LABORATORY EVALUATION OF MODIFIED TRAVELING SCREENS FOR 

PROTECTING FISH AT COOLING WATER INTAKES 

A Thesis Presented 

by 

JONATHAN L. BLACK 

Submitted to the Graduate School of the 

University of Massachusetts Amherst in partial fulfillment 

of the requirements for the degree of 

MASTER OF SCIENCE 

May 2007 

Department of Wildlife and Fisheries Conservation 
LABORATORY EVALUATION OF MODIFIED TRAVELING SCREENS FOR 

PROTECTING FISH AT COOLING WATER INTAKES 

A Thesis Presented 

by 

JONATHAN L. BLACK 

Approved as to style and content by: 

________________________________________ 

Alexander J. Haro, Chair 

________________________________________ 

Martha E. Mather, Member 

________________________________________ 

Bernard J. Morzuch, Member 

________________________________________ 

 Matthew J. Kelty, Department Head 

Natural Resources Conservation
DEDICATION 

To my wife and children for their patience, my father for teaching me to write, 

and E.P.T. – my mentor and friend.
iv 

ACKNOWLEDGMENTS 

Thanks go to my advisor, Alex Haro who provided perceptive guidance 

throughout the process. I also wish to thank my committee members Martha Mather and 

Bernie Morzuch for their consideration and recommendations. I wish to thank everyone 

from Alden Research Laboratory for their input, support, hard work, and helpful reviews 

of the manuscript. Daniel Davis was involved in every aspect of this study and his 

critical advice was invaluable. Brian McMahon developed the facility design and was 

instrumental in its construction. Tom Cook, Greg Allen, Bob Richmond, Kevin Simes, 

Brian O’Coin, Jeremy Sinkus, Michael Briggs, and Michael Comeau all assisted in the 

design and construction of the facility. Ned Taft, Steve Amaral, and Ray Tuttle assisted 

in the development of the study design and shared their experience in overcoming 

logistical hurdles. Daniel Giza, Timothy Sullivan, and Anthony Quinta put in long hours 

marking, testing, and assessing fish. Nate Olken, Erica Matys, and Eric Grady also 

assisted in testing. Elgin Perry provided professional guidance in the statistical analysis. 

Funding for this study was provided by the Electric Power Research Institute 

(EPRI). Doug Dixon of EPRI provided frequent and extensive support without which 

this study would not have been possible. I would also like to thank Dave Michaud (WE 

Energies), Igor Cherko (Omaha Public Power District), Sonya Kim (Omaha Public Power 

District), Robert Reider (Detroit Edison), Michael Peters (Dairyland Power Cooperative), 

Brad Foss (Dairyland Power Cooperative) and John Thiel (Dairyland Power Cooperative) 

for their comments on the draft manuscript.
v 

ABSTRACT 

LABORATORY EVALUATION OF MODIFIED TRAVELING SCREENS FOR 

PROTECTING FISH AT COOLING WATER INTAKES 

MAY 2007 

JONATHAN L. BLACK, B.A., UNIVERSITY OF MASSACHUSETTS AMHERST 

M.S., UNIVERSITY OF MASSACHUSETTS AMHERST 

Directed by: Professor Alexander J. Haro 

Section 316(b) of the Clean Water Act requires thermal power generating 

facilities to minimize adverse environmental impact resulting from the operation of 

cooling water intake structures (CWIS). Adverse environmental impact can occur when 

aquatic organisms are impinged on traveling water screens. Modified traveling screens 

were developed to improve the post-impingement survival of organisms. These screens 

have been used at a few power plants and are now being considered at additional 

facilities to reduce the mortality of juvenile and adult fish. 

Existing biological efficacy data show that post-impingement survival is highly 

variable by species. The majority of previous installations are at estuarine facilities. As 

such, there is a lack of biological efficacy data with many of the freshwater species 

commonly impinged at CWIS. In addition, most of the existing modified screen 

installations were installed prior to 1990. Since that time, improvements in screen 

designs have increased survival. For these reasons, the existing biological efficacy of the 

new screen designs was limited and largely unknown for many freshwater species. 
vi

The mortality, injury, and scale loss rates of 10 species of freshwater fish 

impinged and recovered with a modified traveling screen were evaluated in the 

laboratory. Species tested included: golden shiner (Notemigonus crysoleucas); fathead 

minnow (Pimephales promelas); white sucker (Catostomus commersoni); bigmouth 

buffalo (Ictiobus cyprinellus); channel catfish (Ictalurus punctatus); hybrid striped bass 

(Morone chrysops × M. saxatilis); bluegill (Lepomis macrochirus); largemouth bass 

(Micropterus salmoides); yellow perch (Perca flavescens); and freshwater drum 

(Aplodinotus grunniens). 

Fish were impinged at 0.3, 0.6, or 0.9 m·s-1 velocity. Mortality, injury, and scale 

loss rates were generally low. Mortality rates did not exceed 5% for any species and 

velocity tested, indicating that this technology has potential to substantially reduce 

impingement mortality at CWIS. Despite a general trend toward increasing mortality at 

higher velocities, velocity was only a significant factor in the mortality of bluegill 

(P=0.0005). 

Injury and scale loss rates were low for most species tested, although they were 

more variable than observed rates of mortality. There was a trend toward lower 

mortality, injury, and scale loss in larger fish. In all cases where fish length was a 

significant factor (P<0.05), the pattern of decreasing mortality, injury, and scale loss as 

fish increased in length was constantly observed. 

Additional tests were undertaken with channel catfish, fathead minnow, and 

golden shiner to assess the effect of duration of impingement on mortality, injury, and 

scale loss. Longer durations of impingement appeared to result in higher mortality, 

injury, and scale loss, especially at durations of impingement greater than 6 minutes. 
vii

However, longer durations of impingement could be avoided at most cooling water intake 

structures by continuously rotating screens. 
viii 

CONTENTS 

Page 

ACKNOWLEDGMENTS ................................................................................................. iv

ABSTRACT .........................................................................................................................v

LIST OF TABLES ...............................................................................................................x

LIST OF FIGURES ......................................................................................................... xvi

CHAPTER 

1 Biological Evaluation of Modified Traveling Screens .....................................................1

Introduction ....................................................................................................... 1

Methods............................................................................................................. 4

Test Fish .......................................................................................................4

Fish Holding Facility ...................................................................................5

Test Facility .................................................................................................6

Velocity Measurements ...............................................................................7

Test Parameters ............................................................................................7

Fish Marking ................................................................................................9

Test Procedures ..........................................................................................10

Velocity Tests ................................................................................10

Duration of Impingement Tests .....................................................13

Data Analysis .............................................................................................15

Velocity Tests ................................................................................15

Duration of Impingement Tests .....................................................18

Results ............................................................................................................. 19

Velocity Tests ............................................................................................19

Time to Impingement .....................................................................19

Water Temperature ........................................................................20

Mortality ........................................................................................20

Injury ..............................................................................................22

Scale Loss ......................................................................................24

Duration of Impingement Tests .................................................................25

Discussion ....................................................................................................... 27
ix

APPENDICES 

A PHOTOS OF FACILITIES AND TESTING PROCEDURES .....................................43

B IMPINGEMENT ON TRADITIONAL TRAVELING SCREENS 

C WEEKLY TESTING, WATER SAMPLING, AND FISH CARE SCHEDULE ..........51

D COLLECTION TIME ....................................................................................................52

E STATISTICAL ANALYSIS TABLES – VELOCITY TESTS .....................................54

F STATISTICAL ANALYSIS TABLES – DURATION OF IMPINGEMENT ..............87

BIBLIOGRAPHY ..............................................................................................................94
x 

LIST OF TABLES 

Table Page 

1. Mean fork length (mm) ± standard error (SE), total number of fish tested (n), 

percent dead 48 hours after testing, and the 95% confidence intervals (CI) 

by species and velocity. Confidence intervals were calculated using the 

normal approximation of a binomial distribution. Freshwater drum, lacking 

forked tails, were measured to total length. .............................................................. 33

2. Summary of pertinent p-values from the maximum likelihood estimates for the 

mortality regression models for all species tested. (a

) Significant differences 

at p<0.05; (↓) mortality decreased significantly with increasing fish length; 

(+) treatment fish exhibited significantly greater mortality than the control. ........... 34

3. Percent injury by species and velocity. ........................................................................ 35

4. Summary of pertinent p-values from the maximum likelihood estimates for 

the injury regression models for all species tested. (a

) Significant differences 

at p<0.05; (↓) injury decreased significantly with increasing fish length; (+) 

treatment fish exhibited significantly greater injury than the control. ...................... 36

5. Percent of scale loss category by velocity and species. ............................................... 37

6. Summary of pertinent p-values from the maximum likelihood estimates for the 

scale loss regression models for all species tested. (a) Significant differences 

at p<0.05; (↓) scale loss decreased significantly with increasing fish length; 

(+) treatment fish exhibited significantly greater scale loss than the control. .......... 38

7. Mortality and injury rates (percent) by species and duration of impingement 

(DI) tests. ................................................................................................................... 38

8. Percent of scale loss categories by species and duration of impingement (DI). .......... 39

9. Summary of pertinent p-values from the maximum likelihood estimates for the 

mortality, injury, and scale loss regression models for species tested during 

duration of impingement (DI) testing. Metrics for measuring performance 

included: mortality (M), injury (I), total injury – control injury (I-C), and 

scale-loss (SL). (a

) Significant differences at p<0.05; (↓) metric (mortality, 

injury, or scale loss) decreased with increasing fish length; (↑) metric 

significantly increased with increase in DI. There were no injuries or 

mortality observed among channel catfish................................................................ 39

10. Comparison of laboratory results to those observed in previous pilot- and fullscale field evaluations. Data summarized from: Normandeau 1995 (Roseton); 

Beak Consultants 2000a (Dunkirk), Beak Consultants 2000b (Huntley); 

Fletcher 1990 (Indian Point); Consolidated Edison 1996 (Arthur Kill); PSE&G 

1999 (Salem); PSEG 2004 (Salem). ......................................................................... 40

D-1. Percent of fish collected by species, collection time, and velocity treatment. ........ 52
xi

E-1. Summary of live, dead, and mean length by velocity treatment for bigmouth 

buffalo. ...................................................................................................................... 56

E-2. Analysis of maximum likelihood estimates for the survival regression model 

for bigmouth buffalo. This model was not significant (P=0.8233). ......................... 56

E-3. Summary of injury rate and mean length by velocity treatment for bigmouth 

buffalo. ...................................................................................................................... 57

E-4. Analysis of maximum likelihood estimates for the injury regression model 

for bigmouth buffalo. This model was significant (P=0.0225) ................................ 57

E-5. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for bigmouth buffalo. ................................................................................ 58

E-6. Analysis of maximum likelihood estimates for the scale loss regression model 

for bigmouth buffalo. This model was significant (P<0.0001) ................................ 58

E-7. Summary of live, dead, and mean length by velocity treatment for bluegill. .......... 59

E-8. Analysis of maximum likelihood estimates for the survival regression model 

for bluegill. This model was significant (P<0.0001). .............................................. 59

E-9. Summary of injury rate and mean length by velocity treatment for bluegill. .......... 60

E-10. Analysis of maximum likelihood estimates for the injury regression model 

for bluegill. This model was significant (P<0.0001). .............................................. 60

E-11. Summary of injury rate and mean length by velocity treatment for bluegill 

excluding conspecific aggression injury. .................................................................. 60

E-12. Analysis of maximum likelihood estimates for the injury regression model 

for bluegill excluding conspecific aggression injury. This model was 

significant (P<0.0011). .............................................................................................. 61

E-13. Summary of frequencies of scale loss categories and mean length by 

velocity treatment for bluegill. .................................................................................. 61

E-14. Analysis of maximum likelihood estimates for the scale loss regression 

model for bluegill. This model was significant (P<0.0001). ................................... 62

E-15. Summary of live, dead, and mean length by velocity treatment for channel 

catfish. ....................................................................................................................... 63

E-16. Analysis of maximum likelihood estimates for the survival regression model 

for channel catfish. This model was not significant (P=0.6336). ............................ 63

E-17. Summary of injury rate and mean length by velocity treatment for channel 

catfish. ....................................................................................................................... 63

E-18. Analysis of maximum likelihood estimates for the injury regression model 

for channel catfish. This model was significant (P=0.0202). .................................. 64

E-19. Summary of live, dead, and mean length by velocity treatment for freshwater 

drum. ......................................................................................................................... 65
xii

E-20. Analysis of maximum likelihood estimates for the survival regression model 

for freshwater drum. This model was not significant (P=0.1903). .......................... 65

E-21. Summary of injury rate and mean length by velocity treatment for freshwater 

drum. ......................................................................................................................... 65

E-22. Analysis of maximum likelihood estimates for the injury regression model 

for freshwater drum. This model was significant (P=0.0002). ................................ 66

E-23. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for freshwater drum. ................................................................................. 66

E-24. Analysis of maximum likelihood estimates for the scale loss regression 

model for freshwater drum. This model was significant (P<0.0001). ..................... 67

E-25. Summary of live, dead, and mean length by velocity treatment for fathead 

minnow. .................................................................................................................... 68

E-26. Analysis of maximum likelihood estimates for the survival regression model 

for fathead minnow. This model was not significant (P=0.2147). ........................... 68

E-27. Summary of injury rate and mean length by velocity treatment for fathead 

minnow. .................................................................................................................... 68

E-28. Analysis of maximum likelihood estimates for the injury regression model 

for fathead minnow. This model was significant (P=0.0114). ................................. 69

E-29. Summary of injury rate and mean length by velocity treatment for fathead 

minnow excluding conspecific aggression injury. .................................................... 69

E-30. Analysis of maximum likelihood estimates for the injury regression model 

for fathead minnow excluding conspecific injury. This model was significant 

(P=0,0037). ............................................................................................................... 69

E-31. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for fathead minnow. .................................................................................. 70

E-32. Analysis of maximum likelihood estimates for the scale loss regression 

model for fathead minnow. This model was significant (P=0.0030). ...................... 70

E-33. Summary of live, dead, and mean length by velocity treatment for golden 

shiner. ........................................................................................................................ 71

E-34. Analysis of maximum likelihood estimates for the survival regression model 

for golden shiner. This model was significant (P=0.0003). ..................................... 71

E-35. Summary of injury rate and mean length by velocity treatment for golden 

shiner. ........................................................................................................................ 71

E-36. Analysis of maximum likelihood estimates for the injury regression model 

for golden shiner. This model was not significant (P=0.5768). ............................... 72

E-37. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for golden shiner. ...................................................................................... 72

E-38. Analysis of maximum likelihood estimates for the scale loss regression 

model for golden shiner. This model was significant (P<0.0001). .......................... 73
xiii

E-39. Summary of live, dead, and mean length by velocity treatment for hybrid 

striped bass. ............................................................................................................... 74

E-40. Analysis of maximum likelihood estimates for the survival regression model 

for hybrid striped bass. This model was not significant (P=0.9921). ...................... 74

E-41. Summary of injury rate and mean length by velocity treatment for hybrid 

striped bass. ............................................................................................................... 74

E-42. Analysis of maximum likelihood estimates for the injury regression model 

for hybrid striped bass. This model was not significant (P=0.9929). ...................... 75

E-43. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for hybrid striped bass. .............................................................................. 75

E-44. Analysis of maximum likelihood estimates for the scale loss regression model 

for hybrid striped bass. This model was not significant (P=0.3758). ...................... 76

E-45. Summary of live, dead, and mean length by velocity treatment for 

largemouth bass. ....................................................................................................... 77

E-46. Analysis of maximum likelihood estimates for the survival regression model 

for largemouth bass. This model was marginally significant (P=0.0549). .............. 77

E-47. Summary of injury rate and mean length by velocity treatment for largemouth 

bass. ........................................................................................................................... 77

E-48. Analysis of maximum likelihood estimates for the injury regression model for 

largemouth bass. This model was significant (P=0.0003). ...................................... 78

E-49. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for largemouth bass. .................................................................................. 78

E-50. Analysis of maximum likelihood estimates for the scale loss regression 

model for largemouth bass. This model was not significant (P=0.3131). ............... 79

E-51. Summary of live, dead, and mean length by velocity treatment for white 

sucker. ....................................................................................................................... 80

E-52. Analysis of maximum likelihood estimates for the survival regression model 

for white sucker. This model was significant (P<0.0001). ...................................... 80

E-53. Summary of injury rate and mean length by velocity treatment for white 

sucker. ....................................................................................................................... 80

E-54. Analysis of maximum likelihood estimates for the injury regression model 

for white sucker. This model was significant (P<0.0001). ...................................... 81

E-55. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for white sucker. ....................................................................................... 81

E-56. Analysis of maximum likelihood estimates for the scale loss regression 

model for white sucker. This model was significant (P<0.0001). ........................... 82

E-57. Summary of live, dead, and mean length by velocity treatment for yellow 

perch. ......................................................................................................................... 83
xiv

