University of New Hampshire University of New Hampshire Scholars' Repository Doctoral Dissertations Student Scholarship Winter 2008 Conserving dolphins and fishermen: Combining science and local knowledge to reduce cetacean bycatch Erika A. Zollett University of New Hampshire, Durham Follow this and additional works at: https://scholars.unh.edu/dissertation Recommended Citation Zollett, Erika A., "Conserving dolphins and fishermen: Combining science and local knowledge to reduce cetacean bycatch" (2008). Doctoral Dissertations. 465. https://scholars.unh.edu/dissertation/465 This Dissertation is brought to you for free and open access by the Student Scholarship at University of New Hampshire Scholars' Repository. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contact [email protected]. CONSERVING DOLPHINS AND FISHERMEN: COMBINING SCIENCE AND LOCAL KNOWLEDGE TO REDUCE CETACEAN BYCATCH BY ERIKA A. ZOLLETT Bachelor of Science, Bates College, 2000 Master of Environmental Management, Duke University, 2004 DISSERTATION Submitted to the University of New Hampshire in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Natural Resources and Earth Systems Science December 2008 UMI Number: 3348321 INFORMATION TO USERS The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleed-through, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. ® UMI UMI Microform 3348321 Copyright 2009 by ProQuest LLC. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest LLC 789 E. Eisenhower Parkway PO Box 1346 Ann Arbor, Ml 48106-1346 This dissertation has been examined approved. Dissertation Director, Dr. Andrew A. Rosenberg, J Professor of Natural Resources Q^v^ Dr. Andrew B. Cooper, Associate Professor, Simon Fraser University, Affiliate Research Assistant Professor of Natural Resources and Earth Systems Science QkJ^H <3^S£=i Dr. Chris Gla*^ Director of Northeast Consortium, Research Professor of Zoology fL+j Dr. Andrew J. Re! Associate Professo: Marine Conservation Biology, Nicholas School of the Environment, Duke University^ / Dr. Madeleine Hall-Arber, Anthropologist, Center for Marine Social Sciences, Massachusetts Institute of Technology, Sea Grant College Program 8 QeCft»v*UT /ZOOS Date ACKNOWLEDGEMENTS Many people helped to make this research possible. First, I would like to thank my advisor, Dr. Andrew Rosenberg, whose guidance, support, and encouragement made it all possible. I could not have asked for a more supportive or more generous advisor. I would also like to thank my committee members. Dr. Andrew Cooper worked tirelessly and patiently with me to grasp the statistical concepts used throughout this study. Dr. Madeleine Hall-Arber generously donated her time to making sure I spoke the same language as fishermen, and that my methodology was consistent with social science and anthropology disciplines. She also provided thorough edits that helped strengthen this dissertation. Drs. Andrew Read and Chris Glass also provided crucial guidance in this research. I would like to thank the Northeast Fisheries Observer Program for use of the observer data. I would also like to acknowledge Chris Orphanides at the National Marine Fisheries Service who was instrumental in making this research possible. Chris provided much of the data that was used in the study. Other technical assistance was provided by Jim Manning, Joan Palmer, Tim Miller, Richard Merrick, Debi Palka, Ben Galuardi, Michael Routhier, and Ernst Linder. This study would not have been possible without the New England bottom trawl fishermen. Their willingness to share their knowledge, experiences, and perspectives have made me a better scientist and a more effective conservationist. iii This study was funded by the Northeast Consortium and the United States Marine Mammal Commission. Other travel and research funds were also provided by the University of New Hampshire Graduate School, Marine Program, and Natural Resources and Earth Systems Science graduate program. Finally, I would like to thank my family for their unconditional love and support, which helped me get through many of the challenges I faced during this study. They taught me that I can do anything that I put my mind to. I thank Eric, my husband, for being my partner in this experience and in life. IV TABLE OF CONTENTS ACKNOWLEDGEMENTS iii LIST OF TABLES vii LIST OF FIGURES viii ABSTRACT ix CHAPTER PAGE I. UNDERSTANDING BYCATCH TO DESIGN EFFECTIVE MITIGATION STRATEGIES 1 Introduction 1 Trawl Fisheries .2 Interactions 