Review of Studies of Fish Survival

in Spill at The Dalles Dam

Independent Scientific Advisory Board

Northwest Power Planning Council

National Marine Fisheries Service

851 S.W. 6th Avenue, Suite 1100

Portland, OR 97204

Peter A. Bisson

Charles C. Coutant

Daniel Goodman

Robert Gramling

James Lichatowich

Eric Loudenslager

William Liss

Lyman McDonald

David Philipp

Brian Riddell

Richard R. Whitney

ISAB Report 2000-1

February 15, 2000
ISAB 2000-1 The Dalles Spill Review

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Review of Studies of Fish Survival in Spill at The Dalles Dam

Contents

Assignment................................ ................................ ................................ ............................... 1

Summary of Response ................................ ................................ ................................ ............. 1

Review Process ................................ ................................ ................................ ........................ 1

Background ................................ ................................ ................................ .............................. 2

Description of Studies ................................ ................................ ................................ ............. 3

Results of Studies ................................ ................................ ................................ .................... 3

Answers to Questions ................................ ................................ ................................ .............. 4

Concluding Remarks ................................ ................................ ................................ ............. 11

References ................................ ................................ ................................ .............................. 12

Appendix 1. Materials supplied for ISAB Review (in addition to those listed in the

references) ................................ ................................ ................................ .............................. 14

Appendix 2. Relative Passage Survival of Juvenile Salmon at The Dalles Spillway and

Ice and Trash Sluiceway, 1997-99. ................................ ................................ ....................... 16

Appendix 3. Day vs. Night -- Adult vs. Juvenile Spill Pattern, 1997-99 Data Combined

................................ ................................ ................................ ................................ ................. 17

Appendix 4. Estimated Total Project Survival at The Dalles Dam at the Two Spill Levels

................................ ................................ ................................ ................................ ................. 18
ISAB 2000-1 The Dalles Spill Review

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Review of Studies of Fish Survival in Spill at The Dalles Dam

Assignment

The Independent Scientific Advisory Board (ISAB) was asked in a memo dated

November 10, 1999 from Brian J. Brown, Chair, Implementation Team (IT), addressed to

Michael Schiewe and Chip McConnaha, to review the issue of appropriate spill levels at

The Dalles Dam. The IT asked the ISAB two specific questions: Question 1. Based upon

a comprehensive review and analyses of the study design, methodology, empirical data

and results, are there real and significant differences between the survival of fish through

30% and 64% spill levels at The Dalles Dam? Question 2. Based on a comprehensive

review and analyses of existing empirical data, what are the most appropriate future

research steps, including a recommended study design and methodology, to determine an

operational plan at The Dalles Dam that maximizes juvenile passage survival?

Summary of Response

The studies of 1997-1999 did not include all relevant factors influencing the

mortality of juvenile salmon, but as designed the studies were conducted well and with as

high a level of scientific quality and rigor as can be expected from field studies

constrained by fish availability and dam operations. The weight of evidence suggests that

it is likely that there are real and significant differences in survival of spilled smolts

between spill levels of 30% and 64%, with 64% spill probably resulting in a lower per

capita survival rate. Rather than conducting further studies of survival in spill at either

high or low spill for an entire migration season, we recommend concentrating on several

spill levels in the 30% to 50% range. In future experiments, test spill levels should be

maintained for approximately a week. Required fish sample sizes likely limit

experiments to two spill levels per year. The results at The Dalles cannot be generalized

to other projects because of the unique characteristics of this project.

Review Process

The ISAB reviewed the materials supplied to us by the Systems Configuration

Team (Bill Hevlin, NMFS, personal communication). A subcommittee of the ISAB

attended the U.S. Army Corps of Engineers’ 1999 Annual Research Review of the

Anadromous Fish Evaluation Program held in Walla Walla, Washington, November,

1999. Earl Dawley, NMFS, Tim Counihan, USGS-BRD, Shane Bickford, Douglas

County PUD, Gene Ploskey, USACE, and Bob Heinith, CRITFC presented their research

results at our January 5 and 6, 2000 ISAB meeting in Portland. They were asked to

review research results and to answer a list of questions supplied to them in advance of

the meeting. The presenters provided relevant reports and hard copy material to the ISAB

(all materials are identified in the reference list or Appendix 1).
ISAB 2000-1 The Dalles Spill Review

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Background

There has been controversy for over 20 years about spilling water at The Dalles

Dam for the benefit of migrating juvenile salmon. At a general level, many people

believe that more spill is better for fish passage and survival. Reducing spill has been

thought to be detrimental to survival, because it forces more fish through the turbines,

where mortality is believed to be high. The studies conducted so far at The Dalles have

not convinced all parties that one spill level is better than another or that the best

experimental protocol has been followed to determine an optimum spill level. Several

alternative experimental designs have been proposed. The IT asked the ISAB to provide

an independent assessment of the situation, with emphasis on interpretation of the study

results to date and guidance on future research.