E-58. Analysis of maximum likelihood estimates for the survival regression 

model for yellow perch. This model was significant (P=0.0392). ........................... 83

E-59. Summary of injury rate and mean length by velocity treatment for yellow 

perch. ......................................................................................................................... 83

E-60. Analysis of maximum likelihood estimates for the injury regression model 

for yellow perch. This model was not significant (P=0.1659). ................................ 84

E-61. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for yellow perch. ....................................................................................... 84

E-62. Analysis of maximum likelihood estimates for the scale loss regression 

modelfor yellow perch. This model was not significant (P=0.0753). ...................... 85

F-1. Summary of live, dead and mean length by duration of impingement for 

channel catfish. ......................................................................................................... 88

F-2. Analysis of maximum likelihood estimates for the regression model for the 

duration of impingement of channel catfish. This model was not significant 

(P=0.9927). ............................................................................................................... 88

F-3. Summary of injury rates and mean length by duration of impingement for 

channel catfish. ......................................................................................................... 88

F-4. Summary of live, dead and mean length by duration of impingement for 

fathead minnow. ........................................................................................................ 89

F-5. Analysis of maximum likelihood estimates for the regression model of 

duration of impingement of fathead minnow – survival. This model was not 

significant (P=0.1244). .............................................................................................. 89

F-6. Summary of injury rates and mean length by duration of impingement for 

fathead minnow. ........................................................................................................ 89

F-7. Analysis of maximum likelihood estimates for the regression model of 

duration of impingement for fathead minnow – injury. This model was not 

significant (P=0.3688). .............................................................................................. 90

F-8. Summary of frequencies of scale loss categories and mean length by duration 

of impingement for fathead minnow. ........................................................................ 90

F-9. Analysis of maximum likelihood estimates for the regression model of for 

fathead minnow – scale loss. This model was significant (P=0.0270). ................... 90

F-10. Summary of live, dead and mean length by duration of impingement for 

golden shiner. ............................................................................................................ 91

F-11. Analysis of maximum likelihood estimates for the regression model for the 

duration of impingement of golden shiner – survival. This model was 

significant (P=0.0001). .............................................................................................. 91

F-12. Summary of injury rates and mean length by duration of impingement for 

golden shiner. ............................................................................................................ 91
xv

F-13. Analysis of maximum likelihood estimates for the regression model for 

duration of impingement of golden shiner – injury. This model was 

significant (P=0.0170). .............................................................................................. 92

F-14. Analysis of maximum likelihood estimates for the regression model for 

duration of impingement of golden shiner excluding controls – injury. This 

model was significant (P=0.0073). ........................................................................... 92

F-15. Summary of frequencies of scale loss categories and mean length by duration 

of impingement for golden shiner. ............................................................................ 92

F-16. Analysis of maximum likelihood estimates for the regression model of scale 

loss for golden shiner. This model was significant (P<0.0001). .............................. 93
xvi 

LIST OF FIGURES 

Figure Page 

1. Test flume including isolation screen, traveling water screen, collection trough, 

and collection net. ..................................................................................................... 41

2. Distribution of injury types .......................................................................................... 42

A-1. Overview of modified screen testing facility. .......................................................... 43

A-2. Modified traveling screen in the dewatered test flume. ........................................... 44

A-3. Fish holding facility. ................................................................................................ 44

A-4. Marking fish using marking gun. ............................................................................. 45

A-5. Still image captured from the submersible video camera showing fish 

impingement on the traveling water screen. ............................................................. 45

A-6. Test enclosure showing upstream isolation screen (left) and the ascending 

face of the traveling water screen (right). ................................................................. 46

A-7. Crowding fish (A) and mechanical crowder in the full upright position (B). ......... 46

A-8. Fish collection and transfer to holding facility. ....................................................... 47

A-9 Measuring and examining fish for external injuries. ................................................ 47

A-10. Fish in a water-filled bucket above the flume water line. ...................................... 48

B-1. Comparison of a conventional screen (A) to a modified traveling screen (B) 

showing the angle of the screen faces to the approaching flow. ............................... 50

E-1. Interpreting the hierarchical results of the logistic regression models. .................... 86
1 

CHAPTER 1

BIOLOGICAL EVALUATION OF MODIFIED TRAVELING SCREENS 

Introduction

Section 316(b) of the Clean Water Act requires the use of “best technology 

available” (BTA) for minimizing adverse environmental impact resulting from the 

operation of cooling water intake structures (CWIS). Adverse environmental impact can 

occur from the entrainment of small aquatic organisms through the CWIS and into the 

cooling water system or the impingement of larger life stages on traveling water screens. 

Conventional traveling water screens were originally designed to prevent debris in 

the cooling water from clogging the steam condensers. Beginning with the adoption of 

the Clean Water Act, these traveling screens were modified to improve survival of fish 

during the duration of their impingement on the screens and during spraywash removal 

from the screens. The first modifications to traveling screens to protect fish were made at 

Virginia Electric Power’s Surry Station in 1976. The Ristroph screen, named for the 

engineer that designed it, had a screen basket equipped with a water-filled lifting bucket 

to hold collected organisms as they were carried up with the rotation of the screen (White 

and Brehmer 1977). Modified screens typically operate continuously to reduce 

impingement time. As each bucket passes over the top of the screen, fish are rinsed into 

a collection trough by a low-pressure spraywash system. Once collected, the fish are 

transported back to a safe release location in the source water body. 

Advances in Ristroph screen design have been developed through extensive 

laboratory and field experimentation. Hydraulic buffeting in the fish lifting buckets, 

identified as injurious to fish by Fletcher (1990), was reduced through improvements in 
2

bucket design during the 1980s and 90s. Evaluations of the latest generation of modified 

traveling screens have generally shown improved survival over previous screen designs. 

Examples include: Salem Generation Station (Public Service Electric and Gas [PSE&G] 

1999; Public Service Enterprise Group [PSEG] 2004), Dunkirk Steam Electric Station 

(Beak Consultants, Inc. [Beak] 2000a), Huntley Steam Electric Station (Beak 2000b), 

Indian Point Station (Fletcher 1990), and Arthur Kill Station (Consolidated Edison 1996). 

Unfortunately, results of effectiveness from the full-scale application of modified 

screens have been variable depending upon species-, life stage-, and site-specific factors, 

making it difficult to estimate effectiveness a priori or estimate survival of species that 

have not been tested with modified traveling screens. Thus, while there have been many 

studies of impingement survival, there are many gaps in the available data that need 

filling before they can be used to make accurate predictions of survival at most CWIS. 

To date, the newer screen designs have been installed and evaluated largely on estuaries 

and tidal rivers. As a result, there are few survival data available for many of the species 

impinged at CWIS located on fresh water lakes and rivers. 

Modified traveling screens have the potential for wide-scale application in all 

regions of the country and in all water body types to meet Section 316(b) of the Clean 

Water Act. Modified traveling screens have advantages over many of the other 

impingement reducing options because they are relatively easy to retrofit at facilities that 

currently use traveling screens; they can be cleaned automatically; they do not interfere 

with navigation; they do not alter aesthetics; and they will not generally require 

substantial civil/structural modifications or dredging except for the addition of a fish 

return line. 
3

Typically, modified traveling screens are designed with a relatively low approach 

velocity (e.g., 0.3 m·s-1). This low design velocity is predicated on the assumption that 

fish mortality increases directly with increased velocity. At facilities where existing 

approach velocities are high (e.g., 0.9 m·s-1), redesigning the intake to meet a 0.3 m·s-1

design criteria would require costly civil/structural or operational modifications. 

However, if it could be demonstrated that fish survival at higher velocities (e.g., 0.5 m·s-1

to as high as 0.9 m·s-1), then these screens could be installed at a greatly reduced cost 

without additional modifications to reduce velocity. Therefore, if fish survival is high at 

velocities greater than 0.3 m·s-1, then modified traveling screens would become a more 

desirable option for compliance at a greater number of facilities. 

The depth below the surface that a fish impinges and the frequency and rate of 

screen rotation determine its duration of impingement (DI). Longer impingement 

durations may contribute to greater mortality, injury, and/or scale loss. Therefore, 

additional studies were undertaken to evaluate the effect of extended impingement 

durations. 

The initial study design for velocity tests involved two screen rotation speeds; 

however, the extremely slow rotation speed necessary to achieve longer durations of 

impingement had a substantial drawback. Observing the impingement of fish at 8 ft/min 

rotation speed indicated that there was a behavioral component to the impingement 

process. In many cases, fish would hold position in the flume and fall back to the screen 

surface until their tails touched the screen face. The tail touching would, in turn, 

stimulate the fish to swim forward. This “tail-tapping” often occurred several times 

before the fish entered the bucket. Once in the calm conditions in the bucket, fish 
4

typically remained there. Because the investigation sought to evaluate the entire 

screening process from impingement, through the spray-wash, and finally transfer to the 

return trough, it was deemed necessary to continuously rotate the screen. In addition, 

since modified traveling screens are designed to rotate continuously in the field, rotating 

continuously in the laboratory is more representative of field conditions relative to fish 

behavior. Therefore, a second set of tests was undertaken specifically to simulate longer 

impingement durations. 

Methods

Test Fish

Ten fish species were tested during the evaluation. Species were selected based 

upon their frequent occurrence or abundance in impingement sampling at CWIS, their 

regional, ecological, or economic importance, their absence from post-impingement 

survival data with modified traveling screens, and their availability for testing. Test 

species included: fathead minnow (Pimephales promelas) and white sucker (Catostomus 

commersonii) obtained from Harmon Brook Farms, Canaan, ME; bigmouth buffalo 

(Ictiobus cyprinellus), bluegill (Lepomis macrochirus), largemouth bass (Micropterus 

salmoides), channel catfish (Ictalurus punctatus), and freshwater drum (Aplodinotus 

grunniens) obtained from Osage Catfish Hatchery, Osage Beach, MO; hybrid striped bass 

(Morone chrysops × M. saxatilis), golden shiner (Notemigonus crysoleucas), and yellow 

perch (Perca flavescens) obtained from Delmarva Aquatics, Smyrna, DE. Fathead 

minnow and white sucker were netted from wild populations; all other species were pond 

reared. 
5

Fish Holding Facility

The fish holding facility consisted of a 32,000-L recirculating system. Fish were 

held in one of eight cylindrical tanks (either 800- or 1,600-L) connected to a central pool. 

Water was pumped through water treatment filters before returning to the holding tanks. 

Bag filters and an activated charcoal filter were used to remove particulates (solid waste 

material, chlorine, and other impurities). An ultraviolet light sterilizer and a fluidized bed 

(sand) bio-filter were used to control bacteria and soluble waste products. The holding 

facility was equipped with a five-ton chiller to maintain water temperatures. Dissolved 

oxygen, temperature, and salinity were monitored daily. Salinity levels were maintained 

at approximately 5 ppt to reduce the occurrence of fungal growth common in freshwater 

aquaculture systems. Hardness, alkalinity, and ammonia levels were monitored weekly 

and chemically adjusted as needed. It was not possible to control temperatures within the 

testing facility, so holding facility temperatures were maintained within 2°C of the testing 

facility. 

A circular flow pattern was maintained in the fish holding tanks to keep fish 

active and reduce contact with the tank walls that could cause scale loss. Fish were fed 

age-, size-, and species-specific diets, which included dried brine shrimp, live Artemia 

sp., and solid commercially available pelleted feed. Fish physiology and behavior was 

qualitatively assessed daily to screen for external signs of disease, fungus, or infection by 

parasites. Photographs of the fish holding facility are provided in Appendix A 
6

Test Facility

Testing was conducted at Alden Research Laboratory, Inc. (Alden) in Holden, 

MA. A modified traveling screen was installed in a 208 m3 (55,000 gallon) capacity steel 

flume, which was equipped with a 150 hp bow thruster to produce water velocities up to 

0.9 m·s-1. The flume was also equipped with a bag filter system to remove suspended 

particulates and maintain water quality. The section of the flume where the testing was 

performed had a maximum depth of 2.0 m and a width of 1.8 m. Water temperatures 

were not controlled, but holding facility temperatures were maintained within 2°C of the 

testing facility to avoid thermal shock. The test portion of the flume is shown on Figure 

1. 

Screen baskets were 1.2-m wide and were equipped with 0.64 cm × 1.3 cm 

rectangular, smooth-texTM mesh. Screen wire diameter was 2 mm (14 gauge). The pilotscale screen was 2.4-m tall (1.8 m between the centerlines of the top and bottom screen 

sprockets). The screen was designed to rotate at speeds ranging from 2.4–10.4 m/min. 

The boot section (bottom) of the screen was equipped with a brush to prevent fish from 

passing underneath the screen. The screen had a fish and debris spraywash/return 

system, which included spraywash headers (one external and two internal pairs), a 

neoprene rubber flap seal, and a simulated section of a return trough on the downstream 

side of the screen. Atypical of modern screen designs, a single debris/fish trough was 

used because height limitations prohibited the use of dedicated fish and debris troughs. 

Other than the fish trough and height of the pilot-scale screen, the following features of 

the screen were identical to screens that would be installed at CWIS: basket dimensions, 

gaps between the baskets, spaces between the baskets and the screen frame, spraywash 
7

nozzle orientation and water pressure, and the distance between the flap seal and the 

screen face met manufacturer’s full-scale design specifications. Photos of the facilities 

and testing methods are presented in Appendix A. 

Velocity Measurements

Velocity measurements were recorded at the beginning of the experiments using a 

Swoffer flow meter to verify that the flume operating conditions produced the desired 

approach velocities with a relatively uniform flow distribution upstream of the traveling 

screen. Approach velocities were measured for each test condition, at three locations and 

three depths along a transect that was approximately 1.2 m upstream of the screen face. 

Velocity measurements were used to develop a predicted bow thruster output curve, such 

that bow thruster rpm could be used to set the approach velocity for each replicate. 

Test Parameters

The post-impingement mortality of fish following exposure to the modified 

traveling screen was assessed. A discussion of the difference between impingement on 

traditional traveling screens and modified traveling screens is presented in Appendix B. 

In addition, the rates and types of injury and rates of scale-loss, the length of time 

swimming prior to impingement, the effect of fish length on impingement rates and 

mortality were also evaluated. Finally, qualitative observations of fish behavior as they 

encountered the traveling screen were made using underwater video cameras. 

Testing consisted of exposing the ten species to three different approach velocities 

(0.3, 0.6, and 0.9 m·s-1). Approach velocities were selected based upon an analysis of 
8

approach velocities at existing CWIS. A database of design and operation data from 

many CWISs was analyzed to determine typical water velocities approaching traveling 

water screens. Data from 88 CWISs using once-through cooling were used in the 

analysis. These facilities were selected for analysis because the reports provided by 

power companies had the necessary information to calculate approach velocities. The 

calculated velocities were based on CWIS design information, and it was assumed that 

the intakes were operating at design intake flow (all pumps operational) at expected low 

water depth. Thus the calculated velocities represent the expected highest velocity 

approaching the traveling water screens. The intakes evaluated were located nationwide 

and represent all major water body types (freshwater lakes and rivers, estuaries, marine, 

and Great Lakes). Results of the analysis indicated that the mean approach velocity at 

existing plants is 0.30 m·s-1, with a median value of 0.27 m·s-1 and a range of 0.09 m·s-1

to 0.82 m·s-1. Therefore, the approach velocities selected bracket the range of velocities 

typically observed at CWISs. 

For each species, five replicates at each of the three approach velocities were 

tested. On each day of testing, three treatment replicates and one handling control were 

completed. A weekly testing schedule is provided in Appendix C. Individual species 

were tested alone or with one other species to form a species-group. Species-groups were 

created to reduce the time required to complete testing. Care was taken to select 

compatible species to form the species-groups. Each species was tested sequentially, 

such that all replicates were run for a single species-group prior to testing the next species 

or species-group. A randomized design was used to determine the order of testing within 

each species or species-group. On each day of testing, a handling control group for each 
9

species was tested to separate mortality associated with handling (removal from holding 

facility, marking, counting into test groups, and introduction to and removal from the test 

flume) from mortality associated with impingement and removal from the screens. 

Control groups were randomly assigned a timeslot on each test day to ensure that control 

groups were not tested at the same time each day. 

For duration of impingement (DI) testing in the laboratory, fish were introduced 

at a high velocity (0.9 m·s-1) while the screen remained stationary for a predetermined 

amount of time (2, 4, 6, 8, or 10 min) to simulate longer durations of impingement (DI). 

Early test results showed little injury and no mortality at durations of 2 and 4 min. 

Therefore, these conditions were not included in extended impingement tests to maximize 

the use of a limited number of available test fish. The remaining tests were conducted at 

the longer impingement durations. 

