Acanthuridae

FEATURE || FISH
SURGEONFISHES
FEATURE
ID
Acanthuridae
SURGEONFISHES
This large family is split into three subfamilies: surgeons,
unicorns and sawtails, of which only surgeons and unicorns appear in
our area. There are 69 species, of which 31 are in our area.
They are generally small- to medium-sized, oval in shape, thinbodied and have high-set eyes and a small, terminal mouth. They
all feature one or two pairs of erectable, scalpel-like spines that fold
forward into a groove (sheath) on either side of the base of their tail
when not in use. These spines give the family its common name.
These spines are used during inter-territorial disputes and in defence
and in some species may be venomous.
Surgeonfishes are a very important group of herbivores, as they
help control the growth of algae on reefs which would otherwise
restrict animal resettlement. They are frequently seen grazing in
large gregarious schools over shallow reef flats using their sharp
incisors. By necessity, their intestines are long and thin-walled to
help digest their nutrient-poor diet. S
Pencilled surgeonfish (Acanthurus dussumieri)
Lieutenant surgeonfish (Acanthurus tennenti)
Powder-blue surgeonfish (Acanthurus leucosternon)
Chocolate surgeonfish (Acanthurus thompsoni)
Bluebanded surgeonfish (Acanthurus lineatus)
Convict surgeonfish (Acanthurus triostegus)
Elongated surgeonfish (Acanthurus mata)
Yellowfin surgeonfish (Acanthurus xanthopterus)
Brown surgeonfish (Acanthurus nigrofuscus)
Palette surgeonfish (Paracanthurus hepatus)
Appearance: Attains 50cm. Brown body with thin,
wavy, blue horizontal lines and blue tail, with numerous
black spots, changing to yellow at the base. White tail
spine sheath. Habitat: Offshore coral and rocky reef
slopes, walls, oceanic islands and shipwrecks. Lifestyle:
Common. Occurs solitary or in small groups. Feeds on
surface film covering sand and hard surfaces.
Appearance: Attains 20cm. Strikingly colourful and
unmistakeable species with bright-blue body, black and
white head, yellow dorsal fin and white anal and pelvic
fins. Habitat: Coastal reefs, offshore reefs, oceanic
islands and atolls. Lifestyle: Common. Occurs solitary
or in large groups grazing on the reef. Sometimes forms
large shoals in tropical areas. Feeds on algae.
Appearance: Attains 38cm. Horizontal, black-edged
blue stripes interspersed with yellow and a purple
underside. Peduncle spine is venomous. Habitat:
Shallow rocky reefs in turbulent water. Also reef flats
and channels on deeper reefs. Lifestyle: Common.
Rather aggressive surgeonfish. Occurs solitary or in
groups. Feeds on algae.
Appearance: Attains 50cm. Yellowish-brown body
with longitudinal blue lines and yellow mask. Changes
body colour depending on behavioural mood.
Habitat: Coral and rocky reefs and slopes. Also enters
lagoons with sandy bottoms or congregates in large
caves. Lifestyle: Common. Adults often occur in
schools in mid-water. Feeds on zooplankton.
Appearance: Attains 21cm. This species is somewhat
inconspicuous with a drab, brown body. The head
is covered in small orange spots which are not very
noticeable. Habitat: Tidal pools as well as shallow areas
on rocky and coral reefs that are covered in algae.
Lifestyle: Common. Occurs solitary or in small groups.
Feeds on filamentous algae.
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Appearance: Attains 31cm. Grey-brown to dark-brown
body with two black horizontal lines on shoulder.
Capable of changing from light to dark, depending
on behavioural mood. Habitat: Coral and rocky reefs.
Often reef flats and slopes. Lifestyle: Common. Occurs
solitary, in pairs and at times in groups. Feeds on algae
film on sand and rocks.
Appearance: Attains 27cm. Bluish-grey to darkbrown body while the tail in contrast is white and
striking. Habitat: Coral and rocky reef slopes as well
as drop-offs. Widespread throughout Indo-Pacific
and southern to northern KwaZulu-Natal. Lifestyle:
Common. Occurs solitary or in loose groups. Feeds on
zooplankton above bottom or in front of drop-offs.
Appearance: Attains 27cm. Body colouring is greygreen with a pattern of vertical black bars. Habitat:
Rocky shores, oceanic islands, harbours, estuaries
and lagoons where algae-rich areas occur. Lifestyle:
Common. Occurs in large schools, but also solitary or
in small groups. Feeds on a wide variety of filamentous
algae grazed from hard substrates.
Appearance: Attains 62cm. Purplish-grey to brown
body with narrow, horizontal, brown to dark-grey lines.
Distinctive yellow eye blotch. Yellow pectoral fins and
black spine sheath. Habitat: Coral and rocky reefs
and sand slopes. Lifestyle: Common. Usually occurs
in large aggregations, grazing soft algae on sand and
rubble areas far from the reef.
Appearance: Attains 26cm. Body is bright blue with
a black palette-shape pattern on upper side. Yellow
tail is edged in black. Habitat: Outer coral reef flats in
shallow, clear water with moderate to strong currents.
Lifestyle: Relatively uncommon. Generally occurs in
loose aggregations that swim above the reef. Feeds
on plankton.
Surgeonfishes are some
of the most exquisitely
patterned and coloured
reef fishes.
Unicornfishes have a
more elongated body
and some develop a
horn-like protrusion on
the forehead.
Surgeonfishes have
one or two pairs of
erectable, scalpel-like
spines that fold forward
into a groove (sheath)
when not in use.