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.

Misgurnus anguillicaudatus
Misgurnus anguillicaudatus
(Pond Loach)

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Misgurnus anguillicaudatus (Cantor, 1842)

Common name: Pond Loach

Synonyms and Other Names: Oriental Weatherfish, Dojo, Dojo Loach, Weather Loach, Japanese Weatherfish, Amur Weatherfish

Taxonomy: available through www.itis.govITIS logo

Identification: Eel-like body, brown with greenish grey-brown marble markings dorsally, pale silver ventrum. The mouth is small, narrow and subinferior surrounded by six barbels. The lips are thick and fleshy. Short lateral line, not exceeding the length of the pectoral fin. Has a stout spine on its pectoral fin. Dorsal fin origin is above the pelvic fin origin. There are 9 dorsal rays, 6–7 pelvic rays, and 7–8 anal rays. Distinguishing characteristics were given by Berg (1949), Sterba (1973), Masuda et al. (1984), Page and Burr (1991), and Talwar and Jhingran (1992). The species is included in identification keys provided by Nichols (1943), Berg (1949), Moyle (1976), Talwar and Jhingran (1992), and Laird and Page (1996). Illustrations or photographs appeared in Nichols (1943), Berg (1949), Masuda et al. (1984), and Axelrod et al. (1985).

Size: To 28 cm SL (Kottelat and Freyhof 2007), but averages 10-20 cm.

Native Range: Eastern Asia from Siberia south to northern Vietnam, including Japan (Berg 1949; Masuda et al. 1984; Talwar and Jhingran 1992).

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

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Misgurnus anguillicaudatus are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
AL200920223Cahaba; Lower Coosa; Middle Coosa
CA196320236Coyote; Middle San Joaquin-Lower Chowchilla; Salton Sea; Santa Margarita; Seal Beach; Southern California Coastal
FL198820237Alafia; Hillsborough; Little Manatee; Myakka; Peace; Tampa Bay; Withlacoochee
GA202020232Upper Ocmulgee; Upper Oconee
HI187020224Hawaii; Kauai; Maui; Oahu
ID198520113Lower Boise; Middle Snake-Payette; Upper Snake-Rock
IL198720234Chicago; Des Plaines; Kankakee; Lower Illinois-Senachwine Lake
IN200220233Chicago; Kankakee; Little Calumet-Galien
LA200520051Liberty Bayou-Tchefuncta
MI193920003Flint; Lake Huron; Shiawassee
NJ200720233Hackensack-Passaic; Middle Delaware-Musconetcong; Raritan
NY200120248Conewango; Hudson-Wappinger; Middle Delaware-Mongaup-Brodhead; Middle Hudson; Rondout; Schoharie; Southern Long Island; Upper Susquehanna
OH201920201Upper Scioto
OR199120178Clackamas; Lower Columbia; Lower Columbia-Clatskanie; Lower Malheur; Lower Owyhee; Lower Willamette; Middle Snake-Payette; Middle Snake-Succor
PA201720172Owego-Wappasening; Upper Susquehanna
UT201520223Great Salt Lake; Jordan; Lower Weber
VA201920191Middle Potomac-Anacostia-Occoquan
WA197820245Lake Washington; Lewis; Puget Sound; Puyallup; Upper Yakima
WI200020001Lake Michigan

Table last updated 6/13/2024

† Populations may not be currently present.

Ecology: The Pond Loach is found in muddy or silty substrates in low-gradient, shallow water, often in aquatic macrophyte beds (Tabor et al. 2001; Schmidt and Schmidt 2014). It does not forage by sight, but requires chemical stimuli to induce feeding behavior (Watanabe and Hidaka 1983). Its diet is composed mostly of small benthic invertebrates and detritus; Tabor et al. (2001) found that cladocerans and chironomids were the most frequently ingested prey items collectively; Schmidt and Schmidt (2014) found that amphipods, gastropods and chironomids comprised the most important food items in several New York populations; Urquhart and Koetsier (2014b) identified chironimids and small bivalves as the most frequently ingested prey items in Idaho populations.

Pond Loach is highly tolerant to extreme conditions or marginal habitat quality: Koetsier and Urquhart (2012) found that Pond Loach can withstand desiccation and starvation for more than 81 days, and Urquhart and Koetsier (2014a) estimated a critical thermal minimum of between -1° and -2°C and reported survival of experimental fish partially or fully encased and in direct contact with ice. Further, it can withstand a maximum temperature of around 38°C and O2 concentrations below 2 mg/L (McMahon and Burggren 1987; Rixon et. al. 2005; Urquhart and Koetsier 2014b). It can use its intestine as an accessory respiratory organ, enabling it to live in oxygen-poor waters and to bury itself in soft substrates to survive long droughts (Ip et al. 2004). As a side effect of its ability to breathe air, Pond Loach can also tolerate extremely high concentrations of ammonia (Ip and Chew 2018).

