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The Explorer's Guide contains a treasure trove of aquatic science resources developed for use in K-12 classrooms. Back to Explorer's Guide.

Emperor Angelfish Scientific Name: Pomacanthus imperator
Emperor angelfish completely change their colors and patterns from when they are young to when they reach adulthood. Since adults are territorial, this change is thought to allow juveniles to enter adult territories without being chased out. Juveniles eat different food than adults and wouldn’t be competing for the same food source within the territory.

Region: Philippines

Like two different fish, adult and juvenile emperor angelfish look completely different. It was once thought that the two forms were two completely different species. The body of the juvenile is a dark bluish black. It has a light blue line near the tail with a white circle around it. This white circle is surrounded by alternating light blue and white incomplete circles. When the juvenile reaches a length of 5 inches (12 cm), the colors completely change.

Adults have a very different pattern and colors. They have an eye band or dark line on their body that runs across the eye. This eye band actually makes the fish look like it is wearing a black mask. This mask confuses predators making them wonder which end is which. Predators don't know whether to attack the front end or the back. Adults can grow up to 13 inches (40 cm) long.

Emperor angelfish live near ledges and caves in areas of rich coral growth and on clear lagoon, channel or seaward reefs at depths of 3 to 233 feet (1 to 70 m).

Juvenile emperors live alone, hiding in reef holes and crevices in areas rich in coral growth and in clear lagoons, reef channels and outer reef flats. In some areas, juveniles hang out at shrimp cleaning stations and may occasionally help the shrimp pick off the parasites and dead skin of the fish waiting to be cleaned.

Emperor angelfish live in the warm parts of the Pacific Ocean and the Red Sea.

The emperor angelfish scrapes and scours sponges and sea squirts off rocks and coral with a mouthful of coarse teeth. These teeth are very similar to a rough brush.

The jaw is bulky and super strong, able to chew up sponges, which are made of tiny pieces of needle-like silica. Eating silica would be like eating small slivers of sharp glass. Another way the emperor angelfish protects its digestive system from silica is by coating its food with a layer of slimy mucus. This helps to keep the silica spines from getting lodged inside its body.

Male emperor angelfish are territorial, which means they stick close to a specific area where they always live and mate. Even the females live in specific areas on the reef. Males defend a territory where two or more females also live. This area can be at least 10,760 square feet (1000 m²). Each day, the male visits each of these females.

When they are going to mate, the male visits them more frequently. At night, the male releases his gametes, then chases the female and makes a grunting noise. He will do this with each of the females in his range in the same night.

During courtship and mating, both the males and females change color. Females become bland in color. The mask of the male will turn a dark blue and almost black. The white area surrounding the mouth also darkens. At dusk, a pair of emperor angelfish rush to the surface, getting away from the reef to pelagic spawn, which means they mate in an area that the fertilized eggs will be taken away on the currents to drift into the open ocean. Then they dash back down to reef. By doing this so quickly, many egg eating predators may not see their release and the eggs are left to float off to other reefs which these angelfish will then populate. When the eggs hatch, the larvae remain in the epipelagic zone or the zone in the open ocean near the surface. When the small fish grow large enough to fend for themselves, they will swim down and become part of a coral reef.

Angelfish are sexually dimorphic, which means the males and the females look much different. Males are 20% larger than the females.

>A species or group of organisms that is in danger of extinction or disappearing from the face of the earth in the near future if its situation is not improved.

A species that can be found throughout its natural range but is declining in number and may become endangered in the absence of special protection efforts.

A species that is not declining in number but is of special concern because it is sensitive to pressure by particular human activities or natural events.

A species that is not declining in number and is not sensitive to pressures by human activities or natural events.

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Threats and Management
This angelfish is hard to keep in the home aquarium. It is not frequently found in the pet trade, and when it is, it is very expensive. These reasons may have kept the emperor angelfish population stable.

Did You Know?
Emperor angelfish are so territorial that they will violently attack any other intruding emperors that venture into their turf.

Only those that live in the far western Pacific develop a strand that extends from their dorsal fin or the fin on the back of the fish.

Web Sites:
NOTE: The following Web sites are not maintained by the John G. Shedd Aquarium and will open in a new browser window.


Print Publications:
Debelius, H. 1999. Indian Ocean Reef Guide. Frankfurt, Germany: IKAN. 321p.
ISBN# 3-9317-0267-7.

Hoover, J.P. 1993. Hawaii's Fishes. A Guide for Snorkelers, Divers and Aquarists. Honolulu, Hawaii: Mutual Publishing. 183p. ISBN# 1-56647-001-3.

Myers, R.F. 1999. Micronesian Reef Fishes. Barrigada, Guam: Coral Graphics. 216p.
ISBN# 0-9621564-4-2.

Perrine, D. 1997. Mysteries of the Sea. Lincolnwood, Illinois: Publications International, Ltd. 312p. ISBN# 0-7853-2430-5.

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Vocabulary Words

Dorsal fin - The fin on the back of an animal.

Eye band - A dark line on the body that runs across the eye, camouflaging it.

Pelagic spawners - Fish that gather in an area in the ocean where the fertilized eggs will be taken away on the currents to drift into the open ocean.

Epipelagic zone - The zone of the open ocean near the surface.

Extinction - An organism that has not been present on the face of the earth for over 50 years.

Organism - A living thing.

Pet trade - An industry or business in which animals are taken from the wild and sold to pet stores, zoos, and aquariums.

Sexually dimorphic - In animals when each sex is distinctly different. Males look very different than the females.

Species - A group of organisms capable of breeding and producing fertile offspring; organisms that share the same gene pool.

Territorial - An animal that lives in the same area all the time. This animal reproduces this area and fiercely defends it.

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Emperor Angelfish
Emperor Angelfish

Emperor angelfish (Pomacanthus imperator) Copyright Shedd, Patrice Ceisel
Emperor angelfish (Pomacanthus imperator) Copyright Shedd, Patrice Ceisel

Emperor angelfish (Pomacanthus imperator) Copyright Shedd, Patrice Ceisel
Emperor angelfish (Pomacanthus imperator) Copyright Shedd, Patrice Ceisel

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