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Diet Analysis of Stranded Bottlenose Dolphins (<I>Tursiops Truncatus</I

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Diet Analysis of Stranded Bottlenose Dolphins (<I>Tursiops Truncatus</I Old Dominion University ODU Digital Commons Biological Sciences Theses & Dissertations Biological Sciences Spring 2020 Diet Analysis of Stranded Bottlenose Dolphins (Tursiops truncatus) in Virginia Kristen Marie Volker Old Dominion University, [email protected] Follow this and additional works at: https://digitalcommons.odu.edu/biology_etds Part of the Biology Commons, Ecology and Evolutionary Biology Commons, and the Marine Biology Commons Recommended Citation Volker, Kristen M.. "Diet Analysis of Stranded Bottlenose Dolphins (Tursiops truncatus) in Virginia" (2020). Master of Science (MS), Thesis, Biological Sciences, Old Dominion University, DOI: 10.25777/6bas-rj82 https://digitalcommons.odu.edu/biology_etds/113 This Thesis is brought to you for free and open access by the Biological Sciences at ODU Digital Commons. It has been accepted for inclusion in Biological Sciences Theses & Dissertations by an authorized administrator of ODU Digital Commons. For more information, please contact [email protected]. DIET ANALYSIS OF STRANDED BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) IN VIRGINIA by Kristen Marie Volker B.S. December 2008, University of New England A Thesis Submitted to the Faculty of Old Dominion University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE BIOLOGY OLD DOMINION UNIVERSITY MAY 2020 Approved by: Ian Bartol (Director) Holly Gaff (Member) Kent Carpenter (Member) Damon Gannon (Member) ABSTRACT DIET ANALYSIS OF STRANDED BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) IN VIRGINIA Kristen Marie Volker Old Dominion University, 2020 Director: Dr. Ian Bartol This study describes the diet of bottlenose dolphins (Tursiops truncatus) stranded in Virginia via stomach content analysis and considers factors such as proportion of numerical abundance and reconstructed mass, frequency of occurrence, average reconstructed prey size, prey diversity and quantity, and otolith degradation code. Fish size was estimated via regression equations established from local fish collected during the study that derive wet weight directly from otolith length or width. Squid size is estimated from previously published equations. Soniferous fishes dominated the diet, especially Atlantic croaker, spot, and seatrout spp., adding evidence to the theory that bottlenose dolphins passively listen for their prey. Noise pollution should be an important consideration for the conservation of this species. The diet was influenced by ontogenetic and seasonal changes. Prey that are relatively difficult to capture or not available to calves due to habitat, such as striped bass or longfin inshore squid, were absent in the diet of that age class. However, easy to capture prey, such as spot, became progressively less important with age. Seasonal variation in the diet was observed, with differences likely being due to changes in prey availability (due to seasonal migrations) and detectability (due to increased vocalizing during spawning) rather than changes in prey preference. Lastly, the stomachs of dolphins with external evidence of an entangling interaction contained a significantly higher proportion of recently ingested fish (using otolith code as a proxy) than those that did not. The presence of recently ingested prey is commonly referenced as an indicator of peracute underwater entrapment; however, this is the first study to quantitatively establish a significant relationship. The data presented in this study promise to enhance policy and management by establishing baseline information on natural history as well as a quantitatively assessed indicator for peracute underwater entrapment that can be referenced to study local shifts in natural history or incidence of bycatch. iii This thesis is dedicated to the researchers of “stinky science” iv ACKNOWLEDGMENTS This thesis is due to the love, support, and dirty hands of many people. My mom has always been my biggest cheerleader, but throughout this entire project, she has gone above and beyond to share her enthusiasm with me. From answering my phone calls that ranged from panic to excitement, to sitting there next to me picking through stinky stomach contents, she has been my stabilizing platform, my #1 fan, my rock. Although the mention of stomach contents usually made my sisters’ noses crinkle in disgust, I know that Laura and Rachel, though they really couldn’t believe THAT is what I was working on for my project, really did believe in me. They provided me the comic relief I needed at the end of a stressful day, my distractions from work to come back to reality, as well as the encouraging words I needed to get though my challenges. I don’t know what I’d do without