Population Characteristics and Movement of Blue Catfish in the Kansas River

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POPULATION CHARACTERISTICS AND MOVEMENT OF BLUE CATFISH IN THE KANSAS RIVER

Quintin Dean University of Nebraska-Lincoln, [email protected]

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POPULATION CHARACTERISTICS AND MOVEMENT OF BLUE CATFISH IN

THE KANSAS RIVER

By Quintin J. Dean

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 Professors Martin J. Hamel & Mark A. Pegg Lincoln, Nebraska November, 2020

POPULATION CHARACTERISTICS AND MOVEMENT OF BLUE CATFISH IN

THE KANSAS RIVER

Quintin J. Dean, M.S. University of Nebraska, 2020

Advisors: Martin J. Hamel & Mark A. Pegg Blue Catfish Ictalurus furcatus is a mobile, large-river species native to the

Missouri River and its tributaries, including the Kansas River. Historical data regarding the Kansas River population is negligible, limiting managers’ ability to appropriately manage this population. Multiple anthropogenic barriers along the Kansas River create a gradient of connectivity within the Kansas River, and with the Missouri River, possibly limiting Blue Catfish movement. Additionally, the contribution of tributary-reservoir populations to the Kansas River remains unknown. My objectives were to: 1) describe population characteristics and 2) quantify stock contributions from the Missouri River and Kansas River tributary reservoirs to the lower Kansas River population. Relative abundance and condition were variable among years but similar across the gradient of connectivity. Somatic growth in the disconnected reach were greater than connected reaches; however, mean length of adult age groups were consistent across the study area.

River segments connected with the Missouri River had lower annual mortality and higher proportions of large fish compared to the disconnected reach. Upstream passage was not documented at the second barrier on the Kansas River, suggesting the population upstream of the barrier is isolated from the Missouri River. Adult fish collected within river reaches connected to the Missouri River displayed relatively equal natal contributions from the Kansas River and Missouri River. Half of adult and juvenile fish

sampled in reaches disconnected from the Missouri River originated from Kansas River tributary reservoirs. Our data suggests adopting two spatial scales for investigating and managing Blue Catfish in the Kansas River, with the second barrier as a point of division.

Current statewide regulations are adequate for maintaining high trophy-potential in downstream river reaches. The large number of fish using the Missouri River indicates appropriate management requires a broad spatial scale that incorporates a dendritic river network framework. Future monitoring efforts, particularly for the disconnected reaches, is imperative as large reservoir stock contributions may elicit change in population characteristics.

ACKNOWLEDGEMENTS I would like to thank my advisors, Dr. Marty Hamel, and Dr. Mark Pegg, for their patience, encouragement and leadership over the years. They provided a remarkable avenue to further my career and for that I will always be appreciative. To Dr. Kevin

Pope, thank you for teaching me how to properly answer a question and always challenging me to think for myself. To Dr. Chris Chizinski, thank you for providing a solid foundation in data management, analyses, and interpretation. I owe thanks to Ben

Neely who challenged me with thought provoking questions and whose humor, encouragement and skeptical yet optimistic perspectives contributed greatly to this project. I am also thankful to Jeff Koch who played a principle role in initiating this project and restored my confidence for conducting research on multiple occasions.

On the best of days, the Kansas River remains a fickle beast. Those individuals lucky enough to brave her waters became fine catfish wranglers and deserve recognition.

Katie Schrag, thank you for your friendship, cheerful demeanor and high morale through a challenging summer. Charlie deShazer, thank you for introducing me to the world of bass fishing tactics and being a reliable hand regardless of circumstance. Jake Werner helped in every aspect of this project; from boat modifications, running “diddy poles” and shoveling off muddy boat ramps to database design, analysis and manuscript edits. Jake’s insight and ideas were present throughout this project and his contribution to my graduate experience deserves an enormous thank you. I am thankful to Kansas Department of

Wildlife, Parks and Tourism for providing the funding of this project and to Luke

Kowalewski, Ernesto Flores, Vanessa Salazar, Jeff Conley, and Jessie Hall for assistance v collecting data. I also am thankful to Tim Berger with All American Catfish Tournaments for graciously allowing me to interrupt their tournaments to tag fish.

I am grateful to the members of the Pegg and Poletto labs for contributing to this project and my time at the University of Nebraska-Lincoln in various ways. To Andrew

Karlin, and Quade Brees, thank you for your brief but exciting time in the field. To Zach

Horstman , Sir Alex Engle, and Esther Perisho, thank you for your friendship, encouragement and assistance, academically and otherwise.

Finally, I would like to thank my family for their continuous encouragement as I pursued my passion for fish over the years; my father who instilled within me a love for the outdoors at an early age, my mother who has been my biggest fan since day one, my son whose excitement for life has refreshed my own, and my daughter whose joyful presence has made the worst of days a gift. Finally, I would like to thank my bride,

Rachel, for her reassurance, encouragement, patience, and sacrifice over the past few years.

TABLE OF CONTENTS LIST OF TABLES………………………………………………………………….…. vii

LIST OF FIGURES…………………………………………………………………… vii

CHAPTER 1: GENERAL INTRODUCTION AND STUDY OBJECTIVES…………. 1

LITERATURE CITED……………………………………………………………… 6

CHAPTER 2: POPULATION CHARACTERISTICS OF BLUE CATFISH IN THE KANSAS RIVER ……………………………………………………………………… 11

ABSTRACT ………………………………………………………………………… 11

INTRODUCTION ………………………………………………………………… 12

METHODS ……………………………………………………………………….… 14

RESULTS …………………………………………………………………………… 21

DISCUSSION ……………………………………………………………………… 24

LITERATURE CITED …………………………………………………………… 29

CHAPTER 3: NATAL ORIGINS, ENVIRONMENTAL HISTORY AND MOVEMENT PATTERNS OF BLUE CATFISH IN THE KANSAS RIVER ………. 52

ABSTRACT ………………………………………………………………………… 52

INTRODUCTION ………………………………………………………………… 53

METHODS ………………………………………………………………………… 55

RESULTS …………………………………………………………………………. 60

DISCUSSION ……………………………………………………………………… 63

LITERATURE CITED …………………………………………………………… 67

CHAPTER 4: CONCLUSIONS, FUTURE RESEARCH NEEDS AND MANAGEMENT IMPLICATIONS ………………………………………………… 85

LITERATURE CITED …………………………………………………………… 93 vii

LIST OF TABLES Table 1-1. Summary of stocked Blue Catfish in four northeastern Kansas reservoirs between 1990 and 2017. …………………………………….10 Table 2-1. Sampling effort for low-frequency electrofishing (min) and bank poles for 2018 and 2019. ……………………………………………………………….…35 Table 2-2. Length and weight summary statistics for Blue Catfish sampled with bank poles (BP), low-frequency electrofishing (EF) and catch-release tournaments (TOUR) in the Kansas River. …………………………………………….….36 Table 2-3. Proportional Stock Density (PSD) values for Kansas River Blue Catfish captured with low-frequency electrofishing and combined gears across sampling years and river segments. ………………………………………………………37 Table 2-4. Age-length keys from back calculated age at length for Blue Catfish in the lower Kansas River. …………………...………………….…………………….38 Table 2-5. Von Bertalanffy growth function parameters for Blue Catfish in three river reaches of the lower Kansas River. …………………………………………39 Table 3-1. Summary statistics of Sr:Ca (mmol/mol) for water samples, the peripheral 30 μm of otolith samples and predicted otolith values from linear regression between water and otolith signatures. .………………………………………………….72 Table 3-2. Summary of tagging effort and otolith collection of juvenile (100 – 400 mm) and adult (> 400 mm) Blue Catfish across three reaches of the lower Kansas River. Sites indicate the river reach within each river segment (Figure 3-1). .….73 Table 3-3. Proportional distribution of natal environments for juvenile (< 400 mm) and adult (> 400 mm) Blue Catfish captured in three reaches of the lower Kansas River. ……………………………………………………………………….……74 Table 3-4. Proportional distribution of environmental history movement patterns for juvenile (< 400 mm) and adult (> 400 mm) Blue Catfish captured in three reaches of the lower Kansas River. ……………………...………………………………75

LIST OF FIGURES Figure 2-1 The lower Kansas River (boxed) divided into three segments at the location of anthropogenic barriers; the Johnson County Weir (A), Bowersock Dam (B) and the Topeka Weir (C). Segments are further divided into sampling sites (e.g., KR1, KR2). …………………………………………………………………………40 Figure 2-2. Visual representation of water conditions for the lower Kansas River during the 2018 (solid) and 2019 (dashed) sampling seasons. ………………………….41 viii

Figure 2-3. Length-frequency plots and mean total lengths (dashed) for all Blue Catfish captured for 2018 and 2019 using low-frequency electrofishing (grey) and bank poles (dark grey). Note: y-axes are not the same. ……………………………...42 Figure 2-4. Length-frequency histograms of Blue Catfish collected in three river segments of the lower Kansas River. ……………………………….…………. 43 Figure 2-5. Back-calculated length at age from Blue Catfish lapilli otoliths from three river segments of the lower Kansas River. …………………………………….44 Figure 2-6. Comparison of mean back calculated length at various ages between river segments of the lower Kansas River. Letters indicate differences among river segments. ……………………………………………………………………….45 Figure 2-7. Von Bertalanffy growth function parameter estimates and standard error bars for river three river segments of the lower Kansas Rivers (Table 2-4). ………46 Figure 2-8. Von Bertalanffy growth curves for the lower Kansas River (solid grey), Mississippi River (dotted), Missouri River (dashed; Winders and Mcullen 2019) as well as Lovewell Reservoir (solid squares) and Wilson Reservoir (solid circles; Flores 2019). ……………………………………………………………………………………47 Figure 2-9. Frequency of assigned ages for Blue Catfish captured with low-frequency electrofishing (grey) and bank poles (dark grey) in the lower Kansas River. Gear recruitment determined at age 6 (dashed line). ………………………………….48 Figure 2-10. Weighted catch curves, instantaneous mortality (Z) and annual mortality (A) for three river segments of the lower Kansas River. Dashed line represent age recruited to gear. ……………………………………………………………….49 Figure 2-11. Mean relative weight (Wr) and 95% confidence intervals for Blue Catfish in three segments of the Kansas River for 2018 (open circles) and 2019 (closed circles). ………………………………………………………………………….50 Figure 2-12. Catch per unit effort for stock-length and substock-length Blue Catfish captured with low-frequency electrofishing in three river segments of the lower Kansas River. The proportion of sampling events with zero captures are numerically represented below boxplots. Zero captures are excluded from boxplot………………………………………………………………………….51 Figure 3-1. Location of water sample collection sites (white diamonds) on the Kansas River. Study area was divided into three segments at the location of anthropogenic barriers; the Johnson County Weir (A), Bowersock Dam (B) and the Topeka Weir (C). Segments are further divided into sampling sites (e.g., KR1, KR2). …………………….……………………………………………………………76 ix

Figure 3-2. Example of environmental history plots created to categorize individual fish into four life-long movement patterns; resident, transient, immigrant, and returning emigrant. Shaded regions represent values indicating natal environments. ……………………………………………………………………77 Figure 3-3. Length-frequency distributions and mean lengths (dashed) for juvenile (dark grey) and adult (grey) Blue Catfish used in (a) microchemistry and (b) mark- recapture analyses. ………………………………………………………………78 Figure 3-4. Distance traveled and orientation of individual movement events for Blue Catfish tagged in three river reaches of the Kansas River. Orientation of bars represent the direction a fish traveled within in Kansas River (solid), Delaware River (dotted) or the greater Missouri River system (dashed). Asterisks indicate an individual captured in a Missouri River tributary, excluding the Kansas River. ……………………………………………………………………………………79 Figure 3-5. Summary of distance traveled for Blue Catfish captured through sampling (grey) and anglers black). ……………………………………………………….80 Figure 3-6. Boxplots depicting the median, range, inter-quartile ranges and mean of water Sr:Ca (mmol/mol) from potential natal environments of Blue Catfish collected in the lower Kansas River. …………………………………………………………81 Figure 3-7. Relationship between water Sr:Ca and otolith Sr:Ca for Blue Catfish from this study (solid line; y = 0.3195x – 0.0559; R2 = 0.60, p<0.001) and Laughlin et al. (2016) (dotted line; y = 0.2135x + 0.0668). ……………………………………82 Figure 3-8. Proportional distribution of natal environments for juvenile (TL < 400 mm) and adult (TL > 400 mm) Blue Catfish captured in three reaches of the lower Kansas River (Table 3-3). Vertical lines represent anthropogenic barriers that allow (dashed) or prohibit (solid) upstream passage of Blue Catfish. …………83 Figure 3-9. Proportional distribution of environmental history movement patterns for juvenile (TL < 400 mm) and adult (TL > 400 mm) Blue Catfish captured in three reaches of the lower Kansas River (Table 3-4). Vertical lines represent anthropogenic barriers that allow (dashed) or prohibit (solid) upstream passage of Blue Catfish. …………………………………………………………………….84

CHAPTER 1 GENERAL INTRODUCTION AND STUDY OBJECTIVES

Blue Catfish Ictalurus furcatus is a large, mobile species that historically occupied large, warm-water riverine habitats in the Mississippi River drainage, including the Missouri River and its larger tributaries (Graham 1999). The fast growth and large maximum sizes of Blue Catfish make them a popular sport fish among anglers (Graham

1999). Historically, North American Ictalurids were primarily targeted by harvest- oriented commercial and recreational anglers (Eder 2011; Quinn 2011). An increasing number of contemporary catfish anglers participate in both harvest and catch-and-release practices and support the development of trophy fisheries through stricter regulations

(Arterburn et al. 2002).

