Do Not Remove from the Library 

U, S. Fish and Wildlife Service 

" 

FWSIOBS-82111.24 700 Cajun Dome Boulevard TR EL-82.4 

July 1984 Lafayette, Louisiana 70545 

Species Profiles: Life Histories and 

Environmental Requirements of Coastal Fishes 

and Invertebrates (South Atlantic) 

AMERICAN EEL 
FWS/OBS-82/11.24 

TR EL-82-4 

July 1984 

Species Profiles: Life Histories and Envi rormental 

Requirements of Coastal Fi shes and Invertebrates (South At1 antic) 

AMERICAN EEL 

Michael J. Van Den Avyle 

Georgia Cooperative Fishery Research Unit 

School of Forest Resources 

University of Georgia 

Athens, GA 30602 

Project Manager 

Larry Shanks 

Project Officer 

Norman Benson 

National Coastal Ecosystems Team 

U. S. Fish and Wildlife Service 

1010 Gause Boulevard 

Sl i dell , LA 70458 

This study was performed for 

Coastal Ecol ogy Group 

U.S. Army Corps of Engineers 

Waterways Experiment Station 

Vicksburg, MS 39180 

and 

National Coastal Ecosystems Team 

Division of Bio1 ogical Services 

Research and Development 

Fish and Wild1 ife Service 

U.S. Department of the Interior 

Washing ton, DC 20240 
This series should be referenced as follows: 

U.S. Fish and Wildlife Service. 1983-19-. Species profiles: 1 i fe histories 

and environmental requirements of coastal fi shes and invertebrates. U.S. Fish 

Wildl. Serv. FWS/OBS-82/11. U.S. Army Corps of Engineers, TR EL-82-4. 

This profile should be cited as follows: 

Van Den Avyle, M. J. 1984. Species profiles: life histories and environmental 

requirements of coastal fishes and invertebrates (South At1 antic) -- American 

eel. U.S. Fish Wildl. Serv. FWS/OBS-82D1.24. U.S. Army Corps of Engineers, 

TI? EL-82-4. 20 pp. 
PREFACE 

This species profile is one of a series on coastal aquatic organisms, 

principally fish, of sport, commercial, or ecological importance. The profiles 

are designed to provide coastal managers, engineers, and biologists with a brief 

comprehensive sketch of the bi 01 og ical characteristics and environmental requirements of the species and to describe how populations of the species may be 

expected to react to environmental changes caused by coastal development. Each 

profile has sections on taxonomy, 1 i fe history, ecological role, envi ronmental 

requirements, and economic importance, if appl icabl e. A three-ring binder is 

used for this series so that new profiles can be added as they are prepared. This 

project is jointly planned and financed by the U.S. Army Corps of Engineers and 

the U.S. Fish and Wildlife Service. 

Suggestions or questions regarding this report should be directed to: 

Infonnation Transfer Special ist 

National Coastal Ecosystems Team 

U.S. Fish and Wildlife Service 

NASA-Sl idel 1 Computer Compl ex 

1010 Gause Boulevard 

Sl idel 1 , LA 70458 

U. S. Army Engineer Waterways Experiment Station 

Attention: WESER 

Post Off ice Box 631 

Vicksburg, MS 39180 

iii 
PREFACE 

This species profile is one of a series on coastal aquatic organisms, 

principally fish, of sport, commerci a1 , or ecological importance. The profiles 

are designed to provide coastal managers, engineers, and biologists with a brief 

comprehensive sketch of the bi 01 og ical characteristics and environmental requirements of the species and to describe how populations of the species may be 

expected to react to environmental changes caused by coastal devel opment. Each 

profile has sections on taxonomy, 1 i fe history, ecological role, envi ronmental 

requirements, and economic importance, if appl icabl e. A three-ring binder is 

used for this series so that new profiles can be added as they are prepared. This 

project is jointly planned and financed by the U.S. Army Corps of Engineers and 

the U.S. Fish and Wildlife Service. 

Suggestions or questions regarding this report should be directed to: 

Infonnation Transfer Speci a1 ist 

National Coastal Ecosystems Team 

U.S. Fish and Wildlife Service 

NASA-Sl idel 1 Computer Compl ex 

1010 Gause Boulevard 

Sl idel 1 , LA 70458 

U. S. Army Engineer Waterways Experiment Station 

Attention: WESER 

Post Office Box 631 

Vicksburg, MS 39180 
CONTENTS 

Page 

PREFACE .................................. ii i 

CONVERSION TABLE ............................. v 

ACKNOWLEDGMENTS .............................. v i 

NOMENCLATURE/TAXONOMY /RANGE ........................ 1 

MORPHOLOGY /I DENTIF ICATION A1 DS ...................... 1 

REASON FOR INCLUSION IN SERIES ...................... 3 

LIFE HISTORY ............................... 3 

Spawning ................................ 4 

Larval (Leptocephalus) Stage ...................... 5 

Glass Eel Stage ............................. 6 

Elver Stage ............................... 6 

Yellow Eels and Silver Eels ....................... 7 

GROWTH CHARACTER IST ICS .......................... 8 

COMMERCIAL AND SPORT FIS HER1 ES ...................... 9 

ECOLOGICAL ROLE .............................. 11 

ENVIRONMENTAL REQUIREMENTS ........................ 12 

Temperature ............................... 12 

Sal ini ty ................................ 12 

Dissolved Oxygen ............................ 13 

Habitat Structure ............................ 13 

River and Tidal Currents ........................ 13 

Contaminants .............................. 13 

Environmental Factors and Sex Determination ............... 14 

LITERATURE CITED ............................. 15 
CONVERSION FACTORS 

Metric to U.S. Customary 

mill imeters (mm) 

centimeters (cm) 

meters (m) 

ki 1 ometers ( km) 

square meters (m2) 10.7 6 

square ki 1 ometers ( km2) 0.3861 

hectares (ha) 2.471 

To Obtain 

inches 

inches 

feet 

mil es 

square feet 

square miles 

acres 

liters(1) , cubic meters (m ) 

cubic meters 

0.2642 gal 1 ons 

35.31 cubic feet 

0.0008110 acre- feet 

mil 1 igrams (mg) 0.00003527 ounces 

grams (g) 0.03527 ounces 

kilograms (kg) 2.205 pounds 

metric tons (t) 2205.0 pounds 

metric tons 1.102 short tons 

ki 1 ocal ories ( kcal ) 3.968 British thermal units 

Celsius degrees 1.8(C0) i- 32 Fahrenhei t degrees 

U.S. Customary to Metric 

inches 25.40 

inches 2.54 

feet ( f t) 0.3048 

fa thoms 1.829 

miles (mi) 1.609 

nautical miles (nmi) 1.852 

2 

square feet (ft ) 

