Pacific harbor seal (Phoca vitulina richardii) monitoring at Point Reyes National Seashore and Golden Gate National Recreation Area: 2007 annual report
Truchinski K, Flynn E, Press D, Roberts D, Allen S. 2008. Pacific harbor seal (Phoca vitulina richardii) monitoring at Point Reyes National Seashore and Golden Gate National Recreation Area: 2007 annual report. Natural Resource Technical Report. NPS/SFAN/NRTR—2008/118. Nps. Fort Collins
Pacific harbor seals (Phoca vitulina richardii) 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 and Golden Gate National Recreation Area since 1976. 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. Harbor seal surveys were conducted throughout the 2007 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 completed 252 surveys at eight Marin County locations, contributing an estimated 2152 hours. During the breeding season, a maximum combined total of 2771 adults and immature seals and 903 seal pups were counted at all Marin County monitoring locations. Drakes Estero had the most adults (759), followed by Tomales Bay (481) and Double Point (469). Drakes Estero and Double Point accounted for 54% (488) of pups at Marin County haul outs. From June to July, 4218 animals molted at Marin locations. Disturbances to seals occurred, with 215 incidences recorded during surveys. The most frequent causes were human (35.3%), unknown (20.9%), and motor boat (14.4%). Regional surveys occurred 13 times throughout the season at locations in Sonoma, Marin, San Francisco, and San Mateo counties. Marin County locations accounted for 73.2% (2916/3979) of breeding adults and immatures, 84.4% (765/974) of pups, and 74.1% (3459/4787) of seals during the molting season.
- Type
- Published Report
- Authors
- Truchinski, Kristen; Flynn, Erin; Press, David; Roberts, Dale; Allen, Sarah
- Date of Issue
- 2008-06
- Publisher
- Nps
- Units
- GOGA , NRSS , PORE , SFAN
- Keywords
- Annual Report, Bolinas Lagoon, Double Point, Drakes Estero, Duxbury Reef, Harbor Seal, Marine Mammals, Monitoring, Phoca vitulina, Pinnipeds, Point Bonita, Point Reyes, Tomales Bay, Tomales Point