July 1, 2012
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 an entire year. But on Monday, that many passed the Columbia River dam, and another 41,000 swam over the dam Wednesday — a rate of nearly 30 per minute. That bought the total to 290,000.
A record run of more than 400,000 of the Columbia Basin’s farthest-swimming salmon 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.
Smaller than most salmon at three to five pounds, sockeye also are 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.
Although the Okanagan sockeye never were 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.
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 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.
“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, Graves said. The six species combined accounted for 1.8 million salmon over Bonneville in 2010, compared with 471,144 in 1938.