Richmond Bridge Harbor Seal Survey:
Project Goals and Guidelines

Sarah Allen, Ph.D., Principal Investigator
Hal Markowitz, Ph.D., Principal Investigator
Deborah Green, M.A., Project Manager
Emma Grigg, M.A., Field Coordinator

Radiotracking and Satellite-linked Telemetry of Harbor Seals in  San Francisco Bay, California: Preliminary Results

Richmond Bridge Harbor Seal Survey Project Bibliography

FAQ's: Frequently asked questions about the Harbor Seal Survey: click here .

The Richmond Bridge Harbor Seal Survey (RBHSS) is a joint project of  Caltrans and San Francisco State University .  The project produces weekly reports to Caltrans and the National Marine Fisheries Service (NMFS) concerning the potential effects of the seismic retrofit of the Richmond-San Rafael Bridge on the harbor seals (Phoca vitulina richardsi) at Castro Rocks, located just beneath the bridge.  Reports concerning changes in the behavior and number of seals are communicated to Caltrans and NMFS, relying on comparisons with recent work by other investigators (e.g. Torak, Spencer, Kopec, and Harvey).

This project also provides an excellent opportunity to learn more about the San Francisco Bay population of harbor seals, and learn more about how we can minimize disturbance of the seals during necessary bridge construction.  Findings of this study are presented regularly at scientific meetings, to school groups, and more.

The study includes regular monitoring of two alternate haul out sites (Yerba Buena Island, primarily used by harbor seals during the winter months, and Mowry Slough, a south bay pupping site) that may be affected as a function of the disturbance of harbor seals at Castro Rocks.
 

This study began in May 1998.  Baseline data were collected at all three sites until the start of the seismic retrofit work on the Richmond-San Rafael Bridge in the Spring of 2001.  Monitoring continued at all sites until the completion of the seismic retrofit construction work on the Bridge, in September 2005.  Data were collected using a combination of techniques involving direct observation, analysis of videotape data (collected from three cameras focusing on portions of Castro Rocks where seals are typically seen in greatest abundance), radio telemetry and satellite tracking.  Additional, post-construction monitoring will be conducted in 2005-2006 by Caltrans biologists at a reduced survey frequency.  

If you would like copies of the final report from this project, including results of post-construction monitoring, please contact:  

Background:

Harbor seals come on shore to rest and breed in groups at terrestrial sites called 'haul outs'.  Shoreline habitat preferred by harbor seals has been shrinking at an accelerated rate in the past century; around 90% of California wetlands have been filled or altered by development since the 1800's.  In addition, there is direct evidence of haul out site abandonment because of human disturbance at two sites within SF Bay:  one site at the entrance to the San Francisco-Oakland Bay Bridge and at Strawberry Spit (Bartholomew 1949 ; Risebrough et al. 1979 , Allen 1991 ).  Other indirect evidence suggest that the population of harbor seals in SF Bay may be affected by pollutants and disturbance ( Risebrough et al. 1979 , Kopec and Harvey 1995 , Spencer 1997 ).  Whereas seal numbers are increasing at nearby coastal sites and at most other sites throughout California and Oregon, the harbor seal population in SF Bay has remained unchanged since the mid 1970's at around 400-500 animals (L. Fancher, pers. comm., Stewart et al. 1988 , Allen et al. 1990).

The viability of the Bay's resident harbor seal population depends on the integrity of 12 terrestrial sites which they currently frequent (See Site Map ).  Castro Rocks is the largest haul out site in the north bay and the second largest breeding site in SF Bay ( Kopec and Harvey 1995 , Allen 1991). Haul out sites are resting and breeding areas for congregations of seals, and since enactment of the Marine Mammals Protection Act of 1972, protecting these areas has been an important measure for preserving populations.  There is strong evidence that human related activities may have a negative effect on harbor seal behavior (Calambokidis et al. 1978 , Allen et al. 1985).  Researchers have reported seals shifting from a predominantly diurnal (active during the day) hauling pattern to a nocturnal (active at night) pattern (Paulbitski 1975) . Others have reported reduced reproductive success and site abandonment (Bartholomew 1949 , Calambokidis et al. 1979 ).

Castro Rocks are situated adjacent to the Richmond-San Rafael Bridge, which spans the northern reach of SF Bay. The integrity of this bridge was compromised by the 1989 Loma Prieta earthquake and Caltrans is charged with retrofitting the bridge so as to ensure its safety in future earthquakes.  Because of the proximity of the bridge to the seal haul out site, there is concern that the seals may abandon the colony while the construction work occurs and fail to return after construction is completed.  This project is designed to study the effects of the construction work on the seals, and to try to develop ways to minimize negative impacts on this important SF Bay haul out site.

