On World Fish Migration Day at the end of May, dozens of people gathered in downtown Kennebunk on the banks of the Mousam River.
There were informational booths, a fly tying demonstration and live fish on hand to demonstrate the kinds of species that make the river their home.
Chris Schorn, southern Maine land protection project manager for the Maine Coast Heritage Trust said the 27-mile river snaking through York County is a biodiversity hotspot.
"It has just an astounding density and diversity of rare, different rare, threatened and endangered species that call this watershed home," Schorn said.
It's also one of the most heavily dammed rivers in Maine. There are 11 dams on the Mousam's main stem, almost one every two miles.
The river has been dammed in some form since the 1600s. Nowadays fish trying to make it upstream halt at a series of three aging hydropower dams in Kennebunk, just a few miles from where the Mousam meets the Gulf of Maine.
Despite the historic obstacles, Schorn said migratory species try to make their way further up the river every year.
"They're essentially waiting at the dam, and they have been waiting for hundreds and hundreds of years to be able to continue swimming upstream to their ancestral breeding grounds," Schorn said.
The trust, along with local and state advocacy groups, want the dams taken out and the lower Mousam restored to a free-flowing river.
It's a scenario that's playing out all over Maine, on rivers big and small.
Maine is home to a dozen migratory fish species, such as alewives, shad, and salmon, that spend part of their lives in the ocean, but swim upstream into rivers to spawn.
Unfortunately for those fish, travel up many Maine rivers is blocked by defunct dams that used to be part of the power industry.
That's the case in on the Mousam, where the three dams owned by the Kennebunk Light and Power District haven't produced electricity since 2019.
District general manager Anna Henderson said it has applied to the Federal Energy Regulatory Commission to surrender the dams. But it doesn't want to remove them.
"The proposed plan for decommissioning was to sever the electric equipment, secure the site, but leave the dams in place," Henderson said.
Last year, FERC regulators said the district's plan was the preferred alternative to removing the dams.
But the proposal still doesn't meet Maine's standards for water quality and fish passage. The Maine Department of Environmental Protection said the best way to come into compliance with state regulators is to return the Mousam to a free-flowing river.
A 2016 engineering report estimated that removing the district-owned dams would cost about $2.3 million. Henderson said the district doesn't have an up-to-date estimate of the cost now, but it is certainly much higher.
That expense poses a challenge for a non-profit with 7,500 customers, Henderson added.
"We're dealing with public dollars and ratepayers of a consumer-owned electric utility," Henderson said.
"So we are working with the state to try and address their concerns, but KLPD's focus is to do that with the least cost to taxpayers," Henderson added.
Advocates hope that removing or adding fish passage to the dams could restore migratory species to upper parts of the river.
The removal of a dam at the mouth of the Presumpscot river more than two decades ago helped reintroduce alewives to the river and its tributary Mill Brook after 250 years of obstruction. Thousands of fish now make their way up the river into Highland Lake in Falmouth every year. Other efforts have had similar success on rivers across Maine.
Schorn, of the Maine Coast Heritage Trust, said dam removal on bigger rivers including the Kennebec and Penobscot has invigorated efforts to do the same on the Mousam.
"As more and more success stories emerge it becomes much less of a daunting and scary task to then turn our attention towards rivers that might be a little more overlooked but really punch above their weight in terms of ecological and community benefit," Schorn said.
