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Study Analyzes Survival Tests For Young Salmon/Steelhead Moving Downriver Through Columbia/Snake Dam
Posted on Friday, July 15, 2016 (PST)

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 chinook.


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 continued.


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.”


 “Status 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 (


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.

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