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Spatial and Temporal Distribution, Haulout Use and Movement Patterns of Steller Sea Lions (Eumetopias Jubatus) in Northern California

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Spatial and Temporal Distribution, Haulout Use and Movement Patterns of Steller Sea Lions (Eumetopias Jubatus) in Northern California SPATIAL AND TEMPORAL DISTRIBUTION, HAULOUT USE AND MOVEMENT PATTERNS OF STELLER SEA LIONS (EUMETOPIAS JUBATUS) IN NORTHERN CALIFORNIA. By Allison R. Fuller A Thesis Presented to The Faculty of Humboldt State University In Partial Fulfillment of the Requirements for the Degree Master of Science in Biology Committee Membership Dr. Patricia D. Goley, Committee Chair Dr. Erik Jules, Committee Member Dr. Michael Mesler, Committee Member Dr. Jeffrey Black, Committee Member Dr. Michael Mesler, Graduate Coordinator December, 2012 ABSTRACT SPATIAL AND TEMPORAL DISTRIBUTION, HAULOUT USE AND MOVEMENT PATTERNS OF STELLER SEA LIONS (EUMETOPIAS JUBATUS) IN NORTHERN CALIFORNIA. Allison R. Fuller I describe the spatial and temporal distribution, abundance and habitat use of Steller sea lions (Eumetopias jubatus) in northern California between 2006 and 2011 obtained through shore and at-sea surveys and by tracking branded individuals. Understanding Steller sea lion habitat use is critical in designing and implementing near- shore management initiatives such as the Marine Life Protection Act (MPLA) initiative. The MLPA initiative process began in northern California in 2009, affecting areas offshore of Mendocino, Humboldt and Del Norte counties. Between the Oregon border and Trinidad, California (Humboldt County) there is one rookery (Southwest Seal Rock) and eight non-breeding haulouts. Steller sea lions are more abundant on haulouts in northern California during the late spring and summer months than during the rest of the year. When Steller sea lions are numerous in the area, their distribution is influenced by age/sex class and breeding status. Adult males were seen more frequently on in-shore ii haulouts in both Trinidad and Crescent City, CA in late spring/early summer suggesting that these haulouts serve as staging areas for breeding or near-breeding aged bulls (Otter Rock mean = 7 ± 1, Sea Lion Rock mean = 4 ± 2, Castle Rock mean = 16 ± 5). Breeding Steller sea lion abundance peaked at Southwest Seal Rock during the June and July pupping and breeding season (mean = 574 ± 38). Presence of pups peaked at haulouts in Trinidad the late summer/early fall suggesting that these sites serve as “nurseries” for females and their dependent young (Otter Rock mean = 5 ± 2, Turtle Rocks mean = 6.3 ± 3). Steller sea lion pups were branded on Southwest Seal Rock in 2002 and 2004 by Oregon Department of Fish and Wildlife (ODFW) and National Marine Mammal Lab (NMML) as part of a larger population dynamics study. Females from these cohorts are now actively breeding in northern California, while fewer branded males have come back to the rookery during breeding season (49 females vs. 18 males). Resights of branded females were more common than males. Of the 62 branded animals that were seen in more than one year during the study period, 73% were female. Male Steller sea lions tended to be resighted farther from the natal site than females. Steller sea lions frequented many haulouts during a single year and females, in particular, showed fidelity to the northern California and southern Oregon near shore waters. iii ACKNOWLEDGEMENTS I want to thank my major advisor Dr. Dawn Goley, for introducing me to the exciting world of marine mammal biology. I have seen things, and studied animals that I never thought I would have, and I’m extremely thankful for the opportunity. Thank you to my graduate committee members, Dr. Erik Jules, Dr. Michael Mesler, Dr. Jeffrey Black and Dr. Luke George. Your advice and comments were invaluable throughout the entire process. Thank you to Aicha Ougzin, Carrie Hudson, Greg Hacker, Allison Lui, Kellan Korcheck, Ashley Donnell, Brett Carrothers, Wiley Archibald and Janet Thibault for assistance during the 2009-2011 offshore survey seasons. Special thanks to Janet Thibault for passing on her knowledge to me, and teaching me so much during the 2009 survey season. Thank you to Gerry McChesney (US Fish and Wildlife Service) and Dr. Rick Golightly (HSU) for assistance during the 2009 field season, as well as sparking my interest in the amazing world of seabirds. Thank you to all of the undergraduate MMERP (Marine Mammal Education and Research Program) interns for assistance with Steller sea lion shore surveys from 2006-2011, and for reminding me how exciting this field is when I’ve been bogged down with work. Thanks to Steve Monk (HSU) for all of the lessons in boat operation and maintenance – I learned so much from watching and listening to you. Special thanks to Dr. Robert Van Kirk (HSU) for assistance with statistical analyses. I want to especially thank Greg Hacker for reading hundreds of abstracts