acres 2 

square miles (mi ) 

gal 1 ons ( gal ) 3.785 

cubic feet (ft3) 0.0283 1 

acre- feet 1233.0 

ounces (02) 28.35 

pounds (Ib) 0.4536 

short tons ( ton) 0.9072 

British thermal unit (Btu) 0.2520 

mil 1 imeters 

centimeters 

meters 

meters 

kil ometers 

ki 1 ometers 

square meters 

hectares 

square ki 1 ometers 

1 i ters 

cubic meters 

cubic meters 

grams 

ki 1 og rams 

metric tons 

ki 1 ocal ories 

Fahrenheit degrees 0.5556(F0 - 32) Cel s ius degrees 
ACKNOWLEDGMENTS 

Dr. Gene He1 frnan, Earl Bozman, and Doug Facey, University of Georgia, and 

Dr. Arnold G. Eversole, Clernson University, reviewed earlier drafts of this 

Species Profile and provided current information that otherwise could not have 

been incl uded. 
I 

Figure 1. American eel. 

AMERICAN EEL 

Scientific name . . Anguilla rostrata 

Preferred common name . . . American 

eel (Figure 1) 

Other common names . . . . . Anguil ley 

ye1 1 ow eel , green eel , black eel , 1 ittle eel, bronze eel, glass 

eel , si 1 ver eel, river eel 

Class . . . . . . . . . . Osteichthyes 

Order . . . . . . . . . Anguilliformes 

Family . . . . . . . . . Anguillidae 

Geographic range: Mu1 ts or various 

developmental stages occur i n 

freshwater rivers, coastal 

waters, and the open ocean from 

the southern tip of Greenland, 

Labrador, and Newfoundland southward along the Atlantic coast of 

North America, into the Gulf of 

Mexico as far as Tampico, Mexico, 

and in Panama, the Greater and 

Lesser Antilles, and southward to 

the northern portion of the east 

coast of South America (Tesch 

1977). The species is abundant 

from Maine to Mexico, is resident 

in the Mississippi Valley, and 

occurs in the West Indies and 

Bermuda (Figure 2). Bertin 

(1956) reported the latitudinal 

range for the American eel as 5" 

to 62' N. It occurs in warm 

bracki sh and freshwater streams, 

estuaries, and coastal rivers. 

The American eel sometimes occurs 

in cold freshwater trout streams 

in mountainous regions. Adults 

are occasionally found in landlocked lakes, primarily in the 

Northeastern United States. Its 

distribution has increased 

because of its hardiness and the 

ease with which it can be transplanted into new habitats. 

MORPHOLOGY/IDENTIFICATION AIDS 

American eels undergo a series of 

morphological changes in their 1 i fe 

cycle; these characteristics are 

presented in the LIFE HISTORY section. 

The fol lowing material was summarized 

primarily from Fahay (1978) and Tesch 

(1977). 
Figure 2. Major rivers that support the American eel in the South Atlantic 

Bight. Eels also are common in other freshwater tributaries, and in bays and 

estuaries. 
The body is elongate and snakelike (Figure 1). The dorsal and anal 

fins are confluent with the rudimentary caudal fin. Pectoral fins are 

present, but ventral (pelvic) fins are 

absent. The body is covered by minute 

embedded scales (often causing specimens greater than 3 to 5 years of age 

to appear scaleless). The lateral 

1 ine is we11 developed. The mouth is 

terminal ; jaws contain bands of small, 

pectinate or setiform teeth. A long 

tooth patch also occurs on the vomer. 

The number of vertebrae ranges from 

103 to 111 but usually is 106 to 108 

(Schmidt 1913). 

No other anguill id eels occur in 

North American coastal waters, but the 

American eel 's spawning grounds coincide closelv with those of the Europe- 

&e simi lar; however, the ~uropean eel 

has 111-119 vertebrae (mean = 115). 

Ege (1939) presented comprehensive 

morphological data for A. rostrata. 

Some authors have argued That European 

and American eels should be regarded 

as geographical variants of the same 

species, but this is not generally 

accepted at present (Fahay 1978). 

No data are available that 

conclusively point to geographic vari - 

ations in morphology, and no subpopulations have been distinguished. 

Koehn and Williams (1978) noted 

protein differences among juvenile 

eels collected from different locations along the At1 antic seaboard, but 

they concluded that the differences 

were due to variations in selective 

pressures among environments in which 

growth occurred. 

REASON FOR INCLUSION IN SERIES 

The herican eel supports valuable commercial and 1 imi ted recreational fisheries throughout most of 

its range. Harvested adults often are 

shipped alive or frozen to Europe 

where they frequently are smoked 

before marketing, and a fishery for 

elvers (immature eels typically less 

than 60 mm long) has recently begun in 

the South Atlantic Bight. Elvers are 

shipped to Japan where they are 

cultured in ponds. Pond rearing of 

eels in the United States is in a 

developmental stage, and there is a 

potential for development and expansion of an eel culture industry. 

The American eel is an important 

prey species of larger marine and 

freshwater fishes and is a predator on 

a variety of other animals including 

commercially important crabs and 

clams. Eels contribute to the loss of 

nutrients from freshwater rivers and 

lakes because of their great organic 

intake, large numbers, lengthy stay in 

freshwater, and subsequent migration 

to sea (Barila and Stauffer 1980). 

Alteration of river flow into estuaries could affect upstream migration 

of immature eels. 

LIFE HISTORY 

The life cycle of the American 

eel includes oceanic, estuarine, and 

riverine phases (Figure 3). Many 

details of its life history are only 

generally understood or have been 

i nferred from know1 edge of the congeneric European eel. Little has been 

reported on eel 1 ife history in rivers 

along the South Atlantic Bight; much 

of the information presented below is 

based on work in Middle and North 

Atlantic areas of the United States 

and Canada. 

Different stages of the eel Is 

life cycle are known by a variety of 

common names that are used throughout 

the scientific 1 i terature. The larvae 

are called leptocephali (sing. = 

leptocephalus) ; they first metamorphose into unpigmented "glass eels" 

that gradual 1y devel op pigmentation 

and are then called elvers. Elvers 

migrate into freshwater where they 

remain several (sometimes many) years 

and are called yellow eels. Yellow 
metamorphoslr 

SILVER EEL 

YELLOW EEL 

migration 

metamorphosis 

GLASS EEL/ELVER 

EGO 

SPawnlng 

- - 

Figure 3. Diagrammatic representation 

of the American eel Is 1 ife history. 

eel s may be sexually undifferentiated 

(gonads contain no definable gametes), 

hermaphroditic (oogonia .and spermatogonia present), or sexual 1y differentiated (females with oogonia; males 

with spermatogonia present), but none 

of these stages are capable of reproduction and, hence, all yellow eels 

are immature. Maturation is accompanied by changes in body color and 

morphology; maturing eels mi grate 

downriver and through the ocean to the 

spawning grounds and are known as 

"bronze eels" or ''silver eels." 

