ENVIRONMENT NEWS:

Outgoing tide of eels connects mid-Atlantic to the sea

by Tom Horton
Monday, 13 December 2010
Perhaps only humans exploit every crease and corner of the Bay's six-state watershed as comprehensively as eels.

It's a miracle of nature, a wondrous and deeply mysterious voyage, and it gets underway every autumn on the dark of the moon, when the air gets chill and the creeks run full.

It happens here in downtown Centreville on Maryland's upper Eastern Shore, a few yards off busy highway 213, where Gravel Run rushes between the Dunkin' Donuts and a parking lot.

Actually it happens throughout countless rivers and streams and trickles of Chesapeake Bay's 64,000 square mile watershed and all the Atlantic coastlines of the Americas.

Here in little Centreville is just where Maryland state biologist Keith Whiteford sets his trap that alerts him to when the hour of the silver eel has come 'round again.

Most of us are more focused on fall's arrivals around the Bay of wild swans and geese, loons and ducks. The exodus of eels, the Chesapeake's only catadromous species--one that runs downstream to spawn--goes unheralded, appreciated only by fishermen.

In fact the American eel is one of the bay's high dollar fisheries, with catches in the hundreds of thousands of pounds annually, fetching some years a dollar twenty five a pound, dockside, to supply foreign markets that prize them as seafood.

Ecologically, they are an important top predator, the dominant species in terms of biomass in most streams. Perhaps only humans exploit every crease and corner of the Bay's six-state watershed as comprehensively as eels.

Once they escape the coasts on their spawning run and slip off the continental shelves into depths reaching thousands of feet, no one will ever again see the eels Whiteford seeks.

Thigh-deep in the stream, he hoists the mesh bag attached to the end of his home-made trap. It looks as if he has caught only a few bushels of leaves. Then--a quiver of flesh shows through the meshes, but it's a big bullfrog.

Then, a wriggle, a bulge, a gleam: "Silver eels," the biologist proclaims, extracting two fat, glistening 25-inch females and a skinny little male. "Cool."

Cool indeed. For weeks, on the bottom of Gravel Run, they have been girding themselves for a one-way journey to the Sargasso, the great, languid gyre of seaweed in the heart of the Bermuda Triangle.

Their eyes are twice normal size, their swim fins have enlarged, their swim bladders have toughened and their stomach has shriveled as their sex organs enlarged--all adaptations for the months-long mission of more than a thousand miles.

And the color! Muddy yellow and dully green no more, these eels of autumn are simply glorious, shiny dark backs shading to lustrous bronze, with tints of iridescent green and pink, transitioning to bellies of purest white--all covered by a glossy coat of slime to protect against dehydration in the super-saline ocean depths.

No one knows what makes any eel decide it's time to make the fall run to the Sargasso.

Whiteford estimates their ages, six to eight years. Not every mature eel makes the fall run in a given year, and no one knows what makes any eel decide it's time. Some won't leave for 20 years, and some never do--a 41-year-old found by New York's George Washington Bridge had never left freshwater.

Their actual spawning in the miles-deep Sargasso has never been witnessed. Danish researchers in the early 1900's dragged fine mesh nets through the Atlantic, collecting ever smaller Leptocephali, the eel larvae, until they reached the Sargasso.

We know eels can detect earth's magnetic fields, and smell chemicals in water diluted to about the level of an ounce in the whole volume of the Chesapeake Bay. But how the spawners navigate to the Sargasso is a mystery. We just don't know.

Clockwise ocean currents slowly distribute the non-swimming larval eels, shaped like willow leaves, back to Atlantic coastlines. But what urges them from there as far inland as the Blue Ridge Mountains of the Potomac basin, surmounting multiple dams and the rocky barrier of Great Falls above Washington, D.C.?

We just don't know.

Maybe some things are best left to the imagination. It's a certainty the silver eels have only enough energy to make it to the Sargasso, not to return, but what a way to go.

Just think: billions of silvery projectiles, all converging on the dark Sargassan womb--also their tomb, flesh and bones depleted, disintegrating in a blast of superfecundation, sinking into the abyss even as a whole new galaxy of tiny, transparent willow leaves begins its slow drift back to repopulate every rivulet of the continent.

A Postscript: One day when she was little, my daughter Abigail and I were tramping in woods on the Eastern Shore near where I grew up, and we noticed a stream of tiny, dark wriggles moving up a creek no more than two feet wide.

They are elvers, baby eels, and they have traveled all the way from out in the ocean, I explained.

And where are they headed?, she asked.

Why, they must be headed for Hurlock, I said. I find that both amusing and deeply satisfying.


Tom Horton covered the bay for 33 years for The Sun in Baltimore, and is author of six books about the Chesapeake. He is currently a freelance writer. Distributed by Bay Journal News Service.



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This story was published on December 13, 2010.