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FWSIOBS-82111.24 Lafayetie, La. 7OgO6 TR EL-82-4 July 1984 7 Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (South Atlantic) AMERICAN

QL 155 .S63 no.82- 11.24

/ Coast al Ecology Group Fish and Wildlife Service Waterways Experiment Station U.S. Department of the Interior U.S. Army Corps of Engineers

.-- -

FWS/OBS-82/11.24 TR EL-82-4 July 1984

Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (South Atlantic)

AMERICAN EEL

Michael J. Van Den Avyle Georgia Cooperative 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 Slidell, LA 70458

This study was performed for Coastal Ecology Group U.S. Army Corps of Engineers Waterways Experiment Station Vicksburg, MS 39180

and

National Coastal Ecosystems Team Division of Biological Services Research and Development Fish and Wildlife Service U.S. Department of the Interior Washington, DC 20240 This series should be referenced as follows:

U.S. Fish and Wildlife Service. 1983-19 Species profiles: life histories and environmental requirements of coasta'fishes and invertebrates. U.S. Fish Wildl. Serv. FWS/OBS-82/11. U.S. Army Corps of Engineers, TB 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 Atlantic) -- . U.S. Fish Wildl. Serv. FWS/OBS-82/11.24. U.S. Army Corps of Engineers, lR 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 biological characteristics and environmental require- ments 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, life history, ecological role, environmental requirements, and economic importance, if applicable. 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:

Information Transfer Specialist National Coastal Ecosystems Team U.S. Fish and Wildlife Service NASA-Slide11 Computer Complex 1010 Gause Boulevard Slidell, LA 70458

or

U.S. Army Engineer Waterways Experiment Station Attention: WESER Post Office Box 631 Vicksburg, MS 39180

iii CONTENTS

Page

PREFACE ...... iii CONVERSION TABLE ...... \: ACKNOWLEDGMENTS ...... vi

NOMENCLATURE/TAXONOMY/RANGE ...... 1 MORPHOLOGY/IDENTIFICATION AIDS ...... REASON FCR INCLUSION IN SERIES ...... : LIFEHISTORY ...... Spawning ...... i Larval () Stage ...... 5 z GlassEel Stage ...... ElverStage ...... Yellow and Silver Eels ...... 7 GROWTH CHARACTERISTICS ...... ; COMMERCIAL AND SPORT ...... ECOLOGICAL ROLE ...... '1; ENVIRONMENTAL REQUIREMENTS ...... Temperature ...... :; Salinity ...... Dissolved Oxygen ...... ‘1; Habitat Structure ...... River and Tidal Currents ...... 13 Contaminants ...... 13 Environmental Fait;& and Sex Determination ...... 14

LITERATURE CITED ...... 15

iv CONVERSION FACTORS

Metric to U.S. Customary

Multiply !!Y To Obtain millimeters (mm) 0.03937 inches centimeters (cm) 0.3937 inches meters (m) 3.281 feet kilometers (km) 0.6214 miles square meters (m2) 10.76 square feet square kilometers (km2) 0.3861 square miles hectares (ha) 2.471 acres liters (1) 0.2642 gallons cubic meters (m3) 35.31 cubic feet cubic meters 0.0008110 acre-feet milligrams (mg) 0.00003527 ounces grams (9) 0.03527 ounces kilograms (kg) 2.205 pounds metric tons (t) 2205.0 pounds metric tons 1.102 short tons kilocalories (kcal) 3.968 British thermal units

Celsius degrees 1.8(CP) + 32 Fahrenheit degrees

U.S. Customary to Metric

inches 25.40 millimeters inches 2.54 centimeters feet (ft) 0.3048 meters fathoms 1.829 meters miles (mi) 1.609 kilometers nautical miles (nmi) 1.852 kilometers square feet (ft2) 0.0929 square meters acres 0.4047 hectares square miles (mi2) 2.590 square kilometers gallons (gal) 3.785 liters cubic feet (ft3) 0.02831 cubic meters acre-feet 1233.0 cubic meters

ounces (oz) 28.35 grams pounds (lb) 0.4536 kilograms short tons (ton) 0.9072 metric tons British thermal unit (Btu) 0.2520 kilocalories

Fahrenheit degrees 0.5556(F" 32) Celsius degrees

V ACKNOWLEDGMENTS

Dr. Gene Helfman, Earl Bozeman, and Doug Facey, University of Georgia, and Dr. Arnold G. Eversole, Clemson University, reviewed earlier drafts of this Species Profile and provided current information that otherwise could not have been included.

vi Figure 1. American eel.

AMERICAN EEL

NOMENCLATURE/TAXONOMY/RANGE in the Mississippi Valley, and occurs in the West Indies and Scientific name Anguilla rostrata (Figure 2). Bertin Preferred common Aame . . . American (1956) reported the latitudinal eel (Figure 1) range for the American eel as 5" Other common names . . . . . Anauille. to 62" N. It occurs in warm 1 low eel, green eel, blazk eel; brackish and freshwater streams, 3;: t tle eel, bronze eel, glass estuaries, and coastal rivers. ee 1 , silver eel, river eel The American eel sometimes occurs Class ...... in cold freshwater streams Order ...... Anguilliformes in mountainous regions. Adults Family ...... are occasionally found in land- locked lakes, primarily in the Northeastern United States. Its Geographic range: Adults or various distribution has increased developmental stages occur in because of its hardiness and the freshwater rivers, coastal ease with which it can be trans- waters, and the open ocean from planted into new habitats. the southern tip of Greenland, Labrador, and Newfoundland south- ward along the Atlantic coast of MORPHOLOGY/IDENTIFICATION AIDS , into the as far as Tampico, Mexico, American eels undergo a series of and in Panama, the Greater and morphological changes in their life Lesser , and southward to cycle; these characteristics are the northern portion of the east presented in the LIFE HISTORY section. ;;;;i of South *America (Tesch The following material was summarized . The species is abundant primarily from Fahay (1978) and Tesch from to Mexico, is resident (1977). I MILES

OII 0 50 ii0 i KILOMETERS I

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.

2 The body is elongate and snake- before marketing, and a fishery for like (Figure 1). The dorsal and anal elvers (immature eels typically less fins are confluent with the rudimen- than 60 mm long) has recently begun in tary caudal fin. Pectoral fins are the South Atlantic Bight. Elvers are present, but ventral (pelvic) fins are shipped to where they are absent. The body is covered by minute cultured in ponds. Pond rearing of embedded scales (often causing speci- eels in the United States is in a mens greater than 3 to 5 years of age developmental stage, and there is a to appear scaleless). The lateral potential for development and expan- line is well developed. The mouth is sion of an eel culture industry. terminal; jaws contain bands of small, pectinate or setiform teeth. A long The American eel is an important tooth patch also occurs on the vomer. prey species of larger marine and The number of vertebrae ranges from freshwater fishes and is a predator on 103 to 111 but usually is 106 to 108 a variety of other including (Schmidt 1913). commercially important crabs and clams. Eels contribute to the loss of No other anguillid eels occur in nutrients from freshwater rivers and North American coastal waters, but the lakes because of their great organic American eel's spawning grounds coin- intake, large numbers, lengthy stay in cide closely with those of the - freshwater, and subsequent migration an eel.(+nguillaExternal- anguilhla). to sea (Barila and Stauffer 1980). ly vlslb e traits of t e two specimens Alteration of river flow into estu- are similar; however, the aries could affect upstream migration has 111-119 vertebrae (mean = 115). of immature eels. Ege (1939) presented comprehensive morphological data for A. rostrata. Some authors have argued That European LIFE HISTORY and American eels should be regarded as geographical variants of the same The life cycle of the American species, but this is not generally eel includes oceanic, estuarine, and accepted at present (Fahay 1978). riverine phases (Figure 3). Many details of its life history are only No data are available that generally understood or have been conclusively point to geographic vari- inferred from knowledge of the conge- ations in morphology, and no subpopu- neric European eel. Little has been lations have been distinguished. reported on in rivers Koehn and Williams (1978) noted along the South Atlantic Bight; much protein differences among juvenile of the information presented below is eels collected from different loca- based on work in Middle and North tions along the Atlantic seaboard, but Atlantic areas of the United States they concluded that the differences and Canada. were due to variations in selective pressures among environments in which Different stages of the eel's growth occurred. life cycle are known by a variety of common names that are used throughout the scientific literature. The larvae REASON FOR INCLUSION IN SERIES are called leptocephali (sing. = leptocephalus); they first metamor- The American eel supports valu- phose into unpigmented "glass eels" able commercial and limited recrea- that gradually develop pigmentation tional fisheries throughout most of and are then called elvers. Elvers its range. Harvested adults often are migrate into freshwater where they shipped alive or frozen to Europe remain several (sometimes many) years where they frequently are smoked and are called yellow eels. Yellow 3 Helfman and Bozeman (unpublished MS:l) collected sexually differentiated metamorphosis males and females at age III2 in the / .I SILVER EEL 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 eels. Hansen and Eversole metamorphosis (in press) and Harrell and Loyacano (1980) collected differentiated males and females as young as age II and III, respectively, in the Cooper River, .

