Emperor Angelfish

Quick Take

• For decades, scientists thought juvenile emperor angelfish were an entirely different species. The reason why is stranger than you'd expect. Juveniles once mistaken →
• This small reef fish has a surprisingly bold strategy for dealing with creatures far larger than itself. And it's not what you'd call running away. See the defensive behavior →
• Emperor angelfish are prized aquarium pets, but there's a critical mistake most owners make when acquiring one that shortens its life dramatically. Aquarium capture risks →
• Despite living up to 20 years, emperor angelfish have never once successfully bred in captivity, a fact that reveals just how demanding their wild life really is. Captive breeding challenges →

The emperor angelfish is a species of marine angelfish. This species is commonly found all across the globe, but it is particularly abundant in shallow reefs of the Indian Ocean and Pacific Ocean. This beautiful fish is beloved by divers, marine biologists, and artists alike. First discovered in the 1700s, this remarkable species is a sought-after aquarium fish due to its unique neon stripes.

5 Incredible Emperor Angelfish Facts

• Male and female emperor angelfish can change color during mating or when threatened.
• The shape of an emperor angelfish’s skull is just as round as its body.
• These small fish can live up to 15 years in the wild.
• Emperor angelfish eat parasites off larger species, acting as cleaner fish.
• They make a clicking or grunting noise when they feel threatened.

Classification and Scientific Name

Scientifically known as Pomacanthus imperator, the emperor angelfish was first given the name Chaetodon imperator in 1787 by a German naturalist, Marcus Elieser Bloch. The specific epithet imperator in their name means emperor, a name given due to their colorful and eye-catching appearance. Pomacanthus is a genus of reef fish found across the Indian, Pacific, and Atlantic oceans. Species of this genus are known for the dramatic color transformations they undergo when they reach adulthood.

Appearance

The emperor angelfish is a very captivating fish with eye-catching colors. Like many of the world’s most colorful fish, they are found around coral reefs deep in the ocean. Many reef fish are so colorful because of an adaptation that allows them to identify members of their own species. 

Adult and juvenile emperor angelfish look very different from each other. The juveniles have blue-black bodies covered in concentric white and blue circular stripes. They also have a transparent caudal fin. Conversely, adult emperor angelfish have yellow and blue horizontal stripes all over their bodies. Their face is light blue, with eyes surrounded by a dark blue margin. They have a yellow caudal fin.

In terms of their size, these fish can grow up to 16 inches, which is about the diameter of a large pizza. However, it is rare to find an emperor angelfish this big. They generally reach up to 15 inches long in the wild, though captive specimens typically grow to around 12 inches. They have 13 to 14 spines in their dorsal fin and 3 in their anal fin.

Behavior

The emperor angelfish is a solitary fish that prefers to wander the shallow reefs on its own. In fact, they are generally territorial, and when they see other emperor angelfish, they tend to drive them away by chasing them.

Male emperor angelfish are especially aggressive and will defend their territory. This is why two males should never be kept in the same tank. They take time to adjust to new environments and can be shy at first. But once they have adapted, they become more active.

When threatened, they let out a grunting sound as an auditory cue that they are in distress.

Habitat

The emperor angelfish is found in the Indian and Pacific oceans, usually anywhere between 3 and 328 feet under the sea. They thrive in the warm tropical waters near the equator with temperatures of around 72 to 78 degrees Fahrenheit (or 22 to 26 degrees Celsius). They’re often seen near coral and seaweed and frequently hide in reef cavities. They also live in caves or ledges close to any coral reef colony. As juveniles, they often hide in semi-covered, rocky areas in or around ledges on the seabed.

Diet

The emperor angelfish is an omnivore that will eat just about anything it comes across. Its diet is primarily based on small invertebrates and plants, but it is also known to be a cleaner fish that eats parasites and scraps off of larger fish.

What does the emperor angelfish eat?

As mentioned above, the diet of an emperor angelfish is based on small invertebrates such as tunicates. They also feed on plants and like to eat algae and sponges found around coral reefs. Emperor angelfish rarely venture far to find food, but the species can swim long distances to find its food if needed.

Predators and Threats

Emperor angelfish are likely preyed on by common reef predators such as blacktip reef sharks, blue sharks, and marine mammals such as dolphins and whales. Overall, any omnivorous or carnivorous species in the ocean larger in size than the emperor angelfish might be a potential predator.

Other threats to the survival of the emperor angelfish are humans. Owing to their beauty, these fish are sought after and captured to be kept in aquariums as pets. However, fully grown emperor angelfish take a long time to acclimate to a new environment. In addition, they do not generally breed in captivity because aquariums cannot mimic their natural habitat. For this reason, if an emperor angelfish must be kept in captivity, starting with a juvenile is recommended to allow it to acclimate.

Other factors, such as coral bleaching, warming ocean temperatures, and overfishing, pose potential threats to all reef animals, including the emperor angelfish. At present, their conservation status is Least Concern, but many marine animals are expected to begin declining in population as the effects of climate change set in more and more.

What eats the emperor angelfish?

Being smaller fish, emperor angelfish are preyed on by larger reef animals such as sharks, larger carnivorous fish, and even marine mammals such as dolphins and whales.

Reproduction

During the mating season, both males and females begin to circle each other close to the water’s surface. After a while, the male releases the sperm, and the female releases the eggs to start the fertilization process, which occurs externally.

The female then lays the eggs, which drift away with the water current. This only happens once a year. A female emperor angelfish lays around a thousand eggs, which then spread throughout the water. The eggs hatch into larvae within a few weeks. Then, within the following few weeks, they become small fish that grow into juvenile emperor angelfish.

There has not been a single instance of emperor angelfish breeding in captivity. They would require enormous aquariums and perfect conditions to mate in captivity, making it practically impossible.

Babies

Emperor angelfish babies are called juveniles. As juvenile emperor angelfish, their bodies continue to change until they become fully grown adults. This takes approximately 24 to 30 months, after which these juveniles will have the same color as the adult fish.

For a long period, emperor angelfish juveniles were thought to be a completely different species owing to their patterns and colors, which are very distinct from the adults. In the 1930s, biologists discovered that they were the same animals. The mother plays no maternal role toward the young. In fact, mothers likely have no awareness of where their young are, because once the eggs hatch, the fish fend for themselves entirely. The juveniles are therefore equipped to protect themselves from predators from birth.

Juvenile emperor angelfish live among the rocks of the reef, move into the reef as they age, and finally settle in the coral as adults.

Lifespan

Emperor angelfish can live as long as 20 years, but this fish is less likely to live as long in captivity. However, with proper care and conditions, emperor angelfish in captivity can live as long as 20 years. Unfortunately, these fish are susceptible to several diseases as they age. Among these, the common ones include:

• White Spot Disease — also called Ichthyophthirius multifiliis or just “ich”, this is a potentially fatal parasitic infection where the parasite enters the fish’s body through the dorsal fins.
• Marine Velvet — another parasitic infection in which the fish becomes covered in gold, velvet-looking patches.
• Head and Lateral Line Erosion Disease — the exact reason for this disease is unknown, but it is commonly found in older emperor angelfish. It’s theorized that providing the fish with more light can mitigate the symptoms.

Population

The exact population of emperor angelfish worldwide is unknown. However, these fish are not in danger or at risk of extinction. Hence, their conservation status is Least Concern.

Emperor Angelfish in Zoos

Emperor angelfish are commonly found in zoos and aquariums around the world. You can visit them at the following zoos in the USA.

1. Fort Wayne Children’s Zoo
2. National Aquarium
3. Seattle Aquarium