Dam Study Lays Out Options to Improve St. Croix Fish Passage Along Maine-New Brunswick Border

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Kevin Bunch
August 25, 2021

“There’s huge potential for the St. Croix River to support some of the biggest runs of lots of different sea-run fish species in the region.”

That’s according to Sean Ledwin, director of the Maine Department of Marine Resources’ Sea Run Fisheries and Habitat Division and member of the IJC’s St. Croix River Watershed Board. But there are three dams with aging fish passage infrastructure on the lower end of the river that stand between upriver spawning habitat that could be used by species like alewives, blueback herring, American shad, American eel, sea lamprey and Atlantic salmon.

st croix river basin map
The Milltown, Woodland and Grand Falls dams are all located on the lower end of the St. Croix River. Credit: IJC

New Brunswick Power, which owns the Milltown Dam closest to the river mouth, is in the process of receiving government approval to decommission and remove the barrier.

The next two dams up the river, Woodland and Grand Falls, are owned by Woodland Pulp. That company collaborated in a multi-agency, multi-government study that explored viable options to replace the existing fishways at those stations, which would allow more fish to make their way past the dams.

“(The St. Croix River) has the potential to have largest run of alewives anywhere in the world,” Ledwin said. “You have to have safe, timely fish passage along those three dams to realize that production potential.”

The Woodland Pulp study looked at existing infrastructure at and around the Woodland and Grand Falls dams, including train tracks and buildings, along with the geography of the river, the cost of potential solutions and the behavior and swimming patterns of each of the target fish species. This information was used to draw up a list of preferred alternatives to the current fish ladders. Ledwin said Woodland Pulp also provided detailed information on its own dam operation procedures and physical structures.

A full list of alternatives can be found in the study, prepared for the IJC’s St. Croix board. The options range from vertical slot fish ladders and fish lifts, to modifying the Grand Falls Brook in New Brunswick to move fish upstream and downstream, or repurposing existing downstream systems with new fish bypasses to help fish move back down the river while avoiding power turbines.

A work group of members from Woodland Pulp, the IJC and its St. Croix River board, Fisheries and Oceans Canada, US National Oceanic and Atmospheric Administration, US Geological Survey, US Fish and Wildlife Service, Maine Department of Marine Resources, the Peskotomuhkati Nation in New Brunswick and the Passamaquoddy Tribe in Maine all reviewed the information and considered what options were the most viable. The final study report describes the thought process leading to each of the top alternatives and how these were narrowed down in each location. Ledwin said the study took about a year and a half.

fish ladder grand falls
The fish ladder at the Grand Falls Power House is old, and poorly suited to most of the target species. Credit: IJC

The benefits for improving fish passage on the St. Croix River could be huge, Ledwin said. Ecologically speaking, alewives feed many other species of fish and birds, including other marine species that people like to catch in the nearshore. More fish could be commercially beneficial as well; alewives, for example, also are caught for human consumption or lobster bait.

“Alewives can provide a ton of production potential out into the nearshore ocean - that includes whales, birds, puffins and all types of things,” he said. “Implementing better fish passage would really get the ecological crank going.

Atlantic salmon have not returned to the St. Croix River in decades but were included in the study for future restoration work. American shad and American eel populations have been detected but remain relatively low due to the existing fish passages not being designed for them to maneuver through.

The river already has relatively small annual populations of sea lamprey and blueback herring, so they were among the target species explored in the study. Atlantic and shortnose sturgeon were included at the request of Indigenous workgroup members as those fish also historically spawned in the river.

This study was an important first step, but Ledwin says there is still a lot of work to do before shovels could hit the ground on new fish passageways at the Woodland and Grand Falls dams. More information on what routes the fish are taking in the river and further research into the river bottom around the dams would provide detail on how water moves through the river, and help narrow down the best alternative passageway.

Once Woodland Pulp and any partners are satisfied with the selection, the passageway would need to be designed and built; all of this would likely require outside funding, Ledwin said, through grants from initiatives like the US Bay of Fundy Aquatic Connectivity Project, or general appropriations from the federal governments.

The study was funded by the IJC’s International Watersheds Initiative in partnership with the state, provincial, Indigenous and federal governments, and Woodland Pulp.

Picture of Kevin Bunch
Kevin Bunch

Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.