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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: Walking Catfish

Synonyms and Other Names: magur, pla duk dam

Taxonomy: available through www.itis.gov

Identification: Page and Burr (1991). Keys and distinguishing characteristics were given by Smith (1945), Talwar and Jhingran (1992), and Kottelat et al. (1993). The identity of the fish introduced into the USA is in doubt following an analysis by Ng and Kottelat (2008), which restricted the name, C. batrachus, to fish from Java. A photograph appeared in Kottelat et al. (1993).

Size: 61 cm in native range; rarely

Native Range: Southeastern Asia including eastern India, Sri Lanka, Bangladesh, Burma, Indonesia, Singapore, and Borneo (Lee et al. 1980 et seq.; Talwar and Jhingran 1992; Kottelat et al. 1993). Laos (Baird et al. 1999). Probably introduced into the Philippines.

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Means of Introduction: The walking catfish was imported to Florida, reportedly from Thailand, in the early 1960s for the aquarium trade (Courtenay et al. 1986). The first introductions apparently occurred in the mid-1960s when adult fish imported as brood stock escaped, either from a fish farm in northeastern Broward County or from a truck transporting brood fish between Dade and Broward counties (Courtenay and Miley 1975; Courtenay 1979a; Courtenay and Hensley 1979a; Courtenay et al. 1986). Additional introductions in Florida, supposedly purposeful releases, were made by fish farmers in the Tampa Bay area, Hillsborough County in late 1967 or early 1968, after the state banned the importation and possession of walking catfish (Courtenay and Stauffer 1990). Aquarium releases likely are responsible for introductions in other states (Courtenay and Hensley 1979a; Courtenay and Stauffer 1990; Hartel 1992). Dill and Cordone (1997) reported that this species has been sold by tropical fish dealers in California for some time.

Status: Established in Florida; failed in California, Connecticut, Georgia, Massachusetts, and Nevada.

Impact of Introduction:

Summary of species impacts derived from literature review. Click on an icon to find out more...

Ecological	Economic	Human Health

Largely unknown. 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 (Courtenay and Stauffer 1990). Loftus (1988) reported heavy predation on native fishes in remnant pools during seasonal drying of wetlands. Baber and Babbitt (2003) examined predation impacts on tadpole assemblages in temporary wetlands in south-central Florida, and found that native fishes (e.g., eastern mosquitofish Gambusia holbrooki, golden topminnow Fundulus chrysotus, flagfish Jordanella floridae) had larger impacts and higher predation rates on tadpoles than C. batrachus.

Remarks: In 1968, this species was confined to three south Florida counties; by 1978, it had spread to 20 counties in the southern half of the peninsula (Courtenay 1979a; Courtenay et al. 1986). Dispersal apparently has occurred by way of the interconnected network of canals along the southeastern coastal region; however, spread was accelerated by overland migration, typically during rainy nights (Loftus and Kushlan 1987). Its ability to use atmospheric oxygen assists in survival in low-oxygen habitats (Loftus 1979). The walking catfish has been established in Everglades National Park and in Big Cypress National Preserve since the mid-1970s (Courtenay 1989). Populations suffer periodic die-offs from cold temperatures and subsequent bacterial infection (Loftus and Kushlan 1987); consequently, northward dispersal is limited (Courtenay 1978, Courtenay and Stauffer 1990). Although all Florida imports were originally albinos, albinos in the wild are now rare and descendants have reverted to the dominant, dark-color phase (dark brown to gray) probably a result of natural selection by predators (Courtenay et al. 1974; Courtenay and Stauffer 1990). Guarding of free-swimming young may enhance survivorship over that of native species with less advanced (or no) parental care (Taylor et al. 1984).

Voucher specimens: Florida (USNM 203889, 317282, 317283, UF 16424, 93561, TU 71116, 12099), Massachusetts (MCZ 69534). Minckley (1973) indicated that the specimen taken from the All American Canal, California, was deposited at Arizona State University.

References: (click for full references)

Anonymous. 1983a. Spiny 'walking catfish' moving upstate, spotted in Vero Beach. Sun-Sentinel, 19 October 1983.

