Study aims to shed more light on delayed mortality thesis
January 19, 2007

An Idaho water users group this week cited results from a 2006 study as proof that migrating juvenile salmon do not suffer ill effects from passing down through four lower Snake River federal hydroprojects, and nor does barging the young fish through the hydrosystem hinder their chances of surviving to adulthood.

The study results turn back arguments that the Snake River dams should be breached to ease fish passage, and that barging is an ineffective tool for improving fish survival, according to a Wednesday press release from the Coalition for Idaho Water.

The scientist that led the research this week said the Idaho group is generally correct in its assessments of the findings, but that it's too early to make final pronouncements regarding two of the more scientifically and politically controversial issues faced in Columbia River salmon recovery efforts.

"The Idaho group's statements are fair comment on our recently released study," according to David Welch of Vancouver Island-based Kintama Research. "They are less cautious in extrapolating from the first year's findings than I can be, because my role is that of a scientist trying to answer some key questions.

"The answers are too important for the Columbia Basin for anyone to jump prematurely to a conclusion based on a single year's data," Welch said this week. "However, our 2006 results are strongly different from what had been hypothesized by some to be happening below the dams. Unless contradicted by subsequent year's results, they do not fit with the delayed mortality hypothesis."

The Idaho group says that of the study's findings clearly shows that "the four Snake River dams cause no additional mortality for juvenile salmon originating in Idaho's Clearwater drainage," according to the press release.

"This is extremely significant to Idaho because fish from the Yakima drainage migrate through only the four lower Columbia Dams while the Idaho Clearwater fish migrate through the four lower Snake River dams as well as the lower Columbia River dams," said Norm Semanko, president of the coalition.

"This crucial new data puts a bullet in the heart of arguments that tearing out the dams will somehow become a silver bullet remedy in salmon recovery efforts," said Norm Semanko, president of the Coalition for Idaho Water. The coalition is made up of more than 50 different organizations representing Idaho counties, cities, chambers of commerce, industrial, municipal and commercial water users, and agricultural groups. It has steadily opposed consideration of dam breaching and protested demands for more flows from Idaho reservoirs intended to buoy migrating salmon.

Fishing and conservation groups, tribes and others have over the years continued to press for the breaching of the four Snake River dams to restore more natural, riverine conditions and historic spawning habitat. Snake River steelhead and spring/summer and fall chinook salmon stocks are listed under the Endangered Species Act.

Much research has been focused on determining if the rigors of dam passage, and barge transportation, make the young fish less fit as they enter the ocean and subject to some degree of "delayed mortality."

With mixed results, delayed mortality remains one of the uncertainties in recovery planning.

Welch says new technology utilized in his research could contribute to solving the riddle.

"We have what we believe to be the first data directly measuring the role of the ocean in determining the abundance of Snake River salmon, and we do believe that it is addressing critical issues," he said. "It is clear that our initial findings are opening up a whole new study area --the ocean-- that people could previously only speculate about.

"We have just wrapped up the 2006 results, and we are pleased with our first year's results. However, we were careful not to say what is attributed to us here, simply because it is only the first year's results, and the work has to both pass peer review and be repeated in additional years," Welch said.

The report, "Pacific Ocean Shelf Tracking Project (POST): Results from the Acoustic Tracking Study on Survival of Columbia River Salmon, 2006," was completed Jan. 11.

The research, funded by the Bonneville Power Administration, is two pronged. It is attempting to determine if additional "latent" or "delayed" mortality is experienced after Snake River smolts pass the eight dams they encounter as in-river migrants and thus suffering lesser productivity than fish that pass fewer dams or no dams at all.

And it attempts to answer the question of whether transporting/barging of chinook smolts improves early marine survival rates over run-of-river smolts, thus providing a boost to adult return rates and reducing extinction risk.

"To test the first hypothesis we compared survival of Snake River spring chinook (from Dworshak National Fish Hatchery), which migrate through eight dams, with that of Yakima River chinook (from the Cle Elum Supplementation and Research Facility)," the report says. "The Yakima population enters the Columbia River just upstream of the confluence of the Columbia and Snake Rivers, and only migrates through the four mainstem Columbia River dams.

"This stock was chosen for comparison because historically it has had about a 5.2 times greater smolt to adult return rate" than the Snake River stock, the study says. The reason, some theorize, is delayed mortality from dam passage.

In spring of 2006, a total of 20 long-lived "Vemco" VR3 acoustic receivers were deployed in the main stem Columbia River and lower Snake River to track the movement and survival of the two release groups of specially tagged fish. The newly developed tags are also used to track fish out the river mouth and north along the coast on the continental shelf. The ultrasonic tags allow the identification of individual fish throughout the water column.

The detection data showed that both in-river release groups migrated downstream at a similar rate of speed and survived at comparable rates to below Bonneville Dam. Likewise, survival -- about 20 percent -- was similar at detections at Willapa Bay on the Washington coast, about 260 kilometers from Bonneville Dam and 908 kilometers from the release of the Snake River fish in the Clearwater River. The Yakima fish have 300 kilometers less to travel.

"If subsequent adult return rates in 2008-09 again show that the Yakima River adults return at a SAR similar to historical levels, this would constitute strong evidence that the differential mortality is not expressed before the smolts reach NW Vancouver Island," the report concludes. "This would reduce the likelihood that the different levels of expressed mortality are attributable to cumulative stress from passage through the hydropower system, and increase the evidence for a differential effect of the ocean environment on different stocks of the same species -- an important result."

The Pacific Ocean Shelf Tracking array is a large scale marine acoustic tracking network that now extends from northern Oregon, throughout coastal British Columbia, and up to southeast Alaska.

The test of the second hypothesis focused on the Snake River stock alone. The researchers contrasted the lower river and early marine survival of two groups of transported smolts with the survival of the same two groups of run of river (ROR) Snake River spring chinook smolts used in the comparison with the Yakima stock.

"In comparing the survival of barged and run-of-river (ROR) Snake River chinook smolts, we find that survival to Willapa Bay was precisely double that of the ROR smolts," the report concludes. "This finding is consistent with expectation, as mortality of PIT tagged smolts to Bonneville Dam has historically been approximately 50 percent."

"Our data indicate that the survival of barged smolts to Lippy Point, NW Vancouver Island, remains greater than that of the ROR smolts," the report says. "However, our results also indicate that early marine survival rates are lower than the survival rates experienced in-river which results in substantially lower daily survival rates in the ocean."

"Thus, while the goal of the transportation program is initially met by increasing the number of smolts that reach the ocean, transport could actually be counter-productive if the additional time spent in the ocean means that more mortality is experienced than if the smolts had migrated unaided in freshwater," the report says.

"It is too soon to be able to make a clear case for or against that latter point, but our results do raise that question for, I believe, the first time," Welch said this week. "It adds an additional wrinkle to the debate over the role of transport that I think was overlooked earlier."

"A key point to make here is that survival to the north end of VI was very small, so the sample size is not large, and needs to be treated with caution," Welch said. Detections there numbered only 4 for the in-river fish and 11 for the barged fish.

"I would just make the point that we are not seeing any evidence from the 2006 results that barging itself is hurting the fish, and that barging appears to be getting the fish out to the ocean as originally planned.

"Whether this final point is true cannot be clearly distinguished at this time. While we caution that our first-year results should be viewed as tentative, they strongly suggest that the ocean plays the critical role in the management and conservation of these Columbia River salmon stocks, and that ignoring these issues leads to more blame being ascribed to the hydrosystem than is in fact appropriate," the report concludes.

"It is encouraging that for the first time anywhere that we are able to directly address some of these long standing -- and fascinating -- questions about the role of the ocean in affecting Columbia R salmon populations," Welch said. "One year of data shouldn't be expected to change anyone's mind on these contentious issues, and we are certainly not suggesting that they should. However, the POST array is proving its worth for addressing critical questions that are at the heart of some important policy debates in the Columbia Basin…."

The report is expected to be available by next week on BPA's website at http://www.efw.bpa.gov/Integrated_Fish_and_Wildlife_Program/technicalreports.aspx