PORTLAND — Two Maine-based environmental organizations are seeking a federal court order to shut down turbines at four hydroelectric dams on the Androscoggin and Kennebec rivers this spring.

Shutting down the turbines, which are in Brunswick, Waterville, Skowhegan and Fairfield, will have a minimal effect on energy production and go a long way toward protecting this spring’s Atlantic salmon run, the groups argue.

The shutdown would last for about seven weeks, from April 15 to June 5, the period when young salmon migrate from freshwater to saltwater habitats.

Friends of Merrymeeting Bay and Environment Maine filed the motion for a preliminary injunction last week in U.S. District Court in Portland.

“The Atlantic salmon in the Kennebec and Androscoggin rivers are on the verge of extinction, yet the dam owners and government agencies continue to stall,” said Ed Friedman, spokesman for Friends of Merrymeeting Bay, in a statement issued Tuesday. “This is a situation in which a federal judge, and only a federal judge, can take immediate action to help save this species.”

The court filing names NextEra Energy Resources LLC of Florida and FPL Energy Maine Hydro LLC as the defendants. Those companies, which operate the dams, have three weeks to respond.

A spokesperson for those companies could not be reached Tuesday.

According to the Maine Department of Inland Fisheries and Wildlife, Atlantic salmon migrate from the ocean to fresh water to reproduce in the rivers where they’re born.

When the young salmon, called smolts, grow to 6 inches long, they change physiologically to adapt to life in salt water.

This year’s Atlantic salmon run – when juvenile fish swim from fresh water to salt water – is expected to be significant because of increased stocking by the state and evidence that a huge number of adults returned to Maine rivers to spawn two years ago, said Josh Kratka, an attorney for the National Environmental Law Center in Boston, which filed the court action on behalf of the Maine groups.

Environment Maine and Friends of Merrymeeting Bay estimate that 20,000 smolts are expected to migrate down the Kennebec and about 1,000 are expected to migrate down the Androscoggin.

If the turbines are running, the groups contend, one-third to one-half of the smolts will be killed or injured trying to pass through turbine blades at the Weston Dam in Skowhegan, the Shawmut Dam in Fairfield, the Lockwood Dam in Waterville and the dam next to Fort Andross in Brunswick.

“Our position is that nothing has been done by these companies to keep the salmon from swimming through the turbines,” Kratka said. “And this run would appear to offer the greatest amount of genetic diversity that we have seen in decades.”

Emily Figdor, director of Environment Maine, said in a news release, “It has been nearly four years since Atlantic salmon were listed as endangered, and NextEra still has failed to take action to save these iconic fish.

“Time is running out to save the Atlantic salmon, and we simply can’t delay another season,” she said.

Dennis Hoey can be contacted at 791-6365 or at:

dhoey@pressherald.com