SHASTA LAKE, California—Thigh-deep inside a holding tank, wearing his U.S. Fish and Wildlife Service uniform and waders, Beau Hopkins had to bend over to scoop each netful of squiggling baby salmon. One tank held 40,000 babies. By midafternoon Hopkins had been at it for two and a half hours: three tanks emptied, one more to go.

In the background rose the slope of Shasta Dam, the massive concrete construction that restrains the Sacramento River on its course to the Pacific Ocean. But the hurried campaign for which Hopkins had been pressed into service was remarkably rudimentary: a sort of bucket brigade of men and women passing salmon-heavy scooping nets, one by one, up to the trucks that would give the baby salmon—about 600,000 before the job was done—a lifesaving ride into town.

View Images JEROME N. COOKSON, NG STAFF

Hopkins stretched, made a rueful joke about visiting his chiropractor, and shoved his net back in. Wherever he dipped, the water was dark with squiggling. Each time he pulled up, the net shone with the wet silver and black of hundreds of four-inch (ten-centimeter) salmon, crammed together and panicky-looking. Juveniles, the experts call them; really they're not so much babies as prepubescents, on the verge of the mysterious internal triggering that makes them want to go look for the sea.

But they can't get to the sea from the Livingston Stone National Fish Hatchery on their own, and so every winter, in a wondrous tableau of colliding public priorities, this hatchery is one of the Western venues where diesel-powered trucks chug live little salmon from one place to another, circumventing dams we humans have put in the way of the fish.

This month, as they undertook their salmon-lift for the winter run of California's Chinook, better known as king salmon, state and national fishery officials encouraged a few outsiders to visit Livingston Stone and watch—because drought decimated last year's winter run, and the ongoing drought could decimate this year's. Hatchery workers, hoping an extraordinary boost might help, were tripling the number of young fish they normally load into their trucks.

If you had found yourself on a certain road through the conifers about four hours north of Sacramento late that February afternoon, you might have encountered our small, solemn, fish-ferrying caravan: several dozen people from government agencies (the California Department of Fish and Wildlife, the U.S. Fish and Wildlife Service, the National Oceanic and Atmospheric Administration), a mini-posse of reporters, and two tanker trucks that for the moment amounted to giant aquariums on wheels.

We had no fancy escort, though. It was dusk by the time we rolled out of the hatchery, and unless you understood what was happening—unless you are one of the biologists and fish experts who use words like "miraculous" when describing the extraordinary life journey of the California Chinook salmon, imperiled by man and now doubly imperiled by weather—you would likely have paid us no mind.

A Miraculous Journey

Here's how the miracle begins, when things are going as they're supposed to in the wild: The baby Chinook, one of the five main salmon varieties in the West, hatches from an egg that its fish parents buried in the gravel of a cold-water river before they perished. The cold part is crucial; the water's got to stay below about 60°F (15.5°C).

When the first mystery cue comes—Time to go!—the now-juveniles prepare not only to leave home, but also to change into saltwater fish. Even at tremendous distance, biologists say, they can somehow sense the sea. They want the sea. Water currents, smell, and instinct propel the Chinooks downstream, swimming for weeks toward brackish water, risking attack by birds and bigger fish, until they reach—those that survive the journey—the open ocean.

That's just downstream. The return trip requires battling the current, not to mention more predators. By the time the salmon are back into river water—those that survive the journey—they have retransformed themselves into freshwater fish and find their way exactly home to produce a new generation and die. It is like grand opera.

"Three years in the Pacific!" cried Andrew Hughan, one of the state Fish and Wildlife spokespeople who led us through the high gates of Livingston Stone. "Then they have to turn around and swim back! At the end of the day, we really don't know why they do it. But they will come back and spawn in the same waters where they were spawned. It's unbelievably fascinating."

Hatchery Workers Triple Down

Wild fish hatcheries (not farms to grow fish for food, that is, but egg-cultivating operations to raise fish for release into the wild) exist because people want wild fish—to eat, to hunt, to cherish as part of the ecosystem—and also want agriculture and urban development, both of which require taking some of those wild fishes' water.

The construction of Shasta Dam and the smaller Keswick Dam nearby, back in the 1940s, was part of a vast project redirecting California's river waters to ambitious human endeavors all over the state. The two dams truncated California Chinook migration routes, which had connected high mountain tributaries to the sea. Now the salmon must start and end their lives in the chilly water just below Keswick, the lower of the two dams.