Fish Marking

Test fish were marked a minimum of twenty-four hours prior to testing. A New 

West POW’R-Ject marking gun was used to mark 300 treatment and 100 control fish of 

each species. The marking system used compressed CO2 to inject biologically inert, 

micro-encapsulated photonic dye into the base of individual fins. Species- and sizespecific adjustments to injection pressure and dye volume were made to optimize the 

visibility of marks. Four colors and three fin locations were used to provide 12 unique 

marks, which allowed the resulting combination of color and fin location to be used once 

per week (based on four replicates per day × three testing days per week). Uniquely 

marked release groups allowed fish to be identified to the replicate from which they were 
10

released, regardless of when they were collected. Marking fish in this way was very 

effective. Mark retention was high; of the 15,721 fish collected by impingement during 

velocity testing, only 67 fish (0.4%) did not have discernable fin marks. Similar marking 

procedures were used for the DI testing. 

Test Procedures

Velocity Tests 

In preparation for each treatment replicate, the screen rotation speed (2.4 m/min) 

and spraywash pressure (10 psig) were set to the appropriate levels. The approach 

velocity was initially set at 0.15 m·s-1. The isolation screen that confined fish to the area 

immediately upstream of the traveling screen was lowered into place. A floating net 

collection pen was placed at the discharge of the return trough. The knife-gate valve that 

prevents fish from sluicing into the net collection pen from the fish return trough was 

confirmed to be in the closed position. 

When conducting a treatment replicate, 100 fish of each species were introduced 

just upstream of the traveling screen in the test enclosure at the previously-set 0.15 m·s-1

velocity. Once the fish were swimming normally (approximately 30 sec), the velocity 

was increased rapidly to the target test velocity. During testing, observations of fish 

behavior were recorded using underwater video cameras to determine if a pattern existed 

in the way that fish interacted with the screen under the various test conditions. The first 

15 minutes of each replicate were videotaped for subsequent analysis. 

Fish that impinged on and were washed from the screen were held in the fish 

collection trough and subsequently sluiced into the floating net pen through the opened 
11

knife-gate valve, located at the discharge of the return trough, at set intervals of 15, 60, 

and 120 minutes. 

When conducting a control replicate, 100 marked fish of each species being tested 

were released into the fish return trough. Once the fish were oriented to the flow, the 

knife-gate valve at the discharge was removed and the fish were allowed to sluice into a 

net pen. 

Immediately following each collection (treatment or control), fish were classified 

into one of three categories: 1) live fish – swimming normally, with no signs of injury, 

apparent orientation problem, or abnormal behavior; 2) stunned fish – struggling, 

swimming on side, floating belly-up but alive, bleeding or the presence of wounds, 

missing body parts, severe abrasions or lacerations; and 3) dead fish – no vital signs, no 

body or opercular movement, no response to gentle probing. 

Following the 120-minute collection, the water velocity was reduced to 0.3 m·s-1

and the mechanical crowder was raised to move fish that were still swimming upstream 

of the screen into the screen collection buckets. At the end of each collection event, any 

live or stunned fish recovered from the fish return trough (treatment or control replicate) 

were transferred back to the holding facility in individually marked net pens and held for 

latent impingement mortality (LIM) assessment. 

Fish that were entrained through the screen or did not successfully transfer to the 

collection trough were collected in the downstream collection net once per day at the end 

of testing. These fish were enumerated and their fork lengths (FL) measured to the 

nearest millimeter. The tails of freshwater drum are not forked, so total length was 

measured (TL). 
12

Fish condition was monitored immediately after collection, 24-, and 48-hours 

following impingement. At the end of 48-hours, all fish were killed and examined for 

external injuries and percent scale loss. Any fish unable to maintain equilibrium at 48-

hours after testing was considered dead. External injuries were recorded by type (e.g., 

bruising/hemorrhaging, lacerations, severed body, or eye damage). Using methods 

similar to those reported by Neitzel, et al. (1985) and Basham, et al. (1982), percent scale 

loss (< 3%, 3–20%, 20–40%, and > 40%) was recorded along the length of the body. All 

fish were measured for fork length (or total length in the case of freshwater drum) to the 

nearest millimeter. Fish identified as dead immediately following collection or at 24-

hours were also examined for external injuries and scale-loss using the methods described 

above. 

On the first day of injury and scale loss assessment with each species tested, each 

fish condition evaluator examined 20 sample fish. Injury and scale loss assessments were 

compared among evaluators, discrepancies were discussed, and common evaluation 

criteria were developed by consensus. Subsequently, any fish observed with questionable 

injuries were cross checked by a second evaluator. 

Because water depth in the test flume was limited to 1.5 m, the maximum DI for 

fish during the velocity tests was about 40 seconds (assuming 8 ft/min rotation speed and 

fish impinged at the deepest point in the flume). Therefore, it was not possible to 

evaluate longer durations of impingement during velocity tests while maintaining 

continuous screen rotation, a feature generally considered as important to fish survival. 
13

Duration of Impingement Tests 

To determine the DI that might be observed at existing CWIS, a database of 

design and operational data from several power plants was consulted. A subset of 

facilities from the database was selected based upon the availability of both well depth 

(the height of the screen) and screen rotation speed data. Since both types of data were 

necessary to estimate maximum DI, facilities lacking either data type were removed from 

the analysis. Maximum impingement duration was calculated by dividing the well depth 

by the screen rotation speed. If data were reported for multiple CWIS at the same 

facility, each CWIS was evaluated separately. If more than one screen speed was 

presented for a given CWIS, then each value was used to compute separate predicted 

values. Similarly, if more than one water depth was reported, a value was calculated at 

minimum and maximum water depth. DI values were calculated for 56 CWIS 

representing 39 power plants. Five CWIS reported multiple water depths and 12 CWIS 

reported multiple screen rotation speed yielding a total of 76 data points. The DI values 

calculated are the expected maximum, since this analysis assumes fish impingement at 

the bottom or base of the screen. Fish impinged near the surface or at mid-depth would 

have shorter durations of impingement. The average calculated DI was 2.8 minutes (± 

0.26 SE), with a median value of 2.1 minutes. The minimum and maximum durations of 

impingement were 0.5 and 12 minutes, respectively. 

For DI testing, the number of fish tested and the number of replicates completed 

were determined by availability of test organisms. A total of 40 treatment and control 

replicates were run with channel catfish (12 replicates; n=446), golden shiner (12 

replicates; n=262), and fathead minnow (16 replicates; n=332). A randomized design 
14

was used to determine the order of testing. For each set of treatment replicates, control 

groups were tested to separate mortality, injury, and scale loss associated with handling 

(removal from holding facility, marking, counting into test groups, and introduction to 

and removal from the test flume) from mortality, injury, and scale loss associated with 

testing. Control groups were randomly assigned a timeslot on each test day to ensure that 

control groups were not tested at the same time each day. 

For DI testing, the screen was held stationary and the approach velocity was set at 

0.9 m·s-1. This high velocity was used to maximize the number of fish impinged. 

Marked fish were introduced just upstream of the screen face in the test enclosure. 

For treatment replicates, fish were allowed to interact with the screen for 6, 8, or 

10 min after introduction into the test enclosure. At the end of the 6, 8, or 10 min period, 

the screen was rotated until the screen panels that had been in the water were just above 

the water line. For control replicates, fish were poured directly into a water filled bucket 

above the flume water line. For both treatment and control replicates, fish were removed 

from the water-filled buckets using a small net and transferred to a water filled bucket for 

transport back to the holding facility. 

Immediately following each collection, fish were classified into one of the three 

categories (live, dead, or stunned, as described above) before being transferred back to 

the holding facility, placed into individually marked net pens, and held for a 48-hour LIM 

assessment. 

Fish survival was monitored at 24- and 48-hours intervals. At the end of 48-

hours, all fish were killed using a clove oil solution and examined for external injuries 
15

and percent scale loss. Injury and scale loss were assessed using the same procedures as 

used for velocity tests. 

Data Analysis

Velocity Tests 

During velocity testing, over 19,000 fish were tested (n = 19,401). Of these, 

13,009 were used for data analysis (67.1%). Of the remaining fish, a large majority 

(22.7% of the total number released) were collected downstream of the screen (i.e., were 

entrained or passed between the flap seal and the screen during transfer from the screen 

to the fish return trough). Others were either unaccounted for (1.7%), did not have an 

identifiable mark (0.3%), or were collected in a subsequent trial (8.4%). Because fish 

collected in subsequent trials were exposed to multiple velocities and crowding events, 

they were not included in the statistical analysis. Data were analyzed by logistic 

regression using SAS software (SAS Inst. 1999). Four possible independent variables 

were included in the analysis: approach velocity, collection time (15 minutes after 

introduction, 60 minutes after introduction, 120 minutes after introduction, and at time of 

crowding), observation time (initial, 24-hours, and 48-hours), and fork length. 

Preliminary logistic regression models contained all four variables. However, the 

impingement responses were not sufficiently distributed over two of these variables 

(collection time and observation time) to allow a simultaneous analysis. In the case of 

collection time, fish tended to remain upstream of the screen until crowding at lower 

velocities. Conversely, at higher velocities, the majority of fish tended to be impinged 

and collected during the first 15 minutes. Thus, for any given velocity, the majority of 
16

fish fell into only one collection category. Similarly, very little mortality was observed 

during the initial and 24-hour observation periods. In all cases, this lack of differentiation 

between collection time and observation time prevented the logistic regression models 

from converging on reliable estimates. Therefore, the model design was reduced to 

include only velocity and fork length as variables. 

Under the theory of Generalized Linear Models (McCullagh and Nelder 1989) a 

simple one variable linear expression can be replaced by a linear expression containing 

many independent variables. These variables can be continuous, such as fish length, or 

categorical, such as discrete velocity treatments. Maximum likelihood has become the 

preferred estimation procedure because maximum likelihood can be implemented when 

there is only one subject for each unique combination of independent variables. When 

using maximum likelihood estimation, the statistical significance of each independent 

variable is assessed through a chi-square test, which can be thought of as analogous to the 

F-test that is used in linear regression. 

Thus the final regression model used was: 

( ) 1 log velocity collection forklength

p

p = α + i + j + β ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

−

where: 

α is the intercept term 

velocity i are terms to model velocity treatment i = 1, 3 

collection j are terms to model collection effect j = 1, 3, and 

β is the coefficient for the effect of fork length on the log-odds 
17

The analysis for scale loss was based on an extension of logistic regression to a 

multiple category response variable (McCullagh and Nelder 1989) where the categories 

were strictly ordered: 1 = <3%; 2 = 3–20%; 3 = 20–40%; 4 = >40%. For each treatment, 

the distribution of observations among the categories can be viewed as a cumulative 

distribution. The probabilities predicted by the model are the cumulative probabilities of 

the scale loss categories : p1 = Pr(<=1) = Pr( = 1); p2 = Pr(<=2) = Pr( = 1 or 2); p3 = 

Pr(<=3) = Pr( = 1, 2, or 3); and p4 = Pr(<=4) = Pr( = 1, 2, 3, or 4) = 1.0. Note that p4 is, 

by definition, 1.0 and so the model need only predict the first three. The standard logistic 

model was formulated for each of these three probabilities: 

{ } ( (L )) 1 e ( (L )) p e

0 1 2 k 0 1 2 k

ijk i j i j

/ β β β β + β + β +

+ + =

where: 

pijk = cumulative probability i, for treatment j, for fish k. 

β0i = an intercept value for the first three scale loss categories, i = 1, 2, 3. 

β1j = a parameter for each velocity, j = 1, 2, 3. The control is modeled by the 

intercept and this parameter models the offset from the control for each 

velocity treatment. 

β2 = a coefficient for the effect of length. 

Lk = fork length of fish k. 

e = base of the natural logarithms 

In this model, the term β0 models the increase in probability from one cumulative 

probability to the next, and the term β1 models a shift of the cumulative distribution from 
18

one velocity treatment to the next. This feature causes the predicted probabilities for one 

velocity treatment to be proportional to the predicted probabilities for another. That is, 

there is a constant odds ratio across scale loss categories between a pair of velocity 

treatments. For this reason, this model is sometimes called the "proportional odds 

model." 

Duration of Impingement Tests 

Similar to the velocity tests, duration of impingement data were analyzed using 

logistic regression. Duration of impingement (DI) was treated as a continuous variable 

rather than a categorical variable. That is, it was assumed that the effect of DI is 

monotonic and that its effect on the logarithm of the odds ratio can be quantified by a 

linear model. For analysis purposes, controls were assigned a duration time of zero. The 

model included both fork length and DI as independent variables. 

The logistic regression of injury for the DI study included fork length and DI as 

factors. Analysis followed the injury analysis methods outlined above for velocity tests, 

except that DI was treated as a continuous variable whereas velocity was treated as a 

categorical variable. 

The methods for analyzing scale loss for DI effects were the same as those used 

for analyzing scale loss for velocity effects except that DI was treated as a continuous 

variable whereas velocity was treated as a categorical variable. 
19

Results

Velocity Tests

A total of 163 treatment and control replicates was completed over 33 days 

between 11 May and 24 August, 2005 during the velocity trials. Observed postimpingement mortality was low under all conditions tested (< 5%). Mortality rates were 

higher at higher velocities, but this effect was significant only for bluegill (P=0.0005). 

Injury rates were more variable by species, with significantly higher injury rates (P<0.05) 

observed at higher velocities for many species. Velocity was also a significant indicator 

of scale loss for all six species with successful logistic regression models. Fish length 

was an important factor in mortality, injury, and scale loss. In all cases where length was 

a significant factor (P<0.05), there was a trend toward decreased mortality, injury, and 

scale loss as fish grew larger. In all cases where fish length was a significant factor, the 

pattern of decreased mortality, injury, and scale loss as fish increased in length was 

observed. 

Time to Impingement 

The number of fish collected at each velocity and for each collection time varied 

by species. Because fish tended to impinge either at low-velocity/long collection time or 

high-velocity/short collection time, it was not possible to separate the effects of velocity 

and collection time through statistical analysis. For most species, it appears that there 

was a threshold between 0.3 and 0.6 m·s-1 at which fish could no longer maintain their 

position upstream of the screen. However, for most species a substantial number of fish 

were able to swim at 0.6 m·s-1 for the duration of testing. At 0.3 m·s-1, most fish were 

collected during the crowd, indicating that the fish were capable of swimming for 2 hours 
20

at the target velocity. At 0.9 m·s-1, most fish were collected 15 minutes after 

introduction, indicating that they were unable to swim at this velocity for extended 

periods. A table showing impingement by velocity and collection time is provided in 

Appendix D. 

Water Temperature 

Swimming capacity tends to be positively correlated with temperature (Beamish 

1978). In addition, water temperature can play an important role in post-impingement 

fish survival. Extremes in water temperature can lead to increased mortality (e.g., Burton 

and Graves 1979, Loar et al. 1978, Eisele and Malaric 1978). Recorded mean water 

temperature during testing was 20°C ± 1 SE and ranged from a low of 13.0°C in May to a 

high of 24.6°C in July. Because temperatures and survival rates were fairly uniform 

during testing, temperature likely did not impact the results of this study. 

Mortality 

Review of the 48-hour mortality data indicates that mortality for all species was 

low regardless of approach velocity (Table 1). Confidence intervals (± 95% CI) were 

calculated using the normal approximation of the binomial distribution from the 

descriptive statistics of mortality rates. The results of the logistic regression models for 

survival are presented by species in Appendix E. A summary of the pertinent P-values 

from the species models are presented in Table 2. The model results are hierarchical, 

such that if the model was not significant and failed to converge to a reliable estimate, 

then the length and velocity components were not significant regardless of their P-value. 

A full discussion on interpreting the results of the logistic models is presented in 

Appendix E. 
21

The logistic regression models for mortality did not yield meaningful results for 

five of the ten species tested (bigmouth buffalo, channel catfish, freshwater drum, fathead 

minnow, and hybrid striped bass) (P>0.05; Table 2). In all cases, there were too few 

mortalities for the models to converge to a reliable estimate. Mortality rates for these five 

species did not exceed 3.2% under any of the test conditions (Table 1). 

For largemouth bass, the mortality regression model was marginally significant 

(P=0.0549). Mortality among the velocity treatments for largemouth bass ranged from 

0.8% in the control to 2.8% in the 0.9 m·s-1 treatment (Table 1). These differences were 

not statistically significant (P=0.1170; Table 2). There was weak evidence of a length 

effect (P=0.0773; Table 2). The negative coefficient indicates reduced likelihood of 

mortality at longer lengths. 

The remaining five species (bluegill, golden shiner, hybrid striped bass, white 

sucker, and yellow perch) had significant logistic regression models for mortality 

(P≤0.0392). For bluegill, mortality among the velocity and control treatments ranged 

from 0.9% at 0.3 m·s-1 to 4.6% at 0.6 m·s-1 (Table 1). The 0.3 m·s-1 treatment was not 

significantly different from the control while the 0.6 m·s-1 treatment was significantly 

greater than the control (P=0.0004; Table 2). There was weak evidence that the 0.9 m·s-1

treatment was different from the control (P=0.0601; Table 2). The length effect was 

significant (P<0.0001; Table 2) indicating a reduced likelihood of mortality as fish 

increase in length. 

