SAN FRANCISCO &

The stunning collapse of one of the West Coast's biggest wild salmon runs has prompted even fishermen to call for an unprecedented shutdown of the Pacific salmon fishery this year.

"There's likely no fish, so what are you going to be fishing for?" said Duncan MacLean, a fisherman from Half Moon Bay. "I have no problem sitting out to rebuild this resource if that's what's necessary."

The Pacific Fishery Management Council meets in Seattle this week and will likely impose the most severe restrictions ever on West Coast salmon fishing to protect California's dwindling chinook stocks.

The Sacramento River chinook run is usually one of the most plentiful on the West Coast, providing the bulk of the fish caught by commercial trollers off California and Oregon.

But only about 90,000 adult chinook returned to the Central Valley last fall &

the second lowest number on record and well below what's needed to maintain a healthy fishery. That number is projected to fall to a record low of 58,000 this year, even with fishing allowed. contrast, 775,000 adults were counted in the Sacramento River system as recently as 2002.

"This stock got off-the-charts bad very suddenly," said Donald McIsaac, the council's executive director. "It's a very, very severe situation."

The council, which regulates Pacific Coast fisheries, will choose between three management options at their meetings: the closure of salmon fishing off the coast of California and Oregon; extremely limited fishing; or catch-and-release fishing for scientific research.

A decision is expected April 10.

The council is also expected to set strict limits on salmon fishing off the coast of Washington to protect that state's declining chinook and coho stocks.

The Sacramento River system is considered the "workhorse" of West Coast commercial salmon fishery, usually producing some 80 percent of chinook caught off California and Oregon.

The Central Valley collapse is a blow to fishermen, tackle shops, charter boat operators and other businesses that depend on commercial and recreational salmon fishing.

For consumers, it will be hard to find any chinook, also known as king salmon, which is prized by anglers, seafood connoisseurs and upscale restaurants. There should still be abundant supplies of farm-raised salmon and wild sockeye from Alaska, but prices could be higher.

"It's going to be devastating to the marketplace to have no California king salmon at all," said David Goldenberg, CEO of the California Salmon Council. "For people who want high-quality salmon, they're not going to have that choice."

Biologists and others are trying to figure out what caused the salmon collapse so they can make sure California's chinook populations rebound.

There are many potential factors because wild salmon are born in streams and rivers, migrate to the ocean when they're juveniles and spend two to four years there before returning to spawn in the areas where they were born.

The council has asked state and federal scientists to research 46 possible causes, including water diversions, habitat destruction, dam operations, agricultural pollution, marine predators and ocean conditions.

Many scientists point to unusual weather patterns that disrupted the marine food chain along the Pacific Coast in 2005, when thousands of seabirds washed up dead or starving because they couldn't find enough to eat.

Researchers believe those poor ocean conditions also devastated the juvenile salmon that would have returned to the Central Valley last year. They couldn't find the tiny shrimp and fish they depend on to survive.

"The fish went to the ocean in 2005 and found nothing to eat when they got there. They either starved to death or got so weak from not eating enough that they got eaten by predators," said Bill Peterson, an oceanographer with the National Marine Fisheries Service.

Peterson said ocean conditions have improved since then, which could help revive West Coast salmon populations.

Many fishermen and environmentalists believe the main problem lies in the Sacramento-San Joaquin Delta, which juvenile salmon must swim through to get to the ocean. They say too much water is being diverted to farms and water districts in the San Joaquin Valley and Southern California.

They want the state and federal government to limit pumping from the delta, which disorients migrating salmon and kills young fish that get sucked into the powerful pumps. They're also calling for a reduction in agricultural runoff and the restoration of salmon habitat in the rivers.

"We did have some poor ocean conditions, but that doesn't explain why the Central Valley stocks took such a severe hit," said Zeke Grader, who heads the Pacific Coast Federation of Fishermen's Associations. "Young salmon need a place they can safely migrate through. This is a critical life stage when they need to gain weight and strength so they can survive in the ocean."

But state water officials believe the ocean is the chief culprit. The water pumps continue to meet stringent operating standards, and while more water has been diverted in recent years, there's also been more water available to export, said Jerry Johns, deputy director of the California Department of Water Resources.

"Ocean conditions are the most likely cause here," Johns said. "The requirements that we have to abide by to protect these fish haven't changed in the last several years."

Most scientists agree that a combination of factors caused the Central Valley crash, and the fishery can be revived under the right conditions.

"They do have an amazing capacity to bounce back," said Peter Moyle, a fish biologist at the University of California, Davis. "If you do have good ocean conditions and you fix a lot of problems in freshwater, there's no reason in the near future we can't have good runs."