HALF MOON BAY, Calif. — An unusually weak Dungeness crab harvest is compounding the financial woes of West Coast fishermen who were already struggling with depressed consumer demand and the unprecedented collapse of the Pacific chinook salmon fishery.

Commercial fishermen in California, Oregon and Washington are struggling to stay afloat financially. They say the downturn could force fishermen who depend heavily on crab and salmon to leave the shrinking ranks of the region's fishing fleet.

"With this crab season being slim at best, it's going to be pretty hard to make it through to the next one," said 58-year-old Duncan MacLean, a commercial fisherman since 1972. "I would suspect there are going to be lots of people falling by the wayside."

The Dungeness season that began in mid-November is shaping up to be one of the least productive in years. In Half Moon Bay, about 25 miles south of San Francisco, MacLean and other crabbers are not doing much fishing because the catch is so poor and prices offered by seafood processors are so low.

"It's disappointing to everybody because you want to support your family," said 45-year-old Steve Mills. "Even though we're not catching crab, the bills still pile up."

Last spring, federal regulators for the first time canceled the West Coast's commercial salmon season after a near-record low number of chinook returned to spawn in the rivers of California's Central Valley. Next year's season also could be called off to allow salmon populations to rebound.

Congress approved $100 million in federal disaster relief to help trollers and businesses that depend on West Coast salmon fishing. Many fishermen say they would be hurting even more without the aid, but they still had been counting on a robust Dungeness season.

Scientists attribute the weak crab harvest to increased fishing earlier this year, ocean conditions that disrupted the marine food chain and the natural cycle of crab populations, which tend to peak every seven to 10 years.

This season's California catch is expected to fall below the 8 million pounds caught last year, which was down from 25 million pounds four years ago, according to the state Department of Fish and Game.

"I'd characterize it as near the bottom of the natural cycle," said Peter Kalvass, a state biologist in Fort Bragg who expects the harvest to rebound in a couple of years, based on the large number of young crabs found in fishermen's traps.

In most years, low supply means higher prices, but this year crab fishermen are getting paid less than they got in more abundant years.