Despite some evidence that spill at high levels at The Dalles Dam might be

detrimental to survival (hydraulic models showed tailrace conditions potentially

detrimental to juvenile salmonids above about 40% spill (Dawley et al. 1998)), NMFS’s

1995 Biological Opinion set the goal of high spill, purportedly to achieve an 80% fish

passage efficiency (proportion not going through turbines; FPE). The specific reference

to 64% spill comes from calculations in NMFS reports referenced in the Biological

Opinion. Preference for high spill did not consider survival during spillway passage or in

the tailrace where predation may be high. Presently, there is a working hypothesis that

predator concentrations may be especially severe at certain tailrace locations, e.g., the

sluiceway outfall near the powerhouse (a third route for passage). A working hypothesis

also exists that predators concentrate around a set of islands on the south side of the

tailrace and the river downstream, potentially leading to high mortality of juvenile

salmonids entering that area of slowly moving water.

Most recent evaluations have neglected earlier studies at The Dalles Dam by

Willis (1982), that showed that the 80% fish passage goal of NMFS and the Council

could likely be achieved with about 40% spill. He released marked fish upstream from

the dam and recovered them in the sluiceway. He also showed that spill draws fish away

from the sluiceway, which is effective at passing fish, at a non-linear rate.

In 1995, NMFS began to evaluate spill levels at The Dalles Dam to find an

optimal level for smolt survival through the project. In a memorandum to the IT dated

April 15, 1999, Brian Brown stated the NMFS perspective that “The purpose of the 1999

The Dalles Spillway Study [subsequent to 1995-1998 studies] is to add critical

information regarding the spillway route. In subsequent years, once concerns about the

potential effects of the current spill level are better understood, NMFS will work to

develop necessary information on sluiceway survival, mortality mechanisms, possible

structural modifications, and other relevant information.” The memorandum also states

“Determination of an optimum spill level will require a more complete assessment of fish

passage efficiencies and survivals through all routes of passage at The Dalles Dam... ”. In

addition, the Brown memorandum provided perspective on the specific spill levels used

in the studies. “...NMFS is not saying that either 30% or 64% is the appropriate spill

level for the purposes of the more [all encompassing] project survival estimation that we
ISAB 2000-1 The Dalles Spill Review

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hope to begin in 2000. Rather, these are the parameters selected for the test to maximize

the differences between alternative spill levels and thus confirm or refute other

information that is the basis of NMFS’ concerns.” The ISAB believes that recognition of

this overall perspective is important for resolution of current controversies.

Description of Studies

NMFS first designed a study to evaluate FPE under field operating conditions,

starting in 1995 with radiotelemetry and in 1996 with hydroacoustics. Survival tests were

initiated in 1997 using relative recovery rates of PIT-tagged fish released above the

spillway and at a “reference” location below The Dalles Dam. The PIT-tagged fish were

subsequently detected at Bonneville Dam and below. A comparison of survival in spill

has been made between high spill (64%) and low spill (30%), to conform to NMFS’

objectives stated in the Brian Brown memorandum of April 15 quoted above – to

maximize the difference between alternative spill levels in order to increase the

likelihood of detecting differences in survival. The survival studies conducted are,

however, complicated by different spill locations and daytime and nighttime regimes for

spill patterns and different volumes of river discharge, especially between years. The

comparative study of the effects of high (64%) and low (30%) spill was begun in 1997

but high runoff precluded doing the 30% spill regime that year and data were obtained

only for 64% spill. In 1998 and 1999, both levels were tested.

Hydroacoustic studies were conducted in 1996, 1998 and 1999 to estimate

percentages of fish that passed The Dalles Dam by way of the three passage routes (spill,

sluiceway and turbines) under the two different spill conditions (Ploskey et al.,

presentation at the January 6 ISAB meeting and 1999 draft report). Radio tracking of

juvenile and adult chinook salmon and steelhead was also conducted at The Dalles Dam

in 1999 (Allen et al. 1999, Hansel and Beeman 1999, T. Counihan, USGS, personal

communication).

Results of Studies

The results to date generally have confirmed that higher percentages of spill

carried more fish through that route of passage resulting in fewer fish going through the

sluiceway or turbines. Contrarily, reduced spill caused relatively more fish to go through

the sluiceway and through the turbines (Ploskey et al. 1999, Hansel and Beeman 1999).

Thus, strictly from a passage-route perspective, higher spill appears to be effective as a

means of increasing FPE without reference to project survival.

However, the objective is survival through the project. If the survival rate in spill

is the same at both spill levels and higher than in passage through turbines and sluiceway,

then there is a gain in total survival by having more water spilled. For clarity, we need to

be specific about whether we are considering only relative survival in spill or total

survival past the project including all passage routes. The studies so far have concentrated

on comparing survival in spill at the two spill levels (as this survival is affected by the
ISAB 2000-1 The Dalles Spill Review

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environment experienced to the point of detection at Bonneville Dam or below) and not

the effect of spill on overall survival past the project.

The numerical results of NMFS PIT tag studies are presented in Appendix 2. We

base our analysis on these data. However, the level of precision of point estimates within

years and seasons is low (i.e., there is low power within years and seasons) and hence we

use the consistency of relationships between survival in spill at the two spill levels in

arriving at overall conclusions. Consistent relationships are not expected unless there are

real differences in effects of the two spill levels.

