Federal officials have indicated that they are likely to close the Pacific salmon fishery from northern Oregon to the Mexican border because of the collapse of crucial stocks in California’s major watershed.

That would be the most extensive closing on the West Coast since the federal government started regulating fisheries.

“By far the biggest,” said Dave Bitts, a commercial fisherman from Eureka, Calif., who is at a weeklong meeting of the Pacific Coast Fisheries Management Council in Sacramento.

“The Central Valley fall Chinook salmon are in the worst condition since records began to be kept,” Robert Lohn, regional administrator for the National Marine Fisheries Service in Portland, Ore., said Wednesday in an interview. “This is the largest collapse of salmon stocks in 40 years.”