This species exhibits sexual size dimorphism, with the average length of female Pond Loach being considerably larger than that of the males (Tabor et al. 2001; Schmidt and Schmidt 2014). It is an external fertilizer that spawns multiple times from April to October (Milton et al. 2018). Schmidt and Schmidt (2014) examined the fecundity of introduced New York populations: ovary weight was 4-19% of total wet body weight, and total oocytes in unmated females ranging between 150-18,000 (with fecundity increasing with total length).

Means of Introduction: California populations are apparently descended from individuals that escaped from a local goldfish farm, possibly as early as the 1930s (St. Amant and Hoover 1969). Similarly, populations in the upper Shiawassee River system, Michigan, are believed to have descended from individuals imported from Kobe, Japan, which escaped from a nearby aquarium supply company in Oakland County before 1951, possibly as early as 1939 (Schultz 1960; Courtenay et al. 1984). In Hawaii, the species was presumably introduced by Asian immigrants during the 1800s, probably for food (Maciolek 1984; Devick 1991b). Brock (1960) stated that its use as bait for fish was apparently instrumental in its spread in Hawaii. Collections in Louisiana were the result of escapes from a fish farm. Introductions into other states were presumably the result of aquarium releases.

Status: Established in Shiawassee River and Lake Michigan (Simon et al. 2006; USEPA 2008). Established in Alabama, California, Florida, Hawaii, Idaho, Illinois, Michigan, New Jersey, New York, Oregon, and Washington, and possibly in Louisiana. Status is unknown in Tennessee, North Carolina, and Maryland.

Great Lakes: Overwintering and reproducing in Lake Michigan.

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

EcologicalEconomicHuman HealthOther

It may reduce populations of aquatic insects important as food to native fishes (Page and Laird 1993; USEPA 2008). Based on its preferred habitat and diet, and on its population size, Maciolek (1984) categorized Misgurnus along with several other introduced fishes as species having an intermediate impact on Hawaiian streams. Schmidt and Schmidt (2014) suggested that Pond Loach may compete with native Eastern Mudminnow (Umbra pygmaea) for food where the two species co-occur. Experimentation in Australia on the environmental impacts of Pond Loach suggests it may significantly reduce macroinvertebrate abundance and increase turbidity and nitrogen levels in standing water (Keller and Lake 2007).

Remarks: In addition to appearing in the aquarium trade, Pond Loach has been introduced into several parts of the world for aquaculture and as a bait fish (Welcomme 1988). It is considered a cool-water species (Welcomme 1988); individuals burrow into soft substrates and tolerate low-oxygen conditions by breathing atmospheric air (Sterba 1973). As its name suggests, this fish becomes more active in response to changes in barometric pressure; thus it frequently has been cited as a harbinger of storms (Sterba 1973; Axelrod et al. 1985). There is concern that if Pond Loach becomes more abundant and spreads, it will reduce populations of aquatic insects important as food for native fishes (Page and Laird 1993). Maciolek (1984) categorized Misgurnus, along with several other introduced fishes, as having an intermediate impact on Hawaiian streams based on their preferred habitat and diet and on their numbers. The Bolsa Chica Channel, California, cited by Shapovalov et al. (1981), likely represents the Huntington Beach, Orange County site reported by other authors (e.g., Courtenay et al. 1986; Page and Burr 1991). Shafland et al. (2008) reclassified this species from Established to Possibly Established in Florida because of unreliability of collection of specimens.

Voucher specimens: California (CAS 24192; LACM 36986.002, 36988.002, 56916.001; SIO 68-213; UF 87981); Florida (UF 98633, 98634, 100519, 100533, 119925, 128570, 139432, 139507, 143225, 143230, 143271, 143299, 143309, 143376, 143381, 143386, 143541, 143728, 143738, 148188, 148224, 163658, 163662, 163673, 163681, 163684, 163694, 163695, 163719, 163751, 163777); Hawaii (BPBM 3624, discarded in 1969; ANSP 54151, 89309; UWFC 115671); Idaho (UNLV 1951); Illinois (INHS 61129, 61130, 61131); Michigan (UMMZ 173823, 174568, 198978, 212412, 225614); New Jersey (ANSP 188939); New York (NYSM 53924, 55379, 57313, 54195, 65640, 65919, 65922, 68732, 68734); Oregon (OS 13196, 13215, 13216, 15467, 15473, 15474; Portland State University); Tennessee (UT 46.17); Washington (UF 168231; UWFC 111106)

References: (click for full references)

Aitkin, K. - U.S. Fish and Wildlife Service, Lacey, WA.

