[Articoli Scientifici] Channa gachua

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US Geological Survey / foto di USGS
Tratto da: Snakeheads (Pisces, Channidae): A Biological Synopsis and Risk Assessment
 Di Walter R. Courtenay,James David Williams


Dopo Munro, 1955


Upper image: ZRC 41100, 107.7 mm standard length, from Perlis, Malaysia. Lower image: ZRC 41656, 46.5 mm standard length, from Kerala, India. Reprinted with permission from P.K.L. Ng from: Ng, H.H., P.K.L. Ng, and Ralf Britz. 1999. Channa harcourtbutleri (Annandale, 1918): a valid species of snakehead (Perciformes: Channidae) from Myanmar. J. South Asian Nat. Hist. 4(1):57-63.

Original description: Ophicephalus gachua Hamilton, 1822:68, 367. An account of the fishes found in the river Ganges and its branches. Edinburgh and London, i-xii + 1-405. Type locality: ponds and ditches of Bengal, India. Type specimens unknown.

Synonyms: Ophiocephalus aurantiacus Hamilton, 1822:69, 368, pl. 23, fig. 22.
                   Ophicephalus marginatus Cuvier, 1829:230, fide Roberts, 1993:38,
                           Menon, 1999, and Ng and others, 1999:57.
                   Ophicephalus limbatus Cuvier, 1831, no p., pl. 201, fide Roberts,
                           1993:40, Menon, 1999:275, and Ng and others, 1999:57.
                   Ophicephalus marginatus Cuvier, 1831, no p., pl. 201, fide Roberts,
                           1993:38, Menon, 1999:275, and Ng and others, 1999:57.
                   Ophicephalus coramota Cuvier, 1831:414, fide Menon, 1999:275
                           and Ng and others,1999:57.
                   Ophicephalus fuscus Cuvier, 1831:414, fide Menon, 1999:275
                           and Ng and others, 1999:57.
                   Ophicephalus montanus McClelland, 1842:583, fide Menon,
                           1999:275, and Ng and others, 1999:57.
                   Philypnoides surakartensis Bleeker, 1849:19, fide Menon,
                           1999:275, and Ng and others, 1999:57.
                   Ophiocephalus apus Canestrini, 1861:77, pl. 4, fig. 7.
                   Ophiocephalus kelaartii Gnther, 1861:472, fide Talwar and Jhingran,
                           1991;1019, Menon, 1999:275, and Ng and others, 1999:57.
                   Ophiocephalus guachua [sic] var. malaccensis Peters, 1868.
                   Ophicephalus gachna [sic] Jordan and Seale, 1907.
                   Ophiocephalus gachua kelaarti Gunther: Munro, 1955:100.

         Species is in need of revision; status of many synonyms uncertain (Ng and Lim, 1990; Ng and others, 1999). Roberts (1989), Lim and others (1990), Talwar and Jhingran (1992), and Rainboth (1996) treated this species as a synonym of Channa orientalis, but Ng and others (1999) disagreed with this conclusion. Day (1889), Coad (1981), Lim and others (1990), Kottelat (1998), Musikasinthorn (2000), and others considered C. gachua to be valid. For purposes of this report, we follow the most recent authorities in recognizing the species as valid, but also realizing that it doubtlessly represents a species complex.

Common names: dwarf snakehead; frog snakehead; brown snakehead; dolli or dauli (Pakistan); dheri dhok (Hindu); para korava (Tamil); doarrah (Punjab, India); chen-gah (Assam, India); cheng (West Bengal, India); dheridhok, chainga (Bijar Province, India); chenga (Orissa Province, India); malamatta-gudisa, erramatta, tatimattagudisa (Andrah Pradesh Province, India); koravu, vattudi (Kerala Province, India); mohkorava, mottu (Karnataka Province, India; Talwar and Jhingran, 1992), parandal kanaya (Sri Lanka; Pethiyagoda, 1991); bakak (Malay; Lim and Ng, 1990).


         Native range: Bampur-Haliri basin and Mashkel River, southeastern Iran (Coad, 1979); Kabol (Kabul) drainage of Afghanistan (Coad, 1981); eastern and western Pakistan (Qureshi, 1965); India, Sri Lanka, Bangladesh, Myanmar, Thailand, Laos, Cambodia, Malaysia, Indonesia (Borneo), Java, southern China (Mukerji, 1933; Mendis and Fernando, 1962; Fernando and Indrassna, 1969; Roberts, 1989; Pearl River Fisheries Research Institute, 1991; Pethiyagoda, 1991; Talwar and Jhingran, 1992; Kottelat, 1998, 2001a; Musikasinthorn, 2000). Kullander and others (1999), citing Das and Nath (1971), recorded this species from the Punch Valley, in a tributary of the Jhelum River, in the Kashmir Valley of northeastern Pakistan/western Kashmir. Peter Ng (personal commun., 2003) reported its occurrence in the Toba area of northern Sumatra, and Riau and Jambi in central Sumatra in 1996, as well as in Yunnan Province, China, in 2000.

        Introduced range: There may have been introductions that went unrecorded, but Kottelat's (1985) reference to Channa orientalis from the Greater Sunda Islands doubtlessly refers to some species of the C. gachua complex. Myers and Shapovalov (1932) cited a specimen of C. gachua from Formosa (=Taiwan) that lacked both pelvic fins. Because pelvic fins were absent, they tentatively identified the specimen as C. orientalis but noted other specimens of C. gachua from India that also lacked pelvics based on reports by earlier scientists. They suggested that this fish may have been introduced to Taiwan. This snakehead can be easily transported for great distances with significant altitude and temperature changes (Day, 1877). Peter Ng (personal commun., 2003) found this snakehead in Bali in 2000, perhaps within its native range or an introduction.

        Size: This species is often referred to by authors as the smallest snakehead, reaching a length of about 17 cm (Kottelat, 1998). Lee and Ng (1991) stated that it rarely exceeded 20 cm. The smallest snakehead, however, is Channa orientalis, a species that rarely exceeds 10 cm in length (Pethiyagoda, 1991).

         Habitat preference: Appears to prefer clear pools, shallow streams, and swamps, particularly in forested areas. Nevertheless, Pethiyagoda (1991) noted that it is common "in streams and ponds," but is tolerant of "very stagnant, poorly oxygenated, turbid water." Deraniyagala (1929) stated that it "flourishes in ponds rendered so stagnant as to prove toxic to most fishes." Said to be largely a nocturnal fish. Habitat destruction, due to deforestation near Singapore, is considered a threat to this species (http://www.sci-ctr.edu.sg/ssc/imglib/vertebra/channa.html). Kottelat (1998, 2001a,b) reported this species from hill streams in Laos, Thailand, Cambodia, and Vietnam. Lim and others (1990) recorded finding it in forest streams in peninsular Malaysia. This snakehead is reported to tolerate a wide range of pH levels with 100 percent survival over 72 hours from pH 3.10 to 9.6 (Varma, 1979).

         Lee and Ng (1994) reported the species "from rivers, lakes, ponds, well-shaded, small forest streams less than 20 cm deep, hillstreams not continuous to mountain ranges and in the upper zone of rivers." They indicated that it is found from sea level to an altitude of 1,520 m in India and up to 1,430 m in Malaysia, in waters with flow rates from stationary to rapids with a pH range of 3.1-9.6. Lee and Ng (1991) stated that the species is also found in mountain brooks up to 3,600 m above sea level. Mukerji (1931) reported capture of two specimens from the Billigirirangan Hills of southern India at an altitude of 751 m. The species has been reported surviving in brackish water, but this is doubted by Lee and Ng (1991). Srivastava and others (1980) noted decreasing body weight of this species in salinities as low as 5 ppm. They are capable of overland migrations (Lee and Ng, 1991), and Deraniyagala (1929) commented that it is "exceedingly active on land, pregressing by a series of leaps."

         Temperature range: Lee and Ng (1994) indicated that this species can tolerate temperatures in hot springs in Sri Lanka to as low as 13 oC. The species complex, however, is reported from as far north as Afghanistan (with cold winters) to Borneo and Java (equatorial tropical). Pethiyagoda (1991) cited Deraniyagala (1932) as having recorded this species from hot springs at 36.5 oC.

         Reproductive habits: This species has been cited as a mouthbrooder (Lee and Ng, 1991, 1994; Kottelat, 2001a) and confirmed by Ralf Britz (personal commun., 2003). An interesting factor here is that other authors (for example, Munro, 1955) made no mention of oral brooding of fertilized eggs and young for the dwarf snakehead. Based on Kahn (1924) and Deraniyagala (1929), Breder and Rosen (1966) stated that spawning in India occurs with the female swimming upside-down under the male, with eggs being released and fertilized in groups of 200-300 every minute or two. Females in Indonesia and Malaysia, however, are reported to produce from 20 to 200 eggs per spawning, with the male orally brooding developing eggs and fry (Lee and Ng, 1991, 1994), further evidence that Channa gachua is a species complex. This is one of three species of snakeheads known to spawn in ponds lacking vascular aquatic plants (Parameswaran and Murugesan, 1976b).

         Bhuiyan and Rahman (1982) measured fecundity from 30 female Channa gachua collected near Rajshahi, Bangladesh, which ranged from 487 (94 mm specimen) to 4,482 (164 mm specimen). Mean fecundity of the 30 specimens was 2,307 oocytes for a specimen having a mean length of 132 mm. The relationship between fecundity and length is largely linear, as is the relationship between fecundity and length of ovaries.

         Mishra (1991) described mature (stage V) oocytes as ranging from 2.1 to 2.6 mm in diameter with the highest percentage of stage V oocytes in July from specimens collected near Berhampur, Orissa, India. The highest gonadosomatic index was 6.8 and occurred in June. Estimated fecundity ranged from 2,539 to 7,194 in 15 mature specimens ranging from 13.4 to 17.2 cm in length. Again, the relationship between fecundity and length, as well as fecundity and body weight, was largely linear.

        Feeding habits: Lee and Ng (1994) summarized food preferences as including "mouse, rat, frog, tadpole, fish, Ephemerophtera and other insects, mosquito larvae, prawn (Macrobrachium sp.), crab (Irmengardia johnsoni), and other crustaceans." They cited the species as a nocturnal predator living at or near the substrate and quite capable of migrating overland.

         Characters: No patch of scales in the gular region. Pelvic fins present, although Talwar and Jhingran (1992) stated that pelvics may be present or absent. Lateral line scales 39-47; 31/2 scales between lateral line and base of anterior dorsal rays. Dorsal rays 32-37; anal rays 20-23. Lower jaw with 10-20 canines posterior to a single row of villiform teeth, the latter expanding to about 7 rows at the jaw symphysis. Dorsal, anal, and caudal fins with white (translucent in preserved specimens) margin; ocellated spot often present near posterior end of dorsal fin. The ocellated spot, however, may appear only in juveniles and females as occurs in Channa orientalis. Lim and others (1990) noted that while the fish is alive the dorsal, anal, and caudal fins are margined with red or yellow, and that the pectoral fins have semiconcentric rings and a dark area at the base.

         Commercial importance in the United States: This species is occasionally mentioned on aquarist- oriented websites and has been available for sale from certain aquarium fish dealers. Its small size makes it more appealing as an aquarium species. Too small to be sold in live-food fish markets.

         Commercial importance in native range: Talwar and Jhingran (1992) cited the species as of minor importance in India. According to comments on aquarist-oriented websites and in Ng and Lim (1990), members of this species complex appear to be of importance in the aquarium fish trade with individuals captured from the wild for sale or export. Ng and Lim (1990) cited individuals being sold for S$30-60 in Singapore, although Lim and Ng (1990) listed the species as endangered there. Pethiyagoda (1991) noted that it is largely unused as food or in the aquarium trade in Sri Lanka. Deraniyagala (1929) commented that this snakehead is utilized as food by "only the poorest classes" in Sri Lanka, adding that it is used as live bait to catch larger species, such as Channa striata and C. marulius.

         Environmental concerns: Like other channids, this species is a thrust predator, capable of breathing atmospheric oxygen. This species is noted by many authors as migrating overland.

         Comments: The diploid number of chromosomes for Channa gachua is 78 from India (Banerjee and others, 1988) and 112 for specimens from Thailand (Donsakul and Magtoon, 1991), a strong indication that this represents a species complex.