What does a spawning pair do?

Rise about a metre above the reef together

What do wild mandarinfish mainly eat?

Tiny crustaceans such as copepods

Mandarinfish

Synchiropus splendidus

The mandarinfish (Synchiropus splendidus), also called the mandarin dragonet, is a tiny, scaleless reef fish from the western Pacific, about as long as your little finger. Its orange body is covered in wavy blue-green bands, and the blue comes from special pigment cells that scientists first found in this fish and one close cousin. By day it pecks for tiny animals among coral rubble. Around sunset, pairs rise above the reef to release their eggs.

Also known as Mandarin dragonet, Mandarin goby, Green mandarin

Mandarinfish abilities

1995 blue pigment cells described
The mandarinfish makes its blue with real blue pigment, held in special cells called cyanophores. Almost every other blue animal gets its colour from crystals that reflect light instead.
- In most blue fish, birds and butterflies, the blue is 'structural': stacks of tiny crystals reflect blue light, a bit like the colours on a soap bubble.
- In 1995 two Japanese scientists, Makoto Goda and Ryozo Fujii, found branching cells full of blue pigment in the skin of the mandarinfish and the spotted mandarin. No such cells had been reported before.
- Inside each cyanophore the blue sits in tiny packets the scientists called cyanosomes. The packets bunched up or spread out when the cells were stimulated, which may let the fish shift its shade of blue.
- Blue pigment cells are still known from very few animals, which is one reason scientists sequenced the mandarinfish's whole genome.
Sources [3, 4, 6, 7]
≈ 1 m rise above the reef
Around sunset, mandarinfish gather at spawning spots on the reef. A male and a female line up side by side and rise together about a metre into the water to release eggs and sperm.
- Spawning starts at dusk and carries on into the early night, all year round.
- A female spawns once a night at most, and some nights not at all. A male can spawn with up to 8 different females in one night.
- Females prefer big males: in one field study, females longer than 3 cm spawned with males over 4 cm 94% of the time.
- The rise is risky: both fish and eggs are exposed in open water, away from the shelter of the coral.
Sources [2, 8, 10, 11, 13]
12–205 eggs per spawn
At the top of the rise, the pair releases eggs and sperm into the open water. The tiny eggs float away on the current, and the parents never see them again.
- Scientists counted the eggs of 40 females: each spawn held between 12 and 205 eggs.
- The eggs are clear, round and only 0.7–0.8 mm across. They float in the open water.
- They hatch after about 12 hours. Neither parent looks after the eggs or the young.
- A male releases roughly 50,000–230,000 sperm per spawn, and bigger males release more.
Sources [2, 9, 10, 11]
0 scalesStill debated
With no scales to protect it, the mandarinfish wears a thick coat of smelly, bitter slime. Scientists think it puts predators off, and its bright colours may be a warning.
- The skin is full of mucus cells, plus sacciform cells that release other substances. Among six dragonet species studied, sacciform cells turned up only in the mandarinfish and the spotted mandarin.
- The study's authors linked these secretions to defence against predators and to living in close contact with the reef.
- Some accounts call the secretions toxic, but how harmful they are to predators has not been measured. They are not known to harm people.
- Bright colours that warn 'I taste bad' are called warning colours. That idea fits the mandarinfish, but it has not been tested.
Sources [1, 2, 3, 12]
94% of spawns with males over 4 cm
Males are bigger than females and carry a tall first dorsal fin. Females choose big males, so size and a fine sail pay off at spawning time.
- In 67 spawning pairs watched in Palau, males were 3.1–5.8 cm long and females 2.3–3.8 cm. A female always picked a male bigger than herself.
- In aquarium trials, females tried to pair only with the larger of two males.
- Bigger males release more sperm, and more sperm meant more eggs fertilised.
- Dragonet spawning runs in four stages: a courtship display, pairing up, rising together, then releasing eggs and sperm.
Sources [2, 10, 11, 16]
All day pecking for tiny prey
A mandarinfish spends its day pecking tiny animals off coral and rubble, one bite at a time, across a home patch of many square metres.
- Wild mandarinfish eat copepods, ostracods and amphipods (tiny crustaceans), plus small worms, tiny snails and fish eggs.
- Its small mouth limits it to very small food.
- In aquariums many refuse anything but live copepods and amphipods, which makes them hard to keep.
- Copepods matter from the very start: in a rearing study, adding copepods to the larvae's food raised survival at 12 days from 5.6% to 50%.
Sources [2, 3, 9, 15]
1–18 m deep, in sheltered lagoons
By day the mandarinfish moves slowly among coral branches or tucks into cracks, which makes this bright fish surprisingly hard to spot.
- It lives in sheltered lagoons and inshore reefs, often on silty bottoms with coral and rubble.
- Mandarinfish usually gather in small groups within a small area. Adults seem to stay in one area after settling; no adult migration has been recorded.
- During the day it moves along coral branches or hides in cracks in the reef.
- Its small size and bottom-hugging habits keep it out of sight, even though it is fairly common in its range.
Sources [1, 2, 3, 14]
400+ h of underwater surveys
No two mandarinfish have quite the same swirls. Scientists used each fish's markings like a name tag to follow the same individuals night after night, without catching them.
- In one field study, researchers spent more than 400 hours underwater watching mandarinfish.
- They recognised individual fish from their body markings, a mix of stripes and spots.
- That let them record who spawned with whom, and how often, without disturbing the fish.
- Scientists now use markings like this to identify individuals of many other kinds of bony fish.
Sources [8, 10, 20]

