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Clarias batrachusClarias catfish

By Sarah Rainey

Geographic Range

The walking catfish (Clarias batrachus) is native to southeast Asia. Its native range includes Bangladesh, India, Indonesia, Malaysia, Myanmar, Pakistan, Singapore, Sri Lanka, Laos, and Thailand. However, the walking catfish has a large global distribution due to introductions. Its current range includes the United States, where it was first introduced to Florida from Thailand for cultivation purposes. Since its introduction in the early 1960s, the species has spread from Florida to Georgia, Alabama, South Carolina, and North Carolina. Clarias batrachus has also been found in the New England states of New Jersey, Pennsylvania, New York, Massachusetts, Rhode Island, Vermont, Connecticut, and New Hampshire, but it is not frequent in these areas. On the west coast, the walking catfish has been recorded along the coast of California, ranging eastward to Nevada. (Allen, 2013; Courtenay and Miley, 1975; Froese and Luna, 2015)

Habitat

The walking catfish is found in the muddy substrates of several water systems. This species can be found in freshwater, brackish water, and terrestrial environments. It is common in lowland bodies of water such as irrigation channels, lakes, rice fields, and wetlands. It has been recorded at a depth of one meter but the species’ maximum depth is unknown. Clarias batrachus burrows into the mud during cold and dry months to survive poor weather conditions. It predominately inhabits tropical waters at a temperature of 18 degrees Celsius or above, but tolerates terrestrial habitats with temperatures between 0-18 degrees Celsius. While this species is found in a multitude of water conditions, it is abundant in swampy waters. Clarias batrachus can survive outside of the water and travel on land as long as its gills stay moist. It is most common to see C. batrachus outside of the water after heavy rains. (Allen, 2013; Froese and Luna, 2015)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • temporary pools
  • brackish water
  • Range depth
    1 (low) m
    3.28 (low) ft

Physical Description

Clarias batrachus has an elongated body with a narrow head and irregular bumps on its spine. The walking catfish is characterized by having 54–60 vertebrae, 63–74 dorsal-fin rays, and 47–58 anal-fin rays. It also has a long and thin cavity between the frontal and parietal, or side bones, in the skull. In the wild, the walking catfish is brown with a white underside; however other colorations, such as albino, mottled, and piebald can be found in cultivated individuals. The female walking catfish lays bright orange eggs. Clarias batrachus fingerlings lack pigment and appear translucent. As they develop, they become brown or a dark green-black. The walking catfish can grow to be 8 to 47cm long and weigh up to 1.2kg. Males and females are similar in size and shape, but there are some defining characteristics. A female C. batrachus has a broader belly than a male that is especially prominent during mating season. A male can also be distinguished by the presence of dorsal fin spots. Species of Clarias have been known to have venomous spines located in front of their dorsal fins that can sting predators. (Allen, 2013; Das, 2002; Froese and Luna, 2015; Ng and Kottelat, 2008; Page and Burr, 1998)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    1.2 (high) kg
    2.64 (high) lb
  • Range length
    8 to 47 cm
    3.15 to 18.50 in
  • Average length
    26 cm
    10.24 in

Development

The walking catfish eggs are adhesive in nature and are sensitive to environmental disturbances. Fertilized eggs have very poor survival rates due to this sensitivity and in result, do not yield many fry. Thakur reports that the walking catfish had an average fertilization rate of 68.5 percent, an average hatching percent of 36.5, and an average survival rate of 10.5 percent (1976). The incubation period generally lasts 18-24 hours. Embryos begin to display twitching inside the egg after 12-18 hours and usually hatch in 20-24 hours. Typically, larvae weigh approximately 0.00186g upon hatching. Sex is differentiated physically: male walking catfish have a pointed genital region, while female walking catfish have a thick and rounded genital region. Larval development is very rapid and the larvae are able to swim strongly within 3 days. After 20-30 days following hatching, the walking catfish larvae become fingerlings. The catfish fingerling is an intermediate stage between a larva and an adult. An adult walking catfish has indeterminate growth and males and females are roughly the same size. (Argungu, et al., 2013; Chinabut, et al., 1991; Mookerjee and Mazumdar, 1950; Thakur, 1976; Verreth, et al., 1993)

