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Home › Sea Life Facts › Marine Species › Vertebrates › Surgeonfishes

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 (Acanthuridae), such as where they live, what they eat, and how they reproduce.

Surgeonfish 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:

• Eastern Pacific (e.g. the Galápagos Islands, Gulf of California, Central and South America)
• The Indo-Pacific regions (e.g. Australia, Hawaiian Islands, Philippines, Indonesia, East Africa)
• Most parts of the Western Atlantic (particularly the Gulf of Mexico and the Caribbean Sea) and some regions in the Eastern Atlantic (e.g. Angola, Canary Islands, Cape Verde)

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.

What Do Surgeonfishes 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:

• Cyanobacteria microorganisms
• Detritus
• Plankton (especially the unicornfish species)
• Tiny aquatic invertebrates

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.

Surgeonfish Species List

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 tends to occur during lunar cycles (e.g. new moon) and tidal rhythms.

Threats and Predators

Even though many surgeonfishes have a lifespan up to twenty (20) years in the wild, the ones kept in 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:

• Barracudas
• Groupers
• Moray eels
• Reef sharks
• Snappers

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 surgeonfish species is of "Least Concern" (LC). However, they list the bignose unicornfish (Naso vlamingii) as "Decreasing" in numbers.

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