Introduction of the Oriental Weatherfish, Misgurnus anguillicaudatus (Cantor, 1842) in the United States

Although this fish had been present in the then United States (US) territory of Hawaii since the late 19th century, a growing number of collections in the contiguous US over a century later in the 2000s is noteworthy. The Oriental Weatherfish, also often referred to as the weather loach or dojo, is native to eastern Asia from Siberia to Vietnam thus covering a wide climatic range from subtropical to temperate. Primarily a freshwater species, it is typically found in cool, slow-moving streams with silty or muddy substrates. Individuals can reach 28 cm standard length but usually range from 10-20 cm with females generally larger than males. This species has a very slender body shape with a mottled coloration pattern of brown to green markings and a rounded caudal fin. Surrounding its small inferior mouth are 10 barbels and prey consists of small benthic invertebrates including aquatic insects. It is known to bury itself in the substrate to survive periods of drought as well as breathe air using its intestine as an accessory respiratory organ.
The occurrence of this species in Hawaii beginning in the late 1800s was likely due to Asian immigrants bringing it with them as a food source. Misgurnus was later used in the state as a baitfish. The introduction of this species in the contiguous US occurred in 1939 when it was imported into the state of Michigan from Japan for the aquarium trade. The first collection made in open waters was from the Shiawassee River, northwest of Detroit, Michigan in 1958 and are believed to have escaped from a nearby aquaculture breeding facility. Based on the linear extent of captures in the Shiawassee River, the fish had likely been present for years prior to its discovery. By 1985, specimens had also been collected from California, Idaho, Oregon, and Washington. Since then, collections have been made in 15 additional states, mostly in the Atlantic (including Gulf of Mexico) and Great Lakes drainages. Collections from the Mississippi River basin have been limited to the upper Illinois River in Illinois, and the upper Ohio drainage in central Ohio and southwest New York. Overall, M. anguillicaudatus has been collected in the following states (with year of first collection): Hawaii (~1870), Michigan (1958), California (1963), Oregon (1977), Washington (1978), Idaho (1985), Illinois (1987), Florida (1988), Tennessee (1995), New York (2001), Indiana (2002), Louisiana (2005), Maryland (2007), Alabama (2009), North Carolina (2009), New Jersey (2007), Pennsylvania (2017), Ohio (2019), and Virginia (2019). An anecdotal report states that it may also be present in Utah. Misgurnus anguillicaudatus has been reported as established with stable populations in most of the locations of these states although some are small in the reported number of individuals or range extent. Exceptions may be Maryland, Tennessee, and Virginia where only a few specimens have been reported. Three areas in particular appear to be undergoing either substantial range expansions or further introductions. These areas include the upper Illinois River and various waters of both western peninsular Florida and southeastern New York. Because of the limited number of reports yet broad fragmented distribution of M. anguillicaudatus in the US, each population is likely the result of a separate introduction as opposed to dispersal from the earliest collection location. A majority of the collection locations are clustered in or near large metropolitan areas which reflects probable releases by aquarium hobbyists.