1 BIOLOGY AND CONSERVATION OF SEA TURTLES IN BAJA CALIFORNIA, MEXICO by Wallace J. Nichols _____________________ Copyright © Wallace J. Nichols 2003 A Dissertation Submitted to the Faculty of the SCHOOL OF RENEWABLE NATURAL RESOURCES In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY WITH A MAJOR IN WILDLIFE ECOLOGY In the Graduate College THE UNIVERSITY OF ARIZONA 2 0 0 3 2 Before the final oral defense the student obtains the Approval Pages from the Degree Certification Office. Original signatures are required on both final copies. 3 STATEMENT BY AUTHOR This dissertation has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this dissertation are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author SIGNED: ________________________________ 4 ACKNOWLEDGEMENTS In my first meeting as a graduate student I sat on one side of a large rectangular table in Room 1 in the basement of the Biological Sciences East Building at the University of Arizona. Facing me were an ichthyologist (Dr. Donald Thomson), a wildlife ecologist (Dr. Cecil Schwalbe), and an emeritus sea turtle biologist (Dr. John Hendrickson). After presenting my proposal to study the biology and conservation of sea turtles in Baja California for my doctoral research I was surprised by their response. “There really aren’t enough turtles left to accomplish your goals in a reasonable amount of time,” I was told. With that we set out on what has become nearly a decade of sea turtle research, conservation and education that has reached south to Central America and west to the waters off Japan. Since that day my advisors have provided enthusiastic research advice, constructive criticism and professional guidance as my efforts have been seemingly guided by the wind. I first thank all of them and especially Jeff Seminoff for their encouragement and friendships. In the field, especially during the first months of research, the help of many experienced fishermen probably saved my life. Left to my own devices it is likely that I’d be tangled in a mass of turtle net adrift on the sea, somewhere between Mexico and Japan. I cannot adequately explain the patience of the men who assisted this project. Mil gracias to all of the fishermen who have taught me, and who have opened their boats, homes, kitchens, and minds to me. Antonio and Bety Resendiz have been wonderful colleagues to work with, but also role models and friends. Their commitment to the conservation of marine resources in Bahía de los Angeles sets a standard few can meet but all aspire to. A large, diverse group of people, friends, family, organizations and foundations has contributed in many ways this work. To all of them I owe my confidence in and commitment to the belief that in learning and education lie the restoration and conservation of much of the world’s biological diversity, wilderness, and natural resources. As there are literally thousands of names to mention, and at the risk of leaving one out I’ll simply say, thank you. 5 TABLE OF CONTENTS LIST OF TABLES…………………………………..……………...……………………11 LIST OF FIGURES…………………………………………………….………………..15 ABSTRACT……………………………………………………………….……………..20 GENERAL INTRODUCTION….………………..……………………………………...22 Organization of the Project…………………………………………………..…….….24 Organization of the Dissertation……………………………………………..…….….28 Description of the Region…………………………………………………..…….…...30 Description of Main Study Areas………………………...…………………………...36 Literature Cited…...…………………………………………………………………...39 Tables and Figures…………………………………………………………………….44 CHAPTER 1. ASPECTS OF SEA TURTLE LIFE HISTORY IN BAJA CALIFORNIA, MEXICO Abstract…………………………………...…………………………………………...52 Introduction……………………………………………………………………………53 Identification of the five species of sea turtle inhabiting Baja California waters…………………………………………………...………….....55 Species-specific life history characteristics…………………………………………...60 Green turtle, Chelonia mydas……………………………………………………....60 Loggerhead turtle, Caretta caretta…………………………………………………74 Olive ridley turtle, Lepidochelys olivacea……………………………………….…83 Hawksbill turtle, Eretmochelys imbricata…………………………………….……89 6 TABLE OF CONTENTS—Continued Leatherback turtle, Dermochelys coriacea…………..……………………………97 Summary…………………………………………………………………………..…102 Literature Cited………………………………………………………………………103 Tables & Figures……………………………………………………..………………115 CHAPTER 2. FROM BLACK STEER TO SACRED COW: HISTORIC AND CONTEMPORARY SEA TURTLE USE IN BAJA CALIFORNIA, MEXICO Abstract………………………………………………………………………………135 Introduction & history of sea turtle fisheries………………………………...