Northern Snakehead


Northern snakeheads (Channa argus) are a fish native to eastern Asia (Courtenay and Williams, 2004), and were recently introduced to North America.  The first reproducing population was found in Crofton Pond, MD, in 2002 and was eradicated that year when Maryland DNR poisoned the pond with Rotenone.  In 2004, northern snakeheads were discovered in the lower Potomac River.  Early analysis of the age structure of the population suggested that snakeheads had been in this system since approximately 1998 (Odenkirk and Owens 2005).  Since then, reproducing populations have also been established in ponds in FDR Park, Philadelphia, PA, and Flushing, Queens, NY.  In 2008, reproducing populations were discovered in the Hudson River drainage, NY, and the Mississippi River drainage, AR.  Both state agencies are involved in massive eradication efforts to prevent northern snakeheads from reaching the main rivers of these drainage basins.

Based on their broad environmental tolerances, northern snakeheads have the potential to greatly expand their range throughout North America.  Current analyses of potential northern snakehead distribution suggest that much of North America from Mexico to Hudson Bay may be suitable habitat (Herborg et al. 2007).  Most of the traits of successful fish invaders are shared by northern snakehead, suggesting the threat of spread and impact is high (Courtenay and Williams 2004).  Such traits include wide geographic range, tolerance of adverse chemical conditions and temperatures, ability to spawn multiple times per season, parental care, wide diet breadth, and large body size relative to competitors.  In addition to their gills, northern snakeheads are able to breathe air, allowing them to survive in waters with low dissolved oxygen where other fishes would perish.

Our research, funded by the U.S. Geological Survey (USGS) and the National Science and Engineering Research Council of Canada, and in cooperation with the Virginia Department of Game and Inland Fisheries (VDGIF), and the Maryland Department of Natural Resources (MDDNR), has focused on understanding the basic biology of northern snakeheads, so that interactions with and impacts on native species can be inferred.  We explored the habitat use, movement patterns, dispersal ability and home range size of northern snakehead by capturing fish from the Potomac River, implanting them with radio tags, and releasing them.  These fish were tracked from October 2006 until September 2007.  We also collected data on feeding habits and diet of northern snakehead by capturing fishes by boat electrofishing in 2007 and 2008.  Largemouth bass (Micropterus salmoides), yellow perch (Perca Flavescens), longnose gar (Lepisosteus osseus), and American eel (Anguilla rostrata) were captured to study diet overlap between northern snakehead and North American species.  After extracting gut contents from northern snakehead, genetic samples, and otoliths (for determining age) were extracted and sent to the USGS Leetown Science Center and VDGIF, respectively, for further analysis.  In the course of conducting this research, we collected information on northern snakehead growth rates and spawning habits, and on juvenile feeding habits, schooling behaviour, habitat use, and growth and development.  We are continuing to analyze our data and will report our final results on this website as they become available.


Courtenay, W. R. Jr., and J. D. Williams. 2004. Snakeheads (Pisces, Channidae) - A biological synopsis and risk assessment. U.S. Geological Survey Circular 1251. (link)

Herborg L. M., N. E. Mandrak, B. C. Cudmore, and H. J. MacIsaac. 2007. Comparative distribution and invasion risk of snakehead (Channidae) and Asian carp (Cyprinidae) species in North America. Canadian Journal of Fisheries and Aquatic Sciences. 64:1723-1735.

Odenkirk, J. and S. Owens. 2005. Northern snakeheads in the tidal Potomac River system. Transactions of the American Fisheries Society 134:1605-1609.