Taxonomic name: Clarias batrachus (Linnaeus 1758)
Synonyms: Clarias assamensis Day, 1877, Clarias jagur (Hamilton, 1822), Clarias magur (Hamilton, 1822), Clarias punctatus Valenciennes, 1840, Macropteronotus jagur Hamilton, 1822, Macropteronotus magur Hamilton, 1822, Silurus batrachus Linnaeus, 1758
Common names: alimudan (Visayan-Philippines), cá trê tráng (Vietnamese), cá trèn trang (Vietnamese), clarias catfish (English-USA), climbing perch (English-Bangladesh), freshwater catfish (English-Malaysia), Froschwels (German), hito (Philippines), htong batukan (Tagalog-Philippines), ikan keling (Malay-Indonesia), ikan lele (Malay), Ito (Kapampangan-Philippines), kawatsi (Kuyunon-Philippines), keli (Malay), klarievyi som (Russian), koi (Bengali-Banglade), konnamonni (Finnish), kug-ga (Punjabi-India), leleh, magur, mah-gur (Bengali-India), mangri (Hindi-India), marpoo (Telugu-India), masarai (Tamil-India), mungri (Nepali), nga-khoo (Burmese), pa douk (Lao), paltat (Ilocano-Philippines), pantat, pla duk (Thai), pla duk dam (Thai), pla duk dan (Thai), pla duk nam jued (Thai), pla duk nam juend (Thai), Thai hito (English-Philippines), Thailand catfish (English-Taiwan, province of China), trey andaing roueng (Khmer), trey andeng (Khmer), walking catfish (English), wanderwels (German), Yerivahlay (Malayalam-India)
Organism type: fish Clarias batrachus a voracious predator native to southeastern Asia has been introduced into many places for fish farming. Walking catfish, as it is commonly known (named for their ability to move over land), is an opportunistic feeder and can go for months without food. During a drought large numbers of walking catfish may congregate in isolated pools and consume other species. They are known to have invaded aquaculture farms, entering ponds where they prey on fish stocks. C. batrachus has been described as a benthic, nocturnal, tactile omnivore that consumes detritus and opportunistically forages on large aquatic insects, tadpoles, and fish. Description
"Walking catfish are typically a uniform shade of gray or gray-brown with many minute white spots laterally. The head is flat and broad and the body tapers to the tail in a manner that calls to mind the shape of a slender tadpole. The mouth is broad, although the gape is not great. The lips are fleshy, the upper more so than the lower. The walking catfish possesses very small eyes, a lengthy dorsal and anal fin that each terminate in a lobe near but free from the caudal fin, and pectoral fins with rigid spine-like elements, one each at the fore. It is through the use of these stiff pectoral "spines" accompanied by a back and forth flexion of the body that walking catfish accomplish their ungainly but effective terrestrial locomotion. The walking catfish may be easily distinguished from many of the North American Ictalurid catfishes in that the walking catfish lacks an adipose fin" (Robins, Undated). Genital papilla in males is elongated and pointed, with the female however thick set, short and blunt (Wolfgang, pers. comm., 2004). Occurs in:
estuarine habitats, lakes, water courses, wetlands Habitat description
This species occurs in fresh, brackish as well as marshy, muddy waters over its native range (Sen, 1985). Courtenay et al. (1970), reported walking catfish to occur in intercoastal waterways of up to 18 ppt (Gulf States Marine Fisheries Commission, 2006). Inhabits swamps, ponds, ditches, rice paddies, and pools left in low spots after rivers have been in flood. Usually confined to stagnant, muddy water. Found in medium to large-sized rivers, flooded fields and stagnant water bodies including sluggish flowing canals (FishBase, 2003). General impacts
In Florida, walking catfish are known to have invaded aquaculture farms, entering ponds where these predators prey on fish stocks. In response, fish farmers have had to erect protective fences to protect ponds (Nico, 2005). C. batrachus are known to also prey on native tadpoles (though other predatory fish are more voracious); particularly susceptible are those tadpoles that breed exclusively in temporary wetland habitats that would otherwise serve as refugia from predatory fish (Baber and Babbitt, 2003). Uses
Fisheries: commercial, aquaculture: commercial, aquarium: commercial (FishBase, 2003). An important food fish that is marketed live, fresh and frozen. (FishBase, 2003) Notes
In South East Asia C. batrachus is known to undertakes lateral migrations from the Mekong mainstream, or other permanent water bodies, to flooded areas during the flood season and return to the permanent water bodies at the onset of the dry season. The walking catfish can live out of water for quite sometime and move short distances over land. It can walk and leave water to migrate to other water bodies using its auxiliary breathing organs (FishBase, 2003). Taylor et al. (1984), in Nico, (2005) observe that guarding of free-swimming young in walking catfish may enhance survivorship over that of native species with less advanced (or no) parental care. Geographical range
Native range: Southeastern Asia including eastern India, Sri Lanka, Bangladesh, Burma, Indonesia, Singapore, and Borneo (FishBase, 2003).
