Excerpt from the nearly completed
2014 FCRPS Supplemental Biological Opinion (Section 3.3.3.5.)
In recent Comparative Survival Study Annual Reports, Tuomikoski et al. (2011, 2012, 2013) hypothesize that substantially increasing spill levels (which reduce exposure of juveniles to juvenile bypass systems and turbines) would substantially increase both inriver smolt survival and smolt-to-adult return rates (ocean survival). The reports present prospective modeling results for four scenarios, ranging from current levels of spill at the eight mainstem dams to spilling to
125% of saturated total dissolved gas levels in each tailrace.
1
The CSS participants recommend that the region design and implement a large-scale operational study to evaluate this hypothesis
(CSS Workgroup 2013). NOAA Fisheries has reviewed these reports and recent related journal articles (Tuomikoski et al. 2011, 2012, 2013; Haeseker et al. 2012), attended workshops and presentations of the CSS model results, and reviewed critiques of the approach (Manly 2012;
Schaller et al. 2013; Skalski et al. 2013) and other materials related to this topic (Rechisky et al.
2012; ISAB 2013).
In considering this information, NOAA Fisheries finds that several substantial weaknesses in the analysis exist that would need to be resolved prior to further consideration of any operational study of this magnitude. The data used to construct the models in Haeseker et al. (2012) span a 9year period (1998–2006). Since 2006, spill levels have increased at several of the mainstem projects and the efficiency of spill has increased as well with the addition of spillway weirs (the last spillway weir was installed in 2009). Several configurational improvements have also been made since 2006, which have contributed to increased juvenile survival rates through the hydrosystem.
There is evidence that conventional and surface spill pass a greater proportion of fish for a fixed spill percentage at lower flows than at higher flows (NOAA Fisheries unpublished analyses).
Thus, high spill percentages may not be needed to pass the same proportion of fish in lower flow years. The increased spill recommendation by the CSS also addresses the hypothesis that juvenile fish bypass systems are a significant source of delayed mortality based on adult returns of inriver juvenile migrants (Haeseker et al. 2012). However, an analysis of the Haeseker et al.
(2012) data by Skalski et al. (2013) found that spill percentage also correlated with increased adult returns of transported fish, which conflicted with the Haeseker et al. (2012) conclusions.
The analyses in Haeseker et al. (2012) provide correlative associations only, and should not be interpreted as demonstrating causation. Spill levels are also correlated with many other inriver conditions or mortality factors, some of which are not discussed in Haeseker et al. (2012). These authors investigated only four covariates in their inriver survival models and seven covariates in
1 Current total dissolved gas variances or waivers issued by the States of Oregon and Washington generally preclude the Action Agencies from voluntarily spilling water above the 120% tailrace (and 115% forebay in Washington) limit.

their ocean survival models, and the correlations among those covariates were not provided. The
Skalski et al. (2013) analysis suggests that spill levels must have correlated with other mortality factors, such as ocean conditions, that were also experienced by transported fish. If the CSS modelers had replaced spill with other correlated factors, it is likely that those factors would have also been associated with similarly increased survival. Mortality effects of this array of factors are confounded and not separately estimable with correlation studies alone. Randomized experiments would be necessary to adequately assess direct and indirect effects of spill. In the absence of randomized experiments, we suggest that a more thorough analysis that includes more potentially influential covariates, an assessment of correlation among variables, and an analysis of influential data points.
For example, an obvious variable that is missing from the CSS survival models is total dissolved gas. A model that predicts survival using a monotonic association with spill, and does not include mortality at higher levels of spill and thus total dissolved gas, will make the unrealistic prediction of increasing survival regardless of the level of total dissolved gas. Additional years of data under the current operations and configuration of the system (completed in 2010) will shed light on whether or not the CSS hypothesis is supported by the empirical data. Adult returns from the 2011 and 2012 outmigrations (high flow, high spill years) and 2010 (a lower flow, high spill year) should be especially instructive. NOAA Fisheries supports the CSS researchers’ recent work to assess the proportion of spillway passed fish as an explanatory variable, which takes into account the passage efficiency of spill at each project, not just spill as a surrogate.
NOAA Fisheries is not dismissing the results of these modeling efforts and appreciates the progress made in the CSS modeling. NOAA will continue to monitor the effects of project operations on juvenile survival and adult returns as reported by CSS and the Northwest Fisheries
Science Center. We note the adult returns from the year 2011, a year that had high levels of spill and flow, has produced below average adult return rates. Results such as this reinforce our current management approach to hydrosystem operations. Substantial progress has been made toward improving survival of juvenile anadromous fish in the hydrosystem. Models of the system effects will continue to improve through 2018 as more data from current operations is added, and NOAA Fisheries will continue to consider opportunities to make further improvements to hydrosystem operations or configurations.
Further, NOAA Fisheries recommends that future regional consideration of a spill test or a decision to implement a spill test similar to that being proposed should explicitly consider the following:
(1) Legal requirements and permitting timelines (e.g., CWA, ESA, NEPA, etc);
(2) Biological effects (e.g., the potential for adult passage impacts at specific projects supported by ladder passage and dam fallback information, the likely effect of increased TDG levels and exposure periods on migrating adult and juvenile salmon and steelhead and aquatic biota,

the effect of further reduced transport rates on SARs (particularly Snake River steelhead), etc.)
(3) Energy/System effects (e.g., estimates of energy loss, impacts to system reliability, etc. that affect the authorized project purposes of the FCRPS);
(4) Monitoring/information constraints (e.g., impacts to our regional ability to generate juvenile survival estimates within the Lower Granite to Bonneville Dam reach, potential value of PIT tag detection capabilities at Lower Granite Dam, etc.);
(5) Logistical constraints (e.g., the need for alternative spill patterns, the number of years required to yield a statistically valid result, appropriate metrics for assessing the test, etc.);
(6) Comparison of adult returns, SARs, TIRs etc. starting with the 2010 outmigration (following installation of surface passage routes and other major structural improvements to the mainstem FCRPS dams), with past performance under previous configurations; and
(7) Independent review of (a) data to address potential spurious correlations and (b) alternative experimental design proposals (by the ISAB or other qualified entities).