The Mysterious American Eel
The Mysterious American Eel

The Mysterious American Eel

Anyone who goes fishing for rockfish in the Chesapeake Bay has probably seen an American eel. On the end of a hook, and used as bait, was the first way I encountered this strange fish. However, eels are much more than just rockfish bait.

Everything about the eel is unusual: it has a snake-like appearance, it’s slippery as (well) an eel, and it’s one of only a few catadramous fish.

Most fish are anadramous or semi-anadramous, meaning that they live in the ocean or the lower parts of an estuary as adults and move into smaller tributary rivers to lay their eggs. Salmon are a classic example of an anadramous fish species. American eels do the opposite. Large adult eels live in the upper reaches of an estuary such as the Chesapeake Bay, all the way into rivers and even small streams.

After reaching maturity, adult eels begin their downstream journey to the middle of the Atlantic Ocean. At this stage they are called silver eels and can be up several feet long. Eels from the smallest tributaries may be 30 or more years old.

Once they reach the Sargasso Sea—essentially the middle of the Bermuda Triangle and the same place where many baby sea turtles grow up—the adults spawn and die. Eggs hatch into larval eels (called leptocephali) which go through a metamorphosis as they begin their return to estuaries such as the Chesapeake—as clear glass eels, then elvers, then yellow eels. The yellow eel stage is the phase with which most people are familiar.

As the yellow eels move up into tributary rivers and streams, they pick up some surprising hitchhikers: baby freshwater mussels. The larvae of freshwater mussels (called glochidia) attach to the gills of eels to hitch a ride upstream. The larvae eventually drop off and become adult mussels. These mussels are important filter feeders in many rivers and play an important role in water quality.

Consider, however, what happens when eels are not able to make their upstream journeys because a river has been dammed. Dams on the Susquehanna River, the Bay’s largest tributary, have prevented eel migrations for the last hundred years. When scientists looked for freshwater mussels in parts of the Susquehanna, they found only adults—some over a hundred years old—and no young mussels.

Today, the U.S. Fish and Wildlife Service and other conservation organizations are capturing and transporting eels upstream, past the dams, as a part of restoration efforts.

The American eel is a fascinating creature with an important role in the ecosystem, certainly worthy of being known as more than just bait. Stop by Marshy Point to take an up close look at our eels on exhibit.