Tadpole surveys at Midewin find unusual visitor

An August 2014 Field Note by Erin Cox, Initiative Intern

It was a perfect June day at the Lobelia Meadows project site at Midewin National Tallgrass Prairie when our supervisor, Trevor, suggested we begin our afternoon with an examination of the live tadpole traps we had set the day before.

Lobelia Meadows is a 160-acre plot of land that has been degraded in some areas by decades of industrial use. In partnership with the U.S. Forest Service, the Wetlands Initiative is restoring it back to high-quality wetlands and prairies. To measure progress on the restoration project, TWI staff conduct a variety of surveys to assess the ecological functionality of the habitats. One such inspection is the tadpole survey to determine the reproductive success of amphibians at the developing wetland sites.

Constructed for the entrapment of minnows and crayfish, the traps we set are designed to allow bait to easily enter the trap but not escape it, and they seem to work just as well for tadpoles. The crew places seven traps at various wetland sites throughout Lobelia Meadows and after 24 hours each trap is surveyed. The captured animals are then released and the traps are reset and relocated within a couple feet of the previous locale.

Following Trevor’s lead, the six of us sloshed eagerly through the first pond site to seize the steel mesh cage marked by a red flag, ready to meet our amphibian guests. We raised the cage out of the water and soft mud, unfastened the clips holding the two identical halves together, and examined the collection of creatures. We fervently combed through a crowd of crayfish to observe one large tadpole—plus a mysterious intruder.

Our unidentified friend, with the long, slender body of an eel and the head of a catfish, managed to repeatedly escape our grasp as we huddled over the small container, with only those brave enough taking turns at its hand-held capture. We spent several minutes like this, strategizing how best we could corner the fish and clutch his slick dodging body long enough to snap a picture, all while keeping our balance in the six inches of murky water and suctioning muck.

Somehow our wriggling catch remained still for the half-second required to capture his image, and Trevor sent the photograph to TWI ecologist Iza Redlinski for identification. The next day, Trevor informed us that our find was not a friend at all, but rather an invasive loach originating from Asia. And so the investigation began....

Misgurnus anguillicaudatus, more commonly known as the Oriental weather loach (nicknamed the dojo, Japanese weatherfish, and pond loach), is native to eastern Asia, ranging from Siberia to Vietnam. Averaging less than 28 cm (11 in) with a brown eel-like body, greenish-gray marble markings along its sides, and thick, fleshy lips, the Oriental Weather Loach is a freshwater fish of the family Cobitidae. It thrives in muddy and silty substrates in cool, shallow water, often in aquatic plant beds. Preferred habitats include slow-moving sections of rivers and streams as well as more stagnant environments such as swamps, oxbows, backwaters, and paddy fields with dense vegetation and submerged roots, branches, and leaf litter.

The loach can survive temperatures ranging from 0–38° C (32–100.4º F) and is exceptionally tolerant to extreme conditions including drought and lack of food; it has been known to endure dehydration and starvation for more than 80 days and has also been known to survive contact and enclosure in ice. The loach is able to recruit its intestine as a reserve respiratory organ. It also produces a layer of mucus to trap and utilize atmospheric oxygen as well as to keep itself damp, allowing its persistence in low-oxygen waters and its survival buried beneath substrates during droughts.

The species is a bottom-dwelling scavenger, feeding mainly on organic material such as algae and detritus as well as small invertebrates, and it uses chemical signals to trigger feeding behavior rather than relying on sight. Due to the loach's increased activity in response to barometric pressure changes, it is commonly referred to as a harbinger of storms, and its common name, Oriental weather loach, is derived from this characteristic.

This U.S. Geological Survey map shows locations where the Oriental weather loach has been found.

The Oriental weather loach has been introduced as an exotic species in Australia and the United States, and populations can currently be found in parts of Alabama, Hawaii, Idaho, Florida, Louisiana, Illinois, Indiana, Michigan, Maryland, New York, New Jersey, Washington, North Carolina, Oregon, and Tennessee. Most of these introductions are due to aquarium supply leaks and releases, as well as use as bait and aquaculture escapes (Oriental weather loach is commonly eaten in its native east Asia).

In Illinois, the loach has been found in Cook County (specifically in the North Shore Channel, a drainage canal of Lake Michigan) since 1987, and was also discovered in the Chicago Sanitary and Ship Canal in 1994. The Oriental weather loach is now considered established in Lake Michigan as well.

Misgurnus anguillicaudatus exhibits numerous characteristics displayed by other invasive species: tolerance to a wide range of environmental conditions, low susceptibility to predation, high reproduction rate, and a variable diet. Moreover, the loach has the ability to travel over land to colonize new waterways. As Oriental weather loach populations continue to expand globally, there is concern that it will become a threat to native fish species by competing for space and food (aquatic insects, etc.), preying on native fish eggs, introducing parasites, and disrupting habitat structure. Their burrowing habits also present potential negative impacts on the aquatic environment.

Due to its high risk potential, the Australian government has prohibited the importation of the loach since 1986. In the United States, Michigan has prohibited possessing the species for other than educational or research purposes, and in Wisconsin, the loach is a restricted species that cannot be released and may only be possessed or transported in a secure facility. Further studies must be conducted to gather more evidence of the negative effects of the Oriental weather loach on native fish species and colonized habitats in countries outside of its natural range. Little is known about the species’ impact in Illinois.

“Like any other exotic, [the loach] is probably competing with or displacing certain native species, but I’m not sure about its specific impact; we don’t have much information on it,” said Rob Miller, who is the Illinois Department of Natural Resources (IDNR) fisheries biologist for Will County.

Miller said he’s not surprised the species turned up at Midewin, because IDNR fisheries staff often find the Oriental weather loach in their surveys along the nearby Des Plaines River. The small stream that borders Lobelia Meadows and contained the loach flows into Grant Creek, which in turn connects with the Des Plaines.

Though the loach may pose significant risk elsewhere, it’s not thought to be harming the Lobelia Meadows site.

“The loach’s invasive characteristics likely don’t apply at Lobelia Meadows, because much of the habitat is not suited for it,” said Gary Sullivan, TWI senior ecologist. “The area it lives in is confined to a small stream that borders Lobelia Meadows where there isn’t a large established native fish community, and there is no evidence of the loach having a negative impact on the aquatic environment at Lobelia Meadows.”

Nevertheless, TWI will keep an eye on the loach population in the stream to see if it expands and will investigate whether the loach could be providing competition for amphibians in their larval stage at Lobelia Meadows.

Erin Cox, TWI summer intern (third from left), joined TWI’s all-female field restoration crew at Midewin in summer 2014, led by TWI restoration specialist Trevor Edmonson.

Meanwhile, a total of 3 loaches, 9 sunfish, 3 water bugs, and 7 northern leopard frog tadpoles (along with plenty of crayfish) have been recorded in the Lobelia Meadows tadpole traps (as of June 2014). As TWI continues to conduct tadpole surveys as the restoration progresses and habitat quality increases, we hope to discover increased numbers of tadpoles, a wider range of frog species, and, though it was an exciting experience, an end to the presence of invasive loaches.

To learn more about Oriental weather loach distribution in the U.S. visit: http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=498.

Erin is an Environmental Science major at Lewis University. She interned this summer with the Wetlands Initiative through the Associated Colleges of Illinois’ Conservation Careers Internship Program.