San Diego Bay Native Oyster Living Shoreline

San Diego Bay was historically composed of significant intertidal habitat; however, decades of dredging and channelization have resulted in the loss of 42 percent of San Diego Bay’s shallow subtidal habitat and 84 percent of its intertidal mudflat habitat since the late 1800’s. These modifications and associated shoreline armoring have resulted in the loss of most of the natural shoreline protection that marshes, oyster beds, and other intertidal and shallow subtidal habitats provided. Native Olympia oysters (Ostrea lurida) were a dominant native species in this area until the early 1900’s. Today, viable native oyster stock still exists in San Diego Bay, but a lack of hard substrate habitat prevents oyster populations from re-establishing.
The San Diego Bay Native Oyster Living Shoreline Project (Project) was established as a pilot project in the Chula Vista Wildlife Reserve in South San Diego Bay, CA. In 2021, 360 Reef Balls, composed of concrete, aggregate and oyster shell, were installed in six arrays spread across 23,760 square ft (0.55 acres) along the northern edge of the reserve. The arrays were placed to target native oyster recruitment, enhance the native faunal community, absorb wave energy and stabilize the eroding shoreline as a nature-based shoreline strategy. Five years of annual post-construction monitoring, which includes oyster recruitment, birds, fish and eelgrass surveys, and wave modeling, is ongoing. To date, monitoring results indicate that the project is meeting its goals with a native oyster population establishing on the reef balls. Sediment accretion has also been observed within the reef ball arrays. Although the Project footprint is only 0.55 acres, the project area affected by project improvements is 10 acres.
In May 2025, oyster castles were added to create additional native oyster habitat in the project area. The oyster castles are smaller, stackable concrete units placed at low tidal elevations optimal for native oyster recruitment. 600 oyster castles were deployed across 200 linear feet creating approximately 2,020 square feet of surface area for native oyster establishment. Monitoring of the oyster castles is included in monitoring of the entire Project. Overall, the entire Project’s footprint will protect the shoreline from erosion, restore native oyster habitat that was historically present, improve water quality via oyster filtration, and increase connectivity to intertidal and subtidal lands in San Diego Bay.