Geographic Range:

Anguilla rostrata (Lesueur) is a catadromous species that spawns in the Atlantic Ocean and ascends streams and rivers in North and South America. Found in Atlantic, Great Lakes, Mississippi, the Gulf Basin, and south to South America. This species is more common near the sea rather than inland streams and lakes (Page & Burr, 1991).

Biogeographic Regions: nearctic (Native ); atlantic ocean (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) American eels spawn in the Atlantic Ocean, apparently in the Sargasso Sea. The coastal range extends from southern Greenland (small populations; Nielsen and Bertelsen 1992), Labrador (Hamilton Inlet-Lake Melville Estuary), and Newfoundland southward along the Atlantic coast of North America to southern Florida, and along the coast of the Gulf of Mexico to the northern tip of the Yucatan Peninsula, the Caribbean coast of Central America, the Caribbean and Atlantic coasts of the Greater and Lesser Antilles and other West Indies islands, and occasionally the northern portion of the Atlantic coast of South America (Colombia to at least Guyana) (Ogen et al. 1975, Wenner 1978, Erdman 1984, Van Den Avyle 1984, Böhlke and Chaplin 1993, Claro 1994, Kenny 1995, Bussing 1998, Lim et al. 2002, Miller 2005). Smith (1997) stated that the range extends southward through the Bahamas and Antilles to Trinidad but probably not as far as mainland South America. As part of the native distribution, American eels penetrate far inland in many areas, such as Lake Ontario via the St. Lawrence River (Hubbs et al. 2004), Grand Matagamon Lake at the head of the East Branch of the Penobscot River in Maine, Rangeley Lakes at the head of the Androscoggin River in Maine, the headwaters region of the Connecticut River in New Hampshire, the upper Mississippi River basin to South Dakota, Minnesota (including the Wisconsin River as far as Prairie du Sac dam (Cochran, in press), and Pennsylvania (Cooper 1983), and New Mexico in the Rio Grande basin (Lee et al. 1980, Page and Burr 1991, Collette and Klein-MacPhee 2002). In New York, eels historically penetrated inland throughout much of the state, except the far western end that is west of the Finger Lakes region (see map in Smith 1985).

Construction of canals in the Great Lakes region has influenced the distribution of the American eel. The species first appeared in Ohio in the mid-1800s after completion of the 43-kilometer Welland Canal, which through a series of locks allows access to Lake Ontario from Lake Erie (Trautman 1957). The Welland Canal also provided eels with access to the upper Great Lakes (Scott and Crossman 1973, Bailey et al. 2004). In Wisconsin, a canal connecting the Illinois River (a tributary of the Mississippi River) to Lake Michigan likely also facilitated eel entry into the Fox River above Green Bay, which also may have been accessible through an occasional high water connection between the Wisconsin River drainage and the Fox River drainage near Portage (Cochran, in press).

American eels have been introduced (stocked, released, escaped) in several inland areas, such as the Great Lakes region and several areas in the western United States. As a result, the species is possibly established in Indiana and Ohio but is not known to be established in the western states (Fuller et al. 1999). In an effort to diversify the fishery in southern Saskatchewan, American eels were introduced into Lac Pelletier (1951), a saline lake in southern Saskatchewan. Some escaped into the South Saskatchewan River. The last record of the species in Saskatchewan was in 1981 (Atton and Merkowsky 1983). American eels found on the Canadian side of Lake Superior likely were ballast water introductions (Mandrak and Crossman 1992). Additional introductions include Guam (not established) and Japan (presumably not established) (www.fishbase.org).

ATLANTIC COAST, CANADA TO SOUTHERN FLORIDA

American eels are widely distributed and common in many areas along the Atlantic coast of North America. Collette and Klein-MacPhee (2002) reported that eels are universal along the periphery of the Gulf of Maine and ascend every tributary stream, large or small.

Warfel (1939) documented American eel presence in 50+ lakes, ponds, and reservoirs in the Connecticut River watershed in New Hampshire.

Based on data for 1991-1996, Whittier et al. (2001) found that the American eel was one of the most widely distributed fishes in a sample of 203 lakes in the northeastern United States. It occurred in 19 percent of sampled lakes, especially large lakes at low elevation. Only the banded killifish occurred in a larger percentage of lakes. Eels appeared to be transient occupants of most lakes.

Surveys in the late 1990s found American eels to be one of the most widely distributed fishes in the ponds and brooks in Acadia National Park in Maine (Stone et al. 2001).

American eels occur in most of the Massachusetts portion of the Connecticut River basin basin (Hartel et al. 2002). In Massachusetts, eels are (or were) also widely and densely distributed in the Merrimack River basin and all smaller streams draining the eastern one-third of the state, including Martha's Vinyard and Nantucket (Hartel et al. 2002). In comprehensive fish sampling in Nauset Marsh in the mid-1980s, American eels were the eighth most numerous species among 35 fish species; 475 of 489 eels were larvae (Able et al. 2002).

In fish surveys conducted at 360 stream and pond locations in Rhode Island between 1993 and 2002, American eels were commonly collected throughout most of the state (Libby 2004). They were the fifth most abundant species collected (Libby 2004). Their abundance (number per hour) was only exceeded by the brook trout, bluegill, pumpkinseed, and yellow perch.

In Connecticut, fish surveys conducted during 1988-1994 captured eels in all basins except the Hudson River basin (Hagstrom et al. 1996). The highest densities were in streams adjacent to Long Island Sound or just upstream from large rivers. Large numbers of small eels were collected close to Long Island Sound whereas fewer and larger individuals occurred farther inland. This concurs with previous studies that found that eels occur, often in large numbers, in the lower portions of many coastal streams (Whitworth et al. 1968, Whitworth 1996) and penetrate large distances inland only in the Connecticut River basin.

In New York, Smith (1985) reported that eels are extremely abundant in the lower Hudson River and extend inland in the St. Lawrence River, the Great Lakes, and their tributaries, including the Finger Lakes. Eels are rare in Lake Erie and in the Susquehanna system but abundant in the Delaware system (Smith 1985). Eels are abundant enough in New York to be of commerical importance, and they are frequently caught by anglers (Smith 1985). Referring to the marine water of New York, Briggs and Waldman (2002) reported that American eels are abundant in all bays and harbors. In the freshwater tidal section of the Hudson River in 1998-2001, the American eel was one of the most common prey items in the diet of bald eagles (Thompson et al. 2005).

Recent (1976-1994) sampling at 307 sites in the Schuylkill River drainage in Pennsylvania found American eels at 44 sites (Fairchild et al. 1998). Historical surveys did not record this species, but historical absence probably reflected use of less efficient sampling methods (absence of electroshocking) (Fairchild et al. 1998). The most commonly found species (white sucker) occurred at 81 sites.

The American eel is an abundant resident of all tributaries to Chesapeake Bay (Murdy et al. 1997). In Virginia, eels are widespread in all but one Atlantic Slope drainage; they range inland on the Costal Plain and Piedmont (Jenkins and Burkhead 1994). American eels are generally common or abundant in estuaries and lowland fresh waters of Virginia, usually rare or uncommon in the uplands of the Atlantic drainages (Jenkins and Burkhead 1994). Substantial populations now occur in the Valley and Ridge and Blue Ridge provinces only in the Potomac and Rappahannock drainages, respectively (Jenkins and Burkhead 1994). Eels have been rare above Kanawha Falls on the New River for at least the past 50 years (Jenkins and Burkhead 1994). Eel density often decreases significantly with distance inland. Sampling in the Potomac River basin in Virginia indicates that eel densities are higher in coastal areas than farther inland (Goodwin 1999). American eels occur in many headwater streams of the James River drainage in the George Washington and Jefferson National Forest (Roghair and Nuckols 2005). Eels have been captured recently in many locations during electrofishing in the Shenandoah River drainage (Steve Reeser, pers. comm., 2005).

In North Carolina, American eel occurrences are densely distributed throughout the eastern and central parts of the state (Menhinick 1991).

Eels occurred historically throughout South Carolina, including portions of the Catawba, Broad, Pacolet, Tyger, Enoree, and Saluda rivers (USFWS et al. 2001). In the Santee Basin, American eels historically made extensive migrations into Piedmont regions of North and South Carolina (USFWS et al. 2001). Eels are still widespread in South Carolina and are abundant in the middle Savannah River basin (Marcy et al. 2005).

American eels are abundant and commonly found in several streams and swamps on the Fort Stewart Army Installation in Georgia (Michael W. Biering, pers. comm., 2005).

In Florida, American eels occur throughout most of the state in both fresh and brackish waters of the Atlantic drainages (Florida Fish and Wildlife Conservation Commission; www.floridamarine.org ).

The distribution of American eels varies with eel size, age, and gender; those found inland tend to be larger, older females whereas smaller, younger males dominate estuarine samples For example, in Georgia, Helfman et al. (1984) found that freshwater riverine eels average longer than those in in estuarine habitats. Sampling in Virginia indicated that eels in the Potomac River basin averaged larger and older than those in coastal areas (Goodwin 1999). Inland (Shenandoah River, 500+ river kilometers inland), sampled eels were all females. On a statewide scale in Virginia, Smoger et al. (1995) found that the density of small to medium (< 374 mm) eels declined with distance inland. Large (>374 mm) eel density and median eel length increased with increased distance inland (Smogor et al. 1995). Similarly, in a coastal stream in Rhode Island, inland eels averaged larger and older than those in coastal areas (Haro and Krueger 1991).

