Review of the Comparative Survival Study’s Draft 2012 Annual Report

read full document >


The Council’s 2009 amendments to the Columbia River Basin Fish and Wildlife Program call for a regular system of independent and timely science reviews of the Fish Passage Center’s (FPC) analytical products. This regular system of reviews includes evaluations of the Comparative Survival Study’s draft annual reports. These ISAB reviews began two years ago with the evaluation of the CSS’s draft 2010 Annual Report (ISAB 2010-5), followed by a review of the draft 2011 Annual Report (ISAB 2011-5). This ISAB review of the draft 2012 CSS Annual Report is the ISAB’s third review of CSS annual reports in response to the Council’s 2009 Program.


The ISAB finds that the draft 2012 CSS Annual Report is well organized and well written. The ISAB acknowledges the continued progress by the CSS in addressing key questions and reporting results. As the dataset includes more years and a wider range of environmental conditions, the ability to address how the river environment affects juvenile salmon migration rates and survival continues to improve. The long time series in survival rates by species, hatchery and wild stocks, and watersheds are valuable in this regard. The CSS authors should continue to produce yearly updates.

The ISAB members who attended the CSS Annual Meeting April 12, 2012 acknowledge the very useful exchange of information that took place.

The attached ISAB review begins by suggesting topics for consideration by the region as a whole. These overarching issues, included in this message below, are related to material presented in the draft 2012 CSS Annual Report, but the topics are not specifically limited to consideration by the CSS team. In the attached report, the ISAB also provides general comments as well as specific editorial comments to be considered in revising the draft 2012 CSS report or, if time does not allow, for possible inclusion in subsequent CSS Annual Reports.

Topics for Consideration by the Region

  • An evaluation is needed for whether the NPCC’s 2-6% SAR goals and objectives are sufficient to meet salmonid species conservation, restoration, and harvest goals. Chapter 4 describes SAR Program goals as being for spring/summer Chinook and thus not tailored for other species, races, and age of smolts. These SAR goals should be broken out by species, race, and age at smoltification rather than one goal across all species. Coho, fall Chinook, and steelhead have different juvenile life histories, and it is likely inappropriate to generalize SAR objectives for viability across these species. The analyses in Chapter 5 lead to the important conclusions that overall SARs for Snake River subyearling fall Chinook are "well short of the NPCC goal of 4% SAR needed for recovery" and that there is little or no benefit to transport. But given that fall Chinook migrate as subyearling smolts (whereas spring/summer Chinook migrate as larger, yearling smolts), the NPCC’s 2-6% SAR objectives may be higher than needed to meet conservation, restoration, and harvest goals for fall Chinook. As with other species, the NPCC (2009) SAR objectives should be updated to specify the critical points in the life cycle where smolt and adult numbers should be estimated and to identify ESU-specific SARs necessary for survival and recovery.
  • Development of technology to improve PIT-tag recovery in the estuary is needed. PIT-tags detected on bird colonies in the estuary are used to augment NOAA Trawl detections below Bonneville. The problems with trawl detections indicate this is a difficult area for PIT-tag recovery contributing to uncertainties concerning smolt migration and survival.
  • In response to last year’s ISAB advice to discuss and compare CSS results with other studies using different methods (e.g., McComas et al. 2008, also more recently Harnish et al. 2012) the CSS stated (CSS 2011, Appendix F): "Response: The CSS-OC concludes that it is not currently possible to estimate smolt survival for PIT-tagged fish below BON through the Columbia River estuary. The CSS-OC is aware of the McComas et al. (2008) study; however, the results are not robust enough for application of acoustic tag survival estimates through the estuary to CSS PIT-tag groups, or to the retrospective estimates of S.oa and S.o1." The CSS-OC has made an important conclusion. If PIT-tags cannot be used and acoustic tag results are not "robust enough" to estimate estuarine survival, a thorough review of this issue is needed, especially given the increasing scientific evidence of survival bottlenecks in the Columbia River estuary and extensive efforts to restore estuarine habitats to improve salmonid survival. A review is needed of estimation methods for smolt survival below Bonneville Dam through the Columbia River estuary using PIT-tags, acoustic tags, and other methods. If necessary, existing methods should be improved or new methods developed to estimate estuarine survival of salmonid smolts (see ISAB 2012-6; Levings et al. 1989; Macdonald et al. 1988).
  • Measurement error in SAR estimates associated with PIT-tags needs comprehensive examination and description in a report dedicated to this issue.

See the attached report for detailed comments.

This website was archived in May 2018.

Go to this page on the new site or keep browsing the old site.

Contact Eric Schrepel with any questions or requests for our new (current) site, thank you.