The Livingston Stone hatchery, with its outdoor tanks and long buildings lined with incubator trays, is supposed to bolster those seasonal migrations—especially in winter, when for decades now, California Chinook runs have been low enough to warrant Endangered Species Act protection even during non-drought years. (The hatchery is named for a visionary federal fisheries official and vigorous advocate for preserving salmon runs who asked in a 1892 speech: "What hope is there for the salmon in the end?")

Most years, hatchery workers drive to Keswick and pull about 120 adult fish from a special live trap in the spawning waters. Like in vitro fertilization doctors in hatchery gear, the workers fertilize the eggs in lab trays at Livingston Stone, test them for genetic diversity, and incubate the young. Then they send those tanker trucks back to the spawning grounds to add thousands of new juveniles to the young salmon emerging naturally from the riverbed, all awaiting the summons of the sea.

The California drought, the state's worst on record, has taken a terrible toll on those already-diminished winter Chinook salmon runs.

It's not just that there isn't enough water; there's not enough cold water, especially after competing interests such as urban areas and big agriculture—each equipped with more political muscle than wild salmon advocates have—take their share. In 2014, the returning winter Chinook numbers were the worst that fishery officials had ever seen. In a normal year, about 25 percent of the eggs produce baby salmon healthy enough to migrate; last year, with only 5 percent surviving their infancy in the unusually warm water, nearly the whole winter run was wiped out.

That's why hatchery workers tripled the fish in the truck-lift this month. They had pulled 380 adults from the water and ended up incubating 600,000 babies (yes, each female salmon carries a staggering number of eggs) in tanks that normally hold a third that many.

"We have to do this," Hughan said. "We have to try. We can't just say, 'Oh, the drought's here; we're just going to let the river dry up for fish.' No matter what it costs, no matter what the resources are, we have to try."

Baby Salmon on the Go

Now, as though all these meteorological and human-induced subplots were not enough salmon drama, rain was coming: a big, three-day northern California storm. No one expected these rains to make a real difference in the ongoing drought, but the weather forecasters promised enough water to stir up turbulence in the Sacramento River and help hide those juvenile salmon from their first round of predators—the bigger fish and the fish-eating birds.

The Chinook winter-run rescue team decided to release all 600,000 juveniles in time to take advantage of the rain. In Redding, where a long, illuminated bridge spans the river over the salmon route, city officials had agreed for the first time to darken the whole bridge all night, to keep overhead light from confusing the fish.

Our odd procession passed an AutoZone auto parts store, a Little Caesars pizza shop, a Goodwill store, the Lakeshore Smoke Shop. We turned at a football field. Everybody came to a stop in a city park alongside the Sacramento River. On a sloping boat ramp, the first of the fish trucks eased in backward, and Beau Hopkins, still wearing his rubber fisherman's overalls, waded into the water with a fat, metal hose.

A switch was flipped, the truck made a rude digestive noise, and spray shot from the end of the hose Hopkins was wrangling—white froth, dark water, and the black outlines of thousands and thousands of tiny, darting fish. They kept coming, airborne momentarily and then disappearing beneath the surface of the river, which looked wide and still.

A few of the juveniles bore special acoustic tags, embedded at the hatchery to help researchers track their progress toward the Pacific, 300 miles (483 kilometers) away. Within less than a week, signals from a dozen of those tagged fish would be picked up two-thirds of the way west; the fish were moving faster than expected toward the Sacramento Delta, the wide maze of channels and estuaries where the river first begins meeting the sea.

And the natural world offers plenty of peril, but in California the salmon's greatest threats come from man-made interference like that delta, where pumps and canals direct river water to places human beings have decided it should go. The statewide diversion system changes currents, confuses salmon into swimming in the wrong direction, traps them in drainage canals, and leaves spawning beds too warm to keep salmon alive.

An underwater pilgrimage of more than half a million little fish seems indomitable, when you're visualizing it from a riverbank as night comes on, but the hatchery workers know better: If a few thousand make it back as adults, three or four years from now, they will call this a victory.

The rain was beginning. A hatchery man noticed something at the water's edge and stepped over to inspect: a lone wayward juvenile, already heading the wrong way. He smiled, picked the small fish up, and flicked it back into the river.