Details of life history for these 

stages are provided below. 

Spawning 

The Pmerican eel is catadromous. 

It spawns in the sea but spends most 

of its life in rivers, freshwater 

1 akes, and sometimes estuaries. After 

maturity it returns to the sea (Figure 3). The age at maturity has not 

been well defined; Fahay (1978) reported that maturation occurred beyond 

age I11 for males and at age IV-VII 

for females fran northerly popul ations, but recent data suggest that 

maturation is more rapid in populations along the South Atlantic Bight. 

He1 fman and Bozeman (unpubl ished MS: ') 

c o l l e c t e d sexual ly diffe5entiated 

males and females at age I11 in the 

Altamaha River, Georgia, and concluded 

that females there may have matured at 

earlier ages and smaller sizes than 

eels in northern areas whereas males 

matured at the same age and size as 

northern eel s. Hansen and Eversole 

(in press) and Harrell and Loyacano 

(1980) c o l l e c t e d differentiated males 

and females as young as age I1 and 

111, respectively, in the Cooper 

River, South Carolina. 

Prior to seaward migration in the 

fa1 1 , maturing eels begin a metamorphosis into the silver eel stage, as 

described in the Yellow and Silver 

Eels section. 

Eels mi grating from Chesapeake 

Bay are in a more advanced state of 

metamorphosis than those migrating 

from Canadian waters; this supposedly 

enables eels to reach the southerly 

spawning grounds in relatively similar 

stages of maturity (Wenner and Musick 

1974). The difference in the extent 

of metamorphosis between migrating 

eels from Canada and Chesapeake Bay 

suggests that migrating eels in South 

Atlantic rivers could be even further 

developed than those in Chesapeake Bay 

at the outset of migrationgi Helfman 

and Bozeman (unpublished MSI ) concluded that reproductive migrations from 

the A1 tamaha River, Georgia, occurred 

during late winter or early spring, 

but Hansen and Eversole (in press) and 

Michener (1980) indicated that migrations occurred during the fall in the 

Cooper River, South Carolina. 

l~o~ulation attributes of Ameri - 

can eels in a Georgia river. G. S. 

Helfman and E. L. Bozeman, Department 

of Zoology and Institute of Ecology, 

University of Georgia, Athens, GA 

30602. Submitted to Trans. Am. Fish. 

soc. 

2~n this case, age is the number 

of years spent in freshwater (see the 

GROWTH CHARACTERISTICS section for 

aging methods). 
Few details are known about the 

oceanic spawning migration of the 

American eel. The first collections 

of adults in offshore waters were 

reported by Wenner (1973) in the open 

ocean southeast of Cape Cod, Massachusetts, east of Assateague Island, 

North Carolina, and southeast of 

Chesapeake Bay. The means by which 

eels navigate to spawning grounds are 

poorly understood. Mi 1 es (1968) 

concluded that the eel was capable of 

noncelestial orientation (southward), 

and Rommel and Stasko (1973) indicated 

that eels may use geoelectric fields 

generated by ocean currents to navigate. Robins et al. (1979) photographed two adult An uilla eels on the 

floor of the Atlantic _ea cean in the 

Bahamas at depths of about 2000 m, and 

although it was impossible to determine if the specimens were European or 

Ameri can eel s , the authors be1 ieved 

them to be prespawning - A. rostrata. 

Stasko and Rommel (1977) tracked 

five migrating eels in the lower St. 

Croix River Estuary, New Brunswick, 

Canada, and found that one eel moved 

25 km in 20 hr and another moved 38 km 

in 40 hr. Eels they studied showed 

considerable vertical movements in the 

water column; behavior did not change 

with die1 or tidal cycles. Silver 

European eels traveled at 44 km per 

day when migrating to spawn (Tesch 

1977). Edel (1976) believed that the 

depth at which American eels migrate 

in the ocean varied with light intensity so that swimming depth would vary 

with turbidity of the water. 

Spawning by Ameri can eel s has 

never been directly observed, and 

spawning areas have been delineated on 

the basis of collections of larvae. 

Spawning apparently occurs in the 

Sargasso Sea as early as January or 

February and may continue into August. 

Tesch (1977) summarized work by 

Schmidt (1923), Vladykov (1964), Smith 

(1968), and Vladykov and March (1975), 

and showed a spawning zone south of 

Bermuda and north of the Bahamas that 

is centered at about 25" N and 69" W. 

The youngest stages of American eel 

larvae coexist with European eel 

larvae, but American eel larvae predominate west of 62" W and south of 

24" N (Fahay 1978). Fahay also 

reported that A. rostrata larvae have 

not been foundeast W. 

The depth at which spawning 

occurs is not known, but Taning (1938) 

reported that larvae collected near 

Bermuda occurred only at depths 

between 550 and 2200 m. Egg diameter 

of A. rostrata is about 1.1 mm (Tesch 

1977). Incubation periods of American 

eel eggs are not known. 

Fecundity is 10 to 20 million 

eggs per female (Vladykov 1955, cited 

by Fahay 1978; Eales 1968). Relationships between eel size and fecundity 

for 21 eels were reported by Wenner 

and Musick (1974) as: 

log F = -4.29514 + 3.74418 log TL, or 

log F = 3.2290 + 1.1157 log W; 

Where F = number of eggs per female, 

TL = total length, mm, and 

W = total weight, g. 

Adult eels presumably die after 

spawning. None have been observed to 

migrate up rivers, and occurrences of 

spent eels have not been reported. 

Larval (Leptocephal us) stage 

Hatching occurs from February 

through August (Vladykov and March 

1975; Fahay 1978), and the larval 

stage lasts about 1 year or perhaps 

longer. The body is lanceolate in 

shape, sharply pointed at both ends, 

and deepest at the middle (see Tesch 

[I9771 or Fahay [I9781 for illustrations). The size at hatching has not 

been described, but Schmidt (1925) 

collected 7- to 8-mm larvae in February. The smallest larvae collected by 

Vladykov and March (1975) and Smith 

(1968) were 12 mn and 17 mm, 

respectively. 
During the leptocephalus stage, 

the larvae grow and are transported by 

ocean currents. Larvae c o l l e c t e d by 

Schmidt (1925) were 7 to 8 mm long in 

February, 20 to 25 mm in Apri 1 , 30 to 

35 mm in June, 40 mm in July, 50 to 55 

mm in September, and 60 to 65 mm by 

the end of the first year of life. 