Prior to seaward migration in the fall, maturing eels begin a metamor- phosis into the silver eel stage, as Figure 3. Diagrammatic representation described in the Yellow and Silver of the American eel's life history. Eels section.

Eels migrating from Chesapeake Bay are in a more advanced state of eels may be sexually undifferentiated metamorphosis than those migrating (gonads contain no definable gametes), from Canadian waters; this supposedly hermaphroditic (oogonia .and spermato- enables eels to reach the southerly gonia present), or sexually differen- spawning grounds in relatively similar tiated (females with oogonia; males stages of maturity (Wenner and Musick d with spermatogonia present), but none 1974). The difference in the extent of these stages are capable of repro- of metamorphosis between migrating duction and, hence, all yellow eels eels from Canada and Chesapeake Bay are immature. Maturation is accompa- suggests that migrating eels in South nied by changes in body color and Atlantic rivers could be even further morphology; maturing eels migrate developed than those in Chesapeake Bay downriver and through the ocean to the at the outset of migrations. Helfman spawning grounds and are known as and Bozeman (unpublished MS?) conclud- "bronze eels" or "silver eels." ed that reproductive migrations from Details of life history for these the Altamaha River, Georgia, occurred stages are provided below. during late winter or early spring, but Hansen and Eversole (in press) and Spawning Michener (1980) indicated that migra- tions occurred during the fall in the The American eel is catadromous. Cooper River, South Carolina. It spawns in the sea but spends most of its life in rivers, freshwater 'Population attributes of Ameri- lakes, and sometimes estuaries. After can eels in a Georgia river. G. S. maturity it returns to the sea (Fig- Helfman and E. L. Bozeman, Department ure 3). The age at maturity has not of Zoology and Institute of Ecology, been well defined; Fahay (1978) re- University of Georgia, Athens, GA ported that maturation occurred beyond 30602. Submitted to Trans. Am. Fish. age III for males and at age IV-VII sot. for females fran northerly popula- 21n this case, age is the number tions, but recent data suggest that of years spent in freshwater (see the maturation is more rapid in popula- GROWTH CHARACTERISTICS section for tions along the South Atlantic Bight. aging methods). d Few details are known about the The youngest stages of American eel oceanic spawning migration of the larvae coexist with European eel American eel. The first collections larvae, but American eel larvae ore- of adults in offshore waters were dominate west of 62" W and south of reported by Wenner (1973) in the open 24" N (Fahay 1978). Fahay also ocean southeast of Cape Cod, Massachu- reported that A. rostrata larvae have setts, east of Assateague Island, not been found-east of 50' W. North Carolina, and southeast of Chesapeake Bay. The means by which The depth at which spawning eels navigate to spawning grounds are occurs is not known, but Taning (1938) poorly understood. Miles (1968) reported that larvae collected near concluded that the eel was capable of Bermuda occurred only at depths noncelestial orientation (southward), between 550 and 2200 m. Egg diameter and Rommel and Stasko (1973) indicated of A. rostrata is about 1.1 mm (Tesch that eels may use geoelectric fields 1977). Incubation periods of American generated by ocean currents to navi- eel eggs are not known. gate. Robins et al. (1979) photo- graphed two adult Anguilla eels on the Fecundity is 10 to 20 million floor of the in the eggs per female (Vladykov 1955, cited Bahamas at depths of about 2000 m, and by Fahay 1978; Eales 1968). Relation- although it was impossible to deter- ships between eel size and fecundity mine if the specimens were European or for 21 eels were reported by Wenner American eels, the authors believed and Musick (1974) as: them to be prespawning A. rostrata.

Stasko and Rommel (1977) tracked log F = -4.29514 + 3.74418 log TL, or five migrating eels in the lower St. log F = 3.2290 + 1.1157 log W; Croix River Estuary, New Brunswick, Canada and found that one eel moved Where F = number of eggs per female, 25 km i'n 20 hr and another moved 38 km TL = total length, mm, and in 40 hr. Eels they studied showed W = total weight, g. considerable vertical movements in the ; behavior did not change Adult eels presumably die after with die1 or tidal cycles. Silver spawning. None have been observed to European eels traveled at 44 km per migrate up rivers, and occurrences of day when migrating to (Tesch spent eels have not been reported. 1977). Edel (1976) believed that the depth at which American eels migrate in the ocean varied with light inten- Larval (Leptocephalus) Stage sity so that swimming depth would vary with turbidity of the water. Hatching occurs from February through August (Vladykov and March Spawning by American eels has 1975; Fahay 1978), and the larval never been directly observed, and stage lasts about 1 year or perhaps spawning areas have been delineated on longer. The body is lanceolate in the basis of collections of larvae. shape, sharply pointed at both ends, Spawning apparently occurs in the and deepest at the middle (see Tesch as early as January or [1977] or Fahay [1978] for illustra- February and may continue into August. tions). The size at hatching has not Tesch (1977) summarized work by been described, but Schmidt (1925) Schmidt (1923), Vladykov (1964), Smith collected 7- to 8-mm larvae in Febru- (1968), and Vladykov and March (1975), ary. The smallest larvae collected by and showed a spawning zone south of Vladykov and March (1975) and Smith Bermuda and north of the Bahamas that (1968) were 12 mm and 17 mm, is centered at about 25“ N and 69" W. respectively.