Baber, M.J., and K.J. Babbitt. 2003. The relative impacts of native and introduced predatory fish on a temporary wetland tadpole assemblage. Oecologia 136:289-295.

Baird, I.G., V. Inthaphaisy, P. Kisouvannalath, B. Phylavanh, and B. Mounsouphom. 1999. The fishes of southern Lao. Lao Community Fisheries and Dolphin Protection Project. Ministry of Agricultrue and Forestry, Lao PDR.

Cardoza, J.E., G.S. Jones, T.W. French, and D.B. Halliwell. 1993. Exotic and translocated vertebrates of Massachusetts, 2nd edition. Fauna of Massachusetts Series 6. Massachusetts Division of Fisheries and Wildlife, Publication 17223-110-200-11/93-C.R, Westborough, MA.

Charlotte Harbor National Estuary Program. 2004. Minutes of the Technical Advisory Committe, Habitat Conservation Subcommittee. February 19, 2004, Punta Gorda, FL. http://www.chnep.org/NEP/minutes-2004/HCS2-19-04minutes.pdf

Courtenay, W.R., Jr. 1970. Florida's walking catfish. Ward's Natural Science Bulletin 10(69):1, 4, 6.

Courtenay, W.R., Jr. 1978. Additional range expansion in Florida of the introduced walking catfish. Environmental Conservation 5(4):273-275.

Courtenay, W.R., Jr. 1979a. Continued range expansion of the walking catfish. Environmental Conservation 6(1):20.

Courtenay, W.R., Jr. 1989. Exotic fishes in the National Park System. 237-252 in L.K. Thomas, editor. Proceedings of the 1986 conference on science in the national parks, volume 5. Management of exotic species in natural communities. U.S. National Park Service and George Wright Society, Washington, DC.

Courtenay, W.R., Jr., and J.E. Deacon. 1983. Fish introductions in the American southwest: a case history of Rogers Spring, Nevada. Southwestern Naturalist 28:221-224.

Courtenay, W.R., Jr., and D.A. Hensley. 1979a. Survey of introduced non-native fishes. Phase I Report. Introduced exotic fishes in North America: status 1979. Report submitted to National Fishery Research Laboratory, U.S. Fish and Wildlife Service, Gainesville, FL.

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

Courtenay, W.R., Jr., and J.R. Stauffer, Jr. 1990. The introduced fish problem and the aquarium fish industry. Journal of the World Aquaculture Society 21(3):145-159.

Courtenay, W.R., Jr., D.A. Hensley, J.N. Taylor, and J.A. McCann. 1984. Distribution of exotic fishes in the continental United States. 41-77 in W.R. Courtenay, Jr., and J.R. Stauffer, Jr., eds. Distribution, biology and management of exotic fishes. Johns Hopkins University Press, Baltimore, MD.

Courtenay, W.R., Jr., D.A. Hensley, J.N. Taylor, and J.A. McCann. 1986. Distribution of exotic fishes in North America. 675-698 in C.H. Hocutt, and E.O. Wiley, editors. The zoogeography of North American freshwater fishes. John Wiley and Sons, New York, NY.

Courtenay, W.R., Jr., D.P. Jennings, and J.D. Williams. 1991. Appendix 2: exotic fishes. 97-107 in Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lachner, R.N. Lea, and W.B. Scott. Common and scientific names of fishes from the United States and Canada, 5th edition. American Fisheries Society Special Publication 20. American Fisheries Society, Bethesda, MD.

Deacon, J.E., and J.E. Williams. 1984. Annotated list of the fishes of Nevada. Proceedings of the Biological Society of Washington 97(1):103-118.

Dill, W.A., and A.J. Cordone. 1997. History and status of introduced fishes in California, 1871-1996. California Department of Fish and Game Fish Bulletin, volume 178.

Gennings, R.M. - Georgia Department of Natural Resources, Atlanta, GA. Response to NBS-G nonindigenous questionaire.

Hartel, K.E. 1992. Non-native fishes known from Massachusetts freshwaters. Occasional Reports of the Museum of Comparative Zoology, Harvard University, Fish Department, Cambridge, MA. 2. September. pp. 1-9.

