Atlantic salmon have a challenging life history — and those that hail from U.S. waters have seen things get increasingly difficult in the past 300 years.
Dubbed the "king of fish," Atlantic salmon once numbered in the hundreds of thousands in the United States and ranged up and down most of New England's coastal rivers and ocean waters. But dams, pollution and overfishing have extirpated them from all the region's rivers except in Maine. Today only around 1,000 wild salmon, known as the Gulf of Maine distinct population segment, return each year from their swim to Greenland. Fewer will find adequate spawning habitat in their natal rivers to reproduce.
That's left Atlantic salmon in the United States critically endangered. Hatchery and stocking programs have kept them from disappearing entirely, but experts say recovering healthy, wild populations will require much more, including eliminating some of the obstacles (literally) standing in their way.
Conservation organizations, fishing groups and even some state scientists are now calling for the removal of up to four dams along a 30-mile stretch of the Kennebec River, where about a third of Maine's best salmon habitat remains.
The dams' owner — multinational Brookfield Renewable Partners — has instead proposed building fishways to aid salmon and other migratory fish getting around dams as they travel both up and down the river. But most experts think that plan has little chance of success.
A confusing array of state and federal processes are underway to try and sort things out. None is likely to be quick, cheap or easy. And there's a lot at stake.
"Ultimately the fate of the species in the United States really depends upon what happens at a handful of key dams," says John Burrows, executive director of U.S. programs at the Atlantic Salmon Federation. "If those four projects don't work — or even if just one of them doesn't work — you could basically preclude recovering Atlantic salmon in the United States."
The best place for salmon recovery is in Maine's two largest watersheds.
"The Penobscot River and the Kennebec River have orders of magnitude more habitat, production potential and climate resilient habitat" than other parts of the state, says Burrows.
The rivers and their tributaries run far inland and reach more undeveloped areas with higher elevations. That helps provide salmon with the cold, clean water they need for spawning and rearing. Smaller numbers of salmon are hanging on in lower-elevation rivers along the coastal plain in Maine's Down East region, but climate change could make that habitat unsuitable.
"There's definitely concern about how resilient those watersheds are going to be for salmon in the future," says Burrows. "To recover the population, we need to be able to get salmon to the major tributaries farther upriver, in places where we're still going to have cold water even under predictions with climate change."
One of those key places is the Penobscot, which has already seen a $60 million effort to help recover salmon and other native sea-run fish. A 16-year project resulted in the removal of two dams, the construction of a stream-like bypass channel at a third dam, and new fish lift at a fourth. In all, the project made 2,000 miles of river habitat accessible.
While there's still more work to be done on the Penobscot, says Burrows, attention has shifted to the Kennebec. The river has what's regarded as the largest and best salmon habitat in the state, especially in its tributary, the Sandy River, where hatchery eggs are being planted to help boost salmon numbers.
"That's helped us go from zero salmon in the upper tributaries of Kennebec to getting 50 or 60 adults back, which is still an abysmally small number compared to historical counts," says Burrows. "But these are the last of the wildest fish that we have."
The Sandy may be good salmon habitat, but it's also hard to reach. Brookfield's four dams stand in the way of fish trying to get upriver.
At the lowest dam on the river, Lockwood Dam in Waterville, there's a fish lift — a kind of elevator that should allow fish that enter it to pass up and around the dam. But if fish do find the lift — and only around half of salmon do — they don't get far.
"It's a terminal lift," says Sean Ledwin, division director of Maine's Department of Marine Resources' Sea Run Fisheries and Habitat. "The lift was never completed. So we pick up those fish in a truck and drive them up to the Sandy River."
That taxi cab arrangement isn't a long-term solution, though, and was part of an interim species protection plan.
Only the second dam, Hydro Kennebec, has a modern fish passage system. But how well that actually works hasn't been tested yet since fish can't get by Lockwood Dam. As part of a consultation process related to the Endangered Species Act, Brookfield has submitted a plan proposing to fix the fishway at Lockwood and add passage to the third and fourth dams.
But federal regulators found it inadequate.
"Brookfield's proposal was rejected by the Federal Energy Regulatory Committee [which oversees hydroelectric projects] and all the [federal management] agencies," says Ledwin. The company now has until May 2022 to come up with a new plan.
State scientists aren't convinced Brookfield's plan would work either.
"We have really low confidence that having four fishways would ever result in meaningful runs of all the sea-run fish and certainly not recovery of Atlantic salmon," says Ledwin. "We don't think that it's going to be conducive to recovery."
In addition to considerations related to the Endangered Species Act, Shawmut Dam, the third on the Kennebec, is currently up for relicensing, which triggers a federal review process by FERC.
And at the same time the Maine Department of Marine Resources has drafted a new plan for managing the Kennebec River that recommends removing Shawmut Dam and Lockwood Dam. A public comment period on the proposed plan closed in March.
Brookfield isn't happy with it and responded with a lawsuit against the state.
It was good news to conservation groups, however, which would like to see all four of the dams removed if possible — or at least a few of them.
"There's no self-sustaining population of Atlantic salmon anywhere in the world that we know of that have to go by more than one hydro dam," says Burrows. He believes that having Brookfield spend tens of millions of dollars on new fishways will just result in failure for salmon.