Axelrod, H.R., W.E. Burgess, N. Pronek, and J.G. Walls. Dr. Axelrod's atlas of freshwater aquarium fishes. Tropical Fish Hobbyist Publications, Inc., Neptune City, NJ.

Berg, L.S. 1948-1949. Freshwater fishes of the U.S.S.R. and adjacent countries, 4th edition. Three volumes. Translated from Russian, 1962-1965, for the Smithsonian Institution and the National Science Foundation, by Israel Program for Scientific Translations, Jerusalem, Israel. Volume 1:504 pp.; volume 2:496 pp.; volume 3:510 pp.

Brock, V.E. 1960. The introduction of aquatic animals into Hawaiian waters. Internationale Revue der Gestamen Hydrobiologie 45:463-480.

Chen, J., Z. Liu, S. Xiao, R. Chen, C. Luo, T. Zhu, T. Cao, L. Ni, P. Xie, H. Su, and M. Zhang. 2020. Effects of benthivorous fish disturbance on chlorophyll a contents in water and the growth of two submersed macrophytes with different growth forms under two light regimes. Science of the Total Environment 704:135269. https://doi.org/10.1016/j.scitotenv.2019.135269.

Chen, J., H. Su, G. Zhou, Y. Dai, J. Hu, Y. Zhao, Z. Liu, T. Cao, L. Ni, M. Zhang, and P. Xie. 2020. Effects of benthivorous fish disturbance and snail herbivory on water quality and two submersed macrophytes. Science of the Total Environment 713:136734. https://doi.org/10.1016/j.scitotenv.2020.136734.

Clearwater, S.J., C.W. Hickey, and M.L. Martin. 2008. Overview of potential piscicides and molluscicides for controlling aquatic pest species in New Zealand. Science & Technical Publishing, New Zealand Department of Conservation, Wellington, New Zealand.

Courtenay, W.R., Jr., D.A. Hensley, J.N. Taylor, and J.A. McCann. 1984. Distribution of exotic fishes in the continental United States. Pages 41-77 in W.R. Courtenay, Jr., and J.R. Stauffer, Jr., editors. 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. Pages 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.

Devick, W.S. 1991a. Disturbances and fluctuations in the Wahiawa Reservoir ecosystem. Project F-14-R-15, Job 4, Study I. Division of Aquatic Resources, Hawaii Department of Land and Natural Resources. 21 pp.

Devick, W.S. 1991b. Patterns of introductions of aquatic organisms to Hawaiian freshwater habitats. Pages 189-213 in new directions in research, management and conservation of Hawaiian freshwater stream ecosystems. Proceedings of the 1990 symposium on freshwater stream biology and fisheries management, Division of Aquatic Resources, Hawaii Department of Land and Natural Resources.

Etnier, D. - University of Tennessee, Knoxville, TN.

GLMRIS. 2012. Appendix C: Inventory of Available Controls for Aquatic Nuisance Species of Concern, Chicago Area Waterway System. U.S. Army Corps of Engineers.

Ip, Y.K., and S.F. Chew. 2018. Air-breathing and excretory nitrogen metabolism in fishes. Acta Histochemica 120(7):680–690. https://doi.org/10.1016/j.acthis.2018.08.013.

Ip, Y.K., S.F. Chew, and D.J. Randall. 2004. Five tropical air-breathing fishes, six different strategies to defend against ammonia toxicity on land. Physiological and Biochemical Zoology, 77(5):768-782.

Keller, R.P., and P.S. Lake. 2007. Potential impacts of a recent and rapidly spreading coloniser of Australian freshwaters: Oriental weatherloach (Misgurnus anguillicaudatus). Ecology of Freshwater Fish 16(2):124-132.

Koetsier, P. and A.N. Urquhart. 2012. Desiccation tolerance in a wild population of the invasive Oriental weatherfish Misgurnus anguillicaudatus in Idaho, USA. Transactions of the American Fisheries Society 141(2):365-369.

Kottelat, M. and J. Freyhof. 2007. Handbook of European freshwater fishes. Publications Kottelat, Cornol, Switzerland. 646 p.

Laird, C.A., and L.M. Page. 1996. Non-native fishes inhabiting the streams and lakes of Illinois. Illinois Natural History Survey Bulletin 35(1):1-51.

Maciolek, J.A. 1984. Exotic fishes in Hawaii and other islands of Oceania. Pages 131-161 in W.R. Courtenay, Jr., and J.R. Stauffer, Jr., eds. Distribution, biology, and management of exotic fishes. The Johns Hopkins University Press, Baltimore, MD.

Masuda, H., K. Amaoka, C. Araga, T. Uyeno, and T. Yoshino, editors. 1984. The fishes of the Japanese Archipelago. Tokai University Press. Text: i-xxii + 437 pp.; atlas: pls. 1-370.

