NOBLEBORO, Maine — When the alewives return in the next few weeks to Salt Bay at the head of the Damariscotta River, ready for the arduous journey leaping from pool to pool to reach Damariscotta Lake for spawning, they’ll find a new fish ladder to ease their passage.

Peering up at the 61 new stone pools winding their way up backyards on the border of the two towns, Deb Wilson of Nobleboro said Sunday, “The fish are going to go like wildfire here.”

On Saturday, members of the Damariscotta Mills Fish Ladder Restoration group gathered to “turn on the water” — to remove a board that blocked the lake water from running through the under-construction fish ladder. It was a signal that the ladder was open for business — and ready for fish.

Alewives, or river herring, spend most of their lives at sea, but as anadromous fish, return each spring to travel upstream and spawn. Females deposit eggs in lakes and ponds, and after the eggs hatch, the juvenile alewives migrate to the sea — typically in July in Damariscotta Mills, Wilson said.

The towns of Nobleboro and Newcastle have maintained the fish ladder since it was built in 1807, according to Wilson, who researched Damariscotta Lake during the 1990s.

The towns also harvest the fish, salting them and selling them locally, using them as prized lobster bait or shipping them as a specialty item. Proceeds pay the harvesters and to maintain the fish ladder.

After years of piecemeal maintenance to allow continued migration, in 2007, the two towns and the Nobleboro Historical Society undertook a full-scale restoration effort hoping to provide the alewives with a better passageway, and to maintain a historic industry. The new fishway was designed by an engineer to allow the alewives more oxygen and better resting areas.

“Before the fish could barely get up,” Wilson said. “They would get a little ways and get stuck, and end up spawning in saltwater, which doesn’t work. This is a magic thing compared to what was here. I can see the fish just going pop, pop, pop.”

Sixty-one stone pools are now complete, Wilson’s husband, Mark Becker, said, with 1,500 linear feet of stone walls creating weirs, or passageways, in between. Fourteen pools remain, but construction has halted until November, when the last of the alewives will have descended from the lake.

The group has raised about $650,000 so far — including a $92,500 matching grant from the National Fish and Wildlife Foundation — and spent every penny, according to Wilson. She expects the project to near $1 million before it’s complete.

But for the couple, and the many supporters of the restoration, the cost is outweighed by alewives’ arrival — which could happen any day now. Last year, they showed up the third week of April.

“There have already been sightings in the Kennebec,” Wilson said Sunday. “Here we’re always a little bit later.”