Raleigh Ecological Services Field Office
Conserving the Nature of America

The American Eel in North Carolina

Anguilla rostrata
Class: Actinopterygii
Order: Anguilliformes
Family: Anguillidae
Status:  Under review

Description:
The American eel is one of 15 fish species of the genus Anguilla, whose members spawn in ocean waters, migrate to coastal and inland continental waters to grow, and then return to ocean spawning areas to reproduce - a life history strategy known as catadromy. 


The American eel’s slender body is covered with a mucous layer, which makes the eel appear to be slimy despite the presence of minute scales. A long dorsal fin runs from the middle of the back and is continuous with a similar ventral fin.  Pelvic fins are absent, and a relatively small pectoral fin can be found near the midline, followed by the head and gill-covers. Variations exist in coloration; the back may be olive-green to brown shading to greenish-yellow on the sides and light gray or white on the belly.  Eels from clear water are often lighter than those from dark, tannic acid streams. 


Diet:
The American eel is a nocturnal species, swimming and eating at night.  Eels eat other fish, octopus, shrimps, seaweed, plankton, crayfish, and other items depending on what is available.   With its relatively weak jaws and many small teeth, it jerks or pulls on food that cannot be consumed whole or readily broken into pieces. Holding on with their mouths, adult eels spin their bodies to break apart food, and have been recorded at six to 14 spins per second. In comparison, Olympic ice skaters can spin five times per second.


Wide Distribution:
The American eel is found in the Atlantic Ocean from Greenland to Brazil.  Along the Atlantic coast of the United States, eels between Maine and Florida are considered part of a single population.


Life History:
The American eel begins its life in the Sargasso Sea near Bermuda within the North Atlantic Ocean, where eggs hatch into larvae that are transported by ocean currents to the Atlantic coasts of North America and northern South America, and the Gulf coast. 
American eels are known by several names that describe the coloration of progressive stages of development (glass eel, elver, yellow eel and silver eel) as well as changes in where they occur.
* Juveniles arrival to the coast and migrate to mature in rivers or estuaries
Eel juveniles arrive in coastal waters as colorless “glass eel” in great numbers, though with considerable yearly variation (ICES 2001, p. 2).   Glass eels metamorphose (change) to pigmented “elvers,” that later develop into “yellow eels,” which resemble the adults in size and are usually yellow or green in color.  The timing and duration of yellow eel upstream migration depends on latitude and can occur over a broad period of time from January through October.  Depending on where they cease their upstream migration, some yellow eels reach the extreme upper portions of the rivers while others stay behind in the brackish areas.
* Adults reproduce in the sea
American eels begin sexual differentiation at a length of about 20 to 25 centimeters (cm) (7.9 to 9.8 inches (in)) and, depending on eel density, become male or female. Female eels grow the largest, and any eel greater than 33 cm is female.  Much later they make a final change into a mature stage as “silver eels”, with a distinctive silvery color, and enlarged eyes. Upon nearing sexual maturity, the eels begin migration back downstream, toward the Sargasso Sea, completing sexual maturation en route.  Spawning occurs in the Sargasso Sea.  After spawning, it is assumed that adult eels die.
Habitat in North Carolina
Some scientists consider the highly adaptive American eel to have the broadest diversity of habitats of any fish species in the world.  In North Carolina, estuarine areas like the Albemarle-Pamlico Sound provide suitable habitat for the early glass eel and elver stages.  Fresh water habitat, including lacustrine areas (lakes and ponds) have historically been considered among the most important habitats for eel maturation because eels maturing in such habitats usually become female.  At one time, American eels were found throughout North Carolina, even described by early fish collectors as "everywhere abundant" in the upper Catawba River.  The American eel finds fresh water habitat in North Carolina in streams and large rivers in the Piedmont and Coastal Plain, but numbers are reduced upstream of many dams.
Threats
* Habitat loss and fragmentation
Hydroelectric and other dams block or slow movements of elvers and subadult eels to upstream habitats. American eels continue to be distributed throughout the lower areas of watersheds closest to the sea and sounds. They are prevented from reaching extreme headwaters where they had historically been reported as “everywhere common” in 1889 by early scientist D.S. Jordan.
* Turbine mortality
Silver eel females migrating downstream often die in the turbines of hydropower plants, as a consequence of the eel’s long and slender body form, which does not easily pass through turbine blade openings.
* Diseases
Worm parasites Anguillicolla crassus and Daniconema anguillae may impair the capacity of the eel to undertake the migration to the Sargasso Sea.  In one North Carolina study, the percentage of American eels infected ranged from 10 to 100 percent (Moser et al. 2001, p. 1).   These worms infest the eel swim bladder. While it may not be a problem in shallow water, once the eels mature and begin their long return swim to the Sargasso, a nonfunctioning or even somewhat impaired swim bladder could cause bouyancy and swimming problems in the open ocean, before they have successfully spawned.
* Contaminants
Toxic substances too, may impair eels, although which contaminants and how much harm they do are as yet largely unknown.  Studies have shown American eels are sensitive to petroleum products, and accumulate other contaminants in fat cells.
* Predation
In all its life stages, the American eel serves as an important prey species for many fish, aquatic mammals, reptiles (e.g., rainbow snakes, snapping turtles) and fish-eating birds.
* Harvest
Since the early 17th century, people have harvested American eel for food and cultural sustenance. American eels continue to support valuable seasonal commercial, recreational and subsistence fisheries along the Atlantic coast.  In the Carolinas, harvest has been greatest for small yellow eels used for bait to catch striped bass.  Global markets have been volatile, sometimes commanding high prices for glass eel exports.

