Pacific harbor seal (Phoca vitulina richardsi) monitoring at Point Reyes National Seashore and Golden Gate National Recreation Area: 2010 annual report
Codde S, Press D, Roberts D, Allen S. 2011. Pacific harbor seal (Phoca vitulina richardsi) monitoring at Point Reyes National Seashore and Golden Gate National Recreation Area: 2010 annual report. Natural Resource Technical Report. NPS/SFAN/NRTR—2011/465. National Park Service, Natural Resource Stewardship and Science. Fort Collins, Colorado
Pacific harbor seals (Phoca vitulina richardsi) are the dominant and only year-round resident pinniped in the San Francisco Bay Area, California. Long-term monitoring studies have been conducted at the largest harbor seal colonies in Point Reyes National Seashore since the mid 1970’s. The objectives of monitoring each site and the population as a whole are to i) detect changes in population size, ii) detect changes in reproductive success by way of pup production, and iii) identify anthropogenic or environmental factors that may affect the condition of the population (Adams et al. 2009). Harbor seal surveys were conducted throughout the 2010 breeding (March through May) and molting (June through July) seasons once to twice per week at the largest Point Reyes and Golden Gate harbor seal colonies, collectively referred to as Marin County locations. Members of the Harbor Seal Monitoring Volunteer Program helped to complete 214 surveys at eight Marin County locations, contributing an estimated 422 hours. During the breeding season, 2,128 adult and immature seals and 811 seal pups were counted at all Marin County monitoring locations. Drakes Estero had the most adults (610), followed by Double Point (380). Drakes Estero and Double Point accounted for 56% (453) of pups at Marin haulouts. During the molting season, 2,875 animals were counted at Marin County locations. The adult and pup maximum counts during the breeding season and the molting season maximum count were all the lowest recorded in the past ten years. During surveys, 114 disturbances to seals were recorded. The most frequent causes were human on foot (31%), unknown (26%), and motorboats (24%). Thirteen regional surveys were conducted throughout the season at locations in Sonoma, Marin, San Francisco, and San Mateo counties. Of the counties surveyed, Marin County locations accounted for 62% of breeding season adults/immatures, 78% of pups, and 66% of seals during the molting season.
- Type
- Published Report
- Authors
- Codde, Sarah; Press, David; Roberts, Dale; Allen, Sarah
- Date of Issue
- 2011-06
- Publisher
- National Park Service, Natural Resource Stewardship and Science
- Units
- GOGA , NRSS , PORE
- Keywords
- Abundance (Biodiversity), Annual Report, Bolinas Lagoon, Double Point, Drakes Estero, Duxbury Reef, Harbor Seal, Marin County, Marine Mammals, Monitoring, Observations, Phoca vitulina, Pinnipeds, Point Bonita, Point Reyes Headlands, Presence (Biodiversity), Tomales Bay, Tomales Point