Ecology and Management of Channel Catfish <I>Ictalurus Punctatus</I>

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Dissertations & Theses in Natural Resources Natural Resources, School of

4-2011

Ecology and Management of Channel catfish Ictalurus punctatus and Flathead catfish Pylodictis olivaris populations in the Missouri River, NE

Cameron Wesley Goble University of Nebraska-Lincoln, [email protected]

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Goble, Cameron Wesley, "Ecology and Management of Channel catfish Ictalurus punctatus and Flathead catfish Pylodictis olivaris populations in the Missouri River, NE" (2011). Dissertations & Theses in Natural Resources. 26. https://digitalcommons.unl.edu/natresdiss/26

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ECOLOGY AND MANAGEMENT OF CHANNEL CATFISH ICTALURUS

PUNCTATUS AND FLATHEAD CATFISH PYLODICTIS OLIVARIS POPULATIONS

IN THE MIDDLE MISSOURI RIVER, NE

Cameron W. Goble

A THESIS

Presented to the Faculty of

The Graduate College at the University of Nebraska

In Partial Fulfillment of Requirements

For the Degree of Master of Science

Major: Natural Resource Sciences

Under the Supervision of Professor Mark A. Pegg

Lincoln, NE

April 2011

ECOLOGY AND MANAGEMENT OF CHANNEL CATFISH ICTALURUS

PUNCTATUS AND FLATHEAD CATFISH PYLODICTIS OLIVARIS POPULATIONS

IN THE MIDDLE MISSOURI RIVER, NE

Cameron W. Goble M.S.

University of Nebraska, 2011

Advisor: Mark A. Pegg

Channel catfish Ictalurus punctatus and flathead catfish Pylodictis olivaris are two of the most important freshwater recreational or commercial species in the United

States. Catfish populations in the Missouri River are important resources to the people of

Nebraska and surrounding states. The objective of my study was to determine the present status of catfish populations in the Missouri River, Nebraska. Specifically I evaluated population characteristics such as relative abundance, population size and density, size structure, condition, age structure, growth, and mortality. I used a stratified random sampling design and generalized linear mixed modeling approach to assess differences in population characteristics between segments of the Missouri River, Nebraska and a closed-captures capture-mark-recapture study to estimate density and abundance of channel catfish > 200 mm within a Missouri River, Nebraska study bend. Growth rates of channel catfish and flathead catfish in the Missouri River, Nebraska are relatively slow compared to species‟ standards but are similar to those observed in other Nebraska

Rivers. Differences in population characteristics between segments of the Missouri

River, Nebraska suggest that catfish management in this portion of the Missouri River appears to be well suited for management unit based regulations. Specifically, the upper

channelized segment has a relatively greater density channel catfish population and appears to be able to support relatively greater levels of channel catfish harvest than the other segments. Similarly, the lower channelized segment has a relatively greater density flathead catfish population and appears to be able to support relatively greater levels of flathead catfish harvest than the other segments. The upper unchannelized segment appears to support low density populations of channel catfish and flathead catfish that may be better suited for trophy management regulations designed to minimize harvest and maximize growth potential.

ERRATA

1. The estimated abundance of channel catfish calculated with the Schnabel

estimator reported in Chapter 4 (page 123) was miscalculated. The corrected

abundance is 26,343 fish (18,011 - 39,120; 95 % confidence interval).

2. The confidence interval reported in Chapter 4 (page 123) for the abundance

estimate calculated using Program MARK is incorrect. The interval reported

comes from a model without the p = c constraint described in the methods section

(page 120). The corrected confidence interval for the p = c model as described in

the methods is (18,439 - 36,402; 95 % confidence interval).

3. Appendix table B-2 (page 153) was a duplicate of the mean back-calculated

length-at-age table for channel catfish. This table was updated on 6/31/2011 to

show the correct data for flathead catfish

The calculation errors in Chapter 4 were brought to my attention during the peer-review process of a manuscript based on that chapter and I sincerely apologize for any confusion these errors may have caused.

Cameron W. Goble 11/18/2011

ACKNOWLEDGEMENTS

My family deserves the most credit for this thesis as none of this would have been possible without their love and support. I had the easy part of this whole endeavor. My wonderful, very understanding wife Faith, saw the benefits of quitting a full-time job to return to school, my two beautiful daughters Alyssa and Harper encouraged dad to get his schoolwork done even if it meant less play time, and my parents Ron and Beth instilled in me a love of learning and provided support for me, Faith, and the girls throughout this entire process. This thesis is dedicated to all of them.

First and foremost a huge THANK YOU!!! to Mark Pegg, my graduate advisor at the University of Nebraska for giving me this opportunity. Your guidance and mentoring are a big reason why I chose to continue on and pursue a PhD. Words can‟t fully express how truly grateful I am for everything you have done for me. I have learned so much from you over the last two years and I could not have asked for a better graduate school experience. Let me know when you want to go back up to the Red so we can prove to those guys that we can catch more than carpsuckers!

Thank you to the members of my graduate committee, Kevin Pope, Rick Holland, and Gerald Mestl for contributing your expertise and guidance to my education. I am truly honored to have collaborated with each of you on this project. I also need to thank

Larkin Powell for introducing me to population modeling and advising me on sampling design and analyses for my channel catfish population estimate.

This was a large project and I could not have accomplished anything without the help of all of the technicians who assisted with all aspects of field sampling and sample vi processing: Chad Christiansen, Nick Cole, Eric Ellingson, Matt Gruntorad, Brett

Hulewicz, Nate Kershner, Travis Kinsell, Brian Maronde, Sabrina Negus, Tanner

Stevens, and Derek Tomes. I appreciate all of the hard work, long hours, catfish spine wounds, and falls into the river you all put in.

My fellow graduate students and labmates at the University of Nebraska have helped me in more ways than they can possibly know. Aaron Blank, a top-notch chase boat driver and catfish sampling expert in Nebraska rivers showed me the “tricks of the trade”; Adam Behmer, a Missouri River catfish sampling veteran put in long hours and endured bodily harm teaching me the proper methodology for hoop netting on the

Missouri River; Brenda Pracheil and Dustin Martin, fellow SAS enthusiasts who were always willing to share their vast knowledge of SAS procedures and statistical analyses;

Jeremy Hammen and Marty Hamel, the sturgeon gurus were always willing to lend a hand whenever and wherever they could; Mat Rugg, Luke Kowalewski, Ryan

Lueckenhoff, Carla Knight, and Jason DeBoer, fellow graduate students who graciously took time away from their own research to assist with Missouri River field sampling (I owe you all big time!).

I also would like to thank all the NGPC personnel who assisted with this project: Bill Garvey, Jerrod Hall, and Ken Hatten for providing chase boat support during flathead electrofishing, Gerald Mestl and Tim Porter for their expertise of Missouri River catfish sampling and equipment support, and Schuyler “Skippy” Sampson for statistical/SAS guidance and for convincing me that statistics are in fact interesting and can actually be quite “fun”.

vii

TABLE OF CONTENTS

ABSTRACT…...... ii

ERRATA ………………………………………..……………………………………. iv

ACKNOWLEDGEMENTS .…...... v

LIST OF TABLES .…...... x

LIST OF FIGURES ..…...... xvii

LIST OF APPENDICES …...... xxvi

CHAPTER 1 - GENERAL INTRODUCTION AND STUDY OBJECTIVES ...... 1

Introduction ..…………...... 1

Study Objectives...... …...... 3

Literature Cited ..…………...... 4

CHAPTER 2 - POPULATION CHARACTERISTICS OF CHANNEL CATFISH AND

FLATHEAD CATFISH IN THE MISSOURI RIVER, NEBRASKA ...... 7

Introduction …...... 7

Methods …...... 9

Study Area …...... 9

Field Sampling .…...... 11

Data Analyses …...... 12

Results ...... 15

Channel Catfish …..…...... 16

Relative Abundance …...... 16

Size Structure …...... 17

Condition ...... 18 viii

Flathead Catfish ...... 19

Relative Abundance …...... 19

Size Structure …...... 20

Condition ...... 21

Discussion ...... 22

Literature Cited ...... 29

CHAPTER 3 - AGE, GROWTH, AND MORTALITY OF CHANNEL CATFISH AND

FLATHEAD CATFISH IN THE MISSOURI RIVER, NEBRASKA ...... 76

Introduction ...... 76

Methods ...... 78

Study Area …...... 78

Field Sampling ...... 80

Laboratory Processing …...... 81

Data Analyses...... 82

Results …...... 83

Channel Catfish …..…...... 84

Flathead Catfish …..…...... 85

Discussion ...... 87

Literature Cited ...... 92

CHAPTER 4 - CLOSED-CAPTURES POPULATION ANALYSES OF CHANNEL

CATFISH POPULATION SIZE WITHIN A MISSOURI RIVER, NEBRASKA STUDY

BEND …………..…………...... 116

Introduction ...... 116 ix

Methods ...... 118

Field Sampling ...... 118

Data Analyses...... 119

Population Estimates ...... 120

Population Estimate Vs. C/F ...... 120

Results …...... 122

Schnabel Estimate ...... 123

Program MARK Estimate ...... 123

Relative Abundance ...... 123

Bend-Level Mean Abundance...... 124

Discussion ...... 124

Literature Cited ...... 128

CHAPTER 5 - FUTURE RESEARCH, SAMPLING RECOMMENDATIONS, AND

MANAGEMENT RECOMMENDATIONS ...... 139

Sampling ……...... 141

Management ………...... 145

Literature Cited …...... 146

LIST OF TABLES

Table 2-1. Total catch of channel catfish by year and segment (UU – upper

unchannelized segment, LU – lower unchannelized segment, UC – upper

channelized segment, LC – lower channelized segment) in 25 mm mesh hoop nets

(SHN) and 7 mm mesh hoop nets (MHN)...... 36

Table 2-2. Total catch of flathead catfish by year and segment (UU – upper

unchannelized segment, LU – lower unchannelized segment, UC – upper

channelized segment, LC – lower channelized segment) with pulsed DC

electrofishing (EF)...... 37

Table 2-3. Proportional size distributions (PSD) of channel catfish collected in 25 mm

mesh hoop nets in 2009, 2010, and combined by segment (UU – upper

unchannelized segment, LU – lower unchannelized segment, UC – upper

channelized segment, LC – lower channelized segment). ………………...... 38

Table 2-4. Chi-square (χ²) test values for comparisons of proportional size distribution

(PSD) of channel catfish collected in 25 mm mesh hoop nets between segments in

2009 and 2010 (UU – upper unchannelized segment, LU – lower unchannelized

segment, UC – upper channelized segment, LC – lower channelized segment).

Values in bold indicate significant differences following Bonferroni correction (α

= 0.008). ……………………………………………………………..……...... 39

Table 2-5. Kolmogorov-Smirnov test (p – values) comparing length-frequency

distributions of channel catfish between segments in 2009 (UU – upper

unchannelized segment, LU – lower unchannelized segment, UC – upper

channelized segment, LC – lower channelized segment). Values in bold indicate

significant differences following Bonferroni correction (α = 0.008)...... 40

Table 2-6. Kolmogorov-Smirnov test (p – values) comparing length-frequency

distributions of channel catfish between segments in 2010 (UU – upper

unchannelized segment, LU – lower unchannelized segment, UC – upper

channelized segment, LC – lower channelized segment). Values in bold indicate

significant differences following Bonferroni correction (α = 0.008)...... 41

Table 2-7. Analysis of covariance test (p – values) for comparisons of channel catfish

length-weight relations between segments in 2009 (UU – upper unchannelized

segment, LU – lower unchannelized segment, UC – upper channelized segment,

LC – lower channelized segment). Values in bold indicate significant differences

following Bonferroni correction (α = 0.008). …...... 42

Table 2-8. Analysis of covariance test (p – values) for comparisons of channel catfish

length-weight relations between segments in 2010 (UU – upper unchannelized

segment, LU – lower unchannelized segment, UC – upper channelized segment,

LC – lower channelized segment). Values in bold indicate significant differences

following Bonferroni correction (α = 0.008). ………………………..…...... 43

xii

Table 2-9. Proportional size distributions (PSD) of flathead catfish collected with pulsed

DC electrofishing in 2009, 2010, and combined by segment (UU – upper

unchannelized segment, LU – lower unchannelized segment, UC – upper

channelized segment, LC – lower channelized segment)...... 44

Table 2-10. Chi-square (χ²) test values for comparisons of proportional size distribution

(PSD) of flathead catfish collected with pulsed DC electrofishing between 2009

and 2010 sampling years by segment (UU – upper unchannelized segment, LU –

lower unchannelized segment, UC – upper channelized segment, LC – lower

channelized segment). Values in bold indicate significant differences following

Bonferroni correction (α = 0.013). ……………..……..……..…………...... 45

Table 2-11. Chi-square (χ²) test values for comparisons of proportional size distribution

(PSD) of flathead catfish collected with pulsed DC electrofishing between

segments in 2009 and 2010 (UU – upper unchannelized segment, LU – lower

unchannelized segment, UC – upper channelized segment, LC – lower

channelized segment). Values in bold indicate significant differences following

Bonferroni correction (α = 0.008). ………………………...... 46

Table 2-12. Kolmogorov-Smirnov test (p – values) comparing length frequency

distributions of flathead catfish between segments in 2009 (UU – upper

unchannelized segment, LU – lower unchannelized segment, UC – upper

channelized segment, LC – lower channelized segment). Values in bold indicate

significant differences following Bonferroni correction (α = 0.008)...... 47 xiii

Table 2-13. Kolmogorov-Smirnov test (p – values) comparing length frequency

distributions of flathead catfish between segments in 2010 (UU – upper

unchannelized segment, LU – lower unchannelized segment, UC – upper

channelized segment, LC – lower channelized segment). Values in bold indicate

significant differences following Bonferroni correction (α = 0.008). …...... 48

Table 2-14. Analysis of covariance test (p - values) for comparisons of flathead catfish

length-weight relations between segments in 2009 (UU – upper unchannelized

segment, LU – lower unchannelized segment, UC – upper channelized segment,

LC – lower channelized segment). Values in bold indicate significant differences

following Bonferroni correction (α = 0.008)...... 49

Table 2-15. Analysis of covariance test (p - values) for comparisons of flathead catfish

length-weight relations between segments in 2010 (UU – upper unchannelized

segment, LU – lower unchannelized segment, UC – upper channelized segment,

LC – lower channelized segment). Values in bold indicate significant differences

following Bonferroni correction (α = 0.008). ……………………..……...... 50

Table 3-1. Total number of channel catfish aged by year and segment (UU – upper

unchannelized segment, LU – lower unchannelized segment, UC – upper

channelized segment, LC – lower channelized segment)...... 97

Table 3-2. Total number of flathead catfish aged by year and segment (UU – upper

unchannelized segment, LU – lower unchannelized segment, UC – upper

channelized segment, LC – lower channelized segment). ……………...... 98 xiv

Table 3-3. Segment level instantaneous mortality (Z) and annual mortality (A) estimates

derived from weighted catch curve regression of channel catfish collected in 25

mm mesh hoop nets in 2009 and 2010 (UU – upper unchannelized segment, LU –

lower unchannelized segment, UC – upper channelized segment, LC – lower

channelized segment; LCI and UCI = 95 % confidence intervals)...... 99

Table 3-4. Segment level instantaneous mortality (Z) and annual mortality (A) estimates

derived from weighted catch curve regression of flathead catfish collected with

pulsed DC electrofishing in 2009 and 2010 (UU – upper unchannelized segment,

LU – lower unchannelized segment, UC – upper channelized segment, LC –

lower channelized segment; LCI and UCI = 95 % confidence intervals)...... 100

Table 3-5. Mean back-calculated length-at-age for channel catfish collected in the

Missouri River (Bold) during 2009 and 2010 compared to standard growth

percentiles for channel catfish across their geographic range. Percentiles provided

by Hubert (1999). Superscripts following lengths delineate study segments (UU –

upper unchannelized segment, LU – lower unchannelized segment, UC – upper

channelized segment, LC – lower channelized segment)...... 101

Table 3-6. Mean back-calculated length-at-age for flathead catfish collected in the

Missouri River (Bold) during 2009 and 2010 compared to standard growth

percentiles for flathead catfish across their geographic range. Percentiles provided

by Jackson et al. (2008). Superscripts following lengths delineate study segments

(UU – upper unchannelized segment, LU – lower unchannelized segment, UC –

upper channelized segment, LC – lower channelized segment)...... ……...... 102 xv

Table 3-7. Annual mortality estimates of channel catfish populations in Missouri River

study segments compared to other North American river populations (UU – upper

unchannelized segment, LU – lower unchannelized segment, UC – upper

channelized segment, LC – lower channelized segment). Mortality estimates in

bold are estimates from the current study and represent the 95 % confidence

intervals. Table reprinted with permission and adapted from Barada (2009). . 103

Table 3-8. Table 3-8. Annual mortality estimates of flathead catfish populations in

Missouri River study segments compared to other North American river

populations (UU – upper unchannelized segment, LU – lower unchannelized

segment, UC – upper channelized segment, LC – lower channelized segment).

Mortality estimates in bold are estimates from the current study and represent the

95 % confidence intervals. ………………………………………………...... 104

Table 4-1. Channel catfish capture, recapture, and total number marked data collected

through spatially replicated hoop net sampling used within a 6.2 River Kilometer

Missouri River, Nebraska study bend in 2010...... 132

Table 4-2. Channel catfish encounter histories used for closed-captures analyses

(Program MARK) within a 6.2 River Kilometer Missouri River, Nebraska study

bend in 2010. ……………………………………………………………...... 133

xvi

Table 4-3. Akaike‟s Information Criterion (AIC) values comparing competing closed-

captures model structures (Program MARK; Mo = constant capture probability

and recapture probability, Mt = time varying capture probability and recapture

probability, Mb = variability in recapture probability due to changes in behavior

after capture (Otis et al. 1978, Hayes et al. 2007)...... 134

Table 4-4. Capture and recapture probabilities derived from closed-captures analyses

(Program MARK) and mean (µ) capture probabilities used for calculation of

bend-level mean abundance of channel catfish within a 6.2 River Kilometer

Missouri River, Nebraska study bend in 2010. ....………….……………...... 135

xvii

LIST OF FIGURES

Figure 2-1. Diagram of the Middle Missouri River study area showing the boundaries of

each study section (UU – Upper Unchannelized, LL – Lewis and Clark Lake*, -

LU – Lower Unchannelized, UC – Upper Channelized, LC – Lower

Channelized). * Not included in study...... 51

Figure 2-2. Frequency of channel catfish catch rates in 25 mm mesh hoop nets set in the

Missouri River, Nebraska in 2009 (A) and 2010 (B). …………………...... 52

Figure 2-3. Mean catch per unit effort (C/f; fish per net night) of channel catfish captured

in 25 mm mesh hoop nets by year and segment. An * indicates significant

differences in mean C/f between years within segments. Uppercase letters

indicate significant differences in mean C/f between segments in 2009.

Lowercase letters indicate significant differences in mean C/f between segments

in 2010 (UU – upper unchannelized segment, LU – lower unchannelized segment,

UC – upper channelized segment, LC – lower channelized segment)...... 53

Figure 2-4. Mean catch per unit effort (C/f; fish per net night) of channel catfish captured

in 7 mm mesh hoop nets by year and segment. An * indicates significant

differences in mean C/f between years within segments. Uppercase letters

indicate significant differences in mean C/f between segments in 2009.

Lowercase letters indicate significant differences in mean C/f between segments

in 2010 (UU – upper unchannelized segment, LU – lower unchannelized segment,

UC – upper channelized segment, LC – lower channelized segment)...... 54 xviii

Figure 2-5. Mean catch per unit effort (C/f; fish per net night) of channel catfish captured

in 25 mm mesh hoop nets by bend modification level within segment and year.

Bars with different uppercase letters indicate differences (p < 0.05) in mean C/f

between bend modification levels in 2009. Bars with different lowercase letters

indicate differences (p < 0.05) in mean C/f between bend modification levels in

2010.The dotted line indicates no intersegment comparisons are made. (UC-M –

upper channelized segment, modified bends; UC-U – upper channelized segment,

unmodified bends; LC-M – lower channelized segment, modified bends; LC-U –

lower channelized segment, unmodified bends)...... 55

Figure 2-6. Mean catch per unit effort (C/f ; fish per net night) of channel catfish

captured in 25 mm mesh hoop nets by bend within segment (UU – upper

unchannelized segment, LU – lower unchannelized segment, UC – upper

channelized segment, LC – lower channelized segment)in 2009 (A) and 2010 (B).

……………………………………………………………………………...... 56

Figure 2-7. Length-frequency distributions, by 10 mm length group, of channel catfish

collected in 25 mm mesh hoop nets in 2009 by segment (A – upper unchannelized

segment, B – lower unchannelized segment, C – upper channelized segment, D –

lower channelized segment). …….……...... 57

Figure 2-8. Length-frequency distributions, by 10 mm length group, of channel catfish

collected in 25 mm mesh hoop nets in 2010 by segment (A – upper unchannelized

segment, B – lower unchannelized segment, C – upper channelized segment, D –

lower channelized segment). .………………………………………..……...... 58 xix

Figure 2-9. Length-frequency distributions by 10 mm length group, of channel catfish

collected in 25 mm mesh hoop nets in 2009 by bend modification level within

segment (A – upper channelized segment, modified bends; B – upper channelized

segment, unmodified bends; C – lower channelized segment, modified bends; D –

lower channelized segment, unmodified bends)...... 59

Figure 2-10. Length-frequency distributions by 10 mm length group, of channel catfish

collected in 25 mm mesh hoop nets in 2010 by bend modification level within

segment (A – upper channelized segment, modified bends; B – upper channelized

segment, unmodified bends; C – lower channelized segment, modified bends; D –

lower channelized segment, unmodified bends). ...………………………...... 60

Figure 2-11. Mean relative weight (Wr), by 50 mm length group, of channel catfish

collected in 25 mm mesh hoop nets in 2009 and 2010 by segment (A – upper

unchannelized segment, B – lower unchannelized segment, C – upper channelized

segment, D – lower channelized segment). …………………...... 61

Figure 2-12. Log10 (length – weight) relation of channel catfish collected in hoop nets by

segment in 2009 (A – upper unchannelized segment, B – lower unchannelized

segment, C – upper channelized segment, D – lower channelized segment). .... 62

Figure 2-13. Log10 (length – weight) relation of channel catfish collected in hoop nets by

segment in 2010 (A – upper unchannelized segment, B – lower unchannelized

segment, C – upper channelized segment, D – lower channelized segment). .... 63

Figure 2-14. Frequency of flathead catfish catch rates with pulsed DC electrofishing in

the Missouri River, Nebraska in 2009 (A) and 2010 (B). …….…………...... 64 xx

Figure 2-15. Mean catch per unit effort (C/f; fish per minute) of flathead catfish captured

with pulsed DC electrofishing by year and segment. Bars with different

uppercase letters indicate differences (p < 0.05) in mean C/f between segments in

2009. Bars with different lowercase letters indicate differences (p < 0.05) in

mean C/f between segments in 2010 (UU – upper unchannelized segment, LU –

lower unchannelized segment, UC – upper channelized segment, LC – lower

channelized segment). …………………………………...... 65

Figure 2-16. Mean catch per unit effort (C/f; fish per 100 meters) of flathead catfish

captured with pulsed DC electrofishing by year and segment. Bars with different

uppercase letters indicate differences (p < 0.05) in mean C/f between segments in

2009. Bars with different lowercase letters indicate differences (p < 0.05) in

mean C/f between segments in 2010 (UU – upper unchannelized segment, LU –

lower unchannelized segment, UC – upper channelized segment, LC – lower

channelized segment). …………………………………………………..…...... 66

Figure 2-17. Mean catch per unit effort (C/f; fish per minute) of flathead catfish captured

with pulsed DC electrofishing by bend modification level within segment and

year. Bars with different uppercase letters indicate differences (p < 0.05) in mean

C/f between bend modification levels in 2009. Bars with different lowercase

letters indicate differences (p < 0.05) in mean C/f between bend modification

levels in 2010. The dotted line indicates no intersegment comparisons are made.

