Historical maps and images tell us that Sarasota Bay once supported a vibrant oyster community. Coastal development operations including dredge-and-fill activities destroyed much of this valuable hard-bottom habitat. Although the precise acreage of hard bottom habitat lost due to dredge-and-fill activities has not been determined, nearly 4,500 acres of bay bottom are known to have been covered by dredge-and-fill operations. Without hard bay bottom structure, oyster larvae (known as spat) cannot settle and form new reefs. To compensate for these lost habitats, SBEP has embarked on several oyster restoration and artificial reef creation projects.
Eastern Oyster Restoration
Oyster beds constitute a unique and valuable component of the Sarasota Bay ecosystem. Oyster beds provide structural habitat for many species of fish and invertebrates; in fact, oyster beds often support the highest species diversity and faunal abundance of any given habitat type within the bay. Oysters are also valued for their ability to improve water quality through their prolific filtering capacity. The SBEP supported a study of the historical distribution of oyster beds throughout the estuary and found that many historical beds have been lost, either to physical disturbances accompanying coastal development, through burial by sediments, or other unknown causes. This study led to the decision by the SBEP to initiate an Eastern oyster (Crassostrea virginica) restoration program within Sarasota Bay.
Initially, SBEP selected two locations in Little Sarasota Bay to create oyster habitat. One site is intertidal, where the bottom is exposed at low tide, and the other is subtidal, where it is always under water. Both sites are in areas where oysters are present (or used to be), but habitat expansion is limited by the lack of suitable substrate (oyster shell) necessary to attract new oysters (spat). This project uses fossilized oyster shells in mesh bags, which provides structure onto which the oyster larvae can settle and grow. Subsequent monitoring has shown that oysters attached to the shells within a month of placement and grew to maturity within two years.
This project demonstrated that suitable oyster habitat can be created and enhanced in Sarasota Bay waters through the careful placement of shell substrate. SBEP is using the findings from this pilot project to look for additional opportunities for oyster habitat expansion in Sarasota Bay.
SBEP’s artificial reef program began with the development of a master plan in 1996. One outcome of this plan was the identification of twenty possible sites for the creation of artificial reefs. Two main criteria for site selection were 1) appropriate sediment characteristics (for supporting the reef structure) and 2) proper depth and location so as not to impede navigation.
SBEP currently has nine artificial reefs within Sarasota Bay. These reefs were created primarily from prefabricated habitat “reef ball” modules. Habitat modules are cement domes of various diameters with perforations for the passage of fish. Since 2000, nearly 3,000 habitat modules have been used to create the existing reefs. Other materials, such as PVC pipe, have been used successfully at two additional artificial reefs in Sarasota Bay. Furthermore, reef balls are being deployed around navigation channel markers throughout the bay to create additional open water juvenile fish habitat.
In 2006, the SBEP supported a study by Mote Marine Laboratory to determine the most optimal configuration of artificial reef habitat modules for maximizing fish usage. By direct underwater observations, scientists tabulated fish diversity and abundance on habitat modules of different sizes during each season. The findings from this study identified reef designs and deployments that support desirable fish communities. Read the report here.