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Analysis: Poor Adult Returns
for In-River Migrants in 2001

by Barry Espenson
Columbia Basin Bulletin - May 9, 2003

Favorable ocean conditions are credited in large part with recent years' revival of Columbia River basin salmon and steelhead stocks, but they do not appear to have overridden harm done to juvenile outmigrants as they swam toward the Pacific during 2001's severe drought, according to analysis done by state and federal scientists

"The SAR (smolt-to-adult return) for the 2001 outmigration of chinook will not be complete until the 2004 adult returns are analyzed, but analysis of the composition of the 2003 return provides early and strong indications that the SARs have been reduced due to the poor out migration conditions," Bill Tweit wrote in a Sept. 9 letter that updates earlier information provided to a special National Academies of Science committee formed to evaluate Columbia River water management/fish survival relationships in Washington. Tweit is the Washington Department of Fish and Wildlife's Columbia River lead.

The WDFW called on several regional scientists to conduct a flow-survival analysis as one of the many pieces of information to be considered by the NAS committee. The overall review by the NAS panel of the available science relating to salmon survival and the impacts of hydropower operations, as well as municipal and irrigation water diversions, in the Columbia River Basin in Washington began in February.

The NAS' National Research Council appointed 13 scientists to complete the review and report their findings to the Washington Department of Ecology in the spring of 2004.

The committee has met three times and will meet for a final time Nov. 3-4 in Washington, D.C., to "find out what we agree on and what we don't agree on," said Jeffrey Jacobs, the Academies' "responsible staff officer." A draft report would soon follow and it would then be reviewed by a separate panel of experts. The NAS committee would then respond to any comments made by the reviewers before the report would be finalized by the NAS and delivered to the state Department of Ecology. The process is confidential until the report is released.

The technical analysis produced at WDFW's request, titled "The effects of mainstem flow and water velocity on salmon and steelhead populations of the Columbia River," was first presented to the NAS panel on March 20. Jacobs said he did not know what relative weight the committee would give the analysis amongst the reams of available research on flow/survival relationships in the Columbia River Basin.

The information highlighted in Tweit's Sept. 9 letter was also presented last month during a gathering of regional fish and wildlife managers -- the Columbia Basin Fish and Wildlife Authority. Presenters were Howard Schaller of the U.S. Fish and Wildlife, Tony Nigro of the Oregon Department of Fish and Wildlife, Margaret Filardo of the Fish Passage Center and Charlie Petrosky of the Idaho Department of Fish and Game. The ODFW's Ron Boyce was also involved in the analysis.

"Even though the return of 2001 outmigrants was helped by good ocean conditions, they were not responsible for the good adults returns shown in 2003," Tweit wrote of the analysis done from scales collected this year from adult chinook at Bonneville Dam and from PIT tag detections of returning adults at Lower Granite Dam.

The 2003 adult upriver spring chinook return to the Columbia River, 208,430, was the fifth largest return observed since at least 1960, according to Oregon and Washington officials. The Bonneville Dam count of 14,466 jacks -- spring chinook returning after only one year in the ocean -- was the fourth highest total since at least 1960. The 2003 summer chinook run, estimated at 120,000 adults, is the second largest since 1960.

The overall 2003 return run was dominated by three-ocean fish that migrated to the ocean in 2000.

"This was an unusual and unexpected event," Tweit wrote. Historically the spring chinook return past Bonneville is comprised of 75 to 80 percent two-ocean fish with 15 percent being three-ocean returns. The 2003 return was 38.2 percent two-ocean fish from the 2001 outmigration, 54.2 percent three-ocean fish and 7 percent one-ocean fish.

The ratio at Lower Granite was skewed even more dramatically with only five PIT tagged two-ocean fish returning compared to 118 three-ocean fish.

"The apparent strength of the 2003 total adult chinook return is the result of a strong showing of adult returns from the 2000 outmigration and a strong jack return from the 2002 outmigration," Tweit wrote. "This is a fortunate demonstration of the value of overlapping age classes as a population stability mechanism, and certainly not evidence that poor outmigration conditions have little effect when ocean conditions are positive."

Because of the severe drought, the runoff into the Columbia River system in 2001 was the second lowest on record. Because of the scarcity of water, spill at the dams to aid fish passage was virtually eliminated, as were most attempts to augment flows from storage reservoirs.

"The juvenile survival estimates and travel times, which were presented to the Panel on March 20, reflected those conditions with the lowest juvenile survivals and slowest travel times on recent record," Tweit said.

A summary of the juvenile migration analysis says that "all data collected suggests that decreasing flows increases the risk to the already high risk populations."

According to the flow/survival analysis, the 2001 smolt outmigration from points on both the Columbia and Snake was the most prolonged on record. The average travel time was more than 30 days as flows stayed well below objectives set out in a federal biological opinion that calls for river operations NOAA Fisheries feels will avoid jeopardizing the survival of salmon and steelhead listed under the Endangered Species Act.

During their presentation to the CBFWA members last month, the researchers' said their modeling predicted that the increased travel time would, in effect, counter positive survival effects produced because of the positive ocean environment. Their model predicted poor to mediocre adult returns from the 2001 outmigration.

The NRC, in accepting the assignment to produce the report for the WDOE, said it will specifically review the scientific knowledge related to the conditions that impact salmon survival rates, including hydropower, and will assess the risks to salmon at critical stages of their lives under a variety of water use scenarios.

The scientific review is just one action the state will take as a part of its Columbia River Initiative, a mostly public process that will address water withdrawals and their impacts on flows in the Columbia River needed for salmon survival. Ecology said there are hundreds of pending water withdrawal applications from potential Columbia River water users -- both municipalities and irrigators -- but there is little agreement "on the stream flows needed to support salmon. Litigation is being used increasingly to try to drive water policy, but it is resulting in additional gridlock."

Related Sites:
National Academy of Sciences:
Washington Department of Ecology:

Barry Espenson
Analysis: Poor Adult Returns for In-River Migrants in 2001
Columbia Basin Bulletin, May 9, 2003

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