(UC-M – upper channelized segment, modified bends; UC-U – upper channelized

segment, unmodified bends; LC-M – lower channelized segment, modified bends;

LC-U – lower channelized segment, unmodified bends). .…………..……...... 67 xxi

Figure 2-18. Mean catch per unit effort (C/f ; fish per minute) of flathead catfish

captured with pulsed DC electrofishing by bend within segment (UU – upper

unchannelized segment, LU – lower unchannelized segment, UC – upper

channelized segment, LC – lower channelized segment) in 2009 (A) and 2010

(B). ……………………………………………………………...... 68

Figure 2-19. Length-frequency distributions, by 10 mm length group, of flathead catfish

collected with pulsed DC electrofishing in 2009 by segment (A – upper

unchannelized segment, B – lower unchannelized segment, C – upper channelized

segment, D – lower channelized segment). ...……………………………...... 69

Figure 2-20. Length-frequency distributions, by 10 mm length group, of flathead catfish

collected with pulsed DC electrofishing in 2010 by segment (A – upper

unchannelized segment, B – lower unchannelized segment, C – upper channelized

segment, D – lower channelized segment). …………………...... 70

Figure 2-21. Length-frequency distributions, by 10 mm length group, of flathead catfish

collected with pulsed DC electrofishing in 2009 by bend modification level within

segment (A – upper channelized segment, modified bends; B – upper channelized

segment, unmodified bends; C – lower channelized segment, modified bends; D –

lower channelized segment, unmodified bends). ………...... ……………...... 71

xxii

Figure 2-22. Length-frequency distributions, by 10 mm length group, of flathead catfish

collected with pulsed DC electrofishing in 2010 by bend modification level within

segment (A – upper channelized segment, modified bends; B – upper channelized

segment, unmodified bends; C – lower channelized segment, modified bends; D –

lower channelized segment, unmodified bends). ..………...... 72

Figure 2-23. Mean relative weight (Wr), by 50 mm length group, of flathead catfish

collected with pulsed DC electrofishing in 2009 and 2010 by segment (A – upper

unchannelized segment, B – lower unchannelized segment, C – upper channelized

segment, D – lower channelized segment). ……...... ……….…………...... 73

Figure 2-24. Log10 (length – weight) relationship of flathead catfish collected with

pulsed DC electrofishing by segment in 2009 (A – upper unchannelized segment,

B – lower unchannelized segment, C – upper channelized segment, D – lower

channelized segment). …………………………………...... 74

Figure 2-25. Log10 (length – weight) relationship of flathead catfish collected with

pulsed DC electrofishing by segment in 2010 (A – upper unchannelized segment,

B – lower unchannelized segment, C – upper channelized segment, D – lower

channelized segment). …………………………………………………...... 75

Figure 3-1. Diagram of the Middle Missouri River study area showing the boundaries of

each study section (UU – Upper Unchannelized, LL – Lewis and Clark Lake*, -

LU – Lower Unchannelized, UC – Upper Channelized, LC – Lower

Channelized). * Not included in study...... 105 xxiii

Figure 3-2. Age-frequency distributions of channel catfish collected in 25 mm mesh

hoop nets in 2009 and 2010 (pooled) by study segment (A – upper unchannelized

segment, B – lower unchannelized segment, C – upper channelized segment, D –

lower channelized segment). ..……...... …………………………………...... 106

Figure 3-3. Mean back-calculated length-at-age of channel catfish collected in the

middle Missouri River in 2009 and 2010. A „*‟ indicates a difference in mean

back-calculated length-at-age between 2009 and 2010. (A – upper unchannelized

segment, B – lower unchannelized segment, C – upper channelized segment, D –

lower channelized segment). ..………………...... 107

Figure 3-4. Mean back-calculated length-at-age and von Bertalanffy growth functions of

channel catfish collected in the middle Missouri River in 2009 and 2010 (pooled).

(A – upper unchannelized segment, B – lower unchannelized segment, C – upper

channelized segment, D – lower channelized segment). ....….……………..... 108

Figure 3-5. Segment level mean back-calculated length-at-age comparisons of channel

catfish collected in the upper unchannelized and lower unchannelized segments

(A), upper unchannelized and upper channelized segments (B), upper

unchannelized and lower channelized segments (C), lower unchannelized and

upper channelized segments (D), lower unchannelized and lower channelized

segments (E), and upper channelized and lower channelized segments (F) of the

middle Missouri River in 2009 and 2010 (pooled). A „*‟ indicates a difference in

mean back-calculated length-at-age between segments...... 109 xxiv

Figure 3-6. Catch curve regression of channel catfish collected in 25 mm mesh hoop nets

in the middle Missouri River in 2009 and 2010 (pooled). (A – upper

unchannelized segment, B – lower unchannelized segment, C – upper channelized

segment, D – lower channelized segment). ...……………………………...... 110

Figure 3-7. Age-frequency distributions of flathead catfish collected with pulsed DC

electrofishing in 2009 and 2010 (pooled) by study segment (A – upper

unchannelized segment, B – lower unchannelized segment, C – upper channelized

segment, D – lower channelized segment)...... 111

Figure 3-8. Mean back-calculated length-at-age of flathead catfish collected in the

middle Missouri River in 2009 and 2010. A „*‟ indicates a difference in mean

back-calculated length-at-age between 2009 and 2010. (A – upper unchannelized

segment, B – lower unchannelized segment, C – upper channelized segment, D –

lower channelized segment). .…………………………………………...... 112

Figure 3-9. Mean back-calculated length-at-age and von Bertalanffy growth functions of

flathead catfish collected in the middle Missouri River in 2009 and 2010 (pooled).

(A – upper unchannelized segment, B – lower unchannelized segment, C – upper

channelized segment, D – lower channelized segment). ...………………...... 113

xxv

Figure 3-10. Segment level mean back-calculated length-at-age comparisons of flathead

catfish collected in the upper unchannelized and lower unchannelized segments

(A), upper unchannelized and upper channelized segments (B), upper

unchannelized and lower channelized segments (C), lower unchannelized and

upper channelized segments (D), lower unchannelized and lower channelized

segments (E), and upper channelized and lower channelized segments (F) of the

middle Missouri River in 2009 and 2010 (pooled). A „*‟ indicates a difference in

mean back-calculated length-at-age between segments...... 114

Figure 3-11. Catch curve regression of flathead catfish collected with pulsed DC

electrofishing in the middle Missouri River in 2009 and 2010 (pooled). (A –

upper unchannelized segment, B – lower unchannelized segment, C – upper

channelized segment, D – lower channelized segment). ...……………...... 115

Figure 4-1. Diagram of the Missouri River, Nebraska showing the approximate location

(star) of the study bend (RKM 1,122.8 – RKM 1,116.6) sampled for closed

population estimation in 2010…………………… ...... 136

Figure 4-2. Depiction of hoop net spacing on a study bend. Stars represent hoop net set

locations. ………...... …………………………...... 137

Figure 4-4. Frequency of channel catfish > 200 mm catch rates in 25 mm mesh hoop nets

set in the Missouri River, Nebraska October 18 – 22, 2010...... …………..... 138

xxvi

LIST OF APPENDICES

APPENDIX A. MISSOURI RIVER, NEBRASKA BEND LIST AS DEFINED BY THE

MISSOURI RIVER PALLID STURGEON POPULATION ASSESSMENT PROJECT

……………………………………………………...... 148

APPENDIX B. MEAN BACK-CALCULATED LENGTH-AT-AGE OF CHANNEL

CATFISH AND FLATHEAD CATFISH IN THE MISSOURI RIVER, NEBRASKA

……………………………………………………...... 152

APPENDIX C. TOTAL CATCH BY SPECIES AND GEAR IN THE MISSOURI

RIVER, NEBRASKA IN 2009 AND 2010 …...... 154

APPENDIX D. CLASS LEVEL INFORMATION, FIT STATISTICS AND

PARAMETER INFORMATION FOR MEAN C/f MODELS ...... 163

CHAPTER 1 – GENERAL INTRODUCTION AND STUDY OBJECTIVES

Introduction

The Missouri River rises in western Montana at the confluence of the Jefferson,

Gallatin, and Madison rivers, and flows 3,734 km to its confluence with the Mississippi

River near St. Louis, Missouri. The Missouri River drainage basin covers approximately

1,371,017 km2, or roughly one-sixth of the total land area of the United States (USFWS

2000). Historic accounts describe the Missouri River as a „slow, meandering, silt-laden stream with islands, sandbars, side channels, and oxbow lakes‟ (Schneiders 1996).

Efforts to control the Missouri River began in 1824 when Congress authorized the United

States Army Corps of Engineers (USACOE) to remove snags to aid steamboat travel. In

1910, Congress passed the Rivers and Harbors Act which authorized the USACOE to develop and maintain a 1.8 m navigation channel from the mouth of the Missouri River at

Saint Louis, Missouri to Kansas City, Missouri (Office of the Chief of Engineers, U.S.

Army 1913). Several revised Rivers and Harbors Acts followed, eventually calling for development and maintenance of a 2.7 m deep, 91.4 m wide navigation channel from the mouth of the Missouri River to Sioux City, Iowa (USACOE 2006). The 1935 Rivers and

Harbors Act authorized construction of the Fort Peck Dam in Montana and power generation at this facility was authorized by the 1938 Fort Peck Power Act. Five additional dams on the main stem Missouri River were authorized by the Pick-Sloan

Missouri River Basin Program under the 1944 Flood Control Act. These dams (Fort

Peck was included in the 1944 Act) were authorized to serve multiple purposes including flood control, irrigation supply, navigation, and fish and wildlife conservation (USFWS 2

2000). Bank stabilization and navigation controls were completed from Sioux City, Iowa to Saint Louis, Missouri by 1980 and the Missouri River had become a highly regulated system. Human attempts at control of the Missouri River have led to a system where flows are now regulated by water releases from the dams leading to a drastically altered hydrograph (Hesse and Mestl 1993), bank stabilization and navigation control structures have decreased habitat diversity (Keenlyne 1990), and much of the river has been changed from lotic to lentic habitat (Morris et al. 1968).

Channel catfish Ictalurus punctatus and flathead catfish Pylodictis olivaris are two of the most important freshwater recreational or commercial species in the United

States of America (Vokoun and Rabeni 1999) and have been studied extensively throughout their ranges (Hubert 1999, Jackson 1999, Barada 2009). Michaletz and

Dillard (1999) found that catfish (channel catfish, flathead catfish, blue catfish Ictalurus furcatus, and „other‟ species) were deemed important to anglers by fisheries managers from 32 management agencies, with 28 states allowing some commercial harvest of catfish. A United States Department of Interior survey (2006) estimated that there were

6.95 million catfish anglers in the United States in 2006. A statewide angler survey conducted by the Nebraska Game and Parks Commission in 2002 showed that 13 % of survey respondents preferred to fish for channel catfish and approximately 2 % preferred to fish for flathead catfish (Hurley and Duppong-Hurley 2005). Nearly 40 % of the respondents reported that they had specifically targeted channel catfish at least once during 2002, while ~ 15 % reported specifically targeting flathead catfish at least once during 2002. The same survey showed that channel catfish were the third most targeted species following largemouth bass Micropterus salmoides and crappie Pomoxis spp. in 3 the eastern fisheries districts bordered by the Missouri River (Hurley and Duppong-

Hurley 2005). Use of the Missouri River by Nebraska anglers increased 72 % between

1984 and 1986 to an estimated total of ~ 408,000 trips annually (Zuerlein 1987). A 2005 catfish angler survey indicated that the Missouri River had the highest use of any

Nebraska river by catfish seeking anglers (Hurley and Duppong-Hurley 2007) suggesting that Missouri River catfish populations are important resources to the people of Nebraska and surrounding states.

Study Objectives

The objective of the project is to determine the present status of channel catfish and flathead catfish populations in the Middle Missouri River. Three specific research questions pertaining to this objective were developed and are as follows:

1. Are there differences in population metrics such as: relative abundance, size-

structure, condition (Chapter 2), growth-rates, and mortality (Chapter 3) of

channel catfish and flathead catfish populations between segments of the

Middle Missouri River?

2. Do habitat restoration efforts (bend modifications) have an effect on channel

catfish and/or flathead catfish (Chapter 2) populations?

3. What is the estimated population size and density of channel catfish within a

Missouri River study bend (Chapter 4)?

Literature Cited

Barada, T. J. 2009. Catfish population dynamics in the Platte River, Nebraska. M.S.

Thesis, University of Nebraska, Lincoln.

Hesse, L. W., and G. E. Mestl. 1993. An alternative hydrograph for the Missouri River

based on the precontrol condition. North American Journal of Fisheries

Management 13: 360-366.

Hubert, W. A. 1999. Biology and management of channel catfish. Pages 3-22 in E. R.

Irwin, W. A. Hubert, C. F. Rabeni, H. L. Schramm, Jr., and T. Coon, editors.

Catfish 2000: proceedings of the international ictalurid symposium. American

Fisheries Society, Symposium 24, Bethesda, Maryland.

Hurley, K. L., and K. L. Duppong-Hurley. 2005. 2002 Licensed Angler Survey

Summarized Results. Nebraska Game and Parks Commission, Lincoln,

Nebraska.

Hurley, K. L., and K. L. Duppong-Hurley. 2007. Nebraska catfish anglers: descriptions

and insights derived from the 2002 Nebraska licensed angler survey. Nebraska

Game and Parks Commission, Lincoln, Nebraska.

Jackson, D. C. 1999. Flathead catfish: biology, fisheries, and management. Pages 23-35

in E. R. Irwin, W. A. Hubert, C. F. Rabeni, H. L. Schramm, Jr., and T. Coon,

editors. Catfish 2000: proceedings of the international ictalurid symposium.

American Fisheries Society, Symposium 24, Bethesda, Maryland. 5

Keenlyne, K. D. 1990. Endangered and threatened wildlife and plants: determination of

endangered status for the Pallid sturgeon. United States Fish and Wildlife

Service. Federal Register 55: 36641-36647.

Michaletz, P. H., and J. G. Dillard. 1999. A survey of catfish management in the United

States and Canada. Fisheries 24: 6-11.

Morris, L. A., R. N. Langermeier, T. R. Russel, and A. W. Witt, Jr. 1968. Effects of

mainstem impoundments and channelization upon the limnology of the Missouri

River, Nebraska. Transactions of the American Fisheries Society 97: 380-388.

Schneiders, B. 1996. The myth of environmental management: the Corps, the Missouri

River, and the channelization project. Agricultural History 70: 337-350.

U.S. Army Corps of Engineers. 2006. Missouri River mainstem reservoir system master

water control manual Missouri River basin. United Stated Army Corps of

Engineers Reservoir Control Center Northwestern Division, Omaha, Nebraska.

U. S. Army Office of the Chief of Engineers. 1913. Laws of the United States relating to

the improvement of rivers and harbors from August 11, 1790 to march 4, 1913.

Government Printing Office, Washington D.C.

U.S. Department of the Interior, Fish and Wildlife Service. 2000. Biological opinion on

the operation of the Missouri River main stem Reservoir system, operation and

maintenance of the Missouri River bank stabilization and navigation project, and

operation of the Kansas River reservoir system. U.S. Fish and Wildlife Service,

Bismarck, North Dakota. 6

U.S. Department of the Interior, Fish and Wildlife Service, and U.S. Department of

Commerce, U.S. Census Bureau. 2006 National Survey of Fishing, Hunting, and

Wildlife-Associated Recreation. U.S. Government Printing Office, Washington,

D.C.

Vokoun, J. C., and C. F. Rabeni. 1999. Catfish sampling in rivers and streams: a review

of strategies, gears, and methods. Pages 271-286 in E. R. Irwin, W. A. Hubert,

C. F. Rabeni, H. L. Schramm, Jr., and T. Coon, editors. Catfish 2000:

proceedings of the international ictalurid symposium. American Fisheries

Society, Symposium 24, Bethesda, Maryland.

Zuerlein, G. 1987. Angler use estimates on the Missouri, Platte, Niobrara, and Elkhorn

Rivers in 1986. Nebraska Game and Parks Commission, Lincoln, Nebraska.

CHAPTER 2 – POPULATION CHARACTERISTICS OF CHANNEL CATFISH

AND FLATHEAD CATFISH IN THE MISSOURI RIVER, NEBRASKA

Introduction

Channel catfish Ictalurus punctatus and flathead catfish Pylodictis olivaris are two of the most important freshwater recreational or commercial species in the United

States (Vokoun and Rabeni 1999) and have been studied extensively throughout their ranges (Hubert 1999, Jackson 1999, Barada 2009). Michaletz and Dillard (1999) found that catfish (channel catfish, flathead catfish, blue catfish Ictalurus furcatus, and „other‟ species) were deemed important to anglers by fisheries managers from 32 management agencies, with 28 states allowing some commercial harvest.

A United States Department of Interior survey (2006) estimated that there were

6.95 million catfish anglers in the United States in 2006. A Nebraska angler survey conducted in 2002 showed that ~ 13 % of survey respondents preferred to fish for channel catfish over any other species and ~ 2 % preferred to fish for flathead catfish over any other species (Hurley and Duppong-Hurley 2005). Approximately 40% of the respondents reported that they had specifically targeted channel catfish and ~ 15 % specifically targeted flathead catfish at least once during 2002. The same survey showed that channel catfish were the third most targeted species following largemouth bass

Micropterus salmoides and crappie Pomoxis spp. in the eastern fisheries districts bordered by the Missouri River (Hurley and Duppong-Hurley 2005). Use of the Missouri

River by Nebraska anglers increased 72 percent between 1984 and 1986 to an estimated total of ~ 408,000 trips annually (Zuerlein 1987) and a 2005 catfish angler survey 8 indicated that the Missouri River had the highest use of any Nebraska river by catfish seeking anglers (Hurley and Duppong-Hurley 2007) suggesting that Missouri River catfish populations are important resources to the people of Nebraska and surrounding states.

Estimates of relative abundance, size structure, and condition provide resource managers with important information needed to maximize and sustain the potential of a fisheries stock. Typically fisheries resource managers must balance the needs and desires of multiple user groups (i.e., recreational versus commercial anglers, harvest oriented versus trophy oriented anglers, etc.) while attempting to maintain a sustainable fishery.

Travnichek (2004) proposed that Missouri River flathead catfish populations could be managed based on population characteristics and angler desires (i.e., harvest oriented areas and trophy fishery oriented areas). Lotic channel catfish populations also have the potential to be managed as trophy fisheries. For example, the Red River in Manitoba is managed to restrict harvest and to maximize anglers‟ potential for catching trophy channel catfish (Macdonald 1990).

Catfish management in the portion of the Missouri River bordering Nebraska is a complex issue, as fisheries management falls under the jurisdiction of several states

(Iowa, Kansas, Missouri, Nebraska, and South Dakota). All five states banned commercial catfish harvest from the Missouri River in 1992 due to concerns about declines in catfish stocks (Mestl 1999). However, recreational harvest of catfish from the

Missouri River does still occur. Current (2010) regulations in Kansas, Missouri, and

Nebraska allow anglers to harvest five channel catfish and five flathead catfish per day,

South Dakota allows anglers to harvest 10 catfish of any species per day, and Iowa allows 9 anglers to harvest 15 catfish (channel catfish, or flathead catfish) per day. Therefore, it is important to monitor and evaluate key characteristics of the catfish populations in the

Missouri River, Nebraska to ensure proper management. The objective of my study was to evaluate channel catfish and flathead catfish populations in the Missouri River,

Nebraska to determine relative abundance, size structure, and condition. Specifically, I evaluated the questions: are there differences in population characteristics among study segments, and do habitat restoration efforts have an impact on channel catfish or flathead catfish populations?

Methods

Study Area

Sampling was conducted in the Missouri River from Fort Randall Dam in South

Dakota at river kilometer (RK) 1419 to the Nebraska-Kansas border at RK 794 (Figure 3-

1). The study area encompasses the entire portion of the Missouri River bordering the state of Nebraska, and has been divided into four riverine segments (Lewis and Clark

Lake was not sampled in this study) based on prior research conducted by the Nebraska

Game and Parks Commission, Fisheries Division (Porter and Mestl 2009). Each segment represents a distinct reach of river based on morphological characteristics such as input from a major tributary (e.g., Platte River, Nebraska; Big Sioux River, Iowa), impoundments (e.g., Fort Randall Dam, Gavins Point Dam/Lewis and Clark Lake), channel control (e.g., revetted banks, flow modification structures, navigation channel, etc.), and unchannelized reaches (i.e., “natural” channel morphology). Based on these classifications the segments are as follows (Figure 2-1): 10

1) Upper unchannelized (UU) – Fort Randall Dam to the headwaters of Lewis

and Clark Lake (RK 1352 - 1419),

2) Lower unchannelized (LU) – Gavins Point Dam to the confluence with the

Big Sioux River (RK 1184 – 1308),

3) Upper channelized (UC) – Confluence with the Big Sioux River to the

confluence with the Platte River (RK 960 – 1184),

4) Lower channelized (LC) – Confluence with the Platte River to the Kansas-

Nebraska border (RK 794 – 960).

