AUGUSTA, Maine -- Maine conservationists say four dams on the Kennebec River are the biggest threat to Atlantic salmon populations, and groups intend to sue to get them removed.

Brookfield Renewable Partners is an international energy company that owns four dams on the Kennebec River between Waterville and Skowhegan.

Nick Bennett, staff scientist for the Natural Resources Council of Maine, noted one of the best spawning habitats for Atlantic salmon is in the Sandy River, a tributary above Brookfield's dams. Atlantic salmon are known as "sea-run" fish, they spawn in fresh water but spend much of their lives in salt water.

He said the dams pose an often fatal hazard for the fishes' path to the ocean.

"They really need to be removed if we want to have any chance of restoring Atlantic salmon and the other species of sea-run fish that are necessary for them to be restored like river herring, shad and eels," Bennett asserted.

Groups claim the dams violate the Endangered Species Act (ESA).

The Conservation Law Foundation, Maine Rivers and the Natural Resources Council of Maine have given the required 60-day notice to sue companies under the ESA.

Bennett emphasized when it comes to restoring the species, groups are laser focused on the dams. He pointed out historically, the Kennebec River has been the largest Atlantic salmon run of any river in the U.S.

"These four dams block Atlantic salmon, both from getting up to the Sandy River to spawn, and from getting out of the Sandy River to head back to the ocean to grow into adults," Bennett explained.

Last July, the federal government rejected a Species Protection Plan proposed by Brookfield, and the Maine Department of Marine Resources and the National Marine Fisheries Service have recommended the removal of one of the dams.

The company shut down three of its four dams for salmon migration earlier this month, with operations set to resume May 31.

Coming into the new year, Columbia Riverkeeper is supporting efforts by the Cowlitz Tribe and Yakama Nation to restore salmon migration throughout the Lewis River. Fish passages would enable migration around dams and access to blocked habitats, essential for salmon and steelhead recovery in the culturally vital Lewis River basin.

Miles Johnson, legal director with Columbia Riverkeeper, said he's optimistic about a future of thriving fish and river wildlife.

"We're tentatively pretty excited," Johnson said. "We're going to see fish in parts of the Lewis River, which is a really important tributary of the lower Columbia. We're going to see fish in places that they haven't been in many, many years."

PacifiCorp recently agreed to a new schedule to install fish passage at two of its hydroelectric dams on the Lewis. Johnson said PacifiCorp broke a previous pledge to retrofit its dams to include fish passage, adding that Columbia Riverkeeper will continue to hold the company accountable for promises to tribes and the public.

Johnson said Columbia Riverkeeper will also be watching the project carefully to ensure PacifiCorp follows through, given what he described as its past focus on financial interests over legal obligations.

"These are really expensive projects to build, and PacifiCorp has demonstrated a history of putting its bottom line before its obligations, to the fish and people who use the river," he continued.

Johnson added although things are in motion, until the fish passage facilities are built in a way that's meaningful and going to work, they will continue to monitor the process and if necessary, try to hold PacifiCorp accountable.

He said science shows that reconnecting fish with existing, high-quality spawning habitat is the best way to recover the Lewis River's struggling populations of spring Chinook and coho salmon, steelhead and bull trout.

The Biden administration wants to get serious about restoring salmon populations to the Northwest.

A presidential memorandum directs federal agencies to assess how they can improve fish numbers in the Columbia River Basin.

Mitch Cutter, salmon and steelhead associate for the Idaho Conservation League, applauded the memo, saying other presidents have dodged the issue because it is tricky to address.

"What we're seeing that's very different about this administration is that they are ready to embrace that complexity and ready to get to a level of 'How do we solve this problem?'" Cutter explained. "We've been putting this off across multiple administrations for 30 years now. How do we move this issue forward?"

Cutter pointed out salmon and steelhead populations over the past few decades have been in severe decline in the Columbia River Basin, including on the Snake River stretching into Idaho.

Cutter added working with Indigenous tribes is also prominent in the presidential memo.

"We're seeing this administration treat tribal justice much more seriously than past administrations have," Cutter observed. "At least say the right things about how it is paying attention to what tribes want and is going to factor them in not just as stakeholders but as coequal partners."

Cutter argued breaching the four lower Snake River dams in southeast Washington is important, especially for Idaho fish. He added the Bonneville Power Administration is critical to this decision.

"Because Bonneville Power in large part controls these dams and the energy that is created from them, they are the key player," Cutter contended. "They are someone that we would like this administration to really take a close look at, in regard to how they're treating these fish."

The Biden Administration is considering the future of Pacific Northwest salmon and the effect of dams in the region.

The White House Council on Environmental Quality held listening sessions this spring and is now asking for public comments on dams in the Columbia River basin.

They're especially focused on four dams on the lower Snake River that have been major barriers to the dwindling salmon populations that migrate upstream to Idaho.

Mitch Cutter is the salmon and steelhead associate with the Idaho Conservation League.

"What we've seen so far in both the listening session and in the public comments," said Cutter, "is an overwhelming majority of people saying they want to breach the lower Snake River dams - because it's essential for salmon and steelhead, and because there's other ways of doing the things that the dams provide."

Supporters of keeping the dams say they provide essential energy, irrigation and barging functions. But Cutter noted that during listening sessions, more than three-quarters of commenters were in favor of breaching the dams.

The Council on Environmental Quality public comment period is open through August 31.

Cutter said there is interest in removing the dams from a variety of people in the Northwest.

"We're seeing people from across the region," said Cutter, "come out of the woodwork and say, 'This issue matters to me, even if it didn't two, three, five, ten years ago. We'd like to have this problem solved.'"

During this year's legislative session, Washington state lawmakers approved $7.5 million for planning to replace the dam's services. The four Snake River dams are in southeast Washington.