The popularity of Blue Catfish among anglers has increased with a distributional expansion. Fisheries managers have introduced Blue Catfish into reservoirs to provide additional angling opportunities within and outside its native range (Graham 1999).

Stocking efforts have proven effective at establishing robust populations within some reservoirs (Graham 1999; Goeckler et al. 2003; Bartram et al. 2011), contributing to increased popularity among anglers. Entrainment of individuals from established reservoir populations has supplemented existing populations (Graham and DeiSanti

1999) and established non-native populations in downstream river systems (Homer and

Jennings 2011; Bonvechio et al. 2012). Consequently, fisheries managers are increasingly interested in improving the understanding of Blue Catfish ecology as the popularity and distribution of the species continues to increase (Arterburn et al. 2002). 2

Refined sampling gears and procedures have enabled managers to increase the ecological understanding of Blue Catfish over the past several decades (e.g., Bodine et al.

2013), however additional information is required for a more holistic understanding of this species. Movement patterns of Blue Catfish have been investigated in various systems including the Mississippi River (Pugh and Schramm 1999; Tripp et al. 2011), the

Missouri River (Garrett and Rabeni 2011; Winders and McMullen 2019), small impoundments (Fischer et al. 1999), and large reservoirs (Graham and DeiSanti 1999;

Timmons 1999; Gerber et al. 2018). These studies provide empirical support for seasonal movement patterns, individual variation, and site fidelity. Individual movement is variable and tends to increase with size (Tripp et al. 2011). Blue Catfish characteristically migrate upstream or into tributary habitats for spawning and retreat to large-river habitats for overwintering (Graham 1999). Tributary systems play an important role in some individual’s life-history strategies. For example, 10 – 18% of Blue Catfish occupying the

Missouri River used tributary systems during the putative spawning time (Garrett and

Rabeni 2011). Similarly, 19% of tagged Blue Catfish in the Upper Mississippi River used one or more major tributaries during a three-year study (Tripp et al. 2011). Tributary populations may exhibit different characteristics compared to large-river populations such as site fidelity, mortality, recruitment, and growth (Kwak et al. 2011). Many Blue

Catfish investigations have focused on large-rivers and reservoirs with less attention given to tributary systems. Investigating the characteristics of tributary populations and the relationship between tributary and main-stem systems is essential to create a holistic ecological understanding of lotic Blue Catfish populations. 3

Appropriate management of fish populations relies on accurate information regarding the population characteristics (i.e., growth, mortality, abundance) at an ecologically relevant spatial scale (Peterson and Dunham 2010). Quantifying the population characteristics for species in open systems is challenging as variations of individual movement patterns negate the selection of a singular, ecologically relevant spatial scale. This is further complicated for Blue Catfish in large-river systems as a proportion of the population may frequent different river systems (i.e., tributaries) or regulatory jurisdictions.

Selecting a spatial scale to investigate and manage mobile riverine species can also be affected by the myriad of anthropogenic alterations on large-river systems. Dams operated for hydropower, flood control, or navigation often alter the form and function of lotic systems and their communities (Stanford and Ward 2001; Pegg and McClelland

2004; Eitzmann and Paukert 2010). Additionally, dams acting as barriers to fish movement alter pathways to spawning, feeding, and overwintering habitats among large- river species (McAda et al. 1991; Jennings and Zigler 2009). Diminished connectivity and changes in community structure among river reaches separated by anthropogenic barriers may elicit changes in the vital rates and movement patterns of a population, creating ecologically disconnected populations with unique characteristics (Eitzmann et al. 2007; Hamel et al. 2020a; Hamel et al. 2020b). This effect may be exacerbated in tributary systems that rely on connectivity to main-stem river habitat for life-history strategies. The response of Blue Catfish to habitat fragmentation has been unaddressed and may have large ramifications in tributary systems for this long-lived, large-bodied species. Identifying impacts of fragmentation on the spatial use and vital rates of Blue 4

Catfish populations is essential to determine the spatial scale appropriate for research and management objectives.

The Kansas River is the northwestern periphery of the native distribution for Blue

Catfish and historically produced large, trophy-size individuals (Graham 1999; Lawhorn

2014). The lower Kansas River is believed to have had historically high abundances of

Blue Catfish (Cross 1967, cited by Haslouer et al. 2005). However, Haslouer et al. (2005) suggested listing Blue Catfish as a Species in Need of Conservation (SINC) in Kansas because of fundamental modifications to the limited riverine habitats occupied by Blue

Catfish within the state. For example, three anthropogenic fish barriers of varying size and structure pose as barriers for fish passage at varying water levels on the Kansas River

(Chapter 3, this thesis). The population characteristics of Blue Catfish in these modified systems, including the Kansas River, remained largely uninvestigated despite the suggested SINC listing in 2005.

Concern over Blue Catfish in Kansas soon diminished with the establishment of stocked populations in reservoirs. During 1990 - 2017, Kansas Department of Wildlife,

Parks and Tourism (KDWPT) stocked over 1.3 million Blue Catfish to provide angling opportunities in reservoirs throughout Kansas. A large number of these individuals (n =

550,895) were stocked in four Kansas River tributary reservoirs: Perry, Clinton, Milford, and Tuttle Creek reservoirs (KDWPT, unpublished data) (Table 1-1). Natural recruitment has been documented in all four reservoirs with some populations supporting popular fisheries (B. Neely and B. Miller, KDWPT, unpublished data). For example, Milford reservoir has a robust and self-sustaining population of Blue Catfish resulting from these stocking efforts (Geockler et al. 2003). Multiple tagged Blue Catfish have entrained from 5

Milford and Tuttle Creek reservoirs, entering the downstream river system (B. Neely

KDWPT, unpublished data). In October 2020, approximately 31,750 – 34,000 kg of fish were salvaged from the stilling basin below Tuttle Creek Reservoir, approximately 80% of which was Blue Catfish (Melissa Bean, Army Corp of Engineers, personal communication). All salvaged fish were entrained from the reservoir as a low head dam downstream of Tuttle Creek spillway prohibits upstream movement of fish from lotic environments (Ely Sprenkle, KDWPT, personal communication). Entrainment is suspected among the other reservoirs, however the extent that reservoir entrainment contributes to the downstream riverine populations remains uncertain.

The Kansas River provides a unique opportunity to study Blue Catfish in a tributary system with several important influences, chiefly reservoir entrainment and

Missouri River connectivity. Quantifying the contributions from adjacent systems and examining population characteristics will further our understanding of Blue Catfish in the

Kansas River system. The objectives of my study were to: 1) assess population characteristics (i.e., size structure, growth, mortality, relative abundance, and condition) across the gradient of Missouri-Kansas river habitat connectivity, and 2) quantify stock contributions from adjacent systems (i.e., Missouri River and Kansas River tributary reservoirs) and describe the spatial extent of the lower Kansas River Blue Catfish population. This is the first study to specifically investigate Blue Catfish in the Kansas

River and aims to provide baseline data for future management of this highly regarded fishery. 6

LITERATURE CITED Arterburn, J. E., D. J. Kirby, and C. R. Berry. 2002. A survey of angler attitudes and biologist opinions regarding trophy catfish and their management. Fisheries 27(5):10–21. Bartram, B. L., J. E. Tibbs and P. D. Danley. 2011. Factors affecting blue catfish populations in Texas reservoirs. Pages 187−198 in P. H. Michaletz and V. H. Travnichek, editors. Conservation, Ecology, and Management of Catfish: The Second International Symposium. American Fisheries Society, Symposium 77, Bethesda, Maryland. Bodine, K. A., D. E. Shoup, J. Olive, Z. L. Ford, R. Krogman, and T. J. Stubbs. 2013. Catfish sampling techniques: where we are now and where we should go. Fisheries 38(12):529–546. Bonvechio, T. F., B. R. Bowen, J. S. Mitchell, and J. Bythwood. 2012. Non-indigenous range expansion of the Blue Catfish (Ictalurus furcatus) in the Satilla River, Georgia. Southeastern Naturalist 11(2):355-358. Boxrucker, J. 2007. Annual movement patterns of adult blue catfish in a large reservoir using ultrasonic telemetry. Annual Performance Report - F-50-R-13-23. Oklahoma Department of Wildlife Conservation. Cross, F.B. 1967. Handbook of fishes of Kansas. University of Kansas Museum of Natural History, Miscellaneous Publication 45, p. 1–357. Eder, S. 2011. Missouri’s catfish: a history of utilization, management, and culture. Pages 55–70 in P. H. Michaletz and V. H. Travnichek, editors. Conservation, Ecology, and Management of Catfish: The Second International Symposium. American Fisheries Society, Symposium 77, Bethesda, Maryland. Eitzmann, J. L., A. S. Makinster, and C. P. Paukert. 2007. Distribution and growth of blue sucker in a Great Plains river, USA. Fisheries Management and Ecology 14(4):255–262. Eitzmann, J. L., and C. P. Paukert. 2010. Longitudinal differences in habitat complexity and fish assemblage structure of a Great Plains river. The American Midland Naturalist 163(1):14–32. Fischer, S. A., S. Eder, and E. D. Aragon. 1999. Movements and habitat use of channel catfish and blue catfish in a small impoundment in Missouri. Pages 239-255 in E. R. Irwin, W. A. Huber, 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.

Garrett, D. L., and C. F. Rabeni. 2011. Intra-annual movement and migration of flathead catfish and blue catfish in the lower Missouri River and tributaries. Pages 495−510 in P. H. Michaletz and V. H. Travnichek, editors. Conservation, ecology, and management of catfish: the second international symposium. American Fisheries Society, Symposium 77, Bethesda, Maryland. Gerber, K. M., M. E. Mather, J. M. Smith, and Z. J. Peterson. 2018. Multiple metrics provide context for the distribution of a highly mobile fish predator, the Blue Catfish. Ecology of Freshwater Fish 28(1): 141-155. Goeckler, J. M., M. C. Quist, J. A. Reinke, and C. S. Guy. 2003. Population characteristics and evidence of natural reproduction of Blue Catfish in Milford Reservoir, Kansas. Transactions of the Kansas Academy of Science 106: 149-154. Graham, K. 1999. A review of the biology and management of blue catfish. Pages 37 −50 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. Graham, K., and K. DeiSanti. 1999. The population and fishery of Blue Catfish and Channel Catfish in the Harry S. Truman Dam tailwater, Missouri. Pages 361-376 in E. R. Irwin, W. A. Huber, 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. Haslouer, S. G., M. E. Eberle, D. R. Edds, K. B. Gido, C. S. Mammoliti, J. R. Triplett, J. T. Collins, D. A. Distler, D. G. Huggins, and W. J. Stark. 2005. Current status of native fish species in Kansas. Transactions of Kansas Academy of Science 108:32-46. Hamel, M. J., J. J. Spurgeon, and M. A. Pegg. 2020a. Catfish population characteristics among river segments with altered fluvial-geomorphic conditions in the Missouri River, NE, USA. North American Journal of Fisheries Management. Special issue: Catfish 2020—the 3rd international catfish symposium. Hamel, M. J., J. J. Spurgeon, K. D. Steffensen, and M. A. Pegg. 2020b. Uncovering unique plasticity in life history of an endangered centenarian fish. Scientific Reports 10, 12866. Homer, M. D., and C. A. Jennings. 2011. Historical catch, age and size structure, and relative growth for an introduced population of Blue Catfish (Ictalurus furcatus) in Lake Oconee, Georgia. Pages 383–394 in P. H. Michaletz and V. H. Travnichek, editors. Conservation, Ecology, and Management of Catfish: The Second International Symposium. American Fisheries Society, Symposium 77, Bethesda, Maryland.

