SACO -- The owner of nine dams along the Saco River has agreed to build a series of fish lifts and ladders as part of a long-range effort to restore runs of Atlantic salmon, shad, river herring and eels.

FPL Energy Maine Hydro expects to spend more than $30 million over the next 20 years, ultimately allowing sea-run fish to reach spawning grounds that have been blocked off for generations by dams that produce electricity.

FPL officials announced the agreement at Saco City Hall on Wednesday. Federal and state regulators and local conservationists negotiated with FPL for three years before finalizing the plan. They said it will restore balance between the river's hydropower dams and its value for wildlife habitat and community uses.

"There are many competing interests on the Saco," said Mayor Mark Johnson. The agreement "makes sure the Saco is open to all, including the fish."

The 134-mile-long Saco River provides drinking water to Saco and Biddeford, generates electricity and supports fishing, boating and other uses.

Fish access to upstream spawning grounds has been a source of tension in the Saco River Valley since it caused bloodshed between Europeans and Indians in the late 1600s, Johnson said. The agreement announced Wednesday culminates 13 years of efforts to restore fisheries that are important to the communities along the river and their economies, he said.

For FPL, the deal precludes future disputes and uncertainty about fish passage at its remaining dams on the Saco. Negotiations began as the company faced relicensing of the Bar Mills Dam in Buxton, where fish passage is now scheduled to be installed by 2016.

FPL's Senior Environmental Specialist Frank Dunlap said the balance struck Wednesday is good for the company as well as the fisheries. "It provides a schedule and some predictability for us."

FPL has already spent $16 million to create fish passages at dams on the lower river, including four dams near U.S. Route 1 that are part of a single hydropower facility called Cataract Station. Passages there include ladders that allow sea-run fish to swim up small side channels, occasionally getting help from an elevator-like lift.

Under the agreement, FPL will:

n Install fish passages at its four remaining dams, starting with the Bar Mills Dam in 2016 and ending with the Hiram Dam in 2025. Each fish passage is expected to cost $2 million to $8 million to build.

Salmon, which are now trapped and trucked upriver, will be able to swim more than 40 miles upstream to historic spawning grounds, such as in the Ossipee River and other tributaries. Shad and blueback herring also are expected to return in greater numbers as habitat access expands.

n Install passages for American eels at all nine dams, starting next year at the Cataract Station dams between downtown Biddeford and Saco.

Baby eels, called elvers, swim upriver each spring and remain in ponds and lakes until they return to the ocean to spawn as adults. Because of their different migrating behavior, eels need separate passages from those for salmon and shad. The cost of eel passages is less certain, but tends to be less than passages for fish.

n Establish a Saco River Enhancement Fund of $50,000 a year through 2022, and provide another $100,000 for fisheries management and restoration, $25,000 for public education and $25,700 for raising salmon that are stocked in the river. The agreement is part of a national effort to restore sea-run fisheries that were decimated over the last two centuries by industrial dams. Maine's Penobscot, Kennebec and Presumpscot rivers are the focus of similar efforts.

A deal to restore fisheries on the Presumpscot River is still in final negotiations. It calls for removal of the Cumberland Mills Dam in Westbrook and the gradual installation of fish passages at upstream dams.

Officials said that agreement could be final next month. It will be presented for public comments before it gets submitted for final federal approval. Part of the Saco River plan still needs formal approval from federal and state agencies as part of the Bar Mills Dam relicensing. But regulators, and others who have been pushing for fish restoration on the Saco, said the agreement offers hope for a long-term recovery of the fisheries.

While shad and herring are more abundant, only about 20 to 30 adult Atlantic salmon now swim back into the Saco each spring in an attempt to reach the spawning grounds.

"When you're talking about 30 salmon, it's pretty discouraging," said Mark Woodruff, vice president of the Saco River Salmon Club. "But we're all stewards of this river, and this river is pretty important to the communities. I don't think anyone has given up on the idea."