Conservation Opportunities in North Carolina
Eel passage projects have been completed at the Roanoke Rapids Dam and similar projects are in different stages of planning and construction. While upstream passage facilities are not present everywhere within the American eel’s range, more American eels are passed into the upper reaches of watersheds now, beginning with renewed efforts by fishery scientists in recent years.

The American eel may need federal protection under the Endangered Species Act.  The US Fish & Wildlife Service is conducting a Status Review for the American eel to determine if adding the species to the Federal List of Endangered and Threatened Wildlife is warranted.

References

    • Aieta, Amy E., and K. Oliveria.  2009.  Distribution, prevalence, and intensity of the swim bladder parasite Anguillicola crassus in New England and Canada.  Diseases of Aquatic Organisms.  84: 229-235.  7 pp.
    • American Eel Working Group (AEWG).  2010.  American Eel Working Group Update. April 15, 2010.  Upstream Eel Passage at Roanoke Rapids Dam.  1 p.
    • Aoyama, Jun.  2009.  Life History and Evolution of Migration in Catadromous Eels (Genus Anguilla).  Aqua-BioScience Monographs.  Vol. 2. No. 1.  42 pp.
    • Atlantic States Marine Fisheries Commission (ASMFC).  2004.  Letter to U.S. Fish and Wildlife Service regarding status review for the American eel.  May 27, 2004. 1p.
    • Atlantic States Marine Fisheries Commission (ASFMC).  2007.  Atlantic States Marine Fisheries Commission Addendum II to the Fisheries Management Plan for American Eel.  March 2007.  ASMFC, Washington, D.C.  43 pp.
    • Atlantic States Marine Fisheries Commission (ASMFC).  2008c.  American Eel Prioritized Research Needs 2008.  2 pp.
    • Atlantic States Marine Fisheries Commission-American Eel Plan Review Team (AEPRT).  2008.  Review of the Atlantic States Marine Fisheries Commission Fishery Management Plan for the American Eel (Anguilla rostrata).  15 pp.
    • Atlantic States Marine Fisheries Commission-American Eel Stock Assessment Subcommittee (ASMFC-AESAS).  2008a.  American Eel SLYME Model: Report to the ASMFC American Eel Management Board.  July 2008.  28 pp.
    • Atlantic States Marine Fisheries Commission-American Eel Technical Committee & Stock Assessment Subcommittee Conference (ASMFC-AETC & SAS).  2009c.  DRAFT ASMFC American Eel Technical Committee & Stock Assessment Subcommittee Conference Call Agenda, June 29, 2009, 2:00 p.m.  11 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Bonhommeau, Sylvain, E. Chassot, and E. Rivot. 2008a.  Fluctuations in European Eel (Anguilla anguilla) recruitment resulting from environmental changes in the Sargasso Sea.  Fisheries Oceanography.  17:1, 32-44. 13 pp.
    • Bonhommeau, Sylvain, E. Chassot, B. Planque, E. Rivot, A. Knap, and O. Le Pape. 2008b.  Impact of climate on eel populations of the Northern Hemisphere.  Marine Ecology Progress Series.  373: 71-80.  10 pp.
    • Brown, Leah, A. Haro, and T. Castro-Santos.  2009.  Three-Dimensional Movement of Silver-Phase American Eels in the Forebay of a Small Hydroelectric Facility.  American Fisheries Society Symposium.  58: 277-291.  16 pp.
    • Cairns, D., V. Tremblay, J. Casselman, F. Caron, G. Verreault, Y. Mailhot, P. Dumont, R. Bradford, K. Clarke, Y. de Fontaine, B. Jessop, and M. Feigenbaum.  2005.  Conservation status and population trends of the American eel in Canada.  Canadian Science Advisory Secretariat, Fisheries and Oceans Canada. Draft October 9, 2005.  Section 3.  Biology and Distribution.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Cairns, D., V. Tremblay, F. Caron, J. Casselman, G. Verreault, B. Jessop, Y. de Fontaine, R. Bradford, R. Verdon, P. Dumont, Y. Mailhot, J. Zhu, A. Mathers, K. Oliveira, K. Benhalima, J.P. Dietrich, J.A. Hallett, and M. Lagacé.  2008. American eel abundance indicators in Canada.  Canadian Data Report of Fisheries and Aquatic Sciences 1207.  Fisheries and Ocean Canada.  Moncton, NB.  85 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Cairns, D. K., D. A. Secor, W. E. Morrison, and J. A. Hallett.  2009.  