Tap a pin on the model or a part below.

1995 year its blue pigment cells were described
- In most blue animals the blue is not a pigment: tiny crystals or structures bounce blue light back, like the shine on a soap bubble.
- The mandarinfish is different. Its skin holds blue pigment cells, which the scientists who found them named cyanophores.
- When they were described in 1995, nobody had reported blue pigment cells of this kind before. The only other fish they found them in was its close cousin, the spotted mandarin.
- The blue sits in tiny packets inside each cell. The packets can bunch up or spread out, which may shift the shade of blue.
Sources [4, 6, 7]
2 colours in one pigment cell type found in 2013
- The face is green with bold blue stripes, and the eyes are usually red with black pupils.
- In 2013 the same research team found a second new kind of colour cell in mandarinfish skin: one cell that holds both blue and red pigment.
- Fish only have about a dozen known types of colour cell, and two of them were discovered in the mandarinfish.
Sources [3, 5, 6]
4 spines in the first dorsal fin
- The first fin on the back has 4 spines. In males the first spine grows long, so a big male carries a tall orange-and-blue sail.
- Females have a much lower first dorsal fin, which is one way to tell the sexes apart.
- Collectors for the aquarium trade pick out big males, because their tall fin makes them the showiest fish.
Sources [1, 2, 3, 14]
0 scales
- Mandarinfish have no scales. Instead, a thick coat of slime covers the skin.
- The slime smells bad and tastes bitter, which probably puts predators off.
- The skin is packed with mucus-making cells, plus a second kind called sacciform cells that release other substances. These were found in mandarinfish and spotted mandarins, but not in four other dragonets studied.
- The slime may also help keep out parasites and disease.
Sources [2, 3, 12, 13]
6 kinds of prey found in wild guts
- The mouth is small, so it can only eat very small food.
- Scientists looked inside the guts of 7 wild mandarinfish and found tiny crustaceans called copepods, ostracods and amphipods, plus little worms, tiny snails and fish eggs.
- It feeds all day, pecking one tiny animal at a time off coral and rubble.
Sources [2, 3, 9]
Slow hovering swimmer
- Big, rounded pectoral fins stick out from behind the head like a pair of fans. Their edges are deep blue.
- The mandarinfish is a slow mover. It hovers and creeps over the reef rather than racing about.
Sources [3, 13]
Hand-foot rough meaning of the name Synchiropus
- Under the chest sit wide pelvic fins. By day the fish moves slowly along coral branches and over rubble.
- Dragonets push off the bottom with their pelvic fins when they need a quick burst of speed.
- The genus name Synchiropus is built from Greek words meaning roughly 'together, hand, foot'.
Sources [2, 3, 16]
1 per side spine on the gill cover
- Dragonets have a spine on each gill cover, called the preopercular spine. It is a family trademark.
- In some dragonet species this spine has been reported to be venomous. There is no report of that for the mandarinfish, which fish experts list as harmless to people.
Sources [1, 16]
≈ 1 m rise above the reef when spawning
- The tail fin is rounded and orange, with a deep blue edge.
- Mandarinfish usually stay close to the bottom. The big exception is spawning, when a pair swims up about a metre into open water.
Sources [2, 13]

