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Research:  Adult Salmon Survival 98 Percent Dam to Dam
June 16, 2006 

New "PIT tag" data analysis developed by NOAA Fisheries should better allow the agency to calculate survival rates of adult salmon and steelhead as they attempt their spawning journey up through the Columbia and Snake rivers' system of dams and reservoirs.


The preliminary spreadsheet analysis has shown that survival from one hydroelectric dam to the next is averaging 98 percent and better in recent years, a NOAA Fisheries scientist told the Northwest Power and Conservation Council Tuesday during its meeting in Boise.


"That's real high survival; most people would agree those are good numbers to have," said Ritchie Graves, acting branch chief of NOAA Fisheries' regional Hydropower Division in Portland. NOAA Fisheries is the federal agency that implements the Endangered Species Act for salmon and steelhead in the Northwest.


The estimates are "minimum estimates of direct survival from point to point" that are adjusted to take into account harvests and fish that stray from their anticipated course, Graves said. His analysis plots detections of passive integrated transponder tags that are inserted in many fish before they migrate to the ocean as juveniles. A network of PIT-tag detectors installed at key mainstem dams since 2000 allow researchers to monitor the fish heading both downstream and upstream.


The new technique for estimating adult "conversion rates" -- survival through mainstem reaches -- is being developed by NOAA for possible use in a new Federal Columbia River Power System biological opinion that is due for completion in February. The BiOp judges whether the federal hydrosystem and its operations jeopardize the survival of salmon and steelhead that are listed under the Endangered Species Act.


The "quickie" analysis was presented to the FCRPS BiOp remand Policy Work Group last month, Graves said. The court-ordered remand of a 2004 FCRPS BiOp is being carried out in collaboration with Northwest states and tribes.


The analysis will be fine-tuned in the coming months. The harvest adjustments, as an example, must be further researched to assure that they are all-inclusive.


"We're going to keep moving ahead," Graves of the attempt to better assess the dams' share of salmon mortality.


Graves presented results for adult chinook and steelhead survival between Bonneville and McNary dams, between McNary and Lower Granite Dam and between Bonneville and Lower Granite. Bonneville is the first dam the fish pass on the lower Columbia and Snake River's Lower Granite is the eighth and final dam fish climb. The analysis also charts Upper Columbia adult fishes' progress from Bonneville to McNary, McNary to Wells Dam and from Bonneville to Wells.


The analysis looks at returns from 2002 through 2006.


Wild and hatchery-reared spring chinook released as juveniles above Lower Granite Dam experienced about 99 percent survival between Bonneville and McNary dams when they returned as adults, and 99-100 percent survival between McNary and Lower Granite dams, Graves said. The survival of Snake River summer and fall chinook between McNary and Lower Granite dams, and for upper Columbia steelhead between McNary and Wells dams, averaged 97-98 percent.


"There's kind of a consistent pattern here," Graves said of the high survival estimates.


By detecting the passing fish with electronic signals, information is obtained instantly and without having to trap and handle the adult salmon. In the past, the survival information was obtained with dedicated studies in which shorter-lived radio tags were inserted in adult fish.


The PIT tag technology allows researchers "to get conversion rates a lot quicker, and a lot cheaper" than the labor intensive radio tag technology, according to Jim Ruff, the NPCC's mainstem passage and river operations chief.


Council Chair Tom Karier said the results are encouraging.


"At least the adult salmon do not appear to have difficulty with the dams," Karier said. "This is good news if we are only losing 1 or 2 percent of the fish migrating upstream."


Council Member Judi Danielson of Idaho said the results bode well for salmon and steelhead returning to that state:


"We hear so much about the impact of the dams, but here is data that shows we have done so much to improve passage survival through the hydrosystem; now it is time to sharpen our focus on improving fish survival in other areas, particularly harvest, which has been 9 percent or more on these fish between dams."


Because the tags identify fish by the location where they were released, tagged fish can be tracked through most of their river migration. Some fish can pass undetected at one dam or another, but the accuracy of calculating conversion rates is improving as the detection equipment becomes more sophisticated.




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