This article was published on: 07/16/13 12:00 AM
By Dylan J. Darling
The number of spring-run chinook salmon was down this year even more than last, but the low numbers aren’t dimming the hopes of scientists working to restore the fish upstream of the Pelton Round Butte dam complex on the Deschutes River.
“We are learning from what these fish are doing, and how they behave, to improve their overall survival,” said Greg Concannon, fish and wildlife resources manager for Portland General Electric, which owns the dams near Madras with the Confederated Tribes of the Warm Springs.
Last year was the first in 40 years that adult salmon swam in search of spawning groups above the dams. Released years before in the tributaries upstream of the dams, the fish were helped as youngsters around the dam after being lured in by a $100 million fish tower built by PGE and the tribes.
Fifty of the fish returned in 2012 — half went to the Round Butte Hatchery and half went into trucks that carried them up and around the dams, Concannon said. This year 16 fish returned, and all went into trucks and now swim free in waters above the dams.
Overall spring chinook numbers were down last year and this year in the Columbia River, of which the Deschutes is a tributary. What caused the decline is not clear yet, said Rod French, district fish biologist for the Oregon Department of Fish and Wildlife in The Dalles.
“I don’t have a good explanation for the Deschutes,” he said.
Young salmon start their migration to the ocean as year-old fish, French said. Some, known as jacks, swim back after one full year in the ocean, but most don’t return until they are 3, 4 or even 5 years old. Somewhere along this life history lies a problem that leads to a drastic drop in the number of fish. Mimicking nature, hundreds of thousands of fry have been released into tributaries above the dams in recent years.
“We are still investigating, trying to figure out some causes,” French said. “… There is not a smoking gun.”
Adding to the mystery is that fall-run chinook salmon, which spawn on the Deschutes River downstream of the dam, have seen bumper runs in recent years.
All of the spring chinook released upstream of the dam this year are implanted with radio transmitters, which show that half have swum into the Metolius River from Lake Billy Chinook, where they were released. This hasn’t been a surprise.
Concannon said the river was the primary source for spring-run chinook before the dams were built in 1950s and ’60s. The designs included a 3-mile-long fish ladder and a tramway to move fish swimming upstream around the dams. The system worked, but young fish trying to swim out to the ocean became lost in the cross current of Lake Billy Chinook. In the late 1960s, a hatchery replaced the wild run of salmon.
Plans to restore the spring chinook run, as well as sockeye salmon and steelhead runs, above the dams started in 1994. The massive submerged tower, completed in 2009, is just part of the effort to revive the run. Other projects were meant to restore spawning habitat in the waters above the dams. But more work remains, Concannon said.
“Simply passing fish up- stream is not the answer to this,” he said. “We also have to have good habitat.”
Concannon said no particular size run is targeted, but the hope is to someday have a self-sustaining and harvestable run of spring chinook salmon.
— Reporter: 541-617-7812,
ddarling@bendbulletin.com