The American eel (Anguilla rostrata

The American eel (Anguilla rostrata) is a facultative catadromous fish found on the eastern coast of North America. Eels (Anguilla spp.) are fish belonging to the elopomorph superorder, a group of phylogenetically ancient teleosts.[2] The American eel has a slender snakelike body that is covered with a mucous layer, which makes the eel appear to be naked and slimy despite the presence of minute scales. A long dorsal fin runs from the middle of the back and is continuous with a similar ventral fin. Pelvic fins are absent, and relatively small pectoral fin can be found near the midline, followed by the head and gill-covers. Variations exist in coloration, from olive green, brown shading to greenish-yellow and light gray or white on the belly. Eels from clear water are often lighter than those from dark, tannic acid streams.[3]

The eel lives in fresh water and estuaries and only leaves these habitats to enter the Atlantic ocean to start its spawning migration to the Sargasso Sea.[4] Spawning takes place far offshore where the eggs hatch. The female can lay up to 4 million buoyant eggs a year, and dies after egg-laying. After the eggs hatch and the early-stage larvae develop into leptocephali, the young eels move toward North America where they metamorphose into glass eels and enter freshwater systems where they grow as yellow eels until they begin to mature.

The American eel is found along the Atlantic coast including Chesapeake Bay and the Hudson River and as far north as the St. Lawrence River region. It is also present in the river systems of the eastern Gulf of Mexico and in some areas further south. Like all anguillid eels, American eels hunt at night, and during the day they hide in mud, sand or gravel very close to shore, roughly 5 to 6 feet under. They feed on crustaceans, aquatic insects, small insects, and probably any aquatic organisms that they can find and eat.

American eels are economically important in various areas along the East Coast as bait for fishing for sport fishes such as the striped bass, or as a food fish in some areas. Their recruitment stage, the glass eel, are also caught and sold for use in aquaculture, although this is now restricted in most areas.

Eels were once an abundant species in rivers, and were an important fishery for aboriginal people. The construction of hydroelectric dams has blocked their migrations and locally exterminated eels in many watersheds. For example, in Canada, the vast numbers of eels in the St. Lawrence and Ottawa Rivers have dwindled.[5]






EtymologyEdit

The American Eel Anguilla rostrata was first described in 1817 by Lesueur. Anguilla is Latin for eel, and rostrata is a Latin word that can mean either "beaked or curved" or "long nose". French: Anguille d’Amérique, Spanish: Anguila americana.


DescriptionEdit





Juvenile eels
American eels can grow to 1.22 m (4.0 ft) in length and to 7.5 kg (17 lb) in weight. Females are generally larger than males, lighter in color, with smaller eyes and higher fins.[6] The body is elongate and snake-like. Its dorsal and anal fins are confluent with the rudimentary caudal fin. It lacks ventral fins but pectoral fins are present. The lateral line is well-developed and complete. The head is long and conical, with rather small, well-developed eyes. The mouth is terminal with jaws that are not particularly elongated. The teeth are small, pectinate or setiform in several series on the jaws and the vomer. Minute teeth also present on the pharyngeal bones, forming a patch on the upper pharyngeals. Tongue present with thick lips that are attached by a frenum in front. Nostrils are superior and well separated. Gill openings are partly below pectoral fins, relatively well-developed and well separated from one another. Inner gill slits are wide.[7]

The scales are small, rudimentary, cycloid, relatively well embedded below the epidermis and therefore often difficult to see without magnification.[8] The scales are not arranged in overlapping rows as they often are in other fish species but are rather irregular, in some places distributed like “parquet flooring”. In general, one row of scales lies at right angle to the next, although the rows immediately above and below the lateral line lie at an angle of approximately 45°. Unlike other bony fishes, the first scales do not develop immediately after the larval stage but appear much later on.[9]

Several morphological features distinguish the American eel from other eel species. Tesch (1977)[10] described three morphological characteristics which persist through all stages from larvae to maturing eels: the total number of vertebrae (mean 107.2), the number of myomeres (mean 108.2), and the distance between the origin of the dorsal fin to the anus (mean 9.1% of total length).


Distribution and natural habitatEdit

Geographic rangeEdit

The distribution of the American eel encompasses all accessible freshwater (streams and lakes), estuaries and coastal marine waters acro