GULF OF MEXICO DRAINAGES (EXCLUDING MISSISSIPPI RIVER BASIN)

American eels appear to be less ubiquitous and less common in the western Gulf of Mexico than in areas farther east along the U.S. Gulf Coast.

In Florida, American eels occur throughout most of the state in both fresh and brackish waters of the Gulf of Mexico drainages (Florida Fish and Wildlife Conservation Commission; www.floridamarine.org ). American Eels are common in Florida in caves of spring-fed rivers from the Panhandle to the Peninsula (Florida Department of Environmental Protection, ). Historical and recent (2000-2005) collections of eels have been made in the Apalachicola, Conecuh-Escambia, and Choctawhatchee rivers (Karen Herrington, pers. comm., 2005).

American eels have been collected from every river system of the Mobile basin, as well as from several coastal drainages in southeastern Alabama, from the Apalachicola drainage west to the Escatawpa River system (Mettee et al. 1996, Boschung and Mayden 2004). They are most numerous in the southern part of Alabama, particularly in the Mobile Delta (Mettee et al. 1996). American eels are probably more common in Alabama waters than their numbers in museum collections indicate (Boschung and Mayden 2004).

In Mississippi (Ross 2001), American eels are widespread in the Gulf of Mexico basin (streams that flow into the Gulf of Mexico rather than into the Mississippi River). In the Bogue Chitto River in Mississippi and Louisiana, American eels are rare or at least seldom captured (Stewart et al. 2005). Electrofishing in coastal rivers and elsewhere occasionally yields single captures of American eels in Mississippi, where the species seems to have a wide riverine distribution but is not commonly encountered anywhere (Dennis Riecke, pers. comm., 2005). Sampling by MDWFP biologists of such aquatic habitats in Mississippi is very limited; the state does not have a routine stream sampling program (Dennis Riecke, pers. comm., 2005).

John Forester (pers. comm., 2005) of the U.S. Fish and Wildlife Service's Baton Rouge Fisheries Resource Office, which covers four states in the southeast and is involved in lake and river electroshocking activities, reported that they still routinely see American eels in their surveys, especially in rivers and particularly in submerged rock riprap. Forester reported that state district biologists with the Louisiana Department of Wildlife and Fisheries expressed similar views concerning encounters with this eel. One biologist mentioned a Louisiana marine fishery division study that showed the presence of eels in southeastern Louisiana coastal waters but not in suitable numbers to support a commercial fishery (John Forester, pers. comm., 2005). Along the Gulf Coast, eel density is generally too low to support a commercial fishery, except a small commerical fishery in Louisiana (Ross et al. 1984, Ross 2001).

American eels are uncommon in Texas. In 30 years of sampling coastal waters, the Coastal Fisheries division encounterd only seven eels, in Matagorda/San Antonio Bays and Corpus Christi Bay (three in 1984, one in 1986, one in 1988, and two in 2001) Mike Ray, pers. comm., 2005). Inland Fisheries encountered only 15 eels in 20 years of sampling in freshwater reservoirs and streams (two in the 1980s, ten in the 1990s, and three in 2003-2004. One eel was caught in Lake Anahuac and the rest were from the Matagorda/San Antonio Bay drainage.

American eels occurred historically in the Rio Grande and Pecos River drainages (and probably also the Canadian River) in New Mexico (Sublette et al. 1990). Following apparent extirpation in the state, eels have been found recently in the Rio Grande and Chama River; these presumably derive from aquaculture facilities upstream in Colorado (Sublette et al. 1990).

The map in Lee (1980) indicates no eel occurrences in Colorado, but Beckman (1952) reported that American eels have been reported from the Rio Grande in Colorado. Referring to Colorado, Lynch (in Everhart and Seaman 1971) stated that "historical records indicate that the American eel was once common to the Rio Grande and Arkansas River drainages." Fuller et al. (1999) indicated only nonindigenous occurrences of American eels in Colorado and specifically mentioned only a record of eels that escaped from an aquaculture facility in Conejos County, in the San Luis Valley (Rio Grande drainage).

MISSISSIPPI RIVER BASIN

Historically, American eels penetrated far into the upper reaches of the Mississippi River basin, from South Dakota to Pennsylvania, and today they still inhabit much of the basin. However, American eels appear to have been and continue to be of sporatic occurrence in most areas of the basin, as the following evidence indicates.

American eels are known from several tributaries of the Mississippi River in northern and southern Mississippi, including a few locations in the Yazoo River drainage (Ross 2001).

American eels are regularly observed in the Ouachita and White rivers in Arkansas, but recent observations are limited (at least in part due to fewer large river samples in recent years) (Jeff Quinn, pers. comm., 2005). Sampling in the Ouachita River in the early 1990s yielded at least 29 eels (Arkansas Department of Environemntal Quality data). Eel penetration upstream in the Arkansas River into western Arkansas requires that eels traverse several locks and dams, and eels have not been detected there since 2001; prior to that, eels were seen every couple of years. In the 1980s, "thousands" of eels were observed in the Arkansas River below Dam 2 near Arkansas Post (Manuel Barnes, pers. comm., 2005). Fish surveys with seines, trawls, and electrofishing during the Arkansas River Navigation Study by Jack Kilgore of the ERDC center yielded 17,328 fishes representing 65 species, but the American eel was not observed (Jeff Quinn, pers. comm., 2005). In contrast, Robison and Buchanan (1984) suggested that American eels are especially abundant in the lower Arkansas River. Boat electrofishing in lower Arkansas River in the vicinity of the post canal suggests the presence of a good eel population (Jeff Farwick, pers. comm., 2005). Buchanan et al. (2003) did not find any American eels in the lower Red River in Arkansas, although they were historically found there. However, sampling did not employ small-mesh hoop nets, and trotlines were used on a limited basis.

During the Red River Navigation Study, Jack Kilgore from the ERDC center captured 27,219 individual fishes representing 57 species but failed to capture a single American eel. However, small-mesh hoop nets and trotlines were not used (Jeff Quinn, pers. comm., 2005). Jeff Quinn reported that a commerical fisherman saw a single American eel in a fiddler net in the spring of 2005 in the Red River near Texarkana. The fiddler nets were probably 1.5- inch bar mesh, which capture only relatively large eels.

In Oklahoma, American eels are found throughout much of the eastern half of the state but are quite sporadic in occurrence (Miller and Robison 2004). Moore and Paden (1950) reported that eels are often caught on trotlines in the Illinois River of northeastern Oklahoma and northwestern Arkansas. Systematic fish sampling in the Neosho River of Oklahoma in the 1950s yielded no eel specimens, but two were caught by hook and line (Branson 1967).

American eels are uncommon in Tennessee but are still occasionally taken in direct tributaries to the Mississippi River and in the Cumberland and Tennessee rivers as far upstream as Dale Hollow Reservoir and Knoxville (Wilson and Turner 1982, Etnier and Starnes 1993). In the Tennessee River basin (Tennessee and adjacent states), several eels were captured during 1993-2000 in Kentucky Reservoir, Pickwick Reservoir, and Fort Loudoun Reservoir (TVA data).

In Kentucky, American eels are sporadic in rivers but often common to abundant in collections from the Ohio and Mississippi rivers (Burr and Warren 1986). Eels have been collected in the Tradewater and middle and upper Cumberland rivers, but no recent records exist for those rivers (Burr and Warren 1986).

In Missouri (Pflieger 1997), eels are most common in the Mississippi River and in the larger streams of the Ozarks where access has not been blocked by dams. Some eel localities are from the Missouri River at the extreme northwestern edge of the state. Eels are seldom caught by either sport or commerical anglers (Pflieger 1997). All of the eels that migrate upstream as far as Missouri are females (Pflieger 1997). Details of the distribution and abundance of the American eel are not thoroughly documented because this fish is not readily captured by the kind of equipment ordinarily used in fish surveys (Pflieger 1997). The Missouri Department of Conservation Fish Community Database contain records of only a few eels captured in Missouri in the 1990s; larger numbers are represented in the data for earlier decades, but these data are not comparable due to lack of information on sampling effort. Multiple eels continued to be captured in the Osage River through at least 2001 (Greg Stoner, pes. comm., 2005) and in the Eleven Point River through at least 2003 (John Ackerson, pers. comm., 2005).

In Kansas, historical records indicate that eels were more common 100 years ago than they are now, though most evidence indicates that they were generally uncommon there (Cross and Collins 1995, Haslouer et al. 2005). Until recently, the last Kansas record of this species was from 1987 (Haslouer et al. 2005) (see trend section for further information). However, a 35-inch eel was captured in the spillway of Wilson Reservoir (Saline River), Russell County, central Kansas, in June 2005 (Tom Mosher, pers. comm., 2005).

Lee (1980) indicated no eel occurrences in Colorado, but Beckman (1952) reported that American eels were occasionally taken in the Arkansas River. Referring to Colorado, Lynch (in Everhart and Seaman 1971) stated that "historical records indicate that the American eel was once common to the Rio Grande and Arkansas River drainages." Lynch reported that eels were now found only below John Martin Reservoir (on the Arkansas River in southeastern Colorado) and in sandpits bordering the river. He stated that elvers had been reared to adult size at the Las Animas Fish Production Unit in Bent County (Arkansas River drainage), perhaps indicating that the Arkansas River records might be based on stocked eels. Records of the Colorado Division of Wildlife indicate that a state-record 35-inch American eel was caught in Flagler Reservoir (north of the Arkansas River, on the South Fork Republican River) in 1996. Fuller et al. (1999) indicated only nonindigenous occurrences of American eels in Colorado but did not mention any records for the Mississippi River basin in Colorado.

