Jon Rosenfield and I bushwhack through the scrubby willows that line the American River east of Sacramento. The air is crisp this October morning, and the timing of our visit should be just right to watch California’s Chinook salmon as they return to where their lives began and spawn the next generation. Rosenfield, a biologist, works for a conservation group called the Bay Institute, and he wants me to witness an annual ritual that future generations might not have the opportunity to see.

For the salmon, it’s the end of a hard journey that typically lasts three years. After hatching in the river’s gravelly bottom, the young often hang out in its shallow backwaters, developing the bulk and camouflage they need for survival. They then travel downstream toward the Sacramento-San Joaquin Delta — the tidal estuary where they start their transition from fresh to salt water — and out through San Francisco Bay to the Pacific Ocean. There the fish spend most of their lives, feasting on krill, crab larvae, herring, sardines, and anchovies. This is in preparation for the most arduous part of their life cycle: the swim upstream to close the loop. By the time the salmon reach the spot where Rosenfield and I are standing, their energy has been channeled entirely from survival toward reproduction. They’ve stopped eating. Their skin is falling off. After depositing eggs or fertilizing them, they will die. Their carcasses — “these millions of 20-, 30-, 40-pound bags of fertilizer,” says Rosenfield — will be eaten by coyotes, bears, and eagles, which in turn will spread their droppings across forest floors and agricultural fields. “In watersheds where wine grapes are grown and salmon still spawn,” he says, “you can detect the ocean-nutrient signature in the wine.”

We reach the bank and step onto some rocks. For a moment, I see nothing but the river’s flow. Then a fin pops out, followed by a splash. “You see that red?” Rosenfield asks, pointing to a flash of color. “That’s a sexual signal.” I notice one fish circling another in what the biologist identifies as courtship activity. My eyes adjust, and I realize the water is pocked with these displays of fertility.

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State fish and wildlife officials are studying a new way of transporting hatchery salmon that are intended to repopulate the Sacramento River system, a newspaper reported.

About 100,000 Chinook salmon have been taken to San Francisco Bay, where they were released, in water actually from the Sacramento River, The San Mateo County Times reported this week (http://bit.ly/12h3faP).

The theory being tested is that the fish will develop a memory of the water’s chemical makeup that will improve their ability to get to the river from the bay to spawn.

Fish and Wildlife biologists have raised concerns that too many hatchery fish are straying and not returning to the river.

The experiment could help boost salmon populations and impact how hatcheries release the fish, the newspaper reported.

“We’re hoping that this is the way of the future,” said Andrew Hughan, a Fish and Wildlife spokesman.