
Hawaiian Convict Surgeonfish
acanthurus sandvicensis
The Hawaiian Convict Surgeonfish, known locally in Hawaii as "manini," is a vibrant and highly social reef fish. Renowned for its bold, vertical stripes resembling a traditional prisoner's uniform, this striking species plays a vital role in maintaining the health of Hawaiian coral reefs. They are often seen in massive, synchronized schools, numbering in the hundreds, as they sweep across shallow reef flats to graze. This schooling behavior is not just social; it is a tactical strategy to overwhelm territorial damselfishes that guard their own private algae gardens. As an endemic species to the Hawaiian Islands, the manini holds cultural significance and is a beloved sight for snorkelers and divers alike. Their constant activity and ecological contribution as primary herbivores make them an essential and delightful species to observe in the wild.
Habitat: Found in shallow coral reefs, rocky shorelines, and exposed tide pools throughout the Hawaiian Archipelago.
Appearance
This species features a compressed, oval-shaped body that is predominantly a pale greenish-yellow or silvery-white, accented by six distinct, vertical black bars running down its sides. It has a sharp, spine-like "scalpel" near the base of its tail which is used for defense. The head is rounded with a small, downturned mouth perfectly adapted for scraping algae from rocks, and they typically grow to a length of about 12 to 25 centimeters.

Category
FishRarity
Common
Danger
1/5 ยท Very low
Snaps
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Interesting facts
During spawning cycles, huge aggregations form at dusk to release gametes directly into the water column, utilizing the cover of darkness to protect their eggs.
Its Hawaiian name, 'manini', is so common that it has entered local slang to mean 'small' or 'insignificant', referencing the fish's small size compared to larger game fish.
They possess a sharp, venomous spine on their tail base that can cause painful wounds if handled carelessly.
Special abilities
Tail Scalpel Defense
Possesses sharp, modified scales on either side of the caudal peduncle that can fold out like scalpels to deter predators.
Swarm Grazing
Schools in large numbers to overwhelm aggressive, territorial damselfishes and safely feed in their heavily defended algal lawns.
Rapid Color Shifts
Capably fades or intensifies its dark vertical stripes depending on stress levels, social interactions, or environmental background.
Measurements & details
- Length
- 12-25 cm
- Weight
- 0.1-0.4 kg
- Lifespan
- 5-15 years
- Top Speed
- 15 km/h
- Clutch Size
- 10000-100000
- Incubation
- 1-2 days
Diet & Feeding
Feeds constantly during the day on fine filamentous and turf algae growing on coral rubble and rocks.
Age differences: Larvae and post-larvae feed on plankton before transitioning to a strictly herbivorous diet as they settle onto the reef.
Primary Foods
- Filamentous algae
- Turf algae
- Microalgae
- Detritus
Foraging Method
- Grazing
Ecological connections

Yellow Tang
Zebrasoma flavescens
Competes for filamentous algae on shallow reefs.
Whitetip Reef Shark
Triaenodon obesus
Preys on adult surgeonfish sheltering in reef crevices at night.
Hawaiian Cleaner Wrasse
Labroides phthirophagus
Removes ectoparasites and dead skin from the surgeonfish's body at cleaning stations.
Traits
No trait badges are assigned for this object yet.
Also known as
No aliases listed yet.
Collections
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Safety
Danger
1/5 ยท Very low
No special safety notes yet.
Frequently Asked Questions
How to identify Hawaiian Convict Surgeonfish?
The easiest way to identify Hawaiian Convict Surgeonfish is to use the Snappit nature identifier app.
How long is Hawaiian Convict Surgeonfish?
12-25 cm
How much does Hawaiian Convict Surgeonfish weigh?
0.1-0.4 kg
How long does Hawaiian Convict Surgeonfish live?
5-15 years
How fast can Hawaiian Convict Surgeonfish move?
15 km/h
What does Hawaiian Convict Surgeonfish eat?
Feeds constantly during the day on fine filamentous and turf algae growing on coral rubble and rocks.
Where is Hawaiian Convict Surgeonfish usually found?
Found in shallow coral reefs, rocky shorelines, and exposed tide pools throughout the Hawaiian Archipelago.
How does Hawaiian Convict Surgeonfish hunt?
Grazing
Snap Map
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Where to spot
Hawaii, US
Allerton Garden
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Hawaii, US
Kahaluu Bay
You might spot Gold Dust Day Gecko, Yellow Tang, and Saffron Finch.
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Hawaii, US
Koko Crater Botanical Garden
You might spot Yellow สปilima, Red-Tailed Tropicbird, and White Leadtree.
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Hawaii, US
McBryde Garden
You might spot Brown Anole, Red-Crested Cardinal, and Gold Dust Day Gecko.
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Hawaii, US
Moir Gardens
You might spot Brown Anole, Red-Crested Cardinal, and Gold Dust Day Gecko.
View guide โ

Hawaii, US
Waimea Valley
You might spot Gold Dust Day Gecko, Brown Anole, and White-Rumped Shama.
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