All but one of the 19 American eel specimens from Illinois in the Illinois Natural History Survey collection are from no later than the 1970s. One was collected in the Rock River in 1998. Smith (1979) stated that eels are "extremely sporadic" in Illinois.

In Indiana, American eels historically occurred in all four major drainages: Lake Michgan, Lake Erie, Kankakee River (Illinois River), and Ohio River. Eels probably were most commonly encountered in the Ohio River, where they are still widely distributed but sporadically encountered during fish surveys in all major watersheds, including areas that eels must access by circumventing dams (Brant Fisher, pers. comm., 2005).

A 76-cm American eel was captured in a pond (abandoned gravel pit) along the Little Miami River northeast of Cincinnati in 2004, and a 91-cm eel was caught there in 2006 (Bob Mason, pers. comm., 2005, 2006). There are old historical and occasionally more recent anecdotal reports of American eels in the Ohio River along the southern edge of Ohio, but eels have not been caught in recent systematic fish sampling (Bob Mason, pers. comm., 2005).

American eels have been found in a few locations in the West Virginia section of the New River (Ohio River basin) (Addair 1944, Hocutt et al. 1979) and, farther upstream, are very rare in the New drainage of Virginia (Jenkins and Burkhead 1994).

The American eel is uncommon in the Upper Mississippi River System, ranking 90th of 134 fish species in the Long Term Resource Monitoring Proqram (LTRMP) total catch over the 10-year period 1993-2002 (Ickes et al. 2005, Appendix A.3). Eels have been collected in five of the six LTRMP study reaches (no collections to date at Pool 13, Iowa). Of nearly four million fishes collected since 1993, the LTRMP observed only 75 American eels, with 9-12 annual captures during 1993-1996 and 4-7 captures in 1997-2002. The highest total catches occurred in the northernmost study area (Pool 4) and the southernmost study area (Open River). There were no obvious patterns in annual abundance, but the four highest years in terms of total catch occurred in the first four years of the program. Earlier, extensive fish surveys in Lake Onalaska (Mississippi River Navigation Pool 7), on the east side of the Mississippi River in Wisconsin in 1976-1977 and 1982, yielded very few (only 4) captures of American eels, which made up an insignificant portion of the lake's fish fauna (Held 1982). In 1982, there was only 1 eel captured among a total of 11,751 fishes representing 61 species.

In South Dakota, eels have been reported below the first dam on the Missouri River, Gavins Point Dam. At least one specimen has been taken and positively identified. Fisheries biologists also report taking eels while conducting fish sampling. The last report of eels in South Dakota was in 1992 (Doug Backlund, pers. comm., 2005; South Dakota Department of Game Fish and Parks, S.D. Natural Heritage Program).

In Wisconsin, eels are uncommon in the larger rivers and the Great Lakes (Lyons et al. 2000). American eels are generally uncommon in the upper Great Lakes (Becker 1983). Scott and Crossman (1973) categorized eels as uncommon in lakes Erie, Huron, and Superior.

Available data indicate that American eels have always been uncommon in Minnesota. The vast majority of records consist of one or a few specimens (almost invariably fewer than 10 specimens per year) from the Mississippi River, with relatively few records from the St. Croix River, Lake St. Croix, Minnesota River, and other locations (Konrad Schmidt, unpublished data).

WEST INDIES/CARIBBEAN REGION

Long-term monitoring via snorkeling and electrofishing indicates that American eels currently occur in the Rio Mameyes, one of the last undammed rivers in Puerto Rico (Felipe Cano, pers. comm., 2005). The Illinois Natural History Survey collection includes 18 American eel specimens collected in the Rio Mameyes and adjoining Quebrada Tabonuco in 1993-1995. March and Pringle (2003) documented the American eel in the Río Espíritu Santo in northeastern Puerto Rico. Anecdotal information and some limited river and estuarine sampling suggests that American eels are present but generally quite scarce in Puerto Rico (Craig G. Lilyestrom, pers. comm., 2005).

Eels appear to be more common in the Virgin Island than in Puerto Rico. During fish surveys on St. John, U.S. Virgin Islands, in 2002-2003, mountain mullet, spinycheek sleeper, and American eel were the most widespread species in freshwater and oligohaline habitats (Loftus 2003).

Recent records of American eels in Panama include Rio Robalo in Bocas del Toro, and Rio Cricamola, Rio Cañas, and Rio Caimito (Jorge Garcia, pers. comm., 2005).

Elongate, snakelike body with a small, pointed head. A. rostrata has no pelvic fins, but has one long dorsal fin that extends more than half of the body; dorsal fin is continuous with the caudal and anal fin. The lower jaw projects beyond upper jaw. One small gill slit is found in front of each pectoral fin. Coloration is variable with maturity level, the larval stage is called a leptocephalus, or glass eel. This stage is transparent and leaf-shaped with a prominent black eye. The leptocephalus develops into an elver, characterized by a darker coloring, from gray to greenish brown (Page & Burr, 1991). The next stage, the yellow eel, is the adult form that lives in freshwater; color ranges from yellow to olive-brown. Sexually mature adults, silver eels, are dark brown and gray dorsally, with a silver to white ventral side. Large eyes are prominent in silver eels. Individuals reach lengths up to 152 cm (Page & Burr, 1991).

Average mass: 4031.5 g.

Length: 120 cm

A. rostrata live in freshwater as adults, usually in larger rivers or lakes, primarily swimming near the bottom in search of food. The species prefers to hunt at night and resides in crevices or other shelter from the light during the day, often times burying themselves in the substrate, whether mud, sand or gravel (Landau, 1992).

Aquatic Biomes: lakes and ponds; rivers and streams; coastal

Habitat Type: Freshwater

Comments: Spawning occurs apparently in the Sargasso Sea, a large portion of the western Atlantic Ocean east of the Bahamas and south of Bermuda. Spawning has never been directly observed, and suitable conditions for it remain speculative. Larvae drift and swim in prevailing currents (Antilles Current, Florida Current, and Gulf Stream) that take them to areas near continental coasts or continental slope waters. Glass eels and elvers enter estuaries. Some elvers travel upstream to spend the majority of their life growing as yellow eels in rivers, streams, ponds, and the shallow, more productive areas of lakes; other eels remain in estuaries for their entire development prior to migration to the ocean. Movement into fresh water may not be obligatory but rather perhaps a density-dependent process (Haro and Krueger 1991, Feunteun et al. 2003), but further research is needed. Based on otolith microchemistry, Secor et al. (2002) found three modes of habitat use by yellow-phase eels in the Husdon River: freshwater, brackish water, and "mixed" modes. Freshwater mode eels were all captured in fresh water and showed no evidence of having previously resided in brackish water after metamorphosis into the elver stage. Yellow-phase eels captured in brackish water habitats showed two distinct modes of habitat use. Over half of the eels showed early freshwater habitat use (for 2-19 years), followed by a downstream migration into environments with brackish salinities (mixed mode). The third mode of habitat use showed no use of freshwater environments (brackish mode).

Soft, undisturbed bottom sediments may be important to migrating elvers for shelter (Facey and Van Den Avyle 1987). Postlarval eels tend to be bottom dwellers and hide in burrows, tubes, snags, plant masses, other types of shelter, or in the substrate; they are inactive in bottom mud in winter in the north (Van Den Avyle 1984). Mature adults migrate back downstream to return to the Sargasso Sea. In the ocean, American eels have been taken at depths greater than 6,000 meters. See Facey and Van Den Avyle (1987) for further information.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Individual eels migrate up to thousands of kilometers between spawning and nonspawning habitats. Hatchlings drift and swim in ocean currents. The mechanism by which eels move from the Gulf Stream/continental slope interface to the Atlantic coast and estuaries is unknown (Douglas A. Dixon, pers. comm., 2005). After arriving in coastal areas, glass eels and elvers begin to move into estuaries and streams. Glass eels likely ascend estuaries by drifting on flood tides and holding position near the bottom during; they also actively swim along shore in estuaries and above tidal influence (McCleave and Kleckner 1982, Wippelhauser and McCleave 1987, Barbin and Krueger 1994). The timing and duration of upstream migration by elvers and yellow eels varies with location and may occur from March through October, with a May-July peak in many areas (July-August.in the St. Lawrence River) (Casselman et al. 1997). Upstream migration may extend for months or years (Haro and Krueger 1991). Downstream spawning migration begins summer or fall in northeastern United States.

Radio-tracked eels in Lake Champlain, Vermont, moved 0.6 to 4.9 km in 20 to 67 days (LaBar and Facey 1983). In a Maine tidal estuary, movements of radio-tagged eels averaged 6.7 km in less than 80 hours (Parker 1995).

Low rates of recapture of American eels in streams (e.g., see Oliveira 1997 and Goodwin 1999) suggest the possibility that eels may be highly mobile in riverine habitats, not only during upstream migrations (if they can be termed such) but also during nonmigratory stages (i.e., the major period of riverine residency). Further study of this possibility is needed.

Movie:   eel feeding.

Feeding habits of A. rostrata vary with level of maturity. The leptocephalus is planktivorous as it drifts to coastal waters and develops into an elver, which feeds on aquatic insects, small crustaceans, and dead fish (Landau, 1992). Yellow and Silver eels are primarily nocturnal carnivorous feeders, consuming insects, crustaceans, clams, worms, fish and frogs. Eels at this stage will also eat dead animal matter. Adult eels use rotational feeding to tear portions from prey by causing a twist in their bodies and spinning to generate force to remove pieces of food (Helfman et al., 1999). This behavior actually wastes large portions of food in eel aquaculture systems (Landau, 1992).

