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 (CSS) draft annual reports. This ISAB review of the draft 2022 CSS Annual Report is the ISAB’s thirteenth review of CSS annual reports. CSS reports have thoroughly documented trends in survival and productivity, and these long-term data become more valuable with each additional year.
The annual CSS report is a mature product, produced by the Fish Passage Center since 1998 and reviewed by the ISAB since 2010. The reports typically include mostly updates with the latest year of data, continuation of the analysis of long-term trends, and addition of new analytical approaches. 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.
A few key observations and suggestions for future analyses and reporting from this year’s ISAB review include:
- The ISAB previously encouraged the CSS to describe major applications of the CSS data that have been published or reported over the last year and briefly highlight important findings based on CSS data. The ISAB continues to recommend that the CSS should make the regional importance of its analyses abundantly clear to the Council, BPA, co-managers, and the public.
- In 2021, the ISAB suggested a description of important changes in the hydrosystem over the years and a brief indication of their possible effects on salmonid survival. In response, the CSS developed a new chapter (Chapter 7) for the 2022 Annual Report that provides a thorough and readable account of the history of the hydrosystem, development of management of spill to benefit salmon and steelhead, and the formation and evolution of the CSS study to inform state, federal, and tribal fisheries managers.
- While well beyond the scope of the CSS, the ISAB suggests that summary chapters similar to Chapter 7 be written for hatchery operations; for habitat restoration; for avian predation; for seal and sea lion predation, and such to keep a summary record of major changes to the basin in one easily accessible place. These could be commissioned work by other lead entities with expertise in those areas.
- In Chapter 2, the CSS Oversight Committee presents an Adaptive Management Framework as a response to proposals for Spill Experiments (Chapter 2). This is the first evaluation of the Flex Spill experiment that appears in CSS annual reports. Complete returns of tagged cohorts are not yet available, but initial results for (FTT) and in-river survival indicate these observations appear consistent with modelled values based on 1998-2018 data, but no formal assessment is done. Analyses to date indicate that spill levels that result in up to 125% TDG, or perhaps even greater, would not decrease juvenile survival. The ISAB encourages the CSS to conduct analyses now, even with incomplete data, and offers suggestions for additional improvements in data analysis and the use of results to inform the adaptive management process.
- Chapter 3 continues and expands previous years’ work on the effects of the in-river environment on juvenile travel time and survival. The CSS now analyzes the Upper Columbia River based on PIT tag data from Rocky Reach to McNary dams rather than Rock Island to McNary dams.
- Chapter 4 also continues and extends past years’ work on patterns in annual overall SARs. By now, the low level of SARs relative to the Council’s 2%-6% objectives has been established. The CSS could consider developing an Impact Report, perhaps developed collectively with other groups, to communicate the most critical take-home messages and implications for the Council, BPA, and co-managers.
- Chapter 5 presents analysis of upstream migration success for adult spring and summer Chinook, fall Chinook, and steelhead. All survival probability estimates are very high, with two segments having survival estimates very close to 1.0. The ISAB is concerned that the lack of contrast in survival in many reaches over time will make it difficult to determine effects of other factors. What are the major management implications from these results?
- The premise and motivation for Chapter 6 make it a great addition to the annual report. The link between SARs and abundance targets is fundamental to understanding what restoration and other recovery-related actions must achieve to be successful. The analyses are designed to address the question: “What level of SAR is needed to realize the Columbia Basin Partnership (CBP) benchmarks, and is that level of SAR consistent with the prescribed NPCC goals?” In addressing this question, the analyses also provide a synthetic view of the status of the situation for an impaired population (i.e., Snake River spring/summer Chinook salmon).
- In Chapter 6, the data are examined with a multiple model analysis designed to increase confidence (robustness) when different models (approaches) agree. However, without careful examination of the assumptions and the details of how common data are used across the models, it is impossible to assess the degree to which the predictions from the three approaches are independent. It is clear that the three models are not independent. The assumptions and sources for key inputs are insufficiently documented to assess their commonalities. Approaches 2 and 3 might be better presented as alternatives of the same approach.
- The current version of Chapter 6 needs additional work to explain the three approaches clearly and to resolve the issues identified in our detailed review. Nevertheless, the main message is that substantially larger SARs than the 2%-6% recommended ranges from the CSS reports will be needed to meet the recovery goals. The need to address these management questions should be highlighted in a Conclusions section for the Council and regional decision makers. The many years of CSS reporting should provide valuable information on how to prioritize management actions.
- Chapter 7 summarizes how spill has changed since the completion of the hydroelectric projects in the early 1980s. The ISAB appreciates the difficulty in summarizing spill changes that have occurred on many different temporal scales, and we found this high-level summary very informative. The chapter emphasizes that relatively small changes in spill occurred during the Spill Experiment over a period with high variation in river discharge and ocean conditions. The ISAB encourages the CSS to give this conclusion more prominence because of the many conflicting arguments about the need to change spill over the years.
- As we stated in our review of the 2021 CSS Report, the ISAB strongly emphasizes the importance of the CSS reports. Survival of salmon and steelhead during their life cycle is significantly affected by the hydrosystem, and these data are essential for the Fish and Wildlife Program. The ISAB encourages the Council and BPA to reassess the funding and consequences of flat funding since 2017. This funding policy directly affects the quality of the research and integrity of the long-term records. If funding is to be constrained, then the entire CSS program should be reviewed in detail to assess which parts are essential and which parts can be reduced without critically damaging the overall CSS program.
The ISAB appreciates the CSS’s careful consideration and detailed responses to suggestions provided in previous reviews. The ISAB’s full report contains an overview of the draft 2022 CSS report’s findings, suggested topics for further CSS review, and general comments and specific editorial suggestions on each chapter of the draft 2022 CSS report.