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. We monitor Castro Rocks year round. The study began in May 1998 and will continue until the bridge work is completed.
Harbor seals come on shore to rest and breed in groups at terrestrial sites called 'haul outs'.
Risebrough et al. 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. 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.