Jennings, C. A., and S. J. Zigler. 2009. Biology and life history of the paddlefish: an update. Pages 1-22 in C. P. Paukert and G. D. Scholten, editors. Paddlefish management, propagation, and conservation in the 21st century: building from 20 years of research and management. American Fisheries Society, Symposium 66, Bethesda, Maryland. Kwak, T., M. Porath, P. Michaletz, and V. Travnichek. 2011. Catfish science: status and trends in the 21st century. Pages 755−780 in P. H. Michaletz and V. H. Travnichek, editors. Conservation, ecology, and management of catfish: the second international symposium. American Fisheries Society, Symposium 77, Bethesda, Maryland. Lawhorn, C. 2014. Lawhorn’s Lawrence: When the Kansas River was home to kings. Lawrence Journal-World (June 18). McAda, C. W., and L. R., Kaedin. 1991. Movements of Adult Colorado squawfish during the spawning season in the upper Colorado River. Transactions of the American Fisheries Society 120: 339-345. Pegg, M. A., and M. A. McClelland. 2004. Spatial and temporal patterns in fish communities along the Illinois River. Ecology of Freshwater Fish 13(2):125–135. Peterson, J. T., and J. Dunham. 2010. Scale and fisheries management. Pages 43-77 in W. A. Hubert and M. C. Quist, editors. Inland fisheries management in North America, 3rd edition. American Fisheries Society, Bethesda, Maryland. Pugh, L. L., and H. L. Schramm, Jr. 1999. Movement of tagged catfishes in the lower Mississippi River. Pages 93-197 in E. R. Irwin, W. A. Huber, 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. Quinn, S. 2011. Human interactions with catfish. Pages 3-13 in P. H. Michaletz and V. H. Travnichek, editors. Conservation, ecology, and management of catfish: the second international symposium. American Fisheries Society, Symposium 77, Bethesda, Maryland. Stanford, J. A., and J. V. Ward. 2001. Revisiting the serial discontinuity concept. Regulated Rivers: Research & Management 17(4–5):303–310. Timmons, T. J. 1999. Movement and exploitation of blue and channel catfish in Kentucky Lake. Pages 187 – 191 in E. R. Irwin, W. A. Huber, 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.

Tripp, S. J., M. J. Hill, H. A. Calkins, R. C. Brooks, D. P. Herzog, D. E. Ostendorf, R. A. Hrabik and J. E. Garvey. 2011. Blue catfish movement in the upper Mississippi River. Pages 511−520 in P. H. Michaletz and V. H. Travnichek, editors. Conservation, ecology, and management of catfish: the second international symposium. American Fisheries Society, Symposium 77, Bethesda, Maryland. Winders, K. and J. McMullen. 2019. Assessment of vital rates (exploitation, size structure, age and growth, and total annual mortality) to evaluate the current harvest regulations for blue catfish (Ictalurus furcatus) in the Missouri and Mississippi rivers. Final Report. Missouri Department of Conservation. 10

Table 1-1. Summary of stocked Blue Catfish in four northeastern Kansas reservoirs between 1990 and 2017.

Reservoir Period Size Category Count Clinton 2005-2009 Fingerlings 49,063 2010-2014 Fingerlings 56,121

Milford 1990-1994 Fingerlings 30,768 Intermediates 45,482 1995-1999 Fingerlings 32,110 Intermediates 19,123 2000-2004 Fry 39,182

Perry 2005-2009 Fingerlings 69,897 2010-2014 Fingerlings 34,821 2015-2017 Fingerlings 12,215

Tuttle 2000-2004 Fry 6,300 Intermediates 10,098 2005-2009 Fingerlings 15,021 2010-2014 Fingerlings 81,186 2015-2017 Fingerlings 49,508 11

CHAPTER 2 POPULATION CHARACTERISTICS OF BLUE CATFISH IN THE KANSAS RIVER

ABSTRACT Appropriate management of fish populations relies on accurate information regarding population characteristics and spatial distribution of a population. Diminished habitat connectivity caused by anthropogenic barriers may affect the spatial distribution and population characteristics of mobile riverine species that rely on connected river systems for essential life functions. The response of Blue Catfish Ictalurus furcatus to diminished habitat connectivity has been largely unaddressed and may have ramifications for populations in tributaries of large rivers. We examined population characteristics (i.e., size structure, growth, mortality, condition, and relative abundance) of Blue Catfish across a gradient of tributary-mainstem connectivity within the lower Kansas River to identify the potential impacts of diminished habitat connectivity on a tributary population. Relative abundance and condition varied little among river segments. Mean length of disconnected reaches were greater than connected reaches at ages three and six, and relatively equal at age 10. River segments connected with the Missouri River had lower annual mortality (A = 14% & 15%) and higher proportions of large fish (PSD-M =

9 – 11, PSD-T = 3−5) compared to disconnected reaches (A = 22%; PSD-M = 3, PSD-T

= 0). This study demonstrates the influence of large-river connectivity on tributary population characteristics and provides context for future management of this population.

INTRODUCTION

Appropriate management of fish populations relies on accurate information regarding population characteristics at an ecologically relevant spatial scale (Peterson and

Dunham 2010). Quantifying population characteristics for species in open systems is challenging as individual variation in home range and movement patterns negate the selection of a singular, ecologically relevant spatial scale (Paukert and Galat 2010). For example, mobile species in large rivers may frequent different river systems (i.e., tributaries) or regulatory jurisdictions (Pugh and Schramm 1999; Pracheil et al. 2012) and warrant management decisions that reflect the broad spatial scale of the population.

Selecting a spatial scale to investigate and manage mobile riverine species can also be influenced by the myriad of anthropogenic alterations on large-river systems. Dams operated for hydropower, flood control, or navigation often alter the form and function of lotic systems and their communities (Stanford and Ward 2001; Pegg et al. 2003;

Eitzmann and Paukert 2010). Dams also alter or block pathways to spawning, feeding, and overwintering habitats among large-river species (McAda et al. 1991; Jennings and

Zigler 2009). Diminished connectivity and changes in community structure among river reaches separated by anthropogenic barriers may elicit changes in population vital rates, creating ecologically disconnected populations with unique characteristics (Eitzmann et al. 2007; Hamel et al. 2020a, Hamel et al. 2020b). This effect may be exacerbated in populations that rely on connectivity between tributary and main-stem river habitats for various life-history strategies, such as Blue Catfish Ictalurus furcatus.

Blue Catfish is a large, mobile species that historically occupied large, warm- water riverine habitats in the Mississippi River drainage, including the Missouri River 13 and its larger tributaries (Graham 1999). Blue Catfish characteristically migrate upstream or into tributary habitats for spawning and retreat to large-river habitats for overwintering

(Graham 1999). For example, 10 – 18% of Blue Catfish occupying the Missouri River used tributary systems during the putative spawning time (Garrett and Rabeni 2011).

Similarly, 19% of tagged Blue Catfish in the Upper Mississippi River used one or more major tributaries during a three-year study (Tripp et al. 2011).Tributary populations may exhibit different characteristics compared to large-river populations including site fidelity, mortality, recruitment, and growth (Kwak et al. 2011). Many Blue Catfish investigations have focused on large rivers and reservoirs with few studies investigating the tributary systems connected to the large rivers. Investigating the characteristics of tributary populations and their relationship with main-stem river systems is essential to create a holistic ecological understanding of Blue Catfish populations in lotic systems.

Historically, North American Ictalurids were primarily targeted by harvest- oriented commercial and recreational anglers (Eder 2011; Quinn 2011). An increasing number of contemporary catfish anglers participate in both harvest and catch-and-release practices and support the development of trophy fisheries through stricter regulations

(Arterburn et al. 2002). Fast growth and large maximum sizes make Blue Catfish a popular sport fish among anglers (Graham 1999). The popularity of Blue Catfish among anglers has increased with a distributional expansion of the species. Fisheries managers have introduced Blue Catfish into reservoirs to provide additional angling opportunities within and outside of their native range (Graham 1999). Stocking efforts have proven effective at establishing robust populations within some reservoirs (Graham 1999;

Goeckler et al. 2003; Bartram et al. 2011), contributing to the increased popularity among 14 anglers. Entrainment of individuals from established reservoir populations has supplemented existing populations (Graham and DeiSanti 1999) and established non- native populations in downstream river systems (Homer and Jennings 2011; Bonvechio et al. 2012). Fisheries managers are increasingly interested in improving the understanding of Blue Catfish ecology as the popularity and distribution of the species continues to increase (Arterburn et al. 2002).

The response of Blue Catfish to diminished habitat connectivity has been unaddressed and may have ramifications for tributary populations with restricted connectivity to large-river habitat. Identifying potential impacts of diminished habitat connectivity on vital rates of Blue Catfish populations is essential to determine appropriate management decisions. Here, we document and compare population characteristics (i.e., size structure, growth, mortality, condition, and relative abundance) of Blue Catfish in three reaches of the lower Kansas River. These data provide the first record of Blue Catfish population characteristics within this system and provide insight into the plasticity of Blue Catfish across a gradient of habitat connectivity with a larger river system; the Missouri river.

METHODS

Study Area

The Kansas River originates at the confluence of the Smokey Hill and Republican rivers in north central Kansas and flows 274 river kilometers (rkm) eastward to the

Missouri River (Sanders et al. 1993) (Figure 2-1). The mean daily discharge of the

Kansas River is 200 m3/s (Sanders et al. 1993), however discharge is variable in this system with flows exceeding 2,830 m3/s. The Kansas River basin has 18 federal 15 reservoirs and approximately 13,000 small impoundments that alter the natural flow regime of the Kansas River (Sanders et al. 1993). The Kansas River is shallow with a mean depth <1.5 m. Adjacent land use is primarily agricultural or forested with some urban interface (Paukert and Makinster 2009).

There are three anthropogenic fish barriers along the lower Kansas River. The

Johnson County Weir (rkm 24) and the Topeka Weir (rkm 141) are water diversion structures for local municipalities. These structures may present a barrier to upstream movement of Blue Catfish during low flows, while allowing upstream passage during high flows (Chapter 3, this thesis). Bowersock Dam in Lawrence, KS (rkm 84) is considered a complete barrier to upstream fish passage (Eitzman et al. 2007; J. Werner,

University of Nebraska-Lincoln, unpublished data) with some limited downstream movement (Chapter 3, this thesis). These barriers create a gradient of habitat connectivity between the Kansas River and the greater Missouri River system, where the Johnson

County Weir provides intermittent upstream connectivity dependent on discharge, and

Bowersock Dam provides no upstream connectivity.

The lower Kansas River was divided into three river segments; segment one was between the confluence with the Missouri River and the Johnson County Weir, segment two was between the Johnson County Weir and Bowersock Dam, and segment three was upstream of Bowersock Dam to the Topeka Weir. Each river segment was subdivided into sampling sites using locations of river access (i.e., boat ramps) and anthropogenic barriers as boundaries.

Data Collection

Fish were collected May − August 2018 and 2019 using pulsed-DC, low- frequency electrofishing (4 amps, 15 pulses/sec, 15 hz). Two electrofishing systems were used: a 4.8 m aluminum Jon boat equipped with a MBS-2D Wisconsin control box (ETS

Electrofishing LLC, Madison, WI, USA) powered by a 3,500 watt generator and a Smith-

Root 5.0 GPP electrofisher control box (Smith-Root, Vancouver, Washington, U.S.A.) attached to a larger boat. Electrofishing runs were conducted by drifting along the river bank and shocking suitable backwater and side-channel habitats. Each site was sampled once a month when water conditions allowed safe navigation (i.e., discharge < 1,415 m3/s). The location of sampling runs was chosen at random within each site.

Bank poles, a form of passive angling gear, were also used to increase capture rates of larger Blue Catfish (Dean et al. 2020). Bank poles were made of 1.5 m sections of 19-mm polyvinyl chloride (PVC) pipe equipped with a 7.6-m mainline (75 kg test, braided trotline cord), 85 g lead weight, 6/0 swivel, 1 m leader, and 6/0 Eagle Claw Lazer

Sharp Sea Circle Hook (Model L198F-6/0). Bank poles were baited with fresh or frozen

Silver Carp Hypophthalmichthys molitrix cut bait and deployed randomly within river reaches that had not been sampled via electrofishing within the past 12 hours.

