SPRING FLOW AND HABITAT-MEDIATED EFFECTS ON REPRODUCTIVE EFFORT OF THE FOUNTAIN DARTER by Harlan Thomas Nichols, B.S. A thesis submitted to the Graduate Council of Texas State University in partial fulfillment of the requirements for the degree of Master of Science with a Major in Aquatic Resources December 2015 Committee Members: Timothy Bonner, Chair Kenneth Ostrand Joseph Veech COPYRIGHT by Harlan Thomas Nichols 2015 FAIR USE AND AUTHOR’S PERMISSION STATEMENT Fair Use This work is protected by the Copyright Laws of the United States (Public Law 94-553, section 107). Consistent with fair use as defined in the Copyright Laws, brief quotations from this material are allowed with proper acknowledgement. Use of this material for financial gain without the author’s express written permission is not allowed. Duplication Permission As the copyright holder of this work I, Harlan Thomas Nichols, authorize duplication of this work, in whole or in part, for educational or scholarly purposes only. DEDICATION This work is dedicated to my parents who always took the time to foster my curiosity with the natural world. ACKNOWLEDGEMENTS I would like to thank Dr. Timothy Bonner for his guidance and his dedication. His mentorship has been invaluable throughout this and other projects. I would also like to thank Dr. Kenneth Ostrand at the USFWS and Brad Littrell at Bio-West for their help and advice in the field, Dr. Joseph Veech for serving on my committee, and Dr. Dana Garcia and Melissa Sutton for assistance with histology. Special thanks to David Ruppel for always taking the time to discuss ideas and offer insight about this project. Great appreciation and thanks extends to Cody Craig, Myranda Clark, Cory Scanes, Bianca Hernandez, and Allison Dennehey for their support and efforts in the field and laboratory. Their good nature, understanding, and willingness to sling a dipnet made the process easier. vi TABLE OF CONTENTS Page ACKNOWLEDGEMENTS .................................................................................................v LIST OF FIGURES .......................................................................................................... vii ABSTRACT ....................................................................................................................... ix CHAPTER I. SPRING FLOW, HABITAT, AND REPRODUCTION......................................1 Introduction ..................................................................................................1 Methods........................................................................................................5 Results ........................................................................................................10 Discussion ..................................................................................................13 APPENDIX SECTION ......................................................................................................24 REFERENCES ..................................................................................................................30 vii LIST OF FIGURES Figure Page 1. Flow (m3/s) throughout the study period by site (Top: Site 4-City Park, San Marcos River; Second from top: Site 3- New Channel, Comal River; Dotted line: Site 2-Old Channel, Comal River; Circles: Site 1-upper spring run, Comal River) ..................................................................................................19 2. PC analysis of habitat parameters for Fountain Darters collected across all sites (top), within site (bottom left), and across months (bottom right). ..........20 3. Proportions of ovarian stages (top) and Gonadosomatic indices (bottom) for all ovaries by month throughout the study period. Letters above GSI means indicate significant difference and numbers in parentheses below points denote sample size .......................................................................................21 4. Gonadosomatic indices (left) and proportion of ovarian stage (right) by site, throughout the study period ...................................................................................22 5. Mean Gonadosomatic indices (left) and Batch Fecundity (right) by flow environment (site) within Optimum season (top, Jan-Apr), Tailing season (middle, May-Aug), and Leading Season (bottom, Sep-Dec). Numbers below site indicate mean flow in m3/s for given season and capital letters denote site level significant difference. .................................................................23 viii ABSTRACT Reductions in Edwards Aquifer spring flows are hypothesized to reduce reproductive effort of spring-associated fishes. Purposes of this study were to test relationships among spring flow, associated habitat