EARLY LIFE HISTORY DYNAMICS OF A STOCKED STRIPED BASS (MORONE SAXATILIS) POPULATION AND ASSESSMENT OF STRATEGIES FOR IMPROVING STOCKING. SUCCESS IN SMITH MOUNTAIN LAKE, VIRGINIA by Trent M. Sutton Dissertation submitted to the Faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in Fisheries and Wildlife Sciences APPROVED: UL bes Oe arg OK Alan G. Heath Briar A. urphy Karol| Jett an 7 kc \ A A | J. Orth Eric P. Smith December, 1997 Blacksburg, Virginia Keywords: Striped Bass, Recruitment, Growth, Survival, Stocking _ so ft Cw oo wy Os EARLY LIFE HISTORY DYNAMICS OF A STOCKED STRIPED BASS (MORONE SAXATILIS) POPULATION AND ASSESSMENT OF STRATEGIES FOR IMPROVING STOCKING SUCCESS IN SMITH MOUNTAIN LAKE, VIRGINIA by Trent M. Sutton John J. Ney, Chair Department of Fisheries and Wildlife Sciences (ABSTRACT) The early life history dynamics of stocked, fingerling striped bass (Vorone saxatilis) were evaluated in Smith Mountain Lake, Virginia, from 1994-96 and incorporated into an individual-based model to assess various stocking strategies in terms of their largest percent increases in first-year growth, overwinter survival, and recruitment to age 1. Age-O striped bass exhibited dissimilar patterns of dispersion and size-dependent spatial distribution as a result of differences in habitat availability between stocking sites and water temperature preferences. Although size increased over the growing season, a bimodal length distribution developed by fall during both 1994 and 1995; this distribution consisted of large-mode juveniles (> 180 mm TL) that weighed several times more than small-mode fish (<140 mm TL). Differential growth was attributed primarily to size-dependent differences in food habits and diet quality: small- mode striped bass maintained a mixed, low quality diet of invertebrates and small, age-O cyprinids, while large-mode juveniles consumed only larger, energetically more profitable age-O alewives. This disparity in food habits, largely due to the inability of small-mode striped bass to consume distributionally- and morphologically-invulnerable age-O alewives, resulted in size-dependent differences in physiological well-being as large-mode juveniles had amassed greater absolute energy stores than small-mode fish by the end of the growing season. Spring sampling revealed that the bimodal length distribution had become unimodal and was comprised almost entirely of large- mode juveniles. Because the few surviving small-mode striped bass collected during spring were extremely emaciated, it appears that this size group exhausted their energy stores and, consequently, starved over the winter. Individual-based model simulation results indicated that stocking juvenile striped bass at a median total length of 52 mm on O8 June, while maintaining the current stocking density at 300,000 fingerlings, would result in the largest percent increases in first-year growth, survival, and number of age-1 recruits. This strategy was also less sensitive to perturbations in alewife population parameters and water temperature regime, and was more robust to these variations than the existing stocking scheme (300,000 fingerling striped bass with a median total length = 42 mm introduced on 15 June). ACKNOWLEDGEMENTS Throughout the course of this journey, many people have given freely of their time and thoughts. | would like to express my sincerest gratitude for these significant inputs, without which the completion of this dissertation would not have been possible. Dr. John J. Ney, my major professor, provided the guidance | needed at numerous points during my graduate education and has had a significant impact on my life. His friendship and mentoring over the past four years have been an invaluable component of my development as a professional, and his excellence as an educator, researcher, and writer have provided the standards for which | will measure my own progress in the future. Further, his humor (“] bet that dog won't let you pet him”), wit, and mannerisms have provided for an endless source of amusement and banter. Thank you for giving me the opportunity to be one of your students. The members who have served on my graduate committee, Drs. Alan G. Heath, Louis A. Helfrich, Brian R. Murphy, Richard J. Neves, Donald J. Orth, and Eric P. Smith, encouraged continual attention to scientific principles and provided valuable suggestions during the development and completion of this study. Your insights and advice truly made my graduate experience at Virginia Tech more rewarding. Numerous other people were involved in this study in a variety of ways. | particularly appreciate the efforts of Dr. Kenneth A. Rose for lending his expertise, time, and modeling skills to Chapter Il of this