The fall Chinook salmon run on the Columbia River is the largest ever, and could hit 1 million fish by the time it is done.
The fish count at Bonneville Dam went over 613,700 on Friday, the largest number since the dam was completed in 1938.
At the peak of the run, nearly 64,000 fish passed the viewing windows in a single day.
The unprecedented abundance has prompted fisheries managers to extend sport, commercial and tribal fishing seasons on the river, and expand daily bag limits.
Biologists say it is the result of a perfect combination of abundant food and cool temperatures in the ocean, court-ordered actions over the past decade to make the 14 dams in the Columbia Basin less lethal to fish and improvements at fish hatcheries — particularly those run by the Nez Perce Tribe in Idaho.
Pacific State marine Fisheries Commission biologist Joe Hymer said the total could hit 1 million by the end of December, when the fall Chinook run is officially completed.
“We’re just post-peak and the counts are still strong,” he said. “It’s in the realm of possibility.”
The 10-year average is 243,207 fish at Bonneville.
While the number of fish is the most since Bonneville Dam was completed, conditions were far different in the early days of the dam. Upstream, there were no other major dams, all of which kill a small percentage of young fish migrating to the ocean, said Gilly Lyons of Save Our Wild Salmon, a conservation group.
And there were no restrictions on fishing, which took a much higher percentage of the run, said NOAA Fisheries Service spokesman Brian Gorman.
While fishing seasons and bag limits have been extended, they will remain constrained by fears that other stocks of less abundant fish could be hurt by too much catching, said Hymer.
NOAA Fisheries Service biologist Bill Peterson said fall chinook have enjoyed favorable ocean conditions for the past few years, with lots of high fat content zooplankton to eat, and cool water temperatures in the waters off Oregon and Northern California, where they grow from juveniles to adults before returning to spawn.