All collected fish were identified to species, weighed (kg), and measured (total length, mm). Otolith collection was limited as concurrent research objectives relied on tagged and released individuals (Chapter 3, this thesis). Approximately 50 otoliths were collected per segment, with 25 from fish ≥ 400 mm total length and 25 fish < 400 mm total length. Lapilli otoliths were collected by making an incision through the 17 supraoccipital bone approximately 3-5 mm anterior to the locked pectoral spines and extracted using non-metallic forceps (Buckmeier et al 2002). Otoliths were stored in 2 ml plastic vials with unique identification numbers. In the laboratory, all excess tissue was removed and otoliths were cleaned with Nanopure water. The nuclei were marked with a graphite pencil and embedded in epoxy (Epoxicure Epoxy Resin and Hardener, Buehler

Inc., Lake Bluff, Illinois). Cross sections (0.5 mm) were taken from the transverse plane of each otolith. Annuli were revealed by sanding cross sections with 1,500 and 3,000 grit sandpaper and polished using 3 µm lapping paper. Otoliths were attached to microscope slides using double-sided tape and photographed using a high-resolution digital camera.

Additional light sources were used to optimize annuli clarity. Ages were assigned to each fish by three independent readers and discrepancies were resolved by a concert reading.

We examined size structure, growth, mortality, condition, and relative abundance across both spatial and temporal scales. Analyses examining spatial variation in population characteristics were conducted at the river segment level to mitigate potential bias in site-specific estimates (Bodine et al. 2011). Mortality, size structure, and condition estimates were also compared between low-frequency electrofishing and bank poles to provide insight on the potential effects of gear bias on these estimates.

Size Structure

Proportional size distribution (PSD) indices were used to compare the size structure among years, gears and river segments (Anderson and Neumann 1996; Guy et al. 2007). The following minimum lengths were used to classify each fish into a PSD category: stock (300 mm), quality (510 mm), preferred (760 mm), memorable (890 mm), 18 and trophy (1140 mm) (Gablehouse 1984; Guy et al. 2007). Proportional size distribution metrics were calculated as:

푁푢푚푏푒푟 표푓 푓𝑖푠ℎ ≥ 푠푝푒푐𝑖푓𝑖푒푑 푚𝑖푛𝑖푚푢푚 푙푒푛푔푡ℎ 푃푆퐷 − 푠푝푒푐𝑖푓𝑖푒푑 푐푎푡푒푔표푟푦 = 푁푢푚푏푒푟 표푓 푓𝑖푠ℎ ≥ 푠푡표푐푘 푙푒푛푔푡ℎ

Chi square tests were used to compare PSD indices between years for a given river segment and across river segments (Ogle 2016). The p-values were adjusted using

Bonferroni correction when multiple comparisons were made.

Age, Growth, and Mortality

Length-at-age was determined using the Dahl-Lea method of back-calculation:

푆푖퐿푐 퐿푖 = 푆푐 where Li is the estimated length at age i, Si is the otolith radius at the ith annulus, Lc is total length at capture, and Sc is the radius of the entire structure. Back-calculated length- at-age data were used to create von Bertalanffy growth functions and age-length keys for the lower Kansas River and individual river segments. Bootstrap methods were used to calculate von Bertalanffy growth functions and associated confidence intervals using the nlsboot function in the nlstools package (Baty et al. 2015) in program R (R Core Team

2018). The mean length at ages three, six and ten were compared across river segments using analysis of variances (ANOVA, α=0.05) with Tukey’s studentized range (HSD) test for multiple comparisons. Age three described growth prior to gonadal development

(Graham 1999), age six described growth at the approximate age of sexual maturity 19

(Graham and DeiSanti 1999) and age ten described growth after gonadal development.

Von Bertalanffy growth functions were constructed from back-calculated length-at-age data for each river segment as well as the entire study area. Additionally, we compared

Kansas River Blue Catfish growth to other populations by plotting the growth curve in conjunction with von Bertalanffy growth curves recreated from published accounts of the

Missouri and Mississippi Rivers (Winders and McMullen 2019) and from reservoir systems within the Kansas River basin (i.e., Lovewell and Wilson reservoirs; Flores

2019).

Individual age estimates were assigned to all unaged fish with an age-length key using the Isermann and Knight (2005) method to resolve fractionality. Instantaneous mortality (Z) and annual mortality (A) were estimated across river segments and gears using weighted catch curves where Z is the slope of the weighted linear regression and

A= 1−e-Z (Ricker 1975; Ogle 2016). Mortality estimates of long-lived species are often truncated to reduce the influence of older age groups with relatively few individuals

(Miranda and Bettoli 2007; Maceina and Bettoli 1998). However, this may greatly reduce the number of age groups used in mortality analysis if fish are recruited to the sampling gear later in life. Therefore, we used weighted catch curves to avoid further truncation when calculating Z (Maceina and Bettoli 1998). Combined data from 2018 and 2019 were used to provide sufficient data for each age category and to mitigate effects of variable recruitment (Miranda and Bettoli 2007). Difference in instantaneous mortality estimates were analyzed with analysis of covariance (ANCOVA, α=0.05).

Condition

Relative weight (Wr) was calculated for each fish above the recommended minimum length (160 mm):

푊i 푊푟 = × 100 푊s where Wi is the weight (g) of an individual and Ws is the standard weight for length i calculated using the standard weight equation for Blue Catfish.

log10(푊푠) = − 6.067 + 3.400 log10(TL) (Muoneke and Pope 1999)

Relative weight was compared across spatial and temporal variables using analysis of variance (ANOVA) with Tukey’s studentized range (HSD) test for multiple comparisons (α = 0.05).

Relative Abundance

Catch per unit effort (CPUE) was calculated as the number of Blue Catfish captured per hour of electrofishing. Catch per unit effort was calculated for substock- length (CPUE-substock) and stock-length (CPUE-stock) fish and compared across river segments, years and sampling months using Kruskal-Wallis (K-W) rank sum tests, as data were heavily right skewed (Hubert and Fabrizio 2007). Dunn’s test of multiple comparison using rank sums was used when K-W results were significant (α = 0.05) and p-values were adjusted to account for family-wise error rate when multiple comparisons were made using Holm’s correction method.

RESULTS

Water conditions on the Kansas River varied greatly between years; 2018 was characterized by low discharge and low turbidity with high mean temperature and conductivity, whereas 2019 was characterized by high discharge and turbidity with moderate temperature and conductivity (Figure 2-2). Consequently, sampling effort varied by year, segment and gear type (Table 2-1).

A total of 1,310 Blue Catfish ranging from 37 − 1,310 mm was captured using both gears (n = 822 in 2018 and n = 488 in 2019; Table 2-2). Low-frequency electrofishing captured a wider range of sizes (37 − 1,235mm) and had a smaller mean length (290, SD = 247) compared to bank poles (503 − 1,310 mm; mean = 776, SD =

166). Thirty-three percent (n = 398) of all fish captured with low-frequency electrofishing were stock length and 100% of fish captured with bank poles were stock length (n = 117).

Fish captured with low-frequency electrofishing displayed a bi-modal size distribution, with a high frequency of small (< 300 mm, n = 795) and large (500 − 800 mm, n = 271) size classes with few intermediate size classes (300 − 500 mm, n = 91; Figure 2-3).

2 Size indices did not vary across years for bank poles (χ 4 = 1.50, P = 0.82), low-

2 2 frequency electrofishing (χ 4 = 1.84, P = 0.76), or combined gears (χ 4 = 0.44, P = 0.97).

2 Size indices varied among river segments for combined gears (ꭓ 8 = 25.474, P < 0.01) where segment three varied from both segment one (P < 0.001) and segment two (P <

0.001) (Table 2-3). Size indices of segment three also varied from both segment one (P =

0.04) and segment two (P = 0.03) for fish captured with low-frequency electrofishing.

Segment three displayed a truncated size structure with an absence of trophy length fish and few memorable length fish (PSD-M = 3). Segments one and two contained higher 22 proportions of large fish compared to segment three (PSD-M = 9 – 11, PSD-T = 3 − 5)

(Figure 2-4).

Age structures were collected in 2018. A total of 116 otoliths were collected and estimated ages ranged from 1−19 years. Collections of aging structures varied by river segment; 47 were collected in segment one, 39 from segment two, and 30 from segment three. Maximum age was 13, 19, and 12 from segments one, two, and three, respectively

(Table 2-4; Figure 2-5). The mean age assigned to fish collected in segment two (6.9, SD

= 0.35) was greater than those captured in segment one (5.6 , SD = 0.28; ANOVA: F1, 520

= 8.08, P = 0.004) and segment three (5.3, SD = 0.20; ANOVA: F1, 650 = 18.57, P >

0.001). Segment three had greater mean back-calculated length at ages three and six compared to segment one (Figure 2-6). Mean back calculated length for segment two overlapped with both segment one and three for all age groups examined. Parameter estimates of von Bertalanffy growth functions also varied by segment; segment two had higher L∞ and lower K estimates than segment one and three (Table 2-5; Figure 2-7). The von Bertalanffy growth curve for the lower Kansas River closely resembled the Missouri and Mississippi rivers and Lovewell Reservoir between ages 2 − 8 (Figure 2-8). Wilson

Reservoir displayed greater lengths at ages 2 – 6 compared to the remainder of the populations. The L∞ of the Missouri River (L∞ = 1,294) and Mississippi River (L∞ =

1,243) were greater than the lower Kansas River (L∞ = 941), resulting in a departure of growth curves for ages > 10. The growth coefficient for the lower Kansas River (K =

0.12) was greater than the Mississippi (K = 0.08) and Missouri rivers (K = 0.07) and less than those of Wilson (K = 0.20) and Lovewell (K = 0.29) reservoirs. 23

The number of individuals captured with bank poles was insufficient to calculate mortality, therefore mortality estimates were calculated only for low-frequency electrofishing and combined gears. Individuals were considered recruited to gear at age six (Figure 2-9). Mortality estimates for the lower Kansas River was Z = 0.21 and A =

19% for low-frequency electrofishing and Z = 0.17 and A = 15% for combined gears.

Instantaneous mortality estimates derived from low-frequency data were consistently higher than those of combined gears (Figure 2-10). Segment two had significantly lower instantaneous mortality estimate than segment three when using combined gear data

(ANCOVA: F3, 23 = 29.86, P < 0.001). The remainder of ANCOVA analyses resulted in

P > 0.05.

A total of 433 fish were used to analyze fish condition (2018: n = 83, 2019: n =

350). Spatial variation in condition was limited among river segments within a given year

(ANOVA: F2, 788 = 0.251, P = 0.778); however, temporal variation was observed among years (ANOVA: F1, 789 = 46.821, P < 0.001) and months (ANOVA: F3, 787 = 17.977, P <

0.001) (Figure 2-11).

The number of fish captured per hour of electrofishing was highly variable. The proportion of zero-catch electrofishing events ranged between 35% -72% across years and segments (Figure 2-12). Catch per unit effort of substock-length fish was

2 significantly higher in 2018 compared to 2019 (K-W: χ 1 = 8.82, P = 0.003) whereas

2 CPUE-stock did not vary among years (K-W: χ 1 = 0.028205, P = 0.87). Catch per unit

2 effort of substock-length did not vary across segments in 2018 (K-W: χ 2 = 2.35, P =

0.309), however segment one had significantly higher CPUE-substock compared to segments two (P < 0.001) and three in 2019 (P < 0.001). Spatial variation in CPUE-stock 24

2 2 occurred during 2018 (K-W: χ 2 = 10.836, P = 0.004) and 2019 (K-W: χ 2 = 8.90, P =

0.012), however pooled data indicated no variation in CPUE-stock among river segments

2 (K-W: χ 2 = 5.54, P = 0.06).

DISCUSSION

The population characteristics of Blue Catfish varied at both spatial and temporal scales. Spatial variability observed in size structure, mortality and growth of Blue Catfish across the gradient of habitat connectivity suggests that river segments connected to the

Missouri River have dynamic rates different than river segments without Missouri River connectivity. Condition and relative abundance analyses indicate species-level response to the temporal variability of a Great Plains river system. Specifically, segment three consistently yielded lower proportions of memorable and trophy-length fish compared to segment one and segment two. The truncated size structure of segment three consequently resulted in greater mortality estimates within this segment compared to the other river segments.

