Modelling and mapping trophic overlap between fisheries and the world's seabirds by Vasiliki S. Karpouzi B.Sc, Aristotle University of Thessaloniki, 2001 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Zoology) THE UNIVERSITY OF BRITISH COLUMBIA May, 2005 © Vasiliki S. Karpouzi, 2005 Abstract Seabird food consumption may reveal the potential for competition between seabirds and fisheries. I ndeed, coexistence of foraging seabirds and operating fisheries inevitably results in interactions, one of which is competition for the same resources. I used GIS-based modelling at a scale of 30-min spatial cells to: (a) map the foraging distribution of seabirds; (b) predict their annual food consumption rates in a spatially-explicit manner; and (c) estimate a spatially-explicit seabird - fisheries overlap index. Information on the population size, diet composition and foraging attributes of 351 species of seabirds was compiled into a Microsoft Access database. Trophic levels, expressing the position of seabirds in the marine ecosystem, were estimated for each species using diet composition data. Global annual food consumption by seabirds was estimated to be 96.4 million tonnes (95% CI: 78.0 to 114.7 million tonnes), compared to a total catch of nearly 120 million tonnes by all fisheries. Krill and cephalopods comprised over 58% of the overall food consumed and fishes most of the remainder. The families Procellariidae (albatrosses, petrels, shearwaters, etc.) and Spheniscidae (penguins) were responsible for more than 54% of the overall food consumption. Mapping the foraging distribution of seabirds revealed that, areas near New Zealand, the eastern coast of Australia, and the sub-Antarctic islands have high seabird species richness. Hawaii and the Caribbean were the only areas north of the equator with high species richness. Temperate and polar regions supported high densities of seabirds, and most food extracted by seabirds originated there. In addition, maps of the annual food consumption rates revealed that most of the food consumed by seabirds was extracted from offshore waters rather than nearshore ones, and from areas where overlap between seabirds and fisheries was low. My trophic overlap maps identified 'hotspots' of highest potential for conflict between fisheries and seabirds. Thus, this study may provide useful insight when developing management approaches to manage marine conservation areas. ii Table of Contents ABSTRACT ii TABLE OF CONTENTS iii LIST OF TABLES iv LIST OF FIGURES vi ACKNOWLEDGEMENTS viii CHAPTER 1: GENERAL INTRODUCTION 1 1.1. Introduction 1 1.2. Seabirds in the spotlight of scientific research 3 1.3. Geographic Information Systems (GIS) as a research tool 7 CHAPTER 2: METHODOLOGY 9 2.1. Seabird species 9 2.2. Trophic Levels (TL) 10 2.3. Daily Food Intake (DFI) 12 2.4. Mapping seabirds' foraging distribution using GIS 15 2.5. The spatially-explicit seabird - fishery overlap index 19 CHAPTER 3: RESULTS 20 3.1. Seabirds' global population size 20 3.2. Trophic levels of the world's seabirds 23 3.3. Spatially-explicit foraging distribution of seabirds 26 3.4. Global estimates of total annual food consumption of seabirds 28 3.5. Spatially-explicit annual food consumption of seabirds 29 3.6. Spatially-explicit trophic overlap between seabirds and fisheries 30 3.6a. Spatially-explicit trophic overlap between Procellariidae and fisheries 33 3.6b. Spatially-explicit trophic overlap between Spheniscidae and fisheries 35 CHAPTER 4: DISCUSSION 37 4.1. The trophic position of the world's seabirds 37 4.2. Global estimates of total annual food consumption of seabirds 38 Biases and Limitations 39 4.3. Maps of the food consumption of seabirds and overlap with fisheries 41 4.4. Implications for conservation and management 43 4.5. Conclusions 44 LITERATURE CITED 47 APPENDIX A 89 iii List of Tables TABLE 2.1. 9 Orders and families of seabird species included in the study. TABLE 2.2. 12 Order-specific allometric equations to calculate Basal and Field Metabolic Rates. TABLE 2.3. 13 Food groups used to express standardized diet composition data of seabirds. APPENDIX TABLES 89 TABLE 1. 89 List of seabird species included in the study. TABLE 2. 96 International legal instruments established since the early 1970s to protect seabirds' nesting habitat and reverse seabird population declines. TABLE 3. 97 Percentage of weight or volume contribution of food groups in the diet of seabird species breeding in the Arctic. TABLE 4. 100 Percentage of weight or volume contribution of food groups in the diet of seabird species breeding in the Antarctic and on Sub-Antarctic Islands. TABLE 5. 109 Percentage of weight or volume contribution of food groups in the diet of seabird species breeding around the Indian Ocean. TABLE 6. Ill Percentage of weight or volume contribution of food groups in the diet of seabird species breeding around the Mediterranean Sea. TABLE 7. 