The 1 ongest leptocephal us col 1 ected by 

Vladykov and March (1975) was 69 mm. 

Vladykov and March (1975) suggested that larval A. rostrata may 

spend more than 1 year in the sea. 

Limited evidence a1 so suggests that 

some eels remain in the leptocephalus 

stage for more than 1 year. Smith 

(1968) reported a 50-mm 1 eptocephal us 

near the spawning grounds during 

April. This larva was too long to 

have been spawned in the immediate 

season (Fahay 1978). 

The Northern Equatori a1 Current 

and the Gulf Stream transport larvae 

northward along the eastern seaboard 

of North America. Sampling has shown 

that larvae are abundant in the 

Florida Straits and in the area 

between Bermuda and the Bahamas from 

April through August (Smith 1968), and 

Eldred (1971) found A. rostrata leptocephali in the Gulf of Mexico and 

Yucatan Straits, but mechanisms by 

which the larvae are dispersed into 

the Gulf of Mexico and southward to 

the coast of South America have not 

been determi ned. 

Glass Eel Stage 

During the pelagic phase, leptocephal i reach a size and physiological 

state at which they begin to metamorphose. The early stages of this transition involve: (1) shrinkage in size 

and weight, primarily due to a reduction in water content; (2) changes in 

the configuration of the head and 

jaws ; and (3) accelerated development 

of the digestive system (Fahay 1978). 

After these changes occur, the eels 

are similar in overall morphology to 

yellow eels, but they lack external 

pigmentation and are called "glass 

eels." Glass eels actively migrate 

toward land and freshwater, and as 

they approach coastal areas, external 

pigmentation develops and the body 

becomes uniformly dark brown. At this 

stage, metamorphosis is complete and 

the eel is now called an elver. 

Elver Stage 

Most elvers move into coastal 

areas, estuaries, and up freshwater 

rivers in the late winter or early 

spring . Vl adykov (1966) suggested 

that elvers generally arrive in 

southern estuaries earlier and at 

smaller sizes than in the north, but 

catch records indicate considerable 

overlap in the timing of shoreward 

movements along the Atlantic coast. 

Such movements have occurred during 

April in Narragansett Bay and near 

Washington, D. C. ; February and March 

in Delaware; January in Long Island 

Sound and Rhode Island estuaries; off 

Nova Scotia in A ri 1, and the Bay of 

Fundy in summer [Fahay 1978). In the 

South Atlantic, migrating elvers have 

been collected during January in 

Florida and South Carolina and during 

January through May, with peak catches 

in March and Apri 1 , in North Carolina 

(Smith 1968; Hornberger 1978, cited by 

Sykes 1981; Sykes 1981). Elvers 

moving into South Atlantic estuaries 

and rivers typically are 46 to 60 mm 

long. He1 fman and Bozernan (unpublished MS.3) collected 49- to 56-mm 

glass eels from the A1 tamaha River 

Estuary, Georgia, in 1 ate February; 

daily growth rings on the otoliths 

showed 250 to 300 days of age. 

Small numbers of elvers regularly 

arrive in estuaries in the fall, and 

Fahay. (1978) suggested that these 

3~rowth rates of American eels in 

a Georgia estuary. G. S. Helfman and 

E. L. Bozeman, Department of Zoology 

and Institute of Ecology, University 

of Georgia, Athens, GA 30602. 

Submitted to U.S. Natl. Mar. Fish. 

Serv. Fish. Bull. 
"early" arrivals may be the earliest 

spawned individuals or a segment of 

the main body of leptocephali that is 

moved northward more quickly by 

localized water currents. A1 ternatively, these elvers may be "late" 

arrivals produced from leptocephali 

that did not metamorphose during the 

previous wi nter/spring. 

Elvers occupy f reshwater-sal twater transition areas before ascending rivers. During this period, 

elvers are active at night and burrow 

or rest in deep water during the day 

(Dee1 der 1958). This nocturnal 

behavioral pattern causes the elvers 

to be transported upstream by flood 

tides that occur at night, and they 

drift back down during ebb (Fahay 

1978). Pacheco and Grant (1973) 

reported simi lar patterns for elvers 

at the mouth of the Indian River, 

Delaware, and Tesch (1977) noted 

equivalent behavior by European eel 

elvers. He also indicated that - A. 

anguilla elvers orient to river 

currents for upstream movement, and if 

the current becomes too weak or too 

strong (velocities not specified), 

eels may move into backwater areas, 

severely delaying upstream progress. 

Basic similarities in behavior of 

European and American eel elvers 

suggest that A. rostrata elvers would 

be similarly affected by extremely 

fast or slow river currents. 

Fahay (1978) stated that as 

upstream migration to freshwater 

streams begins, males tend to stay in 

brackish water while females move into 

fresher water, but this is based on 

observed distribution patterns of 

older eels rather than direct observation of elver behavior. When elvers 

cease their migration, they begin a 

growth and differentiation period in 

which they are called yellow eels. 

Yellow and Silver Eels 

Many authors (e.g., Bigelow and 

Schroeder 1953; Vladykov 1966) have 

-stated that yellow eel females occur 

primarily in freshwaters whereas males 

are generally found in salt- or brackish waters. Dolan and Power (1977), 

however, concl uded that an extensive 

review of 1 iterature did not support 

this "female-freshwater, male-saltwater" theory. Recent studies continue to be inconsistent- Helfman and 

Bozeman (unpublished MS~) found that 

females represented 94% of the sexually differentiated yellow eels 

col lected from freshwater areas of 

the A1 tamaha River in Georgia and 64% 

of the differentiated yellow eels in 

estuarine areas. However, collections 

of eels from the Cooper River, South 

Carolina, showed a minor variation of 

sex ratio from fresh- to saltwater. 

Females contributed 97%, 95%, and 93% 

of the differentiated eels collected 

from fresh-, brackish-, and saltwater 

areas, respectively (Harrel 1 and 

Loyacano 1980; Michener 1980; Hansen 

and Eversol e, in press). 

In addition to the freshwatersaltwater variation in the sex ratio, 

a geographic variation in the distribution of the sexes has been hypothesized. Vladykov (1966) stated that 

male eels predominate in middle and 

southern Atlantic populations (New 

Jersey to Florida) whereas females 

predominate from New York to Newfoundland. Work in the Cooper River, South 

Carolina, and the Altamaha River, 

Georgia (described in the preceding 

paragraph), however, does not support 

this hypothesis. Vl adykov be1 ieved 

that a latitudinal change in sex 

composition was related to the sizedifferences in elvers along the coast, 

and he said that smaller elvers 

entering southern streams supposedly 

become males whereas the larger elvers 

entering northern systems probably 

develop into females (see the ENVIRONMENTAL REQUIREMENTS section for 

alternate explanations). As with 

freshwater-sal twater variations in the 

sex ratio, Dolan and Power (1977) 

suggested that latitudinal variations 

were not well documented. They stated 

that the apparent geographic distribution of sex in the American eel could 
-'be a result of incorrect sexing, 

selectivity of sampl i ng gear and the 

possible exclusion of smaller males, 

and the assumption that characteristics for the American eel would 

parallel those of the European eel. 

