On the Wild Side!
E-Newsletter for the Chesapeake Bay Field Office


American eels. Photo by Tim Watts.
American eels. Photo by Tim Watts.

From Chesapeake Bay to Bermuda Waters

The skies are not the only busy places during autumn. The Chesapeake Bay and the waters that feed it are highways for fish and other aquatic life.

The American eel (Anguilla rostrata) is the only catadromous fish found in the Chesapeake Bay, meaning that it lives most of its life in fresh and estuarine water, and migrates into saltwater to spawn. Very few fish matches the American eel’s ability to exist in such a broad diversity of habitats

Late in the summer, American eels which have been maturing in rivers systems of the Chesapeake Bay watershed are readying themselves for a long fall migration. They will swim to the oceanic waters of the Sargasso Sea near Bermuda to spawn. Prior to their migration, eels undergo changes to prepare them for life in the ocean. These changes include an accumulation of fat and degeneration of the gut. They stop feeding, their eyes and pectoral fins enlarge, and their color changes to a gray back and white belly.

American eel hatchling. Photo by Tim Watts.
American eel hatchling. Photo by Tim Watts

Spawning migration takes place between August and December, with adult eels descending streams and rivers being most active during the night. American eels spawn in the western Sargasso Sea between January and March. A female eel may lay between 400,000 and 2 ½ million eggs. Parent eels die after spawning.

The eggs hatch and the young, which look like transparent ribbons, are seized by ocean currents and transported to the mouth of the Chesapeake Bay and other inlets of the Atlantic Ocean. This journey can take months or even years.

After their first year, the young change, taking on the form of tiny, unpigmented eels, known as glass eels. As they move into coastal areas they become pigmented. Now a dark brown, they are now known as elvers. The elvers continue the journey, wriggling upstream into brackish and freshwater streams, rivers and creeks of the Chesapeake Bay.

When elvers stop migrating they undergo a period of growth and are known as yellow eels. Yellow eels remain in the Chesapeake Bay and its tributaries from eight to twenty-four years. About one year before reaching sexual maturity, the American eel undergoes its last transformation, the silver eel phase, and will complete the long fall migration to spawn.

Young eels. Photo by Tim Watts.
Young eels. Photo by Tim Watts.



Last updated: November 4, 2010