, though that is harder to prove.

How deep do lanternfish live?

By day most live in the twilight zone, about 200–1,000 m down. Hygophum hygomii spends the day 600–800 m down and rises to between the surface and 300 m at night.

How many lanternfish are there in the ocean?

Nobody knows exactly. One model puts all twilight-zone fish, of which lanternfish are a big part, at about 1.8–16 billion tonnes, and published estimates range from about 1 to 20 billion tonnes.

What eats lanternfish?

Many animals: tuna, sharks, other deep-sea fish (including other lanternfish), whales, dolphins, salmon, penguins and jumbo squid.

What is the deep scattering layer?

A layer in the ocean that reflects sonar strongly, made of crowds of animals, many of them lanternfish with gas-filled swim bladders. It moves up at night and down by day, and early sonar users mistook it for the sea floor.

Are lanternfish dangerous to humans?

No. They are small fish, mostly under 15 cm, that live far out at sea and deep down. You are only likely to see one on a research ship or in a museum.

Do people fish for lanternfish?

Hardly at all so far: twilight-zone fish are largely unexploited. But there is growing interest in catching them for fishmeal, fish-farm feed and supplements, and scientists urge caution because so much is unknown.

Take the discovery with you