The nursery stage serves as an intermediate step and provides small shellfish seed produced in a hatchery with an adequate food supply and protection from predators until they are ready to be planted on aquaculture leases in open water. Nursery systems built on land usually consist of wellers or raceways. A weller system consists of open-ended cylinders placed in a water reservoir or tank. Seawater circulates through the seed mass, which is suspended on a screen at the bottom of the cylinder. The direction of the water flow defines whether the system is referred to as a downweller or upweller. These systems can be novel, such as barrel wellers or floating upwellers (FLUPYS), which are employed at specific sites, usually marinas.
Raceways consist of shallow tanks or trays with salt water pumped from an adjacent source providing a horizontal flow as opposed to a vertical flow in the wellers. The water flow provides food (naturally occurring phytoplankton) and oxygen to the seed. Depending on water temperatures, 1-2 mm seed require 6-12 weeks to reach a size to be planted in the field, usually 5-6 mm shell length for clams, or 6-8 mm shell height for oysters.
Many growers are attracted to the nursery option as seed costs are lower and, at times, smaller seed are more available. Further, the systems can be constructed inexpensively and maintained on a part-time basis. Currently, over 30 land-based nursery facilities are located statewide.
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