As a participant in the program, you will start with young oysters, called "seed" or "spat," that have been spawned and reared in a hatchery. After oysters are spawned they first go through a free-swimming larval phase and then reach a stage when they must attach to a hard substrate, usually another oyster or shell. In hatcheries, old, whole oyster shells are often used as the hard substrate (called "cultch") on which the larvae are "set." Several spat may set on each oyster shell. This arrangement, where larvae set onto oyster shell, is called "cultched" seed. Alternatively, "cultchless" seed can be produced by allowing larvae to set on tiny fragments of sand or shell. Cultched seed is used in the oyster gardening program because it more closely replicates oysters as they are found in nature.

In producing cultched seed (also called spat-on-shell) in the hatchery, old oyster shell is first dried out on land in order to remove organic material that could degrade water quality in the setting tanks. Shell is placed in plastic mesh bags and stacked in tanks. River water is then added and heated to temperatures that will enhance the setting of the free-swimming larval oysters. Millions of hatchery-produced larvae are then released into the tank. Once the larvae have attached themselves, metamorphosed and set, they are referred to as spat. The spat-on-shell are generally kept in the tanks for several days, then removed to a nursery area where tides and currents provide the water exchange necessary for growth and survival.

Although cultched oysters can exhibit rapid growth, sometimes reaching 25 mm (one inch) in two to three months after settlement, growth is extremely variable and depends on many interacting factors, especially salinity, temperature, food availability and water quality. Data that you collect about your oyster garden will provide valuable insight for oyster restoration projects.

This page was last modified October 17, 2012

The Oyster Gardening Program is a cooperative effort of the Oyster Alliance
Chesapeake Bay Foundation ~ Maryland Sea Grant Extension Program
University of Maryland Center for Environmental Science ~ Oyster Recovery Partnership

This page is part of Maryland Sea Grant's Oyster web site.

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