Real mandarinfish

Photos from Wikimedia Commons. Some of them can repaint the 3D model.

Orange body, wavy blue-green bands and blue-edged fins, Lembeh, Indonesia.Photo: Rickard Zerpe, CC BY 2.0
MaleOrange with wavy blue-green bands, a green face with blue stripes and a tall orange-and-blue first dorsal fin. Males are larger than females, up to about 6 cm.Big males win the most spawnsA male in an aquarium in Liège, Belgium. Note the tall first dorsal fin that only males grow. Photo: Luc Viatour, CC BY-SA 3.0
The green face with bold blue stripes and a red eye, Anilao, Philippines.Photo: Diego Delso, CC BY-SA 4.0
A pair rising together above finger coral at dusk to spawn, Lembeh Strait, Indonesia.Photo: Bernard DUPONT from FRANCE, CC BY-SA 2.0
A spawning pair, side by side and heading up, Anilao, Philippines.Photo: Diego Delso, CC BY-SA 4.0
A male raises his tall first dorsal fin beside another mandarinfish in finger coral, Lembeh Strait, Indonesia.Photo: Bernard DUPONT from FRANCE, CC BY-SA 2.0
Several mandarinfish sharing one clump of finger coral, Lembeh Strait, Indonesia.Photo: Bernard DUPONT from FRANCE, CC BY-SA 2.0
Tiny on a big reef: a mandarinfish on coral rubble, Malapascua, Philippines.Photo: Sodacan, CC BY-SA 4.0
Spotted mandarin (look-alike)A separate species, Synchiropus picturatus. Pale grey-green with dark spots ringed in orange and blue. It also has blue pigment cells.Hides in rubble below living coralThe look-alike spotted mandarin (Synchiropus picturatus), the only other fish known with blue pigment cells when they were discovered. Photo: Rickard Zerpe, CC BY 2.0

Mandarinfish by the numbers

Measured by scientists and fish databases, with comparisons you can picture.

Length: up to 7 cm; usually about 6 cm; males are larger than females; About as long as your little finger⁠[1, 2]
Depth: 1–18 m; sheltered lagoons and inshore reefs⁠[1, 2]
Water temperature: 24–26 °C; warm tropical water⁠[2]
Eggs per spawn: 12–205; counted from 40 females⁠[9]
Egg size: 0.7–0.8 mm; clear, round and floating; Smaller than a grain of sugar⁠[2]
Time to hatch: ≈ 12 hours; no parental care⁠[2]
Drifting larva: ≈ 14 days; before settling on the reef (12–14 days at 24–26 °C)⁠[2, 9]
Spawns per male: up to 8; in a single night; a female spawns once at most⁠[8]
Sperm per spawn: 50,000–230,000; bigger males release more⁠[10, 11]
First dorsal fin: 4 spines; the first spine is long in males⁠[1, 2]

Mandarinfish myths and facts

Some of what you hear about this little fish is true. Some of it isn't.

