Earth Matters: An eel’s journey: The year 1600

  • The leptocephalus state of eel, the larval stage. Uwe Kils/via Wikimedia

  • An American eel elver, the third eel stage. Maryland Fisheries Service

  •  A mature American eel. Duane Raver/U.S. Fish & Wildlife Service

  • American eel, at the fourth, yellow stage, in which specialized gills allow the eel to breathe atmospheric oxygen for many hours. Parks Canada 

  • The glass eel stage of American eel. canopis/via Flickr

For the Gazette
Monday, March 28, 2022

Editor’s note: This is the first of two parts exploring the migration of American eels. Part 2 will run in the next Amherst Bulletin.

In the winter of 1600, Nehoumo (Abenaki for eel) was drifting north with billions of other organisms in the Gulf Stream waters of Sobakw (the Atlantic Ocean).

Nehoumo was a larval eel, which scientists have named leptocephalus (Greek for slim head), a flat, 2-inch-long creature that looked like a transparent willow leaf composed of a jelly-like substance, with a thin layer of muscles and a hint of body organs but no red blood cells.

The great masses of these larvae came from the area of the Sargasso Sea, south of Bermuda and, as they drifted and swam north, they split into two main groups. The first group of larvae grew slowly and continued drifting with the Gulf Stream toward Europe where they would become European eels (Anguilla anguilla).

The second group grew more quickly and became more mobile as they slipped out of the Gulf Stream and made their way to North America as American eels (Anguilla rostrata).

When Nehoumo’s group of larval eels entered Long Island Sound, they metamorphosed into glass eels — round, transparent 3-inch ribbons of fish with the beginnings of circulatory systems and functioning organs but no visible hint of gender differentiation.

They approached the mouth of the Kwinitew (Connecticut River) in late February, two months before the migration of millions of other fish. The migrants in May would include giants, such as Meskouamegou, the 15-pound salmon, plus bands of herring and lamprey.

All the migratory fish, save eels, were coming to spawn in fresh water. Nehoumo, on the other hand, was arriving to grow into adulthood in one of the river’s tributaries.

Nehoumo swam at night on the bottom with a swarm of other glass eels on incoming tides, anchoring themselves in the sand as the tide went out. By swimming along riverbanks, they avoided the heaviest downstream currents. When the glass eels entered fresh water, they began to feed on small invertebrates and metamorphosed into 3-inch-long brown elvers that resembled adult eels. One Haudenosaunee native (known as Iroquois by transplanted Europeans) said that the masses of baby eels caused the waters to shimmer.

Growing quickly on a rich estuarine diet, many millions of elvers remained in the densely populated lower river system. These eels would develop into males toward the end of their five or six years in freshwater before returning to the Sargasso Sea to mate with females 20 years older than themselves. Nehoumo, however, continued upriver with other millions, shimmying up the same cascades and falls that Meskouamegou, the salmon, would leap over.

Nehoumo kept searching for a home in the sparsely populated upper watershed where she was destined to become a female. None of the eels would develop mature testes or ovaries until their final metamorphosis, before they migrated to the ocean.

Once settled into the territory of the Abenaki in what is now New Hampshire, Nehoumo began her penultimate metamorphosis into a “yellow” eel with brownish-yellowish skin, tiny scales and a coating of slime that protected her scales and eased her journey across land to enter ponds and lakes. Her specialized gills and skin allowed her to breathe atmospheric oxygen for up to 20 hours on land.

Migrating at night, Nehoumo climbed rocks and slithered across marshes until she reached the Third Connecticut Lake near the headwaters of the Kwinitekw at the Canadian border. There she remained for 25 years, growing slowly on a diet of invertebrates and vertebrates, almost anything that moved in the waters and marshes.

After 25 years, Nehoumo had reached a length of 3½ feet and weighed 9 pounds. During the summer of 1625, her endocrine system dramatically changed, and she entered puberty as her body prepared her for a return to the sea. Her skin color turned into a uniform blackish top and silvery belly and her eyes became enlarged so she could see better in deep water. Her indeterminate gonads turned into ovaries, and her digestive system shriveled since now she would subsist solely on her enormous fat reserves.

As the late summer rains came, Nehoumo launched herself downriver, about 400 miles over the same falls and riffles she had climbed in 1600. These were the September and October days when Native people gathered by the score at habitual sites on the river where they had built stone weirs, the V-shaped or diagonal underwater structures that forced silver eels into a notch where they could be speared or caught in nets.

Nehoumo managed to avoid capture, and, by the time she reached Long Island Sound, she had become one of millions of other eels to join the long-lived females and the latest cohort of 5- and 6-year-old males in their return to their birthplace.

All the eels by the hundreds of millions were heading southeast. Down through the waters of Sobakw they swam, then into the Sargasso Sea. There they joined the hundreds of millions of European eels who had made the longer two- or three-year trip from northern Europe. Into the depths of the Sargasso Sea they sank to procreate and die.

In Part 2, we will explore the eels’ place in Native America and Europe and ponder their problematic future. 


John Sinton is co-moderator of the Mill River Greenway Initiative, honorary trustee of the Connecticut River Conservancy, author of “Devil’s Den to Lickingwater: The Mill River Through Landscape and History” and co-author of “The Connecticut River Boating Guide.” He is deeply grateful to Steve Gephard for his guidance and corrections.

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