Hartel, K.E., D.B. Halliwell, and A.E. Launer. 2002. Inland fishes of Massachusetts. Massachusetts Audubon Society, Lincoln, MA.

Kottelat, M., A.J. Whitten, S.N. Kartikasari, and S. Wirjoatmodjo. 1993. Freshwater fishes of Western Indonesia and Sulawesi. Periplus Editions, Ltd., Republic of Indonesia.

Lee, D.S., C.R. Gilbert, C.H. Hocutt, R.E. Jenkins, D.E. McAllister, and J.R. Stauffer, Jr. 1980 et seq. Atlas of North American freshwater fishes. North Carolina State Museum of Natural History, Raleigh, NC.

Loftus, W.F. 1979. Synchronous aerial respiration by the walking catfish in Florida. Copeia 1979: 156-158.

Loftus, W.F. 1988. Distribution and ecology of exotic fishes in Everglades National Park. P. 24-34 in L.K. Thomas, editor. Proceedings of the 1986 conference on science in the national parks, volume 5. Management of exotic species in natural communities. U.S. National Park Service and George Wright Society, Washington, D.C.

Loftus, W.F., and J.A. Kushlan. 1987. Freshwater fishes of southern Florida. Bulletin of the Florida State Museum of Biological Science 31(4): 147-344.

Lorenz, J.J., C.C. McIvor, G.V.N. Powell, and P.C. Frederick. 1997. A drop net and removable walkway used to quantitatively sample fishes over wetland surfaces in the dwarf mangroves of the southern Everglades. Wetlands 17:346-359.

Minckley, W.L. 1973. Fishes of Arizona. Arizona Fish and Game Department. Sims Printing Company, Inc., Phoenix, AZ.

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

Nico, L.G. 2005. Changes in teh fish fauna of the Kissimmee RIver basin, penninsular Florida: non-native additions. 523-556 in Rinne, J.N., R.M. Hughes, and B. Calamusso, eds. Historical changes in large river fish assemblages of the Americas. American Fisheries Society, Bethesda, MD.

Page, L.M., and B.M. Burr. 1991. A field guide to freshwater fishes of North America north of Mexico. The Peterson Field Guide Series, volume 42. Houghton Mifflin Company, Boston, MA.

Shapovalov, L., A.J. Cordone, and W.A. Dill. 1981. A list of freshwater and anadromous fishes of California. California Fish and Game 67(1):4-38.

Smith, H.M. 1945. The fresh-water fishes of Siam, or Thailand. Bulletin of the U.S. National Museum (Smithsonian Institution) 188:1-622.

Stockdale, A.W. 1982. Unique catfish 'walk' to Salty Island. A Florida newspaper, 5 November 1982.

Talwar, P.K., and A.G. Jhingran, eds. 1992. Inland fishes of India and adjacent countries. A. A. Balkema, Rotterdam, The Netherlands. Two volumes.

Taylor, J.N., W.R. Courtenay, Jr., and J.A. McCann. 1984. Known impact of exotic fishes in the continental United States. Pages 322-373 in W. R. Courtenay, Jr., and J. R. Stauffer, editors. Distribution, biology, and management of exotic fish. Johns Hopkins Press, Baltimore, MD.

Tilmant, J.T. 1999. Management of nonindigenous aquatic fish in the U.S. National Park System. National Park Service. 50 p.

Whitworth, W.R. 1996. Freshwater Fishes of Connecticut. State Geological and Natural History Survey of Connecticut, Bulletin 114.

Williams, J.D., D.P. Jennings, and D.C. Haney. 1992. Exotics in the Indian River Lagoon System. National Biological Survey, Gainesville, FL. Unpublished manuscript.

Vinyard, G.L. 2001. Fish species recorded from Nevada. Biological Resources Research Center. University of Nevada, Reno. 5 p.

Other Resources:
Clarias batrachus (Global Invasive Species Database)

US Fish and Wildlife Service Ecological Risk Screening Summary for Clarias batrachus

Author: Leo Nico, Matt Neilson, and Bill Loftus

Peer Review Date: 9/7/2012

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.