5 Bycatch Characteristics 7 Bycatch Mitigation 16 Bycatch Management 21 II. MODELING BYCATCH OF ATLANTIC WHITE-SIDED DOLPHINS IN THE NORTHWEST ATLANTIC BOTTOM TRAWL FISHERY USING FISHERY OBSERVATIONS 26 Introduction 26 Methods 43 Results 53 Discussion 55 v III. USING TRADITIONAL ECOLOGICAL KNOWLEDGE OF FISHERMEN TO REDUCE ATLANTIC WHITE-SIDED DOLPHIN BYCATCH IN THE NORTHWEST ATLANTIC BOTTOM TRAWL FISHERY 60 Introduction 60 Methods 80 Results 82 Discussion 101 IV. MANAGEMENT OF MARINE MAMMAL BYCATCH BASED ON DATA FROM SCIENTIFIC RESEARCH AND FISHERMEN'S KNOWLEDGE. Ill Fisheries Management Process Ill Incorporating Fishermen's Knowledge 117 Dolphin Bycatch Management 122 LIST OF REFERENCES 126 APPENDICES 139 INSTITUTIONAL REVIEW BOARD APPROVAL 140 INTERVIEW INFORMED CONSENT 142 INTERVIEW GUIDING QUESTIONS 144 vi LIST OF TABLES Table 1: Parameter estimates and significance levels for the variables in the model 54 vn LIST OF FIGURES Figure 1: Study Area 44 Figure 2: Probability of Bycatch of Atlantic White-sided Dolphin by the Northeast Bottom Trawl Fishery Based on Fishery Observer Records 57 Figure 3: Map Used for Fishery Interviews Depicting the Probability of Bycatch of Atlantic White-sided Dolphins 81 Figure 4: Sizes of Vessels Operated by All Interviewed Fishermen 83 Figure 5: Length of Fishing Trips of All Interviewed Fishermen 83 Figure 6: Primary and Secondary Fishing Areas of All Interviewed Fishermen 84 Figure 7: Seasons with the Most Frequent Dolphin Observations by Interviewed Fishermen 87 Figure 8: Primary and Secondary Fishing Areas of Fishermen with Bycatch 90 viii ABSTRACT CONSERVING DOLPHINS AND FISHERMEN: COMBINING SCIENCE AND LOCAL KNOWLEDGE TO REDUCE CETACEAN BYCATCH By Erika A. Zollett University of New Hampshire, December, 2008 Bycatch is the portion of catch that is neither targeted nor retained by fishermen. It threatens the survival of many marine mammal populations globally, and it occurs in nearly every fishing gear type. Despite its widespread occurrence, observations of bycatch are rare, and scientific data on marine mammal bycatch are limited. Difficulties result in developing models that accurately depict the interactions. This study focuses on developing methodology to combine disparate data sources, specifically data from fishery observer programs and interviews of fishermen, to better understand these interactions and to identify effective mitigation measures. As a case study, this research investigates the spatial and temporal patterns associated with Atlantic white-sided dolphin (Lagenorhynchus acutus) bycatch in the New England bottom trawl fishery for groundfish to aid in the development of an effective bycatch reduction plan. A quasi- binomial model of the fishery observer data was developed using environmental and fishing-related covariates to describe the probability of dolphin bycatch in this fishery. Significant variables in describing dolphin bycatch included sea surface temperature (p<0.001), depth (p<0.001), and an interaction between bottom slope and depth (p<0.05). The model was mapped using geographic information systems and incorporated into ix interviews with bottom trawl fishermen to facilitate discussion on patterns of bycatch. Thirty-one bottom trawl fishermen were interviewed, and results were consistent with the probability model that bycatch was rare and was more likely to occur in offshore fishing areas. Interviewed fishermen did not relate bycatch to environmental variables and did not provide consistent responses regarding spatial or temporal patterns associated with these events. As a result, this study was unable to develop methodology to spatially combine these data sources. However, fishermen did provide useful information to scientists and fishermen. For instance, interview results suggested that area-based management would not be effective in this fishery, contrary to the results of the probability model, due to the occurrence of bycatch throughout the fishing area. Instead broad-scale measures, coupled with incentives, would be a more effective mitigation measure in this fishery. Collaborative research between fishermen and scientists or gear technologists is recommended to better understand operational patterns associated with bycatch. x CHAPTER I UNDERSTANDING BYCATCH TO DESIGN EFFECTIVE MITIGATION STRATEGIES Introduction Incidental capture in fishing activities threatens marine mammals worldwide in nearly every type of fishing gear (Northridge 1991, Read