River bends within each segment were numbered and in channelized segments only, classified as modified or unmodified (Appendix A). The reach between Ponca

State Park, Nebraska and the Big Sioux River confluence is channelized but has historically been considered part of the lower unchannelized section by (Porter and Mestl

2009). Congress passed the 1910 Rivers and Harbors Act which authorized the

USACOE to develop and maintain a 1.8 m deep navigation channel from the mouth of the Missouri River at Saint Louis, Missouri to Kansas City, Missouri. Several revised

Rivers and Harbors Acts followed, eventually calling for development and maintenance of a 2.7 m deep, 91.4 m wide navigation channel from the mouth of the Missouri River to

Sioux City, Iowa (USACOE 2006). Wing dams, pile dikes, and revetted banks were constructed to direct the flow of water into the navigation channel and increase sediment deposition on the inside of river bends. These structures represent the river channel over the past ~ 50 – 100 years and will be termed “unmodified” because they have not been altered since original construction. Bends classified as modified have been altered by the

United States Army Corps of Engineers (USACOE) as part of an effort to restore habitat 11 lost during the channelization of the Missouri River. Modifications can include: constructed backwater areas, notched wing-dams, side channels (chutes), chevron structures, etc. Due to small the low number of modified bends sampled each year (3 bends per segment) no comparisons between modification types were made.

Field Sampling

I randomly selected six river bends per segment for channel catfish sampling and six river bends per segment for flathead catfish sampling during July – September 2009 and 2010. I also stratified the bends by modification level prior to randomly selecting bends for each channelized segment to ensure equal numbers of modified and unmodified bends were sampled.

Channel catfish were sampled with hoop nets following the protocols detailed by

Porter and Mestl (2009). I used 0.6-m diameter 7-hoop, hoop nets with 25-mm mesh

(SHN) and 0.6-m diameter 4-hoop, hoop nets with 7-mm mesh (MHN). A total of 10 hoop nets (8 SHN and 2 MHN) were set on each river bend in areas with depths greater than 0.6 m and sufficient water velocity to keep the nets from collapsing. Five nets (4

SHN and 1 MHN) were set on the inside bend and five nets (4 SHN and 1 MHN) were set on the outside bend. All nets were baited with ~ 1 kg of cheese trimmings, weighted with a concrete block, and anchored to shore with a hoop net hook. Nets were fished overnight with a total set time not exceeding 24 hours.

Flathead catfish were sampled with low frequency (15 Hz), low amperage (< 5 amps), pulsed DC electrofishing (EF). River bends were divided into eight sampling units for electrofishing based on the median bend length within each study section as: 12

MBL U = . 8

Ui = sample unit for segment i, MBLi = median bend length for segment i. Eight sampling units were sampled on each bend with four units on the inside bend, and four units on the outside bend. Sampling units were randomly chosen following this division.

If the total bend length was shorter than 4 sampling units the number of samples was decreased accordingly. A Smith-Root GPP 5.0 boat-mounted electrofisher was used to bring fish to the surface where they were netted from the bow of the boat by a single dipper. A second boat with one dipper and one boat operator was used as a chase-boat to capture fish that surfaced out of range of the electrofisher.

All fish collected were measured to the nearest mm for length and the nearest g for mass. Channel and flathead catfish ≥ 200 mm were marked by clipping the adipose fin and implanting a FD-94 t-bar anchor tag (Floy mfg.) between the dorsal pterygiophores on the fish‟s left side. All fish were returned to the water immediately following processing.

Data Analyses

Gear specific comparisons of relative abundance, size structure, and condition were made between segments and between bend modification levels within the channelized segments. Catch data from the SHN and MHN were used for channel catfish comparisons, and EF catch data were used for flathead catfish comparisons. Gear deployments that did not fish correctly (i.e., net collapse, tangled nets, etc.) were excluded from all analyses. 13

I calculated mean relative abundance (C/f) of channel catfish and flathead catfish within each segment using a generalized linear mixed modeling (GLMM) approach

(Littell et al. 2006, Dobson and Barnett 2008). Channel catfish C/f was calculated as the number of fish per net night and flathead catfish C/f was calculated as the number of fish captured per minute of EF (C/f-time) and the number of fish captured per 100 m of bankline shocked (C/f-distance). Biological data are often characterized by a high occurrence of zero counts, particularly in instances in which the study organism has low densities or patchy distributions (Hubert and Fabrizio 2007). These data cannot be assumed to have a normal distribution in these instances as is required for standard parametric analyses. Generalized linear modeling (GLM) allows the data to be analyzed under different probability distributions such as a Poisson distribution or a negative binomial distribution. Addition of a random variable extends the GLM model to the

GLMM format. The random variable is assumed to represent an interchangeable sample from a larger population with a known probability distribution, which allows for broad inference of overall population parameters and estimation of mean C/f (Littell et al.

2006). Both GLM and GLMM use transformations (link functions) of the model parameters (Xβ) based on the probability distribution of the data to fit a linear model on which statistical testing can be conducted. Inclusion of an inverse link statement in the model back transforms the generalized-scale mean parameter estimates to the original scale (Littell et al. 2006). Therefore river bend nested within segment and year

{Bend(Seg*Yr)} was used as the random variable in the GLMM which allowed the overall mean C/f within each segment to be calculated (Appendix D). I included an offset variable in the model which scales raw count data by the effort (time or distance) 14 expended on each EF run to convert EF count data to C/f (SAS institute 2009). A

Tukey‟s adjustment factor was included to maintain an overall experimental α = 0.05.

Generalized linear models were used to compare the mean relative abundance of channel catfish collected in SHN and flathead catfish collected with EF by bend modification level within segment in the two channelized segments. No random effect was included in this model structure due to only three bends within each modification level being sampled within each segment per year (Appendix D).

I calculated proportional size distributions (PSD, PSD-P, PSD-M, and PSD-T;

Guy et al. 2007) to assess size structure between segments, bend modification levels within segments (channelized segments only), and sampling years. The general form of the PSD equation is:

of fish ≥ minimum (Size Category)length PSD (Size Category)= *100 of fish ≥ minimum stock length

I used Chi-Square (χ²) tests, as recommended by Neumann and Allen (2007), to compare

PSD indices between segments, bend modification levels within segments (channelized segments only), and sampling years. Length-frequency distributions were compared using nonparametric Kolmogorov-Smirnov tests with a Bonferroni correction factor to maintain an overall α = 0.05.

I calculated the mean relative weight (Wr; Wege and Anderson 1978) of channel catfish collected in SHN and flathead catfish collected with EF by 50 mm length groups.

The general equation used to calculate Wr is as follows:

W Wr = *100. Ws 15

W is the measured weight, and Ws is the standard weight for the species. Brown et al.

(1995) provide the standard weight equation for channel catfish:

log10 (Ws) = -5.800 + 3.294*log10 (Total Length).

Bister et al. (2000) provide the standard weight equation for flathead catfish:

log10 (Ws) = -5.542 + 3.230*log10 (Total Length).

Comparisons of mean Wr were made for size (50 mm length groups), segment, and sample year using analysis of variance (ANOVA) with a Tukey‟s adjustment to maintain an overall α = 0.05 following the procedures described by Pope and Kruse (2007).

Comparisons of log10-transformed length-weight regressions between segments were made using analysis of covariance (ANCOVA) to test for differences in slope (Pope and

Kruse 2007). All analyses were conducted using SAS v. 9.2 (SAS Institute 2009).

Results

A total of 1,638 channel catfish were captured in 370 net nights with SHN in 2009 and 2010. An additional 326 channel catfish were captured in 88 net nights with MHN in

2009 and 2010. The greatest catch was observed in the upper channelized segment and the lowest catch in the lower channelized segment (Table 2-1). A total of 3,965 flathead catfish were captured in 373 EF runs in 2009 and 2010, with the greatest catch in the lower channelized segment and the lowest catch in the upper unchannelized segment

(Table 2-2).

Channel catfish

Relative abundance

Visual inspection of channel catfish catch data from hoop nets indicated a substantial deviation from normality (Figure 2-2) and Kolmogorov-Smirnov tests (SAS

9.2) for normality confirmed this assumption (p < 0.01). Models assuming a Poisson probability distribution and a negative binomial probability distribution were constructed and assessed for goodness of fit (AIC, deviance; χ²/degrees of freedom). I found that the models assuming a negative binomial probability distribution provided a better fit

(χ²/degrees of freedom ~ 1). Mean C/f differed between years only in the upper channelized segment following a Bonferroni correction to maintain the experimental α =

0.05 (Figure 2-3). The overall mean C/f was greater in 2010 than in 2009, mainly driven by the difference (P < 0.005) in mean C/f seen in the upper channelized segment (Figure

2-3). No segment level differences (P > 0.05) in mean C/f of channel catfish collected in

SHN in 2009 were found (Figure 2-3). However, in 2010 the mean C/f of channel catfish collected in SHN was greater (P = 0.009; Tukey‟s multiple comparison) in the upper channelized segment than in the lower unchannelized segment (Figure 2-3).

Mean C/f by segment of channel catfish collected in MHN also showed evidence of annual differences (P < 0.005) with greater mean C/f in 2010 than 2009 in two segments (Figure 2-4). No segment level differences (P > 0.05) in mean C/f of channel catfish collected in MHN in 2009 were found (Figure 2-4). However, in 2010 the mean

C/f of channel catfish collected in MHN was greater in the upper channelized segment than the upper unchannelized (P < 0.001), and lower channelized (P < 0.001) segments; 17 and greater in the lower unchannelized segment than the upper unchannelized (P < 0.001) and lower channelized (P = 0.018) segments.

Mean C/f by bend modification level within segment of channel catfish collected in SHN was greater (P < 0.001) on modified bends than on unmodified bends in the upper channelized segment in 2009 (Figure 2-5). No other bend modification level within segment differences (P > 0.05) in mean C/f of channel catfish collected in SHN were found (Figure 2-5). Mean C/f by river bend of channel catfish collected in SHN was highly variable and does not appear to exhibit any well defined spatial trends within segments (Figure 2-6).

Size Structure

Channel catfish less than minimum stock length (280 mm) collected in SHN comprised 52% of the catch in 2009 and 58 % in 2010 (Table 2-3). There were no differences in PSD values between years (P = 0.388). Therefore, I pooled the 2009 and

2010 data (Table 2-3) to make comparisons of PSD values between segments and found differences in four of the six segment level comparisons (Table 2-4).

Differences in length-frequency distributions of channel catfish collected in SHN nets were found for two of the six segment level comparisons in 2009 (Table 2-5; Figure

2-7) where size in the lower channelized segment was greater than the lower unchannelized (P < 0.001) and upper channelized (P = 0.006) segments. Four of the six segment level comparisons differed in 2010 (Table 2-6; Figure 2-8) where the upper unchannelized segment was greater than the lower unchannelized (P < 0.001) and upper channelized (P < 0.001) segments, and the lower channelized segment was greater than 18 the lower unchannelized (P < 0.001) and upper channelized (P < 0.001) segments. No differences (P > 0.05) in length-frequency distributions were found between bend modification levels in 2009 (Figure 2-9) or 2010 (Figure 2-10).

Condition

Channel catfish condition (Wr) varied by segment, body length (50 mm length categories) and sampling year (Figure 2-11). Small fish (< 250 mm) exhibited high (>

100) mean Wr values followed by decreasing mean Wr values as total length increased in all segments. Mean Wr values of channel catfish collected in the channelized segments

(UC and LC) showed an increasing trend at larger (> 450 mm) body lengths.

Length-weight relations of channel catfish revealed greater incremental weight gain in the lower channelized segment in 2009 than in 2010 (P < 0.001) but did not differ in any of the three remaining segments (P > 0.05). However, to maintain consistency across all segments I calculated length-weight relations separately for 2009 and 2010 in all segments. Length-Weight relations differed (P < 0.008) in four of six segment level comparisons in 2009 with greater incremental weight gain observed in the upper unchannelized segment than the lower unchannelized (P < 0.001) and the upper channelized (P < 0.001) segments and greater incremental weight gain in the lower channelized segment than the lower unchannelized (P = 0.002) and upper channelized (P

< 0.001) segments (Table 2-7; Figure 2-12). Three of six segment level comparisons of length weight relations differed (P , 0.008) in 2010 with greater incremental weight gain observed in the upper unchannelized segment than the lower unchannelized segment (P =

0.002) and greater incremental weight gain in the lower channelized segment than the 19 lower unchannelized (P < 0.001) and upper channelized (P < 0.001) segments (Table 2-8;

Figure 2-13).

Flathead catfish

Relative abundance

Visual inspection of flathead catfish catch data from EF indicated a substantial deviation from normality (Figure 2-14) and Kolmogorov-Smirnov tests (SAS 9.2) for normality confirmed this assumption (p < 0.01). Models assuming a Poisson probability distribution and a negative binomial probability distribution were constructed and assessed for goodness of fit (AIC, deviance; χ²/degrees of freedom). I found that the models assuming a negative binomial probability distribution provided a better fit

(χ²/degrees of freedom ~ 1).

Mean C/f-time did not differ (P > 0.05) between years in any of the individual segment level comparisons (Figure 2-15). All mean C/f-distance (Figure 2-16) comparisons were similar to the mean C/f-time comparisons at the segment level.

Therefore I present only C/f -time for clarity. Mean C/f-time of flathead catfish was greater (P < 0.05; Tukey‟s multiple comparison) in the channelized segments than in either of the unchannelized segments in 2009 (Figure 2-15). However, in 2010 the mean

C/f-time of flathead catfish collected with EF in the lower unchannelized segment did not differ (P > 0.05) from either of the channelized segments.

Mean C/f-time by bend modification level within segment of flathead catfish collected with EF was greater (P = 0.023) on unmodified bends than on modified bends in the lower channelized segment in 2010 (Figure 2-17). No other bend modification 20 level within segment differences in mean C/f-time of flathead catfish collected with EF were found. Mean C/f-time by river bend of flathead catfish collected with EF was highly variable and does not appear to exhibit any well defined spatial trends within segments but did show a longitudinal increase from upstream to downstream in 2009

(Figure 2-18).

Size Structure

Flathead catfish less than minimum stock length (350 mm) collected with EF comprised 74 % of the catch in 2009 and 57 % in 2010 (Table 2-9). Chi-square (χ²) comparisons of segment level PSD values revealed an annual difference (p < 0.001) in the upper channelized segment but no other annual differences in segment level PSD values were observed (Table 2-10). I pooled the 2009 and 2010 sampling years (Table 2-

9) to make comparisons of PSD values between segments and found segment level differences in three of the six segment level comparisons (Table 2-11) with greater PSD in the upper unchannelized segment than the upper channelized (P < 0.001) and lower channelized (P < 0.001) segments and greater PSD in the lower unchannelized segment than the upper channelized segment (P = 0.002). Length-frequency distributions of flathead catfish collected with EF did differ between five of the six segment level comparisons in 2009 with median total lengths decreasing from upriver – downriver in

2009 (Table 2-13; Figure 2-19). Four of the six segment level comparisons differed (P <

0.008) in 2010; however no defined pattern in size structure was found (Table 2-14;

Figure 2-20). Length-frequency distributions were also different between bend modification levels in the upper channelized segment in 2009 (p = 0.002; Figure 2-21) 21 and the lower channelized segment in 2010 (p = 0.001; Figure 2-22) with greater median lengths observed on modified bends in both comparisons.

Condition

Flathead catfish condition (Wr) varied by segment, body length (50 mm length categories) and sampling year (Figure 2-23). In all but the upper unchannelized segment, small fish (< 250 mm) exhibited high (> 100) mean Wr values followed by decreasing mean Wr values as total length increased with a subsequent increase for all but the upper unchannelized segment for fish > 500 mm. Mean Wr values of flathead catfish in the upper unchannelized segment showed an opposite pattern.

Length-weight relations of flathead catfish differed by sample year in both channelized segments (P < 0.001) with greater incremental weight gain observed in 2010 than 2009, but did not differ in either of the unchannelized segments (P > 0.05).

However, to maintain consistency across all segments I calculated length-weight relations separately for 2009 and 2010 in all segments. Length-weight relations of flathead catfish differed in four of six segment level comparisons in 2009 with lower incremental weight gain observed in the lower channelized segment than the upper unchannelized (P <

0.001), lower unchannelized (P < 0.001), and upper channelized (P < 0.001) segments; and greater incremental weight gain observed in the lower unchannelized segment than the upper channelized segment (P < 0.001; Table 2-15; Figure 2-24). One of six segment level comparisons of length-weight relations differed in 2010 with greater incremental weight gain observed in the lower unchannelized segment than the upper channelized segment (P = 0.002; Table 2-16; Figure 2-25). 22

Discussion

I found considerable variation in C/f of channel catfish and flathead catfish between river bends and within river bends, highlighting the importance of randomly selecting sampling sites to provide accurate assessments of population characteristics at the segment level. Catches of zero fish per hoop net deployment or EF run were not uncommon, particularly in the upper unchannelized segment suggesting low density populations of both species in that segment. Hesse et al. (1982a) reported mean C/f values for channel catfish collected in 25 mm mesh hoop nets ranged from 2.1 (± 1.2) fish per net night at Sunshine bottoms in the upper unchannelized segment to 8.7 (± 1.7) fish per net night near Blair, Nebraska in the upper channelized segment. Similarly,

Mestl (2001, 2003, 2004) and Porter and Mestl (2008, 2009) reported mean C/f values for flathead catfish ranging from zero fish per minute in the upper unchannelized segment

(Boyd County, Nebraska sample site; 2005) to 10.6 fish per minute in the upper channelized segment (Blair, Nebraska sample site; 2003). Similar trends were observed for both species in 2009 and 2010. Channel catfish mean C/f was greater in the upper channelized segment than the lower unchannelized segment in 2010 and mean C/f of flathead catfish in the upper unchannelized segment was lower than any of the other segments.

Barada (2009) reported that channel catfish relative abundance varied longitudinally along the Platte River, Nebraska with the greatest relative abundance values at the central sites of the study area and the lowest relative abundances at the most upstream and downstream sites. I observed a similar pattern in relative abundance in

Missouri River channel catfish in 2009 and 2010 with the greatest mean C/f values in the 23 central portions of the study area (i.e., the upper portions of the upper channelized segment and the lower portions of the lower unchannelized segment; Figure 2-6).

Flathead catfish mean C/f appears to follow a generally increasing trend from upriver – downriver (Figure 2-18). Several possible theories could explain these trends.

Susceptibility to predation could explain the lower observed C/f of channel catfish in the most upstream and downstream segments of the Missouri River, Nebraska.

Flathead catfish C/f was greatest in the lower channelized segment and bycatch of smallmouth bass Micropterus dolomieu and other sight-feeding piscivorous species was greatest in the upper unchannelized segment (Appendix C). Several studies have documented increased predation on juvenile riverine species in low turbidity conditions

(Johnson and Hines 1999, Gadomski and Parsley 2005) and numerous studies have examined the influence of predation by piscivorous fish such as largemouth bass

Micropterus salmoides (Mestl 1983, Howell and Betsill 1999, Jackson and Francis 1999) and flathead catfish (Quinn 1988) on the recruitment of channel catfish and other ictalurid species. The upper unchannelized segment had the lowest turbidity levels of any of the study segments as well as supporting populations of sight-feeding piscivorous species such as smallmouth bass, rock bass Ambloplites rupestris, northern pike Esox lucius and white bass Morone chrysops. Conversely, the lower channelized segment had greater turbidity levels than the other study segments but also had the highest C/f of flathead catfish of any of the study segments. Morris et al. (1971) reported that catfish species (primarily channel catfish and smaller flathead catfish) made up a significant portion of the diet of adult flathead catfish in the channelized segments of the Missouri 24

River. It is possible that predation might influence the abundance of channel catfish in the Missouri River.

Limited habitat availability may also play a role in distribution of catfish in the

Missouri River. For example, I observed the lowest mean C/f of flathead catfish in the upper unchannelized segment and the greatest mean C/f of flathead catfish in the lower channelized segment during both years of this study. Daugherty and Sutton (2005) reported that habitat use by flathead catfish in the Lower Saint Joseph River, Michigan was “dominated by large woody debris and riprap at water depths < 3 m deep”. At first glance there appears to be ample habitat for flathead catfish throughout the upper unchannelized segment in the form of deep water, large woody debris, aquatic vegetation, and rocky shorelines. The sites within the upper unchannelized segment that yielded the majority of the flathead catfish collected in this study were near tributary confluences such as Ponca Creek, Nebraska; and the Niobrara River, Nebraska. These sites had higher turbidity levels and similar water temperatures when compared with upper unchannelized segment sites not located near tributary mouths (20-40 NTU vs. 3-10

NTU). Hesse and Mestl (1991) reported relative abundance of flathead catfish in the upper unchannelized segment was approximately 10% of the relative abundance found in the lower unchannelized segment and hypothesized that reduced turbidity along with isolation from downstream populations in the form of a barrier (Gavins Point Dam) were the reasons for the low abundance of flathead catfish in this segment of river. The upper unchannelized segment of the Missouri River, Nebraska approaches the Northwestern boundary of the species‟ native range (Jackson 1999). Factors related to climatic differences such as length of growing season, water temperature, etc. are “known to 25 influence growth and yield of fish species with broad geographic distributions” (Durham et al. 2005) suggesting that latitudinal and longitudinal influences combined with habitat factors such as coldwater discharge from Fort Randall Dam and lower relative turbidity may negatively influence flathead catfish populations in the upper unchannelized segment of the Missouri River, Nebraska.

I observed annual differences in the size structures of channel catfish and flathead catfish populations in the Missouri River. Length frequency distribution differences between 2009 and 2010 were observed for both species and flathead catfish PSD was greater in 2009 than in 2010 in the upper channelized segment. Proportional size distribution values were somewhat lower in 2010 than in 2009 in all study segments

(although only statistically significant in the upper channelized segment). The reason(s) for the observed annual difference in flathead catfish PSD between 2009 and 2010 remain unclear. Several factors related to sampling procedures may have contributed to the observed differences between 2009 and 2010. The Missouri River was at or near flood stage during most of the 2010 EF sampling season, multiple chase boat drivers with varying experience were used in 2010 while in 2009 a single, experienced driver was used all season, and all technicians (netters) were new from 2009 – 2010.

The majority of channel catfish sampled in this study were below the minimum stock length (280 mm) with very few individuals of preferred length (≥ 610 mm) sampled. The majority of preferred length fish were sampled at one site in the upper unchannelized segment in the delta area of Lewis and Clark Lake. These individuals appeared to be in post spawn condition and may have been fish that moved from the lake to the river to spawn. Proportional size distribution values and mean lengths of channel 26 catfish collected in SHN were greatest in the upper unchannelized segment and lower channelized segment and lowest in the lower unchannelized segment and upper channelized segment. Density and abundance have been shown to be negatively correlated with PSD for a number of species including catfish (Brown et al.1999). Mean

C/f of channel catfish was greatest in the upper channelized segment and a closed- captures density estimate calculated from a 6.2 RKM bend in the upper channelized segment showed that C/f can be related to density and produced an estimate of ~ 4,164 channel catfish > 200 mm per RKM (See Chapter 4).