McMahon, B.R., and W.W. Burggren. 1987. Respiratory physiology of intestinal air breathing in the teleost fish Misgurnus anguillicaudatus. Journal of Experimental Biology 133:371–393. https://www.researchgate.net/publication/239789534.

Milton, J., B.A. Paray, and I.A. Rather. 2018. A review on the biology and physiology of loach Misgurnus anguillicaudatus in China. Indian Journal of Geo-Marine Sciences 47(4):759–765.

Moyle, P.B. 1976. Inland fishes of California. University of California Press, Berkeley, CA.

Nichols, J.T. 1943. The freshwater fishes of China. Natural history of Central Asia volume IX. The American Museum of Natural History, New York, NY.

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.

Page, L.M., and C.A. Laird. 1993. The identification of the nonnative fishes inhabiting Illinois waters. Report prepared by Center for Biodiversity, Illinois Natural History Survey, Champaign, for Illinois Department of Conservation, Springfield. Center for Biodiversity Technical Report 1993(4). 39 pp.

Pierce, L. - Scappoose Watershed Council, Warren, Oregon.

Reyda, F.B., S.M. Wells, A.V. Ermolenko, M.S. Zietara, and J.I. Lumme. 2020. Global parasite trafficking: Asian Gyrodactylus (Monogenea) arrived to the USA via invasive fish Misgurnus anguillicaudatus as a threat to amphibians. Biological Invasions 22(2):391–402. https://doi.org/10.1007/s10530-019-02097-4.

Rixon, C.A.M., I.C. Duggan, N.M.N. Bergeron, A. Ricciardi, and H.J. MacIssac. 2005. Invasion risks posed by the aquarium and live fish markets on the Laurentian Great Lakes. Biodiversity and Conservation 14:1365-1381.

Shafland, P.L., K.B. Gestring, and M.S. Stanford. 2008. Florida's exotic freshwater fishes - 2007. Florida Scientist 71(3):220-245.

Schmidt, R.E., and A.J. Schmidt. 2014. Observations on Oriental Weatherfish (Misgurnus anguillicaudatus), an exotic species in the Hudson River Valley, New York. Northeastern Naturalist 21(1):134-145. http://www.bioone.org/doi/full/10.1656/045.021.0113

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Tabor, R.A., E. Warner, and S. Hager. 2001. An oriental weatherfish (Misgurnus anguillicaudatus) population established in Washington state. Northwest Science 75(1): 72-76. https://www.fws.gov/wafwo/fisheries/Publications/FP228.pdf

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Urquhart, A.N., and P. Koetsier. 2014b. Diet of a cryptic but widespread invader, the Oriental Weatherfish (Misgurnus anguillicaudatus) in Idaho, USA. Western North American Naturalist 74(1):92-98. http://www.bioone.org/doi/abs/10.3398/064.074.0109

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Wang, X., J. Li, X. Cao, W. Wang, and Y. Luo. 2020. Isolation, identification and characterisation of an emerging fish pathogen, Acinetobacter pittii, from diseased loach (Misgurnus anguillicaudatus) in China. Antonie van Leeuwenhoek 113:21–32. https://doi.org/10.1007/s10482-019-01312-5.

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Watanabe, K., and T. Hidaka. 1983. Feeding behavior of the Japanese loach, Misgurnus anguillicaudatus (Cobitididae). Journal of Ethology, 1(1-2): 86-90.

Welcomme, R.L. 1988. International introductions of inland aquatic species. FAO Fisheries Technical Paper 294. Food and Agriculture Organization of the United Nations (FAO), Rome, Italy. 318 pp.

Zhang, Y., L. Wang, H. Sun, T. Yao, H. Zhu, J. Xu, and X. Liu. 2016. Impacts of loach bioturbation on the selective bioaccumulation of HBCDD diastereoisomers and enantiomers by mirror carp in a microcosm. Chemosphere 163:471–479. https://doi.org/10.1016/j.chemosphere.2016.08.065.

FishBase Summary

Author: Nico, L., P. Fuller, M. Neilson, J. Larson, A. Fusaro, T.H. Makled, B. Loftus, and A. Bartos

Revision Date: 6/16/2023

Peer Review Date: 4/8/2022

Citation Information:
Nico, L., P. Fuller, M. Neilson, J. Larson, A. Fusaro, T.H. Makled, B. Loftus, and A. Bartos, 2024, Misgurnus anguillicaudatus (Cantor, 1842): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=498, Revision Date: 6/16/2023, Peer Review Date: 4/8/2022, Access Date: 6/13/2024

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.


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Citation information: U.S. Geological Survey. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [6/13/2024].

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