Channa gachua


{pronunciation} gash-ow-a

Common name:

Brown Snakehead, (Channa gachua 'Sri Lanka'); Bakak, Malay; pla kang, Thailand; Parandel kannaya, Sri Lanka; Cheng, Bengal; Hili, Nepal.

First description:

Hamilton, F. 1822.
Ophiocephalus gachua
An account of the Fishes found in the River Ganges and its Branches.
Publ. Archibald Constable.; p.68,69.

Meristic:

D: 30-37 A: 20-24 C: 16 P: 15 V: present Ratio: 2.9- 3.25

Ll:

40-45

Description:

The dorsal is greenish, the anal a dirty pale bluish-green; both are edged with black. The upper edge has a red lateral margin and the lower a white sideward band. The rounded caudal fin is greenish, marginally edged, first with black and then red with blue-green interspaces. The pectorals are a pale brick colour, with several rows of blue spots.

The upper body has dark bands which run across the back obliquely forward.

Due to its vast geographical range, the description is of the type specimen, described by Hamilton, which hailed from Bengal,India.

Size:

The largest size recorded is 300 mm.

Sub-species and colour variants:

The respected Sri Lankan ichthyologist, P.E.P.Deraniyagala, in a paper written in 1945, referred to the well-known synonym Ophiocephalus kelaarti (Gunther 1861), which was described from immature specimens from Sri Lanka. Significant morphometric differences between O.kelaartii and O.gachua are; a slightly deeper body, a larger lateral scale count and a longer caudal and pectoral fin. Following Myers & Shapovalov (1931), this fish becomes Channa gachua kelaartii (Gunther 1861).

However, in an excellent discussion on 'The Sub-species Concept and its Taxonomic Application', Wilson & Brown (1953), in a summary of the inadequacies of the present latinized trinomial system, pointed out that if all the geographically distinct sub- species were realised, the system would be overloaded with an excess of futile names. Therefore, the trinomial should incorporate a specific locality (either generally or more specific) rather than a (in many cases) meaningless latin third name, so that variants can be easily distinguished in terminology. This would finally give:

C. gachua 'Sri Lanka'

The Sri Lankan variation has a lower than average dorsal fin count and has a smaller average length, between 125-150mm. The upper body colour is brown, with W-shaped cross bars. The margin of the dorsal fin is orange, whitish tipped; with one or two ocelli markings. The anal fin is green-blue, with the outer margin greyish brown and an orange or red inner stripe. The external margin of the caudal fin is orange/red. A dark lateral stripe, which runs from the snout through the eye to the opercle can be seen on the head.

Several other colour variants are recorded:-

C.gachua Chinese form

The body is brownish olive. The fins are yellowish tipped, with the caudal and dorsal displaying minute white spots.

C.gachua: Bengalese form

In Francis Hamilton's account of the fishes of the Ganges region there is described a 'distinct species with doubt' on page 69, called Ophiocephalus aurantiacus, which several authors have since synonmised. The whole body colour thoughout is of orange peel, with some irregular stains of a redder hue, especially on the sides of the head, the pectoral and on the caudal fins.

C.gachua Thailand form

Fowler (1934) states that the dorsal has a bright red margin (which turns white when preserved in alcohol), the fore part of the belly is greenish white and the posterior purplish-white. The dorsal is speckled with dull yellow and brown. The anal is greenish at the base.

However Smith (1945) found a peculiarity in the lateral line scale counts. Where a break occurred in the line and then resumed, several differing tallys appeared; including differences in counts between the two sides of one individual's body.

Specimens from Koh Chang (Gulf of Siam) have a deep black body colour.

Juvenile differences in colouration:

Young C.gachua 'Sri Lanka' have a pale, reddish-yellow upper part of the body with the lower half dark grey. A vague orange lateral band runs from the snout to the caudal. All fins are pale yellow. At 230 mm, the fish displays an occellus (sometimes two) with an orange aura on the rear of the dorsal fin, which it carries until it is between 440 and 560 mm long. In the young found by Shaw & Shebbeare (1937), this ocellus was never present. The darker cross bars are more conspicuous( becoming obselete in adult fish) and often some black spots are scattered over the body (Weber & de Beaufort 1922).

Synonyms:

Ophiocephalus aurantiacus, Ophiocephalus cora-mota, Ophiocephalus fusca, Ophiocephalus gachua, Ophiocephalus harcourt butleri, Ophiocephalus kelaarti, Ophiocephalus limbatus, Ophiocephalus marginatus, Ophiocephalus montanus, Ophiocephalus surakartensis.

Geographical location:

his stretches over a huge area of Southern Asia, from Iran to China. They can be found in all habitats, from mountain streams to polluted ponds. Its hardiness and ability to cross land when it is wet has contributed to its adeptness to populate all areas.

A more detailed list of countries and authors are as follows:-

China :Herre & Myers (1931) ; Nichols (1943) ; Shih (1936) .

India : Chaunan (1947) ; Das (1939) ; Hamilton (1822) ; Hora & Gupta (1940) ; Shaw & Shebbeare (1937) .

Indo-Australian Archipelago : Beaufort (1939) ; Bleeker (1879) ; Cramphorn 1983 ; Duncker (1904) ; Herre (1937) ; Hardenberg (1936) ; Tweedie (1936) ; Tweedie (1949) ; Volz (1904) ; Weber & de Beaufort (1922).

Iran : Coad (1978).

Kampuchea: Kottelat (1985).

Singapore: Ng and Lim, (1989)

Sri Lanka : Deraniyagala (1929) Deraniyagala (1945) ; Munro (1955) .

Thailand : Fowler (1934) ; Geisler et al (1979) ; Hora (1923) ; Smith (1945).

Maintenance:

Due to its handy aquarium size, if kept with other fish of a similar size and nature, it can make a suitable community subject. A tank of a size of 90x30x30 cm can support a pair of these fish. Simple aquarium decor can be used and in most cases a filter is not a necessity if regular water changes are made.

Ng and Lim (1989) remark on its agility on land and ability to move along in hops, like a frog, emphasising the need to cover the tank well.

Because of its amazing ability to inhabit the most severe biotopes and even waters with a tidal influence, p.H. values are unimportant. Temperatures can be of average aquarium norms but Channa gachua 'Sri Lanka' has even been recorded from the hot springs of Kanniya, Sri Lanka.

C.gachua is highly carnivorous, with all sorts of crustacea, insects and fish fry taken, although in the aquarium, other living foods can be supplemented.

Breeding:

The spawning season is zonal and very much depends on the factors associated with its enviroment. Channa gachua does not build a compact nest at the surface of the water. It scoops out a small hole in the mud, not far from the edge of the pond, in shallow water.

Spawning normally starts in the morning and continues throughout the day. Between 1500- 2000 eggs are laid and then transfered into the hatchery. The eggs are golden yellow in colour and measure 1.5mm, after they have swollen. The oil globule constitutes a quarter of the egg, and this effectively faces the fry downward. Hatching is about 17 hours later and by the 19th day, with a size of 5mm, ( in nature, growth would be advanced to perhaps 10 mm) the yolk sac is spent. Food during the 35-105mm stage is small insect larvae, Daphnia and Cyclops (Mookerjee 1950).

C.gachua with ventral fins, taken by one of us (SBC) from the locality of Vijaweda, India, proved to orally incubate the eggs.After heavy feeding of white maggots in a tank with a peat base,the male was observed with an extended mouth with an aquamarine streak on his chin After ten days, 60 - 80 young fry, approximately 5 mm long were observed and a month later, attained a size of 10 mm. After a further 2 months, the pair spawned again, this time producing an enlarged brood of 100 - 120.