………137 Modern sea turtle fisheries………………………………………………………...…143 History of sea turtle conservation………………………………………………..…..146 The cultural context of sea turtles……………………………………………..……..151 Problems in Baja California sea turtle conservation efforts…………………………154 Recommendation & potential solutions…………………………………………...…158 Summary…………………………………………………………………………..…161 Literature Cited………………………………………………………………………163 Tables & Figures…………………………………………………………..…………169 CHAPTER 3. STRANDINGS, INCIDENTAL TAKE, AND HUNTING: MORTALITY PATTERNS OF SEA TURTLES ALONG THE BAJA CALIFORNIA PENINSULA, MEXICO (1994-1999). Abstract……………………………………………………………………..………..175 Introduction…………………………………………………………………………..176 Methods………………………………………………………..……………………..180 7 Results………………………………………………………………………………..186 TABLE OF CONTENTS—Continued Discussion………………………………………………………………………..…..190 Incidental Capture of Sea Turtles in Baja California Fisheries…………...………191 Directed Capture and Domestic Use of Sea Turtles………………………………194 Other Causes of Sea Turtle Mortality………………………………………..……201 Mortality Synopsis by Species…………………………………………...………..205 Summary…………………………………………………………………………..…209 Recommendations……………………………………………………………………211 Literature Cited………………………………………………………………………213 Tables & Figures…………………………………………………………..…………223 CHAPTER 4. TRANSPACIFIC MIGRATION OF A LOGGERHEAD TURTLE MONITORED BY SATELLITE TELEMETRY Abstract………………………………………………………………………………239 Introduction…………………………………………………………………..………240 Methods………………………………………………………………………………243 Results………………………………………………………………………..………245 Discussion……………………………………………………………………………247 Swimming speeds of migrating turtles…………………………………..………..248 Migration path……………………………………………………………………..249 Navigational cues………………………………………….………………………251 Conservation implications…………………………………………………...……253 8 Literature Cited………………………………………………………………………255 TABLE OF CONTENTS—Continued Tables & Figures………………………………………………………………..……265 CHAPTER 5. HOMING MIGRATIONS OF EAST PACIFIC GREEN TURTLES (CHELONIA MYDAS) INVESTIGATED BY SATELLITE TELEMETRY Abstract………………………………………………………………..……………..270 Introduction……………………………………………………………..……………272 Methods………………………………………………………………………………275 Results………………………………………………………………………..………278 Discussion……………………………………………………………………………284 Homing migrations……………………………………………………………..…284 Station-keeping movements……………………………………………….………286 Swimming speeds…………………………………………………………………288 Conservation implications………………………………...………………………190 Literature Cited………………………………………………………………………293 Tables & Figures……………………………………………………………..………299 CHAPTER 6. ORIGINS OF GREEN TURTLES, CHELONIA MYDAS, FORAGING IN THE WATERS OF THE BAJA CALIFORNIA PENINSULA, MEXICO Abstract……………………………………………………………………...……….313 Introduction…………………………………………………………………………..315 Methods………………………………………………………………………………321 Results and Discussion………………………………………………………………324 9 Literature Cited………………………………………………………………………330 Tables & Figures……………………………………………………………………..339 10 TABLE OF CONTENTS—Continued CHAPTER 7. WHAT IS A BLACK TURTLE? THE EAST PACIFIC GREEN TURTLE PROBLEM Abstract………………………………………………………………………………348 Introduction………………………………………………………………………..…350 Nomenclature and Taxonomy……………………………………………………..…353 Genetics………………………………………………………………………………355 Morphology………………………………………………………..…………………357 War Games: towards an Apolitical Sea Turtle……………………...…………...…..369 The Real East Pacific Green Turtle Problem……………………………………...…376 Conclusions…………………………………………………...……………...………381 Literature Cited………………………………………………………………………385 Tables & Figures………………………………………………………..……………394 CHAPTER 8. TOWARDS A CONSERVATION MOSAIC: A CASE STUDY OF SEA TURTLE PROTECTION IN BAJA CALIFORNIA, MEXICO Abstract………………………………………………………………………………404 Introduction…………………………………………………………………………..406 The Sea Turtle Case Study…………………………………………...………………410 The Community-based Research Approach…………………………………………414 Combining Scientific and Local Research Knowledge…………………...…………417 Education, Broadly Defined…………………………………………………………420 Sea Turtle Reserves and Protected Areas……………………………………...…….423 Globally Relevant Local Action…………………………………………………..…426 11 TABLE OF CONTENTS—Continued Enforcement by Committee……………………………………………….…………428 Monitoring……………………………………………………………………...……432 Signs of Success…………………………………………………………………..…434 Conclusions and Recommendations…………………………………………………438 Literature Cited………………………………………………………………………441 Tables and Figures……………………………………………...……………………452 CHAPTER 9. SUMMARY