Counts predict big year for little salmon

Ocean - Juveniles are flourishing so far in 2007, turning up in among the highest numbers in 10 years  

July 20, 2007

RICHARD L. HILL

The Oregonian

The number of juvenile salmon off the Northwest coast is among the highest that has been recorded since a yearly survey began a decade ago.

Researchers hope it's a sign that adult salmon numbers may increase in the next two years.

Scientists credit this year's rebound of juvenile coho and chinook to an early arrival from Alaskan waters of zooplankton, the tiny algae-eating animals that are the foundation of the Pacific Ocean food chain.

"It's been a fabulous year so far," said Bill Peterson, a National Oceanic and Atmospheric Administration Fisheries oceanographer who conducts the annual survey from Newport to northern Washington . "But conditions can turn sour, and the salmon out there right now could perish in great numbers."

The number of juvenile salmon caught in the coastal trawl surveys has been low the past few years because of warm ocean conditions and delayed upwelling of cold, nutrient-rich water.

This year's survey compares with high catches in 1999 and 2003.

Counts of juvenile spring chinook in June are a good indicator of the return of adults two years later, so spring chinook landings should be above average in 2009, Peterson said. Larger numbers of juvenile spring coho mean that there may be more coho adults as early as next year.

Juvenile salmon migrate from freshwater streams to the ocean, where they feed for one to four years before returning to spawn in the stream where they hatched.

Peterson credits the increase in juvenile salmon to cooler water off Oregon , beginning last summer after nearly four years of warm ocean conditions. He speculates that the cooler ocean may be linked to a powerful climate cycle called the Pacific Decadal Oscillation, a regional phenomenon in which the climate flip-flops every few years between wet-cool and dry-warm phases.

"If it's moving to a cool phase, that would be good news for the fish, seabirds and a lot of other animals," Peterson said. "They've been beaten down and weakened the past four years because of lousy conditions, but they might be able to get their body fat back up if this trend keeps going."

The zooplankton includes high numbers of northern copepod species that aren't often seen off Oregon . Fish, birds and whales feed on the copepods, tiny crustaceans that feed on phytoplankton blooms produced by summer upwelling. Northern species are nutritionally better for marine life because they have more fat than their southern cousins, which are more prevalent during warmer periods.

Roy Lowe, manager of the Oregon Coast National Wildlife Refuge Complex, said he's pleased about the increase in plankton because he was concerned about the many dead seabirds this year.

"But that doesn't instantly produce forage fish for birds and other animals," he said. "There's a lag time, so it's too early to say what effect this will have on getting these birds in better shape."

The subarctic zooplankton began showing up in Northwest waters in March, one of the earliest arrivals on record, Peterson said. The only other years when the zooplankton arrived that early -- 1970 and 1972 -- were characterized by very high salmon survival, he noted.

An upwelling of cold, nutrient-rich water along the Oregon coast has stalled in the past few days, raising concerns that the rebound may fizzle, said Peterson, a courtesy professor at Oregon State University . He cautioned that the counts from research trawls in May and June are preliminary, and final results won't be available until a final survey in September.

Richard L. Hill: 503-221-8238; richardhill@news.oregonian.com

Salmon Survey - showing chinook and coho juveniles: 

http://www.oregonlive.com/cgi-bin/prxy/accessor/nph-repository-cache.cgi/base/pdf_captions/118491452275060.pdf

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