Comments: Yellow eels feed opportunistically on various bottom- and near bottom-dwelling animals,
mostly invertebrates and slower fishes (Denoncourt and Stauffer 1993). In freshwater, they feed on insects (especially Ephemeroptera, Plecoptera, and Trichoptera), worms, crayfish and other crustaceans, and small frogs and fishes; the diet varies geographically, seasonally, and among size classes. Crustaceans, bivalves, and polychaetes are major prey in lower Chesapeake. Larvae feed on plankton.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: > 300

Comments: ATLANTIC COAST, CANADA TO SOUTHERN FLORIDA

American eels have been collected from well over 1,000 sites in hundreds of streams along the Atlantic coast of Canada and the United States. Sources generally do not distinguish between recent and older collections, but in most segments of the range the historical and current distributions of American eel apparently are not very different.

American eels have been found in hundreds of inland locations throughout most of Maine, with the highest density of documented occurrences in the region closest to the coast (Maine Aquatic Biodiversity Project).

Hartel et al. (2002) mapped hundreds of collection sites in several dozen drainages throughout Massachusetts.

In fish surveys conducted at 360 stream and pond locations in Rhode Island between 1993 and 2002, the American eel was collected at 50% of the localities sampled (181 localities) (Libby 2004).

In Connecticut, fish surveys conducted during 1988-1994 captured eels at 182 sites in basins except the Hudson River basin (Hagstrom et al. 1996).

Smith (1985) mapped well over 100 collection sites distributed nearly statewide in New York.

In Maryland, surveys in 1995-2002 found American eels in hundreds of locations throughout the Chesapeake Bay basin (Maryland Biological Stream Survey; http://mddnr.chesapeakebay.net).

Jenkins and Burkhead (1994) mapped more than 200 collection sites in Virginia.

In North Carolina, the species is represented by hundreds of collection sites in all rivers, extending into at least the eastern Piedmont. (Menhinick 1991).

Eels have been collected at more than 100 sampling stations in the middle Savannah River basin in South Carolina and Georgia (Marcy et al. 2005).

Bailey et al. (2004) mapped a dozen locations in the basins of lakes Superior, Michigan, Huron, and Erie in Michigan. These occurrences result from range expansion allowed by canal construction and thus are not a natural (native) part of the distribution.

GULF OF MEXICO DRAINAGES (EXCLUDING MISSISSIPPI RIVER BASIN)

Mettee et al. (1996) mapped 186 collection sites in Alabama and the Mobile basin. Boschung and Mayden (2004) mapped roughly 135 collection sites in Alabama.

Ross (2001) mapped several dozen locations in Mississippi for the period before 1983 and only about a dozen collection sites for 1983-1993. Ross did not explain whether this difference reflects a decline or is an artifact of collection effort.

MISSISSIPPI RIVER BASIN

For the period 1960-1987, Robison and Buchanan (1988) mapped 60+ collection sites in at least a dozen major river drainages in Arkansas. However, they indicated that the species is now scarce in most of those rivers.

Etnier and Starnes (1993) mapped 18 collection sites in Tennessee.

Pflieger (1997) mapped approximately 85 localities in Missouri.

Cross and Collins (1995) mapped occurrences in 16 counties in Kansas.

Smith (1979) mapped 14 locations in Illinois and stated that the species is rarely encountered and extremely sporatic in that state.

>1,000,000 individuals

Comments: Total adult population size is unknown but undoubtedly exceeds 1,000,000.

No information exists on the absolute or relative sizes of eel populations, and little information is available on relative fecundity of eels in different, rivers, estuaries, or regions across their geographic range (Douglas A. Dixon, pers. comm., 2005).

Density estimates for American eels vary widely among different locations. Using traps that captured eels larger than 30 cm, Secor et al. (2002) determined that yellow eel density was 1-30 /ha in the Hudson River in New York; eel density in the Hudson River at Albany was very low and, based on eels greater than 30 cm, relatively low but uniform throughout the remainder of the river down to its mouth (Secor et al. 2002). Using traps with size selectivity similar to that of the Hudson River study, Bozeman et al. (1985) found 182-232 eels/ha in a Georgia tidal creek. Ford and Mercer (1986) used traps to estimate density 875 eels/ha in a Massachusetts tidal stream. By electrofishing, Oliviera and McCleave (2000) estimated density at 8.4-21.8 eels/ha for all eels >10 cm in four freshwater Maine rivers, and electrofishing efforts by Oliviera (1997) and LaBar and Facey (1983) yielded density estimates of 450-3,230 eels/ha in a small Rhode Island River and 232-636 eels/ha in a Vermont lake, respectively; these estimates included substantial numbers of smaller yellow eels and elvers. Roghair and Nuckols (2005) recorded densities of 0.8 - 5.1 eels/100 m2 (80-510/ha) in the upper James River drainge in Virginia.

Important prey species for larger marine and freshwater fishes; predator on various other animals including commercially important crabs and clams (Van Den Avyle 1984). Larger yellow eels may establish territories in lower marsh areas, restricting smaller eels to smaller high marsh creeks (Massachusetts, see Van Den Avyle 1984).

Comments: Telemetry studies indicate that yellow eels in a tidal creek were generally inactive during
the day and active at night (Helfman et al. 1983). Yellow eels are inactive in winter in cold regions.

Average lifespan

Status: captivity: 50.0 years.

A. rostrata is a catadromous species, living most of its life in freshwater, but spawning in saltwater (Sumich, 1999). Sexually mature adults migrate to the Sargasso Sea, to spawn and supposedly die. Eels may reside in freshwater systems for up to 20 years before leaving to spawn at sea. The female lays up to 4 million buoyant eggs, which are fertilized by the male. Despite the use of technologically advanced SONAR tracking methods, adult eels are yet to be conclusively observed or captured in the presumed spawning areas in the Sargasso Sea (Sumich, 1999).

Average age at sexual or reproductive maturity (male)

Sex: male: 1642 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 1642 days.

The following summary is based primarily on Facey and Van Den Avyle (1987) and American Eel Plan Development Team (2000).

Spawning occurs in winter and early spring (McCleave et al. 1987). Each female produces about 0.4-21.9 million eggs. Larvae are transported by currents to areas near the continental margin of North America, but the mechanism by which they arrive in estuarine areas is not known, nor is it known precisely how they arrive in the Gulf of Mexico or the coast of South America. Larvae metamorphose during the pelagic stage (8-12 months after hatching, or perhaps more than a year later), and unpigmented "glass eels" actively move toward land. Glass eels develop external pigmentation as they enter coastal areas and then are referred to "elvers." Young eels begin moving upstream in river systems before pigmentation is complete, generally in spring in the northeastern United States. Eels develop into the "yellow eel" stage, which resemble the adult stage, usually by age II. Some yellow eels move far into stream headwaters whereas others remain in estuaries. In general, eels in fresh water are all or almost all females. Size and age of maturity are greater in the north than in the south (Helfman et al. 1987). For example, maturation occurs in 8 to 24 years in the Chesapeake Bay Region, but may occur earlier in southern regions and later in northern regions. In the south, females older than eight years old or longer than about 70 cm were rare, and males older than five years old or longer than 40 cm were also rare (Hansen and Eversole 1984). In contrast, maturing females in Newfoundland averaged 13 years of age (range 9-18 years) and more than 70 cm long (Bouillon and Haedrich 1985). Female eels from Lake Champlain averaged 16 years old and nearly 70 cm long (Facey and LaBar 1981). Eels greater than age 20 were found in Lake Champlain. Yellow eels captured in freshwater in the Husdon River in New York were up to 25 years old (Secor et al. 2002). No males were captured in the two northernmost studies. Female-dominated populations (or samples) also have been documented in Maryland (Foster and Brady 1982), South Carolina (Hansen and Eversole 1984), and Georgia (Helfman et al. 1984). Inland populations of eels tend to be all or almost all female (Facey and LaBar 1981, Helfman et al. 1987). After the lengthy "yellow eel" stage, eels may undergo a physical and physiological transformation into a distinct, sexually mature "silver eel" stage, which is sexually matures and move downstream and into the ocean to spawn. Morphologically altered silver eels have not been observed in all parts of the range. Adults presumably die after spawning.

Measures are now being taken to decrease the impact of fisheries on A. rostrata populations in the United States, such as more closely regulating harvesting of glass eels and elvers (Landau, 1992). Ongoing studies still track juveniles and adults during their time in freshwater and movements to the Sargasso Sea for spawning (Sumich, 1999).

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Very large range in the Atlantic Ocean and estuaries and rivers of the Atlantic and Gulf coasts of the United States and southeastern Canada, as well as much of the Mississippi River basin and the West Indies and Caribbean regions; hundreds of occurrences or subpopulations; total adult population size likely exceeds 1 million but appears to be decreasing; factors possibly contributing to the decline include barriers to migration, habitat loss and alteration, hydroturbine mortality, oceanic conditions, overfishing, predation, parasitism, and pollution. Better information is needed on the current trend and the relative importance of the various threats.

Intrinsic Vulnerability: Highly vulnerable

Comments: American eels are slow to mature (7 to 30+ years) and reproduce only once during their lifetime. However, individual females often produce millions of eggs.

Environmental Specificity: Broad. Generalist or community with all key requirements common.

Other Considerations: The current status of the American eel is poorly understood, due to limited and (until recently) nonstandardized assessment efforts and protocols across the range of the species (American Eel Plan Development Team 2000). In the past, sampling programs in most jurisdictions were not designed to monitor the abundance of American eels, and resulting survey data may not adequately reflect trends in American eel populations. A widespread concern about the status of various local eel stocks reflects more the absence of knowledge about the stocks rather than a well-founded knowledge of decline (American Eel Plan Development Team 2000).

Because eels have been harvested along the Atlantic coast of the United States for many decades (see Jessop 1997 for a concise summary of the status of the U.S. American eel fishery), harvest data might serve as a source of information applicable to trend determination. Unfortunately, standardized harvest data are often not available, and existing data sets generally are for brief time periods or do not account for fishing effort. Furthermore, harvest data are often a poor indicator of abundance, because harvest is dependent on demand and may consist of annually changing mixes of year classes (American Eel Plan Development Team 2000).

For the past few years, standardized sampling and record keeping have been initiated under the auspices of the Atlantic States Marine Fisheries Commission. Resulting data eventually should allow a better assesssment of trends in American eel populations.

Overall Status. Etnier and Starnes (1993) stated that American eels remain "fairly common in Atlantic and eastern Gulf coastal areas, but impoundments on most rivers in central North America may have reduced inland eel populations."

The Southeastern Fishes Council Technical Advisory Committee (Warren et al. 2000) categorized the American eel as "currently stable" in the southeastern and southcentral United States. This category was defined as "a species or subspecies whose distribution is widespread or stable or a species or subspecies that may have declined in portions of its range but is not in need of immediate conservation management actions."

ATLANTIC COAST, CANADA TO SOUTHERN FLORIDA

Data from resource and fisheries agencies along the Atlantic coast of the United States and Canada suggest that there was a broad decline in eel abundance since the early 1980s (Richkus and Whalen 2000).

Indications from commercial harvest data. Eel catches in Ontario, Quebec, Prince Edward Island, and rivers of New Brunswick and Nova Scotia draining into the Gulf of St. Lawrence have declined since the mid-1980s (Fishes and Oceans Canada, Jessop 2000). The St. Lawrence River-Lake Ontario system accounts for 57% of the commercial catch. Throughout the 1990s, all provincial catches associated with this region "showed a synchronous exponential decline," with a combined catch in the late 1990s that was 59% below the long-term mean.(Casselman 2001).

Commercial landings of American eel in the Atlantic coastal states (Maine to Florida) peaked in the mid-1970s at 3.5 million pounds but have since declined significantly to a near record low of 868,215 pounds in 2001 (National Marine Fisheries Service, Fisheries Statistics and Economics Division; ASMFC Fisheries Focus 12(1), March 2003). Catches averaged 2,540,599 pounds between 1970 and 1984 and 1,356,434 pounds between 1985 and 1998. The significance of these data is uncertain because corresponding information on the level of fishing effort is not avilable. Commercial landings fluctuate widely with market demand and so may not reflect changes in eel abundance.

Annual trends in reported eel catches by individual states (NMFS Fisheries Statistics and Economics Division) comprise three basic groups: declining catch (e.g., Rhode Island, New York); increasing catch (e.g., New Jersey, Delaware, Maryland); and catches that have returned to values typical of those reported prior to the peak catches of the 1970s and early 1980s (e.g., Maine, Massachusetts, Florida). Reported catches in some states declined sharply in 1996 but catch data may be incomplete (American Eel Plan Development Team 2000).

Landings in recent decades in Maine peaked in the 1970s at about 176,000-191,000 pounds. By 2000-2004, landings had declined to about 13,000-35,000 pounds (data from Maine Department of Marine Resources).

In Massachusetts, catches periodically have been much higher in the past than they are now, but they vary with the economy and demand and are not a reliable indicator of eel abundance (Hartel et al. 2002).

In New York, there is a commercial eel fishery in the upper Delaware system, but no readily identifiable trend is evident in the catch (Wayne P. Elliot, pers. comm., 2005). Subjective impressions are that the commercial eel catch is relatively stable (Norm McBride, pers. comm., 2005).

Dramatic evidence for the impact of major dams on eel abundance can be found in the Susquehanna River basin. Prior to completion of four mainstem dams on the lower Susquehanna (the last, Conowingo Dam, was built in 1928), eels were common throughout the Susquehanna basin and were popular with anglers in Pennsylvania lakes (Pennsylvania Commission of Fisheries 1897). Annual harvests of eels in the Susquehanna were nearly 1 million pounds at that time (J. Foster, pers. comm., 1995). For many decades, there have been no recreational or commercial harvests of this species in Pennsylvania. Source: U.S. Environmental Protection Agency, Mid-Atlantic Environmental Assessment (http://www.epa.gov/maia/html/mbss-ch4.html).

The commercial catch in the Chesapeake Bay area declined considerably between 1980 (318,000 kg reported by both Maryland and Virginia) and 1990 (54,000 kg in Maryland and 136,000 kg in Virginia) (Murdy et al. 1997). Trends in eel abundance may vary with location. Geer (2003) reported declines in the lower Chesapeake Bay, whereas Weeder and Uphoff (2003) concluded that commercial landings are either stable or possibly increasing in the upper Chesapeake Bay.

Recreational harvest data. For the most part, eels are caught incidentally by recreational hook and line anglers fishing for other species. A large proportion of the eels caught are released alive. American eels are often collected in minnow traps for use as bait by recreational anglers fishing for striped bass, bluefish, and other species.

The NMFS Marine Recreational Fisheries Statistics Survey (MRFSS), which has surveyed recreational catch in ocean and coastal waters since 1981, shows a declining trend in the eel catch during the latter part of the 1990s. For the Atlantic coast area surveyed, the estimated total annual catch ranged from 212,690 eels per year in 1982 to 36,741 per year in 1997. Recreational harvest in 2001 was 10,805 eels, down an order of magnitude from the peak in the early 1980s.

Fishery-Independent Monitoring. Fishery-independent surveys in the United States and Canada indicate declining or stable numbers in all sampled watersheds; no survey showed an increasing trend (Haro et al. 2000).

A few long-term data sets from fish ladders are available, and these suggest a decline in eel abundance. A severe decline has occurred in the number of eels ascending the eel ladder at the Moses-Saunders Dam (Ontario-New York) during the peak spring migration in the St. Lawrence River-Lake Ontario segment of the range (Castonguay et al. 1994, Casselman et al. 1997, Tremblay 2005). The number of juvenile eels climbing the eel ladder declined from more than one million per year in the early 1980s to fewer than 4,000 per year in the late 1990s and to level approaching zero by 2001. Over the past 20 years (or one generation), the decline exceeds 99 percent (Tremblay 2005). However, the decline in eel counts may be an artifact of lock/water flow usage at the Beauharnois Dam, which is downstream from the Moses-Saunders facility (American Eel Plan Development Team 2000).

A trend analysis of eel migration data for 1984-1995 (including data from the Moses-Saunders eel ladder) found significant negative trends for yellow and/or silver eel abundance in Ontario, Quebec, New York, and Virginia (Richkus and Whalen 1999). Richkus and Whalen found no significant trends for glass eels or elvers, but those data sets were generally not complete and may not have covered the years where the largest declines were observed in other data sets (Richkus and Whalen 1999). Overall, Richkus and Whalen (1999) concluded that there is broad-based evidence for a stock-wide abundance decline of American eel from 1984 to 1995.

Annual counts of migrating fish in the Connecticut River have tallied fewer eels in recent years. In 2002, at all dams on the river up to Holyoke, 275 eels were counted. More recently, counts were as follows: 25 in 2003, 1 in 2004, and none in 2005 (as of July). Eel counts in an eelway in the Westfield River (Connecticut River basin) in Massachusetts have been relatively consistent (roughly 300-500) since the eelway was constructed in 2001 (Caleb Slater, pers. comm., 2005).

A young-of-the-year abundance survey in the Jones River, Kingston, Massachusetts, showed no clear trend in eel abundance for the period 2000-2005 (Chase 2005).

Long-term data (1974 through 1996) from the Conowingo Dam fish lift on the Susquehanna River in Maryland showed a decline in elver counts after the early 1980s (J. Weeder, pers. comm.).

Elver abundance in South Carolina shows no indication of decline over the past few years, and many eels have been seen recently in electrofishing efforts in that state (Mark R. Collins, pers. comm., 2005).

In Florida, annual young-of-the-year sampling was initiated a few years ago at the Guana River Dam and Rodman Reservoir Dam (Bonvechio et al. 2004), but data obtained thus far are insufficient for trend determination.

Misceelaneous and anecdotal reports. George (1981) reported that eel abundance has apparently declined in the Adirondack region of New York, presumably as a result of dams that block eel movements.

In Virginia, eel populations have been largely eliminated in the upper James drainage, much of the middle James, and the upper and middle Roanoke River as a result of dam construction (Jenkins and Burkhead 1994). However, Roghair and Nuckols (2005) recently recorded eel densities of 80-510 eels per hectare in mountain streams in the James River drainage.

In Virginia, annual electrofishing (approximately 1 hour of electrofishing at each location) was conducted in the James River between Scottsville (rkm 304) and the headwaters near Iron Gate (rkm 555) in October-November from 1991-2004 (except 2002). The number of eels caught per year was small (range 13 to 209), with a general increasing trend from 1991 to 2000. [Data from Scott M. Smith, Virginia Department of Game and Inland Fisheries]

Populations of diadromous fishes in the Santee-Cooper Basin of South Carolina are significantly depressed relative to historical levels (USFWS et al. 2001).

GULF OF MEXICO DRAINAGES (EXCLUDING MISSISSIPPI RIVER BASIN)

Currently, the American eel appears to be secure in Alabama (Boschung and Mayden 2004).

Data from rotenone surveys in Fall Line and Coastal Plain pools of the Tallapoosa River downstream of Thurlow Dam, Alabama, in the autumn of 1990, 1992, and 1997 show reduced numbers of eels in the more recent samples (e.g., no eels were found in the Coastal Plain samples in 1992 and 1997) (John Hornsby, Alabama Department of Conservation and Natural Resources). In all samples, American eels made up a small proportion (less than 1.5 percent) of the fish samples. Hornsby observed many eels in the lower Tallapoose River during the late 1950s and early 1960s, including thousands of small eels climbing Thurlow Dam on two separate occasions. A crash in the river's population of migratory fishes, which may have included American eel, occurred around 1969-1970, when three Corps of Engineers navigation locks were under construction on the Alabama River downstream of Thurlow Dam.

In Mississippi, eel abundance varies from year to year (Ross 2001), but no clear trend has been identified.

The America eel is native to much of Texas, but dams now impede upstream migrations, and the species has been eliminated from most central and western areas of the state (Chilton 1997).

MISSISSIPPI RIVER BASIN

In Arkansas, eels are "especially abundant in the lower Arkansas River (Robison and Buchanan 1988). However, statewide eel populations have undergone a "drastic decline" due to the construction of dams on virtually all of the state's major rivers (Robison and Buchanan 1988).

High dams on the Osage and White rivers have eliminated eels from large areas of the Ozarks in Missouri (Pflieger 1997).

In Kansas, historical records indicate that eels were more widely distributed and abundant 100 years ago than they are now (Snow 1875, Cragin 1885, Graham 1885, Cross and Collins 1995, Haslouer et al. 2005). Today, obstructions in the lower Arkansas River and its tributaries in Oklahoma and Arkansas block eel movements such that eels no longer occur in southern Kansas (Cross and Collins 1995). In the Kansas River basin, American eels formerly penetrated at least as far as Rawlins County, but today dams block access to that area; recent collections (1987, 2005) indicate that eels do sometimes still occur in streams in northeastern and central Kansas (Cross and Collins 1995; Haslouer et al. 2005; Tom Mosher, pers. comm., 2005).

Smith (1979) stated that the constuction of dams has undoubtedly decreased the number of eels in Illinois. Available records mapped by Smith suggest that eels were never very common there. A map of collection sites in Illinois produced by the Illinois Natural History Survey indicates 16 eel collection sites before 1979 and none after 1979 ().

The American eel is not abundant in its Iowa range, but Mayhew (1987) stated that it did not appear to be on the decline over the last 20 to 30 years.

Anecdotal evidence suggest that eel numbers may have declined in Indiana since the 1970s and 1980s (Brant Fisher, pers. comm., 2005). Surveys by the Indiana Division of Fish and Wildlife in the White River and Blue River systems in southern and central Indiana also suggest a declining trend (Bob Ball, pers. comm., 2005). However, in all cases, this information is based on very small numbers of eels (fewer than 7 in any single year), so trend determination is problematic.

Coker (1930) reported that catches in the Mississippi River in Wisconsin and Minnesota were never significant and that the eel had been steadily disappearing from the whole basin for at least 30 years.

The Upper Mississippi River Long Term Research Monitoring Program has conducted annual standardized fish sampling in four upper Mississippi River pools (in Minnesota, Wisconsin, Iowa, and Illinois), an open river reach below St. Louis (Cape Girardeau, Missouri), and one reach of the Illinois River (La Grange Pool, Havana, IL) since the late 1980s (). Frequency of occurrence (percentage of samples containing at least one eel) was as follows: Pool 4, 1994 and 1996 (1% frequency of occurrence); Cape Girardeau: 4% in 1993, 2% in 1998, and 1% in the other years). In pools 8, 13, 26 and at Havana, frequency of occurrence of American eel (apparently rounded to two decimal places) was 0.00% in all years. Overall, it appears that eels were rarely or infrequently captured in all areas throughout the sampling period. Eels captures did not appear to decrease in frequency with any particular geographic pattern (e.g., south to north). However, reductions in sampling frequency and gear types used since 1990 (as well as small sample size) make trend analysis difficult. Similarly, statewide population trends in Wisconsin are uncertain (Lyons et al. 2000).

Mettee et al. (1996) reported that recent records of eels in the Tennessee River of Alabama are rare (these few records apparently are the only ones for the Tennesse River in Alabama). Despite widespread distribution in the Mobile basin, the inland distribution of American eels may have declined in recent years because few if any eels are able to traverse high-lift locks and dams; angler reports and sampling efforts indicate a progressive decline in abundance with each upstream dam (Mettee et al. 1996).

WEST INDIES/CARIBBEAN REGION

Anecdotal information and some limited river and estuarine sampling suggests that American eels are quite scarce in Puerto Rico and that over the past 20-25 years their abundance appears to have substantially decreased (Craig G. Lilyestrom, pers. comm., 2005).

Global Short Term Trend: Unknown

Comments: Text exceeds space limitations for trend information. See "Other Rank Considerations" section.

Global Long Term Trend: Increase of 10-25% to decline of 50%

Comments: See "Other Rank Considerations" section.

Comments: Factors possibly contributing to the decline along the Atlantic coast of Canada and the United States include barriers to migration, habitat loss and alteration, hydroturbine mortality, oceanic conditions, overfishing, parasitism, predation, and pollution (Haro et al. 2000, Richkus and Whalen 2000).

OCEANIC CONDITIONS

Oceanic effects on long-term patterns of American eel recruitment are poorly understood, but they may play a role in the changing abundance of eels along the Atlantic coast of North America (Castonguay et al. 1998). The decline in recruitment of the American eel occured at the same time as that of the European eel (Anguilla anguilla). Both species spawn in the Sargassso Sea and migrate as larvae to continental waters, so the coincidence in recruitment failure suggests the likelihood of a common, Atlantic-wide cause.

There is indirect evidence that the Gulf Stream weakened in the 1980s. A slower Gulf Stream could interfere with the drift of leptocephalus larvae from the Sargasso Sea toward the Atlantic coast and might generate observed patterns of declining abundance of American eel in North America (Castonguay et al. 1998). Such changes might result from global warming (American Eel Plan Development Team 2000).

Knights (2003) proposed that warming of the Sargasso Sea/Sub-Tropical Gyre (associated with global warming trends) may inhibit spring thermocline mixing and nutrient circulation, with negative impacts on productivity and hence food for leptocephalus larvae. Knights hypothesized that concurrent gyre spin-up also affects major currents and that slowing of oceanic migration has probably enhanced starvation and predation losses. Knights further noted that local factors, such as unfavourable wind-driven currents, can also affect recruitment of glass eels on continental shelves. Knights discussed evidence indicating that fishing mortality and continental climate change appear to have had lesser impacts on eel populations.

Substantial long-term and short-term changes in ocean temperature, salinity, and upper-ocean transport conditions (Stebbing et al. 2002, Colbourne 2004, Drinkwater and Gilbert 2004, Curry and Mauritzen 2005, Rossby et al. 2005, Sutton and Hodson 2005) recently have been documented, and Attrill and Power (2002) showed that during a recent 16-year period (1977-1992), climatic forcing, by means of the North Atlantic Oscillation, was consistently the most important parameter explaining variation in assemblage composition and abundance and growth of juvenile marine fishes during their estuarine residence in the Thames Estuary, United Kingdom. This information suggests that an investigation of the relationship between oceanic conditions and patterns of abundance and recruitment of the American eel might be fruitful in understanding recent population fluctuations.

The cause(s) of the apparent decline in eel abundance in Canada (Gulf of St. Lawrence, Lake Ontario) is uncertain but may result from a decreased abundance of elvers entering the Gulf of St. Lawrence due to adverse oceanic conditions (Jessop 2000). The decline in the Lake Ontario eel catch is linked to the long-term decline in the number of young eels that pass upstream at hydroelectric dams on the upper St. Lawrence River.

Ross (2001) stated that year to year changes in eel abundance in Mississippi are likely due more to oceanic current patterns impacting the recruitment of larvae from the Sargasso Sea, rather than to local conditions.

HABITAT DESTRUCTION AND ALTERATION

Major habitat perturbations in the St. Lawrence River took place in the 1950s (e.g., construction of the St. Lawrence Seaway and hydroelectric dams), about 30 years before recruitment started declining; this long delay argues against these perturbations being primary causes of the decline (Castonguay et al. 1998). However, an unpublished, long-term CPUE series (1930-1965) provides evidence that the decline occurred simultaneously with the habitat alterations (see Castonguay et al. 1998). Habitat loss resulting from impoundment may contribute to reduced eel abundance in eastern Canada (Jessop 2000).

Most losses of estuarine wetlands along the Atlantic coast occurred well before the decline in American eel abundance was evident. Losses of upstream riverine habitat occurred even earlier with the construction of many mill dams in the 1600s and 1700s. Many larger dams were constructed 50-100 years ago or more. Because of the significant time lapse between these habitat losses and observed reductions in eel abundance, it is difficult to argue that such losses played a major role in the decline (Douglas A. Dixon, pers. comm., 2005).

