PORTLAND – A recent decision by federal regulators could require the Sappi paper mill in Westbrook to install fishways at five dams on the Presumpscot River – but only if sea-run fish can pass through a sixth dam down river.

The river’s first dam, at Cumberland Mills, does not generate hydroelectric power and thus is not subject to Federal Energy Regulatory Commission oversight.

The commission late last month rejected Sappi’s request to remove fishways and other conditions from hydropower licenses granted in October.

The FERC decision is intended to provide a way for migratory fish such as American shad and river herring to get past the Saccarappa, Little Falls, Mallison Falls, Gambo and Dundee dams.

But that cannot happen as long as there is no fish passage at the Cumberland Mills dam, which provides processed water to the mill and water pressure for its hydrants.

Because the dam is not subject to FERC, the state Department of Environmental Protection has no jurisdiction over water quality at the site, said Dana Murch, dams and hydro supervisor for the state.

The state Department of Inland Fisheries and Wildlife regulates fishing in inland waters, and is authorized to hold a public hearing to determine if fish passage is needed at the dam, Murch said. No such hearing has been scheduled.

Murch said fish passage at Cumberland Mills is necessary to make the conditions in the FERC licenses work. “It’s the only way that there will be fish,” he said.

Under the FERC licenses, the installation of fish passages at Saccarappa Dam is contingent on the attainment of fish passage at the Cumberland Mills dam downstream.

Installation of fish passages upstream from the Saccarappa project would be triggered by passage of a predetermined number of American shad and river herring at downstream projects.

In its appeal to federal regulators, the mill argued many of its obligations under the license requirements were “excessive, unnecessary, unduly expensive, and unsupported by the record.”

Dusti Faucher, president of the group Friends of the Presumpscot River, said the decision by FERC affirms her group’s stance that the mill needs to help restore native species to the river.

“Instead of expending more time, energy and money on legal battles, those resources should now be put toward fish restoration, starting with fish passage at Cumberland Mills dam, the first dam on the river, which completely blocks migratory fish and produces no power for Sappi,” Faucher said.