Small channel catfish (< 250 mm) had mean Wr values over 100. Mean Wr declined in S-Q (280 - 410 mm) and Q-P (410 - 610 mm) sized fish and increased in large fish (> 550 mm). The same trend has been reported in other studies of channel catfish in

Midwestern rivers (Doorenbos et al. 1999, Barada 2009). Conversely, Hesse et al.

(1982b) found channel catfish condition in the Missouri River is size dependant with large fish having higher condition relative to small fish. The high Wr values for small channel catfish observed in this and other studies in which the main collection method was baited hoop nets may be somewhat inflated due to the fact that fish are able to consume the bait while in the net that may disproportionately increase recorded weights of smaller fish.

Interactions of sampling location (segment), sampling year, and body length all contributed to the observed differences in mean Wr of channel catfish. Channel catfish condition was generally higher in 2010 than 2009 at all size classes in all segments. The

Missouri River was in flood stage for much of 2010, inundating areas of the floodplain that are generally not connected to the river. The importance of floodplain connectivity 27 to river biota has been well documented (e.g., Junk et al. 1989, Poff et al. 1997, and

Barko et al. 2006). The greater observed condition of channel catfish in 2010 may be due in part to increased food and habitat availability in the floodplain.

Bend modifications do not appear to have a significant influence on channel catfish populations in the channelized segments of the Missouri River. I found no differences in size structure between bend modification levels and relative abundance was different in only one of four possible comparisons. However, bend modifications appear to have had some influence on flathead catfish in the channelized segments of the

Missouri River where I found differences in size structure and relative abundance between bend modification levels. Flathead catfish collected on modified bends generally had greater lengths and lower abundance than those collected on unmodified bends supporting the theory that density may be a factor in catfish population size structure. Jackson (1999) summarized numerous studies (Robinson 1977, Sandheinrich and Atchison 1986) that reported flathead catfish are often associated with pile dike and wing dam pools. Removal or modification of wing dams alters the pool habitats created by unmodified wing dams, which could be the reason for the lower relative abundances observed on modified bends. Continued sampling of modified and unmodified bends is needed to determine if the observed differences in relative abundance were due to natural variability or if they represent true differences.

Travnichek (2004) proposed that flathead catfish populations in the Missouri

River, Missouri may be regulated within management units rather than with river-wide regulation to cater to both harvest oriented anglers and trophy anglers. The current trend in Nebraska has been to streamline and simplify sportfish regulations by creating 28 statewide or basinwide management regulations. However, due to differences in catfish population characteristics between segments, catfish management in this portion of the

Missouri River appears to be well suited for management unit based regulations.

Specifically, the upper channelized segment has a relatively greater density channel catfish population (See Chapter 4) and appears to be able to support relatively greater levels of channel catfish harvest than the other segments. Similarly, the lower channelized segment has a relatively greater density flathead catfish population and appears to be able to support relatively greater levels of flathead catfish harvest than the other segments. The upper unchannelized segment appears to support low density populations of channel catfish and flathead catfish which may be better suited for trophy management regulations designed to minimize harvest and maximize growth potential.

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Table 2-1. Total catch of channel catfish by year and segment (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment) in 25-mm mesh hoop nets (SHN) and 7-mm mesh hoop nets (MHN).

Segment SHN MHN Yr Catch Net Nights Catch Net Nights UU 2009 61 48 3 12 2010 179 47 4 11 LU 2009 179 46 3 11 2010 111 46 92 10 UC 2009 262 46 14 11 2010 608 44 182 11 LC 2009 51 46 13 11 2010 187 47 15 11

Total 1638 370 326 88

Table 2-2. Total catch of flathead catfish by year and segment (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment) with pulsed DC electrofishing (EF).

Segment EF Yr Catch Runs UU 2009 18 43 2010 28 48 LU 2009 224 48 2010 341 48 UC 2009 755 48 2010 629 44 LC 2009 1164 46 2010 807 48

Total 3965 373

Table 2-3. Proportional size distributions (PSD) of channel catfish collected in 25-mm mesh hoop nets in 2009, 2010, and combined by segment (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment).

Segment N % Stock PSD PSD-P PSD-M PSD-T

2009 UU 61 56 21 0 0 0 LU 262 43 8 0 0 0 UC 179 46 10 0 0 0 LC 51 63 34 0 0 0 2010 UU 179 59 29 6 < 1 0 LU 111 22 13 0 0 0 UC 608 33 5 0 0 0 LC 187 70 24 0 0 0 Combined UU 240 58 27 4 < 1 0 LU 373 27 9 0 0 0 UC 787 41 7 0 0 0 LC 238 68 26 0 0 0

Table 2-4. Chi-square (χ²) test values for comparisons of proportional size distribution (PSD) of channel catfish collected in 25-mm mesh hoop nets between segments in 2009 and 2010 combined (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment). Underlined values in bold indicate significant differences following Bonferroni correction (α = 0.008).

Segment LU UC LC

UU χ² = 12.423 χ² = 36.893 χ² = 0.057

P < 0.001 P < 0.001 P = 0.811

LU . χ² = 0.640 χ² = 11.523

P =0.424 P < 0.001

UC . . χ² = 35.491

P < 0.001

Table 2-5. Kolmogorov-Smirnov test (p – values) comparing length-frequency distributions of channel catfish between segments in 2009 (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment). Underlined values in bold indicate significant differences following Bonferroni correction (α = 0.008).

Segment LU UC LC

UU 0.009 0.107 0.028

LU . 0.038 <0.001

UC . . 0.006

Table 2-6. Kolmogorov-Smirnov test (p – values) comparing length-frequency distributions of channel catfish between segments in 2010 (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment). Underlined values in bold indicate significant differences following Bonferroni correction (α = 0.008).

Segment LU UC LC

UU < 0.001 < 0.001 0.179

LU . 0.048 < 0.001

UC . . < 0.001

Table 2-7. Analysis of covariance test (p – values) for comparisons of channel catfish length-weight relations between segments in 2009 (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment). Underlined values in bold indicate significant differences following Bonferroni correction (α = 0.008).

Segment LU UC LC

UU <0.001 <0.001 0.888

LU . 0.312 0.002

UC . . < 0.001

Table 2-8. Analysis of covariance test (p – values) for comparisons of channel catfish length-weight relations between segments in 2010 (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment). Underlined values in bold indicate significant differences following Bonferroni correction (α = 0.008).

Segment LU UC LC

UU 0.002 0.010 0.138

LU . 0.072 < 0.001

UC . . < 0.001

Table 2-9. Proportional size distributions (PSD) of flathead catfish collected with pulsed DC electrofishing in 2009, 2010, and combined by segment (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment).

Segment N % Stock PSD PSD-P PSD-M PSD-T

2009 UU 18 78 50 0 0 0 LU 755 29 32 12 8 3 UC 224 24 21 8 4 2 LC 1164 26 16 3 < 1 0 2010 UU 28 61 35 0 0 0 LU 341 21 16 1 0 0 UC 629 42 7 1 < 1 < 1 LC 807 52 15 < 1 0 0 Combined

UU 46 67 42 0 0 0

LU 565 25 24 6 4 1

UC 1384 33 13 4 2 1

LC 1971 37 15 2 < 1 0

Table 2-10. Chi-square (χ²) test values for comparisons of proportional size distribution (PSD) of flathead catfish collected with pulsed DC electrofishing between 2009 and 2010 sampling years by segment (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment). Underlined values in bold indicate significant differences following Bonferroni correction (α = 0.013).

Segment UU(10) LU(10) UC(10) LC(10)

UU(09) χ² = 0.682 . . .

P = 0.409

LU(09) . χ² = 4.529 . .

P = 0.033

UC(09) . . χ² = 18.285 .

P < 0.001

LC(09) . . . χ² = 0.064

P = 0.800

Table 2-11. Chi-square (χ²) test values for comparisons of proportional size distribution (PSD) of flathead catfish collected with pulsed DC electrofishing between segments in 2009 and 2010 combined (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment). Underlined values in bold indicate significant differences following Bonferroni correction (α = 0.008).

Segment LU UC LC

UU χ² = 4.2513 χ² = 19.9797 χ² = 15.4113

P = 0.039 P < 0.001 P < 0.001

LU . χ² = 10.0609 χ² = 6.0057

P =0.002 P = 0.014

UC . . χ² = 1.5604

P = 0.212

Table 2-12 Kolmogorov-Smirnov test (p – values) comparing length frequency distributions of flathead catfish between segments in 2009 (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment). Underlined values in bold indicate significant differences following Bonferroni correction (α = 0.008).

Segment LU UC LC

UU <0.001 <0.001 <0.001

LU . 0.158 0.003

UC . . < 0.001

Table 2-13. Kolmogorov-Smirnov test (p – values) comparing length frequency distributions of flathead catfish between segments in 2010 (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment). Underlined values in bold indicate significant differences following Bonferroni correction (α = 0.008).

Segment LU UC LC

UU < 0.001 0.025 0.100

LU . < 0.001 < 0.001

UC . . < 0.001

Table 2-14. Analysis of covariance test (p - values) for comparisons of flathead catfish length-weight relations between segments in 2009 (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment). Underlined values in bold indicate significant differences following Bonferroni correction (α = 0.008).

Segment LU UC LC

UU 0.759 0.036 < 0.001

LU . < 0.001 < 0.001

UC . . < 0.001

Table 2-15. Analysis of covariance test (p - values) for comparisons of flathead catfish length-weight relations between segments in 2010 (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment). Underlined values in bold indicate significant differences following Bonferroni correction (α = 0.008).

Segment LU UC LC

UU 0.964 0.790 0.267

LU . 0.002 0.362

UC . . 0.677

Figure 2-1. Diagram of the Middle Missouri River study area showing the boundaries of each study section (UU – Upper Unchannelized, LL – Lewis and Clark Lake*, - LU – Lower Unchannelized, UC – Upper Channelized, LC – Lower Channelized). * Not included in study.

100 A

100 B

Frequency

0 0 10 20 30 40 50 60 70 80 90

Number of fish per net

Figure 2-2. Frequency of channel catfish catch in 25-mm mesh hoop nets set in the Missouri River, Nebraska in 2009 (A) and 2010 (B). 53

2009 2010 18 ab a b ab 16 bb 14

C/f

Mean Mean

6 A A A * A

0 UU LU UC LC Segment

Figure 2-3. Mean catch per unit effort (C/f; fish per net night) of channel catfish captured in 25-mm mesh hoop nets by year and segment. An * indicates significant differences in mean C/f between years within segments. Uppercase letters indicate significant differences in mean C/f between segments in 2009. Lowercase letters indicate significant differences in mean C/f between segments in 2010 (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment).

2009 2010 25 a b b a b

C/f

Mean Mean 10

5 A A * A * A

0 UU LU UC LC Segment

Figure 2-4. Mean catch per unit effort (C/f; fish per net night) of channel catfish captured in 7-mm mesh hoop nets by year and segment. An * indicates significant differences in mean C/f between years within segments. Uppercase letters indicate significant differences in mean C/f between segments in 2009. Lowercase letters indicate significant differences in mean C/f between segments in 2010 (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment).

2009 2010 25 a a z z

A B Z Z 15

C/f

Mean Mean 10

0 UC-M UC-U LC-M LC-U Segment – Bend Modification Level

Figure 2-5. Mean catch per unit effort (C/f; fish per net night) of channel catfish captured in 25-mm mesh hoop nets by bend modification level within segment and year. Bars with different uppercase letters indicate differences (p < 0.05) in mean C/f between bend modification levels in 2009. Bars with different lowercase letters indicate differences (p < 0.05) in mean C/f between bend modification levels in 2010.The dotted line indicates no intersegment comparisons are made. (UC-M – upper channelized segment, modified bends; UC-U – upper channelized segment, unmodified bends; LC-M – lower channelized segment, modified bends; LC-U – lower channelized segment, unmodified bends).

Unmodified bends Modified bends 40 A

UU3UU7 LU3 LU5 UC3 LC9 UU13UU14UU18UU21 LU20LU21LU35LU37 UC23UC33UC38UC40UC46 LC10LC12LC22LC29LC34

C/f

Mean Mean Unmodified bends Modified bends 40 B

UC4 LC5 LC6 UU12UU14UU18UU22UU23UU24LU14LU18LU20LU31LU34LU37 UC12UC18UC33UC34UC43 LC13LC15LC20LC23 Bend

Figure 2-6. Mean catch per unit effort (C/f ; fish per net night) of channel catfish captured in 25-mm mesh hoop nets by bend within segment (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment)in 2009 (A) and 2010 (B). 57

30 A N = 61 B N = 179 25 Median Length = 290 mm Median Length = 270 mm 20

Frequency C N = 262 D N = 51 25 Median Length = 272 mm Median Length = 323 mm 20

0 0 0 50 50 100150200250300350400450500550600650700750800850900950 100150200250300350400450500550600650700750800850900950 100010501100 100010501100 10-mm Length Class

Figure 2-7. Length-frequency distributions, by 10-mm length group, of channel catfish collected in 25-mm mesh hoop nets in 2009 by segment (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment).

60 A N = 179 B N = 111 Median Length = 279 mm Median Length = 247 mm 40

Frequency C N = 608 D N = 187 Median Length = 256 mm Median Length = 301 mm 40

0 0 0 50 50 100150200250300350400450500550600650700750800850900950 100150200250300350400450500550600650700750800850900950 100010501100115012001250 100010501100115012001250 10-mm Length Class

Figure 2-8. Length-frequency distributions, by 10-mm length group, of channel catfish collected in 25-mm mesh hoop nets in 2010 by segment (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment).

25 A N = 251 B N = 11 20 Median Length = 273 mm Median Length = 254 mm

Frequency C N = 22 D N = 29 20 Median Length = 332 mm Median Length = 303 mm

0 0 0 50 50 100150200250300350400450500550600650700750800850900950 100150200250300350400450500550600650700750800850900950 100010501100115012001250 100010501100115012001250

10-mm Length Class

Figure 2-9. Length-frequency distributions by 10-mm length group, of channel catfish collected in 25-mm mesh hoop nets in 2009 by bend modification level within segment (A – upper channelized segment, modified bends; B – upper channelized segment, unmodified bends; C – lower channelized segment, modified bends; D – lower channelized segment, unmodified bends).

40 A N = 377 B N = 231

30 Median Length = 259 mm Median Length = 254 mm

Frequency C N = 109 D N = 78

30 Median Length = 310 mm Median Length = 294 mm

0 0 0 50 50 100150200250300350400450500550600650700750800850900950 100150200250300350400450500550600650700750800850900950 100010501100115012001250 100010501100115012001250 10-mm Length Class

Figure 2-10. Length-frequency distributions by 10-mm length group, of channel catfish collected in 25-mm mesh hoop nets in 2010 by bend modification level within segment (A – upper channelized segment, modified bends; B – upper channelized segment, unmodified bends; C – lower channelized segment, modified bends; D – lower channelized segment, unmodified bends).

150 A 2009 B 2009 2010 2010 125

100

150

Mean W Mean C 2009 D 2009 2010 2010 125

100

50 0 0 50 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 100 150 200 250 300 350 400 450 500 550 600 650 700 750 50-mm Length Class

Figure 2-11. Mean relative weight (Wr), by 50-mm length group, of channel catfish collected in 25-mm mesh hoop nets in 2009 and 2010 by segment (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment).

4 A B

0 Log Wt = -5.50200 + (3.16108*Log TL) Log Wt = -5.09498 + (2.98229*Log TL) 10 10 10 10

Weight (g) Weight

10 C D 3

Log

0 Log Wt = -4.97320 + (2.92970*Log TL) Log Wt = -4.05559 + (2.58462*Log TL) 10 10 10 10 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0

Log10 Length (mm)

Figure 2-12. Log10 (length – weight) relation of channel catfish collected in hoop nets by segment in 2009 (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment).

4 A B

0 Log Wt = -5.34868 + (3.09973*Log TL) Log Wt = -4.80688 + (2.86725*Log TL) 10 10 10 10

Weight (g) Weight 4

10 C D

Log

0 Log Wt = -4.89376 + (2.90948*Log TL) Log Wt = -5.22628 + (3.05439*Log TL) 10 10 10 10 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0

Log10 Length (mm)

Figure 2-13. Log10 (length – weight) relation of channel catfish collected in hoop nets by segment in 2010 (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment).

50 A

50 B

Frequency

0 0 10 20 30 40 50 60 70

Number of fish per electrofishing run

Figure 2-14. Frequency of flathead catfish catch with pulsed DC electrofishing in the Missouri River, Nebraska in 2009 (A) and 2010 (B).

2009 2010 3.0 A B C C

2.5

2.0

time - a b b b

C/f 1.5

Mean Mean 1.0

0.5

0.0 UU LU UC LC Segment

Figure 2-15. Mean catch per unit effort (C/f; fish per minute) of flathead catfish captured with pulsed DC electrofishing by year and segment. Bars with different uppercase letters indicate differences (p < 0.05) in mean C/f between segments in 2009. Bars with different lowercase letters indicate differences (p < 0.05) in mean C/f between segments in 2010 (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment).

2009 2010 8

A B C C

a b b b

distance

- 4

C/f

Mean Mean

0 UU LU UC LC Segment

Figure 2-16. Mean catch per unit effort (C/f; fish per 100 meters) of flathead catfish captured with pulsed DC electrofishing by year and segment. Bars with different uppercase letters indicate differences (p < 0.05) in mean C/f between segments in 2009. Bars with different lowercase letters indicate differences (p < 0.05) in mean C/f between segments in 2010 (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment).

2009 2010 3.0 A A Z Z

2.5

2.0 a a y z

time

C/f 1.5

Mean Mean 1.0

0.5

0.0 UC-M UC-U LC-M LC-U Segment – Bend Modification Level

Figure 2-17. Mean catch per unit effort (C/f; fish per minute) of flathead catfish captured with pulsed DC electrofishing by bend modification level within segment and year. Bars with different uppercase letters indicate differences (p < 0.05) in mean C/f between bend modification levels in 2009. Bars with different lowercase letters indicate differences (p < 0.05) in mean C/f between bend modification levels in 2010. The dotted line indicates no intersegment comparisons are made. (UC-M – upper channelized segment, modified bends; UC-U – upper channelized segment, unmodified bends; LC-M – lower channelized segment, modified bends; LC-U – lower channelized segment, unmodified bends).

Unmodified bends Modified bends 5 A

LU2 LU4 UC1UC6 LC6 LC7 LC8 UU10UU11UU16UU17UU19UU20 LU11LU18LU23LU32 UC28UC29UC41UC42 LC20LC32LC39

time -

C/f Unmodified bends Modified bends

Mean Mean 5 B

UU3UU4UU9 LU8 LU9 LC9 UU17UU18UU21 LU14LU22LU37LU38UC20UC21UC25UC48UC51UC55 LC18LC32LC34LC36LC40

Bend

Figure 2-18. Mean catch per unit effort (C/f ; fish per minute) of flathead catfish captured with pulsed DC electrofishing by bend within segment (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment) in 2009 (A) and 2010 (B). 69

100 A N = 18 B N = 224

80 Median Length = 471 mm Median Length = 291 mm

100

Frequency C N = 755 D N = 1164 80 Median Length = 285 mm Median Length = 270 mm

0 0 0 50 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000105011001150 1000105011001150 10-mm Length Class

Figure 2-19. Length-frequency distributions, by 10-mm length group, of flathead catfish collected with pulsed DC electrofishing in 2009 by segment (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment).

50 A N = 28 B N = 341 40 Median Length = 384 mm Median Length = 230 mm

Frequency C N = 629 D N = 807 40 Median Length = 330 mm Median Length = 354 mm

0 0 0 50 50 100150200250300350400450500550600650700750800850900950 100150200250300350400450500550600650700750800850900950 100010501100115012001250 100010501100115012001250 10-mm Length Class

Figure 2-20. Length-frequency distributions, by 10-mm length group, of flathead catfish collected with pulsed DC electrofishing in 2010 by segment (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment).

60 A N = 364 B N = 391 50 Median Length = 297 mm Median Length = 275 mm 40

Frequency C N = 571 D N = 593 50 Median Length = 268 mm Median Length = 271 mm 40

Figure 2-21. Length-frequency distributions, by 10-mm length group, of flathead catfish collected with pulsed DC electrofishing in 2009 by bend modification level within segment (A – upper channelized segment, modified bends; B – upper channelized segment, unmodified bends; C – lower channelized segment, modified bends; D – lower channelized segment, unmodified bends).

60 A N = 279 B N = 350 50 Median Length = 323 mm Median Length = 334 mm 40

Frequency C N = 342 D N = 465 50 Median Length = 370 mm Median Length = 348 mm 40

0 0 0 50 50 100150200250300350400450500550600650700750800850900950 100150200250300350400450500550600650700750800850900950 100010501100115012001250 100010501100115012001250 10-mm Length Class

Figure 2-22. Length-frequency distributions, by 10-mm length group, of flathead catfish collected with pulsed DC electrofishing in 2010 by bend modification level within segment (A – upper channelized segment, modified bends; B – upper channelized segment, unmodified bends; C – lower channelized segment, modified bends; D – lower channelized segment, unmodified bends).

150 2010 2010 A 2009 B 2009

125

100

150 2010 2010

Mean W Mean C 2009 D 2009

125

100

50 0 0 50 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000105011001150 1000105011001150 50-mm Length Class

Figure 2-23. Mean relative weight (Wr), by 50-mm length group, of flathead catfish collected with pulsed DC electrofishing in 2009 and 2010 by segment (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment).

5 A B 4

Log10 Wt = -5.27535 + (3.11763* Log10 TL) Log10 Wt = -5.12292 + (3.05895*Log10 TL)

Weight (g) Weight 5 10 C D

Log 4

Log10 Wt = -5.09526 + (3.03657*Log10 TL) Log10 Wt = -5.01817 + (2.99759*Log10 TL) 0 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 Log10 Length (mm)

Figure 2-24. Log10 (length – weight) relationship of flathead catfish collected with pulsed DC electrofishing by segment in 2009 (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment).

5 5 A B

4 4

3 3

2 2

1 1

Log10 Wt = -5.04084 + (3.02936* Log10 TL) Log10 Wt = -5.03536 + (3.02759*Log10 TL) 0 0

Weight (g) Weight 5 10 C D

Log 4

Log10 Wt = -4.74373 + (2.91573*Log10 TL) Log10 Wt = -5.16765 + (3.08335*Log10 TL) 0 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 Log10 Length (mm)

Figure 2-25. Log10 (length – weight) relationship of flathead catfish collected with pulsed DC electrofishing by segment in 2010 (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment).

