Pacific harbor seal (Phoca vitulina richardsi) monitoring at Point Reyes National Seashore and Golden Gate National Recreation Area: 2012 annual report
Codde S and Allen S. 2013. Pacific harbor seal (Phoca vitulina richardsi) monitoring at Point Reyes National Seashore and Golden Gate National Recreation Area: 2012 annual report. Natural Resource Technical Report. NPS/SFAN/NRTR—2013/806. National Park Service. Fort Collins, Colorado
Pacific harbor seals (Phoca vitulina richardsi) are the most abundant and only year-round resident pinniped in the San Francisco Bay Area, California. Long-term monitoring studies at the largest harbor seal colonies in Point Reyes National Seashore have been conducted intermittently since the mid-1970s by various groups. Monitoring has been conducted annually by NPS staff, using peer-reviewed methods, since 1996 but not all of the current sites were surveyed until 2000. 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 as indicated by 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 2012 breeding and molting seasons (March-May and June-July, respectively) once to twice per week at the largest Point Reyes National Seashore and Golden Gate National Recreation Area harbor seal colonies, collectively referred to as Marin County locations. Members of the Harbor Seal Monitoring Volunteer Program helped to complete 244 surveys at eight Marin County locations, contributing an estimated 423 hours of monitoring. During the breeding season, peak counts of 2,581 adult and immature seals and 1,286 seal pups were recorded at all Marin County monitoring locations. Drakes Estero had the most adult and immature seals (702), followed by Double Point (579). Drakes Estero and Double Point accounted for 53% (678) of pups at Marin County haul-outs. During the molting season, a peak count of 3,482 animals was recorded at Marin County locations. During surveys, 104 disturbances to seals were recorded. The most frequent causes were unknown source (28%), humans on foot (27%), and motorboat (15%). Twelve regional surveys were conducted throughout the breeding and molting seasons at locations in Sonoma, Marin, and San Mateo counties and San Francisco Bay. Of these areas, Marin County locations accounted for 63% of breeding season adult and immature animals (2,482 of 3,960), 78% of pups (1,250 of 1,612), and 69% of seals during the molting season (3,323 of 4,803).
- Type
- Published Report
- Authors
- Codde, Sarah; Allen, Sarah
- Date of Issue
- 2013-10
- Publisher
- National Park Service
- 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