The gender of adult eels is not external ly apparent, and gonadal tissues 

shoul d be exami ned hi st01 ogical ly to 

avoid errors in sex determination 

(Dolan and Power 1977; Facey and LaBar 

1981). 

Age at maturity and other aspects 

of reproduction are described in the 

Spawning section. Sexual differentiation does not occur until eels reach 

about 200 mm in length (Fahay 1978). 

Prior to completion of the differentiation process, some eels possess 

gonads containing male and female 

gametes (juvenile hermaphroditism; 

Tesch 1977), but after gender is 

established, it does not change (Fahay 

1978). He1 fman and Bozeman (unpub1 i shed MS.~) reported that differenti - 

ated and undifferentiated ye1 low eels 

in the Altamaha River, Georgia, overlapped considerably in size: undifferentiated eels were as large as 363 

mm at age VII; differentiated males 

were as small as 209 mm at age 111; 

differentiated females were as small 

as 186 mm at age 111; and hermaphrodites, which constituted less than 1% 

of the collections, ranged from 267 to 

328 mm at ages IV to V. Hansen and 

Eversol e (in press) reported simi 1 ar 

overlap in size and age of differentiated and undifferentiated eels in the 

Cooper Ri very South Carolina. 

Yellow eels begin to metamorphose 

into silver eels in the fall prior to 

seaward migration. The metamorphosis 

includes: (1) color change (to a 

metal 1 icy bronze-black sheen; pectoral 

fins change from yellow-green to 

black); (2) fattening of the body; (3) 

thickening of the skin; (4) enlargement of the eyes (macrophthalmia) and 

changes in visual pigments in the eye 

in preparation for migrating at dark 

ocean depths (Vladykov 1973; Beatty 

1975); (5) increased length of capillaries in the rete in the swim bladder, which also may be an indication 

of migrating at great depths (Kleckner 

and Kruger 1981); and (6) degeneration 

of the digestive tract. Silver 

(metamorphosed) eels appear to be 

better adapted to swimming than yellow 

eels (Holmberg and Saunders 1979). 

Presumably, ovaries mature fully only 

after the migrating female reaches 

saltwater (Fahay 1978). 

GROWTH CHARACTERISTICS 

Larvae typically reach 40 to 70 

mm after 1 year of growth; Hornberger 

et a1 . (1978) collected glass eels 

from the Cooper River, South Carolina, 

from January through April that averaged 55 mm in length and ranged from 

45 to 65 mm (see the Larval Stage 

section for growth within the first 

year). The metamorphosis into elvers 

is accompanied by a decrease in length 

and weight due to reduction in water 

content of the body. Elvers grow 

slowly and reach about 127 mm after 

the first year in freshwater (Bigelow 

and Schroeder 1953). Yellow eels 

typically grow slowly but can achieve 

weights up to 6.8 kg; females caught 

from the St. Lawrence River range from 

960 to 1270 mm long and 0.9 to 4.5 kg 

(Fahay 1978). Females typical ly 

grow to a larger size than males. 

Eels have been aged from otoli ths 

and scales. Otoliths in eels consist 

of a translucent nucleus (formed at 

sea) surrounded by broad opaque summer 

zones and narrow translucent winter 

zones (Harrel 1 and Loyacano 1980). 

Harrell and Loyacano (1980) used 

otoliths to age American eels from the 

Cooper River in South Carolina. 

Distinct annuli were present in 410 of 

415 otoliths examined; the opaque ring 

first appeared in May and the translucent zone was first evident in November. The third opaque ring corresponds to the eel 's first growing 

season in freshwater. Eels in Canadian waters formed their first scales 

at 160 to 200 mm during their third to 
fifth year of 1 ife and the scales 

formed annual rings in subsequent 

winters (Smith and Saunders 1955). 

Thus, in northerly areas, age in years 

generally will be the number of scale 

rings plus three. The eel, however, 

continues to form scales as it grows, 

leading to a situation in which different scales from the same fish can 

give different ages (Smith and 

Saunders 1955). 

Growth rates within year classes 

are highly variable, leading to considerable variation in length at age 

and poor predictability of age from 

size. Lengths of eels at various ages 

in northerly populations are summarized in Table 1. Few growth data for 

eels in South Atlantic States have 

been reported. Harrel 1 and Loyacano 

(1980) reported that eels in the 

Cooper River grew 45 to 52 mm per year 

for ages II-XV15 Helfman and Bozeman 

(unpubl ished MS. ) tagged ye1 low eel s 

in a Georgia estuary and used recapture data to estimate growth rates. 

There was a slow-growth period during 

November through February when the 

fish grew an average of 0.025 mm per 

day. They grew more rapidly during 

the rest of the year, gaining an 

average of 0.220 mm per day. These 

rates produced an average annual 

length increase of 57 to 63 mm. 

Maximum age of yellow eels collected from northern rivers has been 

reported to be 15 to 20 years (Fahay 

1978). Land1 ocked eel s 1 i berated as 

elvers in Sherman Lake, Michigan, 

1 ived 35 to 40 years (Vladykov 1973). 

Accuracy of estimates of the age at 

maturity may be affected by problems 

with aging techniques. 

COMMERCIAL AND SPORT FISHERIES 

Prior to the 19701s, the eel 

fishery in the South Atlantic Bight 

primarily provided live bait to sport 

Table 1. Leqgths of American eels at various ages. 

lvtal length (cnl) at various locations 

Age Bill's Lake Crec Lake Lake New Rhode Delaware South 

(yr) New 8runswick1 ~ewfoundland~ OntarioC ~ersey~ 1slande ~iverf ~arolina~ 

V I 24-51 

VII 34-56 

VIlI 38-57 

1X 38-57 

X 49-57 

XI --- 

XI1 --- 

Xlll --- 

XIV --- xv --- XVI --- XVI I --- 

XVIII --- XI X --- 

:smith and Saunders 1955. 

Gray and Andrews 1971. 

;tlurley 1972. 

,Ogden 1970. 

,Bleder 1971. 

i~ohnson 1974. 

data combined from Harrell 1977. Hansen 1979, and Michener 1980. 
fishermen and secondarily provided 

bait used in blue crab (Cal linectes 

sapidus) traps. A larger commercial 

fishery for eels in, the reqion is 

devel oping , and gl ass eel s, el vers, 

yellow eels, and silver eels are 

exploited. Techniques for capturing 

and growing elvers to marketable sizes 

are being developed (Easley and Freund 

1977). 