For golden shiner, mortality among the velocity treatments ranged from 1.2% in 

the control to 1.6% in the 0.3 m·s-1 treatment (Table 1). These values were not 

significantly different (P=0.7242; Table 2). There was evidence of a length effect 
22

(P<0.0001; Table 2). The negative coefficient indicates reduced likelihood of mortality 

as fish increased in length. 

For white sucker, mortality among the velocity and control treatments ranged 

from 3.1% in the control to 4.7% in the 0.6 m·s-1 treatment (Table 1). These differences 

were not significantly different (P=0.7423; Table 2). There was evidence of a reduced 

likelihood of mortality as fish increase in length (P<0.0001; Table 2). 

For yellow perch, mortality among the velocity treatments ranged from 0.8% in 

the 0.3 m·s-1 treatment to 2.6% in the 0.6 m·s-1 treatment (Table 1). These differences 

were not significantly different (P=0.3143; Table 1). There was evidence of a reduced 

likelihood of mortality as fish increased in length (P=0.0052; Table 2). 

Injury 

Review of injury data indicates that the rate of injury for most species was low 

regardless of approach velocity. Table 3 presents the rate of injury by species and 

velocity. Fish showing clear signs of fungus or other disease were recorded as diseased. 

The two wild-caught species (fathead minnow and white sucker) showed much 

higher rates of injury. However, the rates of control injury for these two species were 

also much higher, indicating that the higher rates of injury were not exclusively the result 

of screen exposure. The types and frequency of injury observed for all species combined 

are shown on Figure 2. 

Fish that were swimming and behaving normally during the initial assessment, but 

later found dead, descaled, and missing their eyes or fins during the 24 or 48-hour 

assessment were assumed to have died as a result of injuries resulting from conspecific 

aggression (CA) rather than from interaction with the screen. For two of the species 
23

evaluated (bluegill and fathead minnow), there was a substantial amount of CA injury 

that occurred while fish were held in pens during the LIM assessment (48 and 11, 

respectively). To investigate the possibility that CA injuries were influencing the 

outcome of the injury regression analysis, a second regression was completed that 

eliminated fish with CA injuries. In the case of fathead minnow, eliminating CA injury 

did not affect the outcome of the model. In the case of bluegill, with the elimination of 

CA injury, the overall velocity treatment statistic was significant (P=0.0077), with the 

0.3 m·s-1 treatment exhibiting significantly greater injury than the control (P=0.0034) 

(Table 4). 

The logistic regression models for injury did not yield meaningful results for three 

of the ten species tested (golden shiner, hybrid bass, and yellow perch) (P>0.05; Table 4). 

Injury rates for these three species did not exceed 4.6% under any of the test conditions. 

Velocity was not a significant predictor of injury for four of the seven species that had 

meaningful logistic regressions (bigmouth buffalo, bluegill, freshwater drum, and white 

sucker) (P>0.05; Table 4). Interestingly, four of the five comparisons in which velocity 

was a significant factor in predicting injury (bluegill excluding CA injuries, channel 

catfish, and fathead minnow with and without CA injuries), the 0.3 m·s-1 treatment, but 

not the 0.6 m·s-1 and 0.9 m·s-1 treatments, resulted in greater injury than the control 

treatment. For largemouth bass, the 0.6 m·s-1 and 0.9 m·s-1 treatments (P>0.05; Table 4), 

but not the 0.3 m·s-1 treatment showed significantly greater injury than the control 

treatment (P<0.05; Table 4). 

In general, larger fish tended to exhibit fewer injuries than smaller fish. Longer 

fish had significantly lower injury rates in four of the species tested (bigmouth buffalo, 
24

bluegill, freshwater drum, and white sucker) (P<0.05). While not significant at an alpha 

level of 0.05, there was marginal evidence that larger channel catfish experienced fewer 

injuries (P=0.0699; Table 4). 

Scale Loss 

While occurring at a low rate for most species, the effect of velocity on scale loss 

showed a more consistent pattern across species than did injury or mortality. Most 

species exhibited an increase in scale loss at higher velocities and a decrease in scale loss 

with increasing fish length. Species-specific scale loss fell into three distinct groups. 

The first group, which exhibited very little scale loss, included freshwater drum, hybrid 

striped bass, largemouth bass, and yellow perch. For these species, greater than 90% of 

the fish exhibited scale loss levels of 3% or less (Table 5). Ninety percent of the bluegill 

control fish also exhibited 3% or less scale loss, but treatment fish exhibiting scale loss 

levels of 3% or less ranged from 82 to 89%. By contrast, bigmouth buffalo and golden 

shiner exhibited much greater scale loss. For these two species, more than 50% of the 

fish exhibited scale loss greater than 3%, even among control fish. The percentage of 

fish exhibiting scale loss greater than 3% among an intermediate group comprised of 

fathead minnow and white sucker ranged from 15-51% among treatment fish and 14-19% 

among control fish. 

The logistic regression models for scale loss did not yield meaningful results for 

three of the nine species evaluated (hybrid bass, largemouth bass, and yellow perch) 

(P>0.05; Table 6). Channel catfish, a species that lacks scales, were excluded from this 

analysis. Velocity was a significant predictor of scale loss for bigmouth buffalo, bluegill, 

freshwater drum, fathead minnow, golden shiner, and white sucker (P<0.05; Table 6), but 
25

not for hybrid striped bass, largemouth bass, or yellow perch (P>0.05; Table 6). Four of 

the six species exhibiting significant velocity effects on scale loss showed significantly 

greater velocity effects at 0.6 m·s-1 and 0.9 m·s-1, but not at 0.3 m·s-1 (bigmouth buffalo, 

bluegill, freshwater drum, and white sucker; P<0.05; Table 6). Only golden shiner 

exhibited significant scale loss at all three treatment velocities compared to the control 

(P<0.0001; Table 6). Surprisingly, fathead minnow showed significantly more scale loss 

at 0.3 m·s-1 (P=0.0003; Table 6), but not at 0.6 m·s-1 or 0.9 m·s-1 (P>0.5454; Table 6). 

Length was a significant factor in predicting scale loss for five of the six species 

with reliable logistic regressions (bigmouth buffalo, bluegill, freshwater drum, golden 

shiner, and white sucker; P<0.05; Table 6), but not fathead minnow (P=0.7829; Table 6). 

In all five species exhibiting significant length effects, the coefficient for length was 

positive and significant (P<0.05; Table 6) indicating that larger fish tended to have less 

scale loss. 

Duration of Impingement Tests

Increasing DI tended to increase mortality, injury, and scale loss (statistical 

analysis tables for these tests are included in Appendix F). Survival was variable by 

species, but was relatively high for all species. Mortality rates for all species never 

exceeded 10% under any condition. There were no mortalities observed for channel 

catfish with any of the DI treatment conditions (Table 7). Fathead minnow exhibited a 

non-intuitive pattern of mortality; mortality was lowest in the controls (0.7%), which 

does conform to expectation, but mortality was intermediate for 10 min and highest for 

the 6 min (6.4%) and 8 min (6.7%) treatments (Table 7), and the full model was not 
26

significant (P=0.1244; Table 9). With golden shiner, mortality increased with DI, if the 

control treatment was eliminated. However, the mortality response for the controls was 

about midway in the gradient across durations. Even with this anomaly, the analysis 

shows that mortality significantly increased with increasing DI (P=0.0038; Table 9). 

Length had a significant negative effect on mortality (P=0.0001; Table 9), indicating that 

larger fish experienced less mortality. 

Patterns in injury among species were inconclusive. Since no injuries were 

observed for channel catfish it was not necessary to conduct any statistical analysis. 

Fathead minnow and golden shiner showed different responses. Injury rates for fathead 

minnow followed the same non-intuitive pattern that was observed for mortality (i.e., 

injury was highest at an intermediate value – 6 min [8.5%]) (Table 9). The analysis 

shows that the full model is not significant (P=0.3688; Table 9). 

Golden shiner mortality among the controls was unusually high (9.3%; Table 7). 

Excluding the controls, the injury rate tended to increase with duration. Logistic 

regression showed a positive coefficient for DI but was not statistically significant 

(P=0.1464; Table 9). If the controls are excluded, the coefficient increases from 0.0878 

to 0.2483, but this is only marginally significant (P=0.0948; Table 9). Longer fish 

showed a decreased likelihood of injury (P=0.0050; Table 9). 

Fathead minnow experienced relatively low levels of scale loss, with 80% or 

greater having 3% or less scale loss under all conditions. For fathead minnow, there was 

a significant increase in scale loss with increasing DI (P=0.0270; Table 9). Smaller fish 

had less scale loss than larger fish, which is counter to that observed with other species, 

but was not significant (P=0.7066; Table 9). Note that duration and length are 
27

confounded to some degree in this data set because the control fish on average, were 

smaller than the treatment fish. 

Golden shiner exhibited substantial scale loss, even among control fish (Table 8). 

More than half the fish in each of the DI tests exhibited the highest level of scale loss 

(>40%). For golden shiner, scale loss increased with increasing DI (P<0.0001; Table 9). 

There was also a reduction in scale loss as golden shiner increased in length (P=0.0144; 

Table 9). 

Discussion

During velocity tests, post-impingement mortality was low for all species and 

velocities tested (<5%) indicating that modified traveling screens have good potential to 

meet Section 316(b) of the Clean Water Act for these species. While fish mortality was 

low at all velocities tested, higher rates of injury and scale loss were observed at 0.6 m·s-1

and 0.9 m·s-1 than at 0.3 m·s-1. 

Fish length played an important role in mortality, injury, and scale loss. In all 

cases where fish length was a significant factor, the pattern of decreased mortality, injury, 

and scale loss as fish increased in length was observed. Thus, even though mortality of 

all fish tested was low, modified traveling screens offer a higher level of protection to 

larger fish. 

Despite a general trend toward decreasing mortality at lower velocities, velocity 

was only a significant factor in mortality for bluegill. This lack of correlation to velocity 

suggests that modified screens can be used at facilities with approach velocities greater 

than 0.3 m·s-1. It is unclear why bluegill exhibit greater mortality at 0.3 m·s-1 than at 0.6 

m·s

-1 or 0.9 m·s-1. Further research would be required if determining the underlying 
28

mechanism that leads to greater bluegill injury at lower velocities is considered 

important. However, visual observations indicate that velocities greater than 0.3 m·s-1

can create more turbulence in the fish lifting buckets, which may account for the greater 

injury and scale loss observed at higher velocities. 

Injury rates were generally low but were highly variable by species indicating that 

the observed injury of fish in the field will be determined largely on species composition 

and abundance at the individual CWIS. However, the two species with the highest injury 

rates (white sucker and fathead minnow) also exhibited greater handling control injury, 

indicating that these populations of fish may not have been as healthy as the other species 

tested. 

Scale loss levels were highly species-specific with some species, such as 

largemouth bass and yellow perch experiencing almost no scale loss, with other species, 

such as bigmouth buffalo and golden shiner experiencing substantial levels of scale loss 

even among the control fish. It appears that susceptibility to scale loss may be associated 

with scale structure. Although there was considerable variability, fish with cycloid scales 

(bigmouth buffalo, fathead minnow, golden shiner, and white sucker) exhibited greater 

scale loss than species with ctenoid scale structure (bluegill, freshwater drum, hybrid 

striped bass, largemouth bass, and yellow perch). 

It might be assumed that site-specific environmental factors (e.g., debris, water 

quality, water temperature, turbulence, etc.) will impact fish condition and potentially 

increase post-impingement mortality, injury, and scale loss at field sites using modified 

traveling screens. However, a comparison of these laboratory results with results 
29

observed in the field indicate that the high survival observed in the laboratory is within 

the bounds of what has been observed in the field with similar screen designs. 

Intuitively, one might expect that organisms tested in the laboratory would have 

higher survival than those observed in the field. Organisms collected in the field are 

often exposed to site-specific factors that impact physiological condition and potentially 

reduce survival (e.g., disease, extremes in water temperature, debris loading, poor water 

quality, inter- and intra-specific competition for resources, etc.). Laboratory studies, on 

the other hand, are conducted under conditions where the effect of natural stressors, 

particularly disease organisms, is typically more controlled. Therefore, it is not 

necessarily surprising that high survival was observed in this laboratory study. To 

compare the survival observed in these laboratory studies to those observed in previous 

pilot- and full-scale field installations, a database of existing screen survival data was 

queried for studies that: 1) were conducted at facilities with modified Ristroph or other 

screen designs with fish-friendly modifications; 2) were conducted at facilities with the 

more sophisticated bucket designs developed in the 1980s; and 3) had similar species to 

those tested in the laboratory. In most cases, data were limited to the same genus as those 

tested in the laboratory. There were two exceptions: Ameiurus sp. was included in the 

analysis of Ictaluridae (catfishes); until recently these two genera were considered to be 

the same and Notropis sp. (shiner) was included with Notemigonus sp. (shiner). There 

were no field data available for bigmouth buffalo or related species. Field data for 

freshwater drum were intentionally not expanded to other members of the family 

Sciaenidae, since all other members are brackish or marine species and may not exhibit 

similar patterns in post-impingement survival as those observed for freshwater drum. 
30

The weighted mean and 95% CI (normal approximation) for the field and 

laboratory estimates of survival are presented in Table 10. In general, there was a greater 

range of reported values from the field than from the laboratory. The mean survival from 

the field tended to be lower than that observed in the laboratory. For five fish genera, the 

laboratory and field results show similar survival and overlapping confidence intervals 

(Lepomis spp., Micropterus spp., Perca spp., Pimephales spp., and Catostomus spp.) 

indicating no differences in survival between the laboratory and field. For the remaining 

four groups of fish (family Ictaluridae, freshwater drum, Morone spp., and Notropis spp 

+ Notemigonus spp.), laboratory results were higher than those observed in the field. 

Surprisingly, in-field survival of catfish (channel catfish, brown bullhead, and white 

catfish), which are often considered “hardy,” was substantially lower than that observed 

in the laboratory (74.9% vs. 99.6%) (Table 10). It is unclear what factors are 

contributing to the lower survival rates observed for some of the species in the field. 

Previous research has identified several factors that influence the potential for postimpingement organism survival. These factors include: time between screen washes 

(e.g., Chase 1975, King et al. 1978, Tatham et al. 1978), salinity (e.g., Bowser and 

Buttner 1991, Kane et al. 1990, Palawski et al. 1985), debris loading (Landry and Strawn 

1974), and water temperature (e.g, Lankford 1997, Lifton and Storr 1978, Loar et al. 

1979). Additional studies tracking these and other factors in the field concurrent with 

impingement survival studies would be necessary to determine which factors are leading 

to the observed differences in survival for some species between the laboratory and field 

studies. 
31

Underwater observations indicate a substantial amount of turbulence present in 

the fish lifting bucket when velocities were greater than 0.3 m·s-1. Future study aimed at 

improving the hydraulic conditions within the fish buckets at higher velocities could 

further reduce the injury and scale loss levels observed at 0.6 m·s-1 and 0.9 m·s-1. 

Because overall rates of mortality, injury, and scale-loss were low, the relatively small 

amount of improvement that could be achieved through redesign of the fish buckets may 

not warrant the associated cost. 

Longer durations of impingement may result in higher mortality, injury, and scale 

loss, especially at durations of impingement greater than 6 minutes. However, given the 

water depth in most CWIS, there may be considerable leeway in developing an 

operations protocol that would not require continuous rotation but would still reduce 

impingement mortality. 

The results of these studies indicate that modified traveling screens should 

provide sufficient reductions in impingement mortality necessary to meet Section 316(b) 

of the Clean Water Act with the species tested in the laboratory. It should be pointed out 

that these studies only evaluated velocity and duration of impingement and their effects 

on survival in a controlled laboratory environment. Several other biotic, abiotic, and 

plant operational characteristics in real-world situations could introduce additional stress 

to aquatic organisms and increase the mortality of wild fish. Laboratory evaluation is 

only one step in the standardized process established by the American Fisheries Society, 

Bioengineering Section for the effective evaluation and application of fish passage and 

protection technologies (AFS-BES 2000). Now that laboratory evaluations have 

demonstrated the potential for modified traveling screens to protect juvenile and adult 
32

freshwater fish, the next logical step toward wide-scale application would be to conduct a 

prototype evaluation at a field location with similar species as those tested in the 

laboratory. Such an evaluation would allow researchers to assess the biological efficacy 

of modified traveling screens under the operational and environmental conditions present 

in a real-world setting. 
Table 1. Mean fork length (mm) ± standard error (SE), total number of fish tested (n), percent dead 48 hours after testing, a

intervals (CI) by species and velocity. Confidence intervals were calculated using the normal approximation of a binomial d

drum, lacking forked tails, were measured to total length. 

