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Acanthurus tractus, commonly known as the Ocean Surgeonfish, is a species of marine ray-finned fish belonging to the family Acanthuridae, the surgeonfishes, tangs, and unicornfishes. It is a medium-sized surgeonfish characterized by its oval, compressed body and a scalpel-like spine on each side of the caudal peduncle. This species was formerly considered a synonym of Acanthurus bahianus but was revalidated as a distinct species in 2011 based on genetic and morphological evidence. It is a common inhabitant of coral reefs and rocky areas in the western Atlantic Ocean.
Physical Characteristics
- Body shape
- compressed
- Coloration
- Adults typically exhibit a grayish-brown to dark brown body coloration, often with faint, irregular pale spots or lines. The caudal fin is usually dark, sometimes with a pale posterior margin. Juveniles are often bright yellow, gradually changing to the adult coloration as they mature. Some individuals may display a pale bar behind the eye or a pale area on the caudal peduncle. Coloration can vary with mood and environment.
- Scale type
- ctenoid
- Mouth position
- terminal
- Distinctive features
- Oval, compressed body, Scalpel-like spine on each side of the caudal peduncle (retractable), Small, terminal mouth with a single row of spatulate teeth, Continuous dorsal fin
- Dorsal fin
- Single, long dorsal fin with 9 dorsal spines and 23-26 soft rays.
- Tail fin
- Lunate (crescent-shaped) caudal fin.
- Pectoral fin
- Relatively small, fan-shaped pectoral fins.
- Distinctive fins
- Anal fin with 3 spines and 21-24 soft rays. Pelvic fins with 1 spine and 5 soft rays.
Identification Tips
Body Coloration
Adults are generally dark brown to grayish-brown, sometimes with faint mottling. Juveniles are bright yellow.
Caudal Spine
Presence of a sharp, retractable spine on each side of the caudal peduncle (tail base), characteristic of all surgeonfishes.
Body Shape
Distinctly oval and laterally compressed body.
Mouth
Small, terminal mouth with specialized teeth for scraping algae.
Habitat
- Water type
- saltwater
- Depth
- Typically found in shallow waters from 1 to 40 meters (3 to 130 feet), but can occur deeper.
- Environment
- Inhabits coral reefs, rocky shorelines, seagrass beds, and rubble zones. Often found in areas with abundant algal growth for grazing. Juveniles may be found in shallower, more protected areas.
- Geographic range
- Western Atlantic Ocean, from Florida (USA) and Bermuda, throughout the Caribbean Sea, Gulf of Mexico, and south to Brazil.
Aquarium Information
- Care level: intermediate
- Temperament: semi-aggressive
- Diet: herbivore
- Minimum tank size: 125 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 territorial towards other surgeonfishes or similar-bodied fish, especially in smaller tanks. Best kept singly or in very large aquariums with multiple surgeonfish introduced simultaneously.
- Special requirements: Requires a well-established aquarium with ample live rock for grazing and hiding. Excellent water quality and strong filtration are essential. Provide plenty of open swimming space. Susceptible to marine ich (Cryptocaryon irritans) and head and lateral line erosion (HLLE) if not provided with a proper diet and environment.
Wild Information
- Conservation status: least concern
- Seasonality: No specific seasonality for reproduction or migration; present year-round in its habitat.
- Market price: Low
- Commercial importance: low
- Taste: Mild, slightly fishy
- Texture: Firm, white flesh
- Cooking methods: Baked, Grilled, Fried, Steamed
- Nutritional value: Good source of lean protein and omega-3 fatty acids.
Key Facts
Taxonomic Revalidationevolution
Acanthurus tractus was revalidated as a distinct species in 2011, having previously been considered a synonym of Acanthurus bahianus. This reclassification was based on genetic and morphological studies.
Algae Grazerbehavior
Ocean Surgeonfish are primarily herbivorous, playing a crucial role in reef ecosystems by grazing on algae, which helps prevent algal overgrowth and promotes coral health.
Juvenile Colorationinteresting
Juvenile Ocean Surgeonfish are often bright yellow, providing camouflage among yellow gorgonians or sponges, and gradually change to their adult dark coloration as they mature.
Scalpel Defensebehavior
The common name 'surgeonfish' comes from the sharp, retractable, scalpel-like spines located on each side of their caudal peduncle, used for defense against predators and in territorial disputes.
Safety Information
Handle with care- Safety level: caution
- Venomous: No
- Edibility: edible
- Handling notes: The caudal spine (scalpel) is extremely sharp and can inflict painful wounds. While not venomous, these wounds can become infected. Handle with extreme care, avoiding contact with the tail. Use gloves and appropriate tools if handling is necessary.
Similar Species
Doctorfish
Acanthurus chirurgus
Acanthurus chirurgus (Doctorfish) has 9-10 dark, narrow vertical bars on its body, which are typically absent or very faint in Acanthurus tractus. The caudal fin of A. chirurgus often has a distinct pale margin, while in A. tractus it is usually dark or only faintly pale.
Blue Tang
Paracanthurus hepatus
The Blue Tang (Paracanthurus hepatus) is easily distinguished by its vibrant blue body, yellow caudal fin, and black 'palette' mark. It belongs to a different genus within the same family.
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Actinopterygii
- Order
- Acanthuriformes
- Family
- Acanthuridae
- Genus
- Acanthurus
- Species
- Acanthurus tractus
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