SAN FRANCISCO - A record-low number of chinook salmon returned to rivers in California's Central Valley last year, indicating that severe restrictions on salmon fishing are likely again this year, federal regulators said.

The Pacific Fishery Management Council reported this week that 66,264 natural and hatchery chinook or "king" salmon adults were estimated to have returned to the Sacramento River basin in 2008 to spawn, the lowest estimate on record.

The council uses the estimates to determine if it should recommend limits on commercial and recreational fishing.

"Our team is putting together the forecast this week, will come out some time next week," Chuck Tracy, the salmon staff officer for the council, said Wednesday. Its final recommendation on fishing limits will be made in April.

The numbers are down from about 90,000 in 2007, which led to bans in 2008 on commercial and recreational salmon fishing off the coasts of California and most of Oregon. In contrast, more than 750,000 adult salmon were counted in the Sacramento River basin in 2002.

The sharp drop in the king salmon that swam from the Pacific Ocean through San Francisco Bay to spawn in the Sacramento River and its tributaries last fall is part of broader decline in wild salmon runs in rivers across the West in recent years.

The Sacramento River chinook run serves as a bellwether for the Pacific's salmon fishermen - the run often provides the bulk of salmon caught off the coasts of California and Oregon.

In the Sacramento Delta, fishermen and regulators believe large pumps used to move water around for farming and other uses is to blame for the falling numbers. Others say changes in the ocean due to greenhouse gas pollution also are killing the fish.

Environmental advocates blame the state's system of canals, dams and pumps, and have sued the National Marine Fisheries Service to impose restrictions to help save fish.

"These most recent salmon numbers ... are further proof that (pumping) operations ... are harming salmon," said Mike Sherwood, an attorney for environmental advocacy group Earthjustice that filed the suit.

Tracy said returns in the Klamath River, the next big salmon spawning river north of the Sacramento River, were higher overall but still fewer than regulators had expected.

Regulators and fishermen had expected this year would be tough. The decline in the salmon population has been economically devastating for the fishing industry, and the council reported that salmon fishing revenue in 2008 for the entire West Coast was $6.9 million, down from $39.9 million in 2007.

"Realistically, we were looking at the fact that we wouldn't have a season this year. We're looking at 2010 before we can fish again," said Zeke Grader, executive director of the Pacific Coast Federation of Fishermen's Associations, an industry group.

Grader said the fishermen's association has saved millions of dollars in federal assistance received after the collapse of the Pacific Coast salmon industry.

"That money sitting in the account will be distributed to keep people alive for this year," Grader said.

The National Marine Fisheries Service will make its final decision on the fate of this year's fishing season after the Pacific Fishery Management Council makes its recommendation.