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Restoring the Lower Snake River

But biologist says out-of-basin factors remain obstacles

neo 003641-01May 27, 2016

by Greg Moore

The Middle Fork of the Salmon River could become one of the most productive wild Chinook salmon-rearing area in the Columbia River basin, but will not do so until out-of-basin factors, including 325 miles of slack water behind eight dams on the Columbia and Snake rivers, are addressed, a fish research scientist said Tuesday in Ketchum.

Russ Thurow, who works at the U.S. Forest Service’s Rocky Mountain Research Station in Boise, spoke to an audience of almost 100 people at the Community Library at an event co-hosted by Idaho Rivers United and Lost River Outfitters.

Thurow said that before white settlers began to impact the fish in the late 19th century, the Columbia Basin is considered to have been the most productive Chinook salmon habitat in the world, with an estimated 10 million to 16 million fish in the basin, and 2 million to 6 million fish in the Snake River and its tributaries. By 1995, only 1,200 wild Chinook reached the Snake River basin.

“The population collapsed,” Thurow said.

He said federal agencies attributed the decimation of the wild fish population to four H’s—harvest, habitat degradation, hatchery fish and hydropower development.

Thurow’s talk indicated that by far the most significant factor now is the last of those four. He said dams have entirely blocked fish passage to more than 70 percent of the original habitat in the Columbia Basin, and dams built on the Columbia and lower Snake in the 1960s and 1970s have had devastating consequences for both juvenile salmon headed to the Pacific Ocean and adult fish headed back upstream to spawn.

Under natural conditions, Thurow said, water velocity in the two rivers was 6-10 mph, and juvenile fish reached the Columbia estuary in one to two weeks. Now, the rivers flow at less than 1.5 mph, and it takes fish up to six weeks longer to reach salt water.

“The slower the migration, the fewer that survive,” he said.

Thurow said that research by other scientists reported that in the 1960s, the survival rate of smolts to returning adults was 3.5 to 6.5 percent, but by the time the last reservoir on the lower Snake River was filled in 1975, that dropped to less than 1 percent.

Once reaching the ocean, the fish do a long counter-clockwise trip up the coast of Canada and out to the Aleutian Islands, spending up to several years before returning eastward to the mouth of the Columbia to begin their spawning migration. Thurow said that due to a range of times spent by fish in both fresh and salt water, up to 18 age classes of spring and summer Chinook can spawn in the Middle Fork on any one year. He said that diversity of ages contributes to the population’s resiliency.

Thurow said the bad news for salmon in the Middle Fork is that redds, where eggs are deposited in riverbed gravel, have been reduced from possibly 17,000 to 20,000 in the 1950s to an average of 807 between 1995 and 2015. The good news, he said, is that the quality of the habitat remains very high, and if factors outside the drainage can be resolved, the potential still exists for the population to regain its original level. In fact, he said, biologists in the 1940s estimated that there’s suitable gravel in the Middle Fork and its tributaries to support 92,000 redds.

Thurow said the many wildfires that have swept through the Middle Fork drainage, burning 52 percent of the area since 1993, have provided benefits for salmon habitat. He said the resulting debris flows have created gravel fans at the mouths of tributaries, without which the small gravels needed by the fish would eventually get washed downstream.

He said the Chinook population’s potential resiliency is boosted by the fact that each female produces an average of more than 5,000 eggs.

Fish spawning in the Middle Fork of the Salmon drainage reach the highest elevation of any spring and summer Chinook in the world, Thurow said, and that makes the area especially important to fish survival as the climate gets warmer. He said climate researchers have reported that high-elevation habitats like the Middle Fork are probably going to provide “cold-water refugia.”

“So Middle Fork stocks need to be a top priority for recovery in the overall Columbia River basin,” he said.

Thurow said the Middle Fork contains only wild Chinook, and just 4 percent of the historic spring/summer Chinook range in the Columbia Basin now does so. He said the introduction of hatchery fish may have reduced the wild population by competing with it for resources in the Columbia estuary.

Thurow said the Northwest Power Act of 1980 required electricity production and salmon to receive equal priority. However, he said, Chinook salmon were placed on the endangered species list in the early 1990s, and recovery plans that focused on habitat improvements and hatcheries have not brought about restoration of the species.

Thurow said the federal agencies that operate the Columbia and Snake River dams have said a 4 percent mean rate of return of smolts to adult fish is needed for the species to recover, with a range of 2 to 6 percent rate as the goal. However, he said that between 2000 and 2013, the rate has risen to 2 percent only twice.

On May 4, a federal court invalidated the fifth in a series of Columbia Basin salmon recovery plans dating to 2003. The U.S. District Court for the District of Oregon ruled that the 2014 Columbia Basin salmon biological opinion, drawn up by NOAA Fisheries, violated the Endangered Species Act and the National Environmental Policy Act.

Judge Michael Simon ordered that a new biological opinion and full NEPA analysis of “all reasonable alternatives” be completed by March 1, 2018. Though Simon stated that he was not ordering consideration of any specific alternatives, the analysis “may well require” consideration of removing one or more of the four lower Snake River dams.

“This is where, if you’re interested in saving salmon, get involved,” Idaho Rivers United board member Andy Munter told the audience Tuesday. “It’s time to get involved however you can in the public comment process.”

Several people noted that unlike the four dams on the Columbia River, the lower Snake dams produce little power, and were built to enable barge traffic.

“The science has been settled for years,” Munter said. “Now it’s the economics.”

Local salmon advocate Scott Levy also urged people to get involved in a new recovery plan’s environmental impact statement.

“This is going to win,” he said. “If you get involved, you can be part of making a huge change in Idaho.”

To view article with graphs and photos go here.

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