19 Sergeant Major Facts You’ll Never Forget

Read these interesting sergeant major fish facts to learn more about this species of fish that changes its gender over the course of its life due to the process of sequential hermaphroditism.

The sergeant-major damsel is an exceptionally deep-bodied fish, and its tail is extremely forked to increase swimming velocity when they need it. This species is one of the bigger damselfishes, however not the biggest. Their body is silver to greenish in color with five vertical dark bars that resemble the Sergeant Rank's insignia in the military services because of which it got its name. The fins are somewhat clear; however, there is some yellowish hue on the back tips of the dorsal fins. The sergeant-major damsels are omnivores, and they feed on a wide range of food sources, including little fishes, larvae, and numerous kinds of algae.

Look at these interesting facts about the sergeant major fish; if you like these, do read our captivating Florida pompano facts and fathead minnow facts too.

Sergeant Major

Fact File

What do they prey on?

Zooplankton larvae, invertebrates, smaller fishes, algae

What do they eat?


Average litter size?

200,000 eggs

How much do they weigh?

0.44 lb (200 g)

How long are they?

9 in (22.9 cm)

How tall are they?


What do they look like?

Black, blue, yellow

Skin Type


What are their main threats?

Humans, excessive fishing

What is their conservation status?

Least Concern

Where you'll find them

Tropical waters, marine coral reefs, coastal waters


The Atlantic Ocean, Great Barrier Reef, Australia





Scientific Name

Abudefduf saxatilis





Sergeant Major Interesting Facts

What type of animal is a sergeant major?

A sergeant major (Abudefduf saxatilis) is a species of damselfish that is found in the tropical waters of the Atlantic Ocean and parts of the Great Barrier reef. It is a type of marine fish which is very beautiful in appearance possessing vibrant colors like blue, yellow, and black.

What class of animal does a sergeant major belong to?

A sergeant major (Abudefduf saxatilis) belongs to the class of Actinopterygii fishes.

How many sergeant majors are there in the world?

There is no clear estimate of the total population of this species of fish. As they are found in abundance, it is pretty difficult to measure their total number.

Where does a sergeant major live?

Sergeant majors (Abudefduf saxatilis), being a marine fish species, prefers to live in tropical or subtropical waters and marine reef or coastal seawater areas.

What is a sergeant major's habitat?

Sergeant major is a particular species of marine fish and prefers to live in the tropical waters or in the deep blue waters of the ocean. So, they are mostly found in the Atlantic ocean, the Great Barrier Reef, and the north-eastern coast of the U.S.

Who do sergeant majors live with?

Sergeant major fish (Abudefduf saxatilis) lives with their own school of other sergeant majors inside the deep blue-black waters of the Atlantic or the Great Barrier Reef.

How long does a sergeant major live?

A sergeant major fish (Abudefduf saxatilis) has a lifespan of about two to six years.

How do they reproduce?

Being an oviparous species wherein the males make nests, and the female fish lays their eggs on the rocks, wrecks, and pilings. The males effectively pursue the females in romance before the female delivers around 200,000 ovoid eggs, which are connected to the substrate by fiber. The eggs become greenish following a couple of days and are protected by the male. As the male watches the eggs, it acquires pale blue color, guarding them for about a week or more.

What is their conservation status?

The conservation status of Least Concern is given to this species of coral reef fish, as they are found in abundance in the ecosystem.

Sergeant Major Fun Facts

What do sergeant majors look like?

A sergeant major fish, alternatively called the damselfish or the demoiselle, are deep-bodied and usually have forked tails. This species has a solitary nostril on each side of its head and has intruded horizontal lines on its body. Damselfishes have two butt-centric spines and 13 dorsal spines. They are splendidly colored, in vibrant and bright shades of red, orange, yellow, or blue.

This species of coral reef fish is called 'sergeant major' because it has five black bars on its body surface, which resemble the insignia of the Sergeant Rank in the military services.

How cute are they?

The sergeant majors are extremely cute in appearance, possessing vibrant colors on their bodies like black, blue, yellow, and white. Due to their cuteness, they are popular aquarium pets.

How do they communicate?

Not much information is available about the process of communication among the sergeant major fishes, but it is fairly possible that they also communicate with the use of vibrations produced by their fins or bladders inside the sea or ocean water.

How big is a sergeant major?

A common sergeant major is about 4-6 in (10.2-15.2 cm) in length, which is almost three times smaller than an average damselfish which reaches a length of about 12 in (30 cm).

How fast can a sergeant major swim?

The average range of speed that the common sergeant majors can swim at is not estimated yet by the scientists. But these fish species are very good swimmers and swim at a high range like every other fish.

How much does a sergeant major weigh?

The weight of an average sergeant major fish is somewhere around 0.44 lb (200 g), which is around two times less than that of an average damselfish which has a weight of about 2 lb (900 g).

What are the male and female names of the species?

The males or the females of this species do not have any specific name given to them.

What would you call a baby sergeant major?

A baby sergeant major does not have any special name given to it.

What do they eat?

Sergeant majors are omnivore fishes, and they prefer to eat larvae of other smaller fishes, invertebrates, zooplankton, and some algae in their diet. But when kept in aquariums, they also diet on vegetables or some protein-rich fish foods.

Are they eaten by humans?

Yes, sergeant majors are eaten by humans. In fact, they make up for a very protein-rich diet.

Would they make a good pet?

Yes, the sergeant majors make a good pet but only when kept with sea animals of her own category because this species of fish is very territorial and also feeds on other smaller fishes and their larvae. If it is kept with some peaceful or calm fish, it will definitely eat it up. So, to keep it as your pet, you have to choose the other fishes very carefully in order to ensure their safety from this marine fish.

Did you know...

You should keep only one sergeant major fish in a fish tank because they are very territorial, but if you plan on keeping more than one sergeant major fish in a single aquarium, then you should make sure that the others are similar in size and aggressiveness.

Some similar fish to check out include the dusky damselfish, black damselfish, and Garibaldi damselfish.

Keeping sergeant major fish

Keeping a sergeant major fish as a pet in the aquarium is a task in itself. Although these fishes are very beautiful in looks with their vibrant colors and pretty dorsal dins, they are quite territorial in nature and do not like the other fishes to take their place. So, if the other fish is smaller or a quieter one, then this fish will definitely eat it up. Therefore, to ensure the safety of the other fishes, they have to be chosen very wisely, and only the fishes with similar or more aggressiveness should be kept with it.

Do sergeant major fish change their sex?

Yes, the sergeant major changes his gender over the course of his life through the process of sequential hermaphroditism by switching the gonad from ovary to testis, or vice versa.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! Learn more about some other fish from our pomfret facts and rasbora facts pages..

You can even occupy yourself at home by coloring in one of our free printable Sergeant major coloring pages.



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