The European market has been the 

major outlet of U.S. yellow and silver 

eel landings (Fahay 1978). Eels are 

hardy and can be densely packed and 

shipped alive if they are kept moist, 

cool , and supplied with oxygen. Live 

eels are preferred in Europe, but many 

are shipped frozen. 

Commercial fishermen use a 

variety of methods, including 1 ift 

nets, drift nets, traps, weirs, otter 

trawls, pound nets, fyke nets, spears, 

handlines, eel pots, haul seines, and 

gill nets (Fahay 1978). The fyke net 

is the major gear used in North 

Carolina to exploit eels that are 

moving seaward in late summer or early 

fall to begin their spawning migration. Yellow eels in fresh- or 

brackish waters are primarily taken 

with baited traps or eel pots. 

Fahay (1978) summarized catch 

statistics along the Atlantic coast 

for 1955-73. Landings from the Middle 

Atlantic (New Jersey-Virginia) consistently exceeded those from the North 

Atlantic and South Atlantic States, 

but landings from Southern States 

increased in the late 1960's and early 

1970's. For 1955-64, the South 

Atlantic harvest averaged about 37,000 

kg annually, and for 1965-73, annual 

landings were about 630,000 kg. The 

value of these landings ranged from 

$8,000 to $83,000 annually for 1965- 

73. 

Eel harvest and value in North 

Carolina dramatical ly increased in the 

1960's and 1970's (Easley and Freund 

1977). For 1960-70, average annual 

landings were 17,800 kg valbed at 

$O.ll/kg; in 1972-73, the price rose 

to $0.35/kg; and in 1973-76, landings 

averaged 151,200 kg at a price of 

$0.92/kg. Catch value ranged from 

$0.95 to $1.85/kg and harvest averaged 

285,000 kg for 1977-79 (Keefe 1982). 

The bulk of the North Carolina landings is taken from northeastern 

coastal areas. 

In Georgia, commercial fishing 

for eels in freshwater was effectively 

prohibited prior to 1980 because of 

restrictions against using traps in 

inland waters. Harvest in 1979 was 

about 3,900 kg (Helfman, unpublished 

MS~). After a freshwater trap fishery 

was allowed in 1980, harvest was 

50,000 kg, but landings in 1981 and 

1982 were 5,500 kg and 16,800 kg, 

respectively. The 1982 catch was 

valued at $35,000 or $2.08/kg. 

A fishery for European eel elvers 

began in Europe during the late 1960's 

to supply Japan's demand for young 

eels to use in pond aquaculture. 

Experimental work on techniques for 

capturing migrating American eel 

elvers has been done in the St. Johns 

Ri very Florida (Topp and Raul erson 

1973). Elvers were packed live in 

boxes and shipped to Japan, where 

prices paid for local Anguilla 

ja onica elvers were $7/kg in 1965-68, + 300/kg in 1969, and $330 to $925/kg 

in 1971-73 (Fahay 1978; Egusa 1979). 

Prices paid for European eel elvers in 

Japan initial ly were equivalent to 

those paid for local elvers, but 

European eels were inferior in the 

pond culture systems (poor growth and 

disease problems); in 1973, the 

Japanese paid only $30 to $50/kg for 

European elvers (Egusa 1979). 

Accounts of American eel performance 

in Japanese eel culture were not 

1 ocated. 

4 Development and expansion of the 

fishery for American eels in Georgia. 

G. S. He1 fman , Department of Zoo1 ogy, 

University of Georgia, Athens ,. GA. 

30602. Project summary, University of 

Georgia Sea Grant Program, 1983. 
The feasibility of commercial 

grow-out operations in North Carol ina 

was assessed by Easley and Freund 

(1977). Interest in culturing was 

stimulated by rising prices noted 

above during the late 1960's and early 

19701s, but considerable refinement of 

techniques is needed. Development of 

eel aquaculture has focused on methods 

for collecting elvers and on physical 

features of grow-out systems. Hormone 

injections can be used to induce 

maturation of female American eels 

(Edel 1976), but proper spawning conditions are unknown, and eel culture 

remains dependent on capturing wild 

elvers. Hi nton and Eversol e (1978, 

1979, 1980) evaluated the toxic 

effects of chemicals commonly used in 

aquaculture to glass eels (mean length 

of 55 mm), elvers (mean length of 97 

mm) , and yellow eels collected from 

South Carolina rivers. 

The South Atlantic States have 

few, if any, restrictions specifically 

designed to regulate ye1 low or silver 

eel harvest, but fisheries for ye1 low 

eels often have been nonexistent or 

minimal because of prohibitions 

against using traps in freshwaters (as 

mentioned above for Georgia). Such 

restrictions generally are intended to 

prevent incidental catches of sport 

fishes. Mouth diameter and wire mesh 

sizes of traps are regulated in some 

areas to reduce catches of other 

species (e.g., Hornberger et al. 

1978). Elver fishing is illegal in 

Georgia., 

Estimates of density, mortal i ty, 

or other vital statistics of eel 

stocks generally have not been reported, and factors regulating survival or 

stock size have not been evaluated. 

Helfman (unpubl ished MS?) suggested 

that the eel's long life in freshwaters may make the stocks prone to 

1 ocal overharvest. Keefe (1982) 

suggested that recent declines in 

catch per unit effort of eels in North 

Carolina indicated overharvest. 

Because all American eels spawn in the 

Sargasso Sea and there apparently are 

no genetically distinct stocks or 

subpopulations (Koehn and Nil 1 iams 

1978), overharvest in one region could 

affect recruitment in other regions. 

Neverthel ess, some management pol icies 

a1 low or encourage 1 ocal heavy exploitation of migrating silver eels or 

elvers under the assumption that the 

numbers of elvers returning in later 

years wi 11 be mai ntained by escapement 

of spawning stock from other areas. 

No major sport fishery for 

American eels exists in coastal rivers 

of the South Atlantic Bight, but the 

species is caught incidentally by 

anglers in estuaries and rivers. 