The three years of survival studies have consistently shown that the point

estimates of survival of fish passing in spill at the 30% level are larger than the survival

of fish passing in spill at the 64% level. Our conclusion is that survival of fish in 64%

spill is not equal to the survival of fish in 30% spill. In fact, there is an indication that the

survival of fish in 64% spill is less than survival of fish in 30% spill, although the strict

interpretation of statistical significance would leave the answer equivocal. If survival of

fish passing the spillway at 64% spill is truly lower than survival of fish passing the

spillway at 30% spill then the increased FPE may not compensate for the assumed higher

mortality during turbine passage (or sluiceway passage). This is the core of the

controversy, and it is discussed further below.

Based on the velocity maps we reviewed, the hydraulics of the tailrace and river

reach through the islands varies with river discharge and percentage of spill. At lower

river discharge rates and low spill, the water from both spillway and powerhouse passes

mostly in the deep channel at the north side of the tailwater. Only a small portion of the

total river flow, much of it derived from the powerhouse, flows among the bridge islands.

At higher discharges and percentages of spill, the water spreads out southwestward

among and over the islands. Velocities are slower in the islands and there are more

eddies. These hydraulic relationships with discharge and spill are critically important for

understanding overall smolt survival because the islands include habitat for predators and

they create eddies in which smolts can be delayed.

Answers to Questions

Based on our analysis, the ISAB has the following responses to the two questions asked

by the Implementation Team.

Question 1. Based upon a comprehensive review and analyses of the study

design, methodology, empirical data and results, are there real and significant differences

between the survival of fish through 30% and 64% spill levels at The Dalles Dam?

Answer

The short answer is that there probably are differences. The evidence is strongest

that survival in spill at the 64% level is somewhat lower than survival in spill at the 30%
ISAB 2000-1 The Dalles Spill Review

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level. This answer should not be taken at face value, however, without considering the

following analysis.

Study Design and Methodology . The study design employs what has become a rather

straightforward application of the paired release method of estimation of relative survival,

and as such provides useful, though limited, estimates of survival. The study design could

be improved to provide more information, as we note in detail in the answer to question 2

below. The methodology also appears to conform to current standard practice for this sort

of design.

Results. While the study results suggest that survival at the two spill levels is probably

not the same, the extent of the difference is quite variable and seems to depend on

covariates not accounted for. The confidence intervals for the point estimates of survival

at the two spill levels show that the differences in survival between 30% spill and 64%

spill could be large in some cases (e.g., 1998). On the other hand, the 1999 studies

suggested that any differences might be quite small. However, none of the studies

suggested that survival at 64% spill was higher than 30% spill, i.e. all of the estimates of

survival at 30% spill are higher than or approximately equal to those at 64% spill. In the

summer of 1998, tests with fall chinook resulted in particularly low estimates of survival.

The point estimate for 64% spill was 25% mortality and for 30% spill it was 11%

mortality. These estimates could represent no more than ordinary variation in sampling

or some breakdown in the study protocol. On the other hand, they could represent real

estimates of survival of particular groups such as fall chinook under certain conditions,

and in that case should be a stimulus for action to correct a possible problem.

These data suggest that survival at night is higher than during the day (Appe ndix

3). This would comport with the hypothesis that predation may be a factor in survival of

juvenile salmon passing in spill at The Dalles Dam and so is not unexpected. The rate of

survival also seems to be best at the so-called juvenile spill pattern that concentrates spill

near the north shore.

Are there Real and Significant Differences ? Low detection rates for PIT tagged fish at

Bonneville Dam and sites downstream, combined with constraints on the numbers of fish

released, and a limited number of replications of the study (years) do not allow

statistically definitive conclusions regarding the differences in survival of the study fish

at the two spill levels. Biological significance of any difference would be defined in this

case as being a difference in rate of survival associated with spill passage that would

affect the total survival of fish passing the project to a degree that would be of concern to

the IT. The degree of difference that would be of concern remains to be specified by the

IT. No one really knows the level of difference that would be biologically significant for

populations of migrants.

The basic question regarding biological significance is whether total survival of

juveniles passing The Dalles Dam would be different at 64% than at 30% spill, taking

into account different passage routes. To arrive at an estimate of total survival requires

combination of several estimates, including 1) the estimate of survival in spill, 2) an
ISAB 2000-1 The Dalles Spill Review

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estimate of survival in the sluiceway and 3) an estimate of survival through the turbines,

along with 4) estimates of the portions of total fish approaching the dam that pass through

each of the three routes at each spill level. From the hydroacoustic and radio tracking

studies, as well as the studies of Willis (1982), estimates of the portions of fish passing by

the three routes at various spill levels are available. An estimate of survival in sluiceway

passage was made in the 1998 study only. The summary data provided to the ISAB

included graphs showing estimates of total project survival in the 3 years 1997, 1998 and

1999. We transcribed those graphs into tabular form (Appendix 4). The numbers are

useful in identifying the effects of converting the estimates of survival in spill into

estimates of total survival. With the spring studies, the effects of converting point

estimates of survival in spill into estimates of total survival were small, less than 2% and

the average effect was to reduce the estimate of survival in spill by less than 1%.

