SPATIAL, TEMPORAL, AND DIETARY OVERLAP OF LEATHERBACK SEA TURTLES (DERMOCHELYS CORIACEA) AND OCEAN SUNFISHES (FAMILY MOLIDAE) By Nicole A. Desjardin A Thesis Submitted to the Faculty of The Charles E. Schmidt College of Science in Partial Fulfillment of the Requirements for the Degree of Master of Science Florida Atlantic University Boca Raton, FL May 2005 Copyright by Nicole A. Desjardin 2005 i i SPATIAL, TEMPORAL, AND DIETARY OVERLAP OF LEATHERBACK SEA TURTLES (DERMOCHELYS CORIACEA) AND OCEAN SUNFISHES (FAMILY MOLIDAE) By Nicole A. Desjardin This thesis was prepared under the direction of the candidate’s thesis advisor, Dr. Jeanette Wyneken, Department of Biology, and has been approved by the members of her supervisory committee. It was submitted to the faculty of The Charles E. Schmidt College of Science and was accepted in partial fulfillment of the requirements for the degree of Master of Science. SUPERVISORY COMMITTEE: ____________________________ Thesis Advisor ____________________________ ____________________________ ______________________________ Chairman, Department of Biology _____________________________________________ Dean, The Charles E. Schmidt College of Science __________________________________________ _________________ Vice President for Research and Graduate Studies Date ii i ACKNOWLEDGEMENTS This research project would not have been possible if not for the generous supply of aerial and longline bycatch data from the NOAA Fisheries Service, Southeast Fisheries Science Center (Miami and Pascagoula Laboratories) and the Northeast Fisheries Science Center. I thank D. Abercrombie, A. Bertolino, C. Brown, G. Diaz, S. Epperly, L. Garrison, J. Poffenberger, N. Thompson, and W. Witzell from the Miami Lab. Other NMFS personnel guided me in my data analysis including G. Fulling, K. Mullin, W. Hoggard, and D. Palka. Statistical assistance was provided by D. Gawlik, J. Harlin, T. Monson, and M. Salmon. I could not have completed the GIS analysis without the help of and B. Anazeski, C. Johnson, M. Villanueva, and S. Wong. Special thanks also to R. Kenney and the North Atlantic Right Whale Consortium for sharing their ideas and data. Gastrointestinal tract samples for this study were collected with the help of S. Barco, L. Belskis, J. Conrad, P. Davis, C. DeMaye, K. Dodge, K. Durham, M. Godfrey, K. Holloway– Adkins, T. Norton, G. Novak, L. Otlein, and C. Trapani. Special thanks to M. Conti, E. DeMaye, D. Lynch, and K. Singel, with the state and federal Fish and Wildlife departments. The following people provided logistical assistance: J. Garzaniti, A. Pride, Sgt. Mattox, Manalapan Town Manager Dunham. I also thank M. Gardner, E. King, and C. Johnson for assisting with necropsies and photography. D. Calder, R. Condon, M. Frick, J. Higgins, and R. Mariscal provided valuable help in nematocyst identification. Samples obtained outside of Florida were shipped to Florida Atlantic University under the US FWS Regional endangered species blanket permit # 697823 and Florida Marine Turtle Permit # 073. iv I especially thank my advisor, Jeanette Wyneken, and my committee members, Mike Salmon and Nancy Thompson, for their guidance, and my friends and family who encouraged me through it all. v ABSTRACT Author: Nicole A. Desjardin Title: SPATIAL, TEMPORAL, AND DIETARY OVERLAP OF LEATHERBACK SEA TURTLES (DERMOCHELYS CORIACEA) AND OCEAN SUNFISHES (FAMILY MOLIDAE) Institution: Florida Atlantic University Thesis Advisor: Dr. Jeanette Wyneken Degree: Master of Science Year: 2005 Investigation of the spatio-temporal movements of leatherback sea turtles (Dermochelys coriacea) and ocean sunfishes (family Molidae) as well as analyses of their prey support the hypothesis that they may occupy the same ecological niche. This study examined the spatial and temporal occurrences of sunfishes (Mola mola and Masturus lanceolatus) and leatherbacks in the western Atlantic Ocean and assessed dietary overlap. Analyses of leatherback and sunfish distributions, gleaned from aerial surveys, showed greater spatial and temporal overlap along the Northeast coast of North America than in the Gulf of Mexico. Both species co-occur more often during warmer months. Pelagic longline fisheries bycatch data revealed varying patterns of occurrence across the year, and do not correlate with coastal distribution patterns. Nematocysts found within GI tract contents of stranded animals indicate that they may feed on similar prey, identified as cnidarians in the classes Hydrozoa, Scyphozoa, Anthozoa, Cubozoa, and Staurozoa. v i TABLE OF CONTENTS LIST OF TABLES.......................................................................................................................viii LIST OF FIGURES ....................................................................................................................... ix Part I............................................................................................................................................... xi ABSTRACT................................................................................................................................... xi INTRODUCTION .......................................................................................................................... 1 METHODS ..................................................................................................................................... 3 RESULTS ....................................................................................................................................... 7 DISCUSSION............................................................................................................................... 13 APPENDIX................................................................................................................................... 21 LITERATURE CITED ................................................................................................................. 30 Part II ............................................................................................................................................ 60 ABSTRACT.................................................................................................................................. 60 INTRODUCTION ........................................................................................................................ 61 METHODS ................................................................................................................................... 63 RESULTS ..................................................................................................................................... 65 DISCUSSION............................................................................................................................... 66 LITERATURE CITED ................................................................................................................. 74 vi i LIST OF TABLES Part I Table 1: Aerial surveys used to estimate leatherback and sunfish co-occurrence in the U.S. Atlantic shelf waters. .................................................................................................................... 44 Table 2: Survey effort and number of animals sighted for the Northeast. Numbers reflect sightings from aerial surveys (TO 95, TO 98, TO 02, MATS 95, and CETAP).......................... 46 Table 3: Survey effort and number of animals sighted in the GOM. Numbers reflect sightings from aerial surveys (GoMEX 92, 93, 94 and GulfCet I & II). ..................................................... 46 Table 4: Longline fishing effort (# of longlines fished) and numbers of leatherbacks and sunfishes caught in the Northeast (NEC,MAB, NED), taken from POP data set......................... 46 Table 5: Longline fishing effort (# of longlines fished) and numbers of leatherbacks and sunfishes caught in the Gulf of Mexico (GOM), taken from POP data set. ................................. 47 Table 6: Longline fishing effort (# of longlines fished) and numbers of leatherbacks and sunfishes caught in the Northeast (NEC,MAB, NED), taken from FLS data set......................... 47 Table 7: Longline fishing effort (# of longlines fished) and numbers of leatherbacks and sunfishes caught in the Gulf of Mexico (GOM), taken from FLS data set................................... 47 Part II Table 1: Stranded leatherbacks used in this study, listed in order by stranding date. Stranding ID’s are assigned by the stranding coordinators. CCL = curved carapace length in cm, CCW = curved carapace width in cm......................................................................................................... 81 Table 2: Stranded sunfish used in this study, listed in order by stranding date............................ 82 Table 3: Nematocyst types identified in this study and their distribution within five classes of cnidarians. Based upon Mariscal (1974). -, absent; +, present; *, found only in this class .......... 82 Table 4: Distribution of the 6 nematocyst types identified in my study specimens (grouped by season)........................................................................................................................................... 83 Table 5: Estimated size ranges of the 6 nematocyst types observed. Measurements (in micrometers,.................................................................................................................................. 83 vi ii LIST OF FIGURES Part I Fig. 1. Pelagic longline