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NW Fishletter #282, December 10, 2010

[2] Barging Gets High Marks At Research Review

Northwest salmon researchers have been frantically crunching numbers for the past several weeks, getting ready to report on the latest results at the Corps of Engineers' annual research review.

And just as expected, they have come up with more evidence that the court-ordered spill program at Columbia and Snake dams is not producing more adult Snake River spring chinook or steelhead, as proponents have claimed.

The hydro BiOp had called for ending spill two weeks in May at lower Snake dams and collecting as many fish as possible for barging downstream, but U.S. District Judge James Redden sided with plaintiffs in the ongoing litigation over dam operations and called for more spring and summer spill to aid inriver migrants back in 2005 and 2006.

However, the PIT-tag survival data reported last week in Portland by NOAA Fisheries scientist Doug Marsh for the 2007 migration year showed the barging operation that began May 1 improved returns of wild spring chinook over inriver migrating fish.

Water conditions in 2007 were far from ideal--it was a low-flow year, but spill proponents said the court-ordered boost in spill was just what the fish needed to get downstream faster.

However, with the 3-ocean adult returns coming back in 2010, the scientists calculated that the smolt-to-adult return rate [SAR] of the transported wild fish was 0.90 percent, while the inriver return was only 0.66 percent, and 0.47 percent for fish that were bypassed and returned to the river.

The barged SAR may not sound like much, but it's a 36 percent better return rate than for inriver migrants.

(For the 2006 migration reported at the research review last year, SARs for the two components were nearly equal--0.84 percent for inrivers, 0.73 percent for transports).

For wild steelhead, the benefits of barging were even more pronounced. The transport SAR for Snake wild steelies was 2.64 percent, and for inrivers it was 0.47 percent--a return rate more than five times better. Bypassed steelhead showed a 0.28-percent SAR.

For Snake fall chinook, the story is more confusing. After investigating the 2005 outmigration, the scientists said it looks like barging neither helped nor hurt the fish. For Snake River releases, results were close for both barged and inriver fish--0.04 percent and 0.06 percent, respectively.

For releases in the Clearwater River, there was some possible benefit. Inriver fish showed a 0.2-percent SAR, the barged fish 0.32 percent.

But they said the "vast majority" of the fish were never detected, and 50 percent of the returning adults were never detected as juveniles. Studying fall chinook has been a big headache for researchers since they found out that many young fall chinook do not migrate until early fall or the following spring before detection systems are turned on.

The researchers have also been keeping track of the returning fish for another reason--to see if the barging process reduces their ability to find their way home. They found that transported wild spring chinook showed a slightly lower conversion rate from Bonneville to Lower Granite dams than inriver migrants, but it depended on the year-class.

For wild steelhead, the transported fish showed a higher conversion rate back to Lower Granite Dam than inriver migrants.

Other NOAA Fisheries scientists reported that PIT-tag data also showed spring chinook survival through the hydro system was nearly 55 percent this year, and close to 62 percent for juvenile steelhead, the second-highest survival seen for steelhead since the study began. Survival through individual dam reaches averaged 93 percent for chinook and 95 percent for steelhead.

The scientists said high spill rates at Snake dams and a delayed start to transport meant more PIT-tagged smolts were in the river compared to earlier years. They said fewer steelhead were likely eaten by birds near the confluence of the Snake and Columbia than in some previous years. High spill rates and newer surface passage structures at dams helped the rapid migration of smolts despite low-flow conditions.

Cormorants and Caspian terns still ate plenty of young salmonids, though there were 1,500 fewer breeding pairs of terns at East Sand Island than last year.

Still, more than 8,000 pairs were nesting, but researchers reported that productivity was the lowest they have ever seen, which they attributed to the El Niño conditions in 2009-2010. Young salmonids made up about 33 percent of the tern diets this year, similar to earlier findings.

The tern nesting area was shrunk further this year, down to 62 percent of its former area. Four other tern nesting areas in interior Oregon set up by the Corps of Engineers to reduce the Columbia colony met with very little success. No terns at all showed up at three of the four sites.

The group of 12,400 breeding cormorant pairs at East Sand was slightly larger than last year's colony. Another species of cormorant showed up as well--the Brandt's cormorant--and totaled nearly 1,000 breeding pairs.

Young salmonids made up about 17 percent of the cormorants' diet this year, compared to only 9 percent in 2009. Researchers said they expect the birds to have consumed significantly more than the 11 million smolts they were estimated to have eaten last year.

PIT-tag detections on East Sand Island revealed minimum estimates of predation--3 percent of spring/summer chinook, 4 percent of fall chinook, 6 percent of coho, and 10 percent of all steelhead previously detected at Bonneville Dam.

The bird colonies seem to be giving young fall chinook released below Bonneville Dam an especially hard time. It was estimated that cormorants and terns will consume at least 20 percent of those releases.

Acoustic-tag research by other scientists showed that estuary survival continued to worsen the closer young fish got to the mouth of the river. Preliminary estimates by PNNL and Corps scientists found that about 93 percent of spring chinook survived from Bonneville Dam to a point 50 km from the mouth of the Columbia. But only 86 percent made it from there to the Astoria Bridge, and 80 percent to East Sand Island.

They found 88 percent of steelhead made it from Bonneville to Rkm 50, but from Bonneville to Rkm 8, survival was only 55 percent,

For young fall chinook, about 89 percent made it from Bonneville to Rkm 50, but from the dam to Rkm 8, 81 percent survived.

Research by Canadian scientist David Welch found no higher mortality in the estuary. His fish sport different acoustic tags than the Corps' smolts do, so they can be tracked in the ocean, but his own preliminary results showed a 36-percent survival rate for spring chinook from Lower Granite to below Bonneville--considerably lower than the 55-percent rate found for PIT-tagged fish.

Welch found survival of both transported and inriver spring chinook smolts from the Snake River was about 12 percent from below Bonneville to Lippy Point, off the northwest coast of Vancouver Island, "Thus, delayed mortality due to Snake River dam passage was also not evident." -B. R.

The following links were mentioned in this story:

annual research review

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