Record numbers of a once-waning population of sockeye salmon have been returning to the Northwest's Columbia Basin this summer, with thousands more crossing the river's dams in a single day than the total numbers seen in some previous years.
Since Bonneville Dam outside Portland was built in 1938, there have been plenty of times there weren't 38,000 sockeye salmon swimming over the fish ladders in a whole year.
But on Monday that many passed the Columbia River dam, and another 41,000 swam over the dam on Wednesday — a rate of nearly 30 a minute. That bought the total so far to 290,000.
More than 400,000 of the Columbia Basin's farthest-swimming salmon – a record number -- are expected to return this year, almost all of them wild fish bred in rivers, instead of the hatcheries that produce most Northwest salmon.
Sockeye cross nine dams to reach spawning grounds in northern Washington and Canada.
Biologists credit habitat improvements in the Okanagan Basin of northern Washington and Canada, improved dam operations, and favorable ocean conditions for the numbers. Okanagan sockeye swim more than 500 miles to spawn.
The bulk of the record returns are going back to the Okanagan River Basin, which drains a series of lakes straddling the Canadian border and flows into the Columbia.
"I have been telling people if they get the opportunity, to go up and visit the Okanagan," said Bill Tweit, special assistant to the director of the Washington Department of Fish and Wildlife. "It's going to be an incredible natural spectacle."
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Smaller than most salmon at three to five pounds, sockeye are also the brightest in color. They are popularly known as bluebacks for their silvery blue hue as they pass Bonneville Dam, but as they get closer to laying their eggs in the gravels of rivers and lakes in the fall, their bodies turn bright red and their heads green.
Though the Okanagan sockeye were never listed as an Endangered Species, as Snake River sockeye in Idaho were, the future was not looking bright for Okanagan sockeye in the late 1980s and early 1990s, said Joe Peone, fish and wildlife director for the Confederated Tribes of the Colville Indian Reservation, which is in the Okanagan Basin.
Less than 9,000 returned in '95
Fewer than 9,000 sockeye returned to the Columbia Basin in 1995.
The operation of hydroelectric dams regularly washed out the eggs after the fish laid them in the river, or left them high and dry before they hatched.
Sockeye proved difficult to rear in hatcheries, so tribes on both sides of the border teamed up with local utilities that owned the dams to work out rules for maintaining flows that the fish could live with. Natural meanders were restored to rivers that had been straightened to reduce flooding.
"Right now those fish are utilizing maybe a quarter of their historic habitat," Peone said. If more habitat is restored, "You could see 1 million fish coming back here."
Ritchie Graves, a NOAA Fisheries Service biologist who makes sure federally owned dams are living up to their Endangered Species Act obligations not to kill too many salmon, said the survival rate for young salmon swimming downstream to the ocean has been higher than ever the past three years, hitting about 50 percent for sockeye.
Those improved dam operations have also benefited chinook, coho, chums, pinks and steelhead, said Graves. The six species combined accounted for 1.8 million salmon over Bonneville in 2010, compared to 471,144 in 1938.
Once young salmon get to the ocean, scientists have only a vague idea where they go, and an incomplete understanding of why some years they thrive and some years they starve.
Generally, years when climate and weather cause the ocean waters to well up, salting the water column with food, fish do better. But unlike most salmon, which eat other fish, sockeye eat plankton, tiny shrimplike animals.
Though poor ocean conditions have been blamed for a nosedive in chinook salmon in Alaska this year, sockeye have done well, not only in the Columbia, but in Canadian and Alaskan rivers as well.
"Whatever is going on in the ocean is basically being good to sockeye," said Tweit.