[Articoli scientifici] Parachanna obscura

[dalla piet]

Un doveroso ringraziamento a USGS "United States Geological Survey" per permetterci di postare queste preziose informazioni.

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



Reprinted with permission from Guy G. Teugels from: Bonou, C.A., and G.G. Teugels. 1985. Rvision systmatique du genre Parachanna Teugels et Daget 1984 (Pisces: Channidae). Rev. Hydrobiol. Trop. 18(4):267-280.

Original description: Ophiocephalus obscurus Gunther, 1861:476. Catalogue of the acanthopterygian fishes in the collection of the British Museum, 3:i-xxxv + 1-586. Type locality: West Africa. Syntypes: BMNH 1849.12.25.2-3.

Synonyms: Ophiocephalus (Parophiocephalus) obscurus Senna, 1924.
                   Channa obscura Myers and Shapovalov, 1932.
                   Parophiocephalus obscurus Berg, 1940.

Common names: African snakehead; snakehead; fakka (Arabic); ojul (Shilluk); abioth (Dinka); jul (Nuer); woroko (Zande; Bailey, 1994).


         Native range:White Nile, specifically the Jebel and Ghazal systems of Sudan (Bailey, 1994) and Gambela region of Ethiopia (Golubtsov and others, 1995); Lake Chad basin; Zaire (Congo), Cross, Niger, and Senegal River basins (Boulenger, 1907, 1916; Irvine, 1947; Teugels and Daget, 1984; Bonou and Teugels, 1985; Skelton, 1988; Teugels and others, 1992). Boeseman (1957) recorded the species from Stanley Pool, Lualaba (Congo) River. Said to be “widely distributed” in Ghana and noted as both useful as food and aquarium species (Dankwa and others, 1999).

         Introduced range: Not known to have been introduced.

         Size: To 35 cm (Bailey, 1994).

         Habitat preference: Bailey (1994) indicated a preference for marginal vegetation and floodplain habitat in the Sudan. Bonou and Teugels (1985) stated that this species occupies a wide variety of habitats including streams, rivers, lakes, lagoons and marshes. In flowing water, the species occupies calm areas. Lowe-McConnell (1988) indicated this species as “widely distributed” in marshy habitats and also found in bank vegetation of river channels. Teugels and others (1992) listed the species as common in stagnant side channels of the Cross River, Cameroon-Nigeria, and found among waterlogged fallen trees and leaf debris.

         Temperature range: No specific information, but the native range is in equatorial Africa indicating a strictly tropical species.

         Reproductive habits: Bonou and Teugels (1985) stated that little was known of the reproductive behavior of Parachanna obscura. Gosse (1963) stated that young are guarded by a large adult. Likely a nest builder like other channids. Under monoculture conditions in southern Nigeria, reproductive activity was greatest in October and November (Victor and Akpocha, 1992). Fecundity in this monoculture pond varied, with stages III, IV, and V ovaries containing 35-4,010 oocytes. Moreover, fecundity was found not to be correlated to length or weight, but this could result from “poor culture conditions” (Victor and Akpocha, 1992).

        Feeding habits: Bonou and Teugels (1985) cited the species as feeding on other fishes, noting that in Bnin it is used to control the young of tilapias in aquaculture ponds. Citing Blache and others (1964), they recorded the food of young as copepods and insect larvae. Adults appear to prey on other fishes (Copley, 1952; Poll, 1957; Gosse, 1963; Teugels and others, 1992). Adebisi (1981) noted that juveniles fed on prawns, copepods, and aquatic insect larvae whereas adults fed only on fishes in southern Nigeria.

         In monoculture in a Nigerian pond, young of this species (10-16 cm standard length) fed primarily on detritus and larval insects, whereas larger individuals (16-24 cm standard length) contained “fish parts” and juveniles, with insects and fish making up the bulk of the diet (Victor and Akpocha, 1992).

        Characters: Patch of scales present in the gular region. No canine teeth on prevomer or palatines. Transverse scales 19-24; lateral line scales 65-78. Dorsal fin rays 39-45; anal fin rays 26-32. Head depressed anteriorly, relatively long and covered with large scales. Lower jaw slightly longer than upper jaw, with 4-6 well-developed canines. Lateral line typically complete, rarely discontinous. Coloration distinct among African snakeheads in having a series of dark blotches, some of which may coalesce, and no chevronshaped bars across the middle of the back.

        Commercial importance in the United States: Sometimes listed on aquarist-oriented websites. Not known to have been available in live-food fish markets.

        Commercial importance in native range: Probably available in local live-food fish markets. This snakehead is being cultured in Ghana (Morrice, 1991), Nigeria (Ajana, 1983; Victor and Akpocha, 1992), and Bnin (Jackson, 1988), and was recommended for culture in the Central African Republic (Micha, 1974). All these localities are within the native range of this species.

        Environmental concerns: Known to be a predator, particularly of other fishes (Copley, 1952; Poll, 1957; Gosse, 1963; Teugels and others, 1992).