Wednesday, March 5, 2008

Warming May Have Caused Salmon Collapse

Warming May Have Caused Salmon Collapse

Go to Original

Shifting jet stream eyed in 2005 starvation.

Grants Pass, Oregon - Scientists examining the sudden and widespread collapse of West Coast salmon returns are pointing to the unusual changes in weather patterns that caused the bottom to fall out of the ocean food web in 2005.

NOAA Fisheries Service oceanographer Bill Peterson said Monday the juvenile salmon that left their native rivers and entered the Pacific Ocean in 2005 found little food being transported by the California Current, which flows from the northern Pacific south along the West Coast.

The reason was that the jet stream had shifted to the south, delaying the spring onset of winds out of the north that create a condition known as upwelling, which kickstarts the ocean food web by stirring the water from bottom to top, the agency said.

"If there is no upwelling, there is no phytoplankton growth, no zooplankton growth, and basically you have no food chain that develops, because it all depends on the upwelling," Peterson said from Newport.

"We are not dismissing other potential causes for this year's low salmon returns," NOAA Fisheries Service Northwest Science Center Director Usha Varanasi said in a statement. "But the widespread pattern of low returns along the West Coast for (both coho and chinook) salmon indicates an environmental anomaly occurred in the California Current in 2005."

That was the year that countless seabirds, showing signs of starvation, were washing up dead on beaches and nesting colonies were sparse. Off Oregon, water temperatures near shore, where chinook spend much of their time in the ocean, were 5 to 7 degrees warmer than normal and yielded about one-fourth the usual amount of phytoplankton, the tiny plants that are at the bottom of the food web.

Since then, upwelling has been better, but not much, Peterson said.

However, he is looking forward to this year being very good. This winter has been very unusual, with temperatures colder and winds out of the north and west more prevalent than normal, all of which indicates 2008 could be the best year for upwelling since 2000, Peterson said.

Chinook returns in the Sacramento River in California last year were a third of what biologists expected, and forecasts are for an all-time low this year. Coho salmon returns to streams in Oregon and California were also lower than expected.

Federal fisheries managers will be wrestling with the problem when they meet in Sacramento, Calif., next week to set options for commercial, sport and tribal fishing seasons for the ocean off California, Oregon and Washington. The Pacific Fishery Management Council will set the final seasons when it meets in Seattle in April.

While no decisions have been made, there are likely to be some salmon fishing closures, said Chuck Tracy, salmon staff for the council.

The council has said that even with no ocean fishing allowed, Sacramento chinook would have a tough time meeting the minimum of 122,000 to 180,000 adults returning to hatcheries and rivers to spawn the next generation.

Sport and commercial salmon fishing off California and most of Oregon was worth an average of $103 million a year from 1979 through 2000, but dropped to $61 million a year from 2001 through 2005, according to council figures.

Salmon fishing cutbacks this year come on the heels of severe limitations in 2006 to protect weak stocks from the Klamath River in Northern California and a poor catch last year despite relatively open seasons.

No comments: