The hard clam production process consists of three consecutive stages—hatchery, nursery, and growout to a marketable size.
Photo by University of Florida IFAS.
Clam farming begins in the hatchery with production of seed. Adult clams are induced to spawn by manipulating water temperatures.
Photo by Tom Smoyer, HBOI.
In the hatchery, larval clams are reared under controlled conditions in large tanks supplied with filtered seawater.
Photo by Sean Dowie.
During the hatchery phase, cultured marine microalgae are fed at increasing densities to larvae and post-set clams.
Photo by Leslie Sturmer.
Post-set clams are maintained in the hatchery until they reach about 1 mm. Over 100,000 seed are held in this downweller.
Photo by Eric Zamora.
The nursery is an intermediate step, where hatchery-produced seed are reared under semi-controlled conditions in land-based systems, such as these raceways.
Photo by Eric Zamora.
Another method of land-based nursery culture is the upweller system; some designs place the wellers, or cylinders, in the water.
Photo by Leslie Sturmer.
Clams are grown to market-size on coastal submerged lands leased from the State of Florida.
Photo by Florida Department of Agriculture and Consumer Services.
When clam seed reach about 1/4”, they are stocked in polyester mesh bags and staked to the lease bottom for growout.
Photo by Leslie Sturmer.
After 15-18 months depending on season planted, littleneck-sized clams are harvested by pulling the bags off the bottom.
Photo by University of Florida IFAS.
Harvested clams are delivered to a certified shellfish wholesaler where they are prepared for processing and shipping to markets across the country.
Photo by Eric Zamora.
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Nursery
Stage

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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