Oregonian
More than 100,000 fish, including thousands of young endangered suckers, died this week as warm, stagnant water created lethal conditions in the Klamath River and irrigation diversions below Klamath Falls.
The die-off, first noticed Tuesday night, was driven by a runaway algae bloom. When algae explodes into spinach-green mats and then dies, its sudden decay exhausts the water of dissolved oxygen fish need to survive.
Summer fish die-offs are common in the shallow, sullied and heavily manipulated waters of the arid Klamath Basin on the Oregon-California line. But biologists said current conditions -- sustained warm weather and warm water, mainly -- appear especially severe in the Klamath River, fed by water from Upper Klamath Lake.
At least 100,000 dead fish -- mainly blue chubs, tui chubs and minnows -- littered about 7.5 miles of the Klamath River on Wednesday between Klamath Falls and Keno, said Roger Smith, district fish biologist for the Oregon Department of Fish and Wildlife.
"That's a fair amount of real estate to go bad," said Smith, who helped survey the river.
It's happening 200 miles upriver from where more than 30,000 salmon died in similarly warm, fetid water in 2002 at the entrance to the Klamath River from the Pacific Ocean, in California.
In the upper river, near Klamath Falls, a leading concern is the potential death of Lost River and shortnose suckers, federally protected fish that compete with local farmers for the basin's overtapped water supply. The fewer endangered fish, the more likely that competition will continue.
Many farms went without water for much of 2001 after biologists reserved what little there was for suckers in Upper Klamath Lake and protected salmon in the Klamath River.
The Klamath Basin has been plumbed with dams and canals for agriculture, and farm runoff can fertilize algae growth. Although die-offs were known before farming, they appear to strike more often than they would in a natural system, Smith said.
"The concern among researchers is it's happening much more frequently than it should," he said.
The stretch of river where dead fish were found this week deteriorates so commonly in summer that it is not especially important for suckers. The larger concern for biologists is that water conditions could also deteriorate in Upper Klamath Lake, a stronghold of the endangered species.
Catastrophic die-offs of suckers and other fish have hit Upper Klamath Lake, including one in 1996 thought to have killed about half of the adult sucker population.
There is no evidence of that happening yet this year. But a very dense algae bloom is occurring in the Howard Bay area on the west side of Upper Klamath Lake, said Rae Olsen, a spokeswoman for the U.S. Bureau of Reclamation. Suckers, some of which carry radio tags for tracking, appear to be moving away from that area, she said.
"It's very frustrating to see this happen because there is nothing we can do," Olsen said.
Smith said he found no dead suckers in the river. But some could have died there, because he and other biologists did not come close to examining all the fish.
Most measured about three-quarters of an inch to 4 inches in size, he said. However, birds might have quickly consumed adult fish in the roughly 18 hours after the die-off struck and before teams began checking the river.
High temperature, low oxygen
Temperatures in the river reached 82 degrees, and dissolved oxygen levels dropped to zero in the area of Miller Island this week, creating deadly conditions for fish. Air temperatures have hovered in the 90s the past few days, with little wind. Such warm and still air allows algae growth to take off.
Biologists also found several thousand suckers born this year dead in the Lost River Diversion Channel, which is carrying Klamath River water to the slow-flowing Lost River, Olsen said.
They were less than 2 inches long and decomposed, but many are thought to be endangered species.
Suckers are long-lived fish that evolved in the basin's trying conditions by waiting out the difficult years and producing many thousands of young in good years. Tribes consider them sacred.
Biologists would be more concerned about the loss of mature fish of breeding age that are crucial to the future of the species. There are no good estimates of the total number of suckers in the Klamath Basin.
"It makes us really nervous to see this happening," said Bob Gasser, a local fertilizer dealer. "Our goal is to have hundreds of thousands of suckers. If they could tell us what we could do to keep them from dying, we would."
He said the situation shows that weather conditions largely control the die-offs, and restricting or increasing water flows will do little to change it.
But conservationists said the basin lost its natural resilience when croplands replaced wetlands that naturally filtered water.
Michael Milstein: 503-294-7689; michaelmilstein@news.oregonian.com
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