The ISAB Weighs in on Fish Goals, Spill Benefitsby Bill Rudolph
NW Fishletter, November 12, 2012
The Independent Scientific Advisory Board (ISAB), which occasionally weighs in on questions related to salmon recovery, says the region should take a new look at whether the 2- to 6-percent smolt-to-adult return [SAR] rates called for in the region's salmon plan are actually high enough to meet recovery needs and satisfy harvest goals.
The panel used its review of the draft 2012 Comparative Survival Study (CSS) to expand its usual focus, and made several other recommendations. The latest study, written by the CSS Oversight Committee and the Fish Passage Center, compiles juvenile and adult PIT-tag survival information from many hatchery and wild chinook and steelhead stocks, mostly from the Snake River, and estimates SARs for both inriver migrants and juvenile fish transported downstream by barge.
The 2- to 6-percent recovery range in the region's fish and wildlife program was borrowed from the contentious PATH process in the late 1990s, when regional biologists tried to figure out the major causes of fish declines in the Columbia Basin. The PATH people, in turn, had borrowed the 2- to 6-percent estimates of healthy returns from early NMFS survival studies in the 1970s, involving freeze-brand studies that have never been successfully replicated. Unfortunately, the original data from these studies, stored on IBM punch cards, was reportedly lost years ago after a warehouse flood.
This isn't the first time the ISAB has weighed in on policy questions. In 2008, its recommendation to torpedo a proposed NMFS BiOp barging strategy that would have ended spill at federal dams for two weeks in the spring to collect more fish in barges was cited by District Judge James Redden as one of the justifications for his own court-ordered spill regime.
The science panel also said one CSS conclusion could be especially important--that current estimates of estuarine survival from acoustic tags are not robust enough to apply to PIT-tagged fish, which can only be detected by a trawl below Bonneville Dam and from detections of tags deposited at bird colonies in the lower estuary. The panel said estimation methods should be thoroughly reviewed and, if necessary, improved.
The scientists also said measurement error in PIT-tag SAR estimates needs "comprehensive examination and description in a report dedicated to this issue." This recommendation reflects other findings that suggest some PIT-tagged fish return at lower levels than their general population, up to 30 percent or more.
As for the draft CSS report itself, the ISAB said more analysis of the relationship between spill and juvenile fish survival would "be worthy of further investigation." The reviewers noted that a conclusion from a recent "History of Spill Report" from the Fish Passage Center would be a good place to start--"Increasing proportion of spill provided for fish passage at hydroelectric projects has resulted in higher juvenile spring/summer chinook, fall chinook, sockeye and steelhead survival and faster juvenile fish travel time through the FCRPS."
The panel said some evidence was presented that spill had an impact on fish travel time and "instantaneous survival," but little effect on instantaneous survival of sockeye and steelhead below McNary Dam.
"Furthermore," said the review, "a variety of other factors also had similar importance as spill for species where spill was found to be a key variable."
The panel said more effort was needed to model spill and water travel time effects on each species, while holding other variables constant. They also said an analysis of competing models was needed to look into the possibility of model selection bias, along with a clearer explanation about how the results could be used to manage the migration. They said such an analysis "would inform managers as to how much benefit can be expected by altering spill levels and reservoir elevations."
The panel also commended CSS staff for two recent peer-reviewed papers that related climate, river and ocean conditions to annual trends in SAR estimates. "Nevertheless, the ISAB continues to emphasize the need to improve scientific collaboration between CSS staff and estuary-ocean experts working on BPA-funded programs to address migration and survival of Columbia River salmon and steelhead in the estuary and ocean."
Most researchers these days agree that when ocean conditions are good for fish, river conditions are more likely to be good, too, so some correlation is expected. A colder ocean usually means spring upwelling of nutrients, wetter weather and higher river flows.
One of the papers (Haeseker et al., 2012) even suggests that recovery-level SARs for Snake River spring/summer chinook could be reached by spilling 60 percent of dam flows during the juvenile migration. So far, criticism of the paper, which was published in Transactions of the American Fisheries Society, has been anecdotal, but some say the correlation hypothesized between increased juvenile survival from more spill through the hydro system and SARs will not hold up if the analysis excludes data from 2001, a year of extremely low flows--the third lowest in the modern record--with no spill and very low juvenile survival, especially for steelhead.
Biologists have said the low steelhead survival in 2001 was likely because river waters had warmed so much during the slow spring migration that many young fish had "residualized," or quit migrating altogether before they even made it out of the Snake.
CSS proponents presented their analyses at the June 2012 meeting of the Pacific Fishery Management Council's habitat committee, which suggested boosting spill to 60 percent could increase juvenile survival to 85 percent, and lead to a 4-percent SAR for Snake River spring chinook. These conclusions were based on data collected on spring chinook from the John Day River, which only pass three dams on their downstream migration.
But if the analysis had used spring chinook data from the Spring Creek Hatchery just above Bonneville Dam, the result would have been nowhere near as optimistic, since the Spring Creek hatchery SARs were much lower compared to the John Day run. For migration year 2008, the draft CSS pegged the Spring Creek SAR (Bonneville to Bonneville) at about 2 percent, while the John Day SAR (Bonneville to Bonneville) was about 6 percent.
Nor does the analysis include possible adverse effects on migrating juveniles from high levels of dissolved gas from the extra-high spill levels, or fallback of returning adults. Last year's extremely high flows and spill levels actually approached some of the levels called for in the Haeseker paper, said one source, and juvenile survival ended up lower than this year, which was the second highest in recent years.
In 2007, the ISAB had recommended ending upriver and downriver comparisons in CSS reports, echoing earlier criticism from both NOAA Fisheries and BPA that called the comparison between Snake River and John Day stocks bogus--although the ISAB had said it in a much nicer way. "The observation that SARs ... for wild chinook were only one-quarter that of similar downriver populations that migrated through fewer dams does not provide proof that the hydro system is responsible for this SAR difference; there are myriad alternative possible explanations," said the reviewers. "The comparisons are weak because of the limited number of sites compared and the multitude of confounding variables."
Meanwhile, the original purpose seems to have been lost in the whole CSS endeavor--whether PIT-tagged hatchery fish could serve as surrogates for wild fish in survival studies that estimated the benefits of transport. Over the years, the CSS results have shown benefits to most stocks from barging, but has consistently downplayed these results in their conclusions, noting in most cases that SARs have not reached the 2- to 6-percent range that the Northwest Power and Conservation Council has called for.
This year's CSS draft is no different, with some results in for Snake fall chinook. It concluded fall fish got little or no benefit from transport. But the ISAB noted that the "preponderance of higher point estimates for survival of transported fish suggest that conclusions concerning benefits of transportation are premature. Caution in interpreting such results is encouraged."
2011 FCRPS BiOp Report
2012 draft Comparative Survival Study
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