Yerba Buena Island (YBI) is located in the middle of the Bay Bridge running between San Francisco and Oakland, adjacent to Treasure Island.  YBI is owned and managed by the United States Coast Guard, and access is restricted to authorized users only.  Harbor seals haul out on a rocky beach on the island, and this haul out area is our primary alternate site for looking at patterns of harbor seal abundance and behavior prior to and during the construction on the Richmond-San Rafael Bridge.
 

Although seals haul out year round on Yerba Buena Island, it is not considered a pupping site for harbor seals (although pups are occasionally seen there) (Kopec and Harvey, 1995).  This site appears to be particularly important to seals during the winter months, perhaps coinciding with the presence of Pacific herring near the island.   Abundance of harbor seals was highest at YBI during the winter months, and males comprised 83.1% of the seals whose gender could be determined on the haul out site (Spencer, 1997).
 

Harbor seals at Yerba Buena Island are subject to high levels of disturbance, primarily from watercraft.  This is particularly true during the summer, when numbers of small boats, jet skis, kayaks, etc. on San Francisco Bay increase.  Please do your part to keep the seals in S.F. Bay!  Boats, jet skis and kayaks should be kept a minimum of 100 yards (roughly the length of a football field) from the  haul out area, to avoid disturbing the seals.  Disturbing a marine mammal is a violation of the Marine Mammal Protection Act.
 
 
 
 
 
 

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.

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

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