changes, and reproductive effort of the federally-listed Fountain Darter Etheostoma fonticola, a spring-associated fish inhabiting Comal and San Marcos rivers of central Texas. Study objectives were to quantify annual reproductive effort (i.e., ovarian stages, gonadosomatic index, and batch fecundity) across a gradient of flows (0.01 m3/s to 3.7 m3/s) and aquatic habitats using natural and anthropogenically-altered stream reaches (N = 4) within the Comal and San Marcos rivers to represent in situ flow reductions. Contrary to previous studies reporting constant year-round spawning effort, annual reproductive cycle of the Fountain Darter consisted of an optimal reproductive season (January through April), and tailing reproductive season (May through August), lack of spawning in September, and a leading reproductive season (October through December). Among reproductive seasons, stages of ovarian condition, gonadosomatic indices, and batch fecundity generally were not different along a flow gradient or among habitats, though two exceptions were noted. Gonadosomatic index and batch fecundity were greater (P < 0.05) at the higher flow environment (4.1 m3/s) during optimum reproductive season and greater (P < 0.05) at the lowest flow environment (0.01 m3/s) during the leading reproductive season. Collectively, seasonality of reproductive effort was similar to sister taxa (Cypress Darter E. proeliare, Least Darter E. microperca), though protracted, and ix reproductive effort was not related consistently to flow environment observed during the study period. However, other measures of reproductive effort (e.g., numbers of larvae hatched, survival of larvae through recruitment age) are necessary to quantify in order to assess the relationship among Fountain Darter population viability and flow environments. x I. SPRING FLOW, HABITAT, AND REPRODUCTION Introduction Groundwater extraction and subsequent reductions in surface water flows are threats to endemic aquatic fauna (Van der Kamp 1995, Acreman et al. 2000, Kollaus et al. 2015). Within the karst Edwards Plateau region of Texas, numerous springs ranging from seeps (< 0.01 m3/s) to very large spring complexes (> 9 m3/s) emanate from Trinity- Edward aquifers (Brune 1981). Sustained groundwater pumping reduces spring flows (Van der Kamp 1995). Historical record (1975-1995) of average annual pumping in the Balcones Fault Zone of the Edwards Aquifer was greater than the current groundwater extraction limit set by the Edwards Aquifer Authority (Loáiciga et al. 2000). Demand for groundwater is expected to increase as the region shifts towards a more arid climate (Loáiciga et al. 2000). Effects of groundwater extraction and surface water flow reductions are a greater ecological concern during periods of below average precipitation, specifically if surface water flows are insufficient to maintain aquatic habitats within springs inhabited by endemic species (Crowe and Sharp 1997). Spring outflows and corresponding spring runs of streams within the Edwards Plateau, collectively referred to as spring complexes, are considered as evolutionary refugia (Craig et al. 2015) and support many endemic aquatic species (Bowles and Arsuffi 1993). Two of the largest spring complexes within the Edwards Plateau region are the Comal River (8.5 m3/s; USGS Station # 0816900) and upper San Marcos River (5.0 m3/s; 08170500). Upper San Marcos River and Comal River are characterized by exceptional water quality (Groeger et al 1997, Fahlquist and Slattery 1997) and intact fish communities despite being encompassed within urbanized watersheds (Kollaus et al. 2015). 1 Concerns with groundwater extraction and federally-listed threatened and endangered species resulted in policies that restrict groundwater withdrawals in the Edwards Aquifer (Votteler 1998). The Edwards Aquifer Authority was established as an agency responsible for setting critical minimum limits of spring flows, and hence maximum allowable groundwater extraction, to protected species viability (McCarl et al. 1999). Restricting groundwater withdrawal for municipal and agricultural purposes has economic consequences. Current pumping limits are derived from Senate Bill 1477 (Texas Legislature 1993) and restrict pumping to 49,000 hectare-meters per year, which places an estimated $1.1 million loss collectively to businesses, agricultural practices, and other water users dependent upon groundwater (McCarl et al. 1999). Groundwater and surface water uses are increasing as urban and rural development continues to increase (Fitzhugh and Richter 2004). Species protected under the Endangered Species Act exist within Comal River and upper San Marcos River; this requires mediation by agencies like the Edwards Aquifer Authority to strike a balance between the