University of New Orleans ScholarWorks@UNO University of New Orleans Theses and Dissertations Dissertations and Theses Summer 8-5-2019 The development and evaluation of small specialized turtle excluder devices to reduce sea turtle bycatch in various small shrimp gears Meghan P. Gahm University of New Orleans, [email protected] Follow this and additional works at: https://scholarworks.uno.edu/td Part of the Aquaculture and Fisheries Commons Recommended Citation Gahm, Meghan P., "The development and evaluation of small specialized turtle excluder devices to reduce sea turtle bycatch in various small shrimp gears" (2019). University of New Orleans Theses and Dissertations. 2665. https://scholarworks.uno.edu/td/2665 This Dissertation is protected by copyright and/or related rights. It has been brought to you by ScholarWorks@UNO with permission from the rights-holder(s). You are free to use this Dissertation in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Dissertation has been accepted for inclusion in University of New Orleans Theses and Dissertations by an authorized administrator of ScholarWorks@UNO. For more information, please contact [email protected]. The development and evaluation of small specialized turtle excluder devices to reduce sea turtle bycatch in various small shrimp gears A Dissertation Submitted to the Graduate Faculty of the University of New Orleans in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Engineering and Applied Science Earth and Environmental Sciences by Meghan P. Gahm B.S. University of North Carolina Wilmington, 2010 M.S. University of Rhode Island, 2014 August, 2019 Dedication To my parents, Allan and Holly Gahm. For their unwavering support, love, encouragement, and appreciation for nature. Mom and Dad, this manuscript is for you, and most importantly, it is because of you and for that, I am eternally grateful. ii Acknowledgments I would first like to thank my advisor, Dr. Martin O’Connell for this opportunity and entrusting me throughout the research process. His guidance and patience has been instrumental in the success of my dissertation. Thank you to my other committee members, Dr. Ioannis Georgiou, Dr. Malay Hajra, Dr. Pamela Plotkin, and John Mitchell. The collective expertise and input of my entire committee has been invaluable and I will be forever grateful for their guidance. You all have provided me with substantial support and I will continue to look up to you in the years to come. In addition, I would like to thank the other staff in the NMFS Harvesting Systems Unit, especially Jeffrey Gearhart who has served as a mentor throughout this research. His support and assistance, especially with the early fieldwork was monumental in the success of this project. Thank you to the rest of the NMFS staff who participated in the TED development, diving evaluations in Panama City, and try net catch evaluations. From species identification to different knot types and welding tips, the lessons I have learned from you all are ones I could never find in a book. I am so grateful for your patience, sense of humor, and breadth of knowledge you were kind enough to share with me. This research would not have been possible without the participation of the many commercial fishermen who allowed us the opportunity to do the catch evaluations on their vessels. The cooperation of the fishing industry was monumental in the success of this study. Thank you also to John Alexander and Eric Diaddorio who aided in data collection and were an incredible asset in completing the fieldwork, especially during periods of extreme time constraints. Lastly, I would like to thank my friends and family for their endless support and encouragement. My parents, to whom this manuscript is dedicated as well as my siblings, Sarah, Matt, and Shannon. You have been there for me and provided nothing but reassurance every step of the way. You remind me to enjoy the best aspects of this work and have helped me get through the tougher moments and without you all, none of this is possible. Thank you to my family for always being my cheerleaders, comic relief, and constant source of love and support. iii Table of Contents List of Figures ......................................................................................................................v List of Tables .................................................................................................................... vii Abstract ............................................................................................................................ viii Chapter 1 ..............................................................................................................................1 Introduction ..............................................................................................................1 Methods..................................................................................................................10 Results ....................................................................................................................22 Discussion ..............................................................................................................35 References Cited ....................................................................................................41 Chapter 2 ............................................................................................................................45 Introduction ............................................................................................................45 Methods..................................................................................................................52 Results ....................................................................................................................56 Discussion ..............................................................................................................74 References Cited ....................................................................................................80 Chapter 3 ............................................................................................................................83 Introduction ............................................................................................................83 Methods..................................................................................................................89 Results ....................................................................................................................94 Discussion ............................................................................................................107 References Cited ..................................................................................................112 Appendix I-Towing and Catch Data ................................................................................114 Appendix I- IACUC Approval .........................................................................................133 Vita ...................................................................................................................................148 iv List of Figures Figure 1.1 Diagram of a typical TED design .......................................................................2 Figure 1.2 Sea turtle captures in try nets from 1997-2017 ..................................................4 Figure 1.3 Diagram of a typical try net configuration .........................................................5 Figure 1.4 Drawing of prototype TEDs tested in gear evaluations....................................13 Figure 1.5 TED performance with and without additional extension ................................15 Figure 1.6 The R/V Caretta used in all try net testing .......................................................17 Figure 1.7 Study area for inshore 8-ft try net catch evaluations ........................................18 Figure 1.8 Study area for offshore 10-ft try net catch evaluations ....................................19 Figure 1.9 Leatherback model going through 28 x 24-in (71 x 61-cm) TED ....................23 Figure 1.10 Juvenile turtle testing in 28 x 24-in tombstone TED ......................................24 Figure 1.11 Percent difference of catch by category in 8-ft try net testing .......................25 Figure 1.12 Box plots for shrimp, bycatch, and total catch in 8 ft. try net testing.............26 Figure 1.13 Density plot of shrimp catch in 8 ft. try net testing ........................................27 Figure 1.14 Density plot of bycatch in 8-ft try net testing .................................................28 Figure 1.15 Catch composition for the 8-ft try net testing .................................................29 Figure 1.16 Percent difference of catch by category in 10-ft try net testing .....................31 Figure 1.17 Box plots for shrimp, bycatch, and total catch in 10 ft. try net testing...........32 Figure 1.18 Density plot of shrimp catch in 10-ft try net testing .......................................33 Figure 1.19 Density plot of bycatch in 10-ft try net testing ...............................................34 Figure 1.20 Catch composition for the