West Side Flooding Takes Heavy Toll On Salmon Losses Could Be As High As 90 Percent In Some River Systems

Last month’s flooding was hard on humans, but it was lethal to Western Washington’s wild salmon runs.

The only question is the extent of the damage, especially to chinook and sockeye salmon nurseries.

But based on the impact of past flooding, salmon losses could be as high as 90 percent in some Puget Sound river systems, state fisheries biologists said Tuesday.

“We won’t actually know until we can get a count next spring, but the flood levels that we were measuring were similar to levels in the past where we’ve seen very high destruction, either with eggs in the gravel or with juveniles,” said Bill Tweit, a state Department of Fish and Wildlife unit supervisor in charge of resource assessment.

He and other biologists said they fear major losses of chinook in the Skagit River and sockeye in the Cedar River.

“We’re actually real worried about similar losses in the Dungeness, Nooksack, Elwha and Snohomish” rivers, Tweit said.

Biologists also expect big losses in tributaries feeding the Columbia River to the south, but there is less concern there because that system is populated more by hatchery salmon than by wild salmon, and those populations can be replenished more easily.

“Further north, we rely so much more on natural production,” Tweit said.

The impact of any fish losses would be felt four years from now when salmon now in the river systems as eggs or fingerlings would be expected to return from the ocean as adults.

Tweit said biologists are less worried about the flood’s impact on coho salmon populations because their eggs and smolts are found more in tributaries, which may have suffered less damage than main-stem rivers did.

“But again, we won’t know until next spring when we can do some counting,” he said.

The flooding, which turned some rivers into lakes and some creeks into rivers, kills fish in several ways.

Rushing waters scour salmon eggs from their gravel nests, called redds, or cover the redds with silt, smothering the eggs. In some cases, rivers change channels, leaving the eggs high and dry.

The flooding also damages habitat, destroying stream-side vegetation and pools and riffles where juveniles find food and cover while they grow enough to head for the ocean.

“It would be accurate to say we will lose millions of fish from this storm,” Tweit said. “A more meaningful way to put it is we probably will see loss rates in some areas of well more than 90 percent.”

The flooding accompanied one of the state’s wettest Novembers on record - 10.40 inches of rain at Seattle-Tacoma International Airport.

A damage estimate from the American Red Cross showed 1,680 homes damaged in Snohomish, Skagit, King, Pierce, Whatcom, Thurston, Mason, Lewis, Kittitas, Cowlitz, Clark and Yakima counties.