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Fascinating Facts about Convict Surgeonfish
[Phylum: Chordata] [Class: Actinopterygii] [Order: Acanthuriformes] [Species: Acanthurus triostegus]
Most surgeonfishes are easily identified by the bold colouration and unique characteristics. But, the one with a pale yellow body and six black vertical stripes is unmistakable.
This page contains interesting facts about Acanthurus triostegus (also called the manini fish), including where they are found, what they eat, and how they reproduce.
Distribution and Habitats of Convict Tangs
The geographical range of surgeonfishes (Acanthuriformes) in tropical and subtropical marine ecosystems is substantial.
Even though the Acanthuridae family of ray-finned fish includes tangs and unicornfishes, convict surgeonfishes flourish better in some areas, especially:
- Indian Ocean (e.g. Maldive Islands, Seychelles)
- East Africa (including Madagascar)
- Pacific Islands (particularly French Polynesia and Micronesia)
But, they have a specific preference for certain types of habitats. Besides being closely associated with coral reefs and reef flats, surgeonfishes also thrive in lagoons, around rocky coastlines, and in some seagrass beds or areas with algal-covered substrates.
Convict Tang Characteristics and Behaviour
In general, surgeonfish, tangs, and unicornfishes 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.
The convict surgeonfish (scientific name Acanthurus triostegus) also has several common names, including manini fish and fiveband surgeonfish.
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).
But wait - there's more:
The body colour tends to be a subtle combination of light gray and pale yellow. Convict tangs have six (6) vertical black bar markings that display some resemblance to the barred uniforms of jailed convicts (hence their funny fish names). The zebra tang (Acanthurus polyzona) has nine (9) black stripes.
For a relatively large fish that often measures up to 27 centimetres long (11 inches), the mouth is quite small and downturned.
Even so, 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.
Pro Tip: Some of the large schooling convict surgeonfish species can also tolerate lower depth ranges approaching ninety metres (close to 300 feet).
What Do Convict 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:
- 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.
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 fish tanks 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 2010 assessment released by the IUCN Red List of Threatened Species, the conservation status of convict surgeonfish species is of "Least Concern" (LC) and "Stable" in population trend.