smolt-to-adult return information for
both transported and in-river chinook salmon and wild steelhead transiting the federal
hydropower system in the Columbia and Snake rivers was consistent in 2018 with past year’s findings, according to the
Fish Passage Center’s 23rd annual comparative survival study.
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
of the juvenile passage routes – in-river or by barge – resulted during the
year in meeting the Northwest Power and Conservation Council’s SAR objectives
set in its 2014 Fish and Wildlife Program for Snake River wild spring/summer
chinook and steelhead, which is a range of 2 percent to 6 percent, the study
PIT-tag SARs for middle Columbia River wild spring chinook and wild steelhead
generally did fall within the Council’s 2 to 6 percent range. Yet, the overall
SARs for upper Columbia River and Snake River populations of salmon and
steelhead are not meeting this regional goal, while middle Columbia River
populations are meeting the SARs goals in most years.
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.
The Council is currently in a year-long process to update its Fish and Wildlife
back a year, the results of the 2017 analysis showed that for all three
salmonid species – Snake River summer chinook, sockeye and steelhead – the
upstream survival for adult fish that were transported as juveniles were lower
than fish that had migrated in-river as juveniles.
in the 2017 analysis, upstream survival of fish transported as juveniles
started to decrease at lower temperatures compared to fish that had migrated
in-river, the report says.
2018 analysis is an expansion and refinement of earlier analyses of upstream
migration success,” the study says. “Observations from the 2018 study were
consistent with historic analyses: all species in this analysis showed a
decreasing upstream conversion probability in warm water temperatures greater
than 18 (degrees Celsius), and fish that were transported as juveniles had a
lower conversion probability overall and a higher portion of strays compared to
fish that migrated in-river.”
FPC published its final “Comparative Survival Study of PIT-tagged
Spring/Summer/Fall Chinook, Summer Steelhead, and Sockeye 2018 Annual Report”
in December. It can be found at http://www.fpc.org/documents/CSS/2018_Final_CSS.pdf.
All CSS Annual Reports are at http://www.fpc.org/documents/CSS.html.
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.
2018 study was prepared by the Comparative Survival Study Oversight Committee
and the Fish Passage Center (www.fpc.org). The committee includes Jerry
McCann, Brandon Chockley, Erin Cooper and Bobby Hsu, all of the Fish Passage
Center; Steve Haeseker, U.S. Fish and Wildlife Service; Robert Lessard,
Columbia River Inter-Tribal Fish Commission; Charlie Petrosky and Tim Copeland,
Idaho Department of Fish and Game; Eric Tinus and Adam Storch, Oregon
Department of Fish and Wildlife; and Dan Rawding, Washington Department of Fish
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.
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.
study says it includes 23 years of SAR data for wild Snake River spring/summer
chinook (1994–2016), 20 years of SAR data for Snake River hatchery
spring/summer chinook (1997–2016), 19 years of SAR data for Snake River wild
and hatchery steelhead (1997–2015), and eight years of SAR data for Snake River
are eight years of SAR data for Snake River hatchery fall chinook (2006–2012
and 2015). For mid-Columbia and upper-Columbia fall chinook there are varying
numbers of years available. There are 15 years of SAR data for Hanford Reach
wild fall chinook (2000–2015), five years of SAR data for wild Deschutes River
fall chinook (2011–2015), and eight years of SAR data for both Spring Creek
National Fish Hatchery and Little White Salmon NFH fall chinook (2008–2015).
and summer chinook and sockeye returns from outmigration year 2016 should be
considered preliminary, as they include only 2-salt returns and may change with
the addition of 3-salt returns next year, the study says. Similarly, 2015
migration year fall chinook returns include only 2-salt adults.
over 800 page detailed report contains:
2: Life Cycle Evaluation of Upper Columbia Spring Chinook
3: Effects of the in-river environment on juvenile travel time, instantaneous
mortality rates and survival
4: Patterns in Annual Overall SARs
5: SARs AND productivity
6: Estimation of SARs, TIRs and D for Snake River Subyearling Fall Chinook
7: CSS chapter for adult salmon and steelhead upstream migration
8: Comparative analysis of smolt-to-adult return rates for Carson National Fish
Hatchery spring Chinook salmon using passive integrated transponder and coded
9: Preliminary Development of an Approach to Estimate Daily Detection
Probability and Total Passage of Spring Migrant Yearling Chinook Salmon at