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9/22/2006  
An adult female salmon deposits eggs in nesting pockets of shallow water in the Santiam River of Western Oregon. - Mark Rozin/Capital Press
Heat threatens hardy salmon
More energy spent waiting for lower temperatures means less energy to spawn

By PHIL WRIGHT
East Oregonian Publishing Group

It may be hard to believe that chinook salmon or steelhead could be bothered or hurt by a few degrees warmer water.

After all, chinook are survivors, making their way down rivers and through dams until they reach ocean, where they grow big enough to avoid predators and mature. Then they make the arduous journey upriver to spawn.

Steelhead are just as tough. Idaho steelhead have been found south of the Kamchatka Peninsula in Russia. That's about 4,000 miles from fresh water. Add another 900 to 1,000 miles of rivers and streams to that, and the upper migration limit stretches to about 5,000 miles.

But something as seemingly innocuous as a few degrees of temperature change in the Columbia River and its tributaries has significant effects on anadromous fish such as salmon and steelhead.

Temperature readings taken by the U.S. Army Corps of Engineers at the Bonneville Dam starting in 1938 reveal a gradual warming of the Columbia River. When the Corps began recording the water temperature there, the average water temperature was about 65 degrees Fahrenheit. But in 2005, the average water temperature was about 69 degrees.

Four degrees over a course of more than 60 years may not see like much. But according to the federal Environmental Protection Agency, 68 degrees is the upper limit for salmon migration.

Scientists are noticing changes in salmon migration because of that warmer water.

Kyle Dittmer is a meteorologist and hydrologist for the Columbia River Inter-Tribal Fish Commission (CRITFC). He's also the president of the Oregon Chapter of U.S. Meteorological Society. Climate change is here and more is on the way, he said.

"It's like a freight train coming, and no one can stop it," he said.

That freight train already seems to be hitting fish in the Columbia River. Dittmer said changes in water temperatures trigger spikes in fish migration and traffic jams of fish as they try to pass through the dams. Those spikes haven't been seen before.

Don Chapman has been a fisheries biologist for more than 50 years. He acknowledges he's no climatologist, but he knows fish and his analysis concurs.

Chapman said salmon and steelhead are displaying the influence of climate change in their migration patterns.

Fall chinook are delaying in the mouths of cool Columbia River tributaries like the Klickitat, the Deschutes and the Big White Salmon. And they are taking longer to reach spawning grounds.

The fish wait in those pockets in late August or September for water temperatures in the main stem of the Columbia River to drop enough so they can continue along.

While they wait, salmon are not simply resting and summoning energy. Just the opposite is happening.

"Once they start migrating from the estuary, they don't feed," Dittmer said. "So any delay means less energy they will have to spawn."

As temperatures continue to rise, those migration patterns will shift still further, Chapman said, and the summer migrations will be hurt the worst. This includes summer steelhead, juvenile fall chinook moving downstream and adult chinook and sockeye moving upstream. Those summer migrants are either going to change habits and move earlier or later, or they will disappear, Chapman said.

"That's the prognosis," he said.

Not just the dams

Chapman also said examining a regression on Columbia River water temperatures reveals a significant upward trend that is not caused by dams. He said the Fraser River, which isn't dammed, has risen 1.5 degrees Celsius. The Fraser River is the largest river in British Columbia, beginning near Mount Edith Cavell in the Rocky Mountains near Mount Robson and entering the Pacific Ocean at Vancouver, B.C. - some 870 miles away.

Chapman said dams are not the culprits causing increasing temperatures, but rising air temperatures in the Columbia Basin and in other basins are responsible.

Warmer water delaying migration isn't the only problem salmon face as the climate changes.

Dittmer said redds - salmon eggs - develop during the course of winter, but the baby fish are incubating faster and are emerging earlier, in late February or March, because they are accumulating heat from water. That early emergence could mean food sources may not be present.

"That could affect the whole balance," Dittmer said.

Chapman explained that predator fish - pike, shad, carp, small and large mouth bass - that feed on smolts are non-native, warmer water fish, while native salmon are a cooler water fish. The predator fish could easily increase with warmer water, pressuring the salmon still further. These predator fish also have a higher metabolism, and as water temperatures increase, so do their appetites. And smolts are a favorite food.

The warmer water adds stress to the smolts, Chapman said, and that makes them easier prey and increases their risk of disease.

Out at sea may not be much better. Increasing temperatures suggest a reduction in plankton and phytoplankton, the food young salmon eat at the mouth of the Columbia River.

"The moral for fish is grow or die," Chapman said. "When you get a year of poor offshore conditions, particularly in the first six weeks as fish hit the sea, you get poor survival."

Looking to the long term

Dittmer said the Inter-Tribal Fish Commission has been conducting a long-term climate change study concerning average flows through river basins in Oregon and Washington. The study revealed that in every basin, flows are peaking sooner and are reduced compared to years past. Spring and summer flows go down just at the time salmon migrate.

"Every basin I've looked at is impacted," Dittmer said. The Umatilla and Walla Walla basins have been hit the hardest.

In the Umatilla Basin, the flow on average is peaking 16 days earlier compared with 100 years ago. The Walla Walla Basin, though, has the largest shift, with 161/2 days.

The average median - the half-way point in peak flow - has shifted and is now coming sooner.

Dittmer said all the research along the West Coast indicates more runoff is being shifted to autumn and winter from spring and summer. And again, the Umatilla and Walla Walla basins are taking the biggest hit, having dropped by 25 percent.

Dittmer said spring-summer flows only drop by 10 percent when you adjust for 70 years of impact from the dams.

So again, the dams can't be blamed.

Chapman said the net result of what climate change means for salmon is still unclear, but he anticipates the whole southern boundary of salmon and steelhead will move northward.

And that means the Columbia River, once the world's richest salmon fishery, won't be as hospitable to salmon as it once was.

Another view

But not everyone has a view quite so pessimistic.

Gary James, fisheries manager for the Confederated Tribes of the Umatilla Indian Reservation, said climate change now isn't having a major impact on salmon recovery and salmon runs.

"Environmental conditions have always fluctuated," he said.

James said habitat degradation is what needs to be dealt with because of its effect on salmon.

"There's degradation in tributaries, but mainly, the worst impacts are on the main stem, where our river is turning into a series of reservoirs and there're still pretty poor passage of anadromous fish out there."

James seems to agree, however, that climate does play a role in the life of already stressed fish.

"Without man's mortality there used to be a lot of flexibility. The salmon runs could take a lot of environmental flux. Now all those other man-caused killers have pushed salmon sometimes to the edge of the cliff, and sometimes you'll see a bad climate or ocean year really take a hit on salmon."

But again, he said, climate change isn't the only cause, but because the fish are stressed "they don't have the breathing room or the flexibility to absorb the environmental fluctuations."

Dittmer also said salmon are a resilient fish, and people have it in their power to continue and to accelerate endeavors that will help to enhance the natural defense system, by restoring stream beds, planting trees along river banks, and creating curves within the river, among other projects.

But Dittmer said Americans need to think large-scale and long-term when it comes to restoration and conservation efforts.

"We need to have a Manhattan-style project as soon as possible," he said.

 
 
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