The new Federal Energy Regulatory Commission license for the Eel Weir Dam contains major mandated changes at the Eel Weir bypass reach, the 1.25-mile stretch of the Presumpscot River between the Eel Weir Dam and the North Gorham Dam that is one of the most popular fishing spots in southern Maine.

In particular, the 40-year license requires substantially increased minimum water flows from Sebago Lake into the bypass reach, as well as upstream and downstream eel passage at the Eel Weir Dam, which is owned by Westbrook-based Sappi Fine Paper.

While the wide-ranging federal license has worried various interests regarding the management of Sebago Lake levels, the introduction of eels into the river – and the possibility that some fish may migrate downstream through the eel passageway and become trapped in the river – is concerning advocates of Sebago Lake’s landlocked salmon population.

According to ecological historian Doug Watts, a member of the Friends of Sebago Lake advocacy group, the stretch of the Presumpscot River that is now known as the Eel Weir bypass reach was a nationally recognized salmon fishery prior to the construction of the dam in 1907. The dam’s construction dried up the riverbed until 1992, when the commission required Sappi to pump minimum water flows into the bypass reach. Since then, the Department of Inland Fisheries and Wildlife has heavily stocked the bypass reach with trout.

Since the establishment in 1997 of the commission-mandated Lake Level Management Plan, Sappi has been required to pump minimum outflows between 25 and 75 cubic feet per second into the dam depending on the season, with peak minimum flows in the spring and fall, moderate flows in the summer, and the lowest flows in the winter.

The new license requires minimum flows of 125 cubic feet per second into the bypass reach from April 1 to Oct. 31, and minimum flows of 75 cubic feet per second for the rest of the year. The increased flows will affect the river’s ecosystems, depth and the strength of its currents, according to James Pellerin, an assistant regional fisheries biologist for the Sebago Lake region for Maine Department of Inland Fisheries and Wildlife.

“It will be deeper and the flows will be a little faster,” Pellerin said. “It can hold more fish. It’s better for the macro-invertebrates. Basically all the aquatics, it’s going to be better for. Your oxygen levels, your temperatures are going to be a little better.”

According to the license, Sappi opposed the flow increase, on the grounds that the modification would cost more than $100,000, reduce power generation by approximately 1,000 megawatt hours per year, and decrease the size of cold water areas of the bypass reach. Commission staff overruled Sappi’s concerns, finding that the new flow regime would “provide measurable benefits” to aquatic habitats and anglers and may pose a “slight risk” to the cold water areas, which are known as refugia.

No one from Sappi would comment on the mandated bypass reach flows in the new license.

The license also requires Sappi to draft a comprehensive plan to install upstream and downstream eel passage facilities on the Presumpscot River. Sappi has five upstream eel passages that are located downstream of the Eel Weir dam. According to the license, Sappi has two years to install the facilities.

Sappi will be required to open a passage at the base of the dam to allow mature eels, which measure as much as 5 feet long, to pass through. Due to the unique nature of eel migrations – only baby eels head upstream – the upstream eel passageways are likely be very small, according to Watts. In Watts’ view, Sebago Lake’s landlocked salmon will likely be able to use the downstream eel fish passage to enter the Eel Weir bypass reach, which was Sebago Lake’s historic spawning ground for salmon from the last ice age through 1907.

“Salmon are definitely going to go into the Eel Weir reach even though they’re not supposed to,” Watts said. “The thing is that salmon from Sebago will use the downstream passage, which is for eels. They are going to use the same chute that the eels use. It’s going to have to be pretty big because eels are 5 feet long. A good-sized eel, they are the size of a softball and 5 feet long. They’re big fish.”

For Watts, who unsuccessfully lobbied the commission to mandate an upstream and downstream passage for landlocked salmon at the Eel Weir Dam, the required eel passage facilities will cause serious problems for Sebago Lake’s salmon, some of whom, he said, will be trapped downstream of the Eel Weir Dam, and will die due to the high summer water temperatures in the Eel Weir bypass reach.

But the Department of Inland Fisheries and Wildlife argued against the upstream fish passage, according to the license, arguing that the salmon would spawn in the bypass reach instead of the Jordan River in Raymond, “where the department collects broodstock for its landlocked Atlantic salmon hatchery program.” Department officials also expressed concern that the fish passage could introduce invasive fish species and diseases upstream into Sebago Lake.