Migrating salmon on the Columbia River face tough odds for survival as the lack of snowmelt water and searing summer heat have sent water temperatures soaring.

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HOME VALLEY, Skamania County — In a quiet, green pool off the Lower Columbia River, upstream from the Bonneville Dam, dozens of sickly sockeye salmon spend their final days.

They shouldn’t be here. Instead, the fish should have forged deep into the drainages of North Central Washington, the Okanagan region of British Columbia or Redfish Lake in central Idaho.

But their journey has been short-circuited by a startling surge in water temperatures that has turned the Columbia into a kill zone where salmon immune systems are weakened and fish die of infections.

At Bonneville Dam last week, water temperatures were more than 72 degrees, nearly 5 degrees higher than the 10-year average for this time period

So, rather than pushing forward, these sockeye made a last-ditch effort to escape the warm water. They veered off the Columbia to swim into a short inlet that leads to the mouth of the Little White Salmon River, which is fed by glacier melt and provides cool water.

Some still are chrome silver, though suffering from a bacterial disease. Others have backs covered with a mottled white fungus. All are expected to die here — hundreds of miles short of their spawning grounds.

“The water temperatures in the Lower Columbia are physiologically unsustainable for salmon,” said Mary Peters, a microbiologist who works for the U.S. Fish and Wildlife Service. “It’s crazy.”

The plight of these sockeye is stark evidence of how far freshwater conditions have deteriorated for Northwest salmon in a year when a shrunken snowpack provided scant meltwater and searing summer weather stoked up temperatures in creeks and rivers.

Salmon also face challenges in the ocean where they spend most of their lives. There, unusually warm coastal waters have diminished the food supply that nurture young fish as they first emerge from freshwater, and that could mean weaker runs in the near future.

“My guess is that this is going to be one of the poorest years for salmon (ocean) survival” said Bill Peterson, a National Oceanic and Atmospheric Administration (NOAA) Fisheries scientist based in Newport, Ore. “Things do not look good.”

These poor ocean conditions are a sharp reversal from much of the past decade when cooler waters supported nutritious forage that helped boost salmon runs. Last year, more than 2.3 million salmon and steelhead, both wild and hatchery-bred, returned to the Columbia River basin, setting a modern-day record. So far this year, there have also been strong runs.

Longer-term climate change, driven by emissions from fossil fuels, also raises concerns for the fate of salmon as they return to freshwater to spawn. Snowpacks are forecast to decline, putting rivers more at risk of lower flows like those this summer, and higher temperatures.

“It’s just like boiling water in a kettle. When you have less water in there, it gets hotter, faster,” said Ritchie Graves, a NOAA Fisheries supervisory biologist.

Migration blocked

This year, spring chinook arrived in freshwater well before intense heat pushed river temperatures past 70 degrees. Now, many of the wild fish are holding in cool deep pools in higher elevation drainages and will spawn later in the year when water temperatures are hoped to have eased.

But the big summer runs of sockeye are in serious trouble on the Columbia.

Of the more than 500,000 that passed Bonneville Dam on the Lower Columbia River, most are struggling as they try to make their way past a network of dams that create slack pools with large volumes of water exposed to the sun.

“These reservoirs create a huge surface area for solar heating. And it’s an effect of the construction and operation of the hydro system that we haven’t successfully mitigated,” said Michele DeHart, manager of the Portland-based Fish Passage Center that monitors salmon passage over the dams.

Even in a more typical year, sockeye may face some summer temperature problems in the Columbia.

This year, a couple of hundred thousand of these sockeye may already have perished in the river’s warm waters, according to Jeff Korth, a state Department of Fish and Wildlife regional fish manager.

Dead salmon have been spotted around the fish ladders at Bonneville Dam. Diseased fish with red marks that are signs of a bacterial infection have been found in tribal dip nets.

“Some of them actually have red splotches all over, and we threw them back because we didn’t want to keep them,” said Jessie Yallup, a Yakama Nation fisherman who works a dip net downstream of Bonneville Dam.

