POPULATION ASSESSMENT AND MANAGEMENT NEEDS OF A GREEN TURTLE, Chelonia mydas, POPULATION IN THE WESTERN CARIBBEAN By CATHI LYNN CAMPBELL A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2003 Copyright 2003 by Cathi Lynn Campbell This dissertation is dedicated to my mother, Georgianna Carbin, and my grandmother, Martha Bazemore, who have always supported my endeavors and helped me face many challenges throughout my life. ACKNOWLEDGMENTS Special thanks go to my graduate committee: Michael Moulton (committee chair), Jim Nichols, Jeanne Mortimer, Mel Sunquist, and Michael Binford for their guidance and support. I am also very grateful to previous members of my committee, including Richard Bodmer, Jon Allen, and Madan Oli. Selina Heppell (Oregon State University) provided much needed guidance with Chapters 5 and 6, for which I am extremely grateful. Michael Moulton is an exceptional advisor and gave me a great deal of guidance and encouragement during my final year at UF. I am grateful to Richard Franz and George Tanner for substituting for an absent committee member at my qualifying and final exams. William McCoy, a Nicaraguan fisher from Pearl Lagoon, taught me the art of “fishing turtle” and was always willing to go the extra mile to help me catch turtles for this study. I am extremely grateful for his help and for the many conversations we shared about his culture, turtles, and the world in general. I also thank Victor Renales, a turtle fisher from Awastara, who also provided guidance on turtle fishing in the early stages of the study. I am grateful to the turtle fishers of Nicaragua’s Caribbean coast for their cooperation with tag returns and sharing information about sea turtles and their culture. David Godfrey, Director of the Caribbean Conservation Corporation (CCC), allowed me access to their Tortuguero database, tag recovery information, and satellite tracking data on post-nesting females. Sebastian Troëng, CCC, was particularly helpful with providing data on the Tortuguero nesting population. Many thanks go to Cynthia iv Lagueux, Wildlife Conservation Society, for her tireless efforts to recover sea turtle tags on the Caribbean coast of Nicaragua, to the Archie Carr Center for Sea Turtle Research at the University of Florida for its many years of handling tag recoveries for the CCC, and Anne and Peter Meylan for tags recovered in Panama. I also want to thank Sjef van Eijs of DIPAL (Proyecto para el Desarrollo Integral de la Pesca Artesanal en la Región Autónoma Atlántico Sur, Nicaragua–a Dutch development project) for providing invaluable logistical support in Nicaragua. I am very grateful to Jim Hines and William Kendall of the USGS Patuxent Wildlife Research Center for providing additional guidance on band recovery data analysis. The staff of the Department of Wildlife Ecology and Conservation at the University of Florida, especially Delores Tillman, were extremely helpful during the many years of my graduate school “career.” The idea of this research project would not have come to fruition had it not been for the unwavering support and encouragement of Cynthia Lagueux. I will be forever in her debt for believing in me and for helping me face the many challenges of working and living in Nicaragua. I also want to thank my family (my sisters: Vicki Campbell, Carol Boutin, Kelly Mabe, and Amy Osorio; my mother: Georgianna Carbin, and my grandmother: Martha Bazemore) for their encouragement throughout my long tenure in graduate school. This project was financially supported by the Wildlife Conservation Society, Chelonia Institute, Chelonia Research Foundation–The Linnaeus Fund, DIPAL, Lerner- Gray Fund for Marine Research (American Museum of Natural History), and Tropical v Conservation and Development Program (University of Florida): to all of these institutions I am very grateful. This study was part of a larger program on sea turtle conservation on the Caribbean coast of Nicaragua directed by Cynthia Lagueux, of the Wildlife Conservation Society. It is my hope that the results from this study will be used in the development of a management plan for sea turtle conservation in Nicaragua to ensure the long-term survival of healthy sea turtle populations in the region. vi TABLE OF CONTENTS Page ACKNOWLEDGMENTS ................................................................................................. iv LIST OF TABLES...............................................................................................................x LIST OF FIGURES ........................................................................................................... xi ABSTRACT...................................................................................................................... xii CHAPTER 1 INTRODUCTION ........................................................................................................1 Conservation Issue........................................................................................................1 Background Information...............................................................................................3 Determining Population Status.....................................................................................6 Current Study................................................................................................................9 2 STUDY AREA ...........................................................................................................11 Caribbean Nicaragua ..................................................................................................11 Tortuguero, Costa Rica...............................................................................................13 3 ECOLOGY AND HUMAN USE OF CARIBBEAN GREEN TURTLES................17 Ecology of Green Turtles in the Caribbean with Emphasis on the Tortuguero Population ..............................................................................................................17 Life Stages...........................................................................................................18 Growth and Maturation .......................................................................................20 Reproduction .......................................................................................................22 Distribution..........................................................................................................23 Human Use of Green Turtles in the Western Caribbean ............................................26 Green Turtles as a Resource................................................................................26 Historical Use ......................................................................................................27 Current Use..........................................................................................................29 4 SURVIVAL PROBABILITIES FOR LARGE JUVENILE AND ADULT GREEN TURTLES ....................................................................................................31 Introduction.................................................................................................................31 vii Methods ......................................................................................................................33 Capture-Release and Recovery Methods.............................................................33 Nicaragua – foraging grounds ......................................................................33 Costa Rica – nesting beach...........................................................................35 Model Structure, Model Selection, and Parameter Estimates .............................36 Comparison of Survival Estimates Between Sites ..............................................40 Results.........................................................................................................................40 Mixed Large Juvenile/Adult Group (tagged on Nicaragua foraging ground).....40 Adult Female Group (tagged on nesting beach at Tortuguero, Costa Rica) .......43 Comparison Between Tagging Sites ...................................................................45 Discussion...................................................................................................................45 Potential Bias and Precision of Survival Estimates.............................................46 Comparison of Survival Estimates Between Sites ..............................................47 Conservation Implications...................................................................................50 5 ANALYSIS OF A WESTERN CARIBBEAN GREEN TURTLE POPULATION USING DETERMINISTIC MATRIX MODELS ......................................................59 Introduction.................................................................................................................59 Methods ......................................................................................................................60 Model Structure...................................................................................................60 Demographic Parameters and Model Development............................................61 Model Implementation ........................................................................................64 Results.........................................................................................................................67