An Atlantic salmon makes its way to a holding tank at the Milford Dam fishway at Brookfield Energy in Milford, 2014. Credit: Ashley L. Conti / BDN

Environmental advocates said Monday the answer to helping more endangered Atlantic salmon over a Penobscot River dam so they can spawn upstream is simple: add more places where fish can cross.

The Natural Resources Council of Maine said that, according to a state Department of Marine Resources study, most of the Atlantic salmon that traveled up the Penobscot River and through Brookfield Renewable Partners’ hydroelectric dam in Milford failed to clear the dam within 48 hours.

The 48-hour requirement, set by the Endangered Species Act, was meant to give the fish their best chance of reproducing.

Maine is the only state with native Atlantic salmon populations. An estimated 100,000 Atlantic salmon once migrated up the Penobscot River to spawn each year, but dams, logging, pollution and overfishing have brought the Atlantic salmon to the brink of extinction. 

Atlantic salmon have been protected under the federal Endangered Species Act since 2000.

“It is a complex issue when a foreign company is generating electricity for profit in a river that is home to multiple migratory fish species and a sovereign Indian tribe,” said Dan McCaw, fisheries program manager for the Penobscot Indian Nation. “Those fish species not critically endangered occur at historically low numbers because of dams without safe, timely and efficient fish passage.”

A fish lift was added to the Milford Dam in 2014 to allow endangered Atlantic salmon to travel from the ocean and continue upstream to spawn in the Penobscot River. At the time, the standard expectation was that 95 percent of the salmon venturing up the river would pass the dam within 48 hours of approaching it.

Some 79 percent of the salmon failed to pass the Milford dam within 48 hours from 2014 to 2019, according to a Maine Department of Marine Resources analysis. Taking more than 48 hours to find and cross a dam can exhaust salmon and later affect their ability to reproduce.

“Passage delays are very harmful to Atlantic salmon,” John Burrows, U.S. operations executive director for the Atlantic Salmon Federation, wrote Monday. “Such a large proportion of salmon on the Penobscot experiencing these unnatural delays is having a substantial impact on our efforts to recover this great species. These delays directly contribute to mortality and poor spawning success.”

Nick Bennett, staff scientist and healthy waters director at the Natural Resources Council of Maine, said simply adding more places where fish could cross the dam would likely remedy the issue.

Burrows said another fish lift should be added to the western side of the dam where most of the river flow is. River flow attracts fish, he said.

The existing fish lift system is tucked into the eastern corner of the dam, making it harder for salmon to find it.

“There’s also an old fish ladder in the center of the dam that should probably be rehabilitated as well, since we know that salmon will use it,” Burrows said. “Those are the only practicable solutions that will both pass a lot more fish of all species, per goals outlined in the state fisheries plan for the Penobscot, and decrease the major delays experienced by Atlantic salmon at Milford.”

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Kathleen O'Brien

Kathleen O'Brien is a reporter covering the Bangor area. Born and raised in Portland, she joined the Bangor Daily News in 2022 after working as a Bath-area reporter at The Times Record. She graduated from...