Storing enough water to allow humans to live safely and prosperously within the great valleys of California required dams, and the state and nation created a system of dams in the early part of the last century that have served us well; though had the project been completed—Shasta Dam built to it intended height tripling current storage, and Auburn Dam finished—we would have been in even better shape.
A consequence however, was the cessation of the salmon’s ability to travel all the way up the rivers it chose to spawn in. The various methods that have been taken to save the salmon runs—while not creating the conditions originally existing—have been very successful and this story from Smithsonian magazine talks about the major role played by the hatcheries, even during this current decline.
And the role is really major, in fact, as the article notes: “between 50 percent and 90 percent of the Sacramento River's "wild" fall-run chinooks are actually born in hatcheries”, which certainly is a clear call to build more hatcheries.
“The sudden decline of California's chinooks, most of which originate in the Sacramento River, has shaken scientists as well as fishermen. Typically several hundred thousand adult fish return from the sea to the river in the fall. Last autumn, only about 90,000 made it back, and fewer than 60,000 are expected this year, which would be the lowest number on record. "Usually when something like that happens, you can point to something dramatic, an oil spill, closing of hatcheries, an earthquake," said Donald McIsaac, executive director of the Pacific Fishery Management Council, the regulatory group that advised U.S. officials to halt this year's salmon fishing. But no such catastrophe has been definitively linked to the shortage…
“We were there because the hatchery was taking a historic step. Usually, the federal facility—at the northern end of California's Central Valley—releases the juveniles out its back door into Battle Creek, which feeds into the Sacramento River six miles downstream. This year, though, natural resource managers had decided to load 1.4 million fish, about a tenth of Coleman's total stock, into trucks and drive them roughly 200 miles south to San Pablo Bay, above San Francisco Bay, bypassing the entire river, a tactic that state hatcheries have been using for years. I had already been startled to learn that between 50 percent and 90 percent of the Sacramento River's "wild" fall-run chinooks are actually born in hatcheries, which were created to compensate for the loss of spawning grounds to dams. Every autumn, hatchery workers trap returning adults before they spawn and strip them of sperm and eggs. The offspring are incubated in trays and fed pellets. Now this latest batch would not even have to swim down the river.” (highlighting added)