Mean Fork 

Length (mm) ± 

(SE)

0.3 m·s-1 0.6 m·s-1 0.9 m·s-1 

n 

% Dead at 

48 H 95% CI n 

% Dead 

at 48 H 95% CI n 

% Dead 

at 48 H 95% CI n 

Bigmouth Buffalo 

72.1 ± 0.26 245 0.0 0.0 - 0.2 94 0.0 0.0 - 0.5 142 0.0 0.0 - 0.4 29

Bluegill 47.6 ± 0.19 340 0.9 0.0 - 2.1 328 4.6 2.2 – 7.0 317 2.2 0.4 – 4.0 39Channel Catfish 

64.2 ± 0.17 206 1.0 0.0 - 2.6 148 0.0 0.0 - 0.3 246 0.4 0.0 - 1.4 49

Freshwater Drum 

84.7 ± 0.22 243 0.0 0.0 - 0.2 230 0.0 0.0 - 0.2 204 0.5 0.0 - 1.7 51

Fathead Minnow 

54.5 ± 0.16 393 2.3 0.7 - 3.9 343 3.2 1.2 - 5.2 296 1.7 0.1 - 3.3 49

Golden Shiner 

74.3 ± 0.31 365 1.6 0.2 – 

3.0 

374 1.3 0.0 - 2.6 389 1.5 0.2 - 2.8 48

Hybrid Bass 60.6 ± 0.14 243 0.4 0.0 - 1.4 241 0.0 0.0 - 0.2 356 0.3 0.0 – 1.0 49Largemouth Bass 

98.5 ± 0.30 394 1.0 0.0 - 2.1 359 2.2 0.5 - 3.9 361 2.8 1.0 - 4.6 50

White Sucker 79.8 ± 0.35 373 4.3 2.1 - 6.5 339 4.7 2.3 - 7.1 374 4.5 2.3 - 6.7 45Yellow Perch 49.7 ± 0.27 120 0.8 0.0 - 2.8 156 2.6 0.0 - 5.4 162 1.2 0.0 - 3.2 49

33
34 

Table 2. Summary of pertinent p-values from the maximum likelihood estimates for the mortality 

regression models for all species tested. (a

) Significant differences at p<0.05; (↓) mortality 

decreased significantly with increasing fish length; (+) treatment fish exhibited significantly greater 

mortality than the control. 

Species Model Length Velocity 0.3 m·s-1 0.6 m·s-1 0.9 m·s-1

Bigmouth Buffalo 0.8233 -- -- -- -- -- 

Bluegill <0.0001a <0.0001a ↓ 0.0005a 0.8860 0.0004a + 0.0601 +

Channel Catfish 0.6336 -- -- -- -- -- 

Freshwater Drum 0.1903 -- -- -- -- -- 

Fathead Minnow 0.2147 -- -- -- -- -- 

Golden Shiner 0.0003a

 <0.0001a ↓ 0.7242 -- -- -- 

Hybrid Bass 0.9921 -- -- -- -- -- 

Largemouth Bass 0.0549 0.0773 0.1170 -- -- -- 

White Sucker <0.0001a

 <0.0001a ↓ 0.7423 -- -- -- 

Yellow Perch 0.0392a

 0.0052a ↓ 0.3143 -- -- -- 
35 

Table 3. Percent injury by species and velocity.

Species 

Velocity 

(m·s-1) 

Percent 

Injured Species 

Velocity 

(m·s-1) 

Percent 

Injured 

Bigmouth 

Buffalo 

0.3 1.6% Golden Shiner 0.3 2.7%

0.6 1.1% 0.6 4.6%

0.9 3.5% 0.9 2.6%

Control 1.4% Control 3.7%

 

Bluegill 0.3 6.8% Hybrid Bass 0.3 0.0%

0.6 7.3% 0.6 0.0%

0.9 4.4% 0.9 0.3%

Control 4.8% Control 0.0%

 

Channel 

Catfish 

0.3 3.4% Largemouth 

Bass 

0.3 0.8%

0.6 0.0% 0.6 6.1%

0.9 0.4% 0.9 3.9%

Control 0.6% Control 1.6%

 

Freshwater 

Drum 

0.3 0.0% White Sucker 0.3 28.7%

0.6 0.9% 0.6 25.4%

0.9 0.0% 0.9 22.5%

Control 1.0% Control 20.0%

 

Fathead 

Minnow 

0.3 23.4% Yellow Perch 0.3 1.7%

0.6 18.1% 0.6 1.9%

0.9 13.9% 0.9 0.0%

Control 15.0% Control 1.0%
36 

Table 4. Summary of pertinent p-values from the maximum likelihood estimates for the injury 

regression models for all species tested. (a

) Significant differences at p<0.05; (↓) injury 

decreased significantly with increasing fish length; (+) treatment fish exhibited significantly greater 

injury than the control.

Species Model Length Velocity 0.3 m·s-1 0.6 m·s-1 0.9 m·s-1

Bigmouth Buffalo 0.0225a 0.0040a ↓ 0.2683 -- -- -- 

Bluegill <0.0001a <0.0001a ↓ 0.1392 -- -- -- 

Bluegill 

(excluding CA) 

0.0011a

 0.0067a ↓ 0.0077a 0.0034a + 0.3942 0.6589 

Channel Catfish 0.0202a

 0.0699 0.0295a 0.0097a + 0.9714 0.7655 

Freshwater Drum 0.0002a

 <0.0001a ↓ 0.9959 -- -- -- 

Fathead Minnow 0.0114a

 0.1924 0.0150a 0.0088a + 0.3043 0.5823 

Fathead Minnow 

(excluding CA) 

0.0037a

 0.0962 0.0085a 0.0034a + 0.3294 0.8100 

Golden Shiner 0.5768 -- -- -- -- -- 

Hybrid Bass 0.9929 -- -- -- -- -- 

Largemouth Bass 0.0003a

 0.2244 0.0002a 0.2762 0.0009a + 0.0471a +

White Sucker <0.0001a

 <0.0001a ↓ 0.5949 -- -- -- 

Yellow Perch 0.1659 -- -- -- -- -- 
Table 5. Percent of scale loss category by velocity and species.

Species 

Scale 

loss 

Velocity 

Species 

Scale 

loss 

Velo

0.30 

m·s-1

0.61 

m·s-1

0.91 

m·s-1 Ctrl 

0.30 

m·s-1

0.61 

m·s-1

Bigmouth Buffalo 

<3% 42.0 16.0 29.6 48.5 Hybrid Striped 

Bass 

<3% 97.9 99.2 

3–20% 45.3 58.5 21.1 38.0 3–20% 2.1 0.8 

20–40% 9.4 18.1 15.5 10.2 20–40% 0.0 0.0 

>40% 3.3 7.5 33.8 3.4 >40% 0.0 0.0 

Bluegill <3% 88.8 84.8 82.3 91.7 Largemouth 

Bass 

<3% 99.0 99.2 

3–20% 8.5 7.9 7.6 2.5 3–20% 0.5 0.8 

20–40% 1.5 2.7 6.9 2.8 20–40% 0.5 0.0 

>40% 1.2 4.6 3.2 3.0 >40% 0.0 0.0 

Freshwater Drum 

<3% 99.6 95.7 96.1 99.4 White Sucker <3% 72.9 59.3 

3–20% 0.4 3.9 3.9 0.4 3–20% 17.2 20.7 

20–40% 0.0 0.0 0.0 0.0 20–40% 7.5 15.0 

>40% 0.0 0.4 0.0 0.2 >40% 2.4 5.0 

Fathead Minnow 

<3% 76.6 84.8 85.1 86.4 Yellow Perch <3% 100.0 98.1 

3–20% 19.3 12.2 11.5 10.1 3–20% 0.0 0.0 

20–40% 3.8 2.0 3.4 1.6 20–40% 0.0 1.9 

>40% 0.3 0.9 0.0 1.8 >40% 0.0 0.0 

Golden Shiner 

<3% 24.7 23.0 15.9 48.3 

3–20% 40.0 38.5 31.1 40.4 

20–40% 27.1 23.3 28.0 9.5 

>40% 8.2 15.2 24.9 1.9 

37
38 

Table 6. Summary of pertinent p-values from the maximum likelihood estimates for the scale 

loss regression models for all species tested. (a

) Significant differences at p<0.05; (↓) scale loss 

decreased significantly with increasing fish length; (+) treatment fish exhibited significantly greater 

scale loss than the control.

Species Model Length Velocity 0.3 m·s-1 0.6 m·s-1 0.9 m·s-1

Bigmouth Buffalo <0.0001a <0.0001a ↓ <0.0001a 0.2783 <0.0001a + <0.0001a +

Bluegill <0.0001a <0.0001a ↓ 0.0001a 0.1338 0.0004a + <0.0001a +

Freshwater Drum <0.0001a

 <0.0001a ↓ 0.0012a 0.7322 0.0013a + 0.0021a +

Fathead Minnow 0.0030a

 0.7829 0.0011a 0.0003a + 0.5454 0.6294 

Golden Shiner <0.0001a

 <0.0001a ↓ <0.0001a <0.0001a + <0.0001a + <0.0001a +

Hybrid Bass 0.3758 -- -- -- -- -- 

Largemouth Bass 0.3131 -- -- -- -- -- 

White Sucker <0.0001a

 <0.0001a ↓ <0.0001a 0.4865 <0.0001 + <0.0001 +

Yellow Perch 0.0753 -- -- -- -- -- 

Table 7. Mortality and injury rates (percent) by species and duration of impingement (DI) tests.

Species 

Duration of Impingement (min) 

2 4 6 8 10 Control 

Channel Catfish Mortality -- -- 0.0 0.0 0.0 0.8 

 Injury -- -- 0.0 0.0 0.0 0.0 

Fathead Minnow Mortality -- -- 6.4 6.7 2.9 0.7 

 Injury -- -- 8.5 3.3 2.9 1.3 

Golden Shiner Mortality 0.0 0.0 3.8 15.1 12.7 9.3 

 Injury 0.0 0.0 5.0 6.9 9.9 9.3 
39

Table 8. Percent of scale loss categories by species and duration of impingement (DI).

Species 

Scale Loss 

Category 

Duration of Impingement (min) 

2 4 6 8 10 Control 

Fathead Minnow 1 -- -- 95.7 80.0 94.3 98.7 

 2 -- -- 0.0 10.0 2.9 1.3 

 3 -- -- 0.0 6.7 0.0 0.0 

 4 -- -- 4.3 3.3 2.9 0.0 

 

Golden Shiner 1 0.0 0.0 3.8 2.7 14.1 42.9 

 2 28.6 11.1 8.8 9.6 12.7 41.9 

 3 14.3 33.3 16.3 15.1 12.7 7.6 

 4 57.1 55.6 71.3 72.6 60.6 7.6 

Table 9. Summary of pertinent p-values from the maximum likelihood estimates for the mortality, 

injury, and scale loss regression models for species tested during duration of impingement (DI) 

testing. Metrics for measuring performance included: mortality (M), injury (I), total injury – control 

injury (I-C), and scale-loss (SL). (a

) Significant differences at p<0.05; (↓) metric (mortality, injury, 

or scale loss) decreased with increasing fish length; (↑) metric significantly increased with 

increase in DI. There were no injuries or mortality observed among channel catfish.

Species Metric Model Length Duration 

Fathead Minnow M 0.1244 

 I 0.3688 

 SL 0.0270a

 0.0067a ↓ 0.019 ↑

 

Golden Shiner M 0.0001a

 0.0001a ↓ 0.0038a ↑

 I 0.0170a

 0.0050a ↓ 0.1464 

 I-C 0.0073a

 0.0047a ↓ 0.0948 

 SL <0.0001a 0.0144a ↓ <0.0001a ↑
Table 10. Comparison of laboratory results to those observed in previous pilot- and full-scale field evaluations. Data summ

Normandeau 1995 (Roseton); Beak Consultants 2000a (Dunkirk), Beak Consultants 2000b (Huntley); Fletcher 1990 (India

Edison 1996 (Arthur Kill); PSE&G 1999 (Salem); PSEG 2004 (Salem).

Field Laboratory 

Species N 

Weighted

Mean -95% CI +95% CI N 

Weighted 

Mean -95% C

Ictaluridae 1,647 74.9 72.7 77.0 600 99.5 98.

freshwater drum 5 60.0 7.0 100.0 677 99.8 99.Lepomis spp. 499 93.8 91.5 96.0 985 97.4 96.Micropterus spp. 42 92.8 83.8 100.0 1,114 98.0 97.Morone spp. 26,519 60.0 59.3 60.5 840 99.8 99.Notropis spp.& Notemigonus spp. 29,906 79.1 78.6 79.5 1,128 98.5 97.

Perca spp. 280 98.9 97.5 100.0 438 98.4 97.Pimephales spp. 12 91.7 71.8 100.0 1,032 97.6 96.

Catostomus spp. 14 100.0 96.4 100.0 1,086 95.5 94.

40
Figure 1. Test flume including isolation screen, traveling water screen, collection trough, and collection net.

41
42

Bruising or Hemorrhaging (29.7%)

Severed Body (0.2%)

Predation (4.4%)

Lacerations or Tears (2.3%)

Fin Damage (40.3%)

Eye Damage (3.5%)

Disease or Fungus (19.7%)

Figure 2. Distribution of injury types 
43

APPENDIX A

PHOTOS OF FACILITIES AND TESTING PROCEDURES 

Figure A-1. Overview of modified screen testing facility.
44

Figure A-2. Modified traveling screen in the dewatered test flume.

Figure A-3. Fish holding facility.
45

Figure A-4. Marking fish using marking gun.

Figure A-5. Still image captured from the submersible video camera showing fish impingement 

on the traveling water screen.
46

Figure A-6. Test enclosure showing upstream isolation screen (left) and the ascending face of 

the traveling water screen (right).

A B

Figure A-7. Crowding fish (A) and mechanical crowder in the full upright position (B).
47

Figure A-8. Fish collection and transfer to holding facility. 

Figure A-9 Measuring and examining fish for external injuries.
48

Figure A-10. Fish in a water-filled bucket above the flume water line.
49

APPENDIX B

IMPINGEMENT ON TRADITIONAL TRAVELING SCREENS COMPARED TO 

MODIFIED TRAVELING SCREENS 

Fish impingement on a modified traveling screen is different than the 

impingement experience on a conventional traveling screen. On conventional traveling 

screens, the screen face is perpendicular to the flow and there is no refuge for fish until 

they are removed from the flow. By contrast, each screen panel on the modified screen 

tested is slightly inclined to the flow. This slight incline appeared to help fish move 

toward the fish bucket (Figure B-1). However, the extent to which this incline reduces 

the potential for mortality is unknown. 
50

Flow 

Direction of

Rotation 

A. Conventional Screen

Flow

Direction of 

Rotation 

B. Modified Traveling Screen

Screen

Screen Mesh 

Mesh 

Figure B-1. Comparison of a conventional screen (A) to a modified traveling screen (B) showing 

the angle of the screen faces to the approaching flow.
APPENDIX C

WEEKLY TESTING, WATER SAMPLING, AND FISH CARE SCHEDULE 

51
52

APPENDIX D

COLLECTION TIME 

Table D-1. Percent of fish collected by species, collection time, and velocity treatment.

Species Collection Time

0.3 m·s-1 0.6 m·s-1 0.9 m·s-1 Control 

n % n % n % n 

Bigmouth Buffalo 15 min 3 1.2 33 35.1 132 93.0 

1 hr 3 1.2 3 3.2 5 3.5 

2 hr 0.0 0.0 3 2.1 

Crowd 239 97.6 58 61.7 2 1.4 

Control 295 

 

Bluegill 15 min 66 19.4 225 68.6 317 100.0 

1 hr 11 3.2 17 5.2 0.0 

2 hr 17 5.0 10 3.0 0.0 

Crowd 246 72.4 76 23.2 0.0 

Control 397 

 

Channel Catfish 15 min 48 23.3 71 48.0 174 70.7 

1 hr 58 28.2 26 17.6 40 16.3 

2 hr 33 16.0 13 8.8 17 6.9 

Crowd 67 32.5 38 25.7 15 6.1 

Control 490 

 

Freshwater Drum 15 min 15 6.2 46 20.0 203 99.5 

1 hr 6 2.5 9 3.9 0.0 

2 hr 9 3.7 10 4.3 0.0 

Crowd 213 87.7 165 71.7 1 0.5 

Control 512 

 

Fathead Minnow 15 min 164 41.7 307 89.5 295 99.7 

1 hr 25 6.4 16 4.7 0.0 

2 hr 36 9.2 9 2.6 1 0.3 

Crowd 168 42.7 11 3.2 0.0 

Control 493 
53

Table D-1 (Continued) 

Species Collection Time

0.3 m·s-1 0.6 m·s-1 0.9 m·s-1 Control 

n % n % n % n 

Golden Shiner 15 min 80 21.9 350 93.6 385 99.0 

1 hr 0.0 0.0 4 1.0 

2 hr 3 0.8 0.0 0.0 

Crowd 282 77.3 24 6.4 0.0 

Control 485 

 

Hybrid Bass 15 min 13 5.3 16 6.6 270 75.8 

1 hr 5 2.1 19 7.9 45 12.6 

2 hr 13 5.3 26 10.8 21 5.9 

Crowd 212 87.2 180 74.7 20 5.6 

Control 498 

 

Largemouth Bass 15 min 4 1.0 215 59.9 344 95.3 

1 hr 1 0.3 5 1.4 4 1.1 

2 hr 9 2.3 11 3.1 1 0.3 

Crowd 380 96.4 128 35.7 12 3.3 

Control 501 

 

White Sucker 15 min 196 52.5 273 80.5 362 96.8 

1 hr 25 6.7 22 6.5 9 2.4 

2 hr 17 4.6 7 2.1 3 0.8 

Crowd 135 36.2 37 10.9 0.0 

Control 459 

 

Yellow Perch 15 min 18 15.0 118 75.6 159 98.1 

1 hr 10 8.3 10 6.4 3 1.9 

2 hr 5 4.2 7 4.5 0.0 

Crowd 87 72.5 21 13.5 0.0 

Control 498 
54

APPENDIX E

STATISTICAL ANALYSIS TABLES – VELOCITY TESTS 

Species-specific results of the logistic regressions are presented in the following 

tables. For each species, the first table presents the raw frequencies and summary 

statistics by velocity treatment, and the second table presents a summary of logistic 

regression results. The first table for each species shows the frequency of live, dead (or 

injured, not injured), and total recovered for each velocity, as well as percent dead or 

injured and mean length. The second table for each species summarizes various 

estimates obtained from the logistic regression analyses. The first row shows the 

intercept of the model, which is generally not of interest but was given for completeness. 

