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U.S. Department of the Interior
U.S. Geological Survey

The Swamp Eel: A New Invasive Fish

For more up-to-date information, see USGS FAQs about the Asian swamp eel and USGS NAS scientific information about the Asian swamp eel.

A new invasive fish, the swamp eel also known as the Asian rice eel, has been recently discovered in South Florida in urban canals at the edge of the Everglades. It appears to be a nearly unstoppable invader. Scientists at the USGS Southeast Ecological Science Center in collaboration with state, water management district, and university scientists are studying this problem in an effort to develop control strategies and evaluate biological impacts. photo of a swamp eel

Unidentified eels were discovered almost simultaneously in two widely separated places in Florida in late 1997. Florida International University scientists found eels in a storm water retention pond near Miami, and USGS scientists discovered them in several small ditches near Tampa. Investigations by USGS scientists at the Southeast Ecological Science Center in Gainesville, Florida, identified the eels as Monopterus albus, a species with a broad distribution in Asia. Records also show these eels have invaded Hawaii, and an isolated population has existed in Atlanta, Georgia, since at least 1990.

These eels most likely originated from an aquarium release. Recent USGS surveys in the Miami vicinity suggest the eel is widespread and abundant in urban canals. A few individuals were found in the southeast corner of Everglades National Park as early as 2007. It's US distribution can be viewed at http://nas2.er.usgs.gov/viewer/omap.aspx?SpeciesID=974.

Like other exotic species, the swamp eel has the potential to adversely affect native species, specifically by eating them or by competing with them for food or other resources.

Although Florida has about 30 nonindigenous fish species, the swamp eel has certain biological characteristics that have raised concerns about its persistence, potential to spread, and possible damage it may cause. The eels may grow to a length of more than 3 feet and are not restricted to the tropics in its native range in Asia. It can travel over land during rains and can "breathe" air. It eats a wide variety of prey and can survive droughts by burrowing in the mud. Sex reversal occurs with aging, helping to ensure that only a few individuals are needed to colonize new areas. Also, these eels appear resistant to standard chemicals used to control fish.

Research needs to continue on this species. At a minimum, there is an urgent need to assess its current distribution and evaluate possible methods to contain its spread. Information on the eel's basic life history and characteristics are needed to develop control methods and strategies. Information on swamp eel behavior and biological requirements will help to identify potentially vulnerable aspects of its life history. Moreover, research is needed to determine the possible impacts this species may be having on native biological communities.

U.S. Department of the Interior
U.S. Geological Survey
Biological Resources Division
September 1998
(updated 2012)
For more information about this topic contact:

Ken Rice, Ph.D.
Director, Southeast Ecological Science Center
(352) 264-3544

For more up-to-date information, see USGS FAQs about the Asian swamp eel and USGS NAS scientific information about the Asian swamp eel.

Related information:

SOFIA Project: Population Structure and Spatial Delineation of Consumer Communities in the Everglades National Park

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Last updated: 04 September, 2013 @ 02:03 PM(KP)