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Acanthurus nigricans, commonly known as the White-faced Surgeonfish, is a species of marine ray-finned fish belonging to the family Acanthuridae, the surgeonfishes, tangs, and unicornfishes. It is a distinctive surgeonfish recognized by its dark body, prominent white patch below the eye, and a bright yellow caudal fin. This species is a common inhabitant of coral reefs across the Indo-Pacific, where it plays an important ecological role as an herbivore, grazing on benthic algae.
Physical Characteristics
- Body shape
- compressed
- Coloration
- The body is predominantly dark brown to black. A distinctive, prominent white patch is located directly below the eye, extending slightly onto the operculum. The dorsal and anal fins are dark, often with a thin blue or white margin. The pectoral fins are dark with a yellow base. The caudal fin is bright yellow, often with a thin dark posterior margin. Juveniles may have a more yellowish body with the characteristic white cheek patch.
- Scale type
- ctenoid
- Mouth position
- terminal
- Distinctive features
- Prominent white patch below the eye, Bright yellow caudal fin, Dark body coloration, Scalpel-like spine on each side of the caudal peduncle
- Dorsal fin
- Single, long dorsal fin with 8-9 spines and 24-27 soft rays. The spiny and soft-rayed portions are continuous.
- Tail fin
- Lunate (crescent-shaped) caudal fin, bright yellow.
- Pectoral fin
- Relatively small, fan-shaped pectoral fins, dark with a yellow base.
- Distinctive fins
- A single, sharp, retractable scalpel-like spine on each side of the caudal peduncle (tail base), characteristic of all surgeonfishes.
Identification Tips
White patch below eye
This is the most defining characteristic. Look for a distinct, bright white blotch directly beneath the eye.
Caudal fin color
The tail fin is a vibrant yellow, contrasting sharply with the dark body.
Body color
The main body is a uniform dark brown to black.
Pectoral fin base
A yellow coloration at the base of the pectoral fins is often visible.
Habitat
- Water type
- saltwater
- Depth
- Typically found in shallow to moderate depths, from 1 to 30 meters (3 to 100 feet).
- Environment
- Inhabits coral reefs, rocky reefs, and lagoons, often found in areas with rich algal growth. Prefers clear, warm tropical waters. Juveniles may be found in shallower, more protected areas.
- Geographic range
- Widespread throughout the Indo-Pacific region. Its range extends from the Red Sea and East Africa across the Indian Ocean to the central Pacific, including Hawaii, French Polynesia, and the Great Barrier Reef. North to southern Japan and south to Lord Howe Island.
Aquarium Information
- Care level: intermediate
- Temperament: semi-aggressive
- Diet: herbivore
- Minimum tank size: 120 gallons
- Temperature: 72-78°F (22-26°C)
- pH level: 8.1-8.4
- Hardness: 8-12 dKH
- Compatibility: Can be kept with other robust, non-aggressive fish. May be aggressive towards other surgeonfish, especially those of similar shape or color. Best kept singly or in very large tanks with multiple surgeonfish introduced simultaneously.
- Special requirements: Requires a well-established aquarium with ample live rock for grazing and hiding. A strong current is beneficial. High-quality herbivore diet is crucial for long-term health, including various marine algae and spirulina. Susceptible to lateral line erosion (HLLE) if not fed a proper diet and provided with good water quality.
Wild Information
- Conservation status: least concern
- Seasonality: No specific seasonal patterns for availability; present year-round in its natural habitat.
- Market price: Moderate to high for the aquarium trade
- Commercial importance: low
- Taste: Mild, firm white flesh
- Texture: Firm, flaky
- Cooking methods: Baked, Grilled, Steamed, Fried
- Nutritional value: Good source of protein and omega-3 fatty acids. However, surgeonfish are generally not a primary target for commercial fisheries due to their grazing habits and potential for ciguatera in some regions, though A. nigricans is less commonly associated with it than some other species.
Key Facts
Algae Grazerbehavior
Acanthurus nigricans is a crucial herbivore on coral reefs, grazing on filamentous algae and helping to prevent overgrowth that can smother corals.
Territorial Naturebehavior
While generally peaceful towards dissimilar species, White-faced Surgeonfish can be highly territorial towards other surgeonfish, especially those with similar body shapes or colors.
Scalpel Defenseinteresting
Like all surgeonfish, it possesses a sharp, retractable spine on its caudal peduncle, which it uses for defense against predators and rivals.
Color Variationinteresting
The intensity of the white cheek patch and yellow caudal fin can vary slightly depending on the fish's mood, health, and geographic location.
Safety Information
Handle with care- Safety level: caution
- Venomous: Yes
- Edibility: edible
- Handling notes: Surgeonfishes possess a sharp, scalpel-like spine on each side of the caudal peduncle. These spines are used for defense and can inflict painful wounds. While not venomous in the traditional sense (no venom gland), the spine can cause deep cuts, and secondary bacterial infections are a risk. Handle with extreme care, avoiding contact with the tail area. If stung, clean the wound thoroughly and seek medical attention if signs of infection or severe pain develop.
Similar Species
Powder Blue Tang
Acanthurus leucosternon
The Powder Blue Tang has a bright blue body, yellow dorsal fin, and a black face with a white throat patch, whereas A. nigricans has a dark body, yellow caudal fin, and a white patch below the eye.
Achilles Tang
Acanthurus achilles
The Achilles Tang is dark brown to black with a prominent orange tear-drop shaped spot near the caudal peduncle and orange markings on the dorsal and anal fins. A. nigricans lacks these orange markings and has the distinct white cheek patch and yellow caudal fin.
Black Tang
Ctenochaetus hawaiiensis
While also dark-bodied, the Black Tang (a bristletooth tang) has a more elongated snout and a different mouth structure adapted for scraping detritus. It lacks the prominent white cheek patch and bright yellow caudal fin of A. nigricans.
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Actinopterygii
- Order
- Acanthuriformes
- Family
- Acanthuridae
- Genus
- Acanthurus
- Species
- Acanthurus nigricans
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