All-at-once rainfall likely took big toll on salmon runs

By Ashley Bach
Seattle Times Eastside bureau

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Last week's flooding and record rainfall in Western Washington probably made a significant dent in this year's salmon runs, biologists and fish experts say.

The exact impact won't be known until spring, when the state counts the hatched fish, or even years later, when the fish return to spawn. But flooding usually churns up the nests that salmon leave on the river bottom, destroying fragile eggs or leaving them open to predators.

"We're pretty sure that it was not a good thing," said Curt Kramer, a state fish-program manager. "How bad it will be remains to be seen."

The damage is particularly unfortunate, experts say, because the number of pink and chinook salmon arriving this year has been exemplary. Around a million pink salmon already have come up the Skagit River, one of the region's busiest rivers for the species.

The Skagit also experienced some of the area's worst flooding. Many of the hundreds of millions of eggs in the river probably didn't survive the muddy, rapidly moving water. The Nooksack, Stillaguamish and Snohomish rivers probably also were affected, Kramer said. Officials at the Issaquah Salmon Hatchery say the chinook eggs in Issaquah Creek were destroyed by high water.

In previous floods, such as in 1995, the survival rate for salmon eggs was cut by 80 to 90 percent, state officials say. They won't make any estimates this year until the hatchlings can be counted in the spring.

The impact is expected to be significant because the flood occurred so early in the year, Kramer said. In just a few weeks, many of the eggs would have been strong enough to withstand light debris and faster water, but until then they remain delicate. A drastic reduction in eggs would result in smaller runs in a few years, when the fish mature. This fall's pink salmon will return in two years, while most of the chinook will come back in four.

But salmon are resilient, and there's no guarantee the small number of eggs would hurt the fish as much as one would expect, Kramer said. A smaller number of hatchlings, for instance, means less competition, so a higher percentage of the remaining fish could make it to the ocean.

A few years later, the offspring of those fish could find it easier to survive, and after several years the numbers could return to normal.

One obstacle is man-made changes to waterways, such as dikes and channel alterations, Kramer said. The recuperative powers of fish don't react well to unnatural modifications.

"If they rebound from a big flood like we've had, they don't do it as quickly as in the past," Kramer said.

In Issaquah, where the hatchery is one of the centerpieces of the community, the fate of the salmon eggs hit hard. Hatchery officials said they were happy they captured thousands of fish and 2.4 million eggs themselves.

Kevin Boze, a master docent, could look down at Issaquah Creek on tours and see the salmon nests, or redds, were gone. "It just came too fast, too furious and washed them away," he said.

Rivers and streams around the region began to dry up this summer because of a lack of rain, but last week's weather was an answer few people expected.

"We needed cold temperatures and rainfall," Boze said. "What we did not need was for the rain to occur all at once."

Ashley Bach: 206-464-2567 or abach@seattletimes.com

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