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Restoring the Lower Snake River

Tuesday, December 29, 2015

biop.fishOverall smolt to adult return data shows that upper Columbia and Snake river salmon and steelhead populations are not meeting the 2 percent to 6 percent goal set by the Northwest Power and Conservation Council in its 2014 Fish and Wildlife Program.

However, mid-Columbia populations are meeting the SAR goals in most years, according to the 2015 Comparative Survival Study Annual Report, released November 30.

Council targets are set with an assumption of what the historical levels of productivity were prior to 1970 when the Snake River dams were set in place, according to the CSS report.

“Results indicate that pre-harvest SARs in the range of 4 percent – 6 percent are associated with historical (pre-1970) levels of productivity for Snake River spring/summer Chinook,” the report says. Snake River fish are decidedly not reaching this target.

On the other hand, the report says that “Mid-Columbia River wild spring Chinook populations, as represented by the John Day River and Yakima River aggregate groups, have experienced SARs generally within or close to the range of the NPCC 2 percent – 6 percent SAR objective.”

SARS for those chinook populations were 3.9 percent for the John Day River wild spring chinook and 2.4 percent for Yakima River fish (2000 – 2013). John Day, Deschutes and Yakima rivers wild steelhead SARs also fall within the Council range.

Wild Hanford Reach fall chinook SARs from McNary Dam to Bonneville Dam, available for the years 2000 to 2012, ranged from a high of 2.6 percent in 2000 to a low of 0.2 percent in 2004.

Overall, SAR rates to Lower Granite Dam (excluding jacks) for Snake River hatchery subyearling fall chinook were low in three of the seven years they have been analyzed, the report says.

It goes on to say that fall chinook overall SARs ranged from 0.12 percent to 0.56 percent for hatchery releases in 2006 and 0.0 percent to 0.3 percent in 2007.

The highest SARs were observed for migration year 2008, ranging between 0.35 percent and 1.07 percent.

SARs for 2009 were relatively low, ranging between 0.05 percent and 0.23 percent.

For the 2010 migration year, SARs were between the low returns from 2009 and the highest returns from 2008. SARs for 2010 ranged between 0.20
percent and 0.97 percent.

Returns for 2011 migration year are incomplete, the report says, but SARs are similar to 2010. With 3-salt returns now complete, they ranged between 0.08 percent and 0.94 percent.

For migration year 2012, return data only include 2-salt adults.

The first of the CSS studies was in 1996. Its objective was, and continues to be, to establish a “long-term data set of annual estimates of the survival probability of generations of salmon from their outmigration as smolts to their return to freshwater as adults to spawn (smolt-to-adult return rate; SAR).”

The question the study addresses each year is whether collecting juvenile salmon at lower Snake River dams and transporting them downstream of Bonneville Dam where they are released, compensates for the effects of the Federal Columbia River Power System on “the survival of Snake Basin spring/summer Chinook salmon that migrate through the hydrosystem,” the report says.

The Comparative Survival Study of PIT-tagged Spring/Summer/Fall Chinook, Summer Steelhead, and Sockeye, 2015 CSS Annual Report (BPA Contract #19960200) can be found on the Fish Passage Center website at, or at the
Bonneville Power Administration website at

It was prepared by the Comparative Survival Study Oversight Committee and the Fish Passage Center ( The committee includes Jerry McCann, Brandon Chockley, and Erin Cooper, all of the Fish Passage Center; Howard Schaller and Steve Haeseker, U.S. Fish and Wildlife Service; Robert Lessard, Columbia River Inter-Tribal Fish Commission; Charlie Petrosky, Idaho Department of Fish and Game; Eric Tinus and Erick Van Dyke, Oregon Department of Fish and Wildlife; and Robin Ehlke, Washington Department of Fish and Wildlife.

The CSS is a long-term study within the Northwest Power and Conservation Council’s Columbia Basin Fish and Wildlife Program and is funded by the
Bonneville Power Administration. The Fish Passage Center coordinates the PIT-tagging efforts, data management and preparation, and CSSOC work. All draft and final written work products are subject to regional technical and public review.

The overall objective of the annual report is to provide a historical reference for each year to provide a basis for future fish passage mitigation discussions, and a base reference for future analysis of adult returns, the report says. It is the beginning of a longer-term effort, which will need to incorporate effects of density dependence on observed productivity to evaluate population responses relative to SAR rates.

The study is based upon 20 years of SARs data for wild Snake River spring/summer chinook from 1994 to 2013, 17 years of SARs data for Snake River hatchery spring/summer chinook (1997 to 2013), 16 years of SARs data for Snake River wild and hatchery steelhead (1997 to 2012), and 5 years of SARs data for Snake River sockeye (2009 to 2013), listed as endangered under the federal Endangered Species Act.

The annual report’s main focus is the smolt monitoring program, which is designed to provide a long-term consistent and continuous juvenile salmon and steelhead passage characteristics data time series, the report says.

The 2015 CSS Annual Report includes:

-- Complete return data for smolt outmigration year 2012 for wild and hatchery chinook salmon and steelhead (all Snake River returns are to Lower
Granite Dam).

-- Wild and hatchery spring/summer chinook: 3-salt returns from smolt migration year 2012, and 2-salt returns from smolt migration year 2013.

-- Fall chinook, 3-salt returns from smolt migration year 2011, and 2-salt returns from smolt migration year 2012.

-- Wild and hatchery steelhead, 2-salt returns, and Sawtooth Hatchery Snake River sockeye 2-salt returns, both from the 2012 smolt migration.

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