Planning for Planting

Part 1: Broodstock

Oysters pulled from local waterways are the unsung heroes in this process, as they are the “parents” of the juvenile oysters that result. ORP partners with several regional hatcheries who each collect wild adult oysters in winter months to then be held in carefully controlled systems where hot and cold water mimics springtime water conditions, encouraging the oysters to get ready to reproduce.

This video shows how Horn Point staff, one of our hatchery partners, pluck broodstock from the icy waters of the Choptank and bring them into the hatchery for conditioning.

Part 2: Oyster Spawning

Oyster reproduction is an amazing process where all fertilization occurs outside the oyster in the water column. Once adult oysters are ready to spawn (or reproduce) they are placed on a table where warm water flows over them to simulate summer conditions. Females clap, releasing the eggs in a puff, while males release sperm in a continuous stream into the water. Hatchery staff separate spawning oysters to collect the eggs and sperm. Once the eggs are fertilized, they begin to develop into larvae. These larvae are transferred to large tanks to eat and grow…

Example from Horn Point demonstrating their process for spawning…

Part 3: Larval care

Oyster larvae swim freely in large, 10,000-gallon tanks as they grow. They are fed a carefully blended diet of different algae species or microscopic plants. After ~14 days, larvae develop an eye spot and a foot, indicating they will soon be ready to attach to a rigid substrate (like an oyster shell). Larvae are drained from the giant growing tanks and sorted by size. Not all larvae grow at the same rate. The larger, more mature larvae can be removed from the swimming culture and be bundled into a coffee filter for storage until they are needed for setting. The smaller larvae return to the tanks to continue growing until they mature.

Part 4: Oyster Shell Collection and Preparation

Oyster shell is the best natural material for larvae to stick to, or “set on,” to grow into a mature adult. ORP’s Shell Recycling Alliance reclaims oyster shells for use in Chesapeake Bay oyster restoration by collecting shells year-round, free of charge, from restaurants and other seafood businesses throughout Maryland, DC, Virginia, and Pittsburgh, PA. This provides about a quarter of the shell we need for for all of our restoration on an annual basis. We supplement the remainder by purchasing shells in bulk from oyster-shucking houses. The shell is aged outdoors for a year to remove organic material, then washed and placed into heavy-duty steel cages. Our hard-working field crew moves these cages to Horn Point’s setting pier.

This video of our field crew moving and washing shell helps to visualize the work that goes into this process.

Part 5: Setting and Planting

Mature larvae are introduced into setting tanks. ORP’s Remote Setting Facility at Horn Point Lab contains 52 setting tanks, each holding ~160 bushels of oyster shell. ORP also partners with private aquaculture remote-setting facilities across the state to produce spat-on-shell to support our restoration and public fishery replenishment programs.

Once introduced into setting tanks, larvae will attach to the oyster shell and metamorphose into spat. Larvae get one shot at this process. Their future depends on connecting to one of the shells in these tanks. After about 48 hours, most larvae have glued themselves to a shell. They can no longer swim and are referred to as “spat-on-shell.” Once a tank of spat-on-shell has grown in ambient natural conditions for a week, the spat is ready to be transferred to its final planting site. Tanks are then unloaded and the spat-on-shell is transported to a boat to be planted in the Bay. This final step completes the extensive prep process!

Watch a quick, 30-second video of this process at the ORP setting pier…

In addition to producing and planting spat-on-shell to help boost the population, we also plant shell and other alternative substrate materials to help replenish oyster habitat and provide settlement space for new baby oysters created from natural spawning in the wild oyster population. Other oyster restoration practices involve moving natural juvenile oysters (wild seed) from productive areas of the bay to less productive regions to help supplement the natural population and increase spawning in those areas. These oyster restoration tactics are often used in our restoration of oyster fishery or harvested areas of the bay.

Thank you to all of our partners who make oyster restoration possible, including the National Oceanic and Atmospheric Administration (NOAA), the U.S. Army Corps of Engineers, the Maryland Department of Natural Resources, Maryland Watermen, and oyster aquaculture industries.