CHAPTER 3 – AGE, GROWTH, AND MORTALITY OF CHANNEL CATFISH

AND FLATHEAD CATFISH IN THE MISSOURI RIVER, NEBRASKA

Introduction

Fisheries resource managers must balance the needs and desires of multiple user groups (i.e., recreational versus commercial anglers, harvest oriented versus trophy oriented anglers, etc.) while attempting to maintain a sustainable fishery. Isley and

Grabowski (2007) state that fisheries resource managers “attempt to optimize the efficiency of harvest by balancing individual growth, population biomass, and mortality”.

Estimates of growth and mortality and the “interplay between growth and mortality” provide resource managers with information necessary to maximize and sustain the potential of fisheries stocks.

Growth rates of fish are conditional on multiple abiotic and biotic factors (Pegg and Pierce 2001) such as length of growing season and water temperature (Pegg and

Pierce 2001, Pope et al. 2004, Durham et al 2005), food availability (Quist et al. 2004), and population density (Beverton and Holt 1957, Lorenzen and Enberg 2002). Hubert

(1999a) compiled 102 channel catfish age and growth studies from throughout the species‟ range and found no evidence of geographic patterns in channel catfish growth rates. Hubert (1999a) further suggested that growth of channel catfish “has not been related to regional variation in air or water temperatures or length of the growing season”.

Conversely, Durham et al. (2005) found that channel catfish growth in Texas reservoirs was positively related to growing season length and negatively related to longitude.

Jackson (1999) found no apparent latitudinal relation with flathead catfish growth and 77 suggested that growth rates of introduced flathead catfish populations are greater than native populations.

Total annual mortality is a measure of the proportion of a population that dies during one year (Miranda and Bettoli 2007) and is comprised of two unique components: natural mortality and fishing mortality. Natural mortality is the proportion of a population that dies from causes other than harvest, and fishing mortality is the proportion of a population that dies from fishing (commercial and/or recreational). As suggested in previous studies (Gerhardt and Hubert 1981, Makinster and Paukert 2008,

Columbo 2007), catfish population age-structure is somewhat dependant on levels of harvest with older individuals typically found in unexploited or lightly exploited populations.

Catfish management in the portion of the Missouri River bordering Nebraska is a complex issue, as fisheries management falls under the jurisdiction of five states (Iowa,

Kansas, Missouri, Nebraska, and South Dakota). All five states banned commercial catfish harvest from the Missouri River in 1992 due to concerns about declines in catfish stocks (Mestl 1999). However, recreational harvest of catfish from the Missouri River does still occur. Current (2010) regulations in Kansas, Missouri, and Nebraska allow anglers to harvest five channel catfish and five flathead catfish per day, South Dakota allows anglers to harvest 10 catfish of any species per day, and Iowa allows anglers to harvest 15 catfish (channel catfish or flathead catfish) per day. Understanding the effects of harvest is critical in understanding what management actions should be put in place.

Therefore, it is important to monitor and evaluate key characteristics of the catfish populations in the Missouri River, Nebraska to ensure proper management. The 78 objective of my study was to evaluate channel catfish and flathead catfish populations in the Missouri River, Nebraska to determine age structure, growth rates, and mortality.

Specifically, I evaluated the question: are there differences in population characteristics among study segments?

Methods

Study Area

Sampling was conducted in the Missouri River from Fort Randall Dam in South

Dakota at river kilometer (RK) 1419 to the Nebraska-Kansas border at RK 794 (Figure 3-

1). The study area encompasses the entire portion of the Missouri River bordering the state of Nebraska, and has been divided into four riverine segments (Lewis and Clark

Lake was not sampled in this study) based on prior research conducted by the Nebraska

1) Upper unchannelized (UU) – Fort Randall Dam to the headwaters of

Lewis and Clark Lake (RK 1352 - 1419),

2) Lower unchannelized (LU) – Gavins Point Dam to the confluence with the

Big Sioux River (RK 1184 – 1308), 79

3) Upper channelized (UC) – Confluence with the Big Sioux River to the

confluence with the Platte River (RK 960 – 1184),

4) Lower channelized (LC) – Confluence with the Platte River to the Kansas-

Nebraska border (RK 794 – 960).

River bends within each segment were numbered and in channelized segments only, classified as modified or unmodified (Appendix A). The reach between Ponca

State Park, Nebraska and the Big Sioux River confluence is channelized but has historically been considered part of the lower unchannelized section by (Porter and Mestl

2009). Congress passed the 1912 Rivers and Harbors Act which authorized the

USACOE to develop and maintain a 1.8 m deep navigation channel from the mouth of the Missouri River at Saint Louis, Missouri to Kansas City, Missouri. Several revised

Rivers and Harbors Acts followed, eventually calling for development and maintenance of a 2.7 m deep, 91.4 m wide navigation channel from the mouth of the Missouri River to

Modifications can include: constructed backwater areas, notched wing-dams, side channels (chutes), chevron structures, etc. Due to small the low number of modified 80 bends sampled each year (3 bends per segment) no comparisons between modification types were made.

Field Sampling

I randomly selected six river bends per segment for channel catfish sampling and six river bends per segment for flathead catfish sampling during July – September 2009 and 2010. I also stratified the bends by modification level prior to randomly selecting bends for each segment to ensure equal numbers of modified and unmodified bends were sampled in the channelized segments.

Channel catfish were sampled with hoop nets following the protocols detailed by

Porter and Mestl (2009). I used 0.6 m diameter 7-hoop, hoop nets with 25 mm mesh

(SHN) and 0.6 m diameter 4-hoop, hoop nets with 7 mm mesh (MHN). A total of 10 hoop nets (8 SHN and 2 MHN) were set on each river bend in areas with depths greater than 0.6 m and sufficient water velocity to keep the nets from collapsing. Five nets (4

Flathead catfish were sampled with low frequency (15 Hz), low amperage, pulsed

DC electrofishing (EF). River bends were divided into eight sampling units for electrofishing based on the median bend length within each study section as:

MBL U = 8 81

All fish collected were measured to the nearest millimeter for length, and the nearest gram for mass. I removed left pectoral spines from a subsample of five channel catfish and five flathead catfish per 10-mm length group at each site for age and growth determination. No spines were collected from flathead catfish > ~ 800 mm due to concerns about leaving large wounds following spine extraction and increased handling related mortality.

Laboratory processing

Pectoral spines were allowed to air dry for a minimum of one week prior to processing. A scalpel was used to remove any remaining tissue from the spines following the drying period. Spines were embedded in epoxy resin following the methods described by Koch and Quist (2007) and Barada (2009). Three cross sections were cut from the basal recess region of each spine using an IsoMet low-speed saw

(Buehler Inc, Lake Bluff Illinois) and mounted on glass slides to be viewed and photographed under magnification. Each spine was independently viewed by two readers 82 to assign an age estimate and the same two readers were used during both years of the study. If age estimates differed between readers, a tandem viewing of the spine by both readers was used to reach agreement. Digital images of each spine were analyzed using the software package FishBC (Doll and Lauer 2008) to calculate the spine radius and incremental measurements between annuli.

Data Analyses

Age-length keys were constructed using SAS v. 9.2 (SAS Institute 2009) following procedures described by Isley and Grabowski (2007). Age-length keys are used to estimate the ages of fish not included in the subsample of aged individuals.

Comparisons of age-frequency distributions between segments were made using

Kolmogorov-Smirnov non-parametric tests with a Bonferroni correction factor to maintain an experimental α = 0.05.

Back-calculated length-at-age was computed using the Dahl-Lea method (Isley and Grabowski 2007):

Li = (Si/Sc) * Lc

where Li = total length at the time of annulus i formation, Lc = total length at capture, Sc

= spine radius at capture, and Si = spine radius at annulus i. Comparisons of mean back- calculated length-at-age between segments were made using analysis of variance

(ANOVA) with a Tukey‟s adjustment to maintain an experimental α = 0.05.

The 2009 and 2010 data were pooled to fit von Bertalanffy growth functions for channel catfish collected in SHN and flathead catfish collected with EF using an iterative 83 non-linear regression technique in SAS v. 9.2 (SAS Institute 2009) as described by Isley and Grabowski (2007):

Lt = L∞ * (1 – exp (-K (t- t0))), where Lt = length at time t, L∞ = theoretical maximum length, K = growth coefficient, and t0 = time when length equals 0-mm.

Catch curve regression was used to estimate instantaneous mortality (Z) and annual mortality (A) of channel catfish collected in SHN and flathead catfish collected with EF in each segment. The 2009 and 2010 data were pooled to account for variable recruitment, and weighted to allow inclusion of age groups represented by fewer than five individuals (Miranda and Bettoli 2007). Analysis of covariance (ANCOVA) was used to test for differences in slope (Z) of the catch curve regression lines for each segment.

Ninety-five percent confidence intervals (CI 95%) were formed around estimates of A following methods described by Miranda and Bettoli (2007).

Results A total of 1,213 channel catfish (Table 3-1) and 1,897 flathead catfish (Table 3-2) were aged from pectoral spines during 2009 and 2010. Between-reader agreement in

2009 was 63 % total agreement, and 97 % agreement within one year for channel catfish and 42 % total agreement, and 94 % agreement within one year for flathead catfish.

Between-reader agreement in 2010 was 58 % total agreement, and 95 % agreement within one year for channel catfish and 65 % total agreement, and 96 % agreement within one year for flathead catfish. Tandem viewing of the spines indicated that between- 84 reader disagreement stemmed from disagreement over outer annuli and expansion of the central lumen.

Channel catfish

Age-3 and age-4 channel catfish were the most commonly collected age groups in

SHN in all segments of the Missouri River in 2009 and 2010 (Figure 3-2). Catch in

MHN nets was too variable to run gear specific analyses of age and growth or mortality for that gear. Channel catfish up to age-14 were collected in the upper unchannelized segment with age-4 individuals being the most commonly collected age group (Figure 3-

2, A). No channel catfish older than age-10 were collected in the other three segments

(Figure 3-2, B-D). Age-frequency distributions were different (p < 0.001) between the upper unchannelized segment and all other segments with older individuals in the upper unchannelized segment (Figure 3-2, A). No other segment level differences in age- frequency distributions were found (Figure 3-2, B-D).

Age-1 through age-4 channel catfish exhibited rapid growth relative to older age fish in all segments, averaging ~ 100 mm of length gain during the first year of life, ~ 65 mm of length gain per year from age-1 through age-3, and ~ 50 mm of length gain from age-3 through age-4 (Appendix B). Mean back-calculated length-at-age varied by year, driven by differences found in the upper unchannelized segment (Figure 3-3A). Mean back-calculated length-at-age was greater for age-4 through age-11 fish collected in 2010 than 2009 (Figure 3-3A). The only other annual difference in mean back-calculated length-at-age was for age-6 channel catfish collected in the upper channelized segment

(Figure 3-3C). Theoretical maximum length (L∞) of channel catfish derived from von 85

Bertalanffy growth functions of pooled 2009 and 2010 SHN data was greatest in the upper channelized segment and lowest in the lower channelized segment (Figure 3-4).

Mean back-calculated length-at-age was generally greater in the lower channelized segment for younger age groups than in other segments (Figure 3-5) and mean back- calculated length-at-age was generally lower in the lower unchannelized segment relative to the other segments. Annual growth rates (derived from von Bertalanffy growth functions) of older age groups of channel catfish were lower in the lower unchannelized segment and lower channelized segment than in the upper unchannelized segment and upper channelized segment.

Channel catfish fully recruit to SHN by age-4 in the upper unchannelized segment and age-3 in the three other segments (Figures 3-6). Estimates of total annual mortality ranged from approximately 37 % in the upper unchannelized segment to 54 % in the upper channelized segment but the 95 % confidence intervals revealed no differences between segments (Table 3-3). Analyses of covariance (ANCOVA) of catch curve regression instantaneous mortality estimates also were not different (p > 0.05) between study segments.

Flathead catfish

The maximum age of flathead catfish collected and aged from the Missouri River,

Nebraska in 2009 and 2010 was age-12 (Figure 3-7). Older fish were likely sampled but no spines were taken from individuals > ~ 800 mm due to concerns about leaving large wounds following spine extraction and increased handling related mortality. Age-2 and age-3 flathead catfish were the most commonly collected age groups in the lower 86 unchannelized, upper channelized, and lower channelized study segments (Figure 3-7).

Age-4 and age-5 flathead catfish were the most commonly collected age groups in the upper unchannelized study segment. Age-frequency distributions were different (p <

0.001) between the upper unchannelized segment and all other segments, with older individuals in the upper unchannelized segment (Figure 3-7A). No other segment level differences (p > 0.008) in age-frequency distributions were found (Figure 3-7B-D).

Age-1 through age-4 flathead catfish exhibited rapid growth relative to older age fish in all segments, averaging ~ 114 mm of length gain during the first year of life, ~ 95 mm of length gain per year from age-1 through age-2, ~ 85 mm of length gain per year from age-2 through age-3, and ~ 75 mm of length gain from age-3 through age-4

(Appendix B). Few differences in mean back-calculated length-at-age by year were found. Mean back-calculated length-at-age was greater (P < 0.05) in 2010 than 2009 for age-1 through age-6 fish in the lower channelized segment (Figure 3-8D). Theoretical maximum length (L∞) of flathead catfish derived from von Bertalanffy growth functions

(only aged fish < 800 mm; see methods section) of pooled 2009 and 2010 EF data was greatest in the lower unchannelized segment and lowest in the upper unchannelized segment (Figure 3-9). Few differences in mean back-calculated length-at-age between segments were observed (Figure 3-10).

Flathead catfish fully recruit to EF by age-5 in the upper unchannelized segment, age-2 in the lower unchannelized segment, and age-3 in both channelized segments

(Figure 3-11). Estimates of total annual mortality ranged from approximately 42 % in the lower unchannelized segment to 53 % in the upper channelized segment but the 95 % confidence intervals revealed no differences between segments (Table 3-4). I did not 87 estimate flathead catfish mortality in the upper unchannelized segment due to the low number of fish collected (Figure 3-11). Analyses of covariance (ANCOVA) of weighted catch curve regression instantaneous mortality estimates also showed no difference (p >

0.05) in mortality between study segments.

Discussion

Early life stages (age-1 – age-4) dominated the catch of channel catfish in all four study segments with very few individuals older than age-8 collected below Gavins Point

Dam (lower unchannelized segment, upper channelized segment, and lower channelized segment). Older individuals (up to age-14) were collected with some regularity in the upper unchannelized segment. The catch of flathead catfish was also dominated by early life stages (age-2 – age-4) in all segments other than the upper unchannelized segment where older individuals (age-4 – age-5) were more commonly collected with individuals up to age-12 found in all study segments. The greater proportion of older individuals of both species in the upper unchannelized segment relative to the three segments below

Gavins Point Dam may be indicative of lower harvest levels in that segment of river compared to downstream segments. Gerhardt and Hubert (1991) collected channel catfish up to age-21 in the Powder River, Wyoming and suggested that low exploitation

(and thus low annual mortality) explained the presence of older individuals in the population. Similarly, Makinster and Paukert (2008) collected flathead catfish up to age-

19 in the Kansas River, Kansas and estimated annual fishing mortality to be approximately 10 %. Estimates of fishing mortality on the Missouri River are not currently known, but I did observe a mortality rate much greater than the above 88 mentioned studies in conjunction with a reduced age structure. These results suggest that harvest may play a significant role in structuring the age distributions of catfish populations in rivers throughout the species‟ ranges.

Channel catfish growth in the Missouri River, Nebraska appears to be relatively slow when compared to other North American river systems. Mean back-calculated lengths-at-age are typically at or below the 50th percentile of the species standards described by Hubert (1999b; Table 3-5). Mean back-calculated length-at-age of channel catfish in the lower unchannelized segment of the Missouri River fall below the 25th percentile of the species standards for all age groups > age-3 indicating that growth rates in this segment are some of the slowest anywhere in the species‟ range.

Mean back-calculated lengths-at-age of channel catfish collected in the channelized segments of the Missouri River were consistently greater for young (< age-6) age groups than in the unchannelized segments. Hesse et al. (1982) reported similar findings with greater lengths-at-age of channel catfish in channelized segments of the

Missouri River. Pegg and Pierce (2001) found no differences in growth rates of channel catfish relative to a latitudinal gradient along the Missouri River but reported greater lengths-at-age of channel catfish, river carpsuckers Carpiodes carpio, and sauger Sander canadensis in channelized reaches than in unchannelized reaches. The authors attributed the observed rapid growth (relative to unchannelized reaches) and dominance of young age-groups to bioenergetic plasticity within the species and suggested that individuals in the channelized reaches of the river need to grow and mature more rapidly to compensate for the harsher conditions (high flow, reduced habitat availability, etc.) in these areas

(Pegg and Pierce 2001). Alternatively, Barada (2009) found slower growth rates of 89 channel catfish in areas of the Platte River, Nebraska with dramatic diel water level fluctuations similar to those seen in the upper unchannelized segment of the Missouri

River. However, channel catfish in the upper unchannelized segment (a segment subjected to frequent diel flow fluctuations) of the Missouri River exhibit growth rates similar to those observed in the channelized segments. Hubert (1999a) reported that channel catfish growth rates are typically greater in reservoirs than in rivers. Channel catfish in the upper unchannelized segment might be using resources (habitat, food, etc.) in Lewis and Clark Reservoir to mitigate the effects of the diel fluctuations in flow which may explain why channel catfish growth in the upper unchannelized segment was similar to that observed in the channelized segments of the Missouri River. Jordan (2000) observed seasonal variation in channel catfish C/f between two study sites in the upper unchannelized segment of the Missouri River and attributed the differences to seasonal movement patterns related to upstream migrations in the spring. Median C/f decreased from spring to fall at a site ~ 65 km up-river from Lewis and Clark Reservoir, and median

C/f increased from spring to fall at a site ~ 35 km up-river from Lewis and Clark

Reservoir. These findings support the theory of seasonal movement between riverine areas and reservoir areas in the upper unchannelized segment of the Missouri River and therefore support the idea that upper unchannelized segment catfish may be able to cope with varying water levels more than other populations subjected to similar conditions because they have a refuge.

Flathead catfish growth in the Missouri River, Nebraska appears to be relatively slow when compared to other North American systems. All mean back-calculated lengths-at-age in 2009 and 2010 were below the 50th percentile of the species standards 90 described by Jackson et al. (2008; Table 3-6). Older fish (≥ age-6) were below the 25th percentile in all study segments suggesting that growth rates in the Missouri River,

Nebraska are some of the slowest found within the species‟ range. However, the species standards described by Jackson et al. (2008) include introduced populations that have been shown to exhibit faster growth rates when compared to native populations (Jackson

1999, Kwak 2006). The Missouri River, Nebraska is one of the most northern sites compared to the other study sites used to develop the species growth standards. Several studies have shown that growth of warmwater fish species (i.e., catfish) is correlated with environmental variables such as water temperature and the length of growing seasons

(Pegg and Pierce 2001, Durham et al. 2005) that are often determined by latitude/longitude.

Mortality estimates for channel catfish in the four Missouri River study segments fall roughly in the middle of reported mortality estimates from other North American rivers (Table 3-7) and estimated mortality of flathead catfish is higher than any of the other North American rivers listed in Table 3-8. Colombo (2007) found that channel catfish mortality in the Wabash River, Illinois was less and age structure and size structure were greater in river reaches not subjected to heavy commercial fishing pressure. Channel catfish mortality rates have declined in the Missouri River in the years since the closure of the commercial fishery in 1992. Mestl (1999) reported that total mortality had declined from 72 % annual mortality between the years of 1974 and 1990, to 35 % between the years of 1994 and 1998. Additionally, the age distribution of channel catfish had shifted from a population dominated (72 %) by age-1 and age-2 individuals to a more balanced population with a majority (58 %) of individuals between 91 age-4 and age-7 (Mestl 1999). Channel catfish populations in 2009 and 2010 appear to be generally similar to Mestl‟s (1999) observations, but mortality in some segments was greater in 2009 and 2010, suggesting at least some change (possibly increased angler harvest or changes in habitat).

Under current regulations (2010), Nebraska anglers are allowed to harvest five channel catfish and five flathead catfish per day in the Missouri River. Even with the closure of the Missouri River commercial catfish fishery in 1992, exploitation may partially explain the high annual mortality observed in this study. Hurley and Duppong-

Hurley (2007) estimated 20,525 catfish seeking anglers fished the Missouri River at least once in 2002, and observed that approximately one in seven Nebraska catfish anglers harvest every fish they catch. Zuerlein (1987) estimated that the mean number of visits per angler to the Missouri River in 1986 was ~ 9 trips per angler. A conservative estimate of angler harvest (i.e., anglers captured half of the allowed daily bag limit for each species per visit, mean visits per angler have remained at 1986 levels, and 14 % of anglers harvested all catfish caught during each trip) yields an estimate of ~ 66,000 channel catfish and ~ 66,000 flathead catfish harvested annually by Nebraska recreational anglers in the Missouri River. If we assume similar numbers for the other Missouri River border-states (Iowa, Kansas, Missouri, and South Dakota), I conservatively estimated total annual harvest of ~ 330,000 channel catfish and ~ 330,000 flathead catfish. The influence of recreational harvest is unknown at present, but given the above estimates, angler harvest could be a potential driving force in structuring catfish Missouri River catfish populations.

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commercially exploited and unexploited reaches of the Wabash River with

implications for the flathead catfish. PhD Dissertation. Southern Illinois

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characteristics of flathead catfish in the lower St. Joseph River, Michigan. North

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channel catfish in the Harry S. Truman tailwater, Missouri. Pages 361-376 in E.

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Table 3-1. Total number of channel catfish aged by year and segment (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment).

Segment Year Number aged UU 2009 71 2010 110 LU 2009 229 2010 105 UC 2009 341 2010 165 LC 2009 59 2010 133

Total 1213

Table 3-2. Total number of flathead catfish aged by year and segment (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment).

Segment Year Number aged UU 2009 18 2010 26 LU 2009 213 2010 182 UC 2009 490 2010 192 LC 2009 569 2010 207

Total 1897

Table 3-3. Segment level instantaneous mortality (Z) and annual mortality (A) estimates derived from weighted catch curve regression of channel catfish collected in 25 mm mesh hoop nets in 2009 and 2010 (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment; LCI and UCI = 95 % confidence intervals).