5 During the leptocephalus stage, eels." Glass eels actively migrate the larvae grow and are transported by toward land and freshwater, and as ocean currents. Larvae collected by they approach coastal areas, external Schmidt (1925) were 7 to 8 mm long in pigmentation develops and the body February, 20 to 25 mm in April, 30 to becomes uniformly dark brown. At this 35 mm in June, 40 mm in July, 50 to 55 stage, metamorphosis is complete and mm in September, and 60 to 65 mm by the eel is now called an elver. the end of the first year of life. The longest leptocephalus collected by Elver Stage Vladykov and March (1975) was 69 mm. Most elvers move into coastal Vladykov and March (1975) sug- areas, estuaries, and up freshwater gested that larval A. rostrata may rivers in the late winter or early spend more than 1 year in the sea. spring. Vladykov (1966) suggested Limited evidence also suggests that that elvers generally arrive in some eels remain in the leptocephalus southern estuaries earlier and at stage for more than 1 year. Smith smaller sizes than in the north, but (l;;8)treported a. 50-mm leptocephalus catch records indicate considerable spawning grounds during overlap in the timing of shoreward April. This larva was too long to movements along the Atlantic coast. have been spawned in the immediate Such movements have occurred during season (Fahay 1978). April in Narragansett Bay and near Washington, D.C.; February and March The Northern Equatorial Current in Delaware; January in Long Island and the transport larvae Sound and Rhode Island estuaries; off northward along the eastern seaboard Nova Scotia in April, and the Bay of of North America. Sampling has shown Fundy in summer (Fahay 1978). In the that larvae are abundant in the South Atlantic, migrating elvers have Florida Straits and in the area been collected during January in between Bermuda and the Bahamas from Florida and South Carolina and during April through August (Smith 1968), and January through May, with peak catches Eldred (1971) found A. rostrata lepto- in March and April, in North Carolina cephali in the Gurf of Mexico and (Smith 11996881; Hornberger 1978, ci;;t,F; Yucatan Straits, but mechanisms by Sykes ; Sykes 1981). which the larvae are dispersed into moving into South Atlantic estuaries the Gulf of Mexico and southward to and rivers typically are 46 to 60 mm the coast of South America have not long. Helfman and Bozeman (unpub- been determined. lished MS.3) collected 49- to 56-mm glass eels from the Altamaha River Glass Eel Stage Estuary, Georgia, in late February; daily growth rings on the otoliths During the pelagic phase, lepto- showed 250 to 300 days of age. cephali reach a size and physiological state at which they begin to metamor- Small numbers of elvers regularly phose. The early stages of this tran- arrive in estuaries in the fall, and sition involve: (1) shrinkage in size Fahay (1978) suggested that these and weight, primarily due to a reduc- tion in water content; (2) changes in the configuration of the head and 3Growth rates of American eels in jaws; and (3) accelerated development a Georgia estuary. G. S. Helfman and of the digestive system (Fahay 1978). E. L. Bozeman, Department of Zoology After these changes occur, the eels and Institute oLthF;slogy, Univ;;;;;y are similar in overall morphology to of Georgia, GA yellow eels, but they lack external Submitted to U.S. Nail. Mar. Fish: pigmentation and are called "glass Serv. Fish. Bull.

6 "early" arrivals may be the earliest primarily in freshwaters whereas males spawned individuals or a segment of are generally found in salt- or brack- the main body of leptocephali that is ish waters. Dolan and Power (1977), moved northward more quickly by however, concluded that an extensive localized water currents. Alterna- review of literature did not support tively, these elvers may be "late" this "female-freshwater, male-salt- arrivals produced from leptocephali water" theory. Recent studies con- that did not metamorphose during the tinue to be inconsistent. Helfman and previous winter/spring. Bozeman (unpublished MS3) found that females represented 94% of the sexu- Elvers occupy freshwater-salt- ally differentiated yellow eels water transition areas before ascend- collected from freshwater areas of ing rivers. During this period, the Altamaha River in Georgia and 64% elvers are active at night and burrow of the differentiated yellow eels in or rest in deep water during the day estuarine areas. However, collections (Deelder 1958). This nocturnal of eels from the Cooper River, South behavioral pattern causes the elvers Carolina, showed a minor variation of to be transported upstream by flood sex ratio from fresh- to saltwater. tides that occur at night, and they Females contributed 97%, 95%, and 93% drift back down during ebb (Fahay of the differentiated eels collected 1978). Pacheco and Grant (1973) from fresh-, brackish-, and saltwater reported similar patterns for elvers areas, respectively (Harrell and at the mouth of the Indian River, Loyacano 1980; Michener 1980; Hansen Delaware, and Tesch (1977) noted and Eversole, in press). equivalent behavior by European eel elvers. He also indicated that A. In addition to the freshwater- anguilla elvers orient to river saltwater variation in the sex ratio, \k currents for upstream movement, and if a geographic variation in the distri- the current becomes too weak or too bution of the sexes has been hypothe- strong (velocities not specified), sized. Vladykov (1966) stated that eels may move into backwater areas, male eels predominate in middle and severely delaying upstream progress. southern Atlantic populations (New Basic similarities in behavior of Jersey to Florida) whereas females European and American eel elvers predominate from New York to Newfound- suggest that A. rostrata elvers would land. Work in the Cooper River, South be similarly-affected by extremely Carolina, and the Altamaha River, fast or slow river currents. Georgia (described in the preceding paragraph), however, does not support Fahay (1978) stated that as this hypothesis. Vladykov believed upstream migration to freshwater that a latitudinal change in sex streams begins, males tend to stay in composition was related to the size- brackish water while females move into differences in elvers along the coast, fresher water, but this is based on and he said that smaller elvers observed distribution patterns of entering southern streams supposedly older eels rather than direct observa- become males whereas the larger elvers tion of elver behavior. When elvers entering northern systems probably cease their migration, they begin a develop into females (see the ENVIRON- growth and differentiation period in MENTAL REQUIREMENTS section for which they are called yellow eels. alternate explanations). As with freshwater-saltwater variations in the Yellow and Silver Eels sex ratio, Dolan and Power (1977) suggested that latitudinal variations Many authors (e.g., Bigelow and were not well documented. They stated Schroeder 1953; Vladykov 1966) have that the apparent geographic distribu- -stated that yellow eel females occur tion of sex in the American eel could

7 "be a result of incorrect sexing, laries in the rete in the swim blad- selectivity of sampling gear and the der, which also may be an indication possible exclusion of smaller males, of migrating at great depths (Kleckner and the assumption that characteris- and Kruger 1981); and (6) degeneration tics for the American eel would of the digestive tract. Silver parallel those of the European eel. (metamorphosed) eels appear to be The gender of adult eels is not exter- better adapted to swimming than yellow nally apparent, and gonadal tissues eels (Holmberg and Saunders 1979). should be examined histologically to Presumably, ovaries mature fully only avoid errors in sex determination after the migrating female reaches (Dolan and Power 1977; Facey and LaBar saltwater (Fahay 1978). 1981).

Age at maturity and other aspects GROWTH CHARACTERISTICS of reproduction are described in the Spawning section. Sexual differentia- Larvae typically reach 40 to 70 tion does not occur until eels reach mm after 1 year of growth; Hornberger about 200 mm in length (Fahay 1978). et al. (1978) collected glass eels Prior to completion of the differenti- from the Cooper River, South Carolina, ation process, some eels possess from January through April that aver- gonads containing male and female aged 55 mm in length and ranged from gametes (juvenile hermaphroditism; 45 to 65 mm (see the Larval Stage Tesch 1977), but after gender is section for growth within the first established, it does not change (Fahay year). The metamorphosis into elvers 1978). Helfman and Bozeman (unpub- is accompanied by a decrease in length lished MS.3) reported that differenti- and weight due to reduction in water ated and undifferentiated yellow eels content of the body. Elvers grow in the Altamaha River, Georgia, over- slowly and reach about 127 mm after c lapped considerably in size: undif- the first year in freshwater (Bigelow ferentiated eels were as large as 363 and Schroeder 1953). Yellow eels mm at age VII; differentiated males typically grow slowly but can achieve were as small as 209 mm at age III; weights up to 6.8 kg; females caught differentiated females were as small from the St. Lawrence River range from as 186 mm at age III; and hermaphro- 960 to 1270 mm long and 0.9 to 4.5 kg dites, which constituted less than 1% (Fahay 1978). Females typically of the collections, ranged from 267 to grow to a larger size than males. 328 mm at ages IV to V. Hansen and Eversole (in press) reported similar Eels have been aged from otoliths overlap in size and age of differenti- and scales. Otoliths in eels consist ated and undifferentiated eels in the of a translucent nucleus (formed at Cooper River, South Carolina. sea) surrounded by broad opaque summer zones and narrow translucent winter Yellow eels begin to metamorphose zones (Harrell and Loyacano 1980). into silver eels in the fall prior to Harrell and Loyacano (1980) used seaward migration. The metamorphosis otoliths to age American eels from the includes: (1) color change (to a Cooper River in South Carolina. metallic, bronze-black sheen; pectoral Distinct annuli were present in 410 of fins change from yellow-green to 415 otoliths examined; the opaque ring black); (2) fattening of the body; (3) first appeared in May and the translu- thickening of the skin; (4) enlarge- cent zone was first evident in Novem- ment of the (macrophthalmia) and ber. The third opaque ring corre- changes in visual pigments in the sponds to the eel's first growing in preparation for migrating at dark season in freshwater. Eels in Cana- ocean depths (Vladykov 1973; Beatty dian waters formed their first scales 1975); (5) increased length of capil- at 160 to 200 mm during their third to

