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Interesting Facts about Surgeonfishes

[Phylum: Chordata] [Class: Actinopterygii] [Order: Acanthuriformes] [Family: Acanthuridae]

One of the most colourful and conspicuous of all reef fish families is named for the unique 'scalpel-like' spines (like surgeon's knives) seen at the base of the tail (caudal peduncle).

This section contains information about 86 species of surgeonfishes (scientific name Acanthuridae), such as where they live, what they eat, and how they reproduce.

Surgeon Fish Range and Preferred Habitats

The geographical distribution of surgeonfishes (family Acanthuridae) in tropical and subtropical marine ecosystems is extensive.

Even though the Acanthuridae family of ray-finned fish includes tangs and unicornfishes, surgeonfishes tend to thrive best in certain regions, especially:

Even so, they have a distinct preference for certain kinds of habitats. Besides being closely associated with coral reefs and reef flats, they also thrive in lagoons, around rocky coastlines, and in some seagrass beds or areas with algal-covered substrates.

Pro Tip: Acanthurus coeruleus is one of the common species that can also tolerate the temperate waters of the Mid-Atlantic and even the Mediterranean Sea.

Surgeonfish Characteristics and Behaviour

In general, surgeonfish, tangs, and unicornfish all live at a depth range between one (1) and thirty (30) metres (100 feet) - even though some species enjoy life in deeper environments (e.g. around reef drop-offs).

Plus, most of the surgeonfish species are territorial and they will vigorously defend their nesting site and rich algal patches. Furthermore, they fulfill an important role in reef maintenance, especially in the cultivation of overgrown patches of algae on sensitive coral structures.

But wait - there's more:

It's fair to say that almost all surgeonfishes have bright body colours and a range of distinctive patterns, including a combination of spots, stripes, and uniform hues.

Having an oval-shaped thin body (laterally compressed) means they can maneuver with ease through tight cracks, crevices, as well as intertwining and branching reef structures (e.g. staghorn corals).

For a large fish (ranging between 15 and 40 centimetres long), their mouth is quite small. Despite that, they use their chisel-like teeth to graze on algae that covers coral, rocks, and other solid objects, such as dead or damaged reef substrates.

Surgeonfish Fun Facts and Species Information with PicturesWhat Do Surgeonfish Eat?

Almost all species of surgeonfish are herbivores that graze on different types of algae, especially turf algae and macroalgae.

But, depending on their habitat, some species will include supplementary items in their daily diet, such as:

Even though most pick off scraps of planktonic material and detritus, herbivorous species tend to be algae-farmers with a distinct foraging behaviour.

Interesting Fact: Some of the naso fish, such as the orange spine unicornfish (Naso lituratus) are omnivores that also feed on zooplankton.

Types of Surgeonfish Species

Achilles Tang (Acanthurus achilles)

It's commonly known as Achilles tang, but some fishkeeping hobbyists call it Achilles surgeonfish, redspot surgeonfish, and even the redtail surgeonfish.

It is a striking marine ray-finned fish that belongs to the surgeonfish scientific name Acanthuridae, a family that comprises surgeonfishes, tangs, and unicornfishes.

They flourish throughout most of the tropical Pacific Ocean, particularly near Hawai'i, Micronesia, Polynesia, Pitcairn, and Johnston Atoll.

These strong swimmers inhabit the wave-swept shallow coral reef networks and the surf zone of outer reef slopes in moderate depths, ranging between two and twenty metres.

Appearance and Size

Most types of surgeonfish are renowned for their graphic body markings and brilliant colours. Acanthurus achilles is deep chocolate coloured (almost jet black) with an orange teardrop patch located near the base of the tail (caudal peduncle).

They also have thin orange streaks below the dorsal fin and a white margin surrounding the tail fin. Adults exhibit a steep head profile but they rarely grow much bigger than twenty five (25) centimetres long (less than 10 inches).

Even though the diet of most unicornfish often includes small invertebrates, most of the surgeon fish family are herbivores that primarily graze on benthic algae (filamentous and turf algae) that grows on hard corals and rocky surfaces.

It's common to see these agile swimmers gather in pairs or sometimes in small groups. The males can also be quite territorial during the breeding season.

Kept in Captivity

Achilles tangs are one of the highly sought-after surgeonfish types in the aquarium trade, but they can be challenging to keep. They require 100-gallon tank dimensions, a strong flow of excellent water quality, and a plentiful supply of greens for grazing.

In 2010, the IUCN Red List of Threatened Species assessed Acanthurus achilles as "Least Concern" with a "Stable" population trend.


Atlantic Blue Tang (Acanthurus coeruleus)


Blue Tang (Paracanthurus hepatus)


Brown Surgeonfish (Acanthurus nigrofuscus)


Chocolate Surgeonfish (Acanthurus pyroferus)


Convict Tang (Acanthurus triostegus)

Most surgeonfishes can be easily identified by the bold colouration and unique characteristics. But, the one with a pale yellow body and six black vertical stripes is unmistakable.

Check out these interesting facts about Acanthurus triostegus (also called the manini fish), including where they are found, what they eat, and how they reproduce.