and thesis drafts and for listening for the last four years of graduate work – iv you’re the best. Thanks to Wiley Archibald, Mary Beth Pacewicz, Cari Zourdos, Ashley Donnell and Carrie Hudson for being fantastic lab mates (and honorary lab mates) – I’ll be waiting for you all on the outside. A huge amount of gratitude goes to the National Marine Mammal Lab (Pat Gearin, Tom Gelatt and Bob Delong), Oregon Department of Fish and Wildlife (Robin Brown, Bryan Wright and Susan Riemer), Kim Raum-Suryan, and Jonathan Scordino, for sharing of select brand resights. This data added so much to my thesis, and was greatly appreciated. Special thanks to Pat Gearin and Bryan Wright for offering advice and answering numerous questions throughout the process – I appreciate all of your help. Lastly I want to thank my wonderful family for their love and support. Funding for this project was provided by the National Marine Mammal Laboratory and Stuyvesant/Humboldt oil spill (1999) settlement. Travel funds to conferences were provided by the Humboldt State University presidential fund, and from the California State University’s Council on Ocean Affairs, Science and Technology (COAST) program. All offshore work was completed under National Marine Fisheries Service permit no. 14097-01. v TABLE OF CONTENTS ABSTRACT ........................................................................................................................ ii ACKNOWLEDGEMENTS ............................................................................................... iv LIST OF TABLES ............................................................................................................ vii LIST OF FIGURES ........................................................................................................... ix LIST AND ACRONYMS AND THEIR DEFINITIONS ................................................ xii INTRODUCTION .............................................................................................................. 1 MATERIALS AND METHODS ...................................................................................... 10 Study Area ..................................................................................................................... 10 Shore Surveys ................................................................................................................ 16 Offshore Surveys ........................................................................................................... 19 Analysis of Photographs................................................................................................ 21 Multivariate Analysis .................................................................................................... 26 Brand Analysis .............................................................................................................. 27 RESULTS ......................................................................................................................... 29 Spatial and temporal distribution of Steller sea lions .................................................... 29 Haulout use and movement of branded Steller sea lions .............................................. 39 DISCUSSION ................................................................................................................... 51 Spatial and temporal distribution of Steller sea lions .................................................... 51 Haulout use and movement of branded Steller sea lions .............................................. 57 LITERATURE CITED ..................................................................................................... 63 vi LIST OF TABLES Table 1. Steller sea lion pups branded at Oregon and California rookeries from 2001 – 2011. All brands have one to three numerical digits, and one letter – a Y for Southwest Seal Rock brands, and an R for Rogue Reef brands. ........................................................ 12 Table 2. Number of shore-based surveys of Steller sea lion haulouts in per month from 2006-2011 ......................................................................................................................... 18 Table 3. Number of boat surveys of Steller sea lion haulouts per month from 2006 to 2011................................................................................................................................... 20 Table 4. Percentage of monthly average total Steller sea lions counted at Southwest Seal Rock, the rookery site. ...................................................................................................... 31 Table 5. “Scores” or “Correlation coefficients” generated from simple correspondence analysis. Scores were generated for the first two “correspondences” for each survey year – 2009-2011. ....................................................................................................................
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