ECOLOGICAL ROLE 

Yellow eels are nocturnal and a 

significant portion of their feeding 

occurs at night. The diet is diverse 

and generally includes nearly all 

types of aquatic fauna that occupy the 

same habitats. Eels swallow some 

types of prey whole, but they also can 

tear pieces away from larger dead 

fish, crabs, or other items. Eels in 

freshwater feed on insects, worms, 

crayfish and other crustaceans, frogs, 

and fish whereas elvers in saltwater 

are pl an kt ivorou s. El vers col 1 ected 

from the Cooper River, South Carolina, 

consumed aquatic insects (mainly 

chironanid 1 arvae and adults), cl adocerans, amphipods, and fish parts 

(McCord 1977). The diet of yellow 

eels from the Cooper River varied with 

eel size and season. Intermediate 

size classes contained more types of 

food than elvers or maturing eel s; 

fish occurred in the diet primarily in 

winter and spring whereas insects and 

mollusks were eaten from spring 

through fa1 1. Crustaceans, bivalves , and polychaetes were the major prey of 

eels in lower Chesapeake Bay; blue 

crabs and soft clams were significant 

prey (Wenner and Musick 1975). Eels 

shorter than 40 cm in New Jersey 

streams mainly ate aquatic insects 

whereas larger eels fed mostly on fish 

and crustaceans (Ogden 1970). Most 
fish eaten were bottom dwell ers, 

reflecting the eels' tendency to 

remain near the bottom. Fahay (1978) 

concluded that eels depend more on 

scent than sight to obtain food. 

Little has been pub1 i shed about, 

predation on eels. Hornberger et al. 

(1978) reported that elvers and small 

yellow eels were eaten by largemouth 

bass (Micro terus salmoides) and 

striped *esm in the 

Cooper Ri ver, South Carol i na, but eels 

never were a major component of these 

predators ' diets. Leptocephal i , glass 

eels, elvers, and small yellow eels 

probably are consumed by a variety of 

other predatory fishes; grown eels are 

eaten by other species of eels and by 

gulls, bald eagles, and other fisheating birds (Sinha and Jones 1967; 

Seynou r 1974). 

Crane and Eversole (1980) found 

no parasites on glass eels migrating 

into the Cooper River, South Carolina, 

but four genera of protozoans (Trichodina, Ichth o hthirius, Myxidium, and 

~bolkpecies of monogenetic trematode (Gyrodactyl us 

anguillae) were found on elvers. 

Crane and Eversole (in press) reported 

that 214 of 218 yellow eels collected 

from brackish waters of the Cooper 

River, South Carol ina, were parasi tized by one or more of 22 helminth 

species. Parasites of American eels 

in Quebec included protozoans, trematodes, nematodes, cestodes, and 

copepods (Hanek and Molnar 1974). The 

myxosporidian protozoan, Myxidium 

zelandicum, has been found in the 

kidneys and on the gills of A. 

rostrata (Komourdjian et a1 . 1977). 

ENVIRONMENTAL REQUIREMENTS 

Temperature 

The eel's broad geographic range 

and diverse habitats suggest flexible 

temperature requi rements. Elvers and 

yellow eels live in waters ranging 

from cold, high-elevation or highlatitude freshwater streams and lakes 

to warm, brackish coastal bays and 

estuaries in the Gulf of Mexico. 

Jeffries (1960) found elvers at 

temperatures as low as -0.8" C. 

Barila and Stauffer (1980) 

acclimated yellow eels to a range of 

temperatures between 6" C and 30" C 

and then measured preferred temperatures. A1 though preferred temperatures tended to increase with 

increased acclimation temperature, 

differences among groups were nonsignificant, and the authors reported a 

final temperature preference of 16.7" 

C. They also reported that feeding 

ceased at temperatures below 14" C. 

Marcy (1973) reported that American 

eels survived passage through the 

cooling system of a nuclear power 

plant, during which they were exposed 

to elevated temperatures for 1-1.5 hr. 

Pol uhowi ch (1972) suggested that the 

American eel 's mu1 tiple types of hemoglobins serve to maintain a relatively 

constant blood oxygen affinity when 

the eel is exposed to temperature 

changes. 

Sal i ni ty 

The mechanisms by which glass 

eels or elvers orient during their 

shoreward migration have not been 

described, but their movements 

probably are keyed to sal i ni ty 

gradients after they reach coastal 

waters. European glass eels and 

elvers become positively rheotactic 

when they first encounter freshwater 

that is mixed with seawater (Tesch 

1977); thus salinity as well as the 

current itself may provide the gradient for shoreward orientation. 

A1 terations of patterns or magnitudes 

of freshwater inflows to bays or 

estuaries could a1 ter sal inity regimes 

and thereby affect the number, timing, 

and spatial patterns of upstream 

migrations by elvers. 

As with temperature, salinity 

requirements of postlarval eels can be 

generally inferred as "broad" from the 
fact that the species occurs throughout a gradient of strictly fresh to 

brackish waters. Leptocephal i are in 

near-ionic equi 1 i brium with sea water 

(Hulet et a1 . 1972). 

Dissolved Oxygen 

Dissolved oxygen requirements 

have not been thoroughly documented, 

but eels generally will select water 

with high oxygen tension (Hill 1969). 

Commercial shipping of live eels 

indicates that they are especial ly 

hardy. Elvers can be packed densely 

and shipped alive by being dampened 

but not covered with water because 

they can absorb 60% of required oxygen 

through their skin (Sheldon 1974, 

cited by Fahay 1978). Tesch (1977) 

stated : 

"The capacity of the adul t eel 

to survive in both air and water 

is associated with its ability to 

use both branchial and cutaneous 

modes of respiratory gas exchange. The eel survives better 

in air than in poorly oxygenated 

or polluted water ...." 

Habitat Structure 

Postlarval eels tend to be bottom 

dwellers and hide in burrows, tubes, 

snags, plant masses, other types of 

shelter, or the substrate itself 

(Fahay 1978). This behavior is 

reflected in their food habits, protects them from predators, and influences commercial fishing techniques. 

Few other freshwater fishes display 

simi 1 ar habitat use; therefore, interspecific competition for living space 

may be limited. The presence of soft, 

undisturbed bottom sediments is important to migrating elvers as shelter 

(see the Elver Stage section). Edel 

(1979) indicated that eels in his 

experimental systems were less active 

when shelter was present than when it 

was absent. Vladykov (1955, cited by 

Fahay 1978) reported that adult eels 

in northern habitats lie dormant in 

the bottom mud during winter. 

Ford and Mercer (1979) used markrecapture methods to obtain a population estimate of 350 yellow eels in a 

600-m section of a marsh creek in a 

Massachusetts estuary. They studied 

the behavior of yellow eels and found 

that eels shorter than 30 cm predominated in narrow, soft-bottomed, upper 

marsh creeks whereas those longer than 

30 cm predominated in wider, lower 

marsh creeks having mud and sand 

bottoms. Most eels had relatively 

small home ranges and rarely moved 

more than 100 m from the point at 

which they were initially caught. 

The authors believed that large eels 

may establish territories in lower 

marsh areas and thereby restrict 

smaller eels to smaller high marsh 

creeks. 

River and Tidal Currents 

The elver's nocturnal activity 

patterns and reliance on tides and 

river currents for upstream movement 

are presented in the LIFE HISTORY 

section. 

