Mistaken introduction of non-native species is causing incredible damage all over the world. We recently profiled Canadian “Super Pigs,” and reported on Texas and its struggles with fire ants and feral hogs. Colombia is wrestling with introduced hippos. Much has been written about Burmese pythons in Florida. Today the problem is Asian swamp eels.
Now comes news that Florida is also being besieged by Asian swamp eels (Momopterus albus.) The Southeast Asian creatures are reducing some of their prey species by up to 90 percent and very little seems to stop them. These eels have also been found in Georgia, Hawaii and even New Jersey.
Swamp eels have both lungs and gills which makes them especially challenging. predators. The double breathing apparatus lets them can survive drought. Since they have lungs they can travel on land for short distances.
According to the Texas Invasive Species Institute:
“Introduction is believed to be the combined result of aquarium dumping, releases from fish markets, intentional stocking as a food source, escapes from fish farms during flooding events, and potentially also ceremonial releases. With this species being nocturnal in habitat it is not seen often by humans, so it may be more established in the United States than is known. Known for being a food source in Asia and Japan, this species was introduced by Asian immigrants to Oahu, Hawaii before 1900.”
” Introduction to the continental United States in Georgia was first documented in 1994 and is believed likely the result of an aquarium release. Since the late 1990s, the Asian swamp eel has become established in Florida and in 2008 it was found in Silver Lake in New Jersey. In 2016, Asian swamp eels (Amphipnous cuchia) were found in a small lake in the Houston area where they may now be established.”
The institute is a state-wide effort to coordinate response to invasive species and their damage.
As with most invasive species humans are to blame.
The creatures eat crayfish and several other types of fish. Perhaps ironically, one of the crayfish they eat is the non-native Everglades crayfish (Procambarus alleni). Eels may impact the alligator population by preying on young alligators. Alligators are about the only native predators able to put some check on the python population.
According to the United States Geological Survey (USGS):
“Using a 26 year dataset in the Florida Everglades, Pintar et al. (2023) found that Monopterus albus/javenensis reduced the population of the crayfishes Procambarus alleni and P. fallax by >99%, and of the fishes Jordanella floridae by >99%, Fundulus confluentus by >90%, and F. chrysotus and Gambusia holbrooki by >50%. In both Georgia and Florida there is concern that the species will spread to adjacent water bodies as has occurred in the Everglades region of Florida (Kline et al. 2013). The Georgia impoundments are connected to the Chattahoochee River. Shafland et al. (2010) studied swamp eel populations established in south Florida and reported no deleterious ecological effects, although it should be noted that the investigators focused on populations inhabiting canals and associated waterways, habitats already highly disturbed.”
” In addition, their study was largely interested in possible harm caused by swamp eels to sport fishes. Nico et al. (2011) examined the occurrence of internal parasites in both imported, wild-caught swamp eels from a U.S. retail food market and from an introduced population in Florida, finding parasites in nearly all specimens and highlighting the potential of Monopterus as a vector for introduction of macroparasites. Asian Swamp Eels are a known host of multiple Gnathostoma spp. nematodes, and are a potenial source of gnathostomiasis in humans (Cole et al. 2014).”
Gnathostomiasis is a worm borne disease usually spread by eating undercooked eels and other water dwelling edibles. According to the Centers For Disease Control and Prevention the disease can be fatal.
“Human gnathostomiasis is caused by several species of parasitic worms (nematodes) in the genus Gnathostoma. The disease is found and is most commonly diagnosed in Southeast Asia, though it has also been found elsewhere in Asia, in South and Central America, and in some areas of Africa. People become infected primarily by eating undercooked or raw freshwater fish, eels, frogs, birds, and reptiles. The most common manifestations of the infection in humans are migratory swellings under the skin and increased levels of eosinophils in the blood. Rarely, the parasite can enter other tissues such as the liver, and the eye, resulting in vision loss or blindness, and the nerves, spinal cord, or brain, resulting in nerve pain, paralysis, coma and death.”
Animal Diversity Web says the problem is going to remain because these eels have few predators. They hunt at night, burrow and have cryptic coloring. These three attributes make it hard for most predators to find them.
The exception is humans. Asian people eat these eels frequently, sometimes stir-fried with chilies. Geting them on the menu is one possible long-term solution. The other involves an Achilles Heel that probably will be exploited.
All swamp eels are borne female. A proportion become male based on a biological trigger. Find a way to eliminate the males and the population drops. That is where scientific research comes in, as it has with many invasive species.