Therefore, the IT might reasonably conclude that its decisions on spill in the spring could

be based upon the point estimates of survival in spill, without the need to adjust to total

survival (assuming coho are a reasonable surrogate for spring chinook). These survival

estimates in spill have the further advantage of being provided with confidence intervals

to assist in interpretation of any differences. On the other hand, the estimates of total

survival for summer migrants ( fall chinook subyearlings) differed by as much as 5% from

the estimates of survival in spill, a reflection of the poor guidance efficiency of these fish

as estimated by hydroacoustics. Decisions on summer spill levels should be made based

on expected values of total survival, and not survival in spill alone.

There is a strong suspicion that the high volume of river discharge experienced

during the 1997 study may have been responsible for the low survival estimate that

resulted. Not only was the percentage of spill high (64%), but the volume of water spilled

was especially high. Photographs of the dewatered tailwater in Normandeau Associates,

Inc. et al. (1996) show the physical hazards to spilled migrants in the form of concrete

baffles and a vertical end sill in the tailwater. Unfortunately, the high discharge in that

year precluded study at the 30% spill level, so it is impossible to judge from the existing

data whether spill survival at that level would also be lower at high river flows. We

discuss this issue further in response to question 2, as it bears on the issue of study

design.

Question 2. Based on a comprehensive review and analyses of existing empirical data,

what are the most appropriate future research steps, including a recommended study

design and methodology, to determine an operational plan at The Dalles Dam that

maximizes juvenile passage survival?

Answer

The short answer is that a new study design is needed, one that incorporates

covariates, concentrates on spill levels in the 30% to 50% range, and alternates

experimental spill levels within a year. The following points support this answer.
ISAB 2000-1 The Dalles Spill Review

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1. A basic change is needed in the design and analysis of passage survival studies of

juvenile anadromous fishes in the Columbia Basin to take advantage of new

developments that allow for inclusion of covariates in the analysis. The design and

analysis of release-recapture studies presented in Burnham et al. (1987) represent the

basis for the current design and analysis of most of the PIT tag and radio telemetry

survival studies conducted in the basin. Results in that book were constrained by two

problems: first, the perceived need to use batch marks on fish in a given treatment or

control group, and second, models for measuring and assessing the effects of unique

covariates of individual tagged fish were not yet developed (Lebreton et al. 1992, Skalski

et al. 1993). Use of the models of Lebreton et al. and Skalski et al. and extensions of

these models not only eliminate the need for some of the assumptions required by the

models of Burnham et al., but allow the prediction of the effect of covariates such as

route of passage on survival from radio-telemetry studies and number of detections in

bypass systems from PIT-tag studies. We recommend that these newer approaches be

adopted in subsequent studies.

2. Given that PIT-Tag detection is not presently possible at The Dalles Dam, and

that PIT-Tag detection at Bonneville Dam and beyond is lower than radio-tag detection,

both radio telemetry and NMFS PIT-Tag survival studies should be conducted. Both

approaches to survival studies will produce information useful in development of an

operational plan that maximizes juvenile passage survival. These two techniques offer

overlapping, but complementary possibilities, and production of some unique information

concerning survival of juvenile anadromous fishes during their migrations. Procedures

for conducting radio-telemetry studies should continue to be developed and improved for

use in solving unique passage problems over relative short reaches of the rivers.

Investigators need to be reminded, however, that recent studies have shown that estimates

of survival of radio tagged fish may be compromised after useful, but limited time

periods and travel distances (Shane Bickford, personal communication, Hockersmith et

al. 2000). An additional problem arises in judgements as to which radio tag detections are

legitimate versus some that are spurious. We believe this problem can be dealt with in a

properly designed study. We note that the same problem was encountered early in

development of hydroacoustic technology and adjustments had to be made, recognizing

that absolute certainty will not be achieved.

3. Data from radio-telemetry and PIT-TAG studies in the basin are under-analyzed,

including the 1999 radio-tag study conducted at The Dalles Dam ( Counihan et al. 1999).

More useful information can be extracted, which may reduce the need for some

additional field studies. Analysis of past and future radio-tag and PIT-Tag data should

include consideration of methods for estimation of the effects of covariates measured on

individual fish including: route of passage, size of fish, species, hatchery or wild, etc.

(Lebreton et al. 1992, Skalski et al. 1993). Survival by route of passage (turbine,

sluiceway, or spill) as a function of characteristics of dam operations (% spill, volume

spill, tailrace flow conditions, etc.) at the time of passage and characteristics of the

individual fish (size, species, hatchery or wild, etc.) can be modeled and estimated by

techniques which are over seven years old. PIT-Tag data from above Lower Granite and

above the mid-Columbia dams to below Bonneville Dam should be analyzed by these
ISAB 2000-1 The Dalles Spill Review

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techniques which allow the separate estimation of the effects on survival of covariates

such as size and the number of times a fish is detected in bypass systems.

