Oregon salmon beds at risk
Irrigation breach dumps mud into Rogue, Big Butte
GRANTS PASS, Ore. – Biologists are hoping wild spring chinook in the Rogue River “dodged a bullet” after a break in an irrigation ditch sent suffocating muddy water coursing over millions of freshly laid eggs that represent a big chunk of future runs.
If fine particles of clay settled around the millions of eggs laid in gravel beds in recent weeks, the eggs could suffocate and die, Oregon Department of Fish and Wildlife fish biologist Jay Doino said Tuesday.
It will be a few days before surveys of spawning beds on Big Butte Creek and the Rogue River produce an answer, but “we may have dodged a bullet,” said department district fish biologist Dan Van Dyke. Only about half the estimated 4,700 adult females in this year’s wild spring run have laid their eggs so far. The rest should be able to dig clean nests in the river gravel even if silt settled over the spawning beds.
Doino said they also hope the clay particles were fine enough to stay suspended in the water far enough downstream so eggs were not suffocated.
“It could go either way,” he said.
Employees of the Eagle Point Irrigation District were working on repairing the ditch, which was built in 1921 and serves 560 users on more than 8,000 acres, said district consultant Hazel Ellefson. Workers shut off the water on Sunday after discovering the collapse of a 100-foot section of the main canal, which sent water flowing over a clay hillside into Big Butte Creek and down the Rogue River. The cause was not yet known.
Van Dyke said the 4,700 females estimated in this year’s run would lay about 16 million eggs.
The eggs remain vulnerable all winter as they incubate, and hatch in early spring. The adults return four years after they were spawned. The loss of one year-class of wild fish would leave three others returning, plus fish produced in the hatchery.
Rebuilding runs of wild spring chinook has been the top priority of state fish biologists working on the Rogue in recent years, and the population is just starting to build since record lows in 2007, 2008 and 2009 due to poor food-producing conditions in the ocean.