Growth of Blue Catfish varied spatially throughout the study area. Segment two had a greater L∞ and a smaller growth coefficient (K) compared to segment one and segment three. Additionally, fish in segment three displayed greater mean lengths for ages three and six, indicating higher rates of somatic growth rates for juvenile fish in areas without connectivity to the Missouri River. However, little variation was present among the estimated von Bertanlaffy parameters and for mean length of fish past gonadal development (age 10). 25

Water conditions likely contributed to lower relative weight observed across all segments in 2018 compared to 2019. High water conditions and cooler water temperatures observed in 2019 may have diminished suitable spawning conditions for

Blue Catfish. A number of gravid female catfish were collected in September and

October of 2019, suggesting that they had not yet spawned or delayed spawning until the following year. Variable river conditions also influenced the catch rates of substock- length fish and limited size structure analyses to stock-length fish. Catch per unit effort of stock-length fish did not vary across river segments suggesting recruitment is relatively consistent throughout the system.

Low-frequency electrofishing may have produced an inaccurate and misleading perspective of the Blue Catfish density and abundance within this system. Unstable water conditions coupled with variable seasonal movement patterns and response behaviors of

Blue Catfish to electric current likely confound the assumption of constant capture efficiency used to compare CPUE data (Hubert and Fabrizio 2007; Bodine and Shoup

2010). Although spatial variation in relative abundance appears minimal, these data may not accurately depict the true abundance of Blue Catfish along the connectivity gradient.

Passive angling gears such as trotlines or setlines enable managers to capture the largest size classes in a population and increase the sample size for large size classes that may be infrequently captured via low-frequency electrofishing (Gale et al. 1999; Miranda and Killgore 2011; Bodine et al. 2013; Moran 2018). We used bank poles to capture memorable- and trophy-length fish that were rarely captured with low-frequency electrofishing. The information provided through this gear was essential to determine spatial variations in von Bertalanffy growth functions, mortality estimates and trophy 26 potential. Our data provide empirical support for using passive angling gears when monitoring vital rates and size-structure of lotic Blue Catfish, especially in unstable water conditions found in Great Plains rivers.

Mortality estimates of Blue Catfish in the lower Kansas River (A = 14−24%) closely resemble those of Flathead Catfish Pylodictis olivaris within the same system (A

= 14 − 28%; Makinster and Paukert 2008) and are considerably lower than those of the

Missouri (A = 35%) and Mississippi rivers (A = 38%; Winders and McMullen 2019).

Makinster and Paukert (2008) reported low levels of angler exploitation (< 10%) for

Flathead Catfish in the Kansas River. Our observations from angler recaptures of tagged fish also support low exploitation (Chapter 4, this thesis). Exploitation estimates of catfish in the Kansas River closely align with those of the Missouri River (Flathead

Catfish = 12%; Blue Catfish = 13%) and Mississippi River (Flathead Catfish = 10%;

Blue Catfish = 10%; Winders and McMullen 2019), suggesting lower natural mortality for the Kansas River.

In addition to connectivity, spatial variation in habitat and community structure from anthropogenic alterations may also influence population size structure, mortality and growth within the Kansas River. Eitzman and Paukert (2010) reported similar fish communities and habitat between river segments two and three and indicated that the

Johnson County Weir acts as a reset point along the river continuum, significantly altering the habitat and community structure of segment one. The recent establishment of invasive Silver Carp Hypophthalmichthys molitrix within segments one and two may further modify the fish community structure and influence population characteristics of

Blue Catfish (Mosher 2010; J. Werner, University of Nebraska-Lincoln, unpublished 27 data). For example, the presence of juvenile and adult Silver Carp may provide additional food resources for Blue Catfish post ontogenetic dietary shift and contribute to the larger size classes represented in segment one and two (Locher 2018). Anecdotal evidence from the field supports this notion as stomach contents of adult Blue Catfish contained both adult and juvenile Asian carp.

Population contributions from reservoirs within the Kansas River basin may have influenced mortality and growth estimates of segment three. Blue Catfish have been documented entering the upper Kansas River system from Milford and Tuttle Creek reservoirs (B. Neely and E. Sprenkle, Kansas Department of Wildlife, Parks and

Tourism, unpublished data). A substantial number of entrained fish from Kansas River tributary reservoirs could create an influx of fish, thereby influencing population dynamics. For example, size classes of entrained fish from Milford reservoir (mean =

522, SD = 180 mm) represent the first age groups recruited to gear and may overestimate the mortality of a disconnected tributary population if present in high quantities.

Additionally, Blue Catfish occupying adjacent reservoir habitats may experience higher rates of somatic growth than those in the Kansas River (Flores 2019). Contributions of fish that occupied reservoir habitats during stages of somatic growth may have influenced the observed variation among segments. Additional information regarding contributions from tributary reservoirs is needed to further understand their influence on the dynamic rates and size-structure within segment three.

Comparing population characteristics across a gradient of habitat connectivity refines our understanding of Blue Catfish ecology and potential consequences of diminished connectivity for this large-river species. Our data suggests that segments with 28 full or intermittent connectivity with the Missouri River have different vital rates and size structure compared to disconnected populations. Therefore, river reaches below

Bowersock Dam are likely to respond to management actions differently than those above. We recommend future management decisions adopt different management plans for connected and disconnected tributary populations. However, additional understanding is needed regarding movement and dispersal of fish within the Kansas River as well as contributions from the Missouri River and tributary reservoirs. Contributions from other populations may influence population characteristics and negate the Kansas River as an ecologically relevant scale for management.

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Table 2-1. Sampling effort for low-frequency electrofishing (min) and bank poles for 2018 and 2019.

2018 Low-frequency Electrofishing Bank Poles Segment Runs Mean SD Effort min/rkm Hook nights 1 27 21.9 11.1 591 24.8 50 2 50 22.5 11.1 1,123 18.6 174 3 21 24.0 14.3 503 8.9 208

2019 Low-frequency Electrofishing Bank Poles Segment Runs Mean SD Effort min/rkm Hook nights 1 32 29.6 7.5 948 39.8 167 2 65 27.3 6.6 1,774 29.3 144 3 49 30.3 5.4 1,485 26.2 154

Overall 244 26.3 9.5 6,424 107 897

Table 2-2. Length and weight summary statistics for Blue Catfish sampled with bank poles (BP), low-frequency electrofishing (EF) and catch-release tournaments (TOUR) in the Kansas River.

2018 Total length (mm) Weight (Kg) Gear Segment Count Mean SE Min Max Mean SE Min Max BP 1 4 710 42.4 633 801 3.5 0.7 2.1 5.3 2 13 852 54.2 610 1,208 7.0 1.7 2.0 21.3 3 11 716 41.2 538 948 4.2 0.8 1.3 9.1 EF 1 201 308 18.3 56 1,219 2.0 0.3 0.0 17.3 2 270 161 11.5 37 931 1.8 0.3 0.0 11.2 3 323 174 7.1 42 869 0.4 0.1 0.0 7.3 TOUR 1 92 841 17.4 498 1,330 8.5 0.8 1.1 32.1

2019 Total length (mm) Weight (Kg) Gear Segment Count Mean SE Min Max Mean SE Min Max BP 1 38 821 29.1 503 1,310 7.1 1.0 1.0 24.7 2 20 797 39.7 567 1,245 7.4 1.5 1.9 29.6 3 31 704 20.0 525 975 4.5 0.5 1.2 13.2 EF 1 116 292 18.5 81 890 0.8 0.2 0.0 8.6 2 98 478 28.9 41 1,235 3.2 0.4 0.0 19.2 3 185 566 12.4 200 934 2.7 0.2 0.1 10.6 TOUR 1 25 741 24.3 401 995 4.7 0.4 0.8 10.4

Overall Total Length (mm) Weight (Kg) Gear Count Mean SE Min Max Mean SE Min Max BP 117 776 15.4 503 1310 6.1 0.5 1.0 29.6 EF 1,193 291 7.15 37 1,235 1.9 0.1 0.0 19.2 TOUR 117 820 15.08 401 1,330 7.6 0.6 0.8 32.1

Table 2-3. Proportional Size Distribution (PSD) values for Kansas River Blue Catfish captured with low-frequency electrofishing and combined gears across sampling years and river segments.

2018 Low-frequency Electrofishing Combined Gears Segment PSD-Q PSD-P PSD-M PSD-T PSD-Q PSD-P PSD-M PSD-T 1 79 15 7 1 81 17 6 1 2 83 17 3 0 88 31 10 4 3 48 4 0 0 63 16 3 0 74 13 4 1 79 21 7 2

2019 Low-frequency Electrofishing Combined Gears Segment PSD-Q PSD-P PSD-M PSD-T PSD-Q PSD-P PSD-M PSD-T 1 73 7 3 0 87 35 12 6 2 83 17 6 5 87 24 12 5 3 72 16 2 0 76 18 3 0 73 14 3 1 79 22 7 2

Combined Low-frequency Electrofishing Combined Gears Segment PSD-Q PSD-P PSD-M PSD-T PSD-Q PSD-P PSD-M PSD-T 1 78 13 6 1 83 26 9 3 2 83 17 5 3 87 26 11 5 3 69 14 2 0 74 18 3 0 Overall 73 14 4 1 80 22 7 2

Table 2-4. Age-length keys from back calculated age at length for Blue Catfish in the lower Kansas River.

Segment 1 Segment 2 Segment 3 Age Mean (SD) SE n Mean (SD) SE n Mean (SD) SE n 1 145 (40) 6.0 45 139 (45) 7.2 39 172 (47) 8.8 28 2 228 (49) 7.8 39 230 (60) 10.4 33 272 (60) 11.6 27 3 314 (44) 8.8 25 324 (70) 14.3 24 353 (64) 13.1 24 4 381 (53) 11.4 22 390 (80) 16.3 24 431 (67) 14.5 21 5 428 (49) 11.6 18 453 (93) 18.9 24 499 (69) 16.4 18 6 482 (49) 11.6 18 503 (112) 24.5 21 563 (75) 17.7 18 7 532 (59) 15.2 15 528 (113) 27.5 17 614 (83) 20.6 16 8 573 (67) 19.4 12 573 (125) 31.2 16 636 (121) 45.8 7 9 619 (70) 23.4 9 606 (135) 36.0 14 637 (103) 51.3 4 10 631 (72) 29.4 6 622 (133) 38.5 12 686 (105) 52.5 4 11 628 (51) 25.7 4 661 (136) 39.2 12 741 (117) 58.5 4 12 666 (51) 25.5 4 708 (141) 42.5 11 721 1 13 707 (55) 32.0 3 740 (144) 45.4 10 14 777 (148) 46.6 10 15 826 (163) 57.6 8 16 865 (211) 94.3 5 17 887 (242) 121.0 4 18 874 (133) 94.0 2 19 1021 1

Table 2-5. Von Bertalanffy growth function parameters for Blue Catfish in three river reaches of the lower Kansas River.

Segment L∞ (SE) K (SE) t0 (SE) 1 824 (43) 0.14 (0.01) -0.41 (0.13) 2 1062 (87) 0.09 (0.01) -0.73 (0.28) 3 873 (71) 0.16 (0.03) -0.35 (0.2) Combined 941 (36) 0.12 (0.01) -0.56 (0.13)

Figure 2-1. The lower Kansas River (boxed) divided into three segments at the location of anthropogenic barriers; the Johnson County Weir (A), Bowersock Dam (B) and the Topeka Weir (C). Segments are further divided into sampling sites (e.g., KR1, KR2).

Figure 2-2. Visual representation of water conditions for the lower Kansas River during the 2018 (solid) and 2019 (dashed) sampling seasons. 42

Figure 2-4. Length-frequency histograms of Blue Catfish collected in three river segments of the lower Kansas River. 44

Figure 2-5. Back-calculated length at age from Blue Catfish otoliths from three river segments of the lower Kansas River. 45

Figure 2-6. Comparison of mean back calculated length at various ages between river segments of the lower Kansas River. Letters indicate differences among river segments. 46

Figure 2-7. Von Bertalanffy growth function parameter estimates and standard error bars for river three river segments of the lower Kansas Rivers (Table 2-4). 47

Figure 2-8. Von Bertalanffy growth curves for the lower Kansas River (solid grey), Mississippi River (dotted), Missouri River (dashed; Winders and Mcullen 2019) as well as Lovewell Reservoir (solid squares) and Wilson Reservoir (solid circles; Flores 2019).