4. The current proposal for passage survival studies at The Dalles Dam in 2000

(Dawley, et al. 1999b) is an observational monitoring and evaluation study of fixed

operating conditions that seems to offer little new in the way of information useful for

optimizing an operational plan at The Dalles Dam. What is needed is a study to continue

to evaluate several spill levels and establish optimum operating conditions. The proposal

should be modified to incorporate suggestions we made in the three paragraphs above.

It appears, judging by the description in the Methods section, that the design of

the study is hampered by a shortage of fish for marking, as well as the low recovery rates

at Bonneville Dam and below. A useful exercise would be to provide an estimate of the

numbers of fish and recoveries that would need to be employed in order to achieve

estimates of some specified precision. This procedure was used by Normandeau

Associates et al. (1996) to good advantage. The IT should be asked to specify a

biologically significant difference in survival they would hope to detect in the study, and

the study designed accordingly. Otherwise, further studies may only arouse further

controversy.

5. There is little justification for studying spill levels as high as 64% in a continuing

optimization study. The weight of evidence suggests that this level is too high for good

smolt survival. Other levels need testing. However, we are not comfortable with the

conclusion implicit in the study proposal for 2000 that 30% spill is optimum and that it

should be the sole focus of study. With a single fixed spill level each year varied among

years, one can expect the common criticism of observation studies that “this year was

different” and comparative results among years cannot be trusted for decision making.

Studies with a fixed spill level for the entire migration study would not seem to provide

sufficient information for decisions to be made within a reasonable number of years.

One argument for a fixed level of spill throughout a test year was the suspicion

that predators fail to establish territories under the test conditions when flows are

switched back and forth within a few days. This failure would result in higher survival

during switching years than if constant flow were tested. However, setting a constant

percentage of spill does not ensure a constant volume of spill and thus constant predator

habitats throughout spring and summer. Predator habitats are bound to change with

changes in volume of spill even as percentages are held relatively constant. Tests should

be conducted at different spill levels within a year, but holding the spill conditions longer

than previously. Perhaps a week would be sufficient. A concurrent study of predators

and their movements at different flows and spill levels would help interpret the results of

survival studies.

It is difficult for the ISAB to make specific recommendations for study design,

because we are not aware of all logistical constraints, including fish availability and

operation of the hydropower system. We understand that other levels, such as 40% and

50% are being considered. The 40% level is of interest, because Willis’ (1982) estimates
ISAB 2000-1 The Dalles Spill Review

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of spill efficiency suggest something around 40% might lead to the 80% FPE, which is

NMFS and the Council’s goal. Arguments might still be made for further tests at higher

levels, because such spill will occur naturally at times of high flow.

6. Unanswered questions

Legitimate unanswered questions remain regarding expected survival rates during

high flow years and/or a constant 30% spill rate. For example, constant 30% spill rate

may allow predators to increase predation rates on juvenile anadromous fish relative to

the alternating spill pattern (cycling between 30% and 64%) utilized in 1998 and 1999.

Additional effort to answer these questions could clarify the results obtained so far.

There is an unanswered question about the cause of the somewhat higher

mortality in releases from the south spill bay (difference of 3%) compared to releases

from the north bays found by Normandeau Associates Inc. et al. (1996). Information from

the radio tracking study documents “predation events” that were more frequent during

spill from the south spill bays than the north bay, or from control releases near the north

shore. Residence time of radio tagged fish in the tailrace was longer when spill came

from the south bays versus the north at both 30% and 64% spill levels. Evidently, total

residence time was lower at 64% than 30%. The location and cause of higher mortality

from south bay releases need to be identified.

A study useful for the IT decisions might be designed to attempt to reconcile the

differences between the survival estimates of Normandeau Associates Inc. et al. (1996)

and those of Dawley et al. (1998, 1999a). The technique employed by Normandeau et al.

estimated direct mortality in spill at north and south spill bays (1% for the north and 4.5%

for the south). Dawley et al.’s 1999 estimate (4% mortality in spring) includes elements

of indirect or delayed mortality, and the method released fish upstream of the center of

the spillway, so the fish might have passed through a mix of north and south spill bays. It

might be useful to the IT to design a study to locate or identify the cause of the apparent

3% difference in the estimates. Such a design would have to take into account the rather

large sample sizes needed to detect an expected 3% difference.

7. A study plan should be d eveloped to obtain further estimates of juvenile survival

in passing through the sluiceway and through the turbines, which are next on NMFS’ list,

according to the Brian Brown memo cited. We have previously noted that such estimates

ought to be possible using the radio tracking data already available. Future verification

by concurrent PIT tag and radio tracking studies would be desirable, as we suggested

above. These could be compared to the 1998 estimate of Dawley et al. (1998) for

verification. These studies could show opportunities for major improvements in guidance

efficiency and survival by using the sluiceway more effectively.