112 Percentage of weight or volume contribution of food groups in the diet of seabird species breeding around the North Atlantic Ocean. TABLE 8. 118 iv Percentage of weight or volume contribution of food groups in the diet of seabird species breeding around the North Pacific Ocean. TABLE 9. 132 Percentage of weight or volume contribution of food groups in the diet of seabird species breeding around the South Atlantic Ocean. TABLE 10. 135 Percentage of weight or volume contribution of food groups in the diet of seabird species breeding around the South Pacific Ocean. TABLE 11. 141 Energy Density of forage prey known to occur in the diets of seabirds. TABLE 12. 144 Mean trophic levels (TL) of the world's seabirds. List of Figures FIGURE 2.1. 16 Areas of the world for which a seabird population size estimate was available. FIGURE 3.1. 20 Decline in the overall population size (in billions of individuals) of the world's seabirds (1950-2003). FIGURE 3.2. 21 Percentage contribution to the global seabird abundance (in number of individuals) of each family for the 1950s and the 1990s. FIGURE 3.3. 22 Percentage contribution to the global seabird biomass of each family for the 1950s and the 1990s. FIGURE 3.4. 23 Histogram of all trophic levels (TL) of 351 seabird species considered in the study. FIGURE 3.5. 24 Box - Whisker Plot of Trophic Levels (TL) of seabird species by family. FIGURE 3.6. 25 Box - Whisker Plot of the Trophic Level (TL) values of seabird species by foraging habitat. FIGURE 3.7. 27 Map of predicted foraging distribution of seabird species during an average year in the 1990s. FIGURE 3.8. 28 Percentage contribution of food groups to the estimated annual global food consumption of all seabird species combined. FIGURE 3.9. 29 Map of predicted global food consumption rate (in tonnes per km2) of all seabirds combined for an average year in the 1990s. FIGURE 3.10. 31 vi Map of estimated trophic overlap between all seabirds and fisheries for an average year in the 1950s, 1970s, and 1990s. FIGURE 3.11. 32 Proportion of food consumed by seabirds in the 1990s by areas of overlap with fisheries. FIGURE 3.12. 33 Map of predicted global food consumption rate of seabirds of the Procellariidae family for an average year in the 1990s. FIGURE 3.13. 34 Map of estimated trophic overlap between seabirds of the Procellariidae family and fisheries for an average year in the 1950s, 1970s, and 1990s. FIGURE 3.14. 35 Map of predicted global food consumption rate (in tonnes per km2) of seabirds of the Spheniscidae family for an average year in the 1990s. FIGURE 3.15. 36 Map of estimated trophic overlap between seabirds of the Spheniscidae family and fisheries for an average year in the 1950s, 1970s, and 1990s. vii Acknowledgements I wish to first and foremost thank my supervisor Dr. Daniel Pauly for his support, guidance, and patience, as well as for trusting me with such a demanding project. Many thanks to my supervisory committee, Ken Morgan and Dr. Jamie Smith for their assistance throughout my study. I also wish to acknowledge the contributions of many members of the 'Sea Around Us' Project, foremost Dr. Reg Watson, for all the time he sacrificed in modelling and mapping everything I asked for. Without his patience, this work would have never been completed. Many thanks, also, to Dr. Villy Christensen for valuable input and suggestions. Many thanks to Janice Doyle and Allison Barnes, my two favourite graduate secretaries, and to Rosalie and Gerry for saving my database and thesis, when my computer could no longer put up with me. A big hug to all those people who made my life look brighter during difficult times, when this thesis felt it was never going to reach an end. Thank you Yvette, Deng, Telmo, Yajie, Colette, Sheila, Chiara, Denise, Sylvie, for listening and being there for me. Kristin, for your guidance at the beginning of this project. Jean, Pablo, Marta, Simone, Robyn, Chris, Bob H., Bob L., Robby, Nathan, Lyne, for the great times inside and outside the Fisheries Centre. My friends in Greece, Ntoli, Voula, Litsa, Dimitris, for reminding me nearly every day how much they love me. My supervisor and friend, Dr. Kostas Stergiou, whom I hold responsible for viii all the 'brain-washing' that the Fisheries Centre is heaven on earth, and for sending me all the way to the other side of the planet, because he believed I could pull it through. Finally, the biggest Thank You to my family, my father Stavros, my mother Kaiti, and my sister Tina, for s upporting and e ncouraging myd ecision toe ome t o C anada, t heir financial s upport throughout my studies, and their unrestricted, unconditional love and support.