SACRAMENTO -- On a sunny morning in the state capital, Mike McHenry, a fisherman out of Pillar Point Harbor in San Mateo County, guided his boat to a dock on the Sacramento River and readied its 10,000-gallon hold for some special cargo.
 Once the captain had filled the tank with river water, a team of state Fish and Wildlife biologists and technicians aimed a 100-foot tube into the belly of McHenry's 64-foot boat, the Merva W. About 100,000 baby salmon gushed out of a truck into the hold.
In about 10 minutes the vessel was teeming with fish, their speckled backs presenting various shades of greens, browns and yellows. Soon after, McHenry would steer his boat 109 miles to Fort Baker, just east of the Golden Gate Bridge, completing the latest phase of a groundbreaking experiment involving one of California's most vital and popular fish, the Chinook salmon.
"Can you imagine what a trip that is?" said McHenry, peering down at the skittering smolts, which would be shot into the bay 24 hours later. "And they're just beginning their journey."
What happens to these fish once they reach adulthood and make their fall spawning run is the subject of an unusual collaborative study, proposed by commercial fishermen and aided by the state Department of Fish and Wildlife.
The state keeps the Central Valley salmon population alive by hatching millions of fish in captivity, then releasing them into nearby rivers or trucking them to San Pablo Bay. But each of these methods has a drawback. Most juvenile salmon that are released into the river don't make it to the ocean, thanks to natural predation and man-made obstacles, while those dumped right into the bay miss out on a key developmental milestone.
This study analyzes whether shipping them to the bay in tanks circulating with river water is a more effective method of releasing them. The theory is that exposing them to the Sacramento River, allowing them to "smell" it, will optimize their remarkable homing instinct.
The experiment could have a major impact on how hatcheries release salmon in the Sacramento River system, one of two prime breeding grounds in the state. It could also boost the fortunes of the hard-luck salmon themselves.
"We're hoping that this is the way of the future," said Andrew Hughan, a Fish and Wildlife spokesman.
The Feather River Fish Hatchery, 70 miles north of Sacramento, is the busiest state-operated hatchery in California. Last year it produced 12.2 million baby salmon.
Most are transported to the Carquinez Strait in tanker trucks, then spend time in floating pens, acclimating to the temperature and salinity of the water.
The program was developed to sidestep the dangers of the Sacramento River and its tributaries, including the Feather River, which serve as a major source of irrigation for Central Valley farmers. That means there's less water for salmon. And the Sacramento-San Joaquin River Delta Cross Channel in Walnut Grove sucks countless smolts into the Delta, thwarting their migration to sea and delivering them into the mouths of predatory fish and birds.
The downside of the trucking method, however, is that the salmon don't get a sensory fix on their native stream, causing concern among Fish and Wildlife biologists that too many are straying when they return to spawn -- that is, failing to find the river where they were born.
It is widely accepted that salmon develop olfactory memories on their way to the ocean that guide them on their return trip. The process, known as imprinting, etches the water's chemical makeup into their brains. "They know how the water tastes and smells from their river of origin," said Colin Purdy, leader of the three-year study, now in its second year.
Purdy's team will track how many salmon from the Merva W. return to the Sacramento River and continue up to the Feather River Hatchery. The survival and stray rates of these salmon will be compared with two other groups from the same hatchery, all of which have been implanted with tags biologists can collect when the fish are caught or return to spawn.
Purdy's team released 100,000 smolts into the river at the dock where McHenry's boat was loaded, just a short walk from downtown Sacramento. Purdy expects only 10 percent to survive. Another 100,000 were trucked to Fort Baker and pumped into the bay. If McHenry's salmon fare better, fishery managers will consider barging salmon down the river on a much larger scale. The ultimate goal is to strengthen the population of fall-run Chinook and improve the fortunes of professional fishers.
A salmon fisherman for half a century, McHenry volunteered his time and boat to the study for two reasons: solidarity with his fellow fishers and the thrill of hunting salmon on the open ocean and reeling them in.
"It's the one fishery," he said, "that makes your heart go pitter-patter."