Reproduction

The walking catfish mate seasonally in the summer during the months between June and August. Heavy rains have a signaling effect on the catfish and are usually a prerequisite for mating. However, it has been found that the walking catfish, unlike other members of the Clariidae family have the ability to breed in stagnant water. A male and female walking catfish will start swimming together a couple days prior to mating. The pair will look for a cave or terrestrial substrate to lay their eggs. Once a place is found, the male and female will both take part in digging a hole in that area. The female walking catfish will initiate mating by nudging the male's genital area with her snout until he engages. Once the male is engaged, the female, despite having initiated the mating, has to be courted into breeding. The male will make body contact with the female and repeat the same nudging behavior. The male walking catfish will make several circling movements around the female. The male will continue to circle the female pulling her closer and closer until he loops his body around hers in a spawning embrace. The walking catfish spawns in cycles and the first rounds of spawning produce none or few eggs, usually less than five. Later spawnings, with the same mate, produce more eggs and the mating ritual becomes minimal or is absent entirely. Each spawning lasts for around ten seconds. The female will then separate herself from the loop and swim away, only to return shortly thereafter to begin another spawning cycle. The entire spawning process can take up to 20 hours. On average, an adult female lays around 7,000-9,000 eggs. The walking catfish is monogamous during the mating season and has multiple spawning cycles with the same mate. (Areerat, 1987; Cheah, et al., 1990; Das, 2002; Froese and Luna, 2015; Thakur, 1976)

Walking catfish are sexually mature at age one. The breeding season for walking catfish is between the months of June-August. These catfish breed with a single mate during the season via multiple spawning cycles in which increasingly more eggs are produced. The eggs are internally fertilized during the spawning embrace and an adult female will produce an average of 7,000-9,000 eggs a season. The walking catfish fry become independent after three days. (Argungu, et al., 2013; Cheah, et al., 1990; Das, 2002; Thakur, 1976)

  • Breeding interval
    Walking catfish breed via multiple spawning cycles during the summer.
  • Breeding season
    June-August
  • Range number of offspring
    7,000 to 9,000
  • Average number of offspring
    8,000
  • Range time to hatching
    20 to 24 hours
  • Average time to independence
    72 hours
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

The male guards the nest from predators, such as the clown loach (Chromobotia macracanthus) and yoyo loach (Botia lohachata), immediately following spawning. The female will return once the eggs have hatched and the male and female take part in protecting the fry until they are independent. The parental investment only extends to 24 hours following the hatching. By the third day, the fry are capable of swimming strongly and they are no longer guarded by the parents. (Areerat, 1987; Cheah, et al., 1990; Das, 2002; Hossain, et al., 2006; Thakur, 1976)

Lifespan/Longevity

The lifespan of the walking catfish has not been reported. However, a close relative of the walking catfish, the African catfish (Clarias camerunensis) has an expected lifespan of 16.2 years in captivity. It is likely that the walking catfish has a similar longevity. (Carey and Judge, 2000)

Behavior

Clarias batrachus is a solitary fish, but it can cohabitate with other species. The walking catfish is mostly sessile and lies stationary in muddy substrates. It is most notably characterized by its increased activity and movement across land after heavy rains. Clarias batrachus is not a territorial species, unless an intruder makes an attempt to raid its nest during the mating season. Nests are usually made in caves and the male walking catfish will guard the entrance. A male walking catfish uses quick movements to scare other fish away from its nest and will only attack other fish species as a last line of defense to protect its eggs and fry. The walking catfish has an aggressive reputation based on its consumption of a wide variety of smaller fish and its presence in non-native waters as an invasive species. During the breeding season, which correlates with the rainy season (June-August), the walking catfish participates in mass migration to newly-flooded low-lands. (Mookerjee and Mazumdar, 1950; Ng and Kottelat, 2008)

Home Range

The home range of an individual of this species is unknown.

Communication and Perception

Fish have a lateral line that they use to sense vibrations in the water and perceive their surroundings. Additionally, several species of catfish within the Clariidae family communicate using sounds produced by their pectoral spine. However, it is unknown whether the walking catfish communicates this way. (Bleckmann and Zelick, 2009)

Food Habits

The walking catfish is omnivorous. As larvae, C. batrachus feeds entirely on plankton. In the later developmental stage of a fry, it begins to prey on larger organisms. When it progresses into a juvenile, it predominantly eats insects. As an adult, a walking catfish preys on plants (benthic algae), insects (eggs, pupae or nymphs [e.g., dragonfly nymphs, chironomid larvae]), aquatic worms, molluscs, and smaller fish (finfish). The walking catfish is also a dentritivore and eats organic waste. Clarias batrachus has a broad diet and is known to be an opportunistic feeder. (Froese and Luna, 2015; Verreth, et al., 1993)

  • Animal Foods
  • fish
  • insects
  • mollusks
  • aquatic or marine worms
  • other marine invertebrates
  • zooplankton

