San Francisco Bay Olympia Oyster Restoration Methods and Ecological Benefits

Robert Abbott, Rena Obernolte, Brian Mulvey
There has been a significant resurgence in the abundance of the Olympia oyster Ostrea conchaphila in San Francisco Bay in the last 5 years. Several factors may have contributed to the increased abundance including improved water quality, a reduction in the number of competing organisms and habitat restoration projects in different parts of the Bay. Five habitat restoration methods were tested at the Marin Rod and Gun Club site in northern San Francisco Bay including hanging strings, stakes, reef rows at different depths, mounds of bagged shells and reef balls constructed from dredged Bay materials. The aggregate population of native Olympia oysters at the MRGC site on restoration project features was greater than 600,000 in June 2009 compared to just a few thousand along the shore line in 5 years earlier. The mounds of bagged oyster cultch show a progressive decrease in productivity each year due to competition and accumulated sedimentation. Three methods of cleaning the bagged cultch were tested with relative degrees of effectiveness relative to the level of effort to restore functionality. Acoustic receiver placed in the reefs mounds of bagged cultch demonstrated that the reefs are used by acoustically tagged, salmon, steelhead and sturgeon.