Removing Constraints On Natural Aquatic Migrations


Osprey looking for alewives along the Sebasticook River in Maine. The removal of two dams has allowed migratory fish to return. Murray Carpenter

Migration, an ageless natural phenomenon, can be all the more spectacular when we remove its constraints:

‘One Of The Best Nature Shows’: A River Transformed After Dams Come Down


Sea lamprey making a spawning nest in the Sebasticook. Murray Carpenter

Along central Maine’s Sebasticook River, the first thing you’ll notice are the birds. Eagles are everywhere, wading on gravel bars and chattering from the trees.

“A whole bunch of birds, they’re bald eagles, those are all bald eagles!” says conservationist Steve Brooke.


A recent count found nearly 200 bald eagles along the Sebasticook. This one has caught an alewife. Murray Carpenter

It’s a dramatic sight, as the bald eagles swoop to catch fish from the river. And it’s a sight that Brooke predicted for this region, more than 20 years ago. That’s when he began advocating for the removal of a large hydroelectric dam downstream, on the Kennebec River. The Edwards Dam came down in 1999 after the federal government ordered its removal, saying the ecological costs outweighed the benefit of the power it provided.

That was the first such order and it boosted what is a growing trend. Now, dozens of aging dams are removed from U.S. rivers every year.

When Brooke and others began talking about getting rid of the Kennebec dam and another dam at the mouth of this tributary, many Mainers didn’t see the point. There were hints of the Sebasticook’s former productivity; 3,000 year-old fish traps built by the Wabanaki people were found in an upstream lake. But Brooke says many people had never seen a large river system in its natural state.

“In the Pacific, they’re restoring rivers because they still have runs of Pacific salmon,” Brooke says. “Here on the East Coast the rivers have been dammed since the 17th century, and so it’s very hard for people to understand what’s missing.”

Part of what’s missing from many Northeast rivers: alewives.

The half-pound herring swim up from the ocean to spawn in May and June. Brooke says alewives, and their close cousins blueback herring, are keystone species in their native habitat, fundamental building blocks of the ecosystem. They funnel millions of pounds of protein from the ocean into the rivers and everything that moves, it seems, will eat an alewife.

Gail Wippelhauser is a fisheries biologist with Maine’s Department of Marine Resources, and has been working in the Kennebec watershed since 1995. She’s had a river-level view of the recovery. Wippelhauser says in some places, it looks like this river is paved with fish, just like in historical accounts from before the Industrial Revolution…

Read the whole article here.

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