Predation

Species of otters are major predators of the walking catfish. Other predators include large reptiles (crocodiles), birds - namely fish eagles (Haliaeetus)- and mammals, including humans (Homo sapiens). Clarias batrachus has several anti-predator adaptations. The most prevalent coloration is brown with white on its ventral side. This color pattern enables the walking catfish to blend in with its muddy habitat and hide from predators. The sheer size of the walking catfish provides some protection against predation. Additionally, Clarias species have a venomous sting and sharp dagger-like structures located in front of their dorsal fins. (Page and Burr, 1998)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

The walking catfish is host to a variety of helminth parasites that include tapeworms (Cestoda, Lytocestus indicus),and trematodes, (Opegaster, Orientocreadium, Euclinostomum, and Caryophyllaeus indicus). Opegaster is the most prevalent trematode parasite in the walking catfish and it predominately inhabits the gut and gall bladder. Cauyan et al. (2013) found that the gut and gall bladder of a walking catfish was infected with a mean intensity of 20 individuals in Opegaster. Clarias batrachus also had a mean intensity of approximately 8 individuals Opegaster in the spleen and liver. The mean intensity was calculated by dividing the number of parasites by the number of infected fish. The walking catfish has a predatory role in the marine food web and preys on the organisms listed in the food habits section. It also provides nutrients to the marine ecosystem through the excretion of nutrients. (Ash, et al., 2011; Cauyan, et al., 2013; Moghe, 1925)

Commensal/Parasitic Species
  • Cestoda (Lytocestus indicus), Trematodes (Opegaster , Orientocreadium , Euclinostomum , Caryophyllaeus indicus)

Economic Importance for Humans: Positive

Clarias batrachus is used in commercial fisheries, aquaculture, and aquariums. The walking catfish is widely consumed in its native range (Asia) but not in its introduced range. Further, Ohio and other U.S. states have limited or prohibited the possession of the walking catfish to prevent its expansion. ("Wild animal importing, exporting, selling, and possession regulations", 2001; Froese and Luna, 2015; Ng and Kottelat, 2008)

Economic Importance for Humans: Negative

The walking catfish poses a threat as an invasive species. Clarias batrachus, once introduced, is hard to contain and control due to its mass spawning that produces several thousands of eggs, its voracious diet, and ability to survive in muddy and low-oxygenated conditions. Its opportunistic feeding habits may threaten some sport fish in Florida. Costly containment methods, such as the use of barrier fences, have been utilized to prevent walking catfish from invading fish stocks. ("Wild animal importing, exporting, selling, and possession regulations", 2001)

Conservation Status

The walking catfish is listed as a species of "Least Concern" on the IUCN Red List, and has no special status on the US Federal List or by CITES.

Argungu et al. notes that the walking catfish is threatened and is becoming critically endangered in its native range in Asia (2013). Periods of drought and human disruption of the walking catfish's natural habitat has contributed to its decline in Malaysia and India. The introduction of the larger African catfish (Clarias gariepinus) has out competed the walking catfish and reduced the population of C. batrachus. Currently, induced spawning and artificial breeding have been used as means of conservation for the walking catfish in their native range.

There are some forms of anti-conservation in place in the United States to prevent the spread of the species. Ohio has prohibited the possession of the walking catfish and Maryland, Idaho, Rhode Island have placed restrictions on the import, sale, and possession of the walking catfish. Eradication via poison is not an option because no known toxicants are species-specific. More effort has been placed on containment but this has been a difficult task because the walking catfish can move on land. ("Wild animal importing, exporting, selling, and possession regulations", 2001; Argungu, et al., 2013; Froese and Luna, 2015; Hossain, et al., 2006)

Contributors

Sarah Rainey (author), Radford University, Cari Mcgregor (editor), Radford University, Zeb Pike (editor), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Jacob Vaught (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

detritivore

an animal that mainly eats decomposed plants and/or animals

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

herbivore

An animal that eats mainly plants or parts of plants.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

migratory

makes seasonal movements between breeding and wintering grounds

molluscivore

eats mollusks, members of Phylum Mollusca

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

phytoplankton

photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)

piscivore

an animal that mainly eats fish

planktivore

an animal that mainly eats plankton

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

venomous

an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

Ohio Administrative Code. Wild animal importing, exporting, selling, and possession regulations. 1501:31. Ohio: Ohio Administrative Code. 2001.

Allen, D. 2013. "Clarias batrachus" (On-line). The IUCN Red List of Threatened Species 2013: e.T166613A6247551.. Accessed January 27, 2016 at http://dx.doi.org/10.2305/IUCN.UK.2011-1.RLTS.T166613A6247551.en.

Areerat, S. 1987. Clarias culture in Thailand. Aquaculture, 63/1: 355-362.

