PORTLAND, Ore. (AP) -- Big numbers of coho salmon are surging up the Columbia River this fall.

About 700,000 coho were projected to return to the river system this year -- at least 200,000 more than last year, according to the Oregon Department of Fish and Wildlife.

Officials say the coho run remains within the normal range of returns and probably doesn't represent a trend in the much larger effort of salmon recovery in the Columbia system.

But fisheries experts are intrigued by some discoveries, such as a spike in coho returning naturally to the upper Willamette River, which hasn't been stocked with fish for a decade.

Scientists from the National Oceanic and Atmospheric Administration predict a similarly large run next fall then a much smaller return in 2011.

They say ocean conditions are mostly responsible. But those conditions -- temperature, currents, upwelling -- are complex and dynamic. Coastal returns look strong as well.

A week ago, Ken Bourne, who manages the Sandy Fish Hatchery, found his holding ponds jammed with fish.

Cedar Creek, a small stream that flows a mile into the Sandy River, was so plugged "you could have walked across on the backs of salmon," he said.

Bourne had a similar experience in the fall of 1991.

"We had just 600 fish come in, and then we got four days of rain," he said. "As far as you could see, it was tails and fins."

The Oregon Food Bank is one beneficiary of the current run.

Fisheries managers are taking many of the fish for the food bank, which serves 240,000 people a month in Oregon and Southwest Washington.

The surplus fish are trucked to Bellingham, Wash., where they're filleted and flash-frozen for the food bank. The agency has seen demand for food jump 14 percent statewide in the past year as the economy has pushed families financially.

Information from: The Oregonian, http://www.oregonlive.com