Building An Oyster Reef
The Oyster Recovery Partnership has successfully joined together state and federal agencies, scientists, industry, and conservation organizations toward the common goal of oyster restoration. Evidenced by spat on shell production numbers in recent years, ORP is leading the way to a viable future for the Chesapeake Bay’s oyster population. The following are common steps that we apply to rehabilitating an oyster reef:
Step 1: Select the proper site.
Each year Maryland oyster restoration partners convene and review the most recent scientific papers, modeling, and field data, including bottom topography, currents, sediment rates, salinity levels and historical bar locations, to select the oyster reefs that have the greatest likelihood for recovery success. Over the last several years, efforts have focused on rehabilitating reefs in targeted tributaries, including Harris Creek and Little Choptank River.
Step 2: Conduct oyster bar surveys.
Using sonar, bottom mapping is conducted on historic oyster bars by NOAA and Maryland Geological Survey (MGS) to locate areas of exposed shell or lightly covered shell deposits on the river bottom to identify areas least impacted by silt and sediment.
Step 3: Construct reefs and prepare the bar for seeding.
Oysters require hard substrate to thrive. Some of the targeted reefs require rehabilitation or substrate before receiving hatchery-produced spat on shell (baby oysters attached to a large shell) or to receive a natural set (whereby mother nature produces the spat). Watermen are employed to reclaim buried shell or the State or Army Corps of Engineers will plant clean shell or other materials, like concrete and stone, to create a suitable bed for the oysters. Watermen collect large oysters from around the Bay during the cold winter months for use by the hatchery as brood stock. A single pair of oysters can generate millions of new oysters.
Step 4: Visually inspect the new reef.
Prior to planting the reefs with oyster spat, SCUBA divers survey the areas to ensure that the bottom is suitable to plant spat on shell oysters. Divers swim 200 meter transects evaluating the bottom. The data collected allows for refinement of the planting area, which in turn can lead to higher success.
Step 5: Produce, transport and plant oyster spat.
It takes about a month to spawn and grow the microscopic oyster larvae until they are ready to set (or attach) to their host shell. ORP field staff work closely with hatchery crews to set the oyster larvae. Tens of thousands of bushels of aged shell are cleaned and loaded into 12 foot round tanks. Larvae produced by the Horn Point Lab Oyster Hatchery are added to these tanks containing clean shell. The larvae affix themselves to the shell and are then called “spat.” The resulting spat on shell is transferred to ORP’s planting vessel, the Robert Lee, and transported to the prepared bars for planting. Using GPS to guide the planting, the oysters are deposited onto reefs.
Step 6: Monitoring our progress.
Scientists regularly sample the planted oysters to determine oyster survival, growth, population densities, disease levels and other metrics.