0 of 8 answered

“The mandarinfish's blue comes from real blue pigment.”
“The 'mandarin goby' is a goby.”
“Mandarinfish have scales like most fish.”
“Mandarinfish are dangerous to people.”
“Its bright colours warn predators that it tastes bad.”
“Mandarinfish parents guard their eggs.”
“A female mandarinfish can spawn every night.”
“The mandarinfish is a cousin of the Chinese 'mandarin fish'.”

The life of a mandarinfish

From a floating egg to a dancer on the reef, in a couple of months.

Sunset
The rise
A male and a female rise about a metre above the reef and release eggs and sperm into the water.⁠[2, 13]
12 hours
Hatching
The tiny, clear eggs, under 1 mm across, hatch while drifting in open water. No parent is around.⁠[2]
36 hours
Eyes and mouth
The larva's eyes darken and its mouth forms, so it can start catching food.⁠[2]
8–11 days
Tail bends up
The tip of the backbone bends up to form the tail fin, a big step on the way to a fish shape.⁠[2]
12–14 days
Settling down
The larva leaves the open water and settles on the reef. That is one of the shortest drifting stages known for a fish with floating eggs.⁠[2, 9, 14]
18–21 days
Turning orange-brown
The young fish darkens to an orange-brown colour.⁠[2]
Second month
Adult colours
At just 1–1.5 cm long, it gets the blue and orange pattern of an adult.⁠[2]
Adult
Nightly spawner
Adults stay in their home area and spawn at sunset, all year round.⁠[2, 8, 14]

Mandarinfish record-breakers

A small fish with some big firsts.

First blue pigment cells described
1995
Mandarinfish and spotted mandarin
Before then, no blue pigment cells had been reported in any animal.⁠[4, 7]
Busiest night
8 spawns
A male mandarinfish
The most spawns seen for one male in a single night, each with a different female.⁠[8]
Short childhood at sea
≈ 14 days
Mandarinfish larva
One of the shortest drifting larval stages known among sea fish that release floating eggs.⁠[14, 9]

Mandarinfish vs spotted mandarin vs ocellated dragonet

Three small, colourful dragonets that people often mix up.

Mandarinfish vs spotted mandarin (Synchiropus picturatus) vs ocellated dragonet (Synchiropus ocellatus)
	Mandarinfish	Spotted mandarin	Ocellated dragonet
Scientific name⁠[1, 17, 18]	Synchiropus splendidus	Synchiropus picturatus	Synchiropus ocellatus
Longest⁠[1, 17, 18]	7 cm	7 cm	8.9 cm
Colour⁠[3, 18]	Orange with wavy blue-green bands, green face	Light grey-green with ringed dark spots	A starry pattern of small spots
Blue pigment cells⁠[4]	Yes	Yes	Not studied
Depth⁠[1, 17, 18]	1–18 m	Usually 0–20 m	1–30 m
Habitat⁠[1, 17, 18]	Sheltered lagoons and inshore reefs with coral and rubble	Rubble below living coral on sheltered reefs	Sandy lagoons, rubble, algal turf and tide pools
Where⁠[1, 17, 18]	Ryukyu Islands to Australia	Philippines, eastern Indonesia, NW Australia	Indonesia to the Pitcairn Islands, Japan to Australia
IUCN Red List⁠[1, 17, 18]	Least Concern	Least Concern	Least Concern

In dragonets the first dorsal fin often differs between males and females, so it is better for telling the sex than the species. Check the body pattern instead.

Is the mandarinfish endangered?

No. It is listed as Least Concern, but it is caught in large numbers for home aquariums, and that fishing is not managed.