Segment LCI (Z) Z UCI (Z) LCI (A) A UCI (A)

UU 0.172 0.488 0.804 0.158 0.386 0.553 LU 0.461 0.581 0.701 0.369 0.441 0.504 UC 0.643 0.777 0.911 0.474 0.540 0.598 LC 0.409 0.708 1.007 0.336 0.507 0.635

100

Table 3-4. Segment level instantaneous mortality (Z) and annual mortality (A) estimates derived from weighted catch curve regression of flathead catfish collected with pulsed DC electrofishing in 2009 and 2010 (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment; LCI and UCI = 95 % confidence intervals).

Segment LCI (Z) Z UCI (Z) LCI (A) A UCI (A)

UU* ------LU 0.415 0.551 0.688 0.340 0.424 0.497 UC 0.628 0.760 0.892 0.466 0.532 0.590 LC 0.610 0.739 0.867 0.457 0.522 0.580

 Not estimable due to small sample size

101

Table 3-5. Mean back-calculated length-at-age (mm) for channel catfish collected in the Missouri River (Bold) during 2009 and 2010 compared to standard growth percentiles for channel catfish across their geographic range. Percentiles provided by Hubert (1999). Superscripts following lengths delineate study segments (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment).

Growth Percentile

Age 5th 10th 25th 50th 75th 90th 95th 215LU 3 172 192 211 223UC 238 255LC 282 310 331 UU 235 316LC 4 217 243 258LU 268 276UC 291 332 387 396 291UU

365LC 5 240 271 290LU 307 318UC 341 386 444 476 359UU

424LC 6 291 316 330LU 353 363UC 386 429 504 537 399UU

432LC 7 303 331 365LU 388 398UC 434 479 567 596 UU 413 380LU 431LC 8 331 353 417 469 513 595 620 403UC 443UU

399LC 9 340 379 400LU 456 471UU 504 547 628 669 UC 432 450LU 10 363 387 505 520UC 554 597 665 703 489UU

102

Table 3-6. Mean back-calculated length-at-age (mm) for flathead catfish collected in the Missouri River (Bold) during 2009 and 2010 compared to standard growth percentiles for flathead catfish across their geographic range. Percentiles provided by Jackson et al. (2008). Superscripts following lengths delineate study segments (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment).

Growth Percentile

Age 5th 10th 25th 50th 75th 90th 95th 300LC, 280LU, 3 211 231 251 324 382 479 509 294UC, 301UU

384LC, 346LU, 4 254 296 341 446 498 571 605 367UC, 380UU

398LU, 5 280 340 437 443LC 554 621 678 710 429UC, 435UU

489LC, 451LU, 6 366 390 520 613 710 752 765 479UC, 486UU

525LC, 489LU, 7 409 442 603 676 773 821 833 545UC, 456UU

548LC, 519LU, 8 458 503 618 729 827 896 925 586UC, 466UU

566LC, 521LU, 9 500 511 675 762 902 1,000 1,003 587UC, 495UU

103

Table 3-7. Annual mortality estimates of channel catfish populations in Missouri River study segments compared to other North American river populations (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment). Mortality estimates in bold are estimates from the current study and represent the 95 % confidence intervals. Table reprinted with permission and adapted from Barada (2009).

Waterbody Annual Mortality

Ottawa Rivera 16 % Powder Riverb 23 % Crazy Woman Creekc 25 % Central Platte Riverd 15-33 % Wabash River – non commercially fishede 25-33 % Missouri River – 1994-1998f 35 % Missouri River LU Segment* 37-50 % Lower Platte Riverd 29-51 % Missouri River UU Segment* 16-55 % Sacramento Riverg 56 % Missouri River UC Segment* 47-60 % Mississippi Riverh 61 % Missouri River LC Segment* 34-64 % Wabash River – commercially fishede 32-67 % Missouri River – 1974-1990f 72 % Harry Truman Dam Tailwateri 33-83 %

Annual mortality estimates from a Haxton and Punt 2004, b Gerhardt and Hubert 1991, c Smith and Hubert 1988, d Barada 2009, e Colombo 2007, f Mestl 1999, g McCammon and LaFaunce 1961, h Pitlo 1997, i Graham and Deisanti 1999, * current study.

104

Table 3-8. Annual mortality estimates of flathead catfish populations in Missouri River study segments compared to other North American river populations (UU – upper unchannelized segment, LU – lower unchannelized segment, UC – upper channelized segment, LC – lower channelized segment). Mortality estimates in bold are estimates from the current study and represent the 95 % confidence intervals.

Waterbody Annual Mortality

Ocmulgee Rivera 14 % Northeast Cape Fear Riverb 16 % Lumber Riverb 19 % Neuse Riverb 20 % Coosa Rivera 20 % Kansas Riverc 14-28 % St. Joseph Riverd 33 % Satilla Rivera 45 % Missouri River LU Segment* 34-50 % Missouri River UC Segment* 47-59 % Missouri River LC Segment* 46-58 %

Annual mortality estimates from a Sakaris et al. 2006, b Kwak et al. 2006, c Makinster and Paukert 2008, d Daugherty and Sutton 2005, * current study.

105

Figure 3-1. Diagram of the Middle Missouri River study area showing the boundaries of each study section (UU – Upper Unchannelized, LL – Lewis and Clark Lake*, - LU – Lower Unchannelized, UC – Upper Channelized, LC – Lower Channelized). * Not included in study.

106

350 A B

300

250

100

350

Frequency C D

300

250

100

0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age

Figure 3-2. Age-frequency distributions of channel catfish collected in 25-mm mesh hoop nets in 2009 and 2010 (pooled) by study segment (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment).

107

2009 2010 700 * A * B 600 * * 500 * * 400 * * 300

200

100

700 C D 600

Total Length (mm) Length Total 500 * 400

300

200

100

0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age

Figure 3-3. Mean back-calculated length-at-age of channel catfish collected in the middle Missouri River in 2009 and 2010. A „*‟ indicates a difference in mean back- calculated length-at-age between 2009 and 2010. (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment).

108

700 A B 600

500

400

300

) 200

100 Lt = 641.6[1-e-0.1456(t+0.2194)] Lt = 544.0[1-e-0.1496(t+0.2741)]

700 C D 600

Total Length (mm Length Total 500

400

300

200

100 Lt = 762.2[1-e-0.0972(t+0.4875)] Lt = 466.3[1-e-0.3157(t-0.2363)] 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age

Figure 3-4. Mean back-calculated length-at-age and von Bertalanffy growth functions of channel catfish collected in the middle Missouri River in 2009 and 2010 (pooled). (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment).

109

700 A B 600 * * * 500 * * * 400 * * * 300 *

200

100

700 C D 600

500 * 400 * * * * 300

200

Total Length (mm) Length Total 100

700 E F 600

500 * * * * 400 * * * 300 * * * 200 * * 100

0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age

Figure 3-5. Segment level mean back-calculated length-at-age comparisons of channel catfish collected in the upper unchannelized (dotted line) and lower unchannelized (bold- solid line) segments (A), upper unchannelized (dotted line) and upper channelized (solid line) segments (B), upper unchannelized (dotted line) and lower channelized (dashed line) segments (C), lower unchannelized (bold-solid line) and upper channelized (solid line) segments (D), lower unchannelized (bold-solid line) and lower channelized (dashed line) segments (E), and upper channelized (solid line) and lower channelized (dashed line) segments (F) of the middle Missouri River in 2009 and 2010 (pooled). A „*‟ indicates a difference in mean back-calculated length-at-age between segments. 110

7 A R2 = 0.613 B R2 = 0.944 6

5 A = 0.39 A = 0.44

7 C R2 = 0.973 D R2 = 0.887 Ln Frequency 6

5 A = 0.54 A = 0.51

0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age

Figure 3-6. Catch curve regression and annual mortality (A) of channel catfish collected in 25 mm mesh hoop nets in the middle Missouri River in 2009 and 2010 (pooled). (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment).

111

600 550 A B 500 450 400 350 300 250 200 150

100 50 0

600

Frequency 550 C D 500 450 400 350 300 250 200 150 100 50 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age

Figure 3-7. Age-frequency distributions of flathead catfish collected with pulsed DC electrofishing in 2009 and 2010 (pooled) by study segment (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment)

112

2009 2010 800 700 A B 600 500 400 300

200 100

800 C D 700

Total Length (mm) Length Total 600 * 500 * * 400 * 300 * 200 * 100 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age

Figure 3-8. Mean back-calculated length-at-age of flathead catfish collected in the middle Missouri River in 2009 and 2010. A „*‟ indicates a difference in mean back- calculated length-at-age between 2009 and 2010. (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment)

113

800 700 A B 600 500 400 300

200 100 Lt = 532.2[1-e-0.3246(t-0.2465)] Lt = 734.7[1-e-0.1518(t+0.1044)]

ength (mm) ength 800 C D 700

Total L Total 600 500 400 300 200 100 Lt = 683.8[1-e-0.2122(t-0.2421)] Lt = 706.2[1-e-0.1951(t-0.1145)] 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age

Figure 3-9. Mean back-calculated length-at-age and von Bertalanffy growth functions of flathead catfish collected in the middle Missouri River in 2009 and 2010 (pooled). (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment)

114

800 700 A B * 600 * * 500 400 300 200 100 0

800 C D 700 600 * 500 *

400 * 300 200

Total Length (mm) Length Total 100 0

800 F 700 E 600 * 500 * * * 400 * 300 200 100 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age

Figure 3-10. Segment level mean back-calculated length-at-age comparisons of flathead catfish collected in the upper unchannelized (dotted line) and lower unchannelized (bold- solid line) segments (A), upper unchannelized (dotted line) and upper channelized (solid line) segments (B), upper unchannelized (dotted line) and lower channelized (dashed line) segments (C), lower unchannelized (bold-solid line) and upper channelized (solid line) segments (D), lower unchannelized (bold-solid line) and lower channelized (dashed line) segments (E), and upper channelized (solid line) and lower channelized (dashed line) segments (F) of the middle Missouri River in 2009 and 2010 (pooled). A „*‟ indicates a difference in mean back-calculated length-at-age between segments. 115

7 A B R2 = 0.916 6

5 A = 0.42

7 C R2 = 0.964 D R2 = 0.971 Ln Frequency 6

5 A = 0.53 A = 0.52

0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 0 1 2 3 4 5 6 7 8 9 10 11 12 13

Age

Figure 3-11. Catch curve regression and annual mortality (A) of flathead catfish collected with pulsed DC electrofishing in the middle Missouri River in 2009 and 2010 (pooled). (A – upper unchannelized segment, B – lower unchannelized segment, C – upper channelized segment, D – lower channelized segment)

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CHAPTER 4 – CLOSED-CAPTURES POPULATION ANALYSES OF CHANNEL

CATFISH POPULATION SIZE WITHIN A MISSOURI RIVER, NEBRASKA

STUDY BEND

Introduction

Estimates of population characteristics such as relative abundance, size structure, and mortality are metrics commonly used by fisheries resource managers to assess fish populations. Absolute abundance (population size) is less frequently assessed as robust calculations of abundance require more time and resources than are typically available when attempting to manage multiple systems (Hubert and Fabrizio 2007). Fisheries resource managers must balance the needs and desires of multiple user groups (i.e., recreational vs. commercial anglers, harvest oriented vs. trophy oriented anglers, etc.) and multiple systems while attempting to maintain sustainable fisheries.

Measures of relative abundance are most frequently expressed in terms of catch per unit effort (C/f) where C is the number of fish caught and f is a standardized unit of effort (Fabrizio and Richards 1996, Hubert 1996, Hubert and Fabrizio 2007). Relative abundance is assumed to be related to absolute abundance (N) by means of a coefficient of catchability (q) resulting in the general C/f equation:

C/f = qN.

Numerous studies have demonstrated that q is often sensitive to changes in fish distributions (Paloheimo and Dickie 1964 in Hubert and Fabrizio 2007), fish density

(Ricker 1975, Hilborn and Walters 1992 in Hubert and Fabrizio 2007), and environmental factors (Hubert and Fabrizio 2007). Thus, measures of C/f may not be 117 truly reflective of differences in abundance as much as they are reflective of differences related to other factors such as distributions, density, and environmental factors.

Basic population estimation methods such as the Schnabel method use batch- marking methodology where the recapture of specific individuals is not a factor in the model (Hayes et al. 2007). Rather, the proportion of marked individuals versus unmarked individuals during each sampling occasion is used to estimate the total population size. Important parameters such as capture probability and recapture probability are not estimable with the Schnabel method. More advanced population estimation techniques such as closed-captures capture-mark-recapture modeling, open- population capture-mark-recapture modeling, etc. have been developed to address some of the issues associated with estimating animal abundance. These more advanced techniques use encounter histories of uniquely marked individuals to estimate not only abundance and density, but can also be used to estimate population parameters such as capture probability, survival and mortality, and movement.

Catfish management in the portion of the Missouri River bordering Nebraska is a complex issue, as fisheries management falls under the jurisdiction of five states (Iowa,

Kansas, Missouri, Nebraska, and South Dakota). All five states banned commercial catfish harvest from the Missouri River in 1992 due to concerns about declines in catfish stocks (Mestl 1999). However, recreational harvest of catfish from the Missouri River does still occur. Current (2010) regulations in Kansas, Missouri, and Nebraska allow anglers to harvest five channel catfish and five flathead catfish per day, South Dakota allows anglers to harvest 10 catfish of any species per day, and Iowa allows anglers to harvest 15 catfish (channel catfish, or flathead catfish) per day. Therefore, it is important 118 to monitor and evaluate key characteristics of the catfish populations in the Missouri

River, Nebraska to ensure proper management. The current monitoring regime relies on

C/f data to assess the status of catfish populations, but there is a need to understand how relative abundance data are related to absolute abundances. Therefore, the objective of my study was to estimate absolute abundance of channel catfish within a Missouri River study bend and to assess how these estimates compare to measures of C/f.

Methods

Field Sampling

I sampled one river bend (RKM 1,122.8 – RKM 1,116.6) near Decatur, Nebraska

(Figure 4-1) in the Missouri River, Nebraska from October 18, 2010 – October 22, 2010.

All sampling was conducted within this relatively short time-frame (4 days) in an effort to maintain population closure during the course of the study. I selected this bend based on proximity to a boat ramp and large numbers of channel catfish collected during standard sampling in July – September 2010 (See Chapter 2). Channel catfish were sampled with hoop nets following the protocols detailed by Porter and Mestl (2009). I used 0.6 m diameter 7–hoop, hoop nets with 25 mm mesh (SHN). A total of 20 SHN were set on the inside bend in areas with depths greater than 0.6 m and sufficient water velocity to keep the nets from collapsing. Set sites were spaced to ensure there was at least one full wing-dam field (Figure 4-2) between each net. All nets were baited with ~

1 kg of cheese trimmings, weighted with a concrete block, and anchored to shore with a hoop net hook. Nets were fished overnight with a total set time not exceeding 24 hours, and re-set immediately following retrieval for a total of four consecutive net nights at 119 each set site. I collected measurements of habitat variables (depth and water temperature) at each site when the nets were retrieved.

All fish collected were measured to the nearest millimeter for length and the nearest gram for mass. Channel catfish greater than 200 mm were marked by clipping the adipose fin and implanting a FD-94 t-bar anchor tag (Floy mfg.) between the dorsal pterygiophores on the fish‟s left side. All fish were returned to the water immediately following processing.

Data Analyses

Population estimates

I calculated the estimated population size of channel catfish > 200 mm within the

6.2 RKM study bend using two methods. I used the Schnabel method (Schnabel 1938,

Seber 1982, Hayes et al. 2007) to calculate a baseline population estimate to compare with closed-captures mark-recapture analyses conducted in Program MARK (White and

Burnham 1999). The general form of the Schnabel estimator is:

̂ ∑ Equation 1. ∑

Where ̂ = the estimated population size, t = the number of sampling occasions, ni = the number of fish caught in ith sample, mi = the number of fish with marks caught in the ith sample, and Mi = the number of marked fish present in the population for the ith sample

(Hayes et al. 2007). I calculated 95 % confidence intervals around ̂ as recommended in

Hayes et al. (2007) using values provided by Chapman (1948). 120

I created capture histories for each channel catfish > 200 mm collected for the closed-captures population estimate as described by Cooch and White (2009). Each sampling occasion (set-date) was included in an individual‟s capture history as a possible encounter occasion. An encounter (capture or recapture) is designated with a „1‟ while a non-encounter (no initial capture or recapture) is designated with a „0‟. For example a fish captured and marked on day-1 and recaptured on day-3 would have a capture history of „1010‟ for the entire 4-day sampling period. Three model formats were assessed: Mo = constant capture probability ( ) and recapture probability (c), Mt = time varying and c

(constrained so = c), Mb = variability in c due to changes in behavior after capture (Otis et al. 1978, Hayes et al. 2007). All models were run using a LOG link function and

Hessian variance estimation. Program MARK uses maximum likelihood methods to iteratively fit models to the data and selects the best fit model using Akaike‟s Information

Criterion (AIC) where the model with the lowest AIC value is deemed to be the “best” model (White and Burnham 1999).

Population estimate vs. C/f

I calculated the mean relative abundance (C/f) of channel catfish > 200 mm within the study bend using a generalized linear mixed modeling (GLMM) approach (Littell et al. 2006, Dobson and Barnett 2008). Biological data are often characterized by a high occurrence of zero counts, particularly in instances in which the study organism has low densities or patchy distributions (Hubert and Fabrizio 2007). The data cannot be assumed to have a normal distribution in these instances as is required for standard parametric analyses. Generalized linear modeling (GLM) allows the data to be analyzed under different probability distributions such as a Poisson distribution or a negative binomial 121 distribution. Addition of a random variable extends the GLM model to the GLMM format. The random variable is assumed to represent an interchangeable sample from a larger population with a probability distribution, which allows for broad inference of overall population parameters (Littell et al. 2006). Both GLM and GLMM use transformations (link functions) of the model parameters (Xβ) based on the probability distribution of the data to fit a linear model on which statistical testing can be conducted.

Inclusion of an inverse link statement in the model back transforms the generalized-scale mean estimates to the original scale (Littell et al. 2006). Therefore net-set (net-1 – net-

20) nested within set date {Subsample (Set Date)} was used as the random variable in the

GLMM which allowed the overall mean C/f of channel catfish > 200 mm within the river bend to be calculated.

To assess how relative abundance relates to absolute abundance I extrapolated mean C/f to bend level using a two step process (Equations 2 and 3) requiring both the

C/f data derived from GLMM and capture probabilities derived from Program MARK.

First, I divided the mean C/f of channel catfish > 200 mm within the study bend by the mean capture probability ( ) derived from the Mt model structure to calculate the mean number of fish available for capture at each net-set site during each sampling period. I then multiplied the mean number of fish available for capture at each net-set site by the number of net-sets for each day of the study to get daily values of the total number of fish available for capture within the study bend during each sampling period (Equation 2).

Equation 2. = * .

122

Where = the estimated number of fish available for capture within the study bend during sampling period , = the mean relative abundance of channel catfish within the study bend, = the mean capture probability derived from the Mt model structure using Program MARK, and = the number of net sets in sampling period . Secondly, I calculated the mean of (Equation 2) to determine the bend-level mean abundance of channel catfish > 200 mm within the study bend using Equation 3.

∑ Equation 3. µ ̂ = .

Where µ ̂ = the bend-level mean abundance, t = the number of sampling periods. I calculated 95 % confidence intervals around the estimate of µ ̂ by replacing with mean 95 % confidence interval values of derived using Program MARK. The lower 95

% confidence interval of is used to calculate the upper 95 % confidence interval of µ ̂ and the upper 95 % confidence interval of is used to calculate the lower 95 % confidence interval of µ ̂.

Results

A total of 1,704 channel catfish were collected in 75 SHN deployments between

October 18, 2010 and October 22, 2010. Of the 1,704 channel catfish collected 1,496 were > 200 mm and 1,065 were marked with uniquely numbered t-bar anchor tags. I recaptured 29 channel catfish which had been marked between October 18, 2010 and

October 21, 2010 and an additional three channel catfish that had been marked during standard sampling (see Chapter 2) prior to October 18, 2010. I excluded the three individuals which had been previously marked from the closed-captures analyses. 123

Schnabel estimate

A total of 1,496 channel catfish were included in the Schnabel estimate of absolute abundance (Table 4-1). The estimated ̂ of channel catfish > 200 mm within the 6.2 RKM study bend was 23,949 fish (18,011 – 39,120; 95 % confidence interval;

See Errata # 1). Assuming channel catfish are equally distributed throughout the study bend this equates to an estimate of ~ 4,248 (2,905 – 6,310; 95 % confidence interval) channel catfish > 200 mm per RKM within the study bend.

Program MARK estimate

A total of 1,470 channel catfish were included in the closed-captures analyses of absolute abundance using Program MARK. Eleven unique encounter histories were observed (Table 4-2). The Mt model had the lowest AIC (Table 4-3) value and thus the best fit. The estimated ̂ of channel catfish > 200 mm within the 6.2 RKM study bend was 25,817 fish (24,885 – 26,785; 95 % confidence interval; See Errata # 2). Assuming channel catfish are equally distributed throughout the study bend this equates to an estimate of ~ 4,164 (4,014 – 4,320; 95 % confidence interval) channel catfish > 200 mm per RKM within the study bend. Capture and recapture probabilities (constrained to be equal) under the Mt model structure ranged from 0.6 % to 2.0 % (Table 4-4) with a mean of 1.5 %.

Relative abundance

Visual inspection of channel catfish catch data from SHN indicated a substantial deviation from normality (Figure 4-3) and Kolmogorov-Smirnov tests (SAS 9.2) for normality confirmed this assumption (p < 0.01). Models assuming a Poisson probability 124 distribution and a negative binomial probability distribution were constructed and assessed for goodness of fit (AIC, deviance; χ²/degrees of freedom). I found that the models assuming a negative binomial probability distribution provided a better fit

(χ²/degrees of freedom = 1). Mean C/f of channel catfish > 200 mm within the 6.2 RKM study bend was 20.2 (14.7 – 27.8; 95 % confidence interval) fish per net night.

Bend-level mean abundance

Bend-level mean abundance (µ ̂) of channel catfish > 200 mm calculated using equations 2 and 3 was 26,121 (24,755 – 28,056; 95 % confidence interval) fish within the

6.2 RKM study bend. Assuming channel catfish are equally distributed throughout the study bend this equates to an estimate of 4,213 (3,992 – 4,525; 95 % confidence intervals) channel catfish > 200 mm per RKM within the study bend.