8 fifth year of life and the scales ture data to estimate growth rates. formed annual rings in subsequent There was a slow-growth period during winters (Smith and Saunders 1955). November through February when the Thus, in northerly areas, age in years fish grew an average of 0.025 mm per generally will be the number of scale day. They grew more rapidly during rings plus three. The eel, however, the rest of the year, gaining an continues to form scales as it grows, average of 0.220 mm per day. These leading to a situation in which dif- rates produced an average annual ferent scales from the same fish can length increase of 57 to 63 mm. give different ages (Smith and Saunders 1955). Maximum age of yellow eels col- lected from northern rivers has been Growth rates within year classes reported to be 15 to 20 years (Fahay are highly variable, leading to con- 1978). Landlocked eels liberated as siderable variation in length at age elvers in Sherman Lake, Michigan, and poor predictability of age from lived 35 to 40 years (Vladykov 1973). size. Lengths of eels at various ages Accuracy of estimates of the age at in northerly populations are summa- maturity may be affected by problems rized in Table 1. Few growth data for with aging techniques. eels in South Atlantic States have been reported. Harrell and Loyacano (1980) reported that eels in the COMMERCIAL AND SPORT FISHERIES Cooper River grew 45 to 52 mm per year for ages II-XVI. Helfman and Bozeman Prior to the 1970's, the eel (unpublished MS?) tagged yellow eels fishery in the South Atlantic Bight in a Georgia estuary and used recap- primarily provided live bait to sport

Table 1. Lengths of American eels at various ages.

rotal length (CIII) at various locations NW Rhode Age Bi"'s Lakek~ Nek+ Newfound,andb Lake Delaware South (Yr) New Erunswc OntarioC Jerseyd Islande Riverf Carolina9

1 ___ 12-16 20-31 ir -______-_ 14-25 21-50 III 20-26 20-22 ___ la-28 22-59 IV 22-38 21-27 _-- 12 --_ --- 24-32 28-62 V 26-48 25-35 ___ ,;I,, 29-32 ___ 27-46 28-51 26-34 32-66 VI 24-51 29-42 ___ 22-47 41-67 28-51 28-42 31-68 VII 34-56 30-52 ___ 22-47 36-67 29-58 29-43 42-74 VIII 38-57 32-55 ___ 22-47 44-70 33-64 35-47 40-69 IX 38-57 34-59 53-62 32-52 37-74 38-62 35-50 44-73 X 49-57 42-56 60-65 37-62 44-86 37-65 40-52 53-67 XI ___ -__ 58-69 37-62 63-90 46-65 45-54 65-69 XII -__ ___ 58-72 37-62 67-94 --- 43-64 65-74 XIII ______68-76 47-62 68-98 --- __- XIV ___ 72-80 47-67 78-97 --- 56-59 a3 ___ 79-87 47-62 78-104 --- __- 79 KI ___ 88 47-62 77-100 --- ___ XVI I ______92 41-72 95-99 --- -_- XVIII --_ 93 62-72 _-- _-- __- XIX ______a7 _-_ __- __-

bGray aSmith and and Andrews Saunders 1971. 1955.

$lurley 1972. 1970. eBieder Ogden 1971. fJohnson 1974 Ildata combine; from Harrell 1977, Hansen 1979, and Michener 1980.

9 fishermen and secondarily provided $O.ll/kg; in 1972-73, the price rose bait used in blue crab (Callinectes to $0.35/kg; and in 1973-76, landings sapidus) traps. A larger commercial averaged 151,200 kg at a price of fishery for eels in. the reqion is $0.92/kg. Catch value ranged from developing, and glass eels, elvers, $0.95 to $1.85/kg and harvest averaged yellow eels, and silver eels are 285,000 kg for 1977-79 (Keefe 1982). exploited. Techniques for capturing The bulk of the North Carolina land- and growing elvers to marketable sizes ings is taken from northeastern are being developed (Easley and Freund coastal areas. 1977). In Georgia, The European market has been the for eels in freshwater was effectively major outlet of U.S. yellow and silver prohibited prior to 1980 because of eel landings (Fahay 1978). Eels are restrictions against using traps in hardy and can be densely packed and inland waters. Harvest in 1979 was shipped alive if they are kept moist, about 3,900 kg (Helfman, unpublished cool, and supplied with oxygen. Live MS4). After a freshwater trap fishery eels are preferred in Europe, but many was allowed in 1980, harvest was are shipped frozen. 50,000 kg, but landings in 1981 and 1982 were 5,500 kg and 16,800 kg, Commercial fishermen use a respectively. The 1982 catch was variety of methods, including lift valued at $35,000 or $2.08/kg. nets, drift nets, traps, weirs, otter trawls, pound nets, fyke nets, spears, A fishery for European eel elvers handlines, eel pots, haul seines, and began in Europe during the late 1960's nets (Fahay 1978). The fyke net to supply Japan's demand for young is the major gear used in North eels to use in pond . Carolina to exploit eels that are Experimental work on techniques for moving seaward in late summer or early capturing migrating American eel fall to begin their spawning migra- elvers has been done in the St. Johns tion. Yellow eels in fresh- or River, Florida (Topp and Raulerson brackish waters are primarily taken 1973). Elvers were packed live in with baited traps or eel pots. boxes and shipped to Japan, where prices paid for local Anguilla Fahay (1978) summarized catch ja onica elvers were $7/kg in 1965-68, statistics along the Atlantic coast +*3OO/kg in 1969, and $330 to $925/kg for 1955-73. Landings from the Middle in 1971-73 (Fahay 1978; Egusa 1979). Atlantic (-Virginia) consis- Prices paid for European eel elvers in tently exceeded those from the North Japan initially were equivalent to Atlantic and South Atlantic States, those paid for local elvers, but but landings from Southern States European eels were inferior in the increased in the late 1960's and early pond culture systems (poor growth and 1970's. For 1955-64, the South disease problems); in 1973, the Atlantic harvest averaged about 37,000 Japanese paid only $30 to $5O/kg for kg annually, and for 1965-73, annual European elvers (Eg usa 1979). landings were about 630,000 kg. The Accounts of American eel performance value of these landings ranged from in culture were not $8,000 to $83,000 annually for 1965- located. 73. 'Development and expansion of the Eel harvest and value in North fishery for American eels in Georgia. Carolina dramatically increased in the G.S. Helfman, Department of Zoology, 1960's and 1970's (Easley and Freund University of Georgia, Athens,. GA. 1977). For 1960-70, average annual 30602. Project summary, University of landings were 17,800 kg valued at Georgia Sea Grant Program, 1983.