Figure 2-9. Frequency of assigned ages for Blue Catfish captured with low-frequency electrofishing (grey) and bank poles (dark grey) in the lower Kansas River. Gear recruitment determined at age 6 (dashed line). 49

Figure 2-10. Weighted catch curves, instantaneous mortality (Z) and annual mortality (A) for three river segments of the lower Kansas River. Dashed line represent age recruited to gear. 50

Figure 2-11. Mean relative weight (Wr) and 95% confidence intervals for Blue Catfish in three segments of the Kansas River for 2018 (open circles) and 2019 (closed circles). 51

Figure 2-12. Catch per unit effort for stock-length and substock-length Blue Catfish captured with low-frequency electrofishing in three river segments of the lower Kansas River. The proportion of sampling events with zero captures are numerically represented below boxplots. Zero captures are excluded from boxplot 52

CHAPTER 3 NATAL ORIGINS AND MOVEMENT PATTERNS OF BLUE CATFISH IN THE KANSAS RIVER

ABSTRACT Understanding movement and dispersal dynamics of mobile, large-river fishes is essential to adopting an ecologically relevant spatial scale for research and management.

Movement and dispersal patterns of Blue Catfish Ictalurus furcatus, a large-river specialist, have been largely uninvestigated in large-river tributary habitats. Here, we couple otolith microchemistry analyses with mark-recapture data to examine natal origins and movement patterns of Blue Catfish in the Kansas River. Blue Catfish tagged in the

Kansas River were recaptured in five different rivers and individual movement was highly variable (0.01 – 475 rkm). Upstream passage was not documented at Bowersock

Dam, suggesting an isolated population in river reaches upstream of the dam. Adult fish

(> 400 mm) collected within river reaches connected to the Missouri River displayed relatively equal natal contributions from the Kansas River (34% - 48%) and Missouri

River (38% - 65%). A high percentage of adult fish (64% - 87%) sampled in river reaches disconnected from the Missouri River originated from Kansas River tributary reservoirs. Our data provide additional resolution to movement and dispersal patterns of

Blue Catfish within large-river tributary systems, highlight the significance of stock contributions from adjacent systems and provide empirical support for adopting management strategies that incorporate the broad spatial use of populations occupying dendritic river networks.

INTRODUCTION Appropriate management of fish populations relies on accurate information regarding population characteristics at an ecologically relevant spatial scale (Peterson and

Dunham 2010). Quantifying population characteristics for species in open systems is challenging as individual variations in movement patterns or natal environment may negate the selection of a singular, ecologically relevant spatial scale (Paukert and Galat

2010). For example, mobile species occupying dendritic, river networks may frequent different river systems (i.e., tributaries) or regulatory jurisdictions and warrant management decisions that reflect the broad spatial scale of the population (Pugh and

Schramm 1999; Pracheil et al. 2012; Siddons et al. 2017). Selecting a spatial scale to investigate and manage mobile riverine species can be influenced by the myriad of anthropogenic alterations on large-river systems. Dams operated for hydropower, flood control or navigation often alter the form and function of lotic systems and their communities (Stanford and Ward 2001; Pegg et al. 2003; Eitzmann and Paukert 2010;

Liermann et al. 2012). Dams also alter or block pathways to spawning, feeding, and overwintering habitats among large-river species (McAda et al. 1991; Jennings and Zigler

2009). Understanding movement patterns and the influence of anthropogenic alterations is essential to determine appropriate spatial scales for managing mobile, large-river specialists, such as the Blue Catfish Ictalurus furcatus (Smith and Whitledge 2011).

Blue Catfish are a mobile, large-river specialist that historically occupied large, warm-water riverine habitats in the Mississippi drainage, including the Missouri River and its larger tributaries (Graham 1999). Blue Catfish characteristically migrate upstream or into tributary habitats for spawning and retreat to large-river habitats for overwintering

(Graham 1999). For example, 10 – 18% of Blue Catfish occupying the Missouri River 54 used tributary systems during the putative spawning time (Garrett and Rabeni 2011).

Similarly, 19% of tagged Blue Catfish in the Upper Mississippi River used one or more major tributaries during a three-year study (Tripp et al. 2011). The recruitment contribution of tributary systems to large-river populations of Blue Catfish is thought to be minimal (Laughlin et al 2016), however the relative importance of large-river contributions to tributary populations remains uninvestigated. Information regarding movement and dispersal characteristics of tributary populations and their relationship with main-stem river systems is essential to further create a holistic ecological understanding of Blue Catfish populations in lotic systems.

Stocking efforts have proven effective at establishing reservoir populations of

Blue Catfish both within (Goeckler et al. 2003; Bartram et al. 2011) and outside of their native distribution (Graham 1999). Entrainment of Blue Catfish from established reservoir populations has supplemented existing populations (Graham and DeiSanti

1999) and established non-native populations in downstream river systems (Homer and

Jennings 2011; Bonvechio et al. 2012). Contributions of entrained individuals from reservoir populations provides an additional dynamic to movement and dispersal patterns within downstream lotic environments. Quantifying the proportional contribution of fish originating from reservoir environments is imperative to managing downstream populations.

Understanding movement and dispersal patterns within a population relies on accurately identifying natal environments of adult fish stock in addition to spatial range of adult fish (Hanski and Gilpin 1997; Peterson and Dunham 2010). Otolith microchemistry analyses allow fisheries managers to retrospectively identify natal 55 environments of fishes (Whitledge et al. 2007; Laughlin et al. 2016; Spurgeon et al.

2018a) and summarize movement patterns over the lifespan of an individual (Clarke et al.

2015; Svirgsden et al. 2016; Whitney et al. 2017; Duncan 2019). Trace elemental ratios

(e.g., Sr:Ca) deposited in the calcium carbonate matrices of otoliths reflect the environments occupied by an individual (Kennedy et al. 2002; Elsdon et al. 2008) and remain largely unaltered by metabolic processes (Campana and Thorrold 2001).

Here, we couple otolith microchemistry analyses with mark-recapture data to examine natal origins and movement patterns of Blue Catfish in the Kansas River, a large

Missouri River tributary. Spatial variation of natal origins and movements patterns were assessed across a gradient of tributary and main-stem river connectivity created by three anthropogenic fish barriers. These data provide insight into the population contributions from adjacent systems (i.e., the Missouri River and Kansas River tributary reservoirs), highlight movement and dispersal patterns of Blue Catfish occupying the lower Kansas

River and provide additional resolution to the spatial distribution of a tributary population among a dendritic river network.

METHODS

Study Area

The Kansas River originates at the confluence of the Smokey Hill and Republican rivers in north central Kansas and flows 274 river kilometers (rkm) eastward to the

Missouri River (Sanders et al. 1993) (Figure 3-1). There are 18 federal reservoirs within the Kansas River basin. Four reservoirs are located in close proximity to the Kansas

River and have established, self-sustaining populations of Blue Catfish; Perry, Clinton, 56

Milford, and Tuttle Creek reservoirs. We used anthropogenic fish barriers as natural breaks to divide the lower Kansas River into three distinct river segments. Segment one was between the Missouri River confluence and Johnson County Weir (rkm 24), segment two was between the Johnson County Weir and Bowersock Dam (rkm 84), and segment three was between Bowersock Dam and Topeka Weir (rkm 141). Each river segment was subdivided into sampling sites at points of river access (i.e., boat ramps) and barriers.

The size and stature of the anthropogenic fish barriers creates a gradient of habitat connectivity between the Kansas River and the greater Missouri River system. The

Johnson County and the Topeka weirs are municipal water diversion structures that may present a barrier to upstream movement of fish during low flow, while allowing upstream passage during high flow (J. Werner, University of Nebraska-Lincoln, unpublished data).

Bowersock Dam is a low-head dam considered a complete barrier to upstream fish passage (Eitzman et al. 2007; J. Werner, University of Nebraska-Lincoln, unpublished data), but may allow limited downstream movement.

Sampling

Fish were collected between May and August 2018 and 2019 using pulsed DC low-frequency electrofishing (4 amps, 15 pulses/sec, 15hz) and bank poles (Dean et al.

2020). Sampling was conducted along riverbank habitat as well as backwater and side channel habitats. The location of sampling runs was chosen at random within each site.

Catch-and-release catfish angling tournaments were also used to increase the sample size of larger fish for the mark-recapture portion of the study. All fish at tournament events 57 were released at the confluence of the Missouri and Kansas rivers; the location of the initial capture was not recorded.

Total length (mm) and weight (kg) were recorded for each Blue Catfish. Fish between 200 and 400 mm (i.e., juveniles) received a standard Floy tag (FD-94) and fish greater than 400 mm (i.e., adults) received an Extra Wide T Floy tag (FD-94; Floy Tag and Manufacturing, Inc., Seattle, Washington). Tags were inserted below the dorsal fin through the pterygiophores (Daugherty and Buckmeier 2009). Each tag contained a unique identification number, a phone number to report recapture information and notification of reward upon reporting. Anglers that reported capturing tagged fish were interviewed to determine the recapture location. The distance (rkm) between capture events was then calculated using Google Earth. Data provided by recaptured fish included movement orientation (downstream vs upstream), distance traveled (rkm), days at large, fate (harvest or release) and date of recapture.

Microchemistry: Data Collection

Water samples were collected in 2018 and 2019 to assess the spatiotemporal variation in trace elemental composition of the Kansas River basin and Missouri River

(Figure 3-1) (Ciepiela and Walters 2019). Two water samples were collected from sixteen sites along the Kansas River. Additional water samples were collected from the

Missouri River (n = 7) as well as Perry (n = 4), Clinton (n = 6), Milford (n = 4), and

Tuttle Creek (n = 4) reservoirs and their effluences (Table 3-1). Water samples were collected using a syringe filtration technique described by Shiller (2003). Samples were collected by two person teams to safeguard against contamination and immediately 58 filtered upon collection. A pre-cleaned 250 ml vial was thoroughly rinsed and filled with water from a given site. A pre-cleaned polyethylene 50 ml syringe was then rinsed with the sample and approximately 15 ml was filtered through the syringe to limit contamination (Shiller 2003). Approximately 5 ml was initially filtered through a

Whatman Puradisc PP 0.45 µm syringe filter to rinse a 15ml sample vial. The remaining sample was used to fill the 15 ml vial used for analysis. A high resolution Inductively

Coupled Plasma Mass Spectrometry (ICPMS; Thermo-Finnigan Element 2) was used to analyze the elemental concentrations of strontium (Sr), barium (Ba), magnesium (Mg) and calcium (Ca).

Approximately 50 lapilli otoliths were collected from each river segment during

July and August 2018. Otoliths were also taken from adult fish collected in Milford (n =

5), Perry (n = 6), Clinton (n = 5), and Tuttle Creek (n = 5) reservoirs. Otoliths were analyzed using a Thermo X-Series2 inductively coupled plasma mass spectrometer

(ICPMS) paired with a Teledyne-CETAC Technologies LSX-266 laser ablation system.

The laser (beam diameter = 100 μm, scan rate = 5 μm/s, laser pulse rate = 10 Hz, laser energy level = 75%, wavelength = 266 nm) ablated a transect extending from one side of the otolith nucleus to the edge of the opposite side of the otolith. A standard developed by the U.S. Geological Survey (MACS-3; CaCO3 matrix) was used every 15-20 samples to adjust for instrument drift. Each sample was immediately followed by a 30 second gas blank measurement. Data were reported as the Sr:Ca ratio (mmol/mol).

The otolith edge (outer ~30 μm) was used to determine recent environmental history of each fish. Data points from the ablation transect located within the nucleus of 59 the otolith were isolated to examine natal origins. Remaining transect data were used to describe life-long movement patterns of individuals (Duncan 2019).

Microchemistry: Analysis

Distribution of the strontium-calcium (Sr:Ca) ratio data were assessed for normality using a Shapiro-Wilks test and visual inspection of a quantile-quantile plot.

Spatial variation in water signatures were examined using analysis of variance (ANOVA) coupled with Tukey’s studentized range (HSD) test for multiple comparisons.

Threshold values for each potential natal environment were required to identify the natal environment of individuals captured in the Kansas River. The linear relationship between otolith and water Sr:Ca was used to estimate a predicted range of otolith Sr:Ca values representative of Kansas River and Missouri River water signatures. Fish of known sources (i.e., reservoirs) and juvenile fish from segment two were used to mitigate the influence of recent immigrants on model fit. The standard error of the linear regression was calculated using the predict.lm function from the stats package (R Core

Team 2018) and served as threshold values for each environment. Natal origin data were summarized for each segment using the proportional distribution of natal environments.

