VEAZIE – A 25-year effort to restore Atlantic salmon to the Penobscot River has yielded dismal results, and experts are at a loss to figure out what went wrong.

Despite a massive salmon stocking program backed by more than $111 million in public and private funds, only a tiny fraction of the hundreds of thousands of fish raised in hatcheries return from the ocean to spawn.

By the middle of this century, salmon had virtually disappeared from the Penobscot in the face of pollution and dam construction. But two decades later, cleanup measures and construction of fish ladders at dam sites sparked a return of the sleek, silvery species prized by anglers.

Despite a cooperative effort by state and federal agencies and private interests, progress over the past 25 years has been lackluster at best.

Between 1967 and 1989, private dam owners spent $55 million to build and improve fish passageways, according to federal estimates, while state and federal governments spent another $55 million or more on hatchery construction and fish stocking.

The U.S. Fish and Wildlife Service projects that a natural self-sustaining run of about 7,300 salmon will be established on the Penobscot by 2009, a goal that would be impossible to achieve if present trends continue.

Recent counts at the fish trap at Veazie Dam indicate that fewer than 2,000 of the more than 400,000 fish released into the Penobscot as smolts will return to the river as adults.

The Penobscot is not the only Maine river where salmon are disappearing. Similar problems are being noted on clean, unobstructed rivers that supported thriving populations of fish as recently as 10 years ago.

Charles Ritzi, a former state biologist and now a private consultant to dam owners, suggests that the federal projections for the restoration program are unjustifiably optimistic, causing its supporters to crusade for a goal they cannot achieve.

“They’ve got themselves into a real biological crapshoot,” Ritzi said. “They try to restore salmon to a river with dams, and it doesn’t work. So now they ask for dam removal.”

He says it would be wiser to concede that some rivers are simply not suitable candidates for restoration of self-sustaining salmon runs and should be stocked indefinitely with hatchery salmon.

But the program coordinator for the Maine Atlantic Sea Run Salmon Commission counsels patience and says studies are under way to determine why the returns are so poor.

Edward T. Baum says one cause for encouragement is the increasingly greater returns of wild fish that were hatched in the Penobscot.

In the last five years an average of 300 wild fish have returned annually, compared to about 150 annually in the previous five years and almost none before that, he said.

“There are going to be lots of ups and downs,” he said, “but I really honestly believe we’re going to be doing very well.”