Approach of the Loach: Weather Loaches in Georgia

When the first Weather Loach in Georgia was discovered in McNutt Creek near Athens, GA, UGA researchers responded rapidly, involving students in capturing and removing over 30 of the invasive fish within the first two weeks.

Weather Loaches have since been located in four Georgia river drainages: the Middle Oconee River (2020), the Yellow River (2022), the Apalachee River (2023), and the North Oconee River (2024). The Yellow River discovery was made by members of the consulting firm TetraTech, whereas the Apalachee River discovery was made by a member of the public.

In the aquarium trade, this species goes by many names, including: the Oriental Weatherfish, the Dojo Loach, the Golden Loach, the Pond Loach, or the Amur Weatherfish. While their average size is 6-7 inches, they have been known to reach up to 11 inches long!

The Weather Loach (Misgurnus anguillicaudatus) is a popular aquarium pet native to eastern Asia and Japan. Their popularity in the aquarium trade stems from their hardy nature and slender, attractive appearance. They are also a popular food source in many places within their native range.

The hardy nature of this species allows it to thrive in many different systems, including those where it does not belong. The first U.S. invasion of Weather Loach was reported in 1870, in Hawaii. Since then, invasions have been reported in 20 U.S. states. Invasions have also been reported in Australia, Canada, Germany, and Italy. Most of these introductions are thought to be the result of unwanted aquarium fish being released into the environment, instead of being rehomed or humanely euthanized.

Weather Loach are known to be prolific spawners, may outcompete native fish for food, and may consume the eggs of native fish species. These traits may allow them to pressure sensitive species out of certain environments, including the state-threatened Altamaha Shiner, a fish only found in Georgia, which is known to occur in the same reaches as the Weather Loach.

After loaches were detected in multiple locations without a direct connection to each other, it became clear that the problem was worse than we thought: the original introduction was not a recent, isolated event. This led to the creation of a Task Force in early 2022 to assess and document the severity and origin of this invasion.

The Weather Loach Task Force consists of many fisheries professors, staff members, and students at the University of Georgia. We also partner with Georgia Gwinnett College, the Georgia Department of Natural Resources, the United States Fish and Wildlife Service, and the United States Geological Survey. Each summer, the Task Force samples Georgia waters to locate and collect Weather Loach, while learning more about their spread and reproduction.

Interactive Dashboard: Click on points below to see photos of Weather Loach habitats and squares to see potential barriers to their upstream migration.

While sampling for Weather Loach in June 2022, the Task Force documented juveniles in Indian Creek, the first known evidence of natural reproduction in Georgia. Since then, the Task Force has collected young of the year and age one Weather Loaches from a variety of streams, indicating that they are thriving in Georgia waters.

Weather Loaches are very difficult to see underwater in their natural environments, and they are often in hiding. The Task Force uses a standardized method of fish sampling called backpack electrofishing to capture these invasive fish. While we remove all Weather Loaches we catch from affected sites, all native fishes recover quickly and are released unharmed.

Potential impacts of densely populated Weather Loach are decreases in aquatic insect abundance and diversity, which can lead to a decrease in overall fish diversity as competition for the same food resources increases.

The Task Force continues to collect fish and aquatic insect community data to assess any potential effects of the presence of Weather Loach and determine their position within the aquatic food web. Data are quite variable among sites, but we intend to continue sampling to identify any trends that may occur over time.

Interactive Maps: Scroll, zoom, and click on pie charts to see insect feeding group data.

Catch per unit effort (CPUE) allows us to determine how many Weather Loaches are being caught relative to other fish feeding guilds. It also allows us to track trends in feeding guild composition over time - allowing us to see if Weather Loaches are impacting the "normal" feeding guild composition in each stream, and if so, how.

Based on habitat categorizations from the locations of Weather Loach captures, these fish prefer areas with very little flow and detritus or woody debris that they can use to hide from predators. Their cylindrical, eel-like body allows them to use many habitats that other fish cannot, and makes them a difficult target for predators.

Interactive Dashboard: Hover over bars to see frequencies of Weather Loach captures in different habitat, in-stream cover, and substrate types. This dashboard updates automatically whenever Weather Loaches are captured. Keep scrolling to learn more about each habitat type.

Genetic analysis has shown that each drainage basin has a genetically distinct population of Weather Loaches. This suggests that the Yellow River and Middle Oconee River populations were introduced separately, and that they have not made contact with each other. Analysis of fish collected from the Apalachee River is pending.

If we zoom in, we can see that Weather Loaches in the Middle Oconee River have more haplotypes (group of alleles that are inherited from one parent) than those in the Yellow River. Additionally, Indian Creek is a "haplotype hotspot". Every loach captured in the Middle Oconee river shares at least one haplotype with the Indian Creek loaches. This tells us that Indian Creek may be the point of origin of loaches in the Middle Oconee River, and that those loaches have spread across the watershed.

What does a Weather Loach eat? Whenever the Task Force captures a loach, we look at its gut contents to see what each individual has been eating.

Their stomachs are often empty. This may be because of regurgitation. However, in full stomachs, we often see ostracods, chironomids, and cladocerans. These tasty bugs are important food sources for native fish and it is worrisome that Weather Loaches are also consuming them.

Weather Loaches are surprisingly long-lived, with the oldest recorded individual being 17 years old in the Yellow River watershed. The average age across all watersheds is 4 years. Additionally, loaches in the Yellow River watershed are generally longer, but no smaller individuals have been collected. In the Middle Oconee River watershed, juveniles have been collected.

It should be noted that there are no year 0 or 1 fish within the age structure graph due to the difficulty of removing otoliths from fish under 50mm in length.

The University of Georgia has many other ongoing research projects assessing the extent, origin, and potential effects of the Weather Loach. Updates will be posted here when results are available. For now, fish picture...

Want to learn more about Weather Loaches in Georgia? Check out our research, outreach, and news publications!

If you find a Weather Loach in Georgia, please contact your  local Georgia Department of Natural Resources office  and the University of Georgia ( wgerrin@uga.edu  or  jshelton@uga.edu ). Please include details such as GPS coordinates, how many loaches you found, any photos you may have taken, and if you retained the loach(es) or released them.

Scroll to learn more about the members of the Task Force.