Vibratory screener helps raise little neck clams

New Jersey company Clam Daddy’s has been selling hard shell little neck clams (Mercenaria mercenaria) since 1984. The company breeds and grows its own fresh clams in a temperature controlled hatchery. The company focuses on upscale outlets such as gourmet restaurants and seasonal produce markets that demand top quality, rather than mass markets that buy primarily on price.

The clams begin their lives in late March as microscopic organisms invisible to the naked eye, growing to the size of a grain of sand in about 17 days and gradually increasing to market size over three to four years. The hatchlings start growing indoors, where they are moved from the breeding tank through increasingly larger vessels, and then to downwellers in which warmed sea water circulates.


Clams grow in circulating bay water

Once the water in the bay warms to between 10˚ C and 15˚ C, the clams are transferred outdoors to upwellers, through which the bay water, which contains naturally occurring algae, is continuously circulated. When the clams reach a sufficient size, they are transferred to long, shallow raceways on Clam Daddy’s pier, through which bay water is also continuously circulated. As the clams grow, they are transferred from one raceway to the next, each holding clams of the same size. When the largest clams reach the last raceway, they are ready to be planted in the bay.

To prepare same-size clams for each raceway, the larger clams were separated by placing several handfuls in a manual shaker screen – a wooden box with a mesh screen bottom – and shaking it until the smaller clams passed through the mesh. This was not only time consuming but resulted in a lot of sore arms. As sales continued to grow, manual separation became increasingly burdensome. So Mr. Mayer automated his screening process by installing a 914 mm diameter circular vibratory screener manufactured by Kason Corporation. “Our screener eliminated the need for a time-consuming, repetitive task,” he says. “It not only does in minutes what used to take hours, but allows me to deploy my staff to perform more important operations.”

A 914 mm diameter circular vibratory screener automatically sorts the seed clams by size in minutes, replacing the slower, labor-intensive manual shaker screen shown at right.

Vibratory screener automates classification by size

The circular vibratory screener consists of two screening decks, one above the other, with an imbalanced-weight gyratory motor that causes them to vibrate. “When the time comes to remove the larger clams from a raceway, we scoop several handfuls of them into the top deck of the screener, which has a slightly larger mesh than the lower one,” Mr. Mayer explains. “For example, we might have a 9500 micron screen on top and a 6300 micron screen on the bottom. As the clams move toward the periphery, the smaller clams fall through onto the bottom screening deck. Those small enough to pass through the tighter mesh of the lower screen are ejected through a discharge spout into a collection pan. Those too large to pass through the smaller mesh are ejected through another discharge port into a separate collection pan. The largest clams, those that failed to pass through the larger mesh of the upper screen, remain on that screen.”

“Once all the clams in a raceway have been screened, the smallest ones are returned to the raceway from which they were originally taken,” Mr. Mayer explains. “Those slightly larger are placed in the next raceway with clams of their own size, and so on until the largest clams from the last raceway are placed in special leased areas of the bay, where they continue to feed and grow until harvested to fill an order.” When the clams reach their full size after 4 to 5 years, they are harvested, rinsed, sorted by size, counted, bagged and refrigerated, ready for delivery. “The reason restaurants and farm markets prefer our clams is that they are never gritty with sand because we use special rakes to clean the nets and harvest the clams,” Mr. Mayer says proudly. “We also don’t harvest them until they are needed to fill an order, so they are the freshest clams you will find anywhere.”