The second, third, and fourth rows give estimates of the difference in logits between 

mortality or injury in the treatment conditions 0.3 m·s-1, 0.6 m·s-1, and 0.9 m·s-1, 

respectively, and the control. Row 5 reports the cumulative chi-square for all velocity 

treatments. Row 6 presents the coefficient of the covariate Fork Length and row 7 

reports the cumulative chi-square for the full model (velocity treatments and fork length). 

In some cases, there was too little mortality or too few injuries for a successful logistic 

regression (i.e., the model failed to converge to a reliable estimate). 

The logistic regression models are hierarchical. A flow diagram showing the 

steps described below is shown in Figure E-1. To interpret the significance of each 

component of the model (p-value), start by looking at the full model (last row in each 

table). If the p-value for the full model was >0.05, then the model failed to converge to a 

reliable estimate, and the Fork Length and Velocity components of the model were not 

significant regardless of their p-value. By contrast, if the p-value of the full model was 
55

significant (P<0.05), then the model converged to a reliable estimate and it is appropriate 

to look at the velocity and fork length components individually. Fork Length was or was 

not significant depending on the p-value; p-values <0.05 were significant. When pvalues for Velocity were >0.05, then velocity was not significant and individual 

comparisons of velocity treatments to the control were not valid regardless of their pvalue. If the p-value of the Velocity component of the model was significant (P<0.05), 

then it is appropriate to look at the individual comparisons of velocity treatments to the 

controls. When individual velocity comparisons to the control had p-values greater than 

0.05, then they were not significant. When p-values were <0.05, then the comparison 

was statistically significant. Negative estimates in Column 3 (Estimate) indicate that 

there was a decrease in mortality or injury, and positive estimates indicate there was an 

increase in mortality or injury. 

The second scale loss tables are slightly different from those for injury and 

mortality. A positive coefficient of the estimate value means the probability in the lower 

levels of scale loss increases, while a negative coefficient means the probability of lower 

levels of scale loss decreases and thus probability in the higher categories increases. 

Because these are cumulative probabilities, the intercept terms start negative and 

get progressively larger, indicating increasing probability. Cumulative probability 

moving toward levels of greater scale loss must increase because each cumulative 

probability includes the probability of the preceding level of scale loss. 
56

Bigmouth Buffalo

Table E-1. Summary of live, dead, and mean length by velocity treatment for bigmouth buffalo.

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Dead 0 0 0 1 1 

Live 245 94 142 294 775 

Percent Dead 0.00 0.00 0.00 0.34 

Total 245 94 142 295 776 

Mean Length (mm) 71.85 72.34 72.35 72.08 

Table E-2. Analysis of maximum likelihood estimates for the survival regression model for 

bigmouth buffalo. This model was not significant (P=0.8233).

 DF Estimate

Standard 

Error1

Wald 

Chi-Square2

Odds 

Ratio3 p-value4

Intercept5 1 1.6169 5.60 0.08 . 0.7729 

0.3 m·s-1 vs Con6 1 -9.7025 148.90 0.00 0.00 0.9480 

0.6 m·s-1 vs Con 1 -9.6272 243.15 0.00 0.00 0.9684 

0.9 m·s-1 vs Con 1 -9.6711 193.84 0.00 0.00 0.9602 

Velocity Effects7

 3 . . 0.01 . 0.9998 

Fork Length8

 1 -0.1070 0.09 1.51 0.90 0.2191 

Full Model9

 4 . . 1.52 . 0.8233 

 

1

 Standard error is the standard deviation of the difference between the estimated value and the true value. 

Larger numbers indicate greater deviation. A large standard error coupled with a small chi-square indicates 

that the data are not sufficient to allow precise estimates of the effects in the model. This is usually the 

result of either the sample size being too small or of there being too few positive responses. 

2

 Wald chi-squared provides the statistical significance of each independent variable in the model. 3

 Odds Ratio is a measure of effect size or strength of the relationship between two variables. An odds ratio 

of 1 indicates that the observed effect is equally likely regardless of treatment or control condition. An odds 

ratio greater than 1 indicates that the condition or event is more likely under the treatment condition than 

the control. An odds ratio less than 1 indicates that the observed response is less likely in the treatment 

than the control group. 

4

 The p-value in this case is in relation to the odds ratio. It indicates the probability of obtaining a an odds 

ratio at least as high as the predicted value. Small p-values (e.g. p-value < 0.05) indicate statistical 

significance. 

5

 The intercept of the model which is generally not of interest but is given for completeness 

6 The second, third, and fourth rows give estimates of the difference in logits between mortality in the 

treatment conditions 1 ft/s., 2 ft/s, and 3 ft/s, respectively, and the control. 

7 Cumulative chi-square for all velocity treatments 

8 Coefficient of the covariate fork length 

9 Cumulative chi-square for the full model 
57

Table E-3. Summary of injury rate and mean length by velocity treatment for bigmouth buffalo.

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Injured 4 1 5 3 13 

Not Injured 241 93 137 292 763 

Percent Injured 1.63 1.06 3.52 1.02 . 

Total 245 94 142 295 776 

Mean Length 71.85 72.34 72.35 72.08 . 

Table E-4. Analysis of maximum likelihood estimates for the injury regression model for 

bigmouth buffalo. This model was significant (P=0.0225)

 DF Estimate

Standard

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 2.4940 2.39 1.09 . 0.2958 

0.3 m·s-1 vs Con 1 0.5780 0.78 0.55 1.78 0.4598 

0.6 m·s-1 vs Con 1 0.2320 1.18 0.04 1.26 0.8435 

0.9 m·s-1 vs Con 1 1.3971 0.75 3.44 4.04 0.0637 

Velocity Effects 3 . . 3.94 . 0.2683 

Fork Length 1 -0.1031 0.04 8.30 0.90 0.0040 

Full Model 4 . . 11.39 . 0.0225 
58

Table E-5. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for bigmouth buffalo.

Scale Loss 

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

1 Frequency 103 15 42 143 303 

 Percent 42.04 15.96 29.58 48.47 . 

2 Frequency 111 55 30 112 308 

 Percent 45.31 58.51 21.13 37.97 . 

3 Frequency 23 17 22 30 92 

 Percent 9.39 18.09 15.49 10.17 . 

4 Frequency 8 7 48 10 73 

 Percent 3.27 7.45 33.80 3.39 . 

Total Frequency 245 94 142 295 776 

Mean Length 71.85 72.34 72.35 72.08 

Table E-6. Analysis of maximum likelihood estimates for the scale loss regression model for 

bigmouth buffalo. This model was significant (P<0.0001)

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 1 -3.5704 0.71 25.64 . <0.0001

Intercept 2 1 -1.6325 0.70 5.50 . 0.0190 

Intercept 3 1 -0.5722 0.70 0.67 . 0.4120 

0.3 m·s-1 vs. Con 1 -0.1784 0.16 1.18 0.84 0.2783 

0.6 m·s-1 vs. Con 1 -1.1166 0.22 25.09 0.33 <0.0001

0.9 m·s-1 vs. Con 1 -1.7086 0.20 74.67 0.18 <0.0001

Velocity Effects 3 . . 89.80 . <0.0001

Fork Length 1 0.0488 0.01 25.54 1.05 <0.0001

Full Model 4 . . 108.06 . <0.0001
59

Bluegill

Table E-7. Summary of live, dead, and mean length by velocity treatment for bluegill.

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Dead 3 15 7 6 31 

Live 337 313 310 391 1,351 

Percent Dead 0.88 4.57 2.21 1.51 . 

Total 340 328 317 397 1,382 

Mean Length (mm) 47.01 47.27 46.96 45.74 . 

Table E-8. Analysis of maximum likelihood estimates for the survival regression model for 

bluegill. This model was significant (P<0.0001).

 DF Estimate

Standard

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 6.9443 1.65 17.72 . <0.0001

0.3 m·s-1 vs Con 1 -0.1062 0.74 0.02 0.90 0.8860 

0.6 m·s-1 vs Con 1 2.0153 0.57 12.55 7.50 0.0004 

0.9 m·s-1 vs Con 1 1.1757 0.63 3.54 3.24 0.0601 

Velocity Effects 3 . . 17.70 . 0.0005 

Fork Length 1 -0.2728 0.04 39.11 0.76 <0.0001

Full Model 4 . . 43.88 . <0.0001
60

Table E-9. Summary of injury rate and mean length by velocity treatment for bluegill.

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Injured 23 24 14 19 80 

Not Injured 317 304 303 378 1,302 

Percent Injured 6.76 7.32 4.42 4.79 . 

Total 340 328 317 397 1,382 

Mean Length 47.01 47.27 46.96 45.74 . 

Table E-10. Analysis of maximum likelihood estimates for the injury regression model for bluegill. 

This model was significant (P<0.0001).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 1.5870 0.96 2.71 . 0.0995 

0.3 m·s-1 vs Con 1 0.5043 0.32 2.41 1.66 0.1204 

0.6 m·s-1 vs Con 1 0.6403 0.32 3.91 1.90 0.0481 

0.9 m·s-1 vs Con 1 0.0668 0.37 0.03 1.07 0.8551 

Velocity Effects 3 . . 5.49 . 0.1392 

Fork Length 1 -0.1044 0.02 22.20 0.90 <0.0001

Full Model 4 . . 25.80 . <0.0001

Table E-11. Summary of injury rate and mean length by velocity treatment for bluegill excluding 

conspecific aggression injury.

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Injured 23 14 13 6 56 

Not Injured 317 304 303 378 1,302 

Percent Injured 6.76 4.40 4.11 1.56 . 

Total 340 318 316 384 1,358 

Mean Length 47.01 47.41 46.98 45.96 . 
61

Table E-12. Analysis of maximum likelihood estimates for the injury regression model for bluegill 

excluding conspecific aggression injury. This model was significant (P<0.0011).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 -1.1059 1.17 0.90 . 0.3430 

0.3 m·s-1 vs Con 1 1.5913 0.47 11.63 4.91 0.0006 

0.6 m·s-1 vs Con 1 1.1674 0.50 5.52 3.21 0.0188 

0.9 m·s-1 vs Con 1 1.0681 0.50 4.53 2.91 0.0332 

Velocity Effects 3 . . 11.91 . 0.0077 

Fork Length 1 -0.0680 0.03 7.34 0.93 0.0067 

Full Model 4 . . 18.35 . 0.0011 

Table E-13. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for bluegill.

Scale Loss 

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

1 Frequency 302 278 261 364 1,205

 Percent 88.82 84.76 82.33 91.69 . 

2 Frequency 29 26 24 10 89 

 Percent 8.53 7.93 7.57 2.52 . 

3 Frequency 5 9 22 11 47 

 Percent 1.47 2.74 6.94 2.77 . 

4 Frequency 4 15 10 12 41 

 Percent 1.18 4.57 3.15 3.02 . 

Total Frequency 340 328 317 397 1,382

Mean Length 47.01 47.27 46.96 45.74 
62

Table E-14. Analysis of maximum likelihood estimates for the scale loss regression model for 

bluegill. This model was significant (P<0.0001).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 1 -1.7708 0.69 6.53 . 0.0106 

Intercept 2 1 -0.9764 0.69 1.98 . 0.1597 

Intercept 3 1 -0.1596 0.70 0.05 . 0.8202 

0.3 m·s-1 vs. Con 1 -0.3814 0.25 2.25 0.68 0.1338 

0.6 m·s-1 vs. Con 1 -0.8550 0.24 12.65 0.43 0.0004 

0.9 m·s-1 vs. Con 1 -0.9796 0.24 17.12 0.38 <0.0001

Velocity Effects 3 . . 21.19 . 0.0001 

Fork Length 1 0.0938 0.02 35.95 1.10 <0.0001

Full Model 4 . . 50.06 . <0.0001
63

Channel Catfish

Table E-15. Summary of live, dead, and mean length by velocity treatment for channel catfish.

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Dead 2 0 1 0 3 

Live 204 148 245 490 1,087 

Percent Dead 0.97 0.00 0.41 0.00 . 

Total 206 148 246 490 1,090 

Mean Length (mm) 63.53 62.46 63.81 63.13 . 

Table E-16. Analysis of maximum likelihood estimates for the survival regression model for 

channel catfish. This model was not significant (P=0.6336).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 -7.9326 121.52 0.00 . 0.9480 

0.3 m·s-1 vs Con 1 11.2827 121.41 0.01 79435.08 0.9260 

0.6 m·s-1 vs Con 1 -0.0559 249.68 0.00 0.95 0.9998 

0.9 m·s-1 vs Con 1 10.4145 121.41 0.01 33338.53 0.9316 

Velocity Effects 3 . . 0.51 . 0.9173 

Fork Length 1 -0.1312 0.09 2.06 0.88 0.1508 

Full Model 4 . . 2.56 . 0.6336 

Table E-17. Summary of injury rate and mean length by velocity treatment for channel catfish.

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Injured 7 0 1 3 11 

Not Injured 199 148 245 487 1,079 

Percent Injured 3.40 0.00 0.41 0.61 . 

Total 206 148 246 490 1,090 

Mean Length 63.53 62.46 63.81 63.13 . 
64

Table E-18. Analysis of maximum likelihood estimates for the injury regression model for 

channel catfish. This model was significant (P=0.0202).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 -0.0133 2.77 0.00 . 0.9962 

0.3 m·s-1 vs Con 1 1.8068 0.70 6.68 6.09 0.0097 

0.6 m·s-1 vs Con 1 -11.5136 321.34 0.00 0.00 0.9714 

0.9 m·s-1 vs Con 1 -0.3458 1.16 0.09 0.71 0.7655 

Velocity Effects 3 . . 8.99 . 0.0295 

Fork Length 1 -0.0831 0.05 3.29 0.92 0.0699 

Full Model 4 . . 11.65 . 0.0202 
65

Freshwater Drum

Table E-19. Summary of live, dead, and mean length by velocity treatment for freshwater drum.

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Dead 0 0 1 1 2 

Live 243 230 203 511 1,187 

Percent Dead 0.00 0.00 0.49 0.20 . 

Total 243 230 204 512 1,189 

Mean Length (mm) 84.60 84.49 84.95 84.67 . 

Table E-20. Analysis of maximum likelihood estimates for the survival regression model for 

freshwater drum. This model was not significant (P=0.1903).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 6.4441 4.35 2.19 . 0.1386 

0.3 m·s-1 vs Con 1 -10.3575 257.77 0.00 0.00 0.9679 

0.6 m·s-1 vs Con 1 -10.8099 246.42 0.00 0.00 0.9650 

0.9 m·s-1 vs Con 1 1.9176 1.72 1.24 6.80 0.2658 

Velocity Effects 3 . . 1.24 . 0.7429 

Fork Length 1 -0.1731 0.07 6.06 0.84 0.0138 

Full Model 4 . . 6.12 . 0.1903 

Table E-21. Summary of injury rate and mean length by velocity treatment for freshwater drum.

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Injured 0 2 0 5 7 

Not Injured 243 228 204 507 1,182 

Percent Injured 0.00 0.87 0.00 0.98 . 