8. Considering the likely importance of tailwater hydraulics to passage routes, travel

times, physical damage during spill, and probable predation losses around the islands,

additional study of both fish trajectories and hydraulics at different spill levels and river

discharges could be useful for interpreting overall survival through the project. Further

data analysis and synthesis of existing hydraulic and fish data may suffice.
ISAB 2000-1 The Dalles Spill Review

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9. In addition to the suggestions provided above, we give below our specific

recommendations for the design and analysis of future passage survival studies at The

Dalles Dam in 2000, realizing that many details need to be filled in by the Principal

Investigators and Implementation Team. Our recommendations for future study design

and analysis are:

a. More than one spill level should be included in the study, with spill varied over time

periods that would allow some stability to develop in local conditions, perhaps oneweek periods rather than the three-day periods used previously. This would provide

contrasts among levels of important covariates, help identify sources of mortality and

allow modeling of survival in radio telemetry and PIT-tag studies. The design should

include scheduled variation in spill percentage, spill volume, tailrace conditions, etc.

The design should also include radio-telemetry studies of aquatic predators and visual

(or radio-telemetry) observations of avian predators to evaluate distribution of

predators under different spill conditions and the changes, if any, in distribution under

different dam operations.

b. Analyze flow patterns and other hydraulic characteristics that might help adjust the

spill volume (or percentage) relative to sluiceway and powerhouse volumes (or

percentages) to avoid predation and physical injury. Attempt to identify the flow

conditions (splits between powerhouse, sluiceway, and spill, including high flow

conditions) that might lead to high survival. Develop working hypotheses around

which future work could be focused.

c. Use both radio-telemetry and PIT-Tag methods in 2000 to estimate survival by route

of passage so that results can be compared and possible biases eliminated. Maintain

strict randomization in assigning personnel, equipment, and fish to treatment groups

and other quality control to ensure comparable sources of test fish, and equal handling

and transport conditions. Maximize detection probabilities for radio tagged fish to

improve the precision of the estimates as much as is practical.

d. Evaluate the use of one release site for radio-tagged fish rather than one release site

above and one below The Dalles Dam. If a valid sample of run of the river fish are

radio-tagged (i.e., no selection bias), then we see no reason to use two release sites

and suggest that the sample should be concentrated and the sample size increased by

releasing all fish under common conditions above The Dalles Dam. Further, evaluate

if radio-tagged fish released at John Day Dam can be monitored at The Dalles Dam

for the radio-telemetry study of passage survival at The Dalles Dam.

e. Consult with Drs. John R. Skalski and Steve G. Smith on appropriate analyses to fully

utilize currently available and future information and estimate effects of covariates

(route of passage, % spill, volume spill, fish size, etc.) on passage survival of

anadromous fishes from both radio-telemetry and PIT-Tag studies.

f. Use juvenile survival estimates rather than adult returns as a criterion. Evaluation of

the optimum operating conditions at a dam will realistically have to be based on

estimated survival rates of juvenile passage because estimation of adult return rates

associated with different routes of passage would require very large sample sizes and

results would potentially be confounded with downstream operations. Although it is

logical that decisions about operating regimes should be based on adult returns rather
ISAB 2000-1 The Dalles Spill Review

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than juvenile passage, this approach is not attainable now. However, this need

underscores the urgency of fitting dams for better monitoring of tagged adult returns,

better ability to track PIT-tag detections throughout the life cycle and better ways to

effectively search the databases for relevant, long-term survival data.

g. Recognize that tests will not represent all species and life stages. The Radio tracking

study has shown there is a difference in FPE between species (yearling chinook and

steelhead). We recognize that there is a practical limit on the size of fish that can be

PIT tagged successfully, i.e. without inducing undue mortality. The IT needs to be

aware of that problem and to err on the side of being conservative in the absence of

complete knowledge as to differences among species and stocks.

Concluding Remarks

While the 1997-1999 studies did not include all factors influencing mortality of

juveniles, we find that they were conducted well and all reasonable attempts were made

at scientific quality and rigor. They are not perfect, and the region should not expect them

to be. To expect more is unreasonable and reflects a lack of appreciation of the

difficulties of conducting such field studies. However, improvements and logical next

steps can be made based on experience, and these should be tried.

Evaluation of the 1997-1999 survival studies represents a balancing between

scientific (statistical) rigor and professional judgement based on weight of evidence.

Mathematical rigor of hypothesis testing in the complex environment of river and dam

operations is difficult to attain, in spite of noble attempts. Thus, we can often be grateful

for rigor when it is successful but must accept less rigorous (if often subjective)

impressions when that is most of what we have. We applaud the attempts of the

investigators to attain rigor and hope that the research continues in that direction.

The weight of evidence of several years of study appears to us to be as follows:

1. Mortality of smolts at high spill rates (represented by 64%) in the spring is

somewhat higher than at 30% spill. Details of comparisons with 30% spill

and related statistics not withstanding, the level of mortality estimated in

the summer (possibly as high as 11% - 25%) should not be allowed to

persist at any spill levels. Mortality in summer at both spill levels in 1998

was estimated to be at or above levels expected from passage through

turbines. Although an experiment comparing survival in passage through

alternative routes has not yet been done at The Dalles, the generally

accepted mortality rates for turbines and preliminary results for spillway

survival can be used for comparison.