10 The feasibility of commercial no genetically distinct stocks or grow-out operations in North Carolina subpopulations (Koehn and Williams was assessed by Easley and Freund 1978), overharvest in one region could (1977). Interest in culturing was affect recruitment in other regions. stimulated by rising prices noted Nevertheless, some management policies above during the late 1960's and early allow or encourage local heavy exploi- 1970's, but considerable refinement of tation of migrating silver eels or techniques is needed. Development of elvers under the assumption that the eel aquaculture has focused on methods numbers of elvers returning in later for collecting elvers and on physical years will be maintained by escapement features of grow-out systems. Hormone of spawning stock from other areas. injections can be used to induce maturation of female American eels No major sport fishery for (Edel 1976), but proper spawning con- American eels exists in coastal rivers ditions are unknown, and eel culture of the South Atlantic Bight, but the remains dependent on capturing wild species is caught incidentally by elvers. Hinton and Eversole (1978, anglers in estuaries and rivers. 1979, 1980) evaluated the toxic effects of chemicals commonly used in aquaculture to glass eels (mean length ECOLOGICAL ROLE of 55 mm), elvers (mean length of 97 mm), and yellow eels collected from Yellow eels are nocturnal and a South Carolina rivers. significant portion of their feeding occurs at night. The diet is diverse The South Atlantic States have and generally includes nearly all few, if any, restrictions specifically types of aquatic fauna that occupy the designed to regulate yellow or silver same habitats. Eels swallow some eel harvest, but fisheries for yellow types of prey whole, but they also can L eels often have been nonexistent or tear pieces away from larger dead minimal because of prohibitions fish, crabs, or other items. Eels in against using traps in freshwaters (as freshwater feed on , worms, mentioned above for Georgia). Such crayfish and other , frogs, restrictions generally are intended to and fish whereas elvers in saltwater prevent incidental catches of sport are planktivorous. Elvers collected fishes. Mouth diameter and wire mesh from the Cooper River, South Carolina, sizes of traps are regulated in some consumed aquatic insects (mainly areas to reduce catches of other chironomid larvae and adults), clado- cerans, amphipods, and fish parts species E~~~~~~fis~~~be~~e~ll~~al al,, 1978). (McCord 1977). The diet of yellow Georgia. eels from the Cooper River varied with eel size and season. Intermediate Estimates of density, mortality, size classes contained more types of or other vital statistics of eel food than elvers or maturing eels; stocks generally have not been report- fish occurred in the diet primarily in ed, and factors regulating survival or winter and spring whereas insects and stock size have not been evaluated. mollusks were eaten from spring Helfman (unpublished MS?) suggested through fall. Crustaceans, bivalves, that the eel's long life in fresh- and polychaetes were the major prey of waters may make the stocks prone to eels in lower Chesapeake Bay; blue local overharvest. Keefe (1982) crabs and soft clams were significant suggested that recent declines in prey (Wenner and Musick 1975). Eels of eels in North shorter than 40 cm in New Jersey Carolina indicated overharvest. streams mainly ate aquatic insects Because all American eels spawn in the whereas larger eels fed mostly on fish Sargasso Sea and there apparently are and crustaceans (Ogden 1970). Most

.l

. fish eaten were bottom dwellers, latitude freshwater streams and lakes reflecting the eels' tendency to to warm, brackish coastal bays and remain near the bottom. Fahay (1978) estuaries in the Gulf of Mexico. concluded that eels depend more on Jeffries (1960) found elvers at scent than sight to obtain food. temperatures as low as -0.8" C.

