Wallago attu
(Bloch & Schneider, 1801)
|
he name of 'Freshwater Shark" may give you a hint that this
months factsheet (August
2010) is not for the faint hearted and as we follow on from its
cousin Wallago leeri, which
was covered extensively six years ago in Nov. 2004, this is really
not a catfish for the home tank as they can grow in excess of
6ft and are more of a sport for big fish hunters and is an important
food fish in its native habitats. This of course does not stop
us at looking at this interesting species and finding out how
it 'ticks'.
There are at present 5 species of Wallago listed on
Fishbase, our factsheet of the month W.attu, W.hexanema,
(which is probably W.attu) W.leeri, W.maculatus,
and a new species which was described in 2004 by Heok Hee
Ng from mainland Southeast Asia,
W. micropogon.
To distinguish W. attu from
the very similar W. leeri you have to look at the dorsal
fin first. W. attu has a pointed extension while W.
leerii does not and is more rounded at the tip. The mouth
gape of W.attu ( see above) reaches beyond the insertion
of the eye and W. leerii has the mouth only reaching
to the beginning of the eye. W. attu has a longer anal
fin than W. leerii with 77- 97 with the latter possessing
between 64-75 fin rays. You can see below the massive mouth
and the rows of conical teeth.
In the Mekong, it is reported to
migrate to smaller streams, canals and to the floodplain during
the flood season. When the water level in the Mekong drops and
the flood recedes, it moves to the Mekong or larger tributaries,
where it stays in deep pools until the next inundation period.
Destructive to other more valuable food-fishes. Bites strongly
if handled, with its huge mouth, formidable jaws, and band of
conical teeth. W.attu is threatened due to over harvesting.
In Malaysia they are bred commercially in fish farms for food.
It is ritually offered to the goddess
Kali by the Hindus (Talwar and Jhingran 1991)
Dorsal soft rays (total): 5 - 5; Anal soft
rays: 77 - 97. Head broad, snout depressed. Body elongate, strongly
compressed. Mouth very deeply cleft, its corner reaching far behind
eyes. Teeth in jaws set in wide bands; vomerine teeth in two small
patches. Barbels two pairs; maxillary barbels extending to anterior
margin posterior of anal fin, mandibulary barbels to angle of mouth.
Eyes small, with a free orbital margin. Dorsal fin small, anal fin
very long. Mandibular barbel longer than pelvic fin; 24-30 gill
rakers on the first arch. Eye in front of vertical through corner
of mouth.
Body uniform silvery or olive with golden
gloss above, sides a dull white. A faint orange/yellow band along
the lateral line. Anal and caudal fins dusky.
Only juveniles can be kept in aquaria and
fed on tablet food, beef heart and similar foods. This fish is
not deemed suitable for aquarium keeping due to its size, verocity
and its feeding needs for live fish.
In Bangladesh they spawn during the premonsoon
season from June to August. As soon
as the streams are flooded by rains, the fishes run up
the shallow water for breeding, build nests and offer parental
care.
| Sexual
differences |
Not known.
|
| Feeding |
Juveniles feed mainly on insects; adults feed
on smaller fish, crustaceans, and mollusks.
| References |
Mohsin, ABM; Encyclopedia
of Flora and Fauna of Bangladesh.
Vol.23. Freshwater Fishes. Asiatic Society of Bangladesh.
300p.
|
| Etymology |
Walago:
Bleeker, in 1851
took the Indian fish name 'Wallagoo', gave it generic rank,
and used it in connection with a new species.
|
© Jean-Francois
Helias @
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| Synonyms:
|
| Silurus attu, Wallagonia
attu, Wallago attu valeya, Pinniwalago kanpurensis
|
| Common
Name: |
| Wallago,
Freshwater Shark. |
| Family: |
| Siluridae |
| Subfamily: |
Silurinae |
| Distribution: |
| Asia:
Pakistan to Viet Nam and Indonesia. Reported from Afghanistan.
Lower risk - near threatened status in Western Ghats,
India |
| Size: |
| 200cm. (6ft 8ins) |
| Temp: |
| 22-25°C
(71-77°F) |
| pH.: |
| 6.5-8.0. |
| Donation: |
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