IUCN Red List

Least Concern (LC)

The mandarinfish is listed as Least Concern. It has a wide range in the western Pacific and is fairly common where it lives.⁠[1, 3, 19]

IUCN Red List, assessed 2018

Threats

Aquarium collecting
It is collected heavily in Southeast Asia, mainly the Philippines, for the aquarium trade, and the fishery is not managed. Because adults stay in one area, heavy fishing focused on one spot could hit local fish hard.⁠[14, 9]
Big males taken first
Collectors target big males for their tall fins. Females left behind may have to spawn with smaller males that release less sperm.⁠[10, 11, 14]
Hard to keep
Many refuse anything but live copepods and amphipods, which makes wild-caught mandarinfish hard to keep in home aquariums.⁠[3, 2]

What’s helping

Captive breeding
Scientists have reared larvae in the lab and found that copepods as a first food greatly improve survival. Farmed fish could take pressure off wild reefs.⁠[9, 15]
Well-connected populations
A genetic study found that mandarinfish at five sites in the Philippines were well mixed, probably thanks to eggs and larvae drifting between reefs.⁠[14]
Field research
Studies of who spawns with whom show why leaving big males on the reef matters for the next generation.⁠[8, 10]

Relatives

Spotted mandarin (Synchiropus picturatus)Least Concern
The look-alike cousin that also has blue pigment cells; assessed in 2022.⁠[17]
Ocellated dragonet (Synchiropus ocellatus)Least Concern
A widespread, starry-patterned dragonet; assessed in 2022.⁠[18]

Mandarinfish quiz

12 questions. Every answer is somewhere on this page.

Question 1 of 12Score 0

What makes the mandarinfish's blue colour special?

Mandarinfish field notes

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

Diet & Feeding

Mandarinfish are tiny hunters, mainly feasting on small worms and crustaceans found on the seabed.

Primary Foods

Copepods
Amphipods
Small worms
Gastropod larvae
Foraging Method: Foraging

Ecological connections

Red LionfishEaten by
Larger reef fish are opportunistic predators.
Staghorn CoralShelter
Hides among intricate coral branches.
Japanese Rockpool CopepodEats
A primary food source for them.

Safety

Danger 2/5 · Low

Watch quietly from a distance and never try to feed or chase wild animals.

Traits

Collections

Fish

Classification

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Callionymidae
Genus: Synchiropus

Also known as

Mandarin dragonet · Mandarin goby · Green mandarin · Striped mandarinfish · Mandarin Fish

Sources for these mandarinfish facts

20 studies and references · checked Oct 29, 2026

Frequently Asked Questions

How to identify Mandarinfish?

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 Mandarinfish?

6-8 cm

How much does Mandarinfish weigh?

0.005-0.01 kg

How long does Mandarinfish live?

2-4 years

What does Mandarinfish eat?

Mandarinfish are tiny hunters, mainly feasting on small worms and crustaceans found on the seabed.

How fast can Mandarinfish swim?

0.1 km/h

Where is Mandarinfish usually found?

Coral reefs

How does Mandarinfish hunt?

Foraging

Why is the mandarinfish so blue?

Its skin holds blue pigment cells called cyanophores, first described in 1995. Most other blue animals make blue with light-reflecting crystals instead of pigment.

Is the mandarinfish poisonous?

It is harmless to people. It has no scales, and its skin is coated in a smelly, bitter slime that probably keeps predators away. How toxic the slime is has not been measured.

Is the mandarinfish a goby?

No. It is sometimes sold as the 'mandarin goby', but it is a dragonet, from the family Callionymidae.

When and how do mandarinfish mate?

Around sunset. A male and female line up side by side, rise about a metre above the reef and release eggs and sperm. The eggs float away and hatch in about 12 hours.

What do mandarinfish eat?

Tiny animals they peck off coral and rubble all day: copepods, amphipods, ostracods, small worms, tiny snails and fish eggs.

Where do mandarinfish live?

In sheltered lagoons and inshore reefs of the western Pacific, from Japan's Ryukyu Islands to Australia, 1–18 m deep, among coral and rubble.

How can you tell a male mandarinfish from a female?

Males are bigger and have a tall, spiky first dorsal fin. Females are smaller, usually under 4 cm, with a low first dorsal fin.

Is the mandarinfish endangered?

No. It is listed as Least Concern. But it is collected heavily for aquariums, mainly in the Philippines, and collectors take the big males first.

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