Argungu, L., A. Christianus, S. Amin, S. Daud, S. Siraj, M. Aminur Rahman. 2013. Asian catfish Clarias batrachus (Linnaeus, 1758) getting critically endangered. Asian Journal of Animal and Veterinary Advances, 8/2: 168-176. Accessed January 27, 2016 at http://scialert.net/qredirect.php?doi=ajava.2013.168.176&linkid=pdf.

Ash, A., T. Scholz, M. Oros, P. Kumar Kar. 2011. Tapeworms (Cestoda: Caryophyllidea), parasites of Clarias batrachus (Pisces: Siluriformes) in the Indomalayan region. Journal of Parasitology, 97/3: 435-459.

Bleckmann, H., R. Zelick. 2009. Lateral line system of fish. Institute of Zoology, 4/1: 13-25.

Carey, J., D. Judge. 2000. Longevity Records: Life Spans of Mammals, Birds, Amphibians, Reptiles, and Fish. Denmark: Odense University Press.

Cauyan, G., J. Briones, E. De Leon, J. Gonong, E. Pasumbal. 2013. Initial assessment of parasite load in Clarias batrachus, Glossogobius giuris and Oreochromis niloticus in Lake Taal (Philippines). Philippine Science Letters, 6/1: 21-28.

Chandra, K., K. Islam, R. Wootten. 1997. Some aspects of association and development of Lytocestus indicus Moghe in catfish Clarias batrachus (Lin.). Bangladesh Journal of Fisheries Research, 1:2: 31-38.

Cheah, S., S. Siraj, K. Ang. 1990. A preliminary study on induced spawning of the catfish Clarias batrachus (Linnaeus) in Malaysia. Pertanika, 13/1: 63-66.

Chinabut, S., P. Kitsawat, C. Limsuwan. 1991. Histology of the Walking Catfish, Clarias batrachus. Canada: International Development Research Centre.

Courtenay, W., W. Miley. 1975. Range expansion and environmental impress of the introduced walking catfish in the United States. Environmental Conservation, 2/2: 145-148.

Das, S. 2002. Seed production of magur (Clarias batrachus) using a rural model portable hatchery in Assam, India - A farmer proven technology. Aquaculture Asia Magazine, 7/2: 19-21.

Froese, R., S. Luna. 2015. "Clarias batrachus" (On-line). Accessed January 26, 2016 at http://www.fishbase.org/Summary/Clarias-batrachus.

Herath, H. 1988. Hybridization, Early Development of Embryos and Production Characteristics of Larvae of African Catfish Clarias gariepinus (Burchell) and Asian Catfish Clarias batrachus (Linnaeus) (Master's Thesis). Wageningen, Netherlands: Wageningen Agricultural University.

Hossain, Q., M. Hossain, S. Parween. 2006. Artificial breeding and nursery practices of Clarias batrachus (Linnaeus, 1758). Science World, 4/1: 32-37.

Islam, M., S. Islam, S. Alam. 2007. Genetic structure of different populations of walking catfish (Clarias batrachus L.) in Bangladesh. Biochemical Genetics, 45/9: 647-662.

Moghe, M. 1925. Caryophyllaeus incidicus n.sp. (Trematoda) from the Cat-fish (Clarias batrachus BI). Parasitology, 17/02: 232-235.

Mookerjee, H., S. Mazumdar. 1950. Some aspects of the life history of Clarias batrachus (Linn). Proceedings of Zoological Society of Bengal, 3/1: 71-79.

Mukhopadhyay, P. 1976. Studies on the enzymatic activities related to varied pattern of diets in the air-breathing catfish, Clarias batrachus (Linn.). Hydrobiologia, 52/2-3: 235-237.

Ng, H., M. Kottelat. 2008. The identity of Clarias batrachus (Linnaeus, 1758), with the designation of a neotype (Telestei: Clariidae). Zoological Journal of the Linnean Society, 153/1: 725-732.

Page, L., B. Burr. 1998. A Field Guide to Freshwater Fishes of North America North of Mexico. Boston: Houghton Mifflin Harcourt.

Singh, B., G. Hughes. 1971. Respiration of an air-breathing catfish Clarias batrachus (Linn.). Journal of Experimental Biology, 55/1: 421-434.

Thakur, N. 1976. On the spawning behavior of Clarias batrachus (Linn). Japanese Journal of Ichthyology, 23/1: 178-180.

Verreth, J., E. Eding, G. Rao, F. Huskens, H. Segner. 1993. A review of feeding practices, growth and nutritional physiology in larvae of the catfishes Clarias gariepinus and Clarias batrachus. Journal of the World Aquaculture Society, 24/2: 135-144.

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