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Distribution, Abundance, and Behavior of the Cownose Ray, Rhinoptera Bonasus (Mitchill 1815), in Lower Chesapeake Bay

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Distribution, Abundance, and Behavior of the Cownose Ray, Rhinoptera Bonasus (Mitchill 1815), in Lower Chesapeake Bay W&M ScholarWorks Dissertations, Theses, and Masters Projects Theses, Dissertations, & Master Projects 1992 Distribution, abundance, and behavior of the cownose ray, Rhinoptera bonasus (Mitchill 1815), in lower Chesapeake Bay Robert A. Blaylock College of William and Mary - Virginia Institute of Marine Science Follow this and additional works at: https://scholarworks.wm.edu/etd Part of the Ecology and Evolutionary Biology Commons, Environmental Sciences Commons, and the Marine Biology Commons Recommended Citation Blaylock, Robert A., "Distribution, abundance, and behavior of the cownose ray, Rhinoptera bonasus (Mitchill 1815), in lower Chesapeake Bay" (1992). Dissertations, Theses, and Masters Projects. Paper 1539616571. https://dx.doi.org/doi:10.25773/v5-3by6-gq28 This Dissertation is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Dissertations, Theses, and Masters Projects by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. University Microfilms International A Bell & Howell Information Company 3 0 0 North Z eeb Road, Ann Arbor, Ml 48106-1346 USA 313/761-4700 800/521-0600 Order Number 9226639 Distribution, abundance, and behavior of the cownose ray, Rhinoptera bonasus (Mitchill 1815), in lower Chesapeake Bay Blaylock, Robert Alvie, Ph.D. The College of William and Mary, 1992 UMI 300 N. ZeebRd. Ann Arbor, MI 48106 DISTRIBUTION, ABUNDANCE, AND BEHAVIOR OF THE COWNOSE RAY, RHINOPTERA BONASUS (MITCHILL 1815), IN LOWER CHESAPEAKE BAY A Dissertation Presented to The Faculty of the School of Marine Science The College of William and Mary in Virginia In Partial Fulfillment Of the Requirements for the Degree of Doctor of Philosophy by Robert A. Blaylock 1992 This dissertation is submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy & Robert A. Blaylock Approved, June 1992 Roger Maim, Ph.D. Committee Chairman/Advisor jrKksjfr :— Herbert M. Austin, Ph.D. William D. DuPaul, Ph.D. \ ick^Ph.D. Franklin F. Snelsoft, Vrr., Ph.D. University of Centural\ Florida Orlando, Florida Dedicated to the memory of my father, R. A. Blaylock, Jr. TABLE OF CONTENTS Page ACKNOWLEDGMENTS.......................................... vi LIST OP TABLES........................................ viii LIST OP FIGURES.......................................... X ABSTRACT.............. xi CHAPTER 1. INTRODUCTION AND BACKGROUND.................... 2 CHAPTER 2. COWNOSE RAYBIOLOGY ............................ 7 Species Description.................................. 7 Life History........................................ 10 Distribution........................................ 11 Behavior............................................ 13 Feeding Ecology..................................... 14 CHAPTER 3. DISTRIBUTION AND ABUNDANCE OP THE COWNOSE RAY IN LOWER CHESAPEAKE BAY........................... 17 Introduction........................................ 17 Methods............................................. 19 Results............................................. 24 Discussion.......................................... 36 CHAPTER 4. SWIMMING BEHAVIOR OP THE COWNOSE RAY .........45 Introduction........................................ 45 TABLE OF CONTENTS (CONTINUED) Page Methods and Materials.............................. 50 Results........................................ 53 Discussion..........................................86 CHAPTER S. FEEDING ECOLOGY OF THE COWNOSE RAY IN LOWER CHESAPEAKE BAY..................................92 Introduction....................................... 92 Methods ....................... 94 Results.............................................95 Discussion..... 104 CHAPTER 6. ADDITIONAL OBSERVATIONS AND CONCLUSIONS 107 Conclusion........................................ 110 LITERATURE CITED....................................... 