Oriental Weatherfish, Dojo, Dojo Loach, Weather Loach, Japanese Weatherfish, Amur Weatherfish

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).

Great Lakes: Overwintering and reproducing in Lake Michigan.

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

Environmental	Socioeconomic	Beneficial

Potential:

Rixon et al. (2005) predicted that Pond Loach has the potential to continue spreading throughout the Great Lakes (likely via the aquarium trade), despite its current limited distribution.

Pond Loach are a source of various parasites and diseases. It introduced the flatworm Gyrodactylus jennyaye to the American Bullfrog (Lithobates catesbeianus) and several other Gyrodactylus spp. from Asia to North America. Pond Loach and its parasites are also predicted to contribute to the global spread of the amphibian chytrid fungus (Reyda et al. 2020). Pond Loach carries the bacteria Acinetobacter pittii which can cause mass mortality in fish cultures and can cause human infection (Wang et al. 2020).

Pond Loach is able to hybridize with the congeneric Misgurnus fossilis, but this species is  not currently in the United States (Wanzenböck et al. 2021).

There is concern that if Pond Loach becomes more abundant and spreads, it will reduce populations of aquatic insects important as food to native fishes (Page and Laird 1993; Tabor et al. 2001). 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.

Pond Loach disturbs the sediment in pursuit of food, and can contribute to decreased water quality via increased turbidity, elevated nutrient concentrations, and released contaminants (Keller and Lake 2007). Experimentation in Australia on the environmental impacts of Pond Loach suggests that this species may significantly reduce macroinvertebrate abundance and increase turbidity and nitrogen levels in standing water (Keller and Lake 2007). In a laboratory experiment, bioturbation by Pond Loach negatively impacted submersed macrophyte growth in low light conditions (Chen et al. 2020a). It also increased total suspended solids, total nitrogen, ammonia, total phosphorus, and phosphate concentrations (Chen et al. 2020b). In a microcosm experiment, Pond Loach disturbed sediments and subsequently released hexabromocyclododecane diastereoisomers which bioaccumulate in Common Carp (Cyprinus carpio) (Zhang et al. 2016).

There is little or no evidence to support that Misgurnus anguillicaudatus has significant socio-economic impacts in the Great Lakes.

Potential:

Pond loach carries the bacteria Acinetobacter pittii which can cause mass mortality in fish cultures and can cause human infection, but the magnitude of impact on humans is unknown (Wang et al. 2020).

Misgurnus anguillicaudatus has a moderate beneficial impact in the Great Lakes.

Potential:

Pond Loach has been introduced into several parts of the world for aquaculture purposes and as a bait fish; however, the occurrence of such use in the Great Lakes is not currently known (Welcomme 1988). This species is also a popular aquarium fish and is recommended beginner species by various aquarium-keeping guides (e.g., https://www.aqua-imports.com/product/gold-dojo-loach-misgurnus-anguillicaudatus/; https://www.tankarium.com/dojo-loach/).

It is restricted in Michigan and is unlawful to possess, introduce, import, sell or offer this species for sale as a live organism, except under certain circumstances (Natural Resources Environmental Protection Act (Part 413 of Act 451). This species is prohibited in Minnesota and is unlawful (a misdemeanor) to possess, import, purchase, transport, or introduce this species except under a permit for disposal, control, research, or education (Statute 84D.07). It is prohibited in New York and cannot be knowingly possessed with the intent to sell, import, purchase, transport or introduce nor can any of these actions be taken (6 NYCRR Part 575). This species is listed as invasive in Pennsylvania, however, no specific regulations are defined. It is a restricted species in Wisconsin, where there is a ban on the transport, transfer and introduction of this species, but possession is allowed (Chapter NR 40, Wis. Adm. Code).

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control

Biological

There are no known biological control methods for this species.

Physical

There are no known physical control methods for this species.

Chemical

Of the four chemical piscicides registered for use in the United States, antimycin A and rotenone are considered general piscicides, but no studies have been found of their effects on Pond Loach (GLMRIS 2012).

Increasing CO2 concentrations, either by bubbling pressurized gas directly into water or by the addition of sodium bicarbonate (NaHCO3) has been used to sedate fish with minimal residual toxicity, and is a potential method of harvesting fish for removal, though maintaining adequate CO2 concentrations may be difficult in large/natural water bodies (Clearwater et al. 2008). CO2 is approved only for use as an anesthetic for cold, cool, and warm water fishes the US, not for use as euthanasia, and exposure to NaHCO3 concentration of 142-642 mg/L for 5 min. is sufficient to anaesthetize most fish (Clearwater et al. 2008).

When planning control and management of this species, special attention should be given to the high physiological tolerances which place it in the profile of a successful invader. The Pond Loach can survive temperatures that range from 0-38° C, utilize atmospheric oxygen as a facultative air-breather to survive hypoxic conditions, and has been documented surviving desiccation for over 81 days with no food, likely perishing from desiccation before starvation (Koetsier and Urquhart 2012).

It should be noted that chemical treatment will often lead to non-target kills, and so all options for management of a species should be adequately studied before a decision is made to use piscicides or other chemicals. Potential effects on non-target plants and organisms, including macroinvertebrates and other fishes, should always be deliberately evaluated and analyzed. The effects of combinations of management chemicals and other toxicants, whether intentional or unintentional, should be understood prior to chemical treatment.  Other non-selective alterations of water quality, such as reducing dissolved oxygen levels or altering pH, could also have a deleterious impact on native fish, invertebrates, and other fauna or flora, and their potential harmful effects should therefore be evaluated thoroughly.

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.

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)