Salinity-linked growth in anguillid eels and the paradox of temperate-zone catadromy.Journal of Fish Biology.  74: 2094–2114.  21 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Calles, O.,  I. C. Olsson, C. Comoglio, P. S. Kemp, L. Blunden, M. Schmitz, and L. A. Greenberg. 2010.  Size-dependent mortality of migratory silver eels at a hydropower plant, and implications for escapement to the sea.  Size-dependent mortality of migratory silver eels at a hydropower plant, and implications for escapement to the sea.  Freshwater Biology.  55:  2167–2180.  14 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Carr, J.W. and F.G. Whoriskey.  2008.  Migration of silver American eels past a hydroelectric dam and through a coastal zone.  Fisheries Management and Ecology.  15:  393–400.  8 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Casselman, John M. and L.A. Marcogliese. 2007.  Long-term changes in American eel (Anguilla rostrata) commercial harvest and price in relation to declining abundance.  July 2007.  MS report. Prepared for Great Lakes Fishery Commission, Ontario Ministry of Natural Resources, and Department of Fisheries and Oceans by AFishESci Inc., Bath, Ontario K0H 1G094 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Chesapeake Bay Field Office (CBFO).  2009.  Draft Potomac River Watershed American Eel Restoration Project Summary.  2 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Chow, Seinen, H. Kurogi, N. Mochioka, S. Kaji, M. Okazaki, and K. Tsukamoto.  2009.  Discovery of mature freshwater eels in the open ocean.  Fisheries Science.  75:257–259.  2 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Clark, John H.  2009.  The American Eel Fishery in Delaware:  Recent Landings Trends and Characteristics of the Exploited Eel Population.  American Fisheries Society Symposium.  Vol. 58: 229-239.  12 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Connecticut Department of Environmental Protection (CTDEP). 2009.  CONNECTICUT WEEKLY DIADROMOUS FISH REPORT. Report Date: June 23, 2009.  4 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Cote, C.L., M. Castonguay, G. Verreault, and L. Bernatchez. 2009.  Differential effects of origin and salinity rearing conditions on growth of glass eels of the American eel Anguilla rostrata: implications for stocking programmes.  Journal of Fish Biology.74:  1934–1948.  15 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Craig, S.  2006.  USFWS Assistant Project Leader, Maine Fisheries Resource Office.  Personal communication via email with attached pictures of American eel elvers climbing vertical surface just south of Bar Harbor, Maine.  4 pp., including attachments.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Council for Endangered Species Act Reliability (Petition).  2010.  Petition to List the American Eel (Anguilla rostrata) as a Threatened Species Under the Endangered Species Act.  April 30, 2010.  69 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • DeLafontaine, Yves de, M. Lagace, F. Gingras, D. Labonte, F. Marchand, and E. Lacroix. 2009.  Decline of the American Eel in the St. Lawrence River:  Effects of Local Hydroclimatic Conditions on CPUE Indices.  American Fisheries Society Symposium.  58: 207-228.  22 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • DeLeo, Giulio A., P. Melià , M. Gatto, and A.J. Crivelli. 2009.  Eel Population Modeling and its Application to Conservation Management.  17 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Dittman, Dawn E., L. S. Machut, and J. H. Johnson. 2009.  Susquehanna River Drainage: American Eel History, Status, and Management Options.  Final Report for New York State Contract #C005548, Comprehensive Study of the American Eel, and State Wildlife Grant T-3, Project 3. Submitted to NYSDEC, Bureau of Fisheries, Albany, NY.  95 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Durif, C. M. F. and P. Elie.  2008.  Predicting downstream migration of silver eels in a large river catchment based on commercial fishery data.  Fisheries Management and Ecology.  Vol. 15: 127-137.  