Most of the Columbia River sockeye are bound for Canada. But they must first pass through the Okanogan River, where water temperatures have exceeded 76 degrees in recent weeks and created a strong thermal barrier blocking salmon migration.

Currently, an estimated 170,000 sockeye mill around the confluence of the Okanogan and Columbia. Earlier this month, when the Okanogan temperatures dipped just a few degrees, some sockeye tried to make it upstream. But water temperatures rose again, trapping them in lethal waters.

“We probably lost 13,000 or 14,000 fish. None of them survived,” said Korth, the Washington state biologist.

There also is concern about the fate of Idaho’s sockeye, one of 13 Columbia Basin runs listed under the federal Endangered Species Act. They face a challenging upriver migration past the Columbia and Snake River dams, and have been rescued from near extinction at a cost of tens of millions of dollars.

Last year, more than 1,400 sockeye made the 900-mile journey to Redfish Lake in Idaho. This year, though, is shaping up as a significant setback in the restoration effort. So far, less than 400 of these sockeye have made it past Lower Granite, the last dam on the Snake River, prompting the state of Idaho to declare a sockeye emergency.

During a tense teleconference on July 22, Idaho biologist Russ Kiefer pushed his counterparts in other Northwest states to support a new tactic: increasing flows through turbines in an attempt to draw more cooler water and coax more sockeye past the Little Goose Dam on the Snake River.

Other state biologists pressed for more information about the potential benefits. Kiefer erupted in frustration.

“All I hear is, you want more analysis,” Kiefer said. “We’re at the time that the more we delay, the more sockeye die.”

Hatcheries struggling

Elsewhere in the Northwest, biologists are monitoring a multitude of drainages where low flows and warm water pose risks to fish.

The Dungeness River near Sequim is usually flush with cool water from snowmelt off the Olympic Mountains as chinook and pink salmon return from saltwater. But this year, most winter precipitation fell as rain not snow, so water-flow levels have tapered off drastically.

“Some of the riffles are only ankle deep,” said Chris Byrnes, a state Department of Fish and Wildlife biologist. “The chinook, they are going to be sticking out of the water about half way when they come up through the shallow spots.”

Some hatcheries also are struggling due to warm water.

In memos summarizing drought impacts, the state Department of Fish and Wildlife notes that nine hatcheries have lost more than 1.5 million young coho and steelhead. One of the hardest hit was the North Toutle River hatchery in southwest Washington; it lost 103,000 coho — about 78 percent of its production of that species. That prompted the transfer of surviving fish to another hatchery.

“We’re trying to make sure fish are treated for the diseases, and be nimble and come up with alternative supplies of water,” said Guy Norman, southwest Washington regional director for the department.

Praying for rain

There is plenty of uncertainty about how the rest of the summer will play out.

If the weather eases and the mountains get some showers, some river systems such as the Okanogan could cool substantially. That could help salvage at least a fraction of the river’s sockeye run.

“A little bit of rain goes a long way when the water is so low,” said Korf, the state biologist who tracks sockeye. “If we can get those temperatures down to around 70, those fish will shoot up there fast.”

The Columbia reacts more slowly to swings in weather. Typically, the water keeps warming to a peak in August. If that pattern holds true, coho and chinook that have yet to enter the river will have problems.

Warming rivers could become a more persistent problem in the decades ahead.

Scientists modeling the impacts of climate change forecast that maximum weekly water temperatures — on both sides of the Cascades — could climb from 2 degrees to more than 5 degrees by midcentury. Such changes could increase the challenges of the decades-long effort to restore salmon runs already hammered by other human activities.

Salmon returning in the spring or late summer are likely to fare better than others such as the sockeye that come back during the peak summer heat. Over time, perhaps the sockeye will evolve, with fish that return early in the summer having greater success at reproducing and passing on their genes.

Meanwhile, those fish that fail at spawning, like the sockeye circling around the mouth of Little White Salmon, will fade away without passing on their genes.

The first of this year’s sockeye arrived at the confluence several weeks ago, and some already are dead.

This past week, the creek was littered with dozens of carcasses scavenged by sea gulls and a great blue heron.