dissertation. Without his generous help, | would still be trying to figure out the difference between sensitivity and robustness analysis. | also thank Steve Arthur, Mike Duval, Arthur “Bud” LaRoche, and Scott Smith of the Virginia Department of Game and Inland Fisheries for their insights, advice, humor, and assistance during the field and writing aspects of this study. In addition, all of the faculty, staff, and students in the Department of Fisheries and Wildlife Sciences have made my time at Virginia Tech a rich and rewarding experience. | would particularly like to thank Daniel Michaelson for his assistance and perseverence through sometimes difficult and demanding times and conditions at Smith Mountain Lake. Special thanks also go out to David Argent, Jason Bettinger, Michael Cyterski, Ladd Knotek, Kirk Rundle, and Steve Sammons for their technical support in the field; Brian Barr, William Ensign, Kevin Leftwich, Edmund Pert, Roy Smogor, and Marty Underwood for their friendship and _ insightful discussions during my stay in Blacksburg; and Mark Kidd for his considerable devotion to rearing Phase Il striped bass at the Virginia Tech Aquaculture Facility. | am grateful to Dr. Robert Otto for awarding me a graduate research fellowship through the Electric Power Research Institute’s COMPMECH Striped Bass Key Species Program. In addition, | appreciate the financial support provided by American Electric Power/Appalachian Power Company for the field component of this study. | also owe special thanks to the faculty, staff, and students of Lake Superior State University for their patience and understanding over the past year as | completed “my opus”. | cannot adequately describe the importance of the love, support, and encouragement | received from my parents and their impact on my life. Last, but certainly not least, | thank my best friend and wife Michelle for the love, understanding, patience, and encouragement that enabled me to complete what was beginning to seem like a neverending endeavor. TABLE OF CONTENTS Tah dgele [Urey tc) p penn nnn nn 1 Chapter 1........cc cc ccccc ccc cccc eee eeseeeeeeuesseeeeeeugeceeeuseuuteceteenuggentesttnegugaenseneagags 15 INTFOCUCTION. 0... cc cccce eee eect e ene ee ene eee e seen ate ee esate ee eaeeseeeeaeeeeenaneneaes 15 STUY Ala... iccccccccec ence ence eee een ene en EEE EERE SEE E EEE SEES EOE SEER EE ES OEEEE EES 18 Striped Bass Stockings, 1994 & 1995... cccee nese ee teeeeetaeees 22 Methods........cccccccceceneceee ec cece neces eae eeeeneeteeaeeeeesaeeteneeaneeeseneneneneneees 25 Field CollectionS.............ccccccceccescence eens ence eneeeeeeteaeesaeensesenenas 25 Contribution of Phase JI FingerlingS..............scccsseveseeseeeneeeseees 27 Dispersal and Spatial DistriDUtion...............ccccceceeeeeneeeeeeeeuuees 27 First-Year Striped Bass Growth.............ccccccseeseeeeeeeeeeeetesesenas 28 Overwinter Survival.........cccccceeceeeceeeeeeteneeeeeaeeeeanteeaeeeeneenagen 31 FOO [email protected] cece ee eee eee e eee ene eens eeeeeeeseeneeteeeeeaeeneeeaaeeas 32 Diet Overlap.........ccccccccceseeeeeeeseeeeseeeesteesuseteseeeeneeeesaeenanensags 33 Predator-Prey Size Relationships..............ccccceccceeeesseteeeeesaeees 34 Physiological Indices of Health.................cccceecseseeeeeseeeeeseneees 37 Relative COndition...........cccccccceeeeeesecece ee eesaeeeeteensnaneees 37 Liver-SOmatic INGOX.........cccceeeeeeeeetesco eeseeeeneeetneeenseeenas 39 LIPId INGOX....... cece cesceceeeneseeeeeeneesaeeseeteceesaueeteeteseagans 39 Stomach-Fullness INdOX.........ccecceceesceeetear eeetneeeseeaeeaees 42 Statistical ANALYSES......ccceccccceccccceececeeeeeeseteeeseeeeeeeeeteeeeeeeeees 42 RESUITS. 0... cccc ccc cccc eee cere n nee e nn eee en ERE EEE E RHEE EE EEE EEE E EEE E EEE E EEE E EE ES 47 Field CollectionS..........cccccccessecenaeeeeeneeeenneeeeeeaseeennanetenaanenes 47 Contribution of Phase II FingerlingS..................scceeeeeeeeeneeneeee 49 Dispersal and Spatial Distribution...............cccccesecceeeeeeeeeeeeeees 50 First-Year Striped Bass Growth.........ccccccecceseeesseesvneeteeeeeeenens 56 TOF cece cence ene nee e ene ene tees nets een E REO Ee EEE EEE EEE 56 LD ccc cece nee e een e EERE ESE Eee EEE E ESSE EERE SERRE ES 62 Overwinter SUrVIVAl........ cc ccce cece cece eee ee eee eneeeeeeneeeennaeneeeaenenes 66 vi FOO Habits..... 0... cece cece cece cceeneceeecceeeteeusseuuseneuseucesauspeneeeunes 68 Striped BaSS..........ccccccceeeeeneeesceeeneeeeeenaeeeeeesseteneaaeenes 68 Black [email protected] erence eee e cnet eee e nese tte eneeaeee ees 72 Diet OVErIAP.......ccccccece cnet nent eee e net eee eee near teen reat eee teen eneeees 75 Predator-Prey Size RelationshipsS...........cccceceeseeeeeenneeeeeecneeeees