> Subphylum Vertebrate > fishes
|Filefishes or Leatherjackets
learn only 3 things about them ...
| They can change colours and patterns to match the surroundings.
They have a stiff dorsal spine and leathery skin instead
ones (2-3cm) are common in seagrasses. Watch your step!
seen? These strange-looking fishes are quite commonly seen
on many of our shores, especially in areas with seagrasses and among
coral rubble. They can be quite large but are hard to spot as they
blend in well with their surroundings. Some tiny filefishes are hardly
bigger than a seagrass leaf and are often the same colour as the seagrasses!
So do watch your step to avoid squashing these small fishes.
What are filefishes? Filefishes
belong to Family Monacanthidae. According to FishBase:
the family has 31 genera and 95 species. They are found in the Atlantic,
Indian and Pacific Oceans. They range from small fishes about 2cm
long to giants 1m long!
Features: Adults 10-30cm.
Body flattened sideways and disc-shaped to rectangular. Eyes are high
on the head. The gill openings are just slits.
Usually two dorsal spines, the second may be much smaller or absent.
The dorsal spine is usually long stiff with downward pointing barbs
on the edges. This feature gives it its scientific name: 'mono' means 'one' and 'canthus' means 'thorn'. The dorsal spine
can be locked upright to wedge in crevices, safe from predators and
from being swept away by currents. When not in use, the spine is folded
away into a groove on the body. Most have a second dorsal spine but
this is usually small. The pelvic fin is bony and fused with the body
forming a flap under the body.
The scales are small and have prickles on them. So the skin feels
leathery and rough, like sandpaper. These fishes are sometimes also
called leatherjackets. Some have hairy or feathery bits sticking out
of their skin that help break up their body outline.
Filefishes can't swim fast, aside from a short burst of speed to escape
predators by using their tails. Otherwise, they swim slowly by undulating
their other fins. Most rely on camouflage to avoid predators. They
can rapidly change colours and patterns to match their surroundings.
The flattened body allows them to slip quietly among seagrass or squeeze
into crevices. These fishes often flatten out against or 'wrap around'
sponges, rubble and other large objects. They are then really hard
The 'thorn' at the top of the head
can be locked into place. There is usually a flap under the body.
Beting Bronok, Mar 07
Wrapped closely around a sponge.
Chek Jawa, May 04
|What do they eat? Filefishes will
eat almost any food source. These include small bottom-dwelling animals
like small prawns. They also nibble on seaweed, seagrass, the epiphytes
growing on them. Also immobile animals like bryozoans and ascidians,
as well as coral polyps. They will also eat the flesh of other marine
animals. The small mouth at the end of a pointed snout allows them
to suck small prey out of their hiding places, or reach into crevices
to nibble on edible bits. Some have large prominent teeth.
They can change
for perfect camouflage!
Chek Jawa, May 05
Tiny green one resembles a seagrass leaf!
Changi, May 11
Three Feathery fishes resembling flotsam.
Tanah Merah, Sep 11
|Filefish babies: Many filefishes
lay eggs that settle on the bottom, onto a site prepared and guarded
by the male or both parents. Some subtropical species may release
their eggs into open waters.
Human uses: Filefishes are edible
and eaten in some traditional dishes. Unlike most other edible fishes
which are scaled before we eat them, for filefishes, the rough skin
has to be 'peeled' off first.
Status and threats: None of our
filefishes are listed among the threatened animals of Singapore. However,
creatures of the intertidal zone, they are affected by human activities
such as reclamation and pollution. Over-fishing can also have an impact
on local populations.
on Singapore shores
irregular curved yellow or white line along the front of the body
from the gill opening to the middle of the upper body, that resembles
a 'smile'. Body in a wide variety of colours and patterns, usually
||Tail fin small. Adult
males have bristles near the tail fin arranged a well-defined central
Large triangular skin flap on the belly that can be greatly expanded,
but often tucked close to the body. Body with lots of small circular
dots and broad diagonal bars on the sides, in some these bars may
be indistinct. It comes in all shades from brown to green.
fin large. On a large adult, the upper fin rays on
the tail is produced into a filament.
Body with lots of small circular dots and often a broad white stripe
along the centre of the body from the gill opening. May have dark
fin very large.
Monacanthidae recorded for Singapore
Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity
*Lim, Kelvin K. P. & Jeffrey K. Y. Low, 1998. A Guide to the Common
Marine Fishes of Singapore.
+Other additions (Singapore BIodiversity Records, etc)
||+Aluterus scriptus (Scrawled filefish)
barbatus (Bearded filefish)
penicilligerus (Feathery filefish)
Monacanthus chinensis (Fan-bellied
Monacanthus choirocephalus=**Paramonacanthus choirocephalus
(Pig-faced leather jacket)
Monacanthus cryptodon=**Paramonacanthus cryptodon
macrurus (Strapweed filefish)
Monacanthus nemurus=**Paramonacanthus choirocephalus (Pig-faced
Monacanthus sulcatus=**Paramonacanthus sulcatus
tomentosus (Seagrass filefish)
- Lim, Kelvin
K. P. & Jeffrey K. Y. Low, 1998. A
Guide to the Common Marine Fishes of Singapore. Singapore
Science Centre. 163 pp.
sp. Tan, Leo W. H. & Ng, Peter K. L., 1988. A
Guide to Seashore Life. The Singapore Science Centre,
Singapore. 160 pp.
- Monacanthidae from Ecology Asia.
Monacanthidae (Filefishes) and Anacanthus
barbatus (Bearded leatherjacket) and Chaetodermis
penicilligerus (Prickly leatherjacket) and Paramonacanthus
choirocephalus (Pig faced leather jacket) and Paramonacanthus
cryptodon and Pseudomonacanthus
macrurus (Strap-weed file-fish) and Paramonacanthus
sulcatus (Mudbank filefish) and Acreichthys
tomentosus (Bristle-tail file-fish) from FishBase:
Technical fact sheet on the family, including fact sheets on individual
6: Bony fishes part 4 (Labridae to Latimeriidae), estuarine crocodiles,
sea turtles, sea snakes and marine mammals FAO Species Identification
Guide for Fishery Purposes The Living Marine Resources of the
Western Central Pacific.
- Karenne Tun & Kelvin K. P. Lim. Scrawled filefish, Aluterus scriptus, in the Singapore Strait. 31 May 2019. Singapore Biodiversity Records 2019: 73 ISSN 2345-7597. National University of Singapore.
- Abigayle Ng and Kelvin K. P. Lim
. 7 February 2014. Scrawled filefish at Saint John's Island. Singapore Biodiversity Records 2014: 35
- Wee Y.C.
and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore.
National Council on the Environment. 163pp.
- Allen, Gerry,
Fishes of South-East Asia: A Field Guide for Anglers and Divers.
Periplus Editions. 292 pp.
- Kuiter, Rudie
H. 2002. Guide
to Sea Fishes of Australia: A Comprehensive Reference for Divers
New Holland Publishers. 434pp.
Ewald and Robert Myers. 2001. Coral
Reef Fishes of the World
Periplus Editions. 400pp.