It's partly a game of numbers. Not all fish will find or use a fishway. And if you start with a low number of returning fish and expect them to pass through four gauntlets, you won't be left with many at the end.
"If you're passing 50% of salmon that show up at the first dam, and then you've got three more dams passing 50%, that means you're left with only an eighth of the population you started with by the end," says Nick Bennett, a staff scientist at the Natural Resources Council of Maine. "You can't start a restoration program where you're losing seven-eighths of the adults before they even get to their spawning habitat."
And getting upriver is just part of the salmon's journey. Juvenile salmon face threats going downstream to the ocean as well, including predation and warm water in impoundments. They also risk being injured or killed going through spillways or turbines. Only about half are likely to survive the four hydro projects.
Atlantic salmon, unlike their Pacific cousins, don't always die after spawning, either. So some adults will also make the downstream trek, too.
"Just looking at our reality, at least two dams need to go, hopefully three, and it would be amazing if all four would go," says Burrows.
The fate of Atlantic salmon hangs in the balance, but so do the futures of other fishes.
The Pacific coast of the United States is home to five species of salmon. And while the Atlantic side has just the one, it has a dozen other native sea-run species that have also seen their habitat shrink.
"Those dams are preventing other native species like American shad, alewives, blueback herring and American eel from accessing large amounts of historic habitat," says Burrows.
Ledwin says removing dams on the Kennebec could result in populations of more than a million shad, millions of blueback herring, millions of eels and hundreds of thousands of sea lampreys.
"The recovery of those species would actually help Atlantic salmon as well because they provide prey buffers and there are a lot of co-evolved benefits," he says.
Salmon are much more successful at nesting when they can lay their eggs in old sea lamprey nests, explains Bennett. "But sea lamprey are not good at using fish lifts and we've essentially blocked 90% of the historic sea lamprey habitat at Lockwood dam. We need to get those fish upstream, too."
Dam removal advocates don't have to look too far to find an example of how well river ecosystems respond when dams are removed.
The removal of the Edwards Dam on the lower Kennebec River in 1999 and the Fort Halifax Dam just upstream on the Sebasticook in 2008 helped ignite a nationwide dam-removal movement. It also brought back American shad, eel, two native species of sturgeon and millions of river herring to lower parts of the watershed.
"We've got the biggest river herring run in North America now due to the dam removals," says Ledwin. "And the largest abundance of eel we've ever seen on the lower Kennebec."
The resurgence of native fishes helps the whole ecosystem. When they returned, so too did eagles, osprey and other wildlife.
"When people see all those fish in the river and the eagles overhead, it just kind of blows their minds because they never realized what had been lost for so long in our rivers," says Burrows.
Rebuilding key forage fish like herring also benefits species that live not just in the river, but the Gulf of Maine and even the Atlantic Ocean. The tiny fish feed whales, porpoises and seabirds. They're also used for lobster bait and can help rebuild fisheries for cod and haddock, which has economic benefits for the region, too.
"We have to rebalance the scales if we want to have marine industries and commercial fishing industries and if we want the ecological benefits of what sea-run fisheries do for us," says Bennett.
The path ahead
The process to determine whether any — or all — of the four Kennebec dams that stretch from Waterville and Skowhegan are removed will take years, a diverse coalition, financial resources and agreements to meet the concerns of communities and the dam owner.
"These things come down to compromise, so there may be situations where one of those dams might not be a candidate for economic or social reasons," says Burrows. "But it will be interesting to see if in the next couple of years we can get to a place where we can have meaningful conversations with federal agencies, the dam owner and continue to engage the communities about the potential of removal at some of these sites."
And if removal of the four dams did happen, it wouldn't open up the river all the way to its headwaters. Another nine dams still lie upstream in the watershed that obstruct fish passage.
"Some of those are major dams in terms of power, production and economics," says Burrows. "So we're not calling for those to be removed."
The four lower dams provide just 46 megawatts of power — enough to supply about 37,000 homes and 0.43% of the state's annual electricity generation. It's a small amount of power relative to the damage they cause sea-run fish, says Bennett.
"By comparison we expect to add 1,200 megawatts of solar generation in the next five years," he says. "So these four dams aren't particularly important in our climate fight." And removing them would open up substantial amounts of habitat to aid salmon recovery that seem worth the tradeoff in lost power.
That's not the case, he says, for the nine larger dams upstream.
"We need those dams. We need hydroelectric power in Maine," says Bennett. "But we made big mistakes in our past use of our rivers. And we went way overboard in favor of hydroelectric power at the expense of fish."
Outside of the rivers, Atlantic salmon still face a tough road. Climate change is warming ocean temperatures, changing salinity and altering food webs. But having so many unknowns in the marine environment in the coming decades provides more reason to focus efforts on restoring rivers where scientists already know what works, says Burrows.
And if that's done right, the benefits will extend far beyond salmon.
"It's not just about salmon — it's about these other native fish, it's about the wildlife, water quality, economic opportunity for ground fishermen and lobstermen, and more sustainable forms of recreation and community development," says Burrows. "If we remove a dam or two here and rebuild these fish populations to pretty big levels that really impacts a whole bunch of different parts of society. That's what we want to try to do here on the Kennebec."