A potential threat of unknown significance is degradation of spawning habitat caused by the harvest of seaweed/algae (Sargassum) in the Sargasso Sea (American Eel Plan Development Team 2000). Sargassum seaweed has been harvested in the Sargasso Sea since 1987 (SAFMC 1998). It is unknown whether this harvest has had direct or indirect affects on American eel mortality, and the extent of eel bycatch in these operations is unknown. Sargasssum harvest was eliminated in the south Atlantic EEZ in 2001 as a result of a management plan adopted by the South Atlantic Fisheries Management Council (SAFMC 1998).

Channel dredging, shoreline filling, and overboard spoil disposal are common throughout the Atlantic coast, but currently the effects of these activities on American eels are unknown (American Eel Plan Development Team 2000). Changes in salinity in embayments, as a result of dredging projects, could alter American eel distribution but, again, such effects are unsubstantiated (American Eel Plan Development Team 2000).

BARRIERS TO RIVERINE MOVEMENT AND UPSTREAM HABITAT ACCESS

Dams are frequently mentioned as a factor in the apparent declines in American eel abundance. Dams that reduce or restrict upstream movements limit the amount of habitat available to eels. Many surveys indicate that density and population size of American eels tend to decrease with increasing distance inland and with increasing severity of obstructions to movement. Given the dominance of large females in many riverine habitats, such habitat reduction could conceivably lead to reduced eel productivity and abundance. However, the importance of freshwater in eel productivity is still an open question (e.g., Morrison et al. 2003). Abundance declines in freshwater habitats may simply reflect greater use of estuarine habitats where conditions are more favorable for growth and maturation (Douglas A. Dixon, pers. comm., 2005).

Atlantic coastal streams from Maine to Florida have 15,115 dams that can hinder or prevent upstream and downstream fish movement, resulting in a restriction or loss of access to 84 percent of the stream habitat within this historical range (Busch et al. 1998). This is a potential reduction from 556,801 kilometers to 90,755 kilometers of stream habitat available for migratory and diadromous species such as American eel. The analyses excluded obstruction caused by most natural barriers.

Fish passage is getting attention through the licensing or relicensing of dams for hydropower production and navigation, but more than 90% of dams on the eastern seaboard are not hydroelectric facilities and therefore have not been subject to continual relicensing and fish passage analysis (Busch et al. 1998, American Eel Plan Development Team 2000). Only 7% of these dams are covered by regulatory programs that could provide fish passage.

The following examples include some of the many reports that relate reduced eel abundance in rivers to passage obstructions (and distance from salt water).

Obstruction by hydroelectric dams may contribute to reduced eel abundance in eastern Canada (Jessop 2000). Silver eel declines in the St. Lawrence River basin may be due to escapement reductions from upper St. Lawrence dams and water flow control, rather than fisheries (Richkus and Whalen 1999). In Canadian lakes, Smith and Saunders (1955) found smaller standing stocks of eels in lakes that were farther from the ocean and that had obstructions such as dams, falls, and lakes.

Impoundment of the upper estuary of the Petitcodiac River in New Brunswick resulted in reduced abundance of American eels (Locke et al. 2003).

Within a year after the removal of Edwards Dam on the Kennebec River in Maine, large numbers of American eels and other migratory species were observed in upstream habitats that had been inaccessible to these species for more than 150 years (O'Donnell et al. 2001).

In Rhode Island, eels were commonly collected throughout the state but were not well represented in the upper reaches of the Blackstone and Pawtuxet River watersheds, undoubtedly due to the many dams that impede upstream migration (Libby 2004).

In Connecticut, eel densities are much lower in headwater regions of streams that have many, or high, dams or falls; movement upstream appears to be affected by both the number and height of obstructions (Levesque and Whitworth 1987, Whitworth 1996, Hagstrom et al. 1996). In southern New England, several recent projects have removed dams or installed fishways that increase available riverine habitat for American eels (U.S. Fish and Wildlife Serve, Connecticut River Coordinator's Office, ).

In Pennsylvania, American eel passage has been blocked for many years on the Susquehanna River by four large hydroelectric projects on the lower river (Conowingo, Holtwood, Safe Harbor, and York Haven). Fish passage facilities desgned for American shad were installed in each of these facilities within the past 15 years, but eel passage may be limited. No eels were passed at these fishways in 2005 (Leroy M. Young, pers. comm., 2005). So far there has been no consideration for outmigration at these fishways. In the Delaware River basin, elvers use fishways at the Easton, Chain, and Hamilton Street dams, but the fishways are not designed to allow quantification of eel passage. Cementon Dam, upstream of the Hamilton Street Dam, lacks a fishway, but at least some elvers successfully pass this dam (Leroy M. Young, pers. comm., 2005). The Schuylkill River, a major tributary of the Delaware River in Pennsylvania, has nine dams, some of which have fish passage facilities, are breached or partially breached, or are scheduled for fishway installation within the next few years. A dam upstream of the Felix Dam was exposed when the Felix Dam was breached and is currently an impediment to fish passage. There are no plans to remove the two uppermost dams New Kernsville and Auburn) on the Schuylkill River. Some eels pass the dams downstream of New Kernsville, but the efficiency of passage is unknown (Leroy M. Young, pers. comm., 2005).

In Maryland, more than 1,000 human-made barriers to migratory fish (Leasner, DNR, pers. comm.) reduce access of American eels and other fishes to their historical habitats. Maryland Biological Stream Survey data suggest that mainstem dams have been a major factor in this decline by blocking the upstream migration of juvenile eels (U.S. Environmental Protection Agency, Mid-Atlantic Environmental Assessment; , accessed 24 April 2006).

Populations of diadromous fishes in the Santee-Cooper Basin of South Carolina are significantly depressed relative to historical levels, primarily as a result of migration blockages and habitat alterations caused by the more than 50 dams in the basin (USFWS et al. 2001).

In Mississippi, upstream movement of eels could be impeded by dams (Ross 2001).

In Alabama, dams on major rivers impede its progress to far upstream reaches (Boschung and Mayden 2004).

In Kansas, much formerly occupied habitat is now inaccessible as a result of dams and flow diversions (Haslouer et al. 2005).

In Iowa, construction of impassable flood control dams on the Des Moines, Iowa, and Chariton rivers undoubtedly has restricted the migration of eels in these drainages (Mayhew 1987).

Dams are not only barriers to movement but also may alter streamflow patterns. Elvers and young eels are small and not powerful swimmers and seemingly might be affected by alterations in stream flow caused by dams and other structures. However, they successfully move through strong marine, estuarine, and riverine currents, and so altered stream flows may not have much effect on upstream movements.

HYDROTURBINE MORTALITY

Passage through turbines at hydropower dams during downstream migration may represent a major source of eel mortality (Ritter et al 1997). Turbine-induced mortality ranges from 5 to 60%, depending on turbine type, flow rate, and the length of the fish (Hadderingh 1990, 1994; McCleave, pers. comm.). Mortality of eels passing downstream through turbines may contribute to reduced eel abundance in eastern Canada (Jessop 2000). The amount of nonlethal injury to eels that pass through turbines is not well documented.

Hundreds of downstream-migrating eels (large females) have been killed by the turbines of the Benton Falls dam on Maine's Sebasticook River in fall (Northern Sky News, December 2004). A 2001 Maine Department of Marine Resources study that showed fifty percent of the eels passing the dam are killed by the turbines. At a small hydroelectric facility on the Farmington River in Connecticut, all telemetered eels migrating downstream traversed the dam via the turbines (Eltz et al. 2005). Survival rates were not reported.

The design of downstream passageways and the possibilities for use of nongenerating periods to reduce eel mortality is hindered by poor knowledge of downstream migration behavior (e.g., environmental cues that trigger migration; depth of migration; effects of light and water currents) (American Eel Plan Development Team 2000).

OVERFISHING

The American commercial fishery has traditionally supplied American eels for the regional and European food markets, domestic trotline bait, and bait for domestic sport fisheries (American Eel Plan Development Team 2000). Most of the North American eel harvest is exported to Western Europe, but some of it goes to regional domestic markets catering to several ethnic groups (Jessop 2000).

The worldwide demand for eels is greater than can be supplied by harvest of wild populations, and eel farming-widespread in Japan, Taiwan, and China, and to a lesser extent in Holland, France, and Italy-has become a major source of marketable eels (Jessop 2000). In Asia, glass eels and elvers are cultured to marketable size. Since captive reproduction of American eels is not yet feasible, the intensive aquaculture industry in eastern Asia is dependent upon an annual supply of wild-caught glass eels and elvers (Moriarty and Dekker 1997). When Asian domestic stocks are inadequate, a strong market develops for American eels. The Asian market for American glass eels and elvers was strong from 1972-1977, declined dramatically in 1978, and began to strengthen in the 1990s (American Eel Plan Development Team 2000).

The bulk of the commercial eel catch in the United States (80%) occurs in central coastal (mid-Atlantic) states, with less from northern (19%) and southern (1%) states (Casselman, J. M. 2001. Dynamics of American eel, Anguilla rostrata, resources: declining abundance in the 1990s. Extended abstract of a paper presented to Advances in Eel Biology, Tokyo, Japan, September 28-30, 2001). For example, both Massachusetts and Florida have been granted de minimis status by the ASMFC for their commercial American eel fisheries in recent years. This indicates that their landings comprise an insignificant portion of the overall harvest.

