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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Growout
Stage

Shellfish are grown on estuarine or coastal submerged lands leased from the State of Florida. Successful shellfish farming requires good water quality, free of bacteriological and industrial contamination. The Florida Department of Agriculture and Consumer Services, Division of Aquaculture administers the lease program and monitors coastal waters for shellfish harvesting classifications. The lease is for a 10-year term and is renewable and transferable. The lessee pays an initial application fee and an annual rental fee thereafter. In addition, the leaseholder must plant a minimum amount of seed per acre per year to fulfill their agreement.

Hard Clams

Since clams are bottom-dwelling mollusks, growout systems are designed to place the seed in a bottom substrate and provide protection from predators. The system must allow substantial water flow to provide both oxygen and phytoplankton for growth. Many clam growers in the state use soft, polyester mesh bags. The bag culture method is usually a two-step process. The first step involves field nursing seed in small mesh (3-4 mm) bags, which are staked to the bottom using a variety of materials, such as PVC pipe. Typically, about 10-15,000 seed are planted in each 4-foot by 4-foot bag. When the seed reach a size of 12-15 mm (1/2 inch), usually after 3 to 6 months, they are transferred to another mesh bag with larger holes (9-10 mm mesh) at a lower density, about 800 to 1,200 clams per bag. The bag serves as the harvesting device as it contains the clams. Growers in southwest Florida also use the bottom plant method in which clam seed are broadcasted on the bottom and a layer of cover netting is placed over them. A pump-driven device is used to harvest the clams.

A crop of littleneck-sized clams, which are one inch in shell width, can be grown within 12-18 months, depending on water temperatures and food availability. Survival rates are specific not only to planting methods and experience, but also predator abundance. Additional cover netting, such as galvanized wire or plastic netting, placed over the bags is required in some growing areas.

Oysters

Since oysters are reef-building mollusks, culture gear is designed to keep the seed off the bottom. Single-set oyster seed are placed in Vexar mesh containers, such as bags or baskets, which are supported by floats or suspended lines. Oysters grow fast in off-bottom culture and must be thinned and transferred to larger mesh containers several times during growout. Natural tumbling via wave action is another benefit of suspending the gear and results in oysters with a more marketable shell shape and appearance. Market size oysters are about 2.5-3 inches in shell length, which may take 8-12 months of growth prior to harvest. Cultured oysters are typically sold to the premium half shell market.   

Once shellfish are harvested, they are delivered by the grower to a certified shellfish dealer. At the shellfish processing facility, shellfish are prepared for market by washing, sorting, grading by size, counting, packaging, and tagging. Both clams and oysters are generally sold live, and refrigerated trucks are used in transporting product to marketplaces throughout the state and nation.

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