American Eel

Common name(s): American eel, Atlantic eel, Common eel, Silver eel, Yellow eel, Bronze eel, Easgann, Anguille, black eel, green eel, river eel
Scientific name: Anguilla rostrata
Type of Diadromy: Catadromy
A small American eel, Anguilla rostrata.
American eel are long, snake-like fish. Sometimes they are confused with sea lamprey due to their shape, but eels have a large mouth with a distinct jaw. Another difference is that eels have a single fin that stretches from the back, around the tail, and continues onto the bottom of the fish. Lamprey have separate dorsal, tail, and anal fins. Adult eels are usually brownish to blue-black on the top and white or light-colored on the bottom, while juveniles are yellow to greenish-brown and have some yellow on the edges of their fins. They can grow larger than 48 inches, but are typically seen closer to 20″.

The American eel exists on the western side of the Atlantic Ocean from Panama north to Canada, and over to Greenland and Iceland. They are also common throughout the Caribbean and West Indies. Once mature, adults swim to the Sargasso Sea to spawn. The spawning grounds are shared with the European eel (Anguilla anguilla), a closely related species that is found on the opposite side of the Atlantic Ocean.

Life History
American eels are the only catadromous fish in North America. They spend the majority of their lives in freshwater, with adults living in streams, rivers, and mud-bottom lakes(Fahay 1978; Meffe and Sheldon 1988). Small eels prefer faster flowing water, while larger eels like slow, deep, and muddy habitats. American eels are nocturnal, hiding during the day (Van Den Avyle 1984; Baras et al. 1998) and hunting at night. They are not picky eaters, feeding on a wide variety of organisms including insect larvae, snails, worms, shrimp, crabs, fish, and dead animals (Lookabaugh and Angermeier 1992). Growth can be slow though. Males can reach sexual maturity in as little as 3 years and females mature at about 10 years, but individuals as old as 40 years have been observed. In autumn the mature eels migrate from the rivers into the ocean, making a long distance journey to the Sargasso Sea to spawn (Kleckner et al. 1983). It is believed that adults die after spawning, since none have ever been seen migrating back up rivers after (Van Den Avyle 1984). Leptocephali larvae (transparent, leaf-shaped, very cool!) hatch from the eggs and develop at sea for about a year. The thin shape and small size helps them get carried by the currents without much swimming. As they approach estuaries the larvae transform into elvers (look like miniature eels) and enter the rivers in huge groups as the tide flows in. They transform from the elvers (glass eels) into the yellow-phase adult eels once they are in the rivers, where they will continue to grow and mature until it is their time to spawn.

While even small obstructions can stop most diadromous fish from migrating, American eel can  climb out of water to move limited distances over land or around barriers. This is a result of their amazing ability to breathe through their skin as long as it remains wet.

On the east coast of the United States from Maine to Florida, American eel are managed by the Atlantic States Marine Fisheries Commission. The first Fishery Management Plan (FMP) for American eel was developed in the mid-1990s and approved in 1999. Part of the plan was to determine why the populations were in decline. They found that fishing was hurting the populations in several major ways: (1) American eel are slow growers, taking 8 – 24 years to mature; (2) glass eels funnel through rivers in large groups as they return from the sea, making them easy to take huge quantities; and (3) all fish are caught before they can spawn (since they die after spawning), preventing them from contributing young to the population. A stock assessment in 2012 found that the U.S. American eel population was depleted, resulting in two addendum (3,4) to the FMP with the goal of decreasing mortality and increasing conservation.

In Eastern Canada, commercial eel fisheries are managed federally by Fisheries and Oceans Canada with three administrative regions (Newfoundland and Labrador, Maritimes and Gulf), and provincially by Quebec and Ontario. The American eel was declared “endangered” in 2008 under Ontario’s Endangered Species Act  which prohibits the killing, harming, harassing, possessing, buying, selling, trading, leasing or transporting of this species.

News & Stories
Baras, E., D. Jeandrain, B. Serouge, and J. C. Philippart. 1998. Seasonal variations in time and space utilization by radio-tagged yellow eels Anguilla anguilla (L.) in a small stream. Pages 187–198 Advances in Invertebrates and Fish Telemetry. Springer Netherlands. [Source]
Fahay, M. P. 1978. Biological and fisheries data on American eel: Anguilla rostrata (Lesueur). National Marine Fisheries Service, United States.
Kleckner, R. C., J. D. McCleave, and G. S. Wippelhauser. 1983. Spawning of American eel,Anguilla rostrata, relative to thermal fronts in the Sargasso Sea. Environmental Biology of Fishes 9(3–4):289–293. Springer Nature. [Source]
Lookabaugh, P. S., and P. L. Angermeier. 1992. Diet Patterns of American Eel,Anguilla rostrata, in the James River Drainage, Virginia. Journal of Freshwater Ecology 7(4):425–431. Informa UK Limited. [Source]
Meffe, G. K., and A. L. Sheldon. 1988. The Influence of Habitat Structure on Fish Assemblage Composition in Southeastern Blackwater Streams. American Midland Naturalist 120(2):225. JSTOR. [Source]
Van Den Avyle, M. J. 1984. Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (South Atlantic): American eel. U.S. Army Corps of Engineers, FWS/OBS-82D1.24. :20 pp. [PDF]