Historically, in Canada, the most successful eel fisheries have occurred along the St. Lawrence River from Trois-Rivières to Rivière-du-Loup, where the catch consists mainly of the more valuable silver eel. Smaller, but still important, fisheries which harvest mostly yellow eels exist in the Bay of Quinte region of Lake Ontario, in the Saint John River, and along the northeast shore of New Brunswick, on Prince Edward Island and along the southern coast of mainland Nova Scotia, and on Cape Breton Island. Newfoundland has a minor fishery. [Jessop 2000]

Commercial fisheries for elvers and silver eels exist throughout the eel's range in both estuarine and freshwater habitats. Glass eels are vulnerable to heavy harvest because they aggregate seasonally to migrate (Haro and Krueger 1988). Because eels are slow to mature (7 to 30+ years), each prespawning cohort (year class) is vulnerable to harvest and other decimating factors over many years. Changes in year-class abundance are not readily recognizable because harvest abundance data include fish of similar sizes but from a number of year classes (Ritter et. al. 1997).

In the Gulf of Maine, some eels are caught by recreational anglers fishing to other species. There is a small commercial fishery for eels sold as bait for larger sport fishes such as striped bass (Meister and Flagg 1997, Collette and Klein-MacPhee 2002). Recent declines in landings of adults and elvers in Maine and the maritime provinces of Canada may be due to overexploitation of the resource, especially elvers (Meister and Flagg 1997). The lower harvests in recent years may have resulted from a combination of overfishing of the adult stocks (yellow and silver eels) and a reduction in recruitment due to the heavy elver harvest in the mid-1970s (Meister and Flagg 1997). Smithwood and McKeon (1999) reported that the current trend in Maine seems to be one of increasing exploitation of the resource, with a corresponding active role being taken by the state through regulation to ensure the perpetuation of the resource into the future.

Massachusetts has no commercial fishery for elvers or silver eels (Chase 2005). The Massachusetts commercial eel fishery targets yellow eels for both food and bait. Yellow eel landings for 2004 were 5,328 pounds, representing a modest increase from the 4,047 pounds reported in 2003 (Chase 2005). Landings have increased slightly each year since 2000 (2,976 pounds); possibly this is more a response to reporting improvements than increased harvest. (Chase 2005).

In the commercial eel fishery in New York, Werner (1980) reported that 125,000-150,000 pounds are caught annually in the lower Hudson and Delaware rivers, and the annual catch is 25,000-50,000 pounds in Lake Ontario.

There is no commercial fishery in Pennsylvania, and the sport fishery, although not documented, appears to be a minor part of the overall fishery (Leroy M. Young, pers. comm., 2005).

In Chesapeake Bay, American eels support an extensive fishery. Most of the catch is exported to Europe and eastern Asia, but some are consumed locally (Murdy et al. 1997). The declining catch of American eels in the Chesapeake Bay region may be due to overexploitation or may reflect market conditions (Murdy et al. 1997).

There is a small commercial fishery for American eels in Florida, which operates almost exclusively in the St. Johns River system (Florida Fish and Wildlife Conservation Commission; www.floridamarine.org ). The documented annual American eel harvest in Florida is small; commercial landings in 2000 totaled only 6,054 lb (2,752 kg), the lowest harvest year since 1994 (Bonvechio et al. 2004). In 2001, landings more than doubled to 14,218 lb (6,463 kg), but they declined to 7,587 lb (3,441 kg) in 2002 and 8,486 lb (3,849 kg) in 2003. A consistent decline in eel harvest has been observed since the early 1990s, but harvest reported in 2003 was similar to that reported in recent years (Bonvechio et al. 2004). From 1980 to 2003, American eel landings in Florida exhibited a substantial decline; the highest reported harvest during this time period was in 1980-81 and totaled 460,000 lbs (208,652 kg) (Bonvechio et al. 2004). Commercial landings in Florida are of large eels; in recent years, no commercial harvest of the glass eel stage, silver (mature) eel stage, or of bait-sized juvenile eels was reported for Florida (Bonvechio et al. 2004). Currently there is no known recreational fishery for the American eels in Florida; incidently caught eels generally are released alive (Bonvechio et al. 2004).

American eels are caught incidently in commercial and recreational fisheries in Louisiana, but the harvest is an insignificant portion of the U.S. total (Winslow et al. 2005). Beginning in 1995 permits were issued to fishermen wanting to target eels, but the harvest was very small 487 pounds in 1999), and by 2000 no further permits were requested. Anecdotal reports indicate that eel abundance has not changed in the freshwater areas of the state. Data for recreational saltwater angling (corrected for effort) for 1981-2004 indicate high interannual variability; harvest ranged from a high of 66,932 eels in 1988 to a low of 1,377 eels in 1997. Approximately 86% of all caught eels were released alive (indicating lack of value to marine anglers). Nearly 90% of the catch occurred in inshore saltwater and brackish water (10% offshore). The data, the use of which is limited by relatively small sample sizes and changes in fishing effort (Winslow et al. 2005), exhibit no clear trend.

PREDATION

Increased populations of striped bass (Morone saxatilis) since the 1980s (Richards and Rago 1999) could be a factor in the decline in American eel abundance. Bass predation on blueback herring has been proposed as a contributing factor in the recent herring decline in the Connecticut River (Savoy and Crecco 2004).

Pacific salmonids have been introduced into Lake Ontario in efforts to develop a recreational fishery. Initiation and extensive growth of the salmonid fishery coincides with the reported declines of American eel (Douglas A. Dixon, pers. comm., 2005). This factor should be investigated as a factor possibly contributing to the eel decline in that region.

PARASITISM

An exotic, parasitic swim-bladder nematode (Anguillicola crassus) appears to have recently invaded the Hudson River ecosystem and may represent a major stress to eels in the Hudson River and elsewhere (Secor et al. 2002).

CONTAMINANTS

American eels (Anguilla rostrata) from the St. Lawrence River are heavily contaminated with chemicals (Hodson et al. 1994, Couillard et al. 1997, Castonguay et al. 1998). Lethal toxicity from chemical contamination has been known to occur in the St. Lawrence eels for the past 30 years (Castonguay et al. 1998). Chemical contamination may be associated with increased incidence of disease and reproductive impairment, but further studies are needed to confirm the observed associations between chemical contamination and pathological changes (Couillard et al. 1997). The highest concentrations of chemicals in migrating silver eels in the St. Lawrence River are in the gonads; chemical levels in the eggs could exceed the thresholds of toxicity for larvae (Hodson et al. 1994). Due to PCB body burdens in eels, commercial harvest of eels for human consumption has been banned throughout the Hudson River estuary.

American eels are long-lived and may be exposed to endocrine disrupting contaminants (Sumpter and Johnson 2005) that could affect sexual development, maturation, fertility, and fecundity. Further investigation of this possibility and its role in the eel decline is needed (Douglas A. Dixon, pers. comm., 2005).

Management Requirements: See Hadderingh (1990), Haro (1996), and Richkus and Whalen ( 1999) for information on devices that are variably effective in deflecting American eels from water intakes at hydroelectric dams.

Management Research Needs: See American Eel Plan Development Team (2000, Fishery Management Plan for American Eel).

Biological Research Needs: Better information is needed on population trend and on the relative importance of various threats. Also, further research is needed on the importance of freshwater habitats to eel productivity.

Global Protection: Very many (>40) occurrences appropriately protected and managed

Comments: A large number of occurrences are appropriately protected and managed for long-term persistence.

Anguilla rostrata is of major economic importance. In Japan and Taiwan, elvers and adults are considered a delicacy and the elvers are also eaten live in Europe. The largest aquaculture of eels is in Japan, and then Europe and the United States to a lesser extent (Landau, 1992). All forms of A. rostrata, however, are sought after commercially, to be shipped to places where they are used as food. There is concern for A. rostrata populations in the United States recently because of over harvesting the elvers and glass eels so not enough eels are reaching adulthood to migrate back to the ocean and reproduce (NS Dept. of Fisheries website, 1999).

Comments: Supports commercial and limited recreational fisheries. Marketed for human consumption (most shipped to Europe for processing) and for use as bait for crabs and game fishes. Pond rearing of eels is a developing industry in U.S. (Facey and Van Den Avyle 1987, Van Den Avyle 1984). Possession and sale in U.S. of eels from Hudson River and Lake Ontario was banned by New York because of PCB contamination (can be sold to foreign markets that allow higher PCB levels than does U.S. (Facey and Van Den Avyle 1987).

Stewardship Overview: See American Eel Plan Development Team (2000, Fishery Management Plan for American Eel). Objectives of the plan include: improving knowledge of eel utilization through better reporting of harvest, increasing knowledge of eel population dynamics and life history, providing migratory passage and access to historic eel freshwater habitat, and monitoring of abundance levels of various eel life stages (Haro et al. 2000).

Comments: Some authors have argued that European (Anguilla anguilla) and American eels should be regarded as conspecific (vertebral count differences were believed to be entirely ecophenotypic), but this is not generally accepted at present (Van Den Avyle 1984). Separate species status has been confirmed by recent demonstrations that American and European eels comprise two largely separate gene pools (see Avise et al. 1990, Bastrop et al. 2000). Iceland population includes, in low frequency, the products of hybridization between American and European eels (Avise et al. 1990). Lin et al. (2001) contructed a phylogeny of Anguilla eels based on DNA data.

The preponerdance of evidence indicates that American eels do not exhibit significant geographic or latitudinal patterns of genetic variation (Avise et al. 1986, Avise 2003, Wirth and Bernatchez 2003).