2. There seems to be no technical reason to manage project operations to

obtain high spill percentages at The Dalles, if maximal survival is the

objective. The 80% passage efficiency goal can likely be achieved with

40% spill. On the other hand, high spill levels will continue to occur

naturally at high flows, which speaks to the desirability of developing a

better understanding of the low survival estimates at high spill levels.
ISAB 2000-1 The Dalles Spill Review

12

3. The possibility of differences in survival in spring and summer are

difficult to interpret because the test animals were different species and

different in size. There may be differences in behavior or ability to

maintain their orientation. This might result in different routes taken in

the tailrace.

4. There is evidence from both hydraulic models and field studies that at

lower spill more water remains in the main channel, whereas at higher

rates of spill more water overflows the channel and flows among the

bridge islands and islands immediately downstream. The islands slow

water and fish passage, allowing greater opportunity for predation. The

combination of more physical damage in the spillway stilling basin (such

as from striking the momentum-breaking concrete structures) and a

trajectory of damaged fish through predator-laden islands at high spill

would logically add up to heavy losses.

5. The results of studies of survival in spill at The Dalles Dam can not be

generalized to other projects. This project is unique in several respects,

with its shallow stilling basin and downstream islands concentrated on one

side of the river where flow from the powerhouse is concentrated and

where high spill flows spread out.

6. More studies to refine the contrast between 64% and 30% spill are not

likely to provide much stronger evidence than we already have, unless

sample sizes can be increased. Another year will probably only add its

own suite of complications. It would be more productive to move to a next

phase of refining the estimates of survival at lower spill levels in

conjunction with concurrent estimates of survival in the other two routes

of passage, turbines and sluiceway. In this context, survival studies in the

year 2000 of spill rates of about 30%, and 50%, using multiple techniques,

would help define an optimum spill level. If resources and study fish are

available, a third level at about 40% spill would help define the

relationship between survival and spill parameters.

References

Allen, M. B., and 8 co-authors. 1999. Movement, distribution and behavior of radiotagged yearling and subyearling chinook salmon in the tailrace of The Dalles Dam,

1999. U.S. Geological Survey, Cook, Washington.

Burnham, K.P., D.R. Anderson, G.C. White, C. Brownie, and K.H. Pollock. 1987.

Design And Analysis Methods For Fish Survival Experiments Based On ReleaseRecapture. Monograph 5, American Fisheries Society, Bethesda, Maryland.

Counihan, T.D., N.S. Adams, R.S. Shively, H.C. Hansel, and T.P. Poe. 1999. The

feasibility of using statistical methods to extract survival information from the John

Day and The Dalles Dams radio tag studies. Abstract: Anadromous Fish Evaluation

Program 1999 Annual Research Review, U.S. Army Corps of Engineers, Walla

Walla, WA.
ISAB 2000-1 The Dalles Spill Review

13

Dawley, E.M., L.G. Gilbreath, E.P. Nunnallee, and E.P. Sandford. 1998. Relative

survival of juvenile salmon passing through the spillway of The Dalles Dam, 1997.

National Marine Fisheries Service, Seattle, WA. 26 p. plus appendixes.

Dawley, E. M., L. G. Gilbreath, R. F. Absolon, B. P. Sandford, and J. W. Ferguson.

1999a. Relative survival of juvenile salmon passing through the spillway and ice and

trash sluiceway of The Dalles Dam, 1998. National Marine Fisheries Service, Seattle,

Washington.

Dawley, E.M., R. Absolon, and C. Ebel. 1999b. Research Proposal to the U.S. Corps of

Engineers: Relative Survival of Juvenile Salmon Passing Through the Spillway and

Ice and Trash Sluiceway of The Dalles Dam. National Marine Fisheries Service,

Seattle, WA.

Hansel, H. and J. Beeman. 1999. Estimates of Fish-, Spill-, and Sluiceway-Passage

Efficiencies of Radio-tagged Juvenile Chinook Salmon and Steelhead at The Dalles

Dam. Abstract in Anadromous Fish Evaluation Program 1999 Annual Research

Review. November 1999. US Army Corps of Engineers, Walla Walla, WA.

Hockersmith, E.E., W.D. Muir, S.G. Smith, B.P. Sandford, Noah S. Adams, J.M. Plumb,

R.W. Perry, D.W. Rondorf. 2000. Comparative Performance of Sham Radio-tagged

and PIT-tagged Juvenile Salmonids. US Army Corps of Engineers, Walla Walla and

Portland Districts, WA.

Lebreton, J.D., K.P. Burnham, J. Clobert, and D.R. Anderson. 1992. Modeling survival

and testing biological hypotheses using marked animals: case studies and recent

advances. Ecological Monographs 62: 67-118.

Normandeau Associates, J.R. Skalski, and Mid Columbia Consulting. 1996. Potential

effects of modified spillbay configurations on fish conditions and survival at The

Dalles Dam, Columbia River. Report to the U.S. Army Corps of Engineers, Portland

District, Portland, OR. 57 p. plus appendixes.