Discussion

A fundamental assumption of both the Schnabel method and the Program MARK closed-captures analyses is that the population being assessed is closed to immigration, emigration, births, and mortalities during the study period (Darroch 1958, Seber 1965,

Kendall 1999, Hayes et al. 2007, Cooch and White 2009). Otis et al. (1978) point out that the assumption of a closed population is “never completely true in a natural biological population”. However, the assumption of closure “can be met at least approximately” with proper study designs. I attempted to minimize any bias associated with violations of the closure assumption by conducting all sampling within a relatively short period (4 days). 125

The Schnabel method uses batch-marking methodology where the recapture of specific individuals is not a factor in the model. Rather, the proportion of marked individuals vs. unmarked individuals during each sampling occasion is used to estimate the total population size. Closed-captures analyses using Program MARK (White and

Burnham 1999) use encounter histories of uniquely marked individuals to calculate an estimated population size as well as capture and recapture probabilities. Both techniques yielded population estimates of approximately 24,000 – 26,000 channel catfish > 200 mm within the 6.2 RKM study bend. The population estimate derived using Program MARK had tighter confidence intervals around the estimate of ̂ than the estimate derived using the Schnabel method suggesting Program MARK may provide better estimates of abundance than the Schnabel method. Closed-captures analyses using Program MARK also provide valuable information on capture and recapture probabilities that are not possible to estimate using the Schnabel method. However, in situations when uniquely marking all individuals is not feasible the Schnabel method can provide estimates of ̂ similar to those derived from Program MARK although the error associated with the estimate may be larger.

Newcomb (1989) used Program CAPTURE (White et al. 1978) to estimate the density of channel catfish ≥ 250 mm at nearby sites in the Missouri River and estimated densities ranged from 776 - 976 fish per RKM. Density estimates from my study, while not directly comparable due to differences in minimum tagging length (200 mm in the current study vs. 250 mm in Newcomb (1989), suggest that channel catfish density in the upper channelized segment of the Missouri River, Nebraska may have increased since

Newcomb‟s (1989) study (1983 – 1987). A possible explanation for increased channel 126 catfish density is the closure of the Missouri River commercial catfish fishery in 1992.

Channel catfish mortality rates have declined in the Missouri River in the years since the closure of the commercial fishery in 1992. Mestl (1999) reported that total mortality had declined from 72 % annual mortality between the years of 1974 and 1990, to 35 % between the years of 1994 and 1998. Theoretically, reducing annual mortality should increase the number of individuals within a population leading to greater density.

Perhaps the most intriguing finding of this study was that mean relative abundance estimates derived from repeated sampling combined with capture probabilities calculated with closed-captures analyses using Program MARK produce abundance estimates (µ ̂) similar to estimates of ( ̂) from the Schnabel and Program MARK techniques. Estimates of relative abundance are commonly used by fisheries resource managers to assess fish populations as these measures are relatively easy to calculate and the costs associated with relative abundance sampling are typically less than those necessary for capture-mark-recapture sampling. Absolute abundance (population size) is less frequently assessed as robust calculations of abundance require more time and resources than are typically available when attempting to manage multiple systems.

Nelson and Clark (1973) developed a method for estimating the capture rate of small mammals in traps based upon the concept of gear saturation (Beverton and Holt

1957) where capture efficiency of traps must account for all traps that are sprung

(resulting in a capture or an empty trap). Waters and Zabel (1998) applied Nelson and

Clarks‟ (1973) capture rate estimation technique to small mammal populations and found strong correlation between population estimates derived using capture-mark-recapture methods and capture rate. Similarly, Hopkins and Kennedy (2004) found strong 127 correlation between small mammal C/f and estimates of absolute abundance and suggested that relative abundance indices (C/f) “can be used as a more efficient and less costly alternative for monitoring populations.”

Further research will be needed to determine if the technique used in this study to estimate µ ̂ from C/f data can be used on a larger scale (i.e., segment level; See Chapter

2). I recommend using the spatially replicated sampling procedure and closed-captures capture-mark-recapture analyses at multiple sites throughout the Missouri River,

Nebraska study area (Figure 4-1) to assess catfish populations. If the relation between mean C/f and µ ̂ is similar throughout a Missouri River, Nebraska study segment then one week of spatially replicated sampling could lead to an ability to quantify µ ̂ throughout the Missouri River, Nebraska reducing costs and providing valuable insights into population dynamics without losing information.

128

Literature Cited

Beverton, R. J. H., and S. J. Holt. 1957. On the dynamics of exploited fish populations.

Chapman and Hall Fish and Fisheries Series 11, London.

Chapman, D. G. 1948. A mathematical study of confidence limits of salmon populations

calculated from sample tag ratios. International Pacific Salmon Fisheries

Commission Bulletin 2:69-85.

Cooch, E., and G. White, editors. 2009. Program MARK “a gentle introduction” 9th

edition.

Darroch, J. N. 1958. The multiple-recapture census: I. estimation of a closed population.

Biometrika 45:343-359.

Dobson, A. J., and A. G. Barnett. 2008. An introduction to generalized linear models,

3rd edition. Chapman and Hall/CRC. Boca Raton, Florida.

Fabrizio, M. C., and R. A. Richards. 1996. Commercial fisheries surveys. Pages 625-

650 in B. R. Murphy, and D. W. Willis, editors. Fisheries techniques, 2nd edition.

American Fisheries Society, Bethesda, Maryland.

Hayes, D. B., J. R. Bence, T. J. Kwak, and B. E. Thompson. 2007. Abundance, biomass,

and production. Pages 327-374 in C. S. Guy, and M. L. Brown, editors. Analysis

and interpretation of freshwater fisheries data. American Fisheries Society,

Bethesda, Maryland.

Hilborn, R., and C. J. Walters. 1992. Quantitative fisheries stock assessment: choice,

dynamics and uncertainty. Chapman and Hall, New York, New York. 129

Hopkins, H. L., and M. L. Kennedy. 2004. An Assessment of Indices of Relative and

Absolute Abundance for Monitoring Populations of Small Mammals. Wildlife

Society Bulletin 32:1289-1296

Hubert, W. A. 1996. Passive capture techniques. Pages 157-192 in B. R. Murphy, and

D. W. Willis, editors. Fisheries techniques, 2nd edition. American Fisheries

Society, Bethesda, Maryland.

Hubert, W. A. and M. C. Fabrizio. 2007. Relative abundance and catch per unit effort.

Pages 279-325 in C. S. Guy, and M. L. Brown, editors. Analysis and

interpretation of freshwater fisheries data. American Fisheries Society, Bethesda,

Maryland.

Kendall, W. L. 1999. Robustness of Closed Capture-Recapture Methods to Violations of

the Closure Assumption. Ecology 80:2517-2525.

Littell, R. C., G. A. Milliken, W. W. Stroup, R. D. Wolfinger, and O. Schabenberger.

2006. SAS® for mixed models, 2nd edition. SAS Institute Inc. Cary, Indiana.

Mestl, G. E. 1999. Changes in Missouri River channel catfish populations after closing

commercial fishing. Pages 455-460 in E. R. Irwin, W. A. Hubert, C. F. Rabeni,

H. L. Schramm, Jr., and T. Coon, editors. Catfish 2000: proceedings of the

international ictalurid symposium. American Fisheries Society, Symposium 24,

Bethesda, Maryland.

Nelson, L. Jr, and F. W. Clark. 1973. Correction for sprung traps in catch/effort

calculations of trapping results. Journal of Mammalogy 54:295-298. 130

Newcomb, B. A. 1989. Winter abundance of channel catfish in the channelized Missouri

River, Nebraska. North American Journal of Fisheries Management 9: 195-202.

Otis, D. L., K. P. Burnham, G. C. White, and D. R. Anderson. 1978. Statistical

Inference from Capture Data on Closed Animal Populations. Wildlife

Monographs 62:3-135.

Paloheimo, J. E., and L. M. Dickie. 1964. Abundance and fishing success. Rapports et

Proces-Verbaux des Reunions du Conseil International pour l‟Exploration de la

Mer 155:152-163.

Porter, T., and G. E. Mestl. 2009. 2008 Missouri River Ecology F-75-R-26. Nebraska

Game and Parks Commission, Lincoln, Nebraska.

Ricker, W. E. 1975. Computation and interpretation of biological statistics of fish

populations. Fisheries Research Board of Canada Bulletin 191.

Schnabel, Z. E. 1938. The estimation of the total fish population of a lake. American

Mathematical Monographs 45:348-352.

Seber, G. A. F. 1965. A note on the multiple-recapture census. Biometrika 52:249-259.

Seber, G. A. F. 1982. The estimation of animal abundance and related parameters.

Edward Arnold, London.

Waters, J. R., and C. Y. Zabel. 1998. Abundances of small mammals in fir forests in

northeastern California. Journal of mammalogy 79:1244-1253. 131

White, G. C., K. P. Burnham, D. L. Otis, and D. R. Anderson. 1978. Users manual for

Program CAPTURE. Utah State University Press, Logan, Utah.

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populations of marked animals. Bird Study 46 (Supplement):120-138.

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Table 4-1. Channel catfish capture, recapture, and total number marked data collected through spatially replicated hoop net sampling used within a 6.2 River Kilometer Missouri River, Nebraska study bend in 2010.

Set Date Total Number of Channel Number of Number Catfish > 200 mm Recaptures Marked

October 18 155 0 155 October 19 405 7 398 October 20 526 14 512 October 21 410 8 0

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Table 4-2. Channel catfish encounter histories used for closed-captures analyses (Program MARK) within a 6.2 River Kilometer Missouri River, Nebraska study bend in 2010.

Encounter History Number of Fish

1000 140 1100 7 1001 1 1011 1 1010 7 0100 388 0110 8 0101 2 0010 508 0011 4 0001 404

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Table 4-3. Akaike‟s Information Criterion (AIC) values comparing competing closed- captures model structures (Program MARK; Mo = constant capture probability and recapture probability, Mt = time varying capture probability and recapture probability, Mb = variability in recapture probability due to changes in behavior after capture (Otis et al. 1978, Hayes et al. 2007).

Model AIC Δ AIC

Mt -14,317.88 0.00 Mb -14,107.31 210.56 Mo -14,095.50 222.38

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Table 4-4. Capture and recapture probabilities derived from closed-captures analyses (Program MARK) and mean (µ) capture probabilities used for calculation of bend-level mean abundance of channel catfish within a 6.2 River Kilometer Missouri River, Nebraska study bend in 2010.

Sampling Lower 95 % Capture and Upper 95 % Period Confidence Interval Recapture Probability Confidence Interval

1 0.006 0.006 0.006 2 0.014 0.016 0.017 3 0.019 0.020 0.021 4 0.015 0.016 0.017 µ 0.014 0.015 0.015

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Figure 4-1. Diagram of the Missouri River, Nebraska showing the approximate location (star) of the study bend (RKM 1,122.8 – RKM 1,116.6) sampled for closed population estimation in 2010.

137

Wing-dams

Direction of flow

Figure 4-2. Depiction of hoop net spacing on a study bend. Stars represent hoop net set locations.

138

Frequency 10

0 0 10 20 30 40 50 60 70 80 90 100 110 120 Number of Channel Catfish

Figure 4-3. Frequency of channel catfish > 200 mm catch rates in 25-mm mesh hoop nets set in the Missouri River, Nebraska October 18 – 22, 2010.

139

CHAPTER 5 – FUTURE RESEARCH, SAMPLING RECOMMENDATIONS, AND MANAGEMENT RECOMMENDATIONS

Estimates of population characteristics such as relative abundance (C/f) size structure, growth rates, condition, and mortality are necessary to facilitate proper management of fish populations. Typically fisheries resource managers must balance the needs and desires of multiple user groups (i.e., recreational vs. commercial anglers, harvest oriented vs. trophy oriented anglers, etc.) while attempting to maintain a sustainable fishery. Catfish management in the portion of the Missouri River bordering

Nebraska is a complex issue, as fisheries management falls under the jurisdiction of five states (Iowa, Kansas, Missouri, Nebraska, and South Dakota). All five states banned commercial catfish harvest from the Missouri River in 1992 due to concerns about declines in catfish stocks (Mestl 1999). However, recreational harvest of catfish from the

Missouri River does still occur. Current (2010) regulations in Kansas, Missouri, and

Nebraska allow anglers to harvest five channel catfish and five flathead catfish per day,

South Dakota allows anglers to harvest 10 catfish of any species per day, and Iowa allows anglers to harvest 15 catfish (channel catfish, or flathead catfish) per day. Understanding the effects of harvest is critical in understanding what management actions should be put in place. Therefore, it is important to monitor and evaluate key characteristics of the catfish populations in the Missouri River, Nebraska to ensure proper management.

The objective of my study was to evaluate channel catfish and flathead catfish populations in the Missouri River, Nebraska. Specifically, I evaluated the questions:

140

1. Are there differences in population metrics such as: relative abundance, size-

structure, condition (Chapter 2), age structure, growth-rates, and mortality

(Chapter 3) of channel catfish and flathead catfish populations between segments

of the Middle Missouri River?

 Segment level differences in relative abundance, size-structure, condition,

and age structure were observed in 2009 and 2010.

 Few segment level differences in growth rates were observed in 2009 and

2010.

 No segment level differences in mortality were observed in 2009 and

2010.

2. Do habitat restoration efforts (bend modifications) have an effect on channel

catfish and/or flathead catfish (Chapter 2) populations?

 Channel catfish relative abundance was greater on modified bends than

unmodified bends in the upper channelized segment in 2009.

 Flathead catfish relative abundance was greater on unmodified bends than

modified bends in the lower channelized segment in 2010.

 Flathead catfish size structure (median length) was lower on unmodified

bends than on modified bends in the lower channelized segment in 2010.

3. What is the estimated population size and density of channel catfish within a

Missouri River study bend, and how does C/f relate to population size (Chapter 4)

 The estimated population size of channel catfish within bend UC17

(Upper channelized segment bend # 17; RKM 1,122.8 – 1,116.6) was ~

25,000 – 26,000 channel catfish > 200 mm. 141

My evaluation of the above objectives led to the following recommendations for future sampling and management.

Sampling

1 - I found considerable variation in C/f of channel catfish and flathead catfish between river bends and within river bends and catches of zero fish per hoop net deployment or EF run were not uncommon. The variable catch phenomenon highlights the importance of randomly selecting sampling sites to provide accurate assessments of population characteristics at the segment level. Historically, Missouri River catfish population sampling in Nebraska has been conducted using a fixed-site approach (Porter and Mestl 2009). Based on variability of C/f between and within river bends observed in this study I recommend future catfish population sampling adopt a stratified random design similar to that used in this study (See Chapter 2).

2 – Pectoral spines were not collected from flathead catfish > 800 mm during this study and Porter (personal communication) stated that pectoral spine collection from flathead catfish > 750-800 mm has not been conducted in recent years in the Missouri

River, Nebraska. As a result, flathead catfish age, growth, and mortality information for flathead catfish > 800 mm is lacking for this portion of the Missouri River. Nash and

Irwin (1999) found that precision and accuracy of age determination of flathead catfish > age-5 was greater for otoliths than pectoral spines primarily due to expansion of the central lumen of the pectoral spines resulting in loss of early annuli. I recommend collecting otolith subsamples from flathead catfish of all sizes within each Missouri River segment for age, growth, and mortality estimation. Pectoral spines were collected from a 142 subsample of five individuals of each species per 10-mm length group from each study bend in 2009 while in 2010 pectoral spines were collected from a subsample of five individuals of each species per 10-mm length group from each study segment. Mean back-calculated length-at-age of channel catfish in the upper unchannelized segment was greater in 2010 than 2009 (See Chapter 3; Figure 3-5) and channel catfish sampling in

2010 occurred on bends nearer to Lewis and Clark Reservoir than 2009, suggesting that channel catfish growth rates may differ between regions within the upper unchannelized segment. I suggest future collection of aging structures (pectoral spines or otoliths) be conducted using a bend level subsampling approach in an effort to identify intra-segment differences in growth rates.

3 - Perhaps the most intriguing finding of this study was that mean relative abundance estimates derived from repeated sampling combined with capture probabilities calculated with closed-captures analyses using Program MARK (White and Burnham

1999) produce abundance estimates (mean bend-level abundance; µ ̂ ) similar to estimates of ̂ from Program MARK (See Chapter 4). Further research will be needed to determine if the technique used in this study to estimate µ ̂ from C/f data can be used on a larger scale (i.e., segment level; See Chapter 2). I recommend using the spatially replicated sampling procedure and closed-captures capture-mark-recapture analyses at multiple sites throughout the Missouri River, Nebraska study area to assess catfish populations. If the relation between mean C/f and µ ̂ is similar throughout a given

Missouri River, Nebraska study segment, then one week of spatially replicated sampling in each segment could lead to an ability to quantify µ ̂ throughout the Missouri River,

Nebraska. 143

4 – I recommend dropping MHN from standard sampling methods (See Chapter

2) and increasing the number of SHN set within each study bend to 10. I had hoped to use MHN to collect young of the year channel catfish in sufficient numbers to compare young of the year abundance between study segments. However, catch of young of the year channel catfish in MHN was generally poor and highly variable making any comparisons based on this gear nearly impossible.

5 – A detailed study of predator-prey interactions throughout the Missouri River,

Nebraska to examine the effects of predation on channel catfish may help to explain the lower observed abundance of channel catfish in areas with greater abundance of predators

(See Chapter 2). Flathead catfish are the primary predatory species in the channelized segments and estimates of abundance will be calculated annually through standard sampling. I recommended collecting otoliths from a subsample of flathead catfish for age, growth, and mortality estimation and fish sacrificed for otolith removal should have stomach content analyses performed as well. Sampling of predatory species in the upper channelized segment will require gears not used in standard catfish sampling such as gill nets, frame nets, high frequency pulsed DC electrofishing, etc. Currently, the United

States Fish and Wildlife Service (USFWS) samples the upper unchannelized segment with a suite of gears. I recommend collaborating with USFWS biologists to gather the necessary data to make inferences on the abundance of predatory species in the upper unchannelized segment. To determine if channel catfish comprise a large portion of the diet of sight-feeding predators in this segment, I suggest collecting and analyzing stomach content samples from any predatory species collected as bycatch during standard catfish sampling. 144

6 - Understanding the effect of harvest on Missouri River catfish populations is critical in understanding what management actions should be put in place. The Missouri

River public use assessment (Sheriff et al. 2011) provides fishing pressure and harvest information from Gavins Point Dam, South Dakota to the mouth of the Missouri River near Saint Louis, Missouri between January 2004 and January 2005. However, detailed information regarding harvest by rod-and-reel anglers versus setline anglers is still needed to better understand the role of harvest in structuring Missouri River catfish populations. Hurley and Duppong-Hurley (2007) estimated that nearly one-in-seven catfish anglers in Nebraska harvest every fish they catch but did not calculate differences in harvest rates between rod-and-reel anglers and setline anglers. I recommend developing a Missouri River angler survey designed to address the question of whether harvest rates differ between rod-and-reel anglers and setline anglers. Several potential methods for conducting this survey have been discussed including a roving survey by boat, soliciting participants for a fishing diary survey at access points and cabin developments along the river, and attempting to gather contact information for setline anglers from identification labels required on every setline. Based on the number of unlabeled setlines I have observed while sampling on the Missouri River the last method is unlikely to provide a suitable sample. I recommend combining a roving survey with a fishing diary survey to assess potential differences in harvest between rod-and-reel anglers and setline anglers.

145

Management

1 - Travnichek (2004) proposed that flathead catfish populations in the Missouri

River, Missouri may be regulated within management units rather than with river-wide regulation to cater to both harvest oriented anglers and trophy anglers. Lotic channel catfish populations also have the potential to be managed as trophy fisheries. For example, the Red River in Manitoba is managed to restrict harvest which reduces mortality and increases growth potential, maximizing anglers‟ potential for catching trophy channel catfish (Macdonald 1990). The current trend in Nebraska has been to streamline and simplify sportfish regulations by creating statewide or basinwide management regulations. However, due to differences in catfish population characteristics between segments, catfish management in the Nebraska portion of the

Missouri River appears to be well suited for management unit based regulations.

Specifically, the upper channelized segment has a relatively higher density channel catfish population (See Chapter 4) and may be able to support relatively greater levels of channel catfish harvest than the other segments. Similarly, the lower channelized segment has a relatively higher density flathead catfish population and appears to be able to support greater levels of flathead catfish harvest than the other segments. The upper unchannelized segment may be able to support low density populations of channel catfish and flathead catfish (see Chapters 2 and 3) which may be better suited for trophy management regulations designed to minimize harvest and maximize growth potential.

146

Literature Cited

Hurley, K. L., and K. L. Duppong Hurley. 2007. Nebraska catfish anglers: descriptions

and insights derived from the 2002 Nebraska licensed angler survey. Nebraska

Game and Parks Commission, Lincoln, Nebraska.

Macdonald, D. 1990. The channel catfish sport fishery of the lower Red River. Master‟s

thesis. University of Manitoba, Winnipeg.

Mestl, G. E. 1999. Changes in Missouri River channel catfish populations after closing

commercial fishing. Pages 455-460 in E. R. Irwin, W. A. Hubert, C. F. Rabeni,

H. L. Schramm, Jr., and T. Coon, editors. Catfish 2000: proceedings of the

international ictalurid symposium. American Fisheries Society, Symposium 24,

Bethesda, Maryland.

Nash, M. K., and E. R. Irwin. 1999. Use of otoliths versus pectoral spines for aging

adult flathead catfish. Pages 309-316 in E. R. Irwin, W. A. Hubert, C. F. Rabeni,

H. L. Schramm, Jr., and T. Coon, editors. Catfish 2000: proceedings of the

international ictalurid symposium. American Fisheries Society, Symposium 24,

Bethesda, Maryland.

Porter, T., and G. E. Mestl. 2009. 2008 Missouri River Ecology F-75-R-26. Nebraska

Game and Parks Commission, Lincoln, Nebraska.

Sheriff, S. L., R. B. Renken, and T. Treiman. 2011. Missouri River public use

assessment: final report results from the 2004 survey of river users. Missouri

Department of Conservation, Columbia, Missouri. 147

Travnichek, V. H. 2004. Movement of flathead catfish in the Missouri River: examining

opportunities for managing river segments for different fishery goals. Fisheries

Management and Ecology 11: 89-96.

White, G. C., and K. P. Burnham. 1999. Program MARK: Survival estimation from

populations of marked animals. Bird Study 46 Supplement, 120-138.

148

APPENDIX A – MISSOURI RIVER, NEBRASKA BEND LIST AS DEFINED BY THE MISSOURI RIVER PALLID STURGEON POPULATION ASSESSMENT PROJECT

A-1. Bends in the upper unchannelized segment of the Missouri River, Nebraska.

