National Park Service U.S. Department of the Interior Natural Resource Stewardship and Science Pacific Harbor Seal (Phoca vitulina richardii) Monitoring at Point Reyes National Seashore and Golden Gate National Recreation Area 2016 Annual Report Natural Resource Report NPS/SFAN/NRR—2018/1719 ON THE COVER Pacific harbor seals hauled out on rocks at Point Bonita in the Marin Headlands, California. (© DAVID DONNENFIELD) Pacific Harbor Seal (Phoca vitulina richardii) Monitoring at Point Reyes National Seashore and Golden Gate National Recreation Area 2016 Annual Report Natural Resource Report NPS/SFAN/NRR—2018/1719 Sarah Codde1 and Sarah Allen2 1National Park Service, San Francisco Bay Area Network Inventory & Monitoring Program Point Reyes National Seashore 1 Bear Valley Road Point Reyes Station, California 94956 2National Park Service Science Program / Californian Cooperative Ecosystem Studies Unit University of California College of Natural Resources-ESPM 133 Mulford Hall, Berkeley, CA 94720-3114 September 2018 U.S. Department of the Interior National Park Service Natural Resource Stewardship and Science Fort Collins, Colorado The National Park Service, Natural Resource Stewardship and Science office in Fort Collins, Colorado, publishes a range of reports that address natural resource topics. These reports are of interest and applicability to a broad audience in the National Park Service and others in natural resource management, including scientists, conservation and environmental constituencies, and the public. The Natural Resource Report Series is used to disseminate comprehensive information and analysis about natural resources and related topics concerning lands managed by the National Park Service. The series supports the advancement of science, informed decision-making, and the achievement of the National Park Service mission. The series also provides a forum for presenting more lengthy results that may not be accepted by publications with page limitations. All manuscripts in the series receive the appropriate level of peer review to ensure that the information is scientifically credible, technically accurate, appropriately written for the intended audience, and designed and published in a professional manner. This report received peer review by individuals who were not directly involved in the collection, analysis, or reporting of the data, and whose background and expertise put them on par technically and scientifically with the authors of the information. Data in this report were collected and analyzed using methods based on established, peer-reviewed protocols and were analyzed and interpreted within the guidelines of the protocols. Views, statements, findings, conclusions, recommendations, and data in this report do not necessarily reflect views and policies of the National Park Service, U.S. Department of the Interior. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the U.S. Government. This report is available in digital format from the San Francisco Area Network Inventory and Monitoring website and the Natural Resource Publications Management website. If you have difficulty accessing information in this publication, particularly if using assistive technology, please email [email protected]. Please cite this publication as: Codde, S., and S. Allen. 2018. Pacific harbor seal (Phoca vitulina richardii) monitoring at Point Reyes National Seashore and Golden Gate National Recreation Area: 2016 annual report. Natural Resource Report NPS/SFAN/NRR—2018/1719. National Park Service, Fort Collins, Colorado. NPS 612/148209, 641/148209, September 2018 ii Contents Page Figures .................................................................................................................................................... v Tables ..................................................................................................................................................... v Abstract ................................................................................................................................................. vi Acknowledgments ................................................................................................................................ vii Introduction ............................................................................................................................................ 1 Background .................................................................................................................................... 1 Objectives ....................................................................................................................................... 2 Methods .................................................................................................................................................. 4 Study Area ...................................................................................................................................... 4 Sampling Design ............................................................................................................................ 6 Surveys ........................................................................................................................................... 6 Data Management and Analysis ..................................................................................................... 8 Results .................................................................................................................................................. 10 Overall .......................................................................................................................................... 10 Adult and Pup Counts During the Breeding Season ............................................................... 10 Molt Counts ............................................................................................................................. 14 Disturbances ............................................................................................................................ 14 Summaries by Site ........................................................................................................................ 19 Tomales Bay ............................................................................................................................ 19 Tomales Point .......................................................................................................................... 19 Point Reyes Headlands ............................................................................................................ 19 Drakes Estero Complex ........................................................................................................... 19 Double Point ............................................................................................................................ 20 Duxbury Reef .......................................................................................................................... 20 Bolinas Lagoon ........................................................................................................................ 20 Point Bonita ............................................................................................................................. 21 Regional Sites ............................................................................................................................... 21 Sonoma County ....................................................................................................................... 23 iii Contents (continued) Page San Francisco Bay ................................................................................................................... 23 San Mateo County ................................................................................................................... 23 Discussion ............................................................................................................................................ 26 Collaborations............................................................................................................................... 27 Season Highlights ......................................................................................................................... 27 Literature Cited .................................................................................................................................... 29 Appendix A .......................................................................................................................................... 32 iv Figures Page Figure 1. Regional harbor seal survey sites in San Francisco Bay and Sonoma, Marin, and San Mateo counties, California. ...................................................................................................... 5 Figure 2. Maximum counts of harbor seal adults and immatures during the breeding season (March-May) for 2000-2016 at Marin County sites. ................................................................ 11 Figure 3. Maximum harbor seal pup counts for 2000-2016 at Marin County sites. ........................... 11 Figure 4. Maximum harbor seal pup counts at the dominant Marin County pupping locations during the breeding season (March – May), 2000-2016. ..................................................... 12 Figure 5. Maximum harbor seal pup counts at Point Bonita during