Ablation transect data were used to retrospectively examine movement patterns of individual fish throughout their lifespan. Ablation transect data from the nucleus to the otolith edge were plotted and visually inspected (Figure 3-2). Movement between water bodies was noted if 10 consecutive data points (~30 μm) of the ablation transect represented a single water body. Individuals were assigned to one of four movement patterns; resident, transient, immigrant, or returning emigrant. Individuals that originated 60 and remained within the Kansas River for their entire life were classified as residents.

Fish that moved between river systems three or more times were classified as transients, regardless of natal origins. Fish that did not originate from the Kansas River and had a single movement event into the Kansas River were classified as immigrants. Lastly, individuals that originated in the Kansas River, emigrated to another water body and returned to the Kansas River without additional movement events were classified as returning emigrants.

RESULTS

Mark-Recapture

A total of 588 Blue Catfish were tagged between June 2018 and October 2019

(Table 3-2). The mean total length of tagged juvenile fish was 257 mm (range 190 – 396;

SD = 55) and 698 mm (range = 401 – 1330; SD = 167) for adult fish (Figure 3-3a). A total of 63 unique fish were recaptured, with two individuals recaptured twice.

Seventeen fish were recaptured during sampling, however the majority of recaptured fish

(n=48) came from anglers. Eighty-five percent of all recaptured fish were within 50 rkm of the tagging location, 57% were within 10 rkm and 31% were within 5 rkm of tagging location (Figure 3-4; Figure 3-5). The median distance between tagging and recapture location was 8.4 rkm with a mean of 33.04 rkm (SD = 77.54). The mean number of days at large for fish recaptured by anglers was 280 days (SD = 249, range = 12 – 724).

Anglers recaptured fish in five rivers; the Kansas River (n = 24), the Delaware

River downstream of Perry Reservoir (n = 10), the Missouri River (n = 12), the Osage

River, Missouri (n = 1) and the Platte River, Missouri (n = 1). The Johnson County Weir 61 was the most traversed structure, with individuals navigating both downstream (n = 4) and upstream (n = 2). The Topeka Weir was navigated by a single individual in an upstream fashion. One individual was recorded as moving downstream, and none upstream, through Bowersock Dam. Fish that traversed a dam structure were only reported in 2019 or 2020.

Microchemistry

A total of 146 Kansas River otoliths were used for microchemistry analysis. The mean total length for juvenile fish used in microchemistry analysis was 226 mm (range

100 – 400; SD = 74) and 674 mm (range = 424 – 1,208; SD = 140) for adult fish (Figure

3-3b). The mean water Sr:Ca differed among the water bodies sampled (ANOVA: F5 66 =

29.37, P < 0.001) (Figure 3-6). The Kansas River had the highest water Sr:Ca (mean =

4.17 mmol/mol, SD = 0.56). Water Sr:Ca overlapped among Perry, Milford and Tuttle

Creek reservoirs and the Missouri River. Clinton Reservoir exhibited the lowest water

Sr:Ca (mean = 2.34 mmol/mol, SD = 0.24). The Sr:Ca signatures of Perry, Milford and

Tuttle Creek overlapped considerably and were classified as Reservoir signatures.

The recent environmental history of otoliths collected within the Kansas River displayed substantial variation in Sr:Ca values (range = 0.70 – 1.93, SD = 0.25), indicating recent immigrants from other water bodies. Otolith Sr:Ca values of known environments and juvenile fish collected in segment two was positively correlated to water Sr:Ca ( y = 0.3195x – 0.0559; R2 = 0.60, P < 0.001) (Figure 3-7).

Four categories were used for assigning natal environments; the Kansas River, the

Missouri River, Clinton Reservoir, and Reservoir (e.g., Milford/Perry/Tuttle Creek). 62

Values representing regions of significant overlap among water bodies were classified as indistinguishable environments (i.e., Kansas R. / Missouri R., Missouri R. / Clinton Res.,

Kansas R. / Reservoir). Movement patterns observed from mark-recapture events were used to distinguish Reservoir and Missouri River environments. Fish captured in segment three with signatures indicating Missouri River or Clinton Reservoir were classified as

Reservoir signatures as upstream passage of Bowersock Dam was not observed.

Additionally, fish with signatures indicating Reservoir captured in segments one or two were classified as Missouri River as downstream passage of Bowersock Dam was minimal.

Adult fish captured in segments one and two had relatively equal proportions of the adult fish stock originated from the Kansas River and Missouri River (Table 3-3;

Figure 3-8). Additionally, the proportional distribution of natal environments varied little between adult fish collected in segments one and two. A distinguishable difference in the proportional distribution of natal environments was present in segment three. Reservoir environments contributed 50% - 75% of juveniles and 64%- 87% of adults collected upstream of Bowersock Dam. A higher proportion of juvenile fish displayed Kansas

River origins compared to adults of the same river segment, particularly in segment two.

A high percentage (85%) of juvenile fish in segment two had natal origins indicating the

Kansas River, with no contributions from other, distinguishable environments. Natal origins clearly indicating Clinton Reservoir were not observed.

The percent of juvenile residents was relatively high for segments one (59%) and two (80%) compared to segment three (22%), however residents represented a small percentage of adult fish for all segments (Figure 3-9; Table 3-4). Adult returning 63 emigrants were absent in segment three, but the percent of returning emigrants were relatively similar among segment one (26%) and segment two (35%). Segment three contained a high percent of adult reservoir immigrants (75%) and segment two had the highest percentage of transient fish (52%). A higher percentage of immigrant fish were present in segment one (26%) compared to segment two (9%), however similar proportions were observed among other movement patterns for reaches below Bowersock

Dam.

DISCUSSION

Contributions of Blue Catfish from the Missouri River to the Kansas River suggest that connectivity of large-river habitats provide considerable influx of adult stock to connected tributary systems. Additionally, a high proportion of fish within connected reaches of the Kansas River used multiple river systems throughout their lifetime with few classified as residents of the Kansas River. Tributary habitats provide important recruitment contributions and habitat access for main-stem populations of various large- river fishes (Gorman and Stone 1999; Firehammer and Scarnecchia 2006; Neely et al.

2009; Pracheil et al. 2009; Humston et al. 2011; Pracheil et al. 2018). Our observations support the importance of tributary and main-stem connectivity for large-river fish through the viewpoint of a tributary population.

We expected a high proportion of resident catfish in reaches disconnected from the Missouri River. However, we observed relatively equal proportions of resident fish across the gradient of Missouri River connectivity. A high proportion of juvenile and adult fish in segment three originated from tributary reservoirs suggesting that reservoir 64 contributions may act as a surrogate to main-stem connectivity in isolate river reaches.

Unlike large-river connectivity, stock contributions from reservoirs are unidirectional and may impact the abundance, size structure and vital rates of downstream populations

(Jager 2006; Weber et al. 2013; Pracheil et al. 2014). River reaches above Bowersock

Dam also have unidirectional connectivity with downstream reaches, prohibiting the return of entrained individuals as evident by the lack of returning adult emigrants in segment three.

Populations with limited movement and unidirectional stock contributions may experience density-dependent consequences. The population above Bowersock Dam exhibits higher mortality and a truncated size structure compared to downstream river reaches (Chapter 2, this thesis). These results suggest unidirectional connectivity with reservoirs and disconnection from main-stem environments influences population characteristics within this reach. Increased abundance of piscivorous fishes, are likely to influence prey-community abundance, including native or imperiled prey species (Knight et al. 2005). High abundance of Blue Catfish, a generalist omnivore, will likely impact prey-species populations and fish community structure regardless of historical species presence (Schmitt et al. 2019).

Consistent influx of reservoir recruitment provides potential opportunities for relaxed harvest regulations. Relaxed harvest regulations provide additional opportunities for recreational anglers and may be used to mitigate density-dependent consequences for river reaches with high reservoir contributions. However, relaxed harvest regulations may not alleviate over-abundance within the upper Kansas River as angler exploitation is estimated to be low (Chapter 4, this thesis) (Davis et al. 2012). A cooperative strategy 65 incorporating relaxed harvest regulations within both lotic and lentic environments may be used if managers seek to limit reservoir recruitment to lotic environments. Continual monitoring efforts of the fish community and population characteristics within systems receiving reservoir contributions are imperative when considering changes in stocking rates or harvest regulations.

Mark-recapture data provided a useful tool for informing microchemistry analyses but required assumptions that may have decreased the resolution and accuracy of our results. For example, a proportion of fish collected below Bowersock may have occupied reservoir environments, but were labeled as Missouri River because separating these environments was not possible with Sr:Ca data alone. Additional chemical markers are commonly used to provide higher resolution to the environmental history of fish within river systems (Ziegler and Whitledge 2011; Laughlin et al. 2016; Spurgeon et al. 2018a).

Stable oxygen isotopes analysis would assist future efforts to partition reservoir or river habitats within this system, as increased water residence time among lentic environments promotes high evaporation rates of lighter oxygen isotopes compared to lotic environments (Hoefs 2004). This information would provide additional insight into the dispersal of reservoir fish within the entire Kansas River and alleviate concerns about density-dependent effects or ecological ramification of reservoir contributions in upstream reaches.

The similarities observed in population characteristics (Chapter 2, this thesis), movement and environmental history of river reaches below Bowersock Dam coupled with the limited, unidirectional connectivity this barrier provides supports adopting two spatial scales for investigating and managing Blue Catfish in the Kansas River, with 66

Bowersock Dam as a point of division. However, management strategies for Blue Catfish and other mobile, large-river fishes are likely to be ineffective when limited to a single body of water as these species operate across complex river networks (Siddons et al.

2017; Spurgeon et al. 2018b). The mass effects paradigm suggests regional processes

(i.e., movement and dispersal) rather than local environmental effects influence the community structure of large-river specialists (Chase et al. 2005; Grant et al. 2007;

Brown and Swan 2010). Therefore, appropriate management of Blue Catfish and other mobile, large-river fishes relies on regional strategies that incorporate complex movement and dispersal patterns of populations occupying dendritic riverine networks

(Pracheil et al. 2012). Interjurisidictional collaboration across connected river-networks is imperative as large-river systems commonly represent borders for fisheries management agencies (Koehn 2013; Pope et al. 2016; Siddons et al. 2017).

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Table 3-1. Summary statistics of Sr:Ca (mmol/mol) for water samples, the peripheral 30 μm of otolith samples and predicted otolith values from linear regression between water and otolith signatures.

Water Body Water Otolith Predicted Otolith n Mean SD n Mean SD Value SE 95% CI Clinton Res. 6 2.34 0.24 5 0.79 0.11 0.81 0.06 0.44-1.17 Kansas R. 47 4.17 0.56 124 1.23 0.25 1.39 0.04 1.03-1.74 Milford Res. 4 3.30 0.31 5 1.22 0.11 1.11 0.03 0.76-1.46 Missouri R. 7 3.12 0.24 1.05 0.03 0.71-1.40 Perry Res. 4 3.04 0.55 6 1.11 0.12 1.03 0.03 0.68-1.38 Tuttle Creek Res. 4 3.43 0.19 5 1.07 0.15 1.15 0.03 0.80-1.50

Table 3-2. Summary of tagging effort and otolith collection of juvenile (100 – 400 mm) and adult (> 400 mm) Blue Catfish across three reaches of the lower Kansas River. Sites indicate the river reach within each river segment (Figure 3-1).

Segment Site Otolith Collection Tagged Juvenile Adult Juvenile Adult 1 KR1 26 10 8 161 KR2 19 15 14 50 45 25 22 211

2 LR1 2 4 1 LR2 7 1 3 10 LR3 4 15 3 22 LR4 10 6 29 LR5 2 2 14 15 30 15 75

3 TR1 4 3 60 8 TR2 7 2 17 54 TR3 8 15 69 TR4 7 6 36 11 20 98 167

Overall 71 75 135 453

Table 3-3. Proportional distribution of natal environments for juvenile (< 400 mm) and adult (> 400 mm) Blue Catfish captured in three reaches of the lower Kansas River.

