Pacific harbor seal (Phoca vitulina richardsi) monitoring at Point Reyes National Seashore and Golden Gate National Recreation Area: 2011 annual report
Codde S, Press D, Roberts D, Allen S. 2012. Pacific harbor seal (Phoca vitulina richardsi) monitoring at Point Reyes National Seashore and Golden Gate National Recreation Area: 2011 annual report. Natural Resource Technical Report. NPS/SFAN/NRTR—2012/611. 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 have been conducted intermittently at the largest harbor seal colonies in Point Reyes National Seashore since the mid 1970s by various groups. 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 2011 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 224 surveys at eight Marin County locations, contributing an estimated 442 hours. During the breeding season, 2,676 adult and immature seals and 1,302 seal pups were counted at all Marin County monitoring locations. Drakes Estero had the most adult and immature seals (715), followed by Double Point (587). Drakes Estero and Double Point accounted for 59% (770) of pups at Marin haul-outs. During the molting season, 2,883 animals were counted at Marin County locations. The maximum pup count was above the mean count of the monitoring program’s 12 year period; however, the molting season maximum count was one of the lowest recorded. During surveys, 94 disturbances to seals were recorded. The most frequent causes were humans on foot (29%), motorboats (21%), and unknown (20%). Twelve regional surveys were conducted throughout the breeding and molting seasons at locations in Sonoma, Marin, San Francisco, and San Mateo counties. Of these counties, Marin County locations accounted for 69% of breeding season adult and immature animals, 84% of pups, and 65% of seals during the molting season.
- Type
- Published Report
- Authors
- Codde, Sarah; Press, David; Roberts, Dale; Allen, Sarah
- Date of Issue
- 2012-08
- 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, Pinniped, Pinnipeds, Point Bonita, Point Reyes Headlands, Presence (Biodiversity), Tomales Bay, Tomales Point