Eyestripe Surgeonfish (Acanthurus dussumieri)


Fowler's Surgeonfish (Acanthurus fowleri)


Indonesian Sawtail (Prionurus chrysurus)


Japan Surgeonfish (Acanthurus japonicus)


Marquesan Surgeonfish (Acanthurus reversus)


Ocean Surgeon (Acanthurus bahianus)


Orange Band Surgeonfish (Acanthurus olivaceus)


Orangespine Unicornfish (Naso lituratus)


Powder Blue Tang (Acanthurus leucosternon)


Razor Sawtail (Prionurus laticlavius)

It has several common names, like razor surgeonfish and yellow-tail surgeonfish, but Prionurus laticlavius belongs to the family Acanthuridae (the surgeon fishes and the tangs).

In line with the surgeonfish meaning, the genus Prionurus is a tribe most notable for their "saw-plates" on the tail.

Body Shape and Size

Razor surgeonfish have several distinguishing features, especially the oval and laterally compressed body, a steep head profile, and a protruding snout.

Even though there's more yellow colouration in juvenile surgeonfish, the adults have a greyish body with a bright yellow caudal fin. It is rare for razor sawtails to grow much longer than sixty (60) centimetres (24 inches).

Geographic Range

They are most common throughout the Tropical Eastern Pacific, especially the Gulf of California, Costa Rica, Ecuador (the Galápagos Islands) and Peru.

Surgeonfish types such as these tend to school together in large groups at depths ranging between a few metres below the surface and down to the rocky reefs at sixty (60) metres.

Pro Tip: Because of their relative size, schooling nature, and bright yellow tails, razor surgeonfish are of special interest while snorkeling, scuba diving, and taking photographs underwater.


Ringtail Surgeonfish (Acanthurus blochii)


Roundspot Surgeonfish (Acanthurus bariene)


Sixplate Sawtail (Prionurus microlepidotus)


Sixplate Sawtail (Prionurus microlepidotus)


Squarenose Unicornfish (Naso mcdadei)


Striated Surgeonfish (Ctenochaetus striatus)


Striped Surgeonfish (Acanthurus lineatus)


Whitecheek Surgeonfish (Acanthurus nigricans)


Whitechin Surgeonfish (Acanthurus albimento)


Whitemargin Unicornfish (Naso annulatus)


Zebra Tang (Acanthurus polyzona)

How Do Surgeonfish Reproduce?

Surgeonfish are oviparous, meaning the female lays eggs and the males release sperm. Thus, external fertilisation and reproduction often involves energetic courtship with mass spawning events (and no meaningful parental care afterwards).

The majority of the species reach sexual maturity between the age of one and four years old. Moreover, exhibitions of sexual dimorphism means the males often become more brightly coloured than their female counterparts during the breeding season.

Incubation and Hatching

The eggs need less than forty eight hours for incubation, often determined by species and the temperature of the water.

During the acronurus stage, the hatchlings drift as planktonic larvae with ocean currents for several weeks before eventually settling around a suitable reef and developing enough to begin life as juvenile surgeonfish.

Fun Fact: The reproduction cycles of surgeonfishes tend to occur during lunar cycles (e.g. new moon) and tidal rhythms.

Surgeonfish Predators and Threats

Surgeonfish lifespan can be up to twenty (20) years in the wild. But the ones kept in saltwater aquariums as pets tend to have shorter lifetimes.

On top of that, they face some significant threats from predatory fish species outside of captivity. For instance, the natural hunters of surgeonfish, tangs, and unicornfish include:

Other contributing factors for the decline in a few vulnerable areas include certain types of human behaviour (e.g. coral reef destruction and degradation, overfishing, marine pollution, and excessive 'wild-catch' for the aquarium trade).

Pro Tip: According to a 2007 assessment issued by the IUCN Red List of Threatened Species, the conservation status of most ocean surgeonfish species is of "Least Concern" (LC). However, they list the bignose unicornfish (Naso vlamingii) as "Decreasing" in numbers.

Practical Tips for Diving with Ocean Surgeonfish

Acanthuridae are colourful reef fish that help to control excessive algae growth. They also offer rewarding experiences for scuba divers and snorkel swimmers.

Here's a user-friendly collection of diver-specific tips for observing surgeon fishes with respect and safety.

Respecting their Territories

The majority of the species are territorial grazers. Thus, divers should avoid hovering too close while they are feeding. In fact, it's not uncommon for males to make short darting displays if they feel overcrowded.

Where are surgeonfish found? They are common around the coral reefs at most of the tropical dive sites, including:

Even though surgeonfishes rarely bite humans, the 'scalpels' on their caudal spines are sharp enough to cause some laceration. So, always give them plenty of space and avoid blocking their exit from the reef.

Be Mindful of Eco-Ethical Practices

In actual fact, divers feeding fish is strongly discouraged, and even outlawed in some countries, because doing so may alter their natural feeding behaviours.

Moreover, you can help support marine protected areas (MPAs), as well as responsible local dive leaders and guides who understand - and enforce - proper reef etiquette.

It's important for scuba divers to know that gobies and wrasse operate "reef cleaning stations" in certain designated areas.

If you see small tangs pausing for their underwater spa treatment, move slowly and keep your dive fins away from the bottom.

Surgeonfish Facts: Acanthurus achilles and Acanthurus lineatus tend to be solitary species. Whereas, the convict tang, ringtail surgeonfish, and the regal tang often carry out interspecies grazing in small groups.

Related Information and Help Guides

Note: The short video [1:51 minutes] presented by 'Deep Marine Scenes' contains even more surgeonfish facts with footage of the razor sawtail (also known as the yellowtail surgeonfish).

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