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Biosphere, Inc.

Circular Screen Separator Classifies Clams

With the increasing trend to greater consumption of seafood, it was only a matter of time before raising clams rather than simply dipping for them became reality. Biosphere, Inc. of Tuckerton, NJ, is preparing for its first harvest of cultured clams. It takes about two-and-one-half seasons to raise clams that are 1-1/2 inches long — the size required for marketing in New Jersey.

In the natural environment, each clam lays thousands of eggs but most are lost to fish and other predators before the clam gets a chance to form a shell. By raising young clams in its 3-by-20 foot raceways, there are no fish to prey on immature clams. Biosphere usually spawns clams in the spring and fall. The youngest clams are placed in the raceway so that they are densely packed but not on top of each other, explained Jerry Zodel, Biosphere biologist. Seawater at a depth of several inches flows continuously over the clams, he added.

When the small clams reach about 5 mm long, sorting begins. Infant clams are screened to a uniform size range to prevent the larger ones from consuming most of the nutrients, thus starving the smaller ones. By maintaining a relatively uniform size range, each clam has a greater chance to receive nutrients and this results in increased yield.

At various intervals during the Spring, Summer and Fall, the clams are removed from each of the 30 raceways. Biosphere personnel rake them into a fiberglass chute and push them into a VIBROSCREEN Circular Screen Separator to separate the larger clams from the smaller ones. Three separations are made. The large clams are placed in one raceway, mid-size ones in another and very small clams are returned with water to yet another raceway. This classification takes place about once a week. according to Zodel, "We use two stainless steel screens for each sizing operation, choosing from 10 available mesh sizes on hand." By using the different mesh sizes, clams can be grouped by size throughout their life until they are ready to be placed in the bay. The gentle sifting action of the VIBROSCREEN Separator leaves the clams unharmed.

When the clams reach about 15 mm long they are dropped into leased "fields" in the Great Bay which is about 10 miles north of Atlantic City. After two years, the clams are harvested using rakes. Clams measuring 1-1/2 inches can be marketed and the others are returned to a field in the 80-acre leased area.

Screen Tips - Volume 4, Number 3 Fall 1989
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Circular Screen Separator Classified Clams
Clams are screened with a Kason VIBROSCREEN Circular Screen eparator to a uniform size to prevent the larger ones from consuming most of the nutrients, thus starving the smaller ones.