Segment Natal Environment Juvenile Adult Combined n % n % n % Kansas River 24 56 9 33 33 47 Missouri River 10 23 12 44 22 31 1 Kansas R. / Missouri R. 7 16 3 11 10 14 Missouri R. / Clinton Res. 2 5 3 11 5 7

Kansas River 11 85 11 35 22 50 Missouri River 0 10 32 10 23 2 Kansas R. / Missouri R. 2 15 5 16 7 16 Missouri R. / Clinton Res. 5 16 5 11

Kansas River 2 25 3 14 5 17 3 Kansas R. / Reservoir 2 25 5 23 7 23 Reservoir 4 50 14 64 18 60

Table 3-4. Proportional distribution of environmental history movement patterns for juvenile (< 400 mm) and adult (> 400 mm) Blue Catfish captured in three reaches of the lower Kansas River.

Segment Movement Pattern Juvenile Adult Combined n % n % n % Resident 20 59 1 5 21 40 Transient 3 9 8 42 11 21 1 Returning Emigrant 5 15 5 26 10 19 Immigrant 6 18 5 26 11 21

Resident 8 80 1 4 9 27 Transient 1 10 12 52 13 39 2 Returning Emigrant 1 10 8 35 9 27 Immigrant 2 9 2 6

Resident 2 22 1 8 3 14 Transient 1 11 2 17 3 14 3 Returning Emigrant 2 22 2 10 Immigrant 4 44 9 75 13 62

Figure 3-1. Location of water sample collection sites (white diamonds) on the Kansas River. Study area was divided into three segments at the location of anthropogenic barriers; the Johnson County Weir (A), Bowersock Dam (B) and the Topeka Weir (C). Segments are further divided into sampling sites (e.g., KR1, KR2).

Figure 3-3. Length-frequency distributions and mean lengths (dashed) for juvenile (dark grey) and adult (grey) Blue Catfish used in (a) microchemistry and (b) mark-recapture analyses.

Figure 3-4. Distance traveled and orientation of individual movement events for Blue Catfish tagged in the three river reaches of the Kansas River. Orientation of bars represent the direction a fish traveled within in Kansas River (solid), Delaware River (dotted) or the greater Missouri River system (dashed). Asterisks indicate an individual captured in a Missouri River tributary, excluding the Kansas River. 80

Figure 3-5. Summary of distance traveled for Blue Catfish captured through sampling (grey) and anglers (black).

Figure 3-6. Boxplots depicting the median, range, inter-quartile ranges and mean of water Sr:Ca (mmol/mol) from potential natal environments of Blue Catfish collected in the lower Kansas River.

Figure 3-7. Relationship between water Sr:Ca and otolith Sr:Ca for Blue Catfish from this study (solid line; y = 0.3195x – 0.0559; R2 = 0.60, p<0.001) and Laughlin et al. (2016) (dotted line; y = 0.2135x + 0.0668).

Figure 3-8. Proportional distribution of natal environments for juvenile (TL < 400 mm) and adult (TL > 400 mm) Blue Catfish captured in three reaches of the lower Kansas River (Table 3-3). Vertical lines represent anthropogenic barriers that allow (dashed) or prohibit (solid) upstream passage of Blue Catfish.

Figure 3-9. Proportional distribution of environmental history movement patterns for juvenile (TL < 400 mm) and adult (TL > 400 mm) Blue Catfish captured in three reaches of the lower Kansas River (Table 3-4). Vertical lines represent anthropogenic barriers that allow (dashed) or prohibit (solid) upstream passage of Blue Catfish.

CHAPTER 4 CONCLUSIONS, FUTURE RESEARCH AND MANAGEMENT IMPLICATIONS

CHAPTER 2

CONCLUSIONS This study examined vital rates (i.e., growth and mortality), size structure, condition, and relative abundance of Blue Catfish Ictalurus furcatus in the Kansas River.

The size and stature of anthropogenic barriers presented a unique opportunity to examine the influence of main-stem (i.e., Missouri River) connectivity on tributary population characteristics. We observed little variation in relative abundance and condition along the connectivity gradient; however, variation among years was notable. Catch per unit effort of substock-length fish was higher during the low water year in 2018 compared to the high-water year in 2019. Mean relative weights across segments indicated a healthy population despite low water conditions in 2018. Mean length of disconnected reaches were greater than connected reaches at ages three and six, and relatively equal at age ten.

River segments with main-stem connectivity displayed lower annual mortality (A= 14%

& 15%) and higher proportions of large fish (PSD-M =9 – 11, PSD-T = 3−5) compared to disconnected reaches (A= 22%; PSD-M = 3, PSD-T = 0). This study is the first to examine Blue Catfish population characteristics within the Kansas River and provides important baseline data for future population monitoring efforts and regulation modeling. 86

FUTURE RESEARCH 2.1 Future investigation of upstream river reaches

Approximately 100 rkm of the upper Kansas River were not investigated during this study. The population characteristics of the unsampled reaches are likely to reflect those of segment three as in-stream habitat closely resembles that of segment three

(Paukert and Makinster 2009). However, additional sampling effort is needed to verify this assumption. The upper reaches of the Kansas River likely have increased reservoir contributions due to an additive effect of lower natural recruitment and proximity to

Tuttle Creek and Milford reservoirs. Ascertaining vital rates and other population characteristics (i.e., size-structure, relative abundance, condition) within this reach is an important component to ensure future management efforts.

2.2 Regulation modeling

Modeling various harvest restrictions for exploited populations is a critical component for the longevity of recreational fisheries (Taylor 1981; Johnson 1995). The lack of historical information regarding the spatial use and population characteristics of

Blue Catfish in the Kansas River limits the understanding of how this population may be affected by various regulatory strategies. Consequently, Blue Catfish within the Kansas

River are currently managed with a state-wide creel of five individuals with no size restriction. The present study provides baseline information that may be used to model the effects of different harvest regulations. Understanding how this population is likely to be impacted by various management strategies and exploitation levels is a key component to achieving desired results for this fishery. 87

CHAPTER 3

CONCLUSIONS Blue Catfish tagged in the Kansas River were recaptured in five different rivers and individual movement was highly variable (0.01 – 475 rkm). Upstream passage was not documented at Bowersock Dam, suggesting segment three is isolated from Missouri

River contributions. The Topeka Weir was traversed by a single individual traveling upstream and the Johnson County Weir was traversed multiple times in both a downstream (n=4) and upstream (n=2) orientation. Adult fish (> 400 mm) collected within river reaches connected to the Missouri River displayed relatively equal natal contributions from the Kansas River (34% - 48%) and Missouri River (38% - 65%). A high percentage of the adult fish (64% - 87%) sampled in river reaches disconnected from the Missouri River originated from Kansas River tributary reservoirs. A higher proportion of juvenile fish displayed localized natal origins compared to adult fish captured in the same river reaches. Residents represented a small percentage (4% - 8%) of adult fish among all segments. Segment three contained a high percent of adult reservoir immigrants (75%) and segment two had the highest percentage of transient fish (52%).

Our data provide additional resolution to the movement and dispersal patterns of Blue

Catfish within large-river tributary systems, highlight the significance of stock contributions from adjacent river systems, and provide empirical support for adopting management strategies that incorporate the species’ use of dendritic river networks.

FUTURE RESEARCH

3.1 Spatio-temporal resolution of ambient water signatures within the Kansas River basin

Understanding the spatio-temporal variation in ambient water signatures is a key component to accurately summarizing the environmental history of individual fish using otolith microchemistry analyses. Studies that provide high spatial resolution microchemistry results often incorporate multiple years of repetitive water samples

(Ziegler and Whitledge 2011, Laughlin et al. 2016). Maintaining a basin-wide database of annual water samples would benefit future research efforts employing otolith microchemistry of Blue Catfish and other mobile species within the Kansas River basin.

Increased sample size coupled with additional chemical markers (e.g., δ18O) may assist managers in differentiating among Milford, Perry and Tuttle Creek reservoirs. The natural flow regime of the Kansas River is greatly altered by the number of impoundments constructed for flood control and may result in variable ambient water chemistry depending on which reservoir is contributing to the flow the most.

3.2 Kansas River tributary use

The relatively low proportion of fish in segment three that displayed transient movement patterns across their environmental history suggests limited use of Kansas

River tributaries. However, brief forays may not have been reflected in otolith microchemistry analyses as fish must remain in a body of water for a length of time before depositing otolith signatures reflective of ambient water signatures. Multiple fish

(n = 10) tagged in segment three were captured by anglers in the Delaware River downstream of Perry Reservoir where angling pressure appears concentrated. These 89 recaptures suggest the upper Kansas River population use tributary systems seasonally.

Spillways may provide important thermal refugia from the Kansas River during low water conditions and offer an abundance of entrained prey. Seasonal use of spillway areas by Blue Catfish provides opportunities for recreational harvest that may play an important role in future management strategies. Information regarding the seasonal use of tributary systems not within the study area (i.e., Big Blue, Republican and Smokey Hill rivers) is important to further understand the spatial use of the upstream population.

3.3 Angler use

Data provided by angler-recaptured fish indicate lower exploitation within the lower Kansas River compared to adjacent river systems. The proportion of fish harvested by anglers was greater in the Delaware River (0.70) and the Missouri River system (0.86) compared to the Kansas River (0.38). Within the lower Kansas River, a greater percentage of fish captured by anglers were harvested in segment two (40%) and segment three (30%) compared to segment one (6%); however, sample size for segment two (n =

4) and segment three (n = 3) were small compared to segment one (n = 16). A large number of fish captured in segment one were captured by catch-and-release oriented anglers (i.e., tournament anglers), suggesting angler use within this system may differ from historical precedence of harvest oriented catfish anglers (Eder 2011, Quinn 2011).

Additionally, a consumption advisory for bottom feeding fish species has been in effect for several decades from Bowersock Dam to the Wakarusa River confluence. It remains unknown how this advisory affects recreational harvest of Blue Catfish within this reach and downstream reaches. 90

Additional information regarding angler effort and harvest within the Kansas

River and tailwater river systems, coupled with angler attitudes for various regulations, is imperative to understand how the angling public desires this resource’s management.

Creel surveys may be difficult due to limited access and the low number of boat anglers we observed in segments two and three. Supplemental or alternative approaches such as mail surveys or counsel with special interest groups may be required to provide a holistic understanding of this resource’s use at a broad spatial scale. Understanding how this public trust resource is used is an important step for modeling the effect of various regulations.

GENERAL MANAGEMENT IMPLICATIONS FOR BLUE CATFISH

Kansas Department of Wildlife, Parks and Tourism (KDWPT) currently manages reservoir Blue Catfish populations in northeast Kansas for both harvest and trophy opportunities (Ben Neely, KDWPT personal communication). To achieve this objective, the four reservoirs discussed in this study are currently managed with restrictive harvest regulations. Tuttle Creek, Perry and Clinton reservoirs have a five fish daily creel limit with a 35-inch minimal length and Milford Reservoir has a 25 – 40 inch protected slot with a five fish daily creel including one over 40 inches. The Kansas and Missouri rivers are currently managed with a state-wide creel of five individuals with no size restriction despite restrictive harvest regulations on large reservoirs. The size structure represented in this study coupled with anecdotal evidence of trophy-length fish suggests that the lower Kansas River and Missouri River offer ample opportunity for trophy-oriented fishermen within the state of Kansas.

The low harvest rates observed in the Kansas River suggests limited angler exploitation within this system compared to adjacent river systems (i.e., Delaware and

Missouri rivers). Limited public access and reduced navigability limits angler use of the

Kansas River, particularly in segments two and three. The limited number of anglers that reported fish in segment two and segment three fished from the riverbank at either public access points (i.e., boat ramps, dams) or adjacent private land. Conversely, fish captured in segment one were primarily captured by boat anglers who frequently practiced catch- and-release. The high angler harvest within adjacent river systems coupled with the high proportion of transient and immigrant fish suggests that restrictive harvest regulations limited to the Kansas River may not yield desired results for this population. 92

The present study supports adopting two spatial scales for investigating and managing Blue Catfish in the Kansas River, with Bowersock dam as a point of division.

The current state-wide regulation appears adequate to maintain healthy populations for both river reaches as contributions from adjacent systems is high and exploitation appears low. The absence of trophy-length fish, higher mortality estimates and large contribution of reservoir populations observed in segment three suggest that liberal harvest regulations may be suitable for the upstream reaches. Reaches below Bowersock currently offer ample opportunity for anglers to catch memorable- and trophy-length fish, however future regulatory strategies implemented to promote trophy-quality fishing in this system may benefit from more restrictive harvest regulations within the connected river systems, particularly the Missouri River. Additionally, relaxed harvest regulations for the lower population may not illicit changes to the size-structure or estimated mortality due to the transient nature of the population and limited angler exploitation.

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