Little has been published about.. Barila and Stauffer (1980) predation on eels. tiornberger et al. acclimated yellow eels to a range of (1978) reported that elvers and small temperatures between 6' C and 30" C yellow eels were eaten by largemouth and then measured preferred tempera- bass (Microsalmoides) 1terus andtures. Although preferred tempera- striped bass Morone sm in the tures tended to increase with Cooper River, South Carolina, but eels increased acclimation temperature, never were a major component of these differences among groups were nonsig- predators' diets. Leptocephali, glass nificant, and the authors reported a eels, elvers, and small yellow eels final temperature preference of 16.7' probably are consumed by a variety of C. They also reported that feeding other predatory fishes; grown eels are ceased at temperatures below 14' C. eaten by other species of eels and by Marcy (1973) reported that American gulls, bald eagles, and other fish- eels survived passage through the eating birds (Sinha and Jones 1967 ; cooling system of a nuclear power Seymour 1974). plant, during which they were exposed to elevated temperatures for l-l.5 hr. Crane and Eversole (1980) found Poluhowich (1972) suggested that the no parasites on glass eels migrating American eel's multiple types of hemo- into the Cooper River, South Carolina, globins serve to maintain a relatively but four genera of protozoans (Tricho- constant blood oxygen affinity when ~i~~~o~~~,"h~p,"","~,ri~~ec~:idoif"mAo~~d the eel is exposed to temperature changes. genetic trematode (Gyrodactylus anguillae) were found on elvers. Salinity Crane and Eversole (in press) reported that 214 of 218 yellow eels collected The mechanisms by which glass from brackish waters of the Cooper eels or elvers orient during %heir River, South Carolina, were parasit- shoreward migration have not been ized by one or more of 22 helminth described, but their movements species. Parasites of American eels probably are keyed to salinity in Quebec included protozoans, trema- gradients after they reach coastal todes, , cestodes, and waters. European glass eels and copepods (Hanek and Molnar 1974). The elvers become positively rheotactic myxosporidian protozoan, Myxidium when they first encounter freshwater zelandicum, has been found in the that is mixed with seawater (Tesch kidneys and on the of A. 1977); thus salinity as well as the rostrata (Komourdjian et al. 1977). current itself may provide the gradi- ent for shoreward orientation. Alterations of patterns or magnitudes ENVIRONMENTAL REQUIREMENTS of freshwater inflows to bays or estuaries could alter salinity regimes Temperature and thereby affect the number, timing, and spatial patterns of upstream The eel's broad geographic range migrations by elvers. and diverse habitats suggest flexible temperature requirements. Elvers and As with temperature, salinity yellow eels live in waters ranging requirements of postlarval eels can be from cold, high-elevation or high- generally inferred as "broad" from the 12 fact that the species occurs through- Ford and Mercer (1979) used mark- out a gradient of strictly fresh to recapture methods to obtain a popula- brackish waters. Leptocephali are in tion estimate of 350 yellow eels in a near-ionic equilibrium with sea water 600-m section of a marsh creek in a (Hulet et al. 1972). Massachusetts estuary. They studied the behavior of yellow eels and found Dissolved Oxygen that eels shorter than 30 cm predomi- nated in narrow, soft-bottomed, upper Dissolved oxygen requirements marsh creeks whereas those longer than have not been thoroughly documented, 30 cm predominated in wider, lower but eels generally will select water marsh creeks having mud and sand with high oxygen tension (Hill 1969). bottoms. Most eels had relatively Commercial shipping of live eels small home ranges and rarely moved indicates that they are especially more than 100 m from the point at hardy. Elvers can be packed densely which they were initially caught. and shipped alive by being dampened The authors believed that large eels but not covered with water because may establish territories in lower they can absorb 60% of required oxygen marsh areas and thereby restrict through their skin (Sheldon 1974, smaller eels to smaller high marsh cited by Fahay 1978). Tesch (1977) creeks. stated: River and Tidal Currents "The capacity of the adult eel to survive in both air and water The elver's nocturnal activity is associated with its ability to patterns and reliance on tides and use both branchial and cutaneous river currents for upstream movement modes of respiratory gas ex- are presented in the LIFE HISTORY L change. The eel survives better section. in air than in poorly oxygenated or polluted water . ...' Movements of yellow eels in a tidal creek in Georgia were affected Habitat Structure by tides and time of day (Helfman et al. 1983). Daytime movements of eight Postlarval eels tend to be bottom telemetered eels were restricted to dwellers and hide in burrows, tubes, the main creek channel, but at night snags, plant masses, other types of the fish were near the mouths of shelter, or the substrate itself feeder creeks at low tide or in (Fahay 1978). This behavior is flooded marsh areas during high tide. reflected in their food habits, pro- Helfman et al. (1983) termed this tects them from predators, and influ- movement 'a nocturnal activity pattern ences commercial fishing techniques. modified by tidal flow." They sug- Few other freshwater fishes display gested that movements onto the marsh similar habitat use; therefore, inter- at night may have been foraging trips. specific competition for living space may be limited. The presence of soft, Contaminants undisturbed bottom sediments is impor- tant to migrating elvers as shelter Little work has been done on (see the Elver Stage section). Edel American eels regarding toxic effects (1979) indicated that eels in his of pollutants or tolerance limits. experimental systems were less active Tolerance would be expected to vary when shelter was present than when it with developmental phase, and the was absent. Vladykov (1955, cited by eel's long residence in freshwater Fahay 1978) reported that adult eels rivers could lead to repeated doses of in northern habitats lie dormant in toxicants and accumulation to toxic the bottom mud during winter. levels (Holmberg and Saunders 1979). k 3 Work done bv Hinton and Eversole developed in the youngest life stages. (1978, 1979,- 1980) on toxicity of It is possible that male eels prefer aquaculture chemicals to various life higher salinities than females and stages of eels suggests that tolerance move downstream to coastal areas after to chemicals increases with size or they are differentiated, but this age. behavioral pattern has not been observed and it would not explain the latitudinal trend. Environmental Factors and Sex Determination Koehn and Williams (1978) report- ed that eels throughout the species' There is limited evidence which range are part of the same spawning suggests that the gender of American stock. They concluded that differ- eels is determined to some extent by ences in protein characteristics in environmental factors. Fahay (1978) yellow eels from different drainages stated that the sex of the European along the Atlantic coast reflected eel can be environmentally influenced, environmental differences. This but indicated that the factors respon- suggests that latitudinal variations sible could only be speculated upon. in the sex ratio are not genetically The long developmental period in determined but could be due to varia- fresh- or brackish waters in combina- tions of environmental factors. Some tion with juvenile hermaphroditism of the environmental factors that (see the LIFE HISTORY section) pro- could be involved include food quality vides a setting in which environmental and population densit (Fahay 1978). factors could regulate the gender of Parsons et al. (1977y believed that eels. stocking of European eel elvers into Lough Neagh, Northern , led to Female American eels predominate a higher population density and a in upstream freshwater areas as well marked increase in the proportion of as in northerly stocks, but there is male eels that subsequently emigrated no direct evidence of mechanisms that from the lake. Similarly, Egusa lead to these patterns. One possible (1979) indicated that A. anguilla explanation is that male leptocephali elvers grown in Japanese-ponds under and elvers do not migrate as far as crowded conditions produced males females (and hence remain in southerly predominantly, suggesting that varia- or downstream areas [Fahay 19781). tions in the sex ratio of American eel But because eels do not mature until populations may be related to popula- they have lived 3 yr (males) to 7 yr tion density. Salinity apparently is (females) or longer in freshwater, it not an important sex determinant; sex is unlikely that physiological systems ratios were similar in the freshwater capable of causing sex-related differ- and brackish culture ponds studied by ences in migratory patterns would. be Egusa.

.4 LITERATURE CITED

Barila, F. Y., and J. R. Stauffer, Jr. into fresh water. J. Conserv. 1980. Temperature behavioral 24:135-146. responses of the American eel. Anguilla rostrata (LeSueur), from Dolan, J. A., and G. Power. 1977. Sex Maryland. Hydrobiologia 74:49- ratio of American eels, Anguilla 51. rostrata, from the Matamek River system, Quebec, with remarks on Beatty, D. 0. 1975. Visual pigments problems in sexual identifica- of the American eel, Anguilla tion. J. Fish. Res. Board Can. rostrata. Vision Res. 15:771- 34:294-299. 776. Eales, J. G. 1968. The eel fisheries Bertin, L. 1956. Eels: a biological of eastern Canada. Bull. Fish. study. Cleaver-Hume Press Ltd., Res. Board Can.166. 79 pp. London. 197 pp. Easley, J. E., Jr., and J. N. Freund. Bieder, R. C. 1971. Age and growth i977. An economic analysis of ‘L of the American eel, Anguilla eel farming in North Carolina. rostrata (LeSueur), in Rhode N.C. State Univ. Sea Grant Publ. Island. M.S. Thesis. University UNC-SG-77-16, Raleigh. 21 pp. of Rhode Island, Kingston, R.I. 39 PP. Edel , R. K. 1976. Activity rhythms of maturing American eels Bigelow, H. B., and W. C. Schroeder. (Anguilla rostrata). Mar. Biol. 1953. Fishes of the Gulf of 36:283-289. Maine. U.S. Fish Wildl. Serv. Fish. Bul. 53. 577 pp. Edel , R. K. 1979. Locomotor activity of female silver eels (Anguilla Crane, J. S., and A. G. Eversole. rostrata) in response to shelter 1980. Ectoparasitic fauna of and unnatural photoperiods. glass eel a'nd elver stages of Rapp. P.-V. Reun. Cons. Int. Anerican eel (Anguilla rostrata). Explor. Mer 174:98-103. Proc. World. Maricult. sot. 11: 275-280. Ege, V. 1939. A revision of the genus Crane, J. S., and A. G. Eversole. In Anguilla Shaw: a systematic, press. Helminth parasites of phylogenetic and geographical American eels from brackish study. Dana Rep. Carlsberg water. Proc. Annu. Conf. South- Found. No. 16. 256 pp. east. Assoc. Fish Wildl. Agen. 35:357-366. Egusa, S. 1979. Notes on the culture of the European eel (An uilla Deelder, C. L. 1958. On the behavior anguilla L.) in Japanese%z of elvers (Anguilla vulgaris farming ponds. Rapp. P.-V. Reun. Turt.) migrating from the sea Cons. Int. Explor. Mer 174:51-58. b 15 Eldred, B. 1971. First records of Harrell, R. M. 1977. Age, growth, Anguilla rostrata larvae in the and sex ratio of the American Gulf of Mexico and Yucatan eel, Anguilla rostrata (LeSueur), Straits. Fla. Dep. Nat. Resour., the Cooper River, South Mar. Res. Lab. Leafl. Ser. 4:1-3. ilrolina. M.S. Thesis. Clemson University, Clemson, S.C. 55 pp. Facey, D. E., and G. W. LaBar. 1981. Biology of American eels in Lake Harrell, R. M., and H. A. Loyacano, Champlain, Vermont. Trans. Am. Jr. 1980. Age, growth and sex Fish. Sot. 110:396-402. ratio of the American eel in the Cooper River, South Carolina. Fahay, M. P. 1978. Biological and Proc. Annu. Conf. Southeast. fisheries data on American eel, Assoc. Fish. Wildl. Agen. 34:349- Anguilla rostrata (LeSueur). U. 359. S. Dep. Commer. Natl. Mar. Fish. Serv. Tech. Ser. Rep. No. 17, Helfman, G. S., D. L. Stoneburner, E. Northeast Fisheries Center, L. Bozeman, P. A. Christian, and Highlands, N.J. 82 pp. R. Whalen. 1983. Ultrasonic telemetry of American eel move- ments in a tidal creek. Trans. Ford, T., and E. Mercer. 1979. Popu- Am. Fish. Sot. 112:105-110. lation density, size distribu- tion. and home ranoe of the Hill, L. J. 1969. Reactions of the American eel (Anguilla rostrata) American eel to dissolved oxygen in the Great Sippewissett salt tensions. Tex. J. Sci. 20:305- marsh. (Summary only.) Biol. 313. Bull. 157:368.

