Results of survival tests for young salmon and
steelhead that migrate to the ocean through six Federal Columbia River Power
System dams all generally exceeded the survival requirements of NOAA Fisheries’
2008 FCRPS biological opinion for Columbia River salmon and steelhead,
according to a recent study.
The study found survival estimates ranging
from 95.97 to 98.68 percent for yearling chinook, 95.34 to 99.52 percent for
juvenile steelhead and 90.76 to 97.89 percent for summer migrating subyearling
Dam passage survival, which is survival from
the upstream dam face to the tailrace mixing zone, must be greater than 96
percent for spring juvenile yearling chinook and steelhead and greater than 93
percent for the summer subyearling chinook, the study says.
Averages across the six dams exceeded the
survival standards for all three migrant populations, the study concludes.
The study is a summary of 29 separate survival
studies conducted between 2010 and 2014 to evaluate the survival requirements
at the six dams, as mandated by the BiOp, according to study co-author Mark
Weiland, a senior research scientist with Pacific Northwest National Laboratory
at North Bonneville, Wash., but now a senior managing scientist at Anchor QEA.
“Of the 29 studies conducted, 23 met the
survival standard and 26 met the precision requirements set in the BiOp,”
Weiland said. “There are not clear
reasons, or individual factors, as to why the survival standards set in the
BiOp were not met or precision requirements of 3 studies were not met.”
Some 22 of the tests met both the survival and
precision requirements (precision of the test: less than 0.015) of the BiOp,
the study adds.
Of the survival tests, Bonneville Dam (95.97
percent) was barely lower than the required 96 percent for yearling chinook.
The Dalles Dam (95.34 percent) was barely lower for steelhead. Little Goose
(90.76 percent), Lower Monumental (92.97 percent), McNary (92.39 percent) and
John Day (91.69 percent) dams were all lower than the required 93 percent
survival for the summer-migrating subyearling chinook smolts, but still were
close to the requirement.
Overall, the survival studies employed 109,000
acoustic-tagged salmon and steelhead smolts at the six dams, which were Little
Goose and Lower Monumental dams on the lower Snake River, and McNary, John Day,
The Dalles and Bonneville dams on the lower Columbia River. At $200 for each
tag, the total cost just for tagging was $21 million.
Acoustic telemetry was the technology of
choice for evaluating survival because it was the only technology that could
realistically be used to meet the precision requirements, Weiland said.
The fish used were collected at the juvenile
collection facilities at each dam and consisted of both hatchery and wild fish
from multiple hatcheries and wild populations representing the fish runs at
specific dams, the study says.
Studies must be conducted in two years at each
dam for each of the three stocks – yearling chinook and juvenile steelhead in
spring and subyearling chinook in summer – and, if a stock doesn’t meet the
BiOp criteria, mitigation measures, such as structural or hydraulic changes,
need to be made to improve passage survival and then be retested, Weiland
The average passage survival of yearling
chinook and juvenile steelhead through 500 km (311 miles) of the FCRPS – Lower
Granite Dam to Bonneville Dam from 1997 to 2014 has been estimated at about
50.1 percent and 45.7 percent, respectively, the study says.
“Some investigations have speculated that
these values may be as high as historical survival before the introduction of
hydroelectric dams,” it says.
One study found smolt survival in the undammed
Fraser River in British Columbia “to be comparable to existing survival rates
in the Columbia River. Other investigations have suggested in-river survival of
juvenile migrants could be even higher with alternative dam operations.”
“Many structural and hydraulic changes have
been made at the dams on the Columbia and Snake rivers over the past few
decades to improve passage survival resulting from hundreds of studies using
many different technologies,” Weiland said.
“Results of these studies have and will be used to inform management
decisions and operational or structural changes at dams but these studies would
not have met, or come close to meeting, the BiOp survival standards and
precision requirements without the hundreds of previous studies conducted and
the structural and hydraulic changes made at the dams due to those studies.”
“Additional survival compliance studies on the
Snake and Columbia rivers are scheduled over the next several years,” the study
says. “Two dams have yet to be tested, and three dams have not yet completed
their minimum complement of tests.”
after 5 Years of Survival Compliance Testing in the Federal Columbia River
Power System (FCRPS),” was published online June 27, 2016, in the North
American Journal of Fisheries Management (http://www.tandfonline.com/doi/abs/10.1080/02755947.2016.1165775#.V4FWTLgrLIU).
In addition to Weiland, co-authors are John
Skalski, professor at University of Washington; Kenneth Ham, senior research
scientist, Alison Colotelo, research scientist, Tom Carlson, retired managing
scientist, and Gene Ploskey, retired senior research scientist, all at PNNL;
Geoff McMichael, a senior research scientist at PNNL at the time of the study,
now owner of Mainstem Fish Research LLC; Christa Woodley, research ecologist,
ERDC; Brad Eppard, chief, Fish Passage Section Environmental Resources Branch,
U.S. Army Corps of Engineers, Portland District; and Eric Hockersmith, fishery
biologist, USACE, Walla Walla District.