11 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Dutil, J-D., P. Dumont, D. K. Cairns, P.S. Galbraith, G. Verreault, M. Castonguay, and S. Proulx.  2009.  Anguilla rostrata glass eel migration and recruitment in the estuary and Gulf of St Lawrence.  Journal of Fish Biology.  74: 1970–1984.  15 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Eltz, B. M., A. Haro, T. Castro-Santos.  2008.  Downstream Migratory Behavior of Silver-Phase American Eels at a Small Hydroelectric Facility.  60 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Eyler, Shelia. 2009.  Radio Telemetry Study of Silver American Eel Passage Past Hydroelectric Dams on the Shenandoah River.  Project Update.  2 pp. 
    • Eyler, Shelia, S. Welsh, and D. Smith. 2008.  Eel Migration Past Shenandoah River Hydroelectric Dams.  Powerpoint Presentation.  21 slides.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Fenske, Kari Hammarsten.  2009.  Assessment of Local Abundance, Demographics, Health and Exploitation of Chesapeake Bay American Eel.  MS Thesis.  University of Maryland, College Park.  152 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Friedland, Kevin D., M. Miller, and B. Knights.  2007.  Oceanic changes in the Sargasso Sea and declines in recruitment of the European eel.  ICES Journal of Marine Science.  Advance Access version, published March 30, 2007.  12 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Gollock, M. J., C. R. Kennedy, and J.A. Brown.  2005.  European eels, Anguilla anguilla (L.), infected with Anguillicola crassus exhibit a more pronounced stress response to severe hypoxia than uninfected eels.  Journal of Fish Diseases.  28: 429–436.  8 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Hammond, Stephen D. and S. A. Welsh.  2009.  Seasonal Movements of Large Yellow American Eels Downstream of a Hydroelectric Dam, Shenandoah River, West Virginia.  American Fisheries Society Symposium.  58: 309-323.  15 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Helfman, G.S., D.E. Facey, L.S. Hales Jr., and E.L. Bozeman Jr.  1987.  Reproductive ecology of the American eel.  American Fisheries Society Symposium. 1:42-56.  15 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • International Council for the Exploration of the Sea (ICES).  2001.  Report of the EIFAC/ICES Working Group on Eels, St. Andrews, N. B., 28 August-1 September 2000.  Advisory Committee on the Fisheries Management, International Council for the Exploration of the Sea, ICES CM 2001/ACFM:03, Copenhagen.  87p.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • International Council for the Exploration of the Sea (ICES).  2009.  Report of the Study Group on Anguillid Eels in Saline Waters (SGAESAW) 16–18 March 2009, Sackville, Canada; 3–5 September 2009, Gothenburg, Sweden. ICES CM/DFC:06. 183 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Jansen, Henrice M., H. V. Winter, M.C.M. Bruijs, and H. J.G. Polman.  2007.  Just go with the flow? Route selection and mortality during downstream migration of silver eels in relation to river discharge.  International Council for the Exploration of the Sea.  doi:10.1093/icesjms/fsm132.  1437-1443.  7 pp.
    • Bell, Heather.  2007.   Note to the File.  Draft Future Management of the American eel.  May 1, 2007.  1 pp.
    • Jessup, B. M., D. K. Cairns, I. Thabault, and W.-N. Tzeng.  2008.  Life history of American eel Anguilla rostrata:  new insights from otolith microchemistry.  Aquatic Biology.  1:205–216. 12 pp.

 

 

 

Illustration of an adult American eel

American eel adult by Ellen Edmonson and Hugh Chrisp via Wikimedia

 

View photos on Flickr

 

map showing Sargasso Sea location

 

 

elvers, imature American eel

young elvers.

Catadromous? Anadromous? Something else?

The more familiar anadromous fish, like salmon or striped bass, are born in freshwater streams, travel to the ocean to mature, and return to freshwater to spawn. Catadromous fish are born in the ocean, mature in fresh water and return to the ocean to spawn. American eels are the best example of a widespread catadromous fish in North American.  Other examples include the mountain mullet in the Caribbean.  

Last Updated: November 1, 2012