Facts About Regal Blue Tangs
Paracanthurus hepatus is also known as a regal blue tang, palette surgeonfish, hippo tang and many other common names.
Credit: Podolnaya Elena | Shutterstock

One of the biggest movie stars of 2016 is Dory, a precocious and forgetful fish featured in "Finding Dory." Dory is a cartoon depiction of a Paracanthurus hepatus, a type of surgeonfish that also has many common names.

This fish's common names include palette surgeonfish, flagtail surgeonfish, blue surgeonfish, common surgeon, doctorfish, letter six fish, Pacific blue tang, Pacific regal blue tang, regal blue tang, regal tang, royal blue tang, hippo tang, wedgetail blue tang and blue tang. Even someone without Dory's memory issues would be hard-pressed to remember all those names! In addition, Oceana, an environmentalist group, points out that an altogether different species of fish, Acanthurus coeruleus, is also called a blue tang.

Regal blue tangs (the name we're going with in this article) are identified by their bright blue coloring, oval bodies and yellow, flag-shaped tails. Their pectoral fins are also yellow. Adults have a narrow line of dark blue along their dorsal fin that curves back at the tail. Its resemblance to the numeral 6 gives the fish one of its descriptive names.

Coloration changes as regal blue tangs mature, according to the Animal Diversity Web (ADW). Though in "Finding Dory," baby Dory was blue with a yellow tail, in real life juvenile blue tangs are bright yellow with blue spots by their eyes, and their fins have light blue tips. Their bodies become blue as they mature.

Surgeonfish get their name from the scalpel-like spines along the top and bottom of their bodies. These fish have a sharp and venomous spine at the base of their caudal fin, or tail fin, to protect themselves from predators. The caudal spine contains a toxin that can cause severe pain, to small predators as well as humans.

Adult regal blue tang fish typically weigh around 21.15 ounces (600 grams) and are 4.72 to 14.96 inches (12 to 38 centimeters) long. Males are typically larger than females, according to the ADW.

As one name implies, these fish live in the Pacific Ocean, but they are also found in the Indian Ocean, from East Africa to Micronesia, according to the International Union for Conservation of Nature (IUCN). Their homes are the coral reefs that grow along the shores. They especially like to hide in the protecting branches of cauliflower coral, according to the ADW.

These fish typically feed on algae, using their small, sharp teeth to keep their coral protectors clean.

These fish are very important to the lifecycle of the coral reef. They eat excess algae in the reef, which prevents the coral from suffocating. Coral reefs provide homes and food for around one quarter of all ocean species, even though they cover less than 1 percent of the Earth, according to the Smithsonian.

These fish are somewhat social and are usually found in pairs or in small groups. Often, they form schools with 10 to 12 members. Regal blue tangs don’t just hang out with their own kind, either. They include several different species of surgeonfish and tang in their schools.

When faced with a predator, regal blue tangs often "play dead" by lying on their side and remaining motionless until the predator passes them by.

Males are often aggressive toward one another, having "sword fights" with their caudal spines. They achieve dominance this way, and more dominant males have larger breeding grounds, according to the ADW.

When it is time to reproduce, regal blue tangs congregate in breeding groups. Females expel their eggs into the water above the coral, and the males expel sperm, and fertilization occurs externally. About 40,000 eggs are expelled per spawning session, according to the ADW. After spawning, the "parents" swim off, never caring about their offspring.

The fertilized eggs are cast adrift and become part of the plankton "soup," according to the Marine Aquarium Societies of North America (MASNA). About 26 hours after fertilization, the eggs hatch and live in the soup until it is time to metamorphose into juveniles. At that point, they settle into a coral habitat, where they complete the metamorphosis. Baby regal blue tangs are called larvae. Maturity is measures by size rather than age, according to the ADW. Males are considered mature when they reach 11 cm (4.3 inches) in length; females when they are 13 cm (5 inches) in length. Regal blue tangs can live more than 30 years in the wild.

Here is the classification of the Paracanthurus hepatus, according to the Integrated Taxonomic Information System (ITIS):

Kingdom: Animalia
Subkingdom: Bilateria
Infrakingdom: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclass: Osteichthyes
Class: Actinopterygii
Subclass: Neopterygii
Infraclass: Teleostei
Superorder: Acanthopterygii
Order: Perciformes
Suborder: Acanthuroidei
Family: Acanthuridae
Genus: Paracanthurus
Species: Paracanthurus hepatus               

The order Perciformes is the largest vertebrate order and includes over 148 families containing roughly 9,300 species, according to Sea World.

According to the International Union for Conservation of Nature, Paracanthurus hepatus are not endangered and are listed as least concern. Their populations are widespread and it is believed that the population is not declining.

These fish are a popular aquarium species, and some environmentalists are concerned that these fish will be victims of increased popularity due to the movie, "Finding Dory." Other animals have suffered after being featured in recent films.

Some call it the "Finding Nemo Effect." According to the Aquarium Welfare Association (AWA) after that movie came out in 2003, demand soared and hatcheries could not keep up. They had to resort to to buying wild caught specimens. This, in turn, led to population declines in several natural habitat areas.

Also, many people bought the clownfish without knowing how to properly care for them. Inspired by a line in the move, hundreds of children flushed their clownfish down the toilet in the hope of setting them free, according to the AWA.

There has been no success in breeding regal blue tangs in captivity; so increased demand will necessarily cause more fish to be caught, which will decrease populations.