Total 243 230 204 512 1,189 

Mean Length 84.60 84.49 84.95 84.67 . 
66

Table E-22. Analysis of maximum likelihood estimates for the injury regression model for 

freshwater drum. This model was significant (P=0.0002).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 6.7508 2.20 9.39 . 0.0022 

0.3 m·s-1 vs Con 1 -11.8074 221.64 0.00 0.00 0.9575 

0.6 m·s-1 vs Con 1 -0.2255 0.94 0.06 0.80 0.8098 

0.9 m·s-1 vs Con 1 -11.4589 285.35 0.00 0.00 0.9680 

Velocity Effects 3 . . 0.06 . 0.9959 

Fork Length 1 -0.1496 0.03 21.67 0.86 <0.0001

Full Model 4 . . 21.68 . 0.0002 

Table E-23. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for freshwater drum.

Scale Loss 

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

1 Frequency 242 220 196 509 1,167

 Percent 99.59 95.65 96.08 99.41 . 

2 Frequency 1 9 8 2 20 

 Percent 0.41 3.91 3.92 0.39 . 

4 Frequency 0 1 0 1 2 

 Percent 0.00 0.43 0.00 0.20 . 

Total Frequency 243 230 204 512 1,189

Mean Length 84.60 84.49 84.95 84.67 
67

Table E-24. Analysis of maximum likelihood estimates for the scale loss regression model for 

freshwater drum. This model was significant (P<0.0001).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 1 -2.1849 1.59 1.88 . 0.1706 

Intercept 2 1 0.3209 1.70 0.04 . 0.8503 

0.3 m·s-1 vs. Con 1 0.3965 1.16 0.12 1.49 0.7322 

0.6 m·s-1 vs. Con 1 -2.1394 0.66 10.40 0.12 0.0013 

0.9 m·s-1 vs. Con 1 -2.1191 0.69 9.45 0.12 0.0021 

Velocity Effects 3 . . 15.86 . 0.0012 

Fork Length 1 0.0914 0.02 20.38 1.10 <0.0001

Full Model 4 . . 31.67 . <0.0001
68

Fathead Minnow

Table E-25. Summary of live, dead, and mean length by velocity treatment for fathead minnow.

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Dead 9 11 5 6 31 

Live 384 332 291 487 1,494 

Percent Dead 2.29 3.21 1.69 1.22 . 

Total 393 343 296 493 1,525 

Mean Length (mm) 56.38 56.22 55.83 54.14 . 

Table E-26. Analysis of maximum likelihood estimates for the survival regression model for 

fathead minnow. This model was not significant (P=0.2147).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 -2.1728 1.67 1.69 . 0.1933 

0.3 m·s-1 vs Con 1 0.7557 0.54 1.95 2.13 0.1622 

0.6 m·s-1 vs Con 1 1.0930 0.52 4.41 2.98 0.0358 

0.9 m·s-1 vs Con 1 0.4206 0.62 0.47 1.52 0.4943 

Velocity Effects 3 . . 4.79 . 0.1876 

Fork Length 1 -0.0419 0.03 1.81 0.96 0.1783 

Full Model 4 . . 5.80 . 0.2147 

Table E-27. Summary of injury rate and mean length by velocity treatment for fathead minnow.

 Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Injured 88 62 41 74 265 

Not Injured 305 281 255 419 1,260 

Percent Injured 22.39 18.08 13.85 15.01 . 

Total 393 343 296 493 1,525 

Mean Length 56.38 56.22 55.83 54.14 . 
69

Table E-28. Analysis of maximum likelihood estimates for the injury regression model for fathead 

minnow. This model was significant (P=0.0114).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 -2.4897 0.60 17.44 . 0.0000 

0.3 m·s-1 vs Con 1 0.4616 0.18 6.87 1.59 0.0088 

0.6 m·s-1 vs Con 1 0.1950 0.19 1.06 1.22 0.3043 

0.9 m·s-1 vs Con 1 -0.1161 0.21 0.30 0.89 0.5823 

Velocity Effects 3 . . 10.46 . 0.0150 

Fork Length 1 0.0139 0.01 1.70 1.01 0.1924 

Full Model 4 . . 12.98 . 0.0114 

Table E-29. Summary of injury rate and mean length by velocity treatment for fathead minnow 

excluding conspecific aggression injury.

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Injured 88 58 41 69 256 

Not Injured 305 281 255 419 1,260 

Percent Injured 22.39 17.11 13.85 14.14 . 

Total 393 339 296 488 1,516 

Mean Length 56.38 56.27 55.83 54.18 . 

Table E-30. Analysis of maximum likelihood estimates for the injury regression model for fathead 

minnow excluding conspecific injury. This model was significant (P=0,0037).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 -2.7854 0.61 21.00 . <0.0001

0.3 m·s-1 vs Con 1 0.5245 0.18 8.60 1.69 0.0034 

0.6 m·s-1 vs Con 1 0.1905 0.20 0.95 1.21 0.3294 

0.9 m·s-1 vs Con 1 -0.0513 0.21 0.06 0.95 0.8100 

Velocity Effects 3 . . 11.69 . 0.0085 

Fork Length 1 0.0180 0.01 2.77 1.02 0.0962 

Full Model 4 . . 15.52 . 0.0037 
70

Table E-31. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for fathead minnow.

Scale Loss 

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

1 Frequency 301 291 252 426 1,270

 Percent 76.59 84.84 85.14 86.41 . 

2 Frequency 76 42 34 50 202 

 Percent 19.34 12.24 11.49 10.14 . 

3 Frequency 15 7 10 8 40 

 Percent 3.82 2.04 3.38 1.62 . 

4 Frequency 1 3 0 9 13 

 Percent 0.25 0.87 0.00 1.83 . 

Total Frequency 393 343 296 493 1,525

Mean Length 56.38 56.22 55.83 54.14 

Table E-32. Analysis of maximum likelihood estimates for the scale loss regression model for 

fathead minnow. This model was significant (P=0.0030).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 1 1.6749 0.61 7.60 . 0.0058 

Intercept 2 1 3.4052 0.62 30.18 . <0.0001

Intercept 3 1 4.8381 0.67 52.91 . <0.0001

0.3 m·s-1 vs. Con 1 -0.6443 0.18 13.02 0.53 0.0003 

0.6 m·s-1 vs. Con 1 -0.1213 0.20 0.37 0.89 0.5454 

0.9 m·s-1 vs. Con 1 -0.1012 0.21 0.23 0.90 0.6294 

Velocity Effects 3 . . 16.01 . 0.0011 

Fork Length 1 0.0030 0.01 0.08 1.00 0.7829 

Full Model 4 . . 16.03 . 0.0030 
71

Golden Shiner

Table E-33. Summary of live, dead, and mean length by velocity treatment for golden shiner.

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Dead 6 5 6 6 23 

Live 359 369 383 479 1,590 

Percent Dead 1.64 1.34 1.54 1.24 . 

Total 365 374 389 485 1,613 

Mean Length (mm) 75.19 73.36 73.69 73.13 . 

Table E-34. Analysis of maximum likelihood estimates for the survival regression model for 

golden shiner. This model was significant (P=0.0003).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 1.2373 1.15 1.16 . 0.2815 

0.3 m·s-1 vs Con 1 0.6216 0.60 1.08 1.86 0.2990 

0.6 m·s-1 vs Con 1 0.2818 0.62 0.20 1.33 0.6507 

0.9 m·s-1 vs Con 1 0.5513 0.60 0.84 1.74 0.3596 

Velocity Effects 3 . . 1.32 . 0.7242 

Fork Length 1 -0.0876 0.02 21.07 0.92 <0.0001

Full Model 4 . . 21.26 . 0.0003 

Table E-35. Summary of injury rate and mean length by velocity treatment for golden shiner.

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Injured 10 17 10 18 55 

Not Injured 355 357 379 467 1,558 

Percent Injured 2.74 4.55 2.57 3.71 . 

Total 365 374 389 485 1,613 

Mean Length 75.19 73.36 73.69 73.13 . 
72

Table E-36. Analysis of maximum likelihood estimates for the injury regression model for golden 

shiner. This model was not significant (P=0.5768).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 -3.1714 0.77 16.78 . <0.0001

0.3 m·s-1 vs Con 1 -0.3112 0.40 0.60 0.73 0.4380 

0.6 m·s-1 vs Con 1 0.2117 0.35 0.38 1.24 0.5399 

0.9 m·s-1 vs Con 1 -0.3783 0.40 0.89 0.69 0.3448 

Velocity Effects 3 . . 2.86 . 0.4141 

Fork Length 1 -0.0012 0.01 0.01 1.00 0.9087 

Full Model 4 . . 2.89 . 0.5768 

Table E-37. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for golden shiner.

Scale Loss 

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

1 Frequency 90 86 62 234 472 

 Percent 24.66 22.99 15.94 48.25 . 

2 Frequency 146 144 121 196 607 

 Percent 40.00 38.50 31.11 40.41 . 

3 Frequency 99 87 109 46 341 

 Percent 27.12 23.26 28.02 9.48 . 

4 Frequency 30 57 97 9 193 

 Percent 8.22 15.24 24.94 1.86 . 

Total Frequency 365 374 389 485 1,613

Mean Length 75.19 73.36 73.69 73.13 
73

Table E-38. Analysis of maximum likelihood estimates for the scale loss regression model for 

golden shiner. This model was significant (P<0.0001).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 1 -2.1518 0.27 63.72 . <0.0001

Intercept 2 1 -0.3207 0.26 1.47 . 0.2252 

Intercept 3 1 1.1099 0.27 17.28 . <0.0001

0.3 m·s-1 vs. Con 1 -1.1969 0.13 81.71 0.30 <0.0001

0.6 m·s-1 vs. Con 1 -1.3252 0.13 101.23 0.27 <0.0001

0.9 m·s-1 vs. Con 1 -1.9675 0.13 215.66 0.14 <0.0001

Velocity Effects 3 . . 226.75 . <0.0001

Fork Length 1 0.0293 0.00 70.32 1.03 <0.0001

Full Model 4 . . 274.29 . <0.0001
74

Hybrid Striped Bass

Table E-39. Summary of live, dead, and mean length by velocity treatment for hybrid striped 

bass.

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Dead 1 0 1 0 2 

Live 242 241 355 498 1,336 

Percent Dead 0.41 0.00 0.28 0.00 . 

Total 243 241 356 498 1,338 

Mean Length (mm) 60.54 60.59 60.31 60.88 . 

Table E-40. Analysis of maximum likelihood estimates for the survival regression model for 

hybrid striped bass. This model was not significant (P=0.9921).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 -19.3077 167.89 0.01 . 0.9084 

0.3 m·s-1 vs Con 1 10.9720 167.75 0.00 58223.71 0.9478 

0.6 m·s-1 vs Con 1 0.0130 293.80 0.00 1.01 1.0000 

0.9 m·s-1 vs Con 1 10.6148 167.75 0.00 40735.18 0.9495 

Velocity Effects 3 . . 0.07 . 0.9952 

Fork Length 1 0.0463 0.11 0.17 1.05 0.6758 

Full Model 4 . . 0.26 . 0.9921 

Table E-41. Summary of injury rate and mean length by velocity treatment for hybrid striped 

bass.

 Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Injured 0 0 1 0 1 

Not Injured 243 241 355 498 1,337 

Percent Injured 0.00 0.00 0.28 0.00 . 

Total 243 241 356 498 1,338 

Mean Length 60.54 60.59 60.31 60.88 . 
75

Table E-42. Analysis of maximum likelihood estimates for the injury regression model for hybrid 

striped bass. This model was not significant (P=0.9929).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 -8.2805 127.49 0.00 . 0.9482 

0.3 m·s-1 vs Con 1 -0.3006 239.76 0.00 0.74 0.9990 

0.6 m·s-1 vs Con 1 -0.2988 239.60 0.00 0.74 0.9990 

0.9 m·s-1 vs Con 1 9.9702 126.57 0.01 21380.07 0.9372 

Velocity Effects 3 . . 0.01 . 0.9997 

Fork Length 1 -0.1280 0.26 0.24 0.88 0.6265 

Full Model 4 . . 0.25 . 0.9929 

Table E-43. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for hybrid striped bass.

Scale Loss 

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

1 Frequency 238 239 345 489 1,311

 Percent 97.94 99.17 96.91 98.19 . 

2 Frequency 5 2 10 8 25 

 Percent 2.06 0.83 2.81 1.61 . 

3 Frequency 0 0 1 1 2 

 Percent 0.00 0.00 0.28 0.20 . 

Total Frequency 243 241 356 498 1,338

Mean Length 60.54 60.59 60.31 60.88 
76

Table E-44. Analysis of maximum likelihood estimates for the scale loss regression model for 

hybrid striped bass. This model was not significant (P=0.3758).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 1 2.0212 2.48 0.66 . 0.4157 

Intercept 2 1 4.6462 2.57 3.26 . 0.0711 

0.3 m·s-1 vs. Con 1 -0.1169 0.56 0.04 0.89 0.8358 

0.6 m·s-1 vs. Con 1 0.7997 0.79 1.03 2.22 0.3090 

0.9 m·s-1 vs. Con 1 -0.5333 0.46 1.37 0.59 0.2415 

Velocity Effects 3 . . 3.54 . 0.3160 

Fork Length 1 0.0326 0.04 0.64 1.03 0.4254 

Full Model 4 . . 4.23 . 0.3758 
77

Largemouth Bass

Table E-45. Summary of live, dead, and mean length by velocity treatment for largemouth bass.

 Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Dead 4 8 10 4 26 

Live 390 351 351 497 1,589 

Percent Dead 1.02 2.23 2.77 0.80 . 

Total 394 359 361 501 1,615 

Mean Length (mm) 99.38 98.44 97.32 98.59 . 

Table E-46. Analysis of maximum likelihood estimates for the survival regression model for 

largemouth bass. This model was marginally significant (P=0.0549).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 -1.4944 1.91 0.61 . 0.4349 

0.3 m·s-1 vs Con 1 0.2519 0.71 0.13 1.29 0.7231 

0.6 m·s-1 vs Con 1 1.0269 0.62 2.77 2.79 0.0960 

0.9 m·s-1 vs Con 1 1.2290 0.60 4.25 3.42 0.0393 

Velocity Effects 3 . . 5.89 . 0.1170 

Fork Length 1 -0.0345 0.02 3.12 0.97 0.0773 

Full Model 4 . . 9.26 . 0.0549 

Table E-47. Summary of injury rate and mean length by velocity treatment for largemouth bass.

 Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Injured 3 22 14 8 47 

Not Injured 391 337 347 493 1,568 

Percent Injured 0.76 6.13 3.88 1.60 . 

Total 394 359 361 501 1,615 

Mean Length 99.38 98.44 97.32 98.59 . 
78

Table E-48. Analysis of maximum likelihood estimates for the injury regression model for 

largemouth bass. This model was significant (P=0.0003).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 -2.5116 1.36 3.41 . 0.0647 

0.3 m·s-1 vs Con 1 -0.7410 0.68 1.19 0.48 0.2762 

0.6 m·s-1 vs Con 1 1.3882 0.42 10.97 4.01 0.0009 

0.9 m·s-1 vs Con 1 0.8917 0.45 3.94 2.44 0.0471 

Velocity Effects 3 . . 19.21 . 0.0002 

Fork Length 1 -0.0165 0.01 1.48 0.98 0.2244 

Full Model 4 . . 20.85 . 0.0003 

Table E-49. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for largemouth bass.

Scale Loss 

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

1 Frequency 390 356 352 494 1,592

 Percent 98.98 99.16 97.51 98.60 . 

2 Frequency 2 3 4 6 15 

 Percent 0.51 0.84 1.11 1.20 . 

3 Frequency 2 0 3 1 6 

 Percent 0.51 0.00 0.83 0.20 . 

4 Frequency 0 0 2 0 2 

 Percent 0.00 0.00 0.55 0.00 . 

Total Frequency 394 359 361 501 1,615

Mean Length 99.38 98.44 97.32 98.59 
79

Table E-50. Analysis of maximum likelihood estimates for the scale loss regression model for 

largemouth bass. This model was not significant (P=0.3131).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 1 2.6850 1.91 1.97 . 0.1607 

Intercept 2 1 3.7523 1.94 3.76 . 0.0525 

Intercept 3 1 5.1439 2.03 6.42 . 0.0113 

0.3 m·s-1 vs. Con 1 0.3118 0.63 0.24 1.37 0.6211 

0.6 m·s-1 vs. Con 1 0.5258 0.69 0.57 1.69 0.4492 

0.9 m·s-1 vs. Con 1 -0.5802 0.51 1.30 0.56 0.2544 

Velocity Effects 3 . . 3.93 . 0.2692 

Fork Length 1 0.0161 0.02 0.69 1.02 0.4058 

Full Model 4 . . 4.76 . 0.3131 
80

White Sucker

Table E-51. Summary of live, dead, and mean length by velocity treatment for white sucker.

 Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Dead 16 16 17 14 63 

Live 357 323 357 445 1,482 

Percent Dead 4.29 4.72 4.55 3.05 . 

Total 373 339 374 459 1,545 

Mean Length (mm) 76.20 79.39 80.41 82.63 . 