Known introduced range: Indonesia (Sulawesi), USA, Hong Kong, Taiwan, China, UK, Papua New Guinea, Guam, Taiwan, Thailand (FishBase, 2003). Probably introduced into the Philippines (Nico, 2005) Introduction pathways to new locations
Aquaculture: Introduced into Hong Kong from Thailand for aquaculture, (FishBase, 2003).
For ornamental purposes: Introduced into the USA from Thailand and from Java, Indonesia for ornamental purposes, (FishBase, 2003).
Pet/aquarium trade: The walking catfish was imported to Florida, reportedly from Thailand, in the early 1960s for the aquarium trade (Courtenay et al. 1986).
Local dispersal methods
Aquaculture (local): Aquarium releases likely are responsible for introductions in other states of America. (Nico, 2005)
Escape from confinement: In Florida adult fish imported as brood stock escaped from confinement, either from a fish farm in northeastern Broward County or from a truck transporting brood fish between Dade and Broward counties. (Nico, 2005)
Other (local): Dill and Cordone (1997) reported that this species has been sold by tropical fish dealers in California for some time. (Nico, 2005)
Water currents: In America dispersal apparently has occurred by way of the interconnected network of canals along the southeastern coastal region. (Nico, 2005) Reproduction
The following is an observation of the reproduction process of a pair of 38cm walking catfish in a 700 litre aquarium. The breeding pair dig a hollow, which has a diameter of approximately 30cms -about 38cms. On the day of reproduction courting reaches a turbulent level. The animals mate over many hours; thirty, maybe forty times, initially without any eggs delivered. Reproduction dragged on over 20 hours. During mating, the female pushes her head against the center of the male’s body, actually pressing her partner into a u-shape. Throughout this time the pair do not tolerate any other fish in proximity to the nest. Eggs soon after delivary drop to the substrate and remain stuck there. Several hundred to a thousand eggs are laid and one can expect even higher numbers from fully-grown pairs. After the female has laid all her eggs, she seems to avoid the nest, but secures the outer perimeter of the nest and, subsequent to the final spawning activity, the male takes sole responsibility of directly guarding the nest. At 25° C the embryos hatch after approximately 30 hours. During this phase, defence of the nest once more becomes heightened in both partners, with division of responsibilities as before. After a further two days both partners’ defensive vigour weakens, a further three days, the fry, now with barbles visible to the naked eye, swim freely. The walking catfish pair spawned four times within the period of only five months! More details are available in this webpage (Ros, 2004c). Lifecycle stages
In southeast Asia, spawning period is during the rainy season, when rivers rise and fish are able to excavate nests in submerged mud banks and dikes of flooded rice fields (FishBase, 2003). This species has been nominated as among 100 of the "World's Worst" invaders Reviewed by: Major update under progress
Dr. Matthew Baber. Postdoctoral Research Associate, Department of Natural Resources, University of New Hampshire, Durham. USA Principal sources: Nico, L., 2005. Clarias batrachus Nonindigenous Aquatic Species Database, Gainesville, FL.
FishBase, 2003. Species profile Clarias batrachus Walking catfish
Compiled by: IUCN/SSC Invasive Species Specialist Group (ISSG)
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Last Modified: Sunday, 26 June 2005
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