112 VITA.................................................... 129 V ACKNOWLEDGEMENTS This study owes much to the assistance of many people; however, my committee chairman and advisor, Roger Mann was responsible for encouraging and supporting this study from its inception and, for this, I owe him a debt of gratitude. I thank my thesis committee for their comments, and particularly the comments of Jack Musick on several manuscripts which have resulted from aspects of this work. I also appreciate Jack's cooperation in obtaining aerial survey data and specimens. Many VIMS employees and graduate students helped with various phases of this study and their help is greatly appreciated. In particular, I thank D. Keinath and W. Teas for co-observing with me on aerial surveys, J. Keinath, J. Perry, C. Roegner, and P. Baker for assisting in biotelemetry tracking, and J. Defosse and D. Estes for assisting in the collection of rays for stomach content examination. I thank J. Whitcomb for his valuable advice and assistance. The flying skill and dedication of VIMS pilot, Sam White was instrumental in the success of the aerial surveys. Finally, I appreciate the cooperation of Captain Donnie Green of Gloucester Point and Captain Kenny Ethridge of Virginia Beach. Both kindly provided me with live cownose rays for the tracking studies. vii LIST OF TABLES Table Page 3.1. Summary of aerial surveys............................ 26 3.2. Estimated monthly cownose ray abundance..............29 4.1. Cownose ray biotelemetry tracking sessions.......... 55 4.2. Details of cownose ray track No. 86-1...............60 4.3. Details of cownose ray track No. 87-1...............65 4.4. Details of cownose ray track No. 87-2...............70 4.5. Details of cownose ray track No. 87-3.............. 74 4.6. Details of cownose ray track No. 88-1.............. 78 4.7. Details of cownose ray track No. 89-1...............82 4.8. Cownose ray swimming velocity compared with tidal velocity................................. 89 5.1. Catches of cownose rays for stomach and spiral valve collection............................. 96 5.2. Details of trawl-caught cownose ray specimens....... 99 viii LIST OF FIGURES Figure Page 2.1. View of cownose ray.................................. 9 3.1. Chesapeake Bay aerial survey sections...............20 3.2. Frequency distribution of cownose ray school sizes....................................... 22 3.3. Distribution of perpendicular sighting distances and probability density function......... 31 3.4. Relationship between cownose ray school size and perpendicular sighting distance................ 32 3.5. Monthly mean cownose ray abundance................. 33 3.6. Charts of cownose ray sighting locations........... 35 4.1. Schematic of transmitter and harness................51 4.2. Cownose ray tracking locations......................56 4.3. Chart of movements of cownose ray No. 86-1......... 59 4.4. Angular movements of cownose ray No. 86-1.......... 62 4.5. Chart of movements of cownose ray No. 87-1......... 64 4.6. Angular movements of cownose ray No. 87-1.......... 66 4.7. Chart of movements of cownose ray No. 87-2......... 69 4.8. Angular movements of cownose ray No. 87-2.......... 71 4.9. Chart of movements of cownose ray No. 87-3......... 73 X LIST OF FIGURES (CONTINUED) Figure Page 4.10. Angular movements of cownose ray No. 87-3.......... 75 4.11. Chart of movements of cownose ray No. 88-1......... 77 4.12. Angular movements of cownose ray No. 88-1.......... 79 4.13. Chart of movements of cownose ray No. 89-1......... 83 4.14. Angular movements of cownose ray No. 89-1.......... 84 5.1. Chart showing cownose ray capture locations........ 97 5.2. Regression of spiral valve content weight against cownose ray weight........................ 103 ABSTRACT Aspects of the ecology of the cownose ray, Rhinoptera bonasus, in the lower Chesapeake Bay and its tributaries were studied using aerial surveys, biotelemetry, and examination of stomach contents. The Chesapeake Bay was surveyed by airplane during 1986-1989, to examine the distribution of cownose rays and estimate their abundance using line transect methods. Cownose rays resided in Chesapeake Bay throughout the summer months, entering in early June and emigrating
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