(Also see Addendum)
The Columbia River Basin Fish and Wildlife Program calls for a regular system of independent and timely science reviews of the Fish Passage Center’s (FPC) analytical products. These reviews include evaluations of the Comparative Survival Study’s draft annual reports. The ISAB has reviewed these reports annually beginning eight years ago with the evaluation of the CSS’s draft 2010 Annual Report and most recently the draft 2017 Annual Report (ISAB 2010-5, ISAB 2011-5, ISAB 2012-7, ISAB 2013-4, ISAB 2014-5, ISAB 2015-2, ISAB 2016-2, ISAB 2017-2). This ISAB review of the draft 2018 CSS Annual Report is the ISAB’s ninth review of CSS annual reports.
The annual CSS report is a mature product, typically including only updates with the latest year of data and expansion of analyses as more data are acquired. Many of the methods have been reviewed in previous ISAB reports and so now receive only a cursory examination. As more data are acquired, new patterns and questions arise on the interpretation of the results—this is now the primary focus of the ISAB's reviews. The ISAB appreciates the CSS’s detailed responses to suggestions provided in previous reviews and does not expect the CSS to necessarily respond immediately to new requests for further analyses.
The draft CSS report describes many important analyses that are evaluated in the ISAB's full report, but the ISAB highlights a few key observations:
- The ISAB is concerned that the overall pattern of low SARs of Upper Columbia and Snake River spring/summer Chinook and steelhead in 2015-2016, as shown In Chapter 4, is likely to continue, particularly in light of the apparently poor early ocean survival of juvenile salmon in 2017 and unprecedented ocean conditions in 2018 in the Northern California Current and Gulf of Alaska.
- Rather than trying to do a single study to estimate effects of alternative tag-types (PIT and CWT), it may be opportune to do a meta-analysis of the many existing studies to try and figure out why there are different results; for example, is it species specific or just random noise?
- The new methodology described in Chapter 9 to estimate the detection probability (and abundance) of smolts passing Bonneville Dam could be applied at each dam in the hydrosystem, and thus some progress could be made toward understanding density dependence effects on survival, especially if multiple stocks are involved.
The ISAB’s full report contains an overview of the draft 2018 CSS report’s findings, suggested topics for further CSS review, and general comments and specific editorial suggestions on each chapter of the draft 2018 CSS report.