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PATH Updates Fall Chinook Findings

by Mike O'Bryant
Columbia Basin Bulletin
- October 15, 1999

PATH updated its 1998 preliminary report on fall chinook survival and presented those changes at last week's meeting of the inter-agency Implementation Team.

Though the updated report has gone through more extensive review by PATH scientists and the Scientific Review Panel, it lacks any defining conclusions because of wide variances in the uncertainty of juvenile survival rates of transported fish compared to non-transported fish, or D-value.

With a low delayed mortality, or "D" value figured into the analysis, a logical conclusion would be that barging should continue. But if mortality is high, then some might suggest the data points toward the need to stop transporting fish.

"You're telling us that the D-value could be between 0.1 and 1.0," said Jim Yost, Idaho representative to the IT, commenting on the wide range of mortality evaluated in the PATH report. "If it's closer to one, we leave the dams in. If it's closer to 0.1, we remove the dams, but we don't know. Do we flip a coin?"

In its report on fall chinook, PATH looked at four hydrosystem actions. While each action resulted in improvements and survival of fall chinook, only the breaching actions consistently resulted in recovery.

As PATH coordinator Dave Marmorek said, "most transportation actions fall significantly below the recovery level."

PATH used 300 returning adults as the survival number. It used 2,500 returning adults as the recovery level.

The four hydrosystem actions are:

PATH did not assess an A1 action, which is current operations plus transportation because most fall chinook are already transported by truck.

Marmorek said the major changes from the 1998 preliminary fall chinook report include further extensive review by PATH and the SRP and the exclusion of supplemented fish when assessing the National Marine Fisheries Service jeopardy standards, which lowered the number of spawners in the study. PATH also ran passage models from the face of Lower Granite Dam rather than from the head of the pool. It was more effective, he said, because there is "a lot of uncertainty in the Lower Granite pool."

The PATH report said there are major gaps in existing information for measuring the D-value.

"The SRP recommended that PATH assess the benefits and risks of an experimental management approach in reducing the key remaining uncertainties," the report says. The work also will include monitoring of "smolt to adult return rates for both transported and in-river fish." It says PATH will put together a scoping report on experimental management, which Marmorek presented as a follow-up to the fall chinook report at the IT meeting.

In that presentation -- PATH Scoping of Candidate Research, Monitoring and Experimental Management Actions -- Marmorek proposed one research study and three experiments that he believes could reduce uncertainty about barging mortality:

Each is one of ten candidate approaches suggested by PATH for further study of items that could affect survival. Others include: breaching the four dams; breaching the four dams in 2002 and breaching the John Day Dam in 2012; introducing salmon carcasses into streams; manipulation of hatchery production; predator removal; as well as further direct study of mortality and climate change. He said this is a raw list that could ultimately end in some getting cut and others being combined.

Marmorek said PATH is presenting these candidate approaches as a set of experiments to the Northwest Power Planning Council before deciding whether it would be a good idea to conduct any test.

But, there are risks in each of the experiments, he said.

"The longer the experiment, the stronger the power of the test, but also the chance of recovery declines," he said. "On the other hand, doing the experiment could resolve the uncertainty."

Link information:
PATH Fall Chinook Report

Mike O'Bryant
PATH Updates Fall Chinook Findings
Columbia Basin Bulletin, October 15, 1999

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