Gray, R. W., and C. W. Andrews. 1971. Hinton, M. J., and A. G. Eversole. Age and growth of the American 1978. Toxicity of ten commonly eel (Anguilla rostrata (LeSueur)) used chemicals to American eels. in Newfoundland waters. Can. J. Proc. Annu. Conf. Southeast. Zool. 49:121-128. Assoc. Fish. Wildl. Agen. 32:599- 604.

Hanek, G., and K. Molnar. 1974. Para- Hinton, M. J., and A. G. Eversole. sites of freshwater and anadro- 1979. Toxicity of ten chemicals mous fishes from Matamek River commonly used in aquaculture to system, Quebec. J. Fish. Res. the black eel stage of the Board Can. 31:1135-1139. American eel. Proc. World Maricult. Sot. 10:554-560. Hansen, R. A. 1979. Age, growth, and sex ratio of the American eel. Anguilla rostrata (LeSueur), in Hinton, M. J., and A. G. Eversole. brackish water portions of Cooper 1980. Toxicity and tolerance River, South Carolina. M.S. studies with yellow-phase eels. Thesis. Clemson University, Prog. Fish-Cult. 42:201-203. Clemson, S.C. 45 PP. Holmberg, B., and R. L. Saunders. 1979. The effects of penta- Hansen, R. A., and A. G. Eversole. chlorophenol on swimming perfor- In press. Age, growth, and sex mance and oxygen consumption in ratio of the American eel in the American eel (Anauilla brackish water portions of the rostrata). Rapp. P.-V. Reun. Cooper River, South Carolina. Cons. Int. Explor. Mer 174:144- Trans. Pm. Fish. Sot. 149.

16 Hornberger, M. L. 1978. Coastal rostrata during premigration Plains American eel study. Pages metamorphosis. J. Fish Biol. 42-50 in Progress report for 18:569-577. October- 1977 through January 1978. S.C. Wildl. Mar. Res. Koehn, R. K., and G. C. Williams. Dep., Charleston. 1978. Genetic differentiation without isolation in the American Hornberger, M. L., J. S. Tuten, A. eel , Anguilla rostrata. II. Eversole, J. Crane, R. Hansen, Temporal stability of geographic and M. Hinton. 1978. American patterns. Evolution 32:624-637. eel investigations. Completion report for March 1977-Julv 1978. Komourdjian, M. P., W. C. Hulbert, J. S.C. Wildl. Mar5. Res." Dep., C. Fenwick, and T. W. Moon. 1977. Charleston, and Clemson Univ., Descriotion and first occurrence Clemson. 311 pp. of Myxidium zealandicum (Proto- zoa: Myxosporidia) in the North Hulet, W. H., J. F scher, and B. American eel Anguilla rostrata Rietberg. 1972 . Electrolyte LeSueur. Can. J. Zool. 55:52-59. composition of anguilliform leptocephali from the Straits of Marcy, B. C., Jr. 1973. Vulnerability Florida. Bull. Mar. Sci. and survival of young Connecticut 22:432-448. River fish entrained at a nuclear power plant. J. Fish. Res. Board Hurley, D. A. 1972. The American eel Can. 30:1195-1203. (Anguilla rostrata) in eastern Lake Ontario. J. Fish. Res. McCord, J. W. 1977. Food habits and Board Can. 29: 535-543. elver migration of American ,L eel, Anguilla rostrata, Jeffries, H. P. 1960. Winter occur- (LeSueur). in Cooper River, rences of Anguilla rostrata South Carolina. M:S. Thesis: elvers in New England and Middle Clemson University, Clemson, Atlantic estuaries. Limnol. S.C. 47 PP. Oceanogr. 5~338-340. Michener, W. K. 1980. Age, growth, Johnson, J. S. 1974. Sex distribu- and sex ratio of the American tion and age studies of Anguilla eel, Anguilla rostrata (LeSueur), rostrata (American eel) in fresh from Charleston Harbor, South waters of the Delaware River. Carolina. M.S. Thesis. Clemson M.S. Thesis. East Stroudsburg University, Clemson, S.C. 49 pp. State College, East Stroudsburg, Pa. 57 PP. Miles, S. G. 1968. Laboratory experi- ments on the orientation of the Keefe. S. G. 1982. The American eel adult American eel,Re;ng;;;;; (Anguilla rostrata) fishery in rostrata. J. Fish. the commercial waters of North Can. 25:2143-2155. Carolina. Paoes 50-51 in K. H. Loftus, ed. Proceedingsof the Ogden, J. C. 1970. Relative abun- 1980 North American eel confer- dance, food habits, and age of ence. Ontario Fish. Tech. Rep. the American eel, Anguilla Ser. No. 4, Ontario Ministry of rostrata (LeSueur), in certain Nat. Resour., Toronto. 97 pp. New Jersey streams. Trans. Am. Fish. Sot. 99:54-59. Kleckner, R. C., and W. H. Kruger. 1981. Changes in Pacheco, A. L., and G. C. Grant. 1973. retial morphology in Anguilla Immature fishes associated with L larval Atlantic at and holding. Maine Dep. Mar. Indian River Inlet, Delaware, Resour. 27 pp. 1958-61. Pages 78-117 in A. L. Pacheco, ed. Proceedings of a Sinha, V. R. P., and J. W. Jones. workshop on egg, larval, and 1967. On the food of the fresh- juvenile stages of fish in water eels and their feeding Atlantic coast estuaries. Middle relationship with salmonids. J. Atlantic Coastal Fisheries Center Zool. (Lond.) 153:119-137. Tech. Publ. No. 1. Smith, D. G. 1968. The occurrence of Parsons, J., K. U. Vickers, and Y. larvae of the American eel. Warden. 1977. Relationship Anguilla rostrata, in the Straits between elver recruitment and of Florida and nearby areas. chanaes in the sex ratio of Bull. Mar. Sci. 18:280-293. silver eels Anguilla anguilla L. migrating from Lough Neagh, Northern Ireland. J. Fish. Biol. Smith, M. W., and J. W. Saunders. lO:Zll-229. 1955. The American eel in certain fresh waters of the Poluhowich, J. J. 1972. Adaptive Maritime Provinces of Canada. J. significance of eel multiple Fish. Res. board Can. 12:238-269. hemoglobins. Physio 1. Zool. 45:215-222. Sparre, P. 1979. Some necessary adjustments for using the common Robins, C. R., D. M. Cohen, and C. H. methods in eel assessment. Rapp. Robins. 1979. The eels, Anguilla P.-V. Reun. Cons. Int. Explor. Mer 174:41-44. and Histiobranchus, photographed c on the floor of the Atlantic in the Bahamas. Bull. Mar. Sci. Stasko, A. B., and S. A. Rommel, Jr. 29:401-405. 1977. Ultrasonic tracking of Atlantic and eels. Rapp. Rommel, S. A., Jr., and A. B. Stasko. P.-V. Reun. Cons. Int. Explor. 1973. Electronavigation by eels. Mer 179:36-40. Sea Frontiers 19:219-223. Sykes, D. P. 1981. Migration and Schmidt, J. 1913. First report on development of young American eel investigations 1913. Rapp. eels, Anguilla rostrata, in P.-V. Reun. Cons. Int. Explor. coastal North Carolina. N.C. Mer 18:1-30. State Univ. Sea Grant Workina Pap. 81-5, Raleigh. 34 pp. J Schmidt, J. 1923. The breeding places of the eel. Philos. Trans. R. Sot. Lond. B. Biol. Sci. 211:1?9- Taning, A. V. 1938. Deep-sea fishes 208. of the Bermuda Oceanographic Expedition. Family Anguillidae. Schmidt, J. 1925. The breeding places Zoologica (N. Y.) 23:313-318. of the eel. Smithson. Inst. Annu. Rep. for 1924:279-316. Tesch, F. W. 1977. The eel. J. Greenwood, translator. Chapman Seymour, N. R. 1974. Great black- and Hall, London. 422 pp. banded gulls feeding on live eels. Can. Field-Nat. 88:352-353. Topp, R., and R. Raulerson. 1973. Elver investigations in the Sheldon, W. W. 1974. Elvers in Maine; southeast. U.S. Natl. Mar. Fish. techniques of locating, catching, Serv. Mar. Fish. Rev. 35:45-47. 18 Vladykov, V. D. 1955. Eel fishes of Vladykov, V. D., and H. March. 1975. Quebec. Quebec Dep. of Fish. Distribution of leptochephali of Album No. 6:1-12. the two species of Anguilla in the western North Atlantic based on collections made between 1933 Vladykov, V. D. 1964. Quest for the and 1968. true breedino area of the Ameri- Syllogeus 6:1-38. can eel -(Anguilla rostrata Wenner, C. A. 1973. Occurrence of LeSueur). J. Fish. Res. Board American eels, Anguilla rostrata, Can. 21:1523-1530. in water overlyinq the eastern North American ConGnental Shelf. Vladykov, V. D. 1966. Remarks on the J. Fish. Res. Board Can. American eel (Anguilla rostrata 30:1752-1755. LeSueur). Sizes of elvers entering streams; the relative Wenner, C. A., and J. A. Musick. 1974. abundance of adult males and Fecundity and gonad observation females; and present economic of the American eel. Anauilla importance of eels in North rostrata, migrating from Chesa- America. Verh. Int. Verein. peake Bay, Virsinia. J. Fish. Theor. Angew. Limnol. Res. Board Can.-31:1387-1391. 16:1007-1017. Wenner, C. A., and J. A. Musick. 1975. Food habits and seasonal abun- Vladykov, V. D. 1973. Macrophthalmia dance of the American eel, in the American eel (Anauilla Anguilla rostrata, from the lower rostrata). J. Fish. Resm Chesapeake Bay. Chesapeake Sci. Can. 30:689-693. 16:62-66.