Bend # Upper RKM Bend Length (KM)

1 1416.2 1.8 2 1414.5 5.5 3 1409.0 3.2 4 1405.8 2.6 5 1403.2 2.6 6 1400.6 2.9 7 1397.7 4.0 8 1393.7 2.6 9 1391.1 1.6 10 1389.5 3.7 11 1385.8 12.7 12 1373.1 2.4 13 1370.7 1.1 14 1369.6 3.1 15 1366.5 2.6 16 1363.9 2.4 17 1361.5 3.2 18 1358.3 1.3 19 1357.0 1.8 20 1355.2 1.1 21 1354.1 2.3 22 1351.8 5.0 23 1346.9 2.6 24 1344.3 1.9 25 1342.4 8.2

149

A-2. Bends in the lower unchannelized segment of the Missouri River, Nebraska.

Bend # Upper RKM Bend Length (KM) 1 1305.2 1.6 2 1303.6 4.0 3 1299.5 3.2 4 1296.3 3.2 5 1293.1 3.2 6 1289.9 0.8 7 1289.1 2.4 8 1286.7 3.2 9 1283.5 1.6 10 1281.8 2.4 11 1279.4 3.2 12 1276.2 6.4 13 1269.8 2.4 14 1267.4 8.0 15 1259.3 4.8 16 1254.5 0.8 17 1253.7 5.6 18 1248.0 2.4 19 1245.6 0.8 20 1244.8 1.6 21 1243.2 4.0 22 1239.2 1.6 23 1237.6 3.2 24 1234.4 4.0 25 1230.3 1.6 26 1228.7 2.4 27 1226.3 1.6 28 1224.7 1.6 29 1223.1 4.0 30 1219.1 2.4 31 1216.7 0.8 32 1215.9 2.4 33 1213.4 1.6 34 1211.8 1.9 35 1209.9 3.7 36 1206.2 4.3 37 1201.9 6.9 38 1194.9 6.4 150

A-3. Bends in the upper channelized segment of the Missouri River, Nebraska. Underlined bend ‟s indicate bends classified as “modified”.

Bend # Upper RKM Bend length (KM) Bend # Upper RKM Bend length (KM) 1 1186.9 4.0 30 1079.1 6.0 2 1182.9 3.5 31 1073.1 5.8 3 1179.3 1.4 32 1067.3 3.9 4 1177.9 8.9 33 1063.5 4.8 5 1169.0 4.5 34 1058.6 4.5 6 1164.5 2.1 35 1054.1 5.5 7 1162.4 5.3 36 1048.6 3.7 8 1157.1 4.2 37 1044.9 7.2 9 1152.9 3.4 38 1037.7 4.8 10 1149.6 6.3 39 1032.9 3.4 11 1143.3 3.9 40 1029.5 1.9 12 1139.4 2.6 41 1027.6 1.9 13 1136.8 3.9 42 1025.6 5.1 14 1133.0 1.9 43 1020.5 2.3 15 1131.0 2.7 44 1018.2 2.3 16 1128.3 5.5 45 1016.0 2.9 17 1122.8 6.3 46 1013.1 3.2 18 1116.6 4.2 47 1009.9 7.1 19 1112.4 3.4 48 1002.8 9.2 20 1109.0 2.7 49 993.6 3.9 21 1106.3 2.3 50 989.7 3.4 22 1104.0 4.2 51 986.4 6.9 23 1099.8 2.9 52 979.4 6.9 24 1096.9 3.1 53 972.5 5.3 25 1093.9 2.7 54 967.2 2.6 26 1091.1 2.7 55 964.6 1.8 27 1088.4 2.4 56 962.9 3.2 28 1086.0 3.2 57 959.7 3.5 29 1082.8 3.7

151

A-4. Bends in the lower channelized segment of the Missouri River, Nebraska. Underlined bend ‟s indicate bends classified as “modified”.

Bend # Upper RKM Bend length (KM) Bend # Upper RKM Bend length (KM) 1 956.1 3.5 22 872.7 3.5 2 952.6 4.0 23 869.2 4.8 3 948.5 5.0 24 864.4 3.5 4 943.6 5.8 25 860.8 2.4 5 937.8 5.6 26 858.4 2.3 6 932.1 3.9 27 856.2 4.5 7 928.3 3.2 28 851.7 5.0 8 925.1 3.2 29 846.7 3.9 9 921.8 4.8 30 842.8 1.8 10 917.0 7.6 31 841.0 4.0 11 909.4 3.5 32 837.0 2.7 12 905.9 4.0 33 834.3 1.1 13 901.9 6.0 34 833.2 2.1 14 895.9 1.9 35 831.1 6.9 15 894.0 4.2 36 824.1 6.3 16 889.8 3.2 37 817.9 2.6 17 886.6 2.3 38 815.3 3.1 18 884.3 5.1 39 812.2 4.8 19 879.2 2.6 40 807.4 2.3 20 876.6 1.6 41 805.2 1.8 21 875.0 2.3 42 803.4 1.9

152

APPENDIX B – MEAN BACK-CALCULATED LENGTH-AT-AGE OF CHANNEL CATFISH AND FLATHEAD CATFISH IN THE MISSOURI RIVER, NEBRASKA

B-1. Mean back-calculated length-at-age (mm) of channel catfish in the Missouri River, Nebraska in 2009 and 2010.

Upper Unchannelized Segment Lower Unchannelized Segment Upper Channelized Segment Lower Channelized Segment Mean Standard Mean Standard Mean Standard Mean Standard Year Age Length Error Year Age Length Error Year Age Length Error Year Age Length Error 2009 1 106 3.0 2009 1 92 1.6 2009 1 95 1.2 2009 1 109 3.8 2 162 3.4 2 159 2.1 2 159 1.6 2 184 5.7 3 224 4.4 3 216 2.4 3 221 1.8 3 248 7.2 4 272 5.2 4 259 3.1 4 273 2.8 4 310 9.8 5 307 19.0 5 287 5.1 5 310 4.5 5 376 16.9 6 343 29.6 6 326 8.1 6 350 6.9 6 427 18.0 7 338 11.4 7 360 11.0 7 400 10.4 7 402 46.5 8 369 11.1 8 377 10.0 8 406 14.3 8 392 . 9 401 11.2 9 387 16.9 9 421 32.2 9 415 . 10 439 11.1 10 434 18.1 10 489 . . . . 11 472 10.4 11 433 ...... 12 492 19.7 ...... 13 535 28.0 ...... 14 542 33.5 ......

2010 1 106 2.4 2010 1 93 1.9 2010 1 104 1.6 2010 1 116 2.3 2 177 3.4 2 155 3.1 2 168 2.3 2 185 2.9 3 242 4.0 3 214 3.6 3 229 3.1 3 258 4.3 4 302 5.3 4 258 5.7 4 286 5.0 4 319 7.0 5 376 7.1 5 303 9.8 5 335 7.8 5 362 10.3 6 421 9.8 6 353 10.2 6 390 13.7 6 423 11.7 7 465 14.7 7 394 14.5 7 392 16.5 7 450 38.2 8 511 16.7 8 436 . 8 397 16.3 8 450 84.9 9 542 18.4 9 462 . 9 442 30.2 9 383 . 10 567 30.3 10 481 . 10 551 . . . . 11 585 54.1 11 ...... 12 578 ...... 13 622 ...... 14 666 ......

153

B-2. Mean back-calculated length-at-age (mm) of flathead catfish in the Missouri River, Nebraska in 2009 and 2010 (See Errata # 3).

Upper Unchannelized Segment Lower Unchannelized Segment Upper Channelized Segment Lower Channelized Segment Mean Standard Mean Standard Mean Standard Mean Standard Year Age length error Year Age length error Year Age length error Year Age length error 2009 1 121 8.9 2009 1 106 2.2 2009 1 109 1.4 2009 1 108 1.3 2 222 14.7 2 200 2.8 2 206 2.1 2 206 1.8 3 319 18.3 3 280 4.0 3 291 2.8 3 296 2.5 4 404 22.8 4 347 7.2 4 362 4.7 4 376 3.6 5 478 32.6 5 402 11.9 5 429 8.7 5 430 6.0 6 551 36.3 6 448 16.6 6 484 16.9 6 467 12.8 7 490 . 7 472 20.9 7 546 25.1 7 513 20.9 8 537 . 8 517 29.7 8 588 30.3 8 534 32.0 9 577 . 9 513 62.1 9 587 34.5 9 566 44.6 . . . 10 570 93.1 10 549 19.3 10 579 66.6 . . . 11 677 56.4 11 602 20.4 11 620 42.3 ...... 12 643 . 12 666 11.3

2010 1 127 6.0 2010 1 111 2.2 2010 1 117 1.7 2010 1 127 2.3 2 213 9.1 2 203 3.4 2 212 2.3 2 222 3.1 3 288 12.0 3 281 4.1 3 302 3.2 3 313 4.4 4 362 14.4 4 345 5.3 4 376 5.1 4 406 5.7 5 411 18.0 5 393 8.8 5 429 9.2 5 474 8.8 6 437 21.2 6 454 16.7 6 468 16.0 6 529 12.1 7 451 24.0 7 512 21.6 7 543 24.3 7 558 24.6 8 454 15.0 8 524 57.5 8 570 23.3 8 597 64.0 9 478 23.6 9 534 66.3 ...... 10 498 27.7 10 496 25.8 ...... 11 518 31.0 11 538 ...... 12 539 73.9 ......

154

APPENDIX C – TOTAL CATCH BY SPECIES AND GEAR IN THE MISSOURI RIVER, NEBRASKA IN 2009 AND 2010

C-1. Total catch by species and gear in the upper unchannelized segment of the Missouri River, Nebraska in 2009.

Species Hoop nets Electrofishing

Shortnose gar Lepisosteus platostomus 2 0

Red shiner Cyprinella lutrensis 1 0

Spotfin shiner Cyprinella spiloptera 1 0

Common carp Cyprinus carpio 2 6

Shorthead redhorse Moxostoma macrolepidotum 3 0

Channel catfish Ictalurus punctatus 64 8

Flathead catfish Pylodictis olivaris 0 17

Grass pickerel Esox americanus 0 1

Northern pike Esox lucius 2 0

White bass Morone chrysops 0 2

Rock bass Ambloplites rupestris 3 0

Bluegill Lepomis macrochirus 4 0

Bluegill X Green sunfish hybrid L. macrochirus* cyanellus 1 0

Smallmouth bass Micropterus dolomieu 9 0

Black crappie Pomoxis nigromaculatus 1 0

Sauger Sander canadensis 3 0

Walleye Sander vitreus 1 0

155

C-2. Total catch by species and gear in the lower unchannelized segment of the Missouri River, Nebraska in 2009.

Species Hoop nets Electrofishing

Longnose gar Lepisosteus osseus 1 0

Shortnose gar Lepisosteus platostomus 9 0

Red shiner Cyprinella lutrensis 34 0

Shorthead redhorse Moxostoma macrolepidotum 1 0

Channel catfish Ictalurus punctatus 182 51

Flathead catfish Pylodictis olivaris 4 224

Stonecat Noturus flavus 0 1

Northern pike Esox lucius 1 0

Rock bass Ambloplites rupestris 1 0

Bluegill Lepomis macrochirus 29 0

Bluegill X Green sunfish hybrid L. macrochirus* cyanellus 5 0

Smallmouth bass Micropterus dolomieu 3 0

156

C-3. Total catch by species and gear in the upper channelized segment of the Missouri River, Nebraska in 2009.

Species Hoop nets Electrofishing

Shovelnose sturgeon Scaphirhynchus platorynchus 1 2

Longnose gar Lepisosteus osseus 1 1

Shortnose gar Lepisosteus platostomus 5 0

Goldeye Hiodon alosoides 0 4

Gizzard shad Dorosoma cepedianum 1 0

Red shiner Cyprinella lutrensis 2 0

Common carp Cyprinus carpio 1 8

Bighead carp Hypophthalmichthys nobilis 0 1

River carpsucker Carpiodes carpio 0 3

Quillback Carpiodes cyprinus 0 1

Blue sucker Cycleptus elongatus 0 7

Smallmouth buffalo Ictiobus bubalus 0 3

Shorthead redhorse Moxostoma macrolepidotum 0 1

Blue catfish Ictalurus furcatus 2 2

Channel catfish Ictalurus punctatus 276 83

Flathead catfish Pylodictis olivaris 15 755

Stonecat Noturus flavus 0 3 sunfish spp. Lepomis spp. 0 1

Green sunfish Lepomis cyanellus 0 1

Bluegill Lepomis macrochirus 4 0

Bluegill X Green sunfish hybrid L. macrochirus * cyanellus 1 0

Smallmouth bass Micropterus dolomieu 1 3

Sauger X Walleye hybrid S. canadensis* vitreus 0 1

Freshwater drum Aplodinotus grunniens 1 0 157

C-4. Total catch by species and gear in the lower channelized segment of the Missouri River, Nebraska in 2009.

Species Hoop nets Electrofishing

Shovelnose sturgeon Scaphirhynchus platorynchus 1 0

Shortnose gar Lepisosteus platostomus 6 0

Gizzard shad Dorosoma cepedianum 3 0

Common carp Cyprinus carpio 1 1

River carpsucker Carpiodes carpio 1 0

Blue catfish Ictalurus furcatus 0 13

Channel catfish Ictalurus punctatus 64 10

Flathead catfish Pylodictis olivaris 47 1164

Smallmouth bass Micropterus dolomieu 1 0

Freshwater Drum Aplodinotus grunniens 6 0

158

C-5. Total catch by species and gear in the upper unchannelized segment of the Missouri River, Nebraska in 2010.

Species Hoop nets Electrofishing

Skipjack herring Alosa Chrysochloris 0 1

Gizzard shad Dorosoma cepedianum 0 5

Silver chub Macrhybopsis storeriana 0 1

Red shiner Cyprinella lutrensis 0 1

Emerald shiner Notropis atherinoides 0 6

Common carp Cyprinus carpio 4 10

River carpsucker Carpiodes carpio 0 5

Quillback Carpiodes cyprinus 0 1

White sucker Catostomus commersoni 0 1

Blue sucker Cycleptus elongatus 0 1

Smallmouth buffalo Ictiobus bubalus 0 7

Bigmouth buffalo Ictiobus cyprinellus 0 1

Shorthead redhorse Moxostoma macrolepidotum 5 11

Black bullhead Ameiurus melas 0 1

Channel catfish Ictalurus punctatus 183 18

Flathead catfish Pylodictis olivaris 5 28

Stonecat Noturus flavus 0 1

Tadpole madtom Noturus gyrinus 1 0

White bass Morone chrysops 0 11

Rock bass Ambloplites rupestris 7 0

Bluegill Lepomis macrochirus 19 0

159

C-5. Continued

Species Hoop nets Electrofishing

Bluegill X Green sunfish L. macrochirus * cyanellus 3 0

Smallmouth bass Micropterus dolomieu 8 1

White crappie Pomoxis annularis 4 0

Black crappie Pomoxis nigromaculatus 5 0

Sauger Sander canadensis 1 3

Sauger X Walleye hybrid S. canadensis* vitreus 0 2

Walleye Sander vitreus 1 1

Freshwater drum Aplodinotus grunniens 3 0

160

C-6. Total catch by species and gear in the lower unchannelized segment of the Missouri River, Nebraska in 2010.

Species Hoop nets Electrofishing

Shovelnose sturgeon Scaphirhynchus platorynchus 0 3

Shortnose gar Lepisosteus platostomus 3 0

Spotfin shiner Cyprinella spiloptera 1 0

Common carp Cyprinus carpio 1 1

Blue sucker Cycleptus elongatus 4 3

Smallmouth buffalo Ictiobus bubalus 0 2

Bigmouth buffalo Ictiobus cyprinellus 0 1

Shorthead redhorse Moxostoma macrolepidotum 6 1

Black bullhead Ameiurus melas 1 0

Channel catfish Ictalurus punctatus 203 45

Flathead catfish Pylodictis olivaris 22 341

Bluegill Lepomis macrochirus 3 0

Bluegill X Green sunfish L. macrochirus * cyanellus 3 0

White crappie Pomoxis annularis 1 0

Sauger Sander canadensis 0 1

Freshwater drum Aplodinotus grunniens 5 0

161

C-7. Total catch by species and gear in the upper channelized segment of the Missouri River, Nebraska in 2010.

Species Hoop nets Electrofishing

Shovelnose sturgeon Scaphirhynchus platorynchus 1 0

Shortnose gar Lepisosteus platostomus 5 0

Common carp Cyprinus carpio 2 0

Shorthead redhorse Moxostoma macrolepidotum 1 0

Black bullhead Ameiurus melas 1 0

Blue catfish Ictalurus furcatus 0 2

Channel catfish Ictalurus punctatus 790 82

Flathead catfish Pylodictis olivaris 42 629

Stonecat Noturus flavus 3 0

Bluegill Lepomis macrochirus 2 0

White crappie Pomoxis annularis 3 0

Black crappie Pomoxis nigromaculatus 2 0

Freshwater drum Aplodinotus grunniens 7 0

162

C-8. Total catch by species and gear in the lower channelized segment of the Missouri River, Nebraska in 2010.

Species Hoop nets Electrofishing

Shovelnose sturgeon Scaphirhynchus platorynchus 1 0

Longnose gar Lepisosteus osseus 1 0

Shortnose gar Lepisosteus platostomus 10 0

Common carp Cyprinus carpio 23 0

Blue sucker Cycleptus elongatus 1 0

Black bullhead Ameiurus melas 5 0

Blue catfish Ictalurus furcatus 13 17

Channel catfish Ictalurus punctatus 202 11

Flathead catfish Pylodictis olivaris 98 807

Freshwater drum Aplodinotus grunniens 5 0

163

APPENDIX D – CLASS LEVEL INFORMATION, FIT STATISTICS AND PARAMETER INFORMATION FOR MEAN C/f MODELS

D-1. Segment level channel catfish GLMM information for 25-mm mesh hoop nets.

Class Level Information

Class Levels Values YR 2 2009 2010 SEG 4 LC LU UC UU Bend 43 LC10 LC12 LC13 LC15 LC20 LC22 LC23 LC29 LC34 LC5 LC6 LC9 LU14 LU18 LU20 LU21 LU3 LU31 LU34 LU35 LU37 LU5 UC12 UC18 UC23 UC3 UC33 UC34 UC38 UC4 UC40 UC43 UC46 UU12 UU13 UU14 UU18 UU21 UU22 UU23 UU24 UU3 UU7

Fit Statistics

-2 Res Log Pseudo-Likelihood 1308.69 Generalized Chi-Square 342.93 Gener. Chi-Square / DF 0.95

Covariance Parameter Estimates

Standard Cov Parm Estimate Error

Bend(YR*SEG) 0.5128 0.1724 Scale 1.3680 0.1344

Type III Tests of Fixed Effects

Num Den Effect DF DF F Value Pr > F

SEG(YR) 7 40 4.48 0.0009

D-2. Segment level channel catfish GLM information for 7-mm mesh hoop nets. 164

Class Level Information

Class Levels Values

YR 2 2009 2010 SEG 4 LC LU UC UU Bend 43 LC10 LC12 LC13 LC15 LC20 LC22 LC23 LC29 LC34 LC5 LC6 LC9 LU14 LU18 LU20 LU21 LU3 LU31 LU34 LU35 LU37 LU5 UC12 UC18 UC23 UC3 UC33 UC34 UC38 UC4 UC40 UC43 UC46 UU12 UU13 UU14 UU18 UU21 UU22 UU23 UU24 UU3 UU7

Fit Statistics

Pearson Chi-Square 84.66 Pearson Chi-Square / DF 1.06

Type III Tests of Fixed Effects

Num Den Effect DF DF F Value Pr > F

SEG(YR) 7 80 9.58 <.0001

165

D-3. Bend modification level channel catfish GLM information for 25-mm mesh hoop nets.

Class Level Information

Class Levels Values

YR 2 2009 2010 SEG 2 LC UC Mod 2 M U Bend 23 LC10 LC12 LC13 LC15 LC20 LC22 LC23 LC29 LC34 LC5 LC6 LC9 UC12 UC18 UC23 UC3 UC33 UC34 UC38 UC4 UC40 UC43 UC46

Fit Statistics

-2 Log Likelihood 887.44 Pearson Chi-Square 229.99 Pearson Chi-Square / DF 1.31

Type III Tests of Fixed Effects

Num Den Effect DF DF F Value Pr > F

Mod(YR*SEG) 7 175 23.15 <.0001

166

D-4. Segment level flathead catfish GLMM information for pulsed DC electrofishing (effort = time).

Class Level Information

Class Levels Values

YR 2 2009 2010 SEG 4 LC LU UC UU Bend 46 LC18 LC20 LC32 LC34 LC36 LC39 LC40 LC6 LC7 LC8 LC9 LU11 LU14 LU18 LU2 LU22 LU23 LU32 LU37 LU38 LU4 LU8 LU9 UC1 UC20 UC21 UC25 UC28 UC29 UC41 UC42 UC48 UC51 UC55 UC6 UU10 UU11 UU16 UU17 UU18 UU19 UU20 UU21 UU3 UU4 UU9

Fit Statistics

-2 Res Log Pseudo-Likelihood 1032.95 Generalized Chi-Square 417.17 Gener. Chi-Square / DF 1.14

Covariance Parameter Estimates

Standard Cov Parm Estimate Error

Bend(YR*SEG) 0.1491 0.06272 Scale 0.3612 0.04324

Type III Tests of Fixed Effects

Num Den Effect DF DF F Value Pr > F

SEG(YR) 7 40 32.91 <.0001

167

D-5. Segment level flathead catfish GLMM information for pulsed DC electrofishing (effort = distance).

Class Level Information

Class Levels Values

Fit Statistics

-2 Res Log Pseudo-Likelihood 971.76 Generalized Chi-Square 425.82 Gener. Chi-Square / DF 1.17

Covariance Parameter Estimates

Standard Cov Parm Estimate Error

Bend(YR*SEG) 0.1421 0.05577 Scale 0.2580 0.03378

Type III Tests of Fixed Effects

Num Den Effect DF DF F Value Pr > F

SEG(YR) 7 40 35.21 <.0001

168

D-6. Bend modification level flathead catfish GLM information for pulsed DC electrofishing (effort = time).

Class Level Information

Class Levels Values

YR 2 2009 2010 SEG 2 LC UC Mod 2 M U Bend 23 LC18 LC20 LC32 LC34 LC36 LC39 LC40 LC6 LC7 LC8 LC9 UC1 UC20 UC21 UC25 UC28 UC29 UC41 UC42 UC48 UC51 UC55 UC6

Fit Statistics

-2 Log Likelihood 1372.59 Pearson Chi-Square 200.55 Pearson Chi-Square / DF 1.13

Type III Tests of Fixed Effects

Num Den Effect DF DF F Value Pr > F

Mod(YR*SEG) 7 178 5.63 <.0001

Ecology and Management of Channel Catfish &lt;I&gt;Ictalurus Punctatus&lt;/I&gt;

Ecology and Management of Channel Catfish <I>Ictalurus Punctatus</I>