Table E-52. Analysis of maximum likelihood estimates for the survival regression model for white 

sucker. This model was significant (P<0.0001).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 0.5821 0.77 0.57 . 0.4510 

0.3 m·s-1 vs Con 1 0.0113 0.38 0.00 1.01 0.9763 

0.6 m·s-1 vs Con 1 0.2740 0.38 0.52 1.32 0.4695 

0.9 m·s-1 vs Con 1 0.3151 0.37 0.72 1.37 0.3968 

Velocity Effects 3 . . 1.24 . 0.7423 

Fork Length 1 -0.0516 0.01 27.89 0.95 <0.0001

Full Model 4 . . 29.62 . <0.0001

Table E-53. Summary of injury rate and mean length by velocity treatment for white sucker.

 Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Injured 107 86 84 92 369 

Not Injured 266 253 290 367 1,176 

Percent Injured 28.69 25.37 22.46 20.04 . 

Total 373 339 374 459 1,545 

Mean Length 76.20 79.39 80.41 82.63 . 
81

Table E-54. Analysis of maximum likelihood estimates for the injury regression model for white 

sucker. This model was significant (P<0.0001).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 2.1408 0.38 31.40 . <0.0001

0.3 m·s-1 vs Con 1 0.2091 0.17 1.50 1.23 0.2212 

0.6 m·s-1 vs Con 1 0.1704 0.18 0.93 1.19 0.3355 

0.9 m·s-1 vs Con 1 0.0555 0.18 0.10 1.06 0.7514 

Velocity Effects 3 . . 1.89 . 0.5949 

Fork Length 1 -0.0438 0.00 89.81 0.96 <0.0001

Full Model 4 . . 97.94 . <0.0001

Table E-55. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for white sucker.

Scale Loss 

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

1 Frequency 272 201 183 373 1,029

 Percent 72.92 59.29 48.93 81.26 . 

2 Frequency 64 70 95 61 290 

 Percent 17.16 20.65 25.40 13.29 . 

3 Frequency 28 51 75 16 170 

 Percent 7.51 15.04 20.05 3.49 . 

4 Frequency 9 17 21 9 56 

 Percent 2.41 5.01 5.61 1.96 . 

Total Frequency 373 339 374 459 1,545

Mean Length 76.20 79.39 80.41 82.63 
82

Table E-56. Analysis of maximum likelihood estimates for the scale loss regression model for 

white sucker. This model was significant (P<0.0001).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 1 -3.1549 0.36 77.90 . <0.0001

Intercept 2 1 -1.8870 0.35 28.94 . <0.0001

Intercept 3 1 -0.2506 0.36 0.48 . 0.4882 

0.3 m·s-1 vs. Con 1 -0.1215 0.17 0.48 0.9 0.4865 

0.6 m·s-1 vs. Con 1 -1.0766 0.17 41.89 0.34 <0.0001

0.9 m·s-1 vs. Con 1 -1.5568 0.16 94.14 0.21 <0.0001

Velocity Effects 3 . . 130.76 . <0.0001

Fork Length 1 0.0580 0.00 177.33 1.06 <0.0001

Full Model 4 . . 265.31 . <0.0001
83

Yellow Perch

Table E-57. Summary of live, dead, and mean length by velocity treatment for yellow perch.

 Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Dead 1 4 2 5 12 

Live 119 152 160 493 924 

Percent Dead 0.83 2.56 1.23 1.00 . 

Total 120 156 162 498 936 

Mean Length (mm) 50.91 50.22 52.70 48.19 . 

Table E-58. Analysis of maximum likelihood estimates for the survival regression model for 

yellow perch. This model was significant (P=0.0392).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 2.4870 2.42 1.05 . 0.3049 

0.3 m·s-1 vs Con 1 0.1907 1.11 0.03 1.21 0.8641 

0.6 m·s-1 vs Con 1 1.2686 0.69 3.34 3.56 0.0674 

0.9 m·s-1 vs Con 1 0.7535 0.86 0.76 2.12 0.3826 

Velocity Effects 3 . . 3.55 . 0.3143 

Fork Length 1 -0.1581 0.06 7.81 0.85 0.0052 

Full Model 4 . . 10.07 . 0.0392 

Table E-59. Summary of injury rate and mean length by velocity treatment for yellow perch.

 Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

Injured 2 3 0 5 10 

Not Injured 118 153 162 493 926 

Percent Injured 1.67 1.92 0.00 1.00 . 

Total 120 156 162 498 936 

Mean Length 50.91 50.22 52.70 48.19 . 
84

Table E-60. Analysis of maximum likelihood estimates for the injury regression model for yellow 

perch. This model was not significant (P=0.1659).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 1.9616 2.65 0.55 . 0.4588 

0.3 m·s-1 vs Con 1 0.8651 0.86 1.00 2.38 0.3162 

0.6 m·s-1 vs Con 1 0.9431 0.75 1.58 2.57 0.2093 

0.9 m·s-1 vs Con 1 -11.1567 264.45 0.00 0.00 0.9663 

Velocity Effects 3 . . 1.95 . 0.5837 

Fork Length 1 -0.1457 0.06 5.62 0.86 0.0178 

Full Model 4 . . 6.48 . 0.1659 

Table E-61. Summary of frequencies of scale loss categories and mean length by velocity 

treatment for yellow perch.

Scale Loss 

Velocity 

0.3 m·s Total -1 0.6 m·s-1 0.9 m·s-1 Control 

1 Frequency 120 153 159 497 929 

Percent 100.00 98.08 98.15 99.80 . 

2 Frequency 0 0 1 1 2 

Percent 0.00 0.00 0.62 0.20 . 

4 Frequency 0 3 2 0 5 

Percent 0.00 1.92 1.23 0.00 . 

Total Frequency 120 156 162 498 936 

Mean Length 50.91 50.22 52.70 48.19 
85

Table E-62. Analysis of maximum likelihood estimates for the scale loss regression model for 

yellow perch. This model was not significant (P=0.0753).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value

Intercept 1 1 -0.0116 3.10 0.00 . 0.9970 

Intercept 2 1 0.3321 3.11 0.01 . 0.9149 

0.3 m·s-1 vs. Con 1 9.0834 225.29 0.00 8807.50 0.9678 

0.6 m·s-1 vs. Con 1 -2.5644 1.17 4.81 0.08 0.0284 

0.9 m·s-1 vs. Con 1 -2.7416 1.18 5.38 0.06 0.0204 

Velocity Effects 3 . . 5.85 . 0.1192 

Fork Length 1 0.1381 0.07 4.01 1.15 0.0451 

Full Model 4 . . 8.49 . 0.0753 
86

Model

Velocity

is p ≤ 0.05? Model is not 

no significant

yes

is p ≤ 0.05?

Length

yes

Velocity not 

significant

no is p ≤ 0.05? Length is not 

no significant

Length is

significant

yes

Individual Velocity 

Comparisons

1 ft/sec vs. 

control

2 ft/sec vs. 

control

3 ft/sec vs. 

control

is p ≤ 0.05?

Individual Velocity 

Comparison is 

Significant

Individual Velocity 

Comparison is 

not Significant

yes no

Model

Velocity

is p ≤ 0.05? Model is not 

no significant

yes

is p ≤ 0.05?

Length

yes

Velocity not 

significant

no is p ≤ 0.05? Length is not 

no significant

Length is

significant

yes

Individual Velocity 

Comparisons

1 ft/sec vs. 

control

2 ft/sec vs. 

control

3 ft/sec vs. 

control

is p ≤ 0.05?

Individual Velocity 

Comparison is 

Significant

Individual Velocity 

Comparison is 

not Significant

yes no

is p ≤ 0.05?

Individual Velocity 

Comparison is 

Significant

Individual Velocity 

Comparison is 

not Significant

yes no

Figure E-1. Interpreting the hierarchical results of the logistic regression models.
87

APPENDIX F

STATISTICAL ANALYSIS TABLES – DURATION OF IMPINGEMENT 

Species-specific results of the logistic regressions are presented in the following 

tables. For each species, the first table presents the raw frequencies and summary 

statistics by duration of impingement (DI) treatment and the second table presents a 

summary of logistic regression results. The first table for each species shows the 

frequency of live, dead (or injured, not injured), and total recovered for each velocity, as 

well as percent dead or injured and mean length. The second table for each species 

summarizes various estimates obtained from the logistic regression analyses. The first 

row shows the intercept of the model, which is generally not of interest but was given for 

completeness. The second row reports the cumulative chi-square for all DI (2, 4, 6, 8, or 

10 min) and the control. Row 3 gives the coefficient of the covariate Fork Length and 

row 7 reports the cumulative chi-square for the full model (DI and fork length). In some 

cases, there was too little mortality or too few injuries for a successful logistic regression 

(i.e., the model failed to converge on a reliable estimate). 

Guidance on interpreting the results of these hierarchical models is presented in 

Appendix E. 
88

Channel Catfish

Table F-1. Summary of live, dead and mean length by duration of impingement for channel 

catfish.

Duration 

Control 2 min 4 min 6 min 8 min 10 min Total 

Dead 1 -- -- 0 0 0 1 

Live 119 -- -- 115 108 103 445 

Percent Dead 0.83 -- -- 0.00 0.00 0.00 . 

Total 120 -- -- 115 108 103 446 

Mean Length 66.43 -- -- 65.10 64.35 64.59 . 

Table F-2. Analysis of maximum likelihood estimates for the regression model for the duration of 

impingement of channel catfish. This model was not significant (P=0.9927).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 -5.8418 11.36 0.26 . 0.6072 

Duration 1 -1.6227 21.56 0.01 0.20 0.9400 

Fork Length 1 0.0159 0.17 0.01 1.02 0.9249 

Full Model 2 . . 0.01 . 0.9927 

Table F-3. Summary of injury rates and mean length by duration of impingement for channel 

catfish.

Duration 

Control 2 min 4 min 6 min 8 min 10 min Total

Injured 0 -- -- 0 0 0 0 

Not Injured 120 -- -- 115 108 103 446 

Percent Injured 0.00 -- -- 0.00 0.00 0.00 . 

Total 120 -- -- 115 108 103 446 

Mean Length 66.42 -- -- 65.10 64.35 64.59 . 
89

Fathead Minnow

Table F-4. Summary of live, dead and mean length by duration of impingement for fathead 

minnow.

Duration 

Control 2 min 4 min 6 min 8 min 10 min Total 

Dead 1 -- -- 3 2 1 7 

Live 149 -- -- 44 28 34 255 

Percent Dead 0.67 -- -- 6.38 6.67 2.86 . 

Total 150 -- -- 47 30 35 262 

Mean Length 45.49 -- -- 52.49 53.27 53.69 . 

Table F-5. Analysis of maximum likelihood estimates for the regression model of duration of 

impingement of fathead minnow – survival. This model was not significant (P=0.1244).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 -1.2324 3.80 0.11 . 0.7454 

Duration 1 0.2449 0.12 4.00 1.28 0.0456 

Fork Length 1 -0.0718 0.08 0.73 0.93 0.3930 

Full Model 2 . . 4.17 . 0.1244 

Table F-6. Summary of injury rates and mean length by duration of impingement for fathead 

minnow.

Duration 

Control 2 min 4 min 6 min 8 min 10 min Total

Injured 2 -- -- 4 1 1 8 

Not Injured 148 -- -- 43 29 34 254 

Percent Injured 1.33 -- -- 8.51 3.33 2.86 . 

Total 150 -- -- 47 30 35 262 

Mean Length 45.49 -- -- 52.49 53.27 53.69 . 
90

Table F-7. Analysis of maximum likelihood estimates for the regression model of duration of 

impingement for fathead minnow – injury. This model was not significant (P=0.3688).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 -5.4635 3.08 3.15 . 0.0760 

Duration 1 0.0886 0.10 0.72 1.09 0.3950 

Fork Length 1 0.0326 0.06 0.25 1.03 0.6139 

Full Model 2 . . 2.00 . 0.3688 

Table F-8. Summary of frequencies of scale loss categories and mean length by duration of 

impingement for fathead minnow.

Scale loss Category 

Duration 

Control 2 min 4 min 6 min 8 min 10 min Total

1 Frequency 148 -- -- 45 24 33 250 

Percent 98.67 -- -- 95.74 80.00 94.29 

2 Frequency 2 -- -- 0 3 1 6 

Percent 1.33 -- -- 0.00 10.00 2.86 

3 Frequency 0 -- -- 0 2 0 2 

Percent 0.00 -- -- 0.00 6.67 0.00 

4 Frequency 0 -- -- 2 1 1 4 

Percent 0.00 -- -- 4.26 3.33 2.86 

Total Frequency 150 -- -- 47 30 35 262 

Mean length 45.49 -- -- 52.49 53.27 53.69 

Table F-9. Analysis of maximum likelihood estimates for the regression model of for fathead 

minnow – scale loss. This model was significant (P=0.0270).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 1 5.0876 2.69 3.57 . 0.0588 

Intercept 2 1 5.8217 2.71 4.62 . 0.0317 

Intercept 3 1 6.2414 2.73 5.24 . 0.0220 

Duration 1 -0.1991 0.09 4.60 0.82 0.0319 

Fork Length 1 -0.0211 0.06 0.14 0.98 0.7066 

Full Model 2 . . 7.23 . 0.0270 
91

Golden Shiner

Table F-10. Summary of live, dead and mean length by duration of impingement for golden 

shiner.

Duration 

Control 2 min 4 min 6 min 8 min 10 min Total 

Dead 10 0 0 3 11 9 33 

Live 98 7 9 77 62 62 315 

Percent Dead 9.26 0.00 0.00 3.75 15.07 12.68 . 

Total 108 7 9 80 73 71 348 

Mean Length 69.39 67.57 71.56 80.20 76.89 76.73 . 

Table F-11. Analysis of maximum likelihood estimates for the regression model for the duration 

of impingement of golden shiner – survival. This model was significant (P=0.0001).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 0.7334 0.91 0.65 . 0.4185 

Duration 1 0.1689 0.06 8.39 1.18 0.0038 

Fork Length 1 -0.0579 0.01 16.07 0.94 0.0001 

Full Model 2 . . 18.18 . 0.0001 

Table F-12. Summary of injury rates and mean length by duration of impingement for golden 

shiner.

Duration 

Control 2 min 4 min 6 min 8 min 10 min Total

Injured 10 0 0 4 5 7 26 

Not Injured 98 7 9 76 68 64 322 

Percent Injured 9.26 0.00 0.00 5.00 6.85 9.86 . 

Total 108 7 9 80 73 71 348 

Mean Length 69.39 67.57 71.56 80.20 76.89 76.73 . 
92

Table F-13. Analysis of maximum likelihood estimates for the regression model for duration of 

impingement of golden shiner – injury. This model was significant (P=0.0170).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 -0.1208 0.98 0.02 . 0.9015 

Duration 1 0.0878 0.06 2.11 1.09 0.1464 

Fork Length 1 -0.0422 0.02 7.89 0.96 0.0050 

Full Model 2 . . 8.15 . 0.0170 

Table F-14. Analysis of maximum likelihood estimates for the regression model for duration of 

impingement of golden shiner excluding controls – injury. This model was significant (P=0.0073).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 -0.5147 1.76 0.09 . 0.7698 

Duration 1 0.2483 0.15 2.79 1.28 0.0948 

Fork Length 1 -0.0562 0.02 7.99 0.95 0.0047 

Full Model 2 . . 9.83 . 0.0073 

Table F-15. Summary of frequencies of scale loss categories and mean length by duration of 

impingement for golden shiner.

Scale loss Category 

Duration 

Control 2 min 4 min 6 min 8 min 10 min Total

1 Frequency 45 0 0 3 2 10 60 

Percent 42.86 0.00 0.00 3.75 2.74 14.08 

2 Frequency 44 2 1 7 7 9 70 

Percent 41.90 28.57 11.11 8.75 9.59 12.68 

3 Frequency 8 1 3 13 11 9.00 45 

Percent 7.62 14.29 33.33 16.25 15.07 12.68 

4 Frequency 8 4 5 57 53 43.00 170 

Percent 7.62 57.14 55.56 71.25 72.60 60.56 

Total Frequency 105 7 9 80 73 71 345 

 Mean Length 69.39 67.57 71.56 80.20 76.89 76.73 
93

Table F-16. Analysis of maximum likelihood estimates for the regression model of scale loss for 

golden shiner. This model was significant (P<0.0001).

 DF Estimate

Standard 

Error 

Wald 

Chi-Square

Odds 

Ratio p-value 

Intercept 1 1 -1.6711 0.54 9.70 . 0.0018 

Intercept 2 1 -0.2405 0.53 0.21 . 0.6493 

Intercept 3 1 0.5077 0.53 0.91 . 0.3392 

Duration 1 -0.3307 0.03 103.41 0.72 <0.0001 

Fork Length 1 0.0176 0.01 5.99 1.02 0.0144 

Full Model 2 . . 103.79 . <0.0001 
94

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