American eels are members of the Anguillidae family of freshwater eels and are preyed upon by many species at different stages of their existence. They are important forage for such large offshore predators as sharks, haddock, and swordﬁsh; for inshore species like striped bass; and for many species of birds, including bald eagles and various gulls. Larger individuals (10 to 16 inches or so) are used as bait by anglers, especially those seeking big striped bass, and they may be sold as bait in coastal shops.
Identificationhe body is elongate and snakelike, with a pointed head and many teeth. It is covered with thick mucus, hence the phrase “slippery as an eel.” The large mouth extends as far back as the midpoint of the eye or past it. There is a single gill opening just in front of the pectoral ﬁns. There are no pelvic ﬁns, and the soft-rayed dorsal, anal, and caudal ﬁns form one continuous ﬁn. There are no visible scales. Coloring changes with maturity, as described later in this text.
Size/AgeAmerican eels grow to 50 inches and 16 pounds. The average size for adult females is about 3 feet, whereas adult males are considerably smaller, rarely growing more than a foot long. They can live longer than 9 years in rivers, streams, and lakes.
Life history/BehaviorWhen it comes time to spawn, the males and the females stop feeding, change in color from olive to black, and move out to sea. Eels spawn in the same area of the Atlantic Ocean, in deep water at the north edge of the Sargasso Sea. There each female lays as many as 10 to 20 million eggs, and both sexes die after spawning.
The eggs ﬂoat to the surface and soon hatch into slim, transparent larvae (glass eels). The sex an eel becomes is thought to be partly determined by environmental conditions, such as crowding and food abundance, but it is not determined until they are about 8 to 10 inches long and living in their freshwater habitat.
The larvae drift and swim for 1 year with ocean currents toward river mouths. Males stay near the mouths of rivers, whereas females travel upstream, mostly at night. Eels can absorb oxygen through their skin, as well as through their gills, and are known to travel overland, particularly in damp, rainy weather. Balls of intertwined eels have been seen rolling up beaches in search of freshwater for overwintering.
FoodThe diet of the nocturnal feeding American eels includes insect larvae, small ﬁsh, crabs, worms, clams, and frogs. They also feed on dead animals or on the eggs of ﬁsh and are able to tear smaller pieces of food that are too large to be swallowed whole.
Their feeding habits are rather unusual with respect to large quarry. These eels have relatively weak jaws that are mainly suited to grasping, yet they possess many small, round, and rather blunt teeth. Because they are palindromic—that is, they can move equally well forward or backward forcefully—they are able to pull, twist, and spin when tearing apart prey that is too large to be consumed whole.