Ploskey, G. R., and 8 co-authors. 1999 Hydroacoustic evaluation of juvenile salmon

passage at The Dalles Dam: 1999. U.S. Army Corps of Engineers, Waterways

Experiment Station, Vicksburg, Mississippi.

Skalski, J.R., A. Hoffman, and S.G. Smith. 1993. Testing the significance of individual

and cohort-level covariates in animal survival studies. In: J.D. Lebreton, P.M. North,

editors. Advances in Life Sciences: Marked Individuals in the Study of Bird

Populations. Birkhaeuser Verlag, Basel, Switzerland pp. 9-28.

Willis, C. F. 1982. Indexing of juvenile salmonids migrating past The Dalles Dam,

1982. Oregon Department of Fish and Wildlife. Annual; Progress Report to U. S.

Army Corps of Engineers. Contract # DACW57-78-C-0056. 50pp
ISAB 2000-1 The Dalles Spill Review

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Appendix 1. Materials supplied for ISAB Review (in addition to those listed in the

references)

Bonneville Power Administration. 1999. The Dalles and John Day Spill, 1999 (3/2/00

Draft). Portland, Oregon.

Boyce, R. R. February 8, 1999 letter to Bill Hevlin and Jim Ruff, co-chairs of the System

Configuration Team. Oregon Department of Fish and Wildlife, Portland.

Boyce, R. R., and J. Nielsen. 1999. Memorandum to Implementation Team. Oregon

Department of Fish and Wildlife and Washington Department of Fish and Wildlife,

Portland and Olympia.

Brown, B. J. 1999. April 15, 1999 memorandum to Implementation Team. National

Marine Fisheries Service, Portland, Oregon.

Heinith, B. 1999. October 26, 1999 Memorandum to Bill Hevlin (NMFS). Columbia

River Inter-Tribal Fish Commission, Portland, Oregon.

Heinith, B., and T. Lorz. [2000] Memorandum to Independent Scientific Advisory Board.

Columbia River Inter-Tribal Fish Commission, Portland, Oregon.

Hockersmith, E. E., W. D. Muir, S. G. Smith, B. J. Sandford, N. S. Adams, J. M. Plumb,

R. W. Perry, and D. W. Rondorf. 2000. Comparative performance of sham radiotagged and PIT-tagged juvenile salmonids. National Marine Fisheries Service and

U.S. Geological Survey for U.S. Army Corps of Engineers. ( draft report; executive

summary and data tables only)

National Marine Fisheries Service. 1999. The Dalles Dam Survival Study 1999-2000+ (1

page). Seattle, Washington.

Nielsen, J. R. 1999. February 10, 1999 letter to Brian Brown (NMFS). Washington

Department of Fish and Wildlife, Olympia.

Normandeau Associates, Inc., J. R. Skalski, and Mid Columbia Consulting, Inc. 1996.

Potential effects of modified spillway configurations on fish condition and survival at

The Dalles Dam, Columbia River, prepared for U.S, Army Corps of Engineers,

Portland District, Portland, Oregon.

Rowan, J. 1999. October 26, 1999 letter to Bill Hevlin (NMFS). Bonneville Power

Administration, Portland, Oregon.

Sampson, D. 1999. April 14, 1999 letter to Will Stelle, Jr .(NMFS). Columbia River InterTribal Fish Commission, Portland, Oregon.
ISAB 2000-1 The Dalles Spill Review

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System Configuration Team. 1999. Agenda and information packet: The Dalles and John

Day technical discussion of passage information and proposals for spill and studies in

1999 (February 11, 1999). Attachment 1 - The Dalles Dam – Spillway – Sluiceway

Survival and Project FPE Tests (NMFS analysis of the information and proposal for

1999); Attachment 2 - January 21, 1999 memo from Michelle DeHart (Fish Passage

Center) to Brian Brown (NMFS); Attachment 3 - January 21, 1999 memo from Bob

Heinith (CRITFC) to Brian Brown; Attachment 4 – The John Day Dam Spill

Program, 1999, Draft Document CENWP-EC-E from the Portland District, Corps of

Engineers.

U.S. Army corps of Engineers. Undated. Several maps of velocities and current directions

in the forebay and tailwater of The Dalles Dam at different flow rates.
ISAB 2000-1 The Dalles Spill Review

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Appendix 2.
ISAB 2000-1 The Dalles Spill Review

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Appendix 3.
ISAB 2000-1 The Dalles Spill Review

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Appendix 4. Estimated Total Project Survival at The Dalles Dam at the Two Spill

Levels

(From graphs provided by NMFS at the January 5, 2000 briefing.)

(Point estimates of survival in spill are given in parentheses for comparison.)

A. Spring Season

From Radio Telemetry

Spill Level 1997 1998 1999

30% 95 (97) 93 (95)

64% 88 (87) 89 (89) 94 (94)

From Hydroacoustics

Spill Level 1997 1998 1999

30% 95 (97) 94 (95)

64% 88 (97) 90 (89) 93 (94)

B. Summer Season

From Hydroacoustics

Spill Level 1997 1998 1999

30% 89 (89) 95 (100)

64% 91 (92) 80 (75) 94 (96)

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