Habitat Selection of Robust Redhorse Moxostoma Robustum
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HABITAT SELECTION OF ROBUST REDHORSE MOXOSTOMA ROBUSTUM : IMPLICATIONS FOR DEVELOPING SAMPLING PROTOCOLS by DIARRA LEMUEL MOSLEY (Under the Direction of Cecil A. Jennings) ABSTRACT Robust Redhorse, described originally in 1870, went unnoticed until 1991 when they were rediscovered in the lower Oconee River, Georgia. This research evaluated one hypothesis (habitat use) for explaining the absence of juveniles (30 mm – 410 mm TL) from samples of wild-caught robust redhorse. Two mesocosms were used to determine if juvenile robust redhorse use available habitats proportionately. Pond-reared juveniles were exposed to four, flow-based habitats (eddies = - 0.12 to -0.01 m/s, slow flow = 0.00 to 0.15 m/s, moderate flow = 0.16 to 0.32 m/s, and backwaters). Location data were recorded for each fish, and overall habitat use was evaluated with a Log-Linear Model. In winter, the fish preferred eddies and backwaters. In early spring the fish preferred eddies. Catch of wild juveniles may be improved by sampling eddies and their associated transitional areas. INDEX WORDS: backwaters, catostomid, eddies, habitat selection, juvenile fish, mesocosm, Moxostoma robustum, Oconee River, robust redhorse HABITAT SELECTION OF ROBUST REDHORSE MOXOSTOMA ROBUSTUM : IMPLICATIONS FOR DEVELOPING SAMPLING PROTOCOLS by DIARRA LEMUEL MOSLEY BSFR, University of Georgia, 1998 A Thesis Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE ATHENS, GEORGIA 2006 © 2006 Diarra Lemuel Mosley All Rights Reserved HABITAT SELECTION OF ROBUST REDHORSE MOXOSTOMA ROBUSTUM : IMPLICATIONS FOR DEVELOPING SAMPLING PROTOCOLS by DIARRA LEMUEL MOSLEY Major Professor: Cecil A. Jennings Committee: Mary Freeman Gene Helfman Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia May 2006 DEDICATION I dedicate this thesis to everyone who has influenced my life, from members of my immediate family to my favorite street musician and most memorable stranger. Last but not least, I dedicate this thesis to Brenda, my best friend for life! iv ACKNOWLEDGEMENTS Funding for this project was provided by the Georgia Power Company. I would like to acknowledge Jaxk Reeves and his students for assisting me in analyzing my data. I would like to thank Don Dennerline, Rebecca Cull-Peterson, Collin Shea, Steve Zimpfer, John Ruiz, Tom Reinert, and Jeff Zeigweid for their advice and encouragement. I would like to thank Tavis McLean for helping me set up my mesocosms. Special thanks to Cecil Jennings for being my academic advisor and mentor. Also, I would like to thank my committee, Mary Freeman and Gene Helfman for their guidance and support. v TABLE OF CONTENTS Page ACKNOWLEDGEMENTS.............................................................................................................v CHAPTER 1 INTRODUCTION .........................................................................................................1 Status of robust redhorse ...........................................................................................2 Hypothesis of robust redhorse decline ......................................................................3 2 LITERATURE REVIEW ..............................................................................................6 Riverine habitats........................................................................................................6 Lower Oconee River habitat......................................................................................6 Effects of Dams .........................................................................................................7 Negative implications of Sinclair Dam .....................................................................8 Habitat use of fishes ..................................................................................................9 Habitat use of juvenile suckers................................................................................10 Habitat selection of juvenile robust redhorse suckers .............................................12 Habitat selection studies..........................................................................................12 Use of mesocosms ...................................................................................................14 Hypothesis ...............................................................................................................16 Summary .................................................................................................................17 3 METHODS ..................................................................................................................18 Experimental tanks..................................................................................................18 Experimental fish ....................................................................................................25 vi Experimental design ................................................................................................26 Habitat types – flow classes ....................................................................................28 Statistical analysis ...................................................................................................29 4 RESULTS ....................................................................................................................32 Experimental tanks..................................................................................................32 Temperature analysis...............................................................................................32 Habitat use analysis .................................................................................................32 Fish movement ........................................................................................................35 5 DISCUSSION..............................................................................................................40 Preferred habitat use of juvenile robust redhorse..............................................40 Habitats avoided by juvenile robust redhorse ...................................................42 Proportional habitat use of juvenile robust redhorse.........................................43 Differences in riverine habitats .........................................................................43 Implications for sampling the Oconee River.....................................................45 6 CONCLUSION............................................................................................................49 LITERATURE CITED ..................................................................................................................50 vii CHAPTER 1 INTRODUCTION Robust redhorse Moxostoma robustum , of the family Catostomidae (suckers), is a benthic riverine fish that can grow to 760 mm total length and 7 kg in weight (Jenkins and Burkhead 1993; Evans 1994). The species was described originally by Edward Cope in 1870 based on specimens collected from the Yadkin River in North Carolina (Jenkins and Burkhead 1993). Robust redhorse then apparently went unnoticed for 121 years until its rediscovery in 1991 in the Oconee River, GA by the Georgia Department of Natural Resources (GADNR) (Evans 1994). The robust redhorse population in the Oconee River seems to consist primarily of large adults (Evans 1994), as wild juveniles ranging from 30 mm to 410 mm in total length (TL) have not been collected (Evans 1994; Jennings et al. 1996; 1998; 2005). The absence of juveniles in the Oconee River has been attributed to sampling gear inefficiency, sampling in areas that are not inhabited by juvenile robust redhorse, or an actual low abundance of juvenile robust redhorse. Therefore, whether the observed population structure results from failed recruitment or an inability to detect juvenile robust redhorse is not clear. As a result, the status of the Oconee River population and how best to manage it also are unclear. Robust redhorse is listed as an endangered species in Georgia (Evans 1996), and concerns over possible recruitment failure and eventual extinction of the species led to the formation of the Robust Redhorse Conservation Committee (RRCC) in 1995. The RRCC was formed under a Memorandum of Understanding between state and federal resource agencies, private industries, and non-governmental conservation organizations of Georgia, South Carolina, and North Carolina. The goals set by the RRCC were 1) to improve the status of the robust redhorse throughout its former range, 2) identify conservation needs for the robust redhorse and its habitat, and 3) coordinate efforts to address these needs (RRCC 1996). This study aimed to contribute to these goals by investigating the habitat preferences of juvenile robust redhorse. The ultimate objectives for this work were to better evaluate which of the competing hypotheses best explains the apparent absence of juvenile robust redhorse in samples taken from the Oconee River and to help guide efforts to restore and conserve the species. Status of robust redhorse Historically, robust redhorse occupied medium to large rivers of the Atlantic slope drainages from the Pee Dee River system in North Carolina to the Altamaha River system in Georgia (Bryant et al. 1996). Presently, wild populations of the species have been found in 1) an 85-km stretch of the Oconee River between Milledgeville and