Maine dam plans rope climbing passage and turbine screens for migrating American eels

At Upper Barker Dam along the Little Androscoggin River in Auburn, Maine, a major environmental transformation is taking shape. Environmental engineers and hydroelectric operators are tackling a complex ecological puzzle: how to maintain clean renewable energy generation while reconnecting ancient migratory pathways for native river species.

The facility must solve two opposite engineering challenges—preventing mature migrating fish from entering a powerful turbine intake while simultaneously providing young, fragile wildlife with a viable route to bypass a massive vertical barrier.

Why an eel can climb what other fish cannot

American eels do not navigate river obstacles the way salmon or shad do. Rather than leaping through heavy currents, juvenile eels—known as elvers—possess the remarkable biological ability to slither over wet, rough surfaces, squeezing through tiny crevices that would completely block traditional swimming fish. To climb past a dam, these young fish require friction rather than deep water. By installing an angled, continuously wetted climbing ramp lined with coarse, highly textured synthetic fibers, engineers give the tiny climbers a rough surface to grip and push against as they work their way upstream against gravity.

Decades later, fully grown adult American eels must travel back downstream toward the Atlantic Ocean to spawn, putting the powerhouse directly in their path.

The dangerous trip is the other direction

Getting young eels upstream solves only one side of the migration equation. Decades later, fully grown adult American eels must travel back downstream toward the Atlantic Ocean to spawn, putting the powerhouse directly in their path. Upper Barker operates as a run-of-river hydroelectric facility with a single 950-kilowatt turbine-generator that produces approximately 4,681 megawatt-hours of electricity in an average year.

To prevent migrating species from being drawn into the deadly machinery, KEI Power’s January 2026 design plan introduces full-depth overlays across the existing intake trash racks, according to the Federal Register. Utilizing durable metal plates perforated with precise one-inch openings, the design creates a physical screen that keeps fish safely out of the turbine intake while allowing river water to pass through.

The eel is part of a much larger migration

Though Upper Barker is a modest inland facility, its fish passage upgrades impact a vast coastal watershed. The ongoing federal relicensing settlement establishes mandatory passage protocols for five key native species: American eel, river herring, American shad, sea lamprey, and Atlantic salmon.

Each species plays a distinct role in the marine and freshwater ecosystems. While salmon, shad, herring, and sea lamprey migrate from the ocean into inland streams to reproduce, American eels follow the exact opposite trajectory, leaving freshwater rivers to embark on a thousands-of-miles journey to spawn in the open Atlantic. Restoring passage reconnects miles of vital river habitat directly to the ocean corridor.

Another barrier is already coming out

The restoration around Upper Barker is part of a much broader, multi-agency effort across the Little Androscoggin basin. Located roughly four miles upstream from the river’s confluence, crews initiated the complete removal of the defunct Littlefield Dam in 2026, dismantling a barrier that stood for nearly 90 years.

Removing Littlefield opens up more than 70 square miles of watershed and reconnects roughly nine miles of free-flowing river. The project unblocks access to over 8,000 acres of prime pond habitat for river herring and restores more than 200 mapped habitat units for Atlantic salmon, resolving a longstanding bottleneck that previously prevented stocked fish from returning to their nursery grounds.

The hydro plant stays while the route changes

Unlike Littlefield, Upper Barker Dam will remain operational. The federal relicensing process balances active green power generation with ecological stewardship, coordinating water flows with the nearby Lower Barker Dam and establishing a dedicated basin-wide habitat fund. Local officials reported in August 2026 that operational fish passage facilities at Upper Barker are anticipated by roughly 2031.

This leaves engineers to execute two contradictory tasks at the exact same facility: blocking downstream fish from following water into a turbine while engineering a textured climbing path for ascending elvers. The true genius of the solution lies in where that climbing material comes from. The coarse, ultraviolet-stabilized polypropylene rope selected to give climbing eels a grip was not designed for fish at all.

In coastal aquaculture, those exact same fibrous lines hang underwater beneath shellfish farms so microscopic mussel larvae can grab hold and grow.

Kelly Lippke

Kelly is an experienced writer with 15 years of experience exploring the big stories that shape our world, from tech breakthroughs and space exploration to climate, energy, and the fascinating quirks of science. She has a talent for turning complex ideas into sharp, memorable insights that stay with readers long after they’ve finished reading.