These are herbivorous fishes that are important for the reef habitat because they eat algae.  Algae, when it grows too abundantly, inhibits coral growth.  When the reef loses its structure, it loses habitat for other fishes and invertebrates.

Click on the arrow symbol under each fish for more information.

 

 Acanthurus achilles, Achilles tang

    • Max length 24 cm; Dark brown, almost black in color
    • Erectile spine on each side of caudal peduncle.  Mouth small, snout noticeably extended.
    • Light blue ring around chin and presence of spot of same color on gill cover at angle of gill opening
    • Dorsal fin with soft part having longer base than spinous part
    • Juveniles lack the dark orange spot on caudal area
    • Occurs in clear seaward reefs, usually in groups.  Depth range up to 10m, usually up to 4m
    • Feeds on filaments and small fleshy algae
    • Monogamous (stays with mate)
    • High resilience, minimum population doubling time less than 15 months
    • Low vulnerability

Acanthurus gattatus, Whitespotted surgeonfish

  • Max length 26 cm
  • Preserved color is brown; spotted, white spots usually bordered with dark brown
  • Pelvic fins bright yellow
  • Each side of caudal peduncle with a single sharp forward-pointing erectile spine
  • Occurs in surge zone of clear seaward reefs.  Depth range 1-6m
  • Browses on filamentous and calcareous algae
  • Forms schools
  • High resilience, minimum population doubling time less than 15 months
  • Low to moderate vulnerability
 Acanthurus lineatus,  Lined surgeonfish
    • Upper 3/4 of body w/alternating black-edged blue and yellow bands, lower 1/4 of body gray
    • Erectile spine on each side of caudal peduncle is sharp, strong, forward-pointing, and venomous
    • Upper part of head with yellow, oblique stripes
    • Pectoral fins pale with dusky rays; pelvic fins light yellowish brown with black outer margin; vertical markings on caudal fin
    • Minute scales
    • Medium resilience, minimum population doubling time 1.4 – 4.4 years
    • Low vulnerability
Acanthurus nigricauda, Epaulette surgeonfish
    • Max length 40 cm
    • Color in life dark brown without lines on body or spots on head (one phase is purplish gray); horizontal black band behind upper gill opening on juveniles that are less than 6 cm
    • Elongate purple band may be present anterior to dorsal origin; caudal fin brown; outer third of pectoral fin pale
    • Found in clear lagoon and seaward reefs around isolated coral heads, depth range 1-3 m, usually 2-15 m
    • Prefers sandy bottoms of bays and lagoons rather than the coral reefs
    • Sometimes poisonous to eat
    • High resilience, minimum population doubling time less than 15 months
    • Low vulnerability

 

 Acanthurus olivaceus,  Orangespot surgeonfish
    • Max length 35 cm
    • Depth range 3-46m
    • Body of adult dark grayish brown; juveniles yellow; posterior to upper end of gill opening bright orange horizontal band with purplish black border
    • Head and anterior half of body usually abruptly paler than the posterior half
    • Large adult males have more definite convexity of snout profile
Acanthurus tristegus, Convict surgeonfish
    • Max length 27 cm, common length 17 cm
    • Body olivaceous gray with 4 vertical stripes (1 on head across the yellow eye; 1 on caudal peduncle)
    • Sharp, forward pointing erectile spine on each side of caudal peduncle which folds down into a groove
    • Occur in lagoon and seaward reefs with hard substrate; young abundant in tide pool.  Depth range up to 90 m, but usually shallow
    • Often feed near freshwater run-offs where certain algae grow on rocks that are grazed
    • Form schools; feed on filamentous algae in large aggregations
    • Form spawning aggregations.  During spawning, clouds of eggs and sperm are preyed upon by eagle rays which are often present during spawning
    • There have been reports of ciguatera poisoning

Acanthurus xanthopterus, Yellowfin surgeonfish

    • Common length 50 cm
    • Body purplish gray, a region of dull yellow in front of the eye, outer 1/3 of pectoral fin yellow, dorsal and anal fins yellowish gray basally, dull yellow distally; caudal fin base whitish; caudal fin purplish
    • Small caudal fin
    • Live in various reef habitats, sand slopes, and lagoons.  Depth range 1-100m
    • Juveniles inhabit shallow, protected, turbid inshore waters while adults prefer deeper areas of protected bays and lagoons, also in outer reef areas
    • Schooling species, feed on diatoms, detritus film of sands, filamentous algae, hydroids, and pieces of fish
    • Venomous to humans
    • Low resilience, minimum population doubling time 4.5 – 14 years
    • Moderate vulnerability

Naso lituratus, Orangespine unicornfish

    • Max length 46 cm
    • Dorsal fin black, with a pale blue line at base and a broad outer white zone on soft portion; anal fin mainly orange; dorsal and anal fins with a narrow blue margin; caudal fin with a yellow submarginal band posteriorly.  Caudal fin with adult males having trailing filaments from each corner
    • Found in areas of coral, rock, or rubble of lagoon and seaward reefs.  Depth range up to 90 m, usually 5-30 m
    • Adults usually in small groups, juveniles sometimes in small aggregations mixed with other acanthurids of similar size
    • Feed mainly on leafy brown algae (sargassum and dictyota)
    • Seldom poisonous
    • Medium resilience, minimum population doubling time 1.4 – 4.4 years
    • Low to moderate vulnerability

Naso tonganus, Bulbnose Unicornfish

    • Inhabits coral reefs.  Feeds on leafy or fleshy algae and zooplankton
    • Maximum length to 60 cm
    • Found singly or in small groups
    • Medium resilience, minimum population doubling time 1.4 – 4.4 years
    • Medium to high vulnerability

Naso unicornis, Bluespine Unicornfish

    • Max length: 70 cm, Common length: 50 cm
    • Characterized by presence of tapering body horn in adults projecting at level of eye but not extending in front of mouth.  Well-developed forward curving knife-like spines on peduncle.  Caudal fin with filamentous lobes in adult; olivaceous with blue peduncle plates and spines; dorsal and anal fins yellowish with narrow blue stripes
    • Inhabit channels, moats, lagoons, seaward reefs with strong surge.  Reef associated.   1-80 m depth
    • Typically occur in small groups
    • Feed on coarse leafy, brown algae like Sargassum
    • Have been reports of ciguatera poisoning
    • Low resilience, minimum population doubling time 4.5 – 14 years

Zebrasoma scopas, Twotone tang

    • Maximum length to 40 cm
    • Dark brown, with fine pale blue-green longitudinal lines following scale rows, becoming dots anteriorly on body and head.  Small juveniles have yellowish bars and more prominent yellow specks than adults
    • Associated with reefs, 1-60 meters.  Occurs in coral-rich areas of lagoon and seaward reefs.  Graze on algae, usually in groups of 20 individuals
    • Form resident spawning aggregations, monogamous
    • Medium resilience, minimum population doubling time 1.4 – 4.4 years

 

Zebrasoma veliferum, Sailfin tang

    • Maximum length to 40 cm
    • Small juveniles have alternating yellow and black bars.  Dorsal fin very elevated.
    • Occurs in lagoon and seaward reefs from the lower surge zone to a depth of at least 30 m
    • Feeds on leafy macroalgae
    • Medium resilience, minimum population doubling time 1.4 – 4.4 years
    • Moderate vulnerability