FRIANT, Calif. — About 10 miles downstream from Friant Dam, two men gently guided their drift boat toward a spot where the riverbed gravel looked as if it had been swept clean.

FRIANT, Calif. — About 10 miles downstream from Friant Dam, two men gently guided their drift boat toward a spot where the riverbed gravel looked as if it had been swept clean.

There, in about a foot of water, they spied something that had vanished from the San Joaquin River more than 60 years ago: a spawning chinook salmon.

"How sweet," said Matt Bigelow, an environmental scientist with the California Department of Fish and Wildlife. "I put in a lot of work to get to this point."

It was a small victory in a tortuous effort: to revive one of California's most abused rivers by restoring a portion of its long-lost water and salmon runs.

The San Joaquin's spring-run chinook once numbered in the hundreds of thousands. The salmon were so plentiful that farmers fed them to hogs. Settlers were kept awake at night by splashing fish as they struggled upstream to their spawning grounds.

The run dwindled as San Joaquin Valley agriculture sucked more and more water from the river system and hydropower dams blocked salmon from upstream passage. Then, in the 1940s, the U.S. Bureau of Reclamation erected Friant Dam as part of the Central Valley Project, a massive irrigation system.

Most of the upper river flow was sent into two giant canals that fed irrigation ditches up and down the east side of the San Joaquin Valley. Sixty miles of the San Joaquin — the state's second-biggest river — died, its bed turning to a ribbon of dry sand.

The spring-run chinook disappeared. Hatchery releases sustained a small population of fall-run chinook that spawn in the San Joaquin's major tributaries.

In the late 1980s, environmentalists went to court to get back some of the San Joaquin's water — and its salmon. Their legal arguments focused on an old provision of the state Fish and Game Code that required dam owners to release enough water downstream to sustain healthy fish populations.

After a nearly two-decade fight, environmental groups reached a settlement with the federal government and farmers supplied by the Friant operation. The 2006 pact called for irrigators to give up some of their supplies to restore year-round flows, and with them, part of the river's historic salmon runs.

But no one thought that reviving a river as degraded as the San Joaquin would be a matter only of adding water and fish and stirring.

Stretches of the old riverbed were choked with shrubs and trees. In some areas, the channel was hemmed in by flood levees. Farmers accustomed to a half-dead river had for decades grown crops in the old flood plain. When the first test flows were released down the dry riverbed a few years ago, water seeped beneath adjacent fields and damaged crops.

The problems have pushed back by years the date when salmon will be able to swim all the way upriver to spawning grounds below Friant Dam.

"Restoration isn't like a light switch, where you flick it on and flows are flowing and fish are coming back and birds are flying overhead and people are picnicking by the riverside," said Monty Schmitt of the Natural Resources Defense Council, which led the restoration fight. "It is not something that happens all at once."

The salmon that Bigelow and Rene Henery of Trout Unlimited saw didn't get within 10 miles of the dam on its own. It was one of 104 fall-run chinook trapped over a period of weeks late last year and hauled in tank trucks down California 99 — around dry riverbed not yet restored — for release in the upper river at Camp Pashayan on the outskirts of Fresno.

Biologists wanted to know what the salmon would do in a part of the river inaccessible to them since Harry Truman was in the White House. Would they find suitable places to spawn, or swim around in futility?

On a gray day in early December, the two scientists were scanning the San Joaquin for answers.

When they spotted the lone chinook lingering in shallow water, they turned on a portable receiver to see if they could pick up a signal from one of the acoustic tags that had been inserted in some of the trapped fish.

The receiver started clicking. The number 7379 popped up on the instrument screen. A check of the trapping log the next day revealed the fish was a 3-foot-long female, caught in mid-November.

Now she was guarding the gravel bed where she had laid several thousand eggs and covered them with swishes of her tail, leaving behind signs of her nest, or redd, as salmon nests are called.

Studying her, the men could see that she was in bad shape. Her fins were deteriorating. Fungus was growing on her. Soon she would die, her biological role fulfilled.

No. 7379 wasn't the only female to find a gravel bed to her liking. Biologists counted 11 redds upstream of the release point.

Their presence proved that after more than a half-century absence, chinook would spawn in the wild in the upper San Joaquin.

But because water is still not flowing down the river's longest dry stretch, the hatching salmon have nowhere to go. The juveniles will hang out in the upper river until they become a meal for other fish.