Pacific harbor seal (Phoca vitulina richardsi) monitoring at Point Reyes National Seashore and Golden Gate National Recreation Area: 2009 annual report
Codde S, Press D, Roberts D, Allen S. 2010. Pacific harbor seal (Phoca vitulina richardsi) monitoring at Point Reyes National Seashore and Golden Gate National Recreation Area: 2009 annual report. Natural Resource Technical Report. NPS/SFAN/NRTR—2010/345. Natural Resource Program Center. 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 2009 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 227 surveys at eight Marin County locations, contributing an estimated 450 hours. During the breeding season, 2,353 adult and immature seals and 1,018 seal pups were counted at all Marin County monitoring locations. The adult and immature count is the lowest number recorded in the past 10 years. Drakes Estero had the most adults (561), followed by Tomales Bay (438) and Double Point (426). Drakes Estero and Double Point accounted for 56% (570) of pups at Marin haulouts. During the molting season, 3,556 animals were counted at Marin County locations. During surveys, 96 disturbances to seals were recorded. The most frequent causes were unknown (28.1%), motor boat (22.9%), and human on foot (21.9%). Twelve 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 57.6% of breeding season adults/immatures, 77.6% of pups, and 70.2% of seals during the molting season.
- Type
- Published Report
- Authors
- Codde, Sarah; Press, David; Roberts, Dale; Allen, Sarah
- Date of Issue
- 2010-06
- Publisher
- Natural Resource Program Center
- Units
- GOGA , NRSS , PORE , SFAN
- 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