19 SO272 -161 REPORT DOCUMENTATION .L’=mRT NO. 2. 3. Recioienf’f Accession No. PAGE FwS/OBS-82/11.24* 4. ntk and Subtltlo Species Profi 1 es : Life Histories and Environmental s.~*wfloat* Requirements of Coastal Fishes and Invertebrates (South Atlan- July 1984 tic)--American eel 6.

7. Author(s) 6. Performme Oreanirrcion RePi. NO . Michael J. Van Den Avyle

0. Performin Orlanlxatian N.m. and Addrmss 10. Proi*ct/Task/Wwk Unit NO. Georgia Cooperative Fishery Research Unit

School of Forest Resources 11. Contnc~fQ or Cranr(t) NO. University of Georgia (C) Athens, GA 30602 (G)

12 fpmsotine Or6mirwtlon ram* an* Address 13. Tyw of Rewn 6 Period Covered 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 14. Washington, DC 20240 Vicksburg, MS 39180 15. Suppl*mantwy Notes *U.S. Army Corps of Engineers report No. TR EL-82-4

‘16. Abstract (Limir 200 words) Species profiles are literature summaries of taxonomy, life history, and environmental requirements of coastal fishes and aquatic invertebrates. They are prepared to assist with impact assessment. The American eel, Anguilla 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 swimming shoreward and moving upstream into coastal areas, estuaries, and rivers. Developing eels commonly remain in freshwater or brackish areas for lo-12 years before migrating to spawn. American eels tend to be bottom-dwellers and feed on a variety of fauna that occupy the same habitats. Eels occupy areas having wide ranges of temperature, salinity, and other environmental factors, suggesting broad tolerance limits, 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.

17. Doeummt Analy%is 4. D*awifuors Eel Distribution Migration Feedina Rivers- b. Id~ntifi~n/OPmXnd,d Twms Anguilla rostrata Catadromous Life history Environmental requirements

c. COSATI FiddlGtoup

16. AvaIlabilIty StMm%.nt 19. S*cur~:y Class (This ReooR) ) 21. NO. of Pa6CI Unlimited Unclassified 19 I 20. Swurity Clars (This PaSe) i 22. Price - I ! Unclassified 1 (Se* ANSl-239.16) OPTION&,. FORM 272 !--771 (formerly NTIS-35) CIeDanmcnt Of Commercs Kesearch Library U.S. Department of the Interior National Biological Service Southern Science Center 700 Cajundome Blvd. Lafayette, LA 70.506-3 152 . _.. I h ; _~I I Sk T- ./ / ‘I’ 1 -- \ i,_ \

\ p-- \\ I1 I lwaiian Islands ! * Headquarters. Division of Biological Services, Washington, DC x Eastern Energy and Land Use Team Leetown, WV + Natmnal Coastal Ecosystems Team Slidell, LA 0 Western Energy and Land Use Team Ft. Collins, CO l Locations of Regional Offices

REGION 1 REGION 2 REGION 3 Regional Director Regional Director Regional Director U.S. Fish and Wildlife Service U.S. Fish and Wildlife Service U.S. Fish and Wildlife Service Lloyd Five Hundred Building, Suite 1692 P.O. Box 1306 Federal Building, Fort Snelling 500 N.E. Multnomah Street Albuquerque, New Mexico 87 103 Twin Cities, Minnesota 55 I 11 Portland, Oregon 97232

REGION 4 REGION 5 REGION 6 Regional Director Regional Director Regional Director U.S. Fish and Wildlife Service U.S. Fish and Wildlife Service U.S. Fish and Wildlife Service Richard B. Russell Building One Gateway Center P.O. Box 25486 75 Spring Street, S.W. Newton Corner, Massachusetts 02158 Denver Federal Center Atlanta, Georgia 30303 Denver. Colorado 80225

REGION 7 Regional Director U.S. Fish and Wildlife Service 1011 E. Tudor Road Anchorage, Alaska 99503 DEPARTMENT Of THE INTERIOR U.S. FISH AND WILDLIFE SERVICE

As the Nation’s principal conservation agency, the Department of the Interior has respon- sibility for most of our nationally owned public lands and natural resources. This includes fostering the wisest use of our land and water resources, protecting our fish and wildlife, preserving theenvironmental and cultural values of our national parks and historical places, and providing for the enjoyment of life through outdoor recreation. The Department a!$- sesses our energy and mineral resources and works to assure that their development is in the best interests of all our people. The Department also has a major responsibility for American Indian reservation communities and for people who live in island territories under U.S. administration.

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