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Order : Beloniformes
Family : BELONIDAE
Species : Tylosurus crocodylus
Maximum Length : 150 cm
The genus Tylosurus comprises, as of 2022,
ten recognised species of 'longtom', also known as needlefish or
houndfish. According to Fishbase, four of these occur in the waters
of Southeast Asia.
Tylosurus crocodylus (Crocodile Longtom or Hound Needlefish) is
one of the larger species of the genus, potentially reaching a maximum
length of around 150 cm and a maximum weight of 6.4 kg (see
Fishbase).
Its range extends throughout the tropics, in the waters of the
Atlantic, Indian and Pacific oceans. It is associated with coral reefs
and coastal lagoons.
The example shown here was identified as a type of Tylosurus
based on the length of the jaws (somewhat shorter than those of the
genus Strongylura), and more specifically the presence of a dark,
fleshy, lateral keel on the side of its caudal peduncle (the caudal
peduncle is the point at which the tail fin joins the body).
In Tylosurus crocodylus the body colour is greenish or
bluish-green above, and silvery beneath, and the lower lobe
of the tail fin is markedly longer than the upper.
This is a fast-moving, mainly solitary predator; its long, streamlined,
muscular body has evolved to rapidly accelerate towards its
selected prey, which are typically slower-moving fish. The sharp, pointed
jaws, armed with sharp teeth, and sudden bursts of speed can
be hazardous to fishermen wading in shallow waters.
Fig 1 : Crocodile Longtom, photographed at night using camera flash;
this example, found in a boating marina on Sentosa, one of Singapore's
southern islands, had an estimated total length of around 50 cm.
Fig 2 : Singapore's southern islands, as viewed from Sentosa Island;
these include
Tekukor Island with St. John's Island behind, and in the far distance the hills of Batam
Island
(Indonesia). These relatively calm, shallow waters support a population
of Crocodile Longtom.
Fig 3 : Close-ups of the head, showing the moderately long jaws lined
with sharp teeth.
Fig 4 : Close-up of the tail. The small, dark mark on
the caudal peduncle is the lateral keel, which identifies this fish as a
Tylosurus.
Thanks to Kelvin Lim for identifying this fish.
References : F3
Links :
Fishbase
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