Federal fisheries biologists say the 2008 collapse of salmon returning to California's Sacramento River was triggered primarily by climatic conditions that produced too little food in the ocean, compounded by too much reliance on fish produced in hatcheries instead of the wild.

GRANTS PASS — Federal fisheries biologists say the 2008 collapse of salmon returning to California's Sacramento River was triggered primarily by climatic conditions that produced too little food in the ocean, compounded by too much reliance on fish produced in hatcheries instead of the wild.

NOAA Fisheries Service warned in the Wednesday report that there is little federal fisheries managers can do directly to prevent the boom-and-bust cycle from repeating, given the lack of genetic diversity brought about by as many as 90 percent of the young fish each year coming from hatcheries, and the increasing frequency of swings in ocean conditions.

They suggested the Pacific Fishery Management Council, which sets ocean salmon fishing quotas, support the difficult long-term steps of rebuilding habitat in rivers, and reforming practices in hatcheries, to restore the genetic diversity that has allowed salmon to survive a changing environment for thousands of years.

"We have been wedded to this idea that the solution is just hatchery production," said Steve Lindley, a research ecologist for NOAA Fisheries in Santa Cruz, Calif. "I think that is the wrong response in the long run."

Hatcheries have operated for more than 100 years on the West Coast to make up for habitat lost to cities, farms, logging and mining.

Studies in recent years indicate that the system creates fish that are less able to survive in the wild, especially in hard times.

On Tuesday, a 9th U.S. Circuit Court of Appeals ruling upheld NOAA Fisheries' discretion to use hatcheries to bolster endangered runs, but not rely on them to replace wild fish.

In the Sacramento, wild strains of chinook did not collapse so precipitously as the fall run, which is dominated by hatchery fish, the report found.

"I would predict that given ocean conditions improving and a record level of hatchery production, we will see record levels of the fishery again in a few years," Lindley said. "But it's not going to last. We are going to have this problem again. And it may be more severe next time."

Sport and commercial fishing seasons off California and Oregon were practically shut down in 2008 after a sudden drop in the Sacramento fall chinook run, and fishermen qualified for $170 million in federal disaster assistance.

Forecasts call for about twice as many salmon overall on the West Coast this year, but the numbers still are low, and fishing is expected to remain sparse off California and Oregon until next year, when numbers are forecast to rebound thanks to a flip in the climatic cycle that governs food abundance in the ocean.

The report discounted arguments that record irrigation withdrawals from the Sacramento Delta in 2006, the year that the 2008 adults migrated to the ocean, were a factor in the collapse.

Hatchery fish are generally trucked around the delta and released in San Francisco Bay, and those swimming through the delta had gone through by the time heavy pumping occurred in the summer, Lindley said.

Glen Spain of Pacific Coast Federation of Fishermen's Associations, which represents California salmon fishermen, said it was still important to fix the obstacles of fish swimming through the delta, because very few survive the journey.