A key federal advisory panel this week is expected to begin considering an unprecedented ban on salmon fishing in California in response to an alarming collapse of a signature fishery.

Salmon populations are depressed from the Bay Area to Washington state, but the problem is particularly acute for California's most productive run - the Sacramento River fall run, which produces more than 80 percent of the salmon caught off the California coast.

Not only did numbers plunge steeply and unexpectedly last year, but a key indicator suggests things could be much worse a year from now. "The situation is unprecedented and off the charts," said Donald McIsaac, executive director of the Pacific Fishery Management Council.

Though many researchers are pointing the finger at adverse ocean conditions, McIsaac and others said fluctuations in the ocean's currents and surface temperatures alone do not explain the problems.

And that is focusing renewed attention on the delta and California's water delivery system, which is already being blamed at least partially for the collapse of several other fish species.

"I don't think you can say it's just ocean," McIsaac said.

McIsaac cautioned that the cause of the salmon collapse remains a mystery and that researchers have 46 potential factors to investigate.

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