A federal oceanographer says a flip-flop in atmospheric conditions is generating a feast for salmon and other sea life off the West Coast, reversing a trend that contributed to a virtual shutdown of West Coast salmon fishing this summer.

Bill Peterson of NOAA Fisheries in Newport, Ore., said Tuesday the change in cycle of an atmospheric condition known as the Pacific Decadal Oscillation last fall has brought cold water flows from the Gulf of Alaska, which are carrying an abundance of tiny animals known as copepods that are the foundation of the food chain.

It’s unknown how long the good times will last, but Peterson said ocean surveys of chinook salmon in June found lots of yearling juveniles, which should grow up to be plentiful stocks of adults by 2010. Coho surveys start in a couple weeks.

Peterson said last spring that he expected the rebound, and the confirmation of his expectations were reported by The Oregonian.

While the cycle used to last as long as 20 years, it has lately taken about four years for conditions to change; but no one knows for sure what the future will bring, Peterson added.

Ed Bowles, fisheries chief for the Oregon Department of Fish and Wildlife, said salmon that spend most of their time in the ocean close to the coast, such as fall chinook, coho and Willamette River spring chinook, should reap the greatest benefits, but crab, ling cod, rockfish, sea birds and other ocean life are rebounding as well.

Bowles was cautious in his assessment.

“Overall, we are seeing more years of poor ocean conditions than we are good,” he said. “This is a welcome respite in what more typically has been discouraging news.”

Bowles added that Columbia River salmon have also benefited from court-ordered increases in the water spilled over hydroelectric dams, which speeds their migration downriver to the ocean and increases the number that survive.

The Pacific Decadal Oscillation switched last November, developing into the most favorable conditions for West Coast fisheries since 1999, which was the gateway to several good years for fish, Peterson said.

The boost in copepods meant more food for baitfish, such as sand lance and smelt, which are food for larger fish such as salmon.

That changed in 2005, when starvation conditions developed for young salmon migrating from their native streams to the ocean. Three years later, there were so few adults that federal authorities practically shut down commercial and sport fishing off Oregon, Washington and California.

Federal authorities are investigating a variety of factors that could have contributed to the collapse of salmon returns from British Columbia to California.

One of the leading suspects is irrigation withdrawals from the Sacramento-San Joaquin Delta in California. Salmon from the Sacra-mento River saw some of the sharpest declines, and a federal judge is working to reduce the harm on young salmon from irrigation withdrawals from the Sacramento-San Joaquin Delta.