Project Timeline:

This project began May 1, 1998.  Construction began on the Richmond-San Rafael Bridge in the Spring of 2001, and was completed in September 2005.  Baseline data were collected until the start of construction; baseline data will be used for comparison with seal behavior and population dynamics during and after construction occurring near Castro Rocks.   Caltrans will conduct post-construction monitoring in 2005-2006 on a reduced survey schedule. All monitoring work has been done in accordance with National Marine Fisheries Service (NMFS) guidelines and requirements, and the retrofit construction work done under Incidental Harassment Authorizations (IHAs) issued by NMFS.

    The Survey Field Team

Acknowledgments:

This project is funded by the California Department of Transportation (Caltrans), and special thanks go to:

Chuck Morton, Caltrans
Marty Leber, Caltrans
Dennis Reiss, Caltrans
Rob Shipman, Caltrans
The Richmond-San Rafael Bridge tow truck drivers and maintenance crew
William Coats, Caltrans
Fernando Leon, Caltrans
Soheil Mojtahedi, Caltrans

In addition, the RBHSS is indebted to the following people, whose help and support has been essential to this project:

Irma Lagomarsino, National Marine Fisheries Service (NMFS)
Tina Fahy, NMFS
Ken Hollingshead, NMFS
Joseph Koczur, NMFS
Dianne Kopec
Clyde Morris, SFBNWR
Joelle Buffa, San Francisco Bay National Wildlife Refuge (SFBNWR)
Joy Albertson, SFBNWR
Marc Webber, SFBNWR
Norton Bell, SFBNWR volunteer
Chuck Taylor, Cargill Salt
Christy Heath, United States Coast Guard
Vice Admiral Card and family, USCG
Vice Admiral Collins and family, USCG
Vice Admiral Riutta and family, USCG
Jim Harvey and students, Moss Landing Marine Labs
Frances Gulland, DVM, and Marty Haulena, DVM, The Marine Mammal Center, Sausalito, CA
Denise Greig, The Marine Mammal Center
Ellen Hines, SFSU Dept. of Geography
The SFSU Administrative Staff
Carolyn Degnan, USGS
Graham Charles, Ars Indicii Information Design
Lewis Bogdanovic ~ Logo and Web Page Designer

Photos for this page were taken by:

Bob Colin, Caltrans
Lynn Harrison, Caltrans
Chuck Morton, Caltrans
Emma Grigg, SFSU
Debbie Green, SFSU
Ashley Ransom, SFSU
Amy Bohorquez, SFSU
Katie Eckert, SFSU
Erin Blackwood, The Marine Mammal Center*
S. Veil, The Marine Mammal Center*
Sarah Grigg

* All photos taken at The Marine Mammal Center are of animals temporarily at the Center for rehabilitation and eventual release.   They are not permanently captive animals.
 
 

Allen, S.G.  (1991)  Harbor seal habitat restoration at Strawberry Spit, San Francisco Bay.  Point Reyes Bird Observatory Report PB91-212332/GAR.  47pp.

Bartholomew, G.A. Jr. (1949) A census of harbor seals in San Francisco Bay. J. Mammal. 30(1): 34-35.

Calambokidis, J.; Bowman, K.; Carter, S.; Cubbage, J.; Dawson, P.; Fleischner, T.; Schuett-Hames, J.; Skidmore, J.; and Taylor, B. (1978) Chlorinated hydrocarbon concentrations and the ecology and behavior of harbor seals in Washington State waters. NSP funded project provided by Cascadia Research Collective. 121 pp.

Calambokidis, J.A.; Everitt, R.D.; Cubbage, J.C.; and Carter, S.D. (1979) Harbor seal census for the inland waters of washington, 1977-1978.  Murrelet 60(37): 110-112.

Kopec, D. and Harvey, J. (1995) Toxic pollutants, health indices, and population dynamics of harbor seals in San Francisco Bay, 1989-91: a final report.  Technical publication. Moss Landing, CA: Moss Landing Marine Labs.

Paulbitsky, P.A. (1975) The seals of  Strawberry Spit. Pacific Discovery 28(4): 12-15.

Risebrough, R.W.; Alcorn, D.; Allen, S.G.; Anderlini, V.C.; Booren, L.; DeLong, R.L.; Fancher, L.E.; Jone, R.E.; McGinnis, S.M.; and Schmidt, T.T. (1979) Population biology of harbor seals in San Francisco Bay, California.  Unpub. report to the Marine Mammal Commission, Washington, D.C., Contract MM6AC006. 62pp.

Spencer, C.L. (1997) Seasonal haul out patterns of Phoca vitulina richardsi in San Francisco Bay.  M.A. Thesis. San Francisco State University, San Francisco, CA.  98 p.

Stewart, B.S.; Antonelis, G.A. Jr.; DeLong, R.L.; Yochem, P.K. (1988) Abundance of harbor seals on San Miguel Island, California, 1927 through 1986.  Bull. Southern California Acad. Sci. 87: 39-43.

This page was last updated in September 2005.

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