you two, Laurdey Loo and Lil’ Ray! My friends have provided support in so many different forms! From assisting with different aspects of my project, to hysterical cat memes, to a drink or two at Tapped, I could not have completed this without you. Although at the end of my project I was working more on “tummies” than being the “Queen of the Dead” at work, my co-workers/friends never complained. I truly appreciate you guys understanding the work I needed to put into the project and helping me accomplish it. It was a pleasure to work with my academic advisor, Dr. Ian Bartol. His patience and understanding during this adventure to complete my Master’s while maintaining a full-time job, then moving to another state and another full-time job was priceless. He was always encouraging and supportive while demanding excellent work. I’ve also enjoyed learning from Drs. Damon Gannon, Holly Gaff, and Kent Carpenter who served on my committee. Their insights and perspective improved the project and thesis in various aspects, from project design to data presentation. Dr. Gannon also conducted the stomach contents analysis training at a workshop that was part of this project. The project would not have been possible without funding from the John H. Prescott Marine Mammal Grant Program (award number NA11NMF4390098) nor without the support of the Virginia Aquarium & Marine Science Center Foundation and the dedication of the Stranding Response Team staff, volunteers and interns, past and present. v Mark Swingle, Sue Barco, Sarah Mallette, and Maggie Lynott envisioned this project and secured the funding through the Prescott Grant Program. This project, along with a previously completed life history project, has long been a goal for Mark and Sue and I’m glad to have been a part of it. Additionally, there were many individuals and organizations that assisted with this project. Dr. Ann Pabst, Bill McLellan, and Ryan McAlarney graciously hosted and were integral in the development and success of the training workshop (lovingly dubbed “Stomacheddon”). Ryan additionally assisted in squid beak identification and offered advice in diet study logistics and analysis. Jeffrey Thompson, Maureen Fender, Katie Glanton, Alex Balke, and Anthony Bosnengo (Virginia Aquarium Acquisitions and Quarantine Department), Chad Boyce and Evan Shearer (Virginia Department of Game and Inland Fisheries), Rich Hancock (Virginia Marine Resources Commission), Trish Bargo (East Coast Observers, Inc.), and Mike Mizell and Alexis Rabon (Virginia Aquarium Education Department) collected reference specimens for the project. Hank Liao and Jessica Gilmore (Old Dominion University Center for Quantitative Fisheries Ecology) provided additional otoliths and associated data for use in building regression equations. Many Virginia Aquarium Stranding Response volunteers, interns, staff, and contractors contributed over 1,300 hours to assist with sorting stomach contents, measuring otoliths, and organizing the reference collection, especially Shannon Davis, Sarah Rose, Kathy O’Hara, Patti Volker, Karen Moyer, Alison Morin, Melissa Chromik, Bonnie Bailey, Bill Dieffenbach, Peg Goodman, Carrie Rowlands, Sarah DeVed, Ryan Ponseti, Ashley Bunch, Marcy Fundalewicz, Lauren Talley, Salma Abdel-Raheem and many more. vi TABLE OF CONTENTS Page LIST OF TABLES .......................................................................................................................................... vii LIST OF FIGURES ....................................................................................................................................... viii CHAPTER 1. INTRODUCTION ......................................................................................................................... 1 2. LOCAL PREY SIZE ESTIMATION ......................................................................................... 4 INTRODUCTION ............................................................................................................. 4 MATERIALS AND METHODS ..................................................................................... 5 RESULTS ............................................................................................................................. 7 DISCUSSION .................................................................................................................... 17 3. DEMOGRAPHIC PATTERNS OF DIET ............................................................................. 20 INTRODUCTION ........................................................................................................... 20 MATERIALS AND METHODS ................................................................................... 22 RESULTS ..........................................................................................................................
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