Movements of yellow eels in a 

tidal creek in Georgia were affected 

by tides and time of day (Helfman et 

al. 1983). Daytime movements of eight 

telemetered eels were restricted to 

the main creek channel, but at night 

the fish were near the mouths of 

feeder creeks at low tide or in 

flooded marsh areas during high tide. 

Helfman et a1 . (1983) termed this 

movement "a nocturnal activity pattern 

modified by tidal flow." They suggested that movements onto the marsh 

at night may have been foraging trips. 

Contaminants 

Little work has been done on 

American eels regarding toxic effects 

of pollutants or tolerance 1 imits. 

Tolerance would be expected to vary 

with developmental phase, and the 

eel Is 1 ong residence in freshwater 

rivers could lead to repeated doses of 

toxicants and accumulation to toxic 

1 eve1 s (Hol mberg and Saunders 1979). 
Work done by Hinton and Eversole 

(1978, 1979, 1980) on toxicity of 

aquaculture chemicals to various 1 ife 

stages of eels suggests that tolerance 

to chemicals increases with size or 

age. 

Environmental Factors and Sex 

Determi nation 

There is limited evidence which 

suggests that the gender of American 

eels is determined to some extent by 

environmental factors. Fahay (1978) 

stated that the sex of the European 

eel can be environmental ly influenced, 

but indicated that the factors responsible could only be speculated upon. 

The long developmental period in 

fresh- or brackish waters in combination with juvenile hermaphroditism 

(see the LIFE HISTORY section) provides a setting in which environmental 

factors could regulate the gender of 

eels. 

Female American eels predominate 

in upstream freshwater areas as well 

as in northerly stocks, but there is 

no direct evidence of mechanisms that 

lead to these patterns. One possible 

explanation is that male leptocephal i 

and elvers do not migrate as far as 

females (and hence remain in southerly 

or downstream areas [Fahay 19781). 

But because eels do not mature until 

they have 1 ived 3 yr (males) to 7 yr 

(females) or longer in freshwater, it 

is unlikely that physiological systems 

capable of causing sex-re1 ated differences in migratory patterns would. be 

developed in the youngest 1 ife stages. 

It is possible that male eels prefer 

higher salinities than females and 

move downstream to coastal areas after 

they are differentiated, but this 

behavioral pattern has not been 

observed and it would not explain the 

1 ati tudi nal trend. 

Koehn and Will iams (1978) reported that eels throughout the species' 

range are part of the same spawning 

stock. They concluded that differences in protein characteristics in 

ye1 low eels from different drainages 

along the Atlantic coast reflected 

environmental differences. This 

suggests that latitudinal variations 

in the sex ratio are not genetically 

determined but could be due to variations of environmental factors. Some 

of the environmental factors that 

could be involved include food qua1 i ty 

and population density (Fahay 1978). 

Parsons et al. (1977) believed that 

stocking of European eel elvers into 

Lough Neagh, Northern Ireland, led to 

a higher population density and a 

marked increase in the proportion of 

male eels that subsequently emigrated 

from the lake. Similarly, Egusa 

(1979) indicated that A. anguilla 

elvers grown in Japanese ponds under 

crowded conditions produced males 

predominantly, suggesting that variations in the sex ratio of American eel 

populations may be related to population density. Salinity apparently is 

not an important sex determinant; sex 

ratios were similar in the freshwater 

and brackish culture ponds studied by 

Egusa. 
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composition of angui 11 iform 

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waters of the Delaware River. 

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the western North Atlantic based 

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North American Continental She1 f. 

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Chesaoeake Bav. Chesaoeake Sci. 
I REPORT DOCUMENTATION ?L"E~W NO- 1 3. R*cioi*nt'a Accession NO. 

PAGE I FWSIOBS-82111.24' 

I tic)--American eel l 6. 

4. ntle end ~ubtltle Species Profiles: Life Hi stories and Environmental 

Requirements of Coastal Fishes and Invertebrates (South At1 an5. ~eoort oat* 

July 1984 

9. Pedormlng O~anlzatbn Name and Address 10. Pr~~~ttlT~sklW~rk unit NO. 

Georgia Cooperative Fishery Research Unit 

School of Forest Resources 11. fontracllO or Crant(C) No. 

University of Georgia 

Athens, GA 30602 

I 

7. Author(s) 

Michael J. Van Den Avyle 

16. Abstrset (Limit: 200 words) 

Species profiles are literature summaries of taxonomy, life history, and environmental 

requirements of coastal fishes and aquatic invertebrates. They are prepa.red to assist 

with impact assessment. The American eel, Anguil la rostrata, is an ecologically and 

economically important catadromous species that occupies freshwater streams, rivers, 

brackish estuaries, and the open ocean during various phases of its life cycle. Adult 

eels apparently spawn in the Sargasso Sea, and ocean currents transport the developing 

larvae northward until the young metamorphose into juveniles capable of swimning 

shoreward and moving upstream into coastal areas, estuaries, and rivers. Developing 

eels comnonly remain in freshwater or brackish areas for 10-12 years before migrating 

to spawn. American eels tend to be bottom-dwellers and feed on a variety of fauna 

that occup.y the same habitats. Eels occupy areas having wide ranges of temperature, 

salinity, and other environmental factors, suggesting broad tolerance 1 imits , but few 

studies of requirements have been reported. Salinity patterns and water currents 

created by river discharges into coastal areas apparently provide the gradient that 

cues shoreward migration of juvenile eels. Alteration of patterns of freshwater 

inflows to estuaries and bays could affect upstream migrations. 

6. Performing Organiralion Reot. No. 

IZ Soonsoring Organization Name and Address 

National Coastal Ecosystems Team U.S. Army Corps of Engineers 

Fish and Wildlife Service Waterways Experiment Station 

U.S. Department of the Interior P.O. Box 631 

Washington, DC 20240 Vicksburg, MS 39180 

17. Oocummt Arulysls a. Deurimon Eel 

Distribution 

Migration 

Feed i ng 

Rivers 

13. Tyw of ReoOrt 6 Period Covered 

11. 

I b Idontlnen/Op.n.Endad Terms 

15. Suop(ement8~ Notes 

* U.S. Army Corps of Engineers report No. TR EL-82-4 

Anguill a rostrata 

Ca tad romou s 

Life hi story 

Environmental requirements 

I IL Awallablllt). Statement I Unlimited 

1 19. Suur10. Class (This Reoonl 1 21. No. of Pager 1 Unclassified 19 -- ! 20. Securitr Class CThir Paeel i 22. price 

/